U.S. patent application number 09/739259 was filed with the patent office on 2001-06-14 for chemically amplified resist compositions and process for the formation of resist patterns.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Igarashi, Miwa, Kotachi, Akiko, Makino, Yoko, Namiki, Takahisa, Nozaki, Koji, Takahashi, Makoto, Takechi, Satoshi, Watanabe, Keiji, Yano, Ei.
Application Number | 20010003640 09/739259 |
Document ID | / |
Family ID | 27522850 |
Filed Date | 2001-06-14 |
United States Patent
Application |
20010003640 |
Kind Code |
A1 |
Takechi, Satoshi ; et
al. |
June 14, 2001 |
Chemically amplified resist compositions and process for the
formation of resist patterns
Abstract
Alkali-developable, chemically amplified resist composition
which comprises an alkali-insoluble compound having a structural
unit containing a protected alkali-soluble group in which unit a
protective moiety of said protected alkali-soluble group contains
an alicyclic hydrocarbon group having bonded to a carbon atom
thereof a --CH.sub.2--R.sub.1' group wherein R.sub.1' is methyl,
ethyl, propyl or isopropyl, and said alkali-soluble group is
cleaved upon action of an acid generated from a photoacid generator
used in combination with said compound, thereby releasing said
protective moiety from the alkali-soluble group and converting said
compound to an alkali-soluble one, and a photoacid generator
capable of being decomposed upon exposure to a patterning radiation
to thereby produce an acid capable of causing cleavage of said
protective moiety. The resist composition can exhibit a high
sensitivity (not more than 5 mJ/cm.sup.2) and therefore is
particularly suitable for ArF lithography and also can exhibit
stable patterning properties.
Inventors: |
Takechi, Satoshi;
(Kawasaki-shi, JP) ; Kotachi, Akiko;
(Kawasaki-shi, JP) ; Nozaki, Koji; (Kawasaki-shi,
JP) ; Yano, Ei; (Kawasaki-shi, JP) ; Watanabe,
Keiji; (Kawasaki-shi, JP) ; Namiki, Takahisa;
(Kawasaki-shi, JP) ; Igarashi, Miwa;
(Kawasaki-shi, JP) ; Makino, Yoko; (Kawasaki-shi,
JP) ; Takahashi, Makoto; (Kawasaki-shi, JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN, HATTORI,
MCLELAND & NAUGHTON, LLP
1725 K STREET, NW, SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki
JP
|
Family ID: |
27522850 |
Appl. No.: |
09/739259 |
Filed: |
December 19, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09739259 |
Dec 19, 2000 |
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08969368 |
Nov 28, 1997 |
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6200725 |
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08969368 |
Nov 28, 1997 |
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08673739 |
Jun 27, 1996 |
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6013416 |
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Current U.S.
Class: |
430/270.1 ;
430/326; 430/330 |
Current CPC
Class: |
G03F 7/0045 20130101;
G03F 7/039 20130101 |
Class at
Publication: |
430/270.1 ;
430/326; 430/330 |
International
Class: |
G03F 007/039; G03F
007/30; G03F 007/38 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 14, 1995 |
JP |
7-178717 |
Jun 28, 1995 |
JP |
7-162287 |
Nov 30, 1995 |
JP |
7-312722 |
Mar 7, 1996 |
JP |
8-50264 |
Nov 29, 1996 |
JP |
8-320105 |
Claims
1. An alkali-developable, chemically amplified resist composition
for forming resist patterns which comprises: I. an alkali-insoluble
compound having a structural unit containing a protected
alkali-soluble group in which unit a protective moiety of said
protected alkali-soluble group is cleaved upon action of an acid
generated from a photoacid generator used in combination with said
compound, thereby releasing said protective moiety from the
alkali-soluble group and converting said compound to an
alkali-soluble one, said alkali-soluble group being protected with
an alicyclic hydrocarbon group-containing moiety represented by the
following formula (II'): 118in which R.sub.1' is a methyl, ethyl,
propyl or isopropyl group which may be substituted or
unsubstituted, and Z represents atoms necessary to complete an
alicyclic hydrocarbon group along with a carbon atom to which said
--CH.sub.2--R.sub.1' is bonded; and II. a photoacid generator
capable of being decomposed upon exposure to a patterning radiation
to thereby produce an acid capable of causing cleavage of said
protective moiety.
2. The resist composition according to claim 1, in which said
alkali-soluble group is a member selected from the group consisting
of a carboxilic acid group, sulfonic acid group, amide group, imide
group and phenol group.
3. The resist composition according to claim 1, in which said
protected alkali-soluble group is a carboxylic acid group
represented by the following formula (VII'): 119in which R.sub.1'
and Z each is as defined above.
4. The resist composition according to claim 1, in which the
alicyclic hydrocarbon group in said alicyclic hydrocarbon
group-containing moiety contains one or more ring structures or
condensed rings.
5. The resist composition according to claim 4, in which said
alicyclic hydrocarbon group is one member selected from the group
consisting of: (1) adamantane and derivatives thereof; (2)
norbornane and derivatives thereof; (3) perhydroanthracene and
derivatives thereof; (4) perhydronaphthalene and derivatives
thereof; (5) tricyclo[5. 2. 1. 0.sup.2,6]decane and derivatives
thereof; (6) bicyclohexane and derivatives thereof; (7) spiro[4.
4]nonane and derivatives thereof; and (8) spiro[4. 5]decane and
derivatives thereof.
6. The resist composition according to any one of claims 1 to 5, in
which said alkali-insoluble compound is a polymer or copolymer
comprising said structural unit as a repeating unit thereof.
7. The resist composition according to claim 6, in which the
repeating unit of said polymer or copolymer is one member selected
from the group consisting of acrylic acid esters and derivatives
thereof, itaconic acid esters and derivatives thereof, fumaric acid
esters and derivatives thereof, and styrene substituents and
derivatives thereof.
8. The resist composition according to claim 6, in which said
alkali-insoluble compound is a copolymer containing said repeating
unit as the first repeating unit, and the repeating units of said
copolymer other than said first repeating unit include a repeating
unit containing an unprotected alkali-soluble group in a side chain
thereof and/or a repeating unit containing in a side chain thereof
additional protected alkali-soluble group capable of being cleaved
upon action of the acid generated from said photoacid
generator.
9. The resist composition according to claim 8, in which said
copolymer has the structural unit represented by the following
formula (XXIV') or (XXVI'): 120in which R may be the same or
different, and each represents a hydrogen, halogen or a substituted
or unsubstituted, straight chain or branched chain alkyl group of 1
to 4 carbon atoms, A represents a protective moiety capable of
being released upon action of said acid, and R.sub.1' and Z each is
as defined above.
10. The resist composition according to any one of claims 1 to 5,
in which said alkali-insoluble compound is a nonpolymeric compound
which is used in combination with one or more alkali-soluble
polymer or copolymer.
11. A process for the formation of resist patterns which comprises
the steps of: coating a chemically amplified resist composition on
a substrate to be fabricated in order to form a resist coating
thereon, said resist composition comprising: I. an alkali-insoluble
compound having a structural unit containing a protected
alkali-soluble group in which unit a protective moiety of said
protected alkali-soluble group is cleaved upon action of an acid
generated from a photoacid generator used in combination with said
compound, thereby releasing said protective moiety from the
alkali-soluble group and converting said compound to an
alkali-soluble one, said alkali-soluble group being protected with
an alicyclic hydrocarbon group-containing moiety represented by the
following formulae (II'): 121R.sub.1' is a methyl, ethyl, propyl or
isopropyl group which may be substituted or unsubstituted, and Z
represents atoms necessary to complete an alicyclic hydrocarbon
group along with a carbon atom to which said --CH.sub.2--R.sub.1'
is bonded; and II. a photoacid generator capable of being
decomposed upon exposure to a patterning radiation to thereby
produce an acid capable of causing cleavage of said protective
moiety; selectively exposing said resist coating to a patterning
radiation capable of causing generation of an acid from said
photoacid generator; heating the exposed resist coating to a
temperature at which the cleavage of said protective moiety is
induced; and developing a latent image in the exposed and heated
resist coating with an alkaline developer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 08/673,739, filed on Jun. 27, 1996.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a chemically amplified
resist composition and a process for the formation of resist
patterns using the same. More particularly, in one aspect, the
present invention relates to a resist composition which can be
exposed to any patterning radiation having a relatively short
wavelength such as excimer laser light and can also utilize an
alkaline solution as a developer. The chemically amplified resist
composition of the present invention can provide fine
positive-working resist patterns without swelling. Further, the
thus produced resist patterns can provide a practically usable
sensitivity and an excellent resistance to dry etching. In another
aspect, the present invention relates to a resist composition which
can exhibit a higher resolution, higher sensitivity and excellent
resistance to dry etching, and also can effectively avoid cracking
in the resulting resist patterns and peeling-off of the patterns
from the substrate. In still another aspect, the present invention
relates to a resist composition which can exhibit a high
sensitivity and stable patterning properties which are particularly
desired in the field of ArF lithography. Accordingly, the present
invention can be advantageously utilized in the production of
semiconductor devices such as semiconductor integrated circuits,
for example, LSIs, VLSIs, ULSIs and other devices, using a
lithographic process.
[0004] 2. Description of the Related Art
[0005] Recently, in the production of semiconductor integrated
circuits, the degree of integration thereof has been notably
increased and accordingly LSIs and VLSIs have been produced on a
commercial scale. The minimum line width of the circuit patterns in
these devices approaches the sub-half micron or quarter micron
order. In other words, in the production of these high performance
devices, it is required to provide an established fine fabrication
technology.
[0006] In the field of lithography, to satisfy the above
requirements, an approach in which ultraviolet (UV) radiation as an
exposure source is shifted to shorter wavelengths in the far or
deep ultraviolet region has been suggested, along with research for
providing new exposure devices provided with a light source capable
of emitting such short wavelength radiation in the deep ultraviolet
region.
[0007] Currently, photolithograpy using a krypton fluoride (KrF)
excimer laser having a wavelength of 248 nm as an exposure source
has been noted as a novel exposure technology, and it has also been
urged to find novel resist materials suitable for exposure to such
short wavelength radiation and stably showing a high sensitivity
and high resolution. A chemical amplification system and a resist
material based on said system, i.e., chemically amplified resist
composition, have been disclosed by Ito et al. of IBM Corp. to be
useful for KrF lithography (see, for example, J. M. Frechet et al.,
Proc. Microcircuit Eng., 260 (1982); H. Ito et al., Digest of
Technical Papers of 1982 Symposium on VLSI Technology, 86 (1983);
H. Ito et al., "Polymers in Electronics", ACS Symposium Series 242,
edited by T. Davidson, ACS 11 (1984); and U.S. Pat. No. 4,491,628).
As will be easily understood by referring to these articles, the
basic concept of the chemically amplified resist composition
developed by Ito et al. resides in that a catalytic reaction is
first induced in the coating from the resist composition, thereby
increasing an apparent quantum yield to a level sufficient to
highly increase a sensitivity of the resist composition.
[0008] The above concept of the chemically amplified resist
composition will be further clarified with reference to one typical
example of the well-known chemically amplified resist compositions
which have been widely studied by the researchers in the field of
resist chemistry, namely, the chemically amplified resist
composition comprising t-buthoxycarbonyl polyvinylphenol (t-BOCPVP)
and a photoacid generator (PAG) capable of releasing an acid upon
action of the exposure radiation. After it was coated over the
substrate, the resist composition is exposed to the exposure
radiation, and as a result of such exposure, an acid is released
from the PAG. Then, the exposed resist composition or coating is
subjected to post-exposure baking (PEB). As a result of this
baking, in the exposed areas of the resist coating, a t-BOC group
is cleaved from t-BOCPVP to produce isobutene and carbon dioxide.
Further, a protonic acid simultaneously produced during cleavage of
the t-BOC group can act as a catalyst in the above-mentioned
cleavage reaction which therefore proceeds like a chain reaction,
thus largely varying the polarity of the exposed areas. In this
resist composition, if a suitable developer which is compatible
with such a large variation of the polarity in the exposed areas is
selected, satisfactory resist patterns can be easily produced.
[0009] However, conventional chemically amplified resist materials
including the above-discussed t-BOCPVP-based resist composition
have one problem in that because of the restricted chemical
structure of the resin used as a basic component thereof, they
cannot fully satisfy the requirements concerning sensitivity,
transparency to the exposure radiation, stability in storage, ease
in procurement, resolution and the like. Among the possible
restrictions to the chemical structure of the resist resin, the
most important restriction is the restriction to a protective group
which is attached to said resin, but is able to be cleaved
therefrom upon baking of the exposed resin in the presence of a
photoacid generator. Namely, in the film-forming resin in which a
side chain of the monomeric unit of the resin contains a carboxylic
acid ester attached thereto as a chemical amplification-concerning
component, protective groups which are recognized to be suitable
for the carboxyl group of said ester include only t-butyl group,
1,1-dimethylbenzyl group, tetrahydropyranyl group, 3-oxocyclohexyl
group and isobornyl group. These protective groups are
inappropriate, and therefore it is desired to provide a new
protective group which can be more effectively utilized in the
chemically amplified resist materials than the above protective
groups.
[0010] In addition to the improvement in the protective group
introduced into the resist resin, the conventional fine fabrication
technology includes problems concerning some defects in the
resulting resist patterns which defects will be described
hereinafter.
[0011] Using the fine fabrication technology, fine resist patterns
can be generally produced by coating a substrate having on a
surface thereof a layer or coating to be fabricated, such as a
layer to be selectively etched, with a resist material, and
exposing the resist coating to a patterning radiation to thereby
form a latent image corresponding to a pattern of said radiation.
The latent image of the resist coating is then developed with a
suitable developer. A desired resist pattern is thus obtained. The
resist pattern can be effectively utilized as a masking means in
the subsequent etching process to selectively etch the underlying
layer. Said patterning radiation generally includes ultraviolet
radiation such as the g-line (wavelength of 436 nm) and i-line
(wavelength of 365 nm), however, as briefly mentioned in the above
paragraphs, it also includes other radiations having shorter
wavelengths such as deep ultraviolet radiation, vacuum ultraviolet
radiation, electron beam (EB), X-ray and others as well as excimer
laser such as KrF laser of the wavelength of 248 nm and ArF laser
of the wavelength of 193 nm. Note that the term "radiation" used
herein means all of the above-mentioned radiations.
[0012] In the formation of submicron-ordered resist patterns using
as a patterning radiation the radiation in the range of far
ultraviolet or vacuum ultraviolet regions, it is necessary to use
specific resist materials having an excellent transparency to the
patterning radiation and also a high resistance to dry etching. The
inventors of this application have zealously studied this and found
that said need is satisfied by the radiation-sensitive material
comprising a polymer or copolymer of acrylic acid ester or
a-substituted acrylic acid ester in which the ester portion
contains an adamantyl skeleton (see, Japanese Unexamined Patent
Publication (Kokai) No. 4-39665). Similarly, the inventors have
found that the chemically amplified radiation-sensitive material
comprising a polymer or copolymer of acrylic acid ester or
.alpha.-substituted acrylic acid ester in which the ester portion
contains a norbornane skeleton (see, Japanese Unexamined Patent
Publication (Kokai) No. 5-257284).
[0013] Surprisingly, the chemically amplified resist materials
suggested by the inventors have an excellent resistance to dry
etching, in addition to a higher transparency to radiation from
wide variety of light sources, especially excimer laser light
having a wavelength in the far ultraviolet and vacuum ultraviolet
regions. However, these resist materials still have drawbacks
concerning difficulty in obtaining stable patterning
characteristics. For example, depending upon the conditions applied
to the materials, for example, when they are coated at a relatively
larger thickness or the exposed resist coating is developed with a
developer having a higher solubility, the resist materials are
liable to cause cracking of the resist patterns or separation or
peeling off of the patterns from the underlying layer. The exact
reason why such defective resist patterns are produced is unknown,
however, the inventors of the present application understand from
their experience that since alicyclic hydrocarbon moiety in the
skeleton of the resist material has a strong hydrophobic nature and
rigidity, the strain applied to the resist coating during
development is increased.
[0014] Further, due to presence of the alicyclic hydrocarbon moiety
therein, the above-mentioned chemically amplified resist materials
suffer from the drawback that conventional alkaline developers
cannot be used in the development process. Namely, it is understood
that due to a strong hydrophobic nature of the alicyclic
hydrocarbon moiety, the resist materials containing said alicyclic
moiety cannot be sufficiently dissolved in the alkaline developers.
Note, however, that the inventors have found that the above problem
concerning use of the alkaline developers can be solved if the
formation of resist patterns is made by using a resist material
which comprises a polymer or copolymer having a repeating unit
containing a protected alkali-soluble group capable of releasing a
protective group upon exposure to an acid, thereby making the
polymer or copolymer alkali-soluble, and a photoacid generator
capable of producing an acid upon exposure to radiation, and
developing the exposed resist coating with a developer containing
an aqueous solution or alcoholic solution of the specified ammonium
compound or morpholine compound (see, Japanese Patent Application
No. 7-23053 filed on Feb. 10, 1995).
[0015] Furthermore, other problems in the above-mentioned
chemically amplified resist materials are that due to its poor
adhesion to the underlying layer or coating to be etched, the
resist coating can separate from the substrate during development,
and that when the patterning exposure of the resist coating is made
through an exposure mask which is designed to prevent permeation of
the patterning radiation corresponding the circuit pattern to be
printed, the resulting resist patterns have an expanded
configuration larger than that of the exposure mask used. It is
therefore desired to provide a resist material capable of exactly
and faithfully reproducing the fine patterns of the exposure mask
used.
SUMMARY OF THE INVENTION
[0016] The present invention is directed to solve all the
above-discussed problems in the prior art's chemically amplified
resist materials, and in order to attain this aim, the inventors
have selected one approach to improve the resist material itself,
not selecting another approach to improve a developer used in the
resist process.
[0017] One object of the present invention is to provide a novel
chemically amplified resist composition which enables use of a
conventional alkaline solution, especially aqueous alkaline
solution, as a developer, and can provide unswelled fine patterns
with a practically useful sensitivity.
[0018] Another object of the present invention is to provide a
novel chemically amplified resist composition which can be used in
lithography using exposure lights in the deep ultraviolet region,
for example, KrF excimer laser light and the like, and can provide
resist patterns having excellent resistance to dry etching.
[0019] Further, another object of the present invention is to
provide a novel chemically amplified resist composition which can
increase the difference in the polarity between exposed areas and
unexposed areas, thereby simultaneously enabling a high
sensitivity, high contrast and accordingly high resolution.
[0020] Furthermore, another object of the present invention is to
provide a novel chemically amplified resist composition which has a
high transparency to various radiations, particularly shorter
wavelength radiations including KrF and ArF excimer laser light,
and can form positive-working fine resist patterns having an
excellent resistance to dry etching along with the diminished
cracking and peeling off of the resist patterns during the
development step, namely, stabilized patterning
characteristics.
[0021] Still another object of the present invention is to provide
a novel chemically amplified resist composition which can exhibit a
good adhesion to the underlying substrate or layer, when applied
thereto, and can faithfully reproduce in the resulting resist
patterns the pattern of the exposure mask used.
[0022] In addition, still another object of the present invention
is to provide a novel chemically amplified resist composition which
has a high transparency to various radiations including excimer
laser light, can form fine resist patterns having an excellent
resistance to dry etching, along with a particularly high
sensitivity.
[0023] Another object of the present invention is to provide a
novel process for forming resist patterns, especially positive
resist patterns, using the resist composition of the present
invention. In this patterning process, it is desired that the
resist coating from said composition can be developed with a
conventional alkaline developer, after it is exposed to the
patterning radiation.
[0024] The other objects of the present invention will be
appreciated from the descriptions as set forth below with regard to
the preferred embodiments thereof.
[0025] According to one aspect of the present invention, the above
object can be attained by an alkali-developable, chemically
amplified resist composition for forming resist patterns which
comprises:
[0026] I. an alkali-insoluble, film-forming compound having a
structural unit a containing a protected alkali-soluble group in
which unit a protective moiety of said protected alkali-soluble
group is cleaved upon action of an acid generated from a photoacid
generator used in combination with said compound, thereby releasing
a protective moiety from the alkali-soluble group and converting
said compound to an alkali-soluble one, said alkali-soluble group
being protected with the protective moiety selected from the group
consisting of:
[0027] a lactone moiety (A) represented by the following formula
(I): 1
[0028] in which R.sub.1 represents a substituted or unsubstituted,
straight chain or branched chain alkyl group of 1 to 4 carbon
atoms, and
[0029] n represents an integer of 1 to 4; and
[0030] an alicyclic hydrocarbon or alicyclic hydrocarbon
group-containing moiety (B) represented by any one of the following
formulae (II) to (VII): 2
[0031] in which R.sub.I is as defined above, and
[0032] Z represents atoms necessary to complete an alicyclic
hydrocarbon group along with a carbon atom to which said R.sub.I is
bonded; 3
[0033] in which R.sub.II may be the same or different, and each
represents a substituted or unsubstituted, straight chain or
branched chain alkyl group of 1 to 12 carbon atoms or an alicyclic
hydrocarbon group with the proviso that at least one of R.sub.II is
an alicyclic hydrocarbon group; 4
[0034] in which R.sub.II is as defined above; 5
[0035] in which R.sub.III may be the same or different, and each
represents a proton, a substituted or unsubstituted, straight chain
or branched chain alkyl group of 1 to 12 carbon atoms or an
alicyclic hydrocarbon group with the proviso that at least one of
R.sub.III is an alicyclic hydrocarbon group and, in the above
formula, at least one of two R.sub.III is a substituted or
unsubstituted, straight chain or branched chain alkyl group of 1 to
12 carbon atoms or an alicyclic hydrocarbon group; 6
[0036] in which R.sub.II is as defined above; and 7
[0037] in which R.sub.I and Z are as defined above; and
[0038] II. a photoacid generator capable of being decomposed upon
exposure to a patterning radiation to thereby produce an acid
capable of causing cleavage of said protective moiety.
[0039] According to another aspect of the present invention, the
above object can be attained by a process for the formation of
resist patterns which comprises the steps of:
[0040] coating the chemically amplified resist composition
according to the present invention on a substrate to be fabricated
in order to form a resist coating thereon;
[0041] selectively exposing said resist coating to a patterning
radiation capable of causing generation of an acid from said
photoacid generator;
[0042] heating the exposed resist coating to a temperature at which
the cleavage of said protective moiety is induced; and
[0043] developing the heated resist coating with an alkaline
developer.
[0044] The present invention is directed to a chemically amplified
resist composition for forming positive resist patterns on a
substrate to be fabricated which composition, after coating and
selective exposure to a patterning radiation, can be developed with
a conventional alkaline solution. In particular, in one aspect
thereof, the present invention is directed to a chemically
amplified resist composition which comprises (I) a film-forming
polymer or copolymer containing in a side chain of the monomer unit
thereof the protected alkaline-soluble group, such as carboxyl
group protected with the above-mentioned lactone moiety, said
polymer or copolymer being insoluble in an alkaline solution such
as an aqueous alkaline solution, however, being able to exhibit a
good solubility upon cleavage of a protective moiety from the
alkali-soluble group, and (II) a photoacid generator (PAG) capable
of generating an acid upon decomposition thereof as a result of
absorption of the patterning radiation, the acid being able to
cause said cleavage of the protective moiety from the
alkali-soluble group. The mechanism of the chemical amplification
in this resist composition will be explained hereinafter referring
to the film-forming polymer containing a carboxyl group protected
with the lactone moiety.
[0045] Upon exposure of the resist coating to a patterning
radiation, PAG in the resist composition constituting said resist
coating can absorb an energy from said patterning radiation and
generate an acid. The acid generated from PAG can catalytically act
against the film-forming polymer during heating, i.e.,
post-exposure baking (PEB), of the exposed resist coating. Thus,
the following reactions are observed in the exposed areas of the
resist coating: 8
[0046] In the resist composition including the above-referenced
composition of the present invention, since a functional group
capable of being easily cleaved upon heating of the composition in
the presence of an acidic catalyst was introduced into an ester
portion of the monomer unit of the film-forming polymer as a
principal component of the composition, a protonic acid can be
regenerated through said cleavage of the functional group, thus
enabling increase of the sensitivity. Further, since a carboxylic
acid is produced after cleavage of the functional group, the
exposed areas of the resist coating can exhibit a good solubility
in the alkaline solution. Namely, the initially alkali-insoluble
resist coating can be developed with an alkali solution after
exposure followed by heating. After development, the thus obtained
resist patterns are positive-working, because the exposed areas of
the resist coating are dissolved and removed with the alkaline
solution. Note also that swelling of the resist patterns can be
avoided in the patterning process of the present invention, because
the formation of the patterns relies upon variation of the polarity
caused in said polymer.
[0047] Further, when the film-forming polymer used as a principal
component in the resist composition of the present invention is in
the form of a copolymer comprising at least first and second
monomer units, it is possible to design that a functional group
capable of being easily cleaved upon heating of the resist coating
in the presence of an acid catalyst is introduced into an ester
portion of the first monomer unit and at the same time, a similar
functional group is introduced into the second monomer unit. In
such a case, since double functional groups can be simultaneously
cleaved from the copolymer as a function of the acid catalytic
reaction, it is expected to simultaneously attain both higher
sensitivity and higher resolution in comparison with the copolymer
containing the functional group on only one monomer unit.
[0048] In the chemically amplified resist composition of the
present invention, in addition to the lactone moiety referred to in
the above explanation concerning the chemical amplification, the
alicyclic hydrocarbon or alicyclic hydrocarbon group-containing
moiety (briefly referred hereinafter to as "alicyclic hydrocarbon
moiety") can effectively act as the protective group or moiety for
the alkali-soluble group such as carboxyl group, if it is contained
in the film-forming compound including a polymer or copolymer. It
is considered that due to the strong hydrophobic nature thereof,
the alicyclic hydrocarbon moiety can inhibit dissolution of the
exposed areas of the resist coating in an alkaline solution in the
developing process. Thus, it is contemplated in the resist
composition to introduce an alicyclic hydrocarbon moiety as a
cleavable protective group into the film-forming compound to form a
protected alkali-soluble group capable of being released from the
resist structure upon action of an acid, and to expose and bake the
resist coating to thereby release the alicyclic hydrocarbon moiety
followed by removing the same from the exposed areas of the
coating.
[0049] However, since it has a ring structure, the alicyclic
hydrocarbon moiety can be linked only at the restricted angle to
the film-forming compound, and accordingly it is difficult to
produce a double bond-containing compound after cleavage of said
moiety, and it is also difficult to induce the cleavage reaction
itself. The above problems are serious, and to solve these
problems, as briefly described hereinabove, the inventors have
found it to be effective, if the described moiety of the above
formula (II) containing an alicyclic hydrocarbon group and a
suitable lower alkyl substituent substituted at the position of the
carbon atom constituting a ring skeleton of said alicyclic
hydrocarbon group is introduced as at least a portion of the
cleavable protective group to the resist compound to thereby make
the cleavable protective group have an ester structure. Namely, it
has been found that, making the cleavable protective group an ester
structure facilitates cleavage of the protective group. Although
the inventors do not wish to restrict the chemical amplification of
the present invention to those groups of the below mentioned, it is
thought that the protective group can be easily cleaved from the
resist compound, because the formation of a double bond upon
cleavage of the protective group is restricted to a specific site,
i.e., an outer portion of the alicyclic ring showing a diminished
"strain of linkage".
[0050] Thus, the resist material containing the moiety of the above
formula (II) can induce the intended cleavage reaction in which a
protonic acid generated upon exposure acts as a catalyst, thereby
removing the alicyclic group from said moiety, along with
production of a carboxylic acid and similar product. Accordingly,
in the exposed areas of the resist material, a
dissolution-inhibiting effect of the alicyclic group disappears,
and the exposed areas become easily soluble in an alkali solution.
As a result, it becomes possible to smoothly conduct the
development process of the resist material, and attaining the
intended stable patterning characteristics.
[0051] Further, it is thought that in the chemically amplified
resist material in which an alicyclic hydrocarbon group is directly
bonded to a carbon atom constituting the ring structure to form an
ester structure, it is difficult to fully diminish the rigidity due
to presence of the alicyclic hydrocarbon group. It is also thought
that such undesirable rigidity is one cause of cracking or peeling
in the resist patterns, for example, when a thickness of the resist
coating is increased, i.e., when strain is liable to be produced
during development. To solve these problems, the inventors found
that if the cleavable protective groups represented by the above
formulae (III) to (VII) are introduced into the resist structure,
they will produce satisfactory results. Namely, in the structure of
these cleavable protective groups, at least one alicyclic
hydrocarbon group is contained, however, it is distinguished from
the above mentioned moiety of the formula (II) in that an ester
structure is produced through at least one or more atoms bonded to
a carbon atom constituting the ring structure. The atom through
which the ester structure is produced is generally a carbon atom,
however, it is not restricted insofar as the intended cleavage
function is attained, and includes, for example, oxygen, nitrogen,
sulfur and the like. Although it does not restrict the present
invention, the inventors understand that according to the present
invention, a rigidity of the resist structure can be moderated as a
result of positioning the alicyclic hydrocarbon group in a site
remote from the main chain of the resist structure, namely,
introduction of the cleavable protective group having an ester
structure with the indirectly bonded ring structure.
[0052] Thus, the resist material containing the moiety of any one
of the above formulae (III) to (VII) can induce the intended
cleavage reaction in which a protonic acid generated upon exposure
acts as a catalyst, thereby removing the alicyclic group from said
moiety, along with production of a carboxylic acid and similar
product. Accordingly, in the exposed areas of the resist material,
the dissolution-inhibiting effect of the alicyclic group
disappears, and the exposed areas become easily soluble in an
alkali solution. As a result, it becomes possible to smoothly
conduct the development process of the resist material, and
attaining the intended stable patterning characteristics. The above
processes and functions are substantially the same as those of the
moiety of the above formula (II), however, for this particular
resist material, in addition to the described processes and
functions, it is expected that the rigidity of the resulting resist
coating is moderated and therefore an adverse effect of the strain
on the resist coating during development is diminished. Because of
these excellent functions, it becomes possible to prevent cracking
or peeling-off of the resist patterns during development, and
accordingly, to obtain stable patterning characteristics.
[0053] In addition, according to one aspect thereof, the present
invention provides an alkali-developable, chemically amplified
resist composition for forming resist patterns which comprises:
[0054] I. an alkali-insoluble compound having a structural unit a
containing a protected alkali-soluble group in which unit a
protective moiety of said protected alkali-soluble group is cleaved
upon action of an acid generated from a photoacid generator used in
combination with said compound, thereby releasing said protective
moiety from the alkali-soluble group and converting said compound
to an alkali-soluble one, said alkali-soluble group being protected
with an alicyclic hydrocarbon group-containing moiety represented
by the following formulae (II'): 9
[0055] in which
[0056] R.sub.1' is a methyl, ethyl, propyl or isopropyl group which
may be substituted or unsubstituted, and
[0057] Z represents atoms necessary to complete an alicyclic
hydrocarbon group along with a carbon atom to which said
--CH.sub.2--R.sub.1' is bonded; and
[0058] II. a photoacid generator capable of being decomposed upon
exposure to a patterning radiation to thereby produce an acid
capable of causing cleavage of said protective moiety.
[0059] According to another aspect thereof, the present invention
provides a process for the formation of resist patterns which
comprises the steps of:
[0060] coating the above-described chemically amplified resist
composition containing the moiety represented by the above formula
(II') according to the present invention on a substrate to be
fabricated in order to form a resist coating thereon;
[0061] selectively exposing said resist coating to a patterning
radiation capable of causing generation of an acid from said
photoacid generator;
[0062] heating the exposed resist coating to a temperature at which
the cleavage of said protective moiety is induced; and
[0063] developing a latent image in the exposed and heated resist
coating with an alkaline developer.
[0064] According to the present invention, as a result of use of
the chemically amplified resist composition containing the moiety
represented by the above formula (II'), it becomes possible to
obtain a high sensitivity (below 5 mJ/cm.sup.2) required for the
ArF lithography, and also stable patterning properties. In addition
to these advantages, according to the present invention, if the
resist composition is used in combination with a specific
developing solution such as an aqueous or alcoholic solution of
specific ammonium compound or morpholine compound, it becomes
possible to control a compatibility of the developing solution with
the resist composition and solubility of the composition in the
developing solution to thereby moderate a generated stress in the
resist composition during development, thereby diminishing cracking
and peeling off of the resist patterns. Further, since the exposure
margin can be expanded, it becomes possible to stably form fine
resist patterns.
BRIEF DESCRIPTION OF THE DRAWING
[0065] FIG. 1 is an IR absorption spectrum illustrating an exposure
dose dependency of chemically amplified resist composition
according to the present invention; and
[0066] FIG. 2 is a graph illustrating a degree of shrinkage for
various 2-alkyl-AdMA homopolymers with different ArF exposure
doses.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0067] The inventors have found that the above-discussed problems
of the prior art resist materials can be solved, if a protected
alkali-soluble group is introduced into a side chain (not skeleton)
of the film-forming compound including the polymer or copolymer
used as a principal component of the chemically amplified resist
composition, and the described lactone moiety or alicyclic
hydrocarbon or alicyclic hydrocarbon group-containing moiety is
used for a protective group or moiety of said protected
alkali-soluble group.
[0068] In one aspect thereof, the present invention resides in an
alkali-developable, chemically amplified resist composition for
forming resist patterns which comprises:
[0069] I. an alkali-insoluble, film-forming compound having a
structural unit containing a protected alkali-soluble group in
which unit a protective moiety of said protected alkali-soluble
group is cleaved upon action of an acid generated from a photoacid
generator used in combination with said compound, thereby releasing
a protective moiety from the alkali-soluble group and converting
said compound to an alkali-soluble one; and
[0070] II. a photoacid generator capable of being decomposed upon
exposure to a patterning radiation to thereby produce an acid
capable of causing cleavage of said protective moiety.
[0071] In the film-forming compound used as a principal component
of the resist composition according to the present invention, the
protected alkali-soluble group is contained in the structural unit
thereof, particularly a side chain thereof. Examples of suitable
alkali-soluble groups for forming the protected alkali-soluble
group, although they are not restricted to those below-mentioned,
include a carboxylic acid group, sulfonic acid group, amide group,
imide group, phenol group, thiol group, azalactone group and
hydroxyoxime group.
[0072] The above-described alkali-soluble group has to be initially
protected for the purpose of inhibiting dissolution of said
film-forming compound in an alkali, and the protective moiety for
said alkali-soluble group is preferably selected from the moieties
consisting of (1) a lactone moiety (A) represented by the following
formula (I), and (2) an alicyclic hydrocarbon or alicyclic
hydrocarbon group-containing moiety (B) represented by any one of
the following formulae (II) to (VII). 10
[0073] in which R.sub.I represents a substituted or unsubstituted,
straight chain or branched chain alkyl group of 1 to 4 carbon atoms
such as methyl group, ethyl group and propyl group, and
[0074] n represents an integer of 1 to 4.
[0075] The substituent R.sub.I on the carbon atom of the
above-indicated lactone ring or the below-indicated alicyclic ring
contains 1 to 4 carbon atoms. Higher carbon atoms should be
avoided, because they do not ensure satisfactory cleavage of the
protective group from the alkali-soluble group, although the
hydrophobic nature of the compound is increased with an increase of
the number of carbon atoms in the alkyl group. The alkyl group may
be unsubstituted or substituted with any substituent. Suitable
substituents include, for example, halogens such as chlorine,
fluorine and bromine. Use of substituents having a high polarity
should be avoided, because they can adversely affect a stability of
the alkali-soluble group. 11
[0076] in which R.sub.I is as defined above, and
[0077] Z represents atoms necessary to complete an alicyclic
hydrocarbon group along with a carbon atom to which said R.sub.I is
bonded. 12
[0078] in which R.sub.II may be the same or different, and each
represents a substituted or unsubstituted, straight chain or
branched chain alkyl group of 1 to 12 carbon atoms or an alicyclic
hydrocarbon group with the proviso that at least one of R.sub.II is
an alicyclic hydrocarbon group. 13
[0079] in which R.sub.II is as defined above. 14
[0080] in which R.sub.III may be the same or different, and each
represents a proton, a substituted or unsubstituted, straight chain
or branched chain alkyl group of 1 to 12 carbon atoms or an
alicyclic hydrocarbon group with the proviso that at least one of
R.sub.III is an alicyclic hydrocarbon group and, in the above
formula, at least one of two R.sub.III is a substituted or
unsubstituted, straight chain or branched chain alkyl group of 1 to
12 carbon atoms or an alicyclic hydrocarbon group. 15
[0081] in which R.sub.II is as defined above. 16
[0082] in which R.sub.I and Z are as defined above.
[0083] The alkali-insoluble, film-forming compound which is
sensitive to an acid generated from the photoacid generator used in
combination with said film-forming compound includes a wide variety
of compounds ranging from low molecular weight compounds to high
molecular weight compounds, and they may be used alone or as a
mixture of two or more compounds. Generally, the film-forming
compound can be classified into two groups, i.e., (1) a polymer or
copolymer comprising said structural unit as a repeating unit
thereof, and (2) a nonpolymeric compound which is used in
combination with one or more alkali-soluble polymer or
copolymer.
[0084] Said film-forming compound may be in the form of a polymer
or copolymer. The polymer may be a homopolymer consisting
essentially of a single monomer unit or a copolymer comprising two
or more monomer units such as dimer, terpolymer and the like.
Suitable monomer units for the polymer or copolymer, although they
are not restricted to those below-mentioned, include (meth)acrylic
acid esters and derivatives thereof, itaconic acid esters and
derivatives thereof, fumaric acid esters and derivatives thereof,
vinyl phenols and derivatives thereof, N-substituted maleimides and
derivatives thereof, styrene substituents and derivatives thereof
as well as monomeric units containing two or more or polycyclic
cycloaliphatic hydrocarbon moieties. In the monomeric units
containing two or more or polycyclic cycloaliphatic hydrocarbon
moieties, the cycloaliphatic hydrocarbon moieties are preferably
adamantyl group, norbornyl group and similar groups. It should be
noted that when the film-forming compound is in the form of the
polymer, said polymer may contain two or more protected
alkali-soluble groups in the same monomer unit, if desired, and
that when the film-forming compound is in the form of the
copolymer, said copolymer may contain two or more protected
alkali-soluble groups, in combination, in the same or different
monomer units, if desired.
[0085] When said film-forming compound is in the form of copolymer,
the copolymeric compound is preferably a copolymer containing said
repeating unit containing the protected alkali-soluble group as the
first repeating unit, and the repeating units of said copolymer
other than said first repeating unit include a repeating unit
containing an unprotected alkali-soluble group in a side chain
thereof and/or a repeating unit containing in a side chain thereof
an additional protected alkali-soluble group capable of being
cleaved upon action of the acid generated from said photoacid
generator. The unprotected alkali-soluble group advantageously used
herein, although it is not restricted to those below-mentioned,
includes, a carboxylic acid group, sulfonic acid group, amide
group, imide group, phenol group, acid anhydride group, thiol
group, lactonic acid ester group
(.alpha.-.alpha.,.beta.-dimethyl-.gamma.- -butylolactone group),
azalactone group, carbonate group, oxazone group, pyrolidone group,
hydroxyoxime group, nitrile group, nitro group, aldehyde group,
acetyl group, hydroxyl group and thioether group.
[0086] As above mentioned, the film-forming compound used as a
principal component of the resist composition may be in the form of
any nonpolymeric compound, if desired, and in such a case, the
nonpolymeric compound is preferably used in combination with one or
more alkali-soluble polymers or copolymers in order to obtain the
desired resist properties. The alkali-soluble polymer or copolymer
suitable in this embodiment includes those described herein and
others.
[0087] Further, in the resist composition of the present invention,
the film-forming compound may additionally contain one or more
similar acid-sensitive compounds, if desired. The film-forming
compounds useful as an additional component, although they not
restricted to the below mentioned, include those containing one or
more alkali-soluble groups, typical examples of which groups were
described above with reference to the unprotected alkali-soluble
group in the film-forming copolymer.
[0088] In the practice of the present invention, the lactone moiety
(A) of the formula (I) can be advantageously introduced as a
protective moiety into the alkali-soluble group of the film-forming
compound. The lactone moiety may be any desired structure, however,
preferably, it includes (.+-.)-mevalonic lactone represented by the
following formula: 17
[0089] in which R.sub.I is as defined above. Other suitable lactone
moieties (A) will be described hereinafter.
[0090] Similarly, the alicyclic hydrocarbon or alicyclic
hydrocarbon group-containing moieties (B) of the formulae (II) to
(VII) advantageously introduced as the protective moiety in the
practice of the present invention may be any desired structure
which is well-known in the field of chemically amplified resist
compositions, and the alicyclic hydrocarbon group of said alicyclic
moieties (B) is preferably one member selected from the group
consisting of:
[0091] (1) adamantane and derivatives thereof;
[0092] (2) norbornane and derivatives thereof;
[0093] (3) perhydroanthracene and derivatives thereof;
[0094] (4) perhydronaphthalene and derivatives thereof;
[0095] (5) tricyclo[5. 2. 1. 0.sup.2,6]decane and derivatives
thereof;
[0096] (6) bicyclohexane and derivatives thereof;
[0097] (7) spiro[4. 4]nonane and derivatives thereof;
[0098] (8) spiro[4. 5]decane and derivatives thereof; and
[0099] (9) bicyclo[2. 2. 2]octane and derivatives thereof.
[0100] These compounds have the following structures: 18
[0101] In the practice of the present invention, the
above-described and other alicyclic hydrocarbon moieties (B) which
contain two or more ring structures or condensed rings can be
advantageously used, because if the alicyclic moiety (B) contains
only a single ring, i.e., it is a cyclohexyl group, for example, a
satisfactory resistance to dry etching cannot be obtained. Further,
among the above-indicated examples of suitable alicyclic
hydrocarbon groups for said alicyclic moieties (B), if it is
intended to obtain an excellent resistance to dry etching
equivalent to or higher than that of the conventional novolak
resists, it is more preferred to use the alicyclic hydrocarbon
moieties (B) containing condensed ring(s).
[0102] More particularly, suitable alicyclic moieties (B) include,
for example, 2-alkyl-2-adamantyl represented by the following
formula: 19
[0103] in which R.sub.I is as defined above, and the moieties of
the following formulae: 20
[0104] in which R.sub.I and R.sub.II are as defined above. Still
other suitable moieties (B) will be described hereinafter.
[0105] The alkali-soluble group to be temporarily protected by said
protective moiety is preferably a member selected from the group
consisting of a carboxylic acid group, sulfonic acid group, amide
group, imide group, phenol group, thiol group, azalactone group and
hydroxyoxime group.
[0106] For example, the carboxylic acid group as the alkali-soluble
group is a unit capable of producing a carboxylic acid upon
cleavage of the protective moiety therefrom as a result of the
action of the acid, and includes, for example, tertiary carbon
esters such as t-butylester, t-amylester and
.alpha.,.alpha.-dimethylbenzylester, acetal esters such as
tetrapyranylester, .beta.-oxyketone esters such as
3-oxycyclohexylester, and others. Suitable protective moieties for
these carboxylic acid groups and other alkali-soluble groups
include, for example, tertiary hydrocarbon groups such as t-butyl
group or .beta.-oxyketone groups such as 3-oxocyclohexyl group,
cyclic .beta.-hydroxyketone groups such as mevalonic lactone group,
and others.
[0107] More particularly, assuming that the alkali-soluble group is
a carboxylic acid group, the protected carboxylic acid group is
preferably represented by any one of the following formulae (VIII)
to (XIII): 21
[0108] in which R.sub.I, R.sub.II and R.sub.III, Z as well as n
each is as defined above.
[0109] Assuming that the alkali-soluble group is a sulfonic acid
group, the protected sulfonic acid group is preferably represented
by the following formula (XIV) or (XV): 22
[0110] in which R.sub.I, Z and n each is as defined above.
[0111] Assuming that the alkali-soluble group is an imide group,
the protected imide group is preferably represented by the
following formula (XVI) or (XVII): 23
[0112] in which R.sub.I, Z and n each is as defined above.
[0113] Assuming that the alkali-soluble group is a phenol group,
the protected phenol group is preferably represented by the
following formulae (XVIII) or (XIX): 24
[0114] in which R.sub.I, Z and n each is as defined above.
[0115] In the above-indicated protected alkali-soluble groups
except for those containing the lactone ring, the alicyclic
hydrocarbon group completed by Z atoms may include any hydrocarbon
groups, preferably those containing a ring structure with one or
more rings or a condensed ring. The alicyclic hydrocarbon group may
be unsubstituted or substituted with any conventional substituent.
Some typical examples of suitable alicyclic hydrocarbon groups were
indicated above with reference to the structure thereof. Most
preferably, the alicyclic hydrocarbon group used as the protective
group is adamantane and derivatives thereof.
[0116] The alkali-insoluble, film-forming compounds, particularly
film-forming polymers or copolymers, effectively used as a
principal component or basic resin in the chemically amplified
resist composition according to the present invention were
described particularly with reference to the alkali-soluble groups
and the protective moieties for said groups, both included in the
structure of said compounds. The film-forming compounds useful in
the resist composition of the present invention will be further
described particularly with reference to the film-forming polymers
or copolymers which can be advantageously used in the present
invention. Note that the following descriptions will be made first
with reference to the lactone moiety (A)-containing polymers or
copolymers, and then with reference to the alicyclic moiety
(B)-containing polymers or copolymers, however, the descriptions
may be generally applied to both types of the polymers or
copolymers, unless otherwise specified.
[0117] The film-forming polymers or copolymers containing the
lactone moiety (A) as a protective moiety for the alkali-soluble
group are not restricted when they are used in the resist
composition of the present invention, insofar as they can satisfy
the above-mentioned requirements for the basic resin, particularly
the requirements for ensuring the above-described mechanism of
chemical amplification. If it is desired to obtain an excellent
resistance to dry etching equivalent to at least that of a
conventional novolak resin, suitable polymers or copolymers
include, for example, those containing (meth)acrylate monomer unit,
vinyl phenol monomer unit, N-substituted maleimide monomer unit,
styrene monomer unit and others solely or in combination.
Especially, use of the (meth)acrylate polymers or copolymers is
recommended, because such polymers or copolymers can exhibit a
diminished absorption of the radiation having wavelengths in the
deep ultraviolet region, when deep ultraviolet radiation is used as
an exposure source. In other words, using deep ultraviolet
radiation as an exposure source, it is generally desired to use
specific polymers or copolymers having no aromatic rings capable of
absorbing the radiation in the range of the deep ultraviolet region
to a great extent or having no conjugated double bonds and other
chromophores showing a large molar absorption coefficient.
[0118] Further, if any radiation in the range of ultrashort
wavelengths such as an argon fluoride (ArF) excimer laser is used
as the exposure source, it is recommended to use specific
film-forming polymers or copolymers which are basically similar to
those described above, and, in addition, which do not contain any
aromatic ring showing a high absorption of the laser light, but,
however, contain an ester moiety with two or more or polycyclic
alicyclic hydrocarbon groups showing a high resistance to dry
etching, for example, adamantyl or norbornyl groups. Particularly
suitable polymers or copolymers for this purpose include
(meth)acrylate polymers or copolymers containing the described
alicyclic moiety. Typical examples of suitable alicyclic moieties
have been described above along with the structural formulae
thereof.
[0119] Furthermore, the molecular weight (weight average molecular
weight, Mw) of the (meth)acrylate and other film-forming polymers
or copolymers used in the resist composition of the present
invention may be widely varied, depending upon various factors such
as the desired properties of the resist patterns. Generally, the
polymers or copolymers used herein have a molecular weight in the
range of 2,000 to 1,000,000, more preferably 3,000 to 50,000.
[0120] More particularly, the film-forming polymers advantageously
used in the practice of the present invention include the polymers
(1) to (7) described hereinafter, although the present invention
should not be restricted to these polymers. Note in the described
formulae of the film-forming polymers that m is the number of
monomer units or repeating units necessary to obtain the intended
weight average molecular weight, LAC represents the above-described
lactone moiety of the formula (I), and X represents any substituent
such as a hydrogen atom, a halogen atom such as chlorine and
bromine, a lower alkyl group such as methyl and ethyl, a cyano
group and others.
[0121] (1) (meth)acrylate polymer 25
[0122] (2) vinyl phenol polymer 26
[0123] (3) fumarate polymer 27
[0124] in which R' represents either LAC or an alkoxy group such as
methoxy, isopropoxy or t-butoxy, an aryloxy group such as phenoxy
or benzyloxy, and others.
[0125] (4) vinylbenzoate polymer 28
[0126] (5) norbornene carboxylate polymer 29
[0127] (6) itaconate polymer 30
[0128] in which R' is as defined above.
[0129] (7) maleate polymer 31
[0130] in which R' is as defined above.
[0131] Further, as will be appreciated from the above descriptions
concerning the film-forming compounds in the form of polymer or
copolymers that the monomer unit (first monomer unit) constituting
said polymers (1) to (7) may be used in combination with one or
more suitable monomer units which may be the same or different from
said first monomer unit, to form any desired copolymers such as two
component copolymer, terpolymer and the like.
[0132] The film-forming copolymers advantageously used in the
practice of the present invention, if they are shown with reference
to those based on the above-described (meth)acrylate polymers,
include the copolymers represented by the following formulae (XX)
and (XXI): 32
[0133] in which
[0134] R.sup.1 represents a hydrogen atom or any substituent such
as halogen atom, alkyl group or methylol group,
[0135] Y represents any substituent, for example, alkyl group such
as t-butyl, alicyclic group such as adamantyl, norbornyl,
cyclohexyl and tricyclo [5. 2. 1. 0] decane,
[0136] B represents any substituent such as carboxyl group,
[0137] l and m each represents a molar ratio of each monomer unit,
and the sum of l and m is 1, and
[0138] X and LAC each is as defined above.
[0139] Furthermore, it should be noted that among the
above-mentioned (meth)acrylate polymers, the specific
(meth)acrylate polymers found by the inventors, i.e.,
(meth)acrylate polymers containing (.+-.)-mevalonic lactone
(meth)acrylic acid ester as a constitutional component thereof, are
novel.
[0140] These and other (meth)acrylate polymers as well as other
polymers and copolymers of the present invention can be prepared in
accordance with the conventional polymerization methods well-known
in polymer chemistry. For example, the (meth)acrylate polymers and
copolymers, as will be described in detail in the below-mentioned
examples, can be advantageously prepared by conducting a
free-radical polymerization of one or more starting monomers in the
presence of 2,2'-azobisisobutylonitr- ile (AIBN) as a free-radical
initiator. Similarly, the film-forming polymers and copolymers
other than the (meth)acrylate polymers and copolymers can be
prepared in accordance with well-known polymerization methods.
[0141] When the film-forming polymers are especially in the form of
copolymers, a ratio or content of the monomer unit containing the
above-mentioned lactone moiety (A) of the formula (I) in the total
amount of the copolymer is preferably in the range of 20 to 70% by
weight. A content of less than 20% by weight should be avoided,
because it does not ensure satisfactory patterning of the resist
coating. On the other hand, a content higher than 70% by weight
will modify the copolymer so that it can be dissolved in an
alkaline solution. More preferably, the content of the lactone
moiety (A)-containing monomer unit is in the range of 30 to 60% by
weight.
[0142] Moreover, the inventors have found that when the
film-forming copolymer is used in the resist composition of the
present invention, it is also preferred to constitute the copolymer
so that one monomer unit of the copolymer is the unit containing
the protected alkali-soluble group, and another monomer unit to be
copolymerized with said monomer unit contains additional protected
alkali-soluble group in the structure thereof, as previously
mentioned. Namely, the film-forming copolymer may contain a second
monomer unit containing second protected alkali-soluble group, in
addition to a first monomer unit containing a first protected
alkali-soluble group such as the carboxyl group protected with the
lactone moiety (A), and such combination of the first and second
monomer units is advantageously applied in the formation of the
film-forming copolymer used in the present invention. Note that, as
previously mentioned, the above-mentioned second monomer unit may
include any desired structure, however, the second monomer unit is
preferably the monomer unit, a side chain of which unit contains an
additional carboxyl group which further contains a protective
moiety capable of being cleaved upon action of an acid generated
from a photoacid generator also contained in the resist
composition, the protective moiety being preferably the alicyclic
moiety (B) such as the moiety of the above formula (II). In the
second monomer unit, the second protected alkali-soluble group may
include any desired structure, and preferably it can be that of the
above formula (VII).
[0143] More particularly, the film-forming copolymers in which each
monomer unit contains the protected alkali-soluble group and which
can be advantageously used in the practice of the present invention
preferably include the copolymer represented by the following
formula (XXII): 33
[0144] in which
[0145] R, R.sub.I, R.sup.1, X, m and l each is as defined above,
and
[0146] the substituents R.sup.1 and X attached to carbon atoms of
the main chain may be the same or different and preferably
represents a hydrogen atom or a lower alkyl group such as
methyl.
[0147] Accordingly, the film-forming copolymer which can be more
advantageously used in the practice of the present invention is a
copolymer of methacrylic acid (.+-.)-mevalonic lactone and
methacrylic acid 2-methyl-2-adamantyl represented by the following
formula (XXIII): 34
[0148] in which Me represents a methyl group with the proviso that
the substituent Me attached to a carbon atom of the main chain may
be a hydrogen atom, if desired, and
[0149] m and l each is as defined above. In the above-mentioned and
other similar copolymers, a highly improved resistance to dry
etching (RIE resistance) can be accomplished, because they contain
an adamantyl group in an ester portion thereof. Further, if it is
desired to obtain excellent RIE resistance equivalent to that of
the conventional novolak resists, it is necessary to adjust the
content of the second monomer unit, i.e., methacrylic acid
2-methyl-2-adamantyl unit, in the copolymer to about 50% by mole.
Further, since no aromatic ring showing a strong absorption of
ultrashortwave radiation is included in the structure of the
copolymer, the described copolymer can exhibit an excellent
transparency to radiation in the ultrashort region (193 nm) such as
ArF excimer laser light.
[0150] In the above-mentioned film-forming copolymer, generally,
the content of the first monomer unit, i.e., methacrylic acid
(.+-.)-mevalonic lactone ester, is preferably about 20 to 70% by
weight, more preferably about 30 to 60% by weight. And, generally,
the content of the second monomer unit, i.e., methacrylic acid
2-methyl-2-adamantyl, in the described copolymer is preferably
about 20 to 80% by weight, more preferably about 30 to 70% by
weight. As previously explained, if each monomer unit is included
in an amount below or above the described limit, some drawbacks
will result such as difficulty in obtaining satisfactory resist
patterns and developing the exposed resist coating with an alkaline
solution.
[0151] In addition, the mechanism in the chemical amplification in
the above-described film-forming copolymer containing the first and
second monomer units is substantially identical with that of the
film-forming polymer containing, in a side chain of the monomer
unit thereof, the protected alkaline-soluble group, i.e., carboxyl
group protected with the lactone moiety, described above, except
that another chemical amplification reaction based on the second
monomer unit is added to the chemical amplification reaction based
on the first, lactone moiety-containing monomer unit.
[0152] Namely, the (meth)acrylate polymers are well-known to be
highly transparent to radiation in the deep ultraviolet region.
Further, since neither of its two ester portions, included in the
structure thereof, contains a chromophore showing a large molar
absorption coefficient at the wavelength of 190 to 250 nm, if it is
used in combination with a specific compound, i.e. a so-called
"photoacid generator" (PAG) capable of being decomposed upon
absorption of suitable level of patterning radiation, thereby
producing an acid which can then cleave said ester portions, the
copolymer of methacrylic acid (.+-.)-mevalonic lactone and
methacrylic acid 2-methyl-2-adamantyl represented by the above
formula (XXIII) can act as a high sensitivity resist which can be
advantageously subjected to patterning radiation in the range of
deep ultraviolet radiation.
[0153] Upon exposure of the resist coating to the patterning
radiation, the PAG in the resist composition of the resist coating
can absorb an energy from said patterning radiation and generate an
acid. The acid generated from the PAG can catalytically act against
the film-forming copolymer during post-exposure baking (PEB), of
the exposed resist coating. Thus, the following reactions are
observed in the exposed areas of the resist coating: 35
[0154] PC: main chain of the copolymer
[0155] In the above-described film-forming copolymer, since a
functional group capable of being easily cleaved upon heating of
the composition in the presence of an acidic catalyst was
introduced into an ester portion of the monomer units of the
copolymer, a protonic acid can be regenerated through said cleavage
of the functional group, thus enabling increase of the sensitivity.
Further, since a carboxylic acid is produced after cleavage of the
functional group, the exposed areas of the resist coating can
exhibit a good solubility in an alkaline solution. Namely, the
initially alkali-insoluble resist coating can be developed with an
alkali solution after exposure followed by heating. After
development, the thus obtained resist patterns are
positive-working, because the exposed areas of the resist coating
are dissolved and removed with the alkaline solution. Note also
that swelling of the resist patterns can be avoided in the
patterning process of the present invention, because the formation
of the resist patterns relies upon a variation in the polarity in
said copolymer.
[0156] The inventors have further found that the chemically
amplified resist composition according to the present invention can
be also defined with reference to a transmittance measured through
a 1 .mu.m-thick coating of said resist composition on a quartz
substrate at a wavelength of 180 to 300 nm, i.e. in the deep
ultraviolet region, of exposure radiation. The resist composition
of the present invention preferably exhibits a transmittance of at
least 30%, when measured through a 1 .mu.m-thick coating of said
resist composition on a quartz substrate at a wavelength of 180 to
300 nm, i.e., in the deep ultraviolet region, of exposure
radiation.
[0157] The above requirement concerning the transmittance of at
least 30% at the exposure wavelength is important in the resist
design, i.e., the constitution of the resist composition of the
present invention. Accordingly, in the resist composition of the
present invention, which is expected to be patternwise exposed to
the radiation in the deep ultraviolet region, it becomes necessary
to use as the first monomer unit of the copolymer to be included in
the resist composition a monomer unit which contains at least one
carbon-carbon double bond which does not concern itself with any
polymerization reaction, but can be crosslinked, exhibits a low
absorption at the exposure wavelength, and is able to be
copolymerized with an acrylic acid or methacrylic acid ester so
that the transmittance of the copolymer at the exposure wavelength
(the transmittance measured through a 1 .mu.m-thick resist coating
on a quartz substrate; the "transmittance" referred to hereinafter
means a value measured under this condition) amounts to 30% or
more. For example, it is contemplated to use monomers in which no
aromatic ring capable of highly absorbing deep ultraviolet
radiation and/or chromophore of higher molar absorptivity, such as
conjugated double bond, is contained.
[0158] As an alternative to using the above-described lactone
moiety (A)-containing polymers or copolymers, the alicyclic moiety
(B)-containing polymers or copolymers can be advantageously used in
the practice of the present invention. The film-forming polymers or
copolymers containing the alicyclic moiety (B) as a protective
moiety for the alkali-soluble group can be freely selected from a
wide variety of polymers or copolymers satisfying the
above-described requirements, depending on various factors such as
properties of the resist patterns. Suitable film-forming polymers
or copolymers are generally identical to those mentioned above with
regard to the lactone moiety (A)-containing polymers or copolymers,
and some typical examples thereof, although they are not restricted
to those below-mentioned, include those containing as a repeating
unit thereof (meth)acrylic acid and derivatives thereof, itaconic
acid and derivatives thereof, fumaric acid and derivatives thereof,
styrene substituent and derivatives thereof, and others. These
repeating units may be contained solely or in combination. The
inventors have found that the above-listed repeating units, if they
are introduced in the polymer or copolymer, can provide notable
advantages concerning preparation of the polymer or copolymer and
coating of the resist composition, in comparison to other
conventional polymers or copolymers.
[0159] In addition, if desired, the film-forming copolymers for use
in the present invention may have associated with said repeating
unit(s) one or more other repeating units such as acrylonitriles,
olefines, dienes and derivatives thereof, although the present
invention should not be restricted to these repeating units.
[0160] In the film-forming polymers or copolymers used in the
present invention, in order to attain a good adhesion of the resist
composition to the underlying substrate or layer, it is more
preferred that the polymers or copolymers contain a repeating unit
which is by itself soluble in an alkali solution, in addition to
the essential component, i.e., alkali-soluble group. Such
combination of the repeating units in the polymers or copolymers
enables the resulting resist composition to be developed with an
alkaline solution, as a function of a minor amount of carboxylic
acid originated from the protected alkali-soluble group, and
others.
[0161] According to one aspect of the present invention, a resist
composition is provided in which a film-forming compound as a
principal component of the composition is in the form of a
copolymer, and the repeating units of said copolymer contain at
least one repeating unit selected from the repeating unit
containing an alkali-soluble group in a side chain thereof and the
repeating unit containing additional, protected alkali-soluble
group, capable of being cleaved upon action of an acid produced
from the photoacid generator (PAG), in a side chain thereof, in
addition to the above-mentioned repeating unit containing the
alicyclic moiety (B).
[0162] Preferably, the film-forming copolymers useful in the resist
composition of the present invention have the structural unit
represented by the following formula (XXIV), (XXV) or (XXVI):
36
[0163] in which
[0164] R may be the same or different, and each represents a
hydrogen, halogen or a substituted or unsubstituted, straight chain
or branched chain alkyl group of 1 to 4 carbon atoms,
[0165] A represents a protective moiety capable of being released
upon action of said acid, and
[0166] R.sub.I and Z each is as defined above. The substituted or
unsubstituted, straight chain or branched chain alkyl group of 1 to
4 carbon atoms and the protective moiety capable of being released
upon action of the acid have been already defined in the above
paragraphs.
[0167] The structural unit represented by the above formula (XXIV)
is illustrative of introducing in the structure of the copolymer,
in combination, a protective group containing an acyclic moiety
such as adamantane or norbornane and capable of being cleaved upon
exposure to an acid produced from a photoacid generator, and an
alkali-soluble carboxylic acid group. After exposure of the resist
coating to a patterning radiation, an exposed area of the resist
coating can be smoothly dissolved in an alkaline solution as a
developer, since said copolymer contains an acidic group in the
structure thereof. Further, the control of the content of the
acidic group in the copolymer makes the exposed resist coating
developable with a currently standardized alkaline developer such
as an aqueous solution of 2.38% tetramethylammonium hydroxide
(TMAH). In this instance, the content of the carboxylic
acid-containing unit in the copolymer is preferably not less than
5% by mole and less than 2% by mole.
[0168] Further, the structural unit represented by the above
formula (XXV) is illustrative of introducing in the structure of
the copolymer, in combination, a protective group containing an
alicyclic moiety such as adamantane or norbornane and capable of
being cleaved upon exposure to an acid produced from a photoacid
generator and a conventional protective group which is
distinguished from said alicyclic moiety-containing protective and
which can be cleaved upon exposure to the acid originated from the
photoacid generator.
[0169] Furthermore, the structural unit represented by the above
formula (XXVI) is illustrative of introducing in the structure of
the copolymer, in combination, a protective group containing an
alicyclic moiety such as adamantane or norbornane and capable of
being cleaved upon exposure to an acid produced from a photoacid
generator, a conventional protective group which is distinguished
from said alicyclic moiety-containing protective and which is able
to be cleaved upon exposure to the acid originated from the
photoacid generator, and an alkali-soluble carboxylic acid group.
If the resist composition containing the described copolymer is
intended to be used in excimer lithography using ArF excimer laser
light having a wavelength of 193 nm as an exposure source, it is
desired to exclude aromatic rings from the conventional protective
group introduced as the second component. Using the described
structural unit, it becomes possible to attain a smooth development
of the exposed resist coating with an alkaline developer, even if
the intended cleavage of the protective group could not be induced
due to any problem.
[0170] In the above structural units of the formulae (XXIV), (XXV)
and (XXVI), the substituent R.sub.I may include methyl, ethyl, and
halides thereof such as chloride and bromide, as in the
above-mentioned instances. Similarly, the substituent A may include
the above-described conventional protective groups such as
quaternary carbon group or .beta.-oxyketone group such as t-butyl,
t-amyl, 3-oxycyclohexyl and the like. Moreover, the alicyclic
hydrocarbon group completed by the atoms Z may include adamantyl
and derivatives thereof, norbornane and derivatives thereof,
perhydroanthacene and derivatives thereof, perhydronaphthalene and
derivatives thereof, tricyclo[5. 2. 1. 0.sup.2,6]decane and
derivatives thereof, spiro[4. 4]nonane and derivatives thereof as
well as spiro[4. 5]decane and derivatives thereof, mentioned above
with the structures thereof.
[0171] The film-forming polymers or copolymers useful in the
present invention will be further described particularly with
reference to those containing a carboxylic group as the
alkali-soluble group.
[0172] Preferably, the film-forming polymer is (meth)acrylate
polymer represented by the formula (XXVII): 37
[0173] in which
[0174] R represents a proton (hydrogen), halogen or substituted or
unsubstituted alkyl group such as methyl, ethyl or methylol,
[0175] A corresponds to the above-mentioned moieties (II) to (VII),
and represents a protected alicyclic hydrocarbon group, for
example, adamantyl, norbornyl, cyclohexyl, tricyclo[5. 2. 1.
0.sup.2,6]decane and other alicyclic groups protected with
quaternary carbon group or .beta.-oxyketone group such as t-butyl,
t-amyl, 3-oxycyclohexyl and the like, and
[0176] n is any positive integer.
[0177] And, the film-forming copolymer is preferably (meth)acrylate
copolymer represented by the formula (XXVIII) or (XXIX). Although
not shown, the (meth)acrylate terpolymer can be represented by the
similar structure except for the third repeating unit added. 38
[0178] in which
[0179] R, A and n each is as defined above,
[0180] Y represents any substituent such as, preferably, an alkyl
group, for example, t-butyl and the like, an ether group, for
example, phenoxy and the like, an alicyclic hydrocarbon group, for
example, adamantyl, norbornyl, cyclohexyl, tricyclo[5. 2. 1.
0.sup.2,6 ]decane and the like, or the groups represented by the
following formulae: 39
[0181] in which R.sup.1, R.sup.2 and R.sup.3 each represents
hydrogen, substituted or unsubstituted alkyl group such as methyl,
ethyl or methylene, and others,
[0182] B represents any substituent, for example, preferably, a
carboxyl group or the group represented by the following formula:
40
[0183] in which D represents --OR.sup.4, --COOR.sup.4 or
--OCO--R.sup.4 wherein R.sup.1 in the substituent D each represents
hydrogen or substituted or unsubstituted alkyl group such as methyl
or ethyl, and
[0184] l and m each is any positive integer.
[0185] More particularly, the film-forming copolymers
advantageously used in the present invention include the following
copolymers, although the present invention should not be restricted
to these copolymers. Note in the described structures that m and n
each is as defined above. 41
[0186] In addition, if desired, the above-described film-forming
polymers or copolymers may contain alkali-soluble polymers or
copolymers such as novolak resin, phenol resin, imide resin,
carboxylic acid-containing resin and the like.
[0187] Moreover, in the practice of the present invention, any
unpolymerized compound having a relatively low molecular weight
(hereinafter referred to as a "non-polymeric compound") may be used
for the same purpose, in place of the above-described film-forming
polymers or copolymers. The nonpolymeric compounds used herein, as
described above, include any alkali-insoluble and acid-sensitive
compound capable of showing a good solubility in alkali, if the
protected alkali-soluble group contained therein is cleaved with an
acid originated from the photoacid generator used in combination
with said non-polymeric compound. Said non-polymeric compound
should not be restricted, insofar as its protected alkali-soluble
group contains any one of the above-mentioned alicyclic moieties
(B) of the formulae (II) to (VII). Typical examples of suitable
film-forming, non-polymeric compounds include the following
compounds, although the present invention should not be restricted
to these compounds. Note that in the below-mentioned general
formulae, R.sub.I, R.sub.II, Z and n each is as defined above.
42
[0188] These nonpolymeric compounds, if desired, may contain any
other protected moiety in which the protective group can be cleaved
with an acid to thereby produce a carboxylic acid and other
alkali-soluble compound, for example, tertiary carbon esters such
as t-butylester, t-amylester, .alpha.,.alpha.-dimethylester and the
like, acetal esters such as tetrahydropyranyl ester and the like,
.beta.-oxyketone esters such as 3-oxycyclohexyl ester and the
like.
[0189] Since they cannot exhibit the expected resist
characteristics when used alone, the above-mentioned nonpolymeric
compounds have to be used in combination with any alkali-soluble
polymer or copolymer. Typical examples of suitable alkali-soluble
polymer or copolymer include novolak resins, phenol resins, imide
resins, carboxylic acid-containing resins and the like, although
the present invention should not be restricted to these resins. The
mixing ratio of the nonpolymeric compound with the alkali-soluble
polymer or copolymer may be widely varied depending upon various
factors such as the used nonpolymeric compound, the expected resist
characteristics and others.
[0190] The present invention resides in a chemically amplified
resist composition which, as described above, comprises:
[0191] I. an acid-sensitive compound which has a structural unit
containing an alkali-soluble group protected with an alicyclic
hydrocarbon group-containing moiety of the above formula (II') in
which unit said alkali-soluble group can be cleaved upon action of
an acid, thereby making said compound alkali-soluble; and
[0192] II. a photoacid generator (PAG) capable of producing an acid
upon patterning exposure.
[0193] In the above formula (II'), it is essential that R.sub.1' is
a methyl, ethyl, propyl or isopropyl group which may be
substituted, if desired. When R.sub.1' in the formula (II')
represents a hydrogen atom, a satisfactory high sensitivity cannot
obtained, although satisfactory results can be obtained in other
properties. Note that, as will be further clarified in the
below-mentioned explanations, the present invention was
particularly completed as a result of an improvement of the
R.sub.1' substituent in the alicyclic hydrocarbon group-containing
moiety acting as the protective group.
[0194] In the acid-sensitive and film-forming compound used as a
principal component of the resist composition according to the
present invention, the protected alkali-soluble group is contained
in the structural unit thereof, preferably a side chain thereof.
Examples of suitable alkali-soluble groups for forming the
protected alkali-soluble group, although they are not restricted to
those below-mentioned, include a carboxylic acid group, sulfonic
acid group, amide group, imide group and phenol group.
[0195] The above-described alkali-soluble group has to be initially
protected for the purpose of inhibiting dissolution of said
film-forming compound in an alkaline developer, and the protective
moiety for said alkali-soluble group is preferably an alicyclic
hydrocarbon group-containing moiety. The protected alkali-soluble
group is preferably a carboxylic acid group represented by the
following formula (VII'). 43
[0196] in which R.sub.1' and Z each is as defined above.
[0197] The alicyclic hydrocarbon group to be contained in the
alkali-soluble group include a variety of groups which are
well-known in the field of chemistry, and it may be substituted, if
desired. Preferably, the alicyclic hydrocarbon group, as will be
described in detail hereinafter, can contain two or more ring
structures or condensed rings. More preferably, the alicyclic
hydrocarbon group is an adamantane and derivatives thereof.
[0198] Further, the alkali-insoluble, film-forming compound which
is sensitive to an acid generated from the photoacid generator used
in combination with said film-forming compound includes a wide
variety of compounds ranging from low molecular weight compounds to
high molecular weight compounds, insofar as it can satisfy the
described requirements, and they may be used alone or as a mixture
of two or more compounds. Generally, the film-forming compound can
be classified into two groups, i.e., (1) a polymer or copolymer
comprising said structural unit as a repeating unit thereof, and
(2) a nonpolymeric compound which is used in combination with one
or more alkali-soluble polymer or copolymer.
[0199] Said film-forming compound may be in the form of a polymer
or copolymer having a wide variety of molecular weight from a low
range to a high range. The polymer may be a homopolymer consisting
essentially of a single monomer unit or a polymer comprising two or
more monomer units such as copolymer, terpolymer and the like.
Suitable monomer units for the polymer or copolymer, although they
are not restricted to those below-mentioned, include acrylic acid
esters including methacrylic acid esters and derivatives thereof,
itaconic acid esters and derivatives thereof, fumaric acid esters
and derivatives thereof, and styrene substituents and derivatives
thereof. When said film-forming compound is in the form of a
nonpolymeric compound, to obtain the expected resist
characteristics, it is necessary to use any alkali-soluble polymer
or copolymer in combination with said compound.
[0200] In the parent application of this CIP application, as
described above, the inventors have disclosed their following
findings, that is, (1) in the chemically amplified resist
composition, if an alicyclic hydrocarbon group is contained in the
resist structure, dissolution of the exposed film in an aqueous
alkaline solution can be inhibited due to a strong hydrophobic
property of said hydrocarbon group during development of the
exposed film with the alkaline solution; (2) in view of this fact,
it is preferred to introduce a moiety containing an alicyclic group
as a protective group (protected alkali-soluble group capable of
being cleaved from the resist composition upon action of an acid)
into the resist structure to thereby remove the alicyclic group
from the exposed region upon exposure and post exposure baking
(PEB); and (3), to ease said cleaving reaction of the alicyclic
group, it is preferred to introduce a moiety which contains an
alicyclic group wherein a carbon atom constituting the ring
skeleton of the alicyclic group is suitably substituted with a
lower alkyl groups, as a part of the protective group. However, at
the stage of filing this parent application, the invented resist
composition was insufficient to provide a remarkably increased
sensitivity which is required in the ArF lithography.
[0201] The inventors have further continued their studies to fully
solve the problem concerning a high sensitivity of the resist and,
as described above, they now found that a significantly increases
sensitivity can be obtained by using as a moiety of the protective
group in the resist structure the group: --CH.sub.2--R.sub.1'
wherein R.sub.1' is a methyl, ethyl, propyl or isopropyl.
[0202] The chemically amplified resist composition according to the
present invention, as described above, is a chemically amplified
resist composition which contains, in combination, as
acid-sensitive compound in which the protected alkali-soluble group
is cleaved with an acid to thereby make the compound
alkali-soluble, preferably a polymer or copolymer in which
"copolymer" includes a terpolymer or other copolymers of four or
more components, or a non polymeric compound, and a photoacid
generator. The chemically amplified resist composition and its
preparation as well as the formation of resist patterns using this
resist composition will be described hereinafter with reference to
preferred embodiments thereof. Note, however, that the present
invention should not be restricted to the described
embodiments.
[0203] In the chemically to amplified resist composition according
to the present invention, a protected alkali-soluble group to be
contained in the structure of the acid-sensitive compound which is
a principal component of the composition is preferably one member
selected from the group consisting of a carboxylic acid group, a
sulfonic acid group, an amide group, an imido group and a phenol
group, and, more preferably, a carboxylic acid group of the
above-described formula (VII'), an imide group of the following
formula (XVII') or a phenol group of the following formula (XIX'):
44
[0204] wherein R.sub.1' and Z each is as defined above.
[0205] For example, the carboxylic acid group as the alkali-soluble
group is a unit capable of producing a carboxylic acid upon
cleavage of the protective moiety therefrom as a result of the
action of the acid, and includes, for example, tertiary carbon
esters such as t-butylester, t-amylester and
.alpha.,.alpha.-dimethylbenzylester, acetal esters such as
tetrapyranylester, .beta.-oxyketone esters such as
3-oxycyclohexylester, lactone esters such as mevalonic lactone
ester, and others.
[0206] Further, the acid-sensitive compound used in the chemically
amplified resist composition of the present invention may
preferably contain any esters derived from trialkyl carbinols,
acetals, .beta.-oxyketones, .alpha.-oxyalkenes,
.alpha.-oxycycloalkenes and others in the structural unit
thereof.
[0207] Furthermore, the alicyclic hydrocarbon group contained in
the alkali-soluble group includes a variety of groups which are
well-known in the field of chemically amplified resists. Some
typical examples of suitable alicyclic hydrocarbon groups were
indicated above with reference to the structure thereof, and
include those containing the following compounds as the
skeleton:
[0208] (1) adamantane and derivatives thereof;
[0209] (2) norbornane and derivatives thereof;
[0210] (3) perhydroanthracene and derivatives thereof;
[0211] (4) perhydronaphthalene and derivatives thereof;
[0212] (5) tricyclo[5. 2. 1. 0.sup.2,6]decane and derivatives
thereof;
[0213] (6) bicyclohexane and derivatives thereof;
[0214] (7) spiro[4. 4]nonane and derivatives thereof; and
[0215] (8) spiro[4. 5]decane and derivatives thereof.
[0216] In the practice of the present invention, the alicyclic
hydrocarbon groups which contain two or more ring structures or
condensed rings can be advantageously used, because if the
alicyclic group contains only a single ring, i.e., it is a
cyclohexyl group, for example, a satisfactory resistance to dry
etching cannot be obtained. Further, among the above-indicated
examples of suitable alicyclic hydrocarbon groups, if it is
intended to obtain an excellent resistance to dry etching
equivalent to or higher than that of the conventional novolak
resists, it is more preferred to use as the alicyclic hydrocarbon
group those containing condensed ring(s), such as adamantane.
[0217] In the chemically amplified resist composition according to
the present invention, the acid-sensitive, film-forming compound
contained therein is preferably in the form of a polymer or
copolymer. The film-forming polymers or copolymers can be freely
selected from a wide variety of polymers or copolymers satisfying
the above-described requirements, depending on various factors such
as properties of the resist patterns. Suitable film-forming
polymers or copolymers, although they are not restricted to those
below-mentioned, include those containing as a repeating unit
thereof (meth)acrylic acid ester and derivatives thereof, itaconic
acid ester and derivatives thereof, fumaric acid ester and
derivatives thereof, styrene substituent and derivatives thereof,
and others. These repeating units may be contained solely or in
combination. The inventors have found that the above-listed
repeating units, if they are introduced in the polymer or
copolymer, can provide notable advantages concerning preparation of
the polymer or copolymer and coating of the resist composition, in
comparison to other conventional polymers or copolymers.
[0218] In addition, if desired, the film-forming copolymers for use
in the present invention may have associated with said repeating
unit(s) one or more other repeating units such as acrylonitriles,
olefines, dienes and derivatives thereof, although the present
invention should not be restricted to these repeating units.
[0219] In the film-forming polymers or copolymers used in the
present invention, in order to attain a good adhesion of the resist
to the underlying substrate or layer, it is more preferred that the
polymers or copolymers contain a repeating unit having a strong
polarity. Particularly, if they contain a repeating unit which is
by itself soluble in an alkali solution, in addition to the
essential component, i.e., alkali-soluble group, such combination
of the repeating units in the polymers or copolymers enables the
resulting resist composition to be developed with an alkaline
solution, as a function of a small amount of carboxylic acid
originated from the protected alkali-soluble group, and others.
[0220] According to one aspect of the present invention, a resist
composition is provided in which a film-forming compound as a
principal component of the composition is in the form of a
copolymer, and the repeating units of said copolymer contain at
least one repeating unit selected from the repeating unit
containing an alkali-soluble group in a side chain thereof and the
repeating unit containing additional, protected alkali-soluble
group, capable of being cleaved upon action of an acid produced
from the photoacid generator (PAG), in a side chain thereof, in
addition to the above-mentioned repeating unit containing the
alicyclic hydrocarbon group.
[0221] Preferably, the film-forming copolymers useful in the resist
composition of the present invention have the structural unit
represented by the following formula (XXIV') or (XXVI'): 45
[0222] in which
[0223] R may be the same or different, and each represents a
hydrogen, halogen or a substituted or unsubstituted, straight chain
or branched chain alkyl group of 1 to 4 carbon atoms,
[0224] A represents a protective moiety capable of being cleaved
upon action of said acid, and
[0225] R.sub.1' and Z each is as defined above.
[0226] The structural unit represented by the above formula (XXIV')
is illustrative of introducing in the structure of the copolymer,
in combination, a protective group containing an alicyclic skeleton
such as adamantane or norbornane and capable of being cleaved upon
producing an acid from a photoacid generator, and producing an
alkali-soluble carboxylic acid group. After exposure of the resist
film, an exposed area of the resist film can be smoothly dissolved
in an alkaline solution as a developer, since said copolymer
contains a carboxylic group in the structure thereof. Further, the
control of the content of the carboxylic group in the resist
copolymer makes the exposed resist film developable with a
currently standard alkaline developer such as an aqueous solution
of 2.38% tetramethylammonium hydroxide (TMAH). In this instance,
the content of the carboxylic acid-containing unit in the resist
copolymer is preferably not less than 5% by mole or less than 50%
by mole.
[0227] Further, the structural unit represented by the above
formula (XXVI') is illustrative of introducing in the structure of
the copolymer, in combination, a protective group containing an
alicyclic skeleton such as adamantane or norbornane and capable of
being cleaved upon producing an acid from a photoacid generator, a
conventional protective group which is distinguished from said
alicyclic skeleton-containing protective and which is able to be
cleaved upon the acid originated from the photoacid generator, and
an alkali-soluble carboxylic acid group. If the resist composition
containing the described copolymer is intended to be used in
excimer lithography using ArF excimer laser light having a
wavelength of 193 nm as an exposure source, it is preferred to
exclude aromatic ring(s) from the protective group. Using the
described structural unit, it becomes possible to attain a smooth
development of the exposed resist film with an alkaline developer,
even if the intended cleavage of the protective group could not be
induced due to any problem.
[0228] In the above structural units of the formulae (XXIV') and
(XXVI'), the substituent R.sub.1' may be methyl, ethyl, and halides
thereof such as chloride and bromide. The substituent A may be the
conventional protective groups such as quaternary carbon group such
as t-butyl or t-amyl, or .beta.-oxyketone group such as
3-oxycyclohexyl, mevalonic lactone, and the like. Moreover, the
alicyclic hydrocarbon group completed by the atoms Z may be
adamantyl and derivatives thereof, norbornane and derivatives
thereof, perhydroanthacene and derivatives thereof,
perhydronaphthalene and derivatives thereof, tricyclo[5. 2. 1.
0.sup.2,6]decane and derivatives thereof, spiro[4. 4]nonane and
derivatives thereof as well as spiro[4. 5]decane and derivatives
thereof, mentioned above with the structures thereof.
[0229] The film-forming polymers or copolymers useful in the
present invention will be further described particularly with
reference to those containing a carboxylic group as the
alkali-soluble group.
[0230] Preferably, the film-forming polymer is (meth)acrylate
polymer represented by the formula (XXVII'): 46
[0231] in which
[0232] R.sub.1' represents a proton (hydrogen), halogen or
substituted or unsubstituted alkyl group such as methyl, ethyl or
methylol,
[0233] A corresponds to the above-mentioned moiety (II'), and
represents a protective group, preferably a protected group of
alicyclic hydrocarbon group containing an ester bond as a part of
the ring structure and being substituted with a higher alkyl group
than ethyl, more preferably, adamantyl, norbornyl, cyclohexyl,
tricyclo[5. 2. 1. 0.sup.2,6]decane and other alicyclic groups
protected with quaternary carbon group or .beta.-oxyketone group
such as t-butyl, t-amyl, 3-oxycyclohexyl and the like, and
[0234] n is any positive integer.
[0235] And, the film-forming copolymer is preferably (meth)acrylate
copolymer represented by the formula (XXVIII') or (XXIX'). Although
not shown, the (meth)acrylate terpolymer can be represented by the
similar structure except for the third repeating unit added. 47
[0236] in which
[0237] R.sub.1', A and n each is as defined above,
[0238] Y represents any substituent such as, preferably, an alkyl
group, for example, t-butyl and the like, an ether group, for
example, phenoxy and the like, an alicyclic hydrocarbon group, for
example, adamantyl, norbornyl, cyclohexyl, tricyclo[5. 2. 1.
0.sup.2,6]decane and the like, or the groups represented by the
following formulae: 48
[0239] in which R.sup.1, R.sup.2 and R.sup.3 each represents
hydrogen, substituted or unsubstituted alkyl or alkylene group such
as methyl, ethyl or methylene, and others,
[0240] B represents any substituent, for example, preferably, a
carboxyl group or the group represented by the following formula:
49
[0241] in which D represents --OR.sup.4, --COOR.sup.4 or
--OCO--R.sup.4 wherein R.sup.4 in the substituent D each represents
hydrogen or substituted or unsubstituted alkyl group such as methyl
or ethyl, and
[0242] m and n each is any positive integer.
[0243] In addition, if desired, the above-described film-forming
polymers or copolymers may contain alkali-soluble polymers or
copolymers such as novolak resin, phenol resin, imide resin,
carboxylic acid-containing resin and the like.
[0244] Moreover, in the practice of the present invention, any
unpolymerized compound having a relatively low molecular weight
(hereinafter referred to as a "non-polymeric compound") may be used
for the same purpose, in place of the above-described film-forming
polymers or copolymers. The nonpolymeric compounds used herein, as
described above, include any alkali-insoluble and acid-sensitive
compound capable of showing a good solubility in an alkaline
developer, if the protected alkali-soluble group contained therein
is cleaved with an acid originated from the photoacid generator
used in combination with said non-polymeric compound. Said
non-polymeric compound should not be restricted, insofar as said
compound contains an alicyclic ring skeleton, aromatic ring
skeleton such as benzene ring, or alkyl skeleton, and a part of the
skeleton is substituted with a group containing any moiety of the
formula (II'). Typical examples of suitable film-forming,
non-polymeric compounds include the following compounds, although
the present invention should not be restricted to these compounds.
Note that in the below-mentioned general formulae, R.sub.1' and Z
each is as defined above. 50
[0245] In addition to the group containing the moiety represented
by the formula (II'), the nonpolymeric compounds, if desired, may
contain any other protected moiety or unit in which the protective
group can be cleaved with an acid to thereby produce a carboxylic
acid and other alkali-soluble compound, for example, tertiary
carbon esters such as t-butylester, t-amylester,
.alpha.,.alpha.-dimethylester and the like, acetal esters such as
tetrahydropyranyl ester and the like, .beta.-oxyketone esters such
as 3-oxycyclohexyl ester and the like.
[0246] Since they cannot exhibit the expected resist
characteristics when used alone, the above-mentioned nonpolymeric
compounds have to be used in combination with any alkali-soluble
polymer or copolymer. Typical examples of suitable alkali-soluble
polymer or copolymer include novolak resins, phenol resins, imide
resins, carboxylic acid-containing resins and the like, although
the present invention should not be restricted to these resins. The
mixing ratio of the nonpolymeric compound with the alkali-soluble
polymer or copolymer may be widely varied depending upon various
factors such as the used nonpolymeric compound, the expected resist
characteristics and others.
[0247] In the chemically amplified resist composition according to
the present invention, a photoacid generator (PAG) capable of being
decomposed upon exposure to a patterning radiation to thereby
produce an acid capable of causing cleavage of a protective moiety
of the protected alkali-soluble group is used in association with
the above-described film-forming compound such as film-forming
polymer or copolymer as well as a nonpolymeric compound. The
photoacid generator used herein may be any conventional agent which
is well-known as a photoacid generator (PAG) in resist chemistry,
namely, compounds capable of generating a protonic acid upon
exposure of the coating of the resist composition to a patterning
radiation such as ultraviolet radiation, far ultraviolet radiation,
vacuum ultraviolet radiation, electron beam, X-ray and laser light.
Typical examples of the photoacid generator suitably used in the
practice of the present invention include various compounds
described hereinafter, although the present invention should not be
restricted to these compounds.
[0248] (1) diazonium salts represented by the following
formula:
A r--N.sub.2.sup.+X.sup.-
[0249] in which
[0250] Ar represents a substituted or unsubstituted aromatic group,
for example, phenyl group or phenyl group substituted with halogen
such as chlorine, bromine, iodine or fluorine, alkyl such as methyl
or t-butyl, aryl or other substituent groups, or a substituted or
unsubstituted alicyclic hydrocarbon group, and
[0251] X represents halogen, BF.sub.4, BF.sub.6, PF.sub.6,
AsF.sub.6, SbF.sub.6, CF.sub.3SO.sub.3, ClO.sub.4 or anion of
organic sulfonic acids.
[0252] (2) iodonium salts represented by the following formulae:
51
[0253] in which Ar and X are as defined above.
[0254] (3) sulfonium salts represented by the following formulae:
52
[0255] in which R, R.sup.1, R.sup.2, R.sup.3, Ar and X each is as
defined above, and, for example, R is methyl and R.sup.1, R.sup.2
and R.sup.3 each is phenyl, and tBu is t-butyl.
[0256] (4) sulfonic esters represented by the following formulae:
53
[0257] in which Ar and R are as defined above.
[0258] (5) oxazole derivatives represented by the following
formula: 54
[0259] in which X is as defined above with the proviso that at
least one of the substituents --CX.sub.3 is a substituted or
unsubstituted aryl or alkenyl.
[0260] (6) halides represented by the following formula: 55
[0261] in which X is as defined above.
[0262] (7) s-triazine derivatives represented by the following
formula: 56
[0263] in which X is as defined above with the proviso that at
least one of the substituents --CX.sub.3 is a substituted or
unsubstituted aryl or alkenyl.
[0264] (8) disulfone derivatives represented by the following
formula:
A r--SO.sub.2--SO.sub.2--Ar
[0265] in which
[0266] Ar is as defined above.
[0267] (9) imide compounds represented by the following formulae:
57
[0268] in which X is as defined above.
[0269] (10) others such as oxime sulfonate, diazonaphtoquinone,
benzoine tosylate and the like.
[0270] More particularly, some of the above-described compounds can
be represented by the following formulae: triphenylsulfonium
hexafluoroantimonate: 58
[0271] triphenylphosphoni.um hexafluorophosphate: 59
[0272] diphenyliodo hexafluorophosphate: 60
[0273] benzoine tosylate: 61
[0274] The content of the PAG compounds in the resist composition
may be widely varied depending upon factors such as the acid
releasing capability of the PAG compound used, the level of the
patterning radiation and the like. The content of the PAG compounds
in the resist composition is preferably in the range of 0.1 to 50%
by weight, based on the total weight of the film-forming compound.
A content of more than 50% by weight should be avoided, because it
does not ensure satisfactory patterning due to excess absorption of
the patterning radiation. More preferably, the content of the PAG
compounds in the resist composition is in the range of 1 to 30% by
weight, especially 1 to 15% by weight, based on the total weight of
the film-forming compound.
[0275] Using the above-described film-forming compound as a
principal component and the above-described photoacid generator
(PAG), the chemically amplified resist composition according to the
present invention can be produced by conventional methods
well-known in resist chemistry. The resist solution is preferably
provided in the form of solution. For example, if the film-forming
compound constituting the resist composition is the above-mentioned
polymer or copolymer, it is contemplated that suitable monomers for
use in the formation of said polymer or copolymer are first
polymerized in the presence to a suitable polymerization initiator,
followed by adding a photoacid generator to a solution of the
resulting polymer or copolymer, thereby providing the resist
solution. The conditions for the polymerization and the initiators
used may be freely selected from wide variety of well-known
conditions and initiators. Typical examples of suitable
polymerization initiators include, for example, the following
compounds.
[0276] AIBN (azoisobutylonitrile): 62
[0277] MAIB (dimethyl-2,2-azoisobisbutylate): 63
[0278] In the preparation of the resist solution, any organic
solvent may be used to dissolve said film-forming compound and
photoacid generator. The organic solvent used may be widely varied
depending on various factors such as the resist composition used,
coating conditions and the like, and typical examples of suitable
organic solvents, although they are not restricted to the
below-mentioned, include ethyl lactate, methyl amyl ketone,
methyl-3-methoxypropionate, ethyl-3-ethoxypropionate,
propyleneglycol methyletheracetate (PGMEA), diacetoalcohol,
cyclohexanone, ethyl pyruvicate and similar solvents. These organic
solvents may be used alone or, if desired, may be used as a mixture
of two or more solvents. The amount of the organic solvent used is
not restricted, however, it is preferred that the solvent be used
in an amount sufficient to provide a resist coating having a
desired layer thickness and a viscosity for coating such as spin
coating.
[0279] In the preparation of the resist solution, if desired, an
auxiliary solvent may be used in addition to the above-described
organic solvent (hereinafter referred to as "main solvent"). The
auxiliary solvent is not required if the resist components can be
easily dissolved in the main solvent, however, if the resist
components can hardly be dissolved in the main solvent, the
auxiliary solvent will assist in dissolving the resist components
in the main solvent. Useful auxiliary solvents, although they are
not restricted to those below-mentioned, include butyl acetate,
.gamma.-butylolactone, propyleneglycol methylether and similar
solvents. Generally, these auxiliary solvents are preferably used
in an amount of about 1 to 30% by weight, more preferably, about 10
to 20% by weight, with regard to the main solvent.
[0280] In another aspect thereof, the present invention resides in
a novel process for forming resist patterns, particularly
positive-working resist patterns, on a substrate to be fabricated,
said process comprising the steps of:
[0281] coating the chemically amplified resist composition
according to the present invention on the substrate;
[0282] selectively exposing a coating of said resist composition,
produced in the above coating step, to a patterning radiation
capable of causing generation of an acid from the photoacid
generator in said resist composition;
[0283] heating or baking the exposed resist coating to a
temperature at which the cleavage of a protective moiety of the
protected alkali-soluble group in the film-forming compound in said
resist composition is induced; and
[0284] developing the heated resist coating with an alkaline
developer.
[0285] Preferably, in the described process for the formation of
resist patterns, in addition to the Post-Exposure Baking (PEB) made
after patternwise exposure of the resist coating, the resist
coating may be subjected to another heating or baking process,
i.e., "prebaking". In other words, it is preferred that the
patterning process of the present invention may further comprise
the step of heating the resist coating before exposure thereof to
the patterning radiation.
[0286] More preferably, the patterning process of the present
invention comprises the steps of:
[0287] spin-coating the resist composition from a solution thereof
in an organic solvent on the substrate to form a resist coating
having a thickness of 0.1 to 200 .mu.m;
[0288] prebaking the resist coating at 60 to 160.degree. C. for 60
to 180 seconds;
[0289] selectively exposing the prebaked resist coating to a
patterning radiation from an excimer laser or deep UV source;
[0290] post-exposure baking the exposed resist coating at 60 to
150.degree. C. for 60 to 120 seconds; and
[0291] developing the baked resist coating with an alkaline
developer, thereby forming positive resist patterns.
[0292] The patterning process according to the present invention,
including the above-mentioned preferred embodiments thereof, can be
carried out in a manner based on conventional lithographic
processes. A series of process steps which can be advantageously
adopted in the practice of the present invention will be described
hereinafter. Note, however, that the present invention should not
be restricted to the described steps, and accordingly any
modifications or variations can be applied to the described process
of the present invention within the spirit and scope of the present
invention.
[0293] First, the resist composition is coated on a substrate to be
fabricated, to thereby form a resist coating having a predetermined
thickness. The substrate used herein may be any conventional
substrate used in the field of semiconductor devices and other
devices, and typical examples of suitable substrates include a
silicon substrate, a glass substrate, a SOS substrate, a
non-magnetic substrate such as ceramic substrate and the like. If
desired, the substrate may additionally contain one or more
overlaying layers such as polysilicon layer, oxide layer, for
example, silicon oxide layer, nitride layer, for example, silicon
nitride layer, metallic layer, for example, aluminum layer,
insulating interlayer, magnetic layer and the like. Further, the
substrate and/or the overlaying layer(s) may contain any elements
such as wiring or circuits fabricated therein. Furthermore, in
order to increase the adhesion strength of the resist coating to
the substrate, a surface of the substrate may be subjected to a
conventional hydrophobic treatment. Typical examples of the
chemicals advantageously used in this treatment are
1,1,1,3,3,3-hexamethyldisilazane (HMDS) and the like.
[0294] Coating of the resist composition can be made from a resist
solution containing the same composition as set forth in the above
paragraphs. The resist solution can be preferably coated over the
substrate surface by spin-coating, although any other conventional
coating method such as roller coating and dip coating may be used,
if desired. The layer thickness of the resist coating is preferably
in the range of about 0.1 to 200 .mu.m, and it is preferably in the
range of about 0.1 to 2.0 .mu.m for KrF lithography and in the
range of about 0.1 to 2.0 .mu.m for ArF lithography. Moreover, if
the resist composition used contains the alicyclic moiety
(B)-containing compound, it is generally preferred that the layer
thickness be in the range of about 0.3 to 2.0 .mu.m. Note, however,
that the layer thickness of the resist coating may be varied
depending upon different factors such as the intended use of the
resulting resist patterns.
[0295] The resist coating formed on the substrate is generally, and
preferably, prebaked at a temperature of about 60 to 200.degree.
C., more preferably about 60 to 150.degree. C., for about 60 to 180
seconds, before selective exposure of the coating to patterning
radiation. Prebaking may be carried out by using any heating means
conventionally used in the resist process. Suitable heating means
include, for example, a hot plate, infrared (IR) heating oven,
microwave heating oven and the like.
[0296] In addition, if a topcoat layer or protective layer is to be
applied over the resist coating, it is contemplated to spin-coat a
solution of olefinic resin over the resist coating, followed by
baking the olefinic coating at a temperature of about 100.degree.
C.
[0297] Next, the optionally prebaked resist coating is selectively
exposed to a patterning radiation in conventional exposure devices
or aligners. Suitable exposure devices include commercially
available devices such as ultraviolet (far UV, deep UV or vacuum
UV) exposure devices, X-ray exposure devices, electron beam
exposure systems and excimer steppers, for example. The conditions
of exposure can be varied to select the optimum condition in each
process, taking various factors into consideration. Particularly,
in the practice of the present invention, as can be appreciated
from the above descriptions, the patterning exposure can be
advantageously made by using an excimer laser such as a KrF laser
(wavelength of 248 nm) and an ArF laser (wavelength of 193 nm) as
the exposure source. Note, in this connection, that the term
"radiation" used herein is intended to mean any radiation from
various available light sources such as UV radiation, far UV
radiation, deep UV radiation, vacuum UV radiation, electron beam
(EB), laser light and the like. As a result of the selective
exposure, the photoacid generator (PAG) in the exposed areas of the
resist coating is decomposed, and thus the exposed resist coating
is now ready for dissolving off from the substrate in the
subsequent development step using an alkaline developer.
[0298] After completion of the selective exposure, the exposed
resist coating is heated on a heating means such as a hot plate. As
mentioned above, the heating is called Post-Exposure Baking (PEB),
and PEB is preferably carried out at a temperature sufficient to
cause cleavage of the protective group from the protected
alkali-soluble group in the film-forming compound in the resist
coating in the presence of a catalytic acid produced from the
photoacid generator. PEB may be carried out in a manner similar to
that of the above-described prebaking, and generally it can be
carried out at a temperature of about 60 to 160.degree. C.,
preferably about 100 to 150.degree. C., for about 30 to 240
seconds. Further, when the resist coating is used in combination
with the topcoat layer, it is suggested to separate and remove the
topcoat layer in any suitable manner such as use of an organic
solvent, after PEB and before the development.
[0299] As a final step of the present process, the heated resist
coating is developed with an alkaline solution such as an aqueous
alkaline solution or alcoholic alkaline solution as a developer in
accordance with any conventional method. Suitable apparatuses for
use in this development step include the well-known developers such
as a spin developer, dip developer and spray developer.
[0300] Typical examples of the alkaline solution suitable as the
developer include an aqueous or alcoholic solution of hydroxides of
metals belonging to the groups I and II of the periodic table such
as potassium hydroxide or an aqueous or alcoholic solution of
organic bases free from metal ions such as tetraalkylammonium
hydroxide, typical examples of which will be described hereinafter
with reference to the chemical formulas thereof. Further, if
desired, the alkaline solution used as the developer may
additionally contain any additives such as a surface active agent
in order to improve the resulting development effect. Furthermore,
if it is appropriate, as the inventors have suggested in the
above-cited Japanese Unexamined Patent Publication (Kokai) No.
7-23053, the developer used herein may be an aqueous or alcoholic
solution containing as the developer an ammonium compound
represented by the following formula: 64
[0301] in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be the
same or different, and each represents a substituted or
unsubstituted alkyl group of 1 to 6 carbon atoms, a morpholine
compound represented by the following formula: 65
[0302] or a mixture thereof. The ammonium compound useful as the
developer, although it is not restricted to the below-mentioned,
includes:
[0303] tetramethylammonium hydroxide (TMAH),
[0304] tetraethylammonium hydroxide (TEAH),
[0305] tetrapropylammonium hydroxide (TPAH),
[0306] tetrabutylammonium hydroxide (TBAH),
[0307] and the like. More preferably, tetramethylammonium hydroxide
(TMAH) can be used as the developer.
[0308] The developer is dissolved in water or an alcohol such as
methanol, ethanol, isopropyl alcohol and the like to obtain a
developing solution. The concentration of the developer in the
developing solution may be widely varied, however, it is generally
in the range of about 0.1 to 15% by weight, preferably in the range
of about 0.1 to 10% by weight. The developing time may also be
widely varied, however, it is generally about 1 to 5 minutes,
preferably for about 1 to 3 minutes. As a result of development,
the exposed areas of the resist coating are dissolved and removed
from a surface of the substrate, thereby forming the desired
positive resist patterns corresponding to the exposure pattern.
Finally, the resulting resist patterns are rinsed with deionized
water, and dried in accordance with the conventional manner.
[0309] As can be understood from the above-mentioned descriptions
and the appended working examples, according to the present
invention, it becomes possible to produce fine positive resist
patterns having a good sensitivity suitable for practical use and
having no swelling. Further, if the film-forming compound as a
principal component of the resist composition is constituted from
the film-forming copolymer in which the specific monomer skeleton
is introduced in one monomer unit and at the same time said monomer
unit is copolymerized with another monomer unit containing two or
more alicyclic or polycyclic hydrocarbon groups, it becomes
possible to effectively form resist patters at a high sensitivity
upon exposure to ultrashortwave radiation such as ArF exicimer
laser light. Furthermore, if the film-forming copolymer used
contains a second monomer unit having a side chain containing a
carboxyl group protected with a second protective group (ester
group), in addition to a first monomer unit having a side chain
containing a carboxyl group protected with a first protective group
(ester group), since both first and second ester groups protecting
the carboxyl groups can be cleaved upon the acid catalytic
reaction, it becomes possible to easily attain higher sensitivity
and resolution in comparison with the conventional resist
compositions. Moreover, such a film-forming copolymer can also
provide a high sensitivity resist composition suitable for exposure
to ultrashortwave radiation such as ArF exicimer laser light, if
the second monomer unit thereof contains, for example, a polycyclic
hydrocarbon group such as adamantyl group, thereby ensuring a
higher resistance to RIE, and the copolymer itself does not contain
any chromophore showing a large absorption coefficient in the deep
ultraviolet region.
[0310] In addition to these advantages, using the described
chemically amplified resist composition according to the present
invention, and an aqueous or alcoholic solution of the specific
ammonium compound or morpholine compound as the developer in
combination with said use of the specific resist composition, it
becomes possible to diminish peeling-off or cracking of the resist
patterns, thereby enabling stable obtention of patterning
characteristics. Note that the combined use of the specific resist
composition and the specific developer is effective to control the
compatibility of the resist composition with the developer and the
solubility of the resist composition in the developer, thus
moderating the stress generated during the development. Further,
since strain generated in the resist coating during development can
be reduced to a moderate level, it becomes possible to stably
obtain the patterning characteristics. Furthermore, using the
resist composition of the present invention, fine resist patterns
can be stably produced because of the extended margin of exposure,
in addition to the improved adhesion of the resist patterns to the
underlying layer or substrate. Moreover, when an exposure mask for
selectively shielding the patterning radiation in conformity with
the circuit pattern to be printed is used in the exposure step, it
becomes possible to produce a positive resist pattern exactly
corresponding to the pattern of the exposure mask, namely,
undesirable expansion of the pattern can be effectively prevented
in the resulting resist pattern. It should be noted that these
advantages particularly rely upon use of the specific film-forming
compounds containing the alkali-soluble group protected with the
described lactone moiety (A) or alicyclic moiety (B) wherein one
carbon atom constituting the ring skeleton thereof is substituted
with a suitable lower alkyl group R.sub.I, the protective moiety
(A) or (B) being directly or indirectly, i.e., through at least one
linkage atom, bonded with said alkali-soluble group.
[0311] In addition, according to the present invention, since the
chemically amplified resist composition contains a compound having
a protective group represented by the above formula (II') in the
structure thereof, the protective group containing an alicyclic
group, a cyclic skeleton of which has an ester bond formed through
one or more other atoms, it becomes possible to reduce or moderate
a rigidity of the composition due to presence of the alicyclic
hydrocarbon group contained, thus enabling stable patterning
properties.
[0312] The protective group used in the present invention can
particularly exhibit its excellent effects when it is used in the
chemically amplified resist compositions consisting of an alicyclic
unit and a protective unit, however, it is also expected that it
can provide satisfactory effects in other types of the resist
compositions. Note, as mentioned above, that the most remarkable
effects can be obtained if the present protective group is used in
the resist resins containing an alicyclic hydrocarbon group
originated from, for example, adamantane and its derivatives,
norbornane and its derivatives, tricyclo [5. 2. 1. O.sup.2,6]
decane and its derivatives, and others.
EXAMPLES
[0313] The present invention will be further described with
reference to the appended working examples. Note, however, that the
examples are included herein for only explanation purpose and they
are not restrictive of the present invention.
Example 1
[0314] To a sufficiently dried 100 mL-volume eggplant-shaped flask
containing a Teflon.TM.-coated stirring bar, was added 30 mL of
anhydrous methylene chloride, 6 g (46.1 mmol) of (.+-.)-mevalonic
lactone and 4.82 g (46.1 mmol) of methacryloyl chloride, and the
content in the flask was stirred at 0.degree. C. in a dry nitrogen
atmosphere. To the resulting solution, 5.1 g (50.4 mmol) of
triethylamine and 10 mg of N,N-dimethylaminopyridine were added,
and the mixture was stirred at 0.degree. C. for one hour. After
dissipation of the starting materials was confirmed by a thin layer
chromatography, the reaction solution was transferred to a 300
mL-volume separating funnel, and washed with 100 mL of water. The
separated aqueous phase was thrice extracted with methylene
chloride. An organic phase was separated, washed with a saturated
solution of sodium chloride, and dried over anhydrous sodium
sulfate. The dried organic phase was filtered through a filter
paper, and a solvent in the filtrate was distilled off at a reduced
pressure. A brown oil was thus obtained. The oil was then purified
on a silica gel chromatography to obtain a colorless and
transparent oily product, namely, (.+-.)-mevalonic lactone
methacrylate, at a yield of 94 g (65%).
[0315] The results of the analysis of the thus obtained product are
as follows:
[0316] .sup.1H NMR (CDCL.sub.3, .delta., J in Hz): 6.05, 5.58 (each
1H), 4.44-4.35 (2H, m), 3.19 (1H, d, J=17.5), 2.62 (1H, m), 2.60
(1H, d, J=17.5), 2.03 (1H, m), and 1.91, 1.66 (each 3H, s). In the
parenthesized characters, s, d and m represent a "singlet",
"doublet" and "multiplet", respectively.
[0317] Further, the results of the IR analysis of the product are
as follows:
[0318] IR (KBr, neat, cm.sup.-1): 2980 (w), 1743 (s), 1714 (s),
1271 (m), 1173 (s), 1161 (s) and 1074 (m). In the parenthesized
characters, s, m and w are abbreviations for "strong", "medium" and
"weak", respectively.
Example 2
[0319] To a sufficiently dried 100 mL-volume eggplant-shaped flask
containing a Teflon.TM.-coated stirring bar, was added 5.94 g (30
mmol) of (.+-.)-mevalonic lactone methacrylate prepared in Example
1, 5.04 g (30 mmol) of cyclohexyl methacrylate, 20 mL of dioxane
and 1.48 g (9 mmol) of 2,2'-azobisisobutylonitrile (AIBN) as a
polymerization initiator, and the content in the flask was stirred
at 80.degree. C. for 8 hours in a nitrogen atmosphere. After
dilution with tetrahydrofuran (THF), the reaction solution was
dropped to one liter of water-ethanol (1:1) solution containing a
small amount of hydroquinone. The thus produced precipitate was
filtered off on a glass filter, and dried at 0.1 mmHg and
45.degree. C. for 16 hours. The obtained white powders were again
dissolved in THF, and the above-mentioned steps of from
precipitation to drying were twice repeated. The target copolymer,
namely, copolymer of (i)-mevalonic lactone methacrylate and
cyclohexyl methacrylate, as a white product was obtained at a yield
of 69 g (70%).
[0320] The .sup.1H NMR analysis of the thus produced copolymer
indicated that the molar ratio of each monomeric component in the
copolymer is 1:1. The transmittance of the copolymer at the
wavelength of 248 nm, measured through a 1-.mu.m thick coating on a
quartz substrate, was 95%, evidencing excellent transparency. The
results of other analysises are as follows:
[0321] Weight average molecular weight (Mw): 11,860 (polystyrene
standard-equivalent).
[0322] Degree of polydispersion (Mw/Mn): 1.45.
[0323] IR (KRS-5, cm.sup.-1): 2937, 1726, 1259, 1149 and 1112.
Example 3
[0324] To a sufficiently dried 100 mL-volume eggplant-shaped flask
containing a Teflon.TM.-coated stirring bar, was added 5.94 g (30
mmol) of (.+-.)-mevalonic lactone methacrylate prepared in Example
1, 4.87 g (30 mmol) of p-acetoxystyrene, 20 mL of dioxane and 1.48
g (9 mmol) of 2,2'-azobisisobutylonitrile (AIBN), and the content
in the flask was stirred at 80.degree. C. for 8 hours in a nitrogen
atmosphere. After dilution with tetrahydrofuran (THF), the reaction
solution was dropped to one liter of water-methanol (1:1) solution
containing a small amount of hydroquinone. The thus produced
precipitate was filtered off on a glass filter, and dried at 0.1
mmHg and 45.degree. C. for 16 hours. The obtained white powders
were again dissolved in THF, and the above-mentioned steps of from
precipitation to drying were twice repeated. The target copolymer,
namely, copolymer of (.+-.)-mevalonic lactone methacrylate and
p-acetoxystyrene, as a white product was obtained at a yield of
7.78 g (72%).
[0325] The .sup.1H NMR analysis of the thus produced copolymer
indicated that the molar ratio of each monomeric component in the
copolymer is 1:1. The transmittance of the copolymer at the
wavelength of 248 nm, determined through a 1-.mu.m thick coating on
a quartz substrate, was 75%, evidencing excellent transparency. The
results of other analysises are as follows:
[0326] Weight average molecular weight (Mw): 7,620 (polystyrene
standard-equivalent).
[0327] Degree of polydispersion (Mw/Mn): 1.41.
[0328] IR (KRS-5, cm.sup.-1): 3193, 1751, 1726, 1218 and 1201.
Example 4
[0329] The copolymer prepared in Example 2 was dissolved in
propyleneglycol methylether acetate to make a 17 wt. % solution
thereof. Note that 8 wt. % of .gamma.-butylolactone as an auxiliary
solvent was also contained in said copolymer solution. Then,
triphenylsulfonium trifluoromethane sulfonate as a photoacid
generator (PAG) in an amount of 5 wt. % with regard to the
copolymer was added and dissolved in the copolymer solution to make
a resist solution. After it was filtered on a Teflon.TM. membrane
filter having a thickness of 0.2 .mu.m, the resist solution was
spin-coated at 2,000 rpm on a silicon substrate which has been
treated with HMDS to form a hydrophobic surface, and prebaked at
110.degree. C. for 60 seconds to form a 0.7-.mu.m thick resist
coating. The resist coating was patternwise exposed on a KrF
excimer laser stepper (commercially available from Nikon, NA=0.45).
The exposed resist coating was developed with an aqueous solution
of 2.38% tetramethylammonium hydroxide (TMAH), and rinsed for 60
seconds in a deionized water. The positive resist patterns were
thus obtained. The resolution of the patterns was 0.3 .mu.m line
and space (L/S) at an exposure level of 40 mJ/cm.sup.2.
[0330] The resist patterns were then evaluated with regard to the
dry etching resistance, namely, resistance to Reactive Ion Etching
(RIE). The plasma etching rates were determined by disposing the
resist-coated silicon substrate in a parallel plate reactive ion
etcher and conducting the argon (Ar) sputtering etching under the
conditions: Rf power (P.mu.) of 200 W, pressure of 0.02 Torr and
flow rate of Ar gas of 50 sccm. From the thickness of the retained
resist patterns on the silicon substrate, it was observed that the
resistance to RIE is comparable to that of the commercially
available Novolak resist: Nagase Positive Resist NPR-820 (Nagase
& Co.).
Example 5
[0331] The copolymer prepared in Example 3 was dissolved in ethyl
lactate to make a 18 wt. % solution thereof. Then,
triphenylsulfonium trifluoromethane sulfonate in an amount of 2 wt.
% with regard to the copolymer was added and dissolved in the
copolymer solution to make a resist solution. After it was filtered
on a Teflon.TM. membrane filter having a thickness of 0.2 .mu.m,
the resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
110.degree. C. for 60 seconds to form a 0.7-.mu.m thick resist
coating. The resist coating was patternwise exposed on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was developed with an aqueous solution of 2.38% tetramethylammonium
hydroxide (TMAH), and rinsed for 60 seconds in a deionized water.
The positive resist patterns were thus obtained. The resolution of
the patterns was 0.3 .mu.m L/S at an exposure level of 40
mJ/cm.sup.2.
[0332] The resist patterns were then evaluated with regard to the
resistance to RIE in accordance with the manner similar to that of
Example 4. From the thickness of the retained resist patterns on
the silicon substrate, it was observed that the resistance to RIE
is comparable to that of Nagase Positive Resist NPR-820 (Nagase
& Co.).
Example 6
[0333] The copolymer prepared in Example 2 was dissolved in ethyl
lactate to make a 18 wt. % solution thereof. Then, diphenyliodonium
trifluoromethane sulfonate as a photoacid generator (PAG) in an
amount of 2 wt. % with regard to the copolymer was added and
dissolved in the copolymer solution to make a resist solution.
After it was filtered on a Teflon.TM. membrane filter having a
thickness of 0.2 .mu.m, the resist solution was spin-coated at
2,000 rpm on a silicon substrate which has been treated with HMDS,
and prebaked at 110.degree. C. for 60 seconds to form a 0.7-.mu.m
thick resist coating. The resist coating was patternwise exposed on
a ArF excimer laser exposure system (commercially available from
Nikon, NA=0.55). The exposed resist coating was developed with an
aqueous solution of 2.38% tetramethylammonium hydroxide (TMAH), and
rinsed for 60 seconds in a deionized water. The positive resist
patterns were thus obtained. The resolution of the patterns was 0.2
.mu.m L/S at an exposure level of 10 mJ/cm.sup.2.
[0334] The resist patterns were then evaluated with regard to the
resistance to RIE in accordance with the manner similar to that of
Example 4. From the thickness of the retained resist patterns on
the silicon substrate, it was observed that the resistance to RIE
is comparable to that of Nagase Positive Resist NPR-820 (Nagase
& Co.).
Example 7
[0335] To a sufficiently dried 200 mL-volume eggplant-shaped flask
containing a Teflon.TM.-coated stirring bar, was added 10 g (50.5
mmol) of (.+-.)-mevalonic lactone methacrylate prepared in Example
1, 9.90 g (50.5 mmol) of norbornyl methacrylate, 33.7 mL of dioxane
and 2.49 g (15.2 mmol) of 2,2'-azobisisobutylonitrile (AIBN), and
the content in the flask was stirred at 80.degree. C. for 8 hours
in a nitrogen atmosphere. After dilution with tetrahydrofuran
(THF), the reaction solution was dropped to 3 L of water-methanol
(1:1) solution containing a small amount of hydroquinone. The thus
produced precipitate was filtered off on a glass filter, and dried
at 0.1 mmHg and 45.degree. C. for 16 hours. The obtained white
powders were again dissolved in THF, and the above-mentioned steps
of from precipitation to drying were twice repeated. The target
copolymer, namely, copolymer of (.+-.)-mevalonic lactone
methacrylate and norbornyl methacrylate, as a white product was
obtained at a yield of 14.33 g (72%).
[0336] The .sup.1H NMR analysis of the thus produced copolymer
indicated that the molar ratio of each monomeric component in the
copolymer is 1:1. The transmittance of the copolymer at the
wavelength of 248 nm, measured through a 1-.mu.m thick coating on a
quartz substrate, was 95%, evidencing excellent transparency. The
results of other analysises are as follows:
[0337] Weight average molecular weight (Mw): 13,600 (polystyrene
standard-equivalent).
[0338] Degree of polydispersion (Mw/Mn): 1.52.
[0339] IR (KRS-5, cm.sup.-1): 2960, 1727, 1259 and 1148.
Example 8
[0340] To a sufficiently dried 200 mL-volume eggplant-shaped flask
containing a Teflon.TM.-coated stirring bar, was added 10 g (50.5
mmol) of (.+-.)-mevalonic lactone methacrylate prepared in Example
1, 11.13 g (50.5 mmol) of adamantyl methacrylate, 33.7 mL of
dioxane and 2.49 g (15.2 mmol) of 2,2'-azobisisobutylonitrile
(AIBN), and the content in the flask was stirred at 80.degree. C.
for 8 hours in a nitrogen atmosphere. After dilution with
tetrahydrofuran (THF), the reaction solution was dropped to 3 L of
water-methanol (1:1) solution containing a small amount of
hydroquinone. The thus produced precipitate was filtered off on a
glass filter, and dried at 0.1 mmHg and 45.degree. C. for 16 hours.
The obtained white powders were again dissolved in THF, and the
above-mentioned steps of from precipitation to drying were twice
repeated. The target copolymer, namely, copolymer of
(.+-.)-mevalonic lactone methacrylate and adamantyl methacrylate,
as a white product was obtained at a yield of 15.85 g (75%).
[0341] The .sup.1H NMR analysis of the thus produced copolymer
indicated that the molar ratio of each monomeric component in the
copolymer is 1:1. The transmittance of the copolymer at the
wavelength of 248 nm, measured through a 1-.mu.m thick coating on a
quartz substrate, was 95%, evidencing excellent transparency. The
results of other analysises are as follows:
[0342] Weight average molecular weight (Mw): 14,100 (polystyrene
standard-equivalent).
[0343] Degree of polydispersion (Mw/Mn): 1.41.
[0344] IR (KRS-5, cm.sup.-1): 2912, 1722, 1259 and 1093.
Example 9
[0345] The copolymer prepared in Example 7 was dissolved in ethyl
lactate to make a 17 wt. % solution thereof. Then,
triphenylsulfonium trifluoromethane sulfonate in an amount of 5 wt.
% with regard to the copolymer was added and dissolved in the
copolymer solution to make a resist solution. After it was filtered
on a Teflon.TM. membrane filter having a thickness of 0.2 .mu.m,
the resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds to form a 0.7-.mu.m thick resist
coating. The resist coating was patternwise exposed on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was developed with an aqueous solution of 2.38% tetramethylammonium
hydroxide (TMAH), and rinsed for 60 seconds in a deionized water.
The positive resist patterns were thus obtained. The resolution of
the patterns was 0.3 .mu.m L/S at an exposure level of 38
mJ/cm.sup.2.
Example 10
[0346] The copolymer prepared in Example 8 was dissolved in ethyl
lactate to make a 17 wt. % solution thereof. Then,
triphenylsulfonium trifluoromethane sulfonate in an amount of 5 wt.
% with regard to the copolymer was added and dissolved in the
copolymer solution to make a resist solution. After it was filtered
on a Teflon.TM. membrane filter having a thickness of 0.2 .mu.m,
the resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds to form a 0.7-.mu.m thick resist
coating. The resist coating was patternwise exposed on a KrF
excimer laser stepper (Nikon, NA=0.45). After post-exposure baking
(PEB) was made at 100.degree. C. for 60 seconds, the exposed and
baked resist coating was developed with an aqueous solution of
2.38% tetramethylammonium hydroxide (TMAH), and rinsed for 60
seconds in a deionized water. The positive resist patterns were
thus obtained. The resolution of the patterns was 0.3 .mu.m L/S at
an exposure level of 30 mJ/cm.sup.2.
Example 11
[0347] The copolymer prepared in Example 7 was dissolved in ethyl
lactate to make a 17 wt. % solution thereof. Then,
triphenylsulfonium trifluoromethane sulfonate in an amount of 2 wt.
% with regard to the copolymer was added and dissolved in the
copolymer solution to make a resist solution. After it was filtered
on a Teflon.TM. membrane filter having a thickness of 0.2 .mu.m,
the resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds to form a 0.7-.mu.m thick resist
coating. The resist coating was patternwise exposed on a KrF
excimer laser stepper (Nikon, NA=0.45). After post-exposure baking
(PEB) was made at 100.degree. C. for 60 seconds, the exposed and
baked resist coating was developed with an aqueous solution of
2.38% tetramethylammonium hydroxide (TMAH), and rinsed for 60
seconds in a deionized water. The positive resist patterns were
thus obtained. The resolution of the patterns was 0.3 .mu.m L/S at
an exposure level of 20 mJ/cm.sup.2.
Example 12
[0348] The copolymer prepared in Example 8 was dissolved in ethyl
lactate to make a 17 wt. % solution thereof. Then,
triphenylsulfonium trifluoromethane sulfonate in an amount of 2 wt.
% with regard to the copolymer was added and dissolved in the
copolymer solution to make a resist solution. After it was filtered
on a Teflon.TM. membrane filter having a thickness of 0.2 .mu.m,
the resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds to form a 0.7-.mu.m thick resist
coating. The resist coating was patternwise exposed on a KrF
excimer laser stepper (Nikon, NA=0.45). After post-exposure baking
(PEB) was made at 100.degree. C. for 60 seconds, the exposed and
baked resist coating was developed with an aqueous solution of
2.38% tetramethylammonium hydroxide (TMAH), and rinsed for 60
seconds in a deionized water. The positive resist patterns were
thus obtained. The resolution of the patterns was 0.3 .mu.m L/S at
an exposure level of 23 mJ/cm.sup.2.
Example 13
[0349] To a sufficiently dried 100 mL-volume eggplant-shaped flask
containing a Teflon.TM.-coated stirring bar, was added 10 g (50.5
mmol) of (.+-.)-mevalonic lactone methacrylate prepared in Example
1, 5.87 g (25 mmol) of 2-methyl-2-adamantyl methacrylate, 16.7 mL
of dioxane and 1.23 g (9 mmol) of 2,2'-azobisisobutylonitrile
(AIBN), and the content in the flask was stirred at 80.degree. C.
for 8 hours in a nitrogen atmosphere. After dilution with
tetrahydrofuran (THF), the reaction solution was dropped to one
liter of methanol containing a small amount of hydroquinone. The
thus produced precipitate was filtered off on a glass filter, and
dried at 0.1 mmHg and 45.degree. C. for 16 hours. The obtained
white powders were again dissolved in THF, and the above-mentioned
steps of from precipitation to drying were twice repeated. The
target copolymer, namely, copolymer of (.+-.)-mevalonic lactone
methacrylate and 2-methyl-2-adamantyl methacrylate (MLMA-MAdMA), as
a white product was obtained at a yield of 7.44 g (68.7%).
[0350] The .sup.1H NMR analysis of the thus produced copolymer
indicated that the molar ratio of lactone component: adamantyl
component in the copolymer is 46.5:53.5. The transmittance of the
copolymer at the wavelengths of 248 nm and 193 nm, measured through
a 1-.mu.m thick coating on a quartz substrate, were 96% and 64%,
respectively, both evidencing excellent transparency. The results
of other analysises are as follows:
[0351] Weight average molecular weight (Mw): 13,900 (polystyrene
standard-equivalent).
[0352] Degree of polydispersion (Mw/Mn): 1.78.
[0353] IR (KRS-5, cm.sup.-1): 2914, 1724, 1259, 1147 and 1103.
Example 14
[0354] The copolymer prepared in Example 13 was dissolved in
propyleneglycol methylether acetate to make a 19 wt. % solution
thereof. Note that 8 wt. % of .gamma.-butylolactone as an auxiliary
solvent was also contained in said copolymer solution. Then,
triphenylsulfonium trifluoromethane sulfonate in an amount of 5 wt.
% with regard to the copolymer was added and dissolved in the
copolymer solution to make a resist solution. After it was filtered
on a Teflon.TM. membrane filter having a thickness of 0.2 .mu.m,
the resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds to form a 0.7-.mu.m thick resist
coating. The resist coating was patternwise exposed on a KrF
excimer laser stepper (Nikon, NA=0.45). After post-exposure baking
(PEB) was made at 100.degree. C. for 60 seconds, the exposed and
baked resist coating was developed with an aqueous solution of
2.38% tetramethylammonium hydroxide (TMAH), and rinsed for 60
seconds in a deionized water. The positive resist patterns were
thus obtained. The resolution of the patterns was 0.25 .mu.m L/S at
an exposure level of 8.3 mJ/cm.sup.2.
[0355] The resist patterns were then evaluated with regard to the
dry etching resistance, namely, resistance to RIE. The plasma
etching rates were determined by disposing the resist-coated
silicon substrate in a parallel plate reactive ion etcher and
conducting the tetrafluorocarbon (CF.sub.4) sputtering etching for
5 minutes under the conditions: Rf power (P.mu.) of 200 W, pressure
of 0.02 Torr and flow rate of CF.sub.4 gas of 100 sccm. The results
(etching rate and its ratio to that of Nagase Positive Resist
NPR-820) are summarized in the following table.
[0356] Further, for the comparison purpose, the above procedure was
repeated by using as the resist material the commercially available
Novolak resist: Nagase Positive Resist NPR-820 (Nagase & Co.)
and poly(methylmethacrylate) (PMMA). The following results were
obtained.
1 resist etching rate (.ANG./min) rate ratio NPR-820 523 1.00 PMMA
790 1.51 MLMA-MAdMA 610 1.17
[0357] rate ratio: a ratio of the etching rate of the tested resist
to that of NPR-820
[0358] The results in the above table indicate that MLMA-MAdMA,
i.e., resist according to the present invention, has the resistance
to RIE which is comparable to that of Nagase Positive Resist
NPR-820 and is remarkably excellent in comparison with that of
PMMA.
Example 15
[0359] The copolymer prepared in Example 13 was dissolved in ethyl
lactate to make a 18 wt. % solution thereof. Then,
triphenylsulfonium trifluoromethane sulfonate in an amount of 5 wt.
% with regard to the copolymer was added and dissolved in the
copolymer solution to make a resist solution. After it was filtered
on a Teflon.TM. membrane filter having a thickness of 0.2 .mu.m,
the resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds to form a 0.7-.mu.m thick resist
coating. The resist coating was patternwise exposed on a KrF
excimer laser stepper (Nikon, NA=0.45). After post-exposure baking
(PEB) was made at 100.degree. C. for 60 seconds, the exposed and
baked resist coating was developed with an aqueous solution of
2.38% tetramethylammonium hydroxide (TMAH), and rinsed for 60
seconds in a deionized water. The positive resist patterns were
thus obtained. The resolution of the patterns was 0.25 .mu.m L/S at
an exposure level of 7.4 mJ/cm.sup.2.
[0360] The resist patterns were then evaluated with regard to the
resistance to RIE in accordance with the manner similar to that of
Example 14. It was observed from the test results that the tested
MLMA-MAdMA has the resistance to RIE which is comparable to that of
Nagase Positive Resist NPR-820 and is remarkably excellent in
comparison with that of PMMA.
Example 16
[0361] The copolymer prepared in Example 13 was dissolved in ethyl
lactate to make a 18 wt. % solution thereof. Then, diphenyliodonium
trifluoromethane sulfonate in an amount of 2 wt. % with regard to
the copolymer was added and dissolved in the copolymer solution to
make a resist solution. After it was filtered on a Teflon.TM.
membrane filter having a thickness of 0.2 .mu.m, the resist
solution was spin-coated at 2,000 rpm on a silicon substrate which
has been treated with HMDS, and prebaked at 120.degree. C. for 60
seconds to form a 0.7-.mu.m thick resist coating. The resist
coating was patternwise exposed on a ArF excimer laser exposure
system (Nikon, NA=0.55). After post-exposure baking (PEB) was made
at 100.degree. C. for 60 seconds, the exposed and baked resist
coating was developed with an aqueous solution of 2.38%
tetramethylammonium hydroxide (TMAH), and rinsed for 60 seconds in
a deionized water. The positive resist patterns were thus obtained.
The resolution of the patterns was 0.2 .mu.m L/S at an exposure
level of 6 mJ/cm.sup.2.
[0362] The resist patterns were then evaluated with regard to the
resistance to RIE in accordance with the manner similar to that of
Example 14. It was observed from the test results that the tested
MLMA-MAdMA has the resistance to RIE which is comparable to that of
Nagase Positive Resist NPR-820 and is remarkably excellent in
comparison with that of PMMA.
Example 17
[0363] 2-methyl-2-adamantyl methacrylate and t-butyl acrylate in a
ratio of 4:6 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
2 mole/L of the monomers. After addition of 5 mole % of
2,2'-azobisisobutylonitrile (AIBN) as a polymerization initiator to
the 1,4-dioxane solution, the monomers were polymerized at
80.degree. C. for 8 hours. After completion of the polymerization,
the polymerization product was purified by using n-hexane as a
precipitant. The copolymer of 2-methyl-2-adamantyl methacrylate and
t-butyl acrylate represented by the following formula was obtained.
66
[0364] The resulting copolymer had a composition ratio (m:n) of
49:51, weight average molecular weight (Mw) of 6,890 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.89.
Example 18
[0365] Triphenylsulfonium hexafluoroantimonate as a photoacid
generator (PAG) in an amount of 15 wt. % with regard to the
copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and t-butyl acrylate prepared in Example 17, and the
mixture was dissolved in cyclohexanone to make a resist solution.
The resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
100.degree. C. for 100 seconds on a hot plate to form a 0.7-.mu.m
thick resist coating.
[0366] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 130.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 21.2 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 19
[0367] The procedure of Example 18 was repeated with the proviso
that in the development step, the same concentration (0.27N) of
tetrabutylammonium hydroxide (TBAH) was used as a developer in
place of 0.27N tetramethylammonium hydroxide (TMAH). Satisfactory
positive resist patterns comparable to those of Example 18 were
obtained. The threshold energy Eth was 28.6 mJ/cm.sup.2, and the
resolution was 0.275 .mu.m L/S.
Example 20
[0368] This example is a comparative example.
[0369] The procedures of Examples 17 and 18 were repeated. However,
in this example, for the comparison purpose, the copolymer used as
the resist material was a copolymer of adamantyl methacrylate and
t-butyl acrylate represented by the following formula: 67
[0370] The above copolymer had a composition ratio (m:n) of 53:47,
weight average molecular weight (Mw) of 3,830 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.1.
[0371] Using this copolymer, the resist process was carried out in
accordance with the method described in Example 18, however, no
resist pattern was formed on the silicon substrate.
Example 21
[0372] 2-methyl-2-adamantyl acrylate as a starting monomer was
charged into a polymerization container to make a toluene solution
containing 2 mole/L of the monomer. After addition of 2 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the toluene solution, the
monomer was polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using methanol as a precipitant. The polymer of
2-methyl-2-adamantyl acrylate represented by the following formula:
68
[0373] in which n represents a number of the repeating units
necessary to obtain the desired molecular weight, was obtained.
[0374] The resulting polymer had a weight average molecular weight
(Mw) of 8,950 (polystyrene standard-equivalent) and degree of
polydispersion (Mw/Mn) of 1.8.
Example 22
[0375] Triphenylsulfonium hexafluoroantimonate in an amount of 15
wt. % with regard to the polymer was added to the polymer of
2-methyl-2-adamantyl acrylate prepared in Example 21, and the
mixture was dissolved in cyclohexanone to make a resist solution.
The resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
100.degree. C. for 100 seconds on a hot plate to form a 0.7-.mu.m
thick resist coating.
[0376] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 130.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 32 mJ/cm.sup.2, and
the resolution of the patterns was 0.30 .mu.m L/S.
Example 23
[0377] 2-methyl-2-adamantyl methacrylate and 3-oxocyclohexyl
methacrylate in a ratio of 4:6 as starting monomers were charged
into a polymerization container to make a toluene solution
containing 2 mole/L of the monomers. After addition of 5 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the toluene solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using methanol as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and 3-oxocyclohexyl methacrylate
represented by the following formula was obtained. 69
[0378] The resulting copolymer had a composition ratio (m:n) of
49:51, weight average molecular weight (Mw) of 14,400 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.30.
Example 24
[0379] Triphenylsulfonium hexafluoroantimonate in an amount of 5
wt. % with regard to the copolymer was added to the copolymer of
2-methyl-2-adamantyl methacrylate and 3-oxocyclohexyl methacrylate
prepared in Example 23, and the mixture was dissolved in
cyclohexanone to make a resist solution. The resist solution was
spin-coated at 2,000 rpm on a silicon substrate which has been
treated with HMDS, and prebaked at 100.degree. C. for 100 seconds
on a hot plate to form a 0.7-.mu.m thick resist coating.
[0380] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 9.6 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 25
[0381] 2-methyl-2-adamantyl methacrylate and
3-oxo-1,1-dimethylbutyl methacrylate in a ratio of 4:6 as starting
monomers were charged into a polymerization container to make a
1,4-dioxane solution containing 2 mole/L of the monomers. After
addition of 5 mole % of 2,2'-azobisisobutylonitrile (AIBN) to the
1,4-dioxane solution, the monomers were polymerized at 80.degree.
C. for 8 hours. After completion of the polymerization, the
polymerization product was purified by using n-hexane as a
precipitant. The copolymer of 2-methyl-2-adamantyl methacrylate and
3-oxo-1,1-dimethylbutyl methacrylate represented by the following
formula was obtained. 70
[0382] The resulting copolymer had a composition ratio (m:n) of
47:53, weight average molecular weight (Mw) of 7,420 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.40.
Example 26
[0383] Triphenylsulfonium hexafluoroantimonate in an amount of 5
wt. % with regard to the copolymer was added to the copolymer of
2-methyl-2-adamantyl methacrylate and 3-oxo-1,1-dimethylbutyl
methacrylate prepared in Example 25, and the mixture was dissolved
in cyclohexanone to make a resist solution. The resist solution was
spin-coated at 2,000 rpm on a silicon substrate which has been
treated with HMDS, and prebaked at 100.degree. C. for 100 seconds
on a hot plate to form a 0.7-.mu.m thick resist coating.
[0384] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 130.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 32 mJ/cm.sup.2, and
the resolution of the patterns was 0.325 .mu.m L/S.
Example 27
[0385] 2-methyl-2-adamantyl methacrylate and
3-methacryloyloxymethylbutyla- te methacrylate in a ratio of 4:6 as
starting monomers were charged into a polymerization container to
make a 1,4-dioxane solution containing 2 mole/L of the monomers.
After addition of 2 mole % of 2,2'-azobisisobutylonitrile (AIBN) to
the 1,4-dioxane solution, the monomers were polymerized at
80.degree. C. for 8 hours. After completion of the polymerization,
the polymerization product was purified by using n-hexane as a
precipitant. The copolymer of 2-methyl-2-adamantyl methacrylate and
3-methacryloyloxymethylbutylate methacrylate represented by the
following formula was obtained. 71
[0386] The resulting copolymer had a composition ratio (m:n) of
50:50, weight average molecular weight (Mw) of 12,090 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.95.
Example 28
[0387] Triphenylsulfonium hexafluoroantimonate in an amount of 15
wt. % with regard to the copolymer was added to the copolymer of
2-methyl-2-adamantyl methacrylate and 3
-methacryloyloxymethylbutylate methacrylate prepared in Example 27,
and the mixture was dissolved in cyclohexanone to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
100.degree. C. for 100 seconds on a hot plate to form a 0.7-.mu.m
thick resist coating.
[0388] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 130.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 29 mJ/cm.sup.2, and
the resolution of the patterns was 0.30 .mu.m L/S.
Example 29
[0389] The procedure of Example 27 was repeated with the proviso
that 3-methacryloyloxymethylbutylate methacrylate as the starting
monomer was replaced with 2-hydroxyethyl methacrylate. The
copolymer of 2-methyl-2-adamantyl methacrylate and 2-hydroxyethyl
methacrylate represented by the following formula was obtained.
72
[0390] The resulting copolymer had a composition ratio (m:n) of
55:45, weight average molecular weight (Mw) of 11,520 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.38.
[0391] Using this copolymer as the resist material, resist patterns
were produced in accordance with the manner similar to that of
Example 28.
[0392] Triphenylsulfonium hexafluoroantimonate in an amount of 15
wt. % with regard to the copolymer was added to the copolymer of
2-methyl-2-adamantyl methacrylate and 2-hydroxyethyl methacrylate,
and the mixture was dissolved in cyclohexanone to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
100.degree. C. for 100 seconds on a hot plate to form a 0.7-.mu.m
thick resist coating.
[0393] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 130.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 12 mJ/cm.sup.2, and
the resolution of the patterns was 0.325 .mu.m L/S.
Example 30
[0394] 2-methylcyclohexyl methacrylate and 3-oxocyclohexyl
methacrylate in a ratio of 4:6 as starting monomers were charged
into a polymerization container to make a toluene solution
containing 2 mole/L of the monomers. After addition of 5 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the toluene solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using methanol as a precipitant. The copolymer of
2-methylcyclohexyl methacrylate and 3-oxocyclohexyl methacrylate
represented by the following formula was obtained. 73
[0395] The resulting copolymer had a composition ratio (m:n) of
51:49, weight average molecular weight (Mw) of 7,115 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.9.
Example 31
[0396] Triphenylsulfonium hexafluoroantimonate in an amount of 5
wt. % with regard to the copolymer was added to the copolymer of
2-methylcyclohexyl methacrylate and 3-oxocyclohexyl methacrylate
prepared in Example 30, and the mixture was dissolved in
cyclohexanone to make a resist solution. The resist solution was
spin-coated at 2,000 rpm on a silicon substrate which has been
treated with HMDS, and prebaked at 100.degree. C. for 100 seconds
on a hot plate to form a 0.7-.mu.m thick resist coating.
[0397] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 130.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 7.2 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 32
[0398] 2-oxocyclohexylmethylcyclohexylsulfonium trifluorosulfonate
of the following formula: 74
[0399] as a photoacid generator (PAG) in an amount of 5 wt. % with
regard to the copolymer was added to the copolymer of
2-methyl-2-adamantyl methacrylate and 3-oxocyclohexyl methacrylate
prepared in Example 23, and the mixture was dissolved in
cyclohexanone to make a resist solution. The resist solution was
spin-coated at 2,000 rpm on a silicon substrate which has been
treated with HMDS, and prebaked at 100.degree. C. for 100 seconds
on a hot plate to form a 0.7-.mu.m thick resist coating.
[0400] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
130.degree. C. for 60 seconds. The postbaked resist coating was
developed with an aqueous solution of 0.27N tetramethylammonium
hydroxide (TMAH) for 60 seconds, and rinsed for 30 seconds in a
purified water. The positive resist patterns which correspond to
the pattern of the laser light as an exposure source were thus
obtained without peeling-off of the patterns from the substrate. In
this example, a threshold energy Eth of the exposure dose was 6
mJ/cm.sup.2, and the resolution of the patterns was 0.20 .mu.m
L/S.
Example 33
[0401] Triphenylsulfonium hexafluoroantimonate in an amount of 2
wt. % with regard to the copolymer was added to the copolymer of
2-methyl-2-adamantyl methacrylate and p-vinylphenol represented by
the following formula: 75
[0402] and having a composition ratio (m:n) of 23:77, weight
average molecular weight (Mw) of 6,480 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of 3.1,
and the mixture was dissolved in cyclohexanone to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
100.degree. C. for 100 seconds on a hot plate to form a 0.7-.mu.m
thick resist coating.
[0403] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 130.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 82 mJ/cm.sup.2, and
the resolution of the patterns was 0.325 .mu.m L/S.
Example 34
[0404] The polymer of 2-methyl-2-adamantyl acrylate, produced in
Example 21, having a weight average molecular weight (Mw) of 8,950
(polystyrene standard-equivalent) and degree of polydispersion
(Mw/Mn) of 1.8 in an amount of 20 wt. % with regard to the total
amount of the polymers was added to poly(vinyl phenol) represented
by the following formula: 76
[0405] and having a weight average molecular weight (Mw) of 5,150
(polystyrene standard-equivalent) and degree of polydispersion
(Mw/Mn) of 2.8, followed by addition of triphenylsulfonium
hexafluoroantimonate in an amount of 5 wt. % with regard to the
total amount of the polymers. The resulting mixture was dissolved
in cyclohexanone to make a resist solution. The resist solution was
spin-coated at 2,000 rpm on a silicon substrate which has been
treated with HMDS, and prebaked at 100.degree. C. for 100 seconds
on a hot plate to form a 0.7-.mu.m thick resist coating.
[0406] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 110.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 8.9 mJ/cm.sup.2, and
the resolution of the patterns was 0.325 .mu.m L/S.
Example 35
[0407] The adamantyl compound, 1-adamantyl carboxylate
2-methyladamantylester of the following formula: 77
[0408] in an amount of 30 wt. % with regard to the total amount of
the mixture was added to poly(vinyl phenol) which is the same as
that used in Example 34 and has a weight average molecular weight
(Mw) of 5,150 (polystyrene standard-equivalent) and degree of
polydispersion (Mw/Mn) of 2.8, followed by addition of
triphenylsulfonium hexafluoroantimonate in an amount of 5 wt. %
with regard to the total amount of the mixture. The resulting
mixture was dissolved in cyclohexanone to make a resist solution.
The resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
100.degree. C. for 100 seconds on a hot plate to form a 0.7-.mu.m
thick resist coating.
[0409] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 110.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.27N tetramethylammonium hydroxide (TMAH)
for 60 seconds, and rinsed for 30 seconds in a purified water. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 11 mJ/cm.sup.2, and
the resolution of the patterns was 0.35 .mu.m L/S.
Example 36
[0410] The copolymer represented by the following formula was
prepared in accordance with the manner described in the above
examples. 78
[0411] The resulting copolymer had a composition ratio (m:n) of 5:5
and weight average molecular weight (Mw) of 23,000 (polystyrene
standard-equivalent).
[0412] Using this copolymer as the resist material, resist patterns
were produced in accordance with the manner described in the above
examples.
[0413] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the above-mentioned copolymer, and the
mixture was dissolved in ethyl lactate (EL) to make a resist
solution containing the copolymer at a concentration of 15 wt. %.
The resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
100.degree. C. for 60 seconds on a hot plate to form a 1.0-.mu.m
thick resist coating.
[0414] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds. The postbaked resist coating was
developed with an alkaline developer, NMD-3 commercially available
from Tokyo Ohka Kogyo Co., Ltd., for 60 seconds, and rinsed for 30
seconds in a purified water. The positive resist patterns which
correspond to the pattern of the exposure mask used were thus
obtained without cracking and peeling-off of the patterns from the
substrate. In this example, the resolution of the patterns was 0.50
.mu.m L/S.
Example 37
[0415] This example is a comparative example.
[0416] The procedure of Example 36 was repeated. However, in this
example, for the comparison purpose, the copolymer as the resist
material was replaced with the copolymer which is represented by
the following formula: 79
[0417] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 14,000 (polystyrene
standard-equivalent).
[0418] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained with a resolution of
the patterns of 0.50 .mu.m L/S, however, cracking was resulted in
the peripheral portion of the patterns.
Example 38
[0419] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 80
[0420] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 18,000 (polystyrene
standard-equivalent).
[0421] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.50 .mu.m L/S.
Example 39
[0422] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 81
[0423] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 11,000 (polystyrene
standard-equivalent).
[0424] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.50 .mu.m L/S.
Example 40
[0425] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 82
[0426] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 8,000 (polystyrene
standard-equivalent).
[0427] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.50 .mu.m L/S.
Example 41
[0428] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 83
[0429] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 9,000 (polystyrene
standard-equivalent).
[0430] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.50 .mu.m L/S.
Example 42
[0431] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 84
[0432] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 7,800 (polystyrene
standard-equivalent).
[0433] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.50 .mu.m L/S.
Example 43
[0434] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 85
[0435] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 6,500 (polystyrene
standard-equivalent).
[0436] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.50 .mu.m L/S.
Example 44
[0437] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 86
[0438] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 16,000 (polystyrene
standard-equivalent).
[0439] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.60 .mu.m L/S.
Example 45
[0440] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 87
[0441] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 12,500 (polystyrene
standard-equivalent).
[0442] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.50 .mu.m L/S.
Example 46
[0443] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 88
[0444] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 18,000 (polystyrene standard-equivalent),
and a deep UV contact aligner as an exposure system was used in
place of the ArF excimer laser exposure system.
[0445] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.50 .mu.m L/S.
Example 47
[0446] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 89
[0447] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 17,500 (polystyrene standard-equivalent),
and a deep UV contact aligner as an exposure system was used in
place of the ArF excimer laser exposure system.
[0448] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.55 .mu.m L/S.
Example 48
[0449] The procedure of Example 36 was repeated with the proviso
that, in this example, the copolymer as the resist material was
replaced with the copolymer which is represented by the following
formula: 90
[0450] and has a composition ratio (m:n) of 5:5 and weight average
molecular weight (Mw) of 9,500 (polystyrene
standard-equivalent).
[0451] The positive resist patterns which correspond to the pattern
of the exposure mask used were thus obtained without cracking and
peeling-off of the patterns from the substrate. In this example,
the resolution of the patterns was 0.60 .mu.m L/S.
Example 49
[0452] 2-methyl-2-adamantyl methacrylate and methacrylic acid in a
ratio of 7:3 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and methacrylic acid represented
by the following formula was obtained. 91
[0453] The resulting copolymer had a composition ratio (m:n) of
7:3, weight average molecular weight (Mw) of 8,500 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.10.
Example 50
[0454] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and methacrylic acid prepared in Example 49, and the
mixture was dissolved in propyleneglycol monomethyletheracetate
(PGMEA) to make a resist solution. The resist solution was
spin-coated at 2,000 rpm on a silicon substrate which has been
treated with HMDS, and prebaked at 120.degree. C. for 60 seconds on
a hot plate to form a 0.4-.mu.m thick resist coating.
[0455] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 195 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds. The postbaked resist coating was
developed with an aqueous solution of 0.118 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. In this example, a threshold energy Eth of the exposure
dose was 21.5 mJ/cm.sup.2, and the resolution of the patterns was
0.175 .mu.m L/S.
Example 51
[0456] The procedure of Example 50 was repeated with the proviso
that, in this example, a KrF excimer laser stepper (Nikon, NA=0.45)
was used to produce a pattern of laser light having a wavelength of
248 nm, in place of the ArF excimer laser exposure system. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 1.48 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 52
[0457] 2-methyl-2-adamantyl methacrylate, t-butyl methacrylate and
methacrylic acid in a ratio of 8:7:5 as starting monomers were
charged into a polymerization container to make a 1,4-dioxane
solution containing 1 mole/L of the monomers. After addition of 20
mole % of 2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane
solution, the monomers were polymerized at 80.degree. C. for 8
hours. After completion of the polymerization, the polymerization
product was purified by using n-hexane as a precipitant. The
copolymer of 2-methyl-2-adamantyl methacrylate, t-butyl
methacrylate and methacrylic acid
[0458] represented by the following formula was obtained. 92
[0459] The resulting copolymer had a composition ratio (l:m:n) of
50:29:21, weight average molecular weight (Mw) of 7,800
(polystyrene standard-equivalent) and degree of polydispersion
(Mw/Mn) of 2.20.
Example 53
[0460] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate, t-butyl methacrylate and methacrylic acid prepared in
Example 52, and the mixture was dissolved in propyleneglycol
monomethyletheracetate (PGMEA) to make a resist solution. The
resist solution was spin-coated at 2,000 rpm on a silicon substrate
which has been treated with HMDS, and prebaked at 120.degree. C.
for 60 seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0461] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 195 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds. The postbaked resist coating was
developed with an aqueous solution of 0.118 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. In this example, a threshold energy Eth of the exposure
dose was 1.4 mJ/cm.sup.2, and the resolution of the patterns was
0.170 .mu.m L/S.
Example 54
[0462] The procedure of Example 53 was repeated with the proviso
that, in this example, a KrF excimer laser stepper (Nikon, NA=0.45)
was used to produce a pattern of laser light having a wavelength of
248 nm, in place of the ArF excimer laser exposure system. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 14.4 mJ/cm.sup.2, and
the resolution of the patterns was 0.250 .mu.m L/S.
Example 55
[0463] 2-methyl-2-adamantyl methacrylate and itaconic acid in a
ratio of 9:1 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and itaconic acid represented by
the following formula was obtained. 93
[0464] The resulting copolymer had a composition ratio (m:n) of
88:12, weight average molecular weight (Mw) of 6,700 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.18.
Example 56
[0465] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and itaconic acid prepared in Example 55, and the
mixture was dissolved in ethyl lactate (EL) to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0466] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 195 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds. The postbaked resist coating was
developed with an aqueous solution of 0.118 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. In this example, a threshold energy Eth of the exposure
dose was 2.8 mJ/cm.sup.2, and the resolution of the patterns was
0.175 .mu.m L/S.
Example 57
[0467] The procedure of Example 56 was repeated with the proviso
that, in this example, a KrF excimer laser stepper (Nikon, NA=0.45)
was used to produce a pattern of laser light having a wavelength of
248 nm, in place of the ArF excimer laser exposure system. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 25.0 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 58
[0468] 2-methyl-2-adamantyl methacrylate and vinylbenzenesulfonic
acid in a ratio of 8:2 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of 2,2'
-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and vinylbenzenesulfonic acid
represented by the following formula was obtained. 94
[0469] The resulting copolymer had a composition ratio (m:n) of
76:24, weight average molecular weight (Mw) of 6,400 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.42.
Example 59
[0470] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and vinylbenzenesulfonic acid prepared in Example 58,
and the mixture was dissolved in ethyl lactate (EL) to make a
resist solution. The resist solution was spin-coated at 2,000 rpm
on a silicon substrate which has been treated with HMDS, and
prebaked at 120.degree. C. for 60 seconds on a hot plate to form a
0.4-.mu.m thick resist coating.
[0471] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.236 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 12.4 mJ/cm.sup.2, and
the resolution of the patterns was 0.250 .mu.m L/S.
Example 60
[0472] 2-methyl-2-adamantyl methacrylate and methacrylic amide in a
ratio of 7:3 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and methacrylic amide represented
by the following formula was obtained. 95
[0473] The resulting copolymer had a composition ratio (m:n) of
75:25, weight average molecular weight (Mw) of 7,600 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.13.
Example 61
[0474] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and methacrylic amide prepared in Example 60, and the
mixture was dissolved in ethyl lactate (EL) to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0475] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.236 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 24.0 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 62
[0476] 2-methyl-2-adamantyl methacrylate and maleimide in a ratio
of 7:3 as starting monomers were charged into a polymerization
container to make a 1,4-dioxane solution containing 1 mole/L of the
monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and maleimide represented by the
following formula was obtained. 96
[0477] The resulting copolymer had a composition ratio (m:n) of
71:29, weight average molecular weight (Mw) of 8,200 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.55.
Example 63
[0478] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and maleimide prepared in Example 62, and the mixture
was dissolved in ethyl lactate (EL) to make a resist solution. The
resist solution was spin-coated at 2,000 rpm on a silicon substrate
which has been treated with HMDS, and prebaked at 120.degree. C.
for 60 seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0479] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.236 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 30.0 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 64
[0480] 2-methyl-2-adamantyl methacrylate and anhydrous itaconic
acid in a ratio of 8:2 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and maleimide represented by the
following formula was obtained. 97
[0481] The resulting copolymer had a composition ratio (m:n) of
72:28, weight average molecular weight (Mw) of 8,700 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.31.
Example 65
[0482] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and anhydrous itaconic acid prepared in Example 64,
and the mixture was dissolved in ethyl lactate (EL) to make a
resist solution. The resist solution was spin-coated at 2,000 rpm
on a silicon substrate which has been treated with HMDS, and
prebaked at 120.degree. C. for 60 seconds on a hot plate to form a
0.4-.mu.m thick resist coating.
[0483] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.118 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 26.1 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 66
[0484] 2-methyl-2-adamantyl methacrylate and .alpha.-acrylic
acid-(R)-(+)-.beta., .beta.-dimethyl-.gamma.-butylolactone in a
ratio of 7:3 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and a-acrylic acid-(R)-(+
)-.beta., .beta.-dimethyl-.gamma.-butylolactone represented by the
following formula was obtained. 98
[0485] The resulting copolymer had a composition ratio (m:n) of
74:26, weight average molecular weight (Mw) of 6,200 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.25.
Example 67
[0486] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and .alpha.-acrylic acid-(R)-(+ )-.beta.,
.beta.-dimethyl-.gamma.-butylolacto- ne prepared in Example 66, and
the mixture was dissolved in ethyl lactate (EL) to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0487] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds. The postbaked resist coating was
developed with an aqueous solution of 2.38 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. In this example, a threshold energy Eth of the exposure
dose was 1.9 mJ/cm.sup.2, and the resolution of the patterns was
0.170 .mu.m L/S.
Example 68
[0488] The procedure of Example 67 was repeated with the proviso
that, in this example, a KrF excimer laser stepper (Nikon, NA=0.45)
was used to produce a pattern of laser light having a wavelength of
248 nm, in place of the ArF excimer laser exposure system. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 15.0 mJ/cm.sup.2, and
the resolution of the patterns was 0.250 .mu.m L/S.
Example 69
[0489] 2-methyl-2-adamantyl methacrylate and vinylhydroxyloxime in
a ratio of 4:6 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and vinylhydroxyloxime
represented by the following formula was obtained. 99
[0490] The resulting copolymer had a composition ratio (m:n) of
66:44, weight average molecular weight (Mw) of 6,200 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.08.
Example 70
[0491] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and vinylhydroxyloxime prepared in Example 69, and the
mixture was dissolved in ethyl lactate (EL) to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0492] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 2.38 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 34.0 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 71
[0493] 2-methyl-2-adamantyl methacrylate and vinylcarbonate in a
ratio of 1:9 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and vinylcarbonate represented by
the following formula was obtained. 100
[0494] The resulting copolymer had a composition ratio (m:n) of
82:18, weight average molecular weight (Mw) of 9,300 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.99.
Example 72
[0495] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and vinylcarbonate prepared in Example 71, and the
mixture was dissolved in ethyl lactate (EL) to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0496] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 2.38 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 31.0 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 73
[0497] 2-methyl-2-adamantyl methacrylate and vinylazalactone in a
ratio of 7:3 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl- 2-adamantyl methacrylate and vinylazalactone represented
by the following formula was obtained. 101
[0498] The resulting copolymer had a composition ratio (m:n) of
71:29, weight average molecular weight (Mw) of 10,200 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.61.
Example 74
[0499] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and vinylazalactone prepared in Example 73, and the
mixture was dissolved in ethyl lactate (EL) to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0500] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.118 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 28.2 mJ/cm.sup.2, and
the resolution of the patterns was 0.250 .mu.m L/S.
Example 75
[0501] 2-methyl-2-adamantyl methacrylate and vinyloxazine in a
ratio of 7:3 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and vinyloxazine represented by
the following formula was obtained. 102
[0502] The resulting copolymer had a composition ratio (m:n) of
70:30, weight average molecular weight (Mw) of 11,000 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.59.
Example 76
[0503] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
Photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and vinyloxazine prepared in Example 75, and the
mixture was dissolved in ethyl lactate (EL) to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0504] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the Post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.118 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 27.5 mJ/cm.sup.2, and
the resolution of the patterns was 0.250 .mu.m L/S.
Example 77
[0505] 2-methyl-2-adamantyl methacrylate and vinylpyrrolidone in a
ratio of 7:3 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and vinylpyrrolidone represented
by the following formula was obtained. 103
[0506] The resulting copolymer had a composition ratio (m:n) of
68:32, weight average molecular weight (Mw) of 9,000 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.89.
Example 78
[0507] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and vinylpyrrolidone prepared in Example 77, and the
mixture was dissolved in ethyl lactate (EL) to make a resist
solution. The resist solution was spin-coated at 2,000 rpm on a
silicon substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0508] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 0.118 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 30.5 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 79
[0509] 2-methyl-2-adamantyl methacrylate and acrylonitrile in a
ratio of 1:1 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and acrylonitrile represented by
the following formula was obtained. 104
[0510] The resulting copolymer had a composition ratio (m:n) of
80:20, weight average molecular weight (Mw) of 6,000 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.35.
Example 80
[0511] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and acrylonitrile prepared in Example 79, and the
mixture was dissolved in cyclohexanone to make a resist solution.
The resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0512] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 2.38 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 38.2 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 81
[0513] 2-methyl-2-adamantyl methacrylate and nitrostyrene in a
ratio of 1:1 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and nitrostyrene represented by
the following formula was obtained. 105
[0514] The resulting copolymer had a composition ratio (m:n) of
74:26, weight average molecular weight (Mw) of 14,000 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.79.
Example 82
[0515] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and nitrostyrene prepared in Example 81, and the
mixture was dissolved in cyclohexanone to make a resist solution.
The resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0516] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 248 nm on a KrF
excimer laser stepper (Nikon, NA=0.45). The exposed resist coating
was then subjected to the post-exposure baking (PEB) at 150.degree.
C. for 60 seconds. The postbaked resist coating was developed with
an aqueous solution of 2.38 wt. % tetramethylammonium hydroxide
(TMAH) for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 37.5 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 83
[0517] 2-methyl-2-adamantyl methacrylate and acrolein in a ratio of
1:1 as starting monomers were charged into a polymerization
container to make a 1,4-dioxane solution containing 1 mole/L of the
monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and acrolein represented by the
following formula was obtained. 106
[0518] The resulting copolymer had a composition ratio (m:n) of
70:30, weight average molecular weight (Mw) of 10,000 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.10.
Example 84
[0519] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and acrolein prepared in Example 83, and the mixture
was dissolved in cyclohexanone to make a resist solution. The
resist solution was spin-coated at 2,000 rpm on a silicon substrate
which has been treated with HMDS, and prebaked at 120.degree. C.
for 60 seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0520] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds. The postbaked resist coating was
developed with an aqueous solution of 2.38 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. In this example, a threshold energy Eth of the exposure
dose was 1.4 mJ/cm.sup.2, and the resolution of the patterns was
0.170 .mu.m L/S.
Example 85
[0521] The procedure of Example 84 was repeated with the proviso
that, in this example, a KrF excimer laser stepper (Nikon, NA=0.45)
was used to produce a pattern of laser light having a wavelength of
248 nm, in place of the ArF excimer laser exposure system. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 21.0 mJ/cm.sup.2, and
the resolution of the patterns was 0.250 .mu.m L/S.
Example 86
[0522] 2-methyl-2-adamantyl methacrylate and vinyl acetate in a
ratio of 7:3 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
2-methyl-2-adamantyl methacrylate and vinyl acetate represented by
the following formula was obtained. 107
[0523] The resulting copolymer had a composition ratio (m:n) of
74:26, weight average molecular weight (Mw) of 8,200 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.82.
Example 87
[0524] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and vinyl acetate prepared in Example 86, and the
mixture was dissolved in cyclohexanone to make a resist solution.
The resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS, and prebaked at
120.degree. C. for 60 seconds on a hot plate to form a 0.4-.mu.m
thick resist coating.
[0525] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds. The postbaked resist coating was
developed with an aqueous solution of 2.38 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. In this example, a threshold energy Eth of the exposure
dose was 2.2 mJ/cm.sup.2, and the resolution of the patterns was
0.170 .mu.m L/S.
Example 88
[0526] The procedure of Example 87 was repeated with the proviso
that, in this example, a KrF excimer laser stepper (Nikon, NA=0.45)
was used to produce a pattern of laser light having a wavelength of
248 nm, in place of the ArF excimer laser exposure system. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 22.0 mJ/cm.sup.2, and
the resolution of the patterns was 0.250 .mu.m L/S.
Example 89
[0527] .alpha.-2-methyl-2-adamantyl-.beta.-methylitaconic acid as a
starting monomer was charged into a polymerization container to
make a 1,4-dioxane solution containing 1 mole/L of the monomer.
After addition of 20 mole % of 2,2'-azobisisobutylonitrile (AIBN)
to the 1,4-dioxane solution, the monomer was polymerized at
80.degree. C. for 8 hours. After completion of the polymerization,
the polymerization product was purified by using methanol as a
precipitant. The polymer of .alpha.-2-methyl-2-adamantyl-.beta.
-methylitaconic acid represented by the following formula was
obtained. 108
[0528] The resulting polymer had a weight average molecular weight
(Mw) of 18,000 (polystyrene standard-equivalent) and degree of
polydispersion (Mw/Mn) of 1.66.
Example 90
[0529] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the polymer was added to the polymer of
.alpha.-2-methyl-2-adamantyl-.beta.-methylitaconi- c acid prepared
in Example 89, and the mixture was dissolved in cyclohexanone to
make a resist solution. The resist solution was spin-coated at
2,000 rpm on a silicon substrate which has been treated with HMDS,
and prebaked at 120.degree. C. for 60 seconds on a hot plate to
form a 0.4-.mu.m thick resist coating.
[0530] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds. The postbaked resist coating was
developed with an aqueous solution of 2.38 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. In this example, a threshold energy Eth of the exposure
dose was 2.0 mJ/cm.sup.2, and the resolution of the patterns was
0.175 .mu.m L/S.
Example 91
[0531] The procedure of Example 90 was repeated with the proviso
that, in this example, a KrF excimer laser stepper (Nikon, NA=0.45)
was used to produce a pattern of laser light having a wavelength of
248 nm, in place of the ArF excimer laser exposure system. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 28.5 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 92
[0532] Bis-2-methyl-2-adamantyl fumarate and fumaric acid in a
molar ratio of 9:1 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 8 hours. After
completion of the polymerization, the polymerization product was
purified by using n-hexane as a precipitant. The copolymer of
bis-2-methyl-2-adamantyl fumarate and fumaric acid represented by
the following formula was obtained. 109
[0533] The resulting copolymer had a composition ratio (m:n) of
95:5, weight average molecular weight (Mw) of 5,100 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
2.84.
Example 93
[0534] Triphenylsulfonium triflate (TPSSO.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of
bis-2-methyl-2-adamantyl fumarate and fumaric acid prepared in
Example 92, and the mixture was dissolved in cyclohexanone to make
a resist solution. The resist solution was spin-coated at 2,000 rpm
on a silicon substrate which has been treated with HMDS, and
prebaked at 120.degree. C. for 60 seconds on a hot plate to form a
0.4-.mu.m thick resist coating.
[0535] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds. The postbaked resist coating was
developed with an aqueous solution of 0.118 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. In this example, a threshold energy Eth of the exposure
dose was 2.8 mJ/cm.sup.2, and the resolution of the patterns was
0.180 .mu.m L/S.
Example 94
[0536] The procedure of Example 93 was repeated with the proviso
that, in this example, a KrF excimer laser stepper (Nikon, NA=0.45)
was used to produce a pattern of laser light having a wavelength of
248 nm, in place of the ArF excimer laser exposure system. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. In this example, a
threshold energy Eth of the exposure dose was 30.5 mJ/cm.sup.2, and
the resolution of the patterns was 0.275 .mu.m L/S.
Example 95
[0537] 2-methyl-2-adamantyl methacrylate and methacrylic acid in a
molar ratio of 9:1 as starting monomers were charged into a
polymerization container to make a 1,4-dioxane solution containing
1 mole/L of the monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 7 hours. After
completion of the polymerization, the polymerization product was
dissolved in tetrahydrofuran (THF), and the resulting solution was
introduced into much amount of ethanol. The precipitated solution
was filtered to obtain the copolymer of 2-methyl-2-adamantyl
methacrylate and methacrylic acid at a yield of 44%. The resulting
copolymer had a composition ratio (m:n) of 9:1, and weight average
molecular weight (Mw) of 9,600 (polystyrene
standard-equivalent).
Example 96
[0538] Triphenylsulfonium hexafluoroantimonate (TPSSbF.sub.4) as a
photoacid generator (PAG) in an amount of 5 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate and methacrylic acid prepared in Example 95, and the
mixture was dissolved in cyclohexanone to make a resist solution
having a resin concentration of 15 wt. %. The resist solution was
spin-coated at 2,000 rpm on a silicon substrate which has been
treated with HMDS to form a 0.7-.mu.m thick resist coating.
[0539] The resist coating was selectively exposed through a masking
means to a pattern of laser light having a wavelength of 248 nm on
a KrF excimer laser stepper (Nikon, NA=0.45). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
150.degree. C. for 60 seconds on a hot plate. The postbaked resist
coating was developed with an aqueous solution of 2.38 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. The resist patterns of 0.25 .mu.m L/S were resolved at a
ratio of about 1:1.
[0540] Further, the resist coating produced in accordance with the
above-mentioned manner was exposed to a light pattern of holes each
having a diameter of 0.325 .mu.m on a KrF excimer laser stepper.
The resist patterns having the holes of the diameter of 0.325 .mu.m
which correspond to the pattern of the laser light as an exposure
source were obtained.
Example 97
[0541] The procedure of Example 97 was repeated with the proviso
that, in this example, the amount of TPSSbF.sub.4 added was reduced
from 5 wt. % to 2 wt. %, the thickness of the resist coating was
reduced from 0.7 .mu.m to 0.4 .mu.m, and ArF excimer laser exposure
system (Nikon, NA=0.55) was used in place of the KrF excimer laser
stepper. The positive resist patterns which correspond to the
pattern of the laser light as an exposure source were thus obtained
without peeling-off of the patterns from the substrate. The resist
patterns of 0.18 .mu.m L/S were resolved at a ratio of about
1:1.
Example 98
[0542] 2-methyl-2-adamantyl methacrylate, t-butylmethacrylic acid
and methacrylic acid in a molar ratio of 40:35:25 as starting
monomers were charged into a polymerization container to make a
1,4-dioxane solution containing 1 mole/L of the monomers. After
addition of 20 mole % of 2,2'-azobisisobutylonitrile (AIBN) to the
1,4-dioxane solution, the monomers were polymerized at 80.degree.
C. for 7 hours. After completion of the polymerization, the
polymerization product was dissolved in tetrahydrofuran (THF), and
the resulting solution was introduced into much amount of n-hexane.
The precipitated solution was filtered to obtain the copolymer of
2-methyl-2-adamantyl methacrylate, t-butylmethacrylic acid and
methacrylic acid at a yield of 58%. The resulting copolymer had a
composition ratio (l:m:n) of 50:29:21, and weight average molecular
weight (Mw) of 12,000 (polystyrene standard-equivalent).
Example 99
[0543] Triphenylsulfonium hexafluoroantimonate (TPSSbF.sub.4) as a
photoacid generator (PAG) in an amount of 5 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate, t-butylmethacrylic acid and methacrylic acid prepared
in Example 98, and the mixture was dissolved in cyclohexanone to
make a resist solution having a resin concentration of 15 wt. %.
The resist solution was spin-coated at 2,000 rpm on a silicon
substrate which has been treated with HMDS to form a 0.7-.mu.m
thick resist coating.
[0544] The resist coating was selectively exposed through a masking
means to a pattern of laser light having a wavelength of 248 nm on
a KrF excimer laser stepper (Nikon, NA=0.45). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
130.degree. C. for 60 seconds on a hot plate. The postbaked resist
coating was developed with an aqueous solution of 0.17 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. The resist patterns of 0.25 .mu.m L/S were resolved at a
ratio of about 1:1.
[0545] Further, the resist coating produced in accordance with the
above-mentioned manner was exposed to a light pattern of holes each
having a diameter of 0.325 .mu.m on a KrF excimer laser stepper.
The resist patterns having the holes of the diameter of 0.325 .mu.m
which correspond to the pattern of the laser light as an exposure
source were obtained.
Example 100
[0546] The procedure of Example 99 was repeated with the proviso
that, in this example, the amount of TPSSbF.sub.4 added was reduced
from 5 wt. % to 2 wt. %, and ArF excimer laser exposure system
(Nikon, NA=0.55) was used in place of the KrF excimer laser
stepper. The positive resist patterns which correspond to the
pattern of the laser light as an exposure source were thus obtained
without peeling-off of the patterns from the substrate. The resist
patterns of 0.19 .mu.m L/S were resoluted at a ratio of about
1:1.
Example 101
[0547] 2-methyl-2-adamantyl methacrylate,
3-oxocyclohexylmethacrylate and methacrylic acid in a molar ratio
of 50:35:15 as starting monomers were charged into a polymerization
container to make a 1,4-dioxane solution containing 1 mole/L of the
monomers. After addition of 20 mole % of
2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane solution, the
monomers were polymerized at 80.degree. C. for 7 hours. After
completion of the polymerization, the polymerization product was
dissolved in tetrahydrofuran (THF), and the resulting solution was
introduced into much amount of the mixed solvent (10:1) of methanol
and water. The precipitated solution was filtered to obtain the
copolymer of 2-methyl-2-adamantyl methacrylate,
3-oxocyclohexylmethacrylate and methacrylic acid at a yield of 43%.
The resulting copolymer had a composition ratio (l:m:n) of
50:35:15, and weight average molecular weight (Mw) of 11,000
(polystyrene standard-equivalent).
Example 102
[0548] Triphenylsulfonium hexafluoroantimonate (TPSSbF.sub.4) as a
photoacid generator (PAG) in an amount of 5 wt. % with regard to
the copolymer was added to the copolymer of 2-methyl-2-adamantyl
methacrylate, 3-oxocyclohexylmethacrylate and methacrylic acid
prepared in Example 101, and the mixture was dissolved in
cyclohexanone to make a resist solution having a resin
concentration of 15 wt. %. The resist solution was spin-coated at
2,000 rpm on a silicon substrate which has been treated with HMDS
to form a 0.7-.mu.m thick resist coating.
[0549] The resist coating was selectively exposed through a masking
means to a pattern of laser light having a wavelength of 248 nm on
a KrF excimer laser stepper (Nikon, NA=0.45). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
130.degree. C. for 60 seconds on a hot plate. The postbaked resist
coating was developed with an aqueous solution of 0.17 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. The resist patterns of 0.25 .mu.m L/S were resolved at a
ratio of about 1:1.
[0550] Further, the resist coating produced in accordance with the
above-mentioned manner was exposed to a light pattern of holes each
having a diameter of 0.325 .mu.m on a KrF excimer laser stepper.
The resist patterns having the holes of the diameter of 0.325 .mu.m
which correspond to the pattern of the laser light as an exposure
source were obtained.
Example 103
[0551] The procedure of Example 102 was repeated with the proviso
that, in this example, ArF excimer laser exposure system (Nikon,
NA=0.55) was used in place of the KrF excimer laser stepper. The
positive resist patterns which correspond to the pattern of the
laser light as an exposure source were thus obtained without
peeling-off of the patterns from the substrate. The resist patterns
of 0.19 .mu.m L/S were resoluted at a ratio of about 1:1.
Example 104
[0552] 2-methylcyclohexylmethacrylate, t-butylmethacrylate and
methacrylic acid in a molar ratio of 40:35:25 as starting monomers
were charged into a polymerization container to make a 1,4-dioxane
solution containing 1 mole/L of the monomers. After addition of 20
mole % of 2,2'-azobisisobutylonitrile (AIBN) to the 1,4-dioxane
solution, the monomers were polymerized at 80.degree. C. for 7
hours. After completion of the polymerization, the polymerization
product was dissolved in tetrahydrofuran (THF), and the resulting
solution was introduced into much amount of n-hexane. The
precipitated solution was filtered to obtain the copolymer of
2-methylcyclohexylm ethacrylate, t-butylmethacrylate and
methacrylic acid at a yield of 63%. The resulting copolymer had a
composition ratio (l:m:n) of 50:29:21, and weight average molecular
weight (Mw) of 21,000 (polystyrene standard-equivalent).
Example 105
[0553] Triphenylsulfonium hexafluoroantimonate (TPSSbF.sub.4) as a
photoacid generator (PAG) in an amount of 5 wt. % with regard to
the copolymer was added to the copolymer of
2-methylcyclohexylmethacrylate, t-butylmethacrylate and methacrylic
acid prepared in Example 104, and the mixture was dissolved in
cyclohexanone to make a resist solution having a resin
concentration of 15 wt. %. The resist solution was spin-coated at
2,000 rpm on a silicon substrate which has been treated with HMDS
to form a 0.7-.mu.m thick resist coating.
[0554] The resist coating was selectively exposed through a masking
means to a pattern of laser light having a wavelength of 248 nm on
a KrF excimer laser stepper (Nikon, NA=0.45). The exposed resist
coating was then subjected to the post-exposure baking (PEB) at
130.degree. C. for 60 seconds on a hot plate. The postbaked resist
coating was developed with an aqueous solution of 0.17 wt. %
tetramethylammonium hydroxide (TMAH) for 60 seconds, and rinsed for
30 seconds in a purified water. The positive resist patterns which
correspond to the pattern of the laser light as an exposure source
were thus obtained without peeling-off of the patterns from the
substrate. The resist patterns of 0.25 .mu.m L/S were resolved at a
ratio of about 1:1.
[0555] Further, the resist coating produced in accordance with the
above-mentioned manner was exposed to a light pattern of holes each
having a diameter of 0.325 .mu.m on a KrF excimer laser stepper.
The resist patterns having the holes of the diameter of 0.325 .mu.m
which correspond to the pattern of the laser light as an exposure
source were obtained.
Example 106
[0556] The procedure of Example 105 was repeated with the proviso
that, in this example, the amount of TPSSbF.sub.4 added was reduced
from 5 wt. % to 2 wt. %, and ArF excimer laser exposure system
(Nikon, NA=0.55) was used in place of the KrF excimer laser
stepper. The positive resist patterns which correspond to the
pattern of the laser light as an exposure source were thus obtained
without peeling-off of the patterns from the substrate. The resist
patterns of 0.19 .mu.m L/S were resoluted at a ratio of about
1:1.
Example 107
[0557] 2-butyl-2-adamantyl methacrylate and mevalonic lactone
methacrylate in a ratio of 1:1 as starting monomers were charged
into a polymerization container to make a 1,4-dioxane solution
containing 3 mole/L of the monomers. After addition of 15 mole % of
2,2' -azobisisobutylonitrile (AIBN) as a polymerization initiator
to the 1,4-dioxane solution, the monomers were polymerized at
80.degree. C. for about 9 hours. After completion of the
polymerization, the polymerization product was purified by using
methanol as a precipitant. The copolymer of 2-butyl-2-adamantyl
methacrylate and mevalonic lactone methacrylate represented by the
following formula was obtained. 110
[0558] The resulting copolymer had a composition ratio (m:n) of
54:46, weight average molecular weight (Mw) of 7,540 (polystyrene
standard-equivalent) and degree of polydispersion (Mw/Mn) of
1.8.
Example 108
[0559] Triphenylsulfonium triflate (TPSSQ.sub.3CF.sub.3) as a
photoacid generator (PAG) in an amount of 2 wt. % with regard to
the copolymer was added to the copolymer of 2-butyl-2-adamantyl
methacrylate and mevalonic lactone methacrylate prepared in Example
107, and the mixture was dissolved in cyclohexanone to make a
resist solution containing the copolymer in an amount of 14 wt. %.
The resist solution was spin-coated on a silicon substrate which
has been treated with HMDS, and prebaked at 100.degree. C. for 60
seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0560] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) on a
hot plate at 100.degree. C. for 60 seconds. The postbaked resist
coating was developed with an aqueous solution of 2.38% (0.27N)
tetramethylammonium hydroxide (TMAH), NMD-3 (trade name)
commercially available from Tokyo Ohka Co., for 60 seconds, and
rinsed for 30 seconds in a purified water. The positive resist
patterns which correspond to the pattern of the laser light as an
exposure source were thus obtained. In this example, a threshold
energy Eth of the exposure dose was 3 mJ/cm.sup.2, and the
resolution of the patterns was 0.17 .mu.m L/S (line &
space).
Example 109
[0561] This example is a comparative example.
[0562] The procedures of Example 108 was repeated. However, in this
example, for the comparison purpose, the copolymer used as the
resist material was a copolymer of 2-methyl-2-adamantyl
methacrylate and mevalonic lactone methacrylate by represented the
following formula: 111
[0563] The above copolymer was prepared in accordance with the
method similar to that of Example 107, and had a composition ratio
(m:n) of 51:40 and weight average molecular weight (Mw) of
8,900.
[0564] Using this copolymer, the resist process was carried out in
accordance with the method described in Example 108. That is, the
photoacid generator TPSSO.sub.3CF.sub.3 in an amount of 2 wt. %
with regard to the copolymer was added to the copolymer of
2-methyl-2-adamantyl methacrylate and mevalonic lactone
methacrylate, and the mixture was dissolved in cyclohexanone to
make a resist solution containing the copolymer in an amount of 14
wt. %. The resist solution was spin-coated on a silicon substrate
which has been treated with HMDS, and prebaked at 100.degree. C.
for 60 seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0565] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) on a
hot plate at 100.degree. C. for 60 seconds. The postbaked resist
coating was developed with an aqueous solution of 2.38% (0.27N)
tetramethylammonium hydroxide (NMD-3) for 60 seconds, and rinsed
for 30 seconds in a purified water. The positive resist patterns
which correspond to the pattern of the laser light as an exposure
source were thus obtained. In this example, a threshold energy Eth
of the exposure dose was 8 mJ/cm.sup.2, however, the resolution was
poor. That is, the patterns of 0.20 .mu.m L/S could not be produced
due to falling down of the patterns.
Example 110
[0566] This example was carried out to consider the reason why
remarkable differences were produced in the resulting resist
patterns due to a small difference of the substituent group between
Example 108 (containing 2-butyl substituent) and Example 109
(2-methyl substituent; comparative example).
[0567] The procedures of Examples 108 and 109 were repeated with
the proviso that the amount of the photoacid generator
TPSSO.sub.3CF.sub.3 was increased to 5 wt. % with regard to the
copolymer. A 0.4-.mu.m resist coating was thus formed.
[0568] The resist coating was selectively exposed to a pattern of
laser light having a wavelength of 193 nm on a ArF excimer laser
exposure system (Nikon, NA=0.55). To evaluate an exposure dose
dependency of the resist coating, the exposure energy was changed
as is illustrated in the graph of FIG. 1.
[0569] After the selective exposure has been completed, the resist
coating was post-baked on a hot plate at 100.degree. C. for 60
seconds, developed with the developer (NMD-3) for 60 seconds, and
rinsed for 30 seconds in a purified water. The positive resist
patterns which correspond to the pattern of the laser light as an
exposure source were thus obtained.
[0570] To evaluate an exposure dose dependency of the carboxylic
acid generation, each of the obtained resist patterns was subjected
to an infrared (IR) spectral analysis. The IR absorption spectrum
plotted in FIG. 1 was obtained. The obtained absorption spectrum
indicates that a height of carbonyl peak due to presence of --COOH
group is increased with increase of exposure energy, and is
saturated when the exposure energy was increased to a certain
level. However, in comparison of the graph of Example 108 (present
invention; butyl substituent) with that of Example 109 (comparative
example; methyl substituent), it is appreciated that the curve of
Example 108 is rapidly rised than that of Example 109. Thus, it is
considered from this result that the butyl substituent ensures an
effective and significant release of the carboxylic acid, thus
resulting in increase of sensitivity, exposure margin and
environmental resistance.
[0571] Further, the above procedure was repeated to obtain a graph
illustrating a degree of shrinkage for various 2-alkyl-2-AdMA
(adamantyl methacrylate) homopolymers with different ArF exposure
doses with the proviso that the amount of the photoacid generator
TPSSO.sub.3CF.sub.3 was changed from 5 wt. % to 2 wt. %. The degree
of shrinkage, i.e. reduced thickness after PEB, was calculated from
the following equation: 1 degree of shrinkage = shrinkage saturated
shrinkage
[0572] The results plotted in FIG. 2 indicate that the degree for
shrinkage was substantially saturated at the dose of about 2
mJ/cm.sup.2 for 2-butyl and 2-ethyl substituents, whereas it was
substantially saturated at the dose of about 10 mJ/cm.sup.2 for
2-methyl substituent.
Example 111
[0573] The procedure of Example 108 was repeated. However, in this
example, the copolymer used as the resist material was a copolymer
of 2-ethyl-2-adamantyl methacrylate and mevalonic lactone
methacrylate which was prepared in accordance with the method
similar to that of Example 107, is represented by the following
formula, and has a composition ratio (m:n) of 53:47, weight average
molecular weight (Mw) of 9,200 and degree of polydispersion (Mw/Mn)
of 2.0. 112
[0574] Using this copolymer, the resist process was carried out in
accordance with the method described in Example 108. That is, the
photoacid generator TPSSO.sub.3CF.sub.3 in an amount of 2 wt. %
with regard to the copolymer was added to the copolymer of
2-ethyl-2-adamantyl methacrylate and mevalonic lactone
methacrylate, and the mixture was dissolved in cyclohexanone to
make a resist solution containing the copolymer in an amount of 14
wt. %. The resist solution was spin-coated on a silicon substrate
which has been treated with HMDS, and prebaked at 100.degree. C.
for 60 seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0575] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) on a
hot plate at 100.degree. C. for 60 seconds. The postbaked resist
coating was developed with the alkaline developer, NMD-3 (trade
name) commercially available from Tokyo Ohka Co., for 60 seconds,
and rinsed for 30 seconds in a purified water. The positive resist
patterns which correspond to the pattern of the laser light as an
exposure source were thus obtained. In this example, a threshold
energy Eth of the exposure dose was 4 mJ/cm.sup.2, and the
resolution of the patterns was 0.18 .mu.m L/S.
Example 112
[0576] The procedure of Example 108 was repeated. However, in this
example, the copolymer used as the resist material was a copolymer
of 2-butyl-2-adamantyl methacrylate and methacrylic acid which was
prepared in accordance with the method similar to that of Example
107, is represented by the following formula, and has a composition
ratio (m:n) of 65:35, weight average molecular weight (Mw) of 3,900
and degree of polydispersion (Mw/Mn) of 2.5. 113
[0577] Using this copolymer, the resist process was carried out in
accordance with the method described in Example 108. That is, the
photoacid generator TPSSO.sub.3CF.sub.3 in an amount of 2 wt. %
with regard to the copolymer was added to the copolymer of
2-butyl-2-adamantyl methacrylate and methacrylic acid, and the
mixture was dissolved in cyclohexanone to make a resist solution
containing the copolymer in an amount of 14 wt. %. The resist
solution was spin-coated on a silicon substrate which has been
treated with HMDS, and prebaked at 100.degree. C. for 60 seconds on
a hot plate to form a 0.4-.mu.m thick resist coating.
[0578] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) on a
hot plate at 130.degree. C. for 60 seconds. The postbaked resist
coating was developed with the alkaline developer, 20 times-diluted
solution of NMD-3 (trade name) commercially available from Tokyo
Ohka Co., for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained. In
this example, a threshold energy Eth of the exposure dose was 2
mJ/cm.sup.2, and the resolution of the patterns was 0.17 .mu.m
L/S.
Example 113
[0579] The procedure of Example 108 was repeated. However, in this
example, the copolymer used as the resist material was a copolymer
of 2-butyl-2-adamantyl methacrylate and anhydrous itaconic acid
which was prepared in accordance with the method similar to that of
Example 107, is represented by the following formula, and has a
composition ratio (m:n) of 58:42, weight average molecular weight
(Mw) of 6,500 and degree of polydispersion (Mw/Mn) of 1.8. 114
[0580] Using this copolymer, the resist process was carried out in
accordance with the method described in Example 108. That is, the
photoacid generator TPSSO.sub.3CF.sub.3 in an amount of 2 wt. %
with regard to the copolymer was added to the copolymer of
2-butyl-2-adamantyl methacrylate and anhydrous itaconic acid, and
the mixture was dissolved in cyclohexanone to make a resist
solution containing the copolymer in an amount of 14 wt. %. The
resist solution was spin-coated on a silicon substrate which has
been treated with HMDS, and prebaked at 100.degree. C. for 60
seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0581] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) on a
hot plate at 100.degree. C. for 60 seconds. The postbaked resist
coating was developed with the alkaline developer, NMD-3 (trade
name) commercially available from Tokyo Ohka Co., for 60 seconds,
and rinsed for 30 seconds in a purified water. The positive resist
patterns which correspond to the pattern of the laser light as an
exposure source were thus obtained. In this example, a threshold
energy Eth of the exposure dose was 5 mJ/cm.sup.2, and the
resolution of the patterns was 0.20 .mu.m L/S.
Example 114
[0582] This example is a comparative example.
[0583] The procedure of Example 113 was repeated. However, in this
example, for the comparison purpose, the copolymer used as the
resist material was a copolymer of 2-methyl-2-adamantyl
methacrylate and anhydrous itaconic acid which was prepared in
accordance with the method similar to that of Example 107, is
represented by the following formula, and has a composition ratio
(m:n) of 55:45, weight average molecular weight (Mw) of 8,500 and
degree of polydispersion (Mw/Mn) of 1.9. 115
[0584] Using this copolymer, the resist process was carried out in
accordance with the method described in Example 108. That is, the
photoacid generator TPSSO.sub.3CF.sub.3 in an amount of 2 wt. %
with regard to the copolymer was added to the copolymer of
2-methyl-2-adamantyl methacrylate and anhydrous itaconic acid, and
the mixture was dissolved in cyclohexanone to make a resist
solution containing the copolymer in an amount of 14 wt. %. The
resist solution was spin-coated on a silicon substrate which has
been treated with HMDS, and prebaked at 100.degree. C. for 60
seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0585] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) on a
hot plate at 100.degree. C. for 60 seconds. The postbaked resist
coating was developed with the alkaline developer, NMD-3 (trade
name) commercially available from Tokyo Ohka Co., for 60 seconds,
and rinsed for 30 seconds in a purified water. No resist pattern
was formed, because the resist coating was dissolved and removed
from the silicon substrate. In this example, a threshold energy Eth
of the exposure dose was 15 mJ/cm.sup.2, i.e., very low
sensitivity.
Example 115
[0586] The procedure of Example 108 was repeated with the proviso
that in the development step, an aqueous solution of the same
concentration (2.38%; 0.27N) of tetrabutylammonium hydroxide (TBAH)
was used as a developer in place of 0.27N tetramethylammonium
hydroxide (NMD-3). Satisfactory positive resist patterns comparable
to those of Example 108 were obtained. The threshold energy Eth was
5 mJ/cm.sup.2, and the resolution was 0.16 .mu.m L/S.
Example 116
[0587] The procedure of Example 108 was repeated. However, in this
example, the copolymer used as the resist material was a terpolymer
of 2-butyl-2-adamantyl methacrylate, t-butyl methacrylate and
methacrylic acid which was prepared in accordance with the method
similar to that of Example 107, is represented by the following
formula, and has a composition ratio (l:m:n) of 58:22:20, weight
average molecular weight (Mw) of 12,000 and degree of
polydispersion (Mw/Mn) of 2.6. 116
[0588] Using this terpolymer, the resist process was carried out in
accordance with the method described in Example 108. That is, the
photoacid generator TPSSO.sub.3CF.sub.3 in an amount of 2 wt. %
with regard to the terpolymer was added to the terpolymer of
2-butyl-2-adamantyl methacrylate, t-butyl methacrylate and
methacrylic acid, and the mixture was dissolved in cyclohexanone to
make a resist solution containing the terpolymer in an amount of 14
wt. %. The resist solution was spin-coated on a silicon substrate
which has been treated with HMDS, and prebaked at 100.degree. C.
for 60 seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0589] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) on a
hot plate at 100.degree. C. for 60 seconds. The postbaked resist
coating was developed with the alkaline developer, 10 times-diluted
solution of NMD-3 (trade name) commercially available from Tokyo
Ohka Co., for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained. In
this example, a threshold energy Eth of the exposure dose was 3
mJ/cm.sup.2, and the resolution of the patterns was 0.18 .mu.m
L/S.
Example 117
[0590] This example is a comparative example.
[0591] The procedure of Example 116 was repeated. However, in this
example, the terpolymer used as the resist material was a
terpolymer of 2-methyl-2-adamantyl methacrylate, t-butyl
methacrylate and methacrylic acid which was prepared in accordance
with the method similar to that of Example 107, is represented by
the following formula, and has a composition ratio (1:m:n) of
55:27:20, weight average molecular weight (Mw) of 160,000 and
degree of polydispersion (Mw/Mn) of 1.6. 117
[0592] Using this terpolymer, the resist process was carried out in
accordance with the method described in Example 108. That is, the
photoacid generator TPSSO.sub.3CF.sub.3 in an amount of 2 wt. %
with regard to the terpolymer was added to the terpolymer of
2-methyl-2-adamantyl methacrylate, t-butyl methacrylate and
methacrylic acid, and the mixture was dissolved in cyclohexanone to
make a resist solution containing the terpolymer in an amount of 14
wt. %. The resist solution was spin-coated on a silicon substrate
which has been treated with HMDS, and prebaked at 100.degree. C.
for 60 seconds on a hot plate to form a 0.4-.mu.m thick resist
coating.
[0593] After prebaking, the resist coating was selectively exposed
to a pattern of laser light having a wavelength of 193 nm on a ArF
excimer laser exposure system (Nikon, NA=0.55). The exposed resist
coating was then subjected to the post-exposure baking (PEB) on a
hot plate at 100.degree. C. for 60 seconds. The postbaked resist
coating was developed with the alkaline developer, 10 times-diluted
solution of NMD-3 (trade name) commercially available from Tokyo
Ohka Co., for 60 seconds, and rinsed for 30 seconds in a purified
water. The positive resist patterns which correspond to the pattern
of the laser light as an exposure source were thus obtained. In
this example, a threshold energy Eth of the exposure dose was 4
mJ/cm.sup.2, however, the resolution was poor. That is, notable
falling down and breakage of the patterns were observed at the
patterns of 0.19 .mu.m L/S or less.
* * * * *