U.S. patent application number 10/716632 was filed with the patent office on 2004-04-15 for positive-working photoresist composition.
Invention is credited to Maemori, Satoshi, Nakao, Taku, Nitta, Kazuyuki, Sato, Kazufumi.
Application Number | 20040072103 10/716632 |
Document ID | / |
Family ID | 13537353 |
Filed Date | 2004-04-15 |
United States Patent
Application |
20040072103 |
Kind Code |
A1 |
Sato, Kazufumi ; et
al. |
April 15, 2004 |
Positive-working photoresist composition
Abstract
Disclosed is a novel chemical-amplification positive-working
photoresist composition capable of giving a patterned resist layer
with excellent properties such as photosensitivy, pattern
resolution, heat resistance and cross sectional profile of the
patterned resist layer. The composition is characterized by the use
of, as the film-forming resinous component, a hydroxyl-containing
resinous ingredient which is a combination of a first resin of
which from 30 to 60% of the hydroxyl groups are substituted by
acid-dissociable solubility-reducing groups and a second resin of
which from 5 to 20% of the hydroxyl groups are substituted by
acid-dissociable groups of the same kind as in the first resin in a
weight proportion of 1.9 to 9:1.
Inventors: |
Sato, Kazufumi;
(Sagamihara-shi, JP) ; Maemori, Satoshi;
(Sagamihara-shi, JP) ; Nakao, Taku; (Fujisawa-shi,
JP) ; Nitta, Kazuyuki; (Ebina-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
13537353 |
Appl. No.: |
10/716632 |
Filed: |
November 20, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10716632 |
Nov 20, 2003 |
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10114258 |
Apr 3, 2002 |
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6677103 |
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10114258 |
Apr 3, 2002 |
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09521205 |
Mar 8, 2000 |
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6444394 |
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Current U.S.
Class: |
430/311 |
Current CPC
Class: |
G03F 7/0392 20130101;
Y10S 430/106 20130101 |
Class at
Publication: |
430/311 |
International
Class: |
G03C 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 1999 |
JP |
11-74097 |
Claims
What is claimed is:
1. A chemical-amplification positive-working photoresist
composition which comprises, as a uniform solution in an organic
solvent: (A) a polyhydroxystyrene-based resinous ingredient of
which the hydroxyl groups are partly substituted by
acid-dissociable substituent groups capable of being dissociated by
interacting with an acid; and (B) a radiation-sensitive
acid-generating compound capable of releasing an acid by
irradiation with a radiation, the resinous ingredient as the
component (A) being a combination comprising (A1) a first
polyhydroxystyrene resin substituted for a part of the hydroxyl
groups by acid-dissociable substituent groups and (A2) a second
polyhydroxy-styrene resin substituted for a part of the hydroxyl
groups by acid-dissociable substituent groups which are the same as
in the first polyhydroxystyrene resin (A1), of which the degree of
substitution by the substituent groups for a part of the hydroxyl
groups in the first polyhydroxystyrene resin (A1) is larger than
the degree of substitution in the second polyhydroxystyrene resin
(A2) with the proviso that the ratio of the maximum weight-average
molecular weight Mw.sub.max to the minimum weight-average molecular
weight Mw.sub.min in the first and second polyhydroxystyrene resins
(A1) and (A2) is smaller than 1.5.
2. The chemical-amplification positive-working photoresist
composition as claimed in claim 1 in which the overall degree of
substitution in the resinous ingredient as the component (A) for a
part of the hydroxyl groups by the acid-dissociable substituent
groups is in the range from 5 to 60%.
3. The chemical-amplification positive-working photoresist
composition as claimed in claim 1 in which the acid-dissociable
substituent group is selected from the group consisting of tertiary
alkoxycarbonyl groups, tertiary alkyl groups, alkoxyalkyl groups
and cyclic ether groups.
4. The chemical-amplification positive-working photoresist
composition as claimed in claim 3 in which the acid-dissociable
substituent group is selected from the group consisting of
tert-butoxycarbonyl group, tert-butyl group, tetrahydropyranyl
group, tetrahydrofuranyl group, 1-ethoxyethyl group and
1-methoxypropyl group.
5. The chemical-amplification positive-working photoresist
composition as claimed in claim 1 in which the
polyhydroxystyrene-based resinous ingredient as the component (A)
is a combination of (A1) a first polyhydroxystyrene resin
substituted for from 30 to 60% of the hydroxyl groups by the
acid-dissociable substituent groups and (A2) a second
polyhydroxystyrene resin substituted for from 5 to 20% of the
hydroxyl groups by the acid-dissociable substituent groups.
6. The chemical-amplification positive-working photoresist
composition as claimed in claim 5 in which the
polyhydroxystyrene-based resinous ingredient as the component (A)
is a combination of the first and second polyhydroxystyrene resins
(A1) and (A2) in a weight proportion in the range from 1:9 to
9:1.
7. The chemical-amplification positive-working photoresist
composition as claimed in claim 5 in which the
polyhydroxystyrene-based resinous ingredient as the component (A)
is a combination of (A1) a first polyhydroxystyrene resin
substituted for from 35 to 60% of the hydroxyl groups by the
acid-dissociable substituent groups and (A2) a second
polyhydroxystyrene resin substituted for from 5 to 15% of the
hydroxyl groups by the acid-dissociable substituent groups.
8. The chemical-amplification positive-working photoresist
composition as claimed in claim 7 in which the
polyhydroxystyrene-based resinous ingredient as the component (A)
is a combination of the first and second polyhydroxystyrene resins
(A1) and (A2) in a weight proportion in the range from 4:6 to
1:9.
9. The chemical-amplification positive-working photoresist
composition as claimed in claim 5 in which the
polyhydroxystyrene-based resinous ingredient as the component (A)
is a combination of (A1) a first polyhydroxystyrene resin
substituted for from 30 to 60% of the hydroxyl groups by
tert-butoxycarbonyl groups and (A2) a second polyhydroxystyrene
resin substituted for from 5 to 20% of the hydroxyl groups by
tert-butoxycarbonyl groups.
10. The chemical-amplification positive-working photoresist
composition as claimed in claim 1 in which the ratio of the maximum
weight-average molecular weight Mw.sub.max to the minimum
weight-average molecular weight Mw.sub.min in the first and second
polyhydroxystyrene resins (A1) and (A2) is smaller than 1.3.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a positive-working
photoresist composition or, more particularly, to a
positive-working chemical-amplification photoresist composition
capable of being in compliance with various requirements for the
performance of the photoresist relative to photosensitivity,
pattern resolution, heat resistance, focusing-depth latitude, cross
sectional profile of patterned resist layers, holding stability of
coating layers of the composition, dependence on the nature of the
substrate surface and so on as well as good reproducibility of
product quality.
[0002] As compared with conventional photoresist compositions
containing a naphthoquinone diazide sulfonic acid ester as the
photosensitive ingredient and a novolak resin as the film-forming
ingredient, photoresist compositions of the chemical-amplification
type exhibit excellent photosensitivity and pattern resolution so
that they are highlighted in recent years in the photolithographic
technology for the manufacture of fine electronic devices. As a
result of extensive investigations to accomplish improvements of
the photoresist performance, a great variety of
chemical-amplification photoresist compositions have been proposed,
some of which are already under current use in the electronic
industry.
[0003] Chemical-amplification photoresist compositions can be
classified into positive-working and negative-working photoresist
compositions, each of which comprises a radiation-sensitive
acid-generating agent capable of releasing an acid by the
irradiation with a radiation such as ultraviolet light and a
film-forming resinous ingredient which is subject to a change in
the solubility behavior in an aqueous alkaline solution by
interacting with the acid.
[0004] In a positive-working photoresist composition of the
chemical-amplification type, a typical film-forming resinous
ingredient is a polyhydroxystyrene resin of which a part of the
hydroxyl groups are substituted by tertiary alkoxycarbonyl groups
such as tert-butoxycarbonyl groups or cyclic ether groups such as
tetrahydropyranyl groups. In a negative-working photoresist
composition, on the other hand, the film-forming resinous
ingredient is a combination of an acid-crosslinkable compound such
as a melamine resin and urea resin with a polyhydroxystyrene resin
unsubstituted or substituted for a part of the hydroxyl groups as
mentioned above or a novolak resin.
[0005] Various proposals and attempts have been made relative to
each of the ingredients in the chemical-amplification photoresist
compositions with an object to improve the performance of the
photoresist layer in respect of photosensitivity, pattern
resolution, heat resistance, focusing-depth latitude, cross
sectional profile of patterned resist layers, holding stability of
the resist layer as formed by coating, dependence on the nature of
the substrate surface and other properties.
[0006] For example, a positive-working photoresist composition, in
which the film-forming resinous ingredient is a combination of two
resins having different kinds of the acid-dissociable substituent
groups, is disclosed in Japanese Patent Kokai 8-15864, 8-262721,
9-160244, 9-179301, 9-222732, 9-222733, 10-31309 and 10-48826 and
elsewhere. A proposal is made in Japanese Patent Kokai 9-160246,
9-211868, 9-274320 and 9-311452 for the use of a ternary
copolymeric resin consisting of hydroxystyrene units having
acid-dissociable groups of a first type, hydroxystyrene units
having acid-dissociable groups of a second type and unsubstituted
hydroxystyrene units in a positive-working composition. Japanese
Patent Kokai 9-236921 proposes a positive-working photosensitive
composition containing an alkali-soluble resin having phenolic
hydroxyl groups and a weight-average molecular weight of 6000 to
60000 including 10% by weight or less of the fraction of a
molecular weight smaller than 4000 and at least 80% by weight of
the fraction of a molecular weight of 4000 to 70000. Japanese
Patent Kokai 9-90639 proposes a positive-working composition in
which the resinous ingredient is a combination of a high molecular
weight polymer substituted by acid-dissociable groups having a
molecular weight dispersion of 1.5 or smaller and a low molecular
weight polymer substituted by acid-dissociable groups having a
molecular weight dispersion of 5.0 or smaller with the proviso that
the ratio of the high and low weight-average molecular weights of
the resins is at least 1.5. Japanese Patent Kokai 7-199468 proposes
a photosensitive composition containing a compound of low polarity
of the molecules to exhibit a low dissolving velocity in alkali and
another compound of high polarity of the molecules to exhibit a
high dissolving velocity in alkali.
[0007] As these chemical-amplification positive-working photoresist
compositions are produced and consumed in large quantities, various
problems have to be solved by the producers thereof in connection
with the matter of quality control in order to fully comply with
the needs of the consumers.
[0008] As for the base resin as the film-forming resinous
ingredient playing an important role in the photoresist
composition, for example, a serious problem is in the low
reproducibility in the quality of the resin products among the
preparation lots even if the preparation conditions are controlled
constant sometimes leading to an unacceptable product quality.
Another problem recently under attention is occurrence of surface
defects in the patterned resist layer after development along with
the introduction of the surface-defect tester called KLA (a trade
name) into the production line of the photoresist consumers.
[0009] Along with the recent trend in the semiconductor industries
toward finer and finer patterning, some of the photoresist
consumers request very delicate modification of the photoresist
properties to comply with variations in the exposure light system,
nature of the substrate surface, condition of pattern isolation and
so on so that the resinous ingredients in the compositions also
must comply with the respective requests of the consumers.
SUMMARY OF THE INVENTION
[0010] Under the above described technological situations, the
present invention has an object to provide a chemical-amplification
positive-working photoresist composition having good adaptability
to the quality variation among the production lots of the base
resin for the resinous film-forming ingredient thus to provide
various grades of photoresist products to comply with so
diversified requirements of the photoresist consumers.
[0011] Thus, the chemical-amplification positive-working
photoresist composition of the present invention is a uniform
solution in an organic solvent, which comprises:
[0012] (A) a polyhydroxystyrene-based resinous ingredient of which
the hydroxyl groups are partly substituted by acid-dissociable
substituent groups capable of being dissociated by interacting with
an acid; and
[0013] (B) a radiation-sensitive acid-generating compound capable
of releasing an acid by irradiation with a radiation, the resinous
ingredient (A) being a combination comprising (A1) a first
substituted polyhydroxystyrene resin and (A2) a second substituted
polyhydroxystyrene resin, the substituent groups in the first and
second resins (A1) and (A2) being of the same kind, of which the
degree of substitution by the substituent groups for a part of the
hydroxyl groups in the first resin (A1) is larger than that in the
second resin (A2) with the proviso that the ratio of the maximum
weight-average molecular weight Mw.sub.max to the minimum
weight-average molecular weight Mw.sub.min in each of the first and
second resins (A1) and (A2), i.e. Mw.sub.max:Mw.sub.min, does not
exceed 1.5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] It is essential that, in the inventive photoresist
composition, the resinous ingredient (A) is a combination of two
polyhydroxystyrene resins substituted by acid-dissociable groups
for a part of the hydroxyl groups in different degrees of
substitution each from the other. The acid-dissociable substituent
group must have an effect of insolubilizing the polyhydroxystyrene
resin substituted thereby in an aqueous alkaline solution while the
substituent groups are dissociated by interacting with an acid when
irradiated with a radiation so as to increase the solubility of the
resin in an aqueous alkaline solution.
[0015] The substituted hydroxyl group-containing resinous compound
usable in the inventive photoresist composition is not particularly
limitative and can be selected from those used in conventional
chemical-amplification positive-working photoresist compositions
without particular limitations. In order to accomplish adequate
alkali solubility, adhesive bondability to the substrate surface
and heat resistance, a preferable resinous compound is a
polyhydroxystyrene resin of which a part of the hydroxyl groups are
substituted by the acid-dissociable alkali solubility-reducing
substituent groups.
[0016] Any types of known acid-dissociable substituent groups can
be used in the resinous ingredient (A) in the present invention by
selecting from those conventionally utilized in
chemical-amplification positive-working photoresist compositions.
Tertiary alkoxycarbonyl groups, tertiary alkyl groups, alkoxyalkyl
groups and cyclic ether groups are preferred in consideration of
their good acid-dissociability, heat resistance and cross sectional
profile of the patterned resist layer.
[0017] The tertiary alkoxycarbonyl group is exemplified by
tert-butyloxycarbonyl and tert-amyloxycarbonyl groups. The tertiary
alkyl group is exemplified by tert-butyl and tert-amyl groups. The
alkoxyalkyl group is exemplified by 1-ethoxyethyl and
1-methoxypropyl groups. The cyclic ether group is exemplified by
tetrahydropyranyl and tetrahydrofuranyl groups.
[0018] Polymeric resins having hydroxystyrene units substituted for
the hydroxyl group by the above named acid-dissociable substituent
group include (1) a polyhydroxystyrene resin of which from 5 to 60%
of the hydroxyl groups are substituted by the acid-dissociable
substituent groups selected from those mentioned above and (2) a
polyhydroxystyrene resin of which from 10 to 49% of the hydroxyl
groups are substituted by the acid-dissociable substituent groups
selected from tertiary alkoxycarbonyl groups, tertiary alkyl groups
and cyclic ether groups and from 10 to 49% of the hydroxyl groups
are substituted by alkoxyalkyl groups.
[0019] Examples of the combinations of polymeric compounds suitable
as the component (A) in the inventive photoresist composition
include (a1) a combination of a first polyhydroxystyrene resin of
which from 30 to 60% of the hydroxyl groups are substituted by
tert-butoxycarbonyl groups and a second polyhydroxystyrene resin of
which from 5 to 20% of the hydroxyl groups are substituted by
tert-butoxycarbonyl groups, (a2) a combination of a first
polyhydroxystyrene resin of which from 30 to 60% of the hydroxyl
groups are substituted by tetrahydropyranyl groups and a second
polyhydroxystyrene resin of which from 5 to 20% of the hydroxyl
groups are substituted by tetrahydropyranyl groups and (a3) a
combination of a first polyhydroxystyrene resin of which from 30 to
60% of the hydroxyl groups are substituted by 1-ethoxyethyl groups
and a second polyhydroxystyrene resin of which from 5 to 20% of the
hydroxyl groups are substituted by 1-ethoxyethyl groups.
[0020] Other examples of suitable combinations include (a4) a
combination of two copolymers each consisting of from 10 to 49% by
moles of the hydroxystyrene units substituted by
tert-butoxycarbonyl groups, from 10 to 49% by moles of the
hydroxystyrene units substituted by 1-ethoxyethyl groups and from 2
to 80% by moles of unsubstituted hydroxystyrene units assuming that
the total degrees of substitution for the hydroxyl groups are
different between the two resins, (a5) a combination of two
copolymers each consisting of from 10 to 49% by moles of the
hydroxystyrene units substituted by tert-butyl groups, from 10 to
49% by moles of the hydroxystyrene units substituted by
1-ethoxyethyl groups and from 2 to 80% by moles of unsubstituted
hydroxystyrene units assuming that the total degrees of
substitution for the hydroxyl groups are different between the two
resins and (a6) a combination of two copolymers each consisting of
from 10 to 49% by moles of the hydroxystyrene units substituted by
tetrahydropyranyl groups, from 10 to 49% by moles of the
hydroxystyrene units substituted by 1-ethoxyethyl groups and from 2
to 80% by moles of unsubstituted hydroxystyrene units assuming that
the total degrees of substitution for the hydroxyl groups are
different between the two resins.
[0021] Each of the above described polymeric resins should have a
weight-average molecular weight in the range from 2000 to 50000 or,
preferably, from 5000 to 15000 and the molecular weight dispersion
given by the ratio of the weight-average molecular weight Mw to the
number-average molecular weight Mn, i.e. Mw:Mn, does not exceed 5.0
or, preferably, does not exceed 2.0 since the molecular weight
dispersion should be as small as possible in order to accomplish
improvements in the pattern resolution and heat resistance of the
resist.
[0022] The resinous ingredient (A) in the inventive composition is
a combination of at least two kinds of the above described
polyhydroxystyrene-based resins while, in each of the constituent
resins, the ratio of the maximum weight-average molecular weight
Mw.sub.max to the minimum weight-average molecular weight
Mw.sub.min, i.e. Mw.sub.max:Mw.sub.min, should be smaller than 1.5
or, preferably, smaller than 1.3 or, more preferably, about 1.0.
This limitation serves to ensure uniformity of the respective
polymeric resins.
[0023] It is essential that the acid-dissociable substituent groups
in one of the respective polymeric resins constituting the
combination are of the same kind as those in the other constituent
resins having different degrees of substitution. This limitation
has an effect to ensure different velocities of dissolving in an
aqueous alkaline solution so that the photoresist layer of the
inventive composition can be developed with good uniformity in the
light-exposed areas to suppress occurrence of surface defects.
[0024] Assuming that the resinous ingredient (A) in the inventive
composition is a combination of first and second
polyhydroxystyrene-based polymeric resins (A1) and (A2), in
particular, the degrees of substitution for a part of the hydroxyl
groups in the first and second resins are preferably in the ranges
of from 30 to 60% and from 5 to 20%, respectively, or, preferably,
from 35 to 60% and from 5 to 15%, respectively, since the
difference in the degrees of substitution between the two polymeric
resins should preferably be as large as possible in order to fully
suppress occurrence of surface defects in the photoresist
layer.
[0025] When the polyhydroxystyrene-based resins constituting the
resinous ingredient (A) satisfy all of the above described
requirements, occurrence of surface defects after development of
the resist layer can be fully prevented without adversely affecting
other properties such as photosensitivity, pattern resolution and
cross sectional profile of the patterned resist layer.
[0026] The compounding proportion of the two kinds or more of the
polyhydroxystyrene-based resins forming the combination as the
resinous ingredient (A) of the inventive composition can be readily
selected by making reference to the dissolving velocity of the
resinous ingredient in an aqueous alkaline solution. For example,
an appropriate substrate is provided with a coating layer of the
component (A) and immersed in a 2.38% by weight aqueous solution of
tetramethylammonium hydroxide to determine the rate of thickness
reduction of the coating layer. Namely, the compounding proportion
of the constituent resins is selected such that the above mentioned
rate of thickness reduction does not exceed 100 nm per minute at
23.degree. C.
[0027] When the component (A) is the above described combination
(a1), for example, the mixing proportion of the two resins is
selected such that the above mentioned velocity does not exceed 100
nm/minute at 23.degree. C. by considering that the velocities of
the first and second resins are 0 to 50 nm/minute and 100 to 300
nm/minute, respectively.
[0028] Similarly, the mixing proportion of the two resins in the
combination (a2) is selected such that the above mentioned velocity
does not exceed 100 nm/minute at 23.degree. C. by considering that
the velocities of the first and second resins are 0 to 50 nm/minute
and 100 to 300 nm/minute, respectively. Further, the mixing
proportion of the two resins in the combination (a3) is selected
such that the above mentioned velocity does not exceed 100
nm/minute at 23.degree. C. by considering that the velocities of
the first and second resins are 0 to 50 nm/minute and 100 to 300
nm/minute, respectively.
[0029] It is usual in order to effectively prevent occurrence of
surface defects in the patterned resist layer after development
that the first polymeric resin and the second polymeric resin are
combined in a weight proportion in the range from 1:9 to 9:1 or,
preferably, from 4:6 to 1:9. In order to accomplish further
improvement in the resist characteristics such as photosensitivity,
pattern resolution and cross sectional profile of the patterned
resist layer, it is preferable that the component (A) is a mixture
of the combinations (a1) and (a3) or a mixture of the combinations
(a2) and (a3).
[0030] In the positive-working photoresist composition of the
invention, the acid-generating agent as the component (B), which
releases an acid by the irradiation with a radiation, is not
particularly limitative and can be selected from those known
compounds used as an acid-generating agent in the prior art
photoresist compositions of the chemical-amplification type without
particular limitations. Examples of suitable acid-generating
compounds include diazomethane compounds, nitrobenzyl derivatives,
sulfonic acid esters, onium salts, benzoin tosylate compounds,
halogen-containing triazine compounds and cyano group-containing
oxime sulfonate compounds, of which diazomethane compounds and
onium salts of which the anionic part is formed from a
halogenoalkyl sulfonic acid having 1 to 15 carbon atoms are
preferable.
[0031] The diazomethane compound is exemplified by
bis(p-toluenesulfonyl) diazomethane, bis(1,1-dimethylethylsulfonyl)
diazomethane, bis(cyclohexylsulfonyl) diazomethane and
bis(2,4-dimethylphenylsulfonyl) diazomethane. The onium salt above
mentioned is exemplified by bis(4-methoxyphenyl)iodonium
trifluoromethane sulfonate, bis(p-tert-butylphenyl)iodonium
trifluoromethane sulfonate, (4-methoxyphenyl)diphenylsulfonium
trifluoromethane sulfonate and (p-tert-butylphenyl)diphenyl
sulfonium trifluoromethane sulfonate.
[0032] The above named various acid-generating compounds can be
used as the component (B) either singly or as a combination of two
kinds or more according to need. The amount of the component (B) is
in the range, usually, from 0.5 to 30 parts by weight or,
preferably, from 1 to 10 parts by weight per 100 parts by weight of
the resinous ingredient as the component (A). When the amount of
the component (B) is too small, images for patterning cannot be
formed while, when the amount thereof is too large, difficulties
are encountered in the preparation of the composition in the form
of a uniform solution suitable for coating or, even if the
composition could be prepared, the solution suffers a decrease in
the storage stability.
[0033] The positive-working photoresist composition of the present
invention is prepared by uniformly dissolving the components (A)
and (B) each in a specified amount in a suitable organic solvent.
Though not particularly limitative, examples of preferable organic
solvents include, in respect of the coating workability of the
photoresist composition and prevention of occurrence of surface
defects, propyleneglycol monoalkyl ether acetates such as
propyleneglycol monomethyl ether acetate as well as mixtures
thereof with lower alkyl lactates such as methyl lactate, ethyl
lactate, butyl lactate and pentyl lactate or propyleneglycol
mono(lower alkyl) ethers such as propyleneglycol monomethyl ether
and propyleneglycol monoethyl ether.
[0034] It is optional that the positive-working photoresist
composition of the invention is compounded according to need, in
addition to the above described components (A) and (B), with
various kinds of known additives including amine compounds to
improve the holding stability of the resist coating layer or to
prevent excessive diffusion of the acid generated from the
component (B), carboxylic acids to improve the photosensitivity of
the composition and halation-preventing agents each in a limited
amount.
[0035] The procedure for the photolithographic patterning work by
using the positive-working photoresist composition of the invention
can be conventional. Namely, a substrate such as a semiconductor
silicon wafer is coated with the photoresist composition in the
form of a uniform solution on a suitable coating machine such as a
spinner followed by drying to form a resist layer which is
pattern-wise exposed to a radiation such as ultraviolet light, deep
ultraviolet light, excimer laser beams and the like on a minifying
projection light-exposure machine through a photomask bearing a
desired pattern or irradiated by scanning of electron beams
according to the desired pattern to form a latent image of the
pattern followed by a post-exposure baking treatment. Thereafter,
the latent image is developed in a development treatment by using
an aqueous alkaline solution such as a 1 to 10% by weight aqueous
solution of tetramethylammonium hydroxide to dissolve away the
resist layer in the exposed areas leaving a patterned resist layer
having fidelity to the photomask pattern.
[0036] In the following, the present invention is described in more
detail by way of Examples, which, however, never limit the scope of
the invention in any way, as preceded by a description of the
testing procedures for the evaluation of the photoresist
compositions and Reference Examples for preparation and
characterization of the combination of two different resins as the
component (A). In the following description, the term of "parts"
always refers to "parts by weight".
[0037] (1) Photosensitivity of the Photoresist Composition
[0038] A silicon wafer was coated with the photoresist composition
on a spinner followed by drying on a hot plate at 90.degree. C. for
90 seconds to form a dried resist layer having a thickness of 0.7
.mu.m. The resist layer was exposed to light on a minifying
projection exposure machine (Model NSR-2005EX8A, manufactured by
Nikon Co.) in step-wise increased exposure dose by an increment of
1 mJ/cm.sup.2 followed by a post-exposure baking treatment at
110.degree. C. for 90 seconds and then subjected to a development
treatment at 23.degree. C. for 60 seconds in a 2.38% by weight
aqueous solution of tetramethylammonium hydroxide followed by rinse
with water for 30 seconds and drying. The minimum exposure dose by
which the resist layer on the substrate surface had been completely
dissolved away was taken as the photosensitivity of the
composition.
[0039] (2) Cross Sectional Profile of Patterned Resist Layer
[0040] A line-and-space patterned resist layer of 0.25 .mu.m line
width formed in the same manner as in (1) above was examined on a
scanning electron microscopic photograph for the cross section and
the results were rated as A for a good orthogonal profile, B for an
upwardly narrowing profile and C for a profile with a rounded top
flat and trailing skirts.
[0041] (3) Pattern Resolution
[0042] Resist layers were patterned in line-and-space patterns of
varied line widths in the same manner as in (1) above and the
critical line width was recorded as the pattern resolution.
[0043] (4) Surface Defects
[0044] A resist layer patterned in the same manner as in (1) above
on a 8 inch silicon wafer was examined by using a surface-defects
tester (Model KLA, manufactured by KLA Co.) and the number of
defects was counted on the silicon wafer and recorded.
[0045] (5) Heat Resistance
[0046] A line-and-space patterned resist layer of 0.25 .mu.m line
width formed in the same manner as in (1) above was heated on a hot
plate at 120.degree. C. for 90 seconds. Thereafter, the cross
sectional profile of the patterned resist layer was examined on a
scanning electron microscopic photograph to record the results as A
for an orthogonal profile and B for a profile showing thermal flow
of the resist layer.
REFERENCE EXAMPLE 1
[0047] A solution of a base resin for the photoresist composition
was prepared by dissolving, in 400 parts of propyleneglycol
monomethyl ether acetate, 40 parts of a first partially substituted
polyhydroxystyrene resin, of which 45% of the hydroxyl groups were
substituted by tert-butoxycarbonyl groups, having a weight-average
molecular weight of 10000 with a molecular weight dispersion of 1.2
and exhibiting no dissolution in a 2.38% by weight aqueous solution
of tetramethylammonium hydroxide and 60 parts of a second partially
substituted polyhydroxystyrene resin, of which 20% of the hydroxyl
groups were substituted by tert-butoxycarbonyl groups, having a
weight-average molecular weight of 10000 with a molecular weight
dispersion of 1.2 and exhibiting a dissolving velocity of 150
nm/minute in a 2.38% by weight aqueous solution of
tetramethylammonium hydroxide.
[0048] A coating layer formed on a silicon wafer by coating with
the above prepared solution of the base resin combination followed
by drying exhibited a dissolving velocity of 30 nm/minute under the
same testing conditions.
REFERENCE EXAMPLE 2
[0049] A solution of a base resin for the photoresist composition
was prepared by dissolving, in 400 parts of propyleneglycol
monomethyl ether acetate, 30 parts of a first partially substituted
polyhydroxystyrene resin, of which 50% of the hydroxyl groups were
substituted by tetrahydropyranyl groups, having a weight-average
molecular weight of 10000 with a molecular weight dispersion of 1.2
and exhibiting no dissolution in a 2.38% by weight aqueous solution
of tetramethylammonium hydroxide and 70 parts of a second partially
substituted polyhydroxystyrene resin, of which 15% of the hydroxyl
groups were substituted by tetrahydropyranyl groups, having a
weight-average molecular weight of 10000 with a molecular weight
dispersion of 1.2 and exhibiting a dissolving velocity of 170
nm/minute in a 2.38% by weight aqueous solution of
tetramethylammonium hydroxide.
[0050] A coating layer formed on a silicon wafer by coating with
the above prepared solution of the base resin combination followed
by drying exhibited a dissolving velocity of 20 nm/minute under the
same testing conditions.
REFERENCE EXAMPLE 3
[0051] A solution of a base resin for the photoresist composition
was prepared by dissolving, in 400 parts of propyleneglycol
monomethyl ether acetate, 45 parts of a first partially substituted
polyhydroxystyrene resin, of which 45% of the hydroxyl groups were
substituted by 1-ethoxyethyl groups, having a weight-average
molecular weight of 10000 with a molecular weight dispersion of 1.2
and exhibiting a dissolving velocity of 5 nm/minute in a 2.38% by
weight aqueous solution of tetramethylammonium hydroxide and 55
parts of a second partially substituted polyhydroxystyrene resin,
of which 25% of the hydroxyl groups were substituted by
1-ethoxyethyl groups, having a weight-average molecular weight of
10000 with a molecular weight dispersion of 1.2 and exhibiting a
dissolving velocity of 130 nm/minute in a 2.38% by weight aqueous
solution of tetramethylammonium hydroxide.
[0052] A coating layer formed on a silicon wafer by coating with
the above prepared solution of the base resin combination followed
by drying exhibited a dissolving velocity of 40 nm/minute under the
same testing conditions.
REFERENCE EXAMPLE 4
[0053] A solution of a base resin for the photoresist composition
was prepared by dissolving, in 400 parts of propyleneglycol
monomethyl ether acetate, 45 parts of the same first partially
tert-butoxycarbonyl-substit- uted polyhydroxystyrene resin as used
in Reference Example 1 and 55 parts of a second partially
substituted polyhydroxystyrene resin, of which 20% of the hydroxyl
groups were substituted by tert-butoxycarbonyl groups, having a
weight-average molecular weight of 5000 with a molecular weight
dispersion of 1.2 and exhibiting a dissolving velocity of 160
nm/minute in a 2.38% by weight aqueous solution of
tetramethylammonium hydroxide.
[0054] A coating layer formed on a silicon wafer by coating with
the above prepared solution of the base resin combination followed
by drying exhibited a dissolving velocity of 30 nm/minute under the
same testing conditions.
REFERENCE EXAMPLE 5
[0055] A solution of a base resin for the photoresist composition
was prepared by dissolving, in 400 parts of propyleneglycol
monomethyl ether acetate, 35 parts of the same first partially
tetrahydropyranyl-substitut- ed polyhydroxystyrene resin as used in
Reference Example 2 and 65 parts of a second partially substituted
polyhydroxystyrene resin, of which 15% of the hydroxyl groups were
substituted by tetrahydropyranyl groups, having a weight-average
molecular weight of 5000 with a molecular weight dispersion of 1.2
and exhibiting a dissolving velocity of 180 nm/minute in a 2.38% by
weight aqueous solution of tetramethylammonium hydroxide.
[0056] A coating layer formed on a silicon wafer by coating with
the above prepared solution of the base resin combination followed
by drying exhibited a dissolving velocity of 20 nm/minute under the
same testing conditions.
REFERENCE EXAMPLE 6
[0057] A solution of a base resin for the photoresist composition
was prepared by dissolving, in 400 parts of propyleneglycol
monomethyl ether acetate, 50 parts of the same first partially
1-ethoxyethyl-substituted polyhydroxystyrene resin as used in
Reference Example 3 and 50 parts of a second partially substituted
polyhydroxystyrene resin, of which 25% of the hydroxyl groups were
substituted by 1-ethoxyethyl groups, having a weight-average
molecular weight of 5000 with a molecular weight dispersion of 1.2
and exhibiting a dissolving velocity of 150 nm/minute in a 2.38% by
weight aqueous solution of tetramethylammonium hydroxide.
[0058] A coating layer formed on a silicon wafer by coating with
the above prepared solution of the base resin combination followed
by drying exhibited a dissolving velocity of 40 nm/minute under the
same testing conditions. Example 1.
[0059] A positive-working photoresist composition was prepared by
dissolving, in 490 parts of propyleneglycol monomethyl ether
acetate, 30 parts of the same combination of the two partially
tert-butoxycarbonyl-substituted resins as in Reference Example 1,
70 parts of the same combination of the two partially
1-ethoxyethyl-substituted resins as in Reference Example 3, 7 parts
of bis(cyclohexylsulfonyl) diazomethane, 0.1 part of triethylamine
and 0.5 part of salicylic acid followed by filtration of the
solution through a membrane filter of 0.2 .mu.m pore diameter.
[0060] This positive-working photoresist composition was subjected
to the evaluation tests of the above described testing items (1) to
(5) to obtain results including:
[0061] (1) 15 mJ/cm.sup.2 of the photosensitivity;
[0062] (2) grade A of the cross sectional profile of the patterned
resist layer;
[0063] (3) 0.20 .mu.m of the pattern resolution;
[0064] (4) 5 per wafer of the surface defects; and
[0065] (5) grade A of the heat resistance.
EXAMPLE 2
[0066] The formulation of the positive-working photoresist
composition and the evaluation procedure thereof were substantially
the same as in Example 1 excepting for the replacement of the
combination of the partially tert-butoxycarbonyl-substituted
polyhydroxystyrene resins with the same amount of the resin
combination corresponding to Reference Example 2.
[0067] The results of the evaluation tests of this photoresist
composition for the testing items (1) to (5) were as follows
including:
[0068] (1) 16 mJ/cm.sup.2 of the photosensitivity;
[0069] (2) grade A of the cross sectional profile of the patterned
resist layer;
[0070] (3) 0.20 .mu.m of the pattern resolution;
[0071] (4) 7 per wafer of the surface defects; and
[0072] (5) grade A of the heat resistance.
COMPARATIVE EXAMPLE 1
[0073] A positive-working photoresist composition was prepared by
dissolving, in 490 parts of propyleneglycol monomethyl ether
acetate, 30 parts of the same combination of the two partially
tert-butoxycarbonyl-substituted resins as in Reference Example 4,
70 parts of the same combination of the two partially
1-ethoxyethyl-substituted resins as in Reference Example 6, 7 parts
of bis(cyclohexylsulfonyl) diazomethane, 0.1 part of triethylamine
and 0.5 part of salicylic acid followed by filtration of the
solution through a membrane filter of 0.2 .mu.m pore diameter.
[0074] The results of the evaluation tests of this comparative
photoresist composition for the testing items (1) to (5) were as
follows including:
[0075] (1) 15 mJ/cm.sup.2 of the photosensitivity;
[0076] (2) grade A of the cross sectional profile of the patterned
resist layer;
[0077] (3) 0.20 .mu.m of the pattern resolution;
[0078] (4) 1000 per wafer of the surface defects; and
[0079] (5) grade B of the heat resistance.
COMPARATIVE EXAMPLE 2
[0080] The formulation of the positive-working photoresist
composition and the evaluation procedure thereof were substantially
the same as in Comparative Example 1 excepting for the replacement
of the combination of the partially tert-butoxycarbonyl-substituted
polyhydroxystyrene resins with the same amount of the resin
combination corresponding to Reference Example 5.
[0081] The results of the evaluation tests of this comparative
photoresist composition for the testing items (1) to (5) were as
follows including:
[0082] (1) 16 mJ/cm.sup.2 of the photosensitivity;
[0083] (2) grade A of the cross sectional profile of the patterned
resist layer;
[0084] (3) 0.20 .mu.m of the pattern resolution;
[0085] (4) 1500 per wafer of the surface defects; and
[0086] (5) grade B of the heat resistance.
* * * * *