U.S. patent application number 10/630744 was filed with the patent office on 2004-02-05 for positive-working chemical-amplification photoresist composition.
Invention is credited to Oomori, Katsumi, Sawayanagi, Yukihiro, Uchida, Ryusuke, Yukawa, Hiroto.
Application Number | 20040023163 10/630744 |
Document ID | / |
Family ID | 16986337 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040023163 |
Kind Code |
A1 |
Yukawa, Hiroto ; et
al. |
February 5, 2004 |
Positive-working chemical-amplification photoresist composition
Abstract
Disclosed is a positive-working chemical-amplification
photoresist composition used in the patterning works in the
manufacture of semiconductor devices, with which quite satisfactory
patterning of a photoresist layer can be accomplished even on a
substrate surface provided with an undercoating film of silicon
nitride, phosphosilicate glass, borosilicate glass and the like in
contrast to the prior art using a conventional photoresist
composition with which satisfactory patterning can hardly be
accomplished on such an undercoating film. The photoresist
composition comprises, besides a film-forming resin capable of
being imparted with increased solubility in an alkaline solution by
interacting with an acid and a radiation-sensitive acid-generating
compound, a phosphorus-containing oxo acid such as phosphoric acid
and phosphonic acid or an ester thereof.
Inventors: |
Yukawa, Hiroto;
(Yokohama-shi, JP) ; Oomori, Katsumi;
(Chigasaki-shi, JP) ; Uchida, Ryusuke; (Hillsboro,
OR) ; Sawayanagi, Yukihiro; (Iida-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
16986337 |
Appl. No.: |
10/630744 |
Filed: |
July 31, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10630744 |
Jul 31, 2003 |
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10126673 |
Apr 22, 2002 |
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10126673 |
Apr 22, 2002 |
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09376304 |
Aug 18, 1999 |
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Current U.S.
Class: |
430/326 ;
430/270.1; 430/272.1; 430/311; 430/327; 430/910; 430/914; 430/921;
430/925 |
Current CPC
Class: |
Y10S 430/126 20130101;
G03F 7/0045 20130101; Y10S 430/111 20130101; Y10S 430/122 20130101;
Y10S 430/115 20130101 |
Class at
Publication: |
430/326 ;
430/270.1; 430/910; 430/914; 430/921; 430/925; 430/311; 430/327;
430/272.1 |
International
Class: |
G03F 007/039; G03F
007/20; G03F 007/30; G03C 001/73; G03C 001/76 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 21, 1998 |
JP |
10-235453 |
Claims
What is claimed is:
1. A positive-working chemical-amplification photoresist
composition which comprises, as a uniform solution in an organic
solvent: (A) 100 parts by weight of a film-forming resinous
compound having acid-dissociable solubility-reducing groups in the
molecule and capable of being imparted with an increased solubility
in an aqueous alkaline solution by interaction with an acid, which
resinous compound is a copolymeric resin comprising monomeric units
of an ester of acrylic or methacrylic acid; (B) from 1 to 20 parts
by weight of an acid-generating compound which is an onium salt
compound having a fluoroalkylsulfonate as the anionic constituent;
(C) from 0.01 to 5 parts by weight of a phosphorus-containing oxo
acid, and (D) an amine selected from the group consisting of
secondary amines and tertiary amines, in an amount sufficient to
exhibit a quenching effect.
2. The positive-working chemical-amplification photoresist
composition as claimed in claim 1 in which the
phosphorus-containing oxo acid as the component (C) is selected
from the group consisting of phosphoric acid, phosphorous acid,
phosphonic acid, phosphinic acid, phenylphosphinic acid and
phenylphosphonic acid.
3. The positive-working chemical-amplification photoresist
composition as claimed in claim 1 in which the copolymeric resin as
the component (A) consists of from 50 to 85% by moles of the
monomeric units of hydroxystyrene, from 10 to 30% by moles of the
monomeric units of styrene and from 2 to 20% by moles of the
monomeric units of an ester of acrylic acid or methacrylic
acid.
4. The positive-working chemical-amplification photoresist
composition as claimed in claim 3 in which the ester of acrylic or
methacrylic acid is a tert-alkyl acrylate or methacrylate.
5. The positive-working chemical-amplification photoresist
composition as claimed in claim 4 in which the tert-alkyl acrylate
or methacrylate is tert-butyl acrylate or methacrylate.
6. The positive-working chemical-amplification photoresist
composition as claimed in claim 1 in which the amount of the
phosphorus-containing oxo acid as the component (C) is in the range
from 0.1 to 2.0 parts by weight per 100 parts by weight of the
component (A).
7. The positive-working chemical-amplification photoresist
composition according to claim 1 wherein the amine is
triethylamine, tributylamine, dibutylamine or triethanolamine.
8. A process for forming a patterned resist layer which comprises:
a) coating a substrate with a positive-working
chemical-amplification photoresist composition which comprises, as
a uniform solution in an organic solvent: (A) 100 parts by weight
of a film-forming resinous compound having acid-dissociable
solubility-reducing groups in the molecule and capable of being
imparted with an increased solubility in an aqueous alkaline
solution by interaction with an acid, which resinous compound is a
copolymeric resin comprising monomeric units of an ester of acrylic
or methacrylic acid; (B) from 1 to 20 parts by weight of an
acid-generating compound which is an onium salt compound having a
fluoroalkylsulfonate as the anionic constituent; (C) from 0.01 to 5
parts by weight of a phosphorus-containing oxo acid, and (D) an
amine selected from the group consisting of secondary amines and
tertiary amines, in an amount sufficient to exhibit a quenching
effect., b) drying the coated substrate to form a photoresist
layer, c) patternwise exposing the photoresist layer to actinic
rays to form said patterned resist layer.
9. The process according to claim 8 wherein said actinic rays are
from a KrF excimer laser beam of 248 nm.
10. The process according to claim 8 wherein said actinic rays are
X-rays.
11. The process according to claim 8 wherein said actinic rays are
electron beams.
12. The process according to claim 8 wherein the substrate is a
semiconductor wafer.
13. The process according to claim 12 wherein the semiconductor
wafer comprises silicon.
14. The process according to claim 12 wherein the substrate to be
coated has an undercoating film containing nitrogen or containing
phosphorus and/or boron.
15. The process according to claim 14 wherein the undercoating film
comprises at least one nitrogen-containing material which is SiN,
Si.sub.3N.sub.4, SiON or TiN.
16. The process according to claim 14 wherein the undercoating
comprises at least one phosphorus and/or boron material which is
phosphosilicate glass, borosilicate glass or borophosphosilicate
glass.
17. The process according to claim 8 wherein the
phosphorus-containing oxo acid as the component (C) is selected
from the group consisting of phosphoric acid, phosphorous acid,
phosphonic acid, phosphinic acid, phenylphosphinic acid and
phenylphosphonic acid.
18. The process according to claim 8 wherein the copolymeric resin
as the component (A) consists of from 50 to 85% by moles of the
monomeric units of hydroxystyrene, from 10 to 30% by moles of the
monomeric units of styrene and from 2 to 20% by moles of the
monomeric units of an ester of acrylic acid or methacrylic
acid.
19. The process according to claim 18 wherein the ester of acrylic
or methacrylic acid is a tert-alkyl acrylate or methacrylate.
20. The process according to claim 19, wherein the tert-alkyl
acrylate or methacrylate is tert-butyl acrylate or
methacrylate.
21. The process according to claim 8 wherein the amount of the
phosphorus-containing oxo acid as the component (C) is in the range
from 0.1 to 2.0 parts by weight per 100 parts by weight of the
component (A).
22. The process according to claim 8 wherein the amine is
triethylamine, tributylamine, dibutylamine or triethanolamine.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a novel positive-working
chemical-amplification photoresist composition used in the
photolithographic works for the formation of a finely patterned
resist layer on a substrate surface in the manufacturing process of
semiconductor devices and other electronic products. More
particularly, the invention relates to a positive-working
chemical-amplification photoresist composition capable of giving an
extremely finely patterned resist layer having an excellently
orthogonal cross sectional profile free from skirt-trailing on a
substrate surface with high photosensitivity and good pattern
resolution even when the substrate surface is provided with a thin
undercoating film irrespective of the material forming the
undercoating film.
[0002] As is well known, the manufacturing process of semiconductor
devices in the modern electronic technology almost always involves
at least one step of photolithographic patterning work to form a
finely patterned resist layer on the surface of a substrate
material such as a semiconductor silicon wafer by using a
photoresist composition. Namely, the substrate surface is coated
with a photoresist composition in the form of a solution followed
by evaporation of the solvent to form a dried coating layer of the
composition which is patternwise exposed to actinic rays to form a
latent image of the pattern to be developed by using a developer
solution by utilizing the solubility difference between the exposed
and unexposed areas in the resist layer. Photoresist compositions
are classified into positive-working and negative-working ones
depending on the solubility difference caused in the photoresist
layer by the patternwise exposure to actinic rays.
[0003] While several different types of photoresist compositions
are known and employed in the prior art, it is a trend in recent
years that the so-called chemical-amplification photoresist
compositions or, in particular, positive-working
chemical-amplification photoresist compositions are more and more
highlighted by virtue of the extremely fine pattern resolution of
0.25 .mu.m or even finer and high photosensitivity attainable
therewith. Along with the trend in the semiconductor devices toward
a further and further increased density of integration, however,
extensive investigations are now under way to develop a
positive-working chemical-amplification photoresist composition
capable of giving a patterned resist layer having pattern
resolution of 0.20 .mu.m or even finer.
[0004] Chemical-amplification photoresist composition is formulated
by comprising a radiation-sensitive acid-generating compound and a
film-forming resinous ingredient capable of being imparted with an
increased or decreased solubility in an aqueous alkaline developer
solution by interacting with an acid. The principle utilized there
is that the acid released from the acid-generating compound in the
exposed areas interacts with the resinous ingredient resulting in
an increase or decrease in the solubility of the resist layer to
leave a patterned resist layer by the development treatment. By
virtue of the catalytic interaction of the radiation-released acid
with the resinous ingredient, chemical-amplification photoresist
compositions are generally excellent in the photosensitivity and
pattern resolution even with a relatively small amount of the
acid-generating compound.
[0005] In the positive-working chemical-amplification photoresist
composition, the film-forming resinous ingredient is imparted by
interacting with the radiation released acid with an increase in
the solubility in an aqueous alkaline developer solution. A most
typical film-forming resinous ingredient in the positive-working
chemical-amplification photoresist compositions is a homopolymer of
hydroxystyrene monomer or a copolymer thereof with other
copolymerizable monomers, of which at least a part of the aromatic
hydroxyl groups are substituted by acid-dissociable
solubility-reducing groups such as tert-butoxycarbonyl groups,
tetrahydropyranyl groups and the like, which are dissociated by
interacting with the radiation-released acid in the exposed areas
to increase the solubility of the resinous ingredient in the
exposed areas.
[0006] Turning now to the nature of the substrate surface, on which
a photoresist layer is formed by using the photoresist composition
of the present invention, it is rather usual that the photoresist
layer is formed not directly on the surface of a semiconductor
silicon wafer per se but on the surface of a thin undercoating film
of a great variety of materials formed on the silicon surface
depending on the particular object of patterning. Examples of the
materials of the above mentioned undercoating film covering the
intrinsic substrate surface include phosphorus-containing materials
such as phosphosilicate glass (PSG), boron-containing materials
such as borosilicate glass (BSG), boron- and phosphorus-containing
materials such as borophosphosilicate glass (BPSG), nitrogen- and
silicon-containing materials such as silicon nitrides SiN and
Si.sub.3N.sub.4 and silicon oxynitride SiON for interlayer
insulating films and protecting films on a circuit wiring layer as
well as semiconductor materials such as polycrystalline silicon
(Poly-Si) for gate electrodes and resistance elements. Further,
metallic materials such as aluminum, aluminum-silicon-copper
alloys, titanium nitride, tungsten and titanium-tungsten alloys are
used as a material of electrodes and circuit wirings.
[0007] In the manufacturing process of semiconductor devices, a
patterned resist layer is formed by the photolithographic
patterning method on a substrate provided with a thin undercoating
film of a material selected from the above mentioned various
materials. When a patterned resist layer is formed from a
chemical-amplification photoresist composition on the surface of an
undercoating film of a nitrogen-containing material such as silicon
nitride and titanium nitride, it is sometimes the case that the
patterned resist layer has a cross sectional profile slightly
trailing skirts on the substrate surface. Furthermore, when a
patterned resist layer is formed on the surface of an undercoating
film of PSG, BSG, BPSG and the like, the cross sectional profile of
the patterned resist layer is not fully orthogonal but more or less
trapezoidal.
[0008] Needless to say, the above mentioned non-orthogonal cross
sectional profile of the patterned resist layer is very undesirable
against subsequent processing steps in the photolithographic
patterning work in which extreme fineness of patterning of 0.20
.mu.m or even finer is required. Thus, it is eagerly desired to
develop a novel and improved photoresist composition which is free
from the above described problems and disadvantages in the
conventional photoresist compositions.
SUMMARY OF THE INVENTION
[0009] The present invention accordingly has an object to provide a
novel and improved positive-working chemical-amplification
photoresist composition capable of giving a patterned resist layer
which is free from non-orthogonality of the cross sectional profile
mentioned above irrespective of the material of the undercoating
film on which the photoresist layer is formed by using the
photoresist composition.
[0010] The inventors have conducted extensive investigations with
this object particularly directing their attention to a possible
mechanism for the appearance of a skirt-trailing or trapezoidal
cross sectional profile of the patterned resist layer formed from a
chemical-amplification photoresist composition on an undercoating
film containing nitrogen, phosphorus, boron and the like that this
undesirable phenomenon is resulted from deactivation of the acid
released from the radiation-sensitive acid-generating compound
contained in the photoresist composition as a consequence of
combining of the acid with the non-covalent electron pairs
possessed by the atoms of nitrogen, phosphorus, boron and the like,
arriving at a unique measure to prevent deactivation of the acid
released from the acid-generating compound.
[0011] Thus, the positive-working chemical-amplification
photoresist composition provided by the present invention is a
uniform solution, in an organic solvent, which comprises:
[0012] (A) a film-forming resinous compound capable of being
imparted with an increase in the solubility in an aqueous alkaline
solution by interacting with an acid;
[0013] (B) an acid-generating compound capable of releasing an acid
by irradiation with actinic rays; and
[0014] (C) an oxo acid of phosphorus or an ester compound
thereof,
[0015] the amount of the component (C) being in the range from 0.01
to 5% by weight based on the component (A).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] As is described above, the essential ingredients in the
positive-working chemical-amplification photoresist composition
include the components (A), (B) and (C), of which the component (A)
is a film-forming resinous compound capable of being imparted with
an increase in the solubility in an aqueous alkaline solution by
interacting with an acid. A variety of such resinous compounds are
known in the art of chemical-amplification photoresist compositions
and any of them can be used in the present invention without
particular limitations. A typical example of such a resinous
compound is an alkali-soluble resin having phenolic hydroxyl groups
or carboxyl groups, at least a part of which are substituted by
acid-dissociable solubility-reducing groups. Namely, the solubility
of the inherently alkali-soluble resin is decreased by substitution
for the hydroxyl or carboxyl groups by the solubility-reducing
groups while the solubility-reducing groups are dissociated in the
presence of an acid released by irradiation with actinic rays from
the acid-generating compound as the component (B) in the exposed
areas of the photoresist layer to regenerate free hydroxyl or
carboxyl groups resulting in an increase in the alkali-solubility
of the resin.
[0017] The above mentioned acid-dissociable solubility-reducing
group is not particularly limitative and any of known ones can be
used in the component (A). Examples of such a solubility-reducing
group include tertiary alkyloxycarbonyl groups such as
tert-butoxycarbonyl and tert-amyloxycarbonyl groups, tertiary alkyl
groups such as tert-butyl and tert-amyl groups, tertiary
alkyloxycarbonylalkyl groups such as tert-butoxycarbonylmethyl and
tertamyloxycarbonylmethyl groups, cyclic acetal residues such as
tetrahydropyranyl and tetrahydrofuranyl groups, linear acetal
residues such as alkoxyalkyl groups, silyl ether groups such as
trimethylsilyl group, and so on. Preferable among the above named
groups are tertiary alkyloxycarbonyl groups, tertiary alkyl groups,
cyclic acetal residues and linear acetal residues in respects of
high photosensitivity and pattern resolution as well as excellently
orthogonal cross sectional profile of the patterned resist
layer.
[0018] Particular examples of the resinous compounds suitable as
the component (A) include polyhydroxystyrene resins substituted for
from 10 to 50% or, preferably, from 15 to 35% of the hydroxyl
groups by tert-butoxycarbonyl groups, tert-butoxycarbonylmethyl
groups, cyclic acetal residues, such as tetrahydropyranyl and
tetrahydro-furanyl groups, and/or alkoxyalkyl groups, i.e. linear
acetal residues, such as 1-ethoxyethyl and 1-methoxy-n-propyl
groups as well as copolymeric resins consisting of from 50 to 85%
by moles of the monomeric units derived from hydroxystyrene and/or
.alpha.-methyl hydroxystyrene, from 10 to 30% by moles of the
monomeric units derived from styrene and from 2 to 20% by moles of
the monomeric units derived from acrylic or methacrylic acid
esterified with an acid-dissociable solubility-reducing group such
as those mentioned above, which is preferably tert-butyl group, as
the esterifying group.
[0019] Although any one of the above described various resinous
compounds can be used singly as the component (A), it is optional
that the component (A) is a combination of two kinds or more of
these resinous compounds. A particularly preferable resinous
ingredient as the component (A) includes combinations of an
alkoxyalkyl-substituted polyhydroxystyrene resin and a
tert-butoxycarbonyl-substituted polyhydroxystyrene resin or cyclic
acetal residue-substituted polyhydroxystyrene resin. More
preferably, the component (A) is a ternary copolymeric resin
consisting of the monomeric units derived from hydroxystyrene
and/or .alpha.-methyl hydroxystyrene, styrene and tert-butyl
(meth)acrylate used alone in respect of the high pattern resolution
and excellently orthogonal cross sectional profile of the patterned
resist layer as well as in respect of little roughness, i.e. good
smoothness, of edge lines of the resist pattern as viewed from
above.
[0020] When the component (A) is a combination of the above
mentioned two different resins, the proportion of the two resins,
i.e. the weight ratio of the tert-butoxycarbonyl- or cyclic acetal
residue-substituted polyhydroxystyrene resin to the
alkoxyalkyl-substituted polyhydroxystyrene resin, is in the range
from 5:95 to 50:50 or, preferably, from 10:90 to 30:70. The above
mentioned ternary copolymeric resin as the component (A) can be a
combination of two kinds or more of different resins provided that
each of them falls within the above given definition of the
resin.
[0021] The component (B) in the inventive photoresist composition
is a radiation-sensitive acid-generating compound capable of
releasing an acid by irradiation with actinic rays. A variety of
such acid-generating compounds are known in the art of
chemical-amplification photoresist compositions. Although any one
or any combination of those known compounds can be used as the
component (B) in the present invention, it is preferable that the
component (B) is selected from onium salt compounds and
diazomethane compounds in consideration of the strength of the acid
released therefrom by irradiation with actinic rays and activity
for the dissociation of the acid-dissociable solubility-reducing
groups in the component (A) and transparency to the exposure
light.
[0022] Examples of the above mentioned diazomethane compounds
include bis(cyclohexylsulfonyl) diazomethane,
bis(tertbutylsulfonyl) diazomethane, bis(isopropylsulfonyl)
diazomethane, bis(4-methylphenylsulfonyl) diazomethane and
bis(2,4-dimethylphenylsulfon- yl) diazomethane.
[0023] The above mentioned onium salt compound is preferably an
onium salt compound having a fluoroalkylsulfonate as the anion
including diphenyliodonium1 salt compounds represented by the
general formula 1
[0024] in which R.sup.1 and R.sup.2 are each, independently from
the other, a hydrogen atom, an alkyl group having 1 to 4 carbon
atoms or an alkoxy group having 1 to 4 carbon atoms and X.sup.- is
a fluoroalkylsulfonate anion having 1 to 10 carbon atoms, and
triphenylsulfonium salt compounds represented by the general
formula 2
[0025] in which R.sup.1, R.sup.4 and R.sup.5 are each,
independently from the others, a hydrogen atom, an alkyl group
having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon
atoms and X.sup.- has the same meaning as defined above.
[0026] Particular examples of the onium salt compounds as the
component (B) falling within the above given definition of the
compound include diphenyliodonium trifluoromethanesulfonate and
nonafluorobutanesulfonate, bis(4-tert-butylphenyl)iodonium
trifluoromethanesulfonate and nonafluorobutanesulfonate,
triphenylsulfonium trifluoromethanesulfonate and
nonafluorobutanesulfonate and tri(4-methylphenyl)sulfonium
trifluoromethanesulfonate and nonafluorobutanesulfonate, of which
bis(4-tert-butylphenyl)iodonium trifluoromethane- and
nonafluorobutanesulfonates and triphenylsulfonium trifluoromethane-
and nonafluorobutanesulfonates are particularly preferable in
respect of high pattern resolution and excellently orthogonal cross
sectional profile of the patterned resist layer.
[0027] The above described various acid-generating compounds can be
used either singly or as a combination of two kinds or more as the
component (B) according to need. The amount of the component (B) in
the inventive photoresist composition is in the range from 1 to 20
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, image
formation in the photoresist layer can hardly be accomplished by
the patternwise exposure of the layer to actinic rays. When the
amount thereof is too large, on the other hand, a trouble is
encountered that a portion of the compound remains undissolved not
to give a uniform solution as the photoresist composition due to
the limited solubility of the compound in an organic solvent or,
even if a uniform solution could be obtained, the photoresist
composition suffers a decrease in the storage stability.
[0028] The component (C), which is the most characteristic
ingredient in the inventive photoresist composition, is a
phosphorus-containing oxo acid or an ester compound thereof. It is
the most unexpected discovery leading to the present invention that
admixture of a chemical-amplification photoresist composition with
such a phosphorus-containing oxo acid or ester thereof has an
effect of preventing the undesirable phenomenon of
non-orthogonality of the cross sectional profile of the patterned
resist layer formed on a substrate surface having an undercoating
film of a variety of materials including nitrogen-containing
materials such as silicon nitride, silicon oxynitride and titanium
nitride, phosphorus-containing materials such as PSG,
boron-containing materials such as BSG and phosphorus- and
boron-containing materials such as BPSG. The mechanism leading to
this advantageous effect is, though not well understood, presumably
due to the fact that the above mentioned disadvantage in patterning
is caused by the deactivation of the acid released from the
component (B) as a consequence of combining thereof with the
non-covalent electron pairs possessed by the atoms of nitrogen,
phosphorus and boron in the materials of the undercoating film and
the phosphorus-containing oxo acid or an ester thereof acts to
disturb combining of the acid with the non-covalent electron pairs
without adversely affecting the photosensitivity and pattern
resolution in patterning with the photoresist composition.
[0029] Examples of the phosphorus-containing oxo acid include
phosphoric acid, phosphorous acid, phosphonic acid,
phenylphosphonic acid, phosphinic acid and phenylphosphinic acid.
Examples of the ester compound of these acid compounds include
mono-, di- and triesters of the acid with methyl, ethyl, n-butyl,
benzyl and phenyl groups such as phosphoric acid di-n-butyl ester,
phosphoric acid diphenyl ester, phosphonic acid dimethyl ester,
phosphonic acid di-n-butyl ester, phosphonic acid diphenyl ester,
phosphonic acid dibenzyl ester and the like. These
phosphorus-containing oxo acids and esters thereof can be used
either singly or as a combination of two kinds or more according to
need as the component (C). It is preferable that the component (C)
is in the form of an acid rather than in the form of an ester
compound.
[0030] The amount of the component (C) in the inventive photoresist
composition is in the range from 0.01 to 5 parts by weight or,
preferably, from 0.1 to 2.0 parts by weight per 100 parts by weight
of the resinous ingredient as the component (A) in respect of the
improving effect on the appearance of a skirt-trailing or
trapezoidal cross sectional profile of the resist pattern,
suppression of thickness reduction of the resist layer by
development and so on. When the amount of the component (C) is too
small, the advantageous effect to be obtained by the addition of
this component cannot be fully obtained as a matter of course
while, when the amount thereof is too large, an unduly large
thickness reduction may be caused in the unexposed areas of the
photoresist layer by the development treatment with an aqueous
alkaline developer solution.
[0031] Besides the above described essential components (A), (B)
and (C), the positive-working chemical-amplification photoresist
composition can be compounded according to need with a secondary or
tertiary amine compound such as triethylamine, tributylamine,
dibutylamine, triethanolamine and the like to serve as a quenching
agent and an antireflective agent such as benzophenone compounds to
reduce reflection of the exposure light at the substrate
surface.
[0032] It is usual that the photoresist composition of the present
invention comprising the above described essential and optional
ingredients is used in the form of a solution prepared by uniformly
dissolving the various ingredients in an organic solvent. Examples
of suitable organic solvents include ketone compounds such as
acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone
and 2-heptanone, polyhydric alcohols and derivatives thereof such
as ethyleneglycol, ethyleneglycol monoacetate, propyleneglycol,
propyleneglycol monoacetate, diethyleneglycol, diethyleneglycol
monoacetate, dipropyleneglycol and dipropyleneglycol monoacetate as
well as monomethyl, monoethyl, monopropyl, monobutyl and monophenyl
ether compounds thereof, cyclic ethers such as dioxane and ester
compounds such as methyl lactate, ethyl lactate, methyl acetate,
ethyl acetate, butyl acetate, methylpyruvate, ethyl pyruvate,
methyl methoxypropionate and ethyl ethoxypropionate. These organic
solvents can be used either singly or as a mixture of two kinds or
more according to need.
[0033] It is of course optional that the photoresist composition of
the invention prepared in the above described manner is further
admixed with various kinds of known additives having compatibility
each in a limited amount including auxiliary resinous compounds to
improve or modify the properties of the resist film, plasticizers,
stabilizers, coloring agents, surface active agents and the
like.
[0034] The procedure of the patterning work on a substrate surface
by using the photoresist composition of the invention is not
particularly different from conventional procedures. Namely, the
surface of a substrate is coated with the photoresist composition
by using a suitable coating machine such as a spinner followed by
drying to form a photoresist layer which is then patternwise
exposed to actinic rays such as a KrF excimer laser beam of 248 nm
wavelength through a photomask bearing a desired pattern on a
suitable exposure machine to form a latent image of the pattern
followed by a post-exposure baking treatment and a development
treatment of the latent image by using an aqueous alkaline
developer solution such as a 0.1 to 10% by weight aqueous solution
of tetramethylammonium hydroxide to give a patterned resist layer
with high photosensitivity and excellent pattern resolution of 0.2
.mu.m or even finer. The thus obtained patterned resist layer has
high fidelity to the photomask pattern and has an excellently
orthogonal, non-trapezoidal cross sectional profile without
skirt-trailing. The actinic rays for patternwise exposure are not
limited to excimer laser beams but can be X-rays or electron
beams.
[0035] The substrate material to be subjected to the above
mentioned patterning procedure by using the inventive photoresist
composition is not limited to a semiconductor Silicon wafer per se
but the inventive photoresist composition is applicable to a
substrate surface provided with an undercoating thin film
irrespective of the surface nature of the undercoating film. In
particular, the inventive photoresist composition is applicable to
the surface of even an undercoating film of a material containing
nitrogen or containing phosphorus and/or boron in contrast to the
prior art by using a conventional photoresist composition in which
satisfactory patterned resist layer can hardly be obtained on a
substrate surface having an undercoating film of these materials.
Examples of nitrogen-containing materials for the undercoating film
include silicon mononitride SiN, trisilicon tetranitride
Si.sub.3N.sub.4, silicon oxynitride SiON and titanium nitride TiN.
Examples of the phosphorus- and/or boron-containing materials of
the undercoating film include phosphosilicate glass, borosilicate
glass and borophosphosilicate glass.
[0036] In the following, the positive-working
chemical-amplification photoresist composition of the present
invention is described in more detail by way of examples, which,
however, never limit the scope of the invention in any way.
EXAMPLE 1
[0037] A positive-working photoresist composition in the form of a
solution was prepared by uniformly dissolving, in 800 parts by
weight of propyleneglycol monomethyl ether acetate, 60 parts by
weight of a first copolymeric resin consisting of 65% by moles of
hydroxystyrene units, 20% by moles of styrene units and 15% by
moles of tert-butyl acrylate units and having a weight-average
molecular weight of 10,000, 40 parts by weight of a second
copolymeric resin consisting of 65% by moles of hydroxystyrene
units, 30% by moles of styrene units and 5% by moles of tert-butyl
acrylate units and having a weight-average molecular weight of
10,000, 5 parts by weight of triphenylsulfonium
trifluoromethanesulfonate- , 0.29 part by weight of
phenylphosphonic acid and 0.27 part by weight of triethanolamine
followed by filtration of the solution through a membrane filter
having a 0.2 .mu.m pore diameter.
[0038] Nextly, a 6-inch semiconductor silicon wafer provided with
an undercoating film of silicon mononitride was coated with the
above prepared photoresist solution on a spinner followed by
heating on a hot plate at 130.degree. C. for 90 seconds to form a
dried layer of the photoresist composition having a thickness of
0.7 .mu.m. The photoresist layer was then patternwise exposed to a
KrF excimer laser beam through a photomask on a minifying
projection exposure machine (Model FPA-3000EX3, manufactured by
Canon Co.) followed by a post-exposure baking treatment at
110.degree. C. for 90 seconds. The development treatment of the
thus treated photoresist layer was undertaken by puddle development
with a 2.38% by weight aqueous solution of tetramethylammonium
hydroxide at 23.degree. C. for 65 seconds to give a positively
patterned resist layer.
[0039] The pattern resolution of the thus patterned resist layer
was so high as to fully resolve a line-and-space pattern of 0.18
.mu.m line width. The cross sectional profile of the line-patterned
resist layer was excellently orthogonal standing upright on the
substrate surface without trailing of skirts. The photosensitivity
of the photoresist composition, as given by the minimum exposure
dose to obtain a fully resolved line-and-space pattern of 0.18
.mu.m line width, was 40 mJ/cm.sup.2.
EXAMPLE 2
[0040] The experimental procedure was substantially the same as in
Example 1 except that the silicon wafer as the substrate had an
undercoating film of phosphosilicate glass instead of silicon
mononitride.
[0041] The results of inspection of the thus obtained
line-and-space patterned resist layer were that good pattern
resolution was obtained for a line-and-space pattern of 0.18 .mu.m
line width, the cross sectional profile of the line-patterned
resist layer was excellently orthogonal standing upright on the
substrate surface and the photosensitivity was 40 mJ/cm.sup.2.
EXAMPLE 3
[0042] The experimental procedure was substantially the same as in
Example 1 except that the silicon wafer as the substrate had an
undercoating film of borosilicate glass instead of silicon
mononitride.
[0043] The results of inspection of the thus obtained
line-and-space patterned resist layer were that good pattern
resolution was obtained for a line-and-space pattern of 0.18 mm
line width, the cross sectional profile of the line-patterned
resist layer was excellently orthogonal standing upright on the
substrate surface and the photosensitivity was 40 mJ/cm.sup.2.
EXAMPLE 4
[0044] The experimental procedure was substantially the same as in
Example 1 except that the silicon wafer as the substrate had an
undercoating film of borophosphosilicate glass instead of silicon
mononitride.
[0045] The results of inspection of the thus obtained
line-and-space patterned resist layer were that good pattern
resolution was obtained for a line-and-space pattern of 0.18 .mu.m
line width, the cross sectional profile of the line-patterned
resist layer was excellently orthogonal standing upright on the
substrate surface and the photosensitivity was 40 mJ/cm.sup.2.
EXAMPLE 5
[0046] The experimental procedure was substantially the same as in
Example 1 excepting for the replacement of phenylphosphonic acid
with the same amount of phosphoric acid.
[0047] The results of inspection of the thus obtained
line-and-space patterned resist layer were that good pattern
resolution was obtained for a line-and-space pattern of 0.18 .mu.m
line width, the cross sectional profile of the line-patterned
resist layer was excellently orthogonal standing upright on the
substrate surface and the photosensitivity was 40 mJ/cm.sup.2.
EXAMPLE 6
[0048] The experimental procedure was substantially the same as in
Example 5 except that the silicon wafer as the substrate had an
undercoating film of phosphosilicate glass instead of silicon
mononitride.
[0049] The results of inspection of the thus obtained
line-and-space patterned resist layer were that good pattern
resolution was obtained for a line-and-space pattern of 0.18 .mu.m
line width, the cross sectional profile of the line-patterned
resist layer was excellently orthogonal standing upright on the
substrate surface and the photosensitivity was 40 mJ/cm.sup.2.
EXAMPLE 7
[0050] The experimental procedure was substantially the same as in
Example 5 except that the silicon wafer as the substrate had an
undercoating film of borosilicate glass instead of silicon
mononitride.
[0051] The results of inspection of the thus obtained
line-and-space patterned resist layer were that good pattern
resolution was obtained for a line-and-space pattern of 0.18 .mu.m
line width, the cross sectional profile of the line-patterned
resist layer was excellently orthogonal standing upright on the
substrate surface and the photosensitivity was 40 mJ/cm.sup.2.
EXAMPLE 8
[0052] The experimental procedure was substantially the same as in
Example 5 except that the silicon wafer as the substrate had an
undercoating film of borophosphosilicate glass instead of silicon
mononitride.
[0053] The results of inspection of the thus obtained
line-and-space patterned resist layer were that good pattern
resolution was obtained for a line-and-space pattern of 0.18 .mu.m
line width, the cross sectional profile of the line-patterned
resist layer was excellently orthogonal standing upright on the
substrate surface and the photosensitivity was 40 mJ/cm.sup.2.
COMPARATIVE EXAMPLE 1
[0054] The experimental procedure was substantially the same as in
Example 1 excepting for omission of phenylphosphonic acid in the
formulation of the photoresist composition.
[0055] The results of inspection of the thus obtained
line-and-space patterned resist layer were that pattern resolution
was obtained for a line-and-space pattern of 0.25 .mu.m line width
but trailing skirts were found in the cross sectional profile of
the line-patterned resist layer and the photosensitivity was 30
mJ/cm.sup.2 for obtaining the line-and-space pattern of 0.25 .mu.m
line width.
COMPARATIVE EXAMPLE 2
[0056] The experimental procedure was substantially the same as in
Example 1 excepting for replacement of 0.29 part by weight of
phenylphosphonic acid in the formulation of the photoresist
composition with 0.19 part by weight of malonic acid.
[0057] The results of inspection of the thus obtained
line-and-space patterned resist layer were that pattern resolution
was obtained for a line-and-space pattern of 0.22 .mu.m line width
but trailing skirts were found in the cross sectional profile of
the line-patterned resist layer and the photosensitivity was 35
mJ/cm.sup.2 for obtaining the line-and-space pattern of 0.22 .mu.m
line width.
COMPARATIVE EXAMPLE 3
[0058] The experimental procedure was substantially the same as in
Example 1 excepting for replacement of 0.29 part by weight of
phenylphosphonic acid in the formulation of the photoresist
composition with 0.28 part by weight of p-toluenesulfonic acid.
[0059] The result of inspection of the thus patterned resist layer
was that film-thickness reduction in the development on the
unexposed areas was so great that the cross sectional profile of
the line-patterned resist layer was not orthogonal but
semicircular.
COMPARATIVE EXAMPLE 4
[0060] The experimental procedure was substantially the same as in
Example 4 excepting for omission of phenylphosphonic acid in the
formulation of the photoresist composition.
[0061] The results of inspection of the thus obtained
line-and-space patterned resist layer were that pattern resolution
was obtained for a line-and-space pattern of 0.25 .mu.m line width
but the cross sectional profile of the line-patterned resist layer
was trapezoidal narrowing upwardly and the photosensitivity was 30
mJ/cm.sup.2 for obtaining the line-and-space pattern of 0.25 .mu.m
line width.
* * * * *