U.S. patent application number 12/272221 was filed with the patent office on 2009-03-19 for process for forming a pattern including on a semiconductor device.
This patent application is currently assigned to NEC ELECTRONICS CORPORATION. Invention is credited to Masayuki HIROI, Seiji NAGAHARA.
Application Number | 20090075482 12/272221 |
Document ID | / |
Family ID | 33516264 |
Filed Date | 2009-03-19 |
United States Patent
Application |
20090075482 |
Kind Code |
A1 |
NAGAHARA; Seiji ; et
al. |
March 19, 2009 |
PROCESS FOR FORMING A PATTERN INCLUDING ON A SEMICONDUCTOR
DEVICE
Abstract
An objective of this invention is to prevent resist poisoning
and sensitivity deterioration in a chemically amplified resist. The
chemically amplified resist comprises a base resin, a photoacid
generator and a salt exhibiting buffer effect in the base
resin.
Inventors: |
NAGAHARA; Seiji; (Kanagawa,
JP) ; HIROI; Masayuki; (Kanagawa, JP) |
Correspondence
Address: |
YOUNG & THOMPSON
209 Madison Street, Suite 500
ALEXANDRIA
VA
22314
US
|
Assignee: |
NEC ELECTRONICS CORPORATION
Kanagawa
JP
|
Family ID: |
33516264 |
Appl. No.: |
12/272221 |
Filed: |
November 17, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10868968 |
Jun 17, 2004 |
7479361 |
|
|
12272221 |
|
|
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|
Current U.S.
Class: |
438/694 ;
257/E21.294 |
Current CPC
Class: |
G03F 7/0382 20130101;
H01L 21/76807 20130101; H01L 21/76808 20130101; G03F 7/0392
20130101 |
Class at
Publication: |
438/694 ;
257/E21.294 |
International
Class: |
H01L 21/3105 20060101
H01L021/3105 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 20, 2003 |
JP |
2003-176736 |
Claims
1. A process for manufacturing a semiconductor device, comprising
the steps of; forming a film to be etched on a semiconductor
substrate, applying a chemically amplified resist composition on
the film to be etched to form a resist film, patterning the resist
film and etching the film to be etched, using the patterned resist
film as a mask: wherein the chemically amplified resist composition
comprises; a base resin, a photoacid generator which generates an
acid by exposure, and a salt exhibiting buffer effect in the base
resin.
2. A process for manufacturing a semiconductor device, comprising
the steps of; forming a film to be etched on a semiconductor
substrate, on the film to be etched, forming a first resist film
patterned in a predetermined shape and using the first resist film
as a mask, etching the film to be etched to form a concave,
removing the first resist film, on the film to be etched, applying
a chemically amplified resist composition, which is then dried to
form a second resist film, patterning the second resist film to
form an opening such that at least part of the region where the
concave has been formed is exposed, and etching the film to be
etched, using the patterned second resist film as a mask: wherein
the chemically amplified resist composition comprises; a base
resin, a photoacid generator which generates an acid by exposure,
and a salt exhibiting buffer effect in the base resin.
3. The process for manufacturing a semiconductor device as claimed
in claim 2, wherein the step of removing the first resist film
comprises removing a part of the first resist film with an amine
stripper.
4. The process for manufacturing a semiconductor device as claimed
in claim 1, wherein the film to be etched contains nitrogen.
5. The process for manufacturing a semiconductor device as claimed
in claim 2, wherein the film to be etched contains nitrogen.
6. The process for manufacturing a semiconductor device as claimed
in claim 1, wherein the film to be etched is a film having a porous
structure with a specific dielectric constant of 3 or less.
7. The process for manufacturing a semiconductor device as claimed
in claim 2, wherein the film to be etched is a film having a porous
structure with a specific dielectric constant of 3 or less.
8. The process for manufacturing a semiconductor device as claimed
in claim 1, wherein the salt comprises the acid generated from the
photoacid generator by exposure.
9. The process for manufacturing a semiconductor device as claimed
in claim 2, wherein the salt comprises the acid generated from the
photoacid generator by exposure.
10. The process for manufacturing a semiconductor device as claimed
in claim 1, wherein the salt is a sulfonate.
11. The process for manufacturing a semiconductor device as claimed
in claim 2, wherein the salt is a sulfonate.
12. The process for manufacturing a semiconductor device as claimed
in claim 1, wherein the salt is an amine salt.
13. The process for manufacturing a semiconductor device as claimed
in claim 2, wherein the salt is an amine salt.
14. The process for manufacturing a semiconductor device as claimed
in claim 1, wherein the salt is a salt of an alkanolamine or
alkoxyalkylamine with a sulfonic acid.
15. The process for manufacturing a semiconductor device as claimed
in claim 2, wherein the salt is a salt of an alkanolamine or
alkoxyalkylamine with a sulfonic acid.
16. The process for manufacturing a semiconductor device as claimed
in claim 1, wherein the base resin is a resin whose alkali
solubility is changed by the action of the acid.
17. The process for manufacturing a semiconductor device as claimed
in claim 2, wherein the base resin is a resin whose alkali
solubility is changed by the action of the acid.
18. A process for forming a pattern, comprising the steps of;
applying a chemically amplified resist composition on a material to
be etched to form a resist film, patterning the resist film, and
etching and patterning the material to be etched, using the
patterned resist film as a mask: wherein the chemically amplified
resist composition comprises; a base resin, a photoacid generator
which generates an acid by exposure, and a salt exhibiting buffer
effect in the base resin.
19. The process for patterning as claimed in claim 18, wherein the
material to be etched contains nitrogen.
20. The process for patterning as claimed in claim 18, wherein the
film to be etched is a film having a porous structure with a
specific dielectric constant of 3 or less.
21. The process for patterning as claimed in claim 18, wherein the
salt comprises the acid generated from the photoacid generator by
exposure.
22. The process for patterning as claimed in claim 18, wherein the
salt is a sulfonate.
23. The process for patterning as claimed in claim 18, wherein the
salt is an amine salt.
24. The process for patterning as claimed in claim 18, wherein the
salt is a salt of an alkanolamine or alkoxyalkylamine with a
sulfonic acid.
25. The process for patterning as claimed in claim 18, wherein the
base resin is a resin whose alkali solubility is changed by the
action of the acid.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a chemically amplified resist
composition, a process for manufacturing a semiconductor device and
a patterning process.
[0003] 2. Description of the Prior Art
[0004] As a device has become more compact and more accelerated,
lithography using a short-wavelength light source has been employed
because of improving resolution. In addition, there has been used a
chemically amplified resist as a resist material.
[0005] Furthermore, the needs for size reduction and acceleration
in a semiconductor device require using, besides a copper (Cu)
interconnection, a so-called low dielectric constant material. A
copper interconnection is generally formed by a damascene process
in which a trench for an interconnection is formed on an insulating
film between interconnections, the trench is filled with copper and
then excessive copper in an unwanted area outside the
interconnection trench is removed by chemical mechanical polishing
(CMP).
[0006] There will be described formation of a copper
interconnection by a damascene process using a chemically amplified
resist. FIG. 10 is process cross-sections showing the procedure of
a dual damascene process where a via-hole and an interconnection
trench are simultaneously filled. A process where the
interconnection and the via are formed by a so-called via-first
process.
[0007] First, on a lower interconnection layer 108 are sequentially
deposited a first etching stopper film 107, a first interlayer
insulating film 106, a second etching stopper film 105, a second
interlayer insulating film 104 and a third interlayer insulating
film 103. Then, using well-known lithography and etching technique,
a via-hole 111 is formed in the third interlayer insulating film
103, the second interlayer insulating film 104, the second etching
stopper film 105 and the first interlayer insulating film 106 (FIG.
10(a)).
[0008] Then, an anti-reflection film 102 is formed on the third
interlayer insulating film 103 and the first etching stopper film
107, during which the via-hole 111 is partly or totally buried with
the anti-reflection film 102. This figure shows that the via-hole
111 is partly buried with the anti-reflection film 102 (FIG.
10(b)).
[0009] Next, on the anti-reflection film 102 is applied a
chemically amplified resist 201 (FIG. 10(c)). Then, in the
chemically amplified resist 201 is formed an opening pattern 112
for forming an interconnection trench connected to the via-hole 111
(FIG. 10(d)).
[0010] Subsequently, using the chemically amplified resist 201 as a
mask, the anti-reflection film 102 on the third interlayer
insulating film 103, and then the third interlayer insulating film
103 and the second interlayer insulating film 104 are etched off to
form an interconnection trench 113 (FIGS. 10 (e) and (f)).
[0011] Then, the chemically amplified resist 201 and the
anti-reflection film 102 are stripped off by O.sub.2 plasma ashing
and using an organic stripper. Next, the first etching stopper film
107 at the bottom of the via-hole 111 is etched off to provide a
structure where the via-hole 111 is connected to the upper surface
of the interconnection (not shown) in the lower interconnection
layer 108 (FIG. 10(g)).
[0012] Next, a metal film is formed such that it buries the
interconnection trench 113 and the via-hole 111. The metal film can
be formed by first forming a barrier metal film within the
interconnection trench 113 and the via-hole 111 by sputtering and
then burying the interconnection trench 113 and the via-hole 111
with an interconnection metal film by, for example, electroplating.
Subsequently, unwanted barrier metal and interconnection metal
films outside the interconnection trench 113 are removed by CMP to
form an interconnection 109 (FIG. 10(h)).
[0013] In such a via-first process, defective resolution of the
resist on the via-hole 111 tends to occur during forming the
opening pattern 112 in the chemically amplified resist 201. Such a
phenomenon that defective resolution is induced in a particular
area not due to a lower optical resolution, but due to an external
factor inhibiting resolution of a chemically amplified resist is
called "resist poisoning". If resist poisoning occurs, an
interlayer insulating film cannot be processed into a desired
shape. Furthermore, when directly forming an interconnection,
interconnection-defects such as stress-migration and
electro-migration may occur, leading to a less reliable
semiconductor device.
[0014] To solve the problem, it has been proposed that a resist
composition comprising an organic base is used for preventing
resist poisoning of a resist pattern (Tokkai 2000-137328). Tokkai
2000-137328 has described that addition of an organic base is
effective for preventing dimensional fluctuation of a resist
pattern because diffusion or activity of an acid after exposure is
inhibited. Hereinafter, an organic base used for such a purpose is
referred to as a "quencher".
[0015] However, when adding a quencher to a resist composition, it
is effective for preventing resist poisoning during resist
patterning, but it may lead to deteriorate in resist sensitivity. A
resist with excessively lower sensitivity may reduce a throughput
in an exposure process and thus may sometimes lead to significantly
deteriorated mass productivity. For example, a three-fold amount of
the quencher requires an almost three-fold exposure time. Thus,
when adding a sufficient amount of the quencher to completely
prevent poisoning, an exposure time frequently exceed a permissible
limit. Furthermore, in a lithography process with a lower
throughput such as EB direct-drawing lithography, it is difficult
to increase the amount of the quencher for preventing resist
poisoning. Thus, the process cannot be sometimes employed due to
resist poisoning.
[0016] In view of the situation, an objective of this invention is
to provide a technique for preventing occurrence of poisoning and
deterioration in sensitivity in a chemically amplified resist.
[0017] We have intensely investigated the above problems,
conducting extensive experiments, and consequently have found the
followings.
[0018] In a via-first process described above with reference to
FIG. 10, it has been found that sensitivity in a chemically
amplified resist may be lowered because of the mechanism described
below. FIG. 11 is a process cross-section showing occurrence of
defective formation of a chemically amplified resist on a
via-hole.
[0019] First, by the above steps illustrated in FIGS. 10(a) to
10(c), a chemically amplified resist 201 is applied on an
anti-reflection film 102. Then, an opening pattern 112 for forming
an interconnection trench is transferred to the chemically
amplified resist 201. In the process, as shown in FIG. 11(a), a
chemically amplified resist 201 cannot be removed on and around the
upper surface of the via-hole and partly remains (FIG. 11(a)).
[0020] Then, the anti-reflection film 102 is removed (FIG. 11(b)),
and then the third interlayer insulating film 103 and the second
interlayer insulating film 104 are etched off (FIG. 11(c)). In the
process, as shown in FIG. 11(a), the chemically amplified resist
201 remains within the opening pattern 112, so that an
interconnection trench 113 is not formed in conformity to a pattern
and a residual fence 114 of the third interlayer insulating film
103 and the second interlayer insulating film 104 is formed on and
around the upper surface of the via-hole. The residual fence 114 is
not removed by subsequent O.sub.2 plasma ashing or treatment with
an organic stripper (FIG. 11(d)), and remains in the
interconnection trench 113 (FIG. 11(e)).
[0021] We have further analyzed the cause of a defective pattern in
the above process and have obtained a new finding described below.
Specifically, it has been found that an amine or its analogue is
formed in an interlayer insulating film formed on a semiconductor
substrate and the compound is subjected to neutralization with an
acid catalyst in a chemically amplified resist, leading to
deteriorated sensitivity of a resist.
[0022] A variety of sources may be deduced for such an amine; for
example, a nitrogen-containing film formed under a resist, NOx in a
deposition gas used for, e.g., depositing a silicon oxide film, or
an amine present in a stripper used for removing a resist.
SUMMARY OF THE INVENTION
[0023] We have also investigated relationship between tendency to
poisoning and the type of an insulating film and have found that
poisoning tends to occur when using a low dielectric-constant film
with a specific dielectric constant of 3 or less. Although the
reason has not clearly understood, it may be assumed that such a
film has a more porous structure in comparison with, for example,
an SiO.sub.2 film formed by plasma CVD and thus an amine tends to
be easily occluded in the film.
[0024] Based on the new findings above described, we have concluded
that it is essential to reduce influence of an amine compound
present in a system for minimizing deterioration of resist
sensitivity. Further continuing investigation in the light of the
concept, we have demonstrated that a salt exhibiting buffer effect
can be added to a resist composition to minimize influence of an
amine compound and thus to form a stable resist pattern capable of
stably preventing poisoning from occurring while maintain higher
sensitivity.
[0025] This invention provides a chemically amplified resist
composition comprising a base resin; a photoacid generator which
generates an acid by exposure; and a salt exhibiting buffer effect
in the base resin.
[0026] The term, "buffer effect" as used herein means an action of
inhibiting fluctuation of a proton concentration in a resist, and
keeping the proton concentration constant. When being solidified, a
resist composition comprising such a salt exhibits equivalent
buffering behavior in the solid as if the composition is in an
aqueous liquid, so that fluctuation of a proton concentration in a
resist is insusceptible to variation of an acid or base
concentration.
[0027] The resist composition according to this invention comprises
a salt exhibiting buffer effect. Thus, an acid generated from a
photoacid generator can be effectively utilized without excessive
consumption to maintain higher resist sensitivity. Furthermore, it
can prevent fluctuation of the amount of an acid present in a
system due to invasion of, for example, an external amine. That is,
fluctuation of sensitivity or resolution in a resist due to
external factors can be minimized. In addition, the amount of an
acid in a system can be kept constant, so that a resist having a
wide exposure margin can be obtained.
[0028] A salt exhibiting buffer effect herein is a substance
different from a photoacid generator. A photoacid generator is a
substance which can be decomposed by light irradiation to
consequently generate an acid, while a salt exhibiting buffer
effect can generate an acid-base pair in a resist composition
without light irradiation, and thus can behave as if it is a
buffer.
[0029] This invention also provides a process for manufacturing a
semiconductor device, comprising the steps of forming a film to be
etched on a semiconductor substrate; on the film to be etched,
forming a first resist film patterned in a predetermined shape and
using the first resist film as a mask, etching the film to be
etched to form a concave; removing the first resist film; on the
film to be etched, applying a chemically amplified resist
composition, which is then dried to form a second resist film;
patterning the second resist film to form an opening such that at
least part of the region where the concave has been formed is
exposed; and etching the film to be etched or a film formed over or
below the film, using the patterned second resist film as a mask;
wherein the chemically amplified resist composition comprises a
base resin; a photoacid generator which generates an acid by
exposure; and a salt exhibiting buffer effect in the base
resin.
[0030] This invention also provides a process for manufacturing a
semiconductor device, comprising the steps of forming a film to be
etched on a semiconductor substrate; applying a chemically
amplified resist composition on the film to be etched and then
drying the composition to form a resist film; patterning the resist
film; and etching the film to be etched, using the patterned the
resist film as a mask; wherein the chemically amplified resist
composition comprises a base resin; a photoacid generator which
generates an acid by exposure; and a salt exhibiting buffer effect
in the base resin.
[0031] This invention also provides a process for forming a
pattern, comprising the steps of applying a chemically amplified
resist composition on a material to be etched and drying the
composition to form a resist film; patterning the resist film; and
etching and patterning the material to be etched, using the
patterned resist film as a mask; wherein the chemically amplified
resist composition comprises a base resin; a photoacid generator
which generates an acid by exposure; and a salt exhibiting buffer
effect in the base resin.
[0032] In a process according to this invention, a resist film
comprising a salt exhibiting buffer effect in a base resin is used.
Thus, deterioration in sensitivity during patterning can be
minimized and a desired pattern can be reliably formed.
[0033] In this invention, a salt exhibiting buffer effect can be
prepared by reaction between an acid and a base. Hereinafter, such
an acid and a base are referred to as a "salt-forming acid" and a
"salt-forming base", respectively. In this invention, a
salt-forming acid may include an acid generated from the above
photoacid generator by exposure. Thus, buffering action in a resist
composition can be ensured to reliably improve sensitivity during
patterning.
[0034] In this invention, the salt may be a sulfonate, which allows
deterioration in a resist pattern to be further reliably
inhibited.
[0035] In this invention, the salt may include a basic compound
which can be used as a quencher. Herein, a basic compound which can
be used as a quencher means a compound which inhibits diffusion of
an acid generated from a photoacid generator in a resist film; for
example, a nitrogen-containing basic compound. Such a basic
compound may be used to minimize fluctuation of resolution in
patterning and to form reliably a desired pattern. In this
invention, the salt may be an amine. Thus, deterioration in
sensitivity in a resist can be more reliably prevented.
[0036] In this invention, a salt of an alkanolamine with a sulfonic
acid can be used as the salt. The sulfonic acid preferably may
include benzenesulfonic acid, alkylsulfonic acid, camphorsulfonic
acid and these substituted derivatives. Substituted derivatives
include mono and poly-substituted derivatives, those substituted
with an organic group such as alkyl and alkoxy, and those
substituted with a halogen such as fluorine, as well as those
substituted with a fluoroalkyl. When introducing a substituent such
as alkyl and alkoxy, it is preferable to select the proper carbon
number. For example, a substituent with up to three carbon atoms
may give a product having good handling properties.
[0037] A salt constituted with the above combination may be used to
further reliably exert buffering action and thus to further
reliably prevent sensitivity deterioration in lithography.
[0038] In this invention, an alkali solubility of the base resin
may be varied by the action of the acid. In a negative resist, a
generated acid causes a crosslinking reaction to form a site with a
reduced solubility in a developer. In a positive resist, a
generated acid dissociates a protective group in a resin to improve
solubility. Thus, for example in a chemically amplified resist
composition of this invention, the base resin may have an
alkali-soluble group protected with a dissolution-inhibiting group
and the dissolution-inhibiting group may be dissociated by the
action of the acid to give an alkali-soluble resin. A resist
composition according to this invention comprises a salt exhibiting
buffer effect, so that when using such a base resin, fluctuation of
alkali solubility due to variation in exposure can be
prevented.
[0039] In a process for manufacturing a semiconductor device of
this invention, the step of removing a first resist film may
comprise removing a part of the first resist film using an amine
stripper. In the manufacturing process of this invention, a second
resist film comprising a salt exhibiting buffer effect is formed.
Thus, deterioration in sensitivity can be reliably prevented when
an amine component present in a stripper used for removing the
first resist film remains in a film to be etched and permeates into
the second resist film.
[0040] In a process for manufacturing a semiconductor device of
this invention, the film to be etched may contain nitrogen. In a
process for forming a pattern of this invention, the material to be
etched may contain nitrogen. In a manufacturing process of this
invention, a resist film comprising a salt exhibiting buffer effect
is formed. Thus, deterioration in sensitivity can be reliably
prevented when a nitrogen-containing basic compound derived from a
film to be etched or an etching agent permeates into a resist
film.
[0041] In a process for manufacturing a semiconductor device of
this invention, the film to be etched may include a film having a
porous structure with a specific dielectric constant of 3 or less.
In a process for forming a pattern of this invention, the material
to be etched may include a film having a porous structure with a
specific dielectric constant of 3 or less.
[0042] Examples of a "film having a porous structure" include an
HSQ film, an MSQ film, an MHSQ film, a ladder-like hydrogenated
siloxane film, an SiLK.RTM. film, an SiOF film, an SiOC film, an
SiON film and a benzocyclobutene film. These films have a
relatively bulky substituent, so that they have a free volume
larger than a compared with a non-porous film represented by an
SiO.sub.2 film and may, therefore, have a microporous structure. In
such a film, an amine compound present in a system may tend to be
occluded into the film.
[0043] Such a film having a porous structure tends to have a lower
specific dielectric constant than a non-porous film. Any of the
above-described films having a specific dielectric constant of 3 or
less may have a microporous structure.
[0044] In this invention, a resist film comprising a salt
exhibiting buffer effect is used. Thus, deterioration in
sensitivity can be suitably prevented when an amine compound
occluded into a film to be etched permeates into a resist film.
[0045] In this invention, a film to be etched may be a monolayer or
multilayered film.
[0046] Although a configuration of this invention has been
described, any appropriate combination of various components and
modification of this invention to another category are effective as
aspects of this invention. For example, a resist film formed by
applying and drying the above chemically amplified resist
composition or a wafer on which the resist film is applied may be
effective as aspects of this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a cross-sectional view showing a process for
manufacturing a semiconductor device according to an
embodiment.
[0048] FIG. 2 is a cross-sectional view showing a process for
manufacturing a semiconductor device according to an
embodiment.
[0049] FIG. 3 is a cross-sectional view showing a process for
manufacturing a semiconductor device according to an
embodiment.
[0050] FIG. 4 shows a titration curve in an example.
[0051] FIG. 5 is a partial enlarged view of FIG. 4.
[0052] FIG. 6 shows calculated and experimental values of .DELTA.pH
for examples.
[0053] FIG. 7 shows a titration curve for an example.
[0054] FIG. 8 is a partial enlarged view of FIG. 7.
[0055] FIG. 9 shows an SEM photograph for an interconnection trench
pattern in an example.
[0056] FIG. 10 is a cross-sectional view showing a process for
manufacturing a semiconductor device according to the prior
art.
[0057] FIG. 11 is a cross-sectional view showing a process for
manufacturing a semiconductor device according to the prior
art.
[0058] In these drawings, the symbols have the following meanings;
101: chemically amplified resist, 102: anti-reflection film, 103:
third interlayer insulating film, 104: second interlayer insulating
film, 105: second etching stopper film, 106: first interlayer
insulating film, 107: first etching stopper film, 108: lower
interconnection layer, 109: interconnection, 111: via-hole, 112:
opening pattern, 113: interconnection trench, 114: residual fence,
115: interlayer insulating film, 116: first resist film, 117:
second resist film, 118: third resist film, 119: opening pattern,
120: barrier metal film, 121: copper film, 122: opening pattern,
and 201: chemically amplified resist.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0059] There will be described components constituting a chemically
amplified resist according to this invention.
[0060] In this invention, a base resin used is a resin whose alkali
solubility varies by the action of an acid and which is transparent
at a wavelength of a light source used in lithography. A material
having a side chain susceptible to acid hydrolysis is used, to
ensure an adequate solubility difference in a developing solution
before and after exposure.
[0061] Specifically, it may be appropriately selected from known
materials commonly used for a chemically amplified resist. For
example, a positive resist composition can comprise a base resin
having an acidic functional group protected with a
dissolution-inhibiting group which is alkali-insoluble or
alkali-poorly-soluble and which becomes alkali-soluble after
removing the dissolution-inhibiting group. A negative resist
composition may comprise an alkali-soluble base resin which becomes
alkali-poorly-soluble by crosslinking by the action of a
crosslinking agent. The term, "alkali-insoluble" or
"alkali-poorly-soluble" as used herein means that dissolution rate
in a 2.38 wt % aqueous solution of TMAH (tetramethylammonium
hydroxide) is less than 20 .ANG./sec while "alkali-soluble" means
that it is from 20 to 300 .ANG./sec.
[0062] Examples of a base resin for a KrF excimer laser resist at a
wavelength of 248 nm, an EUV resist at a wavelength of 3 to 20 nm,
an EB resist or a X-ray resist include polyhydroxystyrene (PHS),
and a copolymer of hydroxystrene with one or more monomers such as
styrene, (meth)acrylates and the like. Examples of a base resin for
an ArF excimer laser resist at a wavelength of 193 nm include
poly(meth)acrylates, alternating copolymers of norbornene and
maleic anhydride, polynorbornenes and metathesis ring-opened
polymers. Examples of a base resin for an F.sub.2 excimer laser at
a wavelength of 157 nm include the above-mentioned polymers which
are fluorinated. However, the base resin is not limited to these
polymers.
[0063] The term, "(meth)acrylic acid" and (meth)acrylate" as used
herein refers to methacrylic acid or acrylic acid, and methacrylate
or acrylate, respectively. A base resin used in a positive resist
composition is a base resin in which the hydrogen in a phenolic or
carboxylic hydroxy group is replaced with a dissolution-inhibiting
group. Generally, such replacement reduces a dissolution rate in an
unexposed area.
[0064] A dissolution-inhibiting group in a base resin may be
selected from a group of, for example, a tertiary alkyl group
having 4 to 40 carbon atoms, a trialkylsilyl group having 1 to 6
carbon atoms, an oxoalkyl group having 4 to 20 carbon atoms and so
on.
[0065] Specifically, examples of a dissolution-inhibiting group
include, for example, tert-butoxycarbonyl,
tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,
tert-amyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,
2-tetrahydropyranyloxycarbonylmethyl and
2-tetrahydrofuranyloxycarbonylmethyl; straight or branched acetals
such as 1-methoxyethyl, 1-ethoxyethyl, 1-n-propoxyethyl,
1-isopropoxyethyl, 1-n-butoxyethyl, 1-isobutoxyethyl,
1-sec-butoxyethyl, 1-tert-butoxyethyl, 1-tert-amyloxyethyl,
1-cyclohexyloxyethyl, 1-methoxypropyl, 1-ethoxypropyl,
1-methoxy-1-methylethyl and 1-ethoxy-1-methylethyl; and cyclic
acetals such as tetrahydrofuranyl and tetrahydropyranyl, preferably
1-ethoxyethyl, 1-n-butoxyethyl and 1-ethoxypropyl.
[0066] Alternatively, 0.1% or more of hydrogen atoms in hydroxy
groups in a base resin may be inter-molecularly or
intra-molecularly crosslinked via a crosslinking group.
[0067] A weight-average molecular weight of a base resin is
preferably about 5.times.10.sup.3 to 1.times.10.sup.5. A molecular
weight of less than 5.times.10.sup.3 may lead to insufficient
coatability or resolution, while a molecular weight of more than
1.times.10.sup.5 may lead to deteriorated resolution.
[0068] In this invention, a photoacid generator used may be a
compound which generates an acid by irradiation of a high energy
beam. Depending on the type of a light source, it may be
appropriately selected from known materials. For example, for a KrF
resist, it may be selected from a sulfonium salt, an iodonium salt,
a sulfonyldiazomethanes and an N-sulfonyloxyimide type acid
generator, which may be used alone or in combination of two or
more.
[0069] A sulfonium salt is a salt of a sulfonium cation with a
sulfonate. Examples of a sulfonium cation include
triphenylsulfonium, (4-tert-butoxyphenyl)diphenylsulfonium,
bis(4-tert-butoxyphenyl)phenylsulfonium,
tris(4-tert-butoxyphenyl)sulfonium,
(3-tert-butoxyphenyl)diphenylsulfonium,
bis(3-tert-butoxyphenyl)phenylsulfonium,
tris(3-tert-butoxyphenyl)sulfonium,
(3,4-di-tert-butoxyphenyl)diphenylsulfonium,
bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,
tris(3,4-di-tert-butoxyphenyl)sulfonium,
diphenyl(4-thiophenoxyphenyl)sulfonium,
(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,
tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,
(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,
tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,
dimethyl(2-naphthyl)sulfonium, 4-hydroxyphenyldimethylsulfonium,
4-methoxyphenyldimethylsulfonium, trimethylsulfonium,
2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium and
tribenzylsulfonium cations.
[0070] Examples of a sulfonate include trifluoromethanesulfonate,
nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,
2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,
4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,
toluenesulfonate, benzenesulfonate,
4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,
camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,
butanesulfonate and methanesulfonate. A sulfonium salt as a
combination of these may be used.
[0071] An iodonium salt is a salt of iodonium cation with a
sulfonate. Examples of an iodonium cation include aryliodonium
cations such as diphenyliodonium, bis(4-tert-butylphenyl)iodonium,
4-tert-butoxyphenylphenyliodonium and
4-methoxyphenylphenyliodonium.
[0072] Examples of a sulfonate include trifluoromethanesulfonate,
nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,
2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,
4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,
toluenesulfonate, benzenesulfonate,
4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,
camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,
butanesulfonate and methanesulfonate. An iodonium salt as a
combination of these may be used.
[0073] Examples of a sulfonyldiazomethane include
bissulfonyldiazomethanes such as bis(ethylsulfonyl)diazomethane,
bis(1-methylpropylsulfonyl)diazomethane,
bis(2-methylpropylsulfonyl)diazomethane,
bis(,1-dimethylethylsulfonyl)diazomethane,
bis(cyclohexylsulfonyl)diazomethane,
bis(perfluoroisopropylsulfonyl)diazomethane,
bis(phenylsulfonyl)diazomethane,
bis(4-methylphenylsulfonyl)diazomethane,
bis(2,4-dimethylphenylsulfonyl)diazomethane, and
bis(2-naphthylsulfonyl)diazomethane, sulfonylcarbonyldiazomethanes
such as 4-methylphenylsulfonylbenzoyldiazomethane,
tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,
2-naphthylsulfonylbenzoyidiazomethane,
4-methylphenylsulfonyl-2-naphthoyidiazomethane,
methylsulfonylbenzoyidiazomethane, and,
tert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane, and so
on.
[0074] Examples of an N-sulfonyloxyimide type photoacid generator
include a combination of a moiety of an imide such as succinimide,
naphthalenedicarboxylic imide, phathalimide, cyclohexyldicarboxylic
imide, 5-norbornene-2,3-dicarboxylic imide,
7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic imide with a
sulfonate such as trifluoromethanesulfonate,
nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,
2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,
4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,
toluenesulfonate, benzenesulfonate, naphthalenesulfonate,
camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,
butanesulfonate and methanesulfonate.
[0075] Examples of a benzoinsulfonate type photoacid generator
include benzoin tosylate, benzoin mesylate and benzoin
butanesulfonate.
[0076] Examples of a pyrogallol trisulfonate type photoacid
generator include pyrogallol, phloroglucinol, catechol, resorcinol
and hydroquinone derivatives, all of whose hydroxyl groups are
replaced with an appropriate sulfonate such as
trifluoromethanesulfonate, nonafluorobutanesulfonate,
heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,
pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,
4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,
naphthalenesulfonate, camphorsulfonate, octanesulfonate,
dodecylbenzenesulfonate, butanesulfonate and methanesulfonate.
[0077] Examples of a nitrobenzylsulfonate type photoacid generator
include 2,4-dinitrobenzylsulfonate, 2-nitrobenzylsulfonate and
2,6-dinitrobenzylsulfonate. Examples of a sulfonate include
trifluoromethanesulfonate, nonafluorobutanesulfonate,
heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,
pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,
4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,
naphthalenesulfonate, camphorsulfonate, octanesulfonate,
dodecylbenzenesulfonate, butanesulfonate and methanesulfonate.
Alternatively, a compound whose nitro group substituted to the
benzyl moiety is replaced with a trifluoromethyl group may be used
as same as a nitro benzylsulfonate type photoacid generator.
[0078] Examples of a sulfone type photoacid generator include
bis(phenylsulfonyl)methane, bis(4-methylphenylsulfonyl)methane,
bis(2-naphthylsulfonyl)methane, 2,2-bis(phenylsulfonyl)propane,
2,2-bis(4-methylphenylsulfonyl)propane,
2,2-bis(2-naphthylsulfonyl)propane,
2-methyl-2-(p-toluenesulfonyl)propiophenone,
2-(cyclohexylcarbonyl)-2-(p-toluenesulfonyl)propane,
2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one and so on.
[0079] Examples of a glyoxime derivative type photoacid generator
include O,O'-bis(p-toluenesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(p-toluenesulfonyl)-.alpha.-diphenylglyoxime,
O,O'-bis(p-toluenesulfonyl)-.alpha.-dicyclohexylglyoxime,
O,O'-bis(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,
O,O'-bis(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,
O,O'-bis(n-butanesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(n-butanesulfonyl)-.alpha.-diphenylglyoxime,
O,O'-bis(n-butanesulfonyl)-.alpha.-dicyclohexylglyoxime,
O,O'-bis(n-butanesulfonyl)-2,3-pentanedioneglyoxime,
O,O'-bis(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,
O,O'-bis(methanesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(trifluoromethanesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(1,1,1-trifluoroethanesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(tert-butanesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(perfluorooctanesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(cyclohexylsulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(benzenesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(p-fluorobenzenesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(p-tert-butyl benzenesulfonyl)-.alpha.-dimethylglyoxime,
O,O'-bis(xylenesulfonyl)-.alpha.-dimethylglyoxime and
O,O'-bis(camphorsulfonyl)-.alpha.-dimethylglyoxime.
[0080] Among others, a preferable photoacid generator is a
sulfonium salt, a bissulfonyldiazomethane and an N-sulfonyloxyimide
type photoacid generator.
[0081] Photoacid generators may be used alone or in combination of
two or more.
[0082] A content of an acid generator is preferably 0.2 to 50 wt
parts, particularly 0.5 to 40 wt parts to 100 wt parts of the total
base resin. If it is less than 0.2 wt parts, an inadequate amount
of an acid may be generated during exposure, leading to
deteriorated sensitivity or resolution. If it is more than 50 wt
parts, a transparency of a resist may be too low to provide
adequate resolution.
[0083] A resist composition of this invention may contain a
quencher, with which poisoning in a resist can be suitably
prevented. A suitable quencher is a compound which reduces a
diffusion rate of an acid generated from a photoacid generator in a
resist film. Such a material can be added to reduce a diffusion
rate of an acid in a resist film, resulting in improved resolution;
to minimize fluctuation of sensitivity after exposure; and to
minimize substrate- or environment-dependency to improve exposure
margin or pattern profile.
[0084] A quencher is suitably a basic compound including ammonia;
primary, secondary and tertiary aliphatic amines; mixed amines;
aromatic amines; heterocyclic amines; nitrogen-containing compounds
having carboxyl; nitrogen-containing compounds having sulfonyl;
nitrogen-containing compounds having hydroxy; nitrogen-containing
compounds having hydroxyphenyl; alcoholic nitrogen-containing
compounds; amide derivatives; and imide derivatives.
[0085] Examples of a primary aliphatic amine include methylamine,
ethylamine, n-propylamine, isopropylamine, n-butylamine,
isobutylamine, sec-butylamine, tert-butylamine, pentylamine,
tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,
heptylamine, octylamine, nonylamine, decylamine, dodecylamine,
cetylamine, methylenediamine, ethylenediamine and
tetraethylenepentamine. Examples of a secondary aliphatic amine
include dimethylamine, diethylamine, di-n-propylamine,
diisopropylamine, di-n-butylamine, diisobutylamine,
di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine,
dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine,
didecylamine, didodecylamine, dicetylamine,
N,N'-dimethylmethylenediamine, N,N'-dimethylethylenediamine and
N,N''''-dimethyltetraethylenepentamine. Examples of a tertiary
aliphatic amine include trimethylamine, triethylamine,
tri-n-propylamine, triisopropylamine, tri-n-butylamine,
triisobutylamine, tri-sec-butylamine, tripentylamine,
tricyclopentylamine, trihexylamine, tricyclohexylamine,
triheptylamine, trioctylamine, trinonylamine, tridecylamine,
tridodecylamine, tricetylamine,
N,N,N',N'-tetramethylmethylenediamine,
N,N,N',N'-tetramethylethylenediamine and
N,N,N'''',N''''-tetramethyltetraethylenepentamine.
[0086] Examples of a mixed amine include dimethylethylamine,
methylethylpropylamine, benzylamine, phenetylamine and
benzyldimethylamine. Examples of an aromatic or heterocyclic amine
include anilines such as aniline, N-methylaniline, N-ethylaniline,
N-propylaniline, N,N-dimethylaniline, 2-methylaniline,
3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,
trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,
2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline and
N,N-dimethyltoluidine; diphenyl(p-tolyl)amine; methyldiphenylamine;
triphenylamine; phenylenediamine; naphthylamine;
diaminonaphthalene; pyrroles such as pyrrole, 2H-pyrrole,
1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole and
N-methylpyrrole; oxazoles such as oxazole and isoxazole; thiazoles
such as thiazole and isothiazole; imidazoles such as imidazole,
4-methylimidazole and 4-methyl-2-phenylimidazole; pyrazoles;
furazans; pyrrolines such as pyrroline and 2-methyl-1-pyrroline;
pyrrolidines such as pyrrolidine, N-methylpyrrolidine,
pyrrolidinone and N-methylpyrrolidone; imidazolines;
imidazolidines; pyridines such as pyridine, methylpyridine,
ethylpyridine, propylpyridine, butylpyridine,
4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine,
triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine,
4-tert-butylpyridine, diphenylpyridine, benzylpyridine,
methoxypyridine, butoxypyridine, dimethoxypyridine,
4-pyrrolidinopyridine, 2-(1-ethylpropyl)pyridine, aminopyridine and
dimethylaminopyridine; pyridazines; pyrimidines; pyrazines;
pyrazolines; pyrazolidines; piperidines; piperazines; morpholines;
indoles; isoindoles; 1H-indazoles; indolines; quinolines such as
quinoline and 3-quinolinecarbonitrile; isoquinolines; cinnolines;
quinazolines; quinoxalines; phthalazines; purines; pteridines;
carbazoles; phenanthridines; acridines; phenazine;
1,10-phenanthrolines; adenines; adenosines; guanines; guanosines;
uracils; uridines, and so on.
[0087] Examples of a nitrogen-containing compound having a carboxyl
group include aminobenzoic acids; indole carboxylic acids; amino
acid derivatives such as nicotinic acid, alanine, arginine,
aspartic acid, glutamic acid, glycine, histidine, isoleucine,
glycylleucine, leucine, methionine, phenylalanine, threonine,
lysine, 3-aminopyrazine-2-carboxylic acid and methoxyalanine, and
so on.
[0088] Examples of a nitrogen-containing compound having a sulfonyl
group include 3-pyridinesulfonic acid, pyridinium
p-toluenesulfonate, and so on.
[0089] Examples of a nitrogen-containing compound having a hydroxy
group, a nitrogen-containing compound having a hydroxyphenyl group
or an alcoholic nitrogen-containing compound include
2-hydroxypyridine, aminocresol, 2,4-quinolinediol, 3-indolemethanol
hydrate, monoethanolamine, diethanolamine, triethanolamine,
N-ethyldiethanolamine, N,N-diethylethanolamine,
triisopropanolamine, 2,2'-iminodiethanol, 2-aminoethanol,
3-amino-1-propanol, 4-amino-1-butanol,
4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine,
1-(2-hydroxyethyl)piperazine,
1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidineethanol,
1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,
3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,
8-hydroxyyulolidine, 3-quinuclidinol, 3-tropanol,
1-methyl-2-pyrrolidineethanol, 1-aziridineethanol,
N-(2-hydroxyethyl)phthalimide, N-(2-hydroxyethyl)isonicotinamide
and so on.
[0090] Examples of an amide include formamide, N-methylformamide,
N,N-dimethylformamide, acetamide, N-methylacetamide,
N,N-dimethylacetamide, propionamide, benzamide and so on.
[0091] Examples of an imide include phthalimide, succinimide,
maleimide and so on.
[0092] Other examples which can be used as a quencher include
tris(2-methoxymethoxyethyl)amine,
tris[2-(2-methoxyethoxy)ethyl]amine,
tris[2-(2-methoxyethoxymethoxy)ethyl]amine,
tris[2-(1-methoxyethoxy)ethyl]amine,
tris[2-(1-ethoxyethoxy)ethyl]amine,
tris[2-(1-ethoxypropoxy)ethyl]amine,
tris{2-[2-(2-hydroxyethoxy)ethoxy]ethyl}amine,
4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,
4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,
1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane,
1-aza-12-crown-4,1-aza-15-crown-5,1-aza-18-crown-6,
tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine,
tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine,
tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine,
tris(2-pivaloyloxyethyl)amine,
N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,
tris(2-methoxycarbonyloxyethyl)amine,
tris(2-tert-butoxycarbonyloxyethyl)amine,
tris[2-(2-oxopropoxy)ethyl]amine,
tris[2-(methoxycarbonylmethyl)oxyethyl]amine,
tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,
tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,
tris(2-methoxycarbonylethyl)amine,
tris(2-ethoxycarbonylethyl)amine,
N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,
N,N-bis(2-acetoxyethyl).sub.2-[(methoxycarbonyl)methoxycarbonyl]ethylamin-
e, N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylam-
ine,
N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]eth-
ylamine,
N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,
N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,
N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,
N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,
N-(2-hydroxyethyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-(2-acetoxyethyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-(2-hydroxyethyl)bis[2-(ethoxycarbonyl)ethyl]amine,
N-(2-acetoxyethyl)bis[2-(ethoxycarbonyl)ethyl]amine,
N-(3-hydroxy-1-propyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-(3-acetoxy-1-propyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-(2-methoxyethyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-butylbis[2-(methoxycarbonyl)ethyl]amine,
N-butylbis[2-(2-methoxyethoxycarbonyl)ethyl]amine,
N-methylbis(2-acetoxyethyl)amine, N-ethylbis(2-acetoxyethyl)amine,
N-methylbis(2-pivaloyloxyethyl)amine,
N-ethylbis[2-(methoxycarbonyloxy)ethyl]amine,
N-ethylbis[2-(tert-butoxycarbonyloxy)ethyl]amine,
tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,
N-butylbis(methoxycarbonylmethyl)amine,
N-hexylbis(methoxycarbonylmethyl)amine,
.beta.-(diethylamino)-.delta.-valerolactone and so on.
[0093] Quenchers may be used alone or in combination of two or
more.
[0094] Their content is suitably 0 to 2 wt parts, particularly 0.01
to 1 wt part to 100 wt parts of the solid in a resist material. If
it is more than 2 wt parts, sensitivity may be excessively
lowered.
[0095] In this invention, a salt exhibiting buffer effect may be
preferably a compound which can prevent fluctuation of a proton
concentration in a resist to keep the concentration constant as if
equilibrium is established in the resist. Particularly preferably,
a resist composition comprises an anion of an acid generated from a
photoacid generator or its substituted derivative, to effectively
prevent fluctuation of a proton concentration in the resist. Thus,
for example, fluctuation of a proton concentration can be prevented
when an organic base such as an amine permeates into a resist
composition.
[0096] An acid in a photoacid generator may be an acid having a
less volatile anion or an anion which is not extremely diffusible.
Examples of a suitable anion herein include benzenesulfonate anion,
toluenesulfonate anion, xylenesulfonate anion,
4-chlorobenzenesulfonate anion,
4-(4-toluenesulfonyloxy)benzenesulfonate anion,
pentafluorobenzenesulfonate anion, tert-butanesulfonate anion,
2,2,2-trifluoroethanesulfonate anion, nonafluorobutanesulfonate
anion, heptadecafluorooctanesulfonate anion and camphorsulfonate
anion. It may be preferably selected from, for example, the acids
represented by general formulas (A) to (E).
##STR00001##
[0097] A salt exhibiting buffer effect may comprise any of the
bases or their substituted derivatives which can be used as a
quencher, to reliably improve resolution of a resist pattern. Such
a base may be, for example, suitably an amine.
[0098] Examples of a base which can be used as a quencher include
amines such as 2-hydroxypyridine, aminocresol, 2,4-quinolinediol,
3-indolemethanol hydrate, monoethanolamine, diethanolamine,
triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine,
triisopropanolamine, 2,2'-iminodiethanol, 2-aminoethanol,
3-amino-1-propanol, 4-amino-1-butanol,
4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine,
1-(2-hydroxyethyl)piperazine,
1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidineethanol,
1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,
3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,
8-hydroxyyulolidine, 3-quinuclidinol, 3-tropanol,
1-methyl-2-pyrrolidineethanol, 1-aziridineethanol,
tris(2-methoxymethoxyethyl)amine,
tris(2-(2-methoxyethoxy)ethyl)amine,
tris(2-(2-methoxyethoxymethoxy)ethyl)amine,
tris(2-(1-methoxyethoxy)ethyl)amine,
tris(2-(1-ethoxyethoxy)ethyl)amine,
tris(2-(1-ethoxypropoxy)ethyl)amine,
tris[2-(2-(2-hydroxyethoxy)ethoxy)ethyl]amine,
tris(2-formyloxyethyl)amine, tris(2-acetoxyethylamine,
tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine,
tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine,
tris(2-pivaloyloxyethyl)amine,
N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,
tris(2-methoxycarbonyloxyethyl)amine,
tris(2-tert-butoxycarbonyloxyethyl)amine,
tris[2-(2-oxopropoxy)ethyl]amine,
tris[2-(methoxycarbonylmethyl)oxyethyl]amine,
tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,
tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,
tris(2-methoxycarbonylethyl)amine,
tris(2-ethoxycarbonylethyl)amine,
N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethyl amine,
N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,
N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,
N,N-bis(2-hydroxyethyl)2-(2-oxopropoxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,
N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,
N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylam-
ine,
N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]eth-
ylamine,
N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,
N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,
N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,
N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,
N-(2-hydroxyethyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-(2-acetoxyethyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-(2-hydroxyethyl)bis[2-(ethoxycarbonyl)ethyl]amine,
N-(2-acetoxyethyl)bis[2-(ethoxycarbonyl)ethyl]amine,
N-(3-hydroxy-1-propyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-(3-acetoxy-1-propyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-(2-methoxyethyl)bis[2-(methoxycarbonyl)ethyl]amine,
N-butylbis[2-(methoxycarbonyl)ethyl]amine,
N-butylbis[2-(2-methoxyethoxycarbonyl)ethyl]amine,
N-methylbis(2-acetoxyethyl)amine, N-ethylbis(2-acetoxyethyl)amine,
N-methylbis(2-pivaloyloxyethyl)amine,
N-ethylbis[2-(methoxycarbonyloxy)ethyl]amine,
N-ethylbis[2-(tert-butoxycarbonyloxy)ethyl]amine,
tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,
N-butylbis(methoxycarbonylmethyl)amine,
N-hexylbis(methoxycarbonylmethyl)amine and
.beta.-(diethylamino)-.delta.-valerolactone.
[0099] A preferable salt exhibiting buffer effect is a salt of
sulfonic acid with alkanolamine or alkoxyalkylamine. Specific
compounds may be those represented by formulas (F) to (H), which
can be used to reliably improve sensitivity during forming a resist
pattern.
t-BuSO.sub.3HN(C.sub.2H.sub.4CH).sub.3 (F)
C.sub.4F.sub.9SO.sub.3HN(CH.sub.2CCH.sub.3).sub.3 (G)
##STR00002##
[0100] An acid constituting a salt exhibiting buffer effect is
preferably a substance whose pKa (25.degree. C.) is from 3 to 12 in
acetonitrile. Such a substance can be added to a resist composition
to achieve adequate buffer effect for reliable resist
performance.
[0101] A content of a salt exhibiting buffer effect in a resist
composition is not particularly limited as long as it is adequate
to exert buffer effect, and for example, is not less than 0.001 wt
parts, preferably not less than 0.01 wt parts to 100 wt parts of a
solid in the resist composition. Thus, buffer effect can be ensured
in the resist composition. The salt exhibiting buffer effect may be
contained at up to 30 wt parts, preferably up to 10 wt parts to 100
wt parts of a solid in the resist composition. Thus, a desirable
resist shape can be reliably formed.
[0102] When adding a salt exhibiting buffer effect to a resist
composition, it may be added after being formed as a salt, or may
be added as a mixed solution prepared by mixing an acid and a base
in an organic solvent.
[0103] A resist composition of this invention may contain an
organic solvent, which may be capable of dissolving a photoacid
generator and a base resin. Examples of such an organic solvent
include, but not limited to, ketones such as cyclohexanone and
methyl-n-amylketone; alcohols such as 3-methoxybutanol,
3-methyl-3-methoxybutanol, 1-methoxy-2-propanol and
1-ethoxy-2-propanol; ethers such as propyleneglycolmonomethyl
ether, ethyleneglycolmonomethyl ether, propyleneglycolmonoethyl
ether, ethyleneglycolmonoethyl ether, propyleneglycoldimethyl ether
and diethyleneglycoldimethyl ether; and esters such as
propyleneglycolmonomethyl ether acetate, propyleneglycolmonoethyl
ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl
3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,
tert-butyl propionate and propyleneglycol-mono-tert-butyl ether
acetate, which can be used alone or in combination of two or more.
Among these, organic solvents preferably used in this invention are
diethyleneglycoldimethyl ether, 1-ethoxy-2-propanol and ethyl
lactate which exhibit the highest ability of dissolving an acid
generator in a resist composition, and propyleneglycolmonomethyl
ether acetate which is a safe solvent, as well as mixtures
thereof.
[0104] When a resist composition of this invention is a negative
type, it may comprise a crosslinking agent, which may be a compound
having two or more intramolecular hydroxymethyl, alkoxymethyl,
epoxy or vinyl ether groups.
[0105] Suitable examples may include substituted glycolurils, ureas
and hexa(methoxymethyl)melamine. Specific examples include
N,N,N',N'-tetramethoxymethylurea, hexamethylmelamine;
tetrahydroxymethylglycoluril; tetraalkoxymethyl-substituted
glycolurils such as tetramethoxymethylglycoluril; and condensation
products of a phenol compound (e.g., bis(hydroxymethylphenol)s and
bisphenol-A) with epichlorohydrin. Particularly suitable
crosslinking agents include 1,3,4,6-tetrahydroxymethylglycoluril,
1,3,4,6-tetraalkoxymethylglycolurils such as
1,3,4,6-tetramethoxymethylglycoluril, 2,6-dihydroxymethyl-p-cresol,
2,6-dihydroxymethylphenol, 2,2',6,6'-tetrahydroxymethylbisphenol-A,
1,4-bis[2-(2-hydroxypropyl)phenyl]benzene,
N,N,N',N'-tetramethoxymethylurea and hexamethoxymethylmelamine.
[0106] A crosslinking agent may preferably initiate crosslinking by
an acid. Its content may be appropriately determined, and is
generally 1 to 25 wt parts, preferably 5 to 20 wt parts to 100
parts of the total solid in a resist composition. They may be used
alone or in combination of two or more.
[0107] When a resist composition of this invention is a positive
type, it may comprise a dissolution inhibitor. A dissolution
inhibitor may be a compound having a molecular weight of up to
3.times.10.sup.3 whose solubility in an alkali developing solution
varies by the action of an acid; particularly, a phenol or
carboxylic acid derivative having a lower molecular weight of up to
2.5.times.10.sup.3, whose functional groups are partly or entirely
substituted with an acid-labile substituent.
[0108] Examples of a phenol or carboxylic acid derivative having a
molecular weight of up to 2.5.times.10.sup.3 includes bisphenol-A,
bisphenol-F, bisphenol-S, 4,4-bis(4-hydroxyphenyl)valeric acid,
tris(4-hydroxyphenyl)methane, 1,1,1-tris(4-hydroxyphenyl)ethane,
1,1,2-tris(4-hydroxyphenyl)ethane, phenolphthalein and
thymolphthalein. An acid-labile substituent may be selected from
dissolution-inhibiting groups for a base resin.
[0109] Examples of a suitable dissolution inhibitor include
bis[4-(2-tetrahydropyranyloxy)phenyl]methane,
bis[4-(2-tetrahydrofuranyloxy)phenyl]methane,
bis[4-tert-butoxyphenyl]methane,
bis(4-tert-butoxycarbonyloxyphenyl)methane,
bis(4-tert-butoxycarbonylmethyloxyphenyl)methane,
bis[4-(1-ethoxyethoxy)phenyl]methane,
bis[4-(1-ethoxypropyloxy)phenyl]methane,
2,2-bis[4-(2-tetrahydropyranyloxy)phenyl]propane,
2,2-bis[4-(2-tetrahydrofuranyloxy)phenyl]propane,
2,2-bis(4-tert-butoxyphenyl)propane,
2,2-bis(4-tert-butoxycarbonyloxyphenyl)propane,
2,2-bis(4-tert-butoxycarbonylmethyloxyphenyl)propane,
2,2-bis[4-(1-ethoxyethoxy)phenyl]propane,
2,2-bis[4-(1-ethoxypropyloxy)phenyl]propane, tert-butyl
4,4-bis[4-(2-tetrahydropyranyloxy)phenyl]valerate, tert-butyl
4,4-bis[4-(2-tetrahydrofuranyloxy)phenyl]valerate, tert-butyl
4,4-bis(4-tert-butoxyphenyl)valerate, tert-butyl
4,4-bis(4-tert-butoxycarbonyloxyphenyl)valerate, tert-butyl
4,4-bis(4-tert-butoxycarbonylmethyloxyphenyl)valerate, tert-butyl
4,4-bis[4-(1-ethoxyethoxy)phenyl]valerate, tert-butyl
4,4-bis[4-(1-ethoxypropyloxy)phenyl]valerate,
tris[4-(2-tetrahydropyranyloxy)phenyl]methane,
tris[4-(2-tetrahydrofuranyloxy)phenyl]methane,
tris(4-tert-butoxyphenyl)methane,
tris(4-tert-butoxycarbonyloxyphenyl)methane,
tris(4-tert-butoxycarbonyloxymethylphenyl)methane,
tris[4-(1-ethoxyethoxy)phenyl]methane,
tris[4-(1-ethoxypropyloxy)phenyl]methane,
1,1,2-tris[4-(2-tetrahydropyranyloxy)phenyl]ethane,
1,1,2-tris[4-(2-tetrahydrofuranyloxy)phenyl]ethane,
1,1,2-tris(4-tert-butoxyphenyl)ethane,
1,1,2-tris(4-tert-butoxycarbonyloxyphenyl)ethane,
1,1,2-tris(4-tert-butoxycarbonylmethyloxyphenyl)ethane,
1,1,2-tris[4-(1-ethoxyethoxy)phenyl]ethane and
1,1,2-tris[4-(1-ethoxypropyloxy)phenyl]ethane.
[0110] A content of a dissolution inhibitor in a resist composition
used for a chemically amplified resist is preferably up to 20 wt
parts, more preferably up to 15 wt parts to 100 wt parts of a solid
in the resist material. If it is more than 20 wt parts, increased
monomer components may cause deterioration in heat resistance of
the resist material.
[0111] There will be described a semiconductor process using a
resist composition according to this invention with reference to
the drawings. In the following embodiments, the resist compositions
described above are used.
Embodiment 1
[0112] This embodiment illustrates a dual damascene process
employing a via-first method, using a chemically amplified resist
composition. FIG. 1 is cross-sectional views showing a
manufacturing process for a semiconductor device according to this
embodiment.
[0113] First, on a lower interconnection layer 108 are sequentially
deposited a first etching stopper film 107, a first interlayer
insulating film 106, a second etching stopper film 105, a second
interlayer insulating film 104 and a third interlayer insulating
film 103. Then, using well-known lithography and etching technique,
a via-hole 111 is formed in the third interlayer insulating film
103, the second interlayer insulating film 104, the second etching
stopper film 105 and the first interlayer insulating film 106 (FIG.
1(a)).
[0114] Then, an anti-reflection film 102 is formed on the third
interlayer insulating film 103 and the first etching stopper film
107, during which the via-hole 111 is partly or totally buried with
the anti-reflection film 102. This figure shows that the via-hole
111 is partly buried with the anti-reflection film 102 (FIG.
1(b)).
[0115] Next, on the anti-reflection film 102 is applied a
chemically amplified resist 101 (FIG. 1(c)). Then, in the
chemically amplified resist 101 is formed an opening pattern 112
for forming an interconnection trench connected to the via-hole 111
(FIG. 1(d)). Herein, the resist composition described above is used
for forming the chemically amplified resist 101. Such a resist
composition can be used as a chemically amplified resist 101 to
provide a resist pattern exhibiting improved sensitivity and
resolution when forming an opening pattern 112.
[0116] Subsequently, using the chemically amplified resist 101 as a
mask, the anti-reflection film 102 on the third interlayer
insulating film 103, and then the third interlayer insulating film
103 and the second interlayer insulating film 104 are etched off to
form an interconnection trench 113 (FIGS. 1(e) and (f)).
[0117] Then, the chemically amplified resist 101 and the
anti-reflection film 102 are stripped off by O.sub.2 plasma ashing
and using an amine stripper. Next, the first etching stopper film
107 at the bottom of the via-hole 111 is etched off to provide a
structure where the via-hole 111 is connected to the upper surface
of the interconnection metal (not shown) in the lower
interconnection layer 108 (FIG. 1(g)).
[0118] Next, a metal film is formed so that it buries the
interconnection trench 113 and the via-hole 111. The metal film can
be formed by first forming a barrier metal film within the
interconnection trench 113 and the via-hole 111 by sputtering and
then burying the interconnection trench 113 and the via-hole 111
with an interconnection metal film by, for example, electroplating.
Subsequently, unwanted barrier metal and interconnection metal
films outside the interconnection trench 113 are removed by CMP to
form an interconnection 109 (FIG. 1(h)). Thus, a semiconductor
device having a desired pattern can be reliably provided.
[0119] A light source used in lithography of a chemically amplified
resist 101 may be selected from, for example, KrF excimer laser,
ArF excimer laser, F.sub.2 excimer laser, EUV and EB.
[0120] The third interlayer insulating film 103 may be, for
example, an SiO.sub.2, SiOC, SiC or SiCN film. The second
interlayer insulating film 104 and the first interlayer insulating
film 106 may be a low dielectric-constant film made of a material
with a lower dielectric constant such as SiO.sub.2, HSQ, MSQ, MHSQ,
ladder-type hydrogenated siloxane, SiLK.RTM., SiOF, SiOC, SiON and
BCB (benzocyclobutene) films. When the first interlayer insulating
film 106 is a low dielectric-constant film, the film has a lower
density than an SiO.sub.2 film and thus tends to occlude an organic
base such as an amine, but allows the chemically amplified resist
101 to be much more effective, suitably ensuring sensitivity and
resolution of the resist pattern.
[0121] A ladder-type hydrogenated siloxane is a polymer having a
ladder-like molecular structure, which preferably has a dielectric
constant of 2.9 or less in the light of preventing interconnection
delay. For example, preferably, the density of a lower film is from
1.50 g/cm.sup.2 to 1.58 g/cm.sup.2 and its refractive index (at 633
nm) is from 1.38 to 1.40. A specific example of such a film
material is L-Ox.TM. which is called a ladder oxide (hereinafter,
referred to as "L-Ox"). An insulating material prepared by making
an L-Ox porous can be also used.
[0122] The second etching stopper film 105 and the first etching
stopper film 107 may be, for example, an SiC, SiN, SiON or SiCN
film. When the second etching stopper film 105 or the first etching
stopper film 107 is a nitrogen-containing film, a basic component
such as an amine tends to permeate into the second interlayer
insulating film 104 or the first interlayer insulating film 106.
However, when using such a film, a chemically amplified resist 101
can be employed to allow a salt in the chemically amplified resist
101 to be more effective. The chemically amplified resist 101 can
be more suitably used in a process for forming a resist pattern on
an insulating film comprising a concave to be an interconnection
trench or a via-hole.
[0123] As described above, according to this embodiment, a
chemically amplified resist 101 can be used to prevent poisoning of
a resist and to improve sensitivity in lithography.
Embodiment 2
[0124] The interconnection structure in FIG. 1(h) may be also
manufactured by a so-called trench-first method among dual
damascene processes. There will be described a copper
interconnection structure manufactured by a trench-first method
with reference to FIG. 2. In this embodiment, similar components to
those in Embodiment 1 are identified with the same symbols without
any description as appropriate.
[0125] As described in Embodiment 1, on a lower interconnection
layer 108 are sequentially deposited a first etching stopper film
107, a first interlayer insulating film 106, a second etching
stopper film 105, a second interlayer insulating film 104 and a
third interlayer insulating film 103. Then, using well-known
lithography and etching technique, an interconnection trench 113 is
formed in the third interlayer insulating film 103 and the second
interlayer insulating film 104 (FIG. 2(a)).
[0126] Then, an anti-reflection film 102 is formed on the third
interlayer insulating film 103 and the second etching stopper film
105, during which the interconnection trench 113 is partly or
totally buried with the anti-reflection film 102. This Figure shows
that the interconnection trench 113 is partly buried with the
anti-reflection film 102 (FIG. 2(b)).
[0127] Next, on the anti-reflection film 102 is applied a
chemically amplified resist 101 (FIG. 2(c)). Herein, the resist
composition described in Embodiment 1 is used as the chemically
amplified resist 101. Then, in the chemically amplified resist 101
is formed an opening pattern 122 for forming a via-hole connected
between the interconnection trench 113 and a lower interconnection
layer 108 (FIG. 2(d)).
[0128] Subsequently, using the chemically amplified resist 101 as a
mask, the anti-reflection film 102 on the second etching stopper
film 105, and then the second etching stopper film 105 and the
first interlayer insulating film 106 are etched off to form a
via-hole 111 (FIGS. 2(e) and (f)).
[0129] Then, the chemically amplified resist 101 and the
anti-reflection film 102 are stripped off by O.sub.2 plasma ashing
and using an organic stripper. Next, the first etching stopper film
107 at the bottom of the via-hole 111 is etched off to provide a
structure where the via-hole 111 is connected to the upper surface
of the interconnection metal (not shown) in the lower
interconnection layer 108 (FIG. 2(g)). FIG. 2(g) shows the same
structure as that in FIG. 1(g), so that an interconnection 109 can
be formed as described in Embodiment 1 in subsequent processes
(FIG. 2(h)).
[0130] As described above, in a trench-first process, a chemically
amplified resist 101 can be also used to prevent poisoning of a
resist and to improve sensitivity in lithography.
Embodiment 3
[0131] The resist composition used in Embodiment 1 or 2 can be
applied to a via-first dual damascene process using a three-layer
resist method. There will be described this process with reference
to FIG. 3.
[0132] First, on a lower interconnection layer 108 are sequentially
deposited a first etching stopper film 107 and an interlayer
insulating film 115. Then, using well-known lithography and etching
technique, a via-hole 111 is formed in the interlayer insulating
film 115 (FIG. 3(a)).
[0133] Then, an anti-reflection film (not shown) is formed on the
interlayer insulating film 115 and the first etching stopper film
107, during which the via-hole 111 is partly or totally buried with
the anti-reflection film. Then, on the anti-reflection film is
applied a three-layer resist film consisting of a first resist film
116, a second resist film 117 and a third resist film 118, in which
the first resist film 116 comprises the resist composition
described above. Then, in the third resist film 118 is formed an
opening pattern 119 for forming an interconnection trench connected
to the via-hole 111 (FIG. 3(b)).
[0134] Subsequently, using the third resist film 118 as a mask, the
second resist film 117 is etched off (FIG. 3(c)).
[0135] Then, the third resist film 118 is stripped off by O.sub.2
plasma ashing and using an organic stripper, during which the upper
part of the first resist film 116 is partly removed (FIG. 3(d)).
Next, using the second resist film 117 as a mask, the first resist
film 116 on the interlayer insulating film 115 and the interlayer
insulating film 115 are sequentially etched off to form an opening
pattern 119 (FIGS. 3(e) and (f)). Then, the first resist film 116
and the anti-reflection film (not shown) are stripped off by
O.sub.2 plasma ashing and using an organic stripper (FIG. 3(g)).
Then, the first etching stopper film 107 at the bottom of the
via-hole 111 is etched off to provide a structure where the
via-hole 111 is connected to the upper surface of the
interconnection metal (not shown) in the lower interconnection
layer 108 (FIG. 3(h)).
[0136] Next, a metal film is formed such that it buries the opening
pattern 119 (that is, the interconnection trench 113) and the
via-hole 111. The metal film can be formed by first forming a
barrier metal film 120 within the interconnection trench 113 and
the via-hole 111 by sputtering and then burying the interconnection
trench 113 and the via-hole 111 with an interconnection metal film
121 by, for example, electroplating (FIG. 3(i)). Subsequently, the
unwanted barrier metal film 120 and the interconnection metal film
121 outside the interconnection trench 113 are removed by CMP to
form an interconnection 109 (FIG. 3(j)).
[0137] In this embodiment, the first resist film 116 comprises a
salt exhibiting buffer effect, so that a highly sensitive
patterning can be achieved for the first resist film 116 even after
patterning the second resist film 117 and the third resist film
118.
[0138] This invention has been described with reference to some
embodiments. The person skilled in the art will easily appreciate
that these embodiments are only illustrative and there may be a
variety of modifications, all of which are encompassed by this
invention.
[0139] Although a resist composition has been described in terms of
a process used in a dual damascene process, it may be applied to
another semiconductor process or other processes such as a
manufacturing process for a reticule. In such a case, on a chromium
film may be, for example, patterned a chemically amplified resist,
which may be used as a mask for forming an opening with a desired
shape.
[0140] The resist composition in this embodiment can increase an
exposure margin without adding a quencher. It can be, therefore,
applied to not only lithography using a chemically amplified
resist, but also another type of resist such as a resist for EB
(electron beam) exposure. In the latter resist, a pattern with
improved sensitivity and resolution can be also attained.
EXAMPLES
Example 1
[0141] In this example, there was studied the action of a quencher
in a resist composition. As a model for a resist composition, a
solution of a given amount of a quencher in a non-aqueous solvent
was used and pH shift was determined by titration when adding an
acid generated from a photo-acid generator.
[0142] Specifically, acetonitrile and triethanolamine were used as
a non-aqueous solvent and a quencher, respectively. To a given
amount of triethanolamine in acetonitrile solution (100 mL) was
added dropwise 0.1M p-toluenesulfonic acid solution in acetonitrile
by 0.05 mL, using an automatic titrator (Hiranuma Autotitrator
COM-980Win; HIRANUMA SANGYO Co. Ltd.). Table 1 shows the
compositions of the samples titrated. In this table, 1 mM
monoethanolamine was added to Sample Nos. 2, 4, 6 and 8, as a model
for a system comprising a quencher in acetonitrile in a resist
composition, into which an amine permeated.
[0143] Table 1 also shows a point of neutralization determined for
each sample. Titration curves for the individual samples are shown
in FIGS. 4 and 5. FIG. 5 is an enlarged view of a pH range of 8.5
to 10 in the titration curves for the samples.
TABLE-US-00001 TABLE 1 Quencher External amine Point of Sample
Model Model neutralization number compound mM compound mM mM 1
N(C.sub.2H.sub.4OH).sub.3 0.0 NH.sub.2C.sub.2H.sub.4OH 0.0 0.0 2
N(C.sub.2H.sub.4OH).sub.3 0.0 NH.sub.2C.sub.2H.sub.4OH 1.0 1.0 3
N(C.sub.2H.sub.4OH).sub.3 4.0 NH.sub.2C.sub.2H.sub.4OH 0.0 4.0 4
N(C.sub.2H.sub.4OH).sub.3 4.0 NH.sub.2C.sub.2H.sub.4OH 1.0 5.0 5
N(C.sub.2H.sub.4OH).sub.3 8.0 NH.sub.2C.sub.2H.sub.4OH 0.0 8.0 6
N(C.sub.2H.sub.4OH).sub.3 8.0 NH.sub.2C.sub.2H.sub.4OH 1.0 9.1 7
N(C.sub.2H.sub.4OH).sub.3 12.0 NH.sub.2C.sub.2H.sub.4OH 0.0 12.0 8
N(C.sub.2H.sub.4OH).sub.3 12.0 NH.sub.2C.sub.2H.sub.4OH 1.0
13.1
[0144] These results indicate the followings.
[0145] The quencher mechanism in the prior art has proposed that a
quencher causes deprotonation represented by formula (1), resulting
in buffer effect.
--NH.revreaction.--N+H (1)
[0146] However, the equilibrium reaction in formula (1) does not
easily move toward the right side. The pKa of conjugated acid of
amines is usually much higher than the pKa of acids. For example,
the pKa of conjugated acid of triethanolamine is 15.9, while the
pKa of p-toluenesulfonic acid is 8.7 in acetonitrile at 25.degree.
C. (Kimisuke Izutsu, "Hisuiyoueki no Denkikagaku (Electrochemistry
in Nonaqueous solutions)", edited by Baihukan, 1995, p. 48 and 53).
Therefore, in formula (1) under acidic conditions where a photoacid
generator exists, it can be assumed that dissociation of a proton
attached to an amine may be almost negligible.
[0147] Categorizing the results in Table 1 and FIG. 4 in accordance
with relationship between a quencher concentration in a sample
(C.sub.b) and a concentration of an acid added into the sample
(C.sub.a), the following (i) to (iii) have been found.
(i) C.sub.b>C.sub.a
[0148] When a quencher concentration in a sample (C.sub.b) is
larger than an acid added into the sample (C.sub.a), i.e., in an
initial range in the titration curve, the quencher base is
neutralized by the acid added as demonstrated by equation (2):
R.sub.3N+HA.fwdarw.R.sub.3NHA (2)
[0149] wherein R represents C.sub.2H.sub.4OH in triethanolamine;
and A represents CH.sub.3C.sub.6H.sub.4SO.sub.3.sup.- group in
p-toluenesulfonic acid.
(ii) C.sub.b=C.sub.a
[0150] A neutralization point in each titration curve shown in FIG.
4 corresponds to, as shown in Table 1, the total base
concentration, i.e., the sum of a quencher concentration and an
external amine concentration. In samples 1, 3, 5 and 7 without an
external amine, an acid at the same concentration as an initial
concentration of the quencher C.sub.b is used for
neutralization.
[0151] In a practical resist composition, as a neutralization point
is higher, a concentration of the acid used in the reaction of
formula (2) is increased, resulting in reduction of a concentration
ratio of an acid generated from a photoacid generator which can act
on a photosensitive polymer. When this neutralization point is
fluctuated due to the presence of an external amine, a
concentration of the acid which can act on a photosensitive polymer
varies, so that a wide exposure margin cannot be set, which is
undesirable in the light of reliably conducting lithography.
(iii) C.sub.a>C.sub.b
[0152] FIG. 4 demonstrates that in a sample without an external
amine, as a concentration of an acid added (C.sub.a) increases, a
pH rapidly reduces and after a neutralization point, a proton
concentration [H.sup.+] significantly increases. In this range, an
equilibrium expressed by equation (3) is effective, where the acid
is dissociated and then moved to a matrix M for protons. In this
equation, the matrix M is acetonitrile.
HA+M.fwdarw.M.fwdarw.+A.sup.- (3)
[0153] An equilibrium constant Kc in equation (3) can be expressed
as equation (4) using an activity "a", and under approximation that
the "a" is equal to a molar concentration, the equation constant Kc
can be expressed by equation (5):
Kc = a ( H + ) a ( A - ) a ( HA ) a ( M ) ( 4 ) Kc = [ H + ] [ A -
] [ HA ] [ M ] ( 5 ) ##EQU00001##
[0154] Assuming that [MH.sup.+]<<[M] and [M] is a constant in
equation (5), equation (6) can be derived, where an acid
dissociation constant K.sub.a is equal to a constant Kc[M].
Ka = Kc [ M ] = [ H + ] [ A - ] [ HA ] ( 6 ) ##EQU00002##
[0155] When a dissociation equation of an acid is expressed by
equation (7), an acid dissociation constant Ka can be expressed by
equation (8). As described above, the pKa (=-log Ka) of
p-toluenesulfonic acid in acetonitrile at 25.degree. C. is 8.7
(Ka.apprxeq.2.0.times.10.sup.-9), the equilibrium reaction in
equation (3) is substantially shifted to the left.
HA.revreaction.H.sup.++A.sup.- (7)
Ka = [ H + ] [ A - ] [ HA ] ( 8 ) ##EQU00003##
[0156] Furthermore, a neutralization reaction of a quencher with an
acid causes an equilibrium expressed by equation (9), resulting in
increase of a dissociated anion concentration [A.sup.-]. Thus, the
acid dissociation equilibrium of equation (3) is further shifted to
the left.
R.sub.3NHA.revreaction.(R.sub.3NH.sup.+,A.sup.-).sub.solv.revreaction.R.-
sub.3NH.sup.+.sub.solv+A.sup.-.sub.solv (9)
[0157] FIG. 4 demonstrates that the higher a concentration of the
quencher initially added, the more a salt is generated in the
system. A higher pH in the range of C.sub.a>C.sub.b, therefore,
confirms the above description.
[0158] These (i) to (iii) suggest that a system comprising a
quencher behaves as an equilibrium system in an aqueous solution.
The range in (iii) corresponds to the fact that an acidic buffer
solution contains a weak acid or conjugate base to a weak acid.
Thus, there will be discussed a mechanism for action of a quencher
as a buffer when a sample is contaminated with a basic
component.
[0159] In this example, a basic component used was
monoethanolamine. Samples 2, 4, 6 and 8 comprise 1 mM
monoethanolamine as an external amine and an equivalent
concentration of a quencher, corresponding to samples 1, 3, 5 and 7
without monoethanolamine, respectively. FIG. 5 is a partial
enlarged view of FIG. 4 for more clearly demonstrating difference
in an acidic range in a titration curve, depending on presence or
absence of an external amine.
[0160] When an external amine NRH.sub.2 is added to a buffer
system, a reaction expressed by equation (10) is initiated. A large
amount of the undissociated acid HA is present in the buffer
system, which is bound to the external amine to prevent pH
shift.
RN.sub.2H+HA.fwdarw.RN.sub.3H+A.sup.- (10)
[0161] It is assumed that in a sample comprising the external amine
in FIG. 5, a neutralization point (C.sub.b=C.sub.a), i.e., a proton
concentration [H.sup.+] required for an effective acid to be
present in a photopolymer in a practical system, is a point of
pH=9. It can be thus found that the higher a quencher concentration
is, the less a pH shift, .DELTA.pH, in FIG. 5 is. It is, therefore,
confirmed that significant buffering action is effective in the
model of this invention comprising a quencher.
[0162] Next, effect in a system comprising a quencher will be
simulated using an equation for an acid dissociation constant. In
the range of C.sub.a>C.sub.b for acid dissociation equilibrium
expressed by equation (7), there is a relationship expressed by
equations (11) to (13), assuming that a concentration of an ionized
acid is x moles.
[HA]=C.sub.a-C.sub.b-x (11)
[H.sup.+]=x (12)
[A.sup.-]=C.sub.b+x (13)
[0163] From the above relationship, the salt formed by
neutralization of the quencher with the acid, R.sub.3NHA (equation
(2)) can be assumed to be completely dissociated in the system.
Under this assumption, A.sup.- derived from the salt is equal to
the quencher concentration C.sub.b and the total of A.sup.- present
in the system is the sum of C.sub.b and x, wherein x is a
concentration of dissociated A.sup.- in equation (7).
[0164] In this assumption, contribution of self-ionization of the
matrix M or a reaction of the matrix M with the anion A.sup.- is
probably negligible, so that these factors are neglected.
p-Toluenesulfonic acid is homoconjugated to some extent in
acetonitrile, but for simplifying the model herein, a
homoconjucation reaction between the anion A.sup.- and HA expressed
by equation (14) is also neglected.
HA+A-.revreaction.HA.sub.2.sup.- (14)
[0165] Assuming that x is so small to allow approximation of
C.sub.a-C.sub.b-x.apprxeq.C.sub.a-C.sub.b and
C.sub.b-x.apprxeq.C.sub.b, equation (8) for an acid dissociation
constant can be expressed as equation (15). Therefore, under
simplification that an activity of hydrogen ion is equal to its
molar concentration, a pH is expressed by equation (16) from
equation (15).
[ H + ] = Ka C a - C b C b ( 15 ) pH = - log [ H + ] = - log Ka -
log C a - C b C b = pKa - log C a - C b C b ( 16 ) ##EQU00004##
[0166] When a concentration of an external amine in the system is
C.sub.e, fluctuation of a hydrogen-ion concentration and a pH' are
studied as described above, obtaining equations (17) and (18).
[ H + ] ' = Ka C a - C b - C e C b + C e ( 17 ) pH ' = - log [ H +
] ' = pKa - log C a - C b - C e C b + C e ( 18 ) ##EQU00005##
[0167] Thus, subtracting equation (16) from equation (18), equation
(19) for a pH shift, .DELTA.pH, due to incorporation of an external
amine is obtained.
.DELTA. pH = pH ' - pH = log ( 1 + C a C e C b ( C a - C b - C e )
) ( 19 ) ##EQU00006##
[0168] As described above, equation (19) holds only when the total
of the acid is smaller than the sum of the quencher and the
external amine, i.e., when C.sub.a-C.sub.b-C.sub.e>0. Under
these conditions, equation (19) clearly demonstrates that as a
quencher concentration increases, pH shift is reduced.
[0169] FIG. 6 shows a calculated .DELTA.pH at pH=9 and .DELTA.pH
obtained from FIG. 5. When determining a calculated value in FIG.
6, C.sub.a=1.5.times.C.sub.b because a pKa of p-toluenesulfonic
acid is 8.7. FIG. 6 demonstrates that the experimental values are
in excellent agreement with the calculated values. It may confirm
that equation (19) is valid as an approximation.
[0170] From the above investigation, the followings have been
found. Generally, in a resist composition, an acid derived from a
photoacid generator used is a substance corresponding to a strong
acid in an aqueous solution. It has been, however, found that in
acetonitrile, an organic solvent, such an acid exhibits a smaller
dissociation ratio and when adding a salt having buffer effect to
acetonitrile, equilibrium is established. Acetonitrile is an
aprotic and non-aqueous solvent with a higher dielectric constant,
so that it behaves as if such equilibrium is established in a
practical resist composition.
Example 2
[0171] In this example, a solution of predetermined amounts of a
quencher and of a salt in a non-aqueous solvent was used as a
resist composition model, and pH shift after adding an acid
generated from a photoacid generator was determined by
titration.
[0172] Specifically, to samples 3 and 4 in Table 1 in Example 1
containing a quencher at 4 mM was further added triethanolamine
p-toluenesulfonate (formula (H)) to 12 mM, and the resulting
samples were subjected to pH titration as described in Example 1.
The titration curves obtained were compared with those for samples
3 and 4, respectively.
[0173] FIGS. 7 and 8 are titration curves for these samples. FIG. 8
is an enlarged view of the pH=8 to 12 region in the titration
curves in FIG. 7. FIG. 7 demonstrates that comparing presence of
the salt for the samples containing a quencher at 4 mM, addition of
the salt reduces fluctuation before and after the neutralization
point. It may be thus expected that in a practical resist
composition, fluctuation in a system pH can be also minimized by
addition of a salt, resulting in reduced fluctuation of lithography
sensitivity and reliable patterning.
[0174] Furthermore, FIG. 7 demonstrates that by adding a salt, a pH
curve becomes flat in the above regions (i) and (iii), i.e., the
region where a quencher (base) or acid is excessive. It indicates
that pH shift associated with variation in the amount of the acid
in the system is prevented. It may be, therefore, expected that in
a practical resist composition, fluctuation in solubility of a base
polymer associated with variation in the generated acid is
prevented. Thus, even when an exposure varies in patterning a
resist, a pattern can be reliably formed, that is, a wider exposure
margin can be attained by adding a salt.
[0175] Furthermore, FIG. 8 demonstrates that contamination with an
external amine causes a relatively larger pH shift in a system
without a salt, while a pH shift is reduced even when being
contaminated with an external amine in a system comprising a salt.
It suggests that fluctuation of neutralization due to contamination
of a system with an amine is prevented because a salt added
significantly exhibits buffer effect. It may be, therefore,
expected that in a practical resist composition, an acid generated
from a photoacid generator by exposure can minimize reduction in an
amount of an effective acid due to consumption of the acid in
neutralization of the external amine, allowing patterning with
higher sensitivity.
Example 3
[0176] In this example, an interconnection structure was
manufactured on a silicon substrate, using a dual damascene process
by a via-first method described with reference to FIG. 1. Herein, a
lower interconnection layer 108 was an SiO.sub.2 film with a
thickness of 300 nm without an interconnection structure. A first
etching stopper film 107 was an SiCN film with a thickness of 70
nm; a first interlayer insulating film 106 was an SiO.sub.2 film
with a thickness of 600 nm; a second etching stopper film 105 was
an SiC film with a thickness of 50 nm; a second interlayer
insulating film 104 was an L-Ox film with a thickness of 300 nm; a
third interlayer insulating film 103 was an SiO.sub.2 film with a
thickness of 250 nm; and an anti-reflection film 102 was an
anti-reflection film (Clariant Japan, KK.) with a thickness of 60
nm. The chemically amplified resist 101 had a thickness of 600 nm.
The via-hole 111 (diameter ca 200 nm) was formed by the well-known
lithography and etching technique and then the resist for via-hole
forming was removed by O.sub.2 plasma ashing and an amine
stripper.
[0177] The chemically amplified resist 101 comprised a positive KrF
resist mainly made of a polyhydroxystyrene resist protected with an
acetal protecting group and bis(p-toluenesulfonyl)diazomethane (by
Midorikagaku co.) as a photoacid generator. Then, the following
three different compositions were prepared as shown in Table 2. In
sample (c), a salt was the compound represented by formula (F):
[0178] (a) a composition prepared by adding a normal amount of
quencher to a commercially available resist composition (quencher
amount=1 in Table 2);
[0179] (b) a composition prepared by adding an excessive amount of
quencher to a commercially available resist composition (quencher
amount=5 in Table 2); and
[0180] (c) a composition prepared by adding, in addition to a
quencher, a salt to an amount of 0.05 mole per 1 kg of a resist
polymer to a commercially available resist composition (quencher
amount=1, an amount of the salt added=4 in Table 2).
[0181] Using each of samples from (a) to (c) as a chemically
amplified resist 101, KrF laser exposure was conducted to form an
interconnection trench pattern extending to one direction. The
exposure conditions were NA=0.75, .sigma.=0.75 and in normal mode.
Table 2 shows the patterning conditions and the results. An
interconnection trench pattern formed using a KrF resist was
observed the resist pattern over a via by scanning electron
microscopy (SEM). FIG. 9 shows the resulting SEM photograph.
[0182] For an ArF-exposure and an EB-exposure resists, compositions
corresponding to (a) to (c) for each resist were also prepared and
evaluated as well. Table 2 shows the patterning conditions and the
results.
[0183] The ArF-exposure resist was mainly made of an acrylate type
ArF resist and a triphenylsulfonium p-toluenesulfonate as a
photoacid generator. In sample (c), the compound represented by
formula (G) was used as a salt. Exposure was conducted using a KrF
laser at a wavelength of 193 nm under the conditions of NA=0.72,
.sigma.=0.75 and in normal mode.
[0184] In terms of the EB-exposure resist, a negative resist was
mainly made of a polyhydroxystyrene resist whose OH groups were
protected as alkyl ether and a photoacid generator comprising
bis(p-toluenesulfonyl)diazomethane and triphenylsulfonium
p-toluenesulfonate. In sample (c), a salt was the compound
represented by formula (H). Exposure was conducted by direct
drawing with 100 KeV electron beam.
[0185] A positive resist was mainly made of a cresol novolac resin,
a melamine crosslinking agent and a photoacid generator comprising
bis(p-toluenesulfonyl)diazomethane and triphenylsulfonium
p-toluenesulfonate. In sample (c), a salt was the compound
represented by formula (H). Exposure was conducted by
straight-writing drawing with 50 KeV electron beam.
TABLE-US-00002 TABLE 2 Pattern Amount size (nm) Exposure Light
(Relative value) Line/ margin source Type Quencher Salt Space (CD
.+-. 10%) KrF Positive a 1 0 140/140 11% excimer b 5 0 140/140 15%
laser c 1 4 140/140 16% (248 nm) ArF Positive a 1 0 100/100 16%
excimer b 5 0 100/100 21% laser c 1 4 100/100 23% (193 nm) EB
Negative a 1 0 100/100 8% (100 KeV) b 5 0 100/100 13% c 1 4 100/100
15% EB Positive a 1 0 100/100 7% (50 KeV) b 5 0 100/100 14% c 1 4
100/100 24% Resist poisoning in a Light Sensitivity/ via-first
process source Type cm.sup.2 (3-layer resist process) KrF Positive
a 52 mJ Defective resolution excimer b 310 mJ No defects laser c 40
mJ No defects (248 nm) ArF Positive a 30 mJ Defective resolution
excimer b 160 mJ No defects laser c 28 mJ No defects (193 nm) EB
Negative a 9 .mu.C Defective resolution (100 KeV) b 45 .mu.C No
defects c 11 .mu.C No defects EB Positive a 7 .mu.C Defective
resolution (50 KeV) b 36 .mu.C No defects c 6 .mu.C No defects
[0186] Hole patterning was also evaluated as described for
patterning of an interconnection trench. Table 3 shows the
patterning conditions and the results.
TABLE-US-00003 TABLE 3 Additive Pattern Exposure Light (Relative
value) size margin Sensitivity/ source Type Quencher Salt (nm) (CD
.+-. 10%) cm.sup.2 KrF Positive a 1 0 140 10% 60 mJ excimer laser b
5 0 140 15% 320 mJ c 1 4 140 15% 56 mJ (248 nm) ArF Positive a 1 0
120 17% 25 mJ excimer b 5 0 120 24% 130 mJ laser c 1 4 120 25% 24
mJ (193 nm) EB Positive a 1 0 100 6% 9 .mu.C (50 KeV) b 5 0 100 11%
45 .mu.C c 1 4 100 12% 8 .mu.C
[0187] As seen from Tables 2 and 3, with a usual amount of a
quencher, sensitivity was good, but an exposure margin was too
small to attain adequate resolution. With an excessive amount of a
quencher, an exposure margin was increased while sensitivity was
lowered. In a system comprising both a quencher and a salt,
sensitivity and resolution were good and an exposure margin was
adequate.
[0188] FIG. 9(a) to (c) shows an SEM photograph after KrF excimer
laser exposure using resist compositions (a) to (c), respectively.
From FIG. 9(a), it can be observed that defective resolution due to
resist poisoning occurred for a commercially available resist
comprising a normal amount of a quencher. FIG. 9(b) indicates that
when using a resist composition comprising an excess amount of a
quencher, patterning was satisfactorily but sensitivity is not
adequate, and thus there is room for improvement in the light of
mass-productiveness. In contrast, FIG. 9(c) indicates that when
adding, in addition to a quencher, a salt comprising a conjugate
base to an acid, patterning was satisfactory and sensitivity was
not deteriorated.
[0189] These results confirm that a resist comprising a quencher
and a salt comprising a conjugate base to an acid can be used to
prevent poisoning or sensitivity deterioration and to attain
improved patterning.
[0190] As described above, according to this invention, a resist
composition comprising a salt exhibiting buffer effect can be used
to prevent poisoning in a chemically amplified resist.
* * * * *