U.S. patent application number 11/503189 was filed with the patent office on 2007-02-15 for photoresist stripping solution and a method of stripping photoresists using the same.
Invention is credited to Kazumasa Wakiya, Shigeru Yokoi.
Application Number | 20070037087 11/503189 |
Document ID | / |
Family ID | 26619890 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070037087 |
Kind Code |
A1 |
Yokoi; Shigeru ; et
al. |
February 15, 2007 |
Photoresist stripping solution and a method of stripping
photoresists using the same
Abstract
A photoresist stripping solution which comprises (a) a salt of
hydrofluoric acid with a base free from metal ions, (b) a
water-soluble organic solvent, (c) a mercapto group containing
corrosion inhibitor, and (d) water, and a method of stripping
photoresists with the use of the same are disclosed. In case of
using ammonium fluoride as component (a), the photoresist stripping
solution may further contain (e) a salt of hydrof luoric acid with
a quaternary ammonium hydroxide, such as tetramethylammonium
hydroxide, tetrapropylammonium hydroxide, etc., and/or an
alkanolamine. The photoresist stripping solution of the present
invention has an excellent effect of protecting both Al- and
Cu-based metal wiring conductors from corrosion, of efficiently
stripping photoresist films and post-ashing residues, and is free
from the precipitation of the corrosion inhibitor.
Inventors: |
Yokoi; Shigeru;
(Kanagawa-ken, JP) ; Wakiya; Kazumasa;
(Kanagawa-ken, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
26619890 |
Appl. No.: |
11/503189 |
Filed: |
August 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10973302 |
Oct 27, 2004 |
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11503189 |
Aug 14, 2006 |
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10208096 |
Jul 31, 2002 |
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10973302 |
Oct 27, 2004 |
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Current U.S.
Class: |
430/256 |
Current CPC
Class: |
G03F 7/425 20130101;
G03F 7/423 20130101; H01L 21/02071 20130101; G03F 7/426 20130101;
H01L 21/31116 20130101 |
Class at
Publication: |
430/256 |
International
Class: |
G03C 11/12 20060101
G03C011/12 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2001 |
JP |
2001-235884 |
Dec 25, 2001 |
JP |
2001-392290 |
Claims
1. A photoresist stripping solution which comprises (a) a salt of
hydrofluoric acid with a base free from metal ions, (b) a
water-soluble organic solvent, (c) a mercapto group containing
corrosion inhibitor, and (d) water.
2. The photoresist stripping solution according to claim 1, wherein
component (a) is ammonium fluoride.
3. The photoresist stripping solution according to claim 1, wherein
component (b) is at least one member selected from among
dimethylformamide, N-methyl-2-pyrrolidone and dimethyl
sulfoxide.
4. The photoresist stripping solution according to claim 1, wherein
component (c) is a compound having in its structure a hydroxyl
group and/or a carboxyl group at least one of the .alpha.- and
.beta.- positions.
5. The photoresist stripping solution according to claim 1, wherein
component (c) is at least one member selected from among
1-thioglycerol, 3-(2-aminophenylthio)-2-hydroxypropylmercaptan,
3-(2-hydroxyethylthio)-2-hydroxypropylmercaptan,
2-mercaptopropionic acid and 3-mercaptopropionic acid.
6. The photoresist stripping solution according to claim 1, which
further contains, in addition to components (a)-(d), with the
proviso that component (a) is ammonium fluoride, (e) a salt of
hydrofluoric acid with a quaternary ammonium hydroxide represented
by the following general formula (I) and/or an alkanolamine:
##STR6## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are each
independently an alkyl group or a hydroxyalkyl group having 1 to 4
carbon atoms.
7. The photoresist stripping solution according to claim 6, wherein
the composition ratio of component (a):component (e) ranges from
2:8 to 8:2 by mass.
8. A method of stripping photoresists which comprises forming a
photoresist pattern on a substrate, etching the substrate using
said photoresist as a mask, and thereafter stripping away the
photoresist pattern from the substrate using the photoresist
stripping solution according to claim 1.
9. A method of stripping photoresists which comprises forming a
photoresist pattern on a substrate, etching the substrate using
said photoresist as a mask, then plasma ashing the photoresist
pattern, and thereafter stripping away post-plasma ashing residues
from the substrate using the photoresist stripping solution
according to claim 1.
10. The method of stripping photoresists according to claim 8,
wherein the substrate has either Al wiring conductor or Cu wiring
conductor or both thereon.
11. The method of stripping photoresists according to claim 8,
wherein the substrate has at least an Si-based interlevel film
thereof.
12. The method of stripping photoresists according to claim 9,
wherein the substrate has either Al wiring conductor or Cu wiring
conductor or both thereon.
13. The method of stripping photoresists according to claim 9,
wherein the substrate has at least an Si-based interlevel film
thereof.
Description
[0001] This is a continuation of Ser. No. 10/973,302, filed Oct.
27, 20004, which is a continuation of Ser. No. 10/208,096, filed
Jul. 31, 2002, now abandoned.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a photoresist stripping solution
and a method of stripping photoresists using the same. More
particularly, it relates to a photoresist stripping solution which
is excellent in protecting both Al- and Cu-based wiring conductors
and other metal conductors from corrosion and in stripping
photoresist films and post-ashing residues; and a method of
photoresists using the same. The present invention is suitable for
use in the fabrication of semiconductor devices such as ICs and
LSIs, as well as liquid-crystal panel apparatus.
[0004] 2. Description of Relevant Art
[0005] The fabrication of semiconductor devices such as ICs and
LSIs, as well as liquid-crystal panel apparatus, comprises forming
a uniform photoresist coating over conductive metallic layers,
insulation layers such as an SiO.sub.2 film formed on a substrate
(silicon wafer) by CVD; performing selective exposure and
development to form a photoresist pattern; selectively etching the
substrate having the conductive metallic layers, the insulation
layers formed thereon using the photoresist pattern as a mask to
thereby form a microcircuit; and then removing the unwanted
photoresist layer with a stripping solution. For removal of such
unwanted photoresist layers, various organic stripping solutions
has been used from safety and strippability standpoints.
[0006] Examples of the conductive metallic layers formed by CVD as
described above include those of aluminum (Al); aluminum alloys (Al
alloys) such as aluminum--silicon (Al--Si), aluminum copper
(Al--Cu) and aluminum--silicon--copper (Al--Si--Cu); titanium (Ti);
titanium alloys (Ti alloys) such as titanium nitride (TiN) and
titanium--tungsten (TiW); tantalum (Ta), tantalum nitride (TaN),
tungsten (W), tungsten nitride (WN) and copper (Cu). These
conductive metallic films are formed in one or more layers on the
substrate. In recent years, both of devices having Al-based
conductors (Al and Al alloy-based wirings) and devices having
Cu-based conductors are coexisted. Accordingly, it has been
required to protect both of these two types of devices from
corrosion with the use of a single photoresist stripping
solution.
[0007] Furthermore, with the recent tendency toward highly
integrated, high-density circuits, dry etching enabling fine
etching with a higher density has become the major means. Also, it
has been a practice to employ plasma ashing to remove the unwanted
photoresist layers remaining after etching. After these etching and
ashing treatments, residues comprising modified photoresist films
and other components that are referred to horn-like shaped "veil",
"fences" or "side-walls" remain on the bottom or side wall of
patterned grooves. In case of forming a pattern on a substrate
having an Si-based interlayer film, such as an Si-based insulation
film (SiN film, SiO.sub.2 film, etc.) and a low dielectric film
(SOG film, etc.), Si-based residues (Si-based depositions) are
sometimes formed around pattern hole openings. In addition, etching
of metallic layers and ashing treatment builds up metal
depositions. Such post-ashing residues or depositions should be
completely stripped away so as to keep good yields in the
fabrication of semiconductors.
[0008] In recent years, further highly-density and
highly-integrated substrates are needed, and thus the treating
conditions in the etching and ashing steps become more and more
strict. As a result, it is also urgently required to achieve
improved corrosion resistance of metal wirings as well as improved
residue-strippability of stripping solutions, compared with
conventional ones.
[0009] Under these circumstances, there have been frequently
employed stripping solutions for photoresists and post-ashing
residues which contain amines or hydrofluoric acid as the main
component. Among all, those containing hydrofluoric acid as the
main component show excellent strippability especially for
post-ashing residues.
[0010] Examples of stripping solutions containing hydrofluoric acid
as the main component include: a resist stripping solution
composition of pH 5-8 containing a salt of hydrofluoric acid with a
base free from metal ions, a water-soluble organic solvent and
water optionally together with a corrosion inhibitor
(JP-A-9-197681); and a cleaner for semiconductor devices containing
a quaternary ammonium salt and a fluorine compound, and further
adding a water-soluble organic solvent (JP-A-7-201794).
[0011] The resist stripping solution composition in JP-A-9-197681
is to a certain extent effective in strippability and
antiorrosivity on semiconductor devices having Al wiring
conductors, however, it fails to exert any satisfactory effect of
protecting devices having Cu wiring conductors from corrosion.
[0012] In the cleaner in JP-A-7-201794, tetramethylammonium formate
and trimethyl(2-hydroxyethyl)ammonium salt are used as the
quaternary ammonium salt. Although the corrosion of Cu wiring
conductors can be relieved to a certain extent by using these
compounds, there arises another problem that strippability for
Cu-based metallic depositions (residues) is still insufficient.
[0013] JP-A-2000-273666 teaches a cleaner solution containing a
sulfur-based corrosion inhibitor for protecting Cu wiring
conductors from corrosion. However, any satisfactory strippability
for Cu-based metallic depositions (residues) also cannot be
established by using this cleaner solution.
[0014] As discussed above, none of the conventional photoresist
stripping solutions can satisfy both of the requirements for
efficient strippability and effective inhibition of metal
corrosion. This is because strippability offsets the perfoimance of
inhibiting corrosion in a photoresist stripping solution. That is
to say, there is a problem that one of the above-described
requirement cannot be fulfilled unless the other is sacrificed. In
the ultrafine processing employed in these days, in particular, the
strippability for photoresist films and post-ashing residues should
be further improved and it is therefore needed to enhance the
effect of protecting metal wirings from corrosion. Recent models of
semiconductor devices can be divided into two type, one using Al
wiring conductors (Al, Al alloy and other Al-based metal wiring)
and the other using Cu wiring conductors (Cu-based metal wiring).
In addition to the need to protect devices of these two types from
corrosion with the use of a single stripping solution, it is also
required to provide effective protection against corrosion of other
metals on the devices. Further improvements are desired to achieve
effective stripping away of photoresists and post-ashing residues
and to protect metal conductors from corrosion.
SUMMARY OF THE INVENTION
[0015] The present invention has been accomplished under these
circumstances and has as an object of providing a photoresist
stripping solution that is suitable for use in the
photolithographic technology to form today's semiconductor and
liquid-crystal display devices having an ever decreasing feature
size and an increasing number of interlevel films superposed on the
substrate, and that can assure effective protection of Al, Cu and
other wiring metal conductors against-corrosion as well as
efficient stripping of the photoresist film and post-ashing
residues.
[0016] To attain the above-described objects, the present invention
provides a photoresist stripping solution which comprises (a) a
salt of hydrofluoric acid with abase free from metal ions, (b) a
water-soluble organic solvent, (c) a mercapto group containing
corrosion inhibitor, and (d) water.
[0017] The present invention also provides a photoresist stripping
solution which further contains, in addition to components (a)-(d),
with the proviso that component (a) is ammonium fluoride, (e) a
salt of hydrofluoric acid with a quaternary ammonium hydroxide
represented by the following general formula (I) and/or an
alkanolamine: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and
R.sub.4 are each independently an alkyl group or a hydroxyalkyl
group having 1 to 4 carbon atoms.
[0018] The present invention furthermore provides a method of
stripping photoresists which comprises forming a photoresist
pattern on a substrate, etching the substrate using the photoresist
as a mask, and thereafter stripping away the photoresist pattern
from the substrate using the photoresist stripping solution as
described above.
[0019] The present invention still furthermore provides a method of
stripping photoresists which comprises forming a photoresist
pattern on a substrate, etching the substrate using the photoresist
as a mask, then plasma ashing the photoresist pattern, and
thereafter stripping away post-plasma ashing residues from the
substrate using the photoresist stripping solution as described
above.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention will be described below in detail.
[0021] In the present invention, component (a) is a salt of
hydrofluoric acid with a base free from metal ions. Preferable
examples of the base free from metal ions include hydroxylamines,
organic amines such as primary, secondary or tertiary aliphatic
amines, alicyclic amines, aromatic amines and heterocyclic amines,
aqueous ammonia, and lower alkyl quaternary ammonium
hydroxides.
[0022] Specific examples of the hydroxylamines include
hydroxylamine (NH.sub.2OH), N-methylhydroxylamine,
N,N-dimethylhydroxylamine and N,N-diethylhydroxylamine.
[0023] Specific examples of the primary aliphatic amines include
monoethanolamine, ethylenediamine and
2-(2-aminoethylamino)ethanol.
[0024] Specific examples of the secondary aliphatic amines include
diethanolamine, N-methylaminoethanol, dipropylamine and
2-ethylaminoethanol.
[0025] Specific examples of the tertiary aliphatic amines include
dimethylaminoethanol and ethyldiethanolamine.
[0026] Specific examples of the alicyclic amines include
cyclohexylamine and dicyclohexylamine.
[0027] Specific examples of the aromatic amines include
benzylamine, dibenzylamine and N-methylbenzylamine.
[0028] Specific examples of the heterocyclic amines include
pyrrole, pyrrolidine, pyrrolidone, pyridine, morpholine, pyrazine,
piperidine, N-hydroxyethylpiperidine, oxazole and thiazole.
[0029] Specific examples of the lower alkyl quaternary ammonium
salts include tetramethylammonium hydroxide (TMAH),
tetraethylammonium hydroxide, tetrapropylammonium hydroxide,
trimethylethylammonium hydroxide, (2-hydroxyethyl)trimethylammonium
hydroxide, (2-hydroxyethyl)triethylammonium hydroxide,
(2-hydroxyethyl)tripropylammonium hydroxide and
(1-hydroxypropyl)trimethylammonium hydroxide.
[0030] Among these bases, aqueous ammonia, monoethanolamine,
N-methylaminoethanol, tetramethylammonium hydroxide and
(2-hydroxyethyl)trimethylammonium hydroxide are preferable from
availability and safety standpoints.
[0031] The bases free from metal ions may be used either alone or
in combination with one another.
[0032] The salt of hydrofluoric acid with the base free from metal
ions may be prepared using a commercially available hydrofluoric
acid having a concentration of 50-60% and adding thereto the base
free from metal ions. As the salt, ammonium fluoride (NH.sub.4F)
may be the most desirable. Either one or more salts may be used as
component (a).
[0033] The content of component (a) preferably ranges 0.1-10 mass
percent, still preferably 0.2-3 mass percent in the stripping
solution of the invention. In case where the content of component
(a) is too large, Cu wiring conductors tend to corrode. In case
where its content is too small, on the other hand, the
strippability is liable to be lowered.
[0034] As component (b) that is a water-soluble organic solvent,
use may be made of those commonly employed in the art. Such a
water-soluble organic solvent is not specifically restricted so
long as it is miscible with water and other components employed in
the present invention. Specific examples thereof include:
sulfoxides, such as dimethyl sulfoxide; sulfones, such as dimethyl
sulfone, diethyl sulfone, bis(2-hydroxyethyl)sulfone and
tetramethylene sulfone; amides, such as N,N-dimethylformamide,
N-methylformamide, N,N-dimethylacetamide, N-methylacetamide and
N,N-diethylacetamide; lactams, such as N-methyl-2-pyrrolidone,
N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone,
N-hydroxymethyl-2-pyrrolidone and N-hydroxyethyl-2-pyrrolidone;
imidazolidinones, such as 1,3-dimethyl-2-imidazolidinone,
1,3-diethyl-2-imidazolidinone and
1,3-diisopropyl-2-imidazolidinone; and polyhydric alcohols and
derivatives thereof, such as ethylene glycol, ethylene glycol
monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol
monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene
glycol monoethyl ether acetate, diethylene glycol, diethylene
glycol monomethyl ether, diethylene glycol monoethyl ether,
diethylene glycol monobutyl ether, propylene glycol monomethyl
ether, propylene glycol monoethyl ether, propylene glycol
monopropyl ether and propylene glycol monobutyl ether. Among these
organic solvents, preferable ones are dimethylformamide,
N-methyl-2-pyrrolidone and dimethyl sulfoxide. Dimethylformamide is
the most desirable since it can be easily handled after stripping
treatment. Either one or more solvents may be used as component
(b).
[0035] The content of component (b) preferably ranges 30-80 mass
percent, still preferably 40-75 mass percent in the stripping
solution of the present invention. In case where the content of
component (b) is too large, the strippability is liable to be
lowered. In case where its content is too small, on the other hand,
various metal wiring conductors tend to corrode.
[0036] Although the mercapto group containing corrosion inhibitor
to be used as component (c) is not specifically restricted so long
as it can protect metal atoms employed in wiring conductors (in
particular, Al wiring or Cu wiring) from corrosion, it is
preferable to use a compound having in its structure a hydroxyl
group and/or a carboxyl group at least one of the .alpha.- and
.beta.-positions. Specific examples of such a compound include
1-thioglycerol, 3-(2-aminophenylthio)-2-hydroxypropylmercaptan,
3-(2-hydroxyethylthio)-2-hydroxypropylmercaptan,
2-mercaptopropionic acid and 3-mercaptopropionic acid. Among these
compounds, 1-thioglycerol is particularly preferable. In the
present invention, component (c) is used as a corrosion inhibitor
to thereby achieve an excellent effect of protecting Al and Cu
wiring conductors from corrosion as well as an effect of preventing
precipitation of the corrosion inhibitor.
[0037] Either one or more compounds may be used as component (c).
The content of component (c) preferably ranges 0.1-10 mass percent,
still preferably 0.2-5 mass percent in the stripping solution of
the invention. In case where the content of component (a) is too
small, there is a fear that insufficient effect may be provided for
protecting in particular Cu wiring conductors from corrosion.
[0038] Component (d) in the stripping solution of the invention is
water. Although some water is contained inevitably in other
components, water is intentionally added to adjust the content. The
content of component (d) is the balance of the stripping solution
of the present invention.
[0039] In addition to components (a)-(d), with the proviso that
component (a) is ammonium fluoride, the stripping solution of the
invention may further incorporate into the stripping solution (e) a
salt of hydrofluoric acid with a quaternary ammonium hydroxide
represented by the following general formula (I) and/or an
alkanolamine: wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are
each independently an alkyl group or a hydroxyalkyl group having 1
to 4 carbon atoms. Use of component (e) contributes to the
improvement in the strippability without seriously damaging Cu.
[0040] Specific examples of the quaternary ammonium hydroxide
represented by the general formula (I) include tetramethylammonium
hydroxide (TMAH), tetraethylammonium hydroxide, tetrapropylammonium
hydroxide, tetrabutylammonium hydroxide,
monomethyltripropylammonium hydroxide, trimethylethylammonium
hydroxide, (2-hydroxyethyl)trimethylammonium hydroxide,
(2-hydroxyethyl)triethylammonium hydroxide,
(2-hydroxyethyl)tripropylammonium hydroxide and
(1-hydroxypropyl)trimethylammonium hydroxide. Among these
compounds, TMAH, tetraethylammonium hydroxide, tetrapropylammonium
hydroxide, tetrabutylammonium hydroxide,
monomethyltripropylammonium hydroxide, (2-hydroxyethyl)
trimethylammonium hydroxide, etc. are preferable from availability
and safety standpoints.
[0041] Examples of the above-described alkanolamines include
monoethanolamine, diethanolamine, triethanolamine,
2-(2-aminoethoxy)ethanol, N,N-dimethylethanolamine,
N,N-diethylethanolamine, N,N-dibutylethanolamine,
N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine,
N-methyldiethanolamine, monoisopropanolamine, diisopropanolamine
and triisopropanolamine. Among these compounds,
N-methylethanolamine is particularly preferable in terms of
protecting Cu wiring conductors from corrosion.
[0042] Either one or more compounds may be used as component (e).
The content of component (e) preferably ranges 0.1-10 mass percent,
still preferably 0.2-3 mass percent in the stripping solution of
the invention. In case where the content of component (e) is too
large, Al wiring conductors tend to corrode.
[0043] In case of using component (e) in the present invention, it
is preferable to adjust the composition ratio of ammonium fluoride
employed as component (a) to component (e) [ammonium
fluoride:component (e)] to from 2:8 to 8:2 by mass, still
preferably from 3:7 to 7:3. By regulating the composition ratio of
fluoride ammonium to component (e) within the range as specified
above, metal wiring conductors can be more efficiently protected
from corrosion. In case where the content of ammonium fluoride
exceeds the upper limit as specified above, Al-based wiring
conductors are prone to corrode. In case where the content of
component (e) exceeds the upper limit as specified above, on the
other hand, Cu-based wiring conductors are prone to corrode.
[0044] In order to improve penetrating properties, the stripping
solution of the invention may further contain, as an optional
component, an acetylene alcohol/alkylene oxide adduct prepared by
adding an alkylene oxide to an acetylene alcohol.
[0045] As the acetylene alcohol as described above, use may be
preferably made of compounds represented by the following general
formula (II): ##STR2## wherein R.sub.5 is a hydrogen atom or a
group represented by the following formula (III); ##STR3## and
R.sub.6, R.sub.7, R.sub.8 and R.sub.9 are each independently a
hydrogen atom or an alkyl group having 1-6 carbon atoms.
[0046] These acetylene alcohols are commercially available under
trade names of "Surfynol" and "Olfin" series (both are produced by
Air Products and Chemicals Inc.). Among these commercial products,
"Surfynol 104", "Surfynol 82" or mixtures thereof are most
preferred for the physical properties. Use can be also made of
"Olfin B", "Olfin P", "Olfin Y" etc.
[0047] As the alkylene oxide to be added to the acetylene alcohol
as described above, it is preferred to use ethylene oxide,
propylene oxide or a mixture thereof.
[0048] In the present invention, it is preferable to use, as the
acetylene alcohol/alkylene oxide adduct, compounds represented by
the following general formula (IV): ##STR4## wherein R.sub.10 is a
hydrogen atom or a group represented by the following formula (V):
##STR5## and R.sub.11, R.sub.12, R.sub.13 and R.sub.14 are each
independently a hydrogen atom or an alkyl group having 1-6 carbon
atoms; (n+m) is an integer of 1 to 30, which is the number of
ethylene oxide molecules added. This number subtly affects the
properties of the compound such as water solubility and surface
tension.
[0049] The acetylene alcohol/alkylene oxide adducts per se are
known as surfactants. These products are commercially available
under the trade name "Surfynol" series (products of Air Product and
Chemicals Inc.) and "Acetylenol" series (products of Kawaken Fine
Chemicals Co., Ltd.) and have been appropriately utilized. Among
these products, it is preferred to use "Surfynol 440" (n+m=3.5),
"Surfynol 465" (n+m=10). "Surfynol 485" (n+m=30), "Acetylenol EL"
(n+m=4), "Acetylenol EH" (n+m =10) or mixtures thereof, in view of
the changes in their physical properties such as water solubility
and surface tension depending on the number of ethylene oxide
molecules added. A mixture of "Acetylenol EL" with "Acetylenol EH"
in a mass ratio of 2:8 to 4:6 is particularly desirable.
[0050] Use of the acetylene alcohol/alkylene oxide adduct makes it
possible to improve the penetrating properties and wetting
properties of the stripping solution.
[0051] When the stripping solution of the invention contains the
acetylene alcohol/alkylene oxide adduct, the content thereof is
preferably 0.05-5 mass percent, more preferably 0.1-2 mass percent.
When the content exceeds the upper limit as defined above, it tends
to cause foaming but the wetting properties cannot be improved any
more. When the content is less than the lower limit as defined
above, on the other hand, the desired improvement in the wetting
properties can be scarcely obtained.
[0052] To complete the stripping treatment in a short period of
time, the stripping solution of the invention may further contain
an acidic compound. Examples of the acidic compound include
hydrofluoric acid, acetic acid and glycolic acid. In case of using
such an acidic compound, its content is preferably 1 mass percent
or less. When the stripping solution of the invention contains the
acidic compound, the strippability of Si-based depositions can be
particularly improved. Thus, the stripping time can be shortened
and an excellent effect of stripping Si-based depositions can be
established thereby.
[0053] The photoresist stripping solution of the invention can
advantageously be used with all photoresists, whether negative- or
positive-working, that can be developed with aqueous alkaline
solutions. Such photoresists include, but are not limited to, (i) a
positive-working photoresist containing a naphthoquinonediazide
compound and a novolak resin, (ii) a positive-working photoresist
containing a compound that generates an acid upon exposure, a
compound that decomposes with an acid to have a higher solubility
in aqueous alkali solutions, and an alkali-soluble resin, (iii) a
positive-working photoresist containing a compound that generates
an acid upon exposure and an alkali-soluble resin having a group
that decomposes with an acid to have a higher solubility in aqueous
alkali solutions, and (iv) a negative-working photoresist
containing a compound that generates an acid upon illumination with
light, a crosslinker and an alkali-soluble resin.
[0054] According to the invention, photoresists are stripped away
by one of two methods which have the following steps in common:
forming a photoresist pattern by lithography on a substrate having
conductive metallic layers, insulation layers and low-dielectric
layers thereon, and selectively etching the layers with the
photoresist pattern used as a mask to form a fine-line circuit.
After these steps, the photoresist pattern is immediately stripped
away (method I), or the etched photoresist pattern is subjected to
plasma ashing and thereby post-ashing residues, such as the
modified photoresist film (photoresist film residue) and metal
deposition, are stripped away (method II).
[0055] An example of method I in which the photoresist film is
stripped away immediately after etching comprises: [0056] (I)
providing a photoresist layer on a substrate; [0057] (II)
selectively exposing said photoresist layer; [0058] (III)
developing the exposed photoresist layer to provide a photoresist
pattern; [0059] (IV) etching the substrate to form a pattern using
said photoresist pattern as a mask; and [0060] (V) stripping away
the photoresist pattern from the etched substrate using the
photoresist stripping solution of the present invention.
[0061] An example of method II in which the modified photoresist
film and metal deposition resulting from plasma ashing are stripped
away after etching comprises: [0062] (I) providing a photoresist
layer on a substrate; [0063] (II) selectively exposing said
photoresist layer; [0064] (III) developing the exposed photoresist
layer to provide a photoresist pattern; [0065] (IV) etching the
substrate to form a pattern using said photoresist pattern as a
mask; [0066] (V) plasma ashing the photoresist pattern; [0067] (VI)
stripping away the post-ashing residues using the photoresist
stripping solution of the present invention.
[0068] The specific advantage of the present invention resides in
that the photoresist stripping solution has excellent effects of
stripping photoresist films and post-ashing residues (modified
photoresist films, metal depositions, etc.) and protecting a
substrate having metal conductors from corrosion both in stripping
away photoresists formed on a substrate having Al wiring conductors
and formed on a substrate having Cu wiring conductors.
[0069] Examples of the metal wiring conductors include, but are not
limited to, those made of aluminum (Al); aluminum alloys such as
aluminum copper (Al--Cu) and aluminum--silicon--copper
(Al--Si--Cu); titanium (Ti); titanium alloys (Ti alloys) such as
titanium nitride (TiN) and titanium--tungsten (TiW); and copper
(Cu).
[0070] Using conventional photoresist stripping solutions, it is
very difficult to satisfy both of the requirements for efficient
strippability for photoresists and post-ashing residues and
effective inhibition of metal corrosion in Al-based wiring devices
and Cu-based wiring devices. According to the present invention,
however, both of these requirements can be successfully satisfied
by combining components (a)-(d) with each other. Using component
(e) in addition to components (a)-(d), with the proviso that
component (a) is ammonium fluoride, the strippability can be
further improved without seriously damaging Cu.
[0071] In the second stripping method described above, residue
adhere to the substrate surface after plasma ashing, such as
photoresist residue (modified photoresist film) and metal
deposition that formed during etching of the metal film. These
residues are contacted by the stripping solution of the invention
so that they are stripped away from the substrate surface. Plasma
ashing is inherently a method for removing the photoresist pattern
but it often occurs that part of the photoresist pattern remains as
a modified film; the present invention is particularly effective
for the purpose of completely stripping away such modified
photoresist film.
[0072] In forming the photoresist layer, and exposing, developing
and etching treatments, any conventional means may be employed
without particular limitation.
[0073] After the development step (III) or the stripping step (V)
or (VI), conventional rinsing may optionally be performed using
pure water, lower alcohols, etc., followed by drying.
[0074] The photoresist is usually stripped by the dip, shower or
paddle method. The stripping time is not limited to any duration as
long as it is sufficient to achieve removal of the photoresist.
EXAMPLES
[0075] The following examples are provided for the purpose of
further illustrating the present invention but are in no way to be
taken as limiting. Unless otherwise noted, all compounding amounts
are expressed by mass percent.
[Treatment I]
[0076] A silicon wafer having an SiO.sub.2 layer formed thereon was
used as a substrate. On this substrate, a TiN layer, an Al--Si--Cu
layer and another TiN layer were successively formed thereon
respectively as the first, second and third layers. The topmost
layer was spin-coated with a positive-working photoresist
(TDUR-P015 of Tokyo Ohka Kogyo Co., Ltd.), which was prebaked at
80.degree. C. for 90 seconds to form a photoresist layer 0.7 .mu.m
thick.
[0077] The photoresist layer was exposed through a mask pattern
using FPA 3000 EX3 (Canon Inc.), then subjected to post-exposure
bake at 110.degree. C. for 90 seconds and developed with an aqueous
solution of 2.38 mass percent tetraammonium hydroxide (TMAH) to
form a photoresist pattern of 400 nm in line-and-space.
Subsequently it was subjected to dry etching and plasma ashing.
[Treatment II]
[0078] A silicon wafer having Cu layer that is overlaid with an
SiO.sub.2 layer formed by plasma CVD was used as a substrate. The
substrate was spin-coated with a positive-working photoresist
(TDUR-P015 of Tokyo Ohka Kogyo Co., Ltd.), which was prebaked at
80.degree. C. for 90 seconds to form a photoresist layer 0.7 .mu.m
thick.
[0079] The photoresist layer was exposed through a mask pattern
using FPA 3000 EX3 (Canon Inc.), then subjected to post-exposure
bake at 110.degree. C. for 90 seconds and developed with an aqueous
solution of 2.38 mass percent tetraammonium hydroxide (TMAH) to
form a hole pattern of 200 nm in diameter. Subsequently it was
subjected to dry etching and plasma ashing.
EXAMPLES 1-8 and COMPARATIVE EXAMPLES 1-5
[0080] The thusly treated substrate in treatment I or II as
described above was dipped (25.degree. C., 5 minutes) in each
photoresist stripping solution as indicated in Table 1 for
stripping. In Example 8, dipping was carried out for 1 minute.
After the completion of the stripping treatment, each substrate was
rinsed with purified water. Then the substrate was observed under a
scanning electron microscope (SEM) to evaluate strippability of the
post-ashing residues, state of corrosion of metal wiring conductors
and precipitation of the corrosion inhibitor. The results are shown
in Table 2.
[0081] The strippability of the post-ashing residues, state of
corrosion of metal wiring conductors and precipitation of the
corrosion inhibitor were evaluated in accordance with the following
criteria.
[0082] The strippability of the post-ashing residues was evaluated
by using the substrate treated in treatment II. Regarding the
protection of metals from corrosion, the substrate treated in
treatment I was mainly used for Al wiring, and the one treated in
treatment II was mainly used for Cu wiring. The precipitation of
the corrosion inhibitor was evaluated by using the substrate
treated in treatment II.
[Strippability of Post-Ashing Residues (Cu-Based Depositions and
Si-Based Depositions)]
[0083] .circleincircle.: Complete stripping
[0084] .largecircle.: Almost complete stripping
[0085] .DELTA.: Some residues remained
[0086] .chi.: Much residues remained
[Protection of Metal Wiring Conductors (Al and Cu) from
Corrosion]
[0087] .circleincircle.: No corrosion found
[0088] .largecircle.: Little corrosion found
[0089] .DELTA.: Suffered from somewhat corrosion
[0090] .chi.: Suffered from corrosion
[State of Precipitation of Corrosion Inhibitor]
[0091] .circleincircle.: No precipitation of corrosion inhibitor
found
[0092] .largecircle.: Little precipitation of corrosion inhibitor
found
[0093] .DELTA.: Suffered from somewhat precipitation of corrosion
inhibitor
[0094] .chi.: Suffered from precipitation of corrosion inhibitor
TABLE-US-00001 TABLE 1 Photoresist stripping solution (mass %)
Component Component Component Component Other (a) (b) Component (c)
(d) (e) component Ex. 1 NH.sub.4F DMSO Cor. inhib. A water -- --
(0.5) (70) (2) (27.5) Ex. 2 NH.sub.4F DMSO Cor. inhib. B water --
-- (2) (50) (1) (47) Ex. 3 NH.sub.4F DMF Cor. inhib. C water --
acetylene (1) (60) (1) (37.5) alcohol/ alkylene oxide adduct (0.5)
Ex. 4 NH.sub.4F DMSO Cor. inhib. D water HF/TMAH -- (0.5) (70) (1)
(28) (0.5) Ex. 5 NH.sub.4F DMSO Cor. inhib. E water HF/TPAH
acetylene (1.2) (50) (0.5) (45.5) (1.8) alcohol/ alkylene oxide
adduct (1) Ex. 6 NH.sub.4F DMF Cor. inhib. A water HF/TMAH -- (0.6)
(70) (1) (28) (0.4) Ex. 7 NH.sub.4F NMP Cor. inhib. A water HF/TMAH
-- (0.4) (70) (1) (28) (0.6) Ex. 8 NH.sub.4F NMP Cor. inhib. A
water HF/TMAH acetic (0.5) (70) (1) (27.7) (0.5) acid(0.3) Com.
NH.sub.4F DMSO Cor. inhib. X water -- -- Ex. 1 (2) (60) (2) (36)
Com. NH.sub.4F DMSO Cor. inhib. Y water -- -- Ex. 2 (1) (50) (1)
(48) Com. NH.sub.4F DMSO Cor. inhib. Z water -- -- Ex. 3 (0.5) (75)
(2) (22.5) Com. NH.sub.4F DMSO Cor. inhib. X water HF/TMAH -- Ex. 4
(0.5) (70) (1) (28) (0.5) Com. NH.sub.4F DMSO Cor. inhib. X water
HF/TPAH -- Ex. 5 (2) (50) (0.5) (46.5) (1) The symbols used in
Table 1 to indicate respective components have the following
definitions. NH.sub.4F: ammonium fluoride DMSO: dimethyl sulfoxide
DMF: dimethylformamide NMP: N-methyl-2-pyrrolidone Cor. inhib. A:
1-thioglycerol Cor. inhib. B:
3-(2-aminophenylthio)-2-hydroxypropylmercaptan Cor. inhib. C:
3-(2-hydroxyethylthio)-2-hydroxypropylmercaptan Cor. inhib. D:
2-mercaptopropionic acid Cor. inhib. E: 3-mercaptopropionic acid
Cor. inhib. X:
2,2'-{[(4-methyl-1H-benzo-triazol-1-yl)methyl]imino}-bisethanol
("IRGAMET 42") Cor. inhib. Y: pyrogallol Cor. inhib. Z:
pyrocatechol HF/TMAH: salt of hydrofluoric acid (HF) with
tetramethyl-ammonium hydroxide (TMAH) HF/TPAH: salt of hydrofluoric
acid (HF) with tetrapropyl-ammonium hydroxide (TPAH)
[0095] TABLE-US-00002 TABLE 2 Protection of Strippability of metal
conductor Precipitation post-ashing residues from corrosion of
Cu-based Si-based Cu Al corrosion deposition deposition wiring
wiring inhibitor Ex. 1 .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. Ex. 2 .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. Ex. 3 .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. Ex. 4
.largecircle. .largecircle. .circleincircle. .largecircle.
.largecircle. Ex. 5 .largecircle. .largecircle. .circleincircle.
.largecircle. .largecircle. Ex. 6 .largecircle. .largecircle.
.circleincircle. .largecircle. .largecircle. Ex. 7 .largecircle.
.largecircle. .circleincircle. .largecircle. .largecircle. Ex. 8
.largecircle. .circleincircle. .circleincircle. .largecircle.
.largecircle. Com. Ex. 1 .largecircle. .largecircle. .DELTA.
.largecircle. X Com. Ex. 2 .largecircle. .largecircle. X
.largecircle. .largecircle. Com. Ex. 3 .largecircle. .largecircle.
X .largecircle. .largecircle. Com. Ex. 4 .largecircle.
.largecircle. .DELTA. .largecircle. X Com. Ex. 5 .largecircle.
.largecircle. .DELTA. .largecircle. X
[0096] As described above in detail, according to the present
invention, there is provided an excellent photoresist stripping
solution that causes no corrosion of Al and Cu wiring conductors or
any other metals, has excellent strippability for photoresist films
and post-ashing residues and is free from precipitation of a
corrosion inhibitor. Use of the photoresist stripping solution of
the present invention makes it possible to effectively protect both
of devices having Al wiring conductors and devices having Cu wiring
conductors from corrosion.
* * * * *