U.S. patent application number 09/034552 was filed with the patent office on 2002-01-31 for composition and method for removing resist and etching residues using hydroxylammonium carboxylates.
Invention is credited to SAHBARI, JAVAD J..
Application Number | 20020013240 09/034552 |
Document ID | / |
Family ID | 21877134 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020013240 |
Kind Code |
A1 |
SAHBARI, JAVAD J. |
January 31, 2002 |
COMPOSITION AND METHOD FOR REMOVING RESIST AND ETCHING RESIDUES
USING HYDROXYLAMMONIUM CARBOXYLATES
Abstract
A mixture of hydroxylamine partially neutralized with a weak
carboxylic acid and an organic solvent such as an alkyl sulfoxide,
a pyrrolidinone or a sulfone removes hardened photoresist and
polymeric photoresist residues from a substrate with reduced metal
corrosion.
Inventors: |
SAHBARI, JAVAD J.;
(SUNNYVALE, CA) |
Correspondence
Address: |
DAVID H JAFFER
ROSENBLUM PARISH & ISAACS
160 WEST SANTA CLARA ST
FIFTEENTH FLOOR
SAN JOSE
CA
95113
|
Family ID: |
21877134 |
Appl. No.: |
09/034552 |
Filed: |
March 3, 1998 |
Current U.S.
Class: |
510/176 ;
216/100; 252/79.4; 510/109; 510/401 |
Current CPC
Class: |
G03F 7/425 20130101 |
Class at
Publication: |
510/176 ;
510/109; 510/401; 252/79.4; 216/100 |
International
Class: |
C11D 001/00; C23F
011/10 |
Claims
What is claimed is:
1. A composition for removal of photoresist and photoresist
residues from a substrate, comprising: (a) from 2.5% to 40% by
weight hydroxylamine; (b) from 2.5% to 40% by weight water; (c)
from 0.1% to 25% by weight of a monoprotic or diprotic carboxylic
acid with four or fewer carbon atoms; and (d) from 10l to 90% by
weight of an organic solvent selected from the group consisting of
alkyl sulfoxides, alkyl sulfones, and pyrrolidinones.
2. The composition of claim 1, wherein the organic solvent is
selected from the group consisting of dimethyl sulfoxide,
tetramethylene sulfone, n-hydroxyethylpyrrolidinone, and
n-methylpyrrolidinone.
3. The composition of claim 1, wherein the hydroxylamine is present
in an amount of 10% to 20% by weight, the water is present in an
amount of 10% to 20% by weight, and the organic solvent is present
in an amount of 40% to 80% by weight.
4. The composition of claim 3, wherein the acid is present in an
amount sufficient to reduce the pH below 8, when the pH is measured
in water at 19:1 volume dilution.
5. The composition of claim 4, wherein the acid is present in an
amount sufficient to yield a pH between 6 and 7.5, when the pH is
measured in water at 19:1 dilution.
6. The composition of claim 2, wherein the hydroxylamine is present
in an amount of 10% to 20% by weight, the water is present in an
amount of 10% to 20% by weight, and the organic solvent is present
in an amount of 40% to 80% by weight.
7. The composition of claim 6, wherein the acid is present in an
amount sufficient to reduce the pH below 8, when the pH is measured
in water at 19:1 volume dilution.
8. The composition of claim 8, wherein the acid is present in an
amount sufficient to yield a pH between 6 and 7.5, when the pH is
measured in water at 19:1 dilution.
9. A composition for removal of photoresist and photoresist
residues from a substrate, consisting essentially of: (a) from 10%
to 20% by weight hydroxylamine; (b) from 10% to 20% by weight
water; (c) from 0.1% to 25% by weight of a monoprotic or diprotic
carboxylic acid with four or fewer carbon atoms, wherein the acid
is present in an amount sufficient to yield a pH between 6 and 7.5,
when the pH is measured in water at 19:1 dilution; and (d) from 40%
to 80% by weight of an organic solvent selected from the group
consisting of dimethyl sulfoxide, tetramethylene sulfone,
n-hydroxyethylpyrrolidinone, and n-methylpyrrolidinone.
10. A method for removing photoresist and photoresist residues from
a substrate, comprising contacting said substrate with a stripping
solution for a time sufficient to remove the photoresist or
residues from said substrate, wherein the stripping solution
comprises: (a) from 2.5% to 40% by weight hydroxylamine; (b) from
2.5% to 40% by weight water; (c) from 0.1% to 25% by weight of a
monoprotic or diprotic carboxylic acid with four or fewer carbon
atoms; and (d) from 10% to 90% by weight of an organic solvent
selected from the group consisting of alkyl sulfoxides, alkyl
sulfones, and pyrrolidinones.
11. The method of claim 10, wherein the organic solvent is selected
from the group consisting of dimethyl sulfoxide, tetramethylene
sulfone, n-hydroxyethylpyrrolidinone, and
n-methylpyrrolidinone.
12. The method of claim 10, wherein the hydroxylamine is present in
an amount of 10% to 20% by weight, the water is present in an
amount of 10% to 20% by weight, and the organic solvent is present
in an amount of 40% to 80% by weight.
13. The method of claim 12, wherein the acid is present in an
amount sufficient to reduce the pH below 8, when the pH is measured
in water at 19:1 volume dilution.
14. The method of claim 13, wherein the acid is present in an
amount sufficient to yield a pH between 6 and 7.5, when the pH is
measured in water at 19:1 dilution.
15. The method of claim 11, wherein the hydroxylamine is present in
an amount of 10% to 20% by weight, the water is present in an
amount of 10% to 20% by weight, and the organic solvent is present
in an amount of 40% to 80% by weight.
16. The method of claim 15, wherein the acid is present in an
amount sufficient to reduce the pH below 8, when the pH is measured
in water at 19:1 volume dilution.
17. The method of claim 16, wherein the acid is present in an
amount sufficient to yield a pH between 6 and 7.5, when the pH is
measured in water at 19:1 dilution.
18. A method for removing photoresist and photoresist residues from
a substrate, comprising contacting said substrate with a stripping
solution for a time sufficient to remove the photoresist or
residues from said substrate, wherein the stripping solution
consists essentially of: (a) from 10% to 20% by weight
hydroxylamine; (b) from 10% to 20% by weight water; (c) from 0.1%
to 25% by weight of a monoprotic or diprotic carboxylic acid with
four or fewer carbon atoms, wherein the acid is present in an
amount sufficient to yield a pH between 6 and 7.5, when the pH is
measured in water at 19:1 dilution; and (d) from 40% to 80% by
weight of an organic solvent selected from the group consisting of
dimethyl sulfoxide, tetramethylene sulfone,
n-hydroxyethylpyrrolidinone, and n-methylpyrrolidinone.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention is directed to a composition and method for
removal of photoresist and photoresist residues from a substrate,
such as a silicon wafer. Mixtures including hydroxylamine and a
weak organic acid are used to strip hard to remove photoresist
materials, such as photoresist residue which has been subjected to
plasma etching and post-plasma ashing. The composition and method
achieve improved strip rates while significantly reducing metal
corrosion.
[0003] 2. Brief Description of the Prior Art
[0004] Photoresist materials are commonly used as coating masks in
the fabrication of integrated circuits. During the fabrication
process, photoresist materials are applied to a substrate using
various techniques known in the art. The substrate, now coated with
photoresist materials, is then exposed to radiation, usually in the
UV, e-beam or x-ray wave lengths. After exposure, the coated
substrate is developed, leaving a defined pattern of photoresist
materials on the substrate. The photoresist materials that remain
on the substrate after developing are used to mask the substrate
for further processing. After further processing, the photoresist
materials are stripped from the substrate using a photoresist
stripper. Further processing of the photoresist materials after
developing, such as high temperature post-exposure bake, ion
implantation and deep UV radiation hardening lead to highly
cross-linked photoresist polymer materials which are extremely
resistant to dissolution.
[0005] The need for plasma etching or reactive ion etching of the
metal, oxide, and polysilicon layers has increased. As a result of
plasma etching the masking photoresist leaves a substantially
hardened organometallic sidewall polymer due to a complex reaction
of metallic substrate with resist polymer and halogenated plasma
gas molecules. Therefore, the need for post plasma polymer removers
and photoresist strippers which work effectively without damaging
desired features of the microcircuit has increased.
[0006] As semiconductor manufacturing has moved into sub-micron
geometries, the need for photoresist and polymer removers which
work effectively without damaging desired features of the circuit
has increased. Since about 1990, mixtures of hydroxylamine with
alkanolamines have been introduced to facilitate the removal of
hardened photoresist polymer residues and for stripping. See U.S.
Pat. Nos. 5,279,771; 5,334,332, 5,381,807; 5,419,779; and
5,482,566. The alkaline strippers mentioned above may be effective
in removing hardened photoresist from substrates, however, in
removing post-plasma etch cross-linked organometallic polymer
residues from sub-micron geometries they cause undesirable side
effects. The use of these alkaline strippers and polymer removers
on microcircuit substrates containing metal films, particularly
aluminum or various combinations or alloys of active metals such as
aluminum or titanium with more electropositive metal such as copper
or tungsten, has proven problematic, even without plasma treatment,
because of metal corrosion. This problem has been addressed by
employing intermediate rinses with non-alkaline organic solvents
such as isopropyl alcohol, other alcohols, or glycols, but such
rinses add to the expense and complexity of the manufacturing
process. Moreover, hydroxylamine/alkanolamine mixtures in an
aqueous media undergo thermal decomposition, generating an unstable
product.
[0007] Schwartzkopf, U.S. Pat. No. 5,308,745, has addressed metal
corrosion with photoresist stripper compositions containing
stripping solvents such as n-methylpyrrolidinone, an alkaline amine
such as an aminoalkanol, and a weak acid. However, these
compositions are not effective for polymer removal.
[0008] At present, there is a trend toward use of 100% copper in
metal layers. Since copper is more subject to corrosion than the
metals previously used, the need has increased for a non-corrosive
polymer and photoresist remover.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide a
photoresist stripper which is environmentally friendly, stable, and
does not require intermediate rinses to avoid metal corrosion and
which still effectively strips plasma treated or hardened
photoresist and polymeric residues.
[0010] Another object of this invention is to provide a method for
photoresist and polymer removal which can avoid oxygen ashing.
[0011] A further object of this invention is to provide such
improved non-metal corroding stripper compositions without any
undue adverse effect on strip rate of the photoresist for
cross-linked or hardened photoresist.
[0012] Another object of this invention is to provide a photoresist
stripper and post-plasma polymer remover that is stable, having
extended bath life without any adverse effect of ambient
temperature variations on stability and effectiveness of the
stripping composition.
[0013] Another object of this invention is to provide a universally
accepted photoresist stripper and post plasma polymer remover that
does not contain any toxic additives such as catechol, works
effectively on all post plasma etch processes independent of the
dry etch equipment or the type of plasma gas used in processing,
and is not corrosive to sensitive metal layers.
[0014] Briefly, the preferred embodiment of the present invention
utilizes a mixture of hydroxylamine partially neutralized with a
weak carboxylic acid and a biodegradable organic solvent such as an
alkyl sulfoxide, a pyrrolidinone or a sulfone to remove hardened
photoresist and photoresist residues from a substrate with reduced
metal corrosion.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] This invention provides a composition and a method for
stripping photoresist and photoresist residues from a substrate,
even if the photoresist has been baked and exposed to short
wavelength hardening radiation. The composition exhibits short
stripping times, long effective bath life, reduced corrosion of
metals, is effective to strip both photoresist and polymer residues
(thereby avoiding oxygen ashing, which is required for other
compositions), and is thermally stable for long shelf life. These
stripping composition is comprised of:
[0016] (a) from 5% to 50% by weight of a 50% hydroxylamine/50%
water solution;
[0017] (b) from 0.1% to 25% weight of a monoprotic or diprotic
carboxylic acid with four or fewer carbon atoms, such as formic,
acetic, propionic acid and the like; and
[0018] (c) the remainder is an organic solvent system with
components such as dimethylsulfoxide (DMSO),
n-hydroxyethyl-pyrrolidinone (HEP), n-methylpyrrolidinone (NMP),
other pyrrolidinones, tetramethylene sulfone (sulfolane), or other
alkyl sulfoxide or sulfone compounds.
[0019] It is more preferred that the composition contains 20-30% by
weight of hydroxylamine/water solution, sufficient carboxylic acid
component to reduce the pH to below 8, and the remainder of the
solvent component.
[0020] Table 1 shows compositions which were used for tests 1 to 24
described in Table 2. The last column of Table 1 shows summary
performances of the compositions for polymer cleaning and metal
corrosion (on a scale of 1-5, where 1 is best and 5 is worst).
1 TABLE 1 NH.sub.2OH/H.sub.2O Polymer clean/ (50--50) Acid Solvent
H.sub.2O PH/Overnight Stabilizer corrosion 1. 30% 0% 35% Sulfolane
-- 9.77/9.90 1.5% TBC --/5 35% HEP 2. 29% 1% 35% Sulfolane --
7.72/8.04 1.5% TBC --/4.8 Formic 35% HEP 3. 28% 2% 35% Sulfolane --
7.40/7.73 1.5% TBC --/4.5 Formic 35% HEP 4. 25% 5% 35% Sulfolane --
6.87/7.24 1.5% TBC 1/1 Formic 35% HEP 5. 22.5% 7.5% 35% Sulfolane
-- 6.57/6.87 1.5% TBC 1/2 Formic 35% HEP 6. 20% 10% 35% Sulfolane
-- 6.20/6.54 1.5% TBC 1/2 Formic 35% HEP 7. 16.66% 13.34% 35%
Sulfolane -- 4.72/5.36 1.5% TBC 1/2.5 Formic 35% HEP 8. 25% --
62.5% DGA 12.5% 11.92/11.96 5% Catechol 3/3 9. 25% -- 62.5% IPA
12.5% 11.94/11.97 5% Catechol 3/3 10. 25% -- 62.5% MEA 12.5%
11.96/11.98 5% Catechol 3/3 11. 15% -- 42.5% -- 9.65/10.04 -- 5/4
DNH.sub.2OH Sulfolane 42.5% HEP 12. -- 10% 45% Sulfolane --
2.56/2.76 -- 4/-- Formic 45% HEP 13. 22.5% 7.5% 35% Sulfolane --
6.64/6.74 1.5% TBC 1/2 Formic 35% NMP 14. 20% 10% 35% Sulfolane --
6.72/-6.84 1.5% TBC 1/2 Acetic 35% NMP 15. 30% 0% 70% DMSO --
9.82/9.94 -- 2/2 16. 30% 5% 65% DMSO -- 6.58 -- 1/1 Formic 17. 30%
0% 35% DMSO -- 8.52 1% TBC 1/2 35% HEP 18. 25% 5% 35% DMSO -- 6.25
1% TBC 1/1 Formic 35% HEP
[0021] In Table 1, NH.sub.2OH/H.sub.2O refers to a 50%
NH.sub.2OH/50% H.sub.2O solution (available as FH-50 from Howard
Hall Division, R. W. Greef & Co.), DNH.sub.2OH refers to
dehydrated hydroxylamine (less than 5% water), DGA is
diglycolamine, IPA is isopropanolamine, MEA is monoethanolamine,
DMSO is dimethylsulfoxide, HEP is n-hydroxyethyl-pyrrolidone, NMP
is n-methylpyrrolidone, TBC is tertiary butyl catechol (a corrosion
inhibitor), and the pH is measured at 19:1 volume dilution at the
time of preparation and after being left overnight. The percentages
are by weight, with the NH.sub.2OH/H.sub.2O, acid, solvent and
water totaling 100%, and the corrosion inhibitor in addition to
this.
[0022] Table 2 describes tests on wafers from UMC (Taiwan) Fab III,
covered with TOK IP 2550 photoresist and dry etched with Lam
Research (TCP 9600) and Applied Materials (P5000) plasma metal
etchers. "PR" refers to tests in which the photoresist has not been
etched, but is removed with the test solution. The tests described
are for metal films with TiN (500 .ANG.) on Al/Cu (8000 .ANG.) on
Ti/TiN (1200 .ANG.).
[0023] The test solution was heated to the process temperature
(70.degree. C.). The test wafer was immersed in the test solution
for the specified time, transferred into an isopropanol bath at
room temperature for 2 minutes, rinsed with deionized water, and
blow dried with nitrogen gas. The wafer inspection was under
microscope (400.times.) or field emission scanning electron
microscope (FESEM) (JEOL 6320F).
2TABLE 2 Wafer Type Test (Metal Sol'n Temp Time No. Etcher) No.
(.degree. C.) (min) Result 1 TCP 9600 1 70 20 After 14 min metal
line began to lift off. After 20 min 90% metal line lifted off 2
TCP 9600 2 70 20 After 16 min metal line began to lift off. After
20 min 60% metal line lifted off 3 TCP 9600 3 70 20 After 18 min
metal line began to lift off. After 20 min 20% metal line lifted
off 4 TCP 9600 4 70 30 No visible change. From SEM, no sidewall
polymer was found and no attack on metal line. 5 TCP 9600 5 70 30
No visible change. From SEM, no sidewall polymer was found but
slight etching on Al/Cu layer 6 TCP 9600 6 70 30 No visible change.
From SEM, no sidewall polymer but slight etching on Al/Cu layer 7
TCP 9600 7 70 30 No visible change. From SEM, no sidewall polymer
but etching on Al/Cu layer 8 TCP 9600 8 70 30 No visible change.
From SEM, 80% sidewall polymer was clean and little etching on
Ti/TiN bottom layer 9 TCP 9600 9 70 30 No visible change. From SEM,
80% sidewall polymer was clean and little etching on Ti/TiN bottom
layer 10 TCP 9600 10 70 30 No visible change. From SEM, 90%
sidewall polymer was clean and some corrosion on Al/Cu layer, some
etching on Ti/TiN bottom layer 11 TCP 9600 11 70 30 No visible
change. From SEM, <10% sidewall polymer was clean and no attack
12 TCP 9600 12 70 30 No visible change. From SEM, 40% sidewall
polymer was clean and no attack 13 P 5000 6 70 120 No visible
change under microscope (400X). No metal lift off 14 P 5000 8 70
120 After 60 min metal line started to lift off, and metal line was
100% lifted off after 2 hr 15 P 5000 9 70 120 After 60 min metal
line started to lift off, and metal line was 100% lifted off after
2 hr 16 P 5000 10 70 120 After 60 min metal line started to lift
off, and metal line was 100% lifted off after 2 hr 17 P 5000 13 70
30 No visible change. From SEM, 100% sidewall polymer was clean and
no etching on Ti/TiN bottom layer 18 P 5000 14 70 30 No visible
change. From SEM, 100% sidewall polymer was clean and no etching on
Ti/TiN bottom layer 19 P 5000 13 70 120 No visible change under
microscope (400x). No metal lift off 20 P 5000 14 70 120 No visible
change under microscope (400x). No metal lift off 21 w/PR 5 70 30
Photoresist was peeled-off in 2 min 22 w/PR 10 70 30 Photoresist
was peeled-off in 5 min 23 w/PR 12 70 30 Photoresist was peeled-off
in 8 min 24 w/PR 13 70 30 Photoresist was peeled-off in 5 min 25 P
5000 16 70 120 From SEM, 100% sidewall polymer was cleaned and no
metal corrosion 26 P 5000 17 70 120 From SEM, 100% sidewall polymer
was cleaned, slight corrosion on Ti layer, no metal lift off 27 P
5000 18 70 120 From SEM, 100% sidewall polymer was cleaned, slight
corrosion Ti layer, no metal lift off
[0024] The test data summarized in Table 2 demonstrate the
effective stripping capacity of the composition while avoiding
metal corrosion:
[0025] 1. Tests 1, 2 and 3 show that the gradual addition of formic
acid to a hydroxylamine, sulfolane, HEP solution reduces the lift
off of metal lines.
[0026] 2. Tests 4 through 7 show that sidewall polymers can be 100%
cleaned by solutions 4 through 7. The more acidic of these
solutions, 6 and 7, show some etching on an aluminum/copper layer.
Solutions 8, 9, and 10, known in the prior art, show some metal
etching and inadequate sidewall polymer removal. Tests 4 to 7 also
show that as the solution becomes more acidic, it will attack an
Al--Cu layer. The preferred formulation is the solution which is
closest to neutral (pH 7).
[0027] 3. Tests 11 and 12 illustrate that reduction of the amount
of water or hydroxylamine, respectively, in the composition results
in inadequate cleaning of sidewall polymer.
[0028] 4. Tests 13 through 16 show that the solution of the present
invention is less corrosive than solutions using hydroxylamine and
monoethanolamine, isopropanolamine or diglycolamine.
[0029] 5. Tests 17 and 18 show that a solution using
n-methylpyrrolidinone (NMP) instead of HEP is an effective cleaner
for sidewall polymer.
[0030] 6. Test 18 shows that acetic acid is an effective substitute
for formic acid.
[0031] 7. Tests 19 and 20 show that the solutions of tests 17 and
18 do not lift off metal lines after 120 minutes at 70.degree.
C.
[0032] 8. Tests 21 to 24 show that photoresist stripping time for
the compositions of the present invention are comparable to those
for a photoresist stripper using hydroxylamine, monoethanolamine,
and water.
[0033] 9. Tests 25-27 show that addition of formic acid to a
hydroxylamine/DMSO solution or a hydroxylamine/DMSO/HEP solution
reduces the lift off of metal lines, and effectively removed
sidewall polymer.
[0034] 10. A copper corrosion test was conducted by placing pieces
of copper foil in solutions 5 and 8 for 24 hours at room
temperature. After 24 hours, the copper concentration for solution
5 was 360 ppm and the copper concentration for solution 8 was 2,500
ppm measured by an HP-4500 ICP/MS spectrometer. This result is
particularly significant for circuit designs which use primarily
copper as a metal. Recent trends in technology are leading to use
of 100% copper as the metal layer for semiconductor designs
(instead of aluminum/copper).
[0035] Although a preferred embodiment of the present invention has
been described above, it will be appreciated that certain
alterations and modifications thereof will be apparent to those
skilled in the art. It is therefore intended that the appended
claims be interpreted as covering all such alterations and
modifications as fall within the true spirit and scope of the
invention.
* * * * *