U.S. patent application number 11/031118 was filed with the patent office on 2006-07-13 for composition useful for removal of post-etch photoresist and bottom anti-reflection coatings.
This patent application is currently assigned to Advanced Technology Materials, Inc.. Invention is credited to Thomas H. Baum, David D. Bernhard, David W. Minsek, Weihua Wang.
Application Number | 20060154186 11/031118 |
Document ID | / |
Family ID | 36647826 |
Filed Date | 2006-07-13 |
United States Patent
Application |
20060154186 |
Kind Code |
A1 |
Minsek; David W. ; et
al. |
July 13, 2006 |
Composition useful for removal of post-etch photoresist and bottom
anti-reflection coatings
Abstract
An aqueous-based composition and process for removing hardened
photoresist and/or bottom anti-reflective coating (BARC) material
from a substrate having same thereon. The aqueous-based composition
includes at least one chaotropic solute, at least one alkaline
base, and deionized water. The composition achieves high-efficiency
removal of hardened photoresist and/or BARC material in the
manufacture of integrated circuitry without adverse effect to metal
species on the substrate, such as copper, and without damage to
low-k dielectric materials employed in the semiconductor
architecture.
Inventors: |
Minsek; David W.; (New
Milford, CT) ; Wang; Weihua; (Danbury, CT) ;
Bernhard; David D.; (Newtown, CT) ; Baum; Thomas
H.; (New Fairfield, CT) |
Correspondence
Address: |
MOORE & VAN ALLEN PLLC
P.O. BOX 13706
Research Triangle Park
NC
27709
US
|
Assignee: |
Advanced Technology Materials,
Inc.
|
Family ID: |
36647826 |
Appl. No.: |
11/031118 |
Filed: |
January 7, 2005 |
Current U.S.
Class: |
430/331 |
Current CPC
Class: |
G03F 7/425 20130101;
G03F 7/091 20130101 |
Class at
Publication: |
430/331 |
International
Class: |
G03C 5/00 20060101
G03C005/00 |
Claims
1. An aqueous-based removal composition, said composition
comprising at least one chaotropic solute and at least one alkaline
salt in an aqueous medium, wherein the removal composition is
useful for removing photoresist and/or BARC materials from a
substrate having said material(s) thereon.
2. The composition of claim 1, comprising the following components
based on the total weight of the composition: 60.0% wt-98.0% wt.
deionized water 1.0% wt-30.0% wt chaotropic solute; and 1.0%
wt-10.0% wt alkaline salt, wherein the total of the weight
percentages of such components of the composition does not exceed
100% weight.
3. The composition of claim 1, wherein the at least one chaotropic
solute comprises a chaotropic species selected from the group
consisting of: urea; guanidinium chloride; 2-, 3-, and
4-aminobenzoic acid; 2-, 3-, and 4-nitrobenzoic acid; 2-, 3-, and
4-anisic acid; 2-, 3-, and 4-fluoro-, chloro-, bromo-, and
iodo-benzoic acid; 2-, 3-, and 4-methylthio-benzoic acid;
2,4-diamino-6-methyl-1,3,5-triazine; aniline; 2-, 3-, and
4-methylthio-aniline; 2-, 3-, and 4-anisidine; 1,2-, 1,3-, and
1,4-phenylenediamine; 1,3,5-triazine; melamine; acetoguanamine;
2,4-diamino-6-phenyl-1,3,5-triazine;
2-chloro-4,6-diamino-1,3,5-triazine;
2,4,6-trimethoxy-1,3,5-triazine; 2,4,6-trimethoxy-1,3,5-triazine;
2,4-diamino-1,3,5-triazine; 2-amino-1,3,5-triazine;
2-amino-4-ethoxy-6-methylamino)-1,3,5-triazine;
2-methoxy-4-methyl-4-(methylamino)-1,3,5-triazine; 1,2,4-triazole;
imidazole; 2-mercaptoimidazole; 2-nercaptobenzimidazole; chaotropic
anions selected from the group consisting of chloride salts,
bromide salts, iodide salts, nitrate salts, thiocyanide salts,
chlorate salts, and benzoate salts; and combinations thereof.
4. The composition of claim 3, wherein the cation associated with
the chaotropic anion comprises
(NR.sup.1R.sup.2R.sup.3R.sup.4).sup.+, wherein R.sup.1, R.sup.2,
R.sup.3 and R.sup.4 may be the same as or different from one
another and each is independently selected from the group
consisting of hydrogen and C.sub.1-C.sub.6 alkyl groups.
5. The composition of claim 1, wherein the at least one chaotropic
solute comprises a chaotropic anion having an atomic or molecular
radius of greater than or equal to 1.6 .ANG..
6. The composition of claim 1, wherein the at least one chaotropic
solute comprises urea.
7. The composition of claim 1, wherein the at least one alkaline
salt comprises (NR.sup.1R.sup.2R.sup.3R.sup.4)OH, wherein R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 may be the same as or different from
one another and each is independently selected from the group
consisting of hydrogen and C.sub.1-C.sub.6 alkyl groups.
8. The composition of claim 1, having a pH greater than about
13.
9. The composition of claim 1, selected from the group consisting
of Formulations A-G, wherein all percentages are by weight based on
the total weight of the formulation: Formulation A 2.5 wt. %
tetramethylammonium hydroxide; 20.0 wt. % urea; 77.5 wt. %
deionized water; Formulation B 1.5 wt. % tetramethylammonium
hydroxide; 1.6 wt % 2,4-diamino-6-methyl-1,3,5-triazine; 20.0 wt. %
urea; 76.9 wt % deionized water, Formulation C 2.0 wt. %
tetrwnethylammonium hydroxide; 1.0 wt. %
2,4-diamino-6-methyl-1,3,5-triazine; 1.0 wt. % 4-aminobenzoic acid;
96.0 wt. % deionized water, Formulation D 2.0 wt %
tetramethylammonium hydroxide; 2.4 wt. % tetramethylammonium
nitrate; 95.6 wt. % deionized water, Formulation E 5.0 wt. %
tetramethylammonium hydroxide; 9.0 wt. % tetramethylammonium
nitrate; 10.0 wt. % butyl carbitol; 10.0 wt. % sulfolane-w; 66.0
wt. % deionized water. Formulation F from about 1.0 wt % to about
5.0 wt. % tetramethylammonium hydroxide from about 1.0 wt. % to
about 20.0 wt. % of 2-, 3-, or 4-nitrobenzoic acid
tetramethylammonium salt remainder deionized water and Formulation
G from about 1.0 wt. % to about 5.0 wt. % tetramethylammonium
hydroxide from about 1.0 wt. % to about 20.0 wt. % of ortho-,
meta-, or para-phenylenediamine remainder deionized water.
10. A method of removing photoresist and/or BARC material from a
substrate having said material thereon, said method comprising
contacting the substrate with an aqueous-based removal composition
for sufficient time to at least partially remove said material from
the substrate, wherein the aqueous-based removal composition
comprises at least one chaotropic solute and at least one alkaline
salt in an aqueous medium.
11. The method of claim 10, wherein the aqueous-based removal
composition comprises the following components, based on the total
weight of the composition: 60.0% wt.-98.0% wt. deionized water 1.0%
wt.-30.0% wt. chaotropic solute; and 1.0% wt.-10.0% wt. alkaline
salt, wherein the total of the weight percentages of such
components of the composition does not exceed 100% weight.
12. The method of claim 10, wherein the substrate comprises a
semiconductor device structure.
13. The method of claim 10, wherein the material comprises a layer
selected from the group consisting of: photoresist hardened by
plasma etching; photoresist hardened by ion implantation; and
BARC.
14. The method of claim 10, wherein said contacting is carried out
for a time of from about 1 minute to about 60 minutes.
15. The method of claim 10, wherein said contacting is carried out
at temperature in a range of from about 40.degree. C. to about
80.degree. C.
16. The method of claim 10, wherein the at least one chaotropic
solute comprises a chaotropic species selected from the group
consisting of: urea; guanidinium chloride; 2-, 3-, and
4-aminobenzoic acid; 2-, 3-, and 4-nitrobenzoic acid; 2-, 3-, and
4-anisic acid; 2-, 3-, and 4-fluoro-, chloro-, bromo-, and
iodo-benzoic acid; 2-, 3-, and 4-methylthio-benzoic acid;
2,4-diamino-4-methyl-1,3,5-triazine; aniline; 2-, 3-, and
4-methylthio-aniline; 2-, 3-, and 4-anisidine; 1,2-, 1,3-, and
1,4-phenylenediamine; 1,3,5-triazine; melamine; acetoguanamine;
2,4-diamino-6-phenyl-1,3,5-triazine;
2-chloro-4,6-diamino-1,3,5-triazine;
2,4,6-trimethoxy-1,3,5-triazine; 2,4,6-trimethoxy-1,3,5-triazine;
2,4-diamino-1,3,5-triazine; 2-amino-1,3,5-triazine;
2-amino-4-ethoxy-6-methylamino)-1,3,5-triazine;
2-methoxy-4-methyl-6-methylamino)-1,3,5-triazine; 1,2,4-triazole;
imidazole; 2-mercaptoimidazole; 2-mercaptobenzimidazole; chaotropic
anions selected from the group consisting of chloride salts,
bromide salts, iodide salts, nitrate salts, thiocyanide salts,
chlorate salts, and benzoate salts; and combinations thereof.
17. The method of claim 16, wherein the cation associated with the
chaotropic anion comprises (NR.sup.1R.sup.2R.sup.3R.sup.4).sup.+,
wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 may be the same as or
different from one another and each is independently selected from
the group consisting of hydrogen and C.sub.1-C.sub.6 alkyl
groups.
18. The method of claim 10, wherein the at least one alkaline salt
comprises (NR.sup.1R.sup.2R.sup.3R.sup.4)OH, wherein R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 may be the same as or different from
one another and each is independently selected from the group
consisting of hydrogen and C.sub.1-C.sub.6 alkyl groups.
19. The method of claim 10, wherein the aqueous-based removal
composition is selected from the group consisting of Formulations
A-G, wherein all percentages are by weight, based on the total
weight of the formulation: Formulation A 2.5 wt. %
tetramethylammonium hydroxide; 20.0 wt. % urea; 77.5 wt % deionized
water, Formulation B 1.5 wt. % tetramethylammonium hydroxide; 1.6
wt. % 2,4-diamino-4-methyl-1,3,5-triazine; 20.0 wt. % urea; 76.9
wt. % deionized water; Formulation C 2.0 wt. % tetramethylammonium
hydroxide; 1.0 wt. % 2,4-diamino-6-methyl-1,3,5-triazine; 1.0 wt. %
4-aminobenzoic acid; 96.0 wt. % deionized water; Formulation D 2.0
wt. % tetramethylammonium hydroxide; 2.4 wt. % tetramethylammonium
nitrate; 95.6 wt. % deionized water; Formulation E 5.0 wt. %
tetramethylammonium hydroxide; 9.0 wt. % tetramethylammonium
nitrate; 10.0 wt % butyl carbitol; 10.0 wt % sulfolane-w; 66.0 wt.
% deionized water Formulation F from about 1.0 wt % to about 5.0
wt. % tetramethylammonium hydroxide from about 1.0 wt. % to about
20.0 wt. % of 2-, 3-, or 4-nitrobenzoic acid tetramethylammonium
salt remainder deionized water and Formulation G from about 1.0 wt.
% to about 5.0 wt. % tetramethylammonium hydroxide from about 1.0
wt. % to about 20.0 wt. % of ortho-, meta-, or
para-phenylenediamine remainder deionized water
20. The method of claim 10, further comprising rinsing the
substrate with deionized water following contact with the
aqueous-based removal composition.
21. The composition of claim 1, wherein both the at least one
chaotropic solute and the at least one alkaline salt are metal-ion
free.
22. The method of claim 10, wherein both the at least one
chaotropic solute and the at least one alkaline salt are metal-ion
free.
23. The composition of claim 1, further comprising photoresist
material.
24. The composition of claim 1, further comprising BARC
material.
25. The method of claim 10, wherein the aqueous-based removal
composition further comprises photoresist material.
26. The method of claim 10, wherein the aqueous-based removal
composition further comprises BARC material.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to aqueous-based compositions
useful in semiconductor manufacturing for the removal of hardened
photoresist and/or bottom anti-reflection coatings (BARCs) from
substrates having such layers thereon, and to methods of using such
compositions for removal of hardened photoresist and/or BARC layers
from semiconductor substrates.
DESCRIPTION OF THE RELATED ART
[0002] Photolithography techniques comprise the steps of coating,
exposure, and development. A wafer is coated with a positive or
negative photoresist substance and subsequently covered with a mask
that defines patterns to be retained or removed in subsequent
processes. Following the proper positioning of the mask, the mask
has directed therethrough a beam of monochromatic radiation, such
as ultraviolet (UV) light or deep UV (DUV) light
(.lamda..apprxeq.250 nm), to make the exposed photoresist material
more or less soluble in a selected rinsing solution. The soluble
photoresist material is then removed, or "developed," thereby
leaving behind a pattern identical to the mask.
[0003] Currently, there are four developed wavelengths of radiation
used in the photolithographic industry--436 nm, 365 nm, 248 nm, and
193 nm--and recent efforts have focused on 157 nm lithography
processes. In theory, with each wavelength decrease, smaller
features can be created on the semiconductor chip. However, because
the reflectively of the semiconductor substrate is inversely
proportional to the photolithographic wavelength, interference and
unevenly exposed photoresist has limited the consistency of the
critical dimensions of the semiconductor device.
[0004] For example, upon exposure to DUV radiation, it is well
known that the transmissivity of photoresist combined with the high
reflectivity of the substrates to the DUV wavelengths results in
the reflection of the DUV radiation back into the photoresist
thereby producing standing waves in the photoresist layer. The
standing waves trigger further photochemical reactions in the
photoresist causing an uneven exposure of the photoresist,
including in masked portions not intended to be exposed to the
radiation, which results in variations in linewidths, spacing and
other critical dimensions.
[0005] In order to address the transmissivity and reflectivity
problems, bottom anti-reflective coatings (BARCs), both inorganic
and organic in nature, have been developed which are applied to
substrates prior to applying the photoresist. For example, organic
BARCs, including, but not limited to, polysulfones, polyureas,
polyurea sulfones, polyacrylates and poly(vinyl pyridine), are
typically 600-1200 .ANG. thick and deposited using spin-on coating
techniques. Generally, organic BARCs are planarizing layers,
filling up the vias evenly, and highly cross-linked. Organic BARCs
prevent light reflection by matching the reflective index of the
BARC layer with that of the photoresist layer while simultaneously
absorbing radiation thereby preventing radiation reflection and
standing waves.
[0006] During back-end-of-line (BEOL) dual-damascene processing of
integrated circuits, gas-phase plasma etching is used to transfer
the patterns of the developed photoresist coating to an underlying
dielectric coating. During pattern transfer, the reactive plasma
gases react with the developed photoresist, resulting in the
formation of a hardened, crosslinked polymeric material, or
"crust," on the surface of the photoresist. In addition, the
reactive plasma gases react with the sidewalls of the BARC and the
features etched into the dielectric. During front-end-of-line
(FEOL) processing, ion implantation is used to add dopant atoms to
the exposed wafer layers. Ion implant-exposed photoresist is also
highly cross-linked similar to plasma etched photoresist.
[0007] The clean removal of hardened photoresist and/or BARC
materials from the semiconductor wafer has proven to be difficult
and/or costly. If not removed, the layers may interfere with
subsequent silicidation or contact formation. Typically, the layers
are removed by oxidative or reductive plasma ashing or wet
cleaning. However, plasma ashing, whereby the substrate is exposed
to an oxidative or reductive plasma etch, may result in damage to
the dielectric material, either by changing the feature shapes and
dimensions, or by an increase in the dielectric constant of the
dielectric material. The latter problem is more pronounced when
low-k dielectric materials, such as organosilicate glasses (OSG) or
carbon-doped oxide glasses, are the underlying dielectric material.
As such, it is often desirable to avoid the use of plasma ashing to
remove the hardened photoresist and/or BARC layers.
[0008] When a cleaner/etchant composition is used in BEOL
applications to process surfaces having aluminum or copper
interconnected wires, it is important that the composition possess
good metal compatibility, e.g., a low etch rate on copper,
aluminum, cobalt, etc. Aqueous removal solutions are preferred
because of the simpler disposal techniques, however, the
photoresist "crust" is typically extremely insoluble in aqueous
cleaners, especially cleaners that do not damage the dielectric.
Often substantial quantities of co-solvents, wetting agents and/or
surfactants are added to the aqueous solutions to improve the
cleaning ability of the solution.
[0009] For example, co-solvents may increase the ability to remove
hardened photoresist by increasing the solubility of the
photoresist material in the composition and/or decreasing the
solution surface tension, i.e., increasing wettability, however,
the inclusion of co-solvents may increase the undesirable corrosion
of other materials such as metals and low-k dielectrics. Towards
that end, a co-solvent-free aqueous solution is desirable,
preferably one that completely and efficiently removes hardened
photoresist and/or BARC layers from the underlying dielectric.
[0010] The present invention relates to removal compositions
including chaotropic solutes. It is theorized that a chaotropic
solute destructures or breaks-up the hydrogen-bonded structure of
liquid water thus increasing the solubility of other species, e.g.,
polymers, in water. The effects of chaotropes were first noted by
Hofineister in 1888 (Hofineister, F., Arch. Exp. Pathol.
Pharmakol., 24, 247-260 (1888)) as a function of protein solubility
and a "series" of anions was developed based on protein
solubilities in solutions containing those anions (Collins, K. D.,
Washabaugh, M. W., Quart. Rev. Biophysics, 18(4), 323-422 (1985)).
Well known chaotropic anions include Cl.sup.-, NO.sub.3.sup.-,
Br.sup.-, I.sup.-, ClO.sub.4.sup.-, and SCN.sup.-. Other chaotropic
species include the guanidinium ion and nonionic urea, which have
been demonstrated to increase the solubility of hydrocarbons in
aqueous solutions (Wetlaufer, D. B., Malik, S. K., Stoller, L.,
Coffin, R. L., J. Am. Chem. Soc., 86, 508-514 (1964)).
[0011] Recently, Xu et al. reported the swelling behaviors of
poly(4-vinyl phenol) gel in chaotrope-containing solutions (Xu, L.,
Yokoyama, E., Watando, H., Okuda-Fukui, R., Kawauchi, S., Satoh,
M., Langmuir, 20, 7064-7069 (2004)). Poly(4-vinyl phenol) is a
highly cross-linked polymer which was demonstrated to be swollen in
an aqueous tetraalkylammonium chloride solution, the swelling being
demonstrative of increased solubility of the polymer in the
chaotrope-containing solution. Similarly, hardened photoresist and
BARC layers are highly cross-linked and thus, chaotropic solutes
should theoretically swell the cross-linked photoresist and BARC
layers in a similar manner.
[0012] It would therefore be a significant advance in the art to
provide an aqueous-based, co-solvent-free composition that
overcomes the deficiencies of the prior art relating to the removal
of hardened photoresist and/or BARC layers from semiconductor
substrates.
[0013] Further, it would be a significant advance in the art to
provide an aqueous based composition including a chaotropic solute
to increase the solubility of the hardened photoresist and/or BARC
layers in said composition to effectuate removal of the layers from
semiconductor substrates.
SUMMARY OF THE INVENTION
[0014] The present invention relates to aqueous-based compositions
useful in semiconductor manufacturing for the removal of hardened
photoresist and/or BARC layers from substrates having same thereon,
and to methods of using such compositions for removal of hardened
photoresist and/or BARC layers from semiconductor substrates.
[0015] In one aspect, the invention relates to a aqueous-based
removal composition useful for removing photoresist and/or bottom
anti-reflective coating (BARC) materials from a substrate having
such material(s) thereon, said composition comprising at least one
chaotropic solute and at least one alkaline salt in an aqueous
medium.
[0016] In another aspect, the invention relates to a method of
removing photoresist and/or BARC material from a substrate having
said material thereon, said method comprising contacting the
substrate with an aqueous-based removal composition for sufficient
time to at least partially remove said material from the substrate,
wherein the aqueous-based removal composition comprises at least
one chaotropic solute and at least one alkaline salt in an aqueous
medium.
[0017] Other aspects, features and embodiments of the invention
will be more fully apparent from the ensuing disclosure and
appended claims.
DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS
THEREOF
[0018] The present invention is based on the discovery of an
aqueous-based composition that is highly efficacious for the
removal of hardened photoresist and BARC layers from patterned
semiconductor wafers having same thereon. Specifically, the present
invention relates to the removal of hardened photoresist and/or
BARC layers from plasma etched and/or ion implanted semiconductor
wafers.
[0019] "Hardened photoresist" as used herein includes, but is not
limited to, photoresist that has been plasma etched, e.g., during
BEOL dual-damascene processing of integrated circuits, and/or ion
implanted, e.g., during front-end-of-line (FEOL) processing to
implant dopant species in the appropriate layers of the
semiconductor wafer.
[0020] In one aspect, the present invention relates to
aqueous-based removal compositions useful in removing hardened
photoresist and/or BARC layers from a semiconductor substrate. The
formulation of the present invention comprises at least one
chaotropic solute and at least one alkaline salt in an aqueous
medium, present in the following ranges, based on the total weight
of the composition: TABLE-US-00001 component of % by weight
chaotropic solute(s) about 1.0% to about 30.0% alkaline salt(s)
about 1.0% to about 10.0% aqueous medium about 60.0% to about
98.0%
[0021] In the broad practice of the invention, the aqueous-based
removal composition may comprise, consist of, or consist
essentially of at least one chaotropic solute and at least one
alkaline salt in an aqueous medium. In general, the specific
proportions and amounts of chaotropic solute(s), alkaline salt(s)
and aqueous medium, in relation to each other, may be suitably
varied to provide the desired removal action of the aqueous-based
composition for the hardened photoresist and/or BARC layer species
and/or processing equipment, as readily determinable within the
skill of the art without undue effort.
[0022] As used herein, "aqueous medium" may be any aqueous-based
medium which does not alter the removal efficacy of the at least
one chaotropic solute and at least one alkaline salt. Preferably,
the aqueous medium is water, most preferably deionized water.
[0023] The chaotropic solute serves to increase the solubility of
the hardened photoresist and/or BARC constituent species in the
aqueous-based composition. "Chaotropic solutes," as defined herein,
refer to water soluble or aqueous alkaline soluble neutral and
anionic species which increase the ability of an aqueous alkaline
composition to remove hardened photoresist and/or BARC layers.
"Chaotropic anions" preferably have an atomic or molecular radius
of greater than or equal to 1.6 .ANG., for example those anions
conventionally known to be chaotropic including, but not limited
to, chloride, bromide, iodide, nitrate, thiocyanide and chlorate.
Other solutes contemplated herein for use as chaotropic solutes
include, but are not limited to: urea; and guanidinium salts, e.g.,
guanidinium chloride. Additionally, we expect certain solutes to
act as chaotropes based on structural similarities to known
chaotropes. Such solutes may include, but are not limited to:
anionic benzoate salts and benzoate derivatives such as 2-, 3-, or
4-aminobenzoic acids, 2-, 3-, or 4-nitrobenzoic acid, 2-, 3-, or
4-anisic acid, 2-, 3-, or 4-fluoro-, chloro-, bromo-, or
iodo-benzoic acid, 2-, 3-, or 4-methylthio-benzoic acid, and other
mono- or poly-substituted benzoic acid salts;
2,4-diamino-6-methyl-1,3,5-triazine; aniline or substituted aniline
such as 2-, 3-, or 4methylthio-aniline or 2-, 3-, or 4-anisidine;
1,2-, 1,3-, or 1,4-phenylenediamine, nitrogen-containing
heterocyclic compounds such as 1,3,5-triazine or substituted
1,3,5-triazines such as melamine, acetoguanamine,
2,4-diamino-6-phenyl-1,3,5-triazine,
2-chloro-4,6-diamino-1,3,5-triazine,
2,4,6-trimethoxy-1,3,5-triazine, 2,4,6-trimethoxy-1,3,5-triazine,
2,4-diamino-1,3,5-triazine, 2-amino-1,3,5-triazine,
2-amino-4-ethoxy-6-(methylamino)-1,3,5-triazine,
2-methoxy-4-methyl-6-(methylamino)-1,3,5-triazine; 1,2,4-triazole
or substituted 1,2,4-triazoles; imidazole or substituted imidazoles
such as 2-mercaptoimidazole, and 2-mercaptobenzimidazole.
[0024] Preferably, the cations associated with the chaotropic
anions are metal-ion free, e.g.,
(NR.sup.1R.sup.2R.sup.3R.sup.4).sup.+ where R.sup.1, R.sup.2,
R.sup.3 and R.sup.4 may be the same as or different from one
another and each is independently selected from the group
consisting of hydrogen and C.sub.1-C.sub.6 alkyl groups.
Preferably, the cation associated with the chaotropic anion is
tetramethylammonium.
[0025] The alkaline salt(s) serve to attack the hardened
photoresist and/or BARC layer. Although not wishing to be bound by
theory, it is postulated that the chaotropic solute swells the
polymeric layer allowing the alkaline salts to attack every
interface of the hardened photoresist and/or BARC layer. Thus, the
interface between the substrate and the hardened photoresist and/or
BARC layer is compromised and the hardened photoresist and/or BARC
layer delaminates from the substrate. Alkaline salt(s) contemplated
herein include metal-ion free hydroxides, e.g.,
(NR.sup.1R.sup.2R.sup.3R.sup.4)OH where R.sup.1, R.sup.2, R.sup.3
and R.sup.4 may be the same as or different from one another and
each is independently selected from the group consisting of
hydrogen and C.sub.1-C.sub.6 alkyl groups. Preferably, the alkaline
salt is tetramethylammonium hydroxide and the pH of the
aqueous-based removal composition is at least about 13.
[0026] In general, the specific proportions and amounts of
chaotropic solute(s), alkaline salt(s), and deionized water in
relation to each other may be suitably varied to provide the
desired solubilizing action of the aqueous-based composition for
the specific photoresist and/or BARC layers to be cleaned from the
substrate. Such specific proportions and amounts are readily
determinable by simple experiment within the skill of the art
without undue effort.
[0027] The removal efficiency of the aqueous-based removal
composition of the present invention may be enhanced by use of
elevated temperature conditions in the contacting of the
photoresist and/or BARC layers to be removed with the aqueous-based
removal composition.
[0028] The aqueous-based removal compositions of the invention may
optionally be formulated with additional components to further
enhance the removal capability of the composition, or to otherwise
improve the character of the composition. Accordingly, the
composition may be formulated with surfactants, stabilizers,
chelating agents, corrosion inhibitors, complexing agents, etc.
Although the aqueous-based removal compositions of the invention
normally contain no organic co-solvents, an organic co-solvent may
be included so long as they do not corrode other materials such as
metals and low-k dielectrics. Co-solvents contemplated herein
include alkanols (e.g., straight chained or branched
C.sub.1-C.sub.6 alcohols), butyl carbitol and sulfolane-w.
[0029] Preferred aqueous-based removal compositions include
formulations (A)-(G) enumerated hereinbelow:
[0030] Formulation A
[0031] 2.5 wt. % tetramethylammonium hydroxide
[0032] 20.0 wt. % urea
[0033] 77.5 wt. % deionized water
[0034] Formulation B
[0035] 1.5 wt. % tetramethylammonium hydroxide
[0036] 1.6 wt. % 2,4-diamino-6-methyl-1,3,5-triazine
[0037] 20.0 wt. % urea
[0038] 76.9 wt. % deionized water
[0039] Formulation C
[0040] 2.0 wt. % tetramethylammonium hydroxide
[0041] 1.0 wt. % 2,4-diamino-6-methyl-1,3,5-triazine
[0042] 1.0 wt. % 4-aminobenzoic acid
[0043] 96.0 wt. % deionized water
[0044] Formulation D
[0045] 2.0 wt. % tetramethylammonium hydroxide
[0046] 2.4 wt. % tetramethylammonium nitrate
[0047] 95.6 wt. % deionized water
[0048] Formulation E
[0049] 5.0 wt. % tetramethylammonium hydroxide
[0050] 9.0 wt. % tetramethylammonium nitrate
[0051] 10.0 wt. % butyl carbitol
[0052] 10.0 wt. % sulfolane-w
[0053] 66.0 wt. % deionized water
[0054] Formulation F
[0055] from about 1.0 wt. % to about 5.0 wt. % tetramethylammonium
hydroxide
[0056] from about 1.0 wt. % to about 20.0 wt. % of 2-, 3-, or
4-nitrobenzoic acid tetramethylammonium salt
[0057] remainer deionized water
[0058] Formulation G
[0059] from about 1.0 wt. % to about 5.0 wt. % tetramethylammonium
hydroxide
[0060] from about 1.0 wt. % to about 20.0 wt. % of ortho-, meta-,
or para-phenylenediamine
[0061] remainer deionized water
[0062] The aqueous-based compositions of the invention are easily
formulated by simple addition of the respective ingredients and
mixing to homogeneous condition.
[0063] In another aspect, the invention relates to methods of
removal of hardened photoresist and/or BARC layers from a
semiconductor wafer surface using the aqueous-based removal
compositions described herein.
[0064] In hardened photoresist and/or BARC removal application, the
aqueous-based composition is applied in any suitable manner to the
material to be cleaned, e.g., by spraying the aqueous-based
composition on the surface of the material to be cleaned, by
dipping (in a volume of the aqueous-based composition) of the
material or article including the material to be cleaned, by
contacting the material or article to be cleaned with another
material, e.g., a pad, or fibrous sorbent applicator element, that
is saturated with the aqueous-based composition, or by any other
suitable means, manner or technique by which the aqueous-based
composition is brought into removal contact with material to be
cleaned.
[0065] Other methods of cleaning can be utilized for cleaning full
wafers with a diameter of 200 or 300 mm such as typically used for
semiconductor circuit manufacturing, for example, single wafer or
batch immersion, or single wafer or batch spray application.
[0066] As applied to semiconductor manufacturing operations, the
aqueous-based compositions of the present invention are usefully
employed to remove hardened photoresist and/or BARC materials from
substrates and semiconductor device structures on which such
material(s) have been deposited.
[0067] The compositions of the present invention, by virtue of
their selectivity for such hardened photoresist and/or BARC
materials relative to other materials that may be present on the
semiconductor substrate, e.g., ILD structures, metallization,
barrier layers, etc., achieve removal of the hardened photoresist
and/or BARC material(s) in a highly efficient manner.
[0068] In use of the compositions of the invention for removing
photoresist and/or BARC materials from semiconductor substrates
having same thereon, the aqueous-based composition typically is
contacted with the substrate for a time of from about 1 minute to
about 60 minutes, at temperature in a range of from about
40.degree. C. to about 80.degree. C. Such contacting times and
temperatures are illustrative, and any other suitable time and
temperature conditions may be employed that are efficacious to
completely remove the hardened photoresist and/or BARC material
from the substrate using the aqueous-based compositions of the
present invention, within the broad practice of the invention.
[0069] Following the achievement of the desired removal action, the
aqueous-based composition is readily removed from the substrate or
article to which it has previously been applied, e.g., by rinse,
wash, or other removal step(s), as may be desired and efficacious
in a given end use application of the compositions of the present
invention. Preferably, the substrate or article is rinsed with
copious amounts of deionized water and blown dry with nitrogen gas
prior to subsequent processing.
[0070] The features and advantages of the invention are more fully
shown by the illustrative examples discussed below.
EXAMPLE 1
[0071] Cleaning was performed on samples of patterned semiconductor
substrate consisting of layers of hardened photoresist, BARC, low-k
dielectric (specifically carbon-doped oxide), and silicon nitride.
Plasma etching had been previously performed to transfer a pattern
of lines, spaces, and holes of varying dimensions, from about 100
nanometers to greater than 10 microns, from a pattern formed in a
top coating of photoresist to the underlying materials. The pattern
consisted of spaces etched into the substrate, stopping at the
silicon nitride etch-stop layer. The hardened photoresist and BARC
was present as a coating of between 10 to 50 nanometers.
[0072] A section of the substrate was cleaned by immersion for a
fixed time at a fixed temperature in a static bath of the
Formulation A cleaning solution described hereinabove. After
immersion for the set time the sample was removed, rinsed with
copious amounts of de-ionized water, and blown dry with nitrogen. A
cleaning time of 30 minutes at 55.degree. C. was sufficient to
remove 100% of the hardened photoresist and BARC. Cleaning was
observed by top-down optical microscopy and confirmed by scanning
electron microscopy (SEM).
EXAMPLE 2
[0073] Cleaning using Formulation B was performed on a sample of
patterned semiconductor substrate such as that described in Example
1 using the same method described in Example 1. An immersion time
of greater than 20 minutes but less than 30 minutes at 55.degree.
C. was sufficient to clean 100% of the hardened photoresist and
BARC material from the substrate as observed by top-down optical
microscopy and confirmed by scanning electron microscopy (SEM).
EXAMPLE 3
[0074] Cleaning using Formulation C was performed on a sample of
patterned semiconductor substrate such as that described in Example
1 using the same method described in Example 1. An immersion time
of greater than 20 minutes but less than 30 minutes at 55.degree.
C. was sufficient to clean close to 100% of the hardened
photoresist and BARC material from the substrate as observed by
top-down optical microscopy and confirmed by scanning electron
microscopy (SEM).
EXAMPLE 4
[0075] Cleaning using Formulation D was performed on a sample of
patterned semiconductor substrate such as that described in Example
1 using the same method described in Example 1. An immersion time
of greater than 20 minutes but less than 30 minutes at 55.degree.
C. was sufficient to clean about 90% of the photoresist and BARC
material from the substrate as observed by top-down optical
microscopy and confirmed by scanning electron microscopy (SEM).
EXAMPLE 5
[0076] Cleaning using Formulation E was performed on a sample of
patterned semiconductor substrate such as that described in Example
1 using the same method described in Example 1. An immersion time
of about 20 minutes at 55.degree. C. was sufficient to clean 100%
of the photoresist and BARC material from the substrate as observed
by top-down optical microscopy and confirmed by scanning electron
microscopy (SEM).
[0077] Accordingly, while the invention has been described herein
in reference to specific aspects, features and illustrative
embodiments of the invention, it will be appreciated that the
utility of the invention is not thus limited, but rather extends to
and encompasses numerous other aspects, features and embodiments.
Accordingly, the claims hereafter set forth are intended to be
correspondingly broadly construed, as including all such aspects,
features and embodiments, within their spirit and scope.
* * * * *