U.S. patent application number 11/273637 was filed with the patent office on 2006-04-06 for supercritical carbon dioxide/chemical formulation for ashed and unashed aluminum post-etch residue removal.
Invention is credited to Thomas H. Baum, Eliodor G. Ghenciu, Michael B. Korzenski, Chongying Xu.
Application Number | 20060073998 11/273637 |
Document ID | / |
Family ID | 32175064 |
Filed Date | 2006-04-06 |
United States Patent
Application |
20060073998 |
Kind Code |
A1 |
Korzenski; Michael B. ; et
al. |
April 6, 2006 |
Supercritical carbon dioxide/chemical formulation for ashed and
unashed aluminum post-etch residue removal
Abstract
A post-etch residue cleaning composition for cleaning ashed or
unashed aluminum/SiN/Si post-etch residue from small dimensions on
semiconductor substrates. The cleaning composition contains
supercritical CO.sub.2 (SCCO2), alcohol, fluoride source, an
aluminum ion complexing agent and, optionally, corrosion inhibitor.
Such cleaning composition overcomes the intrinsic deficiency of
SCCO2 as a cleaning reagent, viz., the non-polar character of SCCO2
and its associated inability to solubilize species such as
inorganic salts and polar organic compounds that are present in the
post-etch residue and that must be removed from the semiconductor
substrate for efficient cleaning. The cleaning composition enables
damage-free, residue-free cleaning of substrates having ashed or
unashed aluminum/SiN/Si post-etch residue thereon.
Inventors: |
Korzenski; Michael B.;
(Danbury, CT) ; Ghenciu; Eliodor G.; (King of
Prussia, PA) ; Xu; Chongying; (New Milford, CT)
; Baum; Thomas H.; (New Fairfield, CT) |
Correspondence
Address: |
MOORE & VAN ALLEN PLLC
P.O. BOX 13706
Research Triangle Park
NC
27709
US
|
Family ID: |
32175064 |
Appl. No.: |
11/273637 |
Filed: |
November 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10285015 |
Oct 31, 2002 |
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11273637 |
Nov 14, 2005 |
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10249658 |
Apr 29, 2003 |
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11273637 |
Nov 14, 2005 |
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Current U.S.
Class: |
510/175 ; 134/2;
257/E21.228; 257/E21.255; 257/E21.313 |
Current CPC
Class: |
C11D 7/3245 20130101;
H01L 21/32138 20130101; C23G 5/00 20130101; C11D 7/32 20130101;
C11D 7/264 20130101; C11D 7/261 20130101; C11D 7/50 20130101; C11D
7/10 20130101; H01L 21/02052 20130101; C11D 7/08 20130101; C11D
7/265 20130101; H01L 21/02071 20130101; H01L 21/31133 20130101;
C11D 7/28 20130101; C11D 7/5022 20130101; C11D 11/0047
20130101 |
Class at
Publication: |
510/175 ;
134/002 |
International
Class: |
C23G 1/00 20060101
C23G001/00; C11D 7/32 20060101 C11D007/32 |
Claims
1-44. (canceled)
45. A post-etch residue cleaning composition, comprising SCCO2,
alcohol, fluorine source, an aluminum ion complexing agent and,
optionally, corrosion inhibitor.
46. The composition of claim 45, wherein the alcohol comprises at
least one C.sub.1-C.sub.4 alcohol.
47. The composition of claim 45, wherein the alcohol comprises
methanol.
48. The composition of claim 45, wherein the fluorine source
comprises a fluorine-containing compound selected from the group
consisting of hydrogen fluoride (HF), amine trihydrogen fluoride
compounds of the formula NR.sub.3(HF).sub.3 wherein each R is
independently selected from hydrogen and lower alkyl, hydrogen
fluoride-pyridine (pyr-HF), and ammonium fluorides of the formula
R.sub.4NF, wherein each R is independently selected from hydrogen
and lower alkyl.
49. The composition of claim 45, wherein the fluorine source
comprises ammonium fluoride (NH.sub.4F).
50. The composition of claim 45, wherein the aluminum ion
complexing agent comprises a complexing agent selected from the
group consisting of salicylic acid, EDTA, oxalic acid,
beta-diketones, gallic acid, nitrilotriacetic acid,
3-hydroxy-2-naphthoic acid, and oxine.
51. The composition of claim 45, wherein the aluminum ion
complexing agent comprises salicylic acid.
52. The composition of claim 45, comprising corrosion
inhibitor.
53. The composition of claim 52, wherein said corrosion inhibitor
includes boric acid.
54. The composition of claim 45, wherein the alcohol has a
concentration that increases the solubility of the composition for
inorganic salts and polar organic compounds present in
aluminum/SiN/Si post-etch residue, relative to a corresponding
composition lacking such alcohol.
55. The composition of claim 49, comprising ammonium fluoride,
salicylic acid and boric acid.
56. The composition of claim 55, wherein ammonium fluoride has a
concentration of from about 0.01 to about 1.0 wt. %, based on the
total weight of the cleaning composition.
57. The composition of claim 45, wherein the aluminum ion
complexing agent has a concentration of from about 0.01 to about
2.0 wt. %, based on the total weight of the cleaning
composition.
58. The composition of claim 45, comprising corrosion inhibitor,
wherein the corrosion inhibitor has a concentration of from about
0.01 to about 1.0 wt. %, based on the total weight of the cleaning
composition.
59. The composition of claim 49, comprising ammonium fluoride,
salicylic acid, and boric acid in a molar ratio of about
1.50:1.53:1.0 (ammonium fluoride:salicylic acid:boric acid).
60. The composition of claim 59, wherein ammonium fluoride has a
concentration of from about 0.2 to about 2.0 wt. %, based on the
total weight of the cleaning composition.
61. The composition of claim 45, wherein the aluminum ion
complexing agent has a concentration of from about 0.2 to about 4.0
wt. %, based on the total weight of the cleaning composition.
62. The composition of claim 45, comprising corrosion inhibitor,
wherein the corrosion inhibitor has a concentration of from about
0.2 to about 2.0 wt. %, based on the total weight of the cleaning
composition.
63. The composition of claim 49, comprising ammonium fluoride,
salicylic acid, and boric acid in a molar ratio of about
1.10:1.0:0.73 (ammonium fluoride:salicylic acid:boric acid).
64. A method of removing aluminum/SiN/Si post-etch residue from a
substrate having same thereon, said method comprising contacting
the post-etch residue with a cleaning composition comprising SCCO2,
alcohol, fluorine source, an aluminum ion complexing agent and,
optionally, corrosion inhibitor, for sufficient time and under
sufficient contacting conditions to remove the aluminum/SiN/Si
post-etch residue from the substrate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to supercritical carbon
dioxide-based compositions useful in semiconductor manufacturing
for the removal of ashed and unashed aluminum/SiN/Si/Si post-etch
residues from substrates having such residues thereon, and to
methods of using such compositions for removal of post-etch
residues from semiconductor substrates.
DESCRIPTION OF THE RELATED ART
[0002] Semiconductor manufacturing involves the use of photoresists
that are applied to wafer substrates and subsequently developed to
produce specific patterned regions and structures on the wafer.
Subsequent to etching and optionally ashing of the exposed
photoresist, residue remains on the substrate. This residue must be
removed to ensure proper operation of the microelectronic device
that is the ultimate product of the semiconductor manufacturing
process, and to avoid interference or deficiency in relation to
subsequent process steps in the manufacturing process.
[0003] Significant and continuing efforts have been made in the
semiconductor manufacturing industry to develop formulations for
removing photoresist and residue thereof from the semiconductor
substrate, particularly in device structures including aluminum
metalization and aluminum-based interconnect elements. This effort
has been frustrated by the continuing and rapid decrease in
critical dimensions.
[0004] As critical dimensions of chip architectures become smaller,
e.g., <100 nanometers, it becomes progressively more difficult
to remove residue from patterned semiconductor wafers with high
aspect ratio trenches and vias. Conventional wet-cleaning methods
suffer substantial limitations as critical dimension widths
decrease below 100 nm due to the high surface tension
characteristics of liquids used in the cleaning solution.
Additionally, the use of aqueous cleaning solutions has the major
deficiency that the aqueous solutions can strongly affect important
material properties of porous low-k dielectric materials, including
mechanical strength, moisture uptake, coefficient of thermal
expansion, and adhesion to different substrates.
[0005] It would therefore be a significant advance in the art to
provide a cleaning composition that overcomes such deficiencies of
the prior and conventional cleaning compositions used for removal
of ashed and non-ashed post-etch residue on semiconductor
substrates.
SUMMARY OF THE INVENTION
[0006] The present invention relates to supercritical carbon
dioxide-based compositions useful in semiconductor manufacturing
for the removal of ashed and unashed aluminum/SiN/Si post-etch
residues from substrates having such residues thereon, and methods
of using such compositions for removal of post-etch residues from
semiconductor substrates.
[0007] In one aspect, the invention relates to a post-etch residue
cleaning composition, comprising SCCO2, alcohol, fluorine source,
an aluminum ion complexing agent and, optionally, corrosion
inhibitor.
[0008] In another aspect, the invention relates to a post-etch
residue cleaning composition, comprising SCCO2, methanol, ammonium
fluoride, salicylic acid, and boric acid, wherein ammonium fluoride
is present at a concentration of from about 0.01 to about 2.0 wt.
%, salicylic acid is present at a concentration of from about 0.01
to about 4.0 wt. %, and boric acid is present at a concentration of
from about 0.01 to about 2.0 wt. %, based on the total weight of
the cleaning composition.
[0009] A further aspect of the invention relates to a method of
removing aluminum/SiN/Si post-etch residue from a substrate having
same thereon, said method comprising contacting the post-etch
residue with a cleaning composition comprising SCCO2/alcohol
solution, a fluorine source, an aluminum ion complexing agent and,
optionally, corrosion inhibitor, for sufficient time and under
sufficient contacting conditions to remove the aluminum/SiN/Si
post-etch residue from the substrate.
[0010] Other aspects, features and embodiments of the invention
will be more fully apparent from the ensuing disclosure and
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a scanning electron microscope (SEM) image at 50 K
magnification of an ashed post aluminum etch control wafer clearly
showing the crystalline residue including crystallites on the ashed
surfaces.
[0012] FIG. 2 is a scanning electron microscope (SEM) image at 25 K
magnification of a corresponding post-cleaned sample, which was
cleaned of residue by contact of the ashed residue-bearing
substrate with a cleaning composition containing SCCO2/methanol,
ammonium fluoride and salicylic acid.
[0013] FIG. 3 is a scanning electron microscope (SEM) image at 60 K
magnification of an unashed post aluminum etch control wafer
showing "dog-ear-like" residue on the wafer surface at either side
of the trench structure.
[0014] FIG. 4 is a corresponding scanning electron microscope (SEM)
image at 35 K magnification of the unashed post aluminum etch
control wafer of FIG. 3, showing the "dog-ear-like" residue on the
wafer surface at either side of the trench structure.
[0015] FIG. 5 is a scanning electron microscope (SEM) image at 100
K magnification of the unashed post aluminum etch wafer of FIGS.
3-4 after cleaning thereof by contact of the unashed substrate with
the cleaning composition containing SCCO2/methanol, ammonium
fluoride and salicylic acid, showing that the "dog-ear-like"
residue on the wafer surface at either side of the trench structure
as present in the FIGS. 3-4 micrographs has been fully removed.
[0016] FIG. 6 is a scanning electron microscope (SEM) image at 60 K
magnification of the unashed post aluminum etch wafer of FIGS. 3-4
after cleaning thereof by contact of the unashed substrate with the
cleaning composition containing SCCO2/methanol, ammonium fluoride
and salicylic acid, showing that the "dog-ear-like" residue on the
wafer surface at either side of the trench structure as present in
the FIGS. 3-4 micrographs has been fully removed.
DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS
THEREOF
[0017] The present invention is based on the discovery of a
supercritical carbon dioxide-based cleaning composition that is
highly efficacious for the removal of post-etch residue, including
both ashed post-etch residue and non-ashed post-etch residue, from
semiconductor substrates on which same is present.
[0018] Supercritical carbon dioxide (SCCO2) might at first glance
be regarded as an attractive reagent for removal of aluminum
post-etch residues, since supercritical CO.sub.2 has the
characteristics of both a liquid and a gas. Like a gas, it diffuses
rapidly, has low viscosity, near-zero surface tension, and
penetrates easily into deep trenches and vias. Like a liquid, it
has bulk flow capability as a "wash" medium.
[0019] Despite these ostensible advantages, however, supercritical
CO.sub.2 is non-polar. Accordingly, it will not solubilize many
species, including inorganic salts and polar organic compounds that
are present in the post-etch residue and that must be removed from
the semiconductor substrate for efficient cleaning. The non-polar
character of SCCO2 thus has been an impediment to the use of such
reagent for aluminum post-etch residue removal subsequent to
deposition or formation of aluminum on the substrate, e.g., for
fabrication of interconnects, contacts, electrodes, metallization,
conductive base layers for field emitter elements, etc.
[0020] Such deficiency of supercritical CO.sub.2 has been overcome
by the present invention in the provision of a SCCO2-based
composition that is highly effective for cleaning of aluminum
post-etch residues containing Al.sup.3+ ions as well as slightly
fluorinated residues and combinations thereof, and achieves
damage-free, residue-free cleaning of the substrate, e.g., a
patterned wafer, initially having such residues thereon.
[0021] More specifically, the present invention contemplates a
post-etch residue cleaning composition including a SCCO2/alcohol
solution containing (i) fluorine source, (ii) an aluminum ion
complexing agent and (iii) optionally, a corrosion inhibitor, e.g.,
boric acid (H.sub.3BO.sub.3).
[0022] The composition of the invention has utility for cleaning
both ashed and unashed aluminum/SiN/Si post-etch residue from small
dimensions on semiconductor substrates without further attack on
the aluminum surface or Si-containing regions. As used in this
context, the term "aluminum/SiN/Si" refers to aluminum post-etch
residue and/or SiN post-etch residue on a silicon substrate, each
being amenable to high-efficiency cleaning by the cleaning
composition of the present invention.
[0023] In the cleaning composition, the fluorine source aids in the
removal of residual photoresist as well as any silicon impurities
that reside on the post-etch crystalline residue or on the surface
of the etched and patterned aluminum. The fluorine source may be of
any suitable type, e.g., a fluorine-containing compound or other
fluoro species. Illustrative fluorine source components include
hydrogen fluoride (HF), triethylamine trihdyrogen fluoride or other
amine trihydrogen fluoride compound of the formula
NR.sub.3(HF).sub.3 wherein each R is independently selected from
hydrogen and lower alkyl (C.sub.1-C.sub.8 alkyl), hydrogen
fluoride-pyridine (pyr-HF), and ammonium fluorides of the formula
R.sub.4NF, wherein each R is independently selected from hydrogen
and lower (C.sub.1-C.sub.8 alkyl), etc. Ammonium fluoride
(NH.sub.4F) is a presently preferred fluorine source in
compositions of the invention, although any other suitable fluoro
source component(s) may be employed with equal success.
[0024] The aluminum ion complexing agent in the cleaning
composition may comprise any suitable agent that functions to
efficiently complex to Al.sup.3+ ions that are present in the
residue deriving from aluminum carbides and aluminum silicides
therein. Salicylic acid (2-hydroxy benzoic acid,
C.sub.7H.sub.6O.sub.3) is preferred for such purpose, however,
other strong aluminum ion complexing agents such as acids (e.g.,
beta-diketones) and amines may also be used, including for example
EDTA, oxalic acid, gallic acid, nitrilotriacetic acid,
3-hydroxy-2-naphthoic acid, and oxine.
[0025] The optional corrosion inhibitor functions to protect the
exposed silicon regions of the developed wafer (i.e. trenches) from
corrosion. Boric acid is a presently preferred corrosion inhibitor,
although other oxidation inhibitor agents may also be
advantageously employed for such purpose.
[0026] The alcohol used to form the SCCO2/alcohol solution as the
solvent phase of the cleaning composition may be of any suitable
type. In one embodiment of the invention, such alcohol comprises a
C.sub.1-C.sub.4 alcohol (i.e., methanol, ethanol, propanol, or
butanol), or a mixture of two or more of such alcohol species.
[0027] In a preferred embodiment, the alcohol is methanol. The
presence of the alcoholic co-solvent with the SCCO2 serves to
increase the solubility of the composition for inorganic salts and
polar organic compounds present in the aluminum/SiN/Si post-etch
residue. In general, the specific proportions and amounts of SCCO2
and alcohol in relation to each other may be suitably varied to
provide the desired solubilizing (solvating) action of the
SCCO2/alcohol solution for such inorganic salts and polar organic
compounds, as readily determinable within the skill of the art
without undue effort.
[0028] In one embodiment, the cleaning composition of the invention
includes SCCO2, alcohol, ammonium fluoride, salicylic acid, and
boric acid.
[0029] In a preferred composition of such character, as
particularly adapted to cleaning of unashed aluminum/SiN/Si
post-etch residue, ammonium fluoride is present at a concentration
of from about 0.01 to about 1.0 wt. %, salicylic acid is present at
a concentration of from about 0.01 to about 2.0 wt. %, and boric
acid is present at a concentration of from about 0.01 to about 1.0
wt. %, based on the total weight of the cleaning composition. Such
cleaning composition is hereinafter referred to as a Type 1
composition, denoting the particular suitability of the composition
for cleaning of unashed aluminum/SiN/Si post-etch residue on
substrates having same thereon.
[0030] A particularly preferred Type 1 cleaning composition in
accordance with the invention includes ammonium fluoride, salicylic
acid, and boric acid in a molar ratio of about 1.50:1.53:1.0
(ammonium fluoride:salicylic acid:boric acid).
[0031] Type 1 compositions in the general practice of the invention
may be contacted with the residue-bearing substrate under any
suitable process conditions, as readily determinable by empirical
determination, to remove the unashed aluminum/SiN/Si post-etch
residue from the substrate having same thereon.
[0032] In a preferred embodiment, the specific Type 1 cleaning
composition described above is employed to contact a substrate
having unashed aluminum/SiN/Si post-etch residue thereon at a
pressure in a range of from about 2000 to about 4000 psi for
sufficient time to effect the desired removal of the unashed
residue from the substrate, e.g., for a contacting time in a range
of from about 1 to about 15 minutes, although greater or lesser
contacting durations may be advantageously employed in the broad
practice of the present invention, where warranted.
[0033] In another preferred composition including SCCO2, alcohol,
ammonium fluoride, salicylic acid, and boric acid, as particularly
adapted to cleaning of ashed aluminum/SiN/Si post-etch residue,
ammonium fluoride is present at a concentration of from about 0.2
to about 2.0 wt. %, salicylic acid is present at a concentration of
from about 0.2 to about 4.0 wt. %, and boric acid is present at a
concentration of from about 0.2 to about 2.0 wt. %, based on the
total weight of the cleaning composition. Such cleaning composition
is hereinafter referred to as a Type 2 composition, denoting the
particular suitability of the composition for cleaning of ashed
aluminum/SiN/Si post-etch residue on substrates having same
thereon.
[0034] A particularly preferred Type 2 cleaning composition in
accordance with the invention includes ammonium fluoride, salicylic
acid, and boric acid in a molar ratio of about 1.10:1.0:0.73
(ammonium fluoride:salicylic acid:boric acid).
[0035] Type 2 compositions in the general practice of the invention
may be contacted with the residue-bearing substrate under any
suitable process conditions, as readily determinable by empirical
determination, to remove the ashed aluminum/SiN/Si post-etch
residue from the substrate having same thereon.
[0036] In a preferred embodiment, the specific Type 2 cleaning
composition described above is employed to contact a substrate
having ashed aluminum/SiN/Si post-etch residue thereon at a
pressure in a range of from about 2000 to about 4000 psi for
sufficient time to effect the desired removal of the ashed residue
from the substrate, e.g., for a contacting time in a range of from
about 15 to about 35 minutes, although greater or lesser contacting
durations may be advantageously employed in the broad practice of
the present invention, where warranted.
[0037] The cleaning process in a particularly preferred embodiment
includes sequential processing steps including dynamic flow of the
cleaning composition over the substrate having the ashed residue
thereon, followed by a static soak of the substrate in the cleaning
composition, with the respective dynamic flow and static soak steps
being carried out alternatingly and repetitively, in a cycle of
such alternating steps.
[0038] For example, the dynamic flow/static soak steps may be
carried out for three successive cycles in the aforementioned
illustrative embodiment of contacting time of from about 15 to
about 35 minutes, as including a sequence of 2.5 to 10 minutes
dynamic flow, 2.5 to 10 minutes static soak, 2.5 to 10 minutes
dynamic flow, 2.5 to 10 minutes static soak, 2.5 to 10 minutes
dynamic flow, and 2.5 to 10 minutes static soak.
[0039] Following the contacting of the cleaning composition with
the substrate bearing the ashed or unashed residue, the substrate
thereafter preferably is washed with copious amounts of
SCCO2/alcohol solution (not containing any ammonium fluoride,
salicylic acid (or other Al ion complexing agent), or boric acid
components), in a first washing step, to remove any residual
precipitated chemical additives from the substrate region in which
removal of post-etch residue has been effected, and finally with
copious amounts of pure SCCO2, in a second washing step, to remove
any residual alcohol co-solvent and/or precipitated chemical
additives from the substrate region.
[0040] The features and advantages of the invention are more fully
shown by the empirical efforts and results discussed below.
[0041] FIG. 1 is a scanning electron microscope (SEM) image at 50 K
magnification of an ashed post aluminum etch control wafer clearly
showing the crystalline residue including crystallites on the ashed
surfaces.
[0042] FIG. 2 is a scanning electron microscope (SEM) image at 25 K
magnification of a corresponding post-cleaned sample, which was
cleaned of residue by contact of the ashed residue-bearing
substrate with a cleaning composition containing SCCO2/methanol,
ammonium fluoride and salicylic acid.
[0043] FIG. 3 is a scanning electron microscope (SEM) image at 60 K
magnification of an unashed post aluminum etch control wafer
showing "dog-ear-like" residue on the wafer surface at either side
of the trench structure.
[0044] FIG. 4 is a corresponding scanning electron microscope (SEM)
image at 35 K magnification of the unashed post aluminum etch
control wafer of FIG. 3, showing the "dog-ear-like" residue on the
wafer surface at either side of the trench structure.
[0045] FIG. 5 is a scanning electron microscope (SEM) image at 100
K magnification of the unashed post aluminum etch wafer of FIGS.
3-4 after cleaning thereof by contact of the unashed substrate with
the cleaning composition containing SCCO2/methanol, ammonium
fluoride and salicylic acid, showing that the "dog-ear-like"
residue on the wafer surface at either side of the trench structure
as present in the FIGS. 3-4 micrographs has been fully removed.
[0046] FIG. 6 is a scanning electron microscope (SEM) image at 60 K
magnification of the unashed post aluminum etch wafer of FIGS. 3-4
after cleaning thereof by contact of the unashed substrate with the
cleaning composition containing SCCO2/methanol, ammonium fluoride
and salicylic acid, showing that the "dog-ear-like" residue on the
wafer surface at either side of the trench structure as present in
the FIGS. 3-4 micrographs has been fully removed.
[0047] The above-described micrographs of FIGS. 1-6 thus evidence
the efficacy of cleaning compositions in accordance with the
invention, for removal of post etch residue on wafer
substrates.
[0048] The cleaning compositions of the present invention are
readily formulated by simple mixing of ingredients, e.g., in a
mixing vessel under gentle agitation.
[0049] Once formulated, such cleaning compositions are applied to
the substrate for contacting with the residue thereon, at suitable
elevated pressures, e.g., in a pressurized contacting chamber to
which the cleaning composition is supplied at suitable volumetric
rate and amount to effect the desired contacting operation for
removal of the post etch residue removal.
[0050] It will be appreciated that specific contacting conditions
for the cleaning compositions of the invention are readily
determinable within the skill of the art, based on the disclosure
herein, and that the specific proportions of ingredients and
concentrations of ingredients in the cleaning compositions of the
invention may be widely varied while achieving desired removal of
the post etch residue from the substrate.
[0051] 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.
* * * * *