U.S. patent application number 10/659842 was filed with the patent office on 2004-03-11 for methods and compositions for etch cleaning microelectronic substrates in carbon dioxide.
Invention is credited to DeYoung, James P., Gross, Stephen M., McClain, James B., Wagner, Mark I..
Application Number | 20040045588 10/659842 |
Document ID | / |
Family ID | 29418855 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040045588 |
Kind Code |
A1 |
DeYoung, James P. ; et
al. |
March 11, 2004 |
Methods and compositions for etch cleaning microelectronic
substrates in carbon dioxide
Abstract
A method of cleaning a microelectronic substrate is carried out
by providing a cleaning fluid, the cleaning fluid comprising an
adduct of hydrogen fluoride with a Lewis base in a carbon dioxide
solvent; and then cleaning the substrate by contacting the
substrate to the cleaning fluid for a time sufficient to clean the
substrate.
Inventors: |
DeYoung, James P.; (Durham,
NC) ; Gross, Stephen M.; (Chapel Hill, NC) ;
Wagner, Mark I.; (Raleigh, NC) ; McClain, James
B.; (Raleigh, NC) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Family ID: |
29418855 |
Appl. No.: |
10/659842 |
Filed: |
September 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10659842 |
Sep 10, 2003 |
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10146617 |
May 15, 2002 |
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6669785 |
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Current U.S.
Class: |
134/26 ;
257/E21.252; 257/E21.255; 510/175; 510/176; 510/201 |
Current CPC
Class: |
H01L 21/31133 20130101;
H01L 21/31116 20130101; C11D 7/02 20130101; C11D 11/0047 20130101;
C11D 7/08 20130101; B08B 7/0021 20130101 |
Class at
Publication: |
134/026 ;
510/175; 510/176; 510/201 |
International
Class: |
B08B 003/00 |
Claims
That which is claimed is:
1. A method of cleaning a microelectronic substrate, comprising:
providing a cleaning fluid, said cleaning fluid comprising an
adduct of hydrogen fluoride with a Lewis base in a carbon dioxide
solvent; and then cleaning said substrate by contacting said
substrate to said cleaning fluid for a time sufficient to clean
said substrate.
2. The method according to claim 1, wherein said Lewis base has a
pKa of at least 5.
3. The method according to claim 1, wherein said Lewis base is an
amine.
4. The method according to claim 1, wherein said Lewis base is
pyridine or poly(vinylpyridine) or triethylamine.
5. The method according to claim 1, wherein said cleaning fluid
comprises: from 0.001 to 20 percent by weight of said adduct of
hydrogen fluoride and a Lewis base; and from 50 to 99.999 percent
by weight of carbon dioxide.
6. The method according to claim 1, wherein said cleaning fluid is
nonaqueous.
7. The method according to claim 1, wherein said carbon dioxide is
liquid carbon dioxide.
8. The method according to claim 1, wherein said carbon dioxide is
supercritical carbon dioxide.
9. The method according to claim 1, wherein said cleaning step is
followed or preceded by the step of cleaning said substrate with a
rinse fluid, said rinse fluid comprising carbon dioxide.
10. The method according to claim 9, said rinse fluid further
comprising a cosolvent.
11. The method according to claim 1, wherein said substrate has a
photoresist layer formed thereon, and said cleaning step removes
photoresist from said substrate.
12. The method according to claim 1, wherein said substrate has
etch residue deposited thereon, and said cleaning step removes etch
residue from said substrate.
13. The method according to claim 1, wherein said substrate has ash
residue deposited thereon, and said cleaning step removes ash
residue from said substrate.
14. The method according to claim 1, wherein said substrate has
metal residue deposited thereon, and said cleaning step removes
metal residue from said substrate.
15. The method according to claim 1, wherein said substrate
comprises a low k dielectric material having an oxide layer,
photoresist, or etch residue formed thereon, and said cleaning step
removes the oxide, photoresist or etch residue from said low k
dielectric material.
16. The method according to claim 1, wherein said substrate is a
microelectromechanical device, and said cleaning step removes
processing residues and/or environmental contaminants from the
substrate.
17. The method according to claim 1, wherein said adduct is formed
in situ.
18. The method according to claim 1, wherein said adduct is formed
in situ by adding anhydrous hydrogen fluoride to a carbon dioxide
solvent that contains said Lewis base.
19. The method according to claim 1, wherein said substrate
comprises an inorganic oxide containing surface carrying an adhered
processing residue, and said adduct chemically etches said
inorganic oxide containing surface to facilitate the removal of
said adhered processing residue.
20. A fluid composition comprising: from 0.001 to 20 percent by
weight of an adduct of hydrogen fluoride and a Lewis base; and from
50 to 99.999 percent by weight of carbon dioxide.
21. The composition according to claim 20, wherein said composition
is nonaqueous.
22. The composition according to claim 20, wherein said Lewis base
has a pKa of at least 5.
23. The composition according to claim 20, wherein said Lewis base
is pyridine, poly(vinylpyridine), or triethyl amine.
24. The composition according to claim 20, further comprising from
0.1 percent to 40 percent by weight of a cosolvent.
25. The composition according to claim 20, further comprising from
0.1 percent to 5 percent by weight of a surfactant.
26. The composition according to claim 20, wherein said carbon
dioxide is liquid carbon dioxide.
27. The composition according to claim 20, wherein said carbon
dioxide is supercritical carbon dioxide.
28. The composition according to claim 20, said fluid having a
density of from 0.150 g/cc to 1.1 g/cc and a temperature of from 0
to 80 degrees C.
29. A method of cleaning a microelectronic substrate, comprising:
(a) providing a first cleaning fluid, said first cleaning fluid
comprising a single phase solution of an amine and a polar
cosolvent in carbon dioxide; (b) providing a second cleaning fluid,
said second cleaning fluid comprising an adduct of hydrogen
fluoride with a Lewis base in carbon dioxide; (c) cleaning said
substrate by contacting said substrate to said second cleaning
fluid for a time sufficient to clean said substrate; and (d)
cleaning said substrate before, after, or both before and after
said cleaning step (c) by contacting said substrate to said first
cleaning fluid for a time sufficient to facilitate the cleaning of
said substrate.
30. The method according to claim 29, wherein said amine is
morpholine, aniline or dibutylamine.
31. The method according to claim 29, wherein said polar cosolvent
is a C1-C4 alcohol.
32. The method according to claim 29, wherein said Lewis base is
pyridine or poly(vinylpyridine) or triethylamine.
33. The method according to claim 29, wherein said cleaning fluid
comprises: from 0.001 to 20 percent by weight of said adduct of
hydrogen fluoride with a Lewis base; and from 50 to 99.999 percent
by weight of carbon dioxide.
34. The method according to claim 29, wherein said first cleaning
fluid is nonaqueous.
35. The method according to claim 29, wherein said carbon dioxide
is liquid carbon dioxide.
36. The method according to claim 29, wherein said carbon dioxide
is supercritical carbon dioxide.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of commonly owned,
co-pending application Ser. No. 10/146,617, filed May 15, 2002, the
disclosure of which is incorporated by reference herein in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention concerns methods for cleaning
microelectronic substrates, and particularly concerns methods for
removal of photoresist layers, anti-reflective layers, etch
residues, ash residues, and metallic residues from microelectronic
substrates during the manufacturing of microelectronics, MEM's, and
optoelectronic devices.
BACKGROUND OF THE INVENTION
[0003] Approximately one in four processing steps in manufacturing
integrated circuits is a cleaning step. Manufacturing steps
associated with the formation of lines and interconnects, often
referred to as `back end of the line`, BEOL, have evolved
significantly as feature sizes have continued to decrease. The
advent of new low k materials and copper interconnect technologies
enable the evolution of smaller feature sizes but require new and
better cleaning processes. In some cases traditional cleaning
processes are either ineffective or damaging toward the new
materials. Hydrogen fluoride, typically aqueous, has been used at
varying concentrations for traditional aqueous-based and
solvent-based cleaning and stripping processes. Carbon dioxide has
been described for use in cleaning integrated circuits as have
mixtures of carbon dioxide and aqueous hydrogen fluoride or
buffered aqueous hydrogen fluoride.
[0004] Literature of background interest includes U.S. Pat. No.
5,908,510, U.S. Pat. No. 5,976,264, U.S. Pat. No. 5,868,862, U.S.
Pat. No. 6,149,828, and PCT Patent Application WO 02/15251.
[0005] A problem with aqueous cleaning techniques is that the
surface tension of water makes it difficult to deliver chemistry to
small feature sizes. Indeed, if water can get into to very small
features, it is difficult to subsequently remove. Some new
materials incorporate smaller features where aqueous cleaning
systems are incompatible. For such materials, CO.sub.2 cleaning is
advantageous: the lack of surface tension facilitates penetration
into and rinsing of small features, the swellability of some
materials in CO.sub.2 facilitates delivery of chemistry at
interfaces, the density "tunability" of CO.sub.2 gives a wide
window of process variables, and CO.sub.2 is generally considered
to be environmentally benign. Unfortunately, there is currently no
good way to deliver HF in CO.sub.2.
SUMMARY OF THE INVENTION
[0006] A first aspect of the present invention is a method of
cleaning a microelectronic substrate, comprising: providing a
cleaning fluid, the cleaning fluid comprising an adduct of hydrogen
fluoride with a Lewis base in a carbon dioxide solvent; and then
cleaning the substrate by contacting the substrate to the cleaning
fluid for a time sufficient to clean the substrate.
[0007] In some embodiments, the adduct is formed in situ, such as
by adding anhydrous hydrogen fluoride to a carbon dioxide fluid
containing the Lewis base (particularly an amine), so that the
adduct of the hydrogen fluoride and the Lewis base is formed in
situ in the carbon dioxide.
[0008] In some embodiments, the Lewis base has a pKa of at least 5.
In some embodiments, the Lewis base is an amine, such as is
pyridine, poly(vinylpyridine), or triethyl amine.
[0009] In some embodiments, the cleaning fluid is nonaqueous. The
carbon dioxide may be liquid or supercritical carbon dioxide. The
cleaning step may be preceded by, followed by, or both preceded and
followed by the step of cleaning or rinsing the substrate with a
rinse fluid, the rinse fluid comprising, consisting essentially of
or consisting of liquid or supercritical carbon dioxide. In some
embodiments, the rinse fluid may further comprise one or more
cosolvents.
[0010] In some embodiments, the substrate has a photoresist layer
formed thereon, and the cleaning step removes photoresist from the
substrate.
[0011] In some embodiments, the substrate has etch residue
deposited thereon, and the cleaning step removes etch residue from
the substrate.
[0012] In some embodiments, the substrate has ash residue deposited
thereon, and the cleaning step removes ash residue from the
substrate.
[0013] In some embodiments, the substrate has metal residue
deposited thereon, and the cleaning step removes metal residue from
the substrate.
[0014] In some embodiments, the substrate comprises a dielectric
layer such as a low k dielectric material containing an oxide,
photoresist or etch residue formed thereon, and the cleaning step
partially removes the oxide, and completely removes the photoresist
or etch residue from the low k dielectric material.
[0015] In some embodiments, the substrate comprises or includes an
inorganic oxide containing surface carrying an adhered processing
residue, and the adduct chemically etches the inorganic oxide
containing surface to facilitate the removal of the adhered
processing residue.
[0016] In some embodiments, the substrate is a
microelectromechanical device (MEMS), which may have a plurality
(e.g., two or more) mechanically interacting elements, and the
cleaning step is carried out to clean the device, reduce stiction
between mechanically interacting elements of the device, free a
frozen or stuck element of the device, etc.
[0017] In a particularly preferred embodiment of the foregoing, the
adduct is [pyridinium poly(hydrogen fluoride)], also known as
hydrogen fluoride pyridine adduct or triethylamine
trihydrofluoride.
[0018] A second aspect of the present invention is a fluid
composition useful for cleaning a microelectronic substrate,
comprising: from 0.0001, 0.0005 or 0.001 to 5, 10 or 20 percent by
weight of an adduct of hydrogen fluoride and a Lewis base; and from
40 or 50 to 99.999 percent by weight of liquid or supercritical
carbon dioxide. The composition is aqueous in some embodiments and
nonaqueous in other embodiments. The Lewis base may be as described
above. The composition may further comprise from 0.001 or 0.1
percent to 30 or 40 percent by weight of a cosolvent (including
combinations of cosolvents), and/or from 0.001 to 1, 3 or 5 percent
by weight of a surfactant. Typically the fluid has a density of
from 0.15 g/cc to 1.1 g/cc and a temperature of from 0 to 80
degrees C.
[0019] A specific embodiment of the foregoing methods may be
carried out by:
[0020] (a) providing a first (optionally but preferably nonaqueous)
cleaning fluid, the first cleaning fluid comprising a single phase
solution of an amine and a semi-polar to polar cosolvent in carbon
dioxide;
[0021] (b) providing a second cleaning fluid, the second cleaning
fluid comprising an adduct of hydrogen fluoride with a Lewis base
in carbon dioxide;
[0022] (c) cleaning the substrate by contacting the substrate to
the second cleaning fluid for a time sufficient to clean the
substrate; and
[0023] (d) cleaning the substrate before, after, or both before and
after the cleaning step (c) by contacting the substrate to the
first cleaning fluid for a time sufficient to facilitate the
cleaning of the substrate.
[0024] The amine may, for example, be morpholine, and the polar
cosolvent may, for example, be a C1-C4 alcohol. The second cleaning
fluid including the Lewis base may be as described above, and the
substrates to be cleaned may be as described above.
[0025] Without wishing to be bound to any particular theory of the
instant invention, it will be noted that in some embodiments the HF
may clean by etching the material to be cleaned. Relative to the
conventional practice of etching dielectric materials and the scope
of what is the present invention, the word "etching" may be
confusing. Dielectric layers are typically patterned during
manufacturing by anisotropic etching, usually with reactive ions in
a plasma or gas phase but liquid compositions have been disclosed.
Typically, a patterned resist serves as a mask for areas of the
dielectric that are not etched away. Conventionally, the resists
and etch residues are then removed in either an ash and wet clean
process, or by liquid stripping and cleaning processes. It is the
conventional strip and clean step that is being replaced with the
instant invention--not what is conventionally referred to as
etching. Further, the HF compositions described herein are also
useful for cleaning where oxides are not the primary dielectric
composition (organic dielectrics for example, or with steps
involving metal layers.) For these reasons, the minimal etching of
oxide layers is considered one possible mechanism that effects the
cleaning described herein, but is not the only mechanism by which
the cleaning described herein may be carried out.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] The present invention will be carried out on a variety of
substrates including but not limited to semiconductors such as
gallium arsenide, silicon wafers containing process residue,
transient and non-transient layers applied in the manufacturing of
semiconductor devices such as integrated circuits, sapphire wafers,
microelectromechanical devices (MEMs), and optoelectronic
devices.
[0027] Any Lewis base that forms an adduct with hydrogen fluoride
to thereby stabilize or solubilize the hydrogen fluoride in the
carbon dioxide etch solution may be used to carry out the present
invention. Examples include both amine and non-amine Lewis bases.
Examples of suitable amine Lewis bases include, but are not limited
to, pyridine, poly(vinylpyridine), melamine, R.sub.3N wherein R is
ethyl, propyl, butyl, pentyl, etc., triethanolamine, (R) imido
fluoride wherein R is phenyl, alkyl, haloalkyl, etc., 1,3
dimethyl-2-imidazolidinone, hexamethylenetetramine,
1,8-bis(dimethylamino)napthalene, and picoline (See, e.g., Olah, G.
A.; Nojima, M.; Kerekes, I. Synthesis 1973, 779, 780). Non-amine
Lewis bases that may be used to carry out the present invention
include, but are not limited to, trialkyl phosphines, triaryl
phosphines, thiophene, dialkyl sulfides, diaryl sulfides, ethers,
etc. Note that the Lewis base may be a base-functionalized polymer,
such as a polythiophene, a polyether, a crown ether, a polyamine,
etc.
[0028] The terms "low k dielectric material" and "low dielectric
constant dielectric material", as used herein, are intended to
refer to a dielectric material having a dielectric constant below
about 3.5, and preferably about 2.5 or less. Typically the terms
"low k dielectric material" or "low dielectric constant dielectric
material", as used herein, refer to a dielectric material having a
dielectric constant of from as low as about 1.4 to about 3.5. The
current invention may also be useful in cleaning substrates
containing dielectric layers where the k value is between 4.5 and
3.5. The film of low k dielectric material formed on the substrate
usually will range in thickness from about 100 or 200 nanometer
(nm) to about 1,000 nm or 2,000 nm, and preferably from about 400
nm to about 800 nm, although either thinner or thicker films may be
used in the process of the invention if desired. Usually the film
of low k dielectric material is formed over an underlying
integrated circuit structure of which it becomes a part. The film
of low k dielectric material may, for example, comprise a low k
carbon-doped silicon oxide dielectric material which is formed by
reacting a carbon-substituted silane with a mild oxidizing agent
such as hydrogen peroxide to form a film of carbon-doped low k
silicon oxide dielectric material. The invention may also be useful
in the treatment of other types of low k dielectric material such
as hydrogen-doped or fluorinated silicon oxide dielectric films, or
potentially fully organic low k films.
[0029] 2. Substrates Coatings and Residues.
[0030] The transient layer may be a layer of photoresist, or an
anti-reflective coating layer. The process residue may include
inorganic or organic contaminants such as polymers based on
stryenic, acrylic, novolac, cyclic olefinic maleic anhydride
resins; etch and ash residue based on ions of fluorine, chlorine,
bromine or iodine, and oxygen; metallic impurities containing
tantalum, titanium, copper, aluminum or tungsten; and slurry
residue containing silica or alumina abrasives with other common
slurry additives such as oxidizers, buffers, stabilizers,
surfactants, passivating agents, complexing agents, corrosion
inhibitors or other agents.
[0031] Transient layers such as photochemically active resists are
typically applied by spin coating from solvent. The resist
typically comprises a polymeric material, and may be a
positive-acting resist or a negative-acting resist. The resist may
be patterned or unpatterned, developed or undeveloped at the time
the CO.sub.2 treating process is carried out. Preferably in the
application of the invention for stripping photoresist and removing
etch residue, the resist is patterned having served the purpose of
masking portions of the wafer surface for the etch step.
[0032] Any suitable resist composition or anti-reflective coating
can be used in conjunction with the present invention, including
but not limited to those described in U.S. Pat. Nos. 6,042,997;
5,866,304; 5,492,793; 5,443,690; 5,071,730; 4,980,264; and
4,491,628. Conventional etching, ashing, and chemical and
mechanical polishing processes may also be used in conjunction with
the current invention. Applicants specifically intend that the
disclosures of all United States patent references that are cited
herein be incorporated herein by reference in their entirety.
[0033] 3. Carbon Dioxide Compositions.
[0034] Carbon-dioxide compositions used to carry out the present
invention typically comprise:
[0035] (a) carbon dioxide to balance, typically at least 40, 50 60,
or 70 percent;
[0036] (b) optionally, where desired, from 0, 0.01, 0.1, 0.5, 1 or
2 percent to 5 or 10 percent or more of surfactant;
[0037] (c) optionally, where desired, from 0, 0.01, 0.1, 1 or 2 to
30, 40 or 50 percent or more of an organic co-solvent;
[0038] (d) optionally, and in some embodiments less preferably,
from 0.01, or 0.1 to 2, 5 or 10 percent water (and in other
embodiments 0 percent water); and
[0039] (e) from 0.0001% or 0.0005% to 4% or 5% of a hydrogen
fluoride Lewis base adduct
[0040] Percentages herein are expressed as percentages by weight
unless otherwise indicated.
[0041] The composition may be provided as a liquid or supercritical
fluid, including cryogenic liquids. Liquid and supercritical carbon
dioxide are herein together referred to as "densified" carbon
dioxide in accordance with established usage.
[0042] The organic co-solvent may be one compound or a mixture of
two or more ingredients. The organic co-solvent may be or comprise
an alcohol (including diols, triols, etc.), ether, amine, ketone,
carbonate, or alkanes, or hydrocarbon (aliphatic or aromatic) The
organic co-solvent may be a mixture of compounds, such as mixtures
of alkanes as given above, or mixtures of one or more alkanes in
combination with additional compounds such as one or more alcohols
as described above. (e.g., from 0 or 0.1 to 5% of a C1 to C15
alcohol (including diols, triols, etc.)). Any surfactant can be
used to carry out the present invention, including both surfactants
that contain a CO.sub.2-philic group (such as described in PCT
Application WO96/27704 or U.S. Pat. No. 5,783,082) linked to a
CO.sub.2-phobic group (e.g., a lipophilic group) and surfactants
that do not contain a CO.sub.2-philic group (i.e., surfactants that
comprise a hydrophilic group linked to a hydrophobic (typically
lipophilic) group). A single surfactant may be used, or a
combination of surfactants may be used. Numerous surfactants are
known to those skilled in the art. See, e.g., McCutcheon's Volume
1: Emulsifiers & Detergents (1995 North American Edition) (MC
Publishing Co., 175 Rock Road, Glen Rock, N.J. 07452). Examples of
the major surfactant types that can be used to carry out the
present invention include the: alcohols, alkanolamides,
alkanolamines, alkylaryl sulfonates, alkylaryl sulfonic acids,
alkylbenzenes, amine acetates, amine oxides, amines, sulfonated
amines and amides, betaine derivatives, block polymers,
carboxylated alcohol or alkylphenol ethoxylates, carboxylic acids
and fatty acids, a diphenyl sulfonate derivatives, ethoxylated
alcohols, ethoxylated alkylphenols, ethoxylated amines and/or
amides, ethoxylated fatty acids, ethoxylated fatty esters and oils,
fatty esters, fluorocarbon-based surfactants, glycerol esters,
glycol esters, hetocyclic-type products, imidazolines and
imidazoline derivatives, isethionates, lanolin-based derivatives,
lecithin and lecithin derivatives, lignin and lignin derivatives,
maleic or succinic anhydrides, methyl esters, monoglycerides and
derivatives, olefin sulfonates, phosphate esters, phosphorous
organic derivatives, polyethylene glycols, polymeric
(polysaccharides, acrylic acid, and acrylamide) surfactants,
propoxylated and ethoxylated fatty acids alcohols or alkyl phenols,
protein-based surfactants, quaternary surfactants, sarcosine
derivatives, silicone-based surfactants, soaps, sorbitan
derivatives, sucrose and glucose esters and derivatives, sulfates
and sulfonates of oils and fatty acids, sulfates and sulfonates
ethoxylated alkylphenols, sulfates of alcohols, sulfates of
ethoxylated alcohols, sulfates of fatty esters, sulfonates of
benzene, cumene, toluene and xylene, sulfonates of condensed
naphthalenes, sulfonates of dodecyl and tridecylbenzenes,
sulfonates of naphthalene and alkyl naphthalene, sulfonates of
petroleum, sulfosuccinamates, sulfosuccinates and derivatives,
taurates, thio and mercapto derivatives, tridecyl and dodecyl
benzene sulfonic acids, etc.
[0043] The present invention is explained in greater detail in the
following non-limiting Examples.
EXAMPLE 1
Photoresist Removal
[0044] Photoresist is used as a mask to pattern a dielectric layer
on a substrate using reactive ion etching. The photoresist used for
this process is removed in the following steps. The substrate is
loaded into a pressure vessel and supercritical CO.sub.2 is added
to the vessel at 3,000 psi and 45.degree. C. As the supercritical
CO.sub.2 circulates through the vessel, a mixture consisting of
pyridine and HF is added. The mixture composition by weight is
99:1, and the total concentration of adjunct mixture added is 5% of
the overall weight. The solvent mixture is circulated for 1 minute.
This cleaning step precedes a pure supercritical CO.sub.2 rinse
which lasts for 30 seconds. The system is vented and the substrate
removed.
EXAMPLE 2
Plasma Ashing Followed by Photoresist Strip
[0045] The first step of bulk organic removal/photoresist strip is
done by plasma ashing. Ashing is typically stopped just short of
the dielectric surface. Subsequent polymeric photoresist and ash
residue is removed from a test pattern in the following process
steps. The substrate is loaded into the pressure vessel.
Supercritical CO.sub.2 is added to the vessel at 2,500 psi and
55.degree. C. As the supercritical CO.sub.2 circulates through the
vessel, a co-solvent mixture composed of dibutylamine and methanol
and a surfactant containing both a CO.sub.2-philic and
CO.sub.2-phobic portion such as the double tailed phosphate
fluorosurfactant Sodium (Bis 1,1,2,2-tetrahydroperfluoro octyl)
phosphate is added to the vessel with the flow distributed evenly
over the surface of the substrate. The mixture composition by
weight is 85:14:1, and the total concentration of adjunct added is
3% of the overall weight. The solvent mixture circulates through
the vessel for 30 seconds. A supercritical CO.sub.2 rinse then
removes the solvent mixture from the vessel. A mixture consisting
of pyridine and HF is then added. The mixture composition by weight
is 99.5:0.5, and the total concentration of adjunct added is 8% of
the overall weight. The second solvent mixture contacts the
substrate for 10 seconds, and is then followed by a pure
supercritical CO.sub.2 rinse. The system is vented and the
substrate removed.
EXAMPLE 3
Removal of Photoresist and Residue from a Via
[0046] Polymeric photoresist and resist residue is removed from a
via post reactive ion etch (RIE) of a test structure using the
following process steps. The substrate is placed in the pressure
vessel. Morpholine and methanol in supercritical CO.sub.2 is added
to the vessel at 3,000 psi at 75.degree. C. The mixture composition
by weight is 20:80, and the total concentration of the adjunct
added is 2%. The fluid mixture circulates through the vessel for 2
minutes. A second cleaning solution consisting of pyridine, HF and
a high purity surfactant displaces the first cleaning solution. The
mixture composition by weight is 93:6:1, and the total
concentration of the adjunct added is 1% of the overall weight. The
second mixture contacts the substrate for 1 minute. Finally, a pure
supercritical CO.sub.2 rinse is completed by the addition of pure
CO.sub.2 to the vessel. The system is depressurized and the
substrate removed.
EXAMPLE 4
Removal of Photoresist and Residue from a Trench
[0047] Polymeric photoresist and etch residue is removed from a
trench post RIE of a test structure using the following process
steps. The substrate is loaded into the pressure vessel and
supercritical CO.sub.2 is added to the vessel to 2,400 psi at
60.degree. C. As the supercritical CO.sub.2 circulates through the
vessel, a mixture consisting of an amine (isopropylamine) and
methanol is added. The mixture composition by weight is 90:10, and
the total concentration of adjunct added is 7% of the overall
weight. The solvent mixture circulates through the vessel for 30
seconds then a second cleaning solution consisting of pyridine and
HF is added after the first mixture is displaced by a pure CO.sub.2
rinse. The mixture composition by weight is 99.99:0.01, and the
total concentration of adjunct added is 5% of the overall weight.
The mixture circulates through the vessel for 20 seconds and then a
third cleaning solution consisting of 2% pyridine is charged into
the vessel, evenly distributed, and directed to the surface of the
wafer. The system is then rinsed with pure supercritical CO.sub.2
for a period of time sufficient to remove all adjunct chemistry and
the system is depressurized.
EXAMPLE 5
Removal of Residue from a Dual Damascene Structure
[0048] Etch and metallic residue is removed from a post-barrier
breakthrough, dual damascene structure during a back end of the
line cleaning step using the following process. The substrate is
loaded into the vessel and supercritical CO.sub.2 was added to the
vessel to a pressure of 2,700 psi at 70.degree. C. As the
supercritical CO.sub.2 circulates through the vessel, a mixture
consisting of pyridine and HF is added. The mixture composition by
weight is 95:5, and the total concentration of adjunct added is 1%
of the overall weight. The solvent mixture is circulated for 20
seconds. A supercritical CO.sub.2 rinse removes the solvent mixture
from the vessel before a second cleaning solution consisting of an
aqueous solution of a copper chelating complex and a corrosion
inhibitor in a supercritical CO.sub.2 emulsion containing a high
purity CO.sub.2-philic-b-hydrophilic surfactant such as
poly(1,1,-dihydroperfluoro octyl acrylate)-b-poly (ethylene oxide)
is charged into the vessel. The emulsion is in contact with the
substrate for 1 minute. The system is then rinsed with 95%
supercritical CO.sub.2/5% isopropanol followed by pure CO.sub.2 and
the system is depressurized.
EXAMPLE 6
Residue Removal from a Via of a Dual Damascene Structure
[0049] Polymeric photoresist and etch residue is removed from a via
post reactive ion etching (RIE) of a dual damascene structure using
the following process steps. The substrate is placed in the
pressure vessel and an amine (hydroxylamine) and methanol in
supercritical CO.sub.2 is added to the vessel to 3,000 psi at
75.degree. C. The mixture composition by weight is70:30, and the
total concentration of the adjunct added is 5%. The fluid mixture
is circulated through the vessel for 40 seconds. A second cleaning
solution consisting of a Lewis base (thiophene) and HF displaces
the first cleaning solution. The mixture composition by weight is
93:7, and the total concentration of the adjunct added is 2% of the
overall weight. The second solvent mixture is in contact with the
substrate for 15 seconds. The system is then rinsed with pure
supercritical CO.sub.2. A final flush with liquid CO.sub.2 and
CO.sub.2-philic a surfactant such as perfluorooctanoic acid is
performed to remove particles prior to a pure CO.sub.2 flush. The
system is depressurized and the substrate removed.
[0050] The foregoing is illustrative of the present invention, and
is not to be construed as limiting thereof. The invention is
defined by the following claims, with equivalents of the claims to
be included therein.
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