U.S. patent application number 09/755267 was filed with the patent office on 2002-07-11 for process for removing chemical mechanical polishing residual slurry.
This patent application is currently assigned to International Business Machines Corporation. Invention is credited to Cotte, John Michael, Delehanty, Donald J., McCullough, Kenneth John, Moreau, Wayne Martin, Simons, John P., Taft, Charles J., Volant, Richard P..
Application Number | 20020088477 09/755267 |
Document ID | / |
Family ID | 25038412 |
Filed Date | 2002-07-11 |
United States Patent
Application |
20020088477 |
Kind Code |
A1 |
Cotte, John Michael ; et
al. |
July 11, 2002 |
PROCESS FOR REMOVING CHEMICAL MECHANICAL POLISHING RESIDUAL
SLURRY
Abstract
A process of removing residual slurry resulting from chemical
mechanical polishing of a workpiece in which the workpiece is
contacted with a composition of a supercritical fluid, said
supercritical fluid including supercritical carbon dioxide and a
co-solvent, and a surfactant.
Inventors: |
Cotte, John Michael; (New
Fairfield, CT) ; Delehanty, Donald J.; (Wappingers
Falls, NY) ; McCullough, Kenneth John; (Fishkill,
NY) ; Moreau, Wayne Martin; (Wappinger, NY) ;
Simons, John P.; (Wappingers Falls, NY) ; Taft,
Charles J.; (Wappingers Falls, NY) ; Volant, Richard
P.; (New Fairfield, CT) |
Correspondence
Address: |
RICHARD L. CATANIA, ESQ.
SCULLY, SCOTT, MURPHY AND PRESSER
400 Garden City Plaza
Garden City
NY
11530
US
|
Assignee: |
International Business Machines
Corporation
|
Family ID: |
25038412 |
Appl. No.: |
09/755267 |
Filed: |
January 5, 2001 |
Current U.S.
Class: |
134/2 ;
134/22.19; 134/3; 134/36; 134/41; 134/42; 134/902; 510/175;
510/177; 510/178 |
Current CPC
Class: |
C23G 5/00 20130101; C11D
3/43 20130101; H01L 21/02074 20130101; B08B 7/0021 20130101; C11D
3/2075 20130101; H01L 21/02065 20130101; Y10S 134/902 20130101;
C11D 1/004 20130101 |
Class at
Publication: |
134/2 ; 134/3;
134/36; 134/41; 134/22.19; 134/42; 134/902; 510/175; 510/177;
510/178 |
International
Class: |
C23G 001/00; C03C
023/00; C23G 001/02; B08B 009/00; B08B 003/00; B08B 003/14; B08B
007/00; C11D 001/00 |
Claims
What is claimed is:
1. A process of removing residual slurry resulting from chemical
mechanical polishing which comprises removing residual slurry
resulting from chemical mechanical polishing with a composition
which comprises a mixture of a supercritical fluid and a
surfactant.
2. A process in accordance with claim 1 wherein said supercritical
fluid comprises supercritical carbon dioxide and a co-solvent.
3. A process in accordance with claim 2 wherein said co-solvent is
selected from the group consisting of: (a) a compound having the
structural formula HOOC--(CH.sub.2).sub.n--COOH, wherein n is 0, 1
or 2; (b) a compound having the structural formula RSO.sub.3H,
where R is hydrogen, methyl, ethyl or CF.sub.3; (c) a compound
having the structural formula R.sup.1COOH, where R.sup.1 is
CF.sub.3, C.sub.2F.sub.5, hydrogen, methyl, ethyl or propyl; (d)
triethanolamine; (e) methanol; (f) N-methyl pyrrolidine; and (g)
mixtures thereof.
4. A process in accordance with claim 3 wherein said co-solvent is
selected from the group consisting of (a), (b), (c) and (g).
5. A process in accordance with claim 4 wherein said solvent is
selected from the group consisting of oxalic acid, formic acid,
acetic acid and perfluoroacetic acid.
6. A process in accordance with claim 1 wherein said surfactant is
an anionic surfactant.
7. A process in accordance with claim 6 wherein said anionic
surfactant is an ammonium carboxylate or an ammonium sulfonate.
8. A process in accordance with claim 7 wherein said anionic
surfactant is an ammonium carboxylate.
9. A process in accordance with claim 8 wherein said ammonium
carboxylate is ammonium perfluoroethercarboxylate.
10. A process in accordance with claim 7 wherein said anionic
surfactant is an ammonium sulfonate.
11. A process in accordance with claim 10 wherein said ammonium
sulfonate is ammonium perfluoroalkylsulfonate.
Description
BACKGROUND OF THE DISCLOSURE
[0001] 1. Field of the Invention
[0002] The present invention is directed to a process for removing
residual slurry after chemical mechanical polishing employing a
supercritical fluid. More specifically, the present invention is
directed to a process for removing residual slurry arising from
planarizing of workpieces by utilizing composition of a
supercritical fluid, which includes supercritical carbon dioxide
and a co-solvent, and a surfactant.
[0003] 2. Background of the Prior Art
[0004] A common and well established method of planarizing
semiconductor wafers and other workpieces is by polishing surfaces
to be planarized with a chemical mechanical polishing (CMP) slurry.
Those skilled in the art are aware that these slurries are
silica-based, tungsten-based, ceria-based or alumina-based and are
used to remove silicon, metal coatings, silicon oxides and silicon
nitrides and the like on silicon. As a result of this polishing,
residual slurry, combined with the removed material, becomes
deposited on all exposed areas of the workpiece.
[0005] In the past conventional brush and wet cleaning of residual
CMP slurry was utilized. However, in view of the continuing
decreased size of semiconductor devices, this brush and wet
cleaning method, which utilizes water, has been less and less
successful. This is so because water and other aqueous fluids
employed in wet cleaning techniques have relatively high surface
tensions. Water, for example, has a surface tension of about 70
dynes per square centimeter. This relatively high surface tension
makes it very difficult or even impossible to dislodge and remove
debris from vias, trenches and other nanostructures.
[0006] This difficulty is scientifically explained by the force of
particle adhesion to a substrate surface. This adhesive force is
dependent upon the adhesion between the debris particle and the
surface. The major adhesive forces, which hold the debris to the
surface, are Van der Waals and electrostatic forces. The
semiconductor devices of the present day and even more so in the
future have and will have substructures in the order of submicron
dimensions. To remove residual CMP slurry particles left after
chemical mechanical polishing, requires a low surface tension fluid
that is able to penetrate into a depression and into the interface
between a debris particle and the surface in which the particle is
entrapped inside a submicron depression. Thus, it is apparent that
a totally new process must be devised to ensure that debris
particles, resulting from chemical mechanical polishing, are
removed.
[0007] Recent developments have focused on removal of residues from
semiconductor surfaces, albeit not necessarily CMP slurry residues.
U.S. Pat. Nos. 5,908,510 and 5,976,264 involve the removal of
residue from an etched precision surface utilizing supercritical
fluids or liquid carbon dioxide. More specifically, the residue
removed from etched precision surfaces in these disclosures are
fluorine- or chlorine-containing residues. These disclosures also
indicate that a cryogenic aerosol, which may be argon, nitrogen or
carbon dioxide, may be employed as a subsequent step after
processing with a supercritical fluid or liquid carbon dioxide.
[0008] U.S. Pat. No. 5,306,350 describes a method of cleaning
apparatus by removing one or more polymeric compounds therefrom.
This is accomplished by a cleaning composition which includes at
least one compressed fluid, which is a gas at standard conditions,
and a solvent. The at least one or more removed polymeric compounds
are at least partially soluble in the solvent and at least
partially miscible with the compressed fluid. This compressed fluid
may be supercritical carbon dioxide, nitrous oxide or a mixture
thereof. This method is preferably accomplished by spraying.
[0009] European Patent Application 0 572 913 describes a system of
continuously processing items using a supercritical fluid in which
the items to be cleaned or extracted are continuously pressurized
with the supercritical fluid.
[0010] European Patent Application 0 726 099 is directed to a
process of removing surface contaminants from a substrate by
contacting the substrate with a dense phase gas at or above the
critical pressure thereof. A preferred dense phase gas is carbon
dioxide.
[0011] Although the aforementioned references represent advances in
the art, none of them address the specific problem of removing
chemical mechanical polishing slurry residue from semiconductor
surfaces and nanostructures. Thus, there is a continuing need in
the art for a new process to address this important problem.
SUMMARY OF THE INVENTION
[0012] A new process has now been developed for removal of residual
chemical mechanical polishing (CMP) slurry from topographical
structures on semiconductor wafers. This residual CMP slurry
removal eliminates problems in subsequent processing operations
which lead to contamination, electrical device opens, electrical
device shorts and other yield/reliability concerns.
[0013] Although the invention is not limited to any theory
explaining its operation, it is believed that two requirements must
be met in order to overcome the difficulties discussed above.
First, a residual slurry removal fluid must be utilized which has a
low enough surface tension to permit the fluid to penetrate into
very narrow openings. Secondly, the fluid must be able to
neutralize any charge on the slurry particles to allow the fluid to
not only penetrate into the narrow openings but also dislodge the
residual slurry particles. The invention of the present application
provides a cleaning fluid which meets these physical
requirements.
[0014] In accordance with the present invention a process is
provided for removal of residual slurry resulting from chemical
mechanical processing which comprises removing residual slurry
resulting from chemical mechanical polishing with a composition
which comprises a mixture of a supercritical fluid, wherein the
supercritical fluid comprises carbon dioxide and a co-solvent, and
a surfactant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention will be better understood by reference
to the accompanying drawings of which:
[0016] FIG. 1 is a schematic diagram of the apparatus employed in
the present invention for the removal of residual slurry from a
semiconductor wafer after chemical mechanical polishing;
[0017] FIG. 2 illustrates a typical semiconductor wafer prior to
chemical mechanical polishing; and
[0018] FIG. 3 illustrates the semiconductor wafer after chemical
mechanical polishing demonstrating residual CMP slurry debris.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The process of the present invention involves removal of
residual slurry after chemical mechanical polishing (CMP) that
remain on semiconductor wafers. Insofar as CMP is utilized to
planarize surfaces on semiconductor wafers, it is apparent that the
residual material removed therefrom is primarily the CMP slurry,
which is silica-based, tungsten-based, ceria-based or
alumina-based, and wafer debris. In addition, since the debris
includes material removed from a semiconductor wafer, the residual
material may include, in addition to Si and SiO.sub.2, any one or
more of several metals such as Al, W, Ti, Ta, Pt, Pd, Ir, Cr, Cu
and Ag. In addition, polymers, such as polyimides and polyamides,
may also be present in the residual material removed in the process
of the present invention.
[0020] The process of the present invention may be conducted in an
apparatus 10 as depicted in the FIG. 1. Apparatus 10 includes a
process chamber 12 having a sample zone 14 wherein a workpiece,
denoted by reference numeral 16, is disposed. The workpiece 16 may
be a silicon wafer, a microelectrical machine or other
semiconductor device. The process chamber 12 is surrounded by a
heater jacket 18 and may include a stirring mechanism 20.
Additionally, the process chamber contains an inlet line 22, an
outduct 24 and a thermocouple 26. The inlet line 22 contains a high
pressure pump system 28 which is in communication with a gas
cylinder 30 for supplying a supercritical fluid or mixture thereof
to the process chamber 12. Thermocouple 26 is also connected to a
heater control 32 which is utilized for controlling and monitoring
the temperature in the process chamber 12. Apparatus 10 may also
include a reservoir 34 for collecting and/or purifying
supercritical fluids that exit process chamber 12 through outduct
24. This material may then be recycled into the process chamber
through duct 35.
[0021] The term "supercritical" fluid refers to the fact that the
fluid is above its critical point, i.e., critical temperature,
T.sub.c, and critical pressure, P.sub.c, at which the two fluid
phases of a substance, in equilibrium with each other, become
identical, forming one phase. The supercritical fluid comprises
supercritical carbon dioxide and a co-solvent.
[0022] The co-solvent may be (a) a compound having the structural
formula HOOC--(CH.sub.2).sub.n--COOH, where n is 0, 1 or 2; a
compound having the structural formula RSO.sub.3H, where R is
hydrogen, methyl, ethyl or CF.sub.3; (c) a compound having the
structural formula R.sup.1COOH, where R.sup.1 is hydrogen,
CF.sub.3, C.sub.2F.sub.5, methyl, ethyl or propyl; (d) methanol;
(e) triethanolamine; (f) N-methyl pyrrolidine and (g) mixtures
thereof.
[0023] Of the co-solvents within the contemplation of the present
invention those within the scope of components (a), (b) and (c),
the three classes of acid compounds, and mixtures thereof, are
preferred. Amongst these acids, oxalic acid, formic acid, acetic
acid and perfluoroacetic acid are particularly preferred for
employment as the co-solvent.
[0024] The supercritical fluid, which comprises supercritical
carbon dioxide and the co-solvent, is preferably present such that
the co-solvent represents less than about 20% of the total volume
of the supercritical fluid. More preferably, the supercritical
fluid comprises between about 1% and about 10% co-solvent and the
remainder supercritical carbon dioxide, based on the total volume
of the supercritical fluid.
[0025] The purity of the supercritical fluid is not critical to the
practice of the present invention. If a low purity supercritical
fluid is employed, the supercritical fluid can be first purified to
remove the impurities using techniques well known to those skilled
in the art. For instance, a low purity supercritical fluid could be
purified by passing it through a purification column prior to
entering the processing chamber.
[0026] It is also emphasized that the supercritical fluid is
combined with a surfactant to form a composition for removing CMP
slurry residue from the semiconductor wafer. The surfactant forms a
homogeneous mixture with the supercritical fluid under the
thermodynamic conditions extant in the process chamber 12. The
surfactant may be introduced into the chamber 12 prior to the
introduction of the supercritical fluid. In an alternate
embodiment, a surfactant disposed in reservoir 36 is in
communication with a conduit 37, which is also in communication
with conduit 22, is separately introduced into the process chamber
12 concurrent with the introduction of the supercritical fluid
therein.
[0027] Any surfactant effective in removing residual slurry
particles following CMP may be utilized in the present invention.
Of the surfactants that may be utilized in the homogeneous mixture
of supercritical fluid and surfactant to remove CMP residual
slurry, anionic surfactants are preferred. Among the anionic
surfactants particularly preferred for utilization in the present
invention are ammonium carboxylates and ammonium sulfonates. A
particularly preferred example of an ammonium sulfonate, preferred
for use in the present invention, is ammonium
perfluoroalkylsulfonate. A particularly preferred example of an
ammonium carboxylate is ammonium perfluoroethercarboxylate.
[0028] As shown in FIG. 1, the supercritical fluid may be
pre-pressurized by a high pressure pump 28. Typically, the
supercritical fluid is pre-pressurized to a pressure in the range
of between about 1000 psi to about 6000 psi. More preferably, the
supercritical fluid is pre-pressurized to a pressure of about 3000
psi before entering the processing chamber. The pre-pressurized
supercritical fluid is then transferred to the processing chamber
12 through inlet line 22.
[0029] The semiconductor wafer or sample, illustrative of a typical
workpiece 16, employed in the present invention is any
semiconductor sample that is subjected to CMP. Illustrated examples
of suitable semiconductor samples that may be used in the present
invention include, but are not limited to, semiconductor wafers,
semiconductor chips, ceramic substrates, patterned film structures
and the like. For example, the workpiece 16 may include one or more
of the following materials: titanium silicide, tantalum nitride,
tantalum silicide, silicon, polysilicon, silicon nitride,
SiO.sub.2, diamond-like carbon, polyimide, polyamide, aluminum,
aluminum with copper, copper, tungsten, titanium, palladium,
platinum, iridium, chromium, ferroelectric materials and high
dielectric materials such as BaSrTi or PbLaTi oxides.
[0030] In practice, a semiconductor wafer or other workpiece 16
containing CMP slurry residue is placed in sample zone 16 of
process chamber 12 wherein the sample is exposed to the composition
of supercritical fluid and surfactant under conditions which are
sufficient to remove the CMP slurry residue from the sample while
maintaining the supercritical fluid above its critical temperature
and pressure. Typically, the pressure within process chamber 12,
during CMP slurry residue removal, is in the range of from about
1000 psi to about 6000 psi. More preferably, the pressure within
the process chamber is about 3000 psi. The temperature within the
process chamber 12, during CMP slurry residue removal, is in the
range of between about 40.degree. C. to about 100.degree. C. More
preferably, the temperature within the process chamber during CMP
slurry residue removal is about 70.degree. C.
[0031] It is emphasized that temperature conditions in process
chamber 12 are controlled by heat controller 32 which has the
capability to monitor the temperature in chamber 12 by means of
thermocouple 26. The measured temperature is adjusted by heat
jacket 18, controlled by controller 32, in accordance with
temperature control means well known in the art.
[0032] To ensure effective removal of the CMP slurry residue from
the semiconductor sample, the semiconductor sample is exposed to
the supercritical fluid under the above conditions for about 2
minutes to about 30 minutes. More preferably, the time period of
exposure of the workpiece 16 to the supercritical fluid under the
above-identified conditions is about 2 minutes.
[0033] The supercritical fluid exiting the process chamber through
outduct 24 may be cleaned, as described above, and recycled back
into the apparatus. In this manner a closed reactor system is
formed. Such a closed reactor system is illustrated in FIG. 1. Such
an apparatus may or may not be provided in the process of the
present invention. Obviously, a closed reactor system reduces
processing costs at the price of increased capital expense. In the
preferred embodiment illustrated in FIG. 1, where such a system is
employed, the exhaust supercritical fluid enters a reservoir 34
through conduit 24 and is recycled back into chamber 12 through
conduit 35.
[0034] Apparatus 10 is shown provided with a stirring mechanism. In
this preferred embodiment, depicted generally at 20, the speed of
the stirring unit varies from about 100 rpm to about 1000 rpm. More
preferably, stirring occurs at about 500 rpm.
[0035] To better appreciate the process of the present invention,
attention is directed to a typical semiconductor wafer that is
subjected to chemical mechanical polishing. Typically, a
semiconductor wafer 1 is provided with the first film layer 2 and a
second top film layer 3. These film layers may cover the horizontal
surface as well as the surface of a trench or via 4. In order to
remove the layer 3 from the horizontal surface without disturbing
the layer 3 in the via 4, chemical mechanical polishing of the top
surface occurs. However, this chemical mechanical polishing, which
successfully removes layer 3 from the top surface of wafer 1,
leaves CMP slurry residue 5 in via 4. It is this residue that is
removed in apparatus 10.
[0036] The above description and embodiments will make apparent, to
those skilled in the art, other embodiments and examples. These
other embodiments and examples are within the contemplation of the
present invention. Therefore, the present invention should be
limited only by the appended claims. pre-pressurized supercritical
fluid is then transferred to the processing chamber 12 through
inlet line 22.
[0037] The semiconductor wafer or sample, illustrative of a typical
workpiece 16, employed in the present invention is any
semiconductor sample that is subjected to CMP. Illustrated examples
of suitable semiconductor samples that may be used in the present
invention include, but are not limited to, semiconductor wafers,
semiconductor chips, ceramic substrates, patterned film structures
and the like. For example, the workpiece 16 may include one or more
of the following materials: titanium silicide, tantalum nitride,
tantalum silicide, silicon, polysilicon, silicon nitride,
SiO.sub.2, diamond-like carbon, polyimide, polyamide, aluminum,
aluminum with copper, copper, tungsten, titanium, palladium,
platinum, iridium, chromium, ferroelectric materials and high
dielectric materials such as BaSrTi or PbLaTi oxides.
[0038] In practice, a semiconductor wafer or other workpiece 16
containing CMP slurry residue is placed in sample zone 16 of
process chamber 12 wherein the sample is exposed to the composition
of supercritical fluid and surfactant under conditions which are
sufficient to remove the CMP slurry residue from the sample while
maintaining the supercritical fluid above its critical temperature
and pressure. Typically, the pressure within process chamber 12,
during CMP slurry residue removal, is in the range of from about
1000 psi to about 6000 psi. More preferably, the pressure within
the process chamber is about 3000 psi. The temperature within the
process chamber 12, during CMP slurry residue removal, is in the
range of between about 40.degree. C. to about 100.degree. C. More
preferably, the temperature within the process chamber during CMP
slurry residue removal is about 70.degree. C.
[0039] It is emphasized that temperature conditions in process
chamber 12 are controlled by heat controller 32 which has the
capability to monitor the temperature in chamber 12 by means of
thermocouple 26. The measured temperature is adjusted by heat
jacket 18, controlled by controller 32, in accordance with
temperature control means well known in the art.
[0040] To ensure effective removal of the CMP slurry residue from
the semiconductor sample, the semiconductor sample is exposed to
the supercritical fluid under the above conditions for about 2
minutes to about 30 minutes. More preferably, the time period of
exposure of the workpiece 16 to the supercritical fluid under the
above-identified conditions is about 2 minutes.
[0041] The supercritical fluid exiting the process chamber through
outduct 24 may be cleaned, as described above, and recycled back
into the apparatus. In this manner a closed reactor system is
formed. Such a closed reactor system is illustrated in FIG. 1. Such
an apparatus may or may not be provided in the process of the
present invention. Obviously, a closed reactor system reduces
processing costs at the price of increased capital expense. In the
preferred embodiment illustrated in FIG. 1, where such a system is
employed, the exhaust supercritical fluid enters a reservoir 34
through conduit 24 and is recycled back into chamber 12 through
conduit 35.
[0042] Apparatus 10 is shown provided with a stirring mechanism. In
this preferred embodiment, depicted generally at 20, the speed of
the stirring unit varies from about 100 rpm to about 1000 rpm. More
preferably, stirring occurs at about 500 rpm.
[0043] To better appreciate the process of the present invention,
attention is directed to a typical semiconductor wafer that is
subjected to chemical mechanical polishing. Typically, a
semiconductor wafer 1 is provided with the first film layer 2 and a
second top film layer 3. These film layers may cover the horizontal
surface as well as the surface of a trench or via 4. In order to
remove the layer 3 from the horizontal surface without disturbing
the layer 3 in the via 4, chemical mechanical polishing of the top
surface occurs. However, this chemical mechanical polishing, which
successfully removes layer 3 from the top surface of wafer 1,
leaves CMP slurry residue 5 in via 4. It is this residue that is
removed in apparatus 10.
[0044] The above description and embodiments will make apparent, to
those skilled in the art, other embodiments and examples. These
other embodiments and examples are within the contemplation of the
present invention. Therefore, the present invention should be
limited only by the appended claims.
* * * * *