U.S. patent application number 12/730079 was filed with the patent office on 2011-03-24 for point of use recycling system for cmp slurry.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Phil Chandler, Daniel O. Clark, Michael Kiefer, Jamie Stuart Leighton, Andreas Neuber, Clifford C. Stow.
Application Number | 20110070811 12/730079 |
Document ID | / |
Family ID | 43757011 |
Filed Date | 2011-03-24 |
United States Patent
Application |
20110070811 |
Kind Code |
A1 |
Neuber; Andreas ; et
al. |
March 24, 2011 |
POINT OF USE RECYCLING SYSTEM FOR CMP SLURRY
Abstract
The present invention generally relates to apparatus and method
for recycling both polishing slurry and rinse water from CMP
processes. The present invention also relates to rheology
measurements and agglomeration prevention using centrifugal
pumps.
Inventors: |
Neuber; Andreas; (Stuttgart,
DE) ; Chandler; Phil; (Clifton, GB) ; Stow;
Clifford C.; (Boulder Creek, CA) ; Clark; Daniel
O.; (Pleasanton, CA) ; Kiefer; Michael;
(Neuhasen, DE) ; Leighton; Jamie Stuart; (Palo
Alto, CA) |
Assignee: |
APPLIED MATERIALS, INC.
Santa Clara
CA
|
Family ID: |
43757011 |
Appl. No.: |
12/730079 |
Filed: |
March 23, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61211156 |
Mar 25, 2009 |
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61163451 |
Mar 26, 2009 |
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61170413 |
Apr 17, 2009 |
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61185424 |
Jun 9, 2009 |
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Current U.S.
Class: |
451/60 ;
451/88 |
Current CPC
Class: |
B24B 37/04 20130101;
B24B 57/00 20130101 |
Class at
Publication: |
451/60 ;
451/88 |
International
Class: |
B24B 1/00 20060101
B24B001/00; B24C 9/00 20060101 B24C009/00 |
Claims
1. An apparatus for recycling, comprising: a separation unit
comprising: an inlet configured to receive a mixture of used
polishing slurry, rinsing fluid, and polishing waste; a water
outlet configured to output a first stream for waste or water
recycling; and a slurry outlet configured to output a second stream
for slurry recycling polishing; and a slurry filtration unit
comprising: an inlet connected with the slurry outlet of the
separation unit; one or more filtering media configured for
filtration or removal of ions and organics; and a pump disposed
upstream of the one or more filtering media and configured to press
a stream of fluid through the one or more membranes. a product
outlet configured to output a stream of concentrated and recycled
polishing slurry; and a water outlet for water recycling or
waste.
2. The apparatus of claim 1, wherein the separation unit comprises
a diverter valve selectively connecting the inlet to the water
outlet and the slurry outlet.
3. The apparatus of claim 2, wherein the pump of the slurry
filtration unit is one of a piston pump, a diaphragm pump, a bellow
pump, a peristaltic pump, a magnetically levitated centrifugal
pump, and a device for fluid transfer by vacuum draw or
pressurization.
4. The apparatus of claim 2, wherein the filtering media of the
slurry filtration unit and the is a spiral membrane, a hollow fiber
membrane, a tubular membrane, a plate and frame membrane operated
in a dead-end filtration methods, a back flushable filtration
method, a cross flow filtration method, or a filtering media
operated by depth filtration.
5. The apparatus of claim 2, wherein the slurry filtration unit
comprises one or more of a microfiltration membrane, a
nanofiltration membrane, and an ultrafiltration membrane.
6. The apparatus of claim 5, wherein the slurry filtration unit
further comprises a backwash or cross flow clean capability.
7. The apparatus of claim 2, further comprising a UV (ultra violet)
unit configured to reduce bacteria and organic contamination from
fluid passing through, wherein the UV unit comprises: an inlet
connected with the water outlet of the separation unit and/or the
water outlet of the slurry filtration unit; and an outlet
configured to output a stream of sanitized fluid.
8. The apparatus of claim 7, further comprising a water treatment
unit configured to purify the sanitized fluid by removing trace of
chemicals, wherein the treatment unit comprises: an inlet connected
to the outlet of the UV unit; and an outlet configured to output a
stream of purified fluid.
9. The apparatus of claim 2, further comprising a dosing unit
connected to the slurry filtration unit for dosing conditioning
chemicals during processing in the slurry filtration unit.
10. The apparatus of claim 1, wherein the separation unit is a
filtration unit comprising: a filtering media comprising: a
microfiltration membrane; and a nanofiltration membrane disposed
downstream to the microfiltration membrane; and a pump disposed
upstream of the microfiltration membrane and configured to press a
stream of fluid through the filtering media, wherein the slurry
outlet is disposed between the microfiltration membrane and the
nanofiltration membrane, and the water outlet of the separation
unit is disposed downstream to the filtration media.
11. The apparatus of claim 1, further comprising a centrifugal
separator configured to separate polymeric or large particles,
wherein the centrifugal separator is disposed upstream or
downstream of the separation unit.
12. A method for recycling polishing fluid, comprising: generating
a waste water stream and a concentration stream from a mixture of
used polishing slurry, rinsing fluid and polishing waste; filtering
the concentration stream through a slurry filtration unit to
separate a stream of reusable polishing slurry from a water stream;
flowing the stream of reusable polishing slurry to a polishing
slurry source for a polishing station; and flowing the water stream
to a recycled water source.
13. The method of claim 12, wherein generating the waste water
stream and the concentration stream comprises filtering the mixture
through a filtering unit having multiple membranes or using a
diverter valve to selectively direct the mixture to a slurry outlet
and a water outlet.
14. The method of claim 13, further comprising measuring one or
more characteristics of the reusable polishing slurry before
flowing the stream of reusable polishing slurry to a polishing
slurry source for a polishing station, wherein the one or more
characteristics of the reusable polishing slurry comprises one or
more of zeta potential, density, particle size, and particle
distribution.
15. The method of claim 14, further comprising supplying the
reusable polishing slurry to perform a bulk polishing process in
the polishing station.
16. The method of claim 13, further comprising: sanitizing the
water stream to remove organic species from the water stream prior
to flowing the water stream to the recycled water source; purifying
the sanitized water stream by a reversed osmosis process through a
treatment unit; and deionizing the purified water stream by one of
a continuous electrodeionization (CEDI) process, ion exchange, or
ion removal prior to flowing the water stream to the recycled water
source.
17. The method of claim 16, further comprising supplying rinsing
water from the recycled water source to perform one or more initial
rinses in a polishing station; and supplying virgin ultra purified
water to perform final rinses in the polishing station.
18. A polishing slurry unit for a polishing system, comprising: a
slurry reservoir having a reservoir pump, wherein the slurry
reservoir is connected to a virgin slurry source; a recycling unit
comprising one or more filtration units, wherein the one or more
filtration unit comprises a filtration pump, and the recycling unit
is connected to the slurry reservoir and is configured to receive
used polishing slurry, pump the used slurry through the one or more
filtration units and provide filtered polishing slurry to the
slurry reservoir; and a controller connected to at least one of the
reservoir pump and the filtration pump, wherein the controller is
configured to monitor and/or adjust characteristics of the
polishing slurry according to process parameters of the at least
one pump connected thereto.
19. The polishing slurry unit of claim 18, wherein the filtration
pump is a magnetically levitated centrifugal pump.
20. The polishing slurry unit of claim 19, wherein the recycling
unit comprises a valve system configured to divert excessive
polishing slurry during polishing to a slurry recycling unit and
rinse fluid during rinse to a rinse water recycling unit.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Patent
Application Ser. No. 61/211,156 (Attorney Docket No. 14199L01),
filed Mar. 25, 2009, U.S. Provisional Patent Application Ser. No.
61/163,451 (Attorney Docket No. 14199L02), filed Mar. 26, 2009,
U.S. Provisional Patent Application Ser. No. 61/170,413 (Attorney
Docket No. 14199L03), filed Apr. 17, 2009, and U.S. Provisional
Patent Application Ser. No. 61/185,424 (Attorney Docket No.
14199L04), filed Jun. 9, 2009. All the aforementioned patent
applications are herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention generally relate to
apparatus and method for recycling polishing slurry and rinse water
in a chemical mechanical polishing (CMP) system.
[0004] 2. Background
[0005] Due to the high cost of CMP polishing slurry recycling CMP
polishing slurry from CMP process has been the subject of numerous
studies. Polishing slurries are generally comprises about 3% to
about 30% solid particles suspended in water. Polishing slurry
generally accounts about 50% of CMP cost.
[0006] However, recycling and reuse of CMP polishing slurries for
use in semiconductor processing faces significant challenges.
During CMP processing, particle concentration, particle size,
particle homogeneity have profound effect in removal rate and
defect reduction, therefore, must be carefully controlled. However,
these factors are difficult to achieve in recycled polishing slurry
because some particles are crushed and some of the particles
agglomerate during polishing, and particles of removed materials
enter into the polishing slurry.
[0007] Additionally, recycling rinsing water is also of interest to
reduce cost of ownership. However, there is concern that recycled
water is not satisfactory to perform multiple rinses post
polishing.
[0008] Therefore, there is a need for apparatus and method for
recycling polishing slurry and rinse water in a chemical mechanical
polishing system.
SUMMARY OF THE INVENTION
[0009] The present invention generally relates to apparatus and
method for recycling both polishing slurry and rinse water from CMP
processes.
[0010] One embodiment of the present invention provides an
apparatus for recycling comprising a first filtration unit, wherein
the first filtration unit comprises an inlet configured to receive
one or more of used polishing slurry, rinsing fluid, such as water,
glycol or others, and polishing waste, a water outlet configured to
output a first filtered stream for water recycling, and a chemical
outlet configured to output a second stream for recycling polishing
slurry, a second filtration unit, wherein the second filtration
unit comprises an inlet connected with the chemical outlet of the
first filtration unit, a product outlet configured to output a
stream of recycled polishing slurry, and a water outlet configured
to output another filtered stream for water recycling, and an
optional UV (ultra violet) unit, wherein the UV unit comprises an
inlet connected with the water outlet of the first and/or
filtration unit, and an outlet configured to output a stream of UV
treated fluid.
[0011] Another embodiment of the present invention provides a
method for recycling polishing fluid, comprising filtering one or
more of used polishing slurry, rinsing fluid and polishing waste
through a first filtration unit to generate a water stream and a
suspension stream, filtering the suspension stream through a second
filtration unit to separate a stream of reusable polishing slurry
from a water stream, flowing the stream of reusable polishing
slurry to a polishing slurry source for a polishing station,
recycling the water stream, and flowing the recycled water stream
to a recycled water source.
[0012] Yet another embodiment of the present invention provides a
chemical mechanical polishing system comprising one or more
polishing stations, a polishing slurry unit configured to provide
polishing slurry to the one or more polishing stations, a rinse
water unit configured to provide rinse water to the one or more
polishing stations, and a recycling unit configured to recycle
polishing slurry and rinse water, wherein the recycling unit
comprises a first filtration unit, wherein the first filtration
unit comprises an inlet configured to receive a mixture of used
polishing slurry, rinsing fluid, and polishing waste from the one
or more polishing stations, a water outlet configured to output a
first filtered stream for water recycling, and a chemical outlet
configured to output a second stream for recycling polishing
slurry, a second filtration unit, wherein the second filtration
unit comprises an inlet connected with the chemical outlet of the
first filtration unit, a product outlet configured to output a
stream of recycled polishing slurry to the polishing slurry unit,
and a water outlet, to output another filtered stream for water
recycling, an optional UV (ultra violet) unit, wherein the UV unit
comprises an inlet connected with the water outlet of the first
and/or second filtration unit, and an outlet configured to output a
stream of UV treated water, and a treatment unit configured to
purify the UV treated water by removing organic compounds, and or
to kill bacteria wherein the treatment unit comprises, an inlet
connected to the outlet of the UV unit, and an outlet configured to
output a stream of purified water to the rinse water unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0014] FIG. 1 is a schematic chart of a polishing system having a
recycling unit in accordance with one embodiment of the present
invention.
[0015] FIG. 2A is a schematic chart of a polishing system having a
recycling unit in accordance with one embodiment of the present
invention.
[0016] FIG. 2B is a schematic chart of a polishing system having a
recycling unit in accordance and a centrifugal separator with one
embodiment of the present invention.
[0017] FIG. 2C is a schematic chart of a polishing system having a
recycling unit in accordance and a centrifugal separator with one
embodiment of the present invention.
[0018] FIG. 2D is a schematic chart of a polishing system having a
diverter valve and a recycling unit in accordance with one
embodiment of the present invention.
[0019] FIG. 3 is a schematic chart of a polishing station having a
dedicated recycled slurry source in accordance with another
embodiment of the present invention.
[0020] FIG. 4 is a schematic chart of a polishing station having a
dedicated recycled rinse water source in accordance with another
embodiment of the present invention.
[0021] FIG. 5 is a schematic chart of a polishing system having
multiple polishing stations and a recycling unit in accordance with
another embodiment of the present invention.
[0022] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation.
DETAILED DESCRIPTION
[0023] Embodiments of the present invention generally relate to
apparatus and method for recycling slurry and liquid from various
processes that use slurry, such as chemical mechanical polishing,
or wire saw cutting applications.
[0024] Embodiment of the present invention provides apparatus and
method for recycling polishing slurry and rinse water discharged
from a polishing station. The discharge generally comprises one or
more of used polishing slurry, debris from planarized or wire cut
surface, rinsing fluid, and particles of removed and pad material.
One embodiment of the present invention provides a recycling unit
that receives waste mixture and outputs recycled water and recycled
polishing slurry. In one embodiment, the recycling unit comprises
four filtration/treatment units. A first filtration unit is
configured to separate the mixture into a water stream which mainly
includes large particles and a concentrate stream which includes
solids. The concentration stream then goes through a second
filtration unit for further filtration before going back as
recycled slurry. Before going back as recycled slurry, a fourth
filtration step could be implemented as an option for safety
purpose. The stream of water then goes through a third treatment
unit to be further purified including optional deionization.
[0025] Depth filtration, centrifugal separation, microfiltration,
nanofiltration, and ultrafiltration may be used alone or in
combination in the filtration/treatment units. In one embodiment,
magnetically levitated pumps are used in the filtration/treatment
units to apply a pressure without deleteriously impacting in the
nature of the polishing slurry.
[0026] In one embodiment, a centrifugal separation unit is used to
remove large particles, agglomerates, and/or polymeric particles.
The centrifugal separation unit may be positioned before or after a
filtration unit.
[0027] The recycling unit may be configured to recycle polishing
slurries from various CMP processes, such as polishing of copper,
tungsten, silicon oxides, single crystalline silicon,
polycrystalline silicon, or from wire saw applications.
[0028] Embodiments of the present invention also relate to using
centrifugal pumps, such as magnetically levitated pumps, in
pumping, mixing, and metering to reduce and prevent agglomeration
of particles in the CMP polishing slurry and to reduce particle
contamination. In one embodiment, particle agglomeration may be
reduced by controlling the amount of sheer when pumping, mixing and
metering.
[0029] FIG. 1 is a schematic chart of a polishing system 100 having
a recycling unit 104 in accordance with one embodiment of the
present invention. The polishing system 100 may be configured to
planarize substrates comprising variety of materials, such as
polycrystalline silicon, single crystalline silicon, oxides,
tungsten, aluminum, copper, or combinations of different materials.
In one embodiment, the polishing system 100 may be used to prepare
a polycrystalline silicon substrate for solar panel
fabrication.
[0030] The polishing system 100 comprises a polishing station 101
wherein substrates are polished by a polishing slurry with the
assistance of relative motion between the substrate being processed
and a polishing pad. The polishing slurry is usually sprayed on the
substrate or the polishing pad during polishing. After polishing,
one or more rinses of the substrate are carried out by spraying
deionized water.
[0031] The polishing system 100 further comprises a polishing
slurry source 102 configured to supply polishing slurry to the
polishing station 101. In one embodiment, the polishing slurry
source 102 may comprise one or more slurry tanks configured to
store virgin polishing slurry, and/or recycled polishing slurry
therein and one or more pumps configured to supply polishing slurry
in the tanks to the polishing station 101. In one embodiment, the
pumps may be centrifugal pumps, such as magnetically levitated
pumps, configured to provide real time rheology measurements and
torque requirements to a system controller.
[0032] In another embodiment, the polishing slurry source 102 may
comprise a slurry generator configured to manufacturing polishing
slurry in-situ. The slurry generator assures "fresh" polishing
slurry and avoids settling or other aging problems that associated
with pre-made polishing slurry. In one embodiment, the slurry
generator may be connected to a small local slurry tank to assure
steady flow of slurry during processing.
[0033] The polishing system 100 further comprises a rinse water
source 103 configured to supply rinse water to the polishing
station 101 for rinsing of the substrates and/or the polishing
station 101. The rinse water source 103 may be configured to supply
ultra purified water to the polishing station 101.
[0034] In one embodiment, the polishing system 101 may have a tank
119 connected downstream to the polishing station 101 and
configured to receive used polishing slurry and used rinse fluid,
such as water, glycol or others. In one embodiment, the tank 119
may be coupled to multiple polishing stations and configured to
collect mixtures of used polishing slurry and rinsing water from
multiple polishing stations.
[0035] The polishing system 100 further comprises a recycling unit
104 configured to receive the mixture from the tank 119 and to
generate reusable polishing slurry, reusable rinse water or both
from the mixture in the tank 119. In another embodiment, the
recycling unit 104 may be directly connected to the polishing
station 101.
[0036] The recycling unit 104 comprises a first filtration unit 150
configured to split received mixture into a water stream with
chemicals and particles removed and a concentration stream
comprising the majority of chemicals and particles. The first
filtration unit 150 may also have a waste outlet that provides an
exit for waste, such as large particles. The concentration stream
is directed to a second filtration unit 160 to obtain reusable
polishing slurry. The water stream is directed to an optional
sanitization unit 180 and a treatment unit 170 to obtain reusable
clean water.
[0037] The first filtration unit 150 may comprise a suitable
filtering media for depth filtration and/or surface filtration. In
one embodiment, the first filtration unit 150 comprises one or more
membranes or other filtration units configured to remove particles
of different sizes. In one embodiment, the membranes or other
filtration units may be microfiltration membrane, nanofiltration
membrane, or ultrafiltration membrane.
[0038] In one embodiment, the first filtration unit 150 may be a
cross flow filtration unit. The water stream is the permeate stream
that permeates all the one or more membranes and the concentration
stream is the reject stream from one of the membranes. In another
embodiment, the first filtration unit 150 is a dead-end filtration
unit having two or more membranes or other optional filtration
technologies, and the water stream is the permeate stream that
permeates all the two or more separators. This dead-end filtration
unit can optionally utilize a back flush regeneration to clean the
membrane surface. The first filtration unit 150 removes particles
that are too large for polishing slurry from the concentration
stream.
[0039] The second filtration unit 160 is connected downstream to
the first filtration 150 to receive the concentration stream. The
second filtration unit 160 is configured to stabilize particle size
distribution in the output stream. In one embodiment, the second
filtration unit 160 is configured to remove both large particles
and small particles from the stream to obtain qualifying abrasive
particle size for the stream to be reusable. In one embodiment, the
second filtration unit 160 comprises a membrane or other filtering
media and a pump configured to pressure the concentration stream
through the membrane. The pump may be a magnetically levitated pump
that imposes minimal destruction to the abrasive particles in the
polishing slurry. The second filtration unit 160 may be cleaned by
backward flush to remove waste and surplus water. The water may be
exit the second filtration unit 160 through a waste output 165 or
will be fed to the treatment unit 170. In one embodiment, the waste
may be about 10% to about 15% of feed stream. The concentrate
stream from the second filtration unit 160 goes back to polishing
from a slurry output 164.
[0040] In one embodiment, the second filtration unit 160 further
comprises a dosing unit 167 configured for keeping the abrasive
slurries stabilized during processing in the second filtration unit
160. The dosing unit 167 may provide an additional stream of
conditioning chemicals, such as KOH or NH.sub.4OH 167 to the second
filtration unit 160 either before, during or after filtration.
[0041] The stream from the slurry output 164 may be directed back
to a local polishing slurry tank of the polishing station 101 or to
combine with virgin polishing slurry in the polishing slurry source
102. In one embodiment, rinse water or additional chemical,
particles may be blended with the slurry output 164 to obtain
desired concentration of a polishing slurry for reuse.
[0042] In one embodiment, the slurry out of the second filtration
unit may be filtered with a polishing filtration unit 190 before
directed back to a local polishing slurry tank of the polishing
station 101 or to combine with virgin polishing slurry in the
polishing slurry source 102.
[0043] The sanitization unit 180 is optional. In one embodiment,
the sanitation unit 180 is configured to remove organic species
from the fluid flowing therethrough, such as the water stream from
the first filtration unit 150 and/or the water stream from the
second filtration unit 160. In one embodiment, the sanitization
unit 180 may be an ultra violet (UV) unit configured to oxidize the
organic species in the water stream. In another embodiment, the
sanitization unit 180 is configured to reduce and control bacteria
counts.
[0044] In one embodiment, the sanitized water stream out of the
sanitization unit 180 is directly flown back to the polishing
station 101 for rinsing or other function. The sanitized water
stream may be used in a first rinse, which has low requirement for
the purity of the rinse water.
[0045] The treatment unit 170 is configured to purify and/or
deionize the water stream. In one embodiment, the treatment unit
170 may comprise a reverse osmosis membrane for a reverse osmosis
filtration. In another embodiment, the treatment unit 170 may
comprise an ion-exchange resin, which may be continuously
regenerated, to deionize the water stream. In another embodiment,
the treatment unit 170 may comprise both a reverse osmosis membrane
and an ion-exchange resin. The output stream from the treatment
unit 170 results in ultra purified water. The rejected stream from
the treatment unit 170 exits the recycling unit 104 as waste water.
In one embodiment, the waste water is between about 5% to about 20%
of feed stream. The purified water from the treatment unit 170 may
be sent back to directly to the polishing station 101 or to mix
with virgin ultra purified water from the rinse water source
103.
[0046] In one embodiment, the treatment unit 170 may be positioned
locally near the polishing station 101. In another embodiment, the
treatment unit 170 may located remotely. In one embodiment, a
factory water treatment may be used as the treatment unit 170. The
water stream from the first filtration unit 150 and or from the
second filtration unit 160 may be flown to factory water treatment
unit for recycling, which may be located outside the building where
the factory wide water treatment systems are positioned.
[0047] Since both polishing and rinsing comprise multiple phases.
For example, polishing may be performed in three or more steps to
achieve high throughput and high quality. The initial polishing
step, such as bulk polishing, is usually more tolerant to variation
of polishing slurry than the final polishing step, such as buffing.
Therefore, it can be desirable to direct recycled polishing slurry
to the polishing station when it performs bulk polishing and shut
off the recycled polishing slurry when the polishing station is
performing final step buffing. Similarly, initial rinse after
polishing is less sensitive to traces of chemical and ions in the
rinse water than the final rinse. Therefore, it is desirable to
supply recycled rinse water to the polishing station while the
polishing station is performing initial rinsing and shut off the
recycled rinse water when the polishing station is performing final
rinsing.
[0048] In one embodiment, the polishing system 100 further
comprises a system controller 109. In one embodiment, the system
controller 109 may control the multiple valves in the polishing
system 100 to insure that recycled polishing slurry and/or rinse
water is delivered or shut off at desired time. For simplicity of
drawing, connections between the system controllers 109 and the
components of the polishing system 100 are not shown. In one
embodiment, the system controller 109 is a stand alone independent
controller for supplying and recycling polishing slurry. In another
embodiment, the system controller 109 is integrated in to a CMP
tool controller as an integral part.
[0049] FIG. 2A is a schematic chart of a polishing system 200A
having a recycling unit 204 in accordance with another embodiment
of the present invention. The polishing system 200A is similar to
the polishing system 100 of FIG. 1 but with detailed exemplary
embodiments for different units.
[0050] The polishing system 200A may be configured to planarize
substrates comprising variety of materials, such as polycrystalline
silicon, single crystalline silicon, oxides, tungsten, copper,
aluminum, or combinations of different materials. In one
embodiment, the polishing system 200A may be used to prepare a
polycrystalline silicon substrate for solar panel fabrication.
[0051] The polishing system 200A comprises a polishing station 201
wherein a substrate 213 being processed is retained by a polishing
head 212 and pressed against a polishing pad 211. The polishing
head 212 and the polishing pad 211 both rotate and provide relative
motion between the substrate 213 and a polishing surface of the
polishing pad 211. A slurry nozzle 214 provides a polishing slurry
to the polishing pad 211. A rinse nozzle 215 provides rinse water
to the polishing station 201.
[0052] The polishing system 200A further comprises a polishing
slurry unit 202 configured to supply polishing slurry to the
polishing station 201. The polishing slurry unit 202 comprises a
source 221 and a local tank 224. In one embodiment, the source 221
may be a source tank storing pre-generated the polishing slurry.
The source tank is generally much larger than the local tank 224.
In another embodiment, the source 221 may be a slurry generator to
generate polishing slurry on-site. During operation, a pump 222
pumps polishing slurry through a filter 223 to the local tank 224,
and a pump 225 from connected to the local tank 224 pumps the
slurry through a filter 226 to the slurry nozzle 214.
[0053] In one embodiment, the filter 226 may be a point-of-use
depth filter and particle filtration to remove any gels and
agglomerates just prior to dispensing the polishing slurry to the
polishing station 201. In one embodiment, the filter 226 is
disposed downstream to the pump 225 and upstream to a delivery arm
to which the slurry nozzle 214 is connected.
[0054] The polishing system 200A further comprises a rinse water
unit 203 configured to supply rinse water to the polishing station
201 for rinsing of the substrates and/or the polishing station 201.
The rinse water unit 203 may comprise a tank 231 configured for
store rinse water for supplying to the rinse nozzle. The tank 231
usually connects to a source of virgin ultra purified water.
[0055] In one embodiment, the polishing station 201 comprises a
collecting bin 216 configured to receive used polishing slurry,
rinse fluid along with removed material. In one embodiment, the
collecting bin 216 may be lowered during substrate loading and
unloading and raised during polishing and rinsing to catch
polishing slurry and rinsing fluid.
[0056] The polishing system 200A may have a tank 219 connected
downstream to the collecting bin 216. In one embodiment, the tank
219 may be coupled to multiple polishing stations and configured to
collect mixtures of used polishing slurry and rinsing fluid from
multiple polishing stations.
[0057] The polishing system 200A further comprises a recycling unit
204 configured to receive the mixture from the tank 219 and to
generate reusable polishing slurry and reusable rinse water from
the mixture in the tank 219.
[0058] The recycling unit 204 comprises a first filtration unit 250
configured to split received mixture into a water stream with
majority of chemicals and particles removed and a concentration
stream comprising chemicals and particles. The concentration stream
is directed to a second filtration unit 260 to obtain reusable
polishing slurry. In one embodiment, the water stream is directed
to an optional sanitization unit 280 and a treatment unit 270 to
obtain reusable purified water. In another embodiment, the water
stream may be directly going to waste.
[0059] The first filtration unit 250 comprises a pump 251 connected
upstream to a filter unit 252. The pump 251 is configured to
pressurize income stream from the tank 219 through the filter unit
252. The first filtration unit 250 is configured to remove
particles that are too large for polishing slurry from the
concentration stream.
[0060] The filter unit 252 comprises suitable filter media, such as
depth filter and particle filtration unit. In one embodiment, the
filter unit 252 comprises one or more membranes or other filtration
technologies. As shown in FIG. 2A, the filter unit 252 can comprise
one or more membranes, such as a microfiltration membrane, a
nanofiltration membrane or an ultrafiltration membrane. In one
embodiment, the membranes may be disposed in a staged manner. The
income stream would go through the one or more membranes in
sequence. In one embodiment, the filter unit 252 comprises a
microfiltration membrane, a nanofiltration membrane, and an
ultrafiltration membrane in sequence.
[0061] In one embodiment, the first filtration unit 250 comprises a
concentration outlet 257 in fluid communication with stream between
the microfiltration membrane 253 and the nanofiltration membrane
254. As a result, large particles from the income stream do not
permeate the filter unit 252 and small particles permeate the
filter unit 252.
[0062] The first filtration unit 250 further comprises a water
output 258 in fluid communication with the permeate stream out of
the all stages of membranes in the filter unit 252 to output a
water stream with most chemical and particles removed. In another
embodiment, the stream from the water output 258 may also exit the
system as waste.
[0063] The pump 251 may be a diaphragm pump, a bellow pump, or a
magnetically coupled or centrifugal pump. Alternately a vacuum
system or gas pressure can be employed for transfer of fluids. In
one embodiment, the pump 251 may be a magnetically levitated pump.
This low sheer pump has minimum impact on particle size
distribution of the polishing slurry.
[0064] The filter unit 252 may be configured for dead-end
filtration, cross flow filtration, or back flushable filtration. In
one embodiment, the microfiltration membrane 253, the
nanofiltration membrane 254 and the ultrafiltration membrane 255
may be polymeric membranes or ceramic membranes. The one or more
membranes in the filter unit 252 may be spiral membranes, tubular
membranes, plate and frame, or hollow fiber membranes.
[0065] The second filtration unit 260 is connected downstream to
the first filtration unit 250 to receive the concentration stream.
The second filtration unit 260 is configured to stabilize particle
size distribution in the output stream.
[0066] In one embodiment, the second filtration unit 260 comprises
a filter media 262 and a pump 261 configured to pressure the
concentration stream through the filter media 262. In one
embodiment, the filter media 262 comprises a membrane. The pump may
be a magnetically levitated pump that imposes minimal destruction
to the abrasive particles in the polishing slurry.
[0067] The second filtration unit 260 has a slurry output 264
configured to output a permeated stream, and a back flush port 266
configured to receive a rinse fluid to clean the filter media 262
by backwashing to remove waste. The waste may be exit the second
filtration unit 260 through a waste output 265. In one embodiment,
the waste may be about 10% to about 15% of feed stream. In another
embodiment, the waste output 265 may be connected to the water
recycling branch, such as an inlet of the sanitizing unit 280 for
water recycling.
[0068] In one embodiment, the second filtration unit 260 further
comprises a dosing unit 267 configured for keeping the abrasive
slurries stabilized during processing in the second filtration unit
260. The dosing unit 267 may provide an additional stream of
conditioning chemicals, such as KOH or NH.sub.4OH 267 to the second
filtration unit 260 either before, during or after filtration.
[0069] The pump 261 may be a diaphragm pump, a bellow pump, or a
magnetically coupled or centrifugal pump. In one embodiment, the
pump 261 may be a magnetically levitated pump with minimized impact
on particles of the polishing slurry.
[0070] The filter media 262 may be a polymeric membranes or a
ceramic membrane. The filter media 262 may be a spiral membrane, a
tubular membrane, or a hollow fiber membrane.
[0071] The second filtration unit 260 may be a dead-end filtration
or a cross-flow filtration.
[0072] In one embodiment, the slurry out of the second filtration
unit 260 may be further filtered with a polishing filtration unit
290 before directed back to a local polishing slurry tank of the
polishing station 201 or to the polishing slurry unit 202.
[0073] The permeate stream from the slurry output 264 maybe
directed to the source 221 or the local tank 224.
[0074] The sanitization unit 280 is configured to reduce and
control bacteria and or organic contamination from the fluid
flowing therethrough, such as the water stream from the first
filtration unit 250 and/or the second filtration unit 260. In one
embodiment, the sanitization unit 280 may be an ultra violet (UV)
unit configured to oxidize the organic species or kill the bacteria
in the water stream.
[0075] In one embodiment, the sanitized water stream is directly
flown back to the polishing station 201 for rinsing or other
function. The sanitized water stream may be used in a first rinse,
which has low requirement for the purity of the rinse water.
[0076] The treatment unit 270 is configured to purify and deionize
the water stream. In one embodiment, the treatment unit 270
comprises a pump 271, a reverse osmosis membrane 273 and an
ion-exchange resin 274, which may be regenerated continuously via
ion selective membranes. The pump 271 is configured to pressurize
incoming flow to the reverse osmosis membrane 273 and the
ion-exchange resin 274. The output stream from an outlet 276 of the
treatment unit 270 results in ultra purified water. The rejected
stream from the treatment unit 270 exits through a waste output 278
as waste water. In one embodiment, the waste water is between about
5% to about 20% of feed stream. The purified water from the
treatment unit 270 may be sent back to directly to the polishing
station 201 or to mix with virgin ultra purified water from a rinse
water inlet 232.
[0077] In one embodiment, the treatment unit 270 is a stand alone
water recycling unit. In another embodiment, the treatment unit 270
belongs to a pre-existing factory water treatment system.
[0078] In one embodiment, the polishing system 200A further
comprises a system controller 209. In one embodiment, the system
controller 209 may control the multiple valves in the polishing
system 200A to insure that recycled polishing slurry and/or rinse
water is delivered or shut off at desired time. For simplicity of
drawing, connections between the system controllers 209 and the
components of the polishing system 200A are not shown.
[0079] The membranes used in each filtration/treatment unit 250,
260, 270 may be one of depth filter, a spiral membrane, a hollow
fiber membrane, a tubular membrane, a plate and frame membrane
operated in a dead-end filtration method, a back flushable
filtration method, or in a cross flow filtration method.
[0080] In one embodiment, the system controller 209 is a stand
alone independent controller for supplying and recycling polishing
slurry. In another embodiment, the system controller 209 is
integrated in to a CMP tool controller or implemented as a slave to
the CMP tool control system.
[0081] In one embodiment, the system controller 209 is connected to
at least one of the reservoir pumps 222, 225 and the filtration
pumps 251, 261, 271. The system controller 209 is configured to
monitor and/or adjust characteristics of polishing slurry according
to process parameters of the at least one pump connected to the
system controller 209. In one embodiment, the at least pump
connected to the system controller 209 is a centrifugal pump, such
as an electromagnetically levitated centrifugal pump.
[0082] Each of the pumps 222, 225, 251, 261, 271 may be one of a
piston pump, a diaphragm pump, a bellow pump, a peristaltic pump, a
magnetically levitated centrifugal pump, and a device for fluid
transfer by vacuum draw. In one embodiment, each of the pumps 222,
225, 251, 261, 271 may be a centrifugal pump. Centrifugal pumps
provide more controlled shear forces than pumps traditionally used
for polishing slurry and/or polishing slurry waste transportation.
The high sear forces reduce particle agglomeration drastically. In
one embodiment, each of the pumps 222, 225, 251, 261, 271 is a
magnetically levitated centrifugal pump. Magnetically levitated
pumps add very few particles to the fluid, therefore, reducing
particle contamination and damages to substrate being processed. An
exemplary magnetically levitated centrifugal pump may made by
Levitronix, Switzerland.
[0083] In one embodiment, connecting the system controller 209 to
at least one magnetically levitated centrifugal pump enables return
of real time rheology measurements and/or torque requirements on
each slurry blending and recycling step. Rheology measurements
and/torque requirement can be obtained from pumps at one or more of
the following positions: a position where recycled slurry is
blended into virgin slurry, a position wherein slurry recycles back
to a main reservoir, a position driving agglomeration filtration, a
position transport past large reservoir, a position transport past
local reservoir, a position feeding polishing slurry to the
polishing pad.
[0084] In one embodiment, magnetically levitated centrifugal pumps
may be used to meter polishing slurry to local reservoir or to
polishing pads.
[0085] In one embodiment, magnetically levitated centrifugal pumps
may be used to afford appropriate levels of shear to the polishing
slurry to positively impact rheology and minimize
agglomeration.
[0086] In another embodiment, magnetically levitated centrifugal
pumps may be used to inject and mix additives, to mix/combine
various streams of virgin slurry, recycled polishing slurry, water,
and/or chemical additive packages.
[0087] In another embodiment, other metrology sensors positioned
adjacent pump housing may be used in addition to or incorporation
of magnetically levitated centrifugal pumps.
[0088] In another embodiment, magnetically levitated centrifugal
pumps may be used to monitor the back pressure of feed to the
filtration and back wash media to (1) alert to plugging issues that
would require filtration maintenance, (2) adjust pumping power to
compensate for increased pressure drop until process is finished
and shut down without interrupting process, and (3) initiate
additional frequency, increased flow during cross flow or back wash
steps, or optionally inject a cleaning agent bypass the current
polishing slurry and ultra purified water recycle until the clean
agent is purged as predetermined by the control software based on
set point parameters.
[0089] In another embodiment, magnetically levitated centrifugal
pumps may be used to provide feedback to the optional integrated
controls system that manages the CMP water and slurry recycle
system as a holistic set of unit operations along with the CMP tool
and water plant rather than operating as a cluster of individually
controlled circuits.
[0090] In another embodiment, magnetically levitated centrifugal
pumps may be used to lower levels of contamination due to complete
encapsulation of all moving parts with an inert polymer and the
absence of metal or ceramic drive seals in the pumping system.
[0091] FIG. 2B is a schematic view of a polishing system 200B with
one embodiment of the present invention. The polishing system 200B
is similar to the polishing system 200A of FIG. 2A, except that the
polishing system 200B has a separation unit 295 configured to
separate polymeric particles or large particles, such as large
silicon oxide particle, from the flow before recycling. In one
embodiment, the separation unit 295 is a centrifugal separator. The
separated particles may exit the system from an outlet 296.
[0092] FIG. 2C is a schematic view of a polishing system 200C in
accordance with one embodiment of the present invention. The
polishing system 200C is similar to the polishing system 200B of
FIG. 2B except that the separator unit 295 is disposed down stream
of the first filtration unit 250.
[0093] FIG. 2D is a schematic view of a polishing system 200D in
accordance with one embodiment of the present invention. The
polishing system 200D is similar to the polishing system 200A of
FIG. 2D, except that the polishing system 200D use a diverter valve
294 to separate a water stream and a concentrations stream in stead
of using the first filtration unit 250 as in the polishing system
200A.
[0094] The diverter valve 294 is connected to the collecting bin
216 of the polishing station 201. The collecting pin 216 may be
stationary or movable. In one embodiment, the diverter valve 294 is
configured to direct the content in the collecting bin 216 to the
second filtration unit 260 for slurry recycling or to the treatment
unit 270 for water recycling. In one embodiment, the diverter valve
294 is a three way valve. The status of the diverter valve 294 may
be controlled by the system controller according to the process in
the polishing station 201. For example, the diverter valve 294 may
be adjusted to direct the flow to the second filtration unit 260
for slurry recycling when there is polishing slurry flowing from
the slurry nozzle 214 to the polishing station 201, and adjusted to
direct the flow towards the treatment unit 270 during rinsing or
there no slurry flow from upstream.
[0095] In one embodiment, the polishing system 200D comprises an
optional separation unit 295 connected between the diverter valve
294 and the second filtration unit 260 to remove polymeric
particles and/or large particle prior to the slurry recycling.
[0096] FIG. 3 is a schematic chart of a polishing system 300 having
a dedicated recycled slurry tank 324 and a dedicated virgin slurry
tank 327 in accordance with another embodiment of the present
invention. The polishing system 300 is similar to the polishing
system 200 of FIG. 2, except for the difference in the slurry unit
302.
[0097] The slurry unit 302 is configured to provide the polishing
station 301 with virgin polishing slurry without mixing with the
recycled slurry during polishing. This allows the polishing station
301 to perform multiple steps of polishing and use recycled
polishing slurry only when process parameter permits.
[0098] FIG. 4 is a schematic chart of a polishing system 400 having
a dedicated recycled rinse water tank 432 in accordance with
another embodiment of the present invention. The polishing system
400 is similar to the polishing system 200 of FIG. 2, except for
the difference in the rinse water unit 403.
[0099] The rinse water unit 403 comprises a recycled rinse water
tank 432 to receive recycled rinse water and a virgin rinse water
tank 431 without recycled rinse water. This allows the polishing
station 301 to perform multiple rinsing and use recycled rinse
water only when process parameter permits, such as during initial
rinsing.
[0100] FIG. 5 is a schematic chart of a polishing system 500 having
multiple polishing stations 501a, 501b, 501c and a recycling unit
504 in accordance with another embodiment of the present invention.
The polishing system 500 is configured to perform multiple
polishing steps. Each polishing station 501a, 501b, 501c is
dedicated to a polishing step with different polishing rate.
[0101] The polishing waste from the polishing stations 501a, 501b,
501c is gathered in a tank 519 and sent to the recycling unit 504,
which is similar to the recycling units 104 and 204 described
above.
[0102] A polishing source 502 provides recycled and virgin
polishing slurry to the polishing stations 501a, 501b, 501c. In one
embodiment, the recycled polishing slurry is only supplied to the
polishing station that is configured to perform bulk polishing.
[0103] A rinse water source 503 is configured to selectively supply
recycled rinse water and virgin rinse slurry to each polishing
station.
[0104] Even though three polishing stations are shown in FIG. 5,
more or less polishing stations may be used according to process
requirement.
[0105] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *