U.S. patent application number 09/730704 was filed with the patent office on 2001-06-14 for cmp slurry recycling apparatus and method for recycling cmp slurry.
This patent application is currently assigned to LSI Logic Corporation. Invention is credited to Kikuchi, Toru, Mizuno, Hiroshi, Nagamine, Takuya, Ogitsu, Masaaki.
Application Number | 20010003700 09/730704 |
Document ID | / |
Family ID | 18415844 |
Filed Date | 2001-06-14 |
United States Patent
Application |
20010003700 |
Kind Code |
A1 |
Mizuno, Hiroshi ; et
al. |
June 14, 2001 |
CMP slurry recycling apparatus and method for recycling CMP
slurry
Abstract
A polishing table 11 in the CMP apparatus 10 has a diameter
smaller than the diameter of a polishing pad 12. The polishing pad
12 is disposed on the polishing table so as to cover the entire top
surface of the polishing table 11. A space 13 is formed between
outside of the outer peripheral surface of the polishing table 11
and under the outer peripheral bottom surface portion of the
polishing pad 12 projecting outside from the edge of the polishing
table 11. A trough 14 with an opening 14a on top thereof as a
device for withdrawing the used slurry is disposed around the outer
peripheral surface of the polishing table 11 so as to be located a
part thereof in the space 13.
Inventors: |
Mizuno, Hiroshi; (Gresham,
OR) ; Ogitsu, Masaaki; (Tsukuba-Shi, JP) ;
Nagamine, Takuya; (Shimotsuma-Shi, JP) ; Kikuchi,
Toru; (Ibaraki-Ken, JP) |
Correspondence
Address: |
Intellectual Property Law Department
LSI Logic Corporation
M/S D-106
1551 McCarthy Boulevard
Milpitas
CA
95035
US
|
Assignee: |
LSI Logic Corporation
|
Family ID: |
18415844 |
Appl. No.: |
09/730704 |
Filed: |
December 6, 2000 |
Current U.S.
Class: |
451/87 ; 451/36;
451/41; 451/60 |
Current CPC
Class: |
B24D 9/08 20130101; B24B
37/04 20130101; B24B 57/02 20130101 |
Class at
Publication: |
451/87 ; 451/36;
451/41; 451/60 |
International
Class: |
B24C 009/00; B24B
007/19 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 1999 |
JP |
351216/99 |
Claims
What is claimed is:
1. A CMP slurry recycling apparatus for recycling the CMP slurry,
in which the slurry is supplied to a polishing pad disposed on a
polishing table to polish the polishing object, while the used
slurry is withdrawn from the polishing pad: a diameter of the
polishing table is set to be smaller than a diameter of the
polishing pad; and a collecting device with an opening on top is
disposed around an outer peripheral side surface of the polishing
table so as to enable withdrawing the used slurry directly inside
the device from the polishing pad.
2. A CMP slurry recycling apparatus as claimed in claim 1, wherein:
the device comprises a trough of a generally U-shaped form in a
transverse section with an opening on top thereof, a top inner edge
of the top opening of the trough at a polishing table side being
located in a position around the outer peripheral surface of the
polishing table and within a space formed between outside of the
outer peripheral surface thereof and under a portion of the
peripheral bottom surface of the polishing pad projecting outside
from the outermost edge of the polishing table.
3. A CMP slurry recycling method for recycling the CMP slurry, in
which the slurry is supplied to a polishing pad disposed on a
polishing table to polish the polishing object, while the used
slurry is withdrawn from the polishing pad, said method comprising
the steps of: setting a diameter of the polishing table to be
smaller than a diameter of the polishing pad; arranging a generally
U-shaped device having an opening on top thereof around the outer
peripheral surface of the polishing table so as for a top edge of
the device at the inner edge side thereof to be located under the
outer peripheral bottom surface portion of the polishing pad;
withdrawing the used slurry in the device directly from the
peripheral edge of the polishing pad through the opening;
transferring the used slurry withdrawn by the device to a storage
tank after filtering; and supplying the slurry from the storage
tank to the polishing pad disposed on the polishing table after
further filtering.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a chemical-mechanical
polishing (CMP) slurry recycling apparatus for recycling a CMP
slurry and a method for recycling a CMP slurry, which are adapted
to enable a decrease in costs incurred in chemically-mechanically
polishing semiconductor wafers and other objects by repetitive use
of a CMP slurry.
[0003] 2. Description of the Related Art
[0004] A CMP process is used in planarizing the surfaces of wafers,
substrates and other objects before subjecting e.g. semiconductor
wafers to exposure processing. The CMP process is a polishing
process that combines a chemical reaction by a solute in a slurry
as a polishing fluid and a mechanical polishing action produced by
a polishing pad and abrasive particles in the slurry.
[0005] In conventional CMP processes, a slurry is not reused and is
discarded. As polishing slurry is expensive, discarding it after a
single use contributes to the expense of producing semi-conductor
wafers.
[0006] The slurry is collected in a storage tank, and then
discarded. Collection of used slurry is effected by means of a
collecting trough disposed so as to enclose an outer peripheral
surface of a polishing table and a bottom portion thereof. The
slurry supplied to the polishing pad is allowed to flow from the
polishing pad along the outer peripheral surface of the polishing
table and the bottom portion thereof into the collecting trough,
and the slurry flown into the collecting trough is then transferred
to the storage tank for withdrawal of the slurry. In such a
conventional polishing process, the used slurry is comes into
contact with a wide area of the outer peripheral surface and the
bottom surface of the polishing table before it is collected in the
collecting trough. This extensive contact of the used slurry with
the polishing table gives rise to a risk of a portion of the slurry
sticking to and becoming solid on the outer peripheral surface of
the polishing table or the bottom surface when the the slurry is
flown from the polishing pad to the collecting trough. Further,
there is a risk of the slurry scattering from the rotating
polishing table and not reaching the collection trough. Attempts
have so far been made to recycle and reuse slurry deposited in a
storage tank. It has been found necessary, however, for fresh
slurry to be supplemented in a large amount in order to efficiently
reuse the slurry once used, because efficiency of collecting the
used slurry is very low.
SUMMARY OF THE INVENTION
[0007] Therefore, the present invention has the object to provide a
CMP slurry recycling apparatus and a method for recycling a CMP
slurry once used, which enables costs in a planarizing process for
planarizing the surfaces of semiconductor wafers and other objects
to be reduced by reusing and recycling the used CMP slurry in an
efficient way.
[0008] In order to achieve the object in one aspect, the present
invention provides a CMP slurry recycling apparatus for recycling a
CMP slurry, in which the slurry is supplied to a polishing pad
disposed on a polishing table to polish the polishing object, while
the used slurry is withdrawn from the polishing pad, wherein the
polishing table is arranged such that a diameter thereof is set to
be smaller relative to the diameter of the polishing pad and
wherein a collecting device having an opening on top thereof is
disposed around the outer peripheral surface of the polishing table
so as to withdraw the slurry directly from the polishing pad in the
device.
[0009] With the arrangement of the apparatus as described above,
the CMP slurry recycling apparatus according to the present
invention can increase efficiency in withdrawing the used CMP
slurry by directly collecting or withdrawing the used slurry from
the polishing pad because it can prevent the used slurry from
sticking and becoming solid on the surfaces of the polishing table
and from scattering from the polishing pad.
[0010] In a preferred embodiment of the present invention, the
device is composed of a trough in a U-shaped transverse section and
disposed around the outer periphery of the polishing table so as
for a top end at an inner edge side of the trough to be located in
a slightly spaced relationship below the outer peripheral bottom
edge portion of the polishing pad.
[0011] In order to achieve the object in another aspect, the
present invention provides the CMP slurry recycling method for
recycling a CMP slurry, in which the slurry is supplied to a
polishing pad disposed on a polishing table to polish the polishing
object, while the used slurry is withdrawn from the polishing pad,
the method comprising the steps of: setting a diameter of the
polishing table to be smaller than a diameter of the polishing pad;
arranging a generally U-shaped device having an opening on top
thereof around the outer peripheral surface of the polishing table
so as for a top edge of the device at the inner edge side thereof
to be located under the outer peripheral bottom surface portion of
the polishing pad; withdrawing the used slurry in the device
directly from the peripheral edge of the polishing pad through the
opening; transferring the used slurry withdrawn by the device to a
storage tank after filtering to remove contaminants; and supplying
the slurry from the storage tank to the polishing pad disposed on
the polishing table after further filtering to remove
contaminants.
[0012] Other objects, features and advantages of the present
invention will become apparent in the course of the following
description with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a perspective schematic view of an embodiment of a
CMP slurry recycling apparatus, showing the geographical
relationship of a polishing table with a slurry collecting
device.
[0014] FIG. 2 is an illustration showing an overall outline of the
CMP slurry recycling apparatus according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] The chemical-mechanical polishing (CMP) slurry recycling
apparatus according to the present invention will be described in
more detail with reference to the accompanying drawings.
[0016] A description will be given regarding an embodiment of the
CMP slurry recycling apparatus of the present invention. As shown
in FIGS. 1 and 2, a polishing table 11 in a disk form in a CMP
apparatus 10 has a diameter which is smaller than that of a
polishing pad 12 in a disk form. The polishing pad 12 is disposed
on the polishing table 11 so as to cover the entire surface
thereof. The outer peripheral edge portion of the polishing pad 12
projects outside from the peripheral edge of the polishing table 11
by the difference of the diameter between the polishing table 11
and the polishing pad 12. The area outside and around the outer
peripheral surface of the polishing table 11 and under the
projecting bottom surface portion of the polishing pad 12 is
referred to herein as a space 13. In other words, the space 13 is
located outside the outer periphery of the polishing table 11 and
under the bottom surface portion of the polishing pad 12 projecting
outside the outermost edge of the polishing table 11. A collecting
device is disposed around the outer periphery of the polishing
table 11 so as to have an inner side portion thereof located in the
space 13.
[0017] The collecting device may be composed of a trough 14 of a
ring-shaped form in a plane cross section and of a U-shaped form in
a transverse section. The trough 14 comprises an opening 14a on top
thereof, an inner side wall 14b, an outer side wall 14c, and a
bottom face 14d. The inner side wall 14b is located in the space
13. The outer side wall 14c is located out side of the space 13 and
arranged along the inner side wall 14b and the polishing table 11.
The bottom of the outer side wall 14c is connected to the bottom of
the inner side wall 14b via the bottom face 14d to form a U-shaped
recipient portion in which the used slurry is flown from the edge
of the polishing pad 12 and collected or withdrawn.
[0018] More specifically, a top of the inner side wall 14b, that
is, a top of inner edge of the opening 14a of the trough 14 is
located slightly under the outer bottom edge portion of the
polishing pad 12 in order for the used slurry to fall directly into
the U-shaped recipient portion of the trough 14 from the outermost
edge of the polishing pad 12. On the other hand, the outer side
wall 14c of the trough 14 is arranged to be higher than the inner
side wall 14b thereof and the horizontal top surface level of the
polishing pad 12 so as for the used slurry to fail to scatter off
the trough 14.
[0019] With the arrangement of the trough 14, the slurry fed to the
top surface of the polishing object disposed on the polishing pad
12 is allowed to flow on the top surface outward and then directly
into the trough 14 via the inner side wall 14b without flowing
along the outer surface of the polishing table 11. Furthermore, the
used slurry can be received by the outer side wall 14c of the
trough 14, even if it would scatter from the polishing pad 12 due
to the centrifugal force produced by rotation of the polishing
pad.
[0020] Moreover, the inner surface of the U-shaped collecting
trough 14 is surface-treated so as to become smooth enough for the
used slurry to flow smoothly and to fail to stick to the surface
thereof and become solid thereon.
[0021] A circulating pipe 16 is disposed in the bottom face 14d of
the trough 14 connecting to a storage tank 15 for temporarily
storing the used slurry in order to allow recycling it by feeding
it to the polishing pad 12. The slurry used is withdrawn in the
trough 14 and then transferred via the circulating pipe 16 to the
storage tank 15. The circulating pipe 16 is provided with a trap
filter 17 at an appropriate position thereof so as to remove
foreign materials such as polishing chips and so on contaminated in
the slurry during the polishing process.
[0022] Between the storage tank 15 and the polishing table 11 is
also disposed a circulating pipe 18 to allow the storage tank 15 to
feed the used slurry stored therein to the polishing pad 12 for
recycling. At one end of the circulating pipe 18 that is located in
the storage tank 15 is provided a final filer 19 for further
removal of contaminants such as polishing chips and so on, and a
circulating pump 20 is disposed at an appropriate position of the
circulating pipe 18. The other end of the circulating pipe 18
extends toward the polishing table 11 and is located above the
polishing pad 12. This configuration of the circulating pipe 18
allows the used slurry stored in the storage tank 15 to be pumped
up by means of the circulating pump 20 while further removing the
contaminants contained therein by the final filter 19, and to be
fed to the opposite side of the circulating pipe 18. The used
slurry pumped up by the pump 20 is then supplied onto the top
surface of the polishing pad 12 from the supply section 18a of the
pipe 18.
[0023] Above the polishing table 11 is disposed a polishing head 22
that can press a semiconductor wafer 21 as a polishing object
against the top surface of the polishing pad 12 at a predetermined
level of force. The polishing head 22 is set to have a diameter
somewhat larger than that of the semiconductor wafer 21. Further,
the polishing head 22 is driven by a drive unit (not shown) so as
to rotate in the same direction as the polishing table 11 and can
be transferred in the radial direction of the polishing table 11 to
polish the semiconductor wafer 21 uniformly over the entire surface
area thereof. This arrangement of the polishing head 22 can avoid
an occurrence of the irregular and local polishing on the surface
of the semiconductor wafer 21.
[0024] The polishing table 11 may comprise, for example, a metallic
platen in the disk shape and may have a diameter ranging from 48 cm
to 57 cm. The polishing table 11 is rotated by a drive unit (not
shown) to polish a polishing object by means of the polishing pad
12 disposed on the top surface thereof. On the other hand, the
polishing pad 12 may be made, for example, of a polyurethane
material or a non-woven cloth and have a diameter ranging from 53
cm to 61 cm. In order to place the polishing pad 12 on the top
surface of the polishing table 11, the polishing pad 12 is selected
and used which may have a diameter larger by approximately 4 cm to
6 cm than the diameter of the polishing table 11.
[0025] The slurry may be in the form of a suspension containing
abrasive particles, for example, of silica, alumina, or any other
appropriate abrasive material in a liquid, e.g., water adjusted to
an appropriate pH level. Although the flow rate of the slurry to be
supplied may be varied with the kind of the polishing objects, it
may range typically from approximately 1,000 ml to 1,500 ml per
minute. On the other hand, in conventional techniques, the flow
rate of a slurry may be in the range of approximately 175 ml to 200
ml per minute, much smaller than in the case of the present
invention. In the conventional techniques, the slurry is discarded
after use for polishing, and not reused by recycling. Therefore,
the flow rate of the slurry to be supplied was limited to as low a
range as possible in order to avoid an increasein manufacturing
costs.
[0026] Then, a description will be given regarding an embodiment of
the CMP slurry recycling method according to the present invention,
which uses the CMP slurry recycling apparatus of this
invention.
[0027] For operating the CMP slurry recycling method of this
invention, the semiconductor wafer 21 is first placed with its
polishing surface down on the polishing pad 12 and it is pressed
from top by the polishing head 22 at a predetermined amount of
pressure. Then, the circulating pump 20 is operated to transfer the
slurry from the storage tank 15 to the supply section 18a of the
circulating pipe 18 and then supply the slurry to the polishing pad
12 from the supply section 18a of the circulating pipe 18. On the
other hand, the polishing table 11 and the polishing head 22 are
rotated to polish the polishing surface of the semiconductor wafer
21 at a predetermined amount over its entire surface area.
[0028] The slurry supplied to the polishing pad 12 penetrates into
an interface between the polishing surface of the semiconductor
wafer 21 and the top surface of the polishing pad 12 and chemically
and mechanically polish the polishing surface of the semiconductor
wafer 21 with the aid of the CMP slurry. The used slurry is then
allowed to flow out from the interface between the semiconductor
wafer 21 and the polishing pad 12 and flow on and along the top
surface of the polishing pad 12 in the radial direction toward the
outside of the polishing pad, followed by falling down from the
outermost peripheral edge of the polishing pad 12 directly into the
trough 14. Upon the used slurry dropping from the polishing pad 12,
it is guided on and along the inner wall surface of the inner side
wall 14b of the trough 14, thereby preventing the used slurry from
falling down on and along the outer peripheral surface and the
bottom surface of the polishing table 11 and allowing the used
slurry to be collected directly in the trough 14. Moreover, the
outer side wall 14c of the trough 14 can prevent the used slurry
from scattering off the trough 14 as the slurry scatters away from
the peripheral edge of the polishing pad 12 due to the centrifugal
force rendered by the rotation of the polishing pad 12. The
arrangement of the trough 14 in association with the polishing
table 11 and the polishing pad 12 can collect the slurry used for
the CMP process directly in the trough 14 without falling outside
the trough 14.
[0029] The slurry withdrawn in the trough 14 is then transferred to
the storage tank 15 via the circulating pipe 16. Before feeding the
used slurry into the storage tank 15, the slurry is subjected to
filtering through the trap filter 17 to remove polishing chips and
other contaminants contained therein. Upon feeding the slurry
stored in the storage tank 15 to the polishing pad 12, the slurry
is again subjected to filtering by means of the final filter 19 in
order to further remove contaminants therein. After filtering with
the final filter 19, the slurry is supplied to the polishing pad 12
from the supply section 18a of the circulating pipe 18. The supply
of the slurry from the storage tank 15 to the polishing pad 12 via
the circulating pipe 18 is continued during the CMP process.
[0030] The slurry may be adjusted to an appropriate pH and
replenished with water etc., upon supplying to the storage tank 15
or to the circulating pipe 18. A chemical for reproduction use or a
fresh slurry may be added as needed. The temperature of the slurry
may be adjusted with a heat exchanger.
[0031] The CMP slurry recycling method according to the above
embodiment of the present invention can collect or withdraw the
used slurry without causing sticking on the outer peripheral
surface and the bottom surface of the polishing table 11 and
scattering outside the polishing pad 12, so that the efficiency of
collecting the slurry can be increased to a remarkable extent.
Furthermore, the CMP slurry recycling method according to the
present invention can dramatically save the amount of a fresh
slurry to be supplemented, rendering a substantially large amount
of costs to be incurred by the process for planarizing the
semiconductor wafer 21.
[0032] The repetitive recycling of the used slurry enables the
slurry to be used at a larger flow rate than in conventional CMP
process and therefore can accomplish substantial improvements in
the polishing quality while reducing manufacturing costs, because
the used slurry is recycled. This can substantially reduce the
frequency of occurrences of defects on the surface of semiconductor
wafers during the polishing process.
[0033] Having described the present invention in the manner as
described above, it has to be understood that the present invention
is not limited in any respect to the above embodiment and the above
embodiment is described for illustrative purposes. It is further
apparent that the present invention encompasses a variety of
modifications and variations without departing from the scope and
spirit of the invention.
EFFECTS OF THE INVENTION
[0034] As described above, the present invention provides the CMP
slurry recycling apparatus and method for recycling the used CMP
slurry, wherein the diameter of the polishing table is set to be
smaller than that of the polishing pad and the collecting device
with an opening on top is disposed slightly apart from and around
the outer periphery of the polishing table to allow a direct
collection of the used slurry from the polishing pad into the
collecting device. The arrangement of the collecting device in
association with the polishing table and the polishing pad can
improve efficiency of collecting or withdrawing the used slurry
because this can prevent the used slurry from sticking and becoming
solid on the surface of the polishing table as well as dropping and
scattering off outside the collecting device. This naturally
eventually reduces costs of planarizing and manufacturing
semiconductor wafers and other objects.
* * * * *