U.S. patent application number 10/447387 was filed with the patent office on 2003-11-20 for cleaning device and method for cleaning polishing cloths used for polishing semiconductor wafers.
Invention is credited to Gotze, Veit, Hunger, Rudiger.
Application Number | 20030216112 10/447387 |
Document ID | / |
Family ID | 7665052 |
Filed Date | 2003-11-20 |
United States Patent
Application |
20030216112 |
Kind Code |
A1 |
Gotze, Veit ; et
al. |
November 20, 2003 |
Cleaning device and method for cleaning polishing cloths used for
polishing semiconductor wafers
Abstract
A cleaning device is used to clean a polishing pad and has a
first cleaning system with a grinding wheel and a second cleaning
system with a distributor for discharging a gas-water mixture at
high pressure. The polishing pad, which is arranged on a polishing
table, can be set in rotary motion, so that the surface sections
that will be cleaned are first preliminarily cleaned by the
grinding wheel and are then subjected to a second cleaning by the
gas-water mixture of the distributor.
Inventors: |
Gotze, Veit; (Dresden,
DE) ; Hunger, Rudiger; (Radeberg, DE) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
POST OFFICE BOX 2480
HOLLYWOOD
FL
33022-2480
US
|
Family ID: |
7665052 |
Appl. No.: |
10/447387 |
Filed: |
May 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10447387 |
May 29, 2003 |
|
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PCT/DE01/04082 |
Oct 25, 2001 |
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Current U.S.
Class: |
451/56 ;
451/72 |
Current CPC
Class: |
B08B 1/04 20130101; B24B
57/02 20130101; B24B 53/017 20130101; B08B 3/02 20130101 |
Class at
Publication: |
451/56 ;
451/72 |
International
Class: |
B24B 001/00; B24B
007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2000 |
DE |
100 59 180.9 |
Claims
We claim:
1. A cleaning device for cleaning a polishing pad, comprises: a
first cleaning system including a grinding wheel; and a second
cleaning system including a distributor for discharging a gas-water
mixture under high pressure; said distributor having an elongate
shape; said distributor having an outlet side with a plurality of
nozzles; said distributor positionable above a surface of the
polishing pad that will be cleaned while located next to an axis of
rotation of the polishing pad; and said distributor extending in a
longitudinal direction not aligned with the axis of rotation of the
polishing pad.
2. The cleaning device according to claim 1, wherein: the polishing
pad is positionable such that the surface of the polishing pad
faces said grinding wheel and said outlet side of said distributor;
said first cleaning system includes a holding arm for positioning
said grinding wheel opposite a first section of the surface of the
polishing pad; said second cleaning system includes a holding arm
for positioning said distributor opposite a second section of the
surface of the polishing pad; and said polishing pad is mounted to
rotate about the axis of rotation.
3. The cleaning device according to claim 2, wherein at least one
holding arm, which is selected from a group consisting of said
holding arm of said first cleaning system and said holding arm of
said second cleaning system, is pivotable.
4. The cleaning device according to claim 2, further comprising: a
spray nozzle secured to said holding arm of said first cleaning
system; said spray nozzle for washing off abrasive particles that
have been removed from the surface of the polishing pad by said
grinding wheel.
5. The cleaning device according to claim 2, further comprising a
liquid nozzle configured for applying a liquid to a third section
of the surface of the polishing pad.
6. The cleaning device according to claim 5, wherein the liquid is
water.
7. The cleaning device according to claim 1, in combination with
the polishing pad, wherein: the polishing pad is a substantially
circular polishing pad; and said grinding wheel and said
distributor are configured at different circumferential sections of
the polishing pad.
8. The cleaning device according to claim 1, in combination with
the polishing pad, wherein: the polishing pad is a substantially
circular polishing pad; the cleaning device includes a liquid
nozzle that is configured to apply a liquid to the surface of the
polishing pad; and said grinding wheel, said distributor, and said
liquid nozzle are configured at different circumferential sections
of the polishing pad.
9. The cleaning device according to claim 1, in combination with
the polishing pad, wherein the polishing pad is a polishing
cloth.
10. A method for cleaning a polishing pad, which comprises:
constructing a cleaning device from a first cleaning system having
a grinding wheel, and a second cleaning system having a distributor
for discharging a gas-water mixture under high pressure;
configuring the distributor with an elongate shape and configuring
the distributor with an outlet side having a plurality of nozzles;
providing the cleaning device for cleaning the polishing pad;
positioning the distributor above a surface of the polishing pad
that will be cleaned such that the distributor is located next to
an axis of rotation of the polishing pad and a longitudinal
direction of the distributor is not aligned with the axis of
rotation of the polishing pad; and simultaneously or alternately,
grinding down the surface of the polishing pad and directing the
gas-water mixture under high pressure onto the surface of the
polishing pad.
11. The method according to claim 10, which comprises:
simultaneously, grinding down a first section of the surface of the
polishing pad and directing the gas-water mixture onto a second,
different section of the surface of the polishing pad; and setting
the polishing pad into rotary motion about the axis of rotation so
that substantially each section of the surface of the polishing pad
is subjected to both the grinding down and the gas-water mixture at
least once.
12. The method according to claim 10, which comprises first
grinding down the surface of the polishing pad and subsequently
directing the gas-water mixture onto the surface of the polishing
pad.
13. The method according to claim 10, which comprises alternately
grinding down the surface of the polishing pad and subsequently
directing the gas-water mixture onto the surface of the polishing
pad a number of times in succession.
14. The method according to claim 10, which comprises washing the
surface of the polishing pad with a targeted water jet.
15. The method according to claim 10, which comprises using a
targeted water jet to wash a surface of the polishing pad that had
shortly beforehand been acted on by the gas-water mixture.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of copending
International Application No. PCT/DE01/04082, filed Oct. 25, 2001,
which designated the United States and was not published in
English.
BACKGROUND OF THE INVENTION
[0002] Field of the Invention
[0003] The present invention relates to a cleaning device and to a
method that includes using the cleaning device to clean polishing
pads, in particular polishing cloths that are used for chemically
mechanically polishing semiconductor wafers during a fabrication
process.
[0004] In the semiconductor industry, the demand for increasingly
smaller feature sizes and an increasing yield in semiconductor
wafers means that, in addition to process control, a reduction in
the defect density on the wafers is becoming increasingly
important. During a process of patterning and processing a
semiconductor surface, it is possible to provide for certain
materials to be abraded using a polishing pad, for example, a
polishing cloth, by chemical mechanical polishing or the like.
[0005] Examples of known devices used for this purpose are the
IPEC/Westech 472, which is a device used specifically for the
chemical mechanical polishing of silicon wafers. The polishing
process carried out using this device is a single-wafer process in
which the product side of the wafer is subjected to chemical
mechanical polishing. However, the abraded material produced in
this polishing process accumulates in the polishing pad. These
accumulations of material may have adverse effects on the polishing
of subsequent wafers, for example, as a result of forming scratches
on the surface of these wafers. The problem arises in particular in
the case of Cu processes, since contamination of a silicon wafer
which is subsequently polished can lead to components on this
silicon wafer failing.
[0006] To reduce contamination of subsequent wafers caused by
material abraded from wafers that have been polished previously and
to limit the load on the polishing pad caused by abrasion, the
polishing pad has hitherto been changed very frequently. However,
in general terms this constitutes a drawback, since the resultant
costs and changeover times have a significant effect on the
performance of the polishing process.
[0007] Therefore, it has already been proposed for the polishing
pads used in the polishing process to be cleaned to remove the
accumulated abraded material and residues of the slurry used in the
chemical mechanical polishing. Published German Patent Application
DE 197 37 854 A1, which is hereby incorporated by reference in the
content of the present application, describes a device for cleaning
a polishing pad, for example, a polishing cloth for polishing
wafers. This device is substantially formed by a distributor for
discharging a gas-water mixture at a high pressure. The gas-water
mixture is atomized and sprayed onto the polishing pad that is to
be cleaned via nozzles that are arranged on the outlet side of the
distributor. Furthermore, there is a blasting nozzle for blasting a
targeted jet of water onto the polishing pad that is to be cleaned.
The targeted jet of water is likewise discharged from the blasting
nozzle at a high pressure. Although in principle this cleaning
device allows thorough cleaning of the surface of the polishing
pad, it has been found that the cleaning process is ineffective,
since particles of materials which have become fixed to the
polishing pad can only be removed by a relatively high consumption
of the gas-water mixture.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
cleaning device and a method of using the cleaning device to clean
a polishing pad, which overcomes the above-mentioned disadvantages
of the prior art apparatus and methods of this general type.
[0009] In particular, it is an object of the invention to provide a
cleaning device for cleaning polishing pads, in particular
polishing cloths, which enables the surface of the polishing pads
to be cleaned thoroughly and effectively.
[0010] With the foregoing and other objects in view there is
provided, in accordance with the invention, a cleaning device for
cleaning a polishing pad. The cleaning device includes: a first
cleaning system including a grinding wheel; and a second cleaning
system including a distributor for discharging a gas-water mixture
under high pressure. The distributor has an elongate shape. The
distributor has an outlet side with a plurality of nozzles. The
distributor is positionable above a surface of the polishing pad
that will be cleaned such that the distributor is located next to
an axis of rotation of the polishing pad. The distributor extends
in a longitudinal direction not aligned with the axis of rotation
of the polishing pad.
[0011] The present invention is based on the fundamental idea of
cleaning the polishing pads using substantially two cleaning
systems. A first cleaning system is-responsible for a preliminary
or rough cleaning of the surface of the polishing pad and a second
cleaning system is responsible for further cleaning of the surface.
The first cleaning system substantially includes a rotating
grinding wheel for grinding down the surface of the polishing pad.
By contrast, the second cleaning system substantially includes the
distributor for discharging a gas-water mixture onto the surface of
the polishing pad, which is known per se in the prior art and is
described in the abovementioned Published German Patent Application
DE 197 37 854 A1.
[0012] A corresponding method for cleaning the surface of the
polishing pad can take place in such a way that, in a first
cleaning step, first of all, the entire surface of the polishing
pad is ground down, and then, in a second cleaning step, the
surface is acted on by the gas-water mixture under high pressure.
If appropriate, the two cleaning steps can be carried out
alternately a number of times in succession.
[0013] In an advantageous embodiment of the cleaning method,
however, the two cleaning steps are carried out simultaneously, in
which case, simultaneously, different sections of the surface are
either ground down or acted on by the gas-water mixture, and the
polishing pad is set in rotary motion about a main axis, so that
substantially each section of the surface is subjected to both
cleaning steps at least once.
[0014] For this purpose, the cleaning device is preferably designed
in such a way that the polishing pad that will be cleaned can be
positioned in such a manner that the surface of the polishing pad
that will be cleaned faces the grinding wheel and the outlet side
of the gas-water mixture from the distributor. The grinding wheel
and the distributor are each secured to holding arms in such a
manner that they are located opposite different sections of the
surface of the polishing pad. The polishing pad is mounted such
that it can rotate about a main axis. In this case, at least one of
the holding arms for the grinding wheel and the distributor can be
arranged pivotably. In addition, a spray nozzle for washing off
abrasive particles that have been removed from the surface of the
polishing pad by the grinding wheel can be secured to the holding
arm of the grinding wheel.
[0015] The cleaning device may additionally include a liquid
nozzle, through which a further section of the surface of the
polishing pad can be acted on by a liquid, in particular water. As
a result, the surface of the polishing pad, in particular a surface
section which has just been polished with a gas-water mixture, can
be washed using a targeted water jet from the liquid nozzle.
[0016] Since the polishing pads that are used for chemical
mechanical polishing processes in semiconductor process technology
in many cases are round, substantially in the shape of the
semiconductor wafer, the cleaning device is preferably designed in
such a way that a circular polishing pad can be mounted in it for a
cleaning process. The circular polishing pad is preferably placed
on a rotatably mounted base. In this case, the grinding wheel, the
distributor and if appropriate the liquid nozzle can then be
arranged at different circumferential sections of the circular
polishing pad. The arrangement of these components and the rotary
motion of the polishing pad are preferably such that the surface
sections are subjected to a cleaning treatment by the grinding
wheel, are then acted on by the gas-water mixture, and finally are
washed by the targeted water jet from the liquid nozzle.
[0017] Both the grinding wheel and the distributor may be secured
to their respective holding arms in such a manner that they can be
displaced along the holding arm.
[0018] The distributor for discharging a gas-water mixture may be
designed as described in the abovementioned Published German Patent
Application DE 197 37 854 A1. The entire content of this document,
but in particular the sections which relate to the structure of the
distributor for the gas-water mixture and the provision of the
gas-water mixture in the distributor, are hereby incorporated by
reference into the present application. In particular, a gas feed
line and a water feed line are arranged on the inlet side of the
distributor. The individual components of the gas-water mixture are
fed into the distributor from different sources through the water
feed line and the gas feed line. On an outlet side of the
distributor, there is a multiplicity of nozzles that are used to
discharge the gas-water mixture to the outside and/or to atomize
this mixture.
[0019] The cleaning device according to the invention and the
corresponding cleaning method enable abraded particles which are
located on the polishing pad to be removed from the polishing pad
in a way which is simultaneously thorough and effective. At the
same time, the risk of contamination to wafers which are
subsequently to be processed as a result of abrasion from wafers
which have previously been polished is greatly reduced. The fact
that first of all each surface section which is to be cleaned is
subjected to preliminary cleaning by being ground down by means of
the grinding wheel and is only then subjected to further cleaning
by means of the distributor allows the cleaning process as a whole
to be carried out very efficiently and the consumption of the
gas-water mixture for the distributor to be reduced.
[0020] With the foregoing and other objects in view there is
provided, in accordance with the invention, a method for cleaning a
polishing pad. The method includes: providing the cleaning device
that has been described above; positioning the distributor above a
surface of the polishing pad that will be cleaned such that the
distributor is located next to an axis of rotation of the polishing
pad and a longitudinal direction of the distributor is not aligned
with the axis of rotation of the polishing pad; and simultaneously
or alternately, grinding down the surface of the polishing pad and
directing the gas-water mixture under high pressure onto the
surface of the polishing pad.
[0021] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0022] Although the invention is illustrated and described herein
as embodied in a cleaning device for cleaning polishing cloths used
for polishing semiconductor wafers, it is nevertheless not intended
to be limited to the details shown, since various modifications and
structural changes may be made therein without departing from the
spirit of the invention and within the scope and range of
equivalents of the claims.
[0023] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a diagrammatic cross-sectional view of an
exemplary embodiment of a cleaning device; and
[0025] FIG. 2 is a plan view of the cleaning device shown in FIG.
1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Referring now to the figures of the drawing in detail and
first, particularly, to FIG. 1 thereof, there is diagrammatically
shown, a cross section through an exemplary embodiment of a
cleaning device for cleaning a polishing cloth 12 arranged on a
polishing table 11. FIG. 2 shows a plan view of the cleaning
device, illustrating the arrangement of the individual cleaning
elements relative to one another and relative to the surface of the
polishing cloth 12 that will be cleaned.
[0027] The cleaning device substantially includes a first cleaning
system 5 for preliminarily cleaning the surface of the polishing
pad 12 and a second cleaning system 2 for carrying out further
cleaning. The first cleaning system 5 includes a circular grinding
wheel 50 which is set in rotary motion during the cleaning
operation. The grinding wheel 50 is secured to a pivotable holding
arm 51 and can be displaced along the holding arm 51 (See FIG. 2
which shows the grinding wheel depicted in dashed lines at another
position along the holding arm). At the start of a cleaning
operation using the first cleaning system 5, the holding arm 51 is
pivoted in so that the grinding wheel 50 is positioned above the
surface of the polishing pad 12, whereupon the grinding wheel 50 is
placed onto the polishing pad 12 with a defined pressure. The
grinding wheel 50 is a circular wheel that is provided with a
special, rough diamond-coated surface and roughens the surface of
the polishing pad 12 resulting from its rotary motion. In addition
a spray nozzle 52 (See FIG. 2) is secured to the holding arm 51.
The spray nozzle 52 uses a liquid jet 52A to wash the abrasive
particles that have been loosened from the polishing pad 12 by the
roughening operation of the surface of the grinding wheel 50.
[0028] The second cleaning system 2 substantially includes a
distributor 20 that is secured to a holding arm 25 (See FIG. 2). In
the present exemplary embodiment, the holding arm 25 is arranged
immovably. However, it may also be provided in such a way that the
holding arm 25 of the second cleaning system 2 is also pivotable.
On its outlet side 22, the distributor 20 has a multiplicity of
nozzles 23. A gas feed line 40 and a water feed line 41 are
arranged on the inlet side 21 of the distributor 20. The gas feed
line 40 is connected to a nitrogen source (not shown), while the
water feed line 41 is connected to a water source (not shown). The
flow rates in the lines 40, 41 can be set by using corresponding
valves 42, 43, for example, manually actuated valves. To generate a
suitable pressure in the gas feed line 40 and the water feed line
41, there is a compressed-air source or other inert-gas source (not
shown), which is connected via a compressed-air control device 44
and in particular by device of a compressed-air control device 44a
and a valve 45, to the water feed line 41, and via a compressed-air
control device 44b and a valve 46 to the gas feed line 40.
[0029] Deionized water under high pressure is mixed with ultrapure
nitrogen in the distributor 20 of the second cleaning system 2, and
the gas-water mixture is sprayed through the nozzles 23 in a
targeted manner onto the surface of the polishing pad 12. By using
a suitable setting of the valves 42 and 43, a defined incoming flow
of nitrogen is set in the gas feed line 40 and a defined incoming
flow of deionized water is set in the water feed line 41. The
components located in the lines 40 and 41 are acted on by
compressed air via the compressed-air control devices 44, 44a, 44b
and a corresponding position of the valves 45, 46, so that the
components, when they enter the distributor 20, are in each case at
a pressure of, for example, 413.7 kPa (60 psi). After they have
entered the distributor 20 at its inlet side 21, the components are
mixed to form the gas-water mixture, for example, at the pressure
mentioned. Then, the mixture is sprayed through the slot nozzles 23
onto the polishing cloth 12 that will be cleaned. The atomization
of the deionized water and of the nitrogen just before they are
discharged from the spray nozzles 23 results in the production of
extremely small, highly effective drops having a kinetic energy
which leads to loosening the particles which have become jammed and
blasting the particles out of the polishing cloth 12.
[0030] Furthermore, the cleaning device has a blasting nozzle 30,
from which a targeted water jet 30A is directed onto the polishing
cloth 12 at an acute angle of less than 45.degree.. The targeted
water jet 30A is likewise at an elevated pressure. The targeted
water jet 30A washes the particles that have been detached by the
distributor 20 off of the surface of the polishing pad 12. This has
the advantage that cleaning is achieved without damage to the very
sensitive polishing pad surface.
[0031] In order, for example, for residues of a CMP (chemical
mechanical polishing) process on the polishing pad 12 to be
eliminated as effectively as possible, the two cleaning systems 2
and 5 can be used in parallel. In this case, first of all, the
grinding wheel 50 is used to carry out intensive preliminary
cleaning. A second intensive cleaning step is then carried out by
the distributor 20. For this purpose, the polishing pad 12, which
is arranged on the rotatable polishing table 11, is set in rotary
motion in the counterclockwise direction (as indicated in FIG. 2 by
the reference character 12a). The distributor 20 has been designed
in such a way that the spray area cleans the rotating polishing pad
12 over a length of 130 mm. The direction of rotation of the
polishing table 11 is matched to the arrangement of the cleaning
elements, i.e. the grinding wheel 50, the distributor 12, and the
blasting nozzle 30. A section which has been cleaned by the
grinding wheel 50 is inevitably, on account of the rotary motion,
guided under the blasting area of the distributor 20, at which time
the second cleaning step takes place, after which the particles
which have been detached are washed off of the surface of the
polishing pad 12 by the water jet 30A from the blasting nozzle
30.
[0032] In an alternate embodiment, it is also possible for the
holding arm 25 of the second cleaning system likewise to be
pivotable and initially to be in a pivoted-out position. The two
cleaning steps may be carried out separately, in which case, first
of all, in a first cleaning step, substantially the entire surface
of the polishing pad 12 is ground down by the grinding wheel 50
that is secured to the holding arm 51 that has been pivoted in.
After the first cleaning step has been carried out, the holding arm
51 of the first cleaning system can then be pivoted away and the
holding arm 25 of the second cleaning system can be pivoted in,
whereupon substantially the entire surface is subjected to a second
cleaning step as a result of the surface being acted on by the
gas-water mixture from the distributor 20.
* * * * *