U.S. patent application number 11/205382 was filed with the patent office on 2007-02-22 for method and apparatus for cleaning slurry depositions from a water carrier.
Invention is credited to Andres B. Garcia, Frank Miceli, Jose Omar Rodriguez, Margareth Seputro, Charles A. Storey.
Application Number | 20070042686 11/205382 |
Document ID | / |
Family ID | 37696570 |
Filed Date | 2007-02-22 |
United States Patent
Application |
20070042686 |
Kind Code |
A1 |
Rodriguez; Jose Omar ; et
al. |
February 22, 2007 |
METHOD AND APPARATUS FOR CLEANING SLURRY DEPOSITIONS FROM A WATER
CARRIER
Abstract
Disclosed herein is a process for diminishing contamination of
an integrated circuit wafer caused by residual slurry components
disposed on a back side of a carrier for engaging an integrated
circuit wafer. Also disclosed is a CMP machine configured to wash a
back side of a carrier.
Inventors: |
Rodriguez; Jose Omar;
(Orlando, FL) ; Storey; Charles A.; (Orlando,
FL) ; Garcia; Andres B.; (Ocoee, FL) ;
Seputro; Margareth; (Orlando, FL) ; Miceli;
Frank; (Orlando, FL) |
Correspondence
Address: |
HITT GAINES, PC;AGERE SYSTEMS INC.
PO BOX 832570
RICHARDSON
TX
75083
US
|
Family ID: |
37696570 |
Appl. No.: |
11/205382 |
Filed: |
August 17, 2005 |
Current U.S.
Class: |
451/41 ; 451/288;
451/67 |
Current CPC
Class: |
B08B 3/02 20130101; B24B
55/00 20130101; B24B 37/345 20130101 |
Class at
Publication: |
451/041 ;
451/067; 451/288 |
International
Class: |
B24B 7/30 20060101
B24B007/30; B24B 7/00 20060101 B24B007/00; B24B 29/00 20060101
B24B029/00 |
Claims
1. A process for in situ cleaning of a back side of a carrier used
in a CMP tool for holding a semiconductor integrated circuit wafer
onto a polishing pad during a polishing process of the wafer
without interrupting a normal process flow in the CMP tool, wherein
the polishing process employs a slurry containing abrasives which
can be deposited on both a front and back surface of the wafer
carrier, the cleaning process comprising introducing a spray to
wash the back surface of said carrier at a predetermined time in
the process flow so as to remove slurry from the back side of the
carrier whereby contamination of the polishing pad with
agglomerated slurry abrasives is avoided, wherein said spray
washing of the carrier back surface comprises spraying through a
back side spray nozzle mounted within said CMP tool and wherein the
carrier is held by a spindle that is mounted to a turret and
wherein the back side spray nozzle is mounted to the turret.
2. The cleaning process of claim 1 wherein the CMP tool includes a
plurality of spray nozzles for directing a fluid over the front
surface of the carriers at a time when the carriers are not loaded
with a wafer, the process including spray washing the back surface
of the carriers concurrently with spray washing of the front
surface.
3. The process of claim 2, wherein said fluid is deionized
water.
4. (canceled)
5. (canceled)
6. The process of claim 1, wherein said slurry components comprise
silica.
7. A CMP tool having a polishing area containing a spinning
polishing pad and a slurry dispensing system for introducing a
slurry containing an abrasive onto the polishing pad, the tool
further having a semiconductor wafer loading and unloading area
including an indexing table containing defined areas for holding
wafers to be polished and for receiving wafers that have been
polished, the tool including a transport apparatus moveable between
the polishing area and the indexing table, the transport apparatus
including a turret having a plurality of wafer carriers coupled
thereto and driving mechanism for effecting spinning of the
carriers when the carriers are positioned over the polishing pad,
the tool further having a plurality of spray nozzles fixed to the
indexing table for directing a spray of fluid onto the lower front
surface of the carriers as the carriers are transitioned from an
unloading area to a loading area over the indexing table, and a
plurality of fluid spray nozzles mounted on the turret and
positioned to direct a spray of fluid onto the upper back surface
of the carriers concurrently with spraying of fluid onto the front
surface of the carriers whereby slurry accumulating on the front
and back surfaces of the carrier are washed away over the indexing
table.
8. (canceled)
Description
[0001] Conventional chemical/mechanical polishing (CMP) is used to
create smooth topographies of the various layers of a semiconductor
integrated circuit wafer during semiconductor device manufacture.
The CMP process involves holding and rotating, using a wafer
carrier, semiconductor wafer against a rotating polishing pad. The
wafer carrier is typically a plate-like structure having a diameter
slightly larger than the semiconductor wafer. The carrier is
attached to a positioning device through a gimbal on its back side
surface that allows the carrier to be spun and to pivot on the
gimbal. The polishing pad, which is conventionally an open-celled,
polyurethane pad affixed to a polishing platen, is wetted by a
chemical slurry, under controlled chemical, pressure, and
temperature conditions. The chemical slurry contains selected
chemicals which etch or oxidize selected surfaces of the wafer
during CMP in preparation for their mechanical removal. The slurry
also contains a polishing agent, such as alumina or silica that is
used as the abrasive material for the physical removal of the
etched/oxidized material. The combination of chemical and
mechanical removal of material during polishing results in superior
planarization of the polished surface. In this process it is
important to remove a sufficient amount of material to provide a
smooth surface, without removing an excessive amount of underlying
materials at each level of the manufacturing process to insure
uniform and accurate formation of the semiconductor device at all
subsequent levels. Accurate material removal is particularly
important in today's sub-quarter micron technologies where it is
critical to minimize thickness variation because the metal lines
are thinner.
[0002] The inventors have discovered that the slurry sometimes
splashes on the or back-side surface of the carrier during CMP.
Further, when this splashed slurry dries, the silica and/or other
components in the slurry become a contamination issue. Dried silica
particles falling on the polishing pad is one of the causes of
wafer scratches and failing particle counts when process checking a
tool. The scratching results in potential wafer yield losses. The
failing particle counts during process checking results in
diminished tool availability since the tool must be taken out of
production and cleaned.
SUMMARY OF THE INVENTION
[0003] According to one aspect, the subject invention pertains to a
process of cleaning slurry from a back-side of a carrier used for
transporting a wafer without having to interrupt the conventional
CMP process. This process involves spraying the back-side of the
carrier with a cleaning fluid at a predetermined time that is
coordinated so as not to interfere with the CMP process. A specific
aspect of the invention pertains to a process comprising spray
washing the back side of a carrier concurrently with a conventional
spray washing of a front side of the carrier at a time between
unloading and loading of wafer from the carrier. In this form, no
additional steps are needed to effect cleaning of the carrier so
that the cycle time of the CMP process is not effected.
[0004] Another aspect of the invention pertains to a CMP machine
comprising a spray nozzle associated with the CMP machine such that
fluid is ejected out of the nozzle and aimed at the back side of a
carrier so as to wash off undesired slurry components. The spray
nozzle may be mounted to the CMP machine and connected to a fluid
source. Typically, CMP tools comprise a polishing area in which the
CMP process is conducted and an indexing area in which wafers are
loaded into and unloaded from the wafer carrier. In a specific
embodiment, the spray nozzle is mounted within the indexing area
such that it directs fluid to the area of need on the carrier, such
as the back side of the carrier. The indexing area includes spray
nozzles and a spray wash process that washes slurry from the front
or wafer contact surface of the carrier during a time between
unloading of a polished wafer and loading of a next wafer to be
polished. Applicants have modified the CMP tool by addition of a
coupling from the front wafer wash source to a back wafer wash
distribution system. The system includes flexible tubing and a
plurality of spray nozzles mounted to the support mechanism for the
wafer carriers. When the system actuates the fluid source for the
front carrier wash, a flow of fluid is directed to the added tubing
and nozzles to that fluid is sprayed onto the back side of the
wafer carriers. Accordingly, both the back side and front side of
the carriers are washed concurrently.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a top plan view of one form of CMP tool with which
the present invention may be used; and
[0006] FIG. 2 is an elevation view taken along the lines 2-2 of
FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0007] Referring now to FIGS. 1 and 2, FIG. 1 being highly
simplified top plan view and FIG. 2 being an elevation view from
the line 2-2, there is shown one form of a CMP machine 10 including
a polishing pad 12 and an indexing table 14. Above the indexing
table is positioned a movable turret 16 to which is attached a
plurality of wafer carriers 18. The turret 16 is essentially a
plate-like structure having a plurality of wafer carriers 18
mounted thereon. Not shown in either of these views is the mounting
mechanism for the wafer carriers which generally comprises a
plurality of arms that pass through the turret 16 and are attached
to each of the carrier heads through a gimbal (not shown). The
attachment through the gimbal allows each of the carriers to be
spun at a relatively high speed to achieve the uniform polishing
when the turret is moved into the polishing position over the
polishing pad 12. For a more detailed description of the exemplary
machine 10, reference may be had to U.S. Pat. No. 6,520,839.
[0008] The turret 16 is provided with a plurality of
circumferentially spaced slots 20 that provide a path for the
carriers 18 to be moved from a radially outward position around the
turret to a radially inner position. The inner position is used
solely for the purpose of transporting the turret from a loading
and an unloading position over the indexing table to a polishing
position over the polishing pad 12. The carriers are normally
positioned in the outer extreme of each of the slots 20 during the
polishing operation at the pad 12 and during the unloading and
loading functions over the index table 14. During the CMP polishing
process, a slurry flows over the polishing pad 12 and is used to
achieve polishing of the semiconductor wafers. This slurry
accumulates on both the wafers and the carriers 18. When the turret
16 is transported back to the indexing table for unloading of the
polished wafers, the wafers are unloaded into corresponding ones of
a plurality of plastic cups that are located on the indexing table
and are indicated in FIG. 1 at 22. The cups 22 define wafer loading
and unloading stations. Commonly, the indexing table has an outer
wall 24 and an inner wall 26 which defines a trough in which the
plastic cups reside. This trough is generally filled with a
cleaning fluid, typically water, which is constantly circulated and
cleaned and is used to clean the slurry from the wafers. However,
the carriers 18 do not protrude into the water on the indexing
table and are therefore not cleaned when the wafers are unloaded.
As a consequence, it is necessary to clean the carriers 18 between
the steps of unloading polished wafers and loading new wafers to be
polished. As shown in FIG. 2, there are multiple spaced spray
nozzles 30 located on the indexing table that are angled upward and
positioned between the respecting loading and unloading stations
for cleaning the underside of the carriers 18. More particularly,
once the carriers 18 have unloaded the wafers, the turret 16 is
rotated so that the carriers are positioned between loading and
unloading cups 22 and a corresponding one of the spray nozzles
sprays a stream of water upward onto the lower face of a respective
one of the carriers to wash any slurry away from the carriers so
that the slurry will not interfere with the loading of a subsequent
wafer into the carrier.
[0009] In order to improve this cleaning process, applicant's have
attached another plurality of spray nozzles 32 onto the turret 16
and positioned the nozzles to aim downward toward the backs of the
carriers 18 so that a spray of water can be directed onto the back
of the carriers at the same time that the front face of the
carriers is washed by the spray from the nozzles 30. This process
removes any slurry or dried slurry compound from the backside of
the wafer carriers so that such compound is not carried back to the
polishing pad 12 when a next group of wafers are loaded and
transported for polishing. It will be appreciated that the water
for washing the back side of the wafer carriers 18 may come from
the same source as the water used for washing the front face of the
carrier by simply splitting off from the water source and coupling
through a flexible tube to a distribution system mounted to the top
of the turret 16. Such a system is indicated generally at 34.
[0010] The present invention provides a method and apparatus
associated with the CMP machine 10 for assuring that the slurry
which is routinely deposited on the back side of the carriers 18 is
removed from those carriers at the indexing station so that when
the carriers are next positioned over the polishing pad 12, dried
material from the back of the carriers will not be deposited on the
polishing pad. It will be appreciated that any such dried material
could scratch the semiconductor wafers during the polishing
process.
[0011] Those skilled in the art will appreciate in view of the
teachings herein that different types of CMP machines (or tools)
may be configured to implement a spray function designed for
washing the back side of a carrier in conjunction with the
polishing process. CMP machines may be equipped with one or more
spray nozzles and configured such that fluid is ejected out of the
nozzle and aimed at the back side of a carrier so as to wash off
undesired slurry components. The spray nozzle may be mounted to the
CMP machine and connected to a fluid source. The functioning of the
CMP process is typically coordinated by software. CMP machine
software may be configured to include the function of actuating the
spraying of fluid out the spray nozzle at an appropriate time
during a normal routine of a CMP machine. Furthermore, existing
machines may be retrofitted with a spray nozzle and their software
reconfigured to implement the spraying of the back of a
carrier.
[0012] While the invention has been described in what is presently
considered to be preferred embodiment, other modifications and
variations will become apparent to those skilled in the art. It is
intended therefore that the invention not be limited to the
specific disclosed embodiment but be interpreted within the full
spirit and scope of the appended claims.
* * * * *