U.S. patent application number 10/630039 was filed with the patent office on 2005-02-03 for method to improve control in cmp processing.
Invention is credited to Berman, Michael J>, Trattles, Mathew R..
Application Number | 20050026551 10/630039 |
Document ID | / |
Family ID | 34103746 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050026551 |
Kind Code |
A1 |
Berman, Michael J> ; et
al. |
February 3, 2005 |
Method to improve control in CMP processing
Abstract
A method and apparatus for adding slurry using a moveable
outlet, such as one or more moveable arms, in a semiconductor wafer
polishing system. The end of the slurry arm could be set to fan out
the slurry as the slurry is dispensed onto the pad. Preferably, the
arm is set so that the distance and centering of the arm is
controlled by the setup of the process. The arm could be set to
move in an arc, or to move in and out on a set track. Regardless,
the slurry is preferably sprayed onto the pad in the location
needed to place the slurry on the pad, but only in the areas that
are needed. This increases the control of the uniformity of the
process, and preferably reduces the total amount of slurry that is
used in the process.
Inventors: |
Berman, Michael J>; (West
Linn, OR) ; Trattles, Mathew R.; (Troutdale,
OR) |
Correspondence
Address: |
LSI LOGIC CORPORATION
1621 BARBER LANE
MS: D-106
MILPITAS
CA
95035
US
|
Family ID: |
34103746 |
Appl. No.: |
10/630039 |
Filed: |
July 30, 2003 |
Current U.S.
Class: |
451/41 ; 451/287;
451/446; 451/60 |
Current CPC
Class: |
B24B 37/04 20130101;
B24B 57/02 20130101 |
Class at
Publication: |
451/041 ;
451/287; 451/060; 451/446 |
International
Class: |
B24B 001/00; B24B
029/00 |
Claims
What is claimed is:
1. A method of wetting a semiconductor wafer, said method
comprising: using a wafer carrier to hold the wafer to a polishing
pad; dispensing a chemical through at least one outlet to the
polishing pad; and moving the at least one outlet while dispensing
the chemical.
2. A method as recited in claim 1, wherein the step of dispensing a
chemical comprises dispensing a slurry.
3. A method as recited in claim 1, wherein the step of moving the
at least one outlet comprises moving the outlet in an arc
motion.
4. A method as recited in claim 1, wherein the step of moving the
at least one outlet comprises moving the outlet in a back and forth
motion.
5. A method as recited in claim 1, wherein the polishing pad is
disposed on a polishing table and said method further comprises
rotating at least one of the wafer carrier and the polishing
table.
6. A method as recited in claim 1, wherein the step of dispensing a
chemical through at least one outlet comprises dispensing a
chemical through a plurality of outlets to the polishing pad; and
moving the outlets while dispensing the chemical.
7. A method as recited in claim 1, further comprising providing at
least one moveable arm which carries said at least one outlet.
8. A method as recited in claim 7, further comprising moving said
at least one moveable arm while dispensing the chemical.
9. A method as recited in claim 8, further comprising moving the at
least one moveable arm in an arc motion.
10. A method as recited in claim 8, further comprising moving the
at least one moveable arm in a back and forth motion.
11. A machine for polishing a semiconductor wafer, said machine
comprising: a polishing pad; a wafer carrier configured to hold the
semiconductor wafer to the polishing pad; and at least one moveable
outlet configured to dispense a chemical to the polishing pad.
12. A machine as recited in claim 11, wherein the moveable outlet
is configured to move in an arc motion.
13. A machine as recited in claim 11, wherein the moveable outlet
is configured to move in a back and forth motion.
14. A machine as recited in claim 11, wherein the polishing pad is
disposed on a polishing table and at least one of the wafer carrier
and the polishing table is rotatable.
15. A machine as recited in claim 11, wherein the at least one
moveable outlet comprises a plurality of outlets.
16. A machine as recited in claim 11, further comprising at least
one moveable arm which carries said at least one outlet.
17. A machine as recited in claim 16, wherein the at least one
moveable arm is configured to move in an arc motion.
18. A machine as recited in claim 16, wherein the at least one
moveable arm is configured to move in a back and forth motion.
Description
BACKGROUND
[0001] The present invention generally relates to methods and
apparatuses for adding slurry to a semiconductor wafer polishing
system, and more specifically relates to a method for adding slurry
using a moveable outlet, such as one or more moveable arms, in a
semiconductor wafer polishing system.
[0002] An IC chip is a sandwiched, multiple layer structure which
typically includes a silicon substrate, dielectric layers, metal
interconnects, devices and so on. Every layer is formed by
deposition, photolithographic, etching, as well as other,
techniques. Every layer must be planar and, as the features get
smaller, the requirement for planarity gets more stringent.
Chemical Mechanical Polishing (CMP) plays an important part in
planarizing every layer before the next top layer is deposited. The
CMP process involves pressing the face of the wafer to be polished
against a compliant polymeric polishing pad and generating relative
motion between the interface between the wafer and the pad. A
slurry consisting of abrasives and chemicals is fed in between the
interface between the wafer and the pad. The combined chemical
action of the chemicals in the slurry and the mechanical action of
the abrasives cause material to be removed from the wafer. A
typical CMP setup looks very similar to a lapping machine, but the
precision is much higher and there is a lot more
sophistication.
[0003] One of the most commonly-used devices for polishing a
semiconductor wafer is a rotational format CMP machine as
illustrated in FIG. 1. The wafer 10 is held in a wafer carrier 12,
and is pressed against a polishing pad 14 which is disposed on a
polishing table 16. Both the wafer carrier 12 and polishing table
16 are then rotated (as indicated by arrows 18 in FIG. 1), and
slurry is supplied on the pad 14 via a stationary slurry dispense
line 20. The stationary slurry dispense line 20 is used to drip
slurry 22 on the pad 14 in front on the wafer 10. The process can
be manipulated by either increasing or reducing the slurry flow,
but this is not very stable, and does not provide much control.
[0004] In CMP processing, there is a need to control the removal
rate of the material being polished across the wafer. The need to
improve the control is due to many different reasons, including:
non-uniformity introduced in preceding steps, non-uniformity
inherent in the CMP process, and the need to tailor the output to
match the needs of a downstream process. An additional key need is
to reduce the cost and defects of the CMP process.
[0005] Many different ways have been attempted to change the
process uniformity, including: zone adjusting on the process head
(wafer carrier); changing the down force and RPM's of the wafer
carrier; changing the offset of the wafer with respect to the
retaining ring; and changing the radius that the slurry is added to
the platen. Each of the methods which have been attempted have
problems. For example, zone adjusting is limited to the maximum
that the head will permit. In some cases, more is needed. While
this is currently the best widely-used method, it can be expensive
to add to a tool. With regard to changing the down force and RPM's
of the wafer carrier, only a very small adjustment is possible
without reducing the rate of the process. With regard to changing
the offset of the wafer with respect to the retaining ring, this
can only affect the outer few millimeters of the wafer. It is also
a hardware adjustment which cannot be easily and quickly adjusted
(i.e., "on the fly"). It requires changing a major part of the
tool.
OBJECTS AND SUMMARY
[0006] An object of an embodiment of the present invention is to
provide a method and apparatus which allows a CMP process to be
more accurately controlled.
[0007] Another object of an embodiment of the present invention is
to provide a method and apparatus which provides better control
over the profile of the polish in a CMP process.
[0008] Still another object of an embodiment of the present
invention is to provide a method and apparatus which allows less
slurry to be used in a CMP process.
[0009] Yet another object of an embodiment of the present invention
is to provide a method and apparatus which reduces the amount of
defects in a CMP process.
[0010] Yet still another object of an embodiment of the present
invention is to provide a method and apparatus which provides less
dilution of the slurry when purging the line in a CMP process.
[0011] Briefly, and in accordance with at least one of the
foregoing objects, an embodiment of the present invention provides
a method and apparatus for adding slurry using a moveable outlet,
such as one or more moveable arms, in a semiconductor wafer
polishing system. The end of the slurry arm could be set to fan out
the slurry as the slurry is dispensed onto the pad. Preferably, the
arm is set so that the distance and centering of the arm is
controlled by the setup of the process. The arm could be set to
move in an arc, or to move in and out on a set track. Regardless,
the slurry is preferably sprayed onto the pad in the location
needed to place the slurry on the pad, but only in the areas that
are needed. This increases the control of the uniformity of the
process, and preferably reduces the total amount of slurry that is
used in the process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The organization and manner of the structure and operation
of the invention, together with further objects and advantages
thereof, may best be understood by reference to the following
description, taken in connection with the accompanying drawing,
wherein:
[0013] FIG. 1 illustrates a prior art rotational format CMP
machine;
[0014] FIG. 2 illustrates a CMP machine which is in accordance with
an embodiment of the present invention; and
[0015] FIG. 3 is a block diagram of a method which is in accordance
with an embodiment of the present invention, wherein the CMP
machine illustrated in FIG. 2 is used to polish a wafer.
DESCRIPTION
[0016] While the invention may be susceptible to embodiment in
different forms, there is shown in the drawings, and herein will be
described in detail, a specific embodiment with the understanding
that the present disclosure is to be considered an exemplification
of the principles of the invention, and is not intended to limit
the invention to that as illustrated and described herein.
[0017] FIG. 2 illustrates a CMP machine which is in accordance with
an embodiment of the present invention. As shown, the machine
includes a wafer carrier 12 for holding a wafer 10, wherein the
wafer carrier 12 presses the wafer 10 against a polishing pad 14
which is disposed on a polishing table 16. Both the wafer carrier
12 and polishing table 16 are then rotated (as indicated by arrows
18 in FIG. 2), and chemical such as slurry 22 is supplied on the
pad 14 via one or more moveable slurry dispense outlets 32 (two are
shown in FIG. 2).
[0018] As shown in FIG. 2, each moveable slurry dispense outlet 32
may be a line 36 on a moveable arm 38, where the moveable arm 38 is
configured to be moved in an arc (represented in FIG. 2 by arrows
40) or in and out on a set track (represented in FIG. 2 by arrows
42). Each of the outlets 32 can be configured to dispense an
appropriate slurry or other chemical, depending on the process and
application. Each moveable arm 38 could be set so that the distance
and centering of the arm 38 is controlled by the setup of the
process. As discussed above, this could be based on the arm
swinging in an arc or moving in and out on a set track.
[0019] FIG. 3 shows the steps of the process when the CMP machine
shown in FIG. 2 is used to polish a wafer. During the process,
preferably slurry is only sprayed where and when it is needed,
thereby increasing the control over the uniformity of the process,
reducing the total amount of slurry which is used, reducing the
overall cost of the process, and reducing the amount of defects
(i.e., due to the arm(s) being off the pad when it is being purged,
thereby keeping old dry slurry from being purged onto the pad).
Additionally, there is less dilution of the slurry when purging
from the line, as the purging can be performed over the side of the
pad, and not on the process area.
[0020] More than one moveable arm could be employed in the process,
and more than one type of slurry can be used, or water or a pH
buffer (that is the same as the slurry) can be used to dilute the
slurry at the point of use without changing the pH which is very
important for the process. The end of the arm could also be
configured to fan out the slurry as it is dispensed onto the pad,
thereby reducing the amount of slurry which is needed in the
process.
[0021] While an embodiment of the present invention is shown and
described, it is envisioned that those skilled in the art may
devise various modifications of the present invention without
departing from the spirit and scope of the appended claims.
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