U.S. patent application number 09/863559 was filed with the patent office on 2002-01-24 for control of cmp removal rate uniformity by selective heating of pad area.
Invention is credited to Swanson, Leland.
Application Number | 20020009953 09/863559 |
Document ID | / |
Family ID | 22787826 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020009953 |
Kind Code |
A1 |
Swanson, Leland |
January 24, 2002 |
Control of CMP removal rate uniformity by selective heating of pad
area
Abstract
A CMP machine (100, 200, 300) and/or process that uses selective
heating of the polishing pad/belt (120, 220, 320) to improve
uniformity. A heating mechanism (110) is used to heat a selected
area such as the perimeter (130, 230, 330) of the pad or belt (120,
220, 320). Heating the selected area improves the removal rate in
that area. For example, heating along the perimeter of the pad
(120, 220, 320) improves the removal rate at the perimeter of the
semiconductor wafer (150).
Inventors: |
Swanson, Leland; (McKinney,
TX) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
|
Family ID: |
22787826 |
Appl. No.: |
09/863559 |
Filed: |
May 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60211654 |
Jun 15, 2000 |
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Current U.S.
Class: |
451/53 |
Current CPC
Class: |
B24B 37/015 20130101;
B24B 49/14 20130101 |
Class at
Publication: |
451/53 |
International
Class: |
B24B 001/00 |
Claims
1. A method of fabricating an integrated circuit, comprising the
steps of: placing a wafer against a moving polishing pad while
adding a slurry and heating a selected portion of said polishing
piece.
2. The method of claim 1, wherein said polishing pad is a polishing
belt.
3. The method of claim 1, wherein said heating step is accomplished
using a heating mechanism comprising a plurality of heat lamps to
radiantly heat said polishing piece.
4. The method of claim 1, wherein said polishing piece is a
polishing pad and said heating is accomplished using heating wires
placed within the polishing pad.
5. The method of claim 1, wherein said selected portion comprises a
peripheral area of said polishing piece.
6. The method of claim 1, wherein said selected portion is heated
to a temperature on the order of 35.degree. C.
7. The method of claim 1, wherein said heating step supplies a
temperature gradient on the order of 15.degree. C.
8. A method of fabricating an integrated circuit, comprising the
steps of: providing a partially fabricated wafer to a wafer carrier
of a chemical-mechanical polish (CMP) machine; moving a polishing
piece of said CMP machine; adding slurry to a surface of said
polishing piece; placing said wafer against said surface while said
polishing piece is moving; providing a temperature gradient across
said surface of said polishing piece by heating a selected portion
of said polishing piece using a heating mechanism.
9. The method of claim 8, wherein said temperature gradient is
about 15.degree. C.
10. The method of claim 8, wherein said heating mechanism comprises
a plurality of heat lamps to radiantly heat said selected portion
of said polishing piece.
11. The method of claim 8, wherein said polishing piece is a
polishing pad and said heating mechanism comprises heating wires
placed within the polishing pad.
12. The method of claim 8, wherein said selected portion comprises
a peripheral area of said polishing piece.
13. A chemical-mechanical polish (CMP) machine comprising: a
platen; a polishing piece located over said platen; a wafer carrier
for holding a wafer against said polishing pad; and a heating
mechanism for establishing a temperature gradient across said
polishing piece by heating a selected portion of said polishing
piece.
14. The CMP machine of claim 13, wherein said polishing pad
comprises a polishing belt.
15. The CMP machine of claim 13, wherein said heating mechanism
comprises a plurality of heat lamps to radiantly heat said selected
portion of said polishing piece.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The following co-pending application is related and hereby
incorporated by reference:
1 Serial No. Filing Date Inventor(s) TI-30582 Swanson
FIELD OF THE INVENTION
[0002] The invention is generally related to the field of
semiconductor processing and more specifically to
chemical-mechanical polishing semiconductor wafers.
BACKGROUND OF THE INVENTION
[0003] Chemical-mechanical polishing (CMP) for planarizing
semiconductor wafers during fabrication is becoming more and more
common. A CMP system generally consists of a polishing pad, wafer
carrier, and slurry. As a wafer carrier positions a semiconductor
wafer against the polishing pad, slurry is added between the
polishing pad and the wafer. The wafer, the pad, or, more
typically, both are moved to planarize the surface of the wafer.
CMP employs both a mechanical removal of material (due to the
physical abrasion of the polishing pad and slurry particles against
the surface of the wafer) and a chemical removal (etch) of material
(due to the chemical components of the slurry).
[0004] Three basic types of architecture are currently being
manufactured. The first type is a rotary polisher. In a rotary
polisher, the platen (and the polishing pad it holds) has a radius
that is slightly larger than the diameter of the semiconductor
wafer. Both the platen and the wafer are typically rotated. The
second type of CMP machine is an orbital polisher. In an orbital
polisher, the platen diameter is slightly larger than the wafer
diameter. The wafer is rotated, but the pad is not. The wafer's
center orbits around an axis of rotation offset slightly from the
pad center. The third type of CMP machine is a linear belt
polisher. In a linear belt polisher, a continuously fed belt is
moved over the platen. The wafer is rotated during polishing.
[0005] The planarization uniformity on many polishing machines is
difficult to control. This can be due to such process
irregularities as pad conditioning, down force, and slurry
delivery. Hence, achieving good planarization across a wafer is
difficult. This is especially true for copper CMP, which is
currently under development.
SUMMARY OF THE INVENTION
[0006] The invention is an improved CMP machine and/or process that
uses selective heating of the polishing pad/belt to improve
uniformity. A heating mechanism is used to create a temperature
gradient across the polishing pad/belt by heating a selected area
such as the perimeter of the pad or belt. Heating the selected area
improves the removal rate in that area. For example, heating along
the perimeter of the pad improves the removal rate at the perimeter
of the semiconductor wafer.
[0007] An advantage of the invention is a CMP machine and/or
process having improved planarization uniformity.
[0008] This and other advantages will be apparent to those of
ordinary skill in the art having reference to the specification in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] In the drawings:
[0010] FIGS. 1A-1C are top views of a rotary polisher modified to
include a heating mechanism according to the invention;
[0011] FIGS. 2A-2B are top views of an orbital polisher modified to
include a heating mechanism according to the invention; and
[0012] FIGS. 3A-3B are top views of a belt polisher modified to
include a heating mechanism according to the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0013] The invention will now be described in conjunction with
three separate CMP machine architectures. It will be apparent to
those of ordinary skill in the art that the invention may be
applied to other machine architectures as well.
[0014] It is known that the copper removal rate during polish
increases as the pad and slurry temperature rises. This is due to
the fact that the chemical component of the CMP process is
thermally activated. In the invention, the temperature of selective
areas of the pad is adjusted to improve the uniformity across a
wafer during CMP. For example, heat may be applied to selective
areas the pad that correspond to areas of the wafer having a low
removal rate.
[0015] In copper CMP removal rate is lower near the edges of a
wafer (.about.2-5 cm inset from the edge of the wafer by a few mm)
than near the center of the wafer. In order to improve the removal
rate uniformity across the wafer, the area of the polishing pad
that polishes more of the edge of the wafer than the center is
heated. The heat, in turn, increases the removal rate in that area
making it more uniform across the wafer.
[0016] FIGS. 1A-C show a rotary polisher 100 modified to include a
heating mechanism 110 for heating selective areas of the polishing
pad 120. In a rotary polisher 100, the platen 140 had a radius that
is slightly larger than the wafer 150 diameter. Platen 140 is used
to hold pad 120. Wafer 150 is held against polishing pad 120 and
rotated by a wafer carrier (not shown).
[0017] Heating mechanism 110 heats selective areas of the polishing
pad 120 where an increased removal rate is desired. For example, in
copper CMP the removal rate is lower near the edge of the wafer.
Therefore, to improve this non-uniformity, the periphery 130 of the
polishing pad 120 is heated since this area contacts the outer
portions of the wafer 150.
[0018] Heating mechanism 110 may be located within platen 140 as
shown in FIG. 1A. In this case, heating mechanism 110 could include
an array of heaters 112. Alternative heating mechanisms will be
apparent to those of ordinary skill in the art. For example,
heating mechanism 110 may be located above pad 120, as shown in
FIG. 1B. In this case, heating mechanism 110 may comprise radiant
heaters 114 (e.g., lamps). Heating mechanism may alternatively
comprise heated wires 116 embedded in selective areas of pad 120,
as shown in FIG. 1C.
[0019] Heaters 112 are placed in areas of the platen where
increased removal rate is desired. To improve copper CMP
non-uniformity, heaters 112 are placed around the periphery of the
platen to heat the overlying area 130 of the pad 120 that polishes
the outer portions of the wafer 150. Of course, heaters may be
placed throughout the platen for greater flexibility. Then, only
those heaters below specific areas of the pad 120 could be used.
Alternatively, heaters 114 may be placed above area 130 of pad 120
or wires 116 may be placed in area 130 of pad 120.
[0020] If desired, temperature monitoring may be used to actively
control the temperature profile. For example, optical IR (infrared)
radiometers 170 could be used to monitor the pad 120 surface
temperature during CMP. The amount of heating could then be
increased or decreased as desired to establish and maintain the
proper temperature. Alternative means for temperature monitoring
will be apparent to those of ordinary skill in the art.
[0021] In operation, slurry 160 is applied to the pad 120. Wafer
150 is pressed against pad 120 with the desired downforce and both
the pad and wafer are rotated. Selected areas of the pad 120 are
heated using heating mechanism 110 to improve the removal rate in
those areas. For copper CMP, the periphery 130 of the pad 120 is
heated. This results in a more uniform removal rate across the
wafer 150. The temperature difference between the selected areas
and the other areas of the pad may be on the order of 15.degree. C.
In the preferred embodiment, the selected areas are heated to a
temperature of approximately 35-40.degree. C. A maximum temperature
is on the order of 70.degree. C.
[0022] FIGS. 2A-B show an orbital polisher 200 modified to include
a heating mechanism 110 for heating selective areas of the
polishing pad 220. In an orbital polisher 200, the platen 240 had a
diameter that is slightly larger than the wafer 150 diameter.
Platen 240 is used to hold pad 220. Wafer 150 is held against
polishing pad 220 and rotated by a wafer carrier (not shown).
[0023] As with the rotary polisher, heating mechanism 110 heats
selective areas of the polishing pad 220 where an increased removal
rate is desired. For example, in copper CMP the removal rate is
lower near the edge of the wafer. Therefore, to improve this
non-uniformity, the periphery 230 of the polishing pad 220 is
heated since this area contacts the outer portions of the wafer
150.
[0024] Heating mechanism 110 may be located within platen 240 as
shown in FIG. 2A. In this case, heating mechanism 110 could include
an array of heaters 112, as discussed above. Alternative heating
mechanisms will be apparent to those of ordinary skill in the art.
For example, heating mechanism 110 may comprise heated wires 116
embedded in selective areas of pad 220, as shown in FIG. 2B.
Radiant heating from above is difficult in this type of polisher
because almost the entire pad 220 is covered by wafer 150 during
polishing. The heat source would need to be placed above the wafer
150 in the wafer carrier.
[0025] If desired, temperature monitoring may be used to actively
control the temperature profile. For example, thermocouples 280
located behind the wafer 150 or beneath the pad 220 may be used to
provide feedback for effective process control. The amount of
heating could then be increased or decreased as desired to
establish and maintain the proper temperature. Alternative means
for temperature monitoring will be apparent to those of ordinary
skill in the art.
[0026] In operation, slurry 160 is applied to the pad 220 through
holes in the pad 220. Wafer 150 is pressed against pad 220 with the
desired downforce and both the pad 220 and wafer 150 are rotated.
Selected areas of the pad 120 are heated using heating mechanism
110 to improve the removal rate in those areas. For copper CMP, the
periphery 230 of the pad 220 is heated. The temperature difference
between the selected areas and the other areas of the pad may be on
the order of 15.degree. C. In the preferred embodiment, the
selected areas are heated to a temperature of approximately
35-40.degree. C. A maximum temperature is on the order of
70.degree. C. This results in a more uniform removal rate across
the wafer 150.
[0027] A linear belt polisher 300 modified to include heating
mechanism 110 is shown in FIGS. 3A-3B. Linear belt polisher 300
comprises a continuously fed belt 320. Wafer 150 is held against
polishing belt/pad 320 and rotated by a wafer carrier (not
shown).
[0028] Heating mechanism 110 heats selective areas of the polishing
belt 320 where an increased removal rate is desired. For example,
in copper CMP the removal rate is lower near the edge of the wafer
150. Therefore, to improve this non-uniformity, the outer portion
330 of the polishing belt 320 is heated since this area contacts
the outer portions of the wafer 150.
[0029] Heating mechanism 110 may be located below the polishing
belt 320, as shown in FIG. 3A or above, as shown in FIG. 3B.
Heating mechanism 110 could include an array of radiant lamp
heaters 114. Alternative heating mechanisms will be apparent to
those of ordinary skill in the art. Heaters 114 are placed over or
under the polishing belt 320 just prior to the belt 320 moving
under wafer 150. To improve the removal rate at the outer regions
of wafer 150, the heaters 114 are placed at the outer edges of
polishing belt 320.
[0030] If desired, temperature monitoring may be used to actively
control the temperature profile. For example, optical IR (infrared)
radiometers could be used to monitor the pad 320 surface
temperature during CMP. The amount of heating could then be
increased or decreased as desired to establish and maintain the
proper temperature. Alternative means for temperature monitoring
will be apparent to those of ordinary skill in the art.
[0031] In operation, slurry 160 is applied to the pad 320. Wafer
150 is pressed against pad 320 with the desired downforce and both
the pad and wafer are rotated. Selected areas of the pad 320 are
heated using heating mechanism 110 to improve the removal rate in
those areas. For copper CMP, the periphery 330 of the pad 320 is
heated. The temperature difference between the selected areas and
the other areas of the pad may be on the order of 15.degree. C. In
the preferred embodiment, the selected areas are heated to a
temperature of approximately 35-40.degree. C. A maximum temperature
is on the order of 70.degree. C. This results in a more uniform
removal rate across the wafer 150.
[0032] While this invention has been described with reference to
illustrative embodiments, this description is not intended to be
construed in a limiting sense. Various modifications and
combinations of the illustrative embodiments, as well as other
embodiments of the invention, will be apparent to persons skilled
in the art upon reference to the description. It is therefore
intended that the appended claims encompass any such modifications
or embodiments.
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