U.S. patent application number 11/594496 was filed with the patent office on 2007-03-08 for apparatus and method of controlling the temperature of polishing pads used in planarizing micro-device workpieces.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Larry J. Birch, Freddie L. Dunn, Theodore M. Taylor.
Application Number | 20070054599 11/594496 |
Document ID | / |
Family ID | 30443197 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070054599 |
Kind Code |
A1 |
Taylor; Theodore M. ; et
al. |
March 8, 2007 |
Apparatus and method of controlling the temperature of polishing
pads used in planarizing micro-device workpieces
Abstract
Temperature regulation systems and methods for controlling the
temperature of polishing pads used in planarizing micro-device
workpieces are disclosed herein. In one embodiment, an apparatus
for polishing a workpiece includes a platen defining a planarizing
zone and a primary duct system. The platen can have a first duct,
and the primary duct system can have a second duct operatively
coupled to the first duct of the platen. The second duct is
configured to direct a gas flow laterally relative to the
planarizing zone. The apparatus also includes a pad support carried
by the primary duct system, and a polishing pad carried by the pad
support. The pad support can have a plurality of apertures that are
in fluid communication with the gas flow in the second duct.
Inventors: |
Taylor; Theodore M.; (Boise,
ID) ; Birch; Larry J.; (Nampa, ID) ; Dunn;
Freddie L.; (Boise, ID) |
Correspondence
Address: |
PERKINS COIE LLP;PATENT-SEA
PO BOX 1247
SEATTLE
WA
98111-1247
US
|
Assignee: |
Micron Technology, Inc.
Boise
ID
|
Family ID: |
30443197 |
Appl. No.: |
11/594496 |
Filed: |
November 7, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10198881 |
Jul 18, 2002 |
|
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11594496 |
Nov 7, 2006 |
|
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Current U.S.
Class: |
451/6 |
Current CPC
Class: |
B24B 37/26 20130101;
B24B 49/14 20130101 |
Class at
Publication: |
451/006 |
International
Class: |
B24B 49/00 20060101
B24B049/00 |
Claims
1-55. (canceled)
56. A method for controlling the temperature of a polishing pad,
comprising: causing a gas flow through a duct system under a
polishing pad; and maintaining a desired temperature of the
polishing pad with the gas flow.
57. The method of claim 56 wherein causing a gas flow comprises
forcing gas to move through the duct system by coupling the duct
system to a vacuum or a blower.
58. The method of claim 56 wherein causing a gas flow comprises
flowing the gas in apertures in a pad support.
59. The method of claim 56 wherein causing a gas flow comprises
moving gas through a duct extending through a platen.
60. The method of claim 56 wherein causing a gas flow comprises
moving gas through a duct extending through the polishing pad.
61. The method of claim 56 wherein causing a gas flow comprises
flowing gas radially through the duct system.
62. The method of claim 56 wherein causing a gas flow comprises
driving gas into the duct system by rotating ducts with curved
walls.
63. The method of claim 56, further comprising flowing the gas flow
through a heat exchanger.
64. The method of claim 56, further comprising changing the
temperature of the pad.
65. The method of claim 56 wherein maintaining a desired
temperature comprises changing the temperature of the gas.
66. The method of claim 56 wherein maintaining a desired
temperature comprises changing the flow rate of the gas.
67. A method for controlling the temperature of a polishing pad,
comprising: rotating a platen having a plurality of channels;
causing a gas flow through at least some of the plurality of
channels; passing the gas flow at least proximate to the pad; and
regulating the temperature of the pad by controlling the
temperature or flow rate of the gas.
68. The method of claim 67 wherein causing a gas flow comprises
forcing gas to move through the plurality channels by coupling the
plurality of channels to a vacuum or a blower.
69. The method of claim 67 wherein causing a gas flow comprises
moving the gas through a duct extending through the platen.
70. The method of claim 67 wherein passing the gas flow comprises
flowing the gas in apertures in a pad support.
71. The method of claim 67, further comprising flowing the gas flow
through a heat exchanger.
72. The method of claim 67 wherein causing a gas flow comprises
flowing the gas through a duct extending through the pad and a pad
support.
73. A method for controlling the temperature of a polishing pad,
comprising: flowing gas into a duct system between a polishing pad
and a platen; and exhausting the gas from the duct system.
74. The method of claim 73 wherein flowing gas comprises forcing
gas to move through the duct system by coupling the duct system to
a vacuum or a blower.
75. The method of claim 73 wherein flowing gas comprises passing
gas through a duct extending through the platen.
76. The method of claim 73, further comprising moving the gas
proximate to the polishing pad to change the temperature of the
polishing pad.
77. The method of claim 73 wherein flowing gas comprises passing
the gas in apertures in a pad support.
78. The method of claim 73 wherein flowing gas comprises moving gas
through a duct extending through the polishing pad.
79. The method of claim 73 wherein flowing gas comprises flowing
gas radially through the duct system.
80. The method of claim 73 wherein flowing gas comprises driving
gas into the duct system by rotating ducts with curved walls.
81. The method of claim 73, further comprising flowing the gas
through a heat exchanger.
82. The method of claim 73, further comprising changing the
temperature of the pad.
83. The method of claim 73, further comprising changing the
temperature of the gas.
84. The method of claim 73, further comprising changing the flow
rate of the gas.
85. A method for cooling the temperature of a polishing pad,
comprising: moving gas in an inlet and into a channel; passing the
gas through the channel and proximate to a pad support; cooling the
pad support with the passing gas; and reducing the temperature of
the polishing pad coupled to the pad support.
86. The method of claim 85, further comprising flowing gas through
a duct extending through a platen.
87. A method for planarizing a micro-device workpiece with a
temperature control, comprising: pressing the micro-device
workpiece against a pad; imparting relative motion between the
micro-device workpiece and the pad; causing a gas flow through a
duct system under the pad; and regulating the temperature of the
pad by controlling the temperature and/or flow rate of the gas.
88. The method of claim 87 wherein causing a gas flow comprises
flowing gas in apertures in a pad support.
89. The method of claim 87 wherein causing a gas flow comprises
flowing gas radially through the duct system.
Description
TECHNICAL FIELD
[0001] The present invention relates to planarizing and polishing
micro-device workpieces including mechanical and
chemical-mechanical planarization. In particular, the present
invention relates to controlling the temperature of the polishing
pad during the planarizing cycle.
BACKGROUND
[0002] Mechanical and chemical-mechanical planarization processes
(collectively "CMP") remove material from the surface of
micro-device workpieces in the production of microelectronic
devices and other products. FIG. 1 schematically illustrates a
rotary CMP machine 10 with a platen 20, a carrier head 30, and a
planarizing pad 40. The CMP machine 10 may also have an under-pad
25 between an upper surface 22 of the platen 20 and a lower surface
of the planarizing pad 40. A drive assembly 26 rotates the platen
20 (indicated by arrow F) and/or reciprocates the platen 20 back
and forth (indicated by arrow G). Since the planarizing pad 40 is
attached to the under-pad 25, the planarizing pad 40 moves with the
platen 20 during planarization.
[0003] The carrier head 30 has a lower surface 32 to which a
micro-device workpiece 12 may be attached, or the micro-device
workpiece 12 may be attached to a resilient pad 34 under the lower
surface 32. The carrier head 30 may be a weighted, free-floating
carrier head, or an actuator assembly 36 may be attached to the
carrier head 30 to impart rotational motion to the micro-device
workpiece 12 (indicated by arrow J) and/or to reciprocate the
micro-device workpiece 12 back and forth (indicated by arrow
I).
[0004] The planarizing pad 40 and a planarizing solution 44 define
a planarizing medium that mechanically and/or
chemically-mechanically removes material from the surface of the
micro-device workpiece 12. The planarizing solution 44 may be a
conventional CMP slurry with abrasive particles and chemicals that
etch and/or oxidize the surface of the micro-device workpiece 12,
or the planarizing solution 44 may be a "clean" non-abrasive
planarizing solution without abrasive particles. In most CMP
applications, abrasive slurries with abrasive particles are used on
non-abrasive polishing pads, and clean non-abrasive solutions
without abrasive particles are used on fixed-abrasive polishing
pads.
[0005] To planarize the micro-device workpiece 12 with the CMP
machine 10, the carrier head 30 presses the micro-device workpiece
12 face-downward against the planarizing pad 40. More specifically,
the carrier head 30 generally presses the micro-device workpiece 12
against the planarizing solution 44 on a planarizing surface 42 of
the planarizing pad 40, and the platen 20 and/or the carrier head
30 moves to rub the micro-device workpiece 12 against the
planarizing surface 42. As the micro-device workpiece 12 rubs
against the planarizing surface 42, the planarizing medium removes
material from the face of the micro-device workpiece 12.
[0006] The planarity of the finished micro-device workpiece surface
is a function of the distribution of planarizing solution under the
micro-device workpiece during planarization, the chemical reaction
rate, the relative velocity between the polishing pad and the
micro-device workpiece surface, and several other factors. Some of
these factors are temperature-dependent, such as the chemical
reaction rate. Accordingly, it can be difficult to achieve a planar
micro-device workpiece surface because often the temperature varies
across the workpiece surface during planarization. For example,
often the relative velocity between the micro-device workpiece
surface and the rotating polishing pad is different across the
micro-device workpiece surface, consequently creating a temperature
gradient. The temperature gradient can generate different chemical
reaction rates in the planarizing solution and, accordingly,
different polishing rates across the micro-device workpiece that
result in a non-planar micro-device workpiece surface.
[0007] It is, accordingly, desirable to control the temperature of
the planarizing pad to stabilize the temperature-dependent factors
that affect the planarity of the micro-device workpiece surface.
Previously, attempts have been made to control the temperature by
circulating a cooling liquid in the platen. This approach, however,
has several disadvantages. It is difficult and expensive to
manufacture a liquid system for rotary platens. Liquid systems, for
example, require rotary fluid couplings to connect the platen to an
external heat exchanger. Liquid systems also require extensive
maintenance to prevent leaking and failure of the moving parts. In
addition to maintenance expenses, significant downtime may be
required to replace or repair rotary couplings or other components.
Such significant downtime disrupts production and reduces the
throughput of CMP processing.
SUMMARY
[0008] The present invention relates to controlling the temperature
of a polishing pad during planarizing and/or polishing of
micro-device workpieces. In one embodiment, an apparatus for
polishing a workpiece includes a platen defining a planarizing zone
and a primary duct system. The platen can have a first duct, and
the primary duct system can have a second duct operatively coupled
to the first duct of the platen. The second duct is configured to
direct a gas flow laterally relative to the planarizing zone. The
apparatus also includes a pad support carried by the primary duct
system, and a polishing pad carried by the pad support. The pad
support can have a plurality of apertures that are in fluid
communication with the gas flow in the second duct. As a result,
the temperature of the gas flow affects the temperature of the
polishing pad to control the temperature at the pad/workpiece
interface.
[0009] In another embodiment, an apparatus for planarizing a
micro-device workpiece includes a polishing pad having a
planarizing surface for planarizing the micro-device workpiece, a
pad support carrying the polishing pad, and a duct system carrying
the pad support. The duct system has a duct with at least one inlet
and at least one outlet. The duct is configured to direct a gas
flow proximate to the pad support in a direction generally parallel
to the planarizing surface.
[0010] In another embodiment, an apparatus for gas-cooling and/or
gas-heating a polishing pad includes a platen having a duct system
defined by a plurality of channels configured to receive a gas
flow, a pad support carried by the platen, and a polishing pad
carried by the pad. The pad support is positioned proximate to the
plurality of channels so that the gas flow can cool or heat the
pad. The polishing pad has a polishing surface for polishing a
micro-device workpiece.
[0011] An embodiment of a temperature control system for use with a
platen includes a duct system configured for attachment to the
platen, and a pad support carried by the duct system. The duct
system has at least one inlet, at least one outlet, and at least
one duct coupled to the inlet and the outlet. The duct is
configured to direct a gas flow under the pad support to control
the temperature of the pad.
[0012] An embodiment of a method for controlling the temperature of
a polishing pad includes causing a gas to flow through a duct
system under a polishing pad, and maintaining a desired temperature
of the polishing pad with the gas flow. Another embodiment includes
flowing gas into a duct system between a polishing pad and a
platen, and exhausting the gas from the duct system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic cross-sectional view illustrating a
portion of a rotary planarizing machine in accordance with the
prior art.
[0014] FIG. 2 is a side cross-sectional view of a planarizing pad
and a temperature control system in accordance with one embodiment
of the invention.
[0015] FIG. 3 is a top plan view of the pad support of FIG. 2.
[0016] FIG. 4 is a top plan view of a pad support in accordance
with another embodiment of the invention.
[0017] FIG. 5 is a top plan view of the duct system of FIG. 2.
[0018] FIG. 6 is a top plan view of a duct system in accordance
with another embodiment of the invention.
[0019] FIG. 7 is a side cross-sectional view of the planarizing pad
and a temperature control system in accordance with another
embodiment of the invention.
[0020] FIG. 8 is a top cross-sectional view of the platen taken
substantially along line A-A of FIG. 7.
[0021] FIG. 9 is a side cross-sectional view of a planarizing pad
and a temperature control system in accordance with another
embodiment of the invention.
[0022] FIG. 10 is a side cross-sectional view of the planarizing
pad and a temperature control system in accordance with another
embodiment of the invention.
DETAILED DESCRIPTION
[0023] The following disclosure is directed to polishing or
planarizing machines and methods for controlling the temperature of
polishing pads related to mechanical and/or chemical-mechanical
planarization of micro-device workpieces. The term "micro-device
workpiece" is used throughout to include substrates upon which
and/or in which microelectronic devices, micromechanical devices,
data storage elements, and other features are fabricated. For
example, micro-device workpieces can be semiconductor wafers, glass
substrates, insulative substrates, or many other types of
substrates. Furthermore, the terms "planarization" and
"planarizing" mean either forming a planar surface and/or forming a
smooth surface (e.g., "polishing"). Several specific details of the
invention are set forth in the following description and in FIGS.
2-10 to provide a thorough understanding of certain embodiments of
the invention. One skilled in the art, however, will understand
that the present invention may have additional embodiments, or that
other embodiments of the invention may be practiced without several
of the specific features explained in the following description.
For example, even though many of the embodiments are described with
reference to cooling a planarizing pad, they can also be used to
heat or maintain the temperature of the planarizing pad.
[0024] FIG. 2 is a side cross-sectional view of a planarizing
machine 100 having a temperature control system 200 in accordance
with one embodiment of the invention. The temperature control
system 200 of the illustrated embodiment includes a platen 220, a
pad support 250, and a duct system 260. The temperature control
system 200 assists in regulating the temperature of a planarizing
pad 240 to accurately control the polishing rate and other
parameters of the planarization process. Temperature control can be
advantageous, for example, when a temperature gradient exists
across the planarizing pad 240, such as when the temperature of the
planarizing pad 240 is greater toward the edge 241. The temperature
gradient causes different polishing rates across the workpiece,
which, accordingly, result in a non-planar workpiece surface.
Moreover, temperature control can be advantageous with some
workpieces because the stability of the polishing rate is enhanced
when the temperature of the planarizing pad 240 is at or below
approximately 70.degree. F.
[0025] In the illustrated embodiment, the pad support 250 has an
upper surface 252 attached to a backside 244 of the planarizing pad
240, and a lower surface 254 carried by the duct system 260. The
pad support 250 can be stiff to provide support to the planarizing
pad 240 during the planarizing process. The pad support 250, for
example, can be a relatively thin sheet of polymeric material or
organic material. In one embodiment, the pad support 250 is
composed of FR-4, commonly used as a sub-pad in CMP
applications.
[0026] The pad support 250 can also include a plurality of
apertures 251 to facilitate heat transfer between the planarizing
pad 240 and the gas flowing through the duct system 260. Each
aperture 251 extends from the lower surface 254 of the pad support
250 to the upper surface 252. In other embodiments, the apertures
251 might not extend completely through the pad support 250, or the
pad support 250 might not have apertures. The apertures 251 in the
pad support 250 can be arranged in patterns that provide the
desired heat transfer rates across the backside 244 of the
planarizing pad 240.
[0027] FIGS. 3 and 4 are top plan views of embodiments of aperture
patterns suitable for the pad support 250. FIG. 3, for example,
shows a pad support 250a with a uniform distribution of apertures
251 to provide a uniform heat transfer distribution across the
backside 244 (FIG. 2) of the planarizing pad 240 (FIG. 2). FIG. 4
shows a pad support 450 with a non-uniform arrangement of apertures
251. The pad support 450 has a greater number of apertures 251 in a
perimeter region proximate to an edge 452 of the pad support 450
than in a center region. One advantage of the pad support 450 is
that the greater concentration of apertures 251 in the perimeter
region provides for greater heat transfer between a perimeter
region of the planarizing pad 240 (FIG. 2) and the gas in the duct
system 260 (FIG. 2). This can be used to provide more heating or
cooling at the perimeter of the planarizing pad 240. In other
embodiments, other pad supports with different arrangements of
apertures can be used to provide different temperature
distributions.
[0028] Referring to FIG. 2, the platen 220 defines a planarizing
zone "P" in which a workpiece is rubbed against the planarizing pad
240. The platen 220 includes a platen duct 280 that extends from an
upper surface 222 to a lower surface 224 of the platen 220. In the
illustrated embodiment, a vacuum and/or blower 290 is coupled to
the platen duct 280 to facilitate the movement of gas through the
platen duct 280 and the duct system 260. For example, a vacuum
forces gas to flow from the duct system 260, through the platen
duct 280, and out through a port 276. Conversely, a blower forces
gas in through the port 276, through the platen duct 280, and into
the duct system 260. Furthermore, a heat exchanger 292 can be
coupled to the platen duct 280 to cool or heat the gas before it
enters the platen 220. Other embodiments may not have a heat
exchanger, vacuum and/or blower coupled to the duct system 260.
[0029] The duct system 260 includes a plurality of ducts 273 that
channel the gas to the apertures 251 under the planarizing pad 240.
The duct system 260 can also provide a continuous flow of gas under
the planarizing pad 240 to maintain a desired heat transfer rate.
For example, a gas flow "A" can enter the ducts 273 through
openings 268, flow through the ducts 273, and then be exhausted
through a central port 266.
[0030] FIG. 5 is a top plan view of one embodiment of a duct system
560. The duct system 560 includes a plurality of raised sections
510 and a plurality of ducts 573 defined by the plurality of raised
sections 510. The raised sections 510 carry the pad support 250
(FIG. 2) and can be attached to or an integral part of the platen
220 (FIG. 2). In the illustrated embodiment, each duct 573 is
defined by a wall 512 of a first raised section 510a and a wall 514
of a second raised section 510b. Each duct 573 has an opening 568
at the perimeter, and the duct system 560 has a central port 566.
In the operation of one embodiment, gas flows in through the
openings 568, along the ducts 573 to pass laterally relative to a
planarizing zone, and out through the central port 566 (see arrow
A.sub.1). Conversely, in another embodiment, gas can flow in
through the central port 566 and out through the openings 568 (see
arrow A.sub.2).
[0031] FIG. 6 is a top plan view of a duct system 660 in accordance
with another embodiment of the invention. The duct system 660 of
the illustrated embodiment includes a plurality of arcuate raised
sections 610 and a plurality of arcuate ducts 673 defined by the
raised sections 610. Each duct 673 has an opening 668, and the duct
system 660 has a central port 666 similar to the duct system 560
shown in FIG. 5. When the platen 220 (FIG. 2) rotates in a
direction D.sub.1, the arcuate shape of the ducts 673 drives gas
through the openings 668, along the ducts 673 laterally relative to
a planarizing zone, and out through the central port 666.
[0032] FIGS. 5 and 6 show a number of different duct systems that
can be used in the planarizing machine 200 of FIG. 2. It will be
appreciated that duct systems for moving or otherwise providing a
flow of gas under the planarizing pad can have other configurations
in accordance with other embodiments of the invention. For example,
the duct system may not have a plurality of ducts, but rather one
duct or chamber with a plurality of small supports or posts to
support the pad support 250 (FIG. 2). The ducts, therefore, do not
need to be defined by walls that extend along a substantial portion
of the radius of the platen.
[0033] FIG. 7 is a side cross-sectional view of a planarizing
machine 700 having a temperature control system in accordance with
another embodiment of the invention. The temperature control system
of the illustrated embodiment includes a platen 720 having a
plurality of channels or ducts 773 between partitions 732, and a
pad support 750 carried by the partitions 732. In the illustrated
embodiment, the pad support 750 does not have apertures; in
additional embodiments, the pad support 750 may have apertures and
may be similar to the pad support 250 discussed above.
[0034] FIG. 8 is a top cross-sectional view of one embodiment of
the platen 720 taken substantially along line A-A of FIG. 7. The
ducts 773 are defined by the plurality of partitions 732 and an
outer wall 760. The platen 720 also has at least one opening 770 in
each of the ducts 773, and a central duct 777. The central duct 777
defines a first duct, and the radial ducts 773 define second ducts.
The ducts 773 are spaced apart by a gap 772 between the partitions
732 at the central duct 777. Referring to FIG. 7, in one
embodiment, gas can flow in through the openings 770, along the
ducts 773, and out through the gaps 772 (FIG. 8). The gas flow can
then be exhausted through the central duct 777 in the platen 720.
Conversely, in another embodiment, the gas can flow in the opposite
direction and be exhausted through the openings 770. Moreover, the
platen 720 can be coupled to a blower, vacuum and/or heat exchanger
to facilitate the gas flow, as discussed above with reference to
FIG. 2. In other embodiments, the plurality of partitions 732
and/or the plurality of ducts 773 can have different shapes or
configurations. Furthermore, each duct 773 can have more than one
opening 770.
[0035] FIG. 9 is a side cross-sectional view of a planarizing
machine 900 having a temperature control system in accordance with
another embodiment of the invention. The temperature control system
of the illustrated embodiment includes a platen 920 having a
plurality of ducts 973, and a pad support 950 carried by the platen
920. The plurality of ducts 973 are defined by walls or other types
of raised sections similar to those illustrated in FIG. 5 or 6. The
ducts 973 also have a base with an inclined upper surface 922. The
temperature control system also includes an upper duct 980 coupled
to the plurality of ducts 973 to connect the ducts 973 to the
ambient air or gas. The upper duct 980 has a lip 978 that extends
radially outward to prevent the planarizing solution 44 (FIG. 2)
from spilling into the upper duct 980. The pad support 950 has a
first aperture 966 that receives the upper duct 980 and a plurality
of second apertures 951 arranged in a pattern to provide a desired
heat transfer distribution, as explained above. The planarizing
machine 900 can also include a planarizing pad 940 having a
planarizing surface 942 and a hole 944 through which the upper duct
980 passes. In the illustrated embodiment, if planarizing solution
44 (FIG. 2) spills into the upper duct 980 from the planarizing
surface 942, the spilled planarizing solution 44 (FIG. 2) will flow
down the inclined upper surface 922 and run off the platen 920. In
operation, gas can flow in through a port 976 in the upper duct
980, through the upper duct 980, through the plurality of ducts
973, and out through openings 968 (see arrow A.sub.3). Conversely,
gas can flow in through the openings 968 and out through the port
976 (see arrow A.sub.4).
[0036] FIG. 10 is a side cross-sectional view of a planarizing
machine 1000 having a temperature control system in accordance with
another embodiment of the invention. The planarizing pad 240 and
the temperature control system of the illustrated embodiment are
similar to those shown in FIG. 2. In the illustrated embodiment,
however, the planarizing pad 240 is secured to a pad support 1050
by a vacuum 1090. The vacuum 1090 is coupled to four vacuum ducts
1010 (two are shown). The vacuum ducts 1010 extend from the
backside 244 of the planarizing pad 240, through the pad support
1050 and a duct system 1060, to a backside 1044 of a platen 1020.
The vacuum 1090 creates a subatmospheric pressure to hold the
planarizing pad 240 onto the pad support 1050. In other
embodiments, the machine may include a different number of vacuum
ducts.
[0037] An advantage of several of the embodiments discussed above
is the ability to control or regulate the temperature of the
polishing pad during planarization. Controlling the temperature
throughout the polishing pad provides better control of the
chemical reaction rate throughout the pad and, consequently,
results in control of the planarized surface on the micro-device
workpiece. Furthermore, the gas flow temperature control systems
are less expensive and easier to maintain than liquid control
loops. For example, several embodiments of gas duct systems are
less susceptible to downtime for leaks compared to liquid cooling
systems because they do not need rotary liquid couplings.
Furthermore, air can leak through portions of the platen without
creating contamination concerns. Another advantage of many of the
embodiments discussed above is that they can be used by
retrofitting existing planarizing machines. For example, duct
systems can be inserted between polishing pads and platens on
existing planarizing machines.
[0038] From the foregoing, it will be appreciated that specific
embodiments of the invention have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the spirit and scope of the invention.
Accordingly, the invention is not limited except as by the appended
claims.
* * * * *