U.S. patent application number 16/749336 was filed with the patent office on 2021-07-22 for carbon nanotube electrostatic chuck.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Steven M. Anella, Julian G. Blake, Qin Chen, David J. Chipman, Ron Serisky, Dawei Sun.
Application Number | 20210225682 16/749336 |
Document ID | / |
Family ID | 1000005693036 |
Filed Date | 2021-07-22 |
United States Patent
Application |
20210225682 |
Kind Code |
A1 |
Sun; Dawei ; et al. |
July 22, 2021 |
CARBON NANOTUBE ELECTROSTATIC CHUCK
Abstract
A platen having improved thermal conductivity and reduced
friction is disclosed. In one embodiment, vertically aligned carbon
nanotubes are grown on the top surface of the platen. The carbon
nanotubes have excellent thermal conductivity, thus improving the
transfer of heat between the platen and the workpiece. Furthermore,
the friction between the carbon nanotubes and the workpiece is much
lower than that with conventional embossments, reducing particle
generation. In another embodiment, a support plate is disposed on
the platen, wherein the carbon nanotubes are disposed on the top
surface of the support plate.
Inventors: |
Sun; Dawei; (Lynnfield,
MA) ; Anella; Steven M.; (Newbury, MA) ; Chen;
Qin; (Gloucester, MA) ; Serisky; Ron;
(Gloucester, MA) ; Blake; Julian G.; (Gloucester,
MA) ; Chipman; David J.; (Lynn, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
1000005693036 |
Appl. No.: |
16/749336 |
Filed: |
January 22, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/6833 20130101;
B23Q 3/154 20130101 |
International
Class: |
H01L 21/683 20060101
H01L021/683; B23Q 3/154 20060101 B23Q003/154 |
Claims
1. A platen comprising: a dielectric layer having openings on a top
surface, wherein all openings are used for lift pins and/or ground
pins; a base; one or more electrodes disposed between the
dielectric layer and a top surface of the base or embedded in the
base; and a plurality of vertically aligned carbon nanotubes
disposed on the top surface of the dielectric layer, wherein a
height of the plurality of vertically aligned carbon nanotubes is
between 1 and 500 .mu.m and wherein the vertically aligned carbon
nanotubes transfer heat between the platen and a workpiece disposed
on the platen.
2. The platen of claim 1, wherein the plurality of vertically
aligned nanotubes are arranged in a plurality of islands.
3. The platen of claim 2, wherein the number density in each island
is between 10.sup.7 and 10.sup.11 nanotubes/cm.sup.2.
4. (canceled)
5. The platen of claim 1, further comprising lift pins extending
out from the top surface of the dielectric layer.
6. The platen of claim 5, wherein the openings on the top surface
of the dielectric layer accommodate the lift pins.
7. (canceled)
8. An assembly for holding a workpiece, comprising: an
electrostatic chuck; and a support plate, separate from the
electrostatic chuck and disposed on a top surface of the
electrostatic chuck, comprising a plurality of vertically aligned
carbon nanotubes disposed on a top surface of the support plate,
wherein a height of the plurality of vertically aligned carbon
nanotubes is between 1 and 500 .mu.m.
9. The assembly of claim 8, wherein the electrostatic chuck
comprises lift pins operable to extend outward from the top surface
of the electrostatic chuck, and wherein the support plate comprises
openings to allow the lift pins to pass through.
10. The assembly of claim 9, wherein all of the openings in the
support plate are used for the lift pins and ground pins.
11. The assembly of claim 8, wherein the support plate comprises a
dielectric material.
12. The assembly of claim 8, wherein the plurality of vertically
aligned nanotubes are arranged in a plurality of islands.
13. The assembly of claim 12, wherein the number density in each
island is between 10.sup.7 and 10.sup.11 nanotubes/cm.sup.2.
14-18. (canceled)
19. The platen of claim 1, wherein the carbon nanotubes prevent the
workpiece from contacting the top surface of the electrostatic
chuck.
20. The assembly of claim 8, wherein the support plate comprises a
dielectric material.
Description
FIELD
[0001] Embodiments of the present disclosure relate to an
electrostatic chuck for semiconductor processing and more
particularly, an electrostatic chuck with carbon nanotubes.
BACKGROUND
[0002] The fabrication of a semiconductor device involves a
plurality of discrete and complex processes. In certain
embodiments, a workpiece, such as a silicon substrate, may be
disposed on a platen when these processes are performed. The platen
may include an electrostatic chuck, which clamps the workpiece to
the platen using electrostatic forces.
[0003] Additionally, in certain embodiments, it may be advantageous
to allow heat to pass from the platen to the workpiece, and vice
versa. To improve the heat transfer characteristics, a backside gas
may be injected into the volume between the top surface of the
platen and the bottom surface of the workpiece. The molecules in
the backside gas help conduct heat between the workpiece and the
platen. This backside gas may be injected at a pressure of less
than 15 torr and have a thermal conductance of between 50 and 800
W/m.sup.2-K. However, this may be less than optimal for very high
thermal loads and in applications where very high temperature
uniformity of the workpiece is needed.
[0004] Further, to create this volume, embossments are typically
disposed on the top surface of the platen. These embossments are
typically constructed of the same material as the top surface of
the platen. As the workpiece is placed on and removed from the
platen, there may be relative motion between these components.
Consequently, in certain embodiments, friction between the bottom
surface of the workpiece and the platen may generate particles.
[0005] This may result in device performance or yield issues.
[0006] Therefore, it would be advantageous if there were a platen
that had improved heat transfer characteristics as compared to
conventional systems. Furthermore, it would be beneficial if this
platen also reduced the friction between the platen and the
workpiece to minimize particle generation.
SUMMARY
[0007] A platen having improved thermal conductivity and reduced
friction is disclosed. In one embodiment, vertically aligned carbon
nanotubes are grown on the top surface of the platen. The carbon
nanotubes have excellent thermal conductivity, thus improving the
transfer of heat between the platen and the workpiece. Furthermore,
the friction between the carbon nanotubes and the workpiece is much
lower than that with conventional embossments, reducing particle
generation. In another embodiment, a support plate is disposed on
the platen, wherein the carbon nanotubes are disposed on the top
surface of the support plate.
[0008] According to one embodiment, a platen is disclosed. The
platen comprises a dielectric layer; a base; one or more electrodes
disposed between the dielectric layer and the base; and a plurality
of vertically aligned carbon nanotubes disposed on a top surface of
the dielectric layer. In certain embodiments, the plurality of
vertically aligned carbon nanotubes are arranged in a plurality of
islands. In some embodiments, the number density in each island is
between 10.sup.7 and 10.sup.11 nanotubes/cm.sup.2. In certain
embodiments, a height of the plurality of vertically aligned carbon
nanotubes is between 1 and 500 .mu.m. In certain embodiments, the
platen comprises lift pins extending out from the top surface of
the dielectric layer. In some embodiments, the platen comprises
openings on the top surface of the dielectric layer to accommodate
the lift pins. In certain embodiments, all of the openings on the
top surface are used for the lift pins or ground pins.
[0009] According to another embodiment, assembly for holding a
workpiece is disclosed. The assembly comprises an electrostatic
chuck; and a support plate disposed on a top surface of the
electrostatic chuck, comprising a plurality of vertically aligned
carbon nanotubes disposed on a top surface of the support plate. In
certain embodiments, the electrostatic chuck comprises lift pins
operable to extend outward from the top surface of the
electrostatic chuck, and wherein the support plate comprises
openings to allow the lift pins to pass through. In certain
embodiments, all of the openings in the support plate are used for
the lift pins and ground pins. In some embodiments, the support
plate comprises a dielectric material. In certain embodiments, the
plurality of vertically aligned carbon nanotubes are arranged in a
plurality of islands. In some embodiments, wherein the number
density in each island is between 10.sup.7 and 10.sup.11
nanotubes/cm.sup.2. In certain embodiments, the height of the
plurality of vertically aligned carbon nanotubes is between 1 and
500 .mu.m.
[0010] According to another embodiment, an electrostatic chuck is
disclosed. In this embodiment, heat is transferred between the
electrostatic chuck and a workpiece disposed on the electrostatic
chuck by vertically aligned carbon nanotubes disposed on a top
surface of the electrostatic chuck. In some embodiments, the
vertically aligned carbon nanotubes are arranged in a plurality of
islands. In some embodiments, wherein the number density in each
island is between 10.sup.7 and 10.sup.11 nanotubes/cm.sup.2. In
certain embodiments, the height of the vertically aligned carbon
nanotubes is between 1 and 500 .mu.m. In some embodiments, the
carbon nanotubes prevent the workpiece from contacting the top
surface of the electrostatic chuck.
BRIEF DESCRIPTION OF THE FIGURES
[0011] For a better understanding of the present disclosure,
reference is made to the accompanying drawings, which are
incorporated herein by reference and in which:
[0012] FIG. 1 shows a cross-sectional view of a platen with
vertically aligned carbon nanotubes according to one
embodiment;
[0013] FIG. 2 shows a top view of the platen of FIG. 1;
[0014] FIG. 3 shows a cross-sectional view of a platen with
vertically aligned carbon nanotubes according to another
embodiment;
[0015] FIG. 4 shows a cross-sectional view of an assembly including
a platen and a support plate with vertically aligned carbon
nanotubes according to one embodiment; and
[0016] FIG. 5 shows a cross-sectional view of an assembly including
a platen and a support plate with vertically aligned carbon
nanotubes according to another embodiment.
DETAILED DESCRIPTION
[0017] As described above, in certain embodiments, an improved
platen is disclosed. This platen comprises an electrostatic chuck
with vertically aligned carbon nanotubes disposed on the top
surface of the electrostatic chuck. FIG. 1 shows a cross-sectional
view of the platen 100, while FIG. 2 shows a top view of the platen
100.
[0018] As seen in FIG. 1, the platen 100 comprises a plurality of
layers. The top layer, also referred to as the dielectric layer
110, contacts the workpiece, and is made of an electrically
insulating or semiconducting material, such as alumina.
[0019] A second layer, also referred to as the base 120, is
disposed beneath the dielectric layer 110. To create the
electrostatic force, a plurality of electrodes 130 may be disposed
between the dielectric layer 110 and the base 120. In another
embodiment, the plurality of electrodes 130 may be embedded in the
base 120. The plurality of electrodes 130 is constructed from an
electrically conductive material, such as metal. The electrodes 130
are used to produce an electrostatic field. Methods of creating
this electrostatic field are known to those skilled in the art and
will not be described herein.
[0020] Typically, the electrodes 130 are electrically isolated from
each other. As shown in FIG. 2, these electrodes 130 may be
arranged as sectors of a circle, where electrodes that are opposite
the center of the platen have opposite voltages. For example,
electrode 130a may have a positive voltage while electrode 130b may
have a negative voltage. These voltages may be DC, or may vary with
time to maintain the electrostatic force. For example, the voltage
applied to each electrode 130 may be a bipolar square wave. In
certain embodiments, three pairs of electrodes are employed. Each
pair of electrodes is in electrical communication with a respective
power source, such that one electrode receives the positive output
and the other electrode receives the negative output. Each power
source may generate the same square wave output, in terms of period
and amplitude. However, each square wave may be phase shifted from
those adjacent to it. Of course, other numbers of electrodes and
alternate geometries may be used.
[0021] The voltages applied to the electrodes 130 serve to create
an electrostatic force, which clamps the workpiece to the platen
100.
[0022] Vertically aligned carbon nanotubes 140 may be disposed on
the top surface of the dielectric layer 110, as shown in FIG.
1.
[0023] These vertically aligned carbon nanotubes may have a height
between about 1 and 500 .mu.m. Further, each nanotube may be
single-walled or multi-walled.
[0024] Additionally, in certain embodiments, these vertically
aligned carbon nanotubes 140 may be clustered into islands 141 (see
FIG. 2). Each island 141 may have a number density of between
10.sup.7 and 10.sup.11 nanotubes/cm.sup.2. In certain embodiments,
the islands 141 may have a diameter of between 0.1 and 5
millimeters and the edge-to-edge spacing between islands 141 may be
between 0.1 and 20 millimeters. Islands may be employed to ensure
that the electrostatic forces are not grounded by the vertically
aligned carbon nanotubes 140. The specific number and location of
the islands 141 is an implementation specific decision and is not
limited by this disclosure.
[0025] To enable the workpiece to be removed from the platen 100,
the platen 100 may include mechanically actuated lift pins 150. The
lift pins 150 may have a first position, where the lift pins are
extended to a height that is less than the height of the vertically
aligned carbon nanotubes. In this way, the lift pins 150 do not
interfere with the interface between the vertically aligned carbon
nanotubes 140 and the workpiece. The lift pins 150 may also have a
second position, where the lift pins 150 are extended to a height
that is greater than the height of the vertically aligned carbon
nanotubes 140. In this way, the lift pins 150 serve to lift the
workpiece away from the vertically aligned carbon nanotubes
140.
[0026] Thus, in one embodiment, the lift pins are the only openings
on top surface of the platen 100.
[0027] In some embodiments, ground pins 155 may extend from the top
surface of the platen 100. These ground pins 155 are used to
electrically ground the workpiece disposed on the platen. In
another embodiment, the top surface of the platen 100 may also
comprise openings to accommodate ground pins 155. In other words,
in certain embodiments, all of the openings on the top surface of
the platen 100 are used for the lift pins 150 and the ground pins
155.
[0028] In one embodiment, the top surface of the platen 100 is
prepared in the following manner. First, a carbon-containing source
is catalytically decomposed on small metallic particles or clusters
on the platen 100 in those regions where islands 141 are desired.
The metals used for these reactions are typically transition
elements, such as iron (Fe), cobalt (Co) and nickel (Ni). Next, the
platen may be subjected to a catalytic chemical vapor deposition
(CCVD) process, where a feedgas comprising a species that includes
carbon, such as CH.sub.4, C.sub.2H.sub.2, C.sub.2H.sub.4 or
C.sub.6H.sub.6, is introduced. This carbon-containing species may
be used alone or as part of a mixture with either hydrogen
(H.sub.2) or argon (Ar). The process typically takes place at
temperatures of between 600.degree. C. and 1000.degree. C. The
carbon will deposit in these regions where the precursor is
disposed. The carbon atoms will then continue to build upon one
another, forming carbon nanotubes. The CCVD process is continued
until the nanotubes reach the desired height. It is also possible
to form the metal particles in situ in the presence of the carbon
source, making the aforementioned reaction one-step process. Of
course, other techniques may be used to create the vertically
aligned carbon nanotubes.
[0029] Thus, in this embodiment, the vertically aligned carbon
nanotubes 140 are grown directly on the top surface of the
dielectric layer 110.
[0030] FIG. 3 shows another embodiment, wherein like components
have been given identical reference designators. In this
embodiment, the platen 100 may include fluid conduits 170 that pass
through the platen 100 and exit at the top surface. A backside gas
source 180 may be in communication with these fluid conduits 170 to
bring backside gas to the top surface of the platen 100. In these
embodiments, the top surface of the dielectric layer 110 may
include an edge seal 111 near its outer circumference to contain
the backside gas within the enclosed volume.
[0031] In this embodiment, the openings on the top surface of the
platen 100 may be used for lift pins 150, ground pins 155 and the
fluid conduits 170.
[0032] FIGS. 1-3 show a platen 100 with vertically aligned carbon
nanotubes 140 disposed on the top surface of the dielectric layer
110. However, other embodiments are also possible.
[0033] For example, a support plate 250 may be introduced between
the platen 200 and the workpiece, as shown in FIG. 4. FIG. 4 shows
an assembly comprising a platen 200. The platen 200 may have a
dielectric layer 210, a base 220 and one or more electrodes 230
disposed between the dielectric layer 210 and the base 220. As
described above, the electrodes 230 may be in communication with an
electrode power supply. Thus, the platen 200 may be a traditional
electrostatic chuck. In certain embodiments, the platen 200 may
include fluid conduits and a backside gas source, such as that
described above with respect to FIG. 3. In other embodiments, the
platen 200 does not include fluid conduits or a backside gas
source.
[0034] A support plate 250 is disposed on top of the platen 200. In
certain embodiments, the electrostatic field from the electrodes
130 is used to clamp the support plate 250 to the platen 200. In
other embodiments, the support plate 250 may be mechanically
clamped to the platen 200, such as through the use of clips or
screws. The support plate 250 may be constructed of alumina,
aluminum nitride or other dielectric materials.
[0035] In certain embodiments, such as that shown in FIG. 5, the
platen 200 includes fluid conduits 270. In this embodiment,
backside gas from a backside gas source 280 may be introduced into
the volume between the top surface of the platen 200 and the bottom
surface of the support plate 250 to maximize heat transfer between
these components. In this embodiment, the top surface of the
dielectric layer 210 may include an edge seal 211 near its outer
circumference to contain the backside gas within the enclosed
volume between the support plate 250 and the platen 200.
[0036] In both embodiments, the vertically aligned carbon nanotubes
260 are grown on the top surface of the support plate 250. The
nanotubes may be grown using the technique described above or
another suitable process. In certain embodiments, a plurality of
islands, such as those described above, may be created on the top
surface of the support plate 250. Specifically, each island may
have a number density of between 10.sup.7 and 10.sup.11
nanotubes/cm.sup.2. In certain embodiments, the islands may have a
diameter of between 0.1 and 5 millimeters and the edge-to-edge
spacing between islands 141 may be between 0.1 and 20 millimeters.
The specific number and location of the islands is an
implementation specific decision and is not limited by this
disclosure.
[0037] As described above, the vertically aligned carbon nanotubes
260 may have a height of between about 1 and 500 .mu.m. Further,
each nanotube may be single-walled or multi-walled. Each island may
have a number density of between 10.sup.7 and 10.sup.11
nanotubes/cm.sup.2. Islands may be employed to ensure that the
electrostatic forces are not grounded by the vertically aligned
carbon nanotubes. The specific number and location of the islands
is an implementation detail and is not limited by this
disclosure.
[0038] In some embodiments, the support plate 250 comprises a
plurality of holes to allow the lift pins 231 from the platen 200
to extend through the support plate 250 toward the workpiece. In
certain embodiments, all of the holes in the support plate 250 are
used for the lift pins 231. In other words, the backside gas is
contained within the volume between the support plate 250 and the
platen 200.
[0039] In some embodiments, ground pins 235 may extend from the top
surface of the platen 200 and through the support plate 250. These
ground pins 235 are used to electrically ground the workpiece
disposed on the support plate 250. In this embodiment, the support
plate 250 may also comprise openings to accommodate ground pins
235, which are aligned with these openings. In other words, in
certain embodiments, all of the openings in the support plate 250
are used for the lift pins 231 and the ground pins 235.
[0040] In other embodiments, additional holes may be disposed in
the support plate 250. These additional holes may be aligned with
the fluid conduits 270 in the platen 200 that carry the backside
gas.
[0041] In this way, if desired, backside gas may be introduced into
the volume between the top surface of the support plate 250 and the
bottom of the workpiece.
[0042] The present system has many advantages. These advantages are
both mechanical and thermal in nature.
[0043] With respect to the mechanical advantages, the vertically
aligned carbon nanotubes are flexible, and easily bend elastically.
Consequently, the friction between the carbon nanotubes and the
workpiece may be much lower than is currently experienced between
the workpiece and the embossments on the top surface of the platen.
This, in turn, may result in the generation of fewer particles.
Further, any particles that are generated would be carbon
molecules, which are typically not deleterious.
[0044] In certain embodiments, the workpiece may be contact the top
surface of the platen. Rather, the vertically aligned carbon
nanotubes may physically separate the workpiece form the top
surface of the platen, further reducing the risk of particle
generation.
[0045] With respect to thermal advantages, it is known that carbon
nanotubes have excellent thermal conductivity. For example, in one
test, it was found that the difference between the temperature of
the workpiece and the temperature of the surface with the carbon
nanotubes was less than 5.degree. C. In other words, as an example,
if the support plate 250 of FIG. 3 was at a particular temperature,
the workpiece may be less than 5.degree. C. greater than this
temperature.
[0046] This thermal performance was achieved without the use of
backside gas. Thus, in certain embodiments, the platen may be that
shown in FIG. 1 which does not contain channels that allow for the
passage of backside gas. Thus, the only openings on the surface of
the platen may be those used for the lift pins. This may simplify
the design and manufacture of the platen. Further, overall cost may
also be reduced, since the backside gas source and the conduits
between the backside gas source and the platen can be
eliminated.
[0047] This thermal performance was also realized using a support
plate, as shown in FIG. 4. Again, in some embodiments, there is no
backside gas in the volume between the support plate 250 and the
workpiece. Yet, the temperature of the workpiece is within
5.degree. C. of the support plate 250.
[0048] The present disclosure is not to be limited in scope by the
specific embodiments described herein. Indeed, other various
embodiments of and modifications to the present disclosure, in
addition to those described herein, will be apparent to those of
ordinary skill in the art from the foregoing description and
accompanying drawings. Thus, such other embodiments and
modifications are intended to fall within the scope of the present
disclosure. Furthermore, although the present disclosure has been
described herein in the context of a particular implementation in a
particular environment for a particular purpose, those of ordinary
skill in the art will recognize that its usefulness is not limited
thereto and that the present disclosure may be beneficially
implemented in any number of environments for any number of
purposes. Accordingly, the claims set forth below should be
construed in view of the full breadth and spirit of the present
disclosure as described herein.
* * * * *