U.S. patent application number 11/111155 was filed with the patent office on 2006-06-22 for purged vacuum chuck with proximity pins.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Harald Herchen.
Application Number | 20060130767 11/111155 |
Document ID | / |
Family ID | 39193608 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060130767 |
Kind Code |
A1 |
Herchen; Harald |
June 22, 2006 |
Purged vacuum chuck with proximity pins
Abstract
A substrate support structure comprising a first surface and a
second surface opposite the first surface. The substrate support
structure also comprises a plurality of proximity pins projecting
to a first height above the first surface, the first height being
less than 100 .mu.m. In addition, the substrate support structure
further comprises a plurality of purge ports passing from the
second surface to the first surface and a plurality of vacuum ports
passing from the second surface to the first surface. In one
embodiment, the plurality of purge ports are arranged in a first
circular pattern, the first circular pattern having a first radial
dimension less than the radius of the substrate support, and the
plurality of vacuum ports are arranged in a second circular
pattern, the second circular pattern having a second radial
dimension less than the first radial dimension.
Inventors: |
Herchen; Harald; (Los Altos,
CA) |
Correspondence
Address: |
Patent Counsel;APPLIED MATERIALS, INC.
Legal Affairs Department, M/S 2061
P.O. Box 450A
Santa Clara
CA
95052
US
|
Assignee: |
Applied Materials, Inc.
Santa Clara
CA
|
Family ID: |
39193608 |
Appl. No.: |
11/111155 |
Filed: |
April 20, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60639109 |
Dec 22, 2004 |
|
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Current U.S.
Class: |
118/728 ;
156/345.51 |
Current CPC
Class: |
H01L 21/6715 20130101;
H01L 21/67196 20130101; Y10S 414/136 20130101; G05B 2219/49137
20130101; Y10T 29/5323 20150115; H01L 21/6838 20130101; Y10S
414/135 20130101; H01L 21/67754 20130101; H01L 21/67161 20130101;
H01L 21/67173 20130101; H01L 21/67745 20130101; G05B 2219/45031
20130101; Y02P 90/087 20151101; Y10T 29/53187 20150115; G03B 27/32
20130101; H01L 21/67178 20130101; Y02P 90/02 20151101; H01L
21/67225 20130101; G03F 7/40 20130101; G05B 2219/40476 20130101;
H01L 21/67184 20130101; G05B 19/41825 20130101; H01L 21/67748
20130101; H01L 21/6719 20130101; G03D 13/006 20130101; H01L
21/68707 20130101; H01L 22/26 20130101; H01L 21/67109 20130101;
H01L 21/67742 20130101; H01L 21/6831 20130101 |
Class at
Publication: |
118/728 ;
156/345.51 |
International
Class: |
H01L 21/306 20060101
H01L021/306; C23C 16/00 20060101 C23C016/00 |
Claims
1. A substrate support structure, the structure comprising: a
substrate support comprising a first surface and a second surface
opposite the first surface; a plurality of proximity pins
projecting to a first height above the first surface, the first
height being less than 100 .mu.m; a plurality of purge ports
passing from the second surface to the first surface; and a
plurality of vacuum ports passing from the second surface to the
first surface.
2. The substrate support structure of claim 1 wherein the plurality
of purge ports are arranged in a first circular pattern, the first
circular pattern having a first radial dimension less than the
radius of the substrate support; and the plurality of vacuum ports
are arranged in a second circular pattern, the second circular
pattern having a second radial dimension less than the first radial
dimension.
3. The substrate support structure of claim 2 further comprising an
annular spacer ridge characterized by a radial dimension greater
than the second radial dimension and extending a second height
above the first surface, wherein the second height is less than the
first height.
4. The substrate support structure of claim 1 wherein the plurality
of proximity pins comprise materials selected from the group
consisting of silicon, silicon oxides, metals, ceramics, polymers,
diamond, diamond-like carbon, boron nitride, single crystalline
.alpha.-alumina, and polycrystalline .beta.-alumina.
5. The substrate support structure of claim 1 wherein the substrate
support is fabricated from a material selected from the group
consisting of stainless steel, silicon carbide, copper, graphite,
aluminum, aluminum nitride, aluminum oxide, boron nitride, anodized
aluminum, and sealed anodized aluminum.
6. A method of manufacturing a substrate support structure, the
method comprising: providing a substrate support, the substrate
support comprising a first surface and a second surface opposite
the first surface; forming a plurality of recessed regions in the
first surface; providing a plurality of seed crystals having at
least one planar surface; placing the plurality of seed crystals in
the plurality of recessed regions so that the at least one planar
face is substantially coplanar with the first surface; and
selectively depositing a plurality of proximity pins in contact
with the plurality of seed crystals and extending to a first height
above the first surface.
7. The method of claim 6 further comprising: forming a plurality of
vacuum ports passing from the first surface to the second surface;
and forming a plurality of purge ports passing from the second
surface to the first surface.
8. The method of claim 6 wherein selectively depositing comprises a
homoepitaxial growth process.
9. The method of claim 6 wherein the plurality of seed crystals are
fabricated from a material selected from the group consisting of
diamond, silicon, silicon oxide, boron nitride, and aluminum
oxide.
10. The method of claim 6 wherein the first height is less than 100
.mu.m.
11. A method of manufacturing a substrate support structure, the
method comprising: providing a substrate support, the substrate
support comprising a first surface and a second surface opposite
the first surface; forming a plurality of recessed regions in the
first surface, the plurality of recessed regions characterized by a
first depth; providing a plurality of support structures
characterized by a dimension greater than the first depth;
inserting the plurality of support structures into the plurality of
recessed regions; pressing the plurality of support structures into
the plurality of recessed regions to align a surface of the
plurality of support structures with the first surface, thereby
deforming the plurality of recessed regions; removing a portion of
the substrate support defined by a depth measured from the first
surface to a third surface to expose to expose a portion of the
support structures.
12. The method of claim 11 wherein the support structures are
sapphire spheres.
13. The method of claim 12 wherein the dimension is a diameter of
the sapphire spheres.
14. The method of claim 13 wherein the diameter is less than
approximately 4 mm.
15. The method of claim 11 wherein the step of inserting the
plurality of support structures into the plurality of recessed
regions comprises at least a portion of the plurality of support
structures extending to a second height above the first
surface.
16. The method of claim 11 wherein the depth is approximately 30
.mu.m.
17. The method of claim 11 wherein the step of removing a portion
of the substrate support comprises electropolishing portions of the
first surface of the substrate support.
18. The method of claim 17 wherein electropolishing portions of the
first surface removes a layer of the substrate support less than
100 .mu.m in thickness.
19. The method of claim 11 wherein pressing the plurality of
support structures into the plurality of recessed regions and
aligning a surface of the plurality of support structures with the
first surface comprises using a tool with a level of hardness
greater than or equal to a level of hardness of the support
structures, the level of hardness of the support structures being
greater than or a level of hardness of the substrate support.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/639,109, filed Dec. 22, 2004, entitled
"Twin Architecture For Processing A Substrate," which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to the field of
semiconductor processing equipment. More particularly, the present
invention relates to a method and apparatus for supporting a
substrate inside a semiconductor processing chamber. The method and
apparatus can be applied to electrostatic chucks, vacuum chucks,
and other applications as well.
[0003] Substrate support chucks are widely used to support
substrates within semiconductor processing systems. Two examples of
particular types of chucks used in semiconductor processing systems
include electrostatic chucks (e-chucks) and vacuum chucks. These
chucks are used to retain semiconductor wafers, or other
workpieces, in a stationary position during processing.
[0004] In some semiconductor processing systems, a substrate rests
flush against the surface of the chuck body during processing.
During substrate processing, the chuck material can abrade the
material present on the underside of the substrate, resulting in
the introduction of particulate contaminants to the process
environment. Consequently, during substrate processing operations,
the particles can adhere themselves to the underside of the
substrate and be carried to other process chambers or cause defects
in the circuitry fabricated upon the substrate.
[0005] Therefore, a need exists in the art for methods and
apparatus that reduce the amount of contaminant particles that
adhere to the underside of a substrate during semiconductor
processing.
SUMMARY OF THE INVENTION
[0006] According to the present invention, methods and apparatus
related to semiconductor manufacturing equipment are provided. More
particularly, embodiments of the present invention relate to a
method and apparatus for supporting a substrate during
semiconductor processing operations. The method and apparatus can
be applied to electrostatic chucks, vacuum chucks, and other
applications as well.
[0007] In a specific embodiment of the present invention, a
substrate support structure is provided. The substrate support
structure comprises a first surface and a second surface opposite
the first surface. The substrate support structure also comprises a
plurality of proximity pins projecting to a first height above the
first surface, the first height being less than 100 .mu.m. In
addition, the substrate support structure further comprises a
plurality of purge ports passing from the second surface to the
first surface and a plurality of vacuum ports passing from the
second surface to the first surface. In one particular embodiment,
the plurality of purge ports are arranged in a first circular
pattern, the first circular pattern having a first radial dimension
less than the radius of the substrate support, and the plurality of
vacuum ports are arranged in a second circular pattern, the second
circular pattern having a second radial dimension less than the
first radial dimension.
[0008] In another specific embodiment of the present invention, a
method of manufacturing a substrate support structure is provided.
The method comprises providing a substrate support, the substrate
support comprising a first surface and a second surface opposite
the first surface, and forming a plurality of recessed regions in
the first surface. The method also comprises providing a plurality
of seed crystals having at least one planar surface and placing the
plurality of seed crystals in the plurality of recessed regions so
that the at least one planar face is coplanar with the first
surface. The method further comprises selectively depositing a
plurality of proximity pins in contact with the plurality of seed
crystals and extending to a first height above the first
surface.
[0009] In yet another embodiment of the present invention, another
method of manufacturing a substrate support structure is provided.
The method comprises providing a substrate support, the substrate
support comprising a first surface and a second surface opposite
the first surface, and forming a plurality of recessed regions in
the first surface, the plurality of recessed regions characterized
by a first depth. The method also comprises providing a plurality
of support structures characterized by a dimension greater than the
first depth and inserting the plurality of support structures into
the plurality of recessed regions. The method further comprises
pressing the plurality of support structures into the plurality of
recessed regions to align a surface of the plurality of support
structures with the first surface, thereby deforming the plurality
of recessed regions. Additionally, the method includes removing a
portion of the substrate support defined by a depth measured from
the first surface to a third surface to expose a portion of the
support structures.
[0010] Many benefits are achieved by way of the present invention
over conventional techniques. For example, the present technique
reduces the number of particles generated by contact between the
backside surface of the substrate and the support plate. Moreover,
embodiments of the present invention provide reduced height
proximity pins while controlling the pin height to within a desired
tolerance. The reduction in proximity pin height increases the
thermal transfer rate of energy from the substrate to the plate
assembly, thereby decreasing the time the substrate spends
transitioning to a final temperature, increasing system throughput.
Moreover, in some embodiments, an increase in thermal coupling
between the substrate and plate assembly results in improvements in
the thermally dependent properties of one or more films present on
the surface of the substrate. Merely by way of example, for films
in which control of a critical dimension is a function of diffusion
and/or chemical reactions, improvements in control of the critical
dimension may result from increased thermal coupling.
[0011] Additionally, increased thermal coupling between the
substrate and the plate assembly reduces the thermal impact of any
chamber non-uniformities. Some embodiments of the present invention
increase the thermal uniformity of the thermal transfer between the
substrate and the plate assembly. Depending upon the embodiment,
one or more of these benefits may be achieved. These and other
benefits will be described in more detail throughout the present
specification and more particularly below.
[0012] These and other embodiments of the present invention, as
well as its advantages and features, are described in more detail
in conjunction with the text below and attached figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a simplified schematic side view illustration of a
substrate processing chamber according to one embodiment of the
present invention.
[0014] FIG. 2 is a simplified schematic plan view of a vacuum chuck
according to one embodiment of the present invention.
[0015] FIGS. 3A-3C are simplified schematic side view illustrations
of a method of fabricating a substrate support according to one
embodiment of the present invention.
[0016] FIGS. 4A-4D are simplified schematic side view illustrations
of a method of fabricating a substrate support according to another
embodiment of the present invention.
[0017] FIGS. 5A-5D are simplified schematic side view illustrations
of a method of fabricating a substrate support according to yet
another embodiment of the present invention.
[0018] FIG. 5E is a simplified flowchart illustrating a process of
fabricating a substrate support according to yet another embodiment
of the present invention.
[0019] FIGS. 6A-6D are simplified schematic side view illustrations
of a method of fabricating a substrate support according to an
alternative embodiment of the present invention.
[0020] FIG. 6E is a simplified flowchart illustrating a method of
fabricating a substrate support according to an alternative
embodiment of the present invention.
DESCRIPTION OF SPECIFIC EMBODIMENTS
[0021] According to the present invention, methods and apparatus
related to semiconductor manufacturing equipment are provided. More
particularly, embodiments of the present invention relate to a
method and apparatus for supporting a substrate during
semiconductor processing operations. The method and apparatus can
be applied to electrostatic chucks, vacuum chucks, and other
applications as well.
[0022] FIG. 1 is a simplified schematic side view illustration of a
substrate processing chamber according to one embodiment of the
present invention. In the embodiment illustrated in FIG. 1, the
assembly 180 contains a plate assembly 170 and a vacuum source 175,
which are mounted in a processing module 186. The plate assembly
170 generally contains a plate 170B, plate assembly surface 170A,
protrusions 171, and a vacuum source port assembly 172. In this
configuration the vacuum source 175 is used to create a negative
pressure in the vacuum port plenum 172B, thus causing air to flow
into a number of vacuum ports 172A formed in the surface of the
plate assembly 170, thus creating a reduced pressure behind the
substrate W which causes the substrate W to be biased towards to
the surface of the proximity pins 171. The plate 170B may be made
from a thermally conductive material such as aluminum, copper,
graphite, aluminum-nitride, boron nitride, silicon carbide, and/or
other material, and is in communication with a heat exchanging
device 183A. Additionally, the plate may be made from anodized
materials, including anodized aluminum and sealed anodized
aluminum. Although FIG. 1 illustrates a vacuum chuck, this is not
required by the present invention. Alternative embodiments of the
present invention provide methods and apparatus for supporting a
substrate using an electrostatic chuck.
[0023] In one embodiment, the plate assembly 170 also contains a
gas source port assembly 173 and a gas source 174 to purge the edge
of the substrate during processing to prevent evaporating solvent
vapors from being deposited on the plate assembly surface 170A or
the backside of the substrate due to the reduced pressure generated
behind the substrate (e.g., a vacuum chuck configuration). In this
configuration the gas source 174 is used to create a positive
pressure in the gas port plenum 173B, thus causing the gas to flow
out of a plurality of gas ports 173A formed in the surface of the
plate assembly 170. In one embodiment the gas source 174 is adapted
to deliver an inert gas to the edge of the substrate, such as,
argon, xenon, helium, nitrogen, and/or krypton. The gas source 174
may also be adapted to deliver a fluid to the edge of the
substrate. In some embodiments, additional gas ports and their
associated gas lines and sources, may be provided as heat transfer
aids. For example, in one particular embodiment, helium gas is
provided through appropriate ports to the backside of the substrate
to cool the substrate as part of a processing sequence. One of
ordinary skill in the art would recognize many variations,
modifications, and alternatives.
[0024] FIG. 2 is a simplified schematic plan view of a vacuum chuck
according to one embodiment of the present invention. The surface
of the plate assembly 170 is illustrated in FIG. 2 with no
substrate on top of the proximity pins 171. Thus, this figure
illustrates one possible configuration of proximity pins 171 (33
shown), vacuum ports 172A (.about.367 shown), and gas ports 173A
(.about.360 shown). In general a number of proximity pins 171 are
spaced across the surface of the plate assembly 170 so that the
contact area can be minimized and the gap between the substrate and
the plate assembly surface 170A can be maintained at a
substantially uniform distance.
[0025] In addition, a number of vacuum ports 172A are spaced across
the surface of the plate assembly 170 so that the substrate can be
uniformly biased towards the plate assembly 170, providing for a
substantially uniform gap between the substrate and the plate
assembly surface 170A. In one embodiment, as shown in FIG. 2 an
inner array of vacuum ports 172A (see item "A") is mirrored with an
outer array of gas ports 173A (see item "B"), where the diameter of
the inner array "A" is smaller than the substrate diameter. Thus,
vacuum ports are positioned under the substrate. Moreover, the
diameter of the outer array "B" is equal to or larger than the
substrate diameter, but less than the diameter of the plate
assembly. In the embodiment illustrated in FIG. 2, the diameter of
the vacuum ports located across the surface of the plate assembly
varies as a function of position. In one particular embodiment, the
vacuum ports arrayed as item "A" have a diameter smaller than
vacuum ports distributed across the interior portions of the
surface of the plate assembly. However, this is not required by the
present invention. In alternative embodiments, the vacuum port
diameters are equal or varied in other manners. One of ordinary
skill in the art would recognize many variations, modifications,
and alternatives.
[0026] In one embodiment, a small ridge of material is placed
between the inner array of vacuum ports 172 and the outer array of
gas ports 173 to minimize the amount of gas required to purge the
edge of the substrate. As described more fully below, in some
embodiments, material deposited by chemical vapor deposition (CVD)
or physical vapor deposition (PVD) is used to form the proximity
pins 171 and the small ridge of material placed between the inner
array of vacuum ports 172A and the outer array of gas ports
173A.
[0027] FIGS. 1 and 2 also illustrate a configuration having a lift
assembly 87 and lift pin hole 189 extending through the plate
assembly surface 170A to lift the substrate off the plate assembly
surface 170A.
[0028] In one embodiment, the gas delivered from the gas source 174
is heated prior to exiting the gas ports 172A to prevent cooling of
the edge of the substrate W during processing. In another
embodiment, the length of the gas port plenum 173B in the plate
assembly 170 is designed to assure that the gas resides in the gas
port plenum long enough for the injected gas to substantially
achieve the plate temperature before it exits the gas ports 172A.
As discussed above with respect to helium backside cooling, other
gases may be delivered from various ports (not shown) to either
cool or heat the substrate as appropriate.
[0029] Various methods have been employed to increase the thermal
coupling of the substrate to the chuck and consequently the heat
exchanging device. Increased thermal coupling allows for reduction
in the processing time, increased system throughput, and increased
control over critical dimensions (CD). In a specific embodiment of
the present invention, the thermal coupling is increased by
decreasing the distance between the substrate and the chuck. As
evident to one of skill in the art, decreasing the spacing between
the substrate and the chuck will lead to an increase in convective
heat transfer across the gap.
[0030] Moreover, increasing the contact area between the substrate
backside surface and the surface of the plate assembly 170 will
increase the thermal coupling and reduce the time it takes a
substrate to reach the desired process temperature. However,
increasing the contact area is often undesirable since it will
generally increase the number of particles generated on the
backside of the substrate, which can adversely impact the
processing results and cause defects in the circuitry fabricated
upon the substrate.
[0031] One method of reducing the number of particles generated on
the backside of the substrate is to minimize the contact area of
the substrate to the surface of the plate assembly. Accordingly, an
array of proximity pins or proximity pins that space the substrate
off the surface of the plate assembly have been utilized. While the
use of proximity pins reduces the number of particles generated,
they may tend to reduce the thermal coupling between the substrate
and the plate assembly. Therefore, it is often desirable to
minimize the height of the proximity pins above the surface of the
plate assembly to improve the thermal coupling, while also assuring
that the substrate will not touch the surface of the plate
assembly. Some applications have used sapphire spheres that are
pressed or placed into machined holes in the plate assembly surface
to act as proximity pins. However, it is often difficult to
mechanically control the height to which the spheres extend above
the surface of the plate assembly.
[0032] Referring to FIG. 1, one embodiment of the present invention
provides an array of accurately controlled small contact area
proximity pins 171 that are formed on the surface of the plate
assembly 170. In the embodiment illustrated in FIG. 1, the
substrate is biased towards the plate assembly by vacuum ports to
increase the thermal coupling between the substrate and the plate
assembly. As illustrated, the substrate may be biased towards the
plate assembly 170 by use of a vacuum chucking device.
Additionally, other embodiments of the present invention utilize an
electrostatic chucking device or other conventional methods of
forcing the substrate against plate assembly. One of ordinary skill
in the art would recognize many variations, modifications, and
alternatives. The array of accurately controlled small height
proximity pins 171 can be formed by a variety of methods, as
described more fully below.
[0033] In embodiments of the present invention, a number of
proximity pins are distributed across the face of plate assembly
170. For example, in one particular embodiment, 17 proximity pins
are utilized with the following locations: one pin at the center,
four pins arranged at corners of a square concentric with the
center pin, with a side equal to 50 mm, twelve pins arranged near
the periphery of the plate assembly, separated from each other by
arcs of 300. Preferably, the proximity pins are fabricated from a
material with a low coefficient of friction. Accordingly, contact
between the proximity pins and the substrate will produce a reduced
number of particles.
[0034] According to calculations we have performed, it is desirable
to select the distribution pitch of proximity pins across the face
plate surface to achieve goals related to maximum substrate bowing.
Utilizing a 74 mm pitch between adjacent proximity pins, we have
determined that it is possible to support a substrate with a
maximum bowing at the substrate edge of about 5 .mu.m. In designs
with a 50 mm pitch between adjacent proximity pins, the maximum
substrate bowing can be reduced to about 2.8 .mu.m. Of course, the
particular maximum bowing desired by the system operator will
depend on the particular applications.
[0035] In some embodiments of the present invention, a two-step
chucking process is utilized to flatten the wafer in a step-wise
fashion. Generally, substrates or wafers possess a degree of bowing
or warpage before they are place on the chuck. Thus, embodiments of
the present invention use methods and systems to reduce wafer
bowing, providing an increase in the uniformity of the gap between
the wafer and the chuck surface. For example, in an embodiment
utilizing an e-chuck, a first chucking step is used in which a
first chucking voltage is applied to initially remove a first
amount of wafer bowing. After the first chucking voltage is
applied, reducing the wafer bowing to a second value, a second
chucking voltage is applied to maintain the wafer bowing profile
achieved using the first chucking voltage. In a specific
embodiment, the second chucking voltage is less than the first
chucking voltage. As will be apparent to one of skill in the art,
the pressure applied by an e-chuck increases with chucking voltage.
Moreover, the amount of pressure required to flatten a substrate
increases with increased bowing. Thus, in this specific embodiment,
a high chucking voltage is used to apply a first high pressure,
substantially flattening a substrate characterized by a first
amount of wafer bowing. After the initial voltage removes a
significant portion of the substrate bowing, a reduced voltage is
sufficient to maintain the desired substrate flatness. Of course,
one of skill in the art will appreciate that this chucking process
may be performed in more than two steps, incrementally decreasing
the chucking voltage over a number of steps.
[0036] FIGS. 3A-3C are simplified schematic side view illustrations
of a method of fabricating a substrate support according to one
embodiment of the present invention. As illustrated in FIG. 3, a
plate 300 is provided. Generally, the plate is adapted to support a
substrate, for example a silicon wafer, during semiconductor
processing operations. For purposes of clarity, various components
of the plate assembly, including vacuum and purge ports, electrodes
for electrostatic chucking mechanisms, heat exchanger elements,
lift pin holes, etc. are omitted from the figures. One of ordinary
skill in the art will appreciate that the plate is one portion of a
larger plate assembly as illustrated in FIG. 1. In some
embodiments, the plate 300 is an aluminum plate coated with a
polymer. Merely by way of example, the plate may be an aluminum
plate coated with Teflon.RTM. manufactured by Dupont Incorporated
of Wilmington, Del. or Tufram.RTM. manufactured by General
Magnaplate Corporation of Linden, N.J. In alternative embodiments,
plate 405 is fabricated from stainless steel, silicon carbide,
copper, graphite, aluminum, aluminum nitride, aluminum oxide, boron
nitride, or combinations/laminates of these materials.
[0037] As illustrated in FIG. 3A, recessed regions 302 are formed
in an upper surface 304 of the plate 300. The recessed regions 302
are formed by methods well known to one of skill in the art, for
example, etching, ion milling, electric discharge machining, or
laser ablation. After formation of the recessed regions, a seed
crystal 310 is embedded in the plate 300. In one embodiment, the
seed crystal is approximately the same size as the recessed region.
Therefore, embedding of the seed crystal in the plate 300
constitutes a relatively permanent affixing of the seed crystal to
the plate. Merely by way of example, the seed crystal may be
diamond, silicon, silicon oxide, boron nitride, aluminum oxide, and
silicon carbide, or other material that is suitably hard. In this
embodiment, a seed crystal 310 is embedded into each of the
recessed regions 302 so that the top surface of the seed crystal is
substantially flush with the plate surface 304.
[0038] In one aspect of the invention, a tool that has a surface
that is at least as hard as the material from which the seed
crystal 310 is made, is used to embed the seed crystal in the plate
300. In these embodiments, the tool material is preferably
relatively incompressible, has low ductility, and has a polished
face. One example of a suitable tool is a sapphire disk
manufactured by Saint-Gobain Saphikon, Inc., of Miford, N.H. In an
embodiment, the surface of the sapphire disk is preferably
characterized by flatness specifications such as a RMS roughness on
the order of 5,000 .ANG. over a lateral distance of 10 mm and a
radius of curvature of 12.5 m over a lateral distance of 10 mm. The
tool is used in a method that embeds the seed crystal 310 in a
repeatable manner so that the seed crystal is installed
substantially flush with the plate surface 310.
[0039] As illustrated in FIG. 3C, proximity pins 320 are
selectively deposited on the seed crystal 310 using a CVD or PVD
process. For example, CVD and PVD processes enable the deposition
of a thin layer of material of controlled size, producing a uniform
layer of desired thickness on the surface of the plate assembly.
The material deposited on the surface of the plate 300 to form the
proximity pins 320 may be diamond, diamond-like carbon, sapphire,
boron nitride, silicon dioxide (SiO.sub.2), silicon (Si), a metal
(e.g., nickel, titanium, titanium nitride, molybdenum, tungsten), a
ceramic material, a polymeric material (e.g., polyimide or
Teflon.RTM.) or other suitable material. Generally, a suitable
material is hard enough to withstand the biasing force without
appreciable deformation and is not easily abraded by the
interaction with backside of the substrate.
[0040] Preferably, selective epitaxy or deposition processes are
used to form the proximity pins 320 on the seed crystals 310. In
one embodiment, a homoepitaxial growth process performed using a
methane/hydrogen/oxygen environment in a microwave plasma CVD
chamber is used to form the proximity pins. Depending on the growth
parameters, including chamber temperature and chemistry, growth
rates of up to tens of microns per hour can be achieved. Thus,
using CVD or PVD processes, the height 322 of the proximity pin 320
can be controlled to a predetermined tolerance. In one embodiment,
the tolerance is .+-.10 .mu.m. In alternative embodiments, the
tolerance is controlled within a range extending from about .+-.10
.mu.m to about .+-.30 .mu.m. Thus, proximity pins with heights on
the order of several to hundreds of microns are controllably
provided by embodiments of the present invention.
[0041] FIGS. 4A-4D are simplified schematic side view illustrations
of a method of fabricating a substrate support according to another
embodiment of the present invention. As illustrated in FIG. 4A, a
plate 405 is provided. Generally, the plate is adapted to support a
substrate, for example a silicon wafer, during semiconductor
processing operations. For purposes of clarity, various components
of the plate assembly, including vacuum and purge ports, electrodes
for electrostatic chucking mechanisms, heat exchanger elements,
lift pin holes, etc. are omitted from the figures. One of ordinary
skill in the art will appreciate that the plate is one portion of a
larger plate assembly as illustrated in FIG. 1. In some
embodiments, as discussed previously, the plate 405 is an aluminum
plate coated with a polymer. In alternative embodiments, plate 405
is fabricated from stainless steel, silicon carbide, copper,
graphite, aluminum, aluminum nitride, aluminum oxide, boron
nitride, or combinations/laminates of these materials.
[0042] A number of recessed regions 412 are formed in surface 410
of the plate 405. As illustrated in FIG. 4A, the recessed regions
412 are formed through a portion of the plate 405 using methods
well known to one of skill in the art. In a specific embodiment,
the recessed regions are fabricated with a predetermined width 416
and depth 414. In the embodiment of the present invention
illustrated in the figure, the recessed regions are generally
cylindrical in shape, although this is not required by the present
invention. Recessed regions of other shapes, for example, square,
are utilized in alternative embodiments. In a specific embodiment,
the width 416 of the recessed region is 1 mm and the depth 414 is 2
mm. In alternative embodiments, the width ranges from about 0.2 mm
to about 3 mm and the depth ranges from about 0.5 mm to about 5 mm.
In a particular embodiment, the width and depth are equal, forming
a cylinder with a diameter equal to the height.
[0043] Support members 420 are provided and placed in recessed
regions 412. As illustrated in FIG. 4B, the support members 420 are
spherical in shape and have a diameter greater than the width of
the recessed regions. Accordingly, a portion of the support members
extends above the surface 410 of the plate 405 after initial
placement. In embodiments of the present invention, the support
members are sapphire precision spheres of predetermined diameter.
Merely by way of example, sapphire precision spheres of a diameter
of 0.5 mm with a sphericity of 0.000025'' and a basic diameter
tolerance of .+-.0.0001'' are available from Meller Optics, Inc. of
Providence R.I. For sapphire precision spheres within the same lot,
the tolerance can be as low as 0.00005''.
[0044] As illustrated in FIG. 4C, the support members are pressed
into the plate or substrate support 405 so that an upper surface
424 of the support member lies in the plane defined by the upper
surface 410 of the plate. In one aspect of the invention, a tool
that has a surface that is at least as hard as the material from
which the support member is made, is used to embed the support
member in the plate 405. In these embodiments, the tool material is
preferably relatively incompressible, flat, and has a polished
face. One example of a suitable tool is the Supercool 300 mm chuck
manufactured by ERS-GmbH of Munich, Germany. The surface 432 of
plate is characterized by a RMS roughness of 20,000 .ANG. over a
distance of 10 mm. Merely by way of example, as illustrated in FIG.
4C, sapphire precision spheres can be forced into the substrate
support plate by applying downward pressure from a relatively
incompressible, flat plate 432 placed adjacent to surface 410 of
the plate.
[0045] As illustrated in FIG. 4C, flat plate 430 with tool surface
432 is placed adjacent the surface 410 and plates 405 and 430 are
pressed together. Preferably, the material from which the flat
plate 430 is fabricated is selected to possess a level of hardness
greater than or equal to the hardness of the support member
material, which in turn, is selected to possess a level of hardness
greater than or equal to the hardness of the substrate support
plate 405. For example, sapphire, with a hardness of about 40 GPa
(compared to diamond with a hardness of about 90 GPa), is generally
considered one of the hardest materials. Thus, in applications
which utilize flat plates and support members fabricated from
sapphire, applying pressure to the upper surface of a sapphire
ball, as illustrated in FIG. 4C, will deform the a substrate
support plate fabricated from softer materials. Accordingly, the
sapphire spheres will be forced into the recessed region, locally
deforming the regions of the substrate support plate adjacent the
recessed regions.
[0046] After deformation of the substrate support plate, the
support members will be embedded into the plate to a depth greater
than the original depth of the recessed regions, represented by
reference numeral 434. Moreover, the width of the recessed region
will be extended to a width greater than the original width at some
portions of the structure.
[0047] Merely by way of example, if the substrate support plate is
an aluminum plate, which generally has a hardness approximately ten
times less that of sapphire, the substrate support plate will
deform to receive the sapphire spheres as illustrated in the
figure. Some embodiments of the present invention utilize an
embedding tool equal in diameter to the diameter of the plate 405.
In alternative embodiments, an embedding tool with a diameter less
than the diameter of the plate 405 is utilized to force one or more
support members into plate 405 simultaneously or sequentially.
After the step of forcing the support members into the plate
illustrated in FIG. 4C, the support members are flush with the
surface 410.
[0048] FIG. 4D illustrates a process of removing a portion of the
substrate support plate to expose proximity pins extending above a
third surface 438 of the plate by a height 442. One embodiment of
the present invention utilizes an electropolishing process
performed in a bath to remove a predetermined portion of the plate
405 and expose the third surface 438. In an electropolishing
process, an amount of material is removed proportional to the total
charge, providing measurement and control over the amount of
material removed. In some embodiments, the electropolishing process
is utilized to remove an amount of material characterized by a
height equal to a predetermined fraction of the size of the support
member. For example, as illustrated in FIG. 4D, the height 442 of
the material removed from the plate is equal to about 20% of the
diameter of the sapphire precision sphere. Of course, in
alternative embodiments, greater or lesser material is removed as a
percentage of the support member dimensions. One of ordinary skill
in the art would recognize many variations, modifications, and
alternatives.
[0049] In embodiments of the present invention in which the
substrate support plates are coated, the presence of the coating is
accounted for during the fabrication process. For example, in a
substrate support plate coated with Teflon.RTM., an additional
amount of material is removed during the electropolishing process
equal to the thickness of the Teflon.RTM. layer eventually
deposited, for example, 200 .ANG.. Thus, after the substrate
support plate is electropolished, exposing the proximity pins by an
additional height of 200 .ANG., a selective coating process is
performed to form the Teflon.RTM. layer. In one embodiment, the
selective coating process forms the coating layer only on the
substrate support plate and not the proximity pins. Therefore, the
final proximity pin height above the Teflon.RTM. layer, for
example, is controlled by the combination of additional
electropolishing counterbalanced by the formation of the
Teflon.RTM. layer.
[0050] As illustrated in FIG. 4D, an amount of material of depth
438 (measured from the first surface to the third surface) is
removed from the upper surface of the plate, with the
electropolishing process being terminated once the upper plate
surface reaches the plane defined by third surface 438. Thus,
proximity pins of a desired height are produced utilizing
embodiments of the present invention. In a specific embodiment, the
electropolishing process is utilized to remove 30 .mu.m of material
measured from surface 410 of plate 405. Thus, proximity pins 420
extend to a height of 30 .mu.m above surface 438. In alternative
embodiments, the height of the proximity pins is greater or less
than 30 .mu.m. Therefore, embodiments of the present invention
provide methods and apparatus for forming proximity pins of
controllable height on a surface of a substrate support plate.
[0051] FIGS. 5A-5D are simplified schematic side view illustrations
of a method of fabricating a substrate support according to yet
another embodiment of the present invention. As illustrated in FIG.
5A, a plate 500 is provided. Generally, the plate is adapted to
support a substrate, for example a silicon wafer, during
semiconductor processing operations. For purposes of clarity,
various components of the plate assembly, including vacuum and
purge ports, electrodes for electrostatic chucking mechanisms, heat
exchanger elements, lift pin holes, etc. are omitted from the
figures. One of ordinary skill in the art will appreciate that the
plate is one portion of a larger plate assembly as illustrated in
FIG. 1. In some embodiments, as discussed previously, the plate 405
is an aluminum plate coated with a polymer. In alternative
embodiments, plate 405 is fabricated from stainless steel, silicon
carbide, copper, graphite, aluminum, aluminum nitride, aluminum
oxide, boron nitride, or combinations/laminates of these
materials.
[0052] Layer 510, with a thickness 512, is deposited on the plate
500. The material deposited on the surface of the plate 500 to form
layer 510 may be diamond, diamond-like carbon, sapphire, boron
nitride, silicon dioxide (SiO.sub.2), silicon (Si), aluminum
oxynitride, a metal (e.g., nickel, titanium, titanium nitride,
molybdenum, tungsten), a ceramic material, a polymeric material
(e.g., polyimide or Teflon.RTM.) or other suitable material.
Generally, a suitable material is hard enough to withstand the
biasing force without appreciable deformation, is not easily
abraded by the interaction with backside of the substrate, and can
be patterned after deposition. Control of deposition processes to
achieve repeatable and uniform deposition of layers is well known
to one of skill in the art.
[0053] A mask layer is deposited and patterned as illustrated in
FIG. 5B to form a number of masking structures 520 with a lateral
dimension equal to distance 522. Patterning of mask layers is well
known to one of ordinary skill in the art. After patterning of the
mask layer to form masking structures 520, layer 510 is selectively
removed to form a number of proximity pins 530. As illustrated in
FIG. 5C, the making structures 520 are not modified during the
proximity pin formation process. In alternative embodiments, the
masking structures degrade during the proximity pin formation
process, resulting in proximity pins with tapered upper surfaces.
For example, masking structure that erode at the edges permit the
proximity pin formation process to begin removing outer portions of
the proximity pins prior to centrally located portions. Thus, some
embodiments of the present invention provide a method of
manufacturing proximity pins with tapered upper surfaces. One of
ordinary skill in the art would recognize many variations,
modifications, and alternatives.
[0054] The masking structures are removed as illustrated in FIG. 5D
to expose proximity pins 530. Based on the deposition and masking
processes described above, the proximity pins will have
predetermined heights and lateral dimensions. In the embodiment
illustrated in FIG. 5D, proximity pins with a height of 30 .mu.m
and lateral dimensions of several millimeters are provided. In
alternative embodiments, proximity pins with greater or lesser
heights are provided.
[0055] Although the formation of proximity pins utilizing masking
structures deposited on a proximity pin layer were described in
reference to FIGS. 5A to 5D, the present invention as illustrated
in FIGS. 5A to 5D is not limited to this fabrication method. An
alternative formation method utilizes other selective deposition
processes to form the proximity pins. For example, in one
embodiment, a stencil mask (not shown) is placed over the surface
of the plate 500, thereby allowing CVD or PVD material to be
deposited (in lieu of layer 510) on certain defined areas of the
substrate by use of features or holes formed in the stencil mask.
In this way the lateral dimensions of the proximity pins are
controlled by the features formed in the mask and the height of the
proximity pins can be controlled by assuring a certain amount of
material is deposited on the surface of the plate 500 using a known
PVD or CVD process deposition rate. In one embodiment, the
proximity pins which are deposited by a PVD or CVD process are
about 100 .mu.m thick.
[0056] Merely by way of example, a process utilizing a stencil mask
to fabricate a substrate support is illustrated as follows. A
substrate support member is provided, the substrate support member
having a first surface and a second surface opposite the first
surface. A stencil mask is provided having a solid background and a
number of open features arrayed on the solid background. The
stencil mask is positioned in relation to the substrate support
member and the combination is exposed to a deposition process such
that deposited materials pass through the open features to form a
number of proximity pins in contact with the first surface. After
deposition, the stencil mask is removed to expose the number of
proximity pins.
[0057] FIG. 5E is a simplified flowchart illustrating a process of
fabricating a substrate support according to yet another embodiment
of the present invention. In step 560, a substrate support is
provided, the substrate support has a first surface and a second
surface opposite the first surface. In some embodiments, the
substrate support is a thermally conductive material. A spacer
layer is deposited over the first surface in step 562. In
embodiments of the present invention, a PVD or CVD process is
utilized to deposit the spacer layer. Moreover, the thickness of
the spacer layer is a predetermined thickness, for example, less
than 100 .mu.m. In step 564, a masking layer is deposited over the
spacer layer and the masking layer is patterned in step 566 to form
a spacer structure mask. The spacer structure mask has
predetermined lateral dimensions. In a specific embodiment, the
lateral surface area of the spacer structure mask is less than 3%
of the surface area of the first surface.
[0058] In step 568, the spacer layer is selectively removed in
unmasked areas of the spacer layer to form a number of proximity
pins. Techniques for etching and removing materials are well known
to one of skill in the art. In some embodiments, the spacer
structure mask erodes during the spacer layer removal process,
producing proximity pins with tapered upper surfaces. For example,
in embodiments in which the spacer structure mask preferentially
erodes at the edges, proximity pins with an upper surface
characterized by a cross-section defined by an arc of a hemisphere
are produced.
[0059] Moreover, in other embodiments of the present invention, the
etching or removal process are continued to remove an upper strata
of the first surface in unmasked areas of the spacer layer. In step
570, the spacer structure mask is removed to expose the plurality
of proximity pins. Optional steps 572 and 574 form a plurality of
vacuum ports passing from the first surface to the second surface
and a plurality of purge ports passing from the second surface to
the first surface, respectively. In some embodiments employing
optional step 574, the plurality of purge ports are arranged in a
first circular pattern, wherein the first circular pattern has a
first radial dimension less than the radius of the substrate
support plate. Additionally, in some embodiments employing optional
step 572, the plurality of vacuum ports are arranged in a second
circular pattern, the second circular pattern having a second
radial dimension less than the first radial dimension. Moreover, in
some embodiments employing both optional steps, the first circular
pattern and the second circular pattern are concentric.
[0060] FIGS. 6A-6D are simplified schematic side view illustrations
of a method of fabricating a substrate support according to an
alternative embodiment of the present invention. As illustrated in
FIG. 6A, a plate 600 is provided. Generally, the plate is adapted
to support a substrate, for example a silicon wafer, during
semiconductor processing operations. For purposes of clarity,
various components of the plate assembly, including vacuum and
purge ports, electrodes for electrostatic chucking mechanisms, heat
exchanger elements, lift pin holes, etc. are omitted from the
figures. One of ordinary skill in the art will appreciate that the
plate is one portion of a larger plate assembly as illustrated in
FIG. 1. In some embodiments, as discussed previously, the plate 600
is an aluminum plate coated with a polymer. In alternative
embodiments, plate 600 is fabricated from stainless steel, silicon
carbide, copper, graphite, aluminum, aluminum nitride, aluminum
oxide, boron nitride, or combinations/laminates of these
materials.
[0061] In one, embodiment, a mask layer is deposited and patterned
as illustrated in FIG. 6B to form a number of masking structures
610 with predetermined lateral dimensions. Patterning of mask
layers is well known to one of ordinary skill in the art. In
alternative embodiments, individual masking structures are bonded
to surface 605 of plate 600. For example, .beta.-Al.sub.2O.sub.3 or
diamond studs may be epoxied to surface 605 to provide masking
structures 610.
[0062] After the masking structures are provided, a process is
performed to selectively remove a portion 620 of plate 600. In a
particular embodiment of the present invention, a grit-blasting
technique is utilized to remove portion 620 of a silicon carbide
plate, producing the structure illustrated in FIG. 6C. Masking
structures 610 are removed to expose proximity pins 640 with a
predetermined height 642 and predetermined lateral dimensions. In
the embodiment illustrated in FIG. 6D, proximity pins extend to a
predetermined distance above surface 644, for example, a height of
30 .mu.m measured from surface 644 and lateral dimensions of
several millimeters are provided. In alternative embodiments,
proximity pins with greater or lesser heights are provided.
[0063] As illustrated in FIGS. 6B and 6C, making structures 610 are
not modified during the proximity pin formation process. In
alternative embodiments, the masking structures degrade during the
proximity pin formation process, resulting in proximity pins with
tapered upper surfaces. For example, masking structures that erode
at the edges during a grit-blasting process permit the proximity
pin formation process to begin removing outer portions of the
proximity pins prior to centrally located portions. Thus, some
embodiments of the present invention provide a method of
manufacturing proximity pins with tapered upper surfaces. One of
ordinary skill in the art would recognize many variations,
modifications, and alternatives.
[0064] FIG. 6E is a simplified flowchart illustrating a method of
fabricating a substrate support according to an alternative
embodiment of the present invention. In step 670, a substrate
support member is provided, the member comprising a first surface
and a second surface opposite the first surface. In a specific
embodiment, the substrate support member is fabricated from silicon
carbide. A number of spacer structure masks are bonded to the first
surface in step 672. Embodiments according to the present invention
utilize a number of different materials for spacer structure masks,
including .beta.-Al.sub.2O.sub.3, diamond, polymeric resins,
silicone, polyimide, and vinyl. In some embodiments, the spacer
structure masks are polycrystalline. Moreover, in some embodiments
of the present invention, the spacer structure masks are bonded to
the first surface utilizing an epoxy.
[0065] In step 674, a portion of the substrate support member
defined by a depth measured from the first surface to a third
surface is removed to form a plurality of proximity pins projecting
to a first height above a third surface. According to embodiments
of the present invention, the process of removing a portion of the
first surface includes grit blasting the first surface to form the
proximity pins. Moreover, in a particular embodiment, the portion
of the first surface removed by grit blasting is a layer less than
100 .mu.m in thickness. The spacer structure masks are removed in
step 676. In optional steps 678 and 680, a number of vacuum ports
passing from the third surface to the second surface and a number
of purge ports passing from the second surface to the third surface
are formed, respectively.
[0066] Accordingly, while the present invention has been disclosed
in connection with the preferred embodiments thereof, it should be
understood that other embodiments may fall within the spirit and
scope of the invention, as defined by the following claims.
* * * * *