U.S. patent application number 12/851794 was filed with the patent office on 2011-02-10 for dual temperature heater.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Ganesh Balasubramanian, Sanjeev Baluja, Dale R. Du Bois, Thomas Nowak, Juan Carlos Rocha-Alvarez, Lipyeow Yap, Jianhua Zhou.
Application Number | 20110034034 12/851794 |
Document ID | / |
Family ID | 43535135 |
Filed Date | 2011-02-10 |
United States Patent
Application |
20110034034 |
Kind Code |
A1 |
Du Bois; Dale R. ; et
al. |
February 10, 2011 |
DUAL TEMPERATURE HEATER
Abstract
A method and apparatus for heating a substrate in a chamber are
provided. an apparatus for positioning a substrate in a processing
chamber. In one embodiment, the apparatus comprises a substrate
support assembly having a support surface adapted to receive the
substrate and a plurality of centering members for supporting the
substrate at a distance parallel to the support surface and for
centering the substrate relative to a reference axis substantially
perpendicular to the support surface. The plurality of the
centering members are movably disposed along a periphery of the
support surface, and each of the plurality of centering members
comprises a first end portion for either contacting or supporting a
peripheral edge of the substrate.
Inventors: |
Du Bois; Dale R.; (Los
Gatos, CA) ; Rocha-Alvarez; Juan Carlos; (San Carlos,
CA) ; Baluja; Sanjeev; (Campbell, CA) ;
Balasubramanian; Ganesh; (Sunnyvale, CA) ; Yap;
Lipyeow; (Santa Clara, CA) ; Zhou; Jianhua;
(San Jose, CA) ; Nowak; Thomas; (Cupertino,
CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP - - APPM/TX
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
APPLIED MATERIALS, INC.
Santa Clara
CA
|
Family ID: |
43535135 |
Appl. No.: |
12/851794 |
Filed: |
August 6, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61232172 |
Aug 7, 2009 |
|
|
|
Current U.S.
Class: |
438/758 ;
118/500; 257/E21.482; 269/289R |
Current CPC
Class: |
H01L 21/68 20130101;
H01L 21/68728 20130101; C23C 16/4585 20130101; H01L 21/324
20130101; H01L 21/6875 20130101; H01J 37/32091 20130101; B05C 13/00
20130101; H01L 21/67103 20130101 |
Class at
Publication: |
438/758 ;
118/500; 269/289.R; 257/E21.482 |
International
Class: |
H01L 21/46 20060101
H01L021/46; B05C 13/00 20060101 B05C013/00; B23Q 3/00 20060101
B23Q003/00 |
Claims
1. An apparatus for positioning a substrate in a processing
chamber, comprising: a substrate support assembly having a support
surface adapted to receive the substrate; and a plurality of
centering members for supporting the substrate at a distance
parallel to the support surface and for centering the substrate
relative to a reference axis substantially perpendicular to the
support surface, wherein the plurality of the centering members are
movably disposed along a periphery of the support surface, and each
of the plurality of centering members comprises: a first end
portion for either contacting or supporting a peripheral edge of
the substrate, the first end portion comprising: an upper end
portion extending above the support surface of the substrate
support for releasably contacting the peripheral edge of the
substrate; a support tab positioned on the upper end portion; and a
substrate support notch formed by the intersection of the support
tab and the upper end portion, for supporting the substrate,
wherein the first end portion is movable between a first position
and a second position, a movement from the first position to the
second position causes the centering member to release the
peripheral edge of the substrate, and a movement from the second
position to the first position causes the centering member to push
the substrate in a direction toward the reference axis or positions
the centering members for supporting the substrate.
2. The apparatus of claim 1, wherein the substrate support assembly
encapsulates at least one embedded heater operable to controllably
heat the substrate support assembly and the substrate positioned
thereon to a predetermined temperature.
3. The apparatus of claim 1, further comprising a circumscribing
shadow frame positioned to prevent deposition on the peripheral
edge of the substrate, the support assembly, and the plurality of
centering members for reducing flaking and particle contamination
in the process chamber.
4. The apparatus of claim 2, further comprising: a fiber optic
temperature sensor for providing a metric indicative of the
temperature profile of the backside of the substrate.
5. The apparatus of claim 4, wherein the fiber optic temperature
sensor is positioned in the substrate support assembly.
6. The apparatus of claim 2, further comprising: one or more purge
gas inlets coupled with a purge gas source for supplying purge gas
to a backside of the substrate for preventing particle
contamination caused by deposition on the backside of the substrate
when the substrate is supported by the centering members.
7. The apparatus of claim 6, wherein the one or more purge gas
inlets are positioned in the substrate support assembly.
8. The apparatus of claim 1, further comprising an opposing member
for interacting with each of the plurality of centering members to
move the first end portion.
9. The apparatus of claim 8, wherein each of the plurality of
centering members is pivotally mounted on the substrate support via
a shaft.
10. The apparatus of claim 9, wherein the opposing member is
configured to move the first end portion of each of the plurality
of centering members towards the second position, and each of the
plurality of centering members is independently biased towards the
first position, and combination of biasing forces from the
plurality of centering members centers the substrate relative to
the reference axis.
11. The apparatus of claim 10, wherein each of the centering
members further comprises: a weighted portion eccentric from the
shaft, wherein the first end portion and weighted portion are
disposed on opposing sides of the shaft, and the weighted portion
is configured to bias the centering member into the first
position.
12. The apparatus of claim 11, wherein the opposing member
comprises a movable member coupled to a motor.
13. The apparatus of claim 12, further comprising a controller
configured to monitor an operation signal of the motor, wherein the
opposing member is configured to move the first end portion of each
of the plurality of centering members towards the first position,
and the controller is configured to determine an end point of
centering by monitoring the operation signal of the motor.
14. The apparatus of claim 1, wherein each of the centering members
is made of a material including ceramic, aluminum nitride, aluminum
oxide, aluminum, and combinations thereof.
15. The apparatus of claim 1, wherein the support tabs of each of
the plurality of centering members form a substrate receiving
pocket for supporting the substrate.
16. A method for centering a substrate in a processing chamber,
comprising: providing a substrate support having an embedded heater
and a heated support surface adapted to receive a substrate;
providing a plurality of centering members disposed along a circle
centered at a reference axis substantially perpendicular to the
support surface, each centering member comprising: an end portion
configured to contact a peripheral edge of the substrate, and the
end portion is radially movable towards and away from the reference
axis; a support tab positioned on the end portion; and a substrate
support notch formed at an intersection of the support tab and the
end portion, for supporting the substrate at a distance from the
support surface of the substrate support; positioning the substrate
on the support tabs of each of the plurality of centering members;
performing a pre-treatment process on the substrate at a first
processing temperature of the substrate; removing the substrate
from the support tabs; moving the end portion of each centering
member radially outward and away from the reference axis; placing
the substrate on the substrate support, wherein the substrate and
the centering members do not contact; moving the end portion of
each centering members to radially inwards to contact with a
peripheral edge of the substrate for centering the substrate;
positioning the substrate with the end portions of the centering
members; and performing a deposition process on the substrate at a
second processing temperature of the substrate, wherein the first
processing temperature is different than the second processing
temperature.
17. The method of claim 16, wherein the distance between the heated
support surface and the substrate is selected such that the thermal
resistance between the heated support surface and the substrate
create a different temperature on the substrate without changing a
setpoint temperature of the heater.
18. The method of claim 16, wherein a setpoint temperature of the
heater is the same for both the pretreatment process and the
deposition process.
19. The method of claim 16, wherein the first processing
temperature of the substrate is between about 250.degree. C. and
about 270.degree. C. and the second processing temperature of the
substrate is between about 350.degree. C. and about 400.degree.
C.
20. The method of claim 16, wherein moving the end portion of each
centering members comprises pivoting each of the centering members
about a shaft mounted on the substrate support.
21. The method of claim 16, wherein moving the end portion of each
centering member radially inwards comprises releasing a weighted
portion eccentrically coupled to the centering member from the
shaft, and moving the end portion of each centering member radially
outwards comprising lifting the weight portion with an opposing
member.
22. The method of claim 16, wherein moving the end portion of each
centering member radially inwards comprises pivoting the centering
member from the shaft using an opposing member, and moving the end
portion of each centering member radially outwards comprising
releasing the centering member from the opposing member.
23. The method of claim 22, wherein moving the end portion of each
centering member further comprises: monitoring an operational
signal of a motor driving the opposing member, wherein the
operational signal corresponds to a centering force applied from
the centering member to the substrate; and stopping the opposing
member when the centering force reaches a critical value.
24. The method of claim 16, wherein each of the centering members
comprises a resilient member biased radially towards the reference
axis, and moving the end portion of each centering members radially
outwards comprises pushing the resilient member using an opposing
member, and moving the end portion of each centering member
radially inwards comprising releasing the centering member from the
opposing member.
25. The method of claim 16, wherein pivoting the centering members
comprises interacting the centering members with an opposing
member.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. provisional patent
application Ser. No. 61/232,172 (Attorney Docket No. 14440L), filed
Aug. 7, 2009, which is herein incorporated by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention generally relate to
apparatus and methods for processing semiconductor substrates. More
particularly, embodiments of the present invention relate to an
apparatus and methods for heating a substrate in a chamber.
[0004] 2. Description of the Related Art
[0005] The effectiveness of a substrate fabrication process is
often measured by two related and important factors, which are
device yield and the cost of ownership (CoO). These factors are
important since they directly affect the cost to produce an
electronic device and thus a device manufacturer's competitiveness
in the market place. The CoO, while affected by a number of
factors, is greatly affected by the system and chamber throughput,
or simply the number of substrates per hour processed using a
desired processing sequence.
[0006] During certain substrate processing sequences, such as, for
example, chemical vapor deposition processes (CVD) or plasma
enhanced chemical vapor deposition processes (PECVD), it may be
desirable to pre-treat a substrate prior to performing a deposition
process. In certain pre-treatment processes, the substrate may be
heated, for example, using an anneal process, to a first
temperature prior to the deposition process. During the deposition
process, the substrate is heated to a second temperature different
than the first temperature. For many deposition processes, the
substrate is placed on a substrate support comprising a heater.
This heater is used to heat the substrate to both the first
temperature and the second temperature. When there is some variance
between the first temperature and the second temperature, for
example, when the second temperature is higher than the first
temperature, there is a delay between the pre-treatment process and
the deposition process so that the temperature of the heater may be
increased from the first temperature to the second temperature.
This delay leads to an overall increase in substrate processing
time and a corresponding decrease in device yield.
[0007] Therefore there is a need for an apparatus and process that
can position and heat a substrate in a processing chamber in a
cost-effective and accurate manner.
SUMMARY OF THE INVENTION
[0008] Embodiments of the present invention generally relate to
apparatus and methods for processing semiconductor substrates. More
particularly, embodiments of the present invention relate to an
apparatus and methods for heating a substrate in a chamber. In one
embodiment, an apparatus for positioning a substrate in a
processing chamber is provided. The apparatus comprises a substrate
support assembly having a support surface adapted to receive the
substrate and a plurality of centering members for supporting the
substrate at a distance parallel to the support surface and for
centering the substrate relative to a reference axis substantially
perpendicular to the support surface. The plurality of centering
members are movably disposed along a periphery of the support
surface, and each of the plurality of centering members comprises a
first end portion for either contacting or supporting a peripheral
edge of the substrate, the first end portion comprising an upper
end portion extending above the support surface of the substrate
support for releasably contacting the peripheral edge of the
substrate, a support tab positioned on the upper end portion, and a
substrate support notch formed by an intersection of the support
tab and the upper end portion, for supporting the substrate. The
first end portion is movable between a first position and a second
position. Movement from the first position to the second position
causes the centering member to release the peripheral edge of the
substrate and movement from the second position to the first
position causes the centering member to push the substrate in a
direction toward the reference axis or positions the centering
members for supporting the substrate.
[0009] In another embodiment a method for centering a substrate in
a processing chamber is provided. A substrate support having an
embedded heater and a heated support surface adapted to receive a
substrate is provided. A plurality of centering members disposed
along a circle centered at a reference axis substantially
perpendicular to the support surface is provided. Each centering
member comprises an end portion configured to contact a peripheral
edge of the substrate, and the end portion is radially movable
towards and away from the reference axis. A support tab is
positioned on the end portion and a substrate support notch is
formed at an intersection of the support tab and the end portion,
for supporting the substrate at a distance from the support surface
of the substrate support. The substrate is positioned on the
support tabs of each of the plurality of centering members. A
pre-treatment process is performed on the substrate at a first
processing temperature of the substrate. The substrate is removed
from the support tabs. The end portion of each centering member is
moved radially outward and away from the reference axis. The
substrate is placed on the substrate support, wherein the substrate
and the centering members do not contact. The end portion of each
centering member is moved radially inwards to contact a peripheral
edge of the substrate for centering the substrate. The substrate is
positioned with the end portions of the centering members. A
deposition process is performed on the substrate at a second
processing temperature of the substrate, wherein the first
processing temperature is different than the second processing
temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0011] FIG. 1 is a schematic cross-sectional view of one embodiment
of a PECVD system according to embodiments described herein;
[0012] FIG. 2A is a partially enlarged cross-sectional view of one
embodiment of a centering finger of FIG. 1 in a supporting
position;
[0013] FIG. 2B is a partially enlarged cross-sectional view of one
embodiment of a centering finger of FIG. 1 in a centering
position;
[0014] FIG. 2C is a partially enlarged cross-sectional view of one
embodiment of a centering finger of FIG. 1 in a disengaging
position;
[0015] FIG. 3A is a simplified overhead view of one embodiment of a
centering mechanism using three centering fingers to support a
substrate;
[0016] FIG. 3B is a simplified overhead view of one embodiment of a
centering mechanism using three centering fingers to center a
substrate;
[0017] FIG. 4 is a cross-sectional view showing one embodiment of a
centering finger having an eccentric weighed portion;
[0018] FIG. 5A is a partial cross-sectional view illustrating one
embodiment of a centering finger in a supporting position;
[0019] FIG. 5B is a partial cross-sectional view illustrating one
embodiment of a centering finger in a centering position;
[0020] FIG. 5C is a partial cross-sectional view illustrating one
embodiment of a centering finger in a disengaging position;
[0021] FIG. 6 is a partial cross-sectional view illustrating one
embodiment of a centering finger; and
[0022] FIG. 7 is a partial cross-sectional view illustrating one
embodiment of a centering finger.
[0023] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation.
DETAILED DESCRIPTION
[0024] Embodiments described herein relate to an apparatus and
method for heating and centering a substrate that are applicable
for various chamber systems configured to apply diverse
semiconductor processes on a substrate. Although the embodiments
are exemplarily described for use in a deposition chamber, some
embodiments may be applicable for other types of process chambers
that necessitate heating and centering of a substrate. Examples
include, without limitations, loadlock chambers, testing chambers,
deposition chambers, etching chambers, and thermal treatment
chambers.
[0025] FIG. 1 is a schematic cross-sectional view of one embodiment
of a PECVD system 100 having a centering mechanism 140. The system
100 includes a process chamber 102 coupled to a gas source 104. The
process chamber 102 has walls 106 and a bottom 108 that partially
define a process volume 110. The process volume 110 may be accessed
through a port 101 formed in the walls 106 that facilitate movement
of a substrate 112 into and out of the process chamber 102. The
walls 106 and bottom 108 may be fabricated from a unitary block of
aluminum or other material compatible with processing. The walls
106 support a lid assembly 114. The process chamber 102 may be
evacuated by a vacuum pump 116.
[0026] A temperature controlled substrate support assembly 120 may
be centrally disposed within the process chamber 102. The support
assembly 120 may support a substrate 112 during processing. In one
embodiment, the support assembly 120 comprises a support base 122
made of aluminum that may encapsulate at least one embedded heater
103 operable to controllably heat the support assembly 120 and the
substrate 112 positioned thereon to a predetermined temperature. In
one embodiment, the support assembly 120 may operate to maintain
the substrate 112 at a temperature between about 150 degrees
Celsius (.degree. C.) to about 1,000 degrees Celsius (.degree. C.),
depending on the deposition processing parameters for the material
being deposited. In one embodiment, the support assembly may
operate to maintain the substrate 112 at a temperature between
about 250 degrees Celsius (.degree. C.) to about 270 degrees
Celsius (.degree. C.), during a pre-treatment process such as an
anneal process. In one embodiment, the support assembly may operate
to maintain the substrate 112 at a temperature between about 350
degrees Celsius (.degree. C.) to about 400 degrees Celsius
(.degree. C.), during a deposition process.
[0027] The support assembly 120 may have an upper support surface
124 and a lower surface 126. The upper support surface 124 supports
the substrate 112. The lower surface 126 may have a stem 128
coupled thereto. The stem 128 couples the support assembly 120 to a
lift system 131 that moves the support assembly 120 vertically
between an elevated processing position and a lowered position that
facilitates substrate transfer to and from the process chamber 102.
The stem 128 additionally provides a conduit for purge gas and
electrical and temperature monitoring leads between the support
assembly 120 and other components of the system 100. A bellows 130
may be coupled between the stem 128 and the bottom 108 of the
process chamber 102. The bellows 130 provides a vacuum seal between
the process volume 110 and the atmosphere outside the process
chamber 102 while facilitating vertical movement of the support
assembly 120.
[0028] To facilitate the transfer of the substrate 112, the support
base 122 also includes a plurality of openings 133 through which
lift pins 132 are movably mounted. The lift pins 132 are operable
to move between a first position and a second position. The first
position, shown in FIG. 1, allows the substrate 112 to rest on the
upper support surface 124 of the support base 122. The second
position (not shown) lifts the substrate 112 above the support base
122 so that the substrate 112 can be transferred to a substrate
handling robot coming through the port 101. Upward/downward
movements of the lift pins 132 may be driven by a movable plate 134
connected to an actuator 136.
[0029] The support base 122 may be electrically grounded such that
RF power supplied by a power source 138 to a gas distribution plate
assembly 141 positioned between the lid assembly 114 and the
support base 122 (or other electrode positioned within or near the
lid assembly of the chamber) may excite gases present in the
process volume 110 between the support base 122 and the
distribution plate assembly 141. The RF power from the power source
138 may be selected commensurate with the size of the substrate 112
to drive the chemical vapor deposition process.
[0030] The support assembly 120 further comprises a centering
mechanism 140 operable to center the substrate 112 relative to a
vertical reference axis Z perpendicular to the substrate support
plane of the support base 122. The centering mechanism 140 is also
operable to support the substrate 112 at a distance parallel to a
surface of the support base 122. The centering mechanism 140
comprises three or more movable centering fingers 142 positioned at
a periphery of the support base 122, and an opposing plate 144
placed below the fingers 142. Each finger 142 is pivotally mounted
on the support base 122 via a shaft 146. The opposing plate 144 and
the support base 122 are relatively movable so that the opposing
plate 144 may contact and pivot the fingers 142 in a release
position and stay free from the fingers 142 in a centering position
or supporting position.
[0031] In one embodiment, the opposing plate 144 is stationary and
the relative movement between the support base 122 and the opposing
plate 144 is due to the vertical movement of the support base 122.
When there is no substrate 112 positioned on the support base 122,
the fingers 142 engage in a supporting position for supporting the
substrate 112 as shown in FIG. 2A. When the substrate 112 is
positioned on the support base 122, the fingers 142 engage on the
peripheral edge of the substrate 112 to center the substrate 112
when the support assembly 120 is in an elevated position as shown
in FIG. 1 and FIG. 2B, and disengage from the peripheral edge of
the substrate 112 when the support assembly 120 is in a lowered
position as shown in FIG. 2C. Further details of the centering
mechanism 140 and its operation will be described hereafter.
[0032] The process chamber 102 may additionally comprise a
circumscribing shadow frame 150. The shadow frame 150 is positioned
to prevent deposition at the edge of the substrate 112, the support
assembly 120, and the centering mechanism 142 to reduce flaking and
particle contamination in the process chamber 102.
[0033] The lid assembly 114 provides an upper boundary to the
process volume 110. The lid assembly 114 may be removed or opened
to service the process chamber 102. In one embodiment, the lid
assembly 114 may be fabricated from aluminum.
[0034] The lid assembly 114 may include an entry port 160 through
which process gases provided by the gas source 104 may be
introduced into the process chamber 102. A gas distribution plate
assembly 141 may be coupled to an interior side of the lid assembly
114. The gas distribution plate assembly 141 includes an annular
base plate 162 having a blocker plate 164 disposed intermediate to
a faceplate (or shower head) 166. The blocker plate 164 provides an
even gas distribution to a backside of the faceplate 166. The
processing gas from the entry port 160 enters a first hollow volume
168 partially limited between the annular base plate 162 and the
blocker plate 164, and then flows through a plurality of passages
170 formed in the blocker plate 164 into a second volume 172
between the blocker plate 164 and the faceplate 166. The processing
gas then enters the process volume 110 from the second volume 172
through a plurality of passages 174 formed in the faceplate 166.
The faceplate 166 is isolated via an insulator material 176. The
annular base plate 162, blocker plate 164 and faceplate 166 may be
fabricated from stainless steel, aluminum, anodized aluminum,
nickel or any other RF conductive material.
[0035] The power source 138 applies a radio frequency (RF) bias
potential to the annular base plate 162 to facilitate the
generation of plasma between the faceplate 166 and the support base
122. The power source 138 may include a high frequency RF power
source ("HFRF power source") capable of generating an RF power at
about 13.56 MHz, or a low frequency RF power source ("LFRF power
source") generating an RF power at about 300 kHz. The LFRF power
source provides both low frequency generation and fixed match
elements. The HFRF power source is designed for use with a fixed
match and regulates the power delivered to the load, eliminating
concerns about forward and reflected power.
[0036] As shown in FIG. 1, a controller 180 may interface with and
control various components of the substrate processing system. The
controller 180 may include a central processing unit (CPU) 182,
support circuits 184 and a memory 186.
[0037] The substrate 112 is transferred to the lift pins 132 in the
chamber 102 by a conveyor that may be a robot or other transfer
mechanism (not shown), and then placed on the upper support surface
124 of the support assembly 120 by moving the lift pins 132
downward. As will be discussed below, the centering mechanism 140
then is operated to center the substrate 112 relative to the
reference axis Z.
[0038] In one embodiment, one or more temperature sensors 190 are
positioned to monitor the temperature of the backside of the
substrate 112. In one embodiment, the one or more temperature
sensors 190, such as a fiber optic temperature sensor, are coupled
to the controller 140 to provide a metric indicative of the
temperature profile of the backside of the substrate 112. In one
embodiment, the data provided by the one or more temperature
sensors 190 may be used in a feedback loop to control the
temperature of the embedded heater 103. In one embodiment, the one
or more temperature sensors are positioned in the support base.
[0039] In one embodiment a purge gas may be provided to the
backside of the substrate 112 through one or more purge gas inlets
192 connected to a purge gas source 194. The purge gas flown toward
the backside of the substrate 112 helps prevent particle
contamination caused by deposition on the backside of the substrate
112 when the substrate 112 is supported by the centering mechanism
142. The purge gas may also be used as a form of temperature
control to cool the backside of the substrate 112. In one
embodiment, the flow of purge gas may be controlled in response to
the data provided by the one or more temperature sensors 190.
[0040] FIG. 2A is a partially enlarged cross-sectional view of one
embodiment of a centering finger 142 of FIG. 1 in a supporting
position. As shown in FIG. 2A, in the supporting position, the
substrate 112 rests on the centering finger 142. While resting on
the centering finger 142, the substrate 112 is positioned at a
distance "A" from the surface of the support assembly 144. The
distance "A" between the substrate 112 and the upper support
surface 124 of the support base 122 is chosen such that the thermal
resistance between the substrate 112 and the heater 103 creates a
different temperature on the elevated substrate 112 as compared to
when the substrate rests on the upper support surface 124 of the
support assembly 122 without having to change the setpoint
temperature of the heater 103. The ability to change the
temperature of the substrate 112 without changing the setpoint
temperature of the heater 103 allows for back-to-back process steps
to be performed without the delay of waiting for the heater to
either increase in temperature or decrease in temperature in
between processing steps. Thus leading to an overall decrease in
substrate processing time and a corresponding increase in device
yield.
[0041] The centering finger 142 may be made in a single piece, or
formed from the assembly of multiple component parts. Materials
used for the finger 142 may include aluminum nitride, aluminum
oxide, ceramics and similar materials or combinations thereof that
have a low coefficient of thermal expansion and are resistant to
the processing environment in the chamber 102. The finger 142 is
pivotally mounted via the shaft 146 to a joint block 290 protruding
from the lower surface 126 of the support base 122, and passes
through a slot 292 in a peripheral region of the support base 122.
An upper end portion 294 of the finger 142 extends above the
support surface 124 of the support base 122 to releasably contact
with the support surface 124 of the support base 122. A support tab
298 for supporting the substrate 112 is positioned on the upper end
portion 294 of the finger 142. A substrate support notch 299 is
formed at an intersection of the support tab 298 with the upper end
portion 294. A lower end portion 296 of the finger 142 is located
eccentric from the shaft 146. The lower end portion 296 is weighted
to bias the finger 142 by gravity action into a position to contact
with the support surface 124 of the support base 122. As shown,
when the finger 142 loses contact with the opposing plate 144,
which may be achieved by moving the support assembly 120 upward in
one example of implementation, the gravity action G exerted on the
lower end portion 296 thereby causes the finger 142 to pivot about
the shaft 146, so that the upper end portion 294 moves radially
inward to contact the support surface 124 of the support base 122.
As further discussed in FIGS. 3A and 3B, the three or more fingers
242 are evenly distributed along a periphery of the substrate 212
and coordinately move to support the substrate 112.
[0042] FIG. 2B is a partially enlarged cross-sectional view
illustrating one centering finger 142 in a centering position. As
shown in FIG. 2B, when the finger 142 loses contact with the
opposing plate 144, which may be achieved by moving the support
assembly 120 upward in one example of implementation, the gravity
action G exerted on the lower end portion 296 thereby causes the
finger 142 to pivot about the shaft 146, so that the upper end
portion 294 moves radially inward to contact and exert a
displacement force F on the peripheral edge of the substrate 112 in
a direction toward the reference axis Z. It is worth noting that
the thickness of the upper end portion 294 may be designed slightly
higher than the top surface of the substrate 112. When the
displacement force F is applied by the upper end portion 294, the
peripheral edge of the substrate 112 can thereby be prevented from
slipping over the upper end portion 294.
[0043] To release the substrate 112, FIG. 2C is a partially
enlarged cross-sectional view illustrating the centering finger 142
in a disengaging position. The support base 122 may be moved
downward so as to push the lower end portion 296 of the finger 142
into contact against the opposing plate 144, which counteracts the
gravity action exerted on the lower end portion 296. As a result,
the finger 142 is caused to pivot in an opposite direction so that
the upper end portion 294 moves out of contact with the peripheral
edge of the substrate 112.
[0044] As has been described above, the construction of the
centering mechanism 140 thus is able to automatically support the
substrate 112 by using the gravity action to bias each centering
finger 142. The location of the centering fingers 142 on the
support assembly 120 may depend on the contour shape of the
substrate to center.
[0045] FIG. 3A is a simplified overhead view of one embodiment in
which three centering fingers 142 may be used to support a circular
substrate 112 at a distance from the support base 122. The three
centering fingers 142 are regularly spaced around a circle centered
on the reference axis Z. The combination of each support tab 298
and the upper end portion 294 of each finger form a pocket for
supporting the edge of the circular substrate 112. In other
embodiments not shown, more centering fingers may be positioned in
different arrangements to support other substrates of different
contour shapes.
[0046] FIG. 3B is a simplified overhead view of one embodiment of a
centering mechanism 142 using three centering fingers to center a
substrate 112. The three centering fingers 142 are regularly spaced
around a circle centered on the reference axis Z, and each finger
142 is able to apply a radial displacement force F to center the
circular substrate 112. In other embodiments not shown, more
centering fingers may be positioned in different arrangements to
center other substrates of different contour shapes.
[0047] To effectively center the substrate 112, each centering
finger 142 also needs to apply a sufficient amount of displacement
force F to move the substrate 112, which is in relation to the mass
included in the weighted lower end portion 296. In one
implementation, the included mass may be in a range between about
10 grams to about 500 grams. Various ways may be implemented to
include the proper mass in the lower end portion 296, such as by
forming a massive lower end portion 296 of a larger size.
[0048] FIG. 4 illustrates a variant embodiment in which an embedded
solid material 402 of a higher mass density may be used to form the
weighted lower end portion 296 of the centering finger 242. Methods
to embed the solid material 402 in the finger 142 may include, for
example, sintering a ceramic material used for making the finger
142 around the solid material 402. The solid material 402 may be
molybdenum or other suitable materials of a mass density higher
than the surrounding material used for the finger 142. In
implementations that may impose limits on the size of the weighted
lower end portion 296, the use of the embedded material 402 of a
higher mass density allows effectively increasing the mass of the
weighted lower end portion 296 without increasing its size.
[0049] While the foregoing embodiments illustrate certain specific
ways to implement and operate the centering mechanism, many
variations may be envisioned. For examples, in alternate
embodiments described hereafter, other constructions may be
implemented for each centering finger.
[0050] FIGS. 5A-5C are partial cross-sectional views illustrating
another embodiment of a centering finger 542. The centering finger
542 is pivotally mounted to a bracket 543, which extends out of an
outer boundary of the support base 122, via a shaft 546. The
support surface of the support base 122 may be smaller than the
surface area of the substrate 112, so that a peripheral portion of
the substrate 112 in place on the support base 122 is free of
support contact. Like the embodiments described above, the finger
542 includes an upper end portion 594 adapted to contact with the
peripheral edge of the substrate 112 when the finger is in a
centering position as shown in FIG. 5B and a support tab 598 for
supporting the substrate when the finger 542 is in a supporting
position as shown in FIG. 5A. The finger 542 further includes a
weighted lower end portion 596 eccentric from the shaft 546 to bias
the finger 542 into a position against the surface of the support
base 122 when the finger 542 is in a supporting position. The
weighted lower end portion 596 also biases the finger 542 against
the peripheral edge of the substrate 512 when the finger 542 is in
the centering position. In addition, the finger 542 includes a
distal prong 590 that is opposite the lower end portion 596
relative to the shaft 546, and is arranged below an opposing plate
544. As shown in FIG. 5A, to support the substrate 112, the lower
end portion 596 of the centering finger 542 is subject to the
gravity action G that biases the finger 542 and causes the upper
end portion 594 to contact the surface of the support base 122. As
shown in FIG. 5B, to center the substrate 112, the lower end
portion 596 of the centering finger 542 is subject to the gravity
action G that biases the finger 542 and causes the upper end
portion 594 to apply the displacement force F on the peripheral
edge of the substrate 112.
[0051] As shown in FIG. 5C, to disengage the upper end portion 594
from the peripheral edge of the substrate 112 or the surface of the
support base 122, the support assembly 120 may be moved upward so
that the distal prong 590 comes into contact with the opposing
plate 544. As the support assembly 120 moves further upward
relative to the opposing plate 544, the gravity action on the lower
end portion 596 is overcome and the finger 542 rotates about the
shaft 546 to disengage the upper end portion 594 from the
peripheral edge of the substrate 112. In one embodiment, the finger
542 may be released during processing upon centering, thus
preventing undesired deposition on the upper end portion 594, and
reducing non-uniformity of the process due to the presence of the
finger 542. It is worth noting that instead of moving the support
assembly 120 carrying the finger 542 relative to the opposing plate
544, alternate embodiments may design the opposing plate 544
movable relative to the support assembly 120 to contact the distal
prong 590 and cause the upper end portion 594 to disengage from the
substrate 112.
[0052] FIG. 6 is a partial cross-sectional view illustrating
another variant embodiment of a centering finger 642. Like the
previous embodiments, the centering finger 642 is pivotally mounted
on the support base 122 via a shaft 646. The centering finger 642
includes an upper end portion 694 and a support tab 698 adapted to
support the substrate 112, and a weighted lower end portion 696
eccentric from the shaft 646 to bias the finger 642 under the
gravity action. However, unlike the previous embodiments, the
eccentricity of the lower end portion 696 relative to the shaft 646
is configured to bias the finger 642 into a position that
disengages the upper end portion 694 from the substrate 112. To
position the centering finger 642 in a supporting position, an
opposing plate 650 that is coupled to a servo or step motor 652 and
a controller 654 is controllably moved to interact with the finger
642. More specifically, the opposing plate 650 moves upward to push
on the lower end portion 696 and cause the finger 642 to pivot
about the shaft 646 and leave the biased position. The controller
654 receives an operation signal 653 from the motor 652, and
accordingly issues a control signal to the motor 652 to control the
output of the motor 652. The controlled range of upward motion of
the opposing plate 650 thereby causes a controlled displacement of
the upper end portion 694 to move and support the substrate
112.
[0053] In embodiments, where the centering finger 642 is in a
centering position, the support tab 698 contacts a peripheral edge
of the substrate 112 and the weighted lower end portion 696 moves
eccentric from the shaft 646 to bias the finger 642 under the
gravity action.
[0054] In one embodiment, the controller 654 monitors the force
applied to a substrate being centered by each centering finger 642
using the operation signal 653. In one embodiment, the operation
signal 653 may be torque of the motor 652. When the operation
signal 653, e.g., torque of the motor 652, reaches a critical value
indicating the force applied to the substrate being centered
reaches a predetermined amount, thus, the substrate is adequately
centered. The controller 654 then stops to motor 652 to avoid over
centering, thus, preventing damages to the substrate.
[0055] To disengage the upper end portion 694 from substrate 112,
the opposing plate 650 moves downward, which causes the finger 642
to recover the biased position under the gravity action applied on
the weighted lower end portion 696.
[0056] FIG. 7 is a partial cross-sectional view illustrating yet
another embodiment of a centering finger 742. The centering finger
742 is formed as a resilient member, such as an elongated ceramic
spring, that has a first end 752 fixedly mounted on a frame 748
separate from the support base 722, and a second end 754 extending
above the support base 722 through an opening 756 formed in the
support base 722. The second end 754 comprises a support ledge 758
for supporting the substrate 112 when the centering finger 742 is
in a supporting position. In one embodiment, to center the
substrate 112 relative to the reference axis Z, the finger 742 is
biased to push on the peripheral edge of the substrate 112 in a
direction toward the reference axis Z. To disengage the finger 742
from the contact with the substrate 712, an opposing actuator 760
may be controllably moved to interact with the finger 742. The
actuator 760 may come into contact with the finger 742, and push on
the finger 742 that thereby deflects away from its biased position
to disengage from the substrate 712.
[0057] Process:
[0058] Methods for centering a substrate in a processing chamber
are also provided. Although discussed with reference to FIGS.
2A-2C, it should be understood that these methods are applicable to
any processing system involving the heating and centering of a
substrate.
[0059] In one embodiment, a substrate support assembly 120 having
an embedded heater 103 and a heated support surface 124 adapted to
receive a substrate 112 is provided. A plurality of centering
members 142 disposed along a circle centered at a reference axis
"Z" substantially perpendicular to the support surface 124 is
provided. Each centering member 142 comprises an end portion 294
configured to contact a peripheral edge of the substrate 112, and
the end portion 294 is radially movable towards and away from the
reference axis "Z". A support tab 298 is positioned on the end
portion 294 and a substrate support notch 299 is formed at an
intersection of the support tab 298 and the end portion 294, for
supporting the substrate 112 at a distance "A" from the support
surface 124 of the substrate support assembly 120. In one
embodiment, the distance "A" between the heated support surface 124
and the substrate 112 is selected such that the thermal resistance
between the heated support surface 124 and the substrate 112
creates a different temperature on the substrate 112 without
changing a setpoint temperature of the heater 103.
[0060] In one embodiment, the substrate 112 is positioned on the
support tabs 298 of each of the plurality of centering members 124.
In one embodiment, the combination of each support tab 298 and the
upper end portion 294 of each of the plurality of centering members
142 form a pocket for supporting the edge of the circular substrate
112 and the substrate 112 is positioned within the pocket.
[0061] In one embodiment, a pre-treatment process is performed on
the substrate 112 at a first processing temperature of the
substrate 112. In one embodiment, the pre-treatment process is an
anneal process. In one embodiment, the anneal process is performed
at a substrate temperature of between about 250.degree. C. and
about 270.degree. C.
[0062] In one embodiment, after the pre-treatment process, the
substrate 112 is removed from the support tabs 298. The end portion
294 of each centering member 142 is moved radially outward and away
from the reference axis "Z". The substrate 112 is placed on the
substrate support assembly 120, wherein the substrate 112 and the
centering members 142 do not contact. The end portion 294 of each
centering member 142 is moved radially inwards to contact a
peripheral edge of the substrate 112 for centering the substrate
112. The substrate 112 is centered using the end portions 294 of
the centering members 142.
[0063] In one embodiment, after centering the substrate 112, a
deposition process is performed on the substrate 112 at a second
processing temperature of the substrate, wherein the first
processing temperature is different than the second processing
temperature. In one embodiment, the second processing temperature
is between about 350.degree. C. and about 400.degree. C.
[0064] In one embodiment, a setpoint temperature of the heater 103
is the same for both the pretreatment process and the deposition
process. In one embodiment, the setpoint temperature of the heater
103 is the same as the temperature of the deposition process. In
one embodiment, the setpoint temperature of the heater 103 is
between about 350.degree. C. and about 400.degree. C.
[0065] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *