U.S. patent application number 11/028889 was filed with the patent office on 2005-07-14 for heated and cooled vacuum chamber shield.
This patent application is currently assigned to Applied Komatsu Technology, Inc.. Invention is credited to Black, Russell, Demaray, Ernest, Turner, Norman L..
Application Number | 20050150757 11/028889 |
Document ID | / |
Family ID | 25228584 |
Filed Date | 2005-07-14 |
United States Patent
Application |
20050150757 |
Kind Code |
A1 |
Black, Russell ; et
al. |
July 14, 2005 |
Heated and cooled vacuum chamber shield
Abstract
The invention is directed to method for processing substrates
and chamber for the same. In one embodiment, a method for
processing substrates includes transferring a substrate to a
substrate support disposed in a processing chamber, controlling a
temperature of a liner lining a sidewall of the processing chamber,
and processing the substrate in the processing chamber.
Inventors: |
Black, Russell; (Longmont,
CO) ; Turner, Norman L.; (Mountain View, CA) ;
Demaray, Ernest; (Portola Valley, CA) |
Correspondence
Address: |
MOSER, PATTERSON & SHERIDAN, LLP
APPLIED MATERIALS, INC.
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
Applied Komatsu Technology,
Inc.
|
Family ID: |
25228584 |
Appl. No.: |
11/028889 |
Filed: |
January 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11028889 |
Jan 4, 2005 |
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10011590 |
Nov 6, 2001 |
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6881305 |
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10011590 |
Nov 6, 2001 |
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09328503 |
Jan 9, 1998 |
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6432203 |
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09328503 |
Jan 9, 1998 |
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08819599 |
Mar 17, 1997 |
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Current U.S.
Class: |
204/192.1 ;
204/298.01 |
Current CPC
Class: |
C23C 14/564 20130101;
H01L 21/67109 20130101 |
Class at
Publication: |
204/192.1 ;
204/298.01 |
International
Class: |
C23C 014/00 |
Claims
What is claimed is:
1. A method for processing substrates, comprising: positioning a
substrate in a processing chamber; processing the substrate in the
processing chamber; and controlling a temperature of a liner lining
a sidewall of the processing chamber.
2. The method of claim 1, wherein the step of controlling the
temperature of the liner further comprises: heating the liner.
3. The method of claim 1, wherein the step of controlling the
temperature of the liner further comprises: maintaining the
temperature of the liner to minimize stress in a material deposited
on the substrate.
4. The method of claim 1 further comprising: heating the liner
after the substrate has been processed in the chamber; and removing
the processed substrate from the processing chamber; transferring a
second substrate into the processing chamber; and cooling the liner
during processing of the second substrate.
5. The method of claim 1, wherein the step of controlling the
temperature of the liner further comprises: applying power to a
resistive heater disposed in a passage formed in the liner.
6. The method of claim 5, wherein the step of controlling the
temperature of the liner further comprises: flowing a gas through
the passage formed in the liner.
7. The method of claim 1, wherein the step of controlling the
temperature of the liner further comprises: flowing gas through the
passage formed in the liner.
8. The method of claim 7, wherein the step of flowing the gas
through the passage formed in the liner further comprises: flowing
at least one of air, nitrogen or argon through the passage.
9. The method of claim 1 further comprising: electrically biasing
the liner relative to the sidewall.
10. The method of claim 1, wherein the step of controlling the
temperature of the liner occurs during at least a portion of the
processing step.
11. The method of claim 1, wherein the step of controlling the
temperature of the liner occurs during at least a portion of a
bake-out procedure performed prior to the processing step.
12. The method of claim 1, wherein the step of processing the
substrate in the processing chamber further comprises: depositing a
layer of material on the substrate, wherein the material is at
least one of aluminum, tantalum, indium tin oxide or
polysilicon.
13. A method for processing substrates, comprising: positioning a
substrate in a processing chamber having a shield lining a least a
portion of an internal volume of the processing chamber; regulating
a temperature of a passage formed in the shield; and processing a
substrate disposed in the processing chamber.
14. The method of claim 13, wherein the step of regulating the
temperature further comprises: applying power to a resistive heater
disposed in the passage formed in the shield.
15. The method of claim 13, wherein the step of regulating the
temperature further comprises: flowing a gas through the passage
formed in the shield.
16. The method of claim 13, wherein the step of regulating the
temperature further comprises: controlling a characteristic of a
material deposited on the shield.
17. The method of claim 15, wherein the step of regulating the
temperature further comprises: heating the shield during processing
of the substrate.
18. The method of claim 13, wherein the step of regulating the
temperature further comprises: cooling the shield during processing
of the substrate.
19. The method of claim 13 further comprising: replacing the shield
after a number of substrate processing cycles.
20. The method of claim 19 further comprising: heating an internal
passage within a replacement shield prior to resuming substrate
processing.
21. A processing chamber comprising; a chamber body having an
internal wall defining an internal volume; a substrate support
disposed in the internal volume; a removable liner disposed in the
internal volume adjacent to the wall and circumscribing the liner;
and a temperature control passage formed the liner.
22. The processing chamber of claim 21 further comprising: a
resistive heater disposed in the temperature control passage.
23. The processing chamber of claim 22 further comprising: a
controller containing instructions, that when executed by the
controller, cause a temperature of the passage formed through the
liner to be controlled in a manner that regulates a temperature of
a side of the liner facing the substrate support.
24. The processing chamber of claim 23, wherein the instructions,
when executed by the controller, further cause the temperature of
the side of the liner facing the substrate support to be maintained
at a temperature that minimizes flaking of material deposited on
the liner.
25. A processing chamber comprising; a chamber body having an
internal wall defining an internal volume; a substrate support
disposed in the internal volume; a removable liner disposed in the
internal volume adjacent to the wall and circumscribing the liner;
a temperature control passage formed the liner; and a temperature
control medium circulating through the liner.
Description
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 10/011,590, filed Nov. 6, 2001, which is a
divisional of U.S. Pat. No. 6,432,203, filed Jan. 9, 1998, which is
a continuation of now abandoned U.S. patent application Ser. No.
08/819,599, filed Mar. 17, 1997, allow of which are hereby
incorporated by reference in their entireties.
BACKGROUND OF THE INVENTION
[0002] The present invention is directed to a method and apparatus
for processing substrates in a vacuum processing chamber, and more
particularly to a method and apparatus for regulating a shield
disposed in a vacuum processing chamber.
[0003] In substrate processing in general and in physical vapor
deposition (PVD) processes such as sputtering in particular,
particulates are present and are generated in the processing
chamber. These can contaminate and destroy the substrate being
processed. When such particulates (also known as "free"
particulates) land on the substrate being processed, they can
contaminate a small area of the substrate. If the substrate is die
cut into separate chips, the contaminated chips can be discarded.
However, when a large substrate is intended for subsequent use as a
single item, e.g. as a flat panel display, one defect causes the
whole unit to be rejected.
[0004] The contaminating particulates can originate from several
sources. Incomplete or defective chamber cleaning allows
particulates to remain in the chamber and cause contamination. Even
when the processing chamber is clean, contaminants can be generated
during the sputtering process. One type of contaminating
particulate originates from sputter deposited material which has
deposited itself on processing chamber surfaces other than the
substrate intended for deposition. These may subsequentially detach
from the location inside the vacuum processing chamber where they
originally had been deposited. These particulates are usually cool,
multi-molecular sized specks of sputter deposited material which
were hot during the sputtering process, but have since cooled as a
result of their contact with surrounding surfaces. Such specks can
create defects which cause rejection of the substrate.
[0005] Another source of particulates is electrical arcing between
the highly-negatively charged (biased) target and the surrounding
grounded pieces. Arcing occurs in PVD processing chambers at
locations between the target and surrounding surfaces, usually a
shield enclosing the target. Arcing between adjacent pieces causes
a severe localized temperature spike which in most cases releases
molecules of one or both of the materials between which the spark
arcs. At best, if the released molecules settle on the substrate,
they create a slight but acceptable anomaly in the coating pattern.
At worst, when a particulate is a foreign material, the substrate
will be contaminated and will have to be rejected.
[0006] In a PVD processing chamber, the target containing the
material to be sputtered is generally flat and located parallel to
the substrate. Sputtering involves the ionization of gas, e.g.
argon (Ar), molecules in the processing chamber. The gas molecules
are electrically ionized as a result of an electrical bias, usually
a direct current (DC) bias. Once ionized, the positive ions bombard
the oppositely-biased target causing the target material to be
released into the chamber as molecular size ballistic particles. In
the rarified vacuum atmosphere of the vacuum chamber, the target
molecules travel nearly unobstructed until they reach the substrate
being sputter deposited, which is located just a short distance
away.
[0007] This sputtering activity coats the substrate as desired by
the process, but since the target material being sputtered is
emitted in all directions, the surfaces in the processing chamber
around the substrate also tend to become coated with
sputter-deposited material. These surrounding surfaces are
initially generally cold, i.e. at ambient or room temperature. The
sputtered material has a very high temperature, usually several
thousands of degrees. Upon contact, the sputter-deposited material
rapidly cools to the lower temperature of the process chamber
surfaces surrounding the substrate. The effect of its condensation
on the interior surfaces is to raise the temperature of these
interior surfaces to about 180 degrees to 450 degrees.
[0008] This may cause some various problems. For example, some of
the sputter-deposited material eventually peels off the chamber
surface. The tolerances of the components may also be
compromised.
[0009] To combat these problems, PVD chambers may be constructed
with "shield" pieces which act as a lining for the processing
chamber. A shadow frame and shield (collectively "shield") line the
inside of the processing chamber substantially between the edge of
the target being sputtered and the edge of the substrate. The
sputter deposited material then coats the inside of the "shield"
and not the inside of the chamber wall. The "shield" can then be
easily removed and cleaned or replaced which reduces harmful
effects on the chamber wall such as occur if continuously exposed
to the ionized process gas.
[0010] Arcing around the edge of the sputtering target can also
create particulates. Arcing is induced when the biased voltage
between the target and a nearby grounded (or dissimilarly biased)
member is greater than a certain value. This value is a known
function of a multiplicative product of the gas pressure and gap
spacing between the target and the nearby grounded (or dissimilarly
biased) member. The known numerical relationship is given by
Paschen's curves. The curves show conditions which are conducive to
arcing between the target material and the surrounding shield in
the "dark space ring" for a particular gas. An arc jumps between
the edges of the biased target and grounded pieces such as the
"shield." The arc causes specks to erupt from the material. Such
specks can contaminate the substrate.
[0011] The expansion and contraction of process chamber structures
due to changes in their temperature affects the gap or clearance
between pieces which in turn affect when arcing might occur. One
solution to this arcing problem is to maintain the clearance
between adjacent pieces (i.e. the shield and the target) at a
relatively constant value to prevent arcing. However, it is
difficult to keep a constant clearance between the shield and the
target material since the shield expands, and its temperature rises
due to exposure to ionized gas particles and sputtered material
during the process. It is especially difficult to maintain a
desired range of clearance dimensions when sputtering is being done
for liquid crystal display (LCD) applications. In these
applications, the size of the area being sputtered is relatively
large (about 470 mm.times.370 mm), requiring a long and wide shield
(outside dimension, e.g., about 660 mm.times.570 mm) around the
perimeter of the target being sputtered. The larger dimensions
create large movements due to differential thermal expansion.
Further, a slight misalignment or offset of the shield from the
target material during assembly of the processing chamber can
create a clearance at one side of the chamber which is conducive to
arcing, and thus creates particulates. The thermal cycling of the
shield elements, which occurs as sputtering is turned on and off,
strains the adhesive bond between the sputter-deposited material
and the shield pieces. Weakly bonded specks fall or peel off as a
result of the thermal cycling.
[0012] Another solution to this problem is equalizing the
temperature between the shield and the sputter-deposited material
by heating the shield to approximately the temperature of the
sputter-deposited material. In this way, there is little or no
differential thermal expansion between the sputter-deposited
material and the shield surface on which it is deposited.
[0013] In this solution, the temperature of the heat shield is
controlled by an assembly of radiant heaters which are configured
to heat the underside of the shield without affecting the chamber
process. Heating the shield causes it to expand. The target
material also expands so that the actual change in clearance
between the edge of the target and the edge of the shield is
minimized.
[0014] The target material is usually cooled by a liquid such as
water to prevent it from overheating. Even though the
sputter-deposited material ejected from the target raises the
temperature of the surfaces it contacts to about 180 degrees to 450
degrees Celsius, the whole mass of the target material or target
material and backing plate, in those instances where a backing
plate is used, has an average temperature of about 50 degrees to
100 degrees Celsius. In this system, a shield having a chairlike or
"h" type-shaped cross section is provided with the front of the
chair facing the center of the chamber.
[0015] The time required to heat and cool a shield of this
configuration is on the order of several hours, with the cooling
time longer than the heating time. This is partially due to heat
transfer from the heaters to the shield, which in the vacuum
environment of a processing chamber is by radiation. This is not
very efficient. Even venting the chamber with gas does not produce
a cooling time of less than two or three hours. Such venting is
also inefficient because it depends on the transmission of thermal
energy by conduction to the exterior of the hot surfaces. The slow
cooling creates a bottleneck in the chamber opening and closing
process which detrimentally affects the time that the chamber is
available for substrate processing.
[0016] These difficulties need to be overcome in order to increase
the yield in production of sputtered substrates and reduce or
eliminate substrate rejection because of particulate
contamination.
SUMMARY OF THE INVENTION
[0017] The invention is directed to method for processing
substrates and chamber for the same. In one embodiment, a method
for processing substrates includes transferring a substrate to a
substrate support disposed in a processing chamber, controlling a
temperature of a liner lining a sidewall of the processing chamber,
and processing the substrate in the processing chamber.
[0018] In another aspect, the invention is directed to an apparatus
comprising a shield for lining a portion of the interior of a
vacuum processing chamber, the interior of the shield defining a
shield passage; a heater element disposed within the shield
passage; and a gas inlet for providing gases to the interior of the
shield passage.
[0019] Implementations of the invention include the following. The
shield has a substantially rectangular shape. The heater element is
disposed within a channel within the shield passage.
[0020] In another aspect, the invention is directed to a processing
chamber for processing a substrate comprising a vacuum chamber in
which the substrate is supported. The chamber has an inner wall
facing a processing region over the substrate. A shield lines the
inner wall, the shield disposed adjacent the inner wall, the
interior of the shield defining a shield passage in which is
disposed a heater element. A gas inlet is used for providing gases
to the interior of the shield passage.
[0021] In another aspect, the invention is directed to a sputtering
process for a substrate in a sputter chamber having a target within
a vacuum chamber and a shield covering wall portions of the vacuum
chamber between the target and the substrate. The shield defines a
shield passage in which is disposed a heater element and which has
a gas inlet for providing gases to the interior of the shield
passage. The process comprises the steps of sputtering material
from the target onto the substrate to form sputter deposited
material thereupon. During the sputtering step, the temperature of
the shield is controlled to a temperature substantially equal to
the temperature of the sputter deposited material by flowing a
thermally conductive gas through the gas inlet into the shield
passage. The heater element is powered in the presence of the
thermally conductive gas.
[0022] In another aspect, the invention is directed towards a
chamber for processing a rectangular substrate, comprising a vacuum
chamber; a generally rectangular pedestal within the chamber for
supporting a rectangular substrate; a shield member disposed
between the pedestal and a plurality of walls of the vacuum chamber
comprising four joined substantially straight sections. The shield
defines a shield passage in which is disposed a heater element and
has a gas inlet for providing gases to the interior of the shield
passage. The heater element may have substantially the same shape
as the shield member. [0023 Additional advantages of the invention
will be set forth in the description which follows, and in part
will be obvious from the description, or may be learned by practice
of the invention. The objects and advantages of the invention may
be realized and obtained by means of the instrumentalities and
combinations particularly pointed out in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The accompanying drawings, which are incorporated in and
constitute a part of the specification, schematically illustrate
the present invention, and together with the general description
given above and the detailed description given below, serve to
explain the principles of the invention.
[0024] FIG. 1 an exploded view of a PVD vacuum processing chamber
in which an embodiment according to the present invention may be
used.
[0025] FIG. 2 is a close-up cross-sectional view of the left side
of the processing chamber taken along line 2-2 of FIG. 1.
[0026] FIG. 3 is a top-plan view of an embodiment of a shield
according to the present invention.
[0027] FIG. 4 is a cross-sectional side view of an embodiment of a
shield according to the present invention taken along line 4--4 of
FIG. 3.
[0028] FIG. 5(a) is a perspective view of a shield of the present
invention, cut away to show a heater strip installed in a shield
passage.
[0029] FIG. 5(b) is a cross-sectional view of a shield of the
present invention taken along line 5(b)-5(b) of FIG. 5(a).
DETAILED DESCRIPTION
[0030] FIG. 1 shows an exploded view of the pieces which are
generally associated with a PVD sputtering processing chamber. More
details are presented in U.S. Pat. Nos. 5,487,822, 5,336,585 and
5,362,526, all of which are owned by the assignee of the present
application and are incorporated herein by reference in their
entirety.
[0031] A processing chamber 30 having an inside processing chamber
wall 31 and a slit valve 32 is supported on a frame 34 leading to a
gate valve 35 and a cryogenic vacuum pump assembly 36. Processing
chamber 30 contains a susceptor or sputtering pedestal 38 supported
above a fin plate 42. Sputtering pedestal 38 is surrounded by a
sputtering pedestal apron 40. A substrate (not shown in FIG. 1) may
be supported on sputtering pedestal 38. A shadow frame 44 covers
the edges of the substrate during processing to prevent
sputter-deposited material from depositing at the edge and on the
back side of the substrate. The substrate supported on susceptor
pedestal 38 faces a target or target assembly 54 which is supported
on the top flange of processing chamber 30 by an insulating ring 50
and a lower insulator 52. A shield (or shield assembly) 46
surrounds sputtering pedestal 38 and extends closely adjacent to a
target (or target assembly) 54. The top side of target 54 is
covered at its perimeter with an upper insulator 56 which supports
a top cover 58 which both acts as a cap and houses a magnet drive
assembly (not shown).
[0032] Top cover 58 often contains a cooling fluid such as water
which is piped through the cover to cool the back side of target
54. In other configurations, target 54 is cooled by sending fluid
through passages in the target to provide the necessary cooling.
Top cover 58 as shown in the present configuration can be lifted by
a lift handle 60 to swing on hinge system 62, 63 such that the
opening of top cover 58 is assisted by one or more gas-pressurized
gate-assisting rams 64 connected between top cover 58 and frame 34
on either or both sides of hinged processing chamber 30.
[0033] FIG. 2 shows a cross sectional view of the assembled
processing chamber 30 that is shown in FIG. 1 in its unassembled
state. As can be seen at the left side of FIG. 2, processing
chamber 30 supports insulating ring 50 which is in turn surrounded
by lower insulator 52. Insulating ring 50 and lower insulator 52
both support target 54. Target 54 may be solid as shown in FIG. 2
or may have fluid passages for cooling. Target 54, which is
electrically biased, is covered and insulated from the outside by
lower insulator 52 and upper insulator 56. Top cover 58 creates a
chamber into which liquid can be provided to cool the back of
target 54 or in which a vacuum can be pulled to equalize the
pressure with the process chamber. A linearly scanning magnet
carrier 59 is commonly provided in top cover 58 to assist in the
sputtering process and reduces the waste caused by uneven erosion
of the target material.
[0034] A substrate 66 is supported on sputtering pedestal 38. The
edges of sputtering pedestal 38 are covered by sputtering pedestal
apron 40 while the edges of substrate 66 are covered by shadow
frame 44.
[0035] A robot paddle (not shown) moves substrate 66 into position
in processing chamber 30 through slit valve 32, after sputtering
pedestal 38 is lowered to a position shown by its outline in dashed
lines 38a. A lifter assembly 68 lifts substrate 66 from the robot
paddle and the robot paddle withdraws. Sputtering pedestal 38 then
rises to lift substrate 66 and shadow frame 44 to the processing
position. Unloading is performed in reverse order.
[0036] Pedestal 38, apron 40, and shadow frame 44 of the substrate
support assembly (described above) are circumferentially surrounded
by a shield 46. Shield 46 acts as a removable lining in the
processing chamber between the sputtering target and the substrate
being sputtered. Shield 46 is supported from a ledge of processing
chamber wall 31 which holds a series of knife edge support
cylinders (such as 84).
[0037] FIGS. 3, 4, and 5(a)-5(b) show the top, side, and
perspective views, respectively, of shield 46. Shield 46 includes
shield straight sections 47 and shield corner sections 49. Straight
sections 47 and corner sections 49 are welded together using
electron beam welding. Shield 46 is generally made of a metal
(e.g., 316L stainless steel).
[0038] Knife edge support cylinders 84, 85, 86, and 87 loosely fit
in matching vertically extending counterbores on the inside of the
processing chamber 30. Knife edge receiving grooves 97, 98, 99, and
100 are formed in the short linear portions of shield corner
sections 49 and are located on the bottom at the outside edge of
shield 46 along the long sides of the shield rectangle adjacent to
the actual curve of corner sections 49, but are positioned wholly
within shield corner sections 49. The alignment of the ridge (or
swale) of the grooves is along center lines 102 and 103 which run
approximately 45 degrees (in this example actually 46.5 degrees. to
be symmetrical and avoid interfering with other items in the
processing chamber) from the long side of the rectangle of the
shield. The center lines 102 and 103 cross at the rectangular
center of the shield which corresponds to the center of processing
chamber 30 during substrate processing.
[0039] FIG. 4 shows a gas-tight shield passage 141 which is located
on the periphery of shield 46. A heater strip 147 can be located
within a channel in shield passage 141. A fabrication technique may
be to locate heater strip 147 in the channel and to weld the
channel shut. Heater strip 147 can be positioned so as to minimize
thermal expansion and distortion of shield 46 during heating. This
positioning is usually dependent on the precise shape of the
shield, and may be calculated using, for example, finite element
analysis.
[0040] Referring to FIG. 5(a), electrical connections to heater
elements in heater strip 147 are provided by conductor leads (not
shown) through openings 143 and 145. Hoses 149 and 151 carry gas
into and away from shield passage 141. The gas flow is chosen to
allow a substantial amount of conduction to occur throughout the
shield. These hoses may be routed through the vacuum chamber. The
wiring to power heater strip 147 may be located within these
hoses.
[0041] Seals (not shown) may be provided to attach hoses 149 and
151 to openings 143 and 145. These seals prevent gas from escaping
from shield passage 141 to the rest of processing chamber 30. These
seals may be, for example, constructed of a metal. Another set of
seals may be provided to rout hoses 149 and 151 from the vacuum
chamber to gas sources outside of the chamber. Similar seals may
also be provided to rout the heater strip connections from shield
passage 141 to the outside of the chamber.
[0042] During the heating cycle, shield passage 141 is flooded with
a thermally-conductive gas so that conductive heat transfer occurs
between the surface of heater strip 147 and the internal surfaces
of shield passage 141. Typical gases which may be used include air,
nitrogen and argon. Generally, the gas used is chosen such that, at
the temperature attained by shield passage 141, the gas does not
become reactive. Heater strip 147 is configured to provide even
heating throughout shield 46. During the cooling cycle, cooled gas
can be forced through shield passage 141. Shield passage 141 thus
acts as a heat sink or cooling coil, cooling the hot surfaces of
shield passage 141 by contacting them with cool gas molecules. The
cooled gas is continually replenished to cool shield passage 141
rapidly. Immediate removal of heat can take place, thus promoting
highly efficient cooling.
[0043] Shield 46 is isolated from the surrounding process chamber
walls 31 by the knife edge supports. Because of the minimal surface
area and direct contact between the shield and the walls, thermal
losses due to conductive heat transfer are minimal. In some
instances it may be desired to provide an electrical bias
(different from the bias supplied to the target assembly) to shield
46. In this case a set of insulating knife edge supports (e.g.,
ceramic-alumina) isolate shield 46 from the grounded chamber wall
and an electrical bias is provided to shield 46. In other instances
when grounding of shield 46 is required, even though a set of
conductive metal knife edge support cylinders support shield 46, an
extra grounding strap (not shown) is secured between shield 46 and
chamber 30 to assure grounding.
[0044] Heating the shield also assists in maintaining the clearance
between the top edge of shield 46 and the area around target 54 to
prevent arcing between target 54 and shield 46 which could generate
undesirable particulates. In particular, the thermal expansion of
shield 46 may tend to increase the clearance between shield 46 and
target 54.
[0045] Shield 46 can be maintained at different temperatures for
different materials being sputtered. This may be done for purposes
of assisting various growth processes.
[0046] As an example of growth process where the shield would be
heated, silicon may be sputtered to produce a polysilicon layer on
a substrate. Such a process may be performed at high temperatures
to enhance crystallinity, but at otherwise low growth rates and
plasma powers. In this example, the susceptor (and substrate)
temperature may be about 400 degrees Celsius and the temperature of
the shield may be in the range of about 425 degrees Celsius to
about 450 degrees Celsius. The plasma power may be in the range of
about 500 watts to 1 kilowatt. At 1 kilowatt, a growth rate of a
few hundreds of angstroms per minute may be attained. Under these
conditions and the above shield heating, good temperature
uniformity has been attained.
[0047] In a contrasting example of a growth process where the
shield would be cooled, aluminum alloys may be deposited on a
substrate. Such processes may be performed at low temperatures so
that the aluminum alloy does not precipitate out of solution. That
is, a low temperature maintains the amorphous solution of the
aluminum alloy. The low temperature may be maintained by providing
water cooling, although other liquids or gases could be used, such
as heat transfer oil, air, dry nitrogen, etc. The shield
temperature in this case may be approximately 110 degrees Celsius.
In this case, a high power and high growth rate may be used. For
example, the power may be up to or even greater than 20 kilowatts,
while the growth rate may be up to 1 micron per minute or even
higher. Again, a high quality film may be grown, in this case
without the film's constituents precipitating out of solution. In
this case, the film growth cycle may be initiated with a rapid
cycling of the shield temperature to a high temperature, in order
to evaporate contaminants which may have been absorbed on its
surface.
[0048] A bakeout procedure may also be performed with the heated
shield. For example, the shield may be heated to a temperature of
about 450 degrees Celsius to about 500 degrees Celsius A gas flow
of, e.g., argon may be started to create a pressure of, e.g.,
one-half Torr. Infrared lamps or other heating devices may be used
to raise the temperature of the shield even higher if necessary.
Such a procedure accomplishes a number of objectives. First, it
evaporatively cleans any organic particulates which may have
absorbed on the surface of the shield. Second, it outgasses any
water vapor, air, or oxygen which may have absorbed on the surface
of the shield. Third, it activates the metal surface to enhance the
adhesion of the overcoat. For example, after a bakeout procedure,
it is important that the first coating of deposited material on the
shield adhere well--otherwise, flaking of large pieces of
depositants will undesiredly occur in later processes. The heating
of the shield helps to accomplish this surface activation.
[0049] Typical shield temperatures for target materials are as
follows: Aluminum (Al), about 350 degrees Celsius; indium tin oxide
(ITO), about 330 degrees Celsius; Tantalum (Ta), about 300 degrees
Celsius These temperatures should be maintained with reasonable
accuracy (such as within about .+-.15 degrees Celsius). The shield
temperature can be adjusted via heating and cooling and typically
would be adjusted to a range appropriate for the deposition
process. Any of the above materials can be caused to have a
temperature anywhere from ambient to about 450-500 degrees. The
shield temperature is generally adjusted according to the process
for the material.
[0050] The temperature of shield 46 can be increased and controlled
by varying and controlling the temperature of heater strip 147 so
that the temperature of the outside surface of shield 46 closely
approximates the temperature of the sputter-deposited material. The
thermally conductive gas within shield passage 141 allows rapid
heat transfer from heater strip 147 to the rest of shield 46. Under
these conditions, when sputter-deposited material arrives on the
outside of shield 46 very little, if any, temperature difference
exists between the sputter-deposited material and shield 46. When
they are both cooled to ambient temperatures, the interfacial
stress due to differential thermal expansion is negligible. Thermal
cycling, which might contribute to releasing or peeling of
sputter-deposited material, is avoided by using heater strip 147 to
maintain the temperature of shield 46 at its normal operating
temperatures. This can be in the range of approximately ambient to
500 degrees Celsius During sputtering, heater strip 147 may provide
only a small energy input as there is often a large thermal energy
input from the process. Between sputtering events, heater strip 147
may provide a larger energy input so as to maintain the shield
temperature at about ambient to 500 degrees Celsius while the
processed substrate is removed and a new substrate is brought into
position for processing.
[0051] The top surfaces and selected bottom surfaces of shield 46
may be polished to a high gloss of at least about 20 Ra to minimize
the surface adhesion of water molecules to rough surfaces which
prevent a high vacuum from being reached in a short time when
exposed to a high vacuum pumping system. The smooth surface reduces
the molecular force of adhesion and reduces the time needed to pump
down when compared to the time needed to pump down similar surfaces
which are rough or unpolished.
[0052] Referring to FIG. 5(b), the surfaces of shield 46 are
treated so that the outside surface 92 of shield 46 has a low
emissivity (e.g., it is polished) while its inside surfaces 91 have
a high emissivity to better absorb the radiant heat received from
heater strip 147. This difference in surface emissivities reduces
the energy needed to heat shield 46 to process temperature and also
even reduces the time needed to heat shield 46 to a predetermined
bake-out temperature (such as about 450 degrees Celsius).
[0053] The embodiments of the structure of the invention as
discussed above are used to carry out methods of rapidly cycling
the temperature of a shield 46 in a processing chamber 30.
[0054] A method includes the steps of, while sputtering material
from a target 54 onto a substrate 66, determining the temperature
of the material being sputter deposited on shield 46, and heating
shield 46 which is lining the processing chamber 30 to
approximately the temperature of the material being sputtered.
[0055] Shield 46 is heated by heating heater strip 147 within
gas-tight shield passage 141. A thermally-conductive gas is flowed
through the gas-tight shield passage 141 to promote heat transfer
between the heater strip 147 and the interior walls of shield
passage 141.
[0056] Cleaning of the shields may also occur via a bakeout
procedure where the shields are heated to a high temperature to
evaporate the organic or water-containing residues that typically
remain after cleaning procedures. By evaporating these materials,
the initial sputtered material can have a very high adhesion. The
resulting fracture strength may then be quite high.
[0057] The present invention has been described in terms of a
preferred embodiment. The invention, however, is not limited to the
embodiment depicted and described. Rather, the scope of the
invention is defined by the appended claims.
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