U.S. patent application number 11/654669 was filed with the patent office on 2007-05-24 for plasma chamber wall segment temperature control.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Steven T. Fink, William D. Jones, Maolin Long, Andrej S. Mitrovic, Paul Moroz.
Application Number | 20070114206 11/654669 |
Document ID | / |
Family ID | 23194035 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070114206 |
Kind Code |
A1 |
Mitrovic; Andrej S. ; et
al. |
May 24, 2007 |
Plasma chamber wall segment temperature control
Abstract
A device and method for controlling the temperature of a plasma
chamber inside wall or other surfaces exposed to the plasma by a
plurality of temperature control systems. A plasma process within
the plasma chamber can be controlled by independently controlling
the temperature of segments of the wall or other surfaces.
Inventors: |
Mitrovic; Andrej S.;
(Phoenix, AZ) ; Long; Maolin; (Santa Clara,
CA) ; Moroz; Paul; (Marblehead, MA) ; Fink;
Steven T.; (Mesa, AZ) ; Jones; William D.;
(Phoenix, AZ) |
Correspondence
Address: |
PILLSBURY WINTHROP SHAW PITTMAN, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
23194035 |
Appl. No.: |
11/654669 |
Filed: |
January 18, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10765445 |
Jan 28, 2004 |
7186313 |
|
|
11654669 |
Jan 18, 2007 |
|
|
|
PCT/US02/23207 |
Jul 19, 2002 |
|
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|
10765445 |
Jan 28, 2004 |
|
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60308447 |
Jul 30, 2001 |
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Current U.S.
Class: |
216/59 |
Current CPC
Class: |
G05D 23/1934 20130101;
H01L 21/67069 20130101; H01L 21/67109 20130101; H01J 37/32522
20130101; H01L 21/67248 20130101 |
Class at
Publication: |
216/059 |
International
Class: |
G01L 21/30 20060101
G01L021/30 |
Claims
1. A method of controlling a plasma process comprising:
independently controlling the temperature of a plurality of
segments of the plasma chamber wall or other surfaces exposed to
the plasma.
Description
[0001] This is a divisional application of U.S. patent application
Ser. No. 10/765,445, filed on Jan. 28, 2004 (Issue Fee Paid), which
is a continuation of International Application No. PCT/US02/23207,
filed on Jul. 19, 2002, which, in turn, claims the benefit from
U.S. Provisional Patent Application No. 60/308,447, filed Jul. 30,
2001, the entire contents of all of which are incorporated herein
by reference in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates in general to plasma chambers and,
more particularly, to a plasma chamber that has a wall temperature
control system.
[0004] 2. Description of Related Art
[0005] Plasma chambers may be used to contain plasma, for example,
in a plasma semiconductor substrate processing tool. Typically,
plasma ions are accelerated toward a semiconductor substrate within
the plasma chamber. During the course of the process, ions, neutral
particles, and contaminants are pumped out of the chamber while
fresh gas is supplied and formed into plasma.
[0006] The chamber wall temperature affects the local surface
chemistry, e.g. the nature and amounts of different chemical
species adsorbed and emitted from the walls. These species in turn
affect the local gas phase chemistry in the plasma, and thus the
plasma process result, e.g. rate, selectivity, etc.
[0007] With the current trend of introducing in-situ chamber
cleaning steps between wafer batches, fast ramp-up and ramp-down of
wall temperatures can be advantageous.
SUMMARY OF THE INVENTION
[0008] The present invention provides an apparatus and a method of
independently controlling the temperature of different segments of
the plasma chamber inside wall, and/or other surfaces exposed to
the chamber plasma. The temperature of segments of the plasma
chamber inside walls and other surfaces are independently
controlled by a plurality of temperature control systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic representation of two segments of the
plasma chamber wall temperature control system;
[0010] FIG. 2 is a graph showing a temperature distribution along
the chamber wall of FIG. 1;
[0011] FIG. 3 is a schematic representation of a fluid circulation
system used to feed cooling or heating fluid to the plasma chamber
wall temperature control segments;
[0012] FIG. 4 is a schematic representation of a fluid circulation
system used to feed cooling fluid to the plasma chamber wall
temperature control segments.
[0013] FIG. 5 is an overhead view of a plasma chamber utilizing the
plasma chamber wall temperature control system illustrated in FIG.
1;
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0014] FIG. 1 shows the structure of two segments of the plasma
wall temperature control system. The inside of the plasma chamber
is defined by a plasma chamber inside wall, indicated at 10. At
least an inner portion of the plasma chamber inside wall 10 may be
made of a ceramic-type material, which typically has a low thermal
conductivity, such as quartz, alumina, yttria, etc. Materials of
low thermal conductivity allow improved independent temperature
control of various segments of the plasma chamber inside wall 10.
Materials with a higher thermal conductivity, such as anodized
aluminum, stainless steel, or the like can also be used.
[0015] A thermal conductor, indicated at 12, is seated in thermal
contact with the back side of a segment of the plasma chamber
inside wall 10. The thermal conductor 12 may be made of a material
with a high thermal conductivity, for example a metal such as
aluminum. The left and right segments of the plasma wall
temperature control system shown in FIG. 1 each contain a thermal
conductor 12. Each thermal conductor 12 controls the temperature of
a segment of the plasma chamber inside wall 10. Each thermal
conductor 12 is in direct contact with either a thermoelectric
device, indicated at 20, or a "dummy" insert, indicated at 16.
Referring to the left segment, the thermal conductor 12 is in
direct contact with the thermoelectric device 20. Referring to the
right segment, the thermal conductor 12 is in direct contact with a
dummy insert 16. The dummy insert 16 in the segment of the plasma
wall temperature control system without the thermoelectric device
20 mimics the thermal properties, e.g. nominal heat conductance, of
the thermoelectric device 20.
[0016] Referring to the right segment of FIG. 1, the dummy insert
16 is in direct contact with a temperature controlling block,
indicated at 14. Temperature controlling block 14 has a conduit,
indicated at 18, to carry a fluid. For those segments that contain
a thermoelectric device 20, the thermoelectric device 20 is in
direct contact with the temperature controlling block 14. The fluid
in the conduit 18 of the temperature controlling block 14 can
either heat or cool the segment of the plasma chamber inside wall
10, depending on the fluid temperature. Heating or cooling is by
direct thermal conduction, from the fluid to the segment of the
plasma chamber inside wall 10, via the conduit 18 of the
temperature controlling block 14, dummy insert 16 or thermoelectric
device 20, and thermal conductor 12. The thermoelectric device 20
can allow higher precision and generally faster response
temperature control of the segment of the plasma chamber inside
wall 10, by varying the current and voltage supplied to the
thermoelectric device 20 by a variable DC power source (not
illustrated).
[0017] Thermocouples 22 and 24 determine the temperatures on both
sides of the thermoelectric device 20. The thermoelectric device 20
can be disconnected from the DC power source so that the voltage
and current into the known load of the thermoelectric device 20 can
be used to determine the heat flow through it. Heat flow
information can be used for plasma chamber process control. If
higher resolution temperature control is required, all temperature
control segments may have thermoelectric devices 20 installed. If
only measurement of heat flow is required, not all temperature
control segments may have thermoelectric devices 20 installed.
[0018] A layer of heat insulation material, indicated at 26,
prevents heat exchange between temperature controlling blocks 14
via the plasma chamber outside wall, indicated at 28. Segments of
the plasma wall temperature control system are spaced apart so that
they do not touch each other, preventing heat exchange via direct
thermal conduction. The insulation 26 acts to hold the temperature
control systems against the outside surface of chamber inside wall
10. If other means of holding temperature control systems against
wall 10 are used, insulators 26 may be omitted, and the gas that
fills the space between walls 10 and 28 then provides the
insulation.
[0019] RF shielding of the plasma chamber may be included,
depending on the type of plasma generator used. A thin metal foil,
indicated at 30, bridges the space between the thermal conductors
12. Heat exchange between conductors 12 is minimized because the
foil 30 is thin. The foil 30 completes an electrically continuous
RF energy shield around the plasma chamber.
[0020] FIG. 2 shows a graph exemplifying an achievable temperature
distribution along the plasma chamber inside wall 10. The sharp
temperature step, indicated at 40, between the two segments of the
plasma chamber inside wall 10, is partly achievable due to the low
thermal conductivity of the material, partly due to small thickness
of the plasma chamber inside wall 10.
[0021] FIG. 3 shows a fluid circulation system used to supply
heating or cooling fluid to the conduits 18 of the temperature
controlling blocks 14 of the plasma wall temperature control
system. Two high-flow fluid sources can be used. A
higher-temperature fluid source, indicated at 50, provides a fluid
of as high or higher temperature than the highest required
temperature of any plasma chamber process. A lower-temperature
fluid source, indicated at 52, provides a fluid of as low or lower
temperature than the lowest required temperature of any plasma
chamber process.
[0022] A selector valve, indicated at 54, selectively sends either
higher-temperature or lower-temperature fluid to the conduit 18.
Varying which fluid is sent allows control of the temperature of
the plasma chamber inside wall 10. The selector valves 54 and 56
are located near the conduits 18, reducing the amount of fluid
needing replacement when a temperature change is needed.
[0023] The thermoelectric devices 20 provide higher precision
temperature control, and can sustain a temperature difference of,
for example, a few tens of degrees. The temperature difference can
compensate for a fluid that does not yet have the exact desired
temperature necessary for the plasma chamber process. The
thermoelectric devices are provided with varying current and
voltage to compensate for or sustain any temperature differences
required for wall segment temperature control. The thermoelectric
devices are also able to adjust their temperatures more rapidly
than the fluid system.
[0024] If a fluid source 50 or 52 is not in use, it may be put in a
bypass position via a relief valve, indicated at 58. The bypassed
fluid circulates through the fluid circulation system, always ready
for the next temperature change. In another embodiment, the
selector valve 54 may be a liquid mixing valve, allowing selective
combination of the heating and cooling fluids to set the fluid at a
desired temperature for steady state conditions, or heating only or
cooling only, for quick heating or cooling. A further embodiment
eliminates the heating fluid 50 and selector valves 54 and 56 from
the fluid circulation system by using resistive heaters (which may
also be the same device as the thermoelectric device 20) for
heating. FIG. 4 shows the simplified cooling fluid circulation
system. On-off valves (which may also be the same valve as the
relief valve 58) can be used in the simplified cooling fluid
circulation system. This embodiment can provide a highly controlled
heat-up process, via current and voltage supplied to the resistive
heater.
[0025] The temperature and heat flow measured by the thermocouples
22, 24 and the thermoelectric devices 20 can be used in a feedback
control system to maintain a desired plasma chamber inside wall
temperature over each segment of the chamber wall 10. The
temperature and heat flow can also be used to monitor the plasma
process being carried out in the plasma chamber. Plasma processing
can be controlled based on the feedback from the temperature and
heat flow information. The temperature of a portion of the wall can
be measured and correlated to parameters of the plasma process. The
parameters of the plasma process can then be adjusted as necessary
by adjusting the temperature control systems. FIG. 5 shows the
segments of the plasma wall temperature control system arranged to
surround the plasma chamber 60.
[0026] The wall temperature distribution can be correlated to the
process properties, such as etch rate, selectivity, device damage,
repeatability, etc., via a design-of-experiments (DOE) approach, in
which a large number of tests are made, so that a meaningful
correlation is obtained. This correlation may be programmed in the
form of a look-up table database in the tool controller. Then,
during a process, when a temperature distribution on the wall is
known from measurements at each individual segment, an estimate of
the achievable process results can be obtained using various
methods known in the art. If this uniformity is not satisfactory,
then a control signal is sent to all segments to adjust their
temperatures to a setpoint where the desired process results are
obtained, in combination, of course, with other operating
parameters of the current process in the tool. With all segments
individually controllable, one can also achieve azimuthal process
results control. The heat flux information is useful for
quantifying the plasma bombardment of the wall. A high heat flux
means that the wall is subjected to a high ion bombardment flux,
which invariably causes sputtering of the wall material. This can
contaminate the process and reduce the lifetime of the chamber
wall, increasing costs. If a particularly "clean" process needs to
be achieved, then the heat flux information can be used to adjust
process parameters so that wall bombardment is minimized.
[0027] Likewise, the system may be used, for example, to reduce the
time necessary between process steps. For example, between wafers,
the chamber may be cleaned at a temperature higher than the wafer
process. The system according to the present invention allows rapid
chamber heating so that throughput may be increased.
[0028] The same segmented temperature control system may be used on
the substrate holder assembly, the gas injection plate, and in
other locations in the chamber where precise wall temperature
control is required for good process results.
[0029] It will thus be seen that the objects of this invention have
been fully and effectively accomplished. It will be realized,
however, that the foregoing preferred specific embodiments have
been shown and described for the purpose of illustrating the
functional and structural principles of this invention and are
subject to change without departure from such principles.
Therefore, this invention includes all modifications encompassed
within the spirit and scope of the following claims.
* * * * *