U.S. patent application number 11/210986 was filed with the patent office on 2005-12-22 for temperature control system.
This patent application is currently assigned to LSI Logic Corporation. Invention is credited to Bhatt, Hemanshu D., May, Charles E..
Application Number | 20050279284 11/210986 |
Document ID | / |
Family ID | 35344865 |
Filed Date | 2005-12-22 |
United States Patent
Application |
20050279284 |
Kind Code |
A1 |
May, Charles E. ; et
al. |
December 22, 2005 |
Temperature control system
Abstract
An apparatus for controlling the substrate temperature of a
substrate during processing of the substrate at a process energy. A
chuck temperature input receives temperature measurements from
temperature sensors at a substrate chuck, and a temperature set
point input receives temperature set points. The temperature set
points define a range of temperatures within which the apparatus
maintains the substrate temperature. A chuck temperature controller
output sends control signals to a chuck temperature controller,
which signals are operable to selectively increase and decrease the
chuck temperature. A process energy output sends control signals
that are operable to selectively increase and decrease the process
energy during the processing of the substrate. A controller
compares the temperature measurements received from the temperature
sensors at the substrate chuck through the chuck temperature input
to the temperature set points received through the temperature set
point input. The controller sends control signals through the chuck
temperature controller output to the chuck temperature controller
to selectively decrease the chuck temperature when the temperature
measurements received from the temperature sensors at the substrate
chuck are above the temperature set points. The controller further
sends control signals through the process energy output to
selectively decrease the process energy when the temperature
measurements received from the temperature sensors at the substrate
chuck are above the temperature set point. Preferably, the
controller first sends control signals through the chuck
temperature controller output to control the chuck temperature, and
only sends control signals through the process energy output when
the chuck temperature cannot be sufficiently controlled by the
chuck temperature controller.
Inventors: |
May, Charles E.; (Gresham,
OR) ; Bhatt, Hemanshu D.; (Troutdale, OR) |
Correspondence
Address: |
LSI LOGIC CORPORATION
1621 BARBER LANE
MS: D-106
MILPITAS
CA
95035
US
|
Assignee: |
LSI Logic Corporation
Milpitas
CA
|
Family ID: |
35344865 |
Appl. No.: |
11/210986 |
Filed: |
August 24, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11210986 |
Aug 24, 2005 |
|
|
|
09670975 |
Sep 27, 2000 |
|
|
|
Current U.S.
Class: |
118/724 ;
118/723R; 156/345.24; 156/345.51; 438/5 |
Current CPC
Class: |
H01L 21/67248 20130101;
H01L 21/67109 20130101 |
Class at
Publication: |
118/724 ;
118/723.00R; 156/345.51; 156/345.24; 438/005 |
International
Class: |
H01L 021/00; H01L
021/306; C23C 016/00; C23F 001/00 |
Claims
What is claimed is:
1. A method for controlling a substrate temperature of a substrate
during processing of the substrate at a process energy, by
controlling a chuck temperature of a chuck on which the substrate
resides during the processing, comprising: circulating a thermal
transfer media at a thermal transfer media temperature through the
substrate chuck to adjust both the chuck temperature and the
substrate temperature, the thermal transfer media circulating at a
flow rate, sensing the chuck temperature from at least one chuck
temperature sensing location at the chuck, reporting the sensed
chuck temperature to a controller, where the controller is operable
to adjust the process energy and at least one of the thermal
transfer media flow rate and the thermal transfer media
temperature, and when the sensed chuck temperature is outside of a
desired temperature range, then using the controller to adjust at
least one of the thermal transfer media flow rate, the thermal
transfer media temperature, and the process energy to bring the
sensed chuck temperature within the desired temperature range.
2. The method of claim 1 wherein the chuck temperature is sensed
from three different locations at the chuck.
3. The method of claim 1 wherein the chuck temperature is sensed
from locations within the chuck.
4. The method of claim 1 wherein the chuck temperature is sensed
from locations on a surface of the chuck disposed adjacent the
substrate.
5. The method of claim 1 wherein the desired temperature range is
between about fifty centigrade and about five hundred
centigrade.
6. The method of claim 1 wherein the controller first attempts to
bring the sensed temperature within the desired temperature range
by adjusting at least one of the thermal transfer media temperature
and the thermal transfer media flow rate, and when adjusting at
least one of the thermal transfer media temperature and the thermal
transfer media flow rate cannot bring the sensed temperature within
the desired temperature range, then the controller controls the
sensed temperature by additionally adjusting the process
energy.
7. The method of claim 1 wherein the controller is used to adjust
at least one of the thermal transfer media flow rate, the thermal
transfer media temperature, and the process energy to cool the
chuck and the substrate and thereby to bring the sensed temperature
within the desired temperature range.
8. The method of claim 1 wherein the controller is used to adjust
at least one of the thermal transfer media flow rate, the thermal
transfer media temperature, and the process energy to heat the
chuck and the substrate and thereby to bring the sensed temperature
within the desired temperature range.
9. An apparatus for controlling a substrate temperature of a
substrate during processing of the substrate at a process energy,
comprising: a chuck temperature input for receiving temperature
measurements from temperature sensors at a substrate chuck, a
temperature set point input for receiving temperature set points,
the temperature set points defining a range of temperatures within
which the apparatus maintains the substrate temperature, a chuck
temperature controller output for sending control signals operable
to selectively increase and decrease the chuck temperature to a
chuck temperature controller, a process energy output for sending
control signals operable to selectively increase and decrease the
process energy during the processing of the substrate, and a
controller for, comparing the temperature measurements received
from the temperature sensors at the substrate chuck through the
chuck temperature input to the temperature set points received
through the temperature set point input, sending control signals
through the chuck temperature controller output to the chuck
temperature controller to selectively decrease the chuck
temperature when the temperature measurements received from the
temperature sensors at the substrate chuck are above the
temperature set points, and sending control signals through the
process energy output to selectively decrease the process energy
when the temperature measurements received from the temperature
sensors at the substrate chuck are above the temperature set
points.
10. The apparatus of claim 9, wherein the controller is further
operable for: sending control signals through the chuck temperature
controller output to the chuck temperature controller to
selectively increase the chuck temperature when the temperature
measurements received from the temperature sensors at the substrate
chuck are below the temperature set points, and sending control
signals through the process energy output to selectively increase
the process energy when the temperature measurements received from
the temperature sensors at the substrate chuck are below the
temperature set points.
11. The apparatus of claim 9, wherein the controller first sends
control signals through the chuck temperature controller output to
control the chuck temperature, and only sends control signals
through the process energy output when the chuck temperature cannot
be sufficiently controlled by the chuck temperature controller.
12. The apparatus of claim 9, wherein the control signals sent by
the controller through the chuck temperature controller output
further comprise: a thermal transfer media flow control signal for
controlling a flow of a thermal transfer media through the chuck,
and a thermal transfer media temperature control signal for
controlling the temperature of the thermal transfer media flowing
through the chuck.
13. A chuck for controlling a substrate temperature of a substrate
on the chuck during processing of the substrate at a process
energy, the chuck comprising: a chuck surface having a face and a
back side, the face of the chuck surface for receiving the
substrate adjacent the chuck, the chuck surface having a high
thermal conduction zone and a low thermal conduction zone, where
the high thermal conduction zone of the chuck surface has a high
thermal conductivity and is disposed adjacent a portion of the
substrate that receives a greater degree of the process energy
during the processing, and the low thermal conduction zone of the
chuck surface has a low thermal conductivity and is disposed
adjacent a portion of the substrate that receives a lesser degree
of the process energy during the processing, and a heat sink
disposed adjacent the back side of the chuck surface for removing
thermal energy from the chuck surface.
14. The chuck of claim 13 wherein the chuck surface further
comprises a ceramic material embedded with a filler material, where
the ceramic material has a lower thermal conductivity than the
filler material, and the filler material has a higher thermal
conductivity than the ceramic material.
15. The chuck of claim 14 wherein the ceramic material further
comprises at least one of aluminum oxide and silicon oxide.
16. The chuck of claim 14 wherein the filler material further
comprises at least one of aluminum nitride, silicon carbide,
beryllium oxide, and diamond.
17. The chuck of claim 14 wherein the high thermal conduction zone
of the surface of the chuck has a higher ratio of filler material
to ceramic material than the low thermal conduction zone of the
surface of the chuck, and the low thermal conduction zone of the
surface of the chuck has a lower ratio of filler material to
ceramic material than the high thermal conduction zone of the
surface of the chuck.
18. The chuck of claim 13 wherein the surface of the chuck has at
least one intermediate thermal conduction zone, where each of the
intermediate thermal conduction zones has a thermal conductivity
that is between the thermal conductivity of the high thermal
conduction zone and the thermal conductivity of the low thermal
conduction zone, and each of the intermediate thermal conduction
zones has a different thermal conductivity.
19. The chuck of claim 13 wherein the high thermal conduction zone
forms a circle in a center of the surface of the chuck and the low
thermal conduction zone forms an annular ring around the high
thermal conduction zone on the surface of the chuck.
20. The chuck of claim 13 wherein the heat sink further comprises a
flow chamber for receiving a temperature controlled fluid from a
temperature controlled recirculator.
Description
BACKGROUND
[0001] There are several reasons why it is important to control the
amount of thermal energy that a substrate receives during
semiconductor device processing. For example, some of the
structures that are formed at the various stages of processing are
sensitive to thermal energy and tend to change over time as thermal
energy is absorbed by the substrate. Further, many fabrication
processes are sensitive to thermal energy and tend to produce
varying results as the thermal energy absorbed by the substrate
changes. Thus, if the amount of thermal energy absorbed by the
substrate is not controlled, processes tend to produce unexpected
or undesired results, and structures that are initially properly
formed tend to degrade toward unexpected or undesired forms.
Therefore, it is important to control the amount of thermal energy
that the substrate receives during processing.
[0002] The amount of thermal energy absorbed by the substrate can
be controlled in at least two different ways. First, the
temperature at which the substrate is maintained can be controlled.
For example, even if the substrate is in a hot environment, the
substrate itself can be cooled so that the bulk of the substrate
does not experience anything more than a given temperature. Second,
the length of time at which the substrate is exposed to a given
temperature can be controlled. By controlling these two parameters
the amount of thermal energy absorbed by the substrate during
processing can be controlled.
[0003] Unfortunately, it is difficult to control the temperature of
the substrate during processing. Temperature conditions experienced
by the substrate in some processes tend to vary according to one or
more of a number of different parameters, such as position on the
substrate, length of processing time, and processing energy.
Traditional substrate temperature control systems tend to be
ineffectual in controlling the temperature of the substrate when
faced with the interactions between one or more of these and other
thermal energy parameters.
[0004] What is needed, therefore, is a system for controlling the
temperature of a substrate during processing that accounts for
temperature variation parameters such as position, time, and
energy.
SUMMARY
[0005] The above and other needs are met by a method for
controlling the temperature of a substrate during processing of the
substrate at a process energy, by controlling the temperature of
the chuck on which the substrate resides during the processing. A
thermal transfer media is circulated at a thermal transfer media
temperature through the substrate chuck to adjust both the chuck
temperature and the substrate temperature. The thermal transfer
media is circulating at a flow rate. The chuck temperature is
sensed from at least one chuck temperature sensing location at the
chuck, and the sensed chuck temperature is reported to a
controller. The controller is operable to adjust the process energy
and at least one of the thermal transfer media flow rate and the
thermal transfer media temperature. When the sensed chuck
temperature is outside of the desired temperature range, then the
controller is used to adjust at least one of the thermal transfer
media flow rate, the thermal transfer media temperature, and the
process energy to bring the sensed chuck temperature within the
desired temperature range.
[0006] One of the benefits of the method given above is that the
controller is operable to not only control at least one of the
thermal transfer media flow and the thermal transfer media
temperature, but the controller is additionally operable to control
the process energy. In this manner, the controller is operable to,
for example, decrease the process energy to cool the substrate
chuck and the substrate during processing. This may be especially
important when processing conditions are such that the adjustment
of the thermal transfer media flow and the thermal transfer media
temperature are insufficient to adequately control the chuck
temperature and the substrate temperature within the desired
temperature range.
[0007] In various preferred embodiments of the invention, the chuck
temperature is sensed from three different locations at the chuck,
which locations may be either within the chuck or on the surface of
the chuck that is disposed adjacent the substrate. The desired
temperature range at which the sensed chuck temperature is
controlled is between about fifty centigrade and about five hundred
centigrade, and most preferably at about 280 centigrade. In a most
preferred embodiment, the controller first attempts to bring the
sensed temperature within the desired temperature range by
adjusting at least one of the thermal transfer media temperature
and the thermal transfer media flow rate. When adjusting at least
one of the thermal transfer media temperature and the thermal
transfer media flow rate cannot bring the sensed temperature within
the desired temperature range, then the controller preferably
controls the sensed temperature by additionally adjusting the
process energy.
[0008] In another embodiment of the invention, an apparatus is
provided for controlling the substrate temperature of a substrate
during processing of the substrate at a process energy. A chuck
temperature input receives temperature measurements from
temperature sensors at a substrate chuck, and a temperature set
point input receives temperature set points. The temperature set
points define a range of temperatures within which the apparatus
maintains the substrate temperature. A chuck temperature controller
output sends control signals to a chuck temperature controller,
which signals are operable to selectively increase and decrease the
chuck temperature. A process energy output sends control signals
that are operable to selectively increase and decrease the process
energy during the processing of the substrate.
[0009] A controller compares the temperature measurements received
from the temperature sensors at the substrate chuck through the
chuck temperature input to the temperature set points received
through the temperature set point input. The controller sends
control signals through the chuck temperature controller output to
the chuck temperature controller to selectively decrease the chuck
temperature when the temperature measurements received from the
temperature sensors at the substrate chuck are above the
temperature set points. The controller further sends control
signals through the process energy output to selectively decrease
the process energy when the temperature measurements received from
the temperature sensors at the substrate chuck are above the
temperature set point. Preferably, the controller first sends
control signals through the chuck temperature controller output to
control the chuck temperature, and only sends control signals
through the process energy output when the chuck temperature cannot
be sufficiently controlled by the chuck temperature controller.
[0010] As described above, one of the benefits of the apparatus
given above is that when processing conditions are such that the
adjustment of thermal transfer media flow and thermal transfer
media temperature are insufficient to adequately control the chuck
temperature and the substrate temperature within the desired
temperature range, the apparatus is operable to further control the
chuck temperature and the substrate temperature by adjusting the
process energy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Further advantages of the invention are apparent by
reference to the detailed description when considered in
conjunction with the following figures, which are not to scale so
as to more clearly show the details, wherein like reference numbers
refer to like elements within the several views, and wherein:
[0012] FIG. 1 is a functional block diagram of temperature control
system according to the present invention,
[0013] FIG. 2 is a top plan view of a substrate chuck according to
the present invention,
[0014] FIG. 3A is a cross sectional view of a first embodiment of
the substrate chuck of FIG. 2, and
[0015] FIG. 3B is a cross sectional view of a second embodiment of
the substrate chuck of FIG. 2.
DETAILED DESCRIPTION
[0016] Referring now to FIG. 1, there is depicted an embodiment of
a temperature control system apparatus 10 according to the present
invention. The temperature control system 10 works cooperatively
with a reaction chamber 44, such as a high density plasma
deposition chamber or an ion bombardment chamber such as a high
energy etcher. Processes that are conducted in chambers 44 such as
those described tend to impart a relatively high amount of energy
to the substrates 38 processed in the chamber 44, which tends to be
absorbed by the substrate 38 as thermal energy. As mentioned above,
controlling the amount and residence time of the thermal energy
absorbed by a substrate 38 tends to have an impact on the both the
results of the process conducted within the chamber 44 and the
integrity of the previously formed structures on the substrate
38.
[0017] In a typical configuration of the chamber 44, the energy for
the process is emitted from some type of emitter 42, which may be a
device such as a sputter target. The substrate 38 preferably
resides upon some type of substrate holder or chuck 32 during
processing in the chamber 44. The chuck 32 has a surface 36 atop of
which the substrate 38 is received by the chuck 32. The surface 36
provides an interface between the substrate 28 and the other
elements of the chuck 32, as explained in greater detail hereafter.
Most preferably, the surface 36 is designed and manufactured in
consideration with specifically identified heat transfer
properties, also as explained in greater detail hereafter.
[0018] The temperature of the surface 36 of the chuck 32 is sensed
by thermal sensors 40. In practice, there may be one or many
thermal sensors 40 disposed within the chuck 32. If the process
conducted within the chamber 44 is such that the substrate 38 and
the chuck 32 absorb thermal energy with a very uniform profile
across the surface 36 of the chuck 32, then there may be no need
for more than one thermal sensor 40 to be present in the chuck 32.
However, more often than not the thermal energy profile across the
surface 36 of the chuck 32 and also across the substrate 38 is not
very uniform, and therefore in the preferred embodiment a number of
thermal sensors 40 are used, such as the three thermal sensors 40
depicted. In general, the less uniform the thermal energy profile
across the surface 36 of the chuck 32, the more thermal sensors 40
are preferably used to sense the temperature of the substrate 38 at
the surface 36 of the chuck 32. Conversely, the more uniform the
thermal energy profile across the surface 36 of the chuck 32, the
fewer thermal sensors 40 are preferably used to sense the
temperature of the substrate 38 at the surface 36 of the chuck
32.
[0019] The thermal sensors 40 are devices of a type that is
compatible with the operation of the chuck 32, the environment
within the reactor 44, and the other materials used in the
formation of the chuck 32. For example, the thermal sensors 40 are
thermocouples in one embodiment and resistance temperature devices
in another embodiment. Alternately, combinations of these types of
devices and other types of devices are used to exploit the specific
benefits of the different kinds of devices, based upon the specific
configuration of the chuck 32 and the processes to be performed
within the reaction chamber 44.
[0020] The thermal sensors 40 may be located in one or more
different positions relative to the surface 36 of the chuck 32. For
example, the thermal sensors 40 may be located at a position such
that they are very near the upper surface of the surface 36 of the
chuck 32, such that they are in contact with, or very nearly in
contact with the back side of the substrate 38 that resides on the
surface 36 of the chuck 32. In this manner, the thermal sensors 40
tend to be more responsive to the thermal conditions within the
substrate 38. Conversely, the thermal sensors 40 may be underneath
the surface 36 of the chuck 32, at a position that is substantially
inside of the chuck 32. In this position, the thermal sensors 40
tend to be somewhat less responsive to the thermal conditions
within the substrate 38, and somewhat more responsive to the
overall temperature within the chuck 32. In a most preferred
embodiment, the thermal sensors 40 are at a position where they
either make contact with the back side of the substrate 38 or very
nearly make contact with the back side of the substrate 38.
However, in other embodiments, the processing conditions within the
reactor 44 may dictate that the type of thermal sensor 40 selected
is better placed at an alternate location within the chuck 32.
[0021] The chuck 32 preferably has a reservoir 34, within which a
thermal transfer media such as a coolant is circulated. Although
the reservoir 34 is shown as a single open reservoir 34 in the
embodiment depicted in FIG. 1, it is appreciated that this specific
embodiment of the reservoir 34 is for illustration only, and that
in actual construction of the chuck 32, the reservoir 34 is
preferably multi-chambered so as to more specifically control the
characteristics of the heat transfer between the surface 36 of the
chuck 32 and the thermal transfer media circulating within the
reservoir 34.
[0022] For example, if the purpose of the thermal transfer media is
to cool the surface 36 of the chuck 32, and to thereby cool the
substrate 38, then the thermal transfer media is preferably a
coolant. Further, the reservoir 34 of the chuck 32 is in this
example preferably channeled so that the flow of the coolant
through the reservoir 34 tends to remove thermal energy from the
surface 36 of the chuck 32 in a uniform manner, so that the
temperature at the surface 36 of the chuck 32, such as measured by
the thermal sensors 40, tends to likewise be relatively uniform. In
one preferred embodiment, the flow rate and temperature of the
thermal transfer media through the different channels of the
reservoir 34 are all independently variable so as to more fully
provide for a uniform thermal energy profile across the surface 36
of the chuck 32. In this manner, the temperature of the substrate
38 residing atop the surface 36 of the chuck 32 is also maintained
at a relatively uniform temperature.
[0023] In a most preferred embodiment the thermal transfer media is
delivered to the reservoir 34 of the chuck 32 by a flow means 48,
such as a tubing like a stainless steel pipe or a polyvinyl
chloride tubing. The flow means 48 receives the thermal transfer
media from a chuck temperature controller 30, such as a temperature
controlled bath of the thermal transfer media. For example, the
thermal transfer media is in one embodiment a fluid such as water
or a mixture of ethylene glycol and water that flows from a
temperature controlled bath in the chuck temperature controller 30
through the flow means 48 to the reservoir 34 of the chuck 32, and
then back through the flow means 48 and into the temperature
controlled bath in the chuck temperature controller 30. Once back
in the temperature controlled bath of the chuck temperature
controller 30, the thermal transfer media is conditioned to either
remove the thermal energy that it has absorbed from the surface 36
of the chuck 32 or to receive thermal energy to replace that which
it has transferred to the surface 36 of the chuck 32, depending
upon the specific purpose of the thermal transfer media.
[0024] In alternate embodiments of the temperature control system
10 according to the invention where additional thermal energy is to
be added to the surface 36 of the chuck 32 and thereby to the
substrate 38, the chuck 32 may include a heater block, such as an
electrical heater block that delivers thermal energy to the
substrate 38 in a manner as controlled as described in more detail
below.
[0025] In a preferred embodiment of a temperature control system 10
according to the invention, a controller 12 controls the amount of
thermal energy imparted to the substrate 38 and the residence time
of that thermal energy within the substrate 38. Control of these
parameters tends to influence the temperature experienced by the
substrate 38 during processing within the reactor 44, as measured
by the thermal sensors 40. To accomplish these design objectives,
the controller 12 is in communication with other elements as
described herein.
[0026] The emitter 42 is preferably electrically connected to the
controller 12 by a means 28 through a process energy output 20. In
the preferred embodiment, the controller 12 does not provide the
actual power used to energize the emitter 42, but is able to
control the amount of power delivered to the emitter 42. For
example, in the embodiment where the emitter 42 is a target that is
used in a high density plasma deposition reactor, the controller 12
is preferably connected via the process energy output 20 and the
means 28 to the power supply from which the target 42 draws its
energy or to the dedicated controller that directly controls the
amount of power delivered to the emitter 42. In the example of the
high density plasma deposition reactor, by varying the power
delivered to the emitter 42 the controller 12 essentially controls
the deposition rate of the process conducted within the reactor
44.
[0027] The controller 12 is also preferably in communication with
the thermal sensors 40 via means 22 through a chuck temperature
input 14. In this manner the controller 12 receives signals
indicating the temperature sensed by each of the thermal sensors 40
at a point in time at which the signals are generated by the
thermal sensors 40. Additionally, the controller 12 is preferably
in communication with the chuck temperature controller 30 via
communication means 24 through a chuck temperature controller
output 16. Again, in a most preferred embodiment, it is not the
controller 12 that is used to directly provide for circulation and
thermal management of the thermal transfer media, but rather the
controller 12 operates to control the thermal management of the
thermal transfer media through the means of the chuck temperature
controller 30, as described above. In a most preferred embodiment,
the chuck temperature controller 30 is operable to both regulate
the temperature of the thermal transfer media and the flow rate of
the thermal transfer media.
[0028] Further, the controller 12 is operable to receive a
temperature set point from a set point input 46 through
communication means 26 and temperature set point input 18. In this
manner the controller 12 receives a set point temperature that it
compares to the chuck temperature received through the chuck
temperature input 14. If the chuck temperature is higher than the
set point temperature, then the controller 12 sends signals through
the output 20 and the output 16 to exert influence on the amount of
thermal energy delivered to the substrate 38 and the residence time
of that thermal energy within the substrate 38, by attempting to
either decrease the amount of thermal energy delivered to the
substrate 38 or decrease the residence time of the thermal energy
within the substrate 38, or both. On the other hand, if the chuck
temperature is lower than the set point temperature, then the
controller 12 sends signals through the output 20 and the output 16
to exert influence on the amount of thermal energy delivered to the
substrate 38 and the residence time of that thermal energy within
the substrate 38, by attempting to either increase the amount of
thermal energy delivered to the substrate 38 or increase the
residence time of the thermal energy within the substrate 38, or
both.
[0029] In a most preferred embodiment, the controller 12 first
attempts to reconcile the set point temperature with the chuck
temperature by exerting influence on the residence time of the
thermal energy in the substrate by adjusting the chuck temperature
controller 30. Preferably this is accomplished by adjusting either
the temperature of the thermal transfer media or the flow rate of
the thermal transfer media or both. In this manner, the residence
time of the thermal energy absorbed by the substrate 38 in the
reactor 44 is adjusted, and the temperature of the substrate 38 is
similarly influenced.
[0030] For example, if the chuck temperature indicates that the
substrate temperature is higher than desired in comparison to the
set point temperature, then the controller 12 is operable to send
signals to the chuck temperature controller 30 calling for a higher
flow rate of coolant, which tends to remove thermal energy from the
chuck 32 and the substrate 38 at a faster rate. Further, the
controller 12 may alternately send signals to the chuck temperature
controller 30 calling for a reduction in the temperature of the
coolant, which also tends to remove thermal energy from the chuck
32 and the substrate 38 at a faster rate. Both of these two control
mechanisms, either alone or in combination, tend to reduce the
residence time of the thermal energy within the substrate 36, and
thereby reduce the temperature of the substrate 38.
[0031] In a preferred embodiment, sending such control signals from
the controller 12 to the chuck temperature controller 30 is
sufficient to control the temperature of the substrate 38. However,
in some processes, most notably a high density plasma deposition
process, such measures may be insufficient to adequately control
the temperature of the substrate 38. In such situations, the
controller is additionally operable to adjust the amount of energy
delivered by the emitter 42 to the substrate 38 during processing
in the reactor 44.
[0032] Thus, when controlling the residence time of the thermal
energy within the substrate 38 is insufficient to control the
temperature within the substrate 38, the controller 12 reduces the
amount of energy delivered to the substrate 38 by the emitter 42
and thereby influences the temperature of the substrate 38. In a
most preferred embodiment, the controller 12 first acts to control
the temperature of the substrate 38 by use of the chuck temperature
controller 30, and then only when that means is insufficient to
adequately control the temperature of the substrate 38, the
controller 12 next acts to control the temperature of the substrate
38 via the means of reducing the energy output of the emitter 42.
In a preferred embodiment, the temperature of the substrate 38 is
held between about fifty centigrade and about five hundred
centigrade, and most preferably at about 280 centigrade.
[0033] In addition to the means described above, further means can
be employed to exert additional control over the thermal profile of
the substrate 38 and the surface 36 of the chuck 32. Such further
means are shown in FIG. 2, which depicts a surface 36 of a chuck 32
that has thermal conduction zones 52, 54, and 56. Although FIG. 2
depicts a surface 36 having three thermal conduction zones 52, 54,
and 56, it is appreciated that this is by way of illustration only.
While in the preferred embodiment the surface 36 of the chuck 32
has at least two different thermal conduction zones, in various
embodiments the surface 36 of the chuck 32 has more than three
thermal conduction zones. The selection of the number of thermal
conduction zones depends upon the proper balance of several
criteria, such as tolerance of the structures on the substrate 38
to a nonuniform thermal profile, tolerance of the process to a
nonuniform thermal profile, amount of thermal energy delivered to
the substrate 38, and the uniformity of the thermal energy
delivered to the substrate 38.
[0034] The different thermal conduction zones 52, 54, and 56 of the
surface 36 of the chuck 32 each have differing thermal
conductivities and thereby are able to conduct thermal energy from
the substrate 38 and to the heat sink 34 of the chuck 32 at varying
rates. As depicted in FIGS. 3A and 3B, the heat sink 34 is a
reservoir 34 that receives a thermal transfer media as described
above. However, in this embodiment as presently explained the heat
sink 34 may be of a type other than a circulated thermal transfer
media. For example, the heat sink 34 may be fins that dissipate
heat to the ambient environment or the heat sink 34 may be a
thermal mass, such as a mathematically infinite thermal mass, given
the constraints of a specific reactor 44 and process.
[0035] Further, in some embodiments, the thermal conduction zone
52, for example, has the same thermal conductivity as the thermal
conduction zone 56, both of which have a difference thermal
conductivity as compared to the intervening thermal conduction zone
54. Thus, the thermal conductivity of each of the various thermal
conduction zones of the surface 36 of the chuck 32 is selected
according to the anticipated thermal energy absorption of the
substrate 38 at a location above or near the specific thermal
conduction zone in question. In general, processes tend to develop
greater heat near either the center of the substrate 38 or near the
edges of the substrate 38. Thus, in a most preferred embodiment,
the thermal conductivity of the thermal conduction zones 53, 54,
and 56 is selected for the anticipated type of process.
[0036] For example, if the anticipated process is of the type that
tends to deliver a greater amount of thermal energy to the center
of the substrate 38, and it is further desired to remove thermal
energy from the substrate 38 and thus reduce the temperature of the
substrate 38, then the thermal conductivity of the center most
thermal conduction zone 52 is preferably higher than the thermal
conductivity of the middle thermal conduction zone 54, which
preferably has a thermal conductivity that is higher than the
thermal conductivity of the outermost thermal conduction zone 56.
By selecting the thermal conductivity of the various thermal
conduction zones 52, 54, and 56 in this manner, the thermal energy
is drawn off at a faster rate from the center of the substrate 38
where the greatest amount of thermal energy is delivered, and the
thermal energy is drawn off at a slower rate from the edges of the
substrate 38 where the least amount of thermal energy is delivered.
According, the thermal energy is drawn off at an intermediate rate
from the portions of the substrate 38 that reside between the
center portion of the substrate 38 and the edges of the substrate
38, which portions receive an intermediate amount of thermal energy
during processing in the reactor 44.
[0037] Because varying levels of thermal energy are delivered to
the substrate 38 and the thermal energy is likewise drawn off from
the substrate 38 at varying levels that are preferably selected to
match or substantially match the anticipated rates at which thermal
energy is delivered to the substrate 38 at the various positions on
the substrate 38, the thermal profile across the surface of the
substrate 38 is maintained at a more uniform level. This tends to
make control of the temperature of the substrate 38 by the
controller 12 much easier to accomplish, as the controller tends to
receive temperature measurements from the thermal sensors 40 that
are more uniform. FIG. 3A depicts an embodiment in which the
thermal sensors 40 are disposed underneath at least a portion of
the surface 36 of the chuck 32, and FIG. 3B depicts an embodiment
in which the thermal sensors 40 are disposed at the top surface of
the surface 36 of the chuck 32, and are in intimate contact with
the back side of the substrate 38.
[0038] The surface 36 of the chuck 32 is preferably formed of
ceramics such as silicon nitride, silicon oxide, or most preferably
aluminum oxide. The thermal conductivity of the ceramic is adjusted
by blending into the ceramic during formation of the surface 36
varying amounts of a filler material that has either a higher or a
lower thermal conductivity than the other material that is used to
form the surface 36, such as the ceramic material. In a most
preferred embodiment, the filler material has a higher thermal
conductivity than the ceramic that is used to form the rest of the
surface 36. Thus, areas of the surface 36 that are to have higher
thermal conductivity receive a greater amount of the filler
material during formation of the surface 36, and areas of the
surface 36 that are to have lower thermal conductivity receive a
lesser amount of the filler material during formation of the
surface 36.
[0039] The material used for the filler in the formation of the
surface 36 of the chuck 32 is selected so as to be compatible with
the anticipated environment within the reactor 44, the anticipated
temperatures developed during the processing cycles, and to not
have any negative interactions with the substrate 38. The filler
material is preferably a material such as beryllium oxide, silicon
carbide, diamond, or most preferably aluminum nitride.
[0040] Although the shapes of the thermal conductivity zones 52,
54, and 56 as depicted in FIG. 2 are given as annular and circular
regions, it is appreciated that these shapes as given are exemplary
only and that in actual practice of the invention the shapes of the
various thermal conductivity zones may be something other than
circular and annular. For example, in an alternate embodiment, the
thermal conductivity zones may be in the form of bands across the
surface 36 of the chuck 32. Further, the thermal conductivity zones
may be irregularly shaped, which irregular shapes are empirically
determined by placing a number of thermal sensors 40 at various
positions on top of a chuck 32, and measuring the thermal profile
across the chuck 32. Thus, as suggested by this explanation, the
shapes of the various thermal conductivity zones are preferably
selected so as to create a relatively flat thermal profile across
the surface 36 of the chuck 32, and thereby to impart a relatively
flat thermal profile across the substrate 38.
[0041] The foregoing description of preferred embodiments for this
invention have been presented for purposes of illustration and
description. They are not intended to be exhaustive or to limit the
invention to the precise form disclosed. Obvious modifications or
variations are possible in light of the above teachings. The
embodiments are chosen and described in an effort to provide the
best illustrations of the principles of the invention and its
practical application, and to thereby enable one of ordinary skill
in the art to utilize the invention in various embodiments and with
various modifications as is suited to the particular use
contemplated. All such modifications and variations are within the
scope of the invention as determined by the appended claims when
interpreted in accordance with the breadth to which they are
fairly, legally, and equitably entitled.
* * * * *