U.S. patent application number 11/165573 was filed with the patent office on 2006-02-02 for substrate mounting apparatus and control method of substrate temperature.
This patent application is currently assigned to NGK Insulators, Ltd.. Invention is credited to Tomoyuki Fujii, Yasuyoshi Imai, Tetsuya Kawajiri.
Application Number | 20060021705 11/165573 |
Document ID | / |
Family ID | 35730811 |
Filed Date | 2006-02-02 |
United States Patent
Application |
20060021705 |
Kind Code |
A1 |
Imai; Yasuyoshi ; et
al. |
February 2, 2006 |
Substrate mounting apparatus and control method of substrate
temperature
Abstract
A substrate mounting apparatus, comprises a ceramic base having
a substrate mounting surface, and a jointing layer, which is formed
on an opposite surface to the substrate mounting surface of the
ceramic base, and has jointing materials differing in a thermal
conductivity by in-plane regions and arranged in the regions.
Inventors: |
Imai; Yasuyoshi;
(Nagoya-shi, JP) ; Kawajiri; Tetsuya; (Handa-shi,
JP) ; Fujii; Tomoyuki; (Nagoya-shi, JP) |
Correspondence
Address: |
BURR & BROWN
PO BOX 7068
SYRACUSE
NY
13261-7068
US
|
Assignee: |
NGK Insulators, Ltd.
Nagoya-City
JP
|
Family ID: |
35730811 |
Appl. No.: |
11/165573 |
Filed: |
June 23, 2005 |
Current U.S.
Class: |
156/345.52 |
Current CPC
Class: |
C23C 16/4581 20130101;
H01L 21/6831 20130101; H01L 21/67103 20130101; C23C 16/4586
20130101 |
Class at
Publication: |
156/345.52 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 29, 2004 |
JP |
P2004-191106 |
Claims
1. A substrate mounting apparatus, comprising: a ceramic base
having a substrate mounting surface; and a jointing layer, which is
formed on an opposite surface to the substrate mounting surface of
the ceramic base, and has jointing materials differing in a thermal
conductivity by in-plane regions and arranged in the regions.
2. The substrate mounting apparatus according to claim 1, further
comprising a pedestal joined to the ceramic base with the jointing
layer interposed between the pedestal and the ceramic base.
3. The substrate mounting apparatus according to claim 1, wherein
the regions are a central part and a peripheral part; a first
jointing material is arranged in the central part; and a second
jointing material differing in the thermal conductivity from the
first jointing material is arranged in the peripheral part.
4. The substrate mounting apparatus according to claim 3, wherein
the second jointing material has a higher thermal conductivity than
a thermal conductivity of the first jointing material.
5. The substrate mounting apparatus according to claim 1, wherein
the jointing materials include a resin base material and filler
6. The substrate mounting apparatus according to claim 1, further
comprising an electrostatic chuck electrode buried in the ceramic
base.
7. The substrate mounting apparatus according to claim 1, further
comprising a resistance heating element buried in the ceramic
base.
8. The substrate mounting apparatus according to claim 2, wherein
the pedestal includes a cooling unit.
9. The substrate mounting apparatus according to claim 1, wherein
the ceramic base has protrusions on the substrate mounting surface,
and contact area of each of the protrusions with a mounted
substrate differs by the regions.
10. The substrate mounting apparatus according to claim 9, wherein
the contact area is larger in a peripheral part than in a central
part of the substrate mounting surface.
11. The substrate mounting apparatus according to claim 9, wherein
the contact area is larger in a central part than in a peripheral
part of the substrate mounting surface.
12. A control method of substrate temperature, comprising:
controlling temperature distribution of a substrate mounted on a
ceramic base by controlling in-plane thermal conductivity
distribution of a jointing layer formed on an opposite surface to a
substrate mounting surface of the ceramic base.
13. The control method according to claim 12, wherein controlling
the in-plane thermal conductivity distribution of the jointing
layer by arranging a first jointing material in a central part of
the jointing layer and a second jointing material differing in a
thermal conductivity from the first jointing material in a
peripheral part of the jointing layer.
14. The control method according to claim 12, wherein controlling
the temperature distribution of the substrate by controlling
contact areas of respective protrusions formed on the substrate
mounting surface with the substrate by location.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. P2004-191106,
filed on Jun. 29, 2004; the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a substrate mounting
apparatus and a control method of substrate temperature.
[0004] 2. Description of the Related Art
[0005] In a semiconductor manufacturing process and a liquid
crystal display manufacturing process, a substrate mounting
apparatus such as a susceptor, an electrostatic chuck, or a ceramic
heater with a heating element is used to mount a substrate such as
a silicon wafer or a glass substrate.
[0006] In semiconductor manufacturing processes, temperature
distribution in a substrate surface causes in-plane variation of
the substrate in quality of formed thin films and in etching
characteristics. Therefore, the substrate surface having uniform
temperature distribution is desired. However, the temperature
distribution in the substrate surface is significantly affected by
not only temperature distribution of the substrate mounting
apparatus such as a ceramic heater, but also use environment such
as heat input distribution due to plasma.
[0007] Therefore, even if temperature distribution in the substrate
mounting surface of the substrate mounting apparatus itself is
controlled to be uniform, it is difficult to obtain uniform
temperature distribution in the actual substrate surface due to
external factors. Accordingly, to optimize the temperature
distribution of the substrate, optimization of plasma conditions
and adjustments of shape and material arranged around the substrate
mounting apparatus are carried out.
[0008] An electrostatic chuck having a substrate mounting surface,
which is controlled for an unevenness by location based on heat
input distribution due to plasma has been proposed (Japanese patent
application laid-open Hei 7-18438). In addition, a multi-zone
heater, in which ceramic base constituting a substrate mounting
surface is divided into multiple zones, heating elements are buried
in the respective zones, and control heating values of heating
elements respectively has been proposed (Japanese patent
application laid-open 2001-52843).
[0009] However, there is a limited effective control range for
conventional optimization of the temperature distribution of the
substrate through optimization of plasma conditions, adjustments of
shape and material arranged around the substrate mounting
apparatus, and control of the unevenness of the substrate mounting
surface.
[0010] On the other hand, according to a technique of burying
optimal heating elements for respective zones with consideration of
expected plasma irradiation conditions, heater design is great
burden and cost of a substrate mounting apparatus is high.
Moreover, after manufacturing a substrate mounting apparatus, since
it is difficult to correct the substrate mounting apparatus in
accordance with changes in use environments, it does not have
general versatility. Furthermore, in the case of a required
substrate temperature being relatively low, since substrates need
to be cooled rather than being heated by a heater, control of the
temperature distribution of a substrate surface is desired using a
mechanism without a heater.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a substrate
mounting apparatus and a control method of substrate temperature,
which can control temperature distribution of a substrate and are
simple and versatile.
[0012] A substrate mounting apparatus according to an embodiment of
the present invention comprises a ceramic base having a substrate
mounting surface, and a jointing layer, which is formed on an
opposite surface to the substrate mounting surface of the ceramic
base, and has jointing materials differing in a thermal
conductivity by in-plane regions and arranged in the regions.
[0013] According to the substrate mounting apparatus, the
temperature distribution of a substrate mounted on the substrate
mounting surface can be controlled with simple structure.
[0014] According to a control method of substrate temperature of an
embodiment of the present invention comprises controlling
temperature distribution of a substrate mounted on a ceramic base
by controlling in-plane thermal conductivity distribution of a
jointing layer formed on an opposite surface to a substrate
mounting surface of the ceramic base.
[0015] According to the control method of substrate temperature,
the temperature distribution of a substrate mounted on the
substrate mounting surface can be controlled with a simple and
versatile way.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG 1A is a cross-section view of a substrate mounting
apparatus according to an embodiment of the present invention, and
FIG. 1B is a plane view of a jointing layer thereof;
[0017] FIGS. 2A and 2B are plane views showing distributions of
jointing materials in jointing layers according to an embodiment of
the present invention;
[0018] FIGS. 3A and 3B are cross-sectional views showing a
substrate mounting apparatus according to another embodiment of the
present invention;
[0019] FIGS. 4A is a cross-sectional view taken along line 4a-4a of
FIG. 4B of a substrate mounting apparatus according to another
embodiment of the present invention, and FIG. 4B is a plane view
thereof;
[0020] FIG. 5 is a graph showing simulation results of temperature
distribution in a substrate mounting surface of a substrate
mounting apparatus using aluminum nitride as a ceramic base
according to an embodiment of the present invention;
[0021] FIG. 6 is a graph showing simulation results of temperature
distribution in a substrate mounting surface of a substrate
mounting apparatus using alumina as a ceramic base according to an
embodiment of the present invention;
[0022] FIG. 7 shows an apparatus for an evaluation of substrate
mounting apparatuses according to a first and a second working
examples of the present invention; and
[0023] FIG. 8 is a graph showing measurement results of temperature
distribution of a substrate mounted on a mounting apparatus
according to the first and the second working example of the
present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0024] FIG. 1A shows a cross-section of a substrate mounting
apparatus 1 according to an embodiment of the present invention.
The substrate mounting apparatus 1 comprises a ceramic base 10 and
a jointing layer 20. The ceramic base 10 has a substrate mounting
surface 10a. Specifically, one surface of the platy ceramic base 10
is a substrate mounting surface 10a. The jointing layer 20 is
formed on the other surface of the ceramic base 10, i.e., the
opposite surface to the substrate mounting surface 10a. The
jointing layer 20 is divided into multiple regions in its
plane.
[0025] More specifically, the jointing layer 20 is divided into
multiple regions in the same plane extending direction as the
substrate mounting surface 10a extending direction. Jointing
materials differing in a thermal conductivity by the in-plane
regions are arranged in respective regions. It is preferable that
the substrate mounting apparatus 1 comprises a base plate 30 joined
to the ceramic base 10 with the jointing layer 20 interposed
between the base plate 30 and the ceramic base 10, as shown in FIG.
1A. The base plate 30 is a platy pedestal.
[0026] According to the substrate mounting apparatus 1, the
in-plane thermal conductivity distribution of the jointing layer 20
arranged on the opposite surface to the substrate mounting surface
10a of the ceramic base 10 can be controlled. Therefore, cooling
efficiency due to heat transfer from a substrate mounted on the
substrate mounting surface 10a to the ceramic base 10 and the
jointing layer 20 can be changed by location. Accordingly, the
in-plane temperature distribution of the substrate mounted on the
ceramic base 10 can be controlled.
[0027] Moreover, joining of the base plate 30 to the ceramic base
10 with the jointing layer 20 allows thermal conduction to the base
plate 30 from the substrate via the jointing layer 20, thereby
radiating heat. Therefore, the substrate can be cooled more
effectively. As a result, an effect of a temperature control
function by controlling the in-plane thermal conductivity
distribution of the jointing layer 20 can enhance.
[0028] FIG. 1B shows a plane view of the jointing layer 20. The
jointing layer 20 is divided into two regions, which are a central
part and an peripheral part in a plane. In other words, a plurality
of regions are the central part and the peripheral part in a plane.
A first jointing material 20B is arranged in the central part. A
second jointing material 20A differing in a thermal conductivity
from the first jointing material is arranged in the peripheral
part. This allows control of the in-plane thermal conductivity
distribution of the jointing layer 20.
[0029] When using the substrate mounting apparatus 1 in a plasma
processing apparatus such as a plasma CVD apparatus or a plasma dry
etching apparatus, the temperature distribution in the substrate
surface is a higher temperature in the peripheral part of the
substrate than in the central part. This is attributed to the fact
that a temperature in the peripheral part of the substrate surface
tends to be higher than that in the central part of the substrate
surface due to influence of plasma intensity distribution and
apparatus structure. Accordingly, when using the substrate mounting
apparatus 1 in such an environment, a jointing material having a
low thermal conductivity is arranged as the first jointing material
20B in the central part of the jointing layer 20. A jointing
material having a higher thermal conductivity than that of the
first jointing material 20B is arranged as the second jointing
material 20A in the peripheral part of the jointing layer 20.
[0030] According to arranging a jointing material having a high
thermal conductivity in the peripheral part, the peripheral part of
the substrate where the substrate temperature tends to be easily
high, can be effectively cooled. Therefore, an excessive
temperature rising can be prevented. Moreover, according to
arranging a jointing material having a low thermal conductivity in
the central part, cooling the substrate can be suppressed in the
central part of the substrate where the substrate temperature tends
to be easily low. As a result, uneven temperature distribution of
the substrate surface due to the plasma intensity distribution and
apparatus structure can be corrected, providing a uniform
temperature distribution of the substrate surface.
[0031] In FIGS. 1A and 1B, the jointing layer 20 is divided into
two regions, which are the central part and the peripheral part,
and the first jointing material 20B and the second jointing
material 20A differing in a thermal conductivity are arranged in
the central part and the peripheral part, respectively, however,
the jointing layer may be divided into three regions as shown in
FIG. 2A. More specifically, the jointing layer may be divided into
a central part, a peripheral part, and an intermediate part between
the central part and the peripheral part. Then the first jointing
material 20B may be arranged in the central part, the second
jointing material 20A may be arranged in the peripheral part, and
the third jointing material 20C may be arranged in the intermediate
part. For example, jointing materials may be arranged in such a
manner that the further inward the region, the lower the thermal
conductivity. In other words, a jointing material having a low
thermal conductivity may be arranged as the first jointing material
20B, a jointing material having a higher thermal conductivity than
the first jointing material 20B may be arranged as the third
jointing material 20C, and a jointing material having a higher
thermal conductivity than the third jointing material 20C may be
arranged as the second jointing material 20A. Alternatively, the
number of divided regions may be increased as necessary.
[0032] Note that the temperature distribution in the substrate
surface is not limited to a distribution having low temperature in
the central part of the substrate and high temperature in the
peripheral part thereof, and may be a variety of distributions due
to use conditions and apparatus structure. Therefore, it is desired
to control the in-plane thermal conductivity distribution of the
jointing layer in accordance with the temperature distribution in
the substrate surface.
[0033] Moreover, a form of dividing regions for the jointing layer
20 is not limited to concentrically dividing from the center. A
variety of dividing forms may be used based on the necessary
temperature control conditions. For example, when the substrate
mounting apparatus has through-holes for lift pins and a purge gas,
the temperatures of the substrate surface corresponding to regions
where through-holes are formed, may be locally high or low. In this
case, to correct local changes in temperature, jointing materials
having a different thermal conductivity from that of surrounding
regions may be arranged in the regions of the jointing layer
corresponding to the through-holes, as shown in FIG. 2B.
[0034] For example, when the jointing layer has the first jointing
material 20B in the central part and the second jointing material
20A in the peripheral part, the third jointing material 20D
differing in a thermal conductivity from the first jointing
material 20B may be arranged in the regions corresponding to the
through-holes in the first jointing material 20B in the central
part. In addition, when a temperature of a part of the substrate
tends to easily drop due to influence of an exhaust port or other
components in a semiconductor manufacturing apparatus in which the
substrate mounting apparatus 1 is arranged, jointing materials
having a low thermal conductivity may be arranged in regions of the
jointing layer 20 corresponding to regions where the temperature
tends to easily drop.
[0035] According to such controlling method of the in-plane thermal
conductivity distribution of the jointing materials in the jointing
layer 20, the temperature distribution in the substrate surface can
be controlled with a simple way. Moreover, the jointing layer 20
can be easily removed by using an organic jointing material.
[0036] Therefore, modification of thermal conductivity distribution
in the jointing layer 20 can be easily provided according to
changes in use environment for the substrate mounting apparatus 1.
Therefore, the substrate mounting apparatus 1 has high
versatility.
[0037] FIGS. 3A and 3B show substrate mounting apparatus 2 and 3
according to other embodiments. As shown in FIG. 3A, it is
preferable that the substrate mounting apparatus 2 includes an
electrostatic chuck electrode 40 buried in the ceramic base 10 and
thereby having an electrostatic chuck function. The substrate
mounting apparatus 2 can improve heat transfer efficiency from the
substrate mounting apparatus 2 to a substrate by closely fixing the
substrate to a mounting surface of the ceramic base 10 using the
electrostatic chuck function. Therefore, accurate control of the
temperature distribution of the substrate is possible.
[0038] In addition, as shown in FIG. 3B, a substrate mounting
apparatus 3 including a resistance heating element 50 and
electrostatic chuck electrode 40 buried in the ceramic base 10 may
be provided. Alternatively, burying only resistance heating element
50 in the ceramic base 10 without burying the electrostatic chuck
electrode 40 is possible. The substrate mounting apparatus 3 having
the resistance heating element 50 can serve as a heater. Therefore,
the substrate mounting apparatus 3 can raise substrate temperature.
Furthermore, using a multi-zone heater, which can set temperatures
of respective regions as the resistance heating elements 50, allows
control of temperature over a wider range.
[0039] Furthermore, as shown in FIG. 3B, a base plate 30a may
include a cooling unit. The base plate 30a includes a coolant flow
channel 60 through which coolant 10 circulates as a cooling unit. A
substrate mounting apparatus having such a cooling unit may be used
for, for example, a radio frequency plasma processing apparatus or
the like to lower the substrate temperature heightened through
plasma irradiation.
[0040] Moreover, a substrate mounting apparatus can improve
in-plane temperature distribution control function by combining a
means controlling in-plane temperature distribution of a substrate.
As shown in FIGS. 4A and 4B, for example, the ceramic base 10 may
have multiple protrusions on a substrate mounting surface 10a.
Moreover, protrusions are formed such that contact area of each of
the protrusions with a mounted substrate can differ for every
region. In other words, contact areas of the protrusions with the
substrate differ by location. This allows further control of
in-plane temperature distribution of the substrate. Note that those
contact areas correspond to areas of top surface of respective
protrusions.
[0041] In the case of using a substrate mounting apparatus 4 in a
plasma processing apparatus, when the surface temperature of the
central part of the substrate is low and that of the peripheral
part thereof is high, protrusions 70C each having a small contact
area with the substrate are formed in the central part of the
substrate mounting surface 10a of the ceramic base 10, as shown in
FIGS. 4A and 4B, for example. Protrusions 70B each having a larger
contact area than each protrusion 70C are formed surrounding the
protrusions 70C. Protrusions 70A each having a larger contact area
with the substrate than protrusion 70B are formed in the periphery
of the protrusions 70B. In other words, the peripheral part of the
substrate mounting surface 10a has larger contact areas than the
central part thereof. Since the contact areas of the protrusions
70C in the central part of the substrate mounting surface 10a with
a substrate are small, cooling effects due to heat transfer can be
suppressed. Since the contact areas of the protrusions 70A in the
peripheral part of the substrate mounting surface 10a with the
substrate are large, cooling effects due to heat transfer can be
advanced. As a result, uneven temperature distribution of the
substrate due to plasma intensity distribution and the apparatus
structure can be corrected.
[0042] Here, the substrate mounting surface 10a is concentrically
divided into three regions, and protrusions 70A,70B and 70C each
having a predetermined contact area, are formed in respective
regions. However, dividing form of the substrate mounting surface
may change into a various forms according to temperature of the
substrate surface, use conditions or the like. For example,
protrusions each having a large contact area with a substrate may
be formed in the central part of the substrate mounting surface,
while protrusions each having a small contact area with the
substrate may be formed in the peripheral part. This structure is
opposite to that in FIG. 4B. In other words, the contact area in
the central part of the substrate mounting surface is larger than
that in the peripheral part thereof.
[0043] In this manner, controlling the contact area distribution of
the protrusions on the substrate mounting surface 10a in addition
to controlling the in-plane temperature distribution of the
jointing layer 20 can be carried out. This can fine adjust the
temperature distribution of the substrate. Therefore, a desired
accurate temperature distribution can be provided.
[0044] Next, materials of the substrate mounting apparatus are
described. The ceramic base 10 may be made of a variety of
ceramics. For example, oxide ceramics such as alumina
(Al.sub.2O.sub.3), nitride ceramics such as aluminum nitride (AlN)
silicon nitride (Si.sub.3N.sub.4), boron nitride (BN), or sialon,
or carbide ceramics such as silicon carbide (SiC) may be used as a
dense sintered body. Aluminum nitride can be preferably used, since
it has high corrosion resistance and a high thermal
conductivity.
[0045] Note that the shape of the ceramic base 10 may be selected
from a variety of shapes according to the size and the shape of
substrates to be mounted. The shape of the substrate mounting
surface is not limited to circular form, and alternatively, it may
be rectangle or polygon.
[0046] Moreover, the material of the base plate 30 is not limited
either. It is preferable that the base plate 30 is made of metallic
material or composite material including metal and ceramics, which
has a relatively high thermal conductivity, for example. The base
plate 30 may be made of, for example, Al, Cu, brass, SUS or the
like.
[0047] The ceramic material included in the composite material is
not limited. A porous ceramic or the like having the same or
different as from the ceramic base 10 may be used. For example,
alumina, aluminum nitride, silicon carbide, silicon nitride,
sialon, or the like may be used. Meanwhile, it is preferable that a
metal filled in the porous ceramic material has high corrosion
resistance and is easy to fill. For example, alumina, alloy of
alumina and silicon, or the like may be used. Furthermore, it is
preferable that the base plate 30 has a cooling unit such as a
coolant flow channel 60.
[0048] An organic jointing material or an inorganic jointing
material such as inorganic glass may be used as the jointing
material constituting the jointing layer 20. However, it is
preferable to use an organic jointing material as the jointing
material. It is further preferable to use a jointing material
having a low jointing temperature. According to this, the
difference in thermal expansion between the base plate 30 and the
ceramic base 10 decreases.
[0049] In the substrate mounting apparatus 1, the jointing layer 20
is divided into multiple regions in a plane. Jointing materials
differing in a thermal conductivity by regions are used. For
example, jointing materials differing in composition may be used in
respective regions. Alternatively, a jointing material made of an
organic base material such as a resin base material including
filler may be used. In other words a jointing material may include
a resin base material and filler added to the resin base material.
Then, a desired thermal conductivity may be provided by controlling
the content of the filler. For example, it is preferable to use a
resin such as polyimide resin, silicone resin, or acrylic resin as
a base material and add filler such as alumina, aluminum nitride,
titanium boride, or aluminum thereto. In particular, it is
preferable to use acrylic resin as a base material.
[0050] The thermal conductivity of the jointing material is not
limited. For example, in the case of arranging a jointing material
having a high thermal conductivity in one region and a jointing
material having a low thermal conductivity in the other region, the
high thermal conductivity may be about 1.1 to about 100 times the
low thermal conductivity. Alternatively, a jointing material having
more than 100 times the low thermal conductivity may be used as
necessary.
[0051] Note that to facilitate handling in a manufacturing process,
a sheet of an organic jointing material or an adhesive sheet, which
is an organic adhesive is applied to both sides of an organic resin
sheet may be used as the jointing layer 20.
[0052] When using the ceramic base 10 having the electrostatic
chuck electrodes 40 buried therein as shown in FIG. 3A, Coulomb's
force between the electrostatic chuck electrode 40 and a substrate,
or Johnsen-Rahbeck force between a surface of the ceramic base 10
and the substrate may be used as an electrostatic chucking
mechanism. In the case of using Coulomb's force, it is preferable
that the resistivity of the ceramic base 10, more specifically, the
resistivity of the dielectric layer between the substrate mounting
surface and the electrostatic chuck electrode 40 is equal to or
greater than about 10.sup.14 .OMEGA.cm at a working temperature and
a thickness of the dielectric layer is equal to or less than about
0.5 mm. On the other hand, in the case of using Johnsen-Rahbeck
force, it is preferable that the resistivity of the dielectric
layer is about 10.sup.7 .OMEGA.cm to about 10.sup.12 .OMEGA.cm at a
working temperature and a thickness of the dielectric layer is
about 0.2 mm to about 5 mm.
[0053] The electrostatic chuck electrode 40 may be made of a
refractory conductive material such as molybdenum (Mo), tungsten
(W), molybdenum carbide (MoC), or tungsten carbide (WC), and form
thereof is not limited. For example, the electrostatic chuck
electrode 40 may be a filmy electrode formed by printing, drying,
and sintering a metallic paste, or a predetermined patterned
electrode formed by etching a metallic thin film, which is formed
by physical deposition such as sputtering or ion beam deposition or
chemical deposition such as CVD. Alternatively, a bulk metal such
as wire mesh (mesh bulk metal) may be used as the electrostatic
chuck electrode 40.
[0054] In the case of forming the ceramic base 10 having resistance
heating element 50 buried therein as shown in FIG. 3B, the
resistance heating element 50 may be made of a refractory
conductive material such as molybdenum (Mo), tungsten (W),
molybdenum carbide (MoC), or tungsten carbide (WC). Other than
refractory conductive materials, Ni, TiN, TiC, TaC, NbC, HfC,
HfB.sub.2, ZrB.sub.2, carbon or the like may be used. The
resistance heating element 50 may be a variety of forms such as a
linear form, a ribbon form, a mesh form, a coil spring form, a
sheet form, or a printed form.
[0055] Next, a manufacturing method for the substrate mounting
apparatuses 1 to 4 is described. First, the ceramic base 10 and the
base plate 30 are formed. To form the ceramic base 10, a ceramic
raw powder such as aluminum nitride and a sintering aid such as
yttria (Y.sub.2O.sub.3), silica (SiO.sub.2) or alumina
(Al.sub.2O.sub.3) are prepared in a predetermined compounding
ratio, and then mixed using a pot mill or ball mill.
[0056] Such mixing may be carried out using a wet process or a dry
process. When using the wet process, drying is carried out after
mixing, providing the mixed raw powder. Afterwards, the mixed raw
powder as is or a granulated powder prepared by adding a binder and
then granulating is formed into a disc-shaped compact, for example.
A method for forming the compact is not limited, and a variety of
forming methods are available. For example, a metal mold forming
method, a cold isostatic pressing (CIP) method, or a slip casting
method may be used.
[0057] Afterwards, the compact is sintered by a hot pressing
method, atmospheric sintering method or the like to obtain a
sintered body. In the case of aluminum nitride, sintering is
carried out at about 1700.degree. C. to about 1900.degree. C. In
the case of alumina, sintering is carried out at around
1600.degree. C. In the case of sialon, sintering is carried out at
about 1700.degree. C. to about 1800.degree. C. In the case of
silicon carbide, sintering is carried out at about 2000.degree. C.
to about 2200.degree. C.
[0058] Note that in the case of burying the electrostatic chuck
electrode 40 and the resistance heating element 50 in the ceramic
base 10, the electrostatic chuck electrode 40 and the resistance
heating element 50 may be buried in a compact. In the case of the
electrostatic chuck electrode 40, for example, planar electrode
made of a metallic bulk having holes or mesh electrode (wire mesh)
may be buried in the raw powder. In the case of burying the
resistance heating element 50, a metallic bulk processed into a
predetermined form such as a coil form or a spiral form may be
buried in the same manner as the electrostatic chuck electrode 40.
It is preferable that the electrostatic chuck electrode 40 and the
resistance heating element 50 are made of a refractory conductive
material such as molybdenum or tungsten.
[0059] Alternatively, the electrostatic chuck electrode 40 may be
made of a filmy electrode formed by printing, drying, and sintering
a metallic paste. In this case, in a forming a compact process, a
green sheet layered body may be formed. For example, the green
sheet layered body may be formed by preparing two disc-shaped green
sheets, printing metallic paste for electrode on one surface of one
green sheet, and stacking the other green sheet on the printed
electrode. The green sheet layered body is then sintered. The base
plate 30 is made of a composite material or metal. A coolant flow
channel 60 may be formed in the base plate 30a as necessary.
[0060] Next, the ceramic base 10 and the base plate 30 are joined
via the jointing layer 20. First, multiple jointing materials
differing in a thermal conductivity are arranged on the backside of
the ceramic base 10 (the opposite surface to the substrate mounting
surface 10a). Jointing materials are arranged by patterning
jointing materials on the surface of the ceramic base 10 or the
surface of the base plate 30 through printing. Alternatively,
multiple sheets of jointing materials may be arranged at
predetermined positions between the ceramic base 10 and the base
plate 30. Afterwards, the jointing materials are heated in vacuum
or in the air up to a curing temperature, and a certain pressure is
applied, thereby joining the ceramic base 10 and the base plate
30.
[0061] Such substrate mounting apparatus may be used as a
susceptor, an electrostatic chuck, a ceramic heater or the like to
be used in a semiconductor manufacturing process or a liquid
crystal display manufacturing process.
EXAMPLES
[0062] Simulation of temperature distribution in a substrate
mounting surface is carried out for verification of effectiveness
of the present invention and working examples of the present
invention are described.
Simulation
[0063] The jointing layer 20 arranged between the ceramic base 10
and the base plate 30 is divided into multiple regions in a plane,
and simulation of temperature distribution of the ceramic base 10
surface (substrate mounting surface 10a) in the case of arranging
jointing materials differing in a thermal conductivity by regions
is carried out using the finite element method. Note that the
surface temperature of the ceramic base 10 rises due to heat input
from plasma when the substrate mounting apparatus is arranged in a
plasma processing apparatus, however, in this simulation, assuming
that temperature uniformly rises in a plane.
[0064] The object for this simulation is the substrate mounting
apparatus 2 shown in FIG. 3A. It has the ceramic base 10 in which
the electrostatic chuck electrode 40 is buried, and the base plate
30 joined to the ceramic base 10 via the jointing layer 20.
Moreover, the jointing layer 20 is divided into two regions, which
are a central part and a peripheral part. Then jointing materials
differing in a thermal conductivity are arranged in the central
part and the peripheral part, respectively. Specifically, the first
jointing material 20B is arranged in the central part, and the
second jointing material 20A is arranged in the peripheral part.
Table 1 shows sizes, materials and thermal conductivities of
respective constructional members used for this simulation.
TABLE-US-00001 TABLE 1 CONSTRUCTIONAL THERMAL CONDUCTIVITY MEMBER
SIZE MATERIAL [W/mK] CERAMIC BASE DIAMETER: 200 mm AlN 90
THICKNESS: 5 mm Al.sub.2O.sub.3 30 JOINTING LAYER DIAMETER: 200 mm
ACRYLIC NO. 1 1.4 THICKNESS: 0.23 mm RESIN NO. 2 0.6 NO. 3 0.1 BASE
PLATE DIAMETER: 200 mm Al 180 THICKNESS: 15 mm
[0065] Tables 2 and 3 show thermal conductivities and diameters of
the jointing layer, and heat input power. The size of the first
jointing material 20B in the central part is assumed to be 60 mm,
120 mm, and 140 mm in diameter. Note that it is assumed that the
temperature at the bottom surface of the base plate 30 is
20.degree. C., and the energy (heat input power) from plasma
inputting to the ceramic base 10 is 300 W, 500 W, and 700 W.
[0066] Table 2 and FIG. 5 show simulation results in the case of
using aluminum nitride as the ceramic base. Table 3 and FIG. 6 show
simulation results in the case of using alumina as the ceramic
base. Tables 2 and 3 and FIGS. 5 and 6 show temperature differences
.DELTA.T between the center and the end of the substrate mounting
surface as the temperature distribution in the substrate mounting
surface. In FIGS. 5 and 6, a vertical axis represents a temperature
difference .DELTA.T, and a horizontal axis represents a distance
from the center of the substrate mounting surface. TABLE-US-00002
TABLE 2 DIAMETER OF HEAT INPUT TEMPERATURE DISTRIBUTION IN
CORRESPON- JOINTING LAYER JOINTING LAYER CENTRAL PART POWER
SUBSTRATE MOUNTING SURFACE DENCE LINE (PERIPHERAL PART) (CENTRAL
PART) [mm] [W] (TEMPERATURE DIFFERENCE .DELTA.T (.degree. C.)) IN
FIG. 5 NO. 1 NO. 2 60 300 1.5 101 THERMAL THERMAL 500 2.4 102
CONDUCTIVITY: CONDUCTIVITY: 700 3.4 103 1.4 [W/mK] 0.6 [W/mK] 120
300 1.9 104 500 3.2 105 700 4.5 106 140 300 1.9 107 500 3.2 108 700
4.5 109
[0067] TABLE-US-00003 TABLE 3 DIAMETER OF HEAT INPUT TEMPERATURE
DISTRIBUTION IN CORRESPON- JOINTING LAYER JOINTING LAYER CENTRAL
PART POWER SUBSTRATE MOUNTING SURFACE DENCE LINE (PERIPHERAL PART)
(CENTRAL PART) [mm] [W] (TEMPERATURE DIFFERENCE .DELTA.T (.degree.
C.)) IN FIG. 6 NO. 1 NO. 2 60 300 1.9 201 THERMAL THERMAL 500 3.1
202 CONDUCTIVITY: CONDUCTIVITY: 700 4.4 203 1.4 [W/mK] 0.6 [W/mK]
120 300 2.1 204 500 3.5 205 700 4.8 206 140 300 2.1 207 500 3.4 208
700 4.8 209 NO. 1 NO. 3 60 300 10 210 THERMAL THERMAL 500 17 211
CONDUCTIVITY: CONDUCTIVITY: 700 -- -- 1.4 [W/mK] 0.1 [W/mK] 120 300
17 212 500 29 213 700 -- -- 140 300 18 214 500 30 215 700 -- --
[0068] As shown in Tables 2 and 3 and FIGS. 5 and 6, in the case of
heat input power from plasma to the substrate mounting surface 10a
of the ceramic base 10 is uniform in a plane, the jointing layer
arranged between the ceramic base 10 and the base plate 30 is
divided into a central part and an peripheral part, and the first
jointing material 20B having a low thermal conductivity is arranged
in the central part while the second jointing material 20A having a
higher thermal conductivity than the first jointing material 20B is
arranged in the peripheral part. This structure can provide
temperature distribution having a lower temperature in the
peripheral part than that in the central part of the substrate
mounting surface 10a. Note that in the case of jointing layers made
of a single jointing material not shown in the graph, temperature
distribution in the substrate mounting surface of the ceramic base
is nearly even.
[0069] As a result, it is confirmed that in the case of substrate
temperatures being not uniform due to the structure of the
substrate mounting apparatus 2 when it is actually used in a plasma
processing apparatus, changing the thermal conductivity of the
jointing materials in the jointing layer by location allows
provision of uniform temperature distribution of a substrate.
Moreover, it is also confirmed that control of the temperature
distribution of the substrate is possible by dividing the jointing
layer into multiple regions in a plane and arranging jointing
materials having different predetermined thermal conductivities in
the respective regions. Furthermore, it is confirmed that easy and
effective control of temperature distribution in the substrate
mounting surface of the ceramic base is possible by controlling
sizes and shapes of divided regions of the jointing layer and
thermal conductivities of jointing materials.
[0070] For example, in the case of the thermal conductivity of the
jointing material in the central part of the jointing layer being
at least double that of the jointing material in the peripheral
part, a temperature difference between the central part and the
peripheral part of the substrate mounting surface of the ceramic
base is controlled to be about 0.degree. C. to about 5.degree. C.
Furthermore, changing setting of a thermal conductivity and
in-plane distribution of jointing materials allows flexible
temperature control. In the case of the thermal conductivity of the
jointing material in the central part of the jointing layer being
at least ten times that of the jointing material in the peripheral
part, temperature difference between the central part and the
peripheral part of the substrate mounting surface of the ceramic
base is controlled to be about 0.degree. C. to about 30.degree.
C.
Working Examples 1 and 2
[0071] As working examples 1 and 2, a substrate mounting apparatus
shown in FIG. 7 is formed. The substrate mounting apparatus
includes the ceramic base 10 in which the electrostatic chuck
electrode 40 is buried, the base plate 30a having the coolant flow
channel 60, and the jointing layer 20 arranged between the ceramic
base 10 and the base plate 30a. Cooling water flows as a coolant in
the coolant flow channel 60. The jointing layer 20 is divided into
a central part and a peripheral part in a plane, and jointing
materials differing in a thermal conductivity are arranged in the
central part and the peripheral part, respectively.
[0072] Specifically, the ceramic base 10 is formed under the
following conditions. First, an acrylic resin binder is added to
AIN powder obtained through reductive nitriding, and they are
granulated through spray granulation to form granules. These
granules are formed using a metal mold by applying pressure in a
uniaxial direction. When forming a compact, Mo bulk electrode,
which is planar mesh electrode, are buried in the compact. The
compact is sintered by hot pressing method, thereby providing an
integrated sintered body. Note that the pressure applied when hot
pressing is 200 Kg/cm.sup.2, a sintering temperature is risen at a
rate of 10.degree. C./hour up to the maximum sintering temperature
of 1900.degree. C., and the maximum sintering temperature is then
maintained for one hour. As a result, a disc-shaped ceramic base 10
made of AIN having a thickness of 5 mm is formed. The volume
resistivity of the ceramic base 10 is 1.times.10 .OMEGA.cm at room
temperature. Note that the substrate mounting surface of the
ceramic base 10 is formed to be flat without forming
protrusions.
[0073] On the other hand, an alumina plate is processed to have a
diameter of approximately 240 mm and a thickness of 30 mm, and the
coolant flow channel 60 is then formed therein by process. In this
manner, the base plate 30a is formed.
[0074] In the substrate mounting apparatus according to working
example 1, a circular acrylic sheet having a thermal conductivity
of 1.4 W/mK and a diameter of 60 mm and a ring-shaped acrylic sheet
having a thermal conductivity of 0.6 W/mK, an inner diameter of 60
mm, and an outer diameter of 200 mm are arranged between the
ceramic base 10 made of aluminum nitride and base plate 30a, and a
pressure of 200 psi (1.38.times.10.sup.6 Pa) is then applied from
above and below at 100.degree. C. in vacuum, thereby joining the
ceramic base 10 and the base plate 30a.
[0075] In the substrate mounting apparatus according to working
example 2, a circular acrylic sheet having a thermal conductivity
of 1.4 W/mK and a diameter of 140 mm and a ring-shaped sheet having
a thermal conductivity of 0.6 W/mK, an inner diameter of 140 mm,
and an outer diameter of 200 mm are arranged between the ceramic
base 10 made of aluminum nitride and the base plate 30a, and a
pressure of 200 psi (1.38.times.10.sup.6 Pa) is then applied from
above and below at 100.degree. C. in vacuum, thereby joining the
ceramic base 10 and the base plate 30a.
[0076] As shown in FIG. 7, the substrate mounting apparatus
according to working examples 1 and 2 is arranged in a vacuum
chamber 100 having a lamp heater 120. Moreover, a Si substrate 80
having terminals of a thermocouple 90 soldered with Al, is mounted
on the substrate mounting surface of the ceramic base 10.
[0077] The temperature of cooling water flowing through the coolant
flow channel 60 in the base plate 30a is 20.degree. C. Heat input
from plasma to the Si substrate 80, which is generated when using
the substrate mounting apparatus in a plasma processing apparatus,
is simulated. Specifically, the Si substrate 80 is heated using the
lamp heater 120 after setting a pressure of 1 Pa or less in the
vacuum chamber 100. When the lamp heater 120 outputs power of 300W
and 700W, temperatures of the center and the end of the Si
substrate 80 are measured, respectively. Measurement results are
shown in Table 4 and FIG. 8. Table 4 and FIG. 8 show temperature
differences .DELTA.Ts between the center and the end of the Si
substrate 80 as the temperature distribution in the Si substrate
80. In FIG. 8, a vertical axis represents a temperature difference
.DELTA.Ts, and a horizontal axis represents a distance from the
center of the Si substrate 80. TABLE-US-00004 TABLE 4 JOINTING
LAYER JOINTING LAYER (CENTRAL PART) OUTPUT MEASUREMENT SIMULATION
(PERIPHERAL PART) MATERIAL/ POWER OF RESULT RESULT MATERIAL/
THERMAL LAMP TEMPERATURE CORRESPON- TEMPERATURE CORRESPON- WORKING
THERMAL CONDUCTIVITY/ HEATER DIFFERENCE DENCE LINE DIFFERENCE DENCE
LINE EXAMPLE CONDUCTIVITY DIAMETER [W] .DELTA.Ts (.degree. C.) IN
FIG. 8 .DELTA.Ts (.degree. C.) IN FIG. 8 WORKING ACRYLIC RESIN/
ACRYLIC 60 300 1.8 301 1.5 302 EXAMPLE 1.4 W/mK RESIN/ 700 3.8 303
3.4 304 1 0.6 W/mK WORKING 140 300 2.2 305 1.9 306 EXAMPLE 700 4.9
307 4.5 308 2
[0078] Since heat input from the lamp heater 120 to the Si
substrate 80 is controlled to be almost uniform, the jointing layer
made of a single jointing material can provide an even temperature
distribution of the substrate. Meanwhile, it is confirmed that in
the case of dividing the jointing layer 20 in a plane between the
ceramic base 10 and the base plate 30a into a central part and a
peripheral part, and arranging a jointing material having a lower
thermal conductivity in the central part while arranging a jointing
material having a higher thermal conductivity in the peripheral
part, a temperature distribution having a lower temperature in the
peripheral part than in the central part of the substrate mounting
surface of the ceramic base 10 can be provided.
[0079] Furthermore, it is also confirmed that the simulation
results and actual measurement results are consistent and that the
control method of substrate temperature, which is controlling
in-plane thermal conductivity distribution in the jointing layer,
is extremely effective in actual as the simulation.
[0080] Although the inventions have been described above by
reference to certain embodiments of the inventions, the inventions
are not limited to the embodiments described above. Modifications
and variations of the embodiments described above will occur to
those skilled in the art, in light of the above teachings.
* * * * *