U.S. patent application number 09/836434 was filed with the patent office on 2002-02-28 for heating apparatus.
Invention is credited to Endou, Kazunori, Hashimoto, Masayuki, Ishizuka, Masayuki, Kitagawa, Takao, Nagata, Tsuyoshi.
Application Number | 20020023914 09/836434 |
Document ID | / |
Family ID | 26590896 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020023914 |
Kind Code |
A1 |
Kitagawa, Takao ; et
al. |
February 28, 2002 |
Heating apparatus
Abstract
The present invention provides a heating apparatus that displays
a high heating efficiency and a long product life. In addition,
present invention provides a heating apparatus that has no
limitations with respect to the materials comprising its heat
insulating material, which displays an even greater product life
and, moreover, can be manufactured easily at low cost. This heating
apparatus is characterized in comprising: a loading plate on which
an object to be heated is placed; a support plate that is
integrated into a single body with the loading plate; a heating
element that is sandwiched in between the loading plate and the
support plate; and at least one pair of electrodes, one terminal of
which is connected to the aforementioned heating element; wherein,
the aforementioned loading plate and support plate each
respectively comprises a ceramics sintered body, such that the
coefficient of thermal conductivity of the ceramics sintered body
comprising the loading plate is greater than the coefficient of
thermal conductivity of the ceramics sintered body comprising the
support plate. In addition, a heat insulating material may be
installed at the base of at least the aforementioned heating
element.
Inventors: |
Kitagawa, Takao;
(Funabashi-shi, JP) ; Ishizuka, Masayuki;
(Funabashi-shi, JP) ; Endou, Kazunori;
(Funabashi-shi, JP) ; Hashimoto, Masayuki;
(Ichikawa-shi, JP) ; Nagata, Tsuyoshi;
(Tchikawa-shi, JP) |
Correspondence
Address: |
Kenneth D' Alessandro
Sierra Patent Group
P.O. Box 6149
Stateline
NV
89449
US
|
Family ID: |
26590896 |
Appl. No.: |
09/836434 |
Filed: |
April 16, 2001 |
Current U.S.
Class: |
219/444.1 ;
219/468.1 |
Current CPC
Class: |
H05B 3/74 20130101; H01L
21/67103 20130101; H05B 3/143 20130101 |
Class at
Publication: |
219/444.1 ;
219/468.1 |
International
Class: |
H05B 003/68 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2000 |
JP |
2000-126587 |
May 25, 2000 |
JP |
2000-154589 |
Claims
What is claimed is:
1. A heating apparatus characterized in comprising: a loading plate
on which an object to be heated is placed; a support plate that is
integrated into a single body with said loading plate; a heating
element that is sandwiched in between said loading plate and said
support plate; and at least one pair of electrodes, one terminal of
which is connected to said heating element; wherein, said loading
plate and said support plate each respectively comprises a ceramics
sintered body, such that the coefficient of thermal conductivity of
said ceramics sintered body comprising said loading plate is
greater than the coefficient of thermal conductivity of said
ceramics sintered body comprising said support plate.
2. A heating apparatus characterized in comprising: a loading plate
on which an object to be heated is placed; a support plate that is
integrated into a single body with said loading plate; a heating
element that is sandwiched in between said loading plate and said
support plate; and at least one pair of electrodes, one terminal of
which is connected to said heating element; wherein, said loading
plate and said support plate each respectively comprises a ceramics
sintered body; said heating element is loaded onto a concave member
provided at the bonding surface of either or both of said loading
plate and said support plate; and said heating apparatus is further
equipped with a heat insulating material arranged at least at the
base of said heating element.
3. A heating apparatus characterized in comprising: a loading plate
on which an object to be heated is placed; a support plate that is
integrated into a single body with said loading plate; a heating
element that is sandwiched in between said loading plate and said
support plate; and at least one pair of electrodes, one terminal of
which is connected to said heating element; wherein, said loading
plate and said support plate each respectively comprises a ceramics
sintered body, such that the coefficient of thermal conductivity of
said ceramics sintered body comprising said loading plate is
greater than the coefficient of thermal conductivity of said
ceramics sintered body comprising said support plate; said heating
element is loaded within a concave member provided at the bonding
surface of either or both of said loading plate and said support
plate; and said heating apparatus is further equipped with a heat
insulating material arranged at least at the base of said heating
element.
4. A heating apparatus according to one of claims 2 and 3, wherein
said heat insulating material is selected from among a metal or
ceramics such as aluminum nitride, silicon nitride, a siliceous
material, alumina and the like.
5. A heating apparatus according to one of claims 1.about.3,
wherein said ceramics sintered body comprises an aluminum nitride
sintered body using Y.sub.2O.sub.3 as an auxiliary agent or an
aluminum nitride group sintered body using Y.sub.2O.sub.3 as an
auxiliary agent.
6. A heating apparatus according to claim 5, wherein the
Y.sub.2O.sub.3 blending amount of said ceramics sintered body of
said loading plate is greater than the Y.sub.2O.sub.3 blending
amount of said ceramics sintered body of said support plate.
7. A heating apparatus according to one of claims 1 .about.3,
wherein said loading plate and said support plate are bonded
together into a single body by means of a vitreous bonding
layer.
8. A heating apparatus according to one of claims 1.about.3,
wherein said loading plate comprises a head plate and base plate,
and is further equipped with an electrode plate sandwiched between
said head plate and said base plate, and an electrode connected to
said electrode plate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a heating apparatus that is
housed within a reaction chamber, which is used for heating an
object to be heated, such as a wafer or the like, and is able to
achieve marked improvements with respect to both its heating
efficiency and product life.
[0003] 2. Relevant Art
[0004] Conventionally, as an example of a heating apparatus that is
housed within a reaction chamber and used for heating an object to
be heated such as a wafer or the like, a heating apparatus is
known, which comprises a heating block that is divided into two
parts. Among these two divisions of the aforementioned heating
block, the heating block onto which the object to be heated is
placed (hereinafter referred to as "loading plate") comprises a
material that has a comparatively high coefficient of thermal
conductivity, such as stainless steel, iron or the like. The other
heating block (hereinafter referred to as "support plate")
comprises a material that displays a lower coefficient of thermal
conductivity than the material comprising said loading plate, such
as ceramics, chinaware, building stone, or the like. In addition,
the aforementioned conventional heating apparatus comprises a
structure in which a heating element is sandwiched in between the
aforementioned loading plate and support plate. In this manner,
this heating apparatus is able to heat the aforementioned loading
plate by means of concentrating the heat generated by the heating
element to the loading plate, and consequently displays a high
heating efficiency.
[0005] In addition, as another example of a conventional heating
apparatus, a heating apparatus is known which comprises a structure
in which a single layer or multiple layers of a heat insulating
material are provided in between a surface heating member, formed
by means of burying a heating element within a ceramics sintered
body possessing a superior thermal conductivity, corrosion
resistance, and plasma resistance; and a support member, which
supports this heating member and connects to a reaction chamber,
wherein this heat insulating material limits the heat conducted
from the aforementioned surface heating member to said support
member.
[0006] FIG. 5 is a schematic outline showing the cross-sectional
structure of an example of a conventional heating apparatus. The
structure of this heating apparatus 1000 will be described in the
following. This heating apparatus 1000 comprises a surface heating
member 103, a heating element 108, an electrode plate 104, a heat
insulating material 113, and a support member 102.
[0007] As shown in FIG. 5, heating apparatus 1000 internally
comprises a structure in which a single layer of a heat insulating
material 113 is sandwiched in between a surface heating member 103,
comprising a heating element 108 having a predetermined shape
(e.g., spiral-shaped) and a disk-shaped electrode plate 104 for
generating plasma, and a support member 102. In this heating
apparatus 1000, both the heat insulating material 113 and surface
heating member 103, as well as the heat insulating material 113 and
support member 102 are joined in an airtight manner.
[0008] The surface heating member 103 is equipped with a first
ceramics sintered body 103a for holding heating element 108, a
second ceramics sintered body 103b for holding electrode plate 104,
and a third ceramics sintered body 103c onto which the object to be
heated is placed. The first ceramics sintered body 103a and second
ceramics sintered body 103b, as well as, the second ceramics
sintered body 103b and third ceramics sintered body 103c are
respectively joined in an airtight manner by means of bonding
layers 110 and 107, each respectively comprising a heat-resistant
bonding agent.
[0009] In addition, as seen in FIG. 5, heating element 108 is
loaded within concave member 112, which is provided along the shape
of heating element 108, on the upper surface of the first ceramics
sintered body 103a in the figure; and electrode plate 104 is loaded
within concave member 111, which is provided on the upper surface
of the second ceramics sintered body 103b in the figure.
[0010] One pair of heater feeding electrodes 109 is connected to
the aforementioned heating element 108, and a high-frequency/direct
current voltage application electrode 105 is connected to electrode
plate 104. In addition, a thermocouple 106, one terminal of which
is inserted into surface heating member 103, is provided in heating
apparatus 1000 for measuring the temperature within surface heating
member 103.
[0011] However, in this type of heating apparatus wherein the
loading plate comprises a material that has a comparatively high
coefficient of thermal conductivity, such as stainless steel, iron
or the like, while the support plate comprises a material that
displays a lower coefficient of thermal conductivity than that of
the material comprising said loading plate, such as ceramics,
chinaware, building stone, or the like, due to the inferior plasma
resistance of the stainless steel, iron, etc. comprising the
loading plate, there exist problems with respect to the short
product life of the heating apparatus.
[0012] In addition, in the aforementioned heating apparatus, it is
difficult to match the coefficient of thermal expansion of the
support plate, which is able to decrease the amount of heat
dissipated, and the coefficient of thermal expansion of the loading
plate, and thus a difference in these coefficients of thermal
expansion inevitably appears. As a result, the durability of the
bonding interface between the support plate and the loading plate
is insufficient, thereby contributing to the problem of the short
product life of this heating apparatus.
[0013] In addition, in the construction of the heating apparatus
1000 shown in FIG. 5, problematic restrictions on the structural
material of the heat insulating material 113 exist due to the
exposure of the side surface of the heat insulating material 113 to
the anti-corrosive atmospheric gas, plasma, and the like. As a
result, in addition to the restrictions on the structural material
of the heat insulating material 113, since it is difficult to
approximate the difference in the coefficients of thermal expansion
of surface heating member 103 and insulating material 113, or
difference in the coefficients of thermal expansion of insulating
material 113 and support plate 102, the structure of the
aforementioned heating apparatus is extremely complex, leading to a
problematic increase in cost.
[0014] In order to solve the aforementioned problems, the present
invention provides a heating apparatus that displays both a high
heating efficiency and a long product life.
[0015] Specifically, it is an object of the present invention to
provide a heating apparatus comprising a superior plasma
resistance, wherein an improvement of the durability of the
interface generated by the difference in the coefficients of
thermal expansion of the loading plate and support plate is
realized while maintaining a high heating efficiency.
[0016] In addition, the present invention provides a heating
apparatus with a superior heating efficiency, which is free of any
restrictions on the structural material of the heat insulating
material and is, moreover, easily manufactured at low cost, wherein
the product life is further increased.
SUMMARY OF THE INVENTION
[0017] In order to achieve the aforementioned objects, the present
invention utilizes the following construction.
[0018] The present invention provides a heating apparatus
characterized in comprising: a loading plate onto which an object
to be heated is placed; a support plate that is integrated into a
single body with said loading plate; a heating element which is
sandwiched in between said loading plate and said support plate;
and at least one pair of electrodes, one terminal of which is
connected to said heating element; wherein, said loading plate and
said support plate each respectively comprises a ceramics sintered
body, such that the coefficient of thermal conductivity of said
ceramics sintered body comprising said loading plate is greater
than the coefficient of thermal conductivity of said ceramics
sintered body comprising said support plate.
[0019] According to the present invention, since the loading plate
and support plate each respectively comprise a ceramics sintered
body, it is possible to approximate the values of the coefficients
of thermal expansion of the loading plate and support plate, which
in turn results in an improvement of the interface strength between
the aforementioned, thereby allowing for an increase the
durability, plasma resistance, and product life thereof.
[0020] In addition, the coefficient of thermal conductivity of the
loading plate is greater than the coefficient of thermal
conductivity of the support plate, and thus the heat generated from
the heating element can be concentrated in the loading plate and
transferred therefrom. Furthermore, it is possible to effectively
prevent heat dissipation to the support plate, onto to which the
object to be heated does not rest, while maintaining the
coefficient of thermal conductivity of the side onto which the
aforementioned object does rest, and thus dramatically improve the
heating efficiency of this heating apparatus.
[0021] Subsequently, the present invention provides a heating
apparatus characterized in comprising: a loading plate onto which
an object to be heated is placed; a support plate that is
integrated into a single body with said loading plate; a heating
element which is sandwiched in between said loading plate and said
support plate; and at least one pair of electrodes, one terminal of
which is connected to said heating element; wherein, said loading
plate and said support plate each respectively comprises a ceramics
sintered body; said heating element is loaded within a concave
member provided at the bonding surface of either or both of said
loading plate and said support plate; and said heating apparatus is
further equipped with a heat insulating material arranged at least
at the base of said heating element.
[0022] According to the present invention, since the heat
insulating material is loaded within a concave member provided at
the bonding surface of either or both of the base member and plate
to be covered, this heat insulating material is not exposed to
anti-corrosive atmospheric gas, plasma, and the like, and thus the
structural material comprising this heat insulating material is
free of restriction, allowing for an easily manufactured, low cost
heating apparatus with a further improved product life.
[0023] In addition, the heating apparatus of the present invention
is equipped with a heat insulating material arranged at least at
the base of said heating element (i.e., the side onto which the
object to be heated is not placed), and thus it is possible to
prevent dissipation of heat from the side onto which the object to
be heated does not rest, while also maintaining the thermal
conductivity of the side onto which the object to be heated does
rest, which in turn results in a superior heating efficiency.
[0024] In addition, in the heating apparatus of the present
invention, the heat insulating material is preferably selected from
among a metal or ceramics such as aluminum nitride, silicon
nitride, a siliceous material, alumina and the like. In the case
when the heat insulating material is formed from the
aforementioned, it is possible to efficiently insulate the heat
generated by means of the heating element.
[0025] In addition, in the heating apparatus of the present
invention, the ceramics sintered body preferably comprises an
aluminum nitride sintered body using Y.sub.2O.sub.3 as an auxiliary
agent or an aluminum nitride group sintered body using
Y.sub.2O.sub.3 as an auxiliary agent. By means of employing such a
structure, it is possible to reduce the addition amount of the
Y.sub.2O.sub.3, which in turn allows for easy control of the
thermal conductivity of the aluminum nitride group sintered
body.
[0026] In addition, in the heating apparatus of the present
invention, the Y.sub.2O.sub.3 blending amount of said ceramics
sintered body of said loading plate is preferably greater than the
Y.sub.2O.sub.3 blending amount of said ceramics sintered body of
said support plate.
[0027] By constructing the aforementioned loading plate and support
plate in this manner, it is possible to reduce the thermal
conductivity of the support plate to below that of the loading
plate, and also reduce the heat dissipation from the support plate
side, onto which the object to be heated does not rest. As a
result, it is possible to increase the heating efficiency.
[0028] In addition, in the heating apparatus of the present
invention, said loading plate and said support plate are preferably
bonded together into a single body by means of a vitreous bonding
layer. According to this type of structure, it is possible to
improve the strength of the bonding surface between the loading
plate and support plate, in addition to increasing the degree of
air-tightness at the bonding surface of the aforementioned. As a
result, by improving the strength of the bonding surface, it is
possible to increase the product life of the heating apparatus.
[0029] In addition, in the heating apparatus of the present
invention, said loading plate comprises a head plate and base
plate, which in turn allows for the installation of an electrode
plate, sandwiched between said head plate and said base plate, and
an electrode, which is connected to said electrode plate. According
to this structure, it is possible to apply the aforementioned
heating apparatus to various uses by means of varying the usage of
the electrode plate.
BRIEF DESCRIPTION OF THE FIGURES
[0030] FIG. 1 is a schematic outline showing a cross-sectional view
of the structure of the heating apparatus according to a First
Embodiment of the present invention.
[0031] FIG. 2A is a schematic plane view showing the structure of
an electrode plate in the heating apparatus according to a First
Embodiment of the present invention.
[0032] FIG. 2B is a schematic plane view showing the structure of a
heating element in the heating apparatus according to a First
Embodiment of the present invention.
[0033] FIG. 3 is a schematic outline showing a cross-sectional view
of the structure of the heating apparatus according to a Second
Embodiment of the present invention.
[0034] FIG. 4 is a schematic outline showing a cross-sectional view
of the structure of the heating apparatus according to a Third
Embodiment of the present invention.
[0035] FIG. 5 is a schematic outline showing a cross-sectional view
of the structure of a conventional heating apparatus.
PREFERRED EMBODIMENTS
[0036] In the following, the embodiments of the present invention
will be described in detail with reference to the figures. However,
these embodiments are for the purpose of more concretely explaining
the present invention. Hence, the following embodiments are not
particularly limited, and in no manner limit the contents of the
present invention.
[0037] First Embodiment
[0038] In the following, the structure of a heating apparatus 100
according to the First Embodiment will be explained based on FIGS.
1, 2A and 2B. FIG. 1 is a schematic cross-sectional diagram of the
heating apparatus 100, while FIGS. 2A and 2B are schematic plane
views respectively showing the structures of an electrode plate 4
and heating element 8 (concave member 12) of the aforementioned
heating apparatus 100. Furthermore, FIG. 2A shows a plane view of a
loading base plate 3a (to be explained hereinafter) as seen from
the side of the electrode plate 4. FIG. 2B shows a plane view of a
support plate 2 (to be explained hereinafter) as seen from the side
of the heating element 8. In addition, FIG. 1 shows a
cross-sectional view taken along the line A-A' shown in FIG.
2B.
[0039] As shown in FIG. 1, heating apparatus 100 comprises a
support plate 2 manufactured from a ceramics sintered body in which
a concave member 12 having a predetermined shape is provided on the
surface thereof; a heating element 8 comprising a predetermined
shape which is loaded into the aforementioned concave member 12; a
loading plate 3 manufactured from a ceramics sintered body onto
which an object to be heated, e.g., wafer or the like, is placed,
which covers the entire region of the support plate 2 and heating
element 8; at least one pair of heater feeding electrodes 9, one
terminal of which is connected to heating element 8; and a
thermocouple 6 for measuring the temperature of loading plate 3
onto which the object to be heated is placed. The aforementioned
support plate 2 and loading plate 3 are bonded together into a
single body by means of a first bonding layer 10, which is formed
from a heat-resistant bonding agent.
[0040] Furthermore, in FIGS. 1, 2A and 2B, the following are shown
as an example: support plate 2 and loading plate 3 each
respectively comprise a disk shape; concave member 12 and heating
element 8 are arranged in a spiral manner from the center portion
of support plate 2 towards the periphery; and the pair of heater
feeding electrodes 9 is connected to both terminal portions of
heating element 8.
[0041] In addition, as shown in FIG. 1, loading plate 3 comprises a
loading base plate 3a manufactured from a ceramics sintered body in
which a concave member 12 is provided on the upper surface thereof;
an electrode plate 4 manufactured from a metal or a composite
conductive material of metal and ceramic, which is loaded within
concave member 12; a loading head plate 3b manufactured from a
ceramics sintered body which covers the entire region of loading
base plate 3a and electrode plate 4; high-frequency/direct current
voltage application electrode 5, one terminal of which is connected
to electrode plate 4; and thermocouple 6, one terminal of which is
inserted within loading plate 3 for measuring the temperature of
loading plate 3. As shown in FIG. 2A, electrode plate 4 may be
formed, for example, in a disk shape.
[0042] In addition, the aforementioned support plate 2 and loading
base plate 3a are bonded together in an airtight manner by means of
a first bonding layer 10, which is formed from a heat-resistant
bonding agent.
[0043] With regard to loading plate 3, loading base plate 3a and
loading head plate 3b are bonded together by means of a second
bonding layer 7, which is formed from a material having the same
composition or having the same main component as the material
comprising either loading base plate 3a or loading head plate
3b.
[0044] In addition, high-frequency/direct current voltage
application electrode 5 and heater feeding electrodes 9 are formed
from a metal having a superior heat resistance such as nickel,
tungsten, tantalum, or the like.
[0045] Furthermore, as shown in FIG. 1, high-frequency/direct
current voltage application electrode 5, heater feeding electrodes
9, and thermocouple 6 all penetrate into support plate 2, extending
down to the base of this support plate 2.
[0046] In the following, the structural elements comprising the
heating apparatus 100 of the present embodiment will be
respectively explained.
[0047] [Loading Plate]
[0048] Examples of the material comprising loading base plate 3a
and loading head plate 3b may include ceramics sintered bodies such
as an aluminum nitride sintered body, aluminum nitride group
sintered body, magnesium oxide sintered body, boron nitride
sintered body, and the like. Among the aforementioned, an aluminum
nitride sintered body or aluminum nitride group sintered body are
particularly preferred due to their superior conductivity and
mechanical strength, in addition to a superior durability with
respect to plasma cleaning gases, such as CF.sub.4, C.sub.2F.sub.6,
C.sub.2F.sub.8 and the like. The aforementioned aluminum nitride
sintered body and aluminum nitride group sintered body may be
manufactured according to known conventional methods.
[0049] In order to increase the degree of sintering and improve the
plasma resistance, the aforementioned aluminum nitride group
sintered body may be prepared, for example, by means of adding a
total of approximately 0.1.about.20% by weight of at least one
additive selected from among Y.sub.2O.sub.3, CaO, MgO, SiC and
TiO.sub.2.
[0050] However, in the present embodiment, in order to control the
thermal conductivity of loading base plate 3a and loading head
plate 3b, the aluminum nitride group sintered body in which
Y.sub.2O.sub.3 is used as an auxiliary agent is particularly
preferred as the material for the aforementioned loading base plate
3a and loading head plate 3b.
[0051] [Support Plate]
[0052] Examples of the material comprising support plate 2 may
include ceramics sintered bodies such as an aluminum nitride
sintered body, aluminum nitride group sintered body, magnesium
oxide sintered body, boron nitride sintered body, and the like.
Among the aforementioned, an aluminum nitride sintered body or
aluminum nitride group sintered body are preferred due to their
superior conductivity and mechanical strength, in addition to a
superior durability with respect to plasma cleaning gases, such as
CF.sub.4, C.sub.2F.sub.6, C.sub.2F.sub.8 and the like. Furthermore,
an aluminum nitride sintered body or aluminum nitride group
sintered body having a smaller coefficient of thermal conductivity
than that of the aluminum nitride sintered body or aluminum nitride
group sintered body comprising the aforementioned loading base
plate 3a and loading head plate 3b is particularly preferred.
[0053] Similarly, the ceramics sintered body comprising support
plate 2 preferably has a smaller coefficient of thermal
conductivity than that of the ceramics sintered body comprising
loading plate 3. In this manner, the coefficient of thermal
conductivity of loading plate 3 is higher than the coefficient of
thermal conductivity of support plate 2, which in turn allows heat
generated by heating element 8 to be concentrated on loading plate
3. Accordingly, it is possible to efficiently increase the
temperature of the loading plate 3, and as a result increase the
heating efficiency of the heating apparatus 1. In this manner, it
is possible to easily reduce in the amount of heat dissipated from
the base of heating element 8 to support plate 2.
[0054] In addition, the aforementioned support plate 2, loading
base plate 3a and loading head plate 3b are preferably formed from
an aluminum nitride group sintered body in which Y.sub.2O.sub.3 is
used as an auxiliary agent, wherein the blending amount of
Y.sub.2O.sub.3 in the sintered body comprising loading base plate
3a and loading head plate 3b is preferably set to greater than the
blending amount of Y.sub.2O.sub.3 in the sintered body comprising
the support plate 2 for the following reason.
[0055] By means of increasing and decreasing the addition amount of
Y.sub.2O.sub.3 within the range of 0.about.20% by weight, and
preferably 0.about.15% by weight, it is possible to easily control
the thermal conductivity of the aluminum nitride group sintered
body. Here, by setting the blending amount of Y.sub.2O.sub.3 in the
sintered body comprising loading base plate 3a and loading head
plate 3b to greater than the blending amount of Y.sub.2O.sub.3 in
the sintered body comprising the support plate 2, it is possible to
reduce the thermal conductivity of the support plate 2 to less than
those of loading base plate 3a and loading head plate 3b. In this
manner, it is possible to decrease the amount of heat dissipated
from the bottom of the heating element, i.e., from the side of
support plate 2, on which the object to be heated does not rest. As
a result, it is possible to increase the heating efficiency of the
heating apparatus 100.
[0056] Furthermore, the coefficient of thermal expansion of the
aluminum nitride group sintered body remains for the most part
constant, even when increasing or decreasing the amount of
Y.sub.2O.sub.3, and thus it is possible to maintain the durability
of the bonding interface (first bonding layer) between the support
plate 2 and loading base plate 3a even when faced with the added
load of a heat cycle temperature rise or fall. Accordingly, it is
possible to increase the product life of the heating apparatus
100.
[0057] [Heating Element]
[0058] As the material for the aforementioned heating element 8, a
silicon carbonate sintered body, which is sintered without the
addition of any additives and comprises a sintered density of at
least 2.8.times.10.sup.3 kg/m.sup.3, and an electrical resistance
at room temperature of less or equal to 0.1.times.10.sup.-2
.OMEGA.m is preferred.
[0059] In addition, heating element 8 is not joined to either
support plate 2 (concave member 12) or the first bonding layer 10
(loading base plate 3a), such that an interval space exists between
heating element 8 and concave member 12, and between heating
element 8 and first bonding layer 10 (loading base plate 3a),
respectively (not shown in the figure).
[0060] In addition, since the material of heating element 8
comprises a silicon carbonate sintered body (coefficient of thermal
expansion=3.7.times.10.sup.-6/.degree. C.), it is possible to
approximate the coefficient of thermal expansion
(3.8.times.10.sup.-6.about.4.7.times- .10.sup.-6/.degree. C.) of
the aluminum nitride sintered body or aluminum nitride group
sintered body comprising support plate 2.
[0061] By means of providing this type of heating element, it is
possible to drastically improve the durability of the first bonding
layer 10 joining the loading base plate 3a and support plate 2,
since there is no generation of thermal stress, which causes
differences in the coefficients of thermal expansion between the
heating element 8 and support plate 2, and between the heating
element 8, first bonding layer 10 and loading base plate 3a.
[0062] Subsequently, by means of energizing this heating element 8,
it is possible to maintain the loading plate at a predetermined
temperature.
[0063] This type of heating element comprising a silicon carbonate
sintered body may be manufactured, for example, according to the
following method disclosed in Japanese Patent Application, First
Publication No. Hei 4-65361.
[0064] Manufacturing method (1): An elemental gas comprising a
first silicon carbonate powder having an average particle diameter
of 0.1.about.10.times.10.sup.-6 m (0.1.about.10 .mu.m) and a silane
compound within plasma in a non-oxidizing atmosphere, or a
halogenated silicon and hydrogen carbonate, and is introduced and
mixed with a second silicon carbonate powder having an average
particle diameter of no greater than 0.1.times.10.sup.-6 m (0.1
.mu.m), which has been prepared by means of a gas phase reaction in
which the reaction pressure is controlled within a range of 101 kPa
or less to 13 Pa (0.1 Torr). The mixture is then heated and
sintered to yield a silicon carbonate sintered body. This sintered
body subsequently is processed according to a predetermined pattern
via an electric discharge machine to produce a heating element
8.
[0065] In addition, the heating element 8 may also be manufactured,
for example, according to the following method disclosed in
Japanese Patent Application, First Publication No. Hei 4-65361.
[0066] Manufacturing method (2): A silicon carbonate sintered body
is first obtained by means of mixing, heating and sintering an
elemental gas comprising a silane compound within plasma in a
non-oxidizing atmosphere, or a halogenated silicon and hydrogen
carbonate, and a second silicon carbonate powder having an average
particle diameter of no greater than 0.1.times.10.sup.-6 m (0.1
.mu.m), which has been prepared by means of a gas phase reaction in
which the reaction pressure is controlled within a range of 101 kPa
or less to 13 Pa (0.1 Torr). This sintered body subsequently is
processed according to a predetermined pattern via an electric
discharge machine to produce a heating element 8.
[0067] The heating element 8 obtained by means of either of the
aforementioned processes is hence rendered additive free. In other
words, the heating element is a homogenous material formed from a
silicon carbonate sintered body, which has been sintered without
the addition of any foreign substance, and thus there is no partial
generation of abnormal heat. As a result, it is possible to prevent
the occurrence of leaks in the first bonding layer 10 from melting
of a portion of this first bonding layer 10, and thus also further
strengthen and maintain the degree of air-tightness of the
aforementioned first bonding layer 10.
[0068] In addition, since the aforementioned heating element 8
remains free of any additives and is hence extremely pure, and also
comprises a high density sintered body having a sintered density of
at least 2.8.times.10.sup.3 kg/m.sup.3, even if the air-tightness
of the first bonding layer 10 is compromised by means of a leak,
there is no fear of contamination within the reaction chamber
because evaporation of impurities from the heating element, which
is caused by additives, does not occur.
[0069] Furthermore, since the heating element 8 also comprises a
superior heat resistance, distortion, burnout and the like of the
heating element 8 due to thermal shock does not occur. In addition,
the electrical resistance of heating element 8 at a constant
temperature comprises a low electrical resistance value of no
greater than 0.1.times.10.sup.-2 .OMEGA.m, and thus narrowing or
thinning of the heating element 8 is not necessary, such that fear
of burning out the heating element 8 does not exist.
[0070] [Electrode Plate]
[0071] The electrode plate 4 preferably comprises a material having
a coefficient of thermal expansion close to that of the loading
base plate 3a and loading head plate 3b, for example, a
high-melting point metal such as molydbdenum, tungsten, tantalum,
niobium, or alloys of the same; or a conductive composite of a
high-melting point metal and ceramic. According to this type of
electrode plate, both the heat processing temperature and
atmosphere at the time of bonding loading base plate 3a and loading
head plate 3b remains stable with a low intrinsic resistance, such
that use over a long period of time within a practical temperature
region ranging from room temperature to 1000.degree. C. is
possible.
[0072] This electrode plate 4 may be used as an electrode for use
in an electrostatic chuck, heater electrode, plasma generating
electrode, and the like.
[0073] Hence, plasma can be generated by means of applying a
high-frequency voltage from a plasma generating source (not shown
in the figures) via a high-frequency/direct current voltage
application electrode 5. At this time, the electrode plate 4
preferably comprises a sufficient thickness of at least
0.01.times.10.sup.-3 m (0.01 mm). Accordingly, when providing an
electrode plate 4 of these specifications, there is no fear of
hardening and tearing even when applying high-frequency voltage and
heating thereon. In addition, in contrast to the case when using a
grating or mesh-shaped electrode, it is possible to precisely,
stably and uniformly generate plasma over an entire area, with the
advantage of also executing without fail the connection of
electrode plate 4 and high-frequency/direct current voltage
application electrode 5 between the surface/rod.
[0074] In addition, when applying a direct current high voltage of
approximately 500V to the electrode plate 4 from an electrostatic
chuck power source (not shown in the figures) via the
aforementioned high-frequency/direct current voltage application
electrode 5, loading plate 3 functions as an insulating body, and
allows for the electrostatic absorption of an object to be heated,
e.g., a wafer or the like on loading plate 3.
[0075] Furthermore, in the case when applying both high-frequency
voltage from a plasma generating power source and direct current
high voltage from an electrostatic chuck power source to the
aforementioned electrode plate 4, a filter capable of
high-frequency blockade may be arranged between the aforementioned
electrostatic chuck power source and heater feeding electrodes
9.
[0076] [First Bonding Layer]
[0077] The first bonding layer 10 preferably comprises a
heat-resistant bonding agent, for example, a bonding agent
comprising at least two elements selected from the elements of
Group IIIa of the Periodic Table, aluminum, and silicon; a bonding
agent comprising at least one element selected from the elements of
Group IIIa of the Periodic Table, and aluminum; a bonding agent
comprising at least one element selected from the elements of Group
IIIa of the Periodic Table; and a bonding agent comprising at least
one element selected from the elements of Group IIIa of the
Periodic Table, aluminum, silicon, and at least one element
selected from the elements of Group IIa of the Periodic Table. More
preferably, the aforementioned first bonding layer 10 comprises an
oxynitride glass layer containing a bonding agent comprising at
least two elements selected from the elements of Group IIIa of the
Periodic Table, aluminum, and silicon.
[0078] The first bonding layer 10 comprising an oxynitride glass
layer containing a bonding agent comprising at least two elements
selected from the elements of Group IIIa of the Periodic Table,
aluminum, and silicon displays a dramatically improved degree of
air-tightness, which can be maintained over a long period of time.
The reason for this aspect will be explained in the following.
[0079] The oxynitride glass layer possessing the aforementioned
components has an excellent wettability with a ceramics sintered
body and a superior bonding strength, and hence the first bonding
layer 10 displays an excellent air-tightness with little
dispersion, and a superior heat resistance.
[0080] In addition, the coefficient of thermal expansion of the
oxynitride glass layer possessing the aforementioned components is
3.times.10.sup.-6.about.8.times.10.sup.-6/.degree. C., which
approximates the coefficient of thermal expansion
(3.8.times.10.sup.-6.about.4.7.times- .10.sup.-6/.degree. C.) of
the aluminum nitride sintered body or aluminum nitride group
sintered body. Consequently, it is possible to avoid damage of the
first bonding layer 10, i.e., generation of cracks, from repeated
temperature elevation and reduction at the time of thermal loading,
and thus it is also possible to maintain the air-tightness of the
first bonding layer 10 over a long period of time.
[0081] In addition, the glass softening point (Tg) of the
oxynitride glass layer possessing the aforementioned components is
high at 850.about.950.degree. C., and thus degradation of the first
bonding layer 10 does not occur, even when exposing the heating
apparatus 100 to a high temperature atmosphere for a long period of
time.
[0082] In addition, according to the present embodiment, the
thickness of the first bonding layer 10 is preferably
5.about.180.times.10.sup.-6 m (5.about.180 .mu.m). The reason that
a first bonding layer 10 having a thickness of
5.about.180.times.10.sup.-6 m (5.about.180 .mu.m) is preferred will
be explained in the following, however, this aspect also allows for
further stable maintenance of the air-tightness of the first
bonding layer 10.
[0083] A thickness of the first bonding layer 10 of less than
5.times.10.sup.-6 m (5 .mu.m) results in an inability to maintain
the air-tightness of the first bonding layer 10 and an insufficient
bonding strength due to inadequate formation of the fillet at a
terminal portion of the first bonding layer 10. On the other hand,
a thickness of the first bonding layer 10 exceeding
180.times.10.sup.-6 m (180 .mu.m) results in the ability to
maintain the air-tightness of the first bonding layer 10, but also
leads to easy degradation of the bonding strength. In addition, at
the time of forming the first bonding layer 10, the bonding agent,
which is melted during the heating process, flows out and makes it
impossible to join the support plate 2 and loading base plate 3a in
parallel. Consequently, this leads to fear of a decrease in the
yield of the product, and possible hindrance to the bonding
operation.
[0084] [Second Bonding Layer]
[0085] As described in the aforementioned, loading base plate 3a
and loading head plate 3b, which comprise loading plate 3, are
bonded together by means of a second bonding layer 7, which is
formed from a heat-resistant bonding agent, e.g., material having
the same composition or the same main component as the material
comprising either loading base plate 3a or loading head plate
3b.
[0086] For example, when either loading base plate 3a or loading
head plate 3b comprise aluminum nitride, the aluminum nitride
powder is inserted in between loading base plate 3a and loading
head plate 3b, at the bonding surface, without the incorporation of
another bonding agent. As a result, it is possible to join loading
base plate 3a and loading head plate 3b, via a second bonding layer
7 comprising aluminum nitride, by means of applying
high-temperature pressure to the aforementioned loading base plate
3a and loading head plate 3b.
[0087] The heat-processing atmosphere at the time of inserting the
aluminum nitride powder in between loading base plate 3a and
loading head plate 3b, at the bonding surface, and applying
high-temperature pressure to the aforementioned loading base plate
3a and loading head plate 3b, preferably comprises an inactive
atmosphere such as a vacuum, Ar gas, He gas, N.sub.2 gas, or the
like. In addition, the approximate amount of pressure applied is
preferably 2.45.about.19.6 Mpa (25.about.200 kg/cm.sup.2), while a
heat-processing temperature of approximately
1400.about.2000.degree. C. is preferred.
[0088] Furthermore, in the present embodiment, the term "material
having the same main component" refers to a material in which the
contents of components other than the material comprising the
aforementioned loading base plate 3a or loading head plate 3b is no
greater than 50 mol %, e.g., when aluminum nitride comprises
loading base plate 3a or loading head plate 3b, the content of
components other than the aluminum nitride is no greater than 50
mol %.
[0089] In addition, according to the present embodiment, the
thickness of the second bonding layer 7 is preferably
5.about.180.times.10.sup.-6 m (5.about.180 .mu.m). The reason that
a second bonding layer 7 having a thickness of
5.about.180.times.10.sup.-6 m (5.about.180 .mu.m) is preferred will
be explained in the following, however, this aspect also allows for
further stable maintenance of the air-tightness of the second
bonding layer 7.
[0090] A thickness of the second bonding layer 7 of less than
5.times.10.sup.-6 m (5 .mu.m) results in an inability to maintain
the air-tightness of the second bonding layer 7 and an insufficient
bonding strength due to inadequate formation of the fillet at a
terminal portion of the second bonding layer 7. On the other hand,
a thickness of the second bonding layer 7 exceeding
180.times.10.sup.-6 m (180 .mu.m) results in the ability to
maintain the air-tightness of the second bonding layer 7, but also
leads to easy degradation of the bonding strength. In addition, at
the time of forming the second bonding layer 7, the bonding agent,
which is melted during the heating process, flows out and makes it
impossible to join the support plate 2 and loading base plate 3a in
parallel. Consequently, this leads to fear of a decrease in the
yield rate of the product, and possible hindrance to the bonding
operation.
[0091] According to the heating apparatus 100 having the
aforementioned structure of the present embodiment, both the
loading plate 3 and support plate 2 are formed from ceramics
sintered bodies, which in turn leads to a superior plasma
resistance and the ability to approximate the coefficients of
thermal expansion. Consequently, it is possible to improve the
durability of the bonding surface at the interface of the
aforementioned, and thereby increase the product life. In addition,
the coefficient of thermal conductivity of loading plate 3 is set
higher than the coefficient of thermal conductivity of support
plate 2. Thus, it is possible to improve the thermal conductivity
from heating element 8 to loading plate 3, and thereby also improve
the heating efficiency of the heating apparatus 100.
[0092] In addition, the control of the coefficients of thermal
conductivity is accomplished by means of modifying the addition
amount of Y.sub.2O.sub.3 of each ceramics sintered body, such that
this control can be easily executed without changing the
coefficients of thermal expansion of the aforementioned loading
plate 3 and support plate 2.
[0093] In addition, the aforementioned loading plate 3 and support
plate 2 are bonded by means of a bonding layer 10, which improves
the air-tightness, and results in a superior strength, plasma
resistance and the like at the bonding surface of the
aforementioned. In this manner, it is possible to increase the
product life of the heating apparatus 1.
[0094] [Second Embodiment]
[0095] In the following, the Second Embodiment of the present
invention will be explained with reference to FIG. 3. The basic
structure of the heating apparatus of the present embodiment is the
same as that of heating apparatus 100 of the aforementioned First
Embodiment. The only differences are that the concave member 12a
provided in support plate 2 is formed in a manner such that it is
deeper than the concave member 12 shown in FIG. 1, and a heat
insulating material is provided at the base of the heating element
installed in this concave member 12a. Consequently, in FIG. 3, the
structural components that are identical to those of the
aforementioned heating apparatus 100 will be denoted by the same
numeral and their explanations will be omitted. In addition, the
plane structures of electrode plate 4 and heating element 8 of
heating apparatus 200 are identical to those shown in FIGS. 2A and
2B, respectively, and hence their drawings will be omitted.
[0096] The aforementioned heating element 8 and heat insulating
material 13 loaded within concave member 12a are installed in the
base (i.e., the side onto which the object to be heated is not
placed) of heating element 8 of the heating apparatus 200 shown in
FIG. 3. The aforementioned concave member 12a is formed deeper than
the thickness of heating element 8, at the bonding surface of the
loading plate 3 and support plate 2, along the outline of this
heating element 8. Within concave member 12, the aforementioned
heat insulating material 13 is arranged directly underneath of the
heating element 8 along the outline of the concave member 12 and
heating element 8.
[0097] [Heat Insulating Material]
[0098] In the present embodiment, the heat insulating material 13
is provided in a manner loaded within concave member 12, and is
thus not exposed to plasma, anti-corrosive gases, or the like. As a
result, the material comprising this heat insulating material 13
needs only to have superior heat insulating properties, and does
not require superior corrosion resistance, plasma resistance or the
like.
[0099] Consequently, this heat insulating material 13 may include
materials that efficiently insulate the heat emitted from heating
element 8, such as any material with a coefficient of thermal
conductivity not exceeding 100 W/mK. Examples of materials having
such heat insulation properties include, for example, aluminum
nitride (coefficient of thermal conductivity: 80 W/mK), silicon
nitride (coefficient of thermal conductivity: 30 W/mK), siliceous
material such as quartz (coefficient of thermal conductivity: 3
W/mK) and the like, ceramics such as alumina (coefficient of
thermal conductivity: 29 W/mK) and the like, metals such as iron
(coefficient of thermal conductivity: 80 W/mK), manganese
(coefficient of thermal conductivity: 8 W/mK), or multi-porous
materials of the same.
[0100] Furthermore, in the present embodiment, only a description
of the case in which a heat insulating material 13 is provided
solely at the base of the heating element 8. However, the present
invention is not limited to the aforementioned, as this heat
insulating material 13 may also be provided within concave member
12 at both the base and side portions of the aforementioned heating
element 8.
[0101] [Method for Manufacturing a Heating Apparatus]
[0102] In the following the method for manufacturing the
aforementioned heating apparatus 200 will be explained. Moreover,
the manufacturing method described in the following may also be
applied without problems to the case when manufacturing the heating
apparatus 100 shown in FIG. 1.
[0103] The support plate 2 and loading base plate 3a which possess
concave members 12a and 11 on their surfaces, respectively, are
formed by means of concave processing of a disk-shaped (or the
like) aluminum nitride sintered body or aluminum nitride group
sintered body formed according to a conventional method.
Subsequently, an electrode plate 4 is formed within concave member
11, which is provided in loading base plate 3a. In addition, the
loading head plate 3b may be formed according to a conventional
method.
[0104] Subsequently, a material having the same composition or same
main component as the material comprising loading base plate 3a or
loading head plate 3b is inserted in between the aforementioned
loading base plate 3a and loading head plate 3b, at their bonding
surface. Loading base plate 3a and loading head plate 3b are then
bonded via a second bonding layer 8, by means of applying
high-temperature pressure to loading base plate 3a and loading head
plate 3b, to form the loading plate 3.
[0105] For example, in the case when the material comprising
loading base plate 3a or loading head plate 3b is aluminum nitride,
the aluminum nitride powder is placed onto the bonding surface of
loading base plate 3a and loading head plate 3b, and loading base
plate 3a and loading head plate 3b are bonded by means of applying
high-temperature pressure thereon without the use of another
bonding agent.
[0106] Subsequently, the heating element 8 and heat insulating
material 13, formed according to the aforementioned method (1) for
manufacturing heating element 8, are loaded within concave member
12a of support plate 2 in a manner such that the heat insulating
material 13 is positioned at the base of heating element 8.
[0107] Subsequently, support plate 2 and loading plate 3 are bonded
together by means of a first bonding layer 10.
[0108] An example of the bonding method for bonding support plate 2
and loading plate 3, in which the aforementioned first bonding
layer 10 is formed from an oxynitride glass layer containing a
bonding agent comprising at least two elements selected from the
elements of Group IIIa of the Periodic Table, aluminum, and silicon
will be described in the following.
[0109] A finely powdered vitreous bonding agent is first mixed with
screen oil to form a paste. This heat-resistant bonding agent is
then coated in paste form onto the bonding surfaces of support
plate 2, in which heating element 8 is loaded within concave member
12, and loading base plate 3a, and then dried at
100.about.200.degree. C. The manufacturing method of the vitreous
bonding agent used at the time of forming the first bonding layer
10 will be described in detail below.
[0110] Subsequently, support plate 2 and loading plate 3 are
stacked with heating element 8 sandwiched therein between by means
of the surfaces onto which the aforementioned heat-resistant
bonding agent has been coated. The aforementioned stacked structure
is then heated for 5.about.40 minutes in an electric furnace at
1300.about.1500.degree. C., and the vitreous bonding agent,
contained in the heat-resistant bonding agent, is melted and then
cooled, resulting in the bonding of support plate 2 and loading
plate 3 via first bonding layer 10.
[0111] In the above-described process, heating of the
aforementioned heat-resistant bonding agent (vitreous bonding
agent) is conducted under atmospheric pressure or a pressure of no
greater than 10.sup.10 kPa.
[0112] Moreover, the atmosphere at the time of heating the
aforementioned heat-resistant bonding agent (vitreous bonding
agent) differs depending on the vitreous bonding agent used. In the
case when a vitreous bonding agent containing oxynitride glass is
used, since the vitreous bonding agent has been previously treated
to form oxynitride, the heating of the aforementioned
heat-resistant bonding agent (vitreous bonding agent) may be
conducted under a non-nitrogen containing atmosphere. However, even
in the case when using a vitreous vitreous bonding agent containing
oxynitride glass, in order to further promote the formation of
oxynitride, or prevent oxidization of the oxynitride glass, the
aforementioned heating of the heat-resistant bonding agent
(vitreous bonding agent) is more preferably conducted under a
nitrogen-containing atmosphere.
[0113] In contrast, in the case when using a vitreous bonding agent
containing oxide glass, a nitrogen source is required in order to
transform the oxide glass into oxynitride glass, and thus the
heating of the heat-resistant bonding agent (vitreous bonding
agent) must be conducted under a nitrogen-containing atmosphere.
Furthermore, the aforementioned nitrogen-containing atmosphere may
be formed by means of using N.sub.2 gas, a mixed H.sub.2--N.sub.2
gas or NH.sub.3 gas.
[0114] It is possible to bring back the bonding strength by means
of cooling and solidifying the molten vitreous bonding agent,
however, instead of performing rapid cooling, it is preferable to
stabilize the oxynitride glass layer while maintaining a high
uptake amount of the nitrogen by means of gradual cooling.
Consequently, the cooling rate of the vitreous bonding agent is
preferably no greater than 50.degree. C./min, and more preferably
no greater than 30.degree. C./min.
[0115] Furthermore, the thickness of the aforementioned first
bonding layer 10 may be set to within the aforementioned range by
means of appropriately adjusting the processing conditions, such as
the mixing ratio of the finely powdered vitreous bonding agent and
screen oil, coating amount of the heat-resistant bonding agent in
paste form, heating temperature at the time of bonding, heating
duration, and the like.
[0116] Here, an example of the method for manufacturing an
appropriate vitreous bonding agent used at the time of forming the
first bonding layer 10 comprising an oxynitride glass layer
containing a bonding agent comprising at least two elements
selected from the elements of Group IIIa of the Periodic Table,
aluminum, and silicon, will be described in the following.
[0117] To begin with, as the starting material powder of the
vitreous bonding agent, for example, oxides comprising at least two
elements selected from the elements of Group IIIa of the Periodic
Table, silicon dioxide, and aluminum oxide are mixed, or
alternatively a compound that is converted into the aforementioned
by means of heat treatment is mixed.
[0118] This starting material mixed powder is then pulverized to a
particle diameter of 5.times.10.sup.-6 m (5 .mu.m) or less, and
melted at 1500.about.1700.degree. C. Subsequently, the vitreous
cooled material obtained by means of rapid cooling of the
aforementioned is pulverized to yield a particle diameter of
5.times.10.sup.-6 m (5 .mu.m) or less, and the bonding agent of
this molten fine powder having a uniform composition is then
adjusted to yield a vitreous bonding agent.
[0119] Furthermore, examples of the elemental oxide of Group IIIa
of the Periodic Table, are not particularly limited and may include
Y.sub.2O.sub.3, Dy.sub.2O.sub.3, Er.sub.2O.sub.3, Gd.sub.2O.sub.3,
La.sub.2O.sub.3, Yb.sub.2O.sub.3, Sm.sub.2O.sub.3, and the
like.
[0120] Among the aforementioned, from the perspective of cost and
availability, one of the oxides comprising elements of Group IIIa
of the Periodic Table should preferably be Y.sub.2O.sub.3, while
the other elemental oxide of Group IIIa of the Periodic Table may
preferably comprise Dy.sub.2O.sub.3, Er.sub.2O.sub.3, or
Gd.sub.2O.sub.3, which are able to easily form an overall solid
solution with Y.sub.2O.sub.3. In particular, from the perspective
of cost, Dy.sub.2O.sub.3 is particularly preferred.
[0121] In addition, the composition ratios of each aforementioned
component are not particularly limited, however, blending a solid
solution comprising a total amount of the two or more types of
elemental oxides comprising elements selected from Group IIIa of
the Periodic Table of 20.about.50% by weight, silicon dioxide of
30.about.70% by weight, and aluminum oxide of 10.about.30% by
weight is preferred since such a solid solution has a low melting
point and a superior wettability with ceramics and the like.
[0122] Furthermore, in the case of two types of elements from Group
IIIa of the Periodic Table, it is preferable to blend the
aforementioned at a molar ratio of the elemental oxides of Group
IIIa of the Periodic Table of 1:1, since this results in a bonding
agent with the lowest melting point.
[0123] The atmosphere at the time of adjusting this vitreous
bonding agent is not particularly limited, such that conducting the
aforementioned under a nitrogen atmosphere results in oxynitride
glass, while conducting the aforementioned under a non-nitrogen
atmosphere results in oxide glass. However, in the present
embodiment, since an oxynitride glass layer will be formed in the
end, it is preferable to pre-form oxynitride from the vitreous
bonding agent by adjusting the vitreous bonding agent under
nitrogen atmosphere.
[0124] Furthermore, the aforementioned nitrogen-containing
atmosphere may be formed by means of using N.sub.2 gas, a mixed
H.sub.2--N.sub.2 gas or NH.sub.3 gas.
[0125] In addition, blending 1.about.50% by weight of a
Si.sub.3N.sub.4 powder and/or an AlN powder into the aforementioned
vitreous bonding agent is preferred. By means of adding a
Si.sub.3N.sub.4 powder and/or an AlN powder in this manner, it is
possible to decrease the coefficient of thermal expansion of the
oxynitride glass and also improve the heat resistance thereof.
[0126] Furthermore, in the case when the Si.sub.3N.sub.4 powder
and/or an AlN powder is blended in an amount less than 1% by
weight, it is not possible to obtain the aforementioned effects
even with the addition of the Si.sub.3N.sub.4 powder and/or an AlN
powder. In addition, when the blending amount exceeds 50% by
weight, the bonding strength between the support plate 2 and
loading plate 3 is reduced, and thus is not desirable.
[0127] In addition, the particle diameter of the Si.sub.3N.sub.4
powder and/or an AlN powder to be added is not particularly
limited, however, from the standpoint of being able to form an
oxynitride glass having a uniform concentration, an average
particle diameter of no greater than 0.8.times.10.sup.-6 m (0.8
.mu.m) is preferred.
[0128] According to the present embodiment, a heat insulating
material 13 is loaded within concave member 12, which is provided
on the bonding surface with loading plate 3 of support plate 2
(base member), and thus this heat insulating material 13 is not
exposed to anti-corrosive atmospheric gases, plasma, and the like.
As a result, it is possible to provide a heating apparatus that can
be manufactured easily at low cost with a further improved product
life, wherein no limitations exist for the material comprising this
heat insulating material 13.
[0129] In addition, the heating apparatus 200 of the present
embodiment is provided with a heat insulating material 12 at the
base of heating element 8 (i.e., the side on which the object to be
heated does not rest), and thus it is possible to effectively
prevent heat dissipation from the side on which the object to be
heated does not rest, while also maintaining the conductivity of
the side on which the object to be heated rests. This aspect, in
turn, results in a superior heating efficiency.
[0130] Furthermore, in the present embodiment, only a structure in
which a concave member 12a is provided on the bonding surface with
loading plate 3 of support plate 2 (base member), wherein a heat
insulating material 13 and heating element 8 are provided in this
concave member 12a is described. However, the present invention is
not limited to the aforementioned, as long as a structure is
realized in which a concave member is provided on the bonding
surface of one or both of the support plate 2 and loading plate 3,
wherein a heating element and heat insulating material are loaded
within said concave member, such that the heat insulating material
is arranged either at the base of this heating element, or
alternatively at the base and side portions of the aforementioned
heating member.
[0131] [Third Embodiment]
[0132] In the following, the structure of heating apparatus 300
according to a Third Embodiment of the present invention, a
schematic cross-sectional view of which is shown in FIG. 4, will be
explained.
[0133] The basic structure of the heating apparatus 300 of the
present embodiment is the same as that of heating apparatus 200 of
the aforementioned Second Embodiment. The only differences are in
the shape of the concave member and heat insulating material
provided in support plate 2. Consequently, in FIG. 4, the
structural components that are identical to those of the
aforementioned heating apparatus 200 will be denoted by the same
numeral and their explanations will be omitted. In addition, the
plane structures of electrode plate 4 and heating element 8 of
heating apparatus 300 are identical to those respectively shown in
FIGS. 2A and 2B, according to the First Embodiment, and hence their
drawings will be omitted.
[0134] In FIG. 4, a support plate 20, concave member 22, and heat
insulating material 23 are shown.
[0135] In the present embodiment, as shown in FIG. 4, a concave
member 22 is provided on the upper surface of support plate 2
(i.e., at the bonding surface with loading plate 3) which comprises
a surface area larger than that of heating element 8. A heating
element 8 having a predetermined shape (e.g., spiral shape) is
loaded within this concave member 22.
[0136] In addition, a heat insulating material 23 is loaded within
this concave member 22 at the base of heating element 8; however,
this heat insulating material 23, as shown in FIG. 4, is formed
over the entire surface of the base of concave member 22, such that
it is provided within concave member 22 over both the area in which
heating element 8 is formed and also the area in which heating
element 8 is not formed.
[0137] Furthermore, in the present embodiment, only the case in
which a heat insulating member 23 is solely provided on the base of
concave member 22 is shown; however, the present invention is not
limited to the aforementioned, as this heat insulating material 23
may also be provided on the base and sides of the aforementioned
concave member 22.
[0138] In addition, in the present embodiment, the structural
materials of support plate 20 and heat insulating material 23 are
identical to the respective structural materials of support plate 2
and heat insulating material 13 of the First Embodiment, and
heating apparatus 300 may be manufactured in the same manner as
heating apparatus 200 of the
[0139] Second Embodiment.
[0140] According to the present embodiment, in the same manner as
in the above-described Second Embodiment, a heat insulating
material 23 is loaded within a concave member 22, which is provided
on the bonding surface with loading plate 3 of support plate 20
(base member), and thus, this heat insulating material 23 is not
exposed to anti-corrosive atmospheric gases, plasma, and the like.
As a result, it is possible to provide a heating apparatus that can
be manufactured easily at low cost with a further improved product
life, wherein no limitations exist for the material comprising this
heat insulating material 23.
[0141] In addition, the heating apparatus 300 of the present
embodiment is provided with a heat insulating material 23 at the
base of heating element 8, and thus it is possible to effectively
prevent heat dissipation from the side on which the object to be
heated does not rest, while also maintaining the conductivity of
the side on which the object to be heated does rests. This aspect,
in turn, results in a superior heating efficiency.
[0142] Furthermore, in the present embodiment, only a structure in
which a concave member 22 is provided on the bonding surface with
loading plate 3 of support plate 20 (base member), wherein a heat
insulating material 23 and heating element 8 are provided in this
concave member 22 is described. However, the present invention is
not limited to the aforementioned, as long as a structure is
realized in which a concave member is provided on the bonding
surface of one or both of the support plate 20 and loading plate 3,
wherein a heating element is loaded within said concave member, and
a heat insulating material is loaded within said concave member
with said heating element and arranged at least at the base thereof
(i.e., the side on which the object to be heated does not
rest).
EXAMPLES
[0143] In the following, the present invention will be explained
using the examples.
Examples 1 .about.3
[0144] According the present examples, a heating apparatus was
formed having the structure shown in FIG. 1.
[0145] In the following, the formation of a support plate 2 having
a low coefficient of thermal conductivity and comprising an
aluminum nitride group sintered body having a diameter of 220 mm
and a thickness of 15 mm, in which a spiral-shaped concave member
12 for loading a heating element 8 with a width of 5 mm and depth
of 8 mm is provided, will be described.
[0146] An aluminum nitride powder (F-grade powder manufactured by
Tokuyama K.K.) having an average particle diameter of
0.6.times.10.sup.-6 m (0.6 .mu.m) which does not contain
Y.sub.2O.sub.3, and a silicon carbonate powder (manufactured by
Sumitomo Osaka Cement K.K.) having an average particle diameter of
0.03.times.10.sup.-6 m (0.03 .mu.m) were mixed at a proportional
weight ratio of 99.5:0.5 to form a mixed powder. Subsequently,
after adding and mixing in isopropyl alcohol as a dispersing agent,
this mixed powder was granulated using a spray dryer.
[0147] Subsequently, the resultant granules were pressurized and
sintered under the conditions of 1850.degree. C. and 19.6 MPa (200
Kg/cm.sup.2) to form a disk-shaped sintered body. The resultant
disk-shaped sintered body was then ground according to a
conventional grinding method to form a support plate 2 comprising
the aforementioned spiral-shaped concave member 12.
[0148] The coefficient of thermal conductivity was 57.7 W/mK and
the coefficient of thermal expansion was
4.7.times.10.sup.-6/.degree. C. at the time of measuring the
coefficient of thermal conductivity and coefficient of thermal
expansion of this support plate 2 using a laser flash method and
thermal expansion measuring device (TMA), respectively.
[0149] On the other hand, a base plate 3a comprising a disk-shaped,
aluminum nitride group sintered body having a diameter of 220 mm
and a thickness of 8 mm, and a head plate 3b comprising an aluminum
nitride group sintered body having a diameter of 220 mm and a
thickness of 1 mm were formed according to the aforementioned
formation process of support plate 2 with the exception of using a
mixed powder comprising the aforementioned aluminum nitride powder,
silicon carbonate powder, and yttria powder (manufactured by Nihon
yttrium, K.K.) at a weight ratio of 99.5 0.5:3.0.
[0150] Upon measuring the coefficient of thermal conductivity of
this base plate 3a and head plate 3b according to the
aforementioned methods, both displayed an excellent value of 110
W/mK, which was a higher coefficient of thermal conductivity than
that of the support plate 2. In addition, upon measuring the
coefficient of thermal expansion of this base plate 3a and head
plate 3b according to the aforementioned methods, both displayed a
value of 4.4.times.10.sup.-6/.degree. C., which was very close to
the coefficient of thermal expansion of the aforementioned support
plate 2.
[0151] In addition, a heating element 8 was formed, according to
the above-described method for manufacturing a heating element 8
(1), comprising a silicon carbonate sintered body having a sintered
density of 3.1.times.10.sup.-3 kg/cm.sup.3, and an electrical
resistivity of 0.05.times.10.sup.-2 .OMEGA.m, which was sintered
without the addition of a sintering auxiliary agent, additives for
imparting conductivity, and the like. This heating element 8 was
provided with a specific shape and loaded into the aforementioned
spiral-shaped concave member 12.
[0152] The average particle diameter of the first silicon carbonate
powder was 0.7.times.10.sup.-6 m (0.7 .mu.m) and the addition
amount was 95% by weight, while the average particle diameter of
the second silicon carbonate powder was 0.01.times.10.sup.-6 m
(0.01 .mu.m) with an addition amount of 5% by weight. The hot press
sintering conditions comprised a press pressure of 39.2 MPa (400
kg/cm2), sintering temperature of 2200.degree. C., and a sintering
duration of 90 minutes.
[0153] On the other hand, a coating agent containing a tungsten
powder having an average particle diameter of 0.5.times.10.sup.-6 m
(0.5 .mu.m), and a commercially available screen oil was screen
printed onto the base plate in the shape of an electrode. In
addition, a coating agent containing an aluminum nitride powder and
a commercially available screen oil was screen printed onto the
base plate 3a, over the remaining area other than that of the
aforementioned electrode.
[0154] Subsequently, base plate 3a and head plate 3b were first
stacked and joined by means of the aforementioned screen-printed
surface, and then heat-treated under the conditions of 1800.degree.
C. and 7.35 MPa (75 kg/cm.sup.2) to form an integrated body. The
tungsten electrode plate was hence sandwiched between the base
plate 3a and head plate 3b, thereby forming the loading plate
3.
[0155] Thereafter, a vitreous, heat-resistant bonding agent
(average particle diameter of approximately 2.times.10.sup.-6 m
(approximately 2 .mu.m)) having the composition shown in Table 1
was mixed with a commercially available screen oil to form a paste.
This vitreous, heat-resistant bonding agent 10 in paste form was
coated onto the respective bonding surfaces of the aforementioned
support plate 2, comprising a ceramics sintered body onto which the
aforementioned heating element 8 was loaded within the
aforementioned spiral-shaped concave groove 12, and loading plate
3, comprising a ceramics sintered body, and then dried at
100.about.200.degree. C.
[0156] Subsequently, the aforementioned support plate 2 and loading
plate 3 were stacked by means of the aforementioned surfaces onto
which the vitreous, heat-resistant bonding agent 10 had been
coated, with the aforementioned heating element 8 sandwiched
therein between. In this manner, the aforementioned support plate 2
and loading plate 3 were bonded together in an airtight manner by
means of heating within an electric furnace possessing an N.sub.2
gas atmosphere and melting the vitreous, heat-resistant bonding
agent at 1450.degree. C. for 20 minutes. The cooling rate was
25.degree. C./min, and the thickness of the bonding layer 10 after
bonding was 50 .mu.m. In addition, the formation of oxynitride
glass on the bonding interface was confirmed by means of Auger
electron spectral analysis.
[0157] With respect to the resultant heating apparatus 100 of
Examples 1.about.3, each was subjected to a durability test in
order to confirm the air-tightness of the bonding portion of the
aforementioned support plate 2, comprising an aluminum nitride
group sintered body, and base plate 3a, comprising an aluminum
nitride group sintered body.
[0158] In addition, upon examining the bonding interface of the
base plate 3a and head plate 3b with an SEM microscope, it was
confirmed that the base plate 3a and head plate 3b were well bonded
into a single body.
[0159] [Durability Test]
[0160] Electricity was passed through the heating apparatus 100,
and the temperature was increased over the course of one hour from
room temperature to a maximum temperature of 700.degree. C. After
maintaining this maximum temperature for 30 minutes, the
temperature was gradually lowered back to room temperature. The
air-tightness of the aforementioned bonding portion after loading
this heat cycle 100 times was then measured by means of a leak test
using He gas.
[0161] Furthermore, the air-tightness was evaluated according to
the evaluation standard shown below.
[0162] O: The leakage amount of He was less than
1.33.times.10.sup.-7 Pa/sec.
[0163] .DELTA.: The leakage amount of He was 1.33.times.10.sup.-7
Pa/sec.about.1.33.times.10.sup.-6 Pa/sec.
[0164] x: The leakage amount of He was greater than
1.33.times.10.sup.-6 Pa/sec.
[0165] The results of the durability test are shown in Table 1.
1 TABLE 1 Composition of the bonding agent starting material powder
(% by wt) Dy.sub.2O.sub.3 Y.sub.2O.sub.3 Al.sub.2O.sub.3 SiO.sub.2
Air-tightness Example 1 15 10 25 50 O Example 2 15 15 25 45 O
Example 3 15 15 20 50 O
Example 4
[0166] According the present example, a heating apparatus
containing a heat insulating material was formed having the
structure shown in FIG. 3.
[0167] In the following, the formation of a support plate 2
comprising an aluminum nitride group sintered body having a
diameter of 220.times.10.sup.-3 m (220 mm) and a thickness of
15.times.10.sup.-3 m (15 mm), in which a spiral-shaped concave
member 12a for loading a heating element 8 with a width of
5.times.10.sup.-3 m (5 mm) and depth of 8.times.10.sup.-3 m (8 mm)
is provided, will be described.
[0168] An aluminum nitride powder (F-grade powder manufactured by
Tokuyama K.K.) having an average particle diameter of
0.6.times.10.sup.-6 m (0.6 .mu.m) which did not contain yttria, and
a silicon carbonate powder (manufactured by Sumitomo Osaka Cement
K.K.) having an average particle diameter of 0.03.times.10.sup.-6 m
(0.03 .mu.m) were mixed at a proportional weight ratio of 99.5:0.5
to form a mixed powder. Subsequently, after adding and mixing in
isopropyl alcohol as a dispersing agent, this mixed powder was
granulated using a spray dryer.
[0169] Subsequently, the resultant granules were pressurized and
sintered under the conditions of 1850.degree. C. and 19.6 MPa (200
Kg/cm.sup.2) to form a disk-shaped sintered body.
[0170] The resultant disk-shaped sintered body was then ground
according to a conventional grinding method to form a support plate
2 comprising the aforementioned spiral-shaped concave member 12a
(depth 8.times.10.sup.-3 m (8 mm)).
[0171] On the other hand, a loading base plate 3a comprising a
disk-shaped, aluminum nitride group sintered body having a diameter
of 220.times.10.sup.-3 m (220 mm) and a thickness of
8.times.10.sup.-3 m (8 mm), on the surface of which a concave
member having a diameter of 200.times.10.sup.-3 m (200 mm) and a
depth of 0.03.times.10.sup.-3 m (0.03 mm) is provided; and a
loading head plate 3b comprising an aluminum nitride group sintered
body having a diameter of 220.times.10.sup.-3 m (220 mm) and a
thickness of 1.times.10.sup.-3 m (1 mm) were formed according to
the aforementioned formation process of support plate 2 with the
exception of using a mixed powder comprising the aforementioned
aluminum nitride powder, silicon carbonate powder, and yttria
powder (manufactured by Nihon Yttrium, K.K.) at a weight ratio of
99.5:0.5:3.0.
[0172] In addition, a heating element 8 was formed, according to
the above-described method for manufacturing a heating element 8
(1), comprising a silicon carbonate sintered body having a sintered
density of 3.1.times.10.sup.-3 kg/cm.sup.3, and an electrical
resistivity of 0.05.times.10.sup.-2 .OMEGA.m, which was sintered
without the addition of a sintering auxiliary agent, additives for
imparting conductivity, and the like. This heating element 8 was
provided with a specific shape (clearance 1.times.10.sup.-3 m (1
mm)) and thickness of 4.times.10.sup.-3 m (4 mm) to be loaded into
the aforementioned spiral-shaped concave member 12a.
[0173] The average particle diameter of the first silicon carbonate
powder was 0.7.times.10.sup.-6 m (0.7 .mu.m) and the addition
amount was 95% by weight, while the average particle diameter of
the second silicon carbonate powder was 0.01.times.10.sup.-6 m
(0.01 .mu.m) with an addition amount of 5% by weight. The hot press
sintering conditions comprised a press pressure of 39.2 MPa (400
kg/cm.sup.2), sintering temperature of 2200.degree. C., and a
sintering duration of 90 minutes.
[0174] On the other hand, a coating agent containing a tungsten
powder, having an average particle diameter of 0.5.times.10.sup.-6
m (0.5 .mu.m), and a commercially available screen oil was screen
printed in the shape of an electrode within the concave member 11
provided on the surface of loading base plate 3a to form a tungsten
electrode plate 4.
[0175] In addition, a bonding agent containing the aforementioned
aluminum nitride powder and a commercially available screen oil was
screen printed onto the surface of loading base plate 3a, over the
remaining area on which the aforementioned electrode plate 4 was
not formed.
[0176] Subsequently, loading base plate 3a and loading head plate
3b were first stacked and joined by means of the aforementioned
screen-printed surface, and then heat-treated under the conditions
of 1800.degree. C. and 7.35 MPa (75 kg/cm.sup.2). The
aforementioned loading base plate 3a and loading head plate 3b were
hence bonded into an integrated body by means of a second bonding
layer 7 formed from aluminum nitride to form a loading plate 3, in
which the tungsten electrode plate 4 was sandwiched between the
base plate 3a and head plate 3b.
[0177] On the other hand, a heat insulating material 13 (thickness
2.times.10.sup.-3 m (2 mm) and clearance of 1.times.10.sup.-3 m (1
mm)) possessing a shape formed by means of loading into a
spiral-shaped concave member 12a provided in support plate 2, and
comprising a silicon nitride sintered body, was formed according to
a grinding method.
[0178] Subsequently, the heating element 8 and heat insulating
material 13 were loaded into the spiral-shaped concave member 12a
provided in support plate 2, with the heat insulating material 13
positioned at the base of the heating element 8.
[0179] Thereafter, a vitreous, heat-resistant bonding agent
(SiO.sub.2--Dy.sub.2O.sub.3--Al.sub.2O.sub.3--Y.sub.2O.sub.3 type
agent with an average particle diameter of approximately
2.times.10.sup.-6 m (2 .mu.m)) was mixed with a commercially
available screen oil to form a paste. This vitreous, heat-resistant
bonding agent 10 in paste form was coated onto the respective
bonding surfaces of the aforementioned support plate 2, and loading
plate 3 (loading base plate 3a) and then dried at
100.about.200.degree. C.
[0180] Subsequently, the aforementioned support plate 2 and loading
plate 3 were stacked by means of the aforementioned surfaces onto
which the vitreous, heat-resistant bonding agent 10 had been
coated, with the aforementioned heating element 8 and heat
insulating material 13 sandwiched therein between. In this manner,
the aforementioned support plate 2 and loading plate 3 were bonded
together in an airtight manner by means of heating within an
electric furnace possessing an N.sub.2 gas atmosphere, melting the
vitreous, heat-resistant bonding agent at 1450.degree. C. for 20
minutes, and then cooling. The cooling rate was 25.degree.
C./min.
[0181] The thickness of the first bonding layer after bonding was
50.times.10.sup.-6 m (50 .mu.m). In addition, the formation of
oxynitride glass on the first bonding layer was confirmed by means
of Auger electron spectral analysis.
* * * * *