Ceramic heater

Abstract

The present invention relates to a ceramic heater, and the ceramic heater of the present invention comprises: a heater plate made of a ceramic material and provided with a heating element; a shaft which has a tubular shape having a through-hole, is coupled to the lower surface of the heater plate, and accommodates a rod for supplying power to the heating body through the through-hole; and an air bag continuously or intermittently provided in a joint portion through which the heater plate and the shaft are in contact and joined, the air bag being formed along a joint surface of the joint portion.

Description

Technical Field

[0001] The present invention relates to a ceramic heater, and more particularly, to a ceramic heater having a shaft joining structure with reduced heat loss. Background Art

[0002] Generally, semiconductor devices or display devices are manufactured by sequentially stacking a plurality of thin film layers including a dielectric layer and a metal layer on a glass substrate, a flexible substrate, or a semiconductor wafer substrate and then patterning them. These thin film layers are sequentially deposited on the substrate by a Chemical Vapor Deposition (CVD) process or a Physical Vapor Deposition (PVD) process. The CVD process includes a Low Pressure CVD (LPCVD) process, a Plasma Enhanced CVD (PECVD) process, a Metal Organic CVD (MOCVD) process, and the like.

[0003] In these CVD devices and PVD devices, a heater is provided for supporting a glass substrate, a flexible substrate, a semiconductor wafer substrate, etc. and applying a predetermined heat. In an etching process of a thin film layer formed on a support substrate and a plastic process of a photoresist, etc., the heater is also used to heat the substrate. Among the heaters installed in the CVD devices and PVD devices, a ceramic heater is widely used according to the requirements of precise temperature control, fine wiring of semiconductor elements, and precise heat treatment of semiconductor wafer substrates.

[0004] As Figure 1 shown, a conventional ceramic heater 1 includes a heater plate 10 coupled to a shaft 20. The heater plate 10 includes a high-frequency electrode 12 and a heating element 14 disposed between ceramic materials. The shaft 20 provides holes through which rods 21, 23 respectively connected to the high-frequency electrode 12 and the heating element 14 and supplying power pass.

[0005] However, in Figure 1 structures such as the conventional ceramic heater 1, a part of the heat generated by the heating element 14 (for example, above 650 °C in some cases) is released through the shaft 20 in contact with the lower surface of the heater plate 10, thereby increasing the heat loss of the heater plate 10 and reducing the temperature uniformity of the substrate provided on the ceramic heater 1. Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] Therefore, the present invention is proposed to solve the above problems, and the object of the present invention is to provide a ceramic heater, which can reduce heat loss by providing an air pocket at the joint between the heater plate and the shaft, and can reduce crack generation and heat loss paths by reducing leakage in the semiconductor equipment cavity and reducing thermal stress, thereby improving thermal efficiency.

[0008] Means for Solving the Problem

[0009] First, summarize the features of the present invention. The ceramic heater according to the present invention for achieving the above object includes: a heater plate made of a ceramic material and provided with a heating element; a shaft, which is a tubular shape having a through hole, is coupled to the lower surface of the heater plate, and a rod for supplying power to the heating element is accommodated through the through hole; and an air pocket, which is continuously or intermittently provided in the joint portion where the heater plate and the shaft are in contact and coupled, and the air pocket is formed along the joint surface of the joint portion.

[0010] The ceramic heater further includes: a bonding material formed between the heater plate and the shaft along the joint surface of the joint portion, and the air pocket includes a groove formed along the bonding material.

[0011] According to one embodiment, the bonding material may contain 90 to 97 wt% of aluminum nitride and 3 to 10 wt% of yttrium oxide.

[0012] According to another embodiment, the bonding material may contain 45 to 75 wt% of aluminum nitride, 10 to 20 wt% of alumina, 10 to 20 wt% of calcium oxide, and 5 to 15 wt% of yttrium oxide.

[0013] The air pocket may include a groove formed in the heater plate along the joint surface of the joint portion, the cross section of the groove is T-shaped, and is formed to be wider on the heater plate side than on the joint surface side.

[0014] The air pocket may be formed at a position corresponding to the installation path of the heating element along the installation path of the heating element. Wherein, the ceramic heater further includes a bonding material formed between the heater plate and the shaft along the joint surface of the joint portion, and the air pocket may be formed along the bonding material. In addition, the air pocket may be formed in the heater plate along the joint surface of the joint portion.

[0015] The heater plate may further include a high-frequency electrode disposed separately from the heating element, and the high-frequency electrode may receive power through another rod disposed in the through hole of the shaft.

[0016] Advantages of the Invention

[0017] For the ceramic heater according to the present invention, by placing an air bag at the joint between the heater plate and the shaft, heat loss can be reduced. The air bag can reduce crack generation and heat loss paths by reducing leakage in the semiconductor equipment cavity and reducing thermal stress, thereby improving thermal efficiency. Brief Description of the Drawings

[0018] To assist in understanding the present invention, the drawings included as part of the detailed description provide embodiments of the present invention and illustrate the technical concept of the present invention together with the detailed description of the present invention.

[0019] Figure 1 is a schematic cross-sectional view of a conventional ceramic heater.

[0020] Figure 2 is a schematic cross-sectional view of a ceramic heater according to an embodiment of the present invention.

[0021] Figure 3 is Figure 2 an enlarged view of the joint portion.

[0022] Figure 4 is for explaining Figure 2 the air bag in the joint material formed at the joint portion.

[0023] Figure 5a is a schematic cross-sectional view and an enlarged view of the joint portion of a ceramic heater according to another embodiment of the present invention.

[0024] Figure 5b is Figure 5a another embodiment of the air bag at the joint portion.

[0025] Figure 6 is for explaining Figure 5a and Figure 5b the bottom view of the heater plate with the air bag formed in the heater plate.

[0026] Figure 7 is a view for explaining the air bag formed in the arrangement path of the heating element in the ceramic heater according to the embodiment of the present invention. Detailed Description of the Invention

[0027] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. At this time, in each drawing, the same components are denoted by the same reference numerals as much as possible. In addition, detailed descriptions of known functions and / or configurations are omitted. The following disclosure will focus on the parts required to understand the operations according to various embodiments, and descriptions of components that may obscure the gist of the description will be omitted. In addition, some components in the drawings may be enlarged, omitted, or shown schematically. The sizes of each component do not exactly reflect the actual sizes. Therefore, the content described in this specification is not limited by the relative sizes or intervals of the components drawn in each drawing.

[0028] When describing embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the gist of the present invention, its detailed description is omitted. Also, the terms to be described later are terms defined according to the functions in the present invention and may vary depending on the intentions or conventions of users, operators, etc. Therefore, their definitions should be based on the entire content of this specification. The terms used in the detailed description are only for describing the embodiments of the present invention and are by no means restrictive. Unless otherwise clearly stated, singular expressions include the meaning of plural forms. In this specification, expressions such as "including" or "having" refer to certain features, numbers, steps, operations, components, parts thereof, or combinations thereof, and should not be construed as excluding the existence or possibility of one or more other features, numbers, steps, operations, components, parts thereof, or combinations thereof other than those described above.

[0029] In addition, terms such as first, second, etc. may be used to describe various components, but the components are not limited to these terms, and these terms are only used to distinguish one component from other components.

[0030] Figure 2 is a schematic cross-sectional view of a ceramic heater 100 according to an embodiment of the present invention.

[0031] Referring to Figure 2 , a ceramic heater 100 according to an embodiment of the present invention includes a heater plate 110 and a shaft 120.

[0032] A ceramic heater 100 according to an embodiment of the present invention is a semiconductor device that supports various target substrates such as semiconductor wafers, glass substrates, and flexible substrates, and heats the target substrate to a specified temperature. The ceramic heater 100 can also be used in processes such as plasma enhanced chemical vapor deposition.

[0033] The heater plate 110 can be configured such that the high-frequency electrode 112 and / or the heating element 114 are disposed (embedded) at a predetermined interval between ceramic materials. The heater plate 110 is configured to heat using the heating element 114 and / or perform a plasma-enhanced chemical vapor deposition process using the high-frequency electrode 112 while stably supporting the substrate to be processed. The heater plate 110 can be formed of a plate-like structure having a predetermined shape. For example, the heater plate 110 can be formed of a circular plate-like structure, but is not limited thereto. Among them, the ceramic material can be Al 2 O 3 、Y 2 O 3 、Al 2 O 3 / Y 2 O 3 、ZrO 2 、AlC (Autoclaved lightweight concrete), TiN, AlN, TiC, MgO, CaO, CeO 2 、TiO 2 、B x C y 、BN, SiO 2 、SiC, YAG, Mullite, AlF 3 、 at least one of the materials, preferably aluminum nitride (AlN). In addition, each ceramic powder can selectively contain about 0.1 to 10% of yttrium oxide powder, preferably about 1 to 5% of yttrium oxide powder.

[0034] The high-frequency electrode 112 can be composed of tungsten (W), molybdenum (Mo), silver (Ag), gold (Au), niobium (Nb), titanium (Ti), aluminum nitride (AlN) or their alloys, and is preferably composed of molybdenum (Mo). The high-frequency electrode 112 can be connected to an RF (Radio) power supply or ground through a connecting rod 121. The high-frequency electrode 112 has a wire type or sheet type mesh structure. Among them, the mesh structure is a mesh structure formed by intersecting a plurality of metals arranged in a first direction and a plurality of metals arranged in a second direction.

[0035] The heating element 114 can be formed into a plate-like coil shape or a flat plate shape by a heating wire (or resistance wire). In addition, the heating element 114 can also be formed into a multi-layer structure to achieve precise temperature control. Such a heating element 114 is connected to a power supply through a connecting rod 123 in a semiconductor manufacturing process to perform the function of heating the substrate to be processed on the heater plate 110 to a predetermined constant temperature to perform a smooth deposition process and etching process, etc.

[0036] The shaft 120 is of a pipe type with a through-hole and is coupled to the lower surface of the heater plate 110. The shaft 120 can be formed of the same ceramic material as the heater plate 100 and coupled to each other. Among them, the ceramic material can be Al 2 O 3 、Y 2 O 3 、Al 2 O 3 / Y 2 O 3 、ZrO 2 、AlC (Autoclaved lightweight concrete), TiN, AlN, TiC, MgO, CaO, CeO 2 、TiO 2 、B x C y 、BN, SiO 2 、SiC, YAG, Mullite, AlF 3 at least one of the materials, and preferably can be aluminum nitride (AlN). In addition, each ceramic powder can selectively contain about 0.1 to 10% of yttrium oxide powder, and preferably contains about 1 to 5% of yttrium oxide powder.

[0037] As described below, the shaft 120 can be coupled to the heater plate 110 through a bonding substance 125 such as ceramic paste. In some cases, the shaft 120 can also be mechanically connected to the heater plate 110 using bolts, nuts, etc. Through the through-hole of the shaft 120, the respective rods 121, 123 for supplying power to the high-frequency electrode 112 and / or the heating element 114 are accommodated.

[0038] When the shaft 120 and the heater plate 110 are joined through the bonding substance 125, in order to join at a relatively high temperature (for example, 1750 - 1850 °C), the bonding substance 125 can be composed of a binder composed of 90 - 97 wt% of aluminum nitride and 3 - 10 wt% of yttrium oxide. Or, when the shaft 120 and the heater plate 110 are joined through the bonding substance 125, in order to join at a relatively low temperature (for example, 1600 - 1700 °C), the bonding substance 125 can be composed of a binder composed of 45 - 75 wt% of aluminum nitride, 10 - 20 wt% of aluminum oxide, 10 - 20 wt% of calcium oxide, and 5 - 15 wt% of yttrium oxide.

[0039] According to an embodiment of the present invention, the ceramic heater 100 includes an air bag 210, and the air bag 210 is disposed in the joint portion 190, and the heater plate 110 and the shaft 120 are in contact and joined through the joint portion 190.

[0040] Figure 3 is Figure 2An enlarged view of the joint portion 190. Figure 4 It is used to illustrate Figure 2 A diagram of the air pocket 210 formed in the bonding material 125 at the joint portion 190. Figure 4 It is a plan view of the bonding material 125.

[0041] Refer to Figure 3 and Figure 4 , the air pocket 210 is provided in the joint portion 190, the heater plate 110 and the shaft 120 are in contact with and bonded through the joint portion 190, and is formed along the joint surface (contact surface) of the joint portion 190 that forms a closed loop. As Figure 4 shown, a ring-shaped bonding material 125 is formed along the joint surface where the heater plate 110 and the shaft 120 are in contact with and bonded, so that the heater plate 110 and the shaft 120 are tightly bonded. The bonding material 125 as described above is preferably inserted into the joint surface between the heater plate 110 and the shaft 120 and is illustrated by this example. However, it should be noted that in some cases, when the heater plate 110 and the shaft 120 are mechanically bonded using bolts, nuts, etc., the bonding material 125 is not necessarily required.

[0042] As Figure 4 shown, the bonding material 125 inserted into the joint surface to bond the heater plate 110 and the shaft 120 can be a circular ring, so that the joint surface (contact surface) of the heater plate 110 and the shaft 120 forms a circular ring-shaped closed loop (a shape where the joint surface is continuous). However, in some cases, the joint surface (contact surface) of the heater plate 110 and the shaft 120 can be formed into a closed loop such as a square, various polygons, a curved shape, etc. other than a circle.

[0043] As Figure 4 shown, the air pocket 210 formed in the bonding material 125 at the joint portion 190 is a groove (or through hole) formed along the bonding material 125, and is a cavity (hollow) space formed with steps having a different thickness from the surrounding.

[0044] The air pocket 210 as described above includes the groove 211 in a discontinuous form as shown in Figure 4 (a). The shape of the groove 211 can be circular, square, other polygons, etc., and the intervals of the discontinuous grooves 211 are preferably separated at a specified same interval. However, when the joint surface of the heater plate 110 and the shaft 120 forms an irregular polygon, a curved shape, etc. closed loop, the intervals of the grooves 211 do not have to be limited to the same interval, and the intervals of the grooves 211 can be defined at an appropriate interval to ensure no vacuum leakage.

[0045] In addition, the air pocket 210 includes as Figure 4The groove 212 in the continuous form shown in (b). If the joint surface (contact surface) of the heater plate 110 and the shaft 120 forms an annular closed loop, the air bag 210 can also be formed by the groove 212 in the continuous form that forms an annular closed loop.

[0046] Figure 5a It is a schematic cross-sectional view of the ceramic heater 200 according to another embodiment of the present invention and an enlarged view of the joint portion 191. Figure 5b is Figure 5a Another embodiment of the air bag 230 of the joint portion 191.

[0047] Refer to Figure 5a and Figure 5b , in the ceramic heater 200 according to another embodiment of the present invention, the form and composition of the joint portion 191 where the heater plate 110 and the shaft 120 are in contact and joined and the air bag 230 it has are slightly different from those of the joint portion 190 and the air bag 210 it has in Figure 2 . In the ceramic heater 200 according to another embodiment of the present invention, the forms and compositions of other components are similar to those of the components in Figure 2 . It is also possible to combine the joint portion 190 structure of Figure 2 with the joint portion 191 of Figure 5a and Figure 5b .

[0048] In the ceramic heater 200 according to another embodiment of the present invention, the air bag 230 is provided in the joint portion 191 where the heater plate 110 and the shaft 120 are in contact and joined, and is formed along the joint surface of the joint portion 191 that forms a closed loop. An annular joint material 125 (refer to Figure 4 ) is formed along the joint surface of the joint portion 191 where the heater plate 110 and the shaft 120 are in contact and joined, so that the heater plate 110 and the shaft 120 are tightly joined. The joint material 125 as described above is preferably inserted into the joint surface between the heater plate 110 and the shaft 120. However, it should be noted that in some cases, when the heater plate 110 and the shaft 120 are mechanically joined using bolts, nuts, etc., the joint material 125 is not necessarily required.

[0049] As Figure 5a shows, in the ceramic heater 200 according to another embodiment of the present invention, the air bag 230 includes a groove formed in the heater plate 110 along the joint surface of the joint portion 191. That is, the groove-shaped air bag 230 formed along the joint surface of the joint portion 191 on the lower surface of the heater plate 110 is a cavity (hollow) space formed with steps of different thicknesses from the surroundings.

[0050] In the air bag 230 in the ceramic heater 200 according to another embodiment of the present invention, the shape of the groove may be a groove having a rectangular, circular, or other cross-section. In order to further reduce heat loss, as Figure 5b shown, the vertical cross-section of the shape of the groove may also have a T shape. That is, the T-shaped groove forming the air bag 230 may be formed to have a narrower width on the side of the joint surface and a wider width on the heater plate 110 side. Therefore, the heat transfer path to the joint material 125 side is extended, so that heat dissipation can be reduced and heat loss can be minimized.

[0051] Figure 6 is for explaining the Figure 5a and Figure 5b bottom view of the heater plate 110 of the air bag 230 formed in the heater plate 110. Figure 6 (a) of Figure 6 shows that the air bag 230 formed on the heater plate 110 is formed by the intermittent groove 231,

[0052] constitutes Figure 6 (a) of

[0053] shown, the horizontal cross-section shape of the groove 231 forming the air bag 230 formed by the intermittent groove 231 may be circular, square, other polygons, etc. The intervals of the intermittent groove 231 are preferably separated at a specified same interval. However, when the joint surface of the heater plate 110 and the shaft 120 forms an irregular polygon, curved shape, or other closed loop, the intervals of the groove 231 do not have to be limited to the same interval, and the intervals of the groove 231 can be defined at an appropriate interval to ensure no vacuum leakage. Figure 6 (b) of

[0054] Figure 7 is a view for explaining the air bag 250 formed in the setting path of the heating element 114 in the ceramic heater 100 / 200 according to the embodiment of the present invention.

[0055] Figure 7 (a) of Figure 7 shows an example of the setting shape of the heating element 114 provided in the ceramic material of the heater plate 110. Figure 7 (b) ofFigure 7 of (a) and Figure 7 The figure shown after overlapping with (b).

[0056] In Figure 7 In the ceramic heaters 100 / 200 according to embodiments of the present invention, the air bags 210 / 230 can be formed along a path corresponding to the path where a heating element 114 such as a resistance wire is provided, similar to the air bag 250 formed along a corresponding path along the path where the heating element 114 is provided.

[0057] Among them, as Figure 2 shown, the air bag 250 includes a case where it is formed between the heater plate 110 and the shaft 120 along the bonding material 125 on the bonding surface of the insertion joint 190. In addition, as Figure 5a and Figure 5b shown, the air bag 250 includes a case where it is formed in the ceramic material of the heater plate 110 along the bonding surface of the joint 191.

[0058] The path where the heating element 114 such as the resistance wire is provided as described above is the main heat-generating part that generates a large amount of heat. Therefore, by providing the air bag 250 of the present invention as described above, the heat conduction from the heater plate 110 to the shaft 120 can be reduced, and the heat loss radiated to the shaft 120 side can be reduced.

[0059] In the ceramic heaters 100 / 200 according to embodiments of the present invention, the thermal conductivity of the heater plate 110 and the bonding material 125 is about 150 - 170 W / m·K, and the thermal conductivity of the shaft 120 is about 80 - 170 W / m·K. On the contrary, the thermal conductivity of the air bags 210 / 230 is about 0.025 W / m·K.

[0060] When performing deposition processes, etching processes, etc. on a substrate to be processed on the heater plate 110 using the ceramic heaters 100 / 200, the high-temperature heat generated in the heater plate 110 by the heating element 114 is dissipated through the heat transfer path that passes through the bonding material 125 and moves to the shaft 120. Therefore, since the thermal conductivity of the air bags 210 / 230 as described above is much smaller than that of the heater plate 110 and the shaft 120, the heat loss dissipated through the heat transfer path from the heater plate 110 to the shaft 120 can be reduced.

[0061] In addition, for example, as Figure 4 of (a) or (b) and (or) Figure 6As shown in (a) or (b), when the air bags 210 / 230 are composed of intermittent or continuous grooves 211 / 212, 231 / 232, compared with the traditional case without the air bag 210, the generation of cracks around the joints 190 / 191 can be reduced by reducing the thermal stress caused by the temperature difference. That is, in the traditional structure, a large amount of heat transfer and heat dissipation occur between the heater plate 110 and the shaft 120, and the temperature difference between the heater plate 110 and the shaft 120 around the joints 190 / 191 is large, resulting in an increase in thermal stress. Therefore, the generation of cracks in the heater plate 110 and the shaft 120 may increase. On the contrary, the thermal conductivity of the air bags 210 / 230 is much smaller than that of the heater plate 110 and the shaft 120. Therefore, the heat transfer from the heater plate 110 to the shaft 120 is correspondingly reduced, the temperature difference between the heater plate 110 and the shaft 120 around the joints 190 / 191 becomes smaller, and the thermal stress is reduced. Therefore, the generation of cracks in the heater plate 110 and the shaft 120 can be reduced.

[0062] In addition, in the structure of the bonding material 125 of the present invention in which the grooves 211 / 212, 231 / 232 whose wide widths are used for the air bags 210 / 230 are divided into two parts, when the bonding area of the bonding material 125 on the bonding surface (the sum of the areas divided into two parts) is designed to be the same as that of the bonding material 125 on the bonding surface in the traditional structure without the air bags 210 / 230 of the present invention, the structure using the air bags 210 / 230 of the present invention can also reduce vacuum leakage to reduce gas leakage. That is, in the semiconductor equipment cavity, when deposition processes and etching processes are performed on the processing target substrate on the heater plate 110, the empty space inside the shaft 120 is in the atmospheric atmosphere, and the surrounding of the heater plate 110 in the cavity is in a specified vacuum atmosphere. Therefore, even if there is the bonding material 125 on the bonding surface in contact with the joints 190 / 191 between the heater plate 110 and the shaft 120, there will be a certain degree of vacuum leakage. Therefore, as shown in the present invention, when the air bags 210 / 230 are adopted, since the gas leakage path is extended by an amount equivalent to the length of the gas passing through the bonding material 125 on the bonding surface or the air bag 230 of the heater plate 110 inside the equipment, there is an effect of reducing vacuum leakage and maintaining a high vacuum by reducing gas leakage.

[0063] In addition, as Figure 5b described, in order to further reduce heat loss, the T-shaped groove forming the air bag 230 is formed to have a narrower width on the bonding surface side and a wider width on the heater plate 110 side. Therefore, as Figure 5b shown, the heat transfer path toward the bonding material 125 side becomes longer, and there is an effect of reducing heat dissipation and minimizing heat loss.

[0064] As described above, in the ceramic heater 100 / 200 according to the present invention, by disposing the air bag 210 / 230 at the joint portion 190 / 191 between the heater plate 110 and the shaft 120, heat loss can be reduced. The air bag 210 / 230 can reduce the generation of cracks and reduce the heat loss path by reducing leakage in the semiconductor equipment cavity and reducing thermal stress, thereby improving the thermal efficiency.

[0065] As described above, in the present invention, the present invention is described by specific matters such as specific components, limited embodiments, and drawings, but these are provided only to help a more comprehensive understanding of the present invention. The present invention is not limited to the above embodiments, and those of ordinary skill in the art to which the present invention pertains can make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the idea of the present invention should not be limited to the described embodiments, and all technical ideas equivalent to or equivalently modified from the claims should be construed as being included within the scope of the claims of the present invention.

Claims

1. A ceramic heater, wherein, comprising: a heater plate made of a ceramic material and provided with a heating element; a shaft which is tubular with a through hole, is coupled to the lower surface of the heater plate, and accommodates a rod for supplying power to the heating element through the through hole; and an air bag which is continuously or intermittently provided in a joint portion where the heater plate and the shaft are in contact with and coupled to each other, the air bag being formed along a joint surface of the joint portion, the air bag including a groove formed in the heater plate along the joint surface of the joint portion at a bent portion of an upper end of the shaft for coupling with the heater plate, the groove having a T-shaped cross section and being formed to be wider on the heater plate side than on the joint surface side, the heating element including an arc provided along the joint surface of the joint portion at an upper portion of the joint portion, the air bag being provided at a lower portion of a shape of the arc of the heating element and including a region formed at a position overlapping along the shape of the arc.

2. The ceramic heater according to claim 1, wherein, further comprising: a bonding substance formed between the heater plate and the shaft along the joint surface of the joint portion, the air bag including a groove formed along the bonding substance.

3. The ceramic heater according to claim 2, wherein, the bonding substance contains 90 to 97 wt% of aluminum nitride and 3 to 10 wt% of yttrium oxide.

4. The ceramic heater according to claim 2, wherein, the bonding substance contains 45 to 75 wt% of aluminum nitride, 10 to 20 wt% of aluminum oxide, 10 to 20 wt% of calcium oxide, and 5 to 15 wt% of yttrium oxide.

5. The ceramic heater according to claim 1, wherein, further comprising: a bonding substance formed between the heater plate and the shaft along the joint surface of the joint portion, the air bag being formed along the bonding substance.

6. The ceramic heater according to claim 1, wherein, the heater plate further includes a high-frequency electrode provided separately from the heating element, and the high-frequency electrode receives power through another rod provided in the through hole of the shaft.

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