Ceramic heater

Abstract

To provide a ceramic heater capable of homogenizing a temperature distribution of a substrate mounting surface.SOLUTION: A ceramic heater 100 comprises: a ceramic base material 110 that includes a substrate mounting surface 114 onto an upper surface, and includes a base material main body 112 formed in a plate shape by a ceramic sinter body and a convex part 118 that is projected from a lower surface 116 of the base material body that is opposite to the substrate mounting surface 114 to a lower direction, and is integrally formed with the base material main body 112; a heat element body 130 that is embedded to the base material main body 112 of the ceramic base material 110; and a cylinder shaped shaft 140 that is bonded to a lower surface 120 of the convex part that is opposite to the substrate mounting surface 114, and in which a flange 142 is formed on the ceramic base material 110 side. When a parallel distance of the lower surface 116 of the base material body and the lower surface 120 of the convex part is P (mm), and a thickness of the flange 142 is S(mm), the following equality is satisfied: 0.15≤P / S≤5.0 and P≥2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a ceramic heater. Background Art

[0002] Conventionally, as a heater for heating a substrate for semiconductor manufacturing equipment, a structure in which a heating holding member made of a ceramic sintered body is integrated with a shaft supporting the same has been proposed.

[0003] Patent Document 1 relates to a joined body of a ceramic member provided with a main body and a disk-shaped projection, and a cylindrical ceramic body, wherein the disk-shaped projection is inserted inside the cylindrical body, the relative density of the disk-shaped projection is higher than the relative density of the cylindrical body, the cylindrical body comprises a straight cylindrical portion having a constant inner diameter not in contact with the disk-shaped projection, an enlarged-diameter portion having the largest inner diameter that is in contact with the disk-shaped projection, and a connecting portion formed between the straight cylindrical portion and the enlarged-diameter portion, and discloses a ceramic composite in which the difference between the inner diameter of the enlarged-diameter portion and the inner diameter of the straight cylindrical portion is 0.05 mm or more and 0.6 mm or less.

[0004] Patent Document 2 is a method for manufacturing a substrate supporting member with a shaft, comprising a step of diffusion-bonding a flange side of a hollow shaft having a flange at least at one end to the center of the lower surface of a disk-shaped substrate supporting member, wherein when D is the outer diameter of the shaft, L is the longitudinal length of the shaft, and S is the cross-sectional area along a plane having the longitudinal direction of the shaft as a normal direction, when L / D ≧ 2 or L / S0.5 ≧ 3, in the diffusion bonding of the substrate supporting member and the shaft, the flange of the shaft is pressed while the flange of the shaft is in contact with the substrate supporting member, and a method for manufacturing a substrate supporting member with a shaft characterized thereby is disclosed. Prior Art Documents Patent Documents

[0005] Patent Document 1 Japanese Unexamined Patent Publication No. 10-053470 Patent Document 2 Japanese Patent Publication No. 2018-30157 [Overview of the project] [Problems that the invention aims to solve]

[0006] When joining a shaft to a ceramic heater, the surface roughness of the joining surface is reduced. In recent years, with the increase in diameter of ceramic heaters, reducing the surface roughness of the entire surface of one of the joining surfaces has become very time-consuming and costly. Therefore, a protrusion for joining the shaft has been provided on one surface of the ceramic substrate, and only the surface roughness of that protrusion has been reduced.

[0007] When a ceramic substrate and a shaft are joined, thermal resistance (a temperature gradient across the joint) appears across the joint surface. Furthermore, when a protrusion is provided to join the shaft, if the thickness of the protrusion is small, the distance between the joint surface and the top surface of the substrate becomes small, and the thermal resistance of the joint surface affects the temperature distribution of the substrate mounting surface on the top surface of the substrate and the substrate placed on it. In addition, heat transfer from the protrusion on the bottom surface of the substrate to the shaft is affected by the thermal resistance at the joint surface, and consequently affects the temperature distribution of the substrate mounting surface and the substrate. Therefore, there has been a need for a ceramic heater with a shape near the joint that minimizes the influence of thermal resistance at the joint surface.

[0008] Through diligent research, the inventors discovered that when the thickness of the protrusion and the thickness of the shaft flange satisfy a predetermined relationship, the influence of thermal resistance on the joint surface becomes less apparent on the substrate mounting surface, thus completing the present invention.

[0009] This invention has been made in view of these circumstances, and aims to provide a ceramic heater that can homogenize the temperature distribution on the substrate mounting surface. [Means for solving the problem]

[0010] (1) In order to achieve the above objective, the ceramic heater of the present invention employs the following means. That is, the ceramic heater of the application example of the present invention is a ceramic heater comprising: a base body formed in the shape of a flat plate by a ceramic sintered body and having a substrate mounting surface on its upper surface; a ceramic substrate having a protrusion that protrudes downward from the lower surface of the base body facing the substrate mounting surface and is integrally formed with the base body; a heating resistor embedded in the base body of the ceramic substrate; and a cylindrical shaft joined to the lower surface of the protrusion facing the substrate mounting surface and having a flange formed on the ceramic substrate side, wherein the parallel distance between the lower surface of the base body and the lower surface of the protrusion is P (mm), and the thickness of the flange is S (mm). The parallel distance between the upper surface of the substrate body and the lower surface of the substrate body is H (mm) In that case, 0. 42 ≤P / S ≤5.0 ,and, P Aug 5. And, P × H ≥ 70 It is characterized by the following:

[0011] Thus, 0. 42 ≤P / S ≤ 5.0 and P ≥ 5 By doing so, the amount of heat flowing from the ceramic substrate to the shaft can be uniformly distributed and transferred towards the lower end of the shaft without being retained at the flange on the shaft end face, and the thermal resistance of the joint surface between the protrusions of the ceramic substrate and the shaft can not be affected on the substrate mounting surface. As a result, the temperature distribution on the substrate mounting surface can be made uniform.

[0012] moreover, Ceramic heater as an example of application of (1) above So When the parallel distance between the upper surface and the lower surface of the substrate body is H (mm), then P × H ≥ 7 It is 0 。

[0013] This allows the bonding surface and the substrate mounting surface to be separated by a certain distance, thereby making the temperature distribution on the substrate mounting surface more uniform.

[0014] ( 2 ) Also, (1) above ofIn the ceramic heater according to the application example, Ra of the side surface of the convex portion and Ra of the side surface of the flange are each 1.0 μm or less, and a step difference between the side surface of the convex portion and the side surface of the flange at a joint surface between the convex portion and the flange is 0.1 mm or less.

[0015] As described above, by setting Ra of the side surface of the convex portion and the side surface of the flange portion to a predetermined value or less and reducing the step difference, occurrence of cracks on the side surface of the convex portion and the side surface of the flange is suppressed even when thermal stress acts in the vicinity of the joint surface, and the risk of damage to the joint surface and airtight leakage can be reduced.

[0016] ( 3 )Further, in the above ([( 2 ) of In the ceramic heater according to the application example, Ra of a region within a distance of 1 mm from the joint surface among the side surface of the convex portion and the side surface of the flange is each 0.3 μm or less.

[0017] As described above, by sufficiently reducing Ra of a predetermined region in the vicinity of the joint surface between the side surface of the convex portion and the side surface of the flange, the risk of damage to the joint surface and airtight leakage can be further reduced, and processing cost can be suppressed.

Effects of the Invention

[0018] According to the present invention, the temperature distribution on the substrate mounting surface can be homogenized.

Brief Description of Drawings

[0019] [Figure 1] It is a cross-sectional view showing an example of a ceramic heater according to an embodiment of the present invention. [Figure 2] It is a partial cross-sectional view of the ceramic heater in FIG. 1. [Figure 3] It is a cross-sectional view showing a modified example of the ceramic heater according to the embodiment. [Figure 4] It is a table showing shape characteristics of examples and comparative examples and measurement results of temperature distribution evaluation tests. [Figure 5]This table shows the measurement results of the airtightness test for the example. [Modes for carrying out the invention]

[0020] Next, embodiments of the present invention will be described with reference to the drawings. To facilitate understanding of the explanation, the same reference numeral is used for identical components in each drawing, and redundant explanations are omitted. Note that the sizes of each component in the configuration diagrams are conceptual representations and do not necessarily represent actual dimensional ratios.

[0021] [Embodiment] [Ceramic heater configuration] First, the configuration of a ceramic heater according to an embodiment of the present invention will be described. Figure 1 is a schematic cross-sectional view showing an example of a ceramic heater according to an embodiment of the present invention. Figure 2 is a partial cross-sectional view of the ceramic heater of Figure 1. The ceramic heater 100 according to this embodiment comprises a ceramic substrate 110, a heating resistor 130, and a shaft 140. The ceramic heater 100 is applicable to heaters with shafts and the like.

[0022] The ceramic substrate 110 has a base body 112 formed in the shape of a flat plate by a ceramic sintered body, and a protrusion 118 that protrudes downward from the lower surface 116 of the base body facing the substrate mounting surface 114 and is integrally formed with the base body 112. Here, "a protrusion integrally formed with the base body" means that the base body 112 and the protrusion 118 are fired integrally during firing and are not joined after firing. The shape of the substrate mounting surface 114 of the ceramic substrate 110 can be various shapes such as circular, polygonal, or elliptical. The diameter of the ceramic substrate 110 is preferably 100 mm or more and 600 mm or less. The material used for the ceramic sintered body is silicon carbide, aluminum oxide, aluminum nitride, silicon nitride, etc.

[0023] H (mm) is the parallel distance between the upper surface of the base material body (the substrate mounting surface 114 of the base material body) and the lower surface 116 of the base material body. H is preferably 5 mm or more, and more preferably 15 mm or more. If H is less than 5 mm, the temperature difference between the area directly above the part where the heating resistor 130 is present and the area directly above the area where the heating resistor 130 is not present will be large, and the arrangement shape of the heating resistor 130 may be clearly reflected in the temperature distribution of the substrate mounting surface 114. Furthermore, H is preferably 50 mm or less, and more preferably 30 mm or less. If H exceeds 50 mm, manufacturing may become difficult. If the upper surface of the base material body is flat except for predetermined structures such as upper surface protrusions, and the lower surface 116 of the base material body is flat except for predetermined structures such as terminal holes, ends, and corners between the lower surface 116 of the base material body and the side surface 122 of the protrusions, H may be the thickness of the base material body 112.

[0024] Let P (mm) be the parallel distance between the lower surface 116 of the base material body and the lower surface 120 of the protrusion. P is 2 mm or more. If P is less than 2 mm, there is a greater risk that the thermal resistance of the bonding surface will affect the temperature distribution of the substrate mounting surface 114 and the substrate placed thereon. P is preferably 20 mm or less, and more preferably 5 mm or less. If the lower surface 116 of the base material body is flat except for certain structures such as terminal holes 152, ends, and corners between the lower surface 116 of the base material body and the side surface 122 of the protrusion, P may be the thickness of the protrusion 118.

[0025] The heat-generating resistor 130 is embedded in the base body 112 of the ceramic substrate 110. The heat-generating resistor 130 can have various shapes, such as mesh or foil. Furthermore, it can be made from various materials, such as molybdenum or tungsten.

[0026] The shaft 140 is made of a cylindrical ceramic sintered body with a flange 142 formed on the side facing the ceramic substrate 110. The side facing the ceramic substrate 110 may or may not have a flange. Preferably, the ceramic sintered body forming the shaft 140 is mainly composed of the same type of ceramic as the ceramic sintered body forming the ceramic substrate 110. In this case, the presence or absence and amount of sintering aid may differ. The shaft 140 is joined to the lower surface 120 of the protrusion facing the substrate mounting surface 114 and supports the ceramic substrate 110.

[0027] Let S (mm) be the thickness of the flange 142. S is preferably 2 mm or more, and more preferably 5 mm or more. If the flange 142 is thinner than 2 mm, the heat capacity of the flange 142 decreases, causing the temperature to rise easily, and this effect may appear on the substrate mounting surface 114. Also, S is preferably 50 mm or less, and more preferably 20 mm or less. If the flange 142 is thicker than 50 mm, the heat transfer from the ceramic substrate 110 to the shaft 140 increases, making it difficult to maintain a high temperature on the substrate mounting surface 114, and potentially worsening the temperature distribution on the substrate mounting surface 114. Furthermore, the increased heat transfer to the shaft 140 necessitates a larger output from the heating resistor 130. As a result, the temperature difference between the area directly above the heating resistor 130 and the area directly above the area without the heating resistor 130 increases, and the arrangement of the heating resistor 130 may become more pronounced in the temperature distribution of the substrate mounting surface 114.

[0028] In the ceramic heater 100 of the present invention, when the parallel distance between the lower surface 116 of the base body and the lower surface 120 of the protrusion is P (mm) and the thickness of the flange 142 is S (mm), the relationship between 0.15 ≤ P / S ≤ 5.0 and P ≥ 2 is met. This allows the amount of heat flowing from the ceramic base material 110 to the shaft 140 to be uniformly dispersed and transferred towards the lower end of the shaft 140 without being retained at the flange 142 on the end face of the shaft 140, and also reduces the influence of the thermal resistance of the joint surface between the protrusion 118 of the ceramic base material 110 and the shaft 140 on the substrate mounting surface 114. As a result, the temperature distribution of the substrate mounting surface 114 can be made uniform. Making the temperature distribution of the substrate mounting surface 114 uniform means that the temperature distribution of the substrate mounting surface 114 is less affected by the arrangement of the heating resistor 130 and its positional relationship with the joint surface. The homogenization of the temperature distribution on the substrate mounting surface 114 can be confirmed by observing the temperature distribution on the substrate mounting surface 114 or the substrate mounted on the substrate mounting surface 114 using an infrared camera in the region near the outer diameter of the protrusion 118 or the flange 142 of the shaft 140.

[0029] When the parallel distance between the upper surface of the base material (the substrate mounting surface 114 of the base material) and the lower surface 116 of the base material is H (mm), it is preferable that P × H ≥ 50. This allows the bonding surface and the substrate mounting surface 114 to be separated by a certain amount or more, and the temperature distribution of the substrate mounting surface 114 can be made more uniform. It is also preferable that P × H ≤ 1000.

[0030] Preferably, the Ra of the side surface 122 of the protrusion and the side surface 144 of the flange are 1.0 μm or less, and the step difference between the side surface 122 of the protrusion and the side surface 144 of the flange at the joint surface between the protrusion 118 and the flange 142 is 0.1 mm or less. This suppresses the occurrence of cracks in the side surface 122 of the protrusion and the side surface 144 of the flange even when thermal stress acts near the joint surface, and reduces the risk of damage to the joint surface and airtight leaks. More preferably, the step difference between the side surface 122 of the protrusion and the side surface 144 of the flange at the joint surface between the protrusion 118 and the flange 142 is 100 μm or less, and even more preferably 1 μm or less. The step difference between the side surface 122 of the protrusion and the side surface 144 of the flange can be reduced to a range of 100 μm or less using an alignment jig when the side surface 122 of the protrusion and the side surface 144 of the flange are joined after processing, and to a range of 1 μm or less when the surfaces are made flush after joining. The Ra of the side surface 122 of the protrusion and the side surface 144 of the flange, and the step difference between the side surface 122 of the protrusion and the side surface 144 of the flange at the joint surface, shall be measured in a cross-section including the central axis of the ceramic substrate 110 or the central axis of the shaft 140.

[0031] The Ra of the protrusion side 122 and the flange side 144 in the region within 1 mm of the joint surface is preferably 0.01 μm or more and 0.3 μm or less, and more preferably 0.1 μm or less. This further reduces the risk of damage to the joint surface and airtight leaks, and also reduces processing costs. This is because when processing to reduce Ra to a value smaller than a predetermined value, the larger the area to be processed, the higher the cost. On the other hand, the area closer to the joint surface has a greater risk of cracks, etc., so by making the Ra of this area smaller, the risk of damage and airtight leaks can be further reduced. Furthermore, since the thickness of both the protrusion 118 and the flange 142 of the ceramic heater 100 of the present invention is 2 mm or more, whether the polishing of the protrusion side 122 or the flange side 144 is performed before or after joining, the polishing of the region within 1 mm of the joint surface can be easily performed.

[0032] The ceramic heater 100 may be equipped with electrodes other than the heating resistors 130. For example, by providing electrostatic adsorption electrodes in addition to the heating resistors 130, the ceramic heater 100 can be used as a heater-equipped electrostatic chuck.

[0033] The ceramic heater 100 is equipped with terminals 150 and terminal holes 152, which are necessary in addition to the above. This allows power to be supplied to the heating resistor 130.

[0034] Figure 3 is a schematic cross-sectional view showing a modified example of the ceramic heater according to this embodiment. As shown in Figure 3, in the ceramic heater 100, it is preferable that the cross-sections of the lower surface 116 of the base body and the side surface 122 of the protrusion of the ceramic base 110 are formed as continuous curves in a cross-section including the central axis of the ceramic base 110. This relieves the stress generated at the corner of the boundary between the base body 112 and the protrusion 118 due to the thermal resistance of the joint surface between the protrusion 118 of the ceramic base 110 and the shaft 140. As a result, the risk of corner breakage and the risk of airtightness failure can be reduced. Even when the cross-sections of the lower surface 116 of the base body and the side surface 122 of the protrusion of the ceramic base 110 are formed as continuous curves, it is preferable that the area within 1 mm of the joint surface of the protrusion 118 is formed as a vertically extending surface.

[0035] The statement that the cross-sections of the lower surface 116 of the base material and the side surface 122 of the protrusion are formed as continuous curves means that there are no singularities in the middle of the cross-sectional curve from the lower surface 116 of the base material to the side surface 122 of the protrusion. In this specification, a singularity refers to a corner or edge in the cross-section including the central axis of the ceramic base material 110 that corresponds to R0.5 (mm) or less or C0.5 (mm) or less. This is because stress and heat flow tend to concentrate in such corners or edges, making them prone to becoming the starting point for damage such as cracks. Furthermore, this effect becomes more pronounced when used in processes at higher temperatures than conventional methods.

[0036] Furthermore, the fact that the cross-sections of the lower surface 116 of the base material body and the side surface 122 of the protrusion are formed by a continuous curve means, in other words, that the lower surface 116 of the base material body and the side surface 122 of the protrusion are smoothly connected. The continuous curve may include straight lines. Preferably, the continuous curve does not include corners or edges corresponding to R3 (mm) or less or C3 (mm) or less.

[0037] [Manufacturing method for ceramic heaters] Next, a method for manufacturing the ceramic heater according to this embodiment will be described. The ceramic heater according to the embodiment of the present invention is manufactured, for example, by the molded body hot pressing method described below. However, the manufacturing method is not limited to this method, and may be, for example, a powder hot pressing method or the conventional green sheet lamination method. The powder hot pressing method is a method in which ceramic raw material powder and predetermined heating resistors and electrodes are alternately stacked to embed the heating resistors and electrodes inside the ceramic, and then fired using a uniaxial hot pressing method.

[0038] A method for manufacturing a ceramic heater according to an embodiment of the present invention by a molded body hot press method comprises a ceramic molded body formation step, a ceramic degreased body preparation step, a ceramic substrate precursor formation step, a ceramic substrate firing step, a shaft molded body formation step, a shaft degreased body preparation step, a shaft firing step, a surface processing step, and a joining step.

[0039] In the ceramic molded body formation process, for example, multiple ceramic molded bodies are formed from a first ceramic raw material powder, which is mainly composed of AlN and has component Y added as a sintering aid. For example, additives such as Y2O3 as the sintering aid component Y, a binder, a plasticizer, and a dispersant can be appropriately added to the ceramic raw material powder and mixed to prepare a slurry. After granulation of the granules (first ceramic raw material powder) by a spray-drying method or the like, multiple ceramic molded bodies can be formed by pressure molding. In addition to aluminum nitride, other ceramic powders that can be used as raw materials include, for example, silicon carbide, aluminum oxide, and silicon nitride.

[0040] The ceramic raw material powder is preferably of high purity, preferably 96% or higher, and more preferably 98% or higher. Furthermore, the average particle size of the ceramic raw material powder is preferably between 0.1 μm and 1.0 μm.

[0041] The mixing method may be either wet or dry, and mixers such as ball mills and vibratory mills can be used. As for the molding method, known methods such as uniaxial pressure molding or cold isostatic pressing (CIP) can be used. It should be noted that the method for forming the ceramic molded body is not limited to pressure molding; for example, green sheet lamination or casting can also be applied, and the ceramic molded body can be manufactured by appropriately degreasing or further calcining the materials.

[0042] The ceramic molded body may be shaped by machining after molding. Additionally, a groove shaped to match the shape of the heating resistor may be formed on one side of the ceramic molded body (the bonding surface with other ceramic molded bodies). Machining may be performed after degreasing.

[0043] In the ceramic degreased body manufacturing process, multiple ceramic molded bodies are degreased at a predetermined temperature and for a predetermined time to produce multiple ceramic degreased bodies.

[0044] The ceramic molded body is heat-treated, for example, at a temperature of 500°C to 900°C to become a degreased ceramic body. The degreasing time is preferably 1 hour to 120 hours. An air furnace or a nitrogen atmosphere furnace can be used for degreasing, but an air furnace is preferred because it is important to remove the organic components of the binder.

[0045] In the ceramic substrate precursor formation process, a heat-generating resistor is prepared, and the heat-generating resistor and multiple degreased ceramic bodies are combined to form a ceramic substrate precursor that has a substrate mounting surface on its upper surface, is formed in a flat plate shape, and has the heat-generating resistor embedded in it. The protrusions may be roughly formed at this stage, or they may be formed after firing by grinding, polishing, etc.

[0046] The heating resistor is prepared in a shape that matches the design of the ceramic heater. The heating resistor can be in various shapes, such as mesh or foil. Furthermore, it can be made from various materials, such as molybdenum or tungsten.

[0047] In the ceramic substrate firing process, the formed ceramic substrate precursor is fired by uniaxial pressure firing perpendicular to the substrate mounting surface. The firing conditions vary depending on the material, but when using ceramics mainly composed of AlN, the pressing force is preferably 1 MPa or more. The firing temperature is preferably 1700°C to 2000°C. The firing time is preferably 1 hour to 12 hours, and more preferably 1 hour to 5 hours. The firing atmosphere is, for example, a nitrogen or inert gas atmosphere, but it may also be an atmosphere such as vacuum. As a result, multiple degreased ceramic bodies are sintered to form a ceramic sintered body, which is then integrated to obtain a ceramic substrate in which a heat-retaining resistor is embedded.

[0048] In the shaft molding process, for example, a second ceramic raw material powder is formed from which a shaft molded body is formed from a second ceramic raw material powder that mainly consists of AlN and has component Y added as a sintering aid, or without any sintering aid added. The method for producing the second ceramic raw material powder and the method for molding the shaft molded body may be the same as in the ceramic molded body formation process. It is preferable that the second ceramic raw material powder does not contain a sintering aid.

[0049] In the degreasing shaft preparation process, the shaft molded body is degreased at a predetermined temperature and for a predetermined time to produce the degreasing shaft. The numerical range of the degreasing conditions for the shaft molded body may be the same as in the degreasing ceramic body preparation process. The degreasing shaft preparation process may be performed simultaneously with the degreasing ceramic body preparation process.

[0050] In the shaft firing process, the degreased shaft is fired to fire the shaft that supports the ceramic substrate. The firing conditions vary depending on the material, but when using ceramics mainly composed of AlN, it is preferable to fire the shaft at atmospheric pressure. The firing temperature is preferably between 1800°C and 2000°C. The firing time is preferably between 1 hour and 12 hours. The firing atmosphere is, for example, a nitrogen or inert gas atmosphere, but it may also be an atmosphere such as a vacuum.

[0051] In the surface finishing process, the surface roughness Ra of the sides of the convex portion of the ceramic substrate and the sides of the flange of the shaft are polished to a predetermined value or less. The surface finishing process may be performed after the joining process between the ceramic substrate and the shaft.

[0052] In the joining process, the ceramic substrate and the shaft are joined together. The joining can be performed using either a joining method with a joining material or a joining method without a joining material.

[0053] First, a joining method using a bonding material will be described. First, prepare the bonding material and apply it to at least one of the joining portion on the lower surface of the protrusion of the ceramic substrate to which the shaft will be joined, or to the end face of the shaft on the joining portion side. The joining portion and the end face of the shaft on the joining portion side should preferably have a surface roughness Ra of 1.6 μm or less, and more preferably be polished to 0.4 μm or less. The thickness of the bonding material to be applied should preferably be between 5 μm and 30 μm.

[0054] Next, the shaft is placed at the joint and heated while applying pressure perpendicular to the substrate mounting surface. The joining conditions vary depending on the material, but when using ceramics mainly composed of AlN, the applied pressure is preferably 5 kPa or more. The heating temperature is preferably 1500°C to 1800°C. The heating time is preferably 0.5 hours to 5 hours. The heating atmosphere is, for example, a nitrogen or inert gas atmosphere, but it may also be an atmosphere such as a vacuum. This allows the ceramic substrate and the shaft to be joined.

[0055] The bonding material can be anything that can bond the ceramic substrate and the shaft. For example, if the ceramic substrate and shaft are formed from ceramics mainly composed of AlN, the bonding material may be a paste of mixed powder containing at least Y2O3 powder in addition to AlN powder, which has the same main component. Alternatively, the bonding material may be a paste containing 90 wt% to 95 wt% AlN, 5 wt% or more Y2O3, and containing CaO, MgO, ZrO2, or SiO2 as needed to adjust the temperature at which it becomes a melt during bonding.

[0056] Next, a joining method that does not use a bonding material will be described. The shaft is placed in the joint on the lower surface of the protrusion of the ceramic substrate. The joint and the end face of the shaft on the joint side are preferably polished to a surface roughness Ra of 0.1 μm or less. Next, the substrate is heated while applying pressure perpendicular to the substrate mounting surface. The joining conditions vary depending on the material, but when using ceramics mainly composed of AlN, the applied pressure is preferably 1 MPa or more. The heating temperature is preferably 1600°C to 2000°C. The heating time is preferably 0.5 hours to 6 hours. The heating atmosphere is, for example, a nitrogen or inert gas atmosphere, but it may also be an atmosphere such as a vacuum. This allows the ceramic substrate and the shaft to be joined.

[0057] After firing, the ceramic substrate is given the necessary terminal holes. The terminal holes may be drilled before or after joining with the shaft. Then, the terminals are connected to the terminal holes with brazing material. The terminals can be made of nickel, etc. The brazing material can be made of gold, etc.

[0058] Furthermore, a ceramic calcined body manufacturing step may be included between the ceramic degreased body manufacturing step and the ceramic substrate precursor formation step. When a ceramic calcined body manufacturing step is included, the ceramic degreased body is calcined at a predetermined temperature to produce a ceramic calcined body. This allows for higher dimensional accuracy of the ceramic heater. The calcination conditions vary depending on the material, but when using ceramics mainly composed of AlN, the calcination temperature is preferably 1200°C to 1700°C. The calcination time is preferably 0.5 hours to 12 hours. The calcination atmosphere is preferably a nitrogen or inert gas atmosphere, but an atmosphere such as vacuum may also be used. When a calcined body manufacturing step is included, machining may be performed after the calcined body manufacturing step.

[0059] Furthermore, after the surface processing step, a finishing step may be provided in which the sides of the protrusions near the joint and the sides of the flange are machined to be flush with the surface.

[0060] In this way, it is possible to manufacture ceramic heaters that can homogenize the temperature distribution on the substrate mounting surface.

[0061] [Examples and Comparative Examples] (Example 1) A ceramic raw material powder mainly composed of AlN with 5 wt% Y2O3 added was prepared. Using this, ceramic molded bodies with a diameter of 300 mm and a thickness of 20 mm, and ceramic molded bodies with a diameter of 300 mm and a thickness of 35 mm were formed by CIP molding. A groove (φ292 mm, depth 0.12 mm) for embedding a heat-generating resistor was formed on one surface of the ceramic molded body with a diameter of 300 mm and a thickness of 35 mm.

[0062] Next, two degreased ceramic bodies were prepared by degreasing two ceramic molded bodies at 550°C for 12 hours. Then, as a heat-generating resistor, a molybdenum mesh (wire diameter 0.1 mm, mesh size #50) with an outer diameter of 290 mm was cut to a predetermined shape and prepared. The heat-generating resistor was then placed in the groove formed in the degreased ceramic body and sandwiched with the other degreased ceramic body to prepare a ceramic substrate precursor.

[0063] Next, the ceramic substrate precursor was fired using a single-axis hot press at 1800°C for 5 hours while applying a force of 6 MPa perpendicular to the mounting surface. In this way, the ceramic heater body was fired. The size of the fired ceramic substrate was approximately 300 mm in diameter and 33 mm in thickness. The fired ceramic substrate was processed before bonding. The diameter of the substrate body was set to 300 mm, the thickness of the substrate body (parallel distance H between the top and bottom surfaces of the substrate body) to 25 mm, and the heating resistor was processed to a depth of 10 mm from the top surface of the substrate body. In addition, a protrusion of a predetermined thickness was formed on the bottom surface of the ceramic substrate. On the substrate mounting surface, protrusions with a diameter of φ2 mm and a height of 100 μm were formed in a pattern of repeating equilateral triangle vertices at 12 mm intervals. Terminal holes for electrical connection between the heating resistor and the terminals were also processed to reach the embedded heating resistor.

[0064] The size of the protrusion was set to have a diameter of 70 mm on the lower surface of the protrusion and a thickness of 5 mm (parallel distance P between the lower surface of the base body and the lower surface of the protrusion). The shape of the protrusion was such that the space between the lower surface of the ceramic base body and the side surface of the protrusion had a radius of R1 mm. The surface roughness Ra of the side surface of the protrusion was set to 1 μm. The surface roughness Ra of the joint between the lower surface of the protrusion and the shaft was set to 0.1 μm or less.

[0065] Separately, using ceramic raw material powder mainly composed of AlN without added sintering aids, a ceramic molded body was formed using CIP (Cleaning-In-Place) molding so that the shape after firing would be a hollow cylindrical shape with an outer diameter of 55 mm, an inner diameter of 45 mm, a length of 150 mm, an outer diameter of 70 mm for the flange, a flange thickness of S12 mm, an outer diameter of 70 mm for the lower flange, and a lower flange thickness of 15 mm. This was degreased at 550°C for 12 hours to produce a degreased ceramic body. The degreased ceramic body was fired at 1900°C for 5 hours under atmospheric pressure to fire the shaft. The surface roughness Ra of the side surface of the flange was set to 1 μm. The surface roughness Ra of the end surface of the flange was set to 0.1 μm or less.

[0066] Then, a shaft was placed at the joint of the ceramic substrate, and the joint was bonded by heating at 1800°C for 1 hour while applying a force of 1 MPa perpendicular to the mounting surface. As a finishing process, the area near the joint, including the convex portion and the area within 1 mm of the joint of the flange, was machined to be flush, and the surface roughness Ra of this area was set to 0.4 μm. In addition, the other external shapes were machined to the predetermined shape. Finally, a φ5 mm, 200 mm long Ni rod was brazed with Au solder at 1000°C in a vacuum. In this way, the ceramic heater of Example 1 was fabricated.

[0067] (Example 2) In Example 2, the ceramic heater was fabricated under the same conditions as in Example 1, except that the thickness of the protrusions on the ceramic substrate was set to 2 mm.

[0068] (Example 3) In Example 3, the thickness of the ceramic molded body was set to 20 mm and 60 mm. The ceramic heater of Example 3 was manufactured under the same conditions as in Example 1, except that the thickness of the protrusion on the ceramic base material was set to 20 mm and the thickness of the shaft flange was set to 15 mm.

[0069] (Example 4) In Example 4, the thickness of the ceramic molded body was set to 10 mm and 20 mm. The ceramic heater of Example 4 was manufactured under the same conditions as in Example 1, except that the thickness of the main body of the ceramic substrate was set to 8 mm, the thickness of the protrusion was set to 5 mm, the heating resistor was processed to a depth of 4 mm from the top surface of the main body of the substrate, and the thickness of the shaft flange was set to 10 mm.

[0070] (Example 5) In Example 5, the thickness of the ceramic molded body was set to 20 mm and 20 mm. The ceramic heater of Example 5 was manufactured under the same conditions as Example 1, except that the thickness of the main body of the ceramic substrate was set to 14 mm and the thickness of the protrusion was set to 2 mm, the heating resistor was processed to a depth of 7 mm from the top surface of the main body of the substrate, and the thickness of the shaft flange was set to 5 mm.

[0071] (Example 6) In Example 6, the thickness of the ceramic molded body was set to 20 mm and 25 mm. The ceramic heater of Example 6 was manufactured under the same conditions as in Example 1, except that the thickness of the main body of the ceramic substrate was set to 14 mm and the heating resistor was processed to a depth of 7 mm from the top surface of the main body of the substrate.

[0072] (Example 7) In Example 7, the thickness of the ceramic molded body was set to 20 mm and 25 mm. The ceramic heater of Example 7 was manufactured under the same conditions as in Example 1, except that the thickness of the main body of the ceramic substrate was set to 20 mm and the thickness of the protrusions was set to 2 mm.

[0073] (Example 8) In Example 8, the thickness of the ceramic molded body was set to 20 mm and 50 mm. The ceramic heater of Example 8 was manufactured under the same conditions as in Example 1, except that the thickness of the main body of the ceramic substrate was 35 mm and the thickness of the protrusion was 2 mm.

[0074] (Example 9) In Example 9, the thickness of the ceramic molded body was set to 20 mm and 60 mm. The ceramic heater of Example 9 was manufactured under the same conditions as in Example 1, except that the thickness of the ceramic substrate body was 35 mm, the thickness of the protrusion was 10 mm, and the thickness of the shaft flange was 20 mm.

[0075] (Example 10) In Example 10, the thickness of the ceramic molded body was set to 20 mm and 60 mm. The ceramic heater of Example 10 was manufactured under the same conditions as in Example 1, except that the thickness of the ceramic substrate body was 35 mm, the thickness of the protrusion was 10 mm, and the thickness of the shaft flange was 2 mm.

[0076] (Example 11) In Example 11, the thickness of the ceramic molded body was set to 20 mm and 70 mm. The ceramic heater of Example 11 was manufactured under the same conditions as in Example 1, except that the thickness of the ceramic substrate body was 25 mm, the thickness of the protrusion was 25 mm, and the thickness of the shaft flange was 5 mm.

[0077] (Example 12) In Example 12, the ceramic heater was manufactured under the same conditions as in Example 1, except that the surface roughness Ra of the area near the joint was set to 0.1 μm during the flush machining process.

[0078] (Example 13) In Example 13, the ceramic heater was manufactured under the same conditions as in Example 5, except that the surface roughness Ra of the area near the joint was set to 0.1 μm during the flush machining process.

[0079] (Example 14) In Example 14, the ceramic heater was manufactured under the same conditions as in Example 8, except that the surface roughness Ra of the area near the joint was set to 0.1 μm during the flush machining process.

[0080] (Comparative Example 1) In Comparative Example 1, the thickness of the ceramic molded body was set to 10 mm and 10 mm. The ceramic heater of Comparative Example 1 was manufactured under the same conditions as in Example 1, except that the thickness of the main body of the ceramic substrate was set to 8 mm and the thickness of the protrusion was set to 1 mm, the heating resistor was processed to a depth of 4 mm from the top surface of the main body of the substrate, and the thickness of the shaft flange was set to 10 mm.

[0081] (Comparative Example 2) Comparative Example 2 used ceramic molded bodies with thicknesses of 20 mm and 20 mm. The ceramic heater of Comparative Example 2 was manufactured under the same conditions as in Example 1, except that the thickness of the ceramic substrate body was 14 mm, the thickness of the protrusion was 1 mm, and the heating resistor was processed to a depth of 7 mm from the top surface of the substrate body.

[0082] (Comparative Example 3) Comparative Example 3 was manufactured under the same conditions as Example 1, except that the thickness of the protrusions on the ceramic substrate was set to 1 mm.

[0083] (Comparative Example 4) Comparative Example 4 used ceramic molded bodies with thicknesses of 20 mm and 25 mm. The ceramic heater of Comparative Example 4 was fabricated under the same conditions as in Example 1, except that the thickness of the ceramic substrate body was 20 mm and the thickness of the protrusions was 1 mm.

[0084] (Comparative Example 5) Comparative Example 5 used ceramic molded bodies with thicknesses of 20 mm and 50 mm. The ceramic heater of Comparative Example 1 was fabricated under the same conditions as in Example 1, except that the thickness of the ceramic substrate body was 35 mm and the thickness of the protrusions was 1 mm.

[0085] (Comparative Example 6) Comparative Example 6 used ceramic molded bodies with thicknesses of 20 mm and 30 mm. The ceramic heater of Comparative Example 6 was manufactured under the same conditions as in Example 1, except that the thickness of the ceramic substrate body was 25 mm, the thickness of the protrusion was 2 mm, and the thickness of the shaft flange was 20 mm.

[0086] (Comparative Example 7) Comparative Example 7 used ceramic molded bodies with thicknesses of 20 mm and 25 mm. The ceramic heater of Comparative Example 6 was manufactured under the same conditions as in Example 1, except that the thickness of the ceramic substrate body was 14 mm, the thickness of the protrusion was 6 mm, the heating resistor was processed to a depth of 7 mm from the top surface of the substrate body, and the thickness of the shaft flange was 1 mm.

[0087] (Temperature distribution evaluation test) The ceramic heaters of Examples 1 to 11 and Comparative Examples 1 to 7 were each installed in a process chamber, and an external power supply was connected to the heating resistor. A blackbody silicon substrate for temperature measurement was then placed on the substrate mounting surface, and the external power supply was controlled so that the average temperature within φ290 mm of the substrate was 500°C. An IR camera was used to measure the temperature difference between the highest and lowest temperatures of the substrate in the convex portion and the area within the outer diameter of the shaft flange + 10 mm (a φ80 mm area).

[0088] Figure 4 is a table showing the shape characteristics of the examples and comparative examples, as well as the measurement results of the temperature distribution evaluation test. As shown in the table in Figure 4, the comparative examples all had a temperature difference of 3.0°C or more, while the examples all had a temperature difference of 2.9°C or less, confirming that the effect of thermal resistance at the joint between the ceramic substrate and the shaft was less apparent on the substrate mounting surface.

[0089] Furthermore, in Examples 1, 3, 6, and 8-11, where the P×H value was 50 or higher, the temperature difference was 2.5°C or less, confirming that the effect of thermal resistance at the junction was less apparent on the substrate mounting surface compared to the other examples.

[0090] (Thermal cycle test) The ceramic heaters from Examples 1, 5, 8, and 12-14 were installed in a process chamber, and an external power supply was connected to the heating resistor. A blackbody silicon substrate for temperature measurement was then placed on the substrate mounting surface, and a thermal cycle was repeated 50 times in which the average temperature within a φ290 mm area of ​​the substrate changed from 200°C to 600°C to 200°C.

[0091] (Airtightness test) Airtightness tests were performed on each ceramic heater before and after the thermal cycling test. First, the lower flange of the shaft was connected to a helium leak detector, and the inside of the shaft was vented. Then, He gas was blown from the outside of the joint surface between the substrate and the shaft, and the amount of He leak from the joint was measured.

[0092] Figure 5 is a table showing the measurement results of the airtightness test for the examples. As shown in the table in Figure 5, Examples 1, 5, and 8, in which the surface roughness Ra of the side surface of the protrusion near the joint surface and the side surface of the flange was reduced, had a He leak of 10 before the thermal cycling test. -9 Pa·m 3 The rate was in the / s range, but the He leak after the thermal cycling test was 10 -8 Pa·m 3 It had increased to the 1 / s range. In contrast, in Examples 12-14, in which the surface roughness Ra of the side surface of the protrusion near the joint surface and the side surface of the flange was further reduced, the He leak before and after the thermal cycling test was 10 -9 Pa·m 3 It was in the / s range.

[0093] This confirmed that by making the surface roughness Ra of the protrusions near the joint surface and the flange surface 0.3 μm or less, the airtightness of the joint surface can be further improved, resulting in improved durability. Note that in Examples 1, 5, and 8, the He leak after the thermal cycling test was 10 -8 Pa·m 3 Although the leakage rate was in the / s range, this level of helium leakage is not a problem for use with ceramic heaters.

[0094] Based on the above, it has been confirmed that the ceramic heater of the present invention is a ceramic heater that can homogenize the temperature distribution on the substrate mounting surface.

[0095] The present invention is not limited to the embodiments described above, and it goes without saying that it extends to various modifications and equivalents that fall within the spirit and scope of the present invention. Furthermore, the structure, shape, number, position, size, etc., of the components shown in each drawing are for illustrative purposes only and may be modified as appropriate. [Explanation of symbols]

[0096] 100 Ceramic Heaters 110 Ceramic substrate 112 Base material body 114 Substrate mounting surface 116 Lower surface of the base material 118 Convex part 120 Lower surface of the protrusion 122 Side view of the protrusion 130 Heat-generating resistor 140 shaft 142 Flange 144 Side of the flange 150 terminals

Claims

1. It is a ceramic heater, A base material having a substrate mounting surface on its upper surface and formed in a flat plate shape from a ceramic sintered body, and a ceramic substrate having a protrusion that protrudes downward from the lower surface of the base material body facing the substrate mounting surface and is integrally formed with the base material body, A heating resistor embedded in the main body of the ceramic substrate, The system comprises a cylindrical shaft which is joined to the lower surface of the protrusion facing the substrate mounting surface and has a flange formed on the ceramic substrate side, When the parallel distance between the lower surface of the base material body and the lower surface of the protrusion is P (mm), the thickness of the flange is S (mm), and the parallel distance between the upper surface of the base material body and the lower surface of the base material body is H (mm), 0.42 ≤ P / S ≤ 5.0, and P ≥ 5, and P × H ≥ 70 A ceramic heater characterized by the following:

2. The ceramic heater according to Claim 1, characterized in that the Ra of the side surface of the protrusion and the side surface of the flange are each 1.0 μm or less, and the step difference between the side surface of the protrusion and the side surface of the flange at the joint surface between the protrusion and the flange is 0.1 mm or less.

3. The ceramic heater according to claim 2, characterized in that the Ra of the side surface of the protrusion and the side surface of the flange, in a region within 1 mm of the distance from the joining surface, is 0.3 μm or less.

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