Ceramic heaters, and ceramic heaters with shafts

Abstract

To provide a ceramic heater capable of preventing the resistance of an electrode for an inner heater from becoming too low than the resistance of an electrode for an outer heater, and thereby capable of equalizing the temperature distribution on a mounting surface.SOLUTION: A ceramic heater 100 includes: a disc-like substrate 110 having a mounting surface 112, and comprising a ceramic sintered body containing AlN as a main component and a total of 0.1 wt.% or more and 10 wt.% or less of a grain boundary composition that contains yttrium, or other rare earth compound or alkaline earth metal compound; an electrode 120 for a heater embedded in the substrate and including Mo meshes divided into a plurality of areas; and a planar electrode 130 embedded in the substrate and having an area that is 40% or more of an area of the mounting surface in a shape seen through from a mounting surface side. At least an electrode 122 for an inner heater, of the electrode for the heater, located at the innermost position of the substrate in a radial direction contains Mo2C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a ceramic heater and a ceramic heater with a shaft.

Background Art

[0002] A ceramic heater in which heater electrodes are embedded in a ceramic sintered body has been proposed as a member for a semiconductor manufacturing apparatus.

[0003] Patent Document 1 discloses a method for manufacturing a ceramic heater in which a heater electrode layer is formed on a substrate made of a sintered body of aluminum nitride. In this method, a conductive paste containing tungsten monocarbide particles is used to form a heater electrode layer on a green sheet made of aluminum nitride. Then, after performing a heat treatment step of heating the green sheet in a non-oxidizing atmosphere at a temperature range lower than that during the main firing, a main firing step of completely sintering the green sheet is performed.

[0004] Patent Document 2 discloses a method for manufacturing a ceramic sintered body, which includes a film forming step of forming a metal film made of a metal material having a standard formation free energy of metal carbide smaller than that of the heat-resistant metal material on the surface of the heat-resistant metal material, a molding step of disposing the heat-resistant metal material on which the film is formed in a predetermined position in powder that is a raw material of the ceramic substrate, and pressing and molding to form a ceramic molded body, and a sintering step of sintering the ceramic molded body formed in the molding step to produce a ceramic sintered body.

[0005] Patent Document 3 discloses a method for manufacturing a ceramic heater, which includes a step of producing a molded body by embedding a heating element and a metal member surrounding the heating element in ceramic raw material powder that is a raw material of the ceramic substrate so that raw material powder having the same main component as the ceramic raw material powder is interposed between them, and a step of producing a ceramic substrate and a reaction layer by sintering the molded body so that the metal member preferentially carbonizes or oxidizes with respect to the heating element.

[0006] Patent Document 4 discloses a method for manufacturing a ceramic heater comprising a ceramic sintered body and a resistance heating element provided in contact with the ceramic sintered body, wherein a dummy member made of a metal containing one or more metallic elements selected from groups 4a, 5a, and 6a of the periodic table is brought into contact with a molded body of ceramic powder, and the molded body is then sintered to obtain the ceramic sintered body.

[0007] Patent Document 5 discloses a ceramic heater in which a heater electrode is embedded in a substrate containing AlN ceramics, wherein the heater electrode contains Mo and C, and the ratio of the number of C atoms to the sum of the number of Mo atoms and the number of C atoms is 0.20 or more. Furthermore, the substrate contains a Y component, and YAG is formed around the heater electrode in the substrate, and in the X-ray diffraction chart of the substrate around the heater electrode, when the peak intensity of YAG at a position of 2θ = 54.978° is A and the peak intensity of AlN at a position of 2θ = 36.041° is B, the relationship (A / B) ≥ 0.11 is disclosed. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2000-012194 [Patent Document 2] Japanese Patent Publication No. 2012-096948 [Patent Document 3] Japanese Patent Publication No. 2009-295960 [Patent Document 4] Japanese Patent Publication No. 2003-288975 [Patent Document 5] Japanese Patent Publication No. 2021-157948 [Overview of the project] [Problems that the invention aims to solve]

[0009] Mo electrodes embedded in AlN ceramics partially become Mo2C during co-firing. Since Mo and Mo2C have different volume resistivity (specific resistivity), the resistance value of the electrode differs depending on the degree of Mo2C conversion. In particular, ceramic heaters with planar electrodes and heater electrodes divided into multiple regions embedded may have areas where the heater resistance value is obtained as designed and areas where it is not, depending on the position of the heater electrodes, which can cause functional problems such as excessive current or insufficient power. Therefore, there has been a need for a ceramic heater that can adjust the difference in composition (degree of Mo2C conversion) between the inner and outer heater electrodes and reduce the difference in volume resistivity, thereby enabling the resistance values ​​of the inner and outer heater electrodes to be obtained as designed.

[0010] The ceramic heater manufacturing methods described in Patent Documents 1 to 4 attempted to reduce the volume resistivity (increase the electrical conductivity) of the heater electrodes by suppressing the carbonization of heating elements such as W and Mo embedded in AlN ceramics, thereby suppressing variations in volume resistivity. However, these methods resulted in variations in volume resistivity due to partial reductions in the volume resistivity of the heater electrodes, leading to an uneven temperature distribution on the mounting surface.

[0011] Furthermore, while the technology described in Patent Document 5 stabilizes the volume resistivity of the heating element (for heaters) and improves the uniformity of the heating temperature, the conditions that need to be controlled for this purpose are severe, and the manufacturing method is complex. In addition, neither of the patent documents focuses on the difference in the degree of carbonization depending on the position of the heater electrodes in ceramic heaters in which planar electrodes and heater electrodes divided into multiple regions are embedded.

[0012] In other words, the present invention has been made in view of these circumstances, and aims to provide a ceramic heater that can suppress the resistance of the inner heater electrode from becoming too low compared to the resistance of the outer heater electrode by adjusting the difference in composition (degree of Mo2C conversion) between the inner heater electrode and the outer heater electrode and reducing the difference in volume resistivity, thereby enabling a more uniform temperature distribution on the mounting surface. [Means for solving the problem]

[0013] above 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 disc-shaped base material having a mounting surface and made of a ceramic sintered body having a mounting surface and containing a grain boundary composition mainly composed of AlN and containing yttrium or other rare earth compounds or alkaline earth metal compounds in total amount of 0.1 wt% to 10 wt%; a heater electrode embedded in the base material and containing a Mo mesh divided into a plurality of regions; and a planar electrode embedded in the base material, having a shape when viewed from the mounting surface side and having an area of ​​40% or more of the area of ​​the mounting surface, wherein the heater electrode teeth, The inner heater electrode located at the radially innermost part of the substrate. , and having an outer heater electrode located on the outermost part of the substrate and in a different position in the vertical direction from the inner heater electrode, the inner heater electrode It contains Mo2C. The planar electrode is an electrostatic adsorption electrode or a high-frequency electrode, and a connecting electrode that supplies power to the heater electrode, and the inner heater electrode is sandwiched at least in part between the electrostatic adsorption electrode or the high-frequency electrode and the connecting electrode in a cross section perpendicular to the aforementioned mounting surface. It is characterized by the following.

[0014] When there is a large, planar electrode, the inner heater electrode is less prone to carbide formation than the outer heater electrode. However, by including a predetermined amount of grain boundary composition and configuring the inner heater electrode to contain Mo2C, it is possible to prevent the resistance of the inner heater electrode from becoming too low compared to the resistance of the outer heater electrode, thereby equalizing the temperature distribution on the mounting surface.

[0015] above Note SeIn a laminar heater, in a portion of the inner heater electrode that overlaps the planar electrode in a plan view, the ratio of the cross-sectional area of the region that has been Mo2C-ized to the cross-sectional area of the inner heater electrode in a cross-section perpendicular to the placement surface is 10% or more It's okay to have it. .

[0016] The inner heater electrode in the portion overlapping the planar electrode becomes less likely to be carbide-ized. However, by adjusting so that the cross-sectional area of the region that has been Mo2C-ized with respect to the cross-sectional area of the inner heater electrode in this portion is 10% or more, it is possible to sufficiently suppress the resistance of this portion of the inner heater electrode from becoming too low, and the output of the inner heater electrode can be set to a predetermined value.

[0017] above Note Se In a laminar heater, the planar electrode is an electrostatic adsorption electrode or a high-frequency electrode, and a connection electrode for supplying power to the heater electrode It's okay to have it, The inner heater electrode is sandwiched between at least a part of the electrostatic adsorption electrode or the high-frequency electrode and the connection electrode in a cross-section perpendicular to the placement surface It's okay .

[0018] When the inner heater electrode is sandwiched between planar electrodes, the inner heater electrode becomes very difficult to be carbide-ized. However, the ceramic heater of the present invention can be adjusted so that Mo2C is also included in the inner heater electrode that is difficult to be carbide-ized. Therefore, even in a ceramic heater having such a structure, it is possible to suppress the resistance of the inner heater electrode from becoming too low, and the temperature distribution on the placement surface can be made uniform.

[0019] above Note Se In a laminar heater, the width of the inner heater electrode is smaller than the width of the outer heater electrode located outermost on the base material No need .

[0020] In this way, by making the width of the inner heater electrode smaller than the width of the outer heater electrode in advance, and thus increasing the resistance, the decrease in resistance of the inner heater electrode after firing can be compensated for, and the output of the inner heater electrode can be set to a predetermined value.

[0021] above Note Se In a Lamix heater, the planar electrode is an electrostatic adsorption electrode, a high-frequency electrode, or a connecting electrode that supplies power to the heater electrode. It's fine to have it. In a cross section perpendicular to the aforementioned mounting surface, the planar electrode is positioned between the inner heater electrode and the aforementioned mounting surface, or between the inner heater electrode and the lower surface of the substrate facing the aforementioned mounting surface. It's not necessary. .

[0022] In this way, by configuring the system so that no planar electrodes are placed between the inner heater electrode and the mounting surface or between the inner heater electrode and the bottom surface, it becomes easier to carbide the inner heater electrode compared to the case where the inner heater electrode is sandwiched between planar electrodes, and the electrode can be adjusted to contain Mo2C. As a result, it is possible to prevent the resistance of the inner heater electrode from becoming too low, and to set the output of the inner heater electrode to a predetermined value.

[0023] above Note Se In the Lamix heater, the substrate contains a total of 2 wt% or less of the grain boundary composition. That's fine. .

[0024] For example, if no planar electrode is placed between the inner heater electrode and the mounting surface or between the inner heater electrode and the bottom surface, it is possible to adjust the cross-sectional area ratio of the region containing or converted to Mo2C in the electrode near the center to be 10% or more, even if the content of the grain boundary composition in the substrate is reduced. Furthermore, by making the width of the inner heater electrode smaller than the width of the outer heater electrode, it is possible to prevent the resistance of the inner heater electrode from becoming too low. By applying these techniques, the content of the grain boundary composition in the substrate can be reduced, and the properties of the substrate, such as thermal conductivity and volume resistivity, can be selected from a wide range.

[0025] Ma Furthermore, the ceramic heater with a shaft, which is an example of the application of the present invention, before The device comprises a ceramic heater and a cylindrical shaft that is joined to the lower surface of the substrate facing the aforementioned mounting surface and supports the ceramic heater. You may do so. The width of the heater electrode located inside the shaft is smaller than the width of the heater electrode located outside the shaft. No need .

[0026] In this way, by making the width of the heater electrodes located inside the shaft smaller than the width of the heater electrodes located outside the shaft, the temperature drop of the heater electrodes located inside the shaft due to heat transfer from the shaft can be reduced, and the temperature distribution of the mounting surface can be made more uniform.

[0027] Ma Furthermore, the ceramic heater with a shaft, which is an example of the application of the present invention, before The device comprises a ceramic heater and a cylindrical shaft that is joined to the lower surface of the substrate facing the aforementioned mounting surface and supports the ceramic heater. You may .

[0028] This reduces heat transfer between the process chamber and the ceramic heater, allowing for a more uniform temperature distribution on the mounting surface. [Effects of the Invention]

[0029] According to the present invention, in a ceramic heater including a large-area planar electrode, it is possible to suppress the resistance of the inner heater electrode from becoming too low compared to the resistance of the outer heater electrode, thereby equalizing the temperature distribution on the mounting surface. [Brief explanation of the drawing]

[0030] [Figure 1] This is a schematic cross-sectional view showing an example of a ceramic heater according to the embodiment. [Figure 2] (a) to (c) are schematic plan views showing examples of the inner heater electrode, outer heater electrode, and planar electrode of a ceramic heater according to the respective embodiment. [Figure 3] This is a schematic cross-sectional view showing a modified example of the ceramic heater according to the embodiment. [Figure 4] This is a schematic cross-sectional view showing a modified example of the ceramic heater according to the embodiment. [Figure 5] This is a schematic cross-sectional view showing a modified example of the ceramic heater according to the embodiment. [Figure 6] This is a schematic cross-sectional view showing a modified example of the ceramic heater according to the embodiment. [Figure 7] This is a schematic cross-sectional view showing a modified example of the ceramic heater according to the embodiment. [Figure 8] This is a schematic cross-sectional view showing an example of a ceramic heater with a shaft according to the embodiment. [Figure 9] This is a flowchart showing an example of a method for manufacturing a ceramic heater according to the embodiment. [Figure 10] (a) to (c) are schematic cross-sectional views illustrating one step in the manufacturing process of a ceramic heater according to each embodiment. [Figure 11] This is a schematic cross-sectional view showing one step in the manufacturing process of a ceramic heater according to the embodiment. [Figure 12]This table shows the composition of the substrates, electrode embedding configuration, other characteristics, and measurement results for the examples and comparative examples. [Figure 13] This is an SEM image of the cross-section of the inner heater electrode in Example 8. [Modes for carrying out the invention]

[0031] 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.

[0032] The inventors have discovered that the carbide formation of heater electrodes in ceramic heaters including planar electrodes differs depending on the electrode arrangement and the portion of the heater electrode. Specifically, in ceramic heaters including planar electrodes, the inner heater electrodes are less prone to carbide formation than the outer heater electrodes, and this effect becomes more pronounced depending on the electrode arrangement. Therefore, if heater electrodes are designed without considering the electrode arrangement, differences in volume resistivity will occur among the heater electrodes, resulting in excessively large differences in resistance values ​​between the heater electrodes, exceeding the acceptable range.

[0033] Furthermore, the inventors discovered that the carbide formation of heater electrodes varies depending on the concentration of the sintering aid components in the AlN ceramics and the components (grain boundary composition) generated by the reaction between the sintering aid and AlN, and that higher concentrations of the grain boundary composition promote carbide formation of the Mo electrode. However, since the amount of sintering aid added to the AlN ceramics is closely related to the physical properties (functions) of the AlN ceramics, it was not possible to determine the amount of sintering aid solely for the purpose of promoting carbide formation of heater electrodes.

[0034] Therefore, the present invention designs a ceramic heater considering the electrode arrangement, the amount of sintering aid that can be added, and the difference in the allowable range of resistance values. Furthermore, in some cases, the reduction in resistance value is compensated for by reducing the width of the inner heater electrode in advance. As a result, in ceramic heaters that include large planar electrodes, it is possible to prevent the resistance of the inner heater electrode from becoming too low compared to the resistance of the outer heater electrode, and to equalize the temperature distribution on the mounting surface.

[0035] [Embodiment] [Ceramic heater configuration] First, the configuration of the ceramic heater according to this embodiment will be described. Figure 1 is a cross-sectional view showing an example of a ceramic heater according to the present invention. Figures 2(a) to 2(c) are schematic plan views showing examples of the inner heater electrode, outer heater electrode, and planar electrode of the ceramic heater according to the present invention, respectively. The ceramic heater 100 according to this embodiment comprises a base material 110, a heater electrode 120, and a planar electrode 130.

[0036] The base material 110 is made of a ceramic sintered body mainly composed of AlN. The base material 110 being mainly composed of AlN means that it is made of a ceramic sintered body containing 90 wt% or more of AlN. The base material 110 is formed in a flat plate shape and has a mounting surface 112 on one main surface for placing a substrate. The base material 110 is also formed in a disc shape.

[0037] Sintered ceramic bodies primarily composed of AlN may have sintering aids added to alter their thermal conductivity and volume resistivity. Regarding thermal conductivity, it is generally known that increasing the amount of sintering aid increases the thermal conductivity, but adding more than a certain amount causes a decrease in thermal conductivity. Therefore, it is desirable to keep the sintering aid content below 10 wt%. The sintering aid can be yttrium or other rare earth or alkaline earth metal oxides, as described later.

[0038] A ceramic sintered body primarily composed of AlN has high thermal conductivity and excellent heat resistance and plasma resistance. By adjusting the type and amount of sintering aid added, the thermal conductivity and volume resistivity can be easily adjusted. Therefore, by forming a base material 110 using a ceramic sintered body primarily composed of AlN, the thermal conductivity and volume resistivity can be adjusted, resulting in a base material 110 with excellent heat resistance and plasma resistance.

[0039] The substrate 110 contains a grain boundary composition comprising yttrium or other rare earth compounds or alkaline earth metal compounds in a total amount of 0.1 wt% to 10 wt%. In this specification, the grain boundary composition refers to a yttrium compound or other rare earth compound or alkaline earth metal compound or a compound produced by the reaction of these with AlN. Examples of yttrium compounds include Y2O3, as well as complex oxides of Al and Y such as YAG, YAM, and YAP. The same applies to compounds of other rare earth metals and alkaline earth metals. Other rare earth elements include, for example, Nd, Sm, Eu, Gd, Ce, and Er. Alkaline earth metals include Ca, Mg, and Sr. The grain boundary composition exists between AlN particles. The space between AlN particles refers to the triple point surrounded by three AlN particles or the space between the edges of two AlN particles on the polished surface of the substrate 110. The average particle size of AlN particles varies depending on the composition of the AlN ceramics, such as the type and amount of additives used, and the firing conditions, such as the firing temperature and heating rate, but is typically between 2.5 μm and 7.0 μm.

[0040] The grain boundary composition is a compound formed by the reaction of sintering aids added to the raw materials, either alone or with AlN. These grain boundary compositions have a relatively lower melting point compared to AlN and are more fluid during high-temperature firing. At this time, carbon components introduced from the external environment, such as the raw material powder, carbon firing jig, or firing atmosphere, move along with the grain boundary composition, increasing the opportunity for them to react with the electrodes, and at least a portion of the electrodes become Mo2C. Since the grain boundary composition flows within the substrate 110 during firing depending on the positional relationship between the electrodes and the distance between the electrodes and the external environment, the opportunity for the heater electrode 120 to react with carbon components is constrained by the positional relationship between the heater electrode 120 and other electrodes. Therefore, in electrode arrangements where the fluidity of the grain boundary composition is greatly restricted from the perspective of the heater electrode 120, the degree of carbonization of the heater electrode 120 is small, and in arrangements where the restriction is less, the degree of carbonization of the heater electrode 120 is large. For example, if a large-area planar electrode 130, described later, is embedded, the fluidity of the grain boundary composition decreases near the center, making it less likely to form Mo2C. As a result, carbonization of the inner heater electrode 122, described later, is suppressed. When the resistance of the heater electrode 120 becomes locally low, the amount of heat generated in that area decreases, making it easier for low-temperature areas to form and making it difficult to equalize the temperature distribution.

[0041] The ceramic heater 100 of the present invention contains 0.1 wt% to 10 wt% of a grain boundary composition. This facilitates the flow of the grain boundary composition and the associated carbon components. As a result, even when the planar electrode 130 is embedded, the movement of carbon components is promoted, and at least a portion of the inner heater electrode 122 is converted to Mo2C, preventing the resistance of the heater electrode 120 from becoming locally too low, regardless of the electrode placement position. The content of the grain boundary composition can be confirmed by simple quantitative analysis such as quantitative analysis by GDMS or semi-quantitative analysis using EPMA. However, if the grain boundary composition exceeds 10 wt%, it may become difficult to manufacture the sintered body, and the thermal conductivity and volume resistivity of the ceramic sintered body mainly composed of AlN may become unsuitable as a substrate for the heater.

[0042] The base material 110 preferably contains a total of 2 wt% or less of grain boundary composition. For example, if a planar electrode 130 is not placed between the inner heater electrode 122 and the mounting surface 112 or between the inner heater electrode 122 and the bottom surface 114, even if the content of the grain boundary composition in the base material 110 is reduced, it is possible to adjust the ratio of the cross-sectional area of ​​the region containing or converted to Mo2C in the electrode near the center to be 10% or more. Furthermore, as will be described later, by making the width of the inner heater electrode 122 smaller than the width of the outer heater electrode 124, it is possible to prevent the resistance of the inner heater electrode 122 from becoming too low. By applying these techniques individually or in combination, the content of the grain boundary composition in the base material 110 can be reduced, and the properties of the base material 110, such as thermal conductivity and volume resistivity, can be selected from a wide range.

[0043] The heater electrode 120 is embedded in the substrate 110 and includes a Mo mesh divided into multiple regions. Of the heater electrodes 120, at least the inner heater electrode 122 located radially inward of the substrate 110 contains Mo2C. By configuring the inner heater electrode 122 to contain Mo2C in this way, it is possible to prevent the resistance of the inner heater electrode 122 from becoming too low compared to the resistance of the outer heater electrode 124 located radially outward of the substrate 110, thereby equalizing the temperature distribution of the mounting surface 112.

[0044] Furthermore, the heater electrode 120 located radially outward from the substrate 110 compared to the inner heater electrode 122 is more susceptible to carbide formation than the inner heater electrode 122. Therefore, if the inner heater electrode 122 contains Mo2C, it can be assumed that the heater electrode 120 located radially outward from the substrate 110 compared to the inner heater electrode 122 also contains Mo2C. In addition, although the heater electrode 120 is divided into two regions, the inner heater electrode 122 and the outer heater electrode 124, the heater electrode 120 may be divided into three or more regions.

[0045] The presence of Mo2C in the inner heater electrode 122 can be confirmed by performing elemental mapping analysis of the entire cross-section of the inner heater electrode 122 using EPMA. The presence of Mo2C in the inner heater electrode 122 means that, by performing elemental analysis using EPMA and quantifying C and Mo in atom percent by semi-quantitative analysis, there exists a region where the C / (C+Mo) ratio is 0.2 or higher.

[0046] In the portion of the inner heater electrode 122 that overlaps with the planar electrode 130 in a planar view, it is preferable that the ratio of the cross-sectional area of ​​the Mo2C-converted region to the cross-sectional area of ​​the inner heater electrode 122 in a cross-section perpendicular to the mounting surface 112 is 10% or more, and more preferably 20% or more. The portion of the inner heater electrode 122 that overlaps with the planar electrode 130 becomes even less susceptible to carbide formation, but by adjusting the Mo2C-converted region in that portion to be 10% or more, it is possible to sufficiently suppress the resistance of that portion of the inner heater electrode 122 from becoming too low, and the output of the inner heater electrode 122 can be set to a predetermined value.

[0047] In the portion of the inner heater electrode 122 that overlaps with the planar electrode 130 in a plan view, the ratio of the cross-sectional area of ​​the Mo2C region to the cross-sectional area of ​​the inner heater electrode 122 perpendicular to the mounting surface 112 is 10% or more, which can be confirmed by performing elemental mapping analysis of the entire cross-section of the inner heater electrode 122 using EPMA. In the portion of the inner heater electrode 122 that overlaps with the planar electrode 130 in a plan view, the cross-section perpendicular to the mounting surface 112 is exposed, elemental analysis is performed using EPMA, C and Mo are quantified in atom percent by semi-quantitative analysis, and the area ratio of the region where the C / (C+Mo) ratio is 0.2 or more can be determined.

[0048] The wire forming the mesh of the heater electrode 120 preferably has a diameter of 0.02 mm or more and 0.15 mm or less. This makes it easier to design the heater electrode to have a high resistance value and increases the design flexibility of the heater electrode 120. Mo has a high melting point and is difficult to process, so wires with a diameter of less than 0.02 mm are difficult to manufacture. Also, if wires with a diameter larger than 0.15 mm are woven into the mesh, it becomes difficult to increase the resistance value, and it may be difficult to design it to have the required resistance value.

[0049] Furthermore, if the wire diameter is greater than 0.15 mm, the risk of cracking (fissure) in the wire during sintering increases. Also, the mesh thickness at the wire intersections becomes greater than 0.3 mm, and if the AlN ceramic on top of the heater electrode 120 is configured as a thin insulating layer, the risk of cracking in the insulating layer increases. Thus, by constructing the heater electrode 120 with sufficiently thin wire, the risk of cracking in the wire during sintering can be further reduced, and even if the AlN ceramic on top of the heater electrode 120 is configured as a thin insulating layer, the risk of cracking in the insulating layer can be further reduced.

[0050] The width of the inner heater electrode 122 is preferably smaller than the width of the outer heater electrode 124 located on the outermost part of the base material 110. By making the width of the inner heater electrode 122 smaller than the width of the outer heater electrode 124 in advance and increasing its resistance, the decrease in resistance of the inner heater electrode 122 after firing can be compensated for, and the output of the inner heater electrode 122 can be set to a predetermined value.

[0051] The width of the heater electrode 120 refers to the width perpendicular to the center line of the heater electrode 120 pattern in each region. If the width of the heater electrode 120 in one region differs depending on the position, the length of region i with the same width is Li and the width is Wi, and the width is calculated as W = (ΣLi × Wi) / ΣLi. However, the range in which the width cannot be determined, including the corners of the center line of the heater electrode pattern and the parts where the curvature changes, is excluded from the above formula. In addition, the heater electrode 120 in one region may be further divided radially, and the width of each region may be smaller or larger compared to the width of other regions.

[0052] The planar electrode 130 is embedded in the substrate 110 and, when viewed from the mounting surface 112 side, has an area of ​​40% or more of the area of ​​the mounting surface 112. In this way, when there is a planar electrode 130 with a large area, the inner heater electrode 122 is less likely to be carbidized than the outer heater electrode 124. However, by including a predetermined amount of grain boundary composition and configuring the inner heater electrode 122 to contain Mo2C, it is possible to suppress the resistance of the inner heater electrode 122 from becoming too low compared to the resistance of the outer heater electrode 124, thereby equalizing the temperature distribution of the mounting surface 112. The planar electrode 130 can be used, for example, as an electrostatic adsorption electrode, a high-frequency electrode, or as a connecting electrode that is wider than any of the heater electrodes 120 for supplying power to the heater electrode 120. By making the connecting electrode 132 wider than any of the heater electrodes 120 and increasing its area, the resistance value can be reduced and Joule heating can be suppressed. Here, the width of the connecting electrode 132 refers to the width in the direction perpendicular to the direction of the current flowing through the connecting electrode 132. The area of ​​the planar electrode 130 refers to the area defined by the outer contour of the planar electrode when viewed from above. This helps to suppress heat generation in unintended locations. The shape and material of the planar electrode 130 vary depending on the application, but it can be formed from materials such as Mo or W.

[0053] Figures 3 and 4 are schematic cross-sectional views showing modified examples of ceramic heaters according to the present invention. As shown in Figures 3 and 4, the ceramic heater of the present invention can accommodate various electrode arrangements, can prevent the resistance of the inner heater electrode 122 from becoming too low compared to the resistance of the outer heater electrode 124, and can equalize the temperature distribution of the mounting surface 112.

[0054] Figures 5 to 7 are schematic cross-sectional views showing modified examples of ceramic heaters according to the present invention. As shown in Figures 5 to 7, the planar electrode 130 may be an electrostatic adsorption electrode or a high-frequency electrode 134, and a connecting electrode 132 that supplies power to the heater electrode 120.

[0055] As shown in Figure 5 or Figure 6, the inner heater electrode 122 may be positioned so that, at least in part, it is sandwiched between the electrostatic adsorption electrode or high-frequency electrode 134 and the connecting electrode 132 in a cross section perpendicular to the mounting surface 112. When the inner heater electrode 122 is sandwiched between the planar electrode 130, the inner heater electrode 122 becomes very resistant to carbide formation. However, the ceramic heater 100 of the present invention promotes the flow of the grain boundary composition by including a predetermined amount of grain boundary composition, thereby increasing the opportunity for reaction between the electrode and carbon components from the environment, the jig, and the raw materials. This allows the inner heater electrode 122, which is resistant to carbide formation, to also contain Mo2C. Therefore, even with such a ceramic heater 100 structure, it is possible to suppress the resistance of the inner heater electrode 122 from becoming too low, and to equalize the temperature distribution on the mounting surface 112.

[0056] As shown in Figures 1, 3, and 4, the planar electrode 130 is a connecting electrode 132 that supplies power to the heater electrode 120, and it is preferable that the planar electrode 130 is not positioned between the inner heater electrode 122 and the mounting surface 112 or between the inner heater electrode 122 and the lower surface 114 of the base material 110 facing the mounting surface 112 in a cross section perpendicular to the mounting surface 112. Also, as shown in Figure 7, the planar electrode 130 is an electrostatic adsorption electrode or a high-frequency electrode 134 and a connecting electrode 132 that supplies power to the heater electrode 120, and it is preferable that the planar electrode 130 is not positioned between the inner heater electrode 122 and the mounting surface 112 or between the inner heater electrode 122 and the lower surface 114 of the base material 110 facing the mounting surface 112 in a cross section perpendicular to the mounting surface 112.

[0057] As described above, by configuring the device so that the planar electrode 130 is not placed between the inner heater electrode 122 and the mounting surface 112 or between the inner heater electrode 122 and the lower surface 114, compared to the case where the inner heater electrode 122 is sandwiched between the planar electrode 130, the flow of the grain boundary composition is promoted, increasing the opportunities for the electrode to react with carbon components from the environment, the jig, and the raw materials, making it easier to carbide the inner heater electrode 122 and easier to adjust the electrode to contain Mo2C. As a result, it is possible to prevent the resistance of the inner heater electrode 122 from becoming too low, and the output of the inner heater electrode 122 can be set to a predetermined value. Note that the configuration in which the inner heater electrode 122 and the planar electrode 130 are arranged on the same surface is excluded. Furthermore, in Figures 5 to 7, the above advantages are also present and are included in the present invention even when the connecting electrode 132 is not configured as a planar electrode 130.

[0058] The ceramic heater 100 may be provided with terminals and terminal holes for supplying electricity to or electrically connecting to each electrode. The ceramic heater 100 may also be provided with connecting members that are electrically connected between the terminals and electrodes. The terminals can be made of Ni or the like. The terminals are brazed to the electrodes or connecting members with Au solder or the like. The connecting members can be made of Mo, W, or the like. Terminals, terminal holes, connecting members, etc., are not shown in Figure 1, etc.

[0059] Figure 8 is a schematic cross-sectional view showing an example of a shaft-type ceramic heater according to an embodiment of the present invention. As shown in Figure 8, the ceramic heater of the present invention may be a shaft-type ceramic heater 200. This reduces heat transfer between the process chamber and the ceramic heater 100, and allows for a more uniform temperature distribution on the mounting surface 112.

[0060] The shaft 140 supports the ceramic heater 100 described above. The shaft 140 is joined to the lower surface 114 of the base material 110, which faces the mounting surface 112 of the base material 110. A protrusion 116 for joining the shaft 140 may be formed on the lower surface 114 of the base material 110. The shaft 140 is made of a ceramic sintered body and is formed in a cylindrical shape. The ceramic sintered body forming the shaft 140 preferably has AlN as its main component, similar to the ceramic sintered body forming the base material 110. In this case, the presence or absence and amount of sintering aid may differ.

[0061] In the shaft-mounted ceramic heater 200, it is preferable that the width of the heater electrode 120 located inside the outer diameter of the joint of the shaft 140 is smaller than the width of the heater electrode 120 located outside the outer diameter of the joint of the shaft 140. This reduces the temperature drop of the heater electrode 120 located inside the shaft 140 due to heat transfer to the shaft 140, and allows for a more uniform temperature distribution on the mounting surface 112.

[0062] [Manufacturing method for ceramic heaters] Next, a method for manufacturing a ceramic heater according to this embodiment will be described. Figure 9 is a flowchart showing an example of a method for manufacturing a ceramic heater according to an embodiment of the present invention. As shown in Figure 9, the method for manufacturing a ceramic heater according to an embodiment of the present invention comprises a granulation powder preparation step STEP 1, a ceramic molded body formation step STEP 2, a laminate formation step STEP 3, and a firing step STEP 4. In the following, a manufacturing method by a molded body hot press method, in which molded bodies are laminated, will be described. However, in the present invention, it is important to promote the carbide formation of the heater electrodes by adjusting the amount of grain boundary composition contained in the substrate according to the electrode arrangement of the ceramic heater, and the above steps may be replaced with other methods as long as such adjustment is possible.

[0063] Figures 10(a) to 10(c) and 11 are schematic cross-sectional views illustrating one step in the manufacturing process of the ceramic heater according to this embodiment.

[0064] Step 1 of the granulation powder preparation process involves preparing granulation powder from AlN raw material powder. For example, powders that act as sintering aids are added to the AlN raw material powder so that it contains the necessary grain boundary composition according to the electrode arrangement of the ceramic heater. Then, additives such as binders, plasticizers, and dispersants are added as appropriate and mixed to create a slurry, and granulation powder is produced by a spray-drying method or the like.

[0065] The AlN raw material powder is preferably of high purity, preferably 96% or higher, and more preferably 98% or higher. The average particle size of the AlN raw material powder is preferably 0.1 μm to 1.0 μm, and more preferably 0.3 μm to 0.8 μm. When using Y2O3 as a sintering aid, for example, 0.1 wt% to 10 wt% of Y2O3 is added to the AlN raw material powder, and a slurry is prepared by adding a binder such as PVA, a dispersant, and a solvent, and then granulated powder is produced using a spray dryer or the like. The mixing method may be either wet or dry, and mixers such as ball mills and vibration mills can be used.

[0066] Step 2 of the ceramic molded body formation process involves forming multiple ceramic molded bodies 11, 12, and 13 from granulated powder. For example, after granulation, the granulated powder can be pressure-molded to form multiple ceramic molded bodies 11, 12, and 13. When a manufacturing method using a binder is employed in this manner, approximately 100 ppm to 500 ppm of C component derived from the binder will remain in the degreased ceramic body even after the degreasing process described later. It is presumed that this C component, as well as C components from the environment such as jigs, are the cause of carbonization.

[0067] As for the molding method, known methods such as uniaxial pressure molding or cold isostatic pressing (CIP) can be used. Note that the method for forming the ceramic molded body is not limited to pressure molding; for example, green sheet lamination or slip casting can also be applied. These methods can then be used to manufacture the ceramic molded body by appropriately degreasing or calcining the material. In Figure 10, the ceramic molded body is divided into three components, but there may be four or more depending on the design.

[0068] The multiple ceramic molded bodies 11, 12, and 13 may be shaped by machining after molding. Furthermore, recesses shaped to match the shape of electrodes or the like may be formed on one or both sides of a predetermined ceramic molded body.

[0069] Multiple ceramic molded bodies 11, 12, and 13 may be degreased at a predetermined temperature and for a predetermined time to produce multiple degreased ceramic bodies 21, 22, and 23. The ceramic molded bodies 11, 12, and 13 are heat-treated at a temperature of, for example, 400°C to 800°C to become degreased ceramic bodies 21, 22, and 23. The degreasing time is preferably 1 hour to 120 hours. An atmospheric furnace or a nitrogen atmosphere furnace can be used for degreasing. Machining may be performed after degreasing. For example, as shown in Figure 10(b), after degreasing, recesses shaped to match the shape of the heater electrode 120 or the planar electrode 130 may be formed on one or both sides (joint surfaces with other degreased ceramic bodies 21, 22, and 23) of the degreased ceramic bodies 21, 22, and 23.

[0070] The heater electrode precursors 120a (in Figure 10, inner heater electrode precursor 122a and outer heater electrode precursor 124a) and the planar electrode 130 are prepared in shapes according to the design of the ceramic heater 100. The heater electrode precursor 120a is preferably made by cutting a mesh woven with Mo wire into a predetermined shape. The wire diameter forming the mesh of the heater electrode precursor 120a is preferably 0.02 mm to 0.15 mm. The shape and material of the planar electrode 130 will differ depending on whether it is a connecting electrode 132, an electrostatic adsorption electrode, or a high-frequency electrode 134, but it can be formed using, for example, Mo, W, etc.

[0071] The heater electrode precursor 120a is preferably made of Mo. When the heater electrode precursor 120a is made of Mo, it means that it is formed of Mo with a purity of 98 wt% or higher, and that the total amount of other transition metals, rare earth elements or their compounds, and C is 2 wt% or less. The heater electrode precursor 120a made of Mo undergoes the calcination process STEP 4 described later to become the heater electrode 120 containing Mo2C.

[0072] In the laminate formation process STEP 3, a heater electrode precursor 120a, a planar electrode 130, and a plurality of ceramic molded bodies 11, 12, 13 or degreased ceramic bodies 21, 22, 23 are combined to form a laminate 30 that is formed in a flat plate shape and in which the heater electrode precursor 120a and the planar electrode 130 are embedded.

[0073] Alternatively, the laminate 30 may be formed by a powder hot-pressing method. The powder hot-pressing method is a method of embedding heater electrodes 120 and planar electrodes 130 inside ceramics by alternately stacking granulated powder and predetermined heater electrodes 120 and planar electrodes 130.

[0074] In the firing process STEP 4, the laminate 30 is fired under uniaxial pressure perpendicular to the main surface (mounting surface) to obtain the ceramic heater 100. The pressing force is preferably 1 MPa or more. The firing temperature is preferably 1500°C to 2000°C. The firing time is preferably 1 hour to 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. As a result, the multiple ceramic molded bodies 11, 12, 13 or degreased ceramic bodies 21, 22, 23 are sintered to form a ceramic sintered body, which is then integrated to obtain a ceramic heater 100 in which the heater electrode 120 and the planar electrode 130 are embedded.

[0075] Furthermore, if a degreasing process is included, a ceramic calcination process may be added after the degreasing process. If a ceramic calcination process is included, the degreased ceramic body is calcined at a temperature of 1200°C to 1700°C to produce the ceramic calcination body. This allows for higher dimensional accuracy of the outer shape of the ceramic heater 100 and the embedded position of the heater electrodes 120. 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 a vacuum may also be used. If a calcination process is included, machining may be performed after the calcination process.

[0076] A step may be added to the firing process to provide terminal holes (not shown) in the ceramic heater 100 and connect the terminals to the heater electrodes 120, etc. Alternatively, connecting members (not shown) may be embedded in the base material 110 in advance. The terminals can be connected to the surface of the heater electrodes 120, etc., or to the connecting members using brazing material. The terminals can be made of Ni, etc. The brazing material can be made of Au brazing material, etc.

[0077] When manufacturing a ceramic heater with a shaft, the shaft is prepared. For example, a shaft molded body is formed from a second granulated powder, which is mainly composed of AlN and may or may not contain a sintering aid. The method for preparing the second granulated powder and the method for forming the shaft molded body may be the same as the granulated powder preparation process and the ceramic molded body formation process. It is preferable that the second granulated powder does not contain a sintering aid. The shaft molded body may be degreased. The numerical range of the degreasing conditions for the shaft molded body may be the same as that for preparing the degreased ceramic body described above. Note that the preparation of the degreased shaft body may be performed simultaneously with the preparation of the degreased ceramic body.

[0078] The shaft firing process involves firing the shaft molded body or the degreased shaft to create the shaft that supports the base material. The firing of the support member is preferably performed under 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 may also be an atmosphere such as a vacuum.

[0079] The joining process connects the base material and the shaft. Known methods can be applied to join the base material and the shaft; both joining methods using a bonding agent and joining methods without a bonding agent can be used.

[0080] In this way, in ceramic heaters with large-area planar electrodes, it is possible to prevent the resistance of the inner heater electrode from becoming too low compared to the resistance of the outer heater electrode, and to manufacture ceramic heaters that can equalize the temperature distribution on the mounting surface.

[0081] [Examples and Comparative Examples] (Example 1) AlN raw material powder was mixed with 5 wt% Y2O3 (purity 99.9% or higher) by internal ratio, and a binder (PVA), dispersant, and solvent were added to prepare a slurry. Granulated powder was then produced using a spray dryer. The prepared granulated powder was then subjected to CIP molding (pressure 1 ton / cm²). 2) and obtained an ingot of a molded body. By machining this, four ceramic molded bodies with a diameter of 300 mm were formed. The thickness of the four ceramic molded bodies was selected in the range of 5 mm to 15 mm so that the high-frequency electrode, inner heater electrode, and outer heater electrode and connecting electrode of the ceramic heater after firing would be embedded to depths of 1 mm, 7 mm, and 13 mm from the mounting surface, respectively. Next, the ceramic molded bodies were degreased at 550°C for 12 hours to produce degreased ceramic bodies. Then, on one side of the degreased ceramic body of the predetermined thickness, a recess with a depth of 0.1 mm was made, sharing the center of the molded body, for housing the high-frequency electrode, inner heater electrode, or outer heater electrode and connecting electrode.

[0082] Separately, Mo mesh (wire diameter 0.1 mm, plain weave, mesh size #50) was cut into the specified shape to prepare an inner heater electrode precursor with an outer diameter of 210 mm, and an outer heater electrode precursor with an outer diameter of 296 mm and an inner diameter of 220 mm. The width of both the inner and outer heater electrodes was set to 5 mm. In addition, Mo mesh (wire diameter 0.1 mm, plain weave, mesh size #50) was cut into the specified shape to prepare two semicircular connecting electrodes with an outer diameter of 200 mm excluding the connection points.

[0083] Next, the high-frequency electrode, the electrode precursor for the inner heater, the electrode precursor for the outer heater, and the connecting electrode were placed in the recesses of a predetermined degreased ceramic body and stacked in a predetermined order to create a laminate. Next, the laminate was placed in a hot press furnace and fired at 1800°C for 2 hours using a single-axis hot press while applying a force of 10 MPa perpendicular to the main surface (mounting surface) of the laminate. In this way, the ceramic heater was fired. After that, the entire surface was ground and polished to a total thickness of 24 mm and an insulating layer thickness of 1 mm. Then, terminal holes were drilled for connecting terminals to the high-frequency electrode, the electrode for the inner heater, and the connecting electrode, and Ni terminals were connected to each electrode with Au solder. The connecting electrode and the electrode for the outer heater are electrically connected on the same plane inside the substrate. In this way, the ceramic heater of Example 1 was manufactured. That is, the electrode embedding configuration of the ceramic heater of Example 1 is the same as the order and configuration of the electrodes in the schematic cross-sectional view of the ceramic heater illustrated in Figure 5.

[0084] (Example 2) In Example 2, the granulated powder in Example 1 was changed to AlN raw material powder with 5 wt% Nd2O3 added by internal ratio. In addition, the high-frequency electrodes, inner heater electrodes, outer heater electrodes, and connecting electrodes of the ceramic heater after firing were embedded at positions where the embedding depth from the mounting surface was 1 mm, 7 mm, and 13 mm, respectively. The outer diameter of the connecting electrode was 240 mm. The connection between the outer heater electrode and the connecting electrode was made by vias formed by co-firing a W (tungsten) porous body. That is, the electrode embedding configuration of the ceramic heater in Example 2 is the same as the electrode order and configuration in the schematic cross-sectional view of the ceramic heater illustrated in Figure 6. Otherwise, the ceramic heater of Example 2 was manufactured using the same process and conditions as in Example 1.

[0085] (Example 3) In Example 3, the granulated powder from Example 2 was replaced with AlN raw material powder to which 5 wt% CaO was added by internal ratio. Otherwise, the ceramic heater of Example 3 was manufactured using the same process and conditions as in Example 2.

[0086] (Example 4) In Example 4, the granulated powder from Example 1 was changed to an AlN raw material powder with 1.5 wt% Y2O3 added by internal ratio. The high-frequency electrodes, outer heater electrodes and connecting electrodes, and inner heater electrodes of the fired ceramic heater were embedded at positions where the embedding depth from the mounting surface was 1 mm, 7 mm, and 13 mm, respectively. That is, the electrode embedding configuration of the ceramic heater in Example 4 is the same as the order and configuration of the electrodes in the schematic cross-sectional view of the ceramic heater illustrated in Figure 7. Otherwise, the ceramic heater of Example 4 was manufactured using the same process and conditions as in Example 1.

[0087] (Example 5) Example 5 was modified by changing the granulated powder in Example 4 to AlN raw material powder with 5 wt% Y2O3 added by internal ratio. Otherwise, the ceramic heater of Example 5 was manufactured using the same process and conditions as Example 4.

[0088] (Example 6) Example 6 is a modified version of the ceramic heater in Example 1, with the high-frequency electrodes removed. The embedding depths of the outer heater electrodes, connecting electrodes, and inner heater electrodes are the same as in Example 1. That is, the electrode embedding configuration of the ceramic heater in Example 6 is the same as the electrode order and configuration in the schematic cross-sectional view of the ceramic heater illustrated in Figure 1. Otherwise, the ceramic heater of Example 6 was manufactured using the same process and conditions as in Example 1.

[0089] (Example 7) Example 7 is a modified version of Example 4, where the granulated powder is AlN raw material powder with 5 wt% Y2O3 added by internal ratio. Example 7 also modifies the ceramic heater of Example 4 by removing the high-frequency electrodes. The embedding depths of the outer heater electrodes, connecting electrodes, and inner heater electrodes are the same as in Example 4. That is, the electrode embedding configuration of the ceramic heater in Example 7 is the same as the electrode order and configuration shown in the schematic cross-sectional view of the ceramic heater illustrated in Figure 4. Otherwise, the ceramic heater of Example 7 was manufactured using the same process and conditions as in Example 4.

[0090] (Example 8) Example 8 was modified by changing the granulated powder in Example 4 to an AlN raw material powder with 0.3 wt% Y2O3 added by internal ratio. Otherwise, the ceramic heater of Example 5 was manufactured using the same process and conditions as Example 4.

[0091] (Example 9) Example 9 differs from Example 1 in that the width of the inner heater electrode is changed from 5 mm to 3 mm. Otherwise, the ceramic heater of Comparative Example 1 was manufactured using the same process and conditions as Example 1.

[0092] (Example 10) In Example 10, a 200 mm long shaft with an enlarged diameter section of 100 mm outer diameter and 60 mm inner diameter was joined to the lower surface of the ceramic heater of Example 1. Otherwise, the ceramic heater of Example 10 was manufactured using the same process and conditions as Example 1.

[0093] (Example 11) In Example 11, the width of the inner heater electrode outside the 100mm diameter was changed from 3mm to 5mm. The width within the 100mm diameter remained at 3mm. Otherwise, the ceramic heater of Example 11 was manufactured using the same process and conditions as in Example 10.

[0094] (Example 12) Example 12 is a modified version of Example 2, where the granulated powder is AlN raw material powder with 1 wt% Y2O3 added by internal ratio. Example 12 also modifies the ceramic heater of Example 2 by removing the high-frequency electrodes. The embedding depths of the outer heater electrodes, connecting electrodes, and inner heater electrodes are the same as in Example 2. That is, the electrode embedding configuration of the ceramic heater in Example 12 is the same as the electrode order and configuration shown in the schematic cross-sectional view of the ceramic heater illustrated in Figure 3. Otherwise, the ceramic heater of Example 12 was manufactured using the same process and conditions as in Example 2.

[0095] (Example 13) Example 13 was modified by replacing the granulated powder in Example 1 with AlN raw material powder to which 7 wt% Y2O3 was added. Otherwise, the ceramic heater of Example 13 was manufactured using the same process and conditions as in Example 1.

[0096] (Example 14) Example 14 was prepared by changing the granulated powder of Example 1 to an AlN raw material powder to which 3 wt% Al2O3 and 7 wt% Y2O3 were added in an internal ratio. Otherwise, the ceramic heater of Example 14 was manufactured using the same process and conditions as Example 1.

[0097] (Comparative example) The comparative example differed from Example 1 in that the granulated powder was replaced with only AlN raw material powder. Otherwise, the ceramic heater of the comparative example was manufactured using the same process and conditions as Example 1.

[0098] [Performance evaluation] (Measurement of resistance values ​​of inner and outer heater electrodes) For the ceramic heaters of the examples and comparative examples, the heater resistance between terminals was measured by contacting the probes of a tester to the terminals of the inner heater electrode and the outer heater electrode. Figure 12 is a table showing the composition of the substrate, electrode embedding configuration, other characteristics, and measurement results for the examples and comparative examples.

[0099] (Composition analysis of electrodes for the inner heater) The ceramic heaters of each example and comparative example were cut in a vertical cross-section passing through the center of the mounting surface. Then, the cross-section of the inner heater electrode, which overlaps with the planar electrode, was exposed, polished, and elemental mapping was performed using EMPA.

[0100] EPMA performed elemental mapping analysis of the cross-section of the inner heater electrode using FE-EPMA (Field Emission Electron Microanalyzer), and semi-quantitative analysis was performed to identify carbides based on the C / (C+Mo) ratio converted to atom%. Then, the area ratio of regions with a C / (C+Mo) ratio of 0.20 or higher was determined by image analysis of the cross-section.

[0101] Furthermore, the composition of the substrate in the same cross-section and the content of the grain boundary composition were confirmed by quantitative analysis using GDMS. The grain boundary composition is a substance produced by the reaction of the sintering aid added during raw material blending with Al, and the concentration of the grain boundary composition was determined by converting these to oxides.

[0102] Examples 1 to 14 involved sintering raw materials adjusted to the composition of the substrate shown in Figure 12. In all Examples 1 to 14, it was confirmed that the sintered substrate contained between 0.1 wt% and 10 wt% of grain boundary composition. For example, the grain boundary composition in Examples 8 and 13 was 0.2 wt% and 5.3 wt%, respectively. The reason for these differences in grain boundary composition content after firing is thought to be that some of the sintering aid was lost due to volatilization during firing. On the other hand, it was confirmed that at least some remained, or existed as compounds formed by reaction with AlN. Therefore, it is estimated that more than 50% of the amount of sintering aid used in the raw material formulation is included as grain boundary composition.

[0103] On the other hand, it was confirmed that the comparative example did not contain grain boundary composition. Furthermore, it was confirmed that Mo2C was present in the inner heater electrodes of Examples 1 to 14. In addition, the difference in resistance values ​​between the inner and outer heater electrodes was smaller in Examples 1 to 14 compared to the comparative example. It is thought that the difference in resistance values ​​between the inner and outer heater electrodes was suppressed in Examples 1 to 14 because the inner heater electrodes of the ceramic heaters underwent more carbonization than the comparative example.

[0104] Figure 13 is a 500x magnification SEM image of the cross-section of the inner heater electrode of Example 8. In Figure 13, the lighter colored portion of the inner heater electrode indicates Mo2C. The area ratio of the cross-sectional area of ​​the Mo2C-contaminated region to the cross-sectional area of ​​the inner heater electrode at this time is 21%, confirming that the heater electrode of Example 8 contains sufficient Mo2C, as shown in Figure 13.

[0105] The results from Examples 1-3 confirmed that regardless of whether the sintering aid is yttrium oxide, other rare earth oxides, or alkaline earth metal oxides, it creates a grain boundary composition and increases the degree of carbonization of the heater electrodes, including the inner heater electrodes.

[0106] A comparison of Example 1 with Examples 5-7 confirmed that when planar electrodes are placed on both the upper and lower surfaces of the inner heater electrode, the degree of carbonization of the inner heater electrode is lower even when the same amount of sintering aid is added. Furthermore, the results from Examples 1, 4, 8, and 12 confirmed that when a planar electrode is not placed on either the upper or lower surface of the inner heater electrode, the degree of carbonization of the inner heater electrode can be kept to a certain extent even when the amount of sintering aid added is reduced.

[0107] From the results of Examples 1 and 9, it was confirmed that when planar electrodes are arranged on the upper and lower surfaces of the inner heater electrode, the resistance value of the inner heater electrode can be brought sufficiently close to the resistance value of the outer heater electrode by using a technique to narrow the width of the inner heater electrode.

[0108] These results confirm that, compared to the comparative example, Examples 1 to 14 were able to carbonize the heater electrodes, including the inner heater electrode, and reduce the difference in resistance between the inner and outer heater electrodes. Furthermore, it was confirmed that the manufacturing method of the present invention can produce such ceramic heaters.

[0109] 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]

[0110] 11, 12, 13 Ceramic molded bodies 21, 22, 23 Degreased ceramics 30-layer structure 100 Ceramic Heaters 110 Base material 112 Mounting surface 114 Bottom surface 116 Convex part 120 Heater electrodes 120a Heater electrode precursor 122 Electrodes for the inner heater 122a Electrode precursor for inner heater 124 Electrodes for outer heater 124a Electrode precursor for outer heater 130 Planar electrode 132 Connecting electrodes 134 Electrostatic adsorption electrodes or high-frequency electrodes 136 Beer 140 shaft 200 Ceramic Heater with Shaft

Claims

1. It is a ceramic heater, A disc-shaped substrate made of a ceramic sintered body having a mounting surface and containing a grain boundary composition mainly composed of AlN and containing yttrium or other rare earth compounds or alkaline earth metal compounds in a total amount of 0.1 wt% to 10 wt%, A heater electrode, which includes a Mo mesh embedded in the substrate and divided into multiple regions, The substrate comprises a planar electrode embedded in the substrate, having a shape when viewed from the mounting surface side described above, and having an area of ​​40% or more of the area of ​​the mounting surface described above, The heater electrode comprises an inner heater electrode located at the innermost radial position of the substrate, and an outer heater electrode located at the outermost position of the substrate and at a different vertical position from the inner heater electrode. The aforementioned inner heater electrode is Mo ２ C is included, The planar electrode is a connecting electrode that supplies power to an electrostatic adsorption electrode or a high-frequency electrode, and to the heater electrode. The ceramic heater is characterized in that the inner heater electrode is sandwiched at least in part between the electrostatic adsorption electrode or the high-frequency electrode and the connecting electrode in a cross section perpendicular to the mounting surface described above.

2. In the portion of the inner heater electrode that overlaps with the planar electrode in a planar view, Mo is given for the cross-sectional area of ​​the inner heater electrode in a cross section perpendicular to the aforementioned mounting surface. ２ The ceramic heater according to claim 1, characterized in that the ratio of the cross-sectional area of ​​the region that has been converted to carbon is 10% or more.

3. The ceramic heater according to claim 1, characterized in that the width of the inner heater electrode is smaller than the width of the outer heater electrode.

4. The ceramic heater according to Claim 1, characterized in that the substrate contains a total of 2 wt% or less of the grain boundary composition.

5. A ceramic heater with a shaft, The ceramic heater described in claim 1, The system comprises a cylindrical shaft that is joined to the lower surface of the substrate facing the mounting surface and supports the ceramic heater, A ceramic heater with a shaft, characterized in that the width of the heater electrode located inside the shaft is smaller than the width of the heater electrode located outside the shaft.

6. A ceramic heater with a shaft, The ceramic heater according to claim 1 or claim 2, A ceramic heater with a shaft, characterized by comprising a cylindrical shaft that is joined to the lower surface of the substrate facing the mounting surface and supports the ceramic heater.

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