Ceramic heater and method for manufacturing ceramic heater

Abstract

Provided is a ceramic heater that can improve heat uniformity of a plate and suppress crushing of a thermocouple passage, cracking of the plate, or the like when joining the plate and a shaft. The ceramic heater comprises: a sheet-like plate that has a first main surface on which a wafer is placed and a second main surface positioned at a distance from the first main surface in the thickness direction and that incorporates a resistance heating element which generates heat by energization; a cylindrical shaft that supports the plate on the second main surface; and a sheet-like auxiliary member that is joined to the plate. The plate has formed therein a groove that is recessed in a direction from the second main surface toward the first main surface and extends from a starting end positioned inside the shaft to a terminal end positioned outside the shaft. The auxiliary member includes a lid part which extends along an outside portion positioned outside the shaft in the groove and covers the outside portion, and a connection part which is sandwiched between the plate and the shaft and to which a tip part of the shaft is joined.

Description

Ceramic heater and method for manufacturing ceramic heater

[0001] This application claims priority to Japanese Patent Application No. 2024-137019, filed on August 16, 2024, and incorporates by reference the entire contents of said Japanese Patent Application.

[0002] For example, in semiconductor manufacturing equipment, ceramic heaters are used to heat wafers when the wafers are subjected to processes such as chemical vapor deposition (CVD) and etching. As shown in Fig. 41, a ceramic heater 100 includes a plate 101 and a cylindrical shaft 102. The plate 101 has a first main surface 103 and a second main surface 104 spaced apart in the thickness direction. A wafer is placed on the first main surface 103, and the shaft 102 is joined to the second main surface 104.

[0003] The plate 101 has a built-in resistance heating element 105, which is formed of a coil whose main component is, for example, molybdenum, and the entire plate 101 is heated by the resistance heating element 105. To check whether the entire plate 101 is at a uniform temperature, the plate 101 is fitted with a first thermocouple for detecting the temperature near the periphery and a second thermocouple for detecting the temperature near the center.

[0004] A cavity 106 serving as a thermocouple passage is formed inside the plate 101, extending from the center toward the periphery of the plate 101. An opening 107 for inserting a first thermocouple is formed in the second main surface 104 of the plate 101 so as to communicate with the cavity 106. The first thermocouple is passed through the opening 107 into the cavity 106 in the plate 101, and the tip of the first thermocouple is positioned near the periphery of the plate 101, thereby detecting the temperature near the periphery of the plate 101.

[0005] As shown in Figure 42, a conventional ceramic heater is manufactured by bringing a shaft 102 into contact with a second main surface 104 of a plate 101 and bonding them together while heating and pressurizing them. A flux 108 is interposed between the plate 101 and the shaft 102. Here, when a load is applied by the shaft 102 to the plate 101 in which a cavity 106 and an opening 107 are formed, a portion 109 of the plate 101 located above the cavity 106 is prone to bending, and this portion 109 may crush the cavity 106. Alternatively, this portion 109 may cause a problem of breakage or cracks occurring in the plate 101.

[0006] In contrast, Patent Document 1 focuses on the fact that the above-mentioned problems can occur because of the high pressure applied when joining the plate and the shaft, and by interposing an intermediate ring made of aluminum nitride that does not contain yttria between the plate and the shaft made of aluminum nitride that contains yttria, it is possible to join the plate and the shaft with a low pressure, thereby preventing the above-mentioned problems from occurring.

[0007] In Patent Document 2, a thermocouple passage is provided in a plate without forming a cavity in the plate. Specifically, a slide groove extending from the center of the plate toward the periphery is formed on the second main surface of the plate, and a guide groove is formed at the bottom of the slide groove as a thermocouple passage. A lid is slidably attached to the slide groove, and the guide groove is covered by the lid, thereby forming a closed space isolated from the outside. A first thermocouple is inserted into this guide groove, and the tip of the first thermocouple is positioned near the periphery of the plate, allowing the first thermocouple to detect the temperature near the periphery of the plate.

[0008] JP 2023-030646 A JP 2012-028332 A

[0009] In Patent Document 1, it is possible to join a plate and a shaft with a low pressure. However, in Patent Document 1, a thermocouple passage is provided in the plate by forming a cavity in the plate. If the thermocouple passage is provided in the plate without forming a cavity in the plate, it is possible to prevent the thermocouple passage from being crushed when the plate and the shaft are joined, and also to prevent breakage or cracks from occurring in the plate. Therefore, in this respect, the technology described in Patent Document 1 has room for improvement.

[0010] In Patent Document 2, a thermocouple passage is provided in the plate without forming a cavity in the plate. However, in Patent Document 2, the shaft and plate, made of a material with high thermal conductivity, are directly bonded, which facilitates heat transfer from the plate to the shaft. As heat is dissipated from the plate to the shaft, temperature variations occur in the plate, affecting the plate's thermal uniformity. Specifically, ceramic heaters are installed in the vacuum chamber of semiconductor manufacturing equipment, and the vacuum chamber becomes hot when wafers are subjected to processes such as chemical vapor deposition (CVD) and etching. The shaft is fixed to a support member via an O-ring at the end opposite the end bonded to the plate. However, the O-ring's sealing performance deteriorates in the high-temperature environment of the vacuum chamber, so the O-ring is cooled to maintain the O-ring's sealing performance. If the shaft has good thermal conductivity, heat from the plate is easily transferred to the shaft, affecting the plate's thermal uniformity. Furthermore, in Patent Document 2, in addition to the lid, a tube consisting of multiple connected pipes is attached to the plate, which increases the number of components attached to the plate and results in poor symmetry. Therefore, temperature unevenness is likely to occur on the plate, which also affects the temperature uniformity of the plate. Therefore, there is room for improvement in the technology described in Patent Document 2 in terms of improving the temperature uniformity of the plate.

[0011] Therefore, one of the objects of the present disclosure is to provide a ceramic heater that can prevent the thermocouple passage from being crushed or the plate from cracking when the plate and shaft are joined, and that can improve the thermal uniformity of the plate, and a method for manufacturing the ceramic heater.

[0012] A ceramic heater according to the present disclosure includes a plate having a first main surface on which a wafer is mounted and a second main surface spaced apart in the thickness direction from the first main surface and incorporating a resistance heating element that generates heat when current is applied, a cylindrical shaft having a first opening and a second opening at both ends in the axial direction and supporting the plate at the second main surface, and a plate-like auxiliary member joined to the plate. The plate has a groove recessed from the second main surface toward the first main surface and extending from a starting end located inside the shaft to a terminal end located outside the shaft. The auxiliary member includes a lid portion extending along and covering an outer portion of the groove formed in the plate that is located outside the shaft, and a connecting portion sandwiched between the plate and the shaft and to which a tip end of the shaft that surrounds the first opening is joined.

[0013] A method for manufacturing a ceramic heater according to the present disclosure includes the steps of: forming a groove in a flat plate having a built-in resistance heating element that generates heat when current is applied, the groove being recessed from the second of first and second main surfaces positioned at a distance in the thickness direction toward the first main surface and extending from the center of the second main surface toward the outer periphery of the second main surface; installing a flat auxiliary member including a lid portion and an annular connecting portion relative to the plate so that an outer portion of the groove that is closer to the outer periphery of the second main surface is covered by the lid portion extending along the outer portion and an inner portion of the groove that is closer to the center of the second main surface is located inside the connecting portion; installing a cylindrical shaft relative to the auxiliary member so that a tip end portion that is a region surrounding the first opening of first and second openings positioned at both ends in the axial direction abuts against the connecting portion; and simultaneously joining the connecting portion of the shaft and the auxiliary member, and the connecting portion of the auxiliary member and the plate, while applying pressure to the shaft and joining the lid portion of the auxiliary member and the plate, while applying a load to the lid portion of the auxiliary member with a pressing member.

[0014] According to the present disclosure, it is possible to provide a ceramic heater that can prevent the grooves that serve as thermocouple passages from being crushed or the plates from cracking when the plates and shaft are joined, and that can improve the temperature uniformity of the plates.

[0015] FIG. 1 is a perspective view of a ceramic heater according to embodiment 1. FIG. 2 is an exploded perspective view of the ceramic heater according to embodiment 1. FIG. 3 is a plan view of the ceramic heater according to embodiment 1. FIG. 4 is a bottom view of the ceramic heater according to embodiment 1. FIG. 5 is a front view of the ceramic heater according to embodiment 1. FIG. 6 is a rear view of the ceramic heater according to embodiment 1. FIG. 7 is a right side view of the ceramic heater according to embodiment 1. FIG. 8 is a left side view of the ceramic heater according to embodiment 1. FIG. 9 is an enlarged cross-sectional view of a portion of the ceramic heater according to embodiment 1 cut along a vertical plane including line A-A in FIG. 4. FIG. 10 is a cross-sectional view showing a schematic configuration of the ceramic heater according to embodiment 1 used in a semiconductor manufacturing apparatus. FIG. 11 is a bottom view of a plate. FIG. 12 is a plan view of an auxiliary member. FIG. 13 is a side view of the auxiliary member. FIG. 14 is a cross-sectional view showing a portion of a manufacturing process for the ceramic heater according to embodiment 1. FIG. 15 is an exploded perspective view of a ceramic heater according to embodiment 2. FIG. 16 is a plan view of a ceramic heater according to embodiment 2. FIG. 17 is a bottom view of the ceramic heater according to embodiment 2. FIG. 18 is a front view of the ceramic heater according to embodiment 2. FIG. 19 is a rear view of the ceramic heater according to embodiment 2. FIG. 20 is a right side view of the ceramic heater according to embodiment 2. FIG. 21 is a left side view of the ceramic heater according to embodiment 2. FIG. 22 is an enlarged cross-sectional view of a portion of the ceramic heater according to embodiment 2 cut along a vertical plane including line A-A in FIG. 17. FIG. 23 is an exploded perspective view of a ceramic heater according to embodiment 3. FIG. 24 is a plan view of the ceramic heater according to embodiment 3. FIG. 25 is a bottom view of the ceramic heater according to embodiment 3. FIG. 26 is a front view of the ceramic heater according to embodiment 3. FIG. 27 is a rear view of the ceramic heater according to embodiment 3. FIG. 28 is a right side view of the ceramic heater according to embodiment 3. FIG. 29 is a left side view of the ceramic heater according to embodiment 3. FIG. 30 is an enlarged cross-sectional view showing a part of the ceramic heater according to the third embodiment cut along a vertical plane including the line AA in FIG.FIG. 31 is an enlarged cross-sectional view of a portion of the ceramic heater according to embodiment 3 cut along a vertical plane including line B-B in FIG. 25 . FIG. 32 is a bottom view of a plate which is a component of the ceramic heater according to embodiment 3. FIG. 33 is a plan view of a modified auxiliary member. FIG. 34 is a bottom view of a modified auxiliary member. FIG. 35 is a side view of a modified auxiliary member. FIG. 36(A) is a cross-sectional view of a modified auxiliary member cut along a vertical plane including line A-A in FIG. 33 . FIG. 36(B) is a cross-sectional view of a modified auxiliary member cut along a vertical plane including line B-B in FIG. 33 . FIG. 37 is an enlarged cross-sectional view of a portion of the ceramic heater according to embodiment 3 using the modified auxiliary member. FIG. 38 is an enlarged cross-sectional view of a portion of the ceramic heater according to embodiment 3 using the modified auxiliary member. FIG. 39 is an enlarged cross-sectional view of a portion of the ceramic heater according to embodiment 3 using the modified auxiliary member. FIG. 40 is an enlarged cross-sectional view of a portion of the ceramic heater according to embodiment 3. FIG. 41 is a cross-sectional view of a conventional ceramic heater. FIG. 42 is a cross-sectional view showing a part of the manufacturing process of a conventional ceramic heater.

[0016] [Description of Embodiments of the Present Disclosure] First, embodiments of a ceramic heater and a method for manufacturing a ceramic heater according to the present disclosure will be listed and described.

[0017] A ceramic heater according to a first aspect of the present disclosure includes a plate-like plate having a first main surface on which a wafer is mounted and a second main surface spaced apart in the thickness direction from the first main surface and incorporating a resistance heating element that generates heat when current is applied, a cylindrical shaft having a first opening and a second opening located at both ends in the axial direction and supporting the plate at the second main surface, and a plate-like auxiliary member joined to the plate. The plate has a groove formed therein that is recessed from the second main surface toward the first main surface and extends from a starting end located inside the shaft to a terminal end located outside the shaft. The auxiliary member includes a lid portion that extends along and covers an outer portion of the groove formed in the plate that is located outside the shaft, and a connecting portion that is sandwiched between the plate and the shaft and to which a tip end of the shaft that surrounds the first opening is joined.

[0018] In the ceramic heater according to the first aspect, no cavity is formed in the plate as a thermocouple passage for inserting a thermocouple into the plate. Instead, a groove is formed in the plate, recessed from the second main surface toward the first main surface. The outer portion of the groove is covered by a lid portion of an auxiliary member joined to the plate, thereby isolating the interior space from the exterior space. The inner portion of the groove is surrounded by a connecting portion of the auxiliary member joined to the plate, and the shaft is joined to the connecting portion of the auxiliary member, thereby isolating the interior space from the exterior space. Therefore, the thermocouple inserted inside the groove is isolated from the exterior space, and therefore, according to the ceramic heater according to the first aspect, the thermocouple can accurately detect the temperature near the outer periphery of the plate.

[0019] Furthermore, in the ceramic heater according to the first aspect, even if a load is applied to the auxiliary member and the plate when joining the auxiliary member and the shaft to the plate, partial deflection of the auxiliary member and the plate is unlikely to occur. Therefore, with the ceramic heater according to the first aspect, crushing of the grooves that serve as thermocouple passages or cracking of the plate are suppressed when joining the plate and the shaft.

[0020] Furthermore, in the ceramic heater according to the first aspect, the shaft is joined to the connecting portion of the auxiliary member, and the connecting portion is joined to the plate, so that the shaft is indirectly joined to the plate with the connecting portion sandwiched between them. By interposing the auxiliary member between the plate and the shaft in this way, the number of bonding interfaces between the plate and the shaft increases compared to when the shaft is directly bonded to the plate. Because the bonding interface can hinder thermal conduction, increasing the number of bonding interfaces reduces heat transfer from the plate to the shaft. Therefore, the ceramic heater according to the first aspect can suppress temperature unevenness in the plate and improve the thermal uniformity of the plate. Furthermore, in the ceramic heater according to the first aspect, because only the auxiliary member is attached to the plate and there are few components, temperature unevenness in the plate can be suppressed and the thermal uniformity of the plate can be improved.

[0021] A ceramic heater according to a second aspect of the present disclosure may be the ceramic heater according to the first aspect described above, wherein the plate is formed with a recess that recesses from the second main surface toward the first main surface and into which an auxiliary member is fitted, and at least a portion of the groove in the plate is formed so as to recess in the bottom surface of the recess toward the first main surface. By configuring the ceramic heater according to the second aspect in this way, it is easy to position the auxiliary member relative to the plate, and therefore it is easy to position the shaft relative to the plate.

[0022] As a ceramic heater according to a third aspect of the present disclosure, the ceramic heater according to the second aspect described above may be configured so that a gap is formed in at least a portion between the side surface of the support member and the side surface of the recess in the plate. By configuring the ceramic heater according to the third aspect in this manner, lateral heat conduction between the plate and the support member can be suppressed. Therefore, heat from the plate is less likely to transfer to the shaft via the support member, improving the thermal uniformity of the first main surface on which the wafer is placed.

[0023] As a ceramic heater according to a fourth aspect of the present disclosure, in the ceramic heater according to the second or third aspect described above, the connecting portion has an annular shape against which the tip portion of the shaft abuts, the recess in the plate includes a first recess into which the lid portion is fitted and a second recess into which the connecting portion is fitted and connected to the first recess, the second recess being formed annularly so as to have an inner circumferential surface facing the inner circumferential surface of the connecting portion, and the groove in the plate includes first groove portions formed in the bottom surfaces of the first and second recesses of the plate so as to recess toward the first main surface, and second groove portions formed in the second main surface of the plate inside the shaft so as to recess toward the first main surface, the first groove portions and the second groove portions being configured to communicate with each other. By configuring the ceramic heater according to the fourth aspect in this way, the volume of the auxiliary member can be reduced, and the proportion of the auxiliary member in the entire plate including the auxiliary member can be reduced.

[0024] A ceramic heater according to a fifth aspect of the present disclosure may be configured such that the ceramic heater according to the fourth aspect described above is configured so that a gap is formed in at least a portion between the inner circumferential surface of the connecting portion of the auxiliary member and the inner circumferential surface of the second recess of the plate. By configuring the ceramic heater according to the fifth aspect in this manner, lateral heat conduction between the plate and the auxiliary member can be suppressed. Therefore, heat from the plate is less likely to transfer to the shaft via the auxiliary member, improving the thermal uniformity of the first main surface on which the wafer is placed.

[0025] A ceramic heater according to a sixth aspect of the present disclosure may be configured in the ceramic heater according to the second or third aspect described above, such that the connecting portion has an annular shape against which the tip of the shaft abuts, the recess in the plate includes a first recess into which the lid portion is fitted and a second recess into which the connecting portion is fitted and connected to the first recess, the second recess having a flat bottom surface against which the connecting portion abuts and an outer circumferential surface facing the outer circumferential surface of the connecting portion, a space exists inside the connecting portion on the flat bottom surface, and the grooves in the plate are formed in the bottom surfaces of the first and second recesses of the plate so as to recess toward the first main surface. This configuration of the ceramic heater according to the sixth aspect can suppress lateral heat conduction between the plate and the auxiliary member and also suppress heat transfer from the plate to the auxiliary member by thermal radiation. This effectively suppresses heat transfer from the plate to the shaft via the auxiliary member, thereby further improving the thermal uniformity of the first main surface on which the wafer is placed.

[0026] As a ceramic heater according to a seventh aspect of the present disclosure, in the ceramic heater according to any one of the first to sixth aspects described above, at least one of the cover portion and the connecting portion of the auxiliary member may be configured so that at least a portion of the first surface side that abuts against the plate is tapered. By configuring the ceramic heater according to the seventh aspect in this manner, vertical heat conduction between the plate and the auxiliary member can be suppressed. Therefore, heat from the plate is less likely to transfer to the shaft via the auxiliary member, and the thermal uniformity of the first main surface on which the wafer is placed can be further improved.

[0027] As a ceramic heater according to an eighth aspect of the present disclosure, the ceramic heater according to the seventh aspect described above may be configured such that at least a portion of the inner circumferential surface of the connecting portion on the first surface side is a first inclined surface that inclines toward the outer circumferential surface of the connecting portion. By configuring the ceramic heater according to the eighth aspect in this manner, stress generated in the connecting portion when the connecting portion of the auxiliary member is pressed and joined to the plate during manufacturing of the ceramic heater can be dispersed, thereby reducing the risk of damage to the connecting portion.

[0028] As a ceramic heater according to a ninth aspect of the present disclosure, the ceramic heater according to the eighth aspect described above may be configured such that at least a portion of the outer circumferential surface of the connecting portion on the side of the first surface is a second inclined surface that is inclined toward the inner circumferential surface of the connecting portion, and the first inclined surface is inclined over a longer distance than the second inclined surface. By configuring the ceramic heater according to the ninth aspect in this way, stress generated in the connecting portion when the connecting portion of the auxiliary member is pressed and joined to the plate during manufacturing of the ceramic heater can be better dispersed, effectively reducing the risk of damage to the connecting portion.

[0029] As a ceramic heater according to a tenth aspect of the present disclosure, in the ceramic heater according to any one of the third to ninth aspects described above, at least one of the gaps formed between the side surface of the auxiliary member and the side surface of the recessed portion of the plate and the gap formed between the inner circumferential surface of the connecting portion and the inner circumferential surface of the second recessed portion of the plate may be filled with a filler. By adopting such a configuration, the ceramic heater according to the tenth aspect can reduce the risk of unwanted materials such as processing debris and dust accumulating in the gaps of the ceramic heater. This eliminates concerns about unwanted materials being scattered toward the wafer and adversely affecting wafer processing, for example, when performing processes such as chemical vapor deposition (CVD) or etching on wafers in semiconductor manufacturing equipment. It also eliminates concerns about gases used in wafer processing entering the gaps and causing corrosion at the joint surface between the auxiliary member and the plate.

[0030] As a ceramic heater according to an eleventh aspect of the present disclosure, in the ceramic heater according to any one of the first to tenth aspects described above, the plate and shaft may be primarily composed of aluminum nitride, and the auxiliary member may be primarily composed of aluminum nitride but contain no yttria. The plate, shaft, and auxiliary member are integrated by, for example, diffusion bonding using a flux containing a rare earth component, and since the auxiliary member does not contain yttria, diffusion of the rare earth component of the flux is promoted near the bonding interface between the auxiliary member and the plate and near the bonding interface between the auxiliary member and the shaft when bonding the plate and auxiliary member and the shaft and auxiliary member. As a result, with the ceramic heater according to the eleventh aspect, bonding the plate and auxiliary member and the shaft and auxiliary member can be performed at low temperature and low load.

[0031] A method for manufacturing a ceramic heater according to a first aspect of the present disclosure includes the steps of: forming a groove in a flat plate having a built-in resistance heating element that generates heat when current is applied, the groove being recessed from the second of first and second main surfaces positioned at a distance in the thickness direction toward the first main surface and extending from the center of the second main surface toward the outer periphery of the second main surface; installing a flat auxiliary member including a lid portion and an annular connecting portion relative to the plate such that an outer portion of the groove that is closer to the outer periphery of the second main surface is covered by the lid portion extending along the outer portion and an inner portion of the groove that is closer to the center of the second main surface is located inside the connecting portion; installing a cylindrical shaft relative to the auxiliary member such that a tip end portion that is a region surrounding the first opening of first and second openings positioned at both ends in the axial direction abuts against the connecting portion; and simultaneously joining the connecting portion of the shaft and the auxiliary member, and the connecting portion of the auxiliary member and the plate while applying pressure to the shaft and joining the lid portion of the auxiliary member and the plate while applying a load to the lid portion of the auxiliary member with a pressing member.

[0032] In the method for manufacturing a ceramic heater according to the first aspect, the connecting portion of the auxiliary member is pressed against the plate by the tip of the shaft, and at the same time the pressing member presses the cover portion of the auxiliary member against the plate, thereby joining the plate, auxiliary member, and shaft together with a single pressing operation. Therefore, according to the method for manufacturing a ceramic heater according to the first aspect, the plate, auxiliary member, and shaft can be easily integrated, and the manufacturing cost of the ceramic heater can be reduced.

[0033] Furthermore, the plate, auxiliary member, and shaft are joined in a heated state by applying heat, but because the resistance heating element built into the plate is primarily composed of, for example, molybdenum, its electrical resistance changes due to carbonization or the like when heated. Therefore, in order to heat the plate uniformly with the resistance heating element, it is desirable to suppress changes in the electrical resistance of the resistance heating element. By joining the plate, auxiliary member, and shaft to each other with a single pressing, as in the method for manufacturing a ceramic heater according to the first aspect, it is possible to suppress variations in the electrical resistance of the resistance heating element. Therefore, the method for manufacturing a ceramic heater according to the first aspect can improve the heating uniformity of the plate.

[0034] Furthermore, in the method for manufacturing a ceramic heater according to the first aspect, no cavity is formed in the plate as a thermocouple passage for inserting a thermocouple into the plate, but instead a groove is formed in the plate that recesses from the second main surface toward the first main surface. Therefore, even if a load is applied to the auxiliary member and the plate when joining the auxiliary member and the shaft to the plate, partial deflection of the auxiliary member and the plate is unlikely to occur. Therefore, according to the method for manufacturing a ceramic heater according to the first aspect, it is possible to prevent the groove that serves as the thermocouple passage from being crushed or the plate from cracking when joining the plate and the shaft.

[0035] As a ceramic heater according to a second aspect of the present disclosure, the method for manufacturing a ceramic heater according to the first aspect described above may be configured such that at least a portion of the inner circumferential surface of the connecting portion on the side of the first surface that abuts against the plate is inclined toward the outer circumferential surface of the connecting portion. By configuring the ceramic heater according to the second aspect, the method for manufacturing a ceramic heater according to this aspect can distribute stress that occurs in the connecting portion when the connecting portion of the auxiliary member is pressed and joined to the plate during manufacturing of the ceramic heater, thereby reducing the risk of the connecting portion being damaged.

[0036] [Details of the embodiment of the present disclosure] Next, an embodiment of a ceramic heater according to the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

[0037] <Embodiment 1> Fig. 1 is a perspective view of a ceramic heater 1 according to Embodiment 1, and Fig. 2 is an exploded perspective view of the ceramic heater 1 according to Embodiment 1. Figs. 3 to 8 are a plan view, a bottom view, a front view, a back view, a right side view, and a left side view, respectively, of the ceramic heater 1 according to Embodiment 1. The back view, right side view, and left side view are each expressed identically to the front view. Fig. 9 is an enlarged cross-sectional view showing a portion of the ceramic heater 1 according to Embodiment 1 cut along a vertical plane including line A-A in Fig. 4. Fig. 10 is a cross-sectional view showing a schematic configuration of the ceramic heater 1 according to Embodiment 1 used in a semiconductor manufacturing apparatus. Fig. 11 is a bottom view of a plate which is a component of the ceramic heater 1 according to Embodiment 1. Figs. 12 and 13 are a plan view and a front view of an auxiliary member which is a component of the ceramic heater 1 according to Embodiment 1.

[0038] The ceramic heater 1 is installed in a vacuum chamber in, for example, a semiconductor manufacturing device when performing processes such as chemical vapor deposition (CVD) or etching on wafers, and is used to heat the wafers to a desired temperature. The vacuum chamber is maintained in a vacuum atmosphere or a reduced-pressure atmosphere, and processes such as forming a thin film on a wafer using plasma or etching are performed in the vacuum chamber.

[0039] 2, the ceramic heater 1 includes a plate 2, a cylindrical shaft 3, and a plate-like auxiliary member 4. The plate 2 and the shaft 3 are joined by, for example, diffusion bonding, and the shaft 3 and the auxiliary member 4 are joined by, for example, diffusion bonding, thereby integrating the plate 2, the shaft 3, and the auxiliary member 4.

[0040] (Explanation of Plate) With reference to FIGS. 1 to 8 , the plate 2 is formed in a plate shape having a pair of main surfaces, a first main surface 20 and a second main surface 21, spaced apart in the thickness direction. The first main surface 20 constitutes the surface on which a wafer is placed. The plate 2 can be formed, for example, of a circular disk in a plan view. The size of the plate 2 is, for example, approximately 300 mm or more and 330 mm or less in diameter and approximately 20 mm in thickness. In the present disclosure, "plan view" refers to a view perpendicular to the first main surface 20 or the second main surface 21.

[0041] Referring to FIG. 9 , the plate 2 incorporates a resistance heating element 5 that generates heat when electricity is applied. The resistance heating element 5 can be formed, for example, by a coil primarily composed of molybdenum, tungsten, or the like. The resistance heating element 5 is embedded between the first main surface 20 and the second main surface 21 of the plate 2, covering almost the entire area along a plane parallel to the first main surface 20 and the second main surface 21. This allows the entire plate 2 to be heated by the resistance heating element 5, thereby heating a wafer placed on the first main surface 20. The resistance heating element 5 can be divided into, for example, a first resistance heating element disposed in a region toward the center of the plate 2 and a second resistance heating element disposed in a region toward the periphery of the plate 2. In this case, as shown in FIG. 10 , a pair of first metallic power feed rods 17 connected to a pair of terminals 12 at both ends of the first resistance heating element, respectively, and a pair of second metallic power feed rods 18 connected to a pair of terminals 13 at both ends of the second resistance heating element, respectively, are attached to the plate 2.

[0042] 2, 4, 9, and 11, the plate 2 is formed with a recess 22 into which the auxiliary member 4 is fitted. The recess 22 is formed in the second main surface 21 of the plate 2 so as to be recessed from the second main surface 21 toward the first main surface 20. The recess 22 includes a first recess 23 into which the cover portion 40 of the auxiliary member 4 is fitted, and a second recess 24 into which the connecting portion 41 of the auxiliary member 4 is fitted. The first recess 23 and the second recess 24 are continuous.

[0043] The second recess 24 has an annular shape in plan view that matches the shape of the connecting portion 41 of the auxiliary member 4, and is annular in this embodiment. The second recess 24 is formed to include an annular bottom surface 242 against which the annular connecting portion 41 abuts, an outer peripheral surface 240 that faces the outer peripheral surface 410 of the connecting portion 41, and an inner peripheral surface 241 that faces the inner peripheral surface 411 of the connecting portion 41. The center of the second recess 24 in plan view coincides with the center of the second main surface 21, and the second recess 24 is formed on the second main surface 21 so as to be concentric with the second main surface 21. In conjunction with the formation of the second recess 24, a flat, cylindrical protrusion 25 surrounded by the second recess 24 is provided at the center of the second main surface 21 side of the plate 2.

[0044] The first recess 23 is formed in the second main surface 21 so as to extend linearly from the second recess 24 toward the outer periphery of the second main surface 21. Of the start end 230 and the end end 231, which are both ends of the first recess 23, the start end 230 is connected to the second recess 24, and the end end 231 is located just before the outer periphery of the second main surface 21.

[0045] 2 , 9 , and 11 , a groove 26 is formed in the plate 2 as a thermocouple passage through which a thermocouple passes. The groove 26 is formed in the plate 2 so as to recess from the second main surface 21 toward the first main surface 20. The groove 26 also extends, on the second main surface 21 side of the plate 2, from a region inside the shaft 3 to a region outside the shaft 3 toward the outer periphery of the second main surface 21. That is, of the start end 260 and the end end 261, which are both ends of the groove 26, the start end 260 is located inside the shaft 3. The end end 261 is located outside the shaft 3 and is located just before the end 231 of the first recess 23. In this embodiment, the groove 26 extends to just before the outer periphery of the second main surface 21, and the end end 261 of the groove 26 is located just before the outer periphery of the second main surface 21. However, the terminal end 261 of the groove 26 may be located away from the outer periphery of the second main surface 21 as long as it is located outside the shaft 3. The position of the terminal end 231 of the first recess 23 is changed depending on the position of the terminal end 261 of the groove 26.

[0046] In the present embodiment, the groove 26 includes a first groove portion 27 formed in the bottom surface 220 of the recess 22 (the bottom surface 233 of the first recess 23 and the bottom surface 242 of the second recess 24) so ​​as to recess toward the first main surface 20, and a second groove portion 28 formed in the second main surface 21 of the plate 2 (the surface of the protrusion 25) so as to recess toward the first main surface 20. The second groove portion 28 is connected to the first groove portion 27. As shown in FIG. 11 , the first groove portion 27 constitutes an outer portion 262 of the groove 26 that is a portion of the groove 26 near the outer periphery of the second main surface 21 and located outside the shaft 3, and a part of an inner portion 263 of the groove 26 that is a portion of the groove 26 near the center of the second main surface 21 and located inside the shaft 3. The second groove portion 28 constitutes the remainder of the inner portion 263 of the groove 26. The thermocouple is inserted from the second groove portion 28 of the groove 26 and then passed through the first groove portion 27 until it reaches the vicinity of the outer periphery of the plate 2 .

[0047] 10 , a first thermocouple 14 for detecting the temperature near the outer periphery of the plate 2 and a second thermocouple 15 for detecting the temperature near the center of the plate 2 are attached to the plate 2 to confirm whether the resistance heating element 5 maintains a uniform temperature across the entire plate 2. The first thermocouple 14 is configured using, for example, a sheathed thermocouple. The first thermocouple 14 is passed through a groove 26 in the plate 2, so that the temperature measuring portion at the tip of the first thermocouple 14 is located near the outer periphery of the plate 2. This allows the first thermocouple 14 to detect the temperature near the outer periphery of the plate 2. The second thermocouple 15 is inserted into a recess 29 formed in the second main surface 21 of the plate 2, in the region inside the shaft 3, so that the temperature measuring portion at the tip of the second thermocouple 15 is located near the center of the plate 2. This allows the second thermocouple 15 to detect the temperature near the center of the plate 2.

[0048] 10 , the plate 2 may incorporate an electrode 6 made mainly of molybdenum, tungsten, or the like, such as an electrostatic electrode for attracting a wafer or an RF electrode for generating plasma. In this case, a third metal power supply rod 19 connected to a terminal 16 of the electrode 6 is attached to the plate 2.

[0049] 2 and 4 to 8, the shaft 3 is formed in a cylindrical shape having a pair of openings, a first opening 30 and a second opening 31, located at both ends in the axial direction. The shaft 3 supports the plate 2 on the side of the second main surface 21 (the surface opposite the first main surface 20 on which the wafer is placed). The shaft 3 can be configured, for example, as a cylinder having a circular cross section cut along a plane perpendicular to the axial direction. The diameter of the shaft 3 is smaller than the diameter of the plate 2.

[0050] In the shaft 3, a tip end 32 that surrounds the first opening 30 and a base end 33 that surrounds the second opening 31 can be formed, for example, by a flange. The tip end 32 of the shaft 3 is joined to the plate 2 via an auxiliary member 4 interposed between the plate 2 and the shaft 3. The base end 33 of the shaft 3 is connected to a support base 7 via an O-ring 8, as shown in FIG. 10 . This isolates the internal space of the shaft 3 from the external space, i.e., the space inside the vacuum chamber of the semiconductor manufacturing equipment.

[0051] Referring to FIG. 10 , the shaft 3 accommodates a first thermocouple 14 and a second thermocouple 15 in addition to a first power feed rod 17 and a second power feed rod 18 connected to the resistance heating element 5 and a third power feed rod 19 connected to the electrode 6. This isolates these metal components, such as the power feed rods and thermocouples, from the external space within the vacuum chamber of the semiconductor manufacturing equipment, preventing them from being exposed to plasma or the like. While not particularly limited, the first thermocouple 14 is preferably passed through a cylindrical thermocouple guide and then through the groove 26 of the plate 2. The thermocouple guide includes a linear portion extending axially (vertically) within the shaft 3 and a curved portion that changes the direction of extension of the thermocouple guide from the vertical direction to the horizontal direction. The thermocouple guide is positioned so that the curved portion is inserted into the second groove portion of the groove 26 and the outlet of the curved portion faces the inlet of the first groove portion 27 of the groove 26. This allows the first thermocouple 14 to be smoothly inserted into the groove 26 of the plate 2 using the thermocouple guide.

[0052] 2 and 4 to 8 , the shaft 3 may have a shape in which the inner diameter and outer diameter do not change along the axial direction of the shank between the distal end 32 and the proximal end 33. Alternatively, the shank of the shaft 3 may have a shape including a small diameter portion 34 near the proximal end 33 and a large diameter portion 35 having larger inner diameter and outer diameters than the small diameter portion 34 near the distal end 32, as in this embodiment.

[0053] 2 , 4 , 9 , 12 , and 13 , the auxiliary member 4 is formed in a plate shape (including a rod shape) in which the cover portion 40 has a thickness of 1.0 mm or more and 7.5 mm or less, and the connecting portion 41 has a thickness of 4.0 mm or more and 10.5 mm or less. The auxiliary member 4 is joined to the plate 2. The auxiliary member 4 includes the cover portion 40 and the connecting portion 41. The auxiliary member 4 is interposed between the plate 2 and the shaft 3, the connecting portion 41 is sandwiched between the plate 2 and the shaft 3, and the tip portion 32 of the shaft 3 is joined to the connecting portion 41.

[0054] The lid 40 extends along an outer portion 262 of the groove 26 formed in the plate 2, which is located outside the shaft 3. The lid 40 is joined to the plate 2 so as to cover the outer portion 262 of the groove 26. The lid 40 may be formed, for example, from a long, thin, flat plate extending linearly and having a length significantly greater than its width. The width of the lid 40 is greater than the width of the groove 26. The length of the lid 40 is greater than the length of the outer portion 262 of the groove 26. The outer portion 262 of the groove 26 is covered by the lid 40, and an inner portion 263 of the groove 26 near the center of the plate 2 is located inside the shaft 3, thereby isolating the interior space of the groove 26 from the external space, i.e., the space within the vacuum chamber of the semiconductor manufacturing equipment. This allows the first thermocouple 14 to accurately detect the temperature near the outer periphery of the plate 2.

[0055] The connecting portion 41 is joined to the plate 2, and the tip end 32 of the shaft 3 is joined thereto, thereby connecting and integrating the plate 2 and the shaft 3. The shape and size of the outer periphery of the connecting portion 41 in a plan view are not particularly limited, but preferably match the shape and size of the outer periphery of the tip end 32 of the shaft 3 joined to the connecting portion 41. In this embodiment, the shape of the connecting portion 41 in a plan view is annular to match the shape of the tip end 32 of the shaft 3, and the shape and size of the inner periphery of the connecting portion 41 in a plan view are also not particularly limited, but preferably match the shape and size of the inner periphery of the tip end 32 of the shaft 3. The connecting portion 41 can be formed, for example, by an annular ring plate that matches the shape of the tip end 32 of the shaft 3. This allows the tip end 32 of the shaft 3 to abut against the connecting portion 41. 10 , the connecting portion 41 of the auxiliary member 4 is sandwiched between the plate 2 and the tip portion 32 of the shaft 3, and in this state the tip portion 32 of the shaft 3 is pressed against the plate 2, thereby joining the tip portion 32 of the shaft 3 and the connecting portion 41, and at the same time, joining the connecting portion 41 and the plate 2. The tip portion 32 of the shaft 3 abuts against the connecting portion 41, so that the tip portion 32 of the shaft 3 can uniformly join the connecting portion 41, and the connecting portion 41 can be uniformly joined to the plate 2.

[0056] 2 , 4 , and 9 , in this embodiment, the auxiliary member 4 is fitted into a recess 22 formed in the plate 2. The lid portion 40 of the auxiliary member 4 is fitted into the first recess 23 of the recess 22, and the connecting portion 41 of the auxiliary member 4 is fitted into the second recess 24 of the recess 22. This facilitates positioning of the auxiliary member 4 relative to the plate 2, and therefore facilitates positioning of the shaft 3 relative to the plate 2. The surface of the lid portion 40 is not particularly limited, but is preferably flush with the second main surface 21 of the plate 2. The surface of the connecting portion 41 may protrude from the second main surface 21 of the plate 2, or may be flush with the second main surface 21 of the plate 2.

[0057] The surface of the lid portion 40 refers to the second surface 402 opposite to the first surface 401 of the lid portion 40 that abuts against the plate 2. The surface of the connecting portion 41 refers to the second surface 413 of the connecting portion 41 that abuts against the tip portion 32 of the shaft 3 and is the surface opposite to the first surface 401 that abuts against the plate 2. The lid portion 40 includes the first surface 401 and the second surface 402 that are spaced apart in the thickness direction, and a side surface 400 between the first surface 401 and the second surface 402. The connecting portion 41 includes a first surface 412 and a second surface 413 spaced apart in the thickness direction, an outer side surface 410 located between the first surface 412 and the second surface 413 and which is the outer peripheral surface of the connecting portion 41, and an inner side surface 411 located between the first surface 412 and the second surface 413 and radially inward from the outer side surface 410 and which is the inner peripheral surface of the connecting portion 41.

[0058] The width of the lid portion 40 is not particularly limited, but is preferably smaller than the width of the first recess 23. The length of the lid portion 40 is not particularly limited, but is preferably smaller than the length of the first recess 23. Furthermore, the outer diameter of the connecting portion 41 is not particularly limited, but is preferably smaller than the outer diameter of the second recess 24. This results in a gap G being formed between the side surface of the auxiliary member 4 and the side surface of the recess 22. The side surface of the auxiliary member 4 refers to the side surface 400 of the lid portion 40 (surfaces excluding the second surface 402, which is the front surface of the lid portion 40, and the first surface 401, which is the back surface) and the outer side surface 410, which is the outer peripheral surface of the connecting portion 41. The side surface of the recess 22 refers to the side surface 232 of the first recess 23 (surfaces excluding the bottom surface 220) and the outer side surface 240, which is the outer peripheral surface of the second recess 24.

[0059] Furthermore, although not particularly limited, the inner diameter of the connecting portion 41 is preferably larger than the inner diameter of the second recess 24 (the diameter of the protrusion 25). As a result, a gap G is formed between the inner circumferential surface 411 of the connecting portion 41 and the inner circumferential surface of the recess 22. Note that the inner circumferential surface of the recess 22 refers to the inner side surface 241 (the circumferential surface of the protrusion 25), which is the inner circumferential surface of the second recess 24.

[0060] These gaps G are, for example, 300 μm or more and 700 μm or less. By forming gaps G at least one between the side surface of auxiliary member 4 and the side surface of recess 22, and between inner circumferential surface 411 of connecting portion 41 and inner circumferential surface 241 of recess 22, lateral heat conduction between plate 2 and auxiliary member 4 can be suppressed. Therefore, heat from plate 2 is less likely to transfer to shaft 3 via auxiliary member 4, and the thermal uniformity of first main surface 20 on which a wafer is placed can be improved.

[0061] The gap G may be formed only partially between the side surface of the auxiliary member 4 and the side surface of the recess 22, and between the inner peripheral surface 411 of the connecting portion 41 and the inner peripheral surface 241 of the recess 22, but it is preferable to form the gap G over the entire circumference, as this can better suppress lateral heat conduction between the plate 2 and the auxiliary member 4. The presence of the gap G makes it possible to distinguish the plate 2 from the auxiliary member 4.

[0062] (Explanation of ceramic heater material) The plate 2, shaft 3, and auxiliary member 4 that make up the ceramic heater 1 are made of a sintered ceramic such as aluminum nitride, aluminum oxide, silicon carbide, or silicon nitride. Of these, it is preferable that each of the components 2-4 of the ceramic heater 1 contains aluminum nitride, which has high thermal conductivity, as the main component. This improves the thermal conductivity of the plate 2. Note that "main component" means that each of the components 2-4 of the ceramic heater 1 contains 95% by mass or more, and preferably 99% by mass or more, of aluminum nitride.

[0063] The plate 2 and the shaft 3 may be primarily composed of aluminum nitride, but may also contain an oxide of a rare earth element (hereinafter referred to as "rare earth oxide"), an oxide of an alkaline earth element, or an oxide of a transition metal element. Examples of rare earth oxides include yttria (yttrium oxide), cerium oxide, and samarium oxide, with yttria being preferred. Examples of alkaline earth oxides include magnesia (magnesium oxide), and examples of transition metal oxides include titania (titanium oxide). The addition of yttria to aluminum nitride improves its thermal conductivity. Therefore, the addition of yttria to the plate 2, which is primarily composed of aluminum nitride, can improve the thermal conductivity of the plate 2. The yttria content in the plate 2 and the shaft 3 is not particularly limited, but is preferably 0.05% by mass or more. The plate 2 and the shaft 3 may be primarily composed of aluminum nitride and contain yttria, resulting in a gray color.

[0064] Although there are no particular limitations on the auxiliary member 4, it is preferable that the auxiliary member 4 contains aluminum nitride as its main component and does not contain rare earth oxides such as yttria. Here, "the auxiliary member 4 does not contain rare earth oxides" means that the content of rare earth oxides in the auxiliary member 4 is below the detection limit, and does not exclude the auxiliary member 4 from containing trace amounts of rare earth oxides. Note that "below the detection limit" means, for example, that the content of rare earth oxides in the auxiliary member 4 is 5 ppm by mass or less when measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0065] The auxiliary member 4 may contain at least one oxide of an alkaline earth element and an oxide of a transition metal element. Examples of the oxide of the alkaline earth element include magnesia, and examples of the oxide of the transition metal element include titania. The content of the oxide in the auxiliary member 4 is, for example, 0.1 mass% or more and 3.0 mass% or less. The auxiliary member 4 may be composed primarily of aluminum nitride and contain no yttria, resulting in a gray color with a different shade from that of a material containing yttria. The auxiliary member 4 may be composed primarily of aluminum nitride, contain no yttria, and contain magnesia and titania, resulting in a dark gray color. Thus, the auxiliary member 4 has a different color shade in appearance from the plate 2 and shaft 3, which contain yttria. Therefore, the plate 2 and shaft 3 can be distinguished from the auxiliary member 4 by the color shade.

[0066] The plate 2, shaft 3, and auxiliary member 4 are integrated by diffusion bonding using, for example, a flux P shown in FIG. 14 . The flux P can be, for example, a paste containing calcia, alumina, and yttria. Because the auxiliary member 4 does not contain rare earth oxides such as yttria, diffusion of the rare earth components of the flux P is promoted near the bonding interface between the auxiliary member 4 and the plate 2 and near the bonding interface between the auxiliary member 4 and the shaft 3 when bonding the plate 2 and the auxiliary member 4 and the shaft 3 and the auxiliary member 4. This allows the bonding of the plate 2 and the auxiliary member 4 and the bonding of the shaft 3 and the auxiliary member 4 to be performed at low temperatures and with low loads.

[0067] Furthermore, although the auxiliary member 4 that does not contain yttria has inferior thermal conductivity to the plate 2 that contains yttria, the auxiliary member 4 is attached to only a portion of the second main surface 21 of the plate 2. Therefore, compared to when the auxiliary member 4 is attached to the entire second main surface 21 of the plate 2, the time required to make the temperature of the entire plate 2, including the auxiliary member 4, uniform is reduced. In the semiconductor manufacturing process, the temperature of the plate 2 must be raised and lowered to set it to the target temperature, but being able to quickly raise the temperature of the plate 2 to the target temperature stabilizes the operation of the semiconductor device.

[0068] (Explanation of Manufacturing Method of Ceramic Heater) Next, an outline of a manufacturing method of the ceramic heater 1 according to this embodiment will be described with reference to FIG. 14 . First, the plate 2, shaft 3, and auxiliary member 4 are prepared. The plate 2, shaft 3, and auxiliary member 4 are obtained by, for example, preparing a ceramic compact by mold casting and then firing the ceramic compact. Here, the "mold casting" refers to a method of obtaining a green body by injecting a ceramic slurry containing a ceramic raw material powder and a molding agent into a molding die and then causing a chemical reaction of the molding agent within the molding die to mold the ceramic slurry. The connecting portion 41 of the auxiliary member 4 may be formed into a ring plate and then fired, or may be formed into a disk and then fired, and then the center of the disk may be machined to form a ring plate.

[0069] Then, after the recesses 22 are formed on the second main surface 21 of the plate 2, the grooves 26 are formed. The recesses 22 and the grooves 26 can be formed by, for example, cutting or blasting.

[0070] Then, the plate 2 is placed on a workbench so that the second main surface 21 faces upward. After that, a flux P is applied to the portion of the plate 2 on the second main surface 21 side where the auxiliary member 4 will be placed, that is, to the bottom surface 220 of the recess 22 in this embodiment.

[0071] Then, the auxiliary member 4 is fitted into the recess 22 of the plate 2, thereby installing the auxiliary member 4 on the plate 2. At this time, the cover portion 40 of the auxiliary member 4 covers an outer portion 262 near the outer periphery of the second main surface 21 in the groove 26 formed in the plate 2, and an inner portion 263 near the center of the second main surface 21 in the groove 26 is positioned inside the connecting portion 41.

[0072] Then, flux P is applied to the second surface 413, which is the surface of the connecting portion 41 of the auxiliary member 4. Thereafter, the shaft 3 is placed on the auxiliary member 4 with the tip portion 32 facing downward so that the connecting portion 41 is covered by the tip portion 32.

[0073] Finally, for example, in a nitrogen atmosphere and at a temperature of about 1600° C. to 1700° C., a pressure of 10 kg / cm 2 is applied to the shaft 3 from above.2 More than 40kg / cm 2 While applying a load of about 1 / 2 sq. m, the connecting portion 41 of the shaft 3 and auxiliary member 4, and the connecting portion 41 of the auxiliary member 4 and the plate 2 are simultaneously joined. At the same time, the pressing member 9 applies a load of the same surface pressure from above to the lid portion 40 of the auxiliary member 4, and the lid portion 40 of the auxiliary member 4 and the plate 2 are joined. In this way, the plate 2, the shaft 3 and the auxiliary member 4 are integrated, and the ceramic heater 1 is manufactured.

[0074] In addition, through holes are formed in the ceramic heater 1 at positions corresponding to the terminals 12, 13, and 16 on the second main surface 21 of the plate 2. This exposes the terminals 12, 13, and 16, allowing the corresponding power feed rods 17, 18, and 19 to be connected to the terminals 12, 13, and 16. In addition, a recess 29 is formed in the second main surface 21 of the plate 2, into which the second thermocouple 15 can be inserted.

[0075] As described above, in the manufacturing method of the ceramic heater 1 of this embodiment, the tip portion 32 of the shaft 3 presses the connecting portion 41 of the auxiliary member 4 against the plate 2, and at the same time the pressing member 9 presses the lid portion 40 of the auxiliary member 4 against the plate 2, thereby joining the plate 2, auxiliary member 4, and shaft 3 together with a single pressing operation. Therefore, according to the manufacturing method of the ceramic heater 1 of this embodiment, the plate 2, auxiliary member 4, and shaft 3 can be easily integrated, and the manufacturing cost of the ceramic heater 1 can be reduced.

[0076] Furthermore, the plate 2, auxiliary member 4, and shaft 3 are joined in a heated state by applying heat, but the resistance heating element 5 built into the plate 2 is mainly composed of, for example, molybdenum, and therefore changes in electrical resistance due to carbonization or the like when heated. Therefore, in order to uniformly heat the plate 2 with the resistance heating element 5, it is desirable to suppress changes in the electrical resistance of the resistance heating element 5. By joining the plate 2, auxiliary member 4, and shaft 3 to each other by a single pressing operation, as in the manufacturing method of the ceramic heater 1 of this embodiment, it is possible to suppress variations in the electrical resistance of the resistance heating element 5. Therefore, the manufacturing method of the ceramic heater 1 of this embodiment can improve the thermal uniformity of the plate 2.

[0077] (Explanation of Functions and Effects of Ceramic Heater) In the ceramic heater 1 according to the first embodiment, no cavity is formed in the plate 2 as a thermocouple passage for inserting the first thermocouple 14 inside the plate 2. Instead, a groove 26 is formed in the plate 2, recessed from the second main surface 21 toward the first main surface 20. An outer portion 262 of the groove 26 is covered by the lid portion 40 of the auxiliary member 4 joined to the plate 2, thereby isolating the interior space from the exterior space. An inner portion 263 of the groove 26 is surrounded by the connecting portion 41 of the auxiliary member 4 joined to the plate 2, and the shaft 3 is joined to the connecting portion 41 of the auxiliary member 4, thereby isolating the interior space from the exterior space. Therefore, the first thermocouple 14 inserted inside the groove 26 is isolated from the exterior space, so that the temperature near the outer periphery of the plate 2 can be detected accurately by the first thermocouple 14.

[0078] Furthermore, in the ceramic heater 1 according to the first embodiment, even if a load is applied to the auxiliary member 4 and the plate 2 when joining the auxiliary member 4 and the shaft 3 to the plate 2, partial deflection of the auxiliary member 4 and the plate 2 is unlikely to occur. Therefore, when joining the plate 2 and the shaft 3, crushing of the groove 26 serving as a thermocouple passage or cracking of the plate 2 is suppressed.

[0079] Furthermore, in the ceramic heater 1 according to the first embodiment, the shaft 3 is joined to the connecting portion 41 of the auxiliary member 4, and the connecting portion 41 is joined to the plate 2, so that the shaft 3 is indirectly joined to the plate 2 via the connecting portion 41. By interposing the auxiliary member 4 between the plate 2 and the shaft 3 in this way, the number of bonding interfaces between the plate 2 and the shaft 3 is increased compared to when the shaft 3 is directly joined to the plate 2. Because bonding interfaces can hinder heat conduction, the increase in bonding interfaces reduces heat transfer from the plate 2 to the shaft 3. This makes it possible to suppress temperature unevenness in the plate 2 and improve thermal uniformity in the plate 2. Furthermore, because only the auxiliary member 4 is required to attach a small number of components to the plate 2, it is possible to suppress temperature unevenness in the plate 2 and improve thermal uniformity in the plate 2.

[0080] <Embodiment 2> Next, a ceramic heater 10 according to embodiment 2 will be described. The ceramic heater 10 according to embodiment 2 basically has the same structure as the ceramic heater 1 according to embodiment 1, and achieves the same effects. However, in embodiment 1, the method of attaching the auxiliary member 4 to the plate 2 differs from embodiment 1. Below, the differences from embodiment 1 will be mainly described.

[0081] Fig. 15 is an exploded perspective view of the ceramic heater 10 according to embodiment 2. Figs. 16 to 21 are a plan view, a bottom view, a front view, a back view, a right side view, and a left side view, respectively, of the ceramic heater 10 according to embodiment 2. Fig. 22 is an enlarged cross-sectional view showing a part of the ceramic heater 10 according to embodiment 2 cut along a vertical plane including line A-A in Fig. 17.

[0082] In the ceramic heater 1 according to the first embodiment described above, the recess 22 is formed in the plate 2, and the auxiliary member 4 is joined to the plate 2 in a state where it is fitted into the recess 22. In contrast, in the ceramic heater 10 according to the second embodiment, the recess 22 is not formed in the plate 2, and the auxiliary member 4 is joined to the plate 2 in a state where it is placed on the second main surface 21.

[0083] The groove 26 is formed in the second main surface 21 of the plate 2 so as to recess toward the first main surface 20. The groove 26 extends in the second main surface 21 of the plate 2 from a region inside the shaft 3 to a region outside the shaft 3 just before the outer periphery of the second main surface 21. That is, of the start end 260 and the end end 261, which are both ends of the groove 26, the start end 260 is located inside the shaft 3. The end end 261 is located outside the shaft 3 and just before the outer periphery of the second main surface 21. The first thermocouple 14 is inserted into the groove 26 from an inner portion 263 located inside the shaft 3, and then passed through an outer portion 262 located outside the shaft 3, to reach near the outer periphery of the plate 2. In this embodiment, the groove 26 extends to just before the outer periphery of the second main surface 21, and the end 261 of the groove 26 is located just before the outer periphery of the second main surface 21, but the end 261 of the groove 26 may be located away from the outer periphery of the second main surface 21 as long as it is located outside the shaft 3.

[0084] The auxiliary member 4 is joined to the second main surface 21 of the plate 2 so that the outer portion 262 of the groove 26 is covered by the lid portion 40 and the inner portion 263 of the groove 26 is located inside the connecting portion 41. The tip portion 32 of the shaft 3 is joined to the connecting portion 41 of the auxiliary member 4, thereby integrating the shaft 3, the auxiliary member 4, and the shaft 3.

[0085] <Embodiment 3> Next, a ceramic heater 11 according to embodiment 3 will be described. The ceramic heater 11 according to embodiment 3 basically has the same structure as the ceramic heater 1 according to embodiment 1, and achieves the same effects. However, in embodiment 3, the shape of the recess 22 formed in the plate 2 for fitting the auxiliary member 4 is different from that of embodiment 1. Below, the differences from embodiment 1 will be mainly described.

[0086] 23 to 29 are respectively an exploded perspective view, a plan view, a bottom view, a front view, a back view, a right side view, and a left side view of the ceramic heater 11 according to embodiment 3. Fig. 30 and Fig. 31 are enlarged cross-sectional views showing a part of the ceramic heater 11 according to embodiment 3. Fig. 32 is a bottom view of the plate 2 which is a component of the ceramic heater 11 according to embodiment 3.

[0087] In the ceramic heater 1 according to the first embodiment described above, an annular second recess 24 is formed in the plate 2, and the annular connecting portion 41 of the auxiliary member 4 is fitted into the second recess 24 with the protrusion 25 fitted inside. In contrast, in the ceramic heater 11 according to the third embodiment, the second recess 24 formed in the plate 2 so as to be continuous with the first recess 23 has a shallow bowl shape and is formed by hollowing out a solid thin plate from the second main surface 21 side of the plate 2. In this embodiment, the shape of the second recess 24 in a plan view is circular to match the outer shape of the connecting portion 41 of the auxiliary member 4, and the second recess 24 is formed by hollowing out a thin disk from the second main surface 21 side of the plate 2. The second recess 24 is formed to include a flat, circular bottom surface 242 against which the annular connecting portion 41 abuts, and an outer circumferential surface 240 facing the outer circumferential surface 410 of the connecting portion 41. The center of the second recess 24 in a plan view coincides with the center of the second main surface 21 , and the second recess 24 is formed in the plate 2 so as to be concentric with the second main surface 21 .

[0088] Referring to FIG. 31 , the corner between the outer peripheral surface 240 and the bottom surface 242 of the second recess 24 may be chamfered. The chamfering may be C-chamfering or R-chamfering. C-chamfering refers to a corner between the outer peripheral surface 240 and the bottom surface 242 being beveled at a predetermined angle (e.g., 45°). R-chamfering refers to a corner between the outer peripheral surface 240 and the bottom surface 242 being rounded and smoothly cut. The roundness that inevitably forms at the corner between the outer peripheral surface 240 and the bottom surface 242 when forming the second recess 24 in the plate 2 does not qualify as chamfering. By chamfering the corner between the outer peripheral surface 240 and the bottom surface 242 of the second recess 24, stress generated in the second recess 24 of the plate 2 can be prevented from concentrating at the corner between the outer peripheral surface 240 and the bottom surface 242 when the connecting portion 41 of the auxiliary member 4 is pressed and joined to the plate 2 during manufacturing of the ceramic heater 10. This reduces the risk of damage to the second recess 24.

[0089] 30 , the corner between the side surface 232 and the bottom surface 233 of the first recess 23 may also be chamfered in the same manner as the second recess 24. This makes it possible to prevent stress generated in the first recess 23 of the plate 2 from concentrating on the corner between the side surface 232 and the bottom surface 233 when the lid portion 40 of the auxiliary member 4 is pressed and joined to the plate 2 during the manufacture of the ceramic heater 10. This makes it possible to reduce the risk of the first recess 23 being damaged.

[0090] 30 and 31 , in the ceramic heater 11 according to the third embodiment, when the connecting portion 41 of the auxiliary member 4 is fitted into the second recess 24, the bottom surface 242 of the second recess 24 is exposed inside the connecting portion 41. On the second main surface 21 side of the plate 2, no protrusion 25 is present inside the connecting portion 41, and a space S surrounded by the connecting portion 41 exists on the bottom surface 242 of the second recess 24.

[0091] 23 , the groove 26 is formed in the bottom surface 220 of the recess 22 of the plate 2 (the bottom surface 233 of the first recess 23 and the bottom surface 242 of the second recess 24) so ​​as to recess toward the first main surface 20. The groove 26 extends, on the second main surface 21 side of the plate 2, from a region inside the shaft 3 to a region outside the shaft 3 just before the outer periphery of the second main surface 21. That is, of the start end 260 and the end end 261, which are both ends of the groove 26, the start end 260 is located inside the shaft 3. The end end 261 is located outside the shaft 3 and just before the outer periphery of the second main surface 21. The first thermocouple 14 is inserted into the groove 26 from an inner portion 263 located inside the shaft 3, and then passed through an outer portion 262 located outside the shaft 3, until it reaches the vicinity of the outer periphery of the plate 2. In this embodiment, the groove 26 extends to just before the outer periphery of the second main surface 21, and the end 261 of the groove 26 is located just before the outer periphery of the second main surface 21, but the end 261 of the groove 26 may be located away from the outer periphery of the second main surface 21 as long as it is located outside the shaft 3.

[0092] 30 , the auxiliary member 4 is fitted into a recess 22 formed in the plate 2 and joined to the plate 2 at the recess 22, as in the first embodiment. The second surface 402, which is the surface of the lid portion 40, is not particularly limited, but is preferably flush with the second main surface 21 of the plate 2. The second surface 413, which is the surface of the connecting portion 41, may protrude from the second main surface 21 of the plate 2, or may be flush with the second main surface 21 of the plate 2. The tip portion 32 of the shaft 3 is joined to the connecting portion 41 of the auxiliary member 4, thereby integrating the shaft 3, the auxiliary member 4, and the shaft 3.

[0093] In the ceramic heater 11 according to the third embodiment, the auxiliary member 4 is fitted into the recess 22, so that the auxiliary member 4 can be easily positioned relative to the plate 2, and therefore the shaft 3 can be easily positioned relative to the plate 2.

[0094] 30 and 31 , with respect to the connecting portion 41 of the auxiliary member 4 fitted into the recess 22 of the plate 2, the protrusion 25 of the plate 2 is not present inside the connecting portion 41, and a space S exists therebetween. Therefore, it is possible to prevent heat from being transferred from the plate 2 to the auxiliary member 4 due to thermal radiation from the protrusion 25. With reference to FIG. 9 , in the ceramic heater 1 according to the first embodiment, a gap G is formed between the inner circumferential surface 411 of the connecting portion 41 and the inner circumferential surface 241 (the circumferential surface of the protrusion 25) of the second recess 24 in order to suppress heat transfer from the plate 2 to the auxiliary member 4, thereby suppressing lateral heat conduction, in which heat from the plate 2 is directly transferred from the plate 2 to the auxiliary member 4. In the ceramic heater 11 according to the third embodiment, since there are no protrusions 25 inside the connecting portion 41 and a space S larger than the gap G is formed, lateral heat conduction does not occur in which heat from the plate 2 is directly transferred from the plate 2 to the auxiliary member 4 via the protrusions 25, and heat from the plate 2 is not transferred from the plate 2 to the auxiliary member 4 by thermal radiation from the protrusions 25. Therefore, transfer of heat from the plate 2 to the shaft 3 via the auxiliary member 4 is effectively suppressed. This further improves the temperature uniformity of the first main surface 20 of the plate 2 on which a wafer is placed. Furthermore, the absence of protrusions 25 on the plate 2 shortens the time required to heat the plate 2 to a desired temperature.

[0095] 30 and 31, since the protrusions 25 of the plate 2 are not present inside the connecting portions 41, when the connecting portions 41 are pressed and joined to the plate 2 during manufacture of the ceramic heater 10, stress generated in the second recesses 24 of the plate 2 does not concentrate at the corner between the inner circumferential surface 241 (the circumferential surface of the protrusions 25) and the bottom surface 242, as in the ceramic heater 1 according to embodiment 1 shown in Fig. 9. This reduces the risk of damage to the second recesses 24.

[0096] <Other Modification 1> In the ceramic heater 1 according to the above-described embodiment 1, similarly to embodiment 3, the corner between the side surface 232 and the bottom surface 233 of the first recess 23 and the corner between the outer circumferential surface 240 and the bottom surface 242 of the second recess 24 may be chamfered. Similarly, the corner between the inner circumferential surface 241 and the bottom surface 242 of the second recess 24 may also be chamfered. This reduces the risk of damage to the first recess 23 and the second recess 24 of the plate 2 during the manufacture of the ceramic heater 10.

[0097] <Other Modification 2> In the ceramic heater 1 according to the above-described first embodiment, the surface of the protrusion 25 surrounded by the second recess 24 is located at the same height as the second main surface 21 of the plate 2, but it may be located lower than the second main surface 21 of the plate 2 toward the first main surface 20, and a space surrounded by the inner circumferential surface 411 of the connecting portion 41 may be formed on the surface of the protrusion 25. According to this modification, it is possible to prevent heat from the plate 2 from being transferred from the plate 2 to the auxiliary member 4 by thermal radiation from the protrusion 25. Therefore, it is possible to effectively prevent heat from the plate 2 from being transferred to the shaft 3 via the auxiliary member 4, thereby further improving the thermal uniformity of the first main surface 20 of the plate 2 on which a wafer is placed.

[0098] <Other Modification 3> In the ceramic heaters 1, 10, 11 according to the above-described embodiments 1, 2, and 3, the cover portion 40 and the connecting portion 41 of the auxiliary member 4 may have at least a portion tapered on the side of the first surface 401, 412 that contacts the plate 2. Fig. 33 is a plan view of the auxiliary member 4 of the modification. Fig. 34 is a bottom view of the auxiliary member 4 of the modification. Fig. 35 is a side view of the auxiliary member 4 of the modification. Figs. 36(A) and (B) are cross-sectional views of the auxiliary member 4 of the modification. Figs. 37 and 38 are cross-sectional views showing enlarged portions of the ceramic heater 11 according to embodiment 3 that includes the auxiliary member 4 of the modification.

[0099] For example, referring to FIG. 36A , in the lid portion 40 of the auxiliary member 4, a portion of the first surface 401 side of at least one of a pair of opposing side surfaces 400 of the lid portion 40 can be inclined inward to form an inclined surface 403, thereby forming at least a portion of the lid portion 40 on the first surface 401 side in a tapered shape. The side surface 400 of the lid portion 40 may be inclined entirely from the end on the second surface 402 side to the end on the first surface 401 side. However, in this case, the corner between the side surface 400 and the second surface 402 that does not abut the plate 2 becomes sharp, making the lid portion 40 prone to breakage, such as chipping. Therefore, it is preferable that only a portion of the side surface 400 of the lid portion 40 on the first surface 401 side be inclined as the inclined surface 403. The width d1 of the first surface 401 is preferably 15 mm or more to strengthen the bond between the lid portion 40 and the plate 2.

[0100] At least a portion of the lid portion 40 on the first surface 401 side is tapered by C-chamfering the corner between the first surface 401 and the side surface 400, but the corner may be tapered by R-chamfering the corner between the first surface 401 and the side surface 400. In other words, the side surface 400 of the lid portion 40 does not necessarily have to be inclined linearly, and may be inclined curvedly.

[0101] 36(B), in the connecting portion 41 of the auxiliary member 4, a portion of the inner circumferential surface 411 of the connecting portion 41 on the first surface 412 side can be inclined outward, that is, toward the outer circumferential surface 410 of the connecting portion 41, to form a first inclined surface 414, thereby making it possible to form at least a portion of the connecting portion 41 on the first surface 412 side in a tapered shape. Alternatively or in addition to this, a portion of the outer circumferential surface 410 of the connecting portion 41 on the first surface 412 side can be inclined inward, that is, toward the inner circumferential surface 411 of the connecting portion 41, to form a second inclined surface 415, thereby making it possible to form at least a portion of the connecting portion 41 on the first surface 412 side in a tapered shape. The outer peripheral surface 410 and the inner peripheral surface 411 of the connecting portion 41 may be inclined over the entire length from the end on the second surface 413 side to the end on the first surface 412 side. However, in this case, the corners between the outer peripheral surface 410 and the inner peripheral surface 411 and the second surface 413 that does not abut the plate 2 become sharp and sharp, making the connecting portion 41 prone to breakage such as chipping. Therefore, it is preferable that only a portion of the outer peripheral surface 410 and the inner peripheral surface 411 of the connecting portion 41 on the first surface 412 side be inclined surfaces 414, 415. The width d2 of the first surface 412 is preferably 5 mm or more to strengthen the bond between the connecting portion 41 and the plate 2.

[0102] In the cover portion 40 and the connecting portion 41 of the auxiliary member 4, when the areas of the first surfaces 401, 412 that contact the plate 2 are small, vertical heat conduction, in which heat from the plate 2 is directly transferred from the plate 2 to the auxiliary member 4, is suppressed. Therefore, heat from the plate 2 is less likely to transfer to the shaft 3 via the auxiliary member 4, and the thermal uniformity of the first main surface 20 of the plate 2 on which the wafer is placed can be further improved.

[0103] At least a portion of the above-described connecting portion 41 on the first surface 412 side is formed in a tapered shape by C-chamfering the corner between the first surface 412 and the inner circumferential surface 411 and the corner between the first surface 412 and the outer circumferential surface 410, but the corner between the first surface 412 and the inner circumferential surface 411 and the corner between the first surface 412 and the outer circumferential surface 410 may also be formed in a tapered shape by R-chamfering. In other words, the inner circumferential surface 411 and the outer circumferential surface 410 of the connecting portion 41 do not necessarily have to be inclined linearly, and may be inclined curvedly.

[0104] By chamfering the corner between the first surface 401 and the side surface 400 of the lid portion 40, and by chamfering the corner between the first surface 412 and the inner peripheral surface 411 and the corner between the first surface 412 and the outer peripheral surface 410 of the connecting portion 41, it is possible to prevent stress generated in the lid portion 40 and the connecting portion 41 from concentrating on the above-mentioned corners when the lid portion 40 and the connecting portion 41 of the auxiliary member 4 are pressed and joined to the plate 2 during the manufacture of the ceramic heater 10. This reduces the risk of damage to the lid portion 40 and the connecting portion 41 of the auxiliary member 4.

[0105] From the viewpoint of suppressing stress concentration at such corners, it is preferable that the corners between the first surface 401 and the pair of opposing side surfaces 400 of the cover 40 are chamfered. It is also preferable that the corners between the first surface 412 and the outer peripheral surface 410 and the inner peripheral surface 411 of the connecting portion 41 are chamfered.

[0106] Furthermore, from the viewpoint of effectively suppressing stress concentration at the corners, it is preferable that the inclined surfaces 403, 414, and 415 formed by the chamfering be inclined over a long distance. Here, "the inclined surfaces 403, 414, and 415 are inclined over a long distance" refers to a long distance w1 of the inclined surface 403 in the lid portion 40, as shown in FIG. 36(A). Specifically, the distance w1 is the distance by which the inclined surface 403 inwardly slopes from the side surface 400, i.e., the horizontal distance between the end of the inclined surface 403 on the side surface 400 side and the end of the inclined surface 403 on the first surface 401 side. Note that the horizontal distance refers to the distance parallel to the first surface 401 in the cross section of the lid portion 40, and the distance in the width direction in the plane of the lid portion 40.

[0107] 36(B) , in the connecting portion 41, the inclination distance w2 of the first inclined surface 414 and the inclination distance w3 of the second inclined surface 415 are long. Specifically, the distance w2 refers to the distance by which the first inclined surface 414 indents from the inner circumferential surface 411 due to the inclination, i.e., the horizontal distance between the end of the first inclined surface 414 on the inner circumferential surface 411 side and the end of the first inclined surface 414 on the first surface 412 side. Furthermore, the distance w3 refers to the distance by which the second inclined surface 415 indents from the outer circumferential surface 410 due to the inclination, i.e., the horizontal distance between the end of the second inclined surface 415 on the outer circumferential surface 410 side and the end of the second inclined surface 415 on the first surface 412 side. Note that the horizontal distance refers to the distance parallel to the first surface 412 in the cross section of the connecting portion 41, and refers to the distance along the radial direction of the annular connecting portion 41 in the plan view of the connecting portion 41.

[0108] The distances w1, w2, and w3 by which the inclined surfaces 403, 414, and 415 are inclined can be increased by increasing the inclination angle of the inclined surfaces 403, 414, and 415 or by increasing the height of the inclined surfaces 403, 414, and 415 (the vertical distance between both ends of the inclined surfaces 403, 414, and 415).

[0109] Regarding the connecting portion 41, referring to Figure 36 (B), it is preferable that the first inclined surface 414 is inclined over a longer distance than the second inclined surface 415, that is, the distance w2 over which the first inclined surface 414 is inclined is longer than the distance w3 over which the second inclined surface 415 is inclined. Specifically, when the inclination angle of the first inclined surface 414, that is, the angle at which the first inclined surface 414 is inclined with respect to a direction parallel to the first surface 412 in the cross section of the connecting portion 41, and the inclination angle of the second inclined surface 415, that is, the angle at which the second inclined surface 415 is inclined with respect to a direction parallel to the first surface 412 in the cross section of the connecting portion 41, are the same, it is preferable that the height of the first inclined surface 414, that is, the distance along the vertical direction between the end of the first inclined surface 414 on the inner surface 411 side and the end of the first inclined surface 414 on the first surface 412 side, is longer than the height of the second inclined surface 415, that is, the vertical distance between the end of the second inclined surface 415 on the outer surface 410 side and the end of the second inclined surface 415 on the first surface 412 side. In connecting portion 41, if the inclined distance w3 of second inclined surface 415 is increased, the angle between outer peripheral surface 410 and second surface 413 tends to become an acute angle that is prone to breakage. By making the inclined distance w2 of first inclined surface 414 longer than the inclined distance w3 of second inclined surface 415, connecting portion 41 can be shaped so that the angle between outer peripheral surface 410 and second surface 413 does not become an acute angle while ensuring the width d2 of first surface 412 and making inclined surfaces 414, 415, which are effective in suppressing stress concentration, as large as possible.

[0110] <Other Modification 4> In the ceramic heaters 1, 11 according to the above-described first and third embodiments, a gap G is formed between the side surface of the auxiliary member 4 fitted into the recess 22 of the plate 2 (the side surface 400 of the lid portion 40 and the outer peripheral surface 410 of the connecting portion 41) and the side surface of the recess 22 (the side surface 232 of the first recess 23 and the outer peripheral surface 240 of the second recess 24), but this gap G may be filled. Furthermore, in the ceramic heater 1 according to the above-described first embodiment, a gap G is also formed between the inner peripheral surface 411 of the connecting portion 41 and the inner peripheral surface 241 of the second recess 24, but this gap G may be filled.

[0111] 39 and 40 are enlarged cross-sectional views showing a portion of the ceramic heater 11 according to embodiment 3 in which the gap G is filled with a filler 50. Ceramics, resin, or the like is used as the filler 50. For example, ceramic powder made of the same material as the plate 2 is filled into the gap G and fired, thereby filling the gap G with the filler 50. Alternatively, liquid thermosetting resin such as epoxy resin or silicone resin is filled into the gap G and hardened, thereby filling the gap G with the filler 50. The resin may be a composite resin containing a filler such as ceramic or metal.

[0112] Filling the gap G with the filler material 50 reduces the risk of unwanted materials, such as processing chips and dust, accumulating in the gap G of the manufactured ceramic heater 1, 10. For example, when performing processes such as chemical vapor deposition (CVD) and etching on wafers in a semiconductor manufacturing device, if unwanted materials accumulate in the gap G of the ceramic heater 1, 10, there is a concern that the unwanted materials may scatter toward the wafer during wafer processing, adversely affecting the wafer processing. Furthermore, if gas used in wafer processing enters the gap G and causes corrosion at the bonding surface between the auxiliary member 4 and the plate 2, there is a concern that the bonding strength between the auxiliary member 4 and the plate 2 may decrease. Filling the gap G with the filler material 50 eliminates the above-mentioned concerns. Whether to fill the gap G with the filler material 50 or to leave the gap G as is can be selected appropriately, taking into account the advantages of each.

[0113] <Modification 5> In the ceramic heaters 1 and 10 according to the first and second embodiments described above, the connecting portion 41 of the auxiliary member 4 is an annular ring plate, but it may also be a solid disk. In this case, a through hole communicating with the groove 26 formed in the plate 2 is formed in the connecting portion 41. As a result, the first thermocouple 14 is inserted through the through hole in the connecting portion 41 and then passed through the groove 26 in the plate 2, so that it is inserted up to near the outer periphery of the plate 2. Note that when the connecting portion 41 of the auxiliary member 4 is an annular ring plate, the volume of the auxiliary member 4 can be reduced, and the proportion of the auxiliary member 4 in the entire plate 2 including the auxiliary member 4 is reduced. Note that in the ceramic heater 11 according to the third embodiment, the connecting portion 41 of the auxiliary member 4 may also be a solid disk.

[0114] <Other Modification 6> In the ceramic heaters 1 and 10 according to the first and second embodiments described above, a configuration has been exemplified in which one groove 26 is formed in the plate 2 and the auxiliary member 4 includes one lid portion 40 corresponding to this groove, but the number of grooves 26 formed in the plate 2 is not limited to one, and the auxiliary member 4 may include multiple lid portions 40 corresponding to the number of grooves 26. In this case, the multiple lid portions 40 may extend in different directions from different positions on one connecting portion 41. Note that in the ceramic heater 11 according to the third embodiment, the number of grooves 26 formed in the plate 2 is not limited to one, and the auxiliary member 4 may include multiple lid portions 40 corresponding to the number of grooves 26.

[0115] It should be understood that the embodiments disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present invention is defined not by the above description but by the claims, and it is intended to include all modifications within the meaning and scope of the claims.

[0116] DESCRIPTION OF SYMBOLS 1 Ceramic heater according to embodiment 1, 2 Plate, 3 Shaft, 4 Auxiliary member, 5 Resistance heating element, 6 Electrode, 7 Support stand, 8 O-ring, 9 Pressing member, 10 Ceramic heater according to embodiment 2, 11 Ceramic heater according to embodiment 3, 12 Terminal, 13 Terminal, 14 First thermocouple, 15 Second thermocouple, 16 Terminal, 17 First power feed rod, 18 Second power feed rod, 19 Third power feed rod, 20 First main surface, 21 Second main surface, 22 Recess, 23 First recess, 24 Second recess, 25 Protrusion, 26 Groove, 27 First groove portion, 28 Second groove portion, 29 Indentation, 30 First opening, 31 Second opening, 32 Tip end portion of shaft, 33 Base end portion of shaft, 34 Small diameter portion of shaft, 35 Large diameter portion of shaft, 40 Lid portion, 41 Connecting portion, 50 Filler, 220 Bottom surface of recess, 230 Starting end of first recess, 231 End of first recess, 232 Side surface of first recess, 233 Bottom surface of first recess, 240 Outer side surface (outer peripheral surface) of second recess, 241 Inner side surface (inner peripheral surface) of second recess, 242 Bottom surface of second recess, 260 Starting end of groove, 261 End of groove, 262 Outer portion of groove, 263 Inner portion of groove, 400 Side surface of lid portion, 401 First surface of lid portion, 402 Second surface of lid portion, 403 Inclined surface of lid portion, 410 Outer side surface (outer peripheral surface) of connecting portion, 411 Inner side surface (inner peripheral surface) of connecting portion, 412 First surface of connecting portion, 413 Second surface of connecting portion, 414 First inclined surface, 415 Second inclined surface, G Gap, d1 The width of the first surface of the lid portion, d2; the width of the ring of the first surface of the connecting portion, w1; the distance over which the inclined surface extends, w2; the distance over which the first inclined surface extends, w3; the distance over which the second inclined surface extends.

Claims

1. A ceramic heater comprising: a plate-like plate having a first main surface on which a wafer is placed and a second main surface located at a distance in the thickness direction from the first main surface, and containing a resistance heating element that generates heat when current is applied; a cylindrical shaft having a first opening and a second opening located at both ends in the axial direction and supporting the plate at the second main surface; and a plate-like auxiliary member joined to the plate, wherein the plate has a groove formed therein that is recessed from the second main surface toward the first main surface and extends from a starting end located inside the shaft to a terminal end located outside the shaft, and the auxiliary member includes: a lid portion that extends along an outer portion of the groove that is located outside the shaft and covers the outer portion; and a connecting portion that is sandwiched between the plate and the shaft and is joined to a tip end of the shaft that surrounds the first opening.

2. A ceramic heater as set forth in claim 1, wherein said plate is formed with a recess recessed from said second main surface toward said first main surface, into which said auxiliary member is fitted, and at least a portion of said groove is formed on the bottom surface of said recess so as to recess toward said first main surface.

3. The ceramic heater according to claim 2, wherein a gap is formed at least partially between the side surface of said auxiliary member and the side surface of said recess.

4. The ceramic heater according to claim 2, wherein the connecting portion has an annular shape against which the tip portion of the shaft abuts, the recess includes a first recess into which the lid portion is fitted, and a second recess into which the connecting portion is fitted and which is continuous with the first recess, the second recess is formed in an annular shape with an inner circumferential surface that faces the inner circumferential surface of the connecting portion, and the groove includes: first groove portions formed in the bottom surfaces of the first recess and the second recess so as to be recessed toward the first main surface, and second groove portions formed in the second main surface of the plate inside the shaft so as to be recessed toward the first main surface, and the first groove portions and the second groove portions are continuous with each other.

5. The ceramic heater according to claim 4, wherein a gap is formed at least partially between the inner circumferential surface of said connecting portion and the inner circumferential surface of said second recess.

6. The ceramic heater according to claim 2, wherein the connecting portion has an annular shape against which the tip portion of the shaft abuts, the recess includes a first recess into which the lid portion is fitted, and a second recess into which the connecting portion is fitted and which is continuous with the first recess, the second recess is formed to have a flat bottom surface against which the connecting portion abuts and an outer circumferential surface facing the outer circumferential surface of the connecting portion, and a space exists inside the connecting portion on the flat bottom surface, and the grooves are formed in the bottom surfaces of the first recess and the second recess so as to recess toward the first main surface.

7. A ceramic heater according to any one of claims 4 to 6, wherein at least a portion of the first surface of at least one of the cover portion and the connecting portion of the auxiliary member that contacts the plate is tapered.

8. A ceramic heater according to claim 7, wherein at least a portion of the inner peripheral surface of the connecting portion on the side of the first surface is a first inclined surface that is inclined toward the outer peripheral surface of the connecting portion.

9. A ceramic heater as set forth in claim 8, wherein at least a portion of the outer circumferential surface of said connecting portion on the side of said first surface is a second inclined surface inclined toward the inner circumferential surface of said connecting portion, and said first inclined surface is inclined over a longer distance than said second inclined surface.

10. A ceramic heater according to claim 3 or claim 5, wherein the gaps are filled with a filler material.

11. A ceramic heater according to any one of claims 1 to 6, wherein the plate and the shaft are made primarily of aluminum nitride, and the auxiliary member is made primarily of aluminum nitride and does not contain yttria.

12. A process of forming a groove in a flat plate having a built-in resistance heating element that generates heat when current is applied, the groove being recessed from the second main surface toward the first main surface, of a first main surface and a second main surface positioned at an interval in the thickness direction, and extending from the center of the second main surface toward the outer periphery of the second main surface; a process of installing a flat auxiliary member including a lid portion and an annular connecting portion on the plate so that an outer portion of the groove, which is a portion of the groove closer to the outer periphery of the second main surface, is covered by the lid portion extending along the outer portion, and an inner portion of the groove, which is a portion of the groove closer to the center of the second main surface, is located inside the connecting portion; a process of installing a cylindrical shaft on the auxiliary member so that a tip portion, which is a region surrounding the first opening, of a first opening and a second opening positioned at both ends in the axial direction, abuts on the connecting portion; a step of simultaneously joining the connecting portion of the shaft and the auxiliary member, and the connecting portion of the auxiliary member and the plate while applying pressure to the shaft, and joining the lid portion of the auxiliary member and the plate while applying a load to the lid portion of the auxiliary member with a pressing member.

13. A method for manufacturing a ceramic heater as set forth in claim 12, wherein at least a portion of the inner peripheral surface of the connecting portion on the first surface side that abuts against the plate is inclined toward the outer peripheral surface of the connecting portion.

Images