JP6650332B2 - Substrate holding device and method of manufacturing the same - Google Patents

Description

  The present invention relates to a substrate holding device for holding a substrate such as a semiconductor wafer on a base material and a method for manufacturing the same.

  2. Description of the Related Art Conventionally, in order to hold a substrate, a substrate holding device including a base material made of ceramics and supporting the substrate on an upper surface, and a hollow shaft made of ceramics and having a flange portion on an upper portion has been used.

  In Patent Literature 1, a protruding portion (convex portion) is provided at a central portion of a lower surface of a base material so as to protrude downward so as to be thicker than a peripheral portion, and has an upper surface joined to a lower surface of the protruding portion. It is disclosed that a flange portion is provided on an upper portion of a shaft. And, by forming a more continuous surface with the outer peripheral side surface of the protruding portion and the outer peripheral side surface of the flange portion, the temperature gradient at the joint between the base material and the flange portion is reduced, and thermal stress concentration is reduced, It is stated that the risk of cracks occurring at the joint is reduced.

Japanese Patent No. 3810216

  However, as disclosed in Patent Document 1, in order to form a more continuous surface between the outer peripheral side surface of the protrusion and the outer peripheral side surface of the flange portion, the corner portion of the connection portion between the protrusion portion and the flange portion is formed at a right angle. There is a need to. When the corners of the joining portion are right angles, chipping and microcracks are liable to occur therefrom, and there is a high possibility that damage and peeling will occur.

  When a joining material is interposed at the time of joining the base material and the shaft, the joining can be performed with a relatively small pressure, so that the occurrence of chipping and micro cracks at the time of joining is suppressed. However, in the case of solid-state bonding that does not involve a bonding material, assuming the plasma resistance of the bonding material and applications under higher temperatures, a high bonding temperature and a large pressure are required, and chipping and micro cracks may occur. Is big.

  Accordingly, an object of the present invention is to provide a substrate holding device and a method for manufacturing the substrate holding device, which can reduce the possibility of chipping or microcracking occurring from a joint between a substrate and a shaft in solid-state joining without a joining material. And

  The substrate holding device of the present invention is made of ceramics, supports the substrate on the upper surface, a base material having a protruding portion that protrudes downward so as to be thicker than the peripheral portion at the center of the lower surface, and is made of ceramics, A hollow shaft having a flange portion connected to the projecting portion at an upper portion thereof, wherein the projecting portion is entirely formed on at least one of an outer peripheral edge of a lower end portion and an outer peripheral edge of an upper end portion. It is characterized by having a chamfer over the circumference.

  According to the substrate holding device of the present invention, at least one of the joining portions of the base material and the shaft has a chamfered portion over the entire circumference. For this reason, it is possible to reduce the possibility that damage such as chipping or microcracks may occur from the joint, as compared with a case where both of these portions are perpendicular at a conventional angle.

  In the substrate holding device of the present invention, it is preferable that the inner peripheral edge of the upper end portion of the flange portion has a chamfered portion over the entire circumference.

  In this case, the inner peripheral edge of the joint of the shaft also has a chamfer. For this reason, it is possible to reduce the possibility that damage such as chipping or microcracks may occur from the joint, as compared with the case where this portion is a right angle as in the related art.

Further, in the substrate holding apparatus of the present invention, the outer peripheral side of the outer peripheral side and the flange portion of the projection Ru substantially flush der.

  In the present invention, the phrase that the outer peripheral side surface of the protruding portion and the outer peripheral side surface of the flange portion are substantially flush is not limited to the case where they are flush with each other, but is slightly shifted, for example, 0.2 mm, preferably 1 mm or less. It means that you may.

  The method for manufacturing a substrate holding device of the present invention includes a step of preparing a substrate made of ceramics and having a protruding portion that protrudes downward so as to be thicker than a peripheral portion in a central portion of a lower surface; A step of preparing a hollow shaft having a flange portion connected to the projecting portion at an upper portion, and at least one of an outer peripheral edge of a lower end portion of the projecting portion or an outer peripheral edge of an upper end portion of the flange portion over the entire circumference; The method includes a step of chamfering, and a step of joining the surfaces by solid phase joining in a state where the lower surface of the protruding portion and the upper surface of the flange portion are in contact with each other.

  According to the method of manufacturing a substrate holding device of the present invention, in the step of joining by solid-phase joining, at least one of the portions where the base material and the shaft contact each other is chamfered. For this reason, it is possible to reduce the possibility of damage such as chipping and micro cracks occurring in the joining step, as compared with the case where the corners of the contacting parts are both right angles as in the related art.

In the manufacturing method of the substrate holding apparatus of the present invention, Ru comprising the step of machining the outer peripheral side surface substantially flush to the outer peripheral side and the flange portion of the protruding portion.

FIG. 1 is a schematic sectional view of a ceramic heater according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a ceramic heater according to another aspect of the embodiment of the present invention. FIG. 9 is a schematic partial cross-sectional view of a ceramic heater according to a modification of the embodiment of the present invention. FIG. 9 is a schematic partial cross-sectional view of a ceramic heater according to another modification of the embodiment of the present invention.

(Embodiment)
A ceramic heater 100 according to an embodiment of the substrate holding device of the present invention will be described with reference to FIG.

  The ceramic heater 100 includes a base material 10, an electrode 20, a shaft 30, and a power supply rod 40.

  In the present embodiment, in the ceramic heater 100, the electrode 20 functions as a heating resistor (heater), and the heat generated when a voltage is applied to the heater from the power supply rod 40 supports the upper surface of the base material 10. A substrate such as a semiconductor wafer supported on the surface is heated. Note that the ceramic heater 100 may be a multi-zone heater in which a plurality of electrodes 20 that are electrically independent of each other exist, and a voltage supplied to these electrodes 20 can be controlled independently.

  However, the substrate holding device of the present invention may be an electrostatic chuck that attracts the substrate to the surface of the substrate 10 by Coulomb force generated by applying a voltage to the electrode 20 from the power supply rod 40.

  Further, the substrate holding device of the present invention may be an electrostatic chuck with a heater function in which the electrode 20 close to the surface functions as an electrode and the electrode 20 remote from the surface functions as a resistance heating element.

  Note that a protective layer or the like may be formed on the surface of the substrate 10. Further, a cooling structure may be provided in the base material 10.

The base material 10 is made of a ceramic sintered body such as alumina (Al ₂ O ₃ ), aluminum nitride (AlN), or silicon nitride (Si ₃ N ₄ ). However, the base material 10 may be made of a material used as a base material of the ceramic heater or the electrostatic chuck.

  The substrate 10 is made of, for example, a high-purity (eg, 99.9% or more) aluminum nitride powder, alumina powder, silicon nitride powder, silicon carbide powder, zirconia powder, and, if necessary, an appropriate amount of yttrium oxide powder. It is composed of a ceramic sintered body formed by filling a mixed raw material powder with a binder added thereto and performing hot press sintering.

  An electrode 20 made of mesh metal or metal foil is embedded in the base material 10. The electrode 20 is made of a metal such as tungsten, molybdenum, an alloy thereof, platinum, or titanium, and has a thin plate, a thin film, a mesh shape, a linear shape, or the like.

  The base material 10 has a protruding part 12 protruding downward so as to be thicker than the peripheral part 11 at the center of the lower surface. The protruding portion 12 is, for example, 1 mm to 10 mm thicker than the peripheral portion 11.

  The protruding portion 12 is disk-shaped, and has a chamfered portion 12a over the entire periphery at the outer peripheral edge of the lower end portion. For example, the chamfered portion 12a has a chamfer angle of 45 degrees and a chamfer dimension of 0.5 mm to 5 mm. However, the chamfered portion 12a may be, for example, a chamfered portion having a chamfered angle other than 45 degrees or a rounded chamfered portion like the chamfered portion 12Aa with reference to FIG. Good.

  The fact that the chamfered portion 12Aa of the protruding portion 12A is a round chamfered portion means that the outer peripheral edge of the protruding portion 12A is rounded, and the bottom surface and the side peripheral surface of the protruding portion 12A. And both end portions of the chamfered portion 12Aa are smoothly continued.

  However, referring to FIG. 4, the outer peripheral edge of protrusion 12 </ b> B may be formed as a round recess 12 </ b> Ba that is rounded inward and recessed. In this case, a corner portion is formed between the bottom surface and the side peripheral surface of the protruding portion 12B and the round concave portion 12Ba of the outer peripheral edge, and the corner portion has a gentler inclination than the right-angled corner portion. It has become.

  Further, the base end of the protruding portion 12 has a rounded shape over the entire periphery thereof, so that stress concentration is eased.

The shaft 30 is made of a ceramic sintered body such as alumina (Al ₂ O ₃ ), aluminum nitride (AlN), or silicon nitride (Si ₃ N ₄ ), and is formed in a substantially cylindrical shape having a hollow as a whole.

  The shaft 30 is attached to the lower surface of the substrate 10. The shaft 30 has a flange portion 32 whose diameter is larger than that of the intermediate portion 31 at an upper portion. The outer peripheral side surface of the flange portion 32 and the outer peripheral side surface of the protrusion 12 are flush with each other.

  However, the outer peripheral side surface of the flange portion 32 and the outer peripheral side surface of the protruding portion 12 need not be flush with each other, and may be slightly shifted, for example, 0.2 mm, preferably 1 mm or less. Good.

  The flange portion 32 has a short cylindrical shape, and has a chamfered portion 32a over the entire periphery at the outer peripheral edge of the upper end portion. For example, the chamfered portion 32a has a chamfer angle of 45 degrees and a chamfer dimension of 0.5 mm to 5 mm. However, the chamfered portion 32a may be, for example, a chamfered portion having a chamfered angle other than 45 degrees or a rounded chamfered portion like the chamfered portion 32Ba with reference to FIG. Good.

  The fact that the chamfered portion 32Ba of the flange portion 32B is a round chamfered portion means that the outer peripheral edge of the flange portion 32B is rounded, and the upper surface and the side peripheral surface of the flange portion 32B. And both end portions of the chamfered portion 32Ba are continuous.

  However, referring to FIG. 4, the outer peripheral edge of flange portion 32C may be formed as a round concave portion 32Ca that is rounded inward and concave. In this case, a corner portion is formed between the bottom surface and the side peripheral surface of the flange portion 32C and the round concave portion 32Ca on the outer peripheral edge, and the corner portion has a smaller inclination than the right-angled corner portion. It has become moderate. In particular, when the outer peripheral edge of the protruding portion 12B is also formed so as to be rounded inward and depressed, the round concave portion 12Ba of the protruding portion 12B and the round concave portion 32Ca of the flange portion 32C have the same or substantially the same ends. Is preferred.

  Further, the base end of the flange portion 32 has a rounded shape over the entire periphery thereof, so that stress concentration is eased.

  The lower surface of the protruding portion 12 and the upper surface of the flange portion 32 are brought into contact with each other, and the base material 10 and the shaft 30 are joined by solid-phase joining without using a joining material. Since the bonding material is not used, the plasma resistance of the bonding material, which has been a concern in the past, does not matter, and the bonding material can be used at a temperature higher than the heat-resistant temperature.

  The power supply rod 40 is formed of a metal having excellent heat resistance, acid resistance, and conductivity, such as titanium (Ti) and nickel (Ni), and has a round bar shape in the present embodiment. The power supply rod 40 is electrically connected to a power source (not shown) at a lower end thereof.

  The upper end surface of the power supply rod 40 is in contact with the back surface of the electrode 20, and these are electrically connected.

  In the ceramic heater 100 described above, the base member 10 and the shaft 30 have chamfered portions 12a and 32a at joints, respectively. Therefore, as compared with the case where both the corners of the joining portion are right angles as disclosed in Patent Document 1, it is possible to reduce the possibility that damage such as micro cracks may occur from these corners. In addition, since the possibility of peeling due to damage can be reduced, these can make it possible to use the ceramic heater 100 for a long period of time.

  In addition, it is only necessary to have the chamfered portions 12a and 32a at the joining portion of either the base material 10 or the shaft 30. Also in this case, it is possible to reduce the risk of damage such as microcracks from these corners, as compared to the case where the corners are both right angles.

(Production method)
Next, a method for manufacturing the ceramic heater 100 will be described.

  First, a ceramic powder composed of aluminum nitride powder, alumina powder, silicon nitride powder, silicon carbide powder, zirconia powder, or the like, which is a raw material powder of a ceramic sintered body forming the base material 10, is mixed with a sintering aid or the like. Obtain raw material powder. Then, using the mixed raw material powder, sintering is performed by a known method to obtain a ceramic sintered body. As a sintering method, a known method such as normal pressure sintering, hot pressing (hot pressing), and reaction sintering may be used.

  The electrode 20 made of a mesh metal or a metal foil is embedded in the base material 10 by baking the electrode 20 between ceramic sintered bodies. However, the embedding method is not limited to this. For example, the metal as the material of the electrode 20 may be sandwiched between the raw material powders and the whole may be sintered. Alternatively, a concave portion may be formed in the ceramic molded body, the electrode 20 may be embedded, and then the ceramic molded bodies may be stacked and fired. Alternatively, a concave portion may be formed on the joining surface of the ceramic sintered body to embed the electrode 20, and thereafter, the ceramic sintered body may be joined.

  Cutting is performed on the ceramic sintered body as necessary so that the peripheral portion 11 and the protruding portion 12 have a predetermined shape. Chamfering is performed on the entire outer periphery of the lower end of the protruding portion 12 to form a chamfered portion 12a. The lower surface of the protrusion 12 is mirror-finished to have a surface roughness Ra of 0.01 μm or more and 0.1 μm or less and a flatness of 1 μm or less. Thereby, the base material 10 is completed.

  Next, IPA, an organic binder, and a plasticizer are added to a ceramic powder composed of aluminum nitride powder, alumina powder, silicon nitride powder, silicon carbide powder, zirconia powder, and the like, which are raw material powders of the ceramic sintered body forming the shaft 30. , Mixing and spray-drying to obtain ceramic granules. The granules are subjected to CIP molding and fired under normal pressure to obtain a ceramic sintered body. As the sintering method, a known method such as normal pressure sintering, hot pressing (hot pressing), and reaction sintering may be used.

  Cutting is performed on the ceramic sintered body as necessary so that the intermediate portion 31 and the flange portion 32 have predetermined shapes. Chamfering is performed on the entire outer periphery of the upper end of the flange portion 32 to form a chamfered portion 32a. The upper surface of the flange portion 32 is mirror-finished to have a surface roughness Ra of 0.01 μm or more and 0.1 μm or less and a flatness of 1 μm or less. Thereby, the shaft 30 is completed.

  Next, the base material 10 and the shaft 30 are pressurized at 1 MPa or more and 10 MPa or less, and placed in a furnace in a state where the lower surface of the protruding portion 12 and the upper surface of the flange portion 32 are in contact with each other. The state heated to 1500 ° C. or more and 1900 ° C. or less is maintained for 0.2 hours or more and 10 hours or less. Thereby, the base material 10 and the shaft 30 are joined by solid-phase joining.

  After joining, grinding is performed by cylindrical grinding so that the outer peripheral side surface of the protruding portion 12 of the base material 10 and the outer peripheral side surface of the flange portion 32 of the shaft 30 have substantially the same outer diameter. After the grinding, a part of the chamfered portion 12a of the protruding portion 12 of the base material 10 and a portion of the chamfered portion 32a of the flange portion 32 of the shaft 30 remain in appearance.

  Thereafter, the upper end surface of the power supply rod 40 is fixed by brazing in a state of being in contact with the back surface of the electrode 20, and the electrical connection is established. Thereby, the ceramic heater 100 can be obtained.

  However, the electrical connection between the electrode 20 and the power supply rod 40 is not limited to brazing, and may be any connection method used in a known ceramic heater. For example, a terminal may be fixed to the back surface of the electrode 20, and the tip of the power supply rod 40 may be detachably fixed to this terminal.

  In the above-described method for manufacturing the ceramic heater 100, the base material 10 and the shaft 30 that are pressed against each other during sintering have chamfered portions 12a and 32a, respectively, at their abutting portions. Therefore, as compared with the case where the corner portion in the contact portion is a right angle as disclosed in the above-mentioned Patent Document 1, it is possible to reduce the possibility that microcracks and the like are generated by pressure during sintering. It is possible to improve the yield.

  In addition, the base material 10 and the shaft 30 may be joined by a joining method other than solid-phase joining, for example, glass joining.

(Modification of Embodiment)
The present invention is not limited to the ceramic heater 100 in the above embodiment.

  For example, the case where the chamfered portion 32a is provided over the entire periphery only at the outer peripheral edge of the upper end portion of the flange portion 32 of the shaft 30 has been described. However, like the ceramic heater 100A shown in FIG. 2, it is preferable that the inner peripheral edge of the upper end of the flange portion 32A of the shaft 30A also have a chamfered portion 32Ab over the entire circumference.

  As a result, as compared with the case where the inner peripheral edge of the upper end of the flange portion 32A is at a right angle, the risk of damage such as chipping and microcracks from this portion can be reduced, and the risk of peeling due to damage can be reduced. Thus, it can be used for a long time. Further, also at the time of sintering, the possibility that chipping, micro cracks and the like are generated from the corners due to the pressure at the time of sintering can be reduced, so that the yield at the time of manufacturing can be improved.

  Furthermore, the case where the protruding portion 12 of the base material 10 has a disk shape has been described. However, referring to FIG. 4, projecting portion 12B of base material 10B may have a donut plate shape. In this case, although not shown, it is preferable that the protruding portion 12B has a chamfered portion that is chamfered over the entire periphery at the inner peripheral edge of the lower end portion. This chamfered portion may be the same as or different from the chamfered portion 12Ba chamfered over the entire outer periphery of the lower end portion.

  The inner peripheral side surface of the donut-shaped protrusion 12B is preferably substantially flush with the inner peripheral side surface of the flange portion. Further, it is preferable that the inner peripheral edge of the lower end portion of the protruding portion 12B be rounded over its entire periphery to reduce stress concentration.

  Further, as shown in FIG. 4, the inner peripheral edge of the protruding portion 12B is formed as a round concave portion 12Bb that is rounded inward and is depressed, and the inner peripheral edge of the flange portion 32C is rounded and depressed inward. It may be formed as the recess 32Cb. In this case, it is preferable that the round concave portion 12Bb of the protruding portion 12B and the circular concave portion 32Cb of the flange portion 32C have the same or substantially the same end.

  Hereinafter, the present invention will be described with specific examples and comparative examples of the present invention.

(Example 1)
In Example 1, with reference to FIG. 1, a ceramic heater 100 was obtained by joining a base material 10 made of aluminum nitride doped with yttrium oxide in which a metal electrode 20 was embedded and a shaft 30 made of only aluminum nitride. .

[Preparation of base material]
A powder mixture consisting of 97% by mass of aluminum nitride powder and 3% by mass of yttrium oxide powder was obtained, filled in a mold, and subjected to a uniaxial pressing treatment. Thus, a first layer having a diameter of 240 mm and a thickness of 10 mm was formed.

  Next, a molybdenum mesh (diameter: 0.1 mm, mesh size: 50 mesh) having a diameter of 190 mm serving as the electrode 20 was placed on the first layer. Subsequently, the previously formed powder mixture was filled on the electrode 20 to a predetermined thickness to form a second layer. Then, hot press firing was performed at a pressure of 10 MPa and a firing temperature of 1800 ° C. for a firing time of 2 hours to obtain a ceramic sintered body having a diameter of 240 mm and a thickness of 20 mm.

  The back surface of the ceramic sintered body was ground 5 mm in thickness while leaving a region 60 mm in diameter from the center, and a protrusion 12 having a diameter of 60 mm and a height of 5 mm was formed in the center. Next, C3 mm chamfering was performed on the outer peripheral edge of the protruding portion 12 to form a chamfered portion 12a. Thereafter, the lower surface of the protrusion 12 was polished to have a surface roughness Ra of 0.03 μm and a flatness of 0.4 μm. Thereby, the base material 10 was obtained.

[Production of shaft]
IPA, an organic binder, and a plasticizer were added to aluminum nitride powder as a raw material, mixed, and spray-dried to obtain aluminum nitride granules. The granules are subjected to CIP molding, baked at a sintering temperature of 1900 ° C. for 6 hours, baked at normal pressure, and then subjected to cylindrical processing. The shaft 30 having an inner diameter of 32 mm and a length of 160 mm was obtained. Chamfering of C3 mm was performed on the outer peripheral edge of the end surface of the flange portion 32 to form a chamfered portion 32a. Thereafter, the upper surface of the flange portion 32 was polished to have a surface roughness Ra of 0.04 μm and a flatness of 0.5 μm.

[Joining, processing]
The joining surface of the base material 10 and the joining surface of the shaft 30 were overlapped and joined by hot press firing. The temperature was 1600 ° C., the pressure was 6 MPa, and the time was 4 hours. After the joining, the outer peripheral side surface of the protruding portion 12 of the base material 10 and the outer peripheral side surface of the flange portion 32 of the shaft 30 were ground by cylindrical grinding so as to have substantially the same outer diameter. At this time, a part of the chamfered portion 12a of the protruding portion 12 of the base material 10 and a part of the chamfered portion 32a of the flange portion 32 of the shaft 30 which were processed before joining remained in the appearance.

[Evaluation]
The joint was visually inspected, but no damage such as chipping or crack was found, and it was good. Note that a fiberscope was used inside the shaft 30. Then, the air density of the joint was measured by a helium leak detector by a bombing method. It was determined that there was no leak at the measurement limit of 1 × 10 ⁻¹² Pam ³ / s.

(Example 2)
A ceramic heater 100A was manufactured in the same manner as in Example 1 except for the following manufacturing conditions.

[Preparation of base material]
The rear surface of the ceramic sintered body was ground with a thickness of 3 mm while leaving a region with a diameter of 60 mm from the center, and a projection 12 with a diameter of 60 mm and a height of 3 mm was formed at the center. Next, the outer peripheral edge of the protruding portion 12 was chamfered by 1.5 mm to form a chamfered portion 12a. Thereafter, the lower surface of the protrusion 12 was polished to have a surface roughness of Ra 0.02 μm and a flatness of 0.3 μm. Thereby, the base material 10 was obtained.

[Production of shaft]
Referring to FIG. 2, a shaft 30A having an outer diameter of the flange portion 32A of 60 mm, a thickness of the flange portion 32A of 5 mm, an outer diameter of the intermediate portion 31A of 38 mm, an inner diameter of 30 mm, and a length of 120 mm was obtained. The outer peripheral edge and the inner peripheral edge of the end face of the flange portion 32A were chamfered by 1.5 mm to form chamfered portions 32Aa and 32Ab. Thereafter, the upper surface of the flange portion 32A was polished to have a surface roughness Ra of 0.03 μm and a flatness of 0.3 μm.

[Evaluation]
The joint was visually inspected, but no damage such as chipping or crack was found, and it was good. Note that a fiberscope was used inside the shaft 30. Then, the air density of the joint was measured by a helium leak detector by a bombing method. It was determined that there was no leak at the measurement limit of 1 × 10 ⁻¹² Pam ³ / s.

(Example 3)
Example 1 was the same as Example 1 except that both the chamfered portion 12a and the chamfered portion 32a were round chamfers having a radius of curvature of 3 mm.

[Evaluation]
The joint was visually inspected, but no damage such as chipping or crack was found, and it was good. Note that a fiberscope was used inside the shaft 30. Then, the air density of the joint was measured by a helium leak detector by a bombing method. It was determined that there was no leak at the measurement limit of 1 × 10 ⁻¹² Pam ³ / s.

(Comparative example)
As a comparative example, the substrate 10 and the shaft 30 were joined without chamfering the outer edge of the protruding portion 12 of the substrate 10 and the outer edge of the end surface of the flange portion 32 of the shaft 30. The other manufacturing conditions were the same as in Example 1.

[Evaluation]
The joint was visually observed, but cracks were found on the joint surface. Then, the air density of the joint was measured by a helium leak detector by a bombing method. Leakage occurred at 1 × 10 ⁻⁶ Pam ³ / s.

  Table 1 summarizes the evaluation results of Examples 1 to 3 and Comparative Example.

  10, 10A, 10B: base material, 11: peripheral portion, 12, 12A, 12B: projecting portion, 12a, 12Aa, 12Ba: chamfered portion, 12Ba, 12Bb: round hollow portion, 20: electrode, 30, 30A, 30B , 30C: shaft, 31: middle part, 32, 32A, 32B, 32C: flange part, 32a, 32Aa, 32Ab: chamfered part, 32Ca, 32Cb: round hollow part, 40: power supply rod, 100, 100A: ceramic heater (Substrate holding device).

Claims (3)

A base material made of ceramics, supporting the substrate on the upper surface, and having a protruding portion that protrudes downward at the center of the lower surface so as to be thicker than the peripheral portion;
A substrate holding device comprising a ceramic, and a hollow shaft having a flange portion on an upper portion connected to the protruding portion,
The protruding portion has a chamfered portion on at least one of an outer peripheral edge of a lower end portion and an outer peripheral edge of the upper end portion, and an outer peripheral side surface of the protruding portion and an outer peripheral side surface of the flange portion are substantially flat. substrate holding apparatus, characterized in that one.   The substrate holding device according to claim 1, further comprising a chamfered portion on an inner peripheral edge of an upper end portion of the flange portion over the entire periphery. A step of preparing a base material made of ceramics and having a protruding portion that protrudes downward so as to be thicker than a peripheral portion in a central portion of the lower surface,
A step of preparing a hollow shaft made of ceramics and having a flange portion on the upper portion connected to the protrusion,
A step of chamfering at least one of an outer peripheral edge of a lower end portion of the protruding portion or an outer peripheral edge of an upper end portion of the flange portion over the entire circumference,
A step of joining these surfaces by solid-phase joining in a state where the lower surface of the protruding portion and the upper surface of the flange portion are in contact with each other ;
A method of processing the outer peripheral side surface of the projecting portion and the outer peripheral side surface of the flange portion so as to be substantially flush with each other.