JP7783018B2 - Electrode embedding material - Google Patents

Description

The present invention relates to an electrode-embedding member.

Conventionally, a structure has been proposed for use in semiconductor manufacturing equipment as a heater for heating substrates, integrating a heating and holding member made of a sintered ceramic body with a support member that supports the heating and holding member.

Patent Document 1 discloses a mounting structure for a susceptor and a support member, which aims to suppress heat transfer from the susceptor into the support member and alleviate stress concentrated in the support member even when the susceptor is heated to a high temperature. The mounting structure includes a susceptor for heating the workpiece, a support member joined to the susceptor and having an internal space, and a chamber joined to the support member and having an opening, the opening of the chamber communicating with the internal space of the support member, the internal space of the support member being airtightly sealed from the internal space of the chamber, the support member having a cylindrical main body and an expanded diameter portion at the end of the support member facing the susceptor, and the outer contour of the vertical cross section of the support member having one or multiple continuous rounded portions between the main body and the expanded diameter portion.

Patent Document 2 discloses a heating device having a heating base and a support member joined to the heating base. The heating device, which aims to effectively prevent cracks from occurring near the joint between the heating base and the support member, includes a plate-shaped heating base with a heating surface and a hollow, cylindrical support member joined to the back surface of the heating base. Near the outer edge of the joint interface between the heating base and the support member, a concave curved surface is formed that smoothly connects the back surface of the heating base to the outer surface of the support member. The concave curved surface is made of ceramic and has an elliptical arc whose minor axis direction is parallel to the axial direction of the support member in a cross section including the axis of the support member.

Japanese Patent Application Laid-Open No. 2004-247745 Japanese Patent Application Laid-Open No. 2008-270197

The inventors have discovered that while simply providing a seat (convex portion) on the underside of a plate, joining a support member to the seat, and providing an R-shaped cross section of the seat, as in Patent Document 1 or Patent Document 2, can suppress damage to the joint of the support member to a certain extent, if the corner of the boundary between the plate and the seat and the joint of the support member are close to each other, it may not be sufficient to prevent damage to the corner or joint due to stress concentrated unevenly on one side of the corner or joint of the seat provided on the underside of the plate, or to prevent leaks due to poor airtightness, and this effect becomes more pronounced when used in processes at higher temperatures than conventional methods.

Through extensive research, the inventors discovered that by creating a specific cross-sectional shape from the underside of the plate to the side of the seat, stress generated at the joints of the support members is alleviated, as is stress generated at the corners where the plate and seat meet, leading to the completion of this invention.

The present invention was made in light of these circumstances, and aims to provide an electrode-embedding member that alleviates stress that occurs in corners and at the joints of support members, thereby reducing the risk of damage to corners and joints and the risk of poor airtightness.

(1) In order to achieve the above object, the electrode-embedding member of the present invention comprises a ceramic base having a substrate mounting surface on its upper surface and a substrate main body formed in a flat plate shape from a sintered ceramic body, and a convex portion formed integrally with the substrate main body and protruding downward from the lower surface of the substrate main body facing the substrate mounting surface; an electrode embedded in the substrate main body of the ceramic base; and a support member joined to the lower surface of the convex portion facing the substrate mounting surface, wherein in a cross section including the central axis of the ceramic base, the cross sections of the lower surface of the substrate main body of the ceramic base and the side surface of the convex portion are formed by a continuous curve, and the curve has an inflection point.

In this way, the cross sections of the underside of the base body and the side of the convex portion are formed by a continuous curve, and because this curve has an inflection point, the corners at the boundary between the base body and the convex portion and the joints of the support members can be separated, alleviating stress that occurs in the corners and also in the joints of the support members. As a result, the risk of damage and poor airtightness at the corners and joints can be reduced.

Furthermore, the electrode-embedded member of the present invention is characterized in that, when the diameter of the boundary between the convex portion and the substrate main body is Ds1 and the diameter of the lower surface of the convex portion is Ds2, 1.1≦Ds1/Ds2≦1.5 is satisfied throughout the entire convex portion having the inflection point.

When the diameter of the boundary between the convex portion and the substrate body is Ds1 and the diameter of the underside of the convex portion is Ds2, by setting Ds1/Ds2 within a predetermined range throughout the entire convex portion having the inflection point, the stress generated at the corners and the joints of the support member can be further alleviated.

(2) To achieve the above object, the present invention provides an electrode-embedding member, comprising: a ceramic substrate having a substrate mounting surface on its upper surface, a substrate body formed into a flat plate shape from a sintered ceramic body, and a protrusion projecting downward from a lower surface of the substrate body opposite the substrate mounting surface and integrally formed with the substrate body; an electrode embedded in the substrate body of the ceramic substrate; and a support member joined to the lower surface of the protrusion opposite the substrate mounting surface, wherein, in a cross section including the central axis of the ceramic substrate, the lower surface of the substrate body and the side surface of the protrusion are formed by a continuous curve, and the curve has an inflection point. Furthermore, the present invention is characterized in that, where Ds1 is the diameter of the boundary of the protrusion with the substrate body, Ds2 is the diameter of the lower surface of the protrusion, and T is the thickness of the protrusion, then (Ds1 - Ds2)/2 ≧ T.

In this way, by specifying the relationship between (Ds1-Ds2)/2 and T, the difference between the diameter of the boundary between one side of the convex and the substrate body and the diameter of the underside of the convex can be made larger than the thickness of the convex, and the corners and joints can be spaced farther apart, thereby further alleviating the stress generated in the corners and joints.

(3) In the electrode-embedding member of the present invention, the curve has two or more inflection points .

By making the cross-sectional curve a curve with two or more inflection points, the shape of the lower surface of the substrate body and the side surface of the convex portion can be varied, which alleviates stress at the corners and also at the joints of the support member.It can also accommodate thicker convex portions.

This invention alleviates stress at the corners of the boundary between the base material body and the protrusion, as well as stress at the joints of the support members, reducing the risk of damage to the corners and joints and the risk of poor airtightness.

FIG. 2 is a cross-sectional view showing an example of an electrode-embedded member according to the embodiment. FIG. 2 is a partial cross-sectional view of the electrode-embedded member of FIG. 1 . FIG. 10 is a cross-sectional view showing a modified example of an electrode-embedded member according to the embodiment. FIG. 4 is a partial cross-sectional view of the electrode-embedded member of FIG. 3 . 1 is a table showing shape characteristics and measurement results of examples and comparative examples.

Next, an embodiment of the present invention will be described with reference to the drawings. To facilitate understanding, the same reference numbers will be used in each drawing to refer to the same components, and duplicate explanations will be omitted. Note that in the structural diagrams, the size of each component is shown conceptually and does not necessarily represent the actual dimensional ratio.

[Embodiment]
[Configuration of electrode-embedded member]
First, the configuration of the electrode-embedded member according to this embodiment will be described. Fig. 1 is a schematic cross-sectional view showing an example of the electrode-embedded member according to this embodiment. Fig. 2 is a partial cross-sectional view of the electrode-embedded member of Fig. 1. The electrode-embedded member 100 according to this embodiment includes a ceramic substrate 110, an electrode 130, and a support member 140. The electrode-embedded member 100 is applied to a heater with a shaft, etc.

The ceramic substrate 110 has a substrate body 112 formed into a flat plate from a ceramic sintered body, and a convex portion 118 formed integrally with the substrate body 112 and protruding downward from the lower surface 116 of the substrate body facing the substrate mounting surface 114. Here, "convex portion formed integrally with the substrate body" means that the substrate body 112 and the convex portion 118 are not joined with a bonding material. The substrate mounting surface 114 of the ceramic substrate 110 can have a variety of shapes, including a disk, polygon, or ellipse. Materials used for the ceramic sintered body include silicon carbide, aluminum oxide, aluminum nitride, and silicon nitride.

In a cross section of the ceramic substrate 110 including the central axis, the cross sections of the lower surface 116 of the substrate body and the side surfaces 122 of the convex portions of the ceramic substrate 110 are formed by a continuous curve. This curve also has an inflection point 124. In this way, the cross sections of the lower surface 116 of the substrate body and the side surfaces 122 of the convex portions are formed by a continuous curve, and this curve has an inflection point 124, allowing the corners 128 of the boundaries 126 between the substrate body 112 and the convex portions 118 and the ends of the joints 142 of the support member 140 to be spaced apart to a certain extent, thereby alleviating stresses generated in the corners 128 and the joints 142 of the support member 140. As a result, the risk of damage to the corners 128 and the joints 142 and the risk of poor airtightness can be reduced. The tangent direction of the inflection point 124 in the cross section may be various directions, not just vertical or horizontal.

The cross section of the lower surface 116 of the substrate body and the side surface 122 of the convex portion being formed by a continuous curve means that there is no singular point midway along the cross-sectional curve extending from the lower surface 116 of the substrate body to the side surface 122 of the convex portion. In this specification, a singular point refers to a corner or edge corresponding to an R of 0.5 (mm) or less or a C of 0.5 (mm) or less in a cross section including the central axis of the ceramic substrate 110. This is because such corners or edges are prone to stress and heat flow concentration, making them prone to becoming the starting point for damage such as cracks. Furthermore, this effect becomes more pronounced when used in processes at higher temperatures than conventional processes.

Furthermore, the cross section of the lower surface 116 of the base body and the side surface 122 of the convex portion being formed by a continuous curve can be rephrased as meaning that the lower surface 116 of the base body and the side surface 122 of the convex portion are smoothly connected. The continuous curve may include a straight line. Furthermore, the continuous curve may have a shape in which an inflection point is included in the straight line. It is preferable that the continuous curve does not include any corners or angles equivalent to R3 (mm) or less or C3 (mm) or less.

The electrode 130 is embedded in the substrate body 112 of the ceramic substrate 110. The electrode 130 can be in a variety of shapes, such as mesh or foil. It can also be made of a variety of materials, such as molybdenum or tungsten.

The support member 140 is bonded to the underside 120 of the convex portion facing the substrate mounting surface 114. The support member 140 is made of a ceramic sintered body and supports the ceramic substrate 110. The ceramic sintered body that forms the support member 140 preferably contains the same type of ceramic as the ceramic sintered body that forms the ceramic substrate 110 as its main component. In this case, the presence or absence of a sintering aid and its amount may differ.

When the diameter of the boundary 126 of the convex portion with the base material body is Ds1 and the diameter of the lower surface 120 of the convex portion is Ds2, it is preferable that 1.1≦Ds1/Ds2≦1.5. In this way, when the diameter of the boundary 126 of the convex portion with the base material body is Ds1 and the diameter of the lower surface 120 of the convex portion is Ds2, by setting Ds1/Ds2 within a specified range, stress generated in the corner portion 128 and the joint portion 142 of the support member 140 can be further alleviated.

When the diameter of the boundary 126 of the convex portion with the base material main body is Ds1, the diameter of the lower surface 120 of the convex portion is Ds2, and the thickness of the convex portion 118 is T, it is preferable that (Ds1 - Ds2)/2 ≧ T. By specifying the relationship between (Ds1 - Ds2)/2 and T in this way, the difference between the diameter of the boundary of one side of the convex portion 118 with the base material main body 112 and the diameter of the lower surface 120 of the convex portion can be made larger than the thickness of the convex portion 118. This allows the corner portion 128 and the joint portion 142 to be sufficiently spaced apart, thereby further mitigating stress generated in the corner portion 128 and the joint portion 142.

If the corner 128 and the joint 142 are spaced too far apart, the effect of mitigating the stress generated in the corner 128 and the joint 142 in a balanced manner will be reduced, so it is preferable that the upper limit of (Ds1 - Ds2)/2 be (Ds1 - Ds2)/2 ≦ 20T.

The electrode-embedded member 100 may be provided with multiple electrodes 130. For example, by providing a heater electrode and an electrostatic attraction electrode, the electrode-embedded member 100 can be used as a heater-equipped electrostatic chuck.

The electrode-embedded member 100 also includes the necessary terminals 150 and terminal holes 152, which allow power to be supplied to the electrode 130.

Figure 3 is a schematic cross-sectional view showing a modified example of an electrode-embedded member according to this embodiment. Figure 4 is a partial cross-sectional view of the electrode-embedded member of Figure 3. As shown in Figures 3 and 4, the cross-sectional curve extending from the lower surface 116 of the substrate body to the side surface 122 of the convex portion preferably has two or more inflection points 124. By making the cross-sectional curve a curve with two or more inflection points 124, the lower surface 116 of the substrate body and the side surface 122 of the convex portion can be shaped in a variety of shapes, which reduces stress at the corners 128 and at the joints 142 of the support member 140. It can also accommodate shapes in which the thickness of the convex portion 118 is increased.

Furthermore, as shown in Figures 3 and 4, when the cross-sectional curve is a curve with two or more inflection points 124, it is preferable that the cross section of the side surface 122 of the convex portion near the joint and the side surface of the support member near the joint be a continuous curve. This allows the side surface 122 of the convex portion and the side surface of the support member to be smoothly connected, further mitigating stress generated at the joint 142 of the support member 140. Furthermore, even if the number of inflection points is two or more, the side surface 122 of the convex portion and the lower surface 120 of the convex portion may be smoothly connected.

The electrode-embedding member 100 of the present invention alleviates stress that occurs in corners and at the joints of the support member, thereby reducing the risk of damage and poor airtightness at corners and joints.

[Method of manufacturing electrode-embedded member]
Next, a method for manufacturing the embedded electrode member according to the present embodiment will be described. The embedded electrode member according to the present embodiment is manufactured, for example, by a molded body hot pressing method described below. Note that the manufacturing method is not limited to this method, and may be, for example, a powder hot pressing method or a conventional green sheet lamination method. The powder hot pressing method is a method in which ceramic raw material powder and predetermined heating resistors and electrodes are alternately stacked to embed the heating resistors and electrodes inside the ceramic, and then the resultant is uniaxial hot press fired.

The manufacturing method for an electrode-embedded member according to an embodiment of the present invention using a molded body hot pressing method includes a ceramic molded body forming process, a ceramic degreased body fabricating process, a ceramic substrate precursor forming process, a ceramic substrate firing process, a curved surface processing process, a support member molded body forming process, a support member degreased body fabricating process, a support member firing process, and a joining process.

In the ceramic molded body forming process, for example, multiple ceramic molded bodies are formed from a first ceramic raw material powder containing AlN as the main component and Y as a sintering aid. For example, _Y2O3 as the Y component of the sintering aid, and additives such as a binder, plasticizer, and dispersant are appropriately added to the ceramic raw material powder and mixed to prepare a slurry, which _is then granulated by a spray-drying method or the like to produce granules (first ceramic raw material powder), which are then pressure-molded to form multiple ceramic molded bodies. In addition to aluminum nitride, silicon carbide, aluminum oxide, silicon nitride, and the like can be used as the raw ceramic powder.

The ceramic raw material powder is preferably highly pure, with a purity of preferably 96% or higher, and more preferably 98% or higher. The average particle size of the ceramic raw material powder is preferably 0.1 μm or higher and 1.0 μm or lower.

The mixing method may be either wet or dry, and a mixer such as a ball mill or vibration mill may be used. Forming may be performed using known methods such as uniaxial pressing or cold isostatic pressing (CIP). The method of forming the ceramic compact is not limited to pressure forming; other methods, such as green sheet lamination or slip casting, can also be used. The ceramic compact can be manufactured by degreasing these appropriately or by further calcining them.

After forming, the ceramic compact may be machined to adjust its shape. Also, a groove shaped to match the shape of the electrode may be formed on one side of the ceramic compact (the surface to be bonded to another ceramic compact). Machining may be performed after degreasing.

In the ceramic degreased body production process, multiple ceramic molded bodies are degreased at a predetermined temperature or higher for a predetermined period of time or longer to produce multiple ceramic degreased bodies.

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

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

The electrodes are prepared in a shape that matches the design of the electrode-embedding member. The electrodes can be in a variety of shapes, such as mesh or foil. They can also be made of a variety of materials, such as molybdenum or tungsten.

In the ceramic substrate firing process, the formed ceramic substrate precursor is uniaxially pressurized and fired in a direction perpendicular to the substrate mounting surface to fire the ceramic substrate. Firing conditions vary depending on the material, but when using a ceramic primarily composed of AlN, a pressure of 1 MPa or more is preferred. The firing temperature is preferably 1700°C or higher and 2000°C or lower. The firing time is preferably 1 hour or higher and 12 hours or lower, and more preferably 1 hour or higher and 5 hours or lower. The firing atmosphere is, for example, a nitrogen or inert gas atmosphere, but may also be a vacuum atmosphere. As a result, multiple degreased ceramic bodies are sintered to form a ceramic sintered body, which is then integrated to produce a ceramic substrate with embedded electrodes.

In the curved surface processing step, the surface of the ceramic substrate extending from the lower surface of the substrate body to the side surface of the convex portion is processed so that, in a cross section including the central axis of the ceramic substrate, the cross section of the lower surface of the substrate body of the ceramic substrate and the cross section of the side surface of the convex portion are formed as a continuous curve with an inflection point. The curved surface processing step may be performed after the joining step with the support member.

It is preferable that there are two or more inflection points in the cross-sectional curve. Furthermore, it is preferable that the processing be performed so that the diameter Ds1 of the boundary between the protrusion and the substrate body and the diameter Ds2 of the lower surface of the protrusion satisfy the relationship 1.1≦Ds1/Ds2≦1.5. Furthermore, it is preferable that the processing be performed so that the diameter Ds1 of the boundary between the protrusion and the substrate body, the diameter Ds2 of the lower surface of the protrusion, and the thickness T of the protrusion satisfy the relationship (Ds1-Ds2)/2≧T.

In the support member compact formation process, the support member compact is formed from a second ceramic raw material powder, which may contain, for example, AlN as the main component and a Y component as a sintering aid, or no sintering aid. The method for producing the second ceramic raw material powder and the method for forming the support member compact may be the same as those in the ceramic compact formation process. It is preferable that the second ceramic raw material powder does not contain a sintering aid.

In the support member degreased body production process, the support member molded body is degreased at a predetermined temperature or higher for a predetermined time or longer to produce a support member degreased body. The numerical ranges and other conditions for degreasing the support member molded body may be the same as those in the ceramic degreased body production process. The support member degreased body production process may also be carried out simultaneously with the ceramic degreased body production process.

In the support member firing process, the degreased support member is fired to form a support member that supports the ceramic substrate. Firing conditions vary depending on the material, but when using ceramics whose main component is AlN, the support member is preferably fired at atmospheric pressure. The firing temperature is preferably 1800°C or higher and 2000°C or lower. The firing time is preferably 1 hour or higher and 12 hours or lower. The firing atmosphere is, for example, a nitrogen or inert gas atmosphere, but may also be a vacuum atmosphere.

In the bonding process, the ceramic substrate and the support member are bonded together. Bonding can be performed using either a bonding method that uses a bonding material or a bonding method that does not use a bonding material.

First, we will explain the joining method using a joining material. First, prepare the joining material and apply it to at least one of the joining portion where the support member is joined to the underside of the convex portion of the ceramic substrate or the end face of the support member facing the joining portion. The joining portion and the end face of the support member facing the joining portion preferably have a surface roughness Ra of 1.6 μm or less, and more preferably are polished to 0.4 μm or less. The thickness of the applied joining material is preferably 5 μm or more and 30 μm or less.

Next, a support member is placed on the joining portion and heated while applying pressure perpendicular to the substrate mounting surface. The joining conditions vary depending on the material, but when using ceramics whose main component is AlN, a pressure of 5 kPa or more is preferable. The heating temperature is preferably 1500°C or higher and 1800°C or lower. The heating time is preferably 0.5 hours or higher and 5 hours or lower. The heating atmosphere is, for example, a nitrogen or inert gas atmosphere, but a vacuum atmosphere or other atmosphere is also acceptable. This allows the ceramic substrate and support member to be joined.

The bonding material may be any material capable of bonding the ceramic substrate and the support member. For example, if the ceramic substrate and the support member are made of ceramics primarily composed of AlN, the bonding material may be a paste of a mixed powder containing AlN powder, which is the same primary component as the _ceramic substrate and the support member, and at least _Y2O3 powder. Alternatively, the bonding material may be a paste containing 90 wt% to 95 wt% AlN _and 5 wt% or more _Y2O3 , and optionally containing CaO, MgO, _ZrO2 , and _SiO2 to adjust the temperature at which the material becomes molten during bonding.

Next, a bonding method that does not use a bonding material will be described. A support member is placed at the bonding section where the support member is bonded to the underside of the protruding portion of the ceramic substrate. The bonding section and the end face of the support member on the bonding side are preferably polished to a surface roughness Ra of 0.1 μm or less. Next, the substrate is heated while being pressurized in a direction perpendicular to the substrate mounting surface. Bonding conditions vary depending on the material, but when using ceramics whose main component is AlN, a pressure of 1 MPa or more is preferred. The heating temperature is also preferably 1600°C or higher and 2000°C or lower. The heating time is preferably 0.5 hours or higher and 6 hours or lower. The heating atmosphere is, for example, a nitrogen or inert gas atmosphere, but a vacuum atmosphere or other atmosphere may also be used. This allows the ceramic substrate and support member to be bonded.

The necessary terminal holes are drilled in the fired ceramic substrate. The terminal holes can be drilled before or after joining to the support member. Terminals are then connected to the terminal holes using brazing material or the like. Ni or other materials can be used for the terminals. Au brazing material or the like can also be used for the brazing material.

By doing this, stress generated at the corners and at the joints of the support members is alleviated, resulting in the manufacture of an electrode-embedded member that reduces the risk of damage and poor airtightness at the corners and joints.

A ceramic calcined body preparation process may be performed between the ceramic degreased body preparation process and the ceramic substrate precursor formation process. When the ceramic calcined body preparation process is performed, the ceramic degreased body is calcined at a predetermined temperature to prepare a ceramic calcined body. This allows for higher dimensional accuracy of the electrode-embedded member. Calcination conditions vary depending on the material, but when using a ceramic whose main component is AlN, the calcination temperature is preferably 1200°C or higher and 1700°C or lower. The calcination time is preferably 0.5 hours or higher and 12 hours or lower. The calcination atmosphere is preferably a nitrogen or inert gas atmosphere, but may also be a vacuum or other atmosphere. When the calcined body preparation process is performed, machining may be performed after the calcined body preparation process.

[Examples and Comparative Examples]
(Example 1-1)
A ceramic raw material powder containing 5 _wt % _Y2O3 as the main component of AlN was prepared. Using this, a ceramic compact measuring 330 mm in diameter and 20 mm in thickness and a ceramic compact measuring 330 mm in diameter and 25 mm in thickness were formed by CIP. A groove (Φ292 mm, depth 0.12 mm) for embedding an electrode was formed on one side of the 330 mm diameter, 25 mm thick ceramic compact.

Next, the two ceramic compacts were degreased at 550°C for 12 hours to produce two ceramic degreased bodies. Next, a molybdenum mesh (wire diameter 0.1 mm, mesh size #50) made of molybdenum with an outermost diameter of 290 mm, cut to a specified shape, was prepared as a heating resistor (electrode). The heating resistor was then placed in the groove of the ceramic degreased body, which had grooves formed in it, and sandwiched between the other ceramic degreased body to produce a ceramic substrate precursor.

Next, the ceramic substrate precursor was subjected to uniaxial hot press firing at 1800°C for 5 hours while applying a force of 6 MPa in the direction perpendicular to the mounting surface. In this way, the electrode-embedded member body was fired. The ceramic substrate after firing measured approximately 330 mm in diameter and 36 mm in thickness. The fired ceramic substrate was then processed prior to bonding. The substrate body had a diameter of 320 mm and a thickness of 20 mm. A convex portion with a specified size and side shape was formed on the underside of the ceramic substrate, and the surface roughness of the underside of the convex portion at the position that would become the joint with the support member was finished to an Ra of 0.1 μm or less. In addition, a terminal hole for electrical connection between the electrode and terminal was machined to reach the embedded electrode.

The size of the convex portion was such that the diameter Ds1 of the boundary with the substrate body was 65 mm, the diameter Ds2 of the underside of the convex portion was 60 mm, and the thickness T was 5 mm. The shape of the side of the convex portion was such that the underside of the substrate body of the ceramic substrate and the side of the convex portion were smoothly connected, and the side of the convex portion and the underside of the convex portion were smoothly connected, with no singular point in between and one inflection point on the side of the convex portion. In other words, in a cross section including the central axis of the ceramic substrate, the cross section of the underside of the substrate body of the ceramic substrate and the side of the convex portion are formed by a continuous curve, and this curve has a shape with an inflection point.

Separately, a ceramic compact was formed using CIP using ceramic raw material powder primarily composed of AlN with no added sintering aids, so that after firing it would have a hollow cylindrical shape with an outer diameter of 60 mm, an inner diameter of 50 mm, and a height of 210 mm. This was degreased at 550°C for 12 hours to produce a degreased ceramic body. This degreased ceramic body was then fired at 1900°C for 5 hours at atmospheric pressure to produce a support member. The surface roughness of the end face on the joint side of the fired support member was finished to Ra 0.1 μm or less.

A support member was then placed at the joining portion of the ceramic substrate, and the substrate was heated at 1700°C for 1 hour while applying a force of 1 MPa in the direction perpendicular to the mounting surface to bond the two together. A Ni rod measuring 5 mm in diameter and 270 mm in length was then brazed to the substrate using Au solder at 1000°C in a vacuum. Finally, the outer shape was machined to the specified shape as a finishing process. In this way, the heater with a shaft of Example 1-1 was produced.

(Example 1-2)
In Example 1-2, the heater with a shaft of Example 1-2 was produced under the same conditions as Example 1-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the substrate main body was 70 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 6 mm.

(Examples 1-3)
In Example 1-3, the heater with a shaft of Example 1-3 was produced under the same conditions as Example 1-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the substrate main body was 90 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 10 mm.

(Examples 1 to 4)
In Example 1-4, the heater with a shaft of Example 1-4 was produced under the same conditions as Example 1-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the substrate main body was 100 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 10 mm.

(Example 2-1)
In Example 2-1, the shape of the side of the convex portion was such that the lower surface of the substrate body of the ceramic substrate and the side of the convex portion were smoothly connected, and the side of the convex portion had two inflection points without any singular point in between. That is, in a cross section including the central axis of the ceramic substrate, the cross section of the lower surface of the substrate body of the ceramic substrate and the side of the convex portion was formed by a continuous curve, and this curve had a shape with two inflection points. In addition, after joining the shaft, the side of the convex portion and the side of the shaft were processed so that they were smoothly connected. Otherwise, the heater with a shaft of Example 2-1 was produced under the same conditions as Example 1-1.

(Example 2-2)
In Example 2-2, the heater with a shaft of Example 2-2 was produced under the same conditions as Example 2-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the substrate main body was 70 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 8 mm.

(Example 2-3)
In Example 2-3, the heater with a shaft of Example 2-3 was produced under the same conditions as Example 2-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the substrate main body was 90 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 12 mm.

(Example 2-4)
In Example 2-4, the heater with a shaft of Example 2-4 was produced under the same conditions as Example 2-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the substrate main body was 100 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 12 mm.

(Example 3-1)
In Example 3-1, the size of the convex portion was such that the diameter Ds1 of the boundary with the substrate body was 65 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 5 mm. The lower surface of the substrate body of the ceramic substrate and the side surface of the convex portion were smoothly connected, and the side surface of the convex portion and the lower surface of the convex portion were smoothly connected, and the side surface of the convex portion had three inflection points without any singular points in between. In other words, in a cross section including the central axis of the ceramic substrate, the cross section of the lower surface of the substrate body of the ceramic substrate and the side surface of the convex portion was formed by a continuous curve, and this curve had a shape with three inflection points. Otherwise, the heater with a shaft of Example 3-1 was produced under the same conditions as Example 1-1.

(Example 3-2)
In Example 3-2, the heater with a shaft of Example 3-2 was produced under the same conditions as Example 3-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the substrate main body was 70 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 8 mm.

(Example 3-3)
In Example 3-3, the heater with a shaft of Example 3-3 was produced under the same conditions as Example 3-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the substrate main body was 90 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 15 mm.

(Examples 3-4)
In Example 2-4, the heater with a shaft of Example 3-4 was produced under the same conditions as Example 3-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the substrate main body was 100 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, and the thickness T was 15 mm.

(Comparative Example 1)
In Comparative Example 1, the heater with a shaft of Comparative Example 1 was produced under the same conditions as in Example 1-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the main substrate body was 60 mm, the diameter Ds2 of the lower surface of the convex portion was 60 mm, the thickness T was 5 mm, and the shape of the side surface of the convex portion was such that the cross section was a straight line perpendicular to the lower surface of the main substrate body and had no inflection points. The cross section of the corner between the lower surface of the main substrate body and the side surface of the convex portion was a singular point corresponding to C0.2 mm.

(Comparative Example 2)
In Comparative Example 1, the heater with a shaft of Comparative Example 1 was produced under the same conditions as in Example 1-1, except that the size of the convex portion was such that the diameter Ds1 of the boundary between the convex portion and the main substrate body was 70 mm, the diameter Ds2 of the underside of the convex portion was 60 mm, and the thickness T was 8 mm, and the shape of the side surface of the convex portion was such that the cross section was curved with two inflection points, and further a corner corresponding to C0.3 mm, i.e. a singular point, was provided midway along the curve.

(Visual inspection of damage)
The fabricated electrode-embedded members of the Examples and Comparative Examples were placed in a process chamber, and an external power source was connected to the heating resistor, and repeated temperature cycles of 650°C to 200°C were applied. After each cycle, the corners between the underside of the base body of the electrode-embedded member and the side of the protrusion, as well as the joints of the support members, were visually inspected to check for damage. As a result, no visual damage was observed in either the Examples or Comparative Examples, even after 12 cycles.

(Airtightness test)
A helium leak detector was connected to the end of the support member and He gas was sprayed from the outside of the support member to evaluate the presence or absence of He leak from the joint. A He leak of less than ^10-8 Pa· ^m3 /s was judged to be no leak and passed, and a He leak of ^10-8 Pa· ^m3 /s or more was judged to be leak and failed.

All of the electrode-embedded materials used in the examples met the He leakage criteria even after 12 cycles.

On the other hand, Comparative Example 1 had a stress of 10 ^-8 Pa·m ³ /s or more after two cycles and was therefore judged to have failed. Furthermore, Comparative Example 2 had a stress of 10 ^-8 Pa·m ³ /s or more after eight cycles and was therefore judged to have failed. This is thought to be due to the occurrence of invisible cracks at the corners or joints. In other words, it was found that the shape of the cross-sectional curve of the Comparative Example was unable to alleviate stress at both the corners and joints.

From the above, it has been confirmed that the electrode-embedding member of the present invention alleviates stress that occurs at the corners of the boundary between the substrate body and the protrusion, as well as stress that occurs at the joints of the support member, thereby reducing the risk of damage to corners and joints and the risk of poor airtightness.

The present invention is not limited to the above-described embodiments, and naturally includes various modifications and equivalents that fall within the spirit and scope of the present invention. Furthermore, the structure, shape, number, position, size, etc. of the components shown in each drawing are for convenience of explanation and may be changed as appropriate.

100 Electrode-embedding member 110 Ceramic substrate 112 Substrate body 114 Substrate mounting surface 116 Lower surface of substrate body 118 Convex portion 120 Lower surface of convex portion 122 Side surface of convex portion 124 Inflection point 126 Boundary 128 between substrate body and convex portion Corner portion 130 Electrode 140 Support member 142 Bonding surface 150 Terminal 152 Terminal hole

Claims (3)

An electrode embedding member,
a ceramic substrate having a substrate body formed into a flat plate shape from a ceramic sintered body and having a substrate mounting surface on an upper surface thereof, and a protrusion protruding downward from a lower surface of the substrate body facing the substrate mounting surface and formed integrally with the substrate body;
an electrode embedded in the substrate body of the ceramic substrate;
a support member joined to a lower surface of the convex portion facing the substrate mounting surface,
In a cross section including a central axis of the ceramic base, a cross section of the lower surface of the base body of the ceramic base and a cross section of a side surface of the protrusion are formed by a continuous curve,
the curve has an inflection point;
When the diameter of the boundary between the protrusion and the substrate body is Ds1 and the diameter of the lower surface of the protrusion is Ds2, in the entire protrusion having the inflection point,
1.1≦Ds1/Ds2≦1.5
An electrode-embedding member characterized by : An electrode embedding member,
a ceramic substrate having a substrate body formed into a flat plate shape from a ceramic sintered body and having a substrate mounting surface on an upper surface thereof, and a protrusion protruding downward from a lower surface of the substrate body facing the substrate mounting surface and formed integrally with the substrate body;
an electrode embedded in the substrate body of the ceramic substrate;
a support member joined to a lower surface of the convex portion facing the substrate mounting surface,
In a cross section including a central axis of the ceramic base, a cross section of the lower surface of the base body of the ceramic base and a cross section of a side surface of the protrusion are formed by a continuous curve,
the curve has an inflection point;
When the diameter of the boundary between the protrusion and the substrate body is Ds1, the diameter of the lower surface of the protrusion is Ds2, and the thickness of the protrusion is T, in the entire protrusion having the inflection point,
(Ds1-Ds2)/2≧T
An electrode-embedding member characterized by : 3. The electrode-embedding member according to claim 1, wherein the curve has two or more inflection points .