JP2023023670A - ceramic heater - Google Patents

Abstract

To provide a ceramic heater capable of suppressing heat from escaping from a ceramic base material to a shaft.SOLUTION: A ceramic heater 100 includes a ceramic substrate 110, an electrode foil 120, and a shaft 130, and in a region where a groove 114 is formed on the side surface of a bonding portion 113 of the ceramic substrate 110, there are a first position P1, a second position P2, and a third position P3 arranged in order upward from the bonding surface 113a, the width L1 of the bonding portion 113 at the first position P1, the width L2 of the bonding portion 113 at the second position P2, and the width L3 of the bonding portion 113 at the third position P3 satisfying L2<L1 and L2<L3<2LS.SELECTED DRAWING: Figure 3

Description

The present invention relates to ceramic heaters.

In Patent Document 1, a ceramic substrate on which an object to be heated is placed, a heating resistor embedded in the ceramic substrate, and a support member (shaft) for supporting the ceramic substrate. A ceramic heater is disclosed. The support member is provided with a substantially cylindrical tubular portion and an enlarged portion disposed at the upper end of the tubular portion and having an outer diameter larger than that of the tubular portion. The upper surface of the extension and the lower surface of the ceramic base are joined together. In addition, a recessed portion surrounding the tubular portion is formed at the boundary portion between the tubular portion and the enlarged portion on the lower surface of the extended portion.

JP 2019-220554 A

Since the concave portion is formed on the lower surface of the extended portion at the boundary between the cylindrical portion and the extended portion, the heat that has flowed from the ceramic base material to the extended portion is suppressed from escaping to the cylindrical portion. . However, it is not possible to prevent heat from escaping from the ceramic base material to the support member (shaft) at the joint between the ceramic base material and the support member (shaft).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ceramic susceptor capable of suppressing heat from escaping from a ceramic base material to a shaft.

According to the aspect of the present invention, an upper surface on which an object to be heated is placed, a lower surface facing the upper surface in the vertical direction, and a joint portion projecting downward in the vertical direction from the lower surface, the upper surface A ceramic substrate having a joint having a joint surface parallel to the
a heating element embedded in the ceramic base;
a cylindrical shaft having an upper surface joined to the joint surface;
Side surfaces of the joint portion of the ceramic base material are arranged in order from the joint surface upward in the vertical direction, the second position, and the third position,
L1 is the width of the joint portion in the first position in the horizontal direction orthogonal to the vertical direction;
Let L2 be the width in the horizontal direction of the joint at the second position,
L3 is the width in the horizontal direction of the joint portion at the third position;
When the horizontal width of the shaft on the upper surface is LS,
L1 > L2
and L2<L3<2LS
There is provided a ceramic susceptor characterized by having a first position, a second position, and a third position that satisfy:

In the above aspect, the side surface of the joining portion of the ceramic substrate has a first position, a second position, and a third position where L2<L1 and L2<L3<2LS. In this case, at least at the second position, a constriction is formed that temporarily narrows the cross-sectional area of the joint. Thereby, the flow of heat from the ceramic base material to the shaft can be suppressed.

FIG. 1 is a schematic diagram of a ceramic susceptor 100. FIG. FIG. 2 is a schematic diagram of electrode foil 120 . FIG. 3 is an explanatory diagram for explaining the ceramic susceptor 100. FIG. 4A to 4E are diagrams showing the flow of the method for manufacturing the ceramic substrate 110. FIG. 5A to 5E are diagrams showing the flow of another manufacturing method for the ceramic substrate 110. FIG. 6A to 6C are diagrams showing the flow of the manufacturing method of the ceramic susceptor 100. FIG. 7A and 7B are diagrams showing the flow of the manufacturing method of the ceramic susceptor 100A. 8A and 8B are diagrams showing the flow of the manufacturing method of the ceramic susceptor 100B. FIG. 9 is a view corresponding to FIG. 3 of the ceramic heater 100 of Example 1. FIG. FIG. 10 is a view equivalent to FIG. 3 of the ceramic heater 100 of Example 2. FIG. FIG. 11 is a view corresponding to FIG. 3 of the ceramic heater 100 of Example 3. FIG. FIG. 12 is a view corresponding to FIG. 3 of the ceramic susceptor 100B of Example 5. FIG. FIG. 13 is a view corresponding to FIG. 3 of a ceramic susceptor 100C of a comparative example. 1 is a table summarizing the results of Examples 1 to 5 and Comparative Examples.

<Ceramic heater 100>
A ceramic susceptor 100 according to an embodiment of the present invention will be described with reference to FIG. A ceramic heater 100 is used to heat a semiconductor wafer such as a silicon wafer (hereinafter simply referred to as wafer 10). In the following description, the vertical direction 5 is defined based on the state in which the ceramic susceptor 100 is installed so as to be usable (state shown in FIG. 1). As shown in FIG. 1, a ceramic susceptor 100 according to this embodiment includes a ceramic substrate 110, an electrode foil 120, a shaft 130, and a feeder line 140. As shown in FIG.

The ceramic base 110 is a member having a circular plate-like shape with a diameter of 12 inches (approximately 300 mm), and the wafer 10 to be heated is mounted on the mounting surface 111 which is the upper surface of the ceramic base 110 . In FIG. 1, the wafer 10 and the mounting surface 111 of the ceramic substrate 110 are separated from each other for easy viewing of the drawing. Further, although not shown in FIG. 1, a plurality of projections (a plurality of convex portions) are formed on the mounting surface 111 by performing sandblasting as will be described later. Further, as shown in FIG. 3, a joint portion 113 (an example of the joint portion of the present invention) protruding downward is provided approximately in the center of the rear surface 112, which is the lower surface of the ceramic substrate 110. As shown in FIG. The ceramic base 110 can be made of, for example, a ceramic sintered body such as aluminum nitride, alumina, or silicon nitride.

As shown in FIG. 1, an electrode foil 120 (an example of the heating element of the present invention) is embedded inside the ceramic base 110 . As shown in FIG. 2, the electrode foil 120 is a metal foil cut into strips and has a symmetrical shape. The outer diameter of the electrode foil 120 is approximately 300 mm. At approximately the center of the electrode foil 120, a terminal portion 121 connected to the feeder line 140 (see FIG. 1) is provided. The electrode foil 120 is formed of a heat-resistant metal (high melting point metal) foil such as a tungsten (W) foil, a molybdenum (Mo) foil, or an alloy foil containing molybdenum and/or tungsten. The purity of tungsten foil and molybdenum foil is preferably 99% or higher. The electrode foil 120 has a thickness of 0.15 mm or less. From the viewpoint of reducing the current consumption of the ceramic heater 100 by increasing the resistance value of the electrode foil 120, it is preferable to set the thickness of the electrode foil 120 to 0.1 mm or less. The width of the electrode foil 120 cut into strips is preferably 2.5 mm to 20 mm, more preferably 5 mm to 15 mm. In this embodiment, the electrode foil 120 is cut into the shape shown in FIG. 2, but the shape of the electrode foil 120 is not limited to this and can be changed as appropriate. Inside the ceramic base 110, in addition to the electrode foil 120, an electrostatic chuck electrode for attracting the wafer 10 to the mounting surface 111 by the Johnsen-Rahbek force and an electrode for generating plasma above the ceramic base 110 are provided. At least one of the plasma electrodes may be buried.

As shown in FIG. 3, a convex portion (hereinafter referred to as joint portion 113) protruding downward is provided at substantially the center of back surface 112 of ceramic base 110. As shown in FIG. The joint portion 113 has a substantially cylindrical shape extending in the vertical direction 5 (longitudinal direction 6 of the shaft 130 to be described later). A groove 114 is formed in the side surface of the joint 113 so as to surround the joint 113 in the circumferential direction.

A shaft 130 is connected to a joint surface 113 a that is a lower end surface of the joint portion 113 . The shaft 130 has a hollow cylindrical portion 131 and a large diameter portion 132 (see FIG. 1) provided below the cylindrical portion 131 . The large diameter portion 132 has a diameter larger than that of the cylindrical portion 131 . In the following description, the longitudinal direction of the cylindrical portion 131 is defined as the longitudinal direction 6 of the shaft 130 . As shown in FIG. 1, the longitudinal direction 6 of the shaft 130 is parallel to the vertical direction 5 when the ceramic heater 100 is in use.

The upper surface of the cylindrical portion 131 is fixed to the joint portion 113 of the ceramic base 110 with a bonding agent such as ceramics or glass. Alternatively, the cylindrical portion 131 and the shaft 130 may be fixed by diffusion bonding without using a bonding agent. It should be noted that the shaft 130 may be made of a ceramic sintered body such as alumina, aluminum nitride, or silicon nitride, like the ceramic base 110 . Alternatively, it may be formed of a material having a lower thermal conductivity than the ceramic base 110 in order to improve heat insulation.

As shown in FIG. 3, the shaft 130 has a hollow cylindrical shape and a through hole extending in the longitudinal direction 6 is formed therein. As shown in FIG. 1 , a feeder line 140 for supplying power to the electrode foil 120 is arranged in the hollow portion (through hole) of the shaft 130 . The upper end of the feeder line 140 is electrically connected to the terminal portion 121 (see FIG. 2) arranged in the center of the electrode foil 120 . A power supply terminal is provided at the lower end of the power supply line 140 and is connected to a heater power supply (not shown). Thereby, power is supplied to the electrode foil 120 through the feeder line 140 .

Next, a method for manufacturing the ceramic susceptor 100 will be described. A case in which the ceramic base 110 and the shaft 130 are made of aluminum nitride will be described below as an example.

First, a method for manufacturing the ceramic substrate 110 will be described. As shown in FIG. 4( a ), granulated powder P containing aluminum nitride (AlN) powder as a main component is put into a floored mold 501 made of carbon and temporarily pressed with a punch 502 . The floored mold 501 is provided with a depression for forming the joint portion 113 . The granulated powder P preferably contains 5 wt % or less of a sintering aid (for example, Y ₂ O ₃ ). Next, as shown in FIG. 4B, an electrode foil 120 cut into a predetermined shape is placed on the granulated powder P that has been temporarily pressed. In addition, the electrode foil 120 is arranged so as to be parallel to the surface (bottom surface of the floored mold 501) perpendicular to the pressurizing direction. At this time, a pellet of W or a pellet of Mo may be embedded in the position of the terminal 121 of the electrode foil 120 .

As shown in FIG. 4(c), granulated powder P is put into a floored mold 501 so as to cover the electrode foil 120, and is pressed with a punch 502 to be molded. Next, as shown in FIG. 4D, the granulated powder P in which the electrode foil 120 is embedded is pressed and fired. The pressure applied during firing is preferably 1 MPa or more. Moreover, it is preferable to bake at the temperature of 1800 degreeC or more. Next, as shown in FIG. 4(e), in order to form terminals 121, necessary processing such as blind hole drilling up to the electrode foil 120 is performed, and the ceramic substrate 110 is formed. In addition, when the pellet is embedded, a blind hole may be drilled to the pellet.

Note that the ceramic base 110 can also be manufactured by the following method. As shown in FIG. 5A, a binder is added to aluminum nitride granulated powder P, CIP molding is performed, and the mixture is processed into a disk shape to produce an aluminum nitride compact 510 . Next, as shown in FIG. 5B, the compact 510 is degreased to remove the binder.

As shown in FIG. 5C, recesses 511 for embedding the electrode foils 120 are formed in the degreased compact 510 . The electrode foil 120 is arranged in the concave portion 511 of the molded body 510, and another molded body 510 is laminated. Next, as shown in FIG. 5(d), the molded body 510 laminated so as to sandwich the electrode foil 120 is fired while being pressed. The pressure applied during firing is preferably 1 MPa or more. Moreover, it is preferable to bake at the temperature of 1800 degreeC or more. Next, as shown in FIG. 5(e), in order to form terminals 121, necessary processing such as blind hole drilling up to the electrode foil 120 is performed, and the ceramic base 110 is formed.

The upper surface (mounting surface 111) of the ceramic substrate 110 thus formed is subjected to surface grinding and lapping (mirror polishing). Furthermore, by sandblasting the mounting surface 111 , a plurality of projections (a plurality of convex portions) (not shown) are formed on the mounting surface 111 . Sandblasting is suitable as a processing method for forming the plurality of projections on the mounting surface 111, but other processing methods can also be used.

Further, as shown in FIG. 6A, the lower surface (rear surface 112) of the ceramic substrate 110 is cut to form a joint portion 113 substantially at the center of the rear surface 112. As shown in FIG. The outer diameter of the joint portion 113 is preferably the same as the outer diameter of the cylindrical portion 131 of the shaft 130 to be joined later. The outer diameter (diameter) of the joint portion 113 is preferably 100 mm or less. The height (length in the vertical direction 5) of the joint 113 is preferably 2 mm or more, more preferably 5 mm or more. Although there is no upper limit to the height of the joint 113, it is preferably 20 mm or less in view of ease of manufacture. A joint surface 113 a of the joint portion 113 is parallel to the mounting surface 111 . The surface roughness Ra of the joint surface 113a of the joint portion 113 is preferably 1.6 μm or less.

As shown in FIG. 6B, the cylindrical portion 131 of the shaft 130 is fixed to the joint surface 113a of the joint portion 113. As shown in FIG. The length of the cylindrical portion 131 of the shaft 130 can be, for example, 50 mm to 500 mm. In addition, the shaft 130 can be formed as follows. First, granulated powder P of aluminum nitride to which several wt % of binder is added is compacted under hydrostatic pressure (approximately 1 MPa), and the compact is processed into a predetermined shape. After that, it is fired in a nitrogen atmosphere. For example, it is baked at a temperature of 1900° C. for 2 hours. Then, the shaft 130 is formed by processing the sintered body into a predetermined shape after firing. The upper surface of the cylindrical portion 131 and the bonding surface 113a of the bonding portion 113 of the ceramic base 110 can be fixed by diffusion bonding at 1600° C. or higher and under a uniaxial pressure of 1 MPa or higher. In this case, the surface roughness Ra of the joint surface 113a of the joint portion 113 is preferably 0.4 μm or less, more preferably 0.2 μm or less. Alternatively, the upper surface of the cylindrical portion 131 and the joint surface 113a of the joint portion 113 of the ceramic base 110 may be joined using a joint agent. As the bonding agent, for example, AlN bonding material paste to which 10 wt % of Y ₂ O ₃ is added can be used. For example, the above-described AIN bonding agent paste is applied to the interface between the upper surface of the cylindrical portion 131 and the bonding surface 113a of the bonding portion 113 of the ceramic base 110 to a thickness of 15 μm, and is applied in a direction perpendicular to the mounting surface 111 (the shaft 130 It can be joined by heating at a temperature of 1700° C. for 1 hour while applying a force of 5 kPa in the longitudinal direction 6). Alternatively, the upper surface of the cylindrical portion 131 and the joint surface 113a of the joint portion 113 of the ceramic base 110 can be fixed by screwing, brazing, or the like.

Next, as shown in FIG. 6C, the side surface of the joining portion 113 of the ceramic substrate 110 is cut or ground to form a groove 114. Next, as shown in FIG. In this embodiment, the cross section of groove 114 is substantially semicircular. The groove 114 is formed so as to encircle the side surface of the joint portion 113 . In this embodiment, the upper end of the groove 114 is not in contact with the back surface 112 of the ceramic base 110, and there is a gap in the vertical direction 5 between the upper end of the groove 114 and the back surface 112 of the ceramic base 110. is open In the following description, the outer diameter (width in the horizontal direction) of the surface of shaft 130 that is joined to joint surface 113a of joint portion 113 is referred to as the outer diameter LS of the upper surface of shaft 130 . As shown in FIG. 6(c), in the area of the side surface of the joint 113 where the groove 114 is formed, there are three positions (first position P1, first position P1, second 2 position P2, third position P3), the width (horizontal length) L1 of the joint 113 at the first position P1 and the width (horizontal length) of the joint 113 at the second position P2 L2 and the width (horizontal length) L3 of the joint 113 at the third position P3 satisfy L2<L1 and L2<L3<2LS. exists. In the example shown in FIG. 6C, the lower end of the groove 114 corresponds to the first position P1, the vertical center of the groove 114 corresponds to the second position P2, and the upper end of the groove 114 corresponds to the third position P1. It corresponds to position P3.

In the above description, the groove 114 is formed in the side surface of the joint portion 113 of the ceramic substrate 110 after the cylindrical portion 131 of the shaft 130 is fixed to the joint surface 113a of the joint portion 113 . However, the cylindrical portion 131 of the shaft 130 may be fixed to the joint surface 113a of the joint portion 113 after forming the groove 114 in the side surface of the joint portion 113 of the ceramic base material 110 in advance.

Consider a case where the joint portion 113 of the ceramic substrate 110 is cut or ground before the cylindrical portion 131 of the shaft 130 is fixed to the joint surface 113 a of the joint portion 113 . In this case, instead of the ceramic susceptor 100 having the groove 114, the corner portion of the joint surface 113a of the joint portion 113 is chamfered along the circumferential direction like the ceramic susceptor 100A shown in FIG. may As a result, a chamfered concave portion 115 is formed in the corner portion of the joint surface 113 a of the joint portion 113 . The cross-sectional shape of the concave portion 115 has a curved shape with a radius of curvature of 1 mm or more. After forming the concave portion 115 in the joint surface 113a of the joint portion 113, the cylindrical portion 131 of the shaft 130 is fixed to the joint surface 113a of the joint portion 113 as shown in FIG. 7B. The fixing method is the same as the method described above. The outer diameter (horizontal width) Lb of the joint surface 113 a of the joint portion 113 is smaller than the outer diameter (horizontal width) LS of the upper surface of the flange 133 . Also, the surface roughness Ra of the concave portion 115 is preferably 0.1 μm or less.

Alternatively, as in the ceramic susceptor 100B shown in FIG. 8A, cutting or grinding may be performed so that the side surface of the joint 113 tapers toward the joint surface 113a. can. The cross-sectional shape of the joint portion 113 has a curved shape with a radius of curvature of 1 mm or more. In addition, as shown in FIG. 8( a ), a flange 133 having an outer diameter larger than that of the cylindrical portion 131 is provided at the upper end of the shaft 130 . Then, as shown in FIG. 8B, the flange 133 of the shaft 130 is fixed to the joint surface 113a of the joint portion 113. As shown in FIG. The outer diameter (horizontal width) Lb of the joint surface 113 a of the joint portion 113 is smaller than the outer diameter (horizontal width) LS of the upper surface of the flange 133 . Further, the surface roughness Ra of the side surface of the tapered joining portion 113 is preferably 0.1 μm or less.

Thus, the ceramic susceptors 100, 100A, and 100B according to this embodiment can be manufactured. As shown in FIG. 6(c), in the case of the ceramic susceptor 100 in which the groove 114 is formed in the joint 113, the horizontal cross-sectional area at the center of the groove 114 in the joint 113 (the position where the outer diameter is L2) is , the horizontal cross-sectional area of the lower end of the groove 114 (the position where the outer diameter is L1) and the upper end of the groove 114 (the position where the outer diameter is L3). That is, a constriction that temporarily narrows the horizontal cross-sectional area of the joint portion 113 is formed in the region where the groove 114 of the joint portion 113 is formed. Thereby, the flow of heat from the ceramic base 110 to the shaft 130 can be suppressed. In other words, it is possible to suppress heat from escaping from the ceramic base 110 toward the shaft 130 .

In the case of the ceramic susceptor 100A in which the recessed portion 115 is formed in the joint portion 113 (see FIGS. 7A and 7B), or the side surface of the joint portion 113 is tapered toward the joint surface 113a. In the case of the ceramic susceptor 100B having a shape (see FIGS. 8A and 8B), the outer diameter (horizontal width) Lb of the joint surface 113a of the joint portion 113 is equal to that of the cylindrical portion 131 of the shaft 130. It is smaller than the outer diameter (horizontal width) LS at the top surface. Also in this case, the flow of heat from the ceramic base 110 to the shaft 130 can be suppressed. That is, it is possible to suppress heat from escaping from the ceramic base 110 toward the shaft 130 .

The present invention will be further described below using examples and comparative examples. However, the present invention is not limited to the examples and comparative examples described below.

[Example 1]
FIG. 9 shows the ceramic heater 100 of Example 1. As shown in FIG. Although not shown in FIG. 9, the electrode foil 120 was prepared by cutting a molybdenum mesh (wire diameter 0.1 mm, mesh size #50, plain weave) into the shape shown in FIG. Then, a ceramic substrate 110 having a diameter of 310 mm and a thickness of 25 mm in which such electrode foil 120 was embedded was produced. A joint portion 113 having an outer diameter of 70 mm and a height of 10 mm was formed on the back surface 111 of the ceramic substrate 110 . The joint surface 113a of the joint portion 113 was processed so that the surface roughness Ra was 0.2 μm. Also, a shaft 130 having an outer diameter of 70 mm and an inner diameter of 60 mm was produced. The inner diameter of the upper surface of the shaft 130 is 50 mm. The surface roughness of the upper surface of shaft 130 is 0.2 μm. The upper surface of the shaft 130 and the bonding surface 113a of the bonding portion 113 were bonded by diffusion bonding according to the procedure described above. After that, a groove 114 was formed on the side surface of the joint 113 . The cross section of the groove 114 has a substantially rectangular shape with a width of 6 mm and a depth of 3 mm, and the center of the groove 114 in the width direction (vertical direction) is positioned 5 mm away from the rear surface 111 in the vertical direction. That is, the vertical distance between the upper end of the groove 114 and the rear surface 111 is 2 mm. In the cross section of the groove 114, the curvature radius (R dimension) of the corner is approximately the same as the R dimension of the corner of the tool (0.3 mm or less). Moreover, the surface roughness Ra of the inner surface of the groove 114 was 1.0 μm.

The airtightness evaluation of the ceramic susceptor 100 was performed in the following procedure. First, the produced ceramic heater 100 was installed in a process chamber. Then, a current was supplied to the ceramic heater 100 from an external power source (not shown), and the temperature cycle was repeated at set temperatures of 650.degree. C. to 200.degree. A check for the presence or absence of damage by visual inspection and a leak check using a helium leak detector were performed every cycle. In the leak check, after connecting the lower opening of the shaft 130 to a helium leak detector, helium gas was blown from the outside of the shaft 130 to evaluate whether there was a helium leak from the joint 180 or the like. When a leak of 10 ⁻⁸ Pa·m ³ /s or more was observed, it was determined that a leak occurred. In this example, no leakage was observed even after repeating the temperature cycle four times.

Furthermore, temperature evaluation of the ceramic susceptor 100 was performed according to the following procedure. A current was applied to the ceramic heater 100 from an external power source (not shown), and the temperature was controlled at a set temperature of 400° C. by a thermocouple (not shown). A silicon wafer for temperature evaluation was placed on the mounting surface 111 of the ceramic substrate 110 while the set temperature was maintained at 400.degree. Then, the temperature distribution in a region with a diameter of 290 mm on the silicon wafer for temperature evaluation was measured with an infrared camera. The silicon wafer for temperature evaluation was obtained by coating the upper surface of a silicon wafer with a diameter of 300 mm with a black body film with a thickness of 30 μm. A black body film is a film having an emissivity (emissivity) of 90% or more, and can be formed by coating a black body paint containing carbon nanotubes as a main raw material, for example. A value obtained by subtracting the minimum temperature from the maximum temperature of the temperature distribution of the silicon wafer for temperature evaluation measured with an infrared camera was obtained as the temperature difference Δ. The temperature difference Δ serves as an index of variations in temperature distribution on the mounting surface 111 of the ceramic substrate 110 . In Example 1, the temperature difference Δ with respect to the set temperature of 400°C was 3.5°C.

[Example 2]
FIG. 10 shows a ceramic susceptor 100 of Example 2. As shown in FIG. In the ceramic susceptor 100 of Example 2, the cross-sectional shape of the groove 114 is a semicircular shape with a radius of curvature of 3 mm, and the center of the groove 114 in the width direction (vertical direction) is positioned vertically away from the back surface 111 by 3 mm. It is the same as the ceramic susceptor 100 of Example 1 except that Note that the vertical distance between the upper end of the groove 114 and the back surface 111 is 0 mm. The surface roughness of the inner surface of the groove 114 was 1.0 μm. In Example 2, no leakage was observed even after repeating the temperature cycle 12 times. Moreover, the temperature difference Δ with respect to the set temperature of 400°C was 3.7°C.

[Example 3]
FIG. 11 shows a ceramic heater 100 of Example 3. As shown in FIG. The ceramic susceptor 100 of Example 3 is the same as the ceramic susceptor 100 of Example 1 except that a groove 114 having a constricted shape toward the center of the ceramic substrate 110 is formed. In the cross-sectional shape of the groove 114, the tip of the groove 114 in the depth direction has a semicircular shape with a radius of curvature of 3 mm. The distance D between the centers of the radii of curvature is 50 mm. Also, the vertical distance between the center of the radius of curvature and the back surface 111 is 3 mm. The surface roughness Ra of the inner surface of the groove 114 is 1.0 μm. In Example 3, no leakage was observed even after repeating the temperature cycle 12 times. Also, the temperature difference Δ with respect to the set temperature of 400°C was 3.3°C.

[Example 4]
The ceramic susceptor 100 of Example 4 is the same as that of Example 1 except that the radius of curvature of the cross-sectional corner of the groove 114 is 1 mm and the surface roughness of the inner surface of the groove 114 is 0.09 μm. is similar to In Example 4, no leakage was observed even after repeating the temperature cycle 12 times. Moreover, the temperature difference Δ with respect to the set temperature of 400°C was 3.5°C.

[Example 5]
FIG. 12 shows a ceramic heater 100B of Example 5. As shown in FIG. The side surface of the joint portion 113 of the ceramic susceptor 100 of Example 5 is a tapered curved surface tapering toward the joint surface 113a. The height of the joint 113 (the vertical distance from the back surface 112 to the joint surface 113a) is 5 mm, and the sectional shape of the joint 113 has an arcuate curved portion with a curvature radius of 5 mm. The surface roughness Ra of the side surface of the joint 113 is 0.08 μm. Further, the shaft 130 is provided with a flange portion 133 having an outer diameter larger than that of the cylindrical portion 131 at the upper end portion of the cylindrical portion 131 . The cylindrical portion 131 has an outer diameter of 60 mm and an inner diameter of 50 mm, while the flange 133 has an outer diameter of 70 mm and an inner diameter of 50 mm. In Example 5, no leakage was observed even after repeating the temperature cycle 12 times. Also, the temperature difference Δ with respect to the set temperature of 400°C was 5.7°C.

[Comparative example]
FIG. 13 shows a ceramic susceptor 100C of a comparative example. In the comparative example, the vertical cross-sectional shape of the joint portion 113 of the ceramic base material 110 is substantially rectangular, and does not have a tapered shape that tapers toward the joint surface 113a. Further, the side surface of the joint portion 113 is not provided with a concave portion or a groove that temporarily narrows the outer diameter. The joint portion 113 has an outer diameter of 90 mm. A flange portion 133 having an outer diameter larger than that of the cylindrical portion 131 is provided at the upper end portion of the cylindrical portion 131 of the shaft 130 . The cylindrical portion 131 has an outer diameter of 70 mm and an inner diameter of 50 mm. The flange 133 has an outer diameter of 90 mm, an inner diameter of 60 mm, and a thickness of 15 mm. In the comparative example, after repeating the temperature cycle twice, leakage was observed. Moreover, the temperature difference Δ with respect to the set temperature of 400°C was 6.1°C.

<Summary of Examples and Comparative Examples>
FIG. 14 shows a table summarizing the results of Examples 1 to 5 and Comparative Example described above.

As shown in FIGS. 9 to 11, in the ceramic heaters 100 of Examples 1 to 4, grooves 114 are formed on the side surfaces of the joining portion 113. As shown in FIGS. In Examples 1 to 4, three positions (first position P1, second position P2, third position P3), the width (horizontal length) L1 of the joint 113 at the first position P1, the width (horizontal length) L2 of the joint 113 at the second position P2, and the A first position P1, a second position P2, and a third position where the width (horizontal length) L3 of the joint portion 113 at the third position P3 satisfies L2<L1 and L2<L3<2LS. P3 exists. In this case, a constriction is formed in which the horizontal cross-sectional area of the joint portion 113 is temporarily narrowed at least at the second position P2. Thereby, the flow of heat from the ceramic base 110 to the shaft 130 can be suppressed. On the other hand, in the comparative example (see FIG. 13), such first position P1 to third position P3 do not exist, and a portion where the horizontal cross-sectional area is temporarily narrowed is not formed in the joint portion 113. not Therefore, it is considered that the variation in the temperature distribution of the mounting surface 111 in the ceramic heaters 100 of Examples 1 to 4 could be reduced as compared with the ceramic heater 100C of the comparative example.

As shown in FIG. 12, in Example 5, the side surface of the joint portion 113 of the ceramic susceptor 100B is a tapered curved surface tapering toward the joint surface 113a. The outer diameter (horizontal width) Lb of the joint surface 113 a of the joint portion 113 is smaller than the outer diameter (horizontal width) LS of the upper surface of the cylindrical portion 131 of the shaft 130 . As a result, the flow of heat from the ceramic base 110 to the shaft 130 can be suppressed, as in the first to fourth embodiments. Therefore, it is considered that the variation in the temperature distribution of the mounting surface 111 of the ceramic heater 100B of Example 5 could be made smaller than that of the ceramic heater 100C of the comparative example.

Comparing Example 1 and Example 4, in the ceramic heater 100 of Example 1, the radius of curvature of the corner of the cross-sectional shape of the groove 114 is less than 0.3 mm, whereas the ceramic heater of Example 4 In the heater 100, the radius of curvature of the corner of the cross-sectional shape of the groove 114 is 1 mm. Thus, by setting the radius of curvature of the corners of the cross-sectional shape of the groove 114 to 1 mm or more, the stress generated at the corners can be alleviated, and the occurrence of cracks at the corners can be suppressed. . As a result, the ceramic heater 100 of Example 4 is less prone to leakage than the ceramic heater 100 of Example 1. Furthermore, in Example 1, the surface roughness Ra of the inner surface of the groove 114 including the corners was 1.0 μm, whereas in Example 4, the surface roughness Ra of the inner surface of the groove 114 including the corners was 1.0 μm. The height Ra is 0.09 μm. By setting the surface roughness Ra of the inner surface of the groove 114 including the corners to 0.1 μm or less in this way, it is possible to suppress the occurrence of cracks in the corners. This is also considered to contribute to the fact that the ceramic heater 100 of Example 4 is less likely to leak than the ceramic heater 100 of Example 1.

<Action and effect of the embodiment>
In the above embodiments and examples, the ceramic susceptor 100 includes the ceramic base 110 , the metal electrode foil 120 embedded in the ceramic base 110 , and the shaft 130 . A joint portion 113 is provided on a rear surface 112 of the ceramic base 110 that faces the mounting surface 111 . A groove 114 is provided on the side surface of the joint portion 113 . As described above, in the region of the side surface of the joint 113 where the groove 114 is formed, there are the first position P1, the second position P2, and the third position P3 arranged in order upward from the joint surface 113a. The width (horizontal length) L1 of the joint 113 at the first position P1, the width (horizontal length) L2 of the joint 113 at the second position P2, and the joint 113 at the third position P3 There are a first position P1, a second position P2, and a third position P3 where L2<L1 and L2<L3<2LS. In this case, a constriction is formed in which the horizontal cross-sectional area of the joint portion 113 is temporarily narrowed at least at the second position P2. Thereby, the flow of heat from the ceramic base 110 to the shaft 130 can be suppressed.

In the embodiments and examples described above, the side surfaces of the joint portions 113 of the ceramic heaters 100A and 100B have tapered curved surfaces that taper toward the joint surface 113a. The outer diameter (horizontal width) Lb of the joint surface 113 a of the joint portion 113 is smaller than the outer diameter (horizontal width) LS of the upper surface of the cylindrical portion 131 of the shaft 130 . Thereby, the flow of heat from the ceramic base 110 to the shaft 130 can be suppressed.

In the above embodiments and examples, the cross-sectional shape of the groove 114 of the ceramic heater 100 may have a curved portion with a radius of curvature of 1 mm or more. In particular, the radius of curvature of the smallest radius of curvature, such as corners, of the cross-sectional shape of the groove 114 of the ceramic heater 100 can be set to 1 mm or more. Similarly, the cross-sectional shape of the ceramic heaters 100A and 100B can have a curved portion with a curvature radius of 1 mm or more. The stress can be relieved at the curved portion with a radius of curvature of 1 mm or more, and the occurrence of cracks at this portion can be suppressed. Thereby, it is possible to suppress the occurrence of leakage in the ceramic heaters 100, 100A, and 100B.

In the above embodiments and examples, the surface roughness Ra of the inner surface of the groove 114 of the ceramic heater 100 can be set to 0.1 μm or less. Similarly, the surface roughness Ra of the tapered curved surface tapering toward the joint surface 113a of the joint portion 113 of the ceramic heaters 100A and 100B can be reduced to 0.1 μm or less. As a result, it is possible to suppress the occurrence of cracks in the portions where the surface roughness Ra is 0.1 μm or less, and it is possible to suppress the occurrence of leaks in the ceramic heaters 100, 100A, and 100B.

<Change form>
The above-described embodiment is merely an example, and can be changed as appropriate. For example, the shape and dimensions of the ceramic substrate 110 and the shaft 130 are not limited to those of the above embodiment, and can be changed as appropriate. The shape and dimensions of the joint 113 and the cross-sectional shape, width and other dimensions of the groove 114 can also be changed as appropriate. Also, the shape, dimensions, etc. of the tapered curved surface provided on the side surface of the joint 113 can be changed as appropriate. In the above embodiments, molybdenum foil, tungsten foil, and alloy foil containing molybdenum and/or tungsten are used as the electrode foil, but the present invention is not limited to such an aspect. For example, metal foils other than molybdenum and tungsten, or alloy foils may be used.

In the above-described embodiment and Examples 1 to 5, when the flange 133 was not formed on the upper end of the shaft 130, the diameter of the upper surface of the shaft 130 and the diameter of the joint surface 113a of the joint portion 113 were the same. is not limited to such an aspect, and the diameter of the upper surface of the shaft 130 and the diameter of the joint surface 113a of the joint portion 113 can be changed to appropriate sizes.

Although the embodiments of the invention and their modifications have been described above, the technical scope of the invention is not limited to the scope of the above description. It will be apparent to those skilled in the art that various modifications or improvements may be made to the above embodiments. It is also clear from the description of the scope of claims that forms with such modifications or improvements can also be included in the technical scope of the present invention.

The execution order of each process in the manufacturing method shown in the specification and drawings is not specified in particular, and unless the output of the previous process is used in the subsequent process, in any order can be executed. For the sake of convenience, "first", "next", etc. are used for explanation, but it does not mean that it is essential to carry out in this order.

REFERENCE SIGNS LIST 100 ceramic heater 110 ceramic substrate 113 junction 114 groove 115 recess 120 electrode foil 130 shaft 140 feeder line

Claims (6)

A bonding having an upper surface on which an object to be heated is placed, a lower surface that faces the upper surface in the vertical direction, and a joint portion that projects downward in the vertical direction from the lower surface and has a joint surface parallel to the upper surface. a ceramic base having a portion;
a heating element embedded in the ceramic base;
a cylindrical shaft having an upper surface joined to the joint surface;
Side surfaces of the joint portion of the ceramic base material are arranged in order from the joint surface upward in the vertical direction, the second position, and the third position,
L1 is the width of the joint portion in the first position in the horizontal direction orthogonal to the vertical direction;
Let L2 be the width in the horizontal direction of the joint at the second position,
L3 is the width in the horizontal direction of the joint portion at the third position;
When the horizontal width of the shaft on the upper surface is LS,
L1 > L2
and L2<L3<2LS
A ceramic susceptor characterized by having a first position, a second position, and a third position that satisfy: 3. A cross section parallel to the vertical direction of a region including the first position, the second position, and the third position of the joint portion of the ceramic base material has a curved portion with a radius of curvature of 1 mm or more. 2. The ceramic susceptor according to 1. 3. The surface roughness Ra of a region including the first position, the second position, and the third position of the side surface of the joint portion of the ceramic base material according to claim 1 or 2, wherein the surface roughness Ra is 0.1 μm or less. ceramic heater. A bonding having an upper surface on which an object to be heated is placed, a lower surface that faces the upper surface in the vertical direction, and a joint portion that projects downward in the vertical direction from the lower surface and has a joint surface parallel to the upper surface. a ceramic base having a portion;
a heating element embedded in the ceramic base;
a flange having an upper surface joined to the joint surface; and a shaft having a tubular portion extending downward in the vertical direction from the flange,
The joint portion has a tapered shape in which a width in a horizontal direction perpendicular to the vertical direction tapers toward the joint surface,
A ceramic susceptor, wherein the horizontal width of the joint surface of the joint portion is smaller than the horizontal width of the upper surface of the flange. 5. The ceramic susceptor according to claim 4, wherein the joint portion of the ceramic base material has a curved portion with a curvature radius of 1 mm or more in a cross section parallel to the vertical direction. 6. The ceramic susceptor according to claim 4, wherein the surface roughness Ra of the joint portion of the ceramic substrate is 0.1 [mu]m or less.

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