Sample holder

Abstract

This sample holder includes a ceramic plate, a heat-resistant member, and a base member. The ceramic plate, the heat-resistant member, and the base member are disposed in the order of the ceramic plate, the heat-resistant member, and the base member. The heat-resistant member has a lower thermal expansion coefficient than the ceramic plate and is not joined to the ceramic plate.

Description

Technical Field

[0001] The disclosed embodiments relate to a sample holder.

Background Art

[0002] There is a sample holder for holding a sample such as a semiconductor wafer to be plasma-treated. Such a sample holder is configured by joining a ceramic plate having a sample holding surface to a metal cooling member.

[0003] Also, as a sample holder, a structure has been proposed in which a composite material having a coefficient of thermal expansion relatively close to that of the ceramic plate is disposed between the ceramic plate and the cooling member, the composite material and the cooling member are joined with an adhesive, and the composite material and the ceramic plate are joined with a metal (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The sample holder according to one aspect of the embodiment includes a ceramic plate, a heat-resistant member, and a base member. The ceramic plate, the heat-resistant member, and the base member are positioned in this order from the ceramic plate to the heat-resistant member and the base member. The heat-resistant member has a coefficient of thermal expansion smaller than that of the ceramic plate and is not joined to the ceramic plate.

Brief Description of the Drawings

[0006] [Figure 1] FIG. 1 is a perspective view schematically showing the configuration of a sample holder according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the sample holder shown in FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a sample holder according to another Embodiment 1. [Figure 4] Figure 4 is a schematic cross-sectional view showing a sample holder according to another embodiment 2. [Figure 5] Figure 5 is an enlarged view of region A shown in Figure 4. [Figure 6] Figure 6 shows an example of the external configuration of each protrusion shown in Figure 5. [Figure 7] Figure 7 shows another example of the external configuration of each protrusion shown in Figure 5. [Figure 8] Figure 8 is a schematic cross-sectional view showing a sample holder according to another embodiment 3. [Figure 9] Figure 9 is a schematic cross-sectional view showing a sample holder according to another embodiment 4. [Figure 10] Figure 10 shows an example of a coating configuration using a coating layer according to another embodiment 4. [Figure 11] Figure 11 shows another example of a coating configuration using a coating layer according to another embodiment 4. [Figure 12] Figure 12 is a schematic cross-sectional view showing a sample holder according to another embodiment 5. [Figure 13] Figure 13 is a planar perspective view of the ceramic plate shown in Figure 12, viewed from the second surface. [Modes for carrying out the invention]

[0007] The embodiments of the sample holder disclosed herein will be described below with reference to the attached drawings. However, the embodiments described below do not limit this disclosure. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from reality. Additionally, there may be differences in dimensional relationships and ratios between different parts of the drawings.

[0008] Furthermore, in the embodiments described below, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not require strict adherence to "constant," "orthogonal," "perpendicular," or "parallel" conditions. In other words, each of the above expressions allows for deviations such as manufacturing accuracy or installation accuracy.

[0009] <Embodiment> Figure 1 is a schematic perspective view showing the configuration of a sample holder according to an embodiment. Figure 2 is a schematic cross-sectional view showing the sample holder shown in Figure 1.

[0010] As shown in Figures 1 and 2, the sample holder 100 comprises a ceramic plate 10, a base member 20, and a heat-resistant member 30.

[0011] The ceramic plate 10 is a component formed by shaping a ceramic-containing raw material into a roughly disc-like form and firing it. The ceramic plate 10 uses electrostatic force to adsorb and hold samples such as semiconductor wafers. The ceramic plate 10 mainly contains aluminum oxide (Al2O3), aluminum nitride (AlN), yttria (Y2O3), etc.

[0012] The ceramic plate 10 has a first surface 10a and a second surface 10b located on the opposite side of the first surface 10a. A sample such as a semiconductor wafer is held on the first surface 10a. In other words, the first surface 10a becomes the sample holding surface for holding the sample.

[0013] Electrostatic adsorption electrodes are located inside the ceramic plate 10. The ceramic plate 10 may also incorporate, for example, heater electrodes for heating the ceramic plate 10. These electrodes can be made from materials such as platinum, tungsten, or molybdenum.

[0014] The ceramic plate 10 is fixed to the base member 20 via the fixing member 40. In FIG. 1, for convenience of explanation, the illustration of the fixing member 40 is omitted. As the fixing member 40, for example, bolts and clamps can be used. Note that the ceramic plate 10 may be fixed to the base member 20 by other mechanical means instead of the fixing member 40.

[0015] The base member 20 is located on the second surface 10b side of the ceramic plate 10, that is, on the side opposite to the ceramic plate 10 with the heat-resistant member 30 interposed therebetween. The base member 20 is a support member that supports the ceramic plate 10 (and the heat-resistant member 30). The base member 20 is attached to, for example, a semiconductor manufacturing apparatus and functions as a semiconductor holding device that holds a sample such as a semiconductor wafer with the sample holder 100.

[0016] The base member 20 is a substantially columnar member. The material of the base member 20 may be, for example, a metal such as aluminum, titanium, or stainless steel, or a composite material of ceramics such as silicon carbide and a metal such as aluminum. In such a case, the base member 20 may also serve as, for example, a high-frequency electrode.

[0017] The base member 20 functions as a cooling member that cools the ceramic plate 10 heated by plasma treatment on the sample. The base member 20 may be, for example, a heat exchanger. In such a case, the base member 20 may have a flow path through which a liquid or gas heat exchange medium flows.

[0018] The heat-resistant member 30 is located between the ceramic plate 10 and the base member 20. The heat-resistant member 30 has heat resistance and a smaller coefficient of thermal expansion than the ceramic plate 10. Since the coefficient of thermal expansion of the heat-resistant member 30 is smaller than that of the ceramic plate 10, the heat-resistant member 30 can reduce deformation due to a temperature difference in the thickness direction of the heat-resistant member 30 even when heated to 300°C or higher. Such a heat-resistant member 30 may be, for example, cordierite or glass.

[0019] Furthermore, the heat-resistant member 30 is positioned between the ceramic plate 10 and the base member 20, but is not bonded to the ceramic plate 10.

[0020] If the heat-resistant member 30 and the ceramic plate 10 are joined together by a bonding material or the like, warping of the heat-resistant member 30 and the ceramic plate 10 may occur due to the difference in thermal expansion between the heat-resistant member 30 and the ceramic plate 10. When warping occurs due to the difference in thermal expansion between the heat-resistant member 30 and the ceramic plate 10, the heat transfer between the heat-resistant member 30 and the base member 20 becomes uneven, and the heat transfer between the first surface 10a of the ceramic plate 10, i.e., the sample holding surface and the base member 20, becomes uneven in the in-plane direction, impairing the uniform heating of the sample holder 100.

[0021] In contrast, since the heat-resistant member 30, which has a lower coefficient of thermal expansion than the ceramic plate 10, is not joined to the ceramic plate 10, the heat-resistant member 30 and the ceramic plate 10 are more slippery compared to the case where the heat-resistant member 30 and the ceramic plate 10 are joined, and warping caused by the difference in thermal expansion between the heat-resistant member 30 and the ceramic plate 10 can be reduced. As a result, the unevenness of heat transfer between the heat-resistant member 30 and the base member 20 can be reduced, and the unevenness of heat transfer in the in-plane direction between the sample holding surface and the base member 20 can be reduced, thereby improving the uniformity of heat transfer within the plane of the sample holder 100.

[0022] Furthermore, the heat-resistant member 30 is positioned between the ceramic plate 10 and the fixing member 40, as the ceramic plate 10 is fixed to the base member 20 via the fixing member 40. By sandwiching the heat-resistant member 30 between the ceramic plate 10 and the fixing member 40, the position of the heat-resistant member 30 can be fixed even if the heat-resistant member 30 is not joined to the ceramic plate 10 and the base member 20.

[0023] <Another embodiment> Figure 3 is a schematic cross-sectional view showing a sample holder according to another embodiment 1. The sample holder 100 shown in Figure 3 further comprises a bonding material 50.

[0024] The bonding material 50 is positioned between the heat-resistant member 30 and the base member 20. The bonding material 50 joins the heat-resistant member 30 and the base member 20. By joining the heat-resistant member 30 and the base member 20 with the bonding material 50, the warping of the heat-resistant member 30 due to thermal cycling can be reduced compared to when the heat-resistant member 30 and the base member 20 are not joined. As a result, the unevenness of heat transfer between the ceramic plate 10 and the heat-resistant member 30 can be reduced, and the unevenness of heat transfer in the in-plane direction between the sample holding surface and the base member 20 can be further reduced, thereby improving the uniform heating of the sample holder 100 in the plane.

[0025] Furthermore, by joining the heat-resistant member 30 and the base member 20 with the joining material 50, the misalignment between the heat-resistant member 30 and the base member 20 can be reduced.

[0026] The bonding material 50 may have a lower heat transfer coefficient than the heat-resistant member 30. For example, a silicone resin-based adhesive can be used as the bonding material 50. If the bonding material 50 has a low heat transfer coefficient, it functions as an insulating layer, which reduces the temperature difference between the surface of the heat-resistant member 30 on the ceramic plate 10 side and the surface on the bonding material 50 side, thereby further reducing warping of the heat-resistant member 30 caused by temperature differences in the thickness direction of the heat-resistant member 30.

[0027] Figure 4 is a schematic cross-sectional view showing a sample holder according to another embodiment 2. In the sample holder 100 shown in Figure 4, the heat-resistant member 30 has a plurality of protrusions 31 (an example of a first protrusion) that contact the ceramic plate 10 and spaces 32 (an example of a first space) located around each protrusion 31 on the surface facing the ceramic plate 10. The plurality of protrusions 31 and spaces 32 can be formed, for example, by blasting the surface of the heat-resistant member 30 facing the ceramic plate 10. By having a plurality of protrusions 31 and spaces 32 in the heat-resistant member 30, the contact area between the heat-resistant member 30 and the ceramic plate 10 can be reduced. As a result, the ceramic plate 10 becomes more slippery against the heat-resistant member 30, and the stress generated by the difference in expansion and contraction between the heat-resistant member 30 and the ceramic plate 10 due to the thermal cycle can be alleviated.

[0028] The space 32 is located around each protrusion 31, between the ceramic plate 10 and the heat-resistant member 30. The space 32 has a depth corresponding to the height of each protrusion 31. A heat transfer gas, such as helium, may be introduced into the space 32. In other words, the space 32 may be a passage for the heat transfer gas. In this case, for example, the heat transfer gas may be introduced into the space 32 from a gas supply mechanism (not shown) via a gas introduction hole 321. The gas introduction hole 321 penetrates the base member 20, the joining material 50, and the heat-resistant member 30, and communicates with the space 32. By introducing the heat transfer gas into the space 32, the heat transfer gas can be delivered to the second surface 10b of the ceramic plate 10, improving the heat transfer between the heat-resistant member 30 and the ceramic plate 10 via the space 32.

[0029] Here, the details of each protrusion 31 will be further explained using Figures 5 and 6. Figure 5 is an enlarged view of region A shown in Figure 4. Figure 6 is a diagram showing an example of the external configuration of each protrusion shown in Figure 5.

[0030] As shown in Figures 5 and 6, the sides of each protrusion 31 may be tapered, narrowing in width towards the ceramic plate 10. In other words, each protrusion 31 may be formed in a tapered shape, narrowing in width as it approaches the top of the protrusion 31. By forming each protrusion 31 in a tapered shape, the surface area of ​​the end face 31a of each protrusion 31 that contacts the ceramic plate 10 can be reduced, thereby reducing the contact area between the heat-resistant member 30 and the ceramic plate 10. As a result, the ceramic plate 10 becomes more slippery against the heat-resistant member 30, and the stress generated by the difference in expansion and contraction between the heat-resistant member 30 and the ceramic plate 10 due to the thermal cycle can be further relieved.

[0031] Furthermore, the surface roughness Ra of the end face 31a of each protrusion 31 that contacts the ceramic plate 10 may be smaller than the surface roughness Ra of the bottom surface 32a of the space 32. This allows the end face 31a of each protrusion 31 and the ceramic plate 10 to be in uniform contact in the in-plane direction, and equalizes the heat transfer from the ceramic plate 10 to the multiple protrusions 31. Also, if the surface roughness Ra of the end face 31a of each protrusion 31 that contacts the ceramic plate 10 is small, the ceramic plate 10 becomes more slippery against the heat-resistant member 30, and the stress generated by the difference in expansion and contraction between the heat-resistant member 30 and the ceramic plate 10 due to the thermal cycle can be further reduced. In addition, if the surface roughness Ra of the bottom surface 32a of the space 32 is large, the surface area of ​​the bottom surface 32a of the space 32 can be increased. This allows, for example, when a heat transfer gas is introduced into the space 32, to promote heat exchange between the heat transfer gas and the heat-resistant member 30.

[0032] Furthermore, the side surfaces of each protrusion 31 may have grooves 311, as shown in Figure 7. Figure 7 is a diagram showing another example of the external configuration of each protrusion shown in Figure 5. By providing grooves 311 on the side surfaces of each protrusion 31, the flow of heat transfer gas introduced into the space 32 can be disturbed, thereby promoting heat exchange between the heat transfer gas and the heat-resistant member 30.

[0033] The grooves 311 may extend from the end face 31a of each protrusion 31 that contacts the ceramic plate 10 toward the bottom surface 32a of the space 32. This causes the flow direction of the heat transfer gas introduced into the space 32 to intersect with the extending direction of the grooves 311, thereby efficiently disrupting the flow of the heat transfer gas and further promoting heat exchange between the heat transfer gas and the heat-resistant member 30.

[0034] Note that the direction in which the groove 311 extends is not limited to the direction shown in Figure 7. The groove 311 may extend in any direction on the side surface of each protrusion 31.

[0035] Furthermore, although the example shown in Figure 7 illustrates the case where grooves 311 are provided on the side surface of each protrusion 31, projections may be provided on the side surface of each protrusion 31 instead of grooves 311. Alternatively, both grooves 311 and projections may be provided on the side surface of each protrusion 31.

[0036] Figure 8 is a schematic cross-sectional view showing a sample holder according to another embodiment 3. In the sample holder 100 shown in Figure 8, the ceramic plate 10 has a plurality of protrusions 11 (an example of second protrusions) that contact the heat-resistant member 30 and spaces 12 (an example of second spaces) located around each protrusion 11 on the surface facing the heat-resistant member 30, i.e., the second surface 10b. The plurality of protrusions 11 and spaces 12 can be formed, for example, by blasting the second surface 10b of the ceramic plate 10. By having a plurality of protrusions 11 and spaces 12 on the ceramic plate 10, the contact area between the heat-resistant member 30 and the ceramic plate 10 can be reduced. As a result, the ceramic plate 10 becomes more slippery against the heat-resistant member 30, and the stress generated by the difference in expansion and contraction between the heat-resistant member 30 and the ceramic plate 10 due to the thermal cycle can be alleviated.

[0037] Each protrusion 11 may be formed in a tapered shape, similar to each protrusion 31 shown in Figures 5 and 6. Furthermore, the surface roughness Ra of the end face of each protrusion 11 that contacts the heat-resistant member 30 may be smaller than the surface roughness Ra of the bottom surface of the space 12. Additionally, each protrusion 11 may have at least one of a projection and a groove on its side surface.

[0038] Space 12 is located around each protrusion 11, between the ceramic plate 10 and the heat-resistant member 30. Space 12 has a depth corresponding to the height of each protrusion 11. A heat transfer gas, such as helium, may be introduced into such space 12. In other words, space 12 may be a passage for the heat transfer gas. In this case, for example, the heat transfer gas may be introduced into space 12 from a gas supply mechanism (not shown) via a gas introduction hole 121. The gas introduction hole 121 penetrates the base member 20, the joining material 50, and the heat-resistant member 30, and communicates with space 12. By introducing the heat transfer gas into space 12, the heat transfer gas can be delivered to the second surface 10b of the ceramic plate 10, improving the heat transfer between the heat-resistant member 30 and the ceramic plate 10 via space 32.

[0039] Figure 9 is a schematic cross-sectional view showing a sample holder according to another embodiment 4. The sample holder 100 shown in Figure 9 further comprises a coating layer 60 (an example of a first intermediate layer, a second intermediate layer, and a third intermediate layer).

[0040] The coating layer 60 is located between the heat-resistant member 30 and the ceramic plate 10. The coating layer 60 covers the surface of the heat-resistant member 30 that is on the side facing the ceramic plate 10.

[0041] The coating layer 60 may have a lower coefficient of friction than the heat-resistant member 30. The coating layer 60 may also have a higher hardness than the heat-resistant member 30. Furthermore, the coating layer 60 may have a lower electrical resistance than the ceramic plate 10. For example, DLC (Diamond-Like Carbon) or SiC can be used as the coating layer 60. If the coating layer 60 has a low coefficient of friction, the frictional force acting on the heat-resistant member 30 and the ceramic plate 10 due to the difference in thermal expansion between them is reduced, thereby reducing the generation of particles from the heat-resistant member 30 and the ceramic plate 10. If the coating layer 60 has high hardness, even if frictional force acts on the heat-resistant member 30 due to the difference in thermal expansion between the heat-resistant member 30 and the ceramic plate 10, wear on the heat-resistant member 30 is reduced, thereby reducing the generation of particles from the heat-resistant member 30. If the electrical resistance of the coating layer 60 is low, the charge remaining on the first surface 10a of the ceramic plate 10, i.e., the sample holding surface, can be released into the coating layer 60, thereby reducing the decrease in sample release ability caused by residual charge on the ceramic plate 10. Furthermore, the electrical resistance of the coating layer 60 may be lower than that of the heat-resistant member 30. This makes it even easier to release the charge remaining on the sample holding surface.

[0042] Here, the details of the coating layer 60 will be further explained using Figures 10 and 11. Figure 10 is a diagram showing an example of a coating configuration using the coating layer according to another embodiment 4. Figure 11 is a diagram showing another example of a coating configuration using the coating layer according to another embodiment 4. Figures 10 and 11 correspond to enlarged views of region B shown in Figure 9.

[0043] As shown in Figure 10, the coating layer 60 may be positioned to cover only the end face 31a (see Figure 6) of each protrusion 31 that is in contact with the ceramic plate 10. This reduces the reduction in the cross-sectional area of ​​the flow path space 32, which becomes the flow path for the heat transfer gas, when, for example, a heat transfer gas is introduced into the space 32.

[0044] Furthermore, as shown in Figure 11, the coating layer 60 may be positioned to cover the end faces 31a (see Figure 6) of each protrusion 31 that contact the ceramic plate 10, the sides of each protrusion 31, and the bottom surface 32a of the space 32. This allows the coating layer 60 to cover the entire surface of the heat-resistant member 30 on the ceramic plate 10 side, making it easier to release any residual charge on the first surface 10a of the ceramic plate 10, i.e., the sample holding surface, into the coating layer 60.

[0045] Figure 12 is a schematic cross-sectional view showing a sample holder according to another embodiment 5. As shown in Figure 12, two first electrodes 13, 13, which are electrostatic adsorption electrodes for adsorbing and holding a sample such as a semiconductor wafer, may be located inside the first surface 10a side of the ceramic plate 10. Also, two second electrodes 14, 14, which are electrostatic adsorption electrodes for adsorbing and holding a heat-resistant member 30, may be located inside the second surface 10b side of the ceramic plate 10.

[0046] Figure 13 is a plan perspective view of the ceramic plate 10 shown in Figure 12, viewed from the second surface 10b side. As shown in Figure 13, the second electrodes 14, 14 are, for example, comb-shaped electrodes in which one second electrode 14 and the other second electrode 14 are finely arranged alternately. The second electrodes 14, 14 having this shape can attract and hold not only conductors and semiconductors but also insulators by the gradient force generated when a positive voltage is applied to one second electrode 14 and a negative voltage is applied to the other second electrode 14. The heat-resistant member 30 is attracted and held to the ceramic plate 10 by the second electrodes 14, 14 of the electrostatic attraction electrodes. The ceramic plate 10 is attracted and held to the heat-resistant member 30 and is also fixed to the base member 20 via the fixing member 40.

[0047] Since the ceramic plate 10 is adsorbed to the heat-resistant member 30, including its central portion, deformation of the first surface 10a, which is the sample holding surface, is reduced, and a decrease in temperature uniformity within the surface of the sample holding surface is less likely to occur. Furthermore, compared to the case where only the outer periphery of the ceramic plate 10 is mechanically fixed, the deformation of the first surface 10a, which is the sample holding surface, is reduced, making it less likely for the sample to peel off the sample holding surface or for the processing accuracy of the sample to decrease. Thus, the sample holder 100 according to another embodiment 5 can withstand use in high-temperature environments while reducing deformation of the sample holding surface.

[0048] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0049] 10 Ceramic plates 10a 1st page 10b 2nd side 11 Convex part 12 Space 13 1st electrode 14 2nd electrode 20 Base members 30 Heat-resistant material 31 Convex part 31a End face 32 Space 32a Bottom 40 Fixing member 50 Bonding material 60 coating layers 100 Sample holders 311 Groove

Claims

1. Ceramic plate and Heat-resistant material, A base member and The ceramic plate is positioned in the order of the heat-resistant member and the base member, The heat-resistant member has a lower coefficient of thermal expansion than the ceramic plate and is not bonded to the ceramic plate. The heat-resistant member is a sample holder having a plurality of first protrusions that contact the ceramic plate and a first space located around the first protrusions.

2. The sample holder according to claim 1, further comprising a fixing member for fixing the ceramic plate.

3. The sample holder according to claim 1 or 2, further comprising a joining member located between the heat-resistant member and the base member.

4. The sample holder according to claim 1, wherein the side surface of the first protrusion is tapered, becoming narrower in width toward the ceramic plate.

5. The sample holder according to claim 1 or 4, wherein the surface roughness of the end face of the first protrusion that contacts the ceramic plate is smaller than the surface roughness of the bottom surface of the first space.

6. The sample holder according to claim 1, wherein a heat transfer gas is introduced into the first space.

7. The sample holder according to claim 4, wherein the side surface of the first protrusion has at least one of a projection and a groove.

8. The sample holder according to claim 7, wherein at least one of the projection and the groove extends in a direction toward the bottom surface of the first space from the end face of the first protrusion that contacts the ceramic plate.

9. A ceramic plate and Heat-resistant material, A base member and The ceramic plate is positioned in the order of the heat-resistant member and the base member, The heat-resistant member has a lower coefficient of thermal expansion than the ceramic plate and is not bonded to the ceramic plate. The ceramic plate has a plurality of second protrusions that contact the heat-resistant member and a second space located around the second protrusions. The second space contains a sample holder into which a heat transfer gas is introduced.

10. A ceramic plate and Heat-resistant material, A base member and The ceramic plate is positioned in the order of the heat-resistant member and the base member, The heat-resistant member has a lower coefficient of thermal expansion than the ceramic plate and is not bonded to the ceramic plate. A first intermediate layer is provided between the heat-resistant member and the ceramic plate. The first intermediate layer has a lower coefficient of friction than the heat-resistant member, and is used as a sample holder.

11. A ceramic plate and Heat-resistant material, A base member and The ceramic plate is positioned in the order of the heat-resistant member and the base member, The heat-resistant member has a lower coefficient of thermal expansion than the ceramic plate and is not bonded to the ceramic plate. A second intermediate layer is provided between the heat-resistant member and the ceramic plate. The second intermediate layer is a sample holder having higher hardness than the heat-resistant member.

12. A ceramic plate and Heat-resistant material, A base member and The ceramic plate is positioned in the order of the heat-resistant member and the base member, The heat-resistant member has a lower coefficient of thermal expansion than the ceramic plate and is not bonded to the ceramic plate. A third intermediate layer is provided between the heat-resistant member and the ceramic plate. The third intermediate layer has lower electrical resistance than the ceramic plate, and is used as a sample holder.

13. A ceramic plate and Heat-resistant material, A base member and The ceramic plate is positioned in the order of the heat-resistant member and the base member, The heat-resistant member has a lower coefficient of thermal expansion than the ceramic plate and is not bonded to the ceramic plate. The ceramic plate has an electrostatic adsorption electrode inside, The heat-resistant member is a sample holder that is adsorbed onto the ceramic plate by the electrostatic adsorption electrode.

14. A ceramic plate and Heat-resistant material, A base member and The ceramic plate is positioned in the order of the heat-resistant member and the base member, The heat-resistant member has a lower coefficient of thermal expansion than the ceramic plate and is not bonded to the ceramic plate. The ceramic plate has a plurality of second protrusions that contact the heat-resistant member and a second space located around the second protrusions. The side surface of the second protrusion is tapered, becoming narrower towards the heat-resistant member, in the sample holder.

15. The sample holder according to claim 14, wherein the side surface of the second protrusion has at least one of a projection and a groove.

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