Sample holder

Abstract

A sample holder according to the present disclosure comprises a ceramic body, a base plate, a cylindrical member, and a porous body. The ceramic body has a sample retaining surface and a first through hole. The base plate includes a second through hole connected to the first through hole and supports the ceramic body. The cylindrical member is positioned inside the second through hole and has a third through hole connected to the first through hole. The porous body is located inside the third through hole. The porous body includes a first part and a second part positioned along the direction in which the ceramic body and the base plate are arranged. The first and second parts have different porosities.

Description

Sample holder

[0001] The present disclosure relates to a sample holder.

[0002] A sample holder used in a semiconductor manufacturing apparatus or the like is known. The sample holder has, for example, a structure in which a ceramic body on which a sample such as a wafer is placed and a conductive base member that supports the ceramic body are joined via a bonding material.

[0003] In this type of sample holder, a plurality of through holes penetrating the ceramic body and the base member are formed, and a gas such as helium is supplied to the sample placed on the ceramic body through these through holes.

[0004] Patent Document 1 discloses a sample holder in which porous bodies are respectively located in portions of the above-described through holes that penetrate the ceramic body and the base member. With this configuration, the inflow of plasma into the through hole portion is reduced, and arcing, which is discharge in the through hole portion, and corrosion of the base member due to arcing can be reduced.

[0005] Japanese Patent Application Laid-Open No. 2019-165193

[0006] The sample holder according to one aspect of the present disclosure includes a ceramic body, a base plate, a cylindrical member, and a porous body. The ceramic body has a sample holding surface and a first through hole. The base plate has a second through hole connected to the first through hole and supports the ceramic body. The cylindrical member is located inside the second through hole and has a third through hole connected to the first through hole. The porous body is located inside the third through hole. The porous body includes a first portion and a second portion located along the arrangement direction of the ceramic body and the base plate. The first portion and the second portion have different porosity.

[0007] Figure 1 is a cross-sectional view showing an example of the configuration of a sample holder according to the first embodiment. Figure 2A is a cross-sectional view showing an example of the configuration of a cylindrical member and a porous body according to the first embodiment. Figure 2B is a cross-sectional view showing another example of the configuration of a cylindrical member and a porous body according to the first embodiment. Figure 2C is a cross-sectional view showing another example of the configuration of a cylindrical member and a porous body according to the first embodiment. Figure 3 is a perspective view showing an example of a first part constituting the porous body according to the first embodiment. Figure 4A is a cross-sectional view showing an example of the configuration of a cylindrical member and a porous body according to the second embodiment. Figure 4B is a cross-sectional view showing an example of a sample holder having the cylindrical member shown in Figure 4A. Figure 4C is a cross-sectional view showing another example of the configuration of a cylindrical member and a porous body according to the second embodiment. Figure 5A is a cross-sectional view showing an example of the configuration of a cylindrical member and a porous body according to the third embodiment. Figure 5B is a cross-sectional view showing another example of the configuration of a cylindrical member and a porous body according to the third embodiment. Figure 6 is a cross-sectional view showing an example of the configuration of a cylindrical member and a porous body according to the fourth embodiment. Figure 7A is a cross-sectional view showing an example of the configuration of a cylindrical member and a porous body according to the fifth embodiment. Figure 7B is a cross-sectional view showing another example of the configuration of the cylindrical member and porous body according to the fifth embodiment. Figure 7C is a cross-sectional view showing another example of the configuration of the cylindrical member and porous body according to the fifth embodiment. Figure 7D is a cross-sectional view showing another example of the configuration of the cylindrical member and porous body according to the fifth embodiment. Figure 8 is a cross-sectional view showing another example of the configuration of the cylindrical member and porous body according to the fifth embodiment. Figure 9 is a cross-sectional view showing an example of the configuration of the sample holder according to the sixth embodiment.

[0008] The embodiments for implementing the sample holder according to this disclosure (hereinafter referred to as "Embodiments") will be described in detail below with reference to the drawings. However, this disclosure is not limited by these embodiments. Furthermore, each embodiment can be combined as appropriate, provided that the processing content is not inconsistent. Also, the same parts are denoted by the same reference numerals in each of the following embodiments, and redundant descriptions are omitted.

[0009] 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.

[0010] Furthermore, in the drawings referenced below, for the sake of clarity, mutually orthogonal X, Y, and Z axis directions are sometimes defined, and a Cartesian coordinate system is shown with the positive Z axis pointing vertically upward.

[0011] In the sample holder described in Patent Document 1, the boundary between the two porous bodies is the boundary between the ceramic body and the base plate. With this structure, gas may flow into the adhesive area between the ceramic body and the base plate after prolonged use. Also, when the boundary between the two porous bodies is located on the ceramic body or the base plate, gas may leak from between the two porous bodies and flow into the aforementioned through-holes. When gas leaks in this way without following the desired flow, the temperature of the leaked area drops locally, which may reduce the uniformity of the heat distribution of the sample holder.

[0012] Therefore, it is hoped that the above-mentioned problems can be overcome and a sample holder with excellent heat uniformity can be realized.

[0013] (First Embodiment) First, the configuration of the sample holder 1 according to the first embodiment will be described with reference to Figure 1. Figure 1 is a cross-sectional view showing an example of the configuration of the sample holder 1 according to the first embodiment.

[0014] As shown in Figure 1, the sample holder 1 comprises a ceramic body 10, a base plate 20, a cylindrical member 30, a porous body 40, and a bonding layer 50. The sample holder 1 is constructed by bonding a disc-shaped base plate 20 made of metal to the lower side of a disc-shaped ceramic body 10.

[0015] The sample holder 1 has multiple gas holes arranged in a plan view, penetrating from the first surface 10a of the ceramic body 10, which is the top surface of the sample holder 1, to the fourth surface 20b of the base plate 20, which is the bottom surface of the sample holder 1. Through these gas holes, a plasma generation gas such as helium is supplied from the bottom of the sample holder 1 to the space on the first surface 10a, which is the sample holding surface. Specifically, the gas flows in the order of the second through-hole 21, the porous body 40, and the first through-hole 11.

[0016] The ceramic body 10 is made of ceramic. The ceramic body 10 may be formed from a ceramic-containing raw material into a flat plate shape, for example, a disc shape. The ceramic body 10 may be made of, for example, aluminum oxide (Al ２ O ３ (Hereafter, it may be referred to as alumina.) Aluminum nitride (AlN), or yttrium oxide (Y ２ O ３ ) may also contain as a main component.

[0017] The ceramic body 10 has a first surface 10a which is a sample holding surface, and a second surface 10b located opposite the first surface 10a. The second surface 10b is the surface that is joined to the base plate 20 via a bonding layer 50, which will be described later.

[0018] The ceramic body 10 has a first through-hole 11 that penetrates the first surface 10a and the second surface 10b. This first through-hole 11 constitutes a part of the gas hole in the sample holder 1.

[0019] In this embodiment, the sample holder 1 is an electrostatic chuck that holds the sample by electrostatic force, and as shown in Figure 1, it is equipped with an electrode 12 for electrostatic adsorption inside the ceramic body 10, which is an insulator. The electrode 12 is a thin, flat conductive layer. The electrode 12 is positioned, for example, parallel to the first surface 10a of the ceramic body 10.

[0020] The electrode 12 may be made of a conductor mainly composed of a metal such as molybdenum (Mo), platinum (Pt), or tungsten (W). When a voltage is applied to the electrode 12 from the outside, an electrostatic force is generated between the first surface 10a and the sample, thereby adsorbing and holding the sample.

[0021] Although Figure 1 shows an example where two electrodes 12 are visible in the cross-sectional view, the configuration of the electrodes 12 is not limited to this.

[0022] The base plate 20 is a disc-shaped member that supports the ceramic body 10. The base plate 20 is bonded to the second surface 10b of the ceramic body 10 via a bonding layer 50. The base plate 20 is made of a metal such as aluminum.

[0023] The base plate 20 has a third surface 20a that is joined to the ceramic body 10 via a bonding layer 50, which will be described later, and a fourth surface 20b located opposite the third surface 20a.

[0024] The base plate 20 has a second through-hole 21 that penetrates the third surface 20a and the fourth surface 20b. The second through-hole 21 connects to the first through-hole 11. The second through-hole 21 constitutes part of the aforementioned gas hole in the sample holder 1.

[0025] The cylindrical member 30 is a cylindrical member made of an insulating material and is located inside at least one of the first through-hole 11 and the second through-hole 21. In the example shown in Figure 1, the cylindrical member 30 is located inside the second through-hole 21. Specifically, the cylindrical member 30 is positioned to cover the circumferential surface of the second through-hole 21. This makes it less likely for the circumferential surface of the second through-hole 21, which is a metal surface, to be exposed to the plasma entering the gas hole.

[0026] A ceramic material can be used as the insulating material for the cylindrical member 30. For example, alumina or aluminum nitride can be used as the ceramic material.

[0027] The cylindrical member 30 has a third through-hole 31 that connects to the first through-hole 11.

[0028] The porous body 40 is located inside the third through-hole 31. The porous body 40 has a porosity sufficient to allow gas to pass through. The porous body 40 serves as a gas channel and is a component that can suppress the plasma used on the first surface 10a, which is the sample holding surface, from entering through the first through-hole 11 and flowing downward (in this case, in the negative Z-axis direction). As the material constituting the porous body 40, a ceramic material such as alumina can be used.

[0029] The bonding layer 50 is a layer located between the ceramic body 10 and the base plate 20, and it joins the two together. The bonding layer 50 is formed by curing an adhesive made of an insulating material. For example, a silicone-based adhesive can be used as such an adhesive.

[0030] Next, the configuration of the porous body 40 according to the first embodiment will be described with reference to Figures 2A to 2C and Figure 3. Figure 2A is a cross-sectional view showing an example of the configuration of the cylindrical member 30 and porous body 40 according to the first embodiment. Figures 2B and 2C are cross-sectional views showing another example of the configuration of the cylindrical member 30 and porous body 40 according to the first embodiment. Figure 3 is a perspective view showing an example of the first part 41 constituting the porous body 40 according to the first embodiment.

[0031] As shown in Figure 2A, the porous body 40 includes a first portion 41 and a second portion 42. The first portion 41 and the second portion 42 are located along the alignment direction (here, the Z-axis direction) of the ceramic body 10 (see Figure 1) and the base plate 20 (see Figure 1). Specifically, the second portion 42 is located further from the first surface 10a of the ceramic body 10 than the first portion 41.

[0032] In the first embodiment, the first portion 41 and the second portion 42 of the sample holder 1 have different porosity. With this configuration, since the first portion 41 and the second portion 42, which have different porosity, are located inside a single cylindrical member 30, even if gas leaks from between the first portion 41 and the second portion 42, the gas remains inside the cylindrical member 30 and is less likely to flow into the second through-hole 21. Therefore, the sample holder 1 according to this embodiment has excellent heat uniformity because the temperature around the second through-hole 21 is less likely to drop locally. Porosity can be determined by analyzing images of the cross-section of the sample to be measured using a scanning electron microscope or the like. Commercially available image analysis software may be used for this image analysis. Alternatively, porosity may be determined by a mercury intrusion method using a mercury intrusion porosimeter.

[0033] Furthermore, within the porous body 40, the gas flow is limited in areas with low porosity, while in areas with high porosity, the gas spreads radially through the porous body 40, in other words, in a direction intersecting the direction of gas flow (in this case, the X-axis direction). As a result, the temperature of the porous body 40 tends to become uniform, and the temperature of the gas passing through the porous body 40 also tends to become uniform. Therefore, the sample holder 1 according to this embodiment has excellent heat uniformity.

[0034] As shown in the example in Figure 2A, the first part 41 and the second part 42 may be separate components. Here, "separate components" means that the first part 41 and the second part 42 are made of materials with different porosity, and that the first part 41 and the second part 42 are not fixed together. Separate components may also mean that the first part 41 and the second part 42 are manufactured separately during the manufacturing process.

[0035] Furthermore, as shown in Figure 2B, the first portion 41 and the second portion 42 may be formed integrally. That is, one porous body 40 may have a first portion 41 and a second portion 42 having different porosity levels. Such a porous body 40 can be manufactured, for example, by arranging ceramic materials with different porosity levels and then firing them.

[0036] Furthermore, as shown in Figure 2C, the porous body 40 may have a first portion 41, a second portion 42, and a third portion 43. The first portion 41, the second portion 42, and the third portion 43 may have different porosities. The first portion 41, the second portion 42, and the third portion 43 may be separate or integrally formed.

[0037] Furthermore, the porous body 40 may have four or more porous bodies with different porosity. One porous body 40 may have four or more parts with different porosity.

[0038] The first section 41 may have a lower porosity than the second section 42. With this configuration, within the porous body 40, the gas flow is limited in the first section 41 with low porosity, while the gas spreads throughout the porous body 40 in the second section 42 with high porosity. Also, within the porous body 40, gas introduced into the second section 42 with high porosity tends to flow more easily to the first section 41 with low porosity. As a result, the temperature of the porous body 40 tends to become uniform, and the sample holder 1 has excellent heat uniformity.

[0039] Furthermore, as shown in Figure 2C, if the porous body 40 has a first portion 41, a second portion 42, and a third portion 43, the porosity may be higher in the order of the first portion 41, the second portion 42, and the third portion 43. With this configuration, within the porous body 40, the gas flow is limited in the first portion 41, which has low porosity, while the gas is distributed throughout the porous body 40 in the second portion 42 and the third portion 43, which have high porosity. Therefore, the sample holder 1 has excellent heat uniformity.

[0040] The porous body 40 may have a three-dimensional network structure. Figure 3 shows an example where the first part 41 has a three-dimensional network structure. The entire porous body 40 may also have a three-dimensional network structure. That is, the second part 42 may also have a three-dimensional network structure. When the porous body 40 has a three-dimensional network structure, multiple pores extend in a meandering manner.

[0041] When the porous body 40 has such a three-dimensional network structure, inside the porous body 40, since the gas diffuses in the radial direction of the porous body 40, the gas easily spreads throughout the porous body 40. Therefore, the temperature of the porous body 40 is likely to be uniform, so the sample holder 1 has excellent heat uniformity.

[0042] As described above, the porosity of the first part 41 and the second part 42 of the sample holder 1 according to the first embodiment is different. According to such a configuration, since the first part 41 and the second part 42 with different porosities are located inside one cylindrical member 30, even when gas leaks between the first part 41 and the second part 42, the gas remains inside the cylindrical member 30 and does not easily flow into the second through-hole 21. Therefore, the sample holder 1 according to the present embodiment has excellent heat uniformity because the temperature around the second through-hole 21 is not likely to locally decrease.

[0043] In FIGS. 1 and 2A, an example is shown in which the thicknesses of the first part 41 and the second part 42 of the porous body 40, in other words, the dimensions in the arrangement direction (Z-axis direction) of the first part 41 and the second part 42 are the same, but the size relationship of the thicknesses is not limited to this. For example, the thickness of the first part 41 may be thicker than the thickness of the second part 42. Also, the thickness of the second part 42 may be thicker than the thickness of the first part 41.

[0044] In FIG. 3, an example is shown in which the first part 41 of the porous body 40 has a three-dimensional network structure, but at least one of the first part 41 and the second part 42 (see FIG. 2A) of the porous body 40 may have a three-dimensional network structure. When the first part 41 has a three-dimensional network structure, the gas flowing out from the surface of the first part 41 has a uniform temperature over the entire surface. Therefore, the sample holder 1 has excellent heat uniformity. Also, when the second part 42 has a three-dimensional network structure, in the second part 42 with a high porosity, the gas easily spreads throughout the second part 42. Therefore, the sample holder 1 has excellent heat uniformity. In this case, the part that does not have a three-dimensional network structure may have, for example, a honeycomb structure.

[0045] (Second Embodiment) FIG. 4A is a cross-sectional view showing an example of the configuration of the cylindrical member 30 and the porous body 40 according to the second embodiment. FIG. 4B is a cross-sectional view showing an example of the sample holder 1 having the cylindrical member 30 shown in FIG. 4A. FIG. 4C is a cross-sectional view showing another example of the configuration of the cylindrical member 30 and the porous body 40 according to the second embodiment.

[0046] As shown in FIGS. 4A and 4C, the third through-hole 31 of the cylindrical member 30 may have a plurality of portions with different diameters. Specifically, the third through-hole 31 may have a large-diameter portion 311 and a small-diameter portion 312 that is connected to the large-diameter portion 311 and has a smaller diameter than the large-diameter portion 311. The porous body 40 is located in the large-diameter portion 311. The small-diameter portion 312 is located farther from the first surface 10a (see FIG. 1) than the large-diameter portion 311. In the plan view of the cylindrical member 30 and the porous body 40, the small-diameter portion 312 may overlap with the central portion of the large-diameter portion 311 or the porous body 40.

[0047] According to such a configuration, since the cylindrical member 30 has excellent mechanical strength, it is not easily broken even when the temperature of the usage environment of the sample holder 1 changes. Also, when gas is introduced from the negative Z-axis direction side of the third through-hole 31, the gas passes through the small-diameter portion 312 and enters the porous body 40, so the gas easily diffuses in the radial direction from the central portion of the porous body 40. Therefore, the gas easily spreads throughout the porous body 40, and the temperature inside the porous body 40 easily becomes uniform, so the sample holder 1 has excellent heat uniformity.

[0048] The cylindrical member 30 shown in FIG. 4A may be located in a part of the second through-hole 21 of the base plate 20. Specifically, as shown in FIG. 4B, the second through-hole 21 may have a third portion 211 and a fourth portion 212 that has a smaller diameter than the third portion 211. The third portion 211 is located closer to the first through-hole 11 (ceramic body 10) than the fourth portion 212. In other words, the third portion 211 is located near the joint portion between the ceramic body 10 and the base plate 20 in the gas hole. The cylindrical member 30 may be located in the third portion 211 of the second through-hole 21. Specifically, the cylindrical member 30 may be located covering the peripheral surface of the third portion 211 of the second through-hole 21.

[0049] Furthermore, as shown in Figure 4C, the small-diameter portion 312 of the cylindrical member 30 may extend along the gas flow direction (in this case, the Z-axis direction). In other words, the cylindrical member 30 shown in Figure 4C may be positioned to cover the entire circumferential surface of the second through hole 21.

[0050] (Third Embodiment) Figure 5A is a cross-sectional view showing an example of the configuration of the cylindrical member 30 and porous body 40 according to the third embodiment. Figure 5B is a cross-sectional view showing another example of the configuration of the cylindrical member 30 and porous body 40 according to the third embodiment.

[0051] The cylindrical member 30 may have different wall thicknesses in the portion 3111 where the first portion 41 of the porous body 40 is located and the portion 3112 where the second portion 42 is located. That is, the large-diameter portion 311 of the cylindrical member 30 may have a step. With this configuration, the step causes turbulence in the gas flow, and the inside of the porous body 40 is stirred by the gas, making it easier for the temperature inside the porous body 40 to become uniform. Therefore, the sample holder 1 has excellent heat uniformity.

[0052] For example, as shown in Figure 5A, in the cylindrical member 30, the wall thickness of the portion where the first portion 41 is located may be thinner than the wall thickness of the portion where the second portion 42 is located. In other words, the diameter of the portion 3111 where the first portion 41 is located in the large-diameter portion 311 of the third through-hole 31 may be larger than the diameter of the portion 3112 where the second portion 42 is located. The diameter of the first portion 41 of the porous body 40 may be larger than the diameter of the second portion 42. With such a configuration, gas flows easily and can withstand long-term use.

[0053] Furthermore, as shown in Figure 5B, in the cylindrical member 30, the wall thickness of the portion where the first portion 41 is located may be thicker than the wall thickness of the portion where the second portion 42 is located. In other words, the diameter of the portion 3112 where the second portion 42 is located in the large-diameter portion 311 of the third through-hole 31 may be larger than the diameter of the portion 3111 where the first portion 41 is located. The diameter of the second portion 42 of the porous body 40 may be larger than the diameter of the second portion 42. With this configuration, since the gas diffuses greatly in the radial direction in the second portion 42, the temperature inside the porous body 40 tends to become uniform, and the sample holder 1 has excellent heat uniformity.

[0054] (Fourth Embodiment) Figure 6 is a cross-sectional view showing an example of the configuration of the cylindrical member 30 and the porous body 40 according to the fourth embodiment.

[0055] The thickness of the cylindrical member 30 may gradually increase along the direction in which the first portion 41 and the second portion 42 are aligned (here, the Z-axis direction). For example, as shown in Figure 6, the thickness of the cylindrical member 30 may increase as it moves away from the first surface 10a (see Figure 1). In other words, the diameter of the large-diameter portion 311 of the third through hole 31 may decrease as it moves away from the first surface 10a. The diameter of the porous body 40 may decrease as it moves away from the first surface 10a.

[0056] In this way, the thickness of the cylindrical member 30 gradually increases along the direction in which the first portion 41 and the second portion 42 are aligned. As a result, the cylindrical member 30 has excellent mechanical strength and is resistant to thermal shock, making it less likely to break even when the temperature of the environment in which the sample holder 1 is used changes. Therefore, the sample holder 1 has excellent durability.

[0057] Furthermore, the thickness of the cylindrical member 30 may increase as it approaches the first surface 10a. In other words, the diameter of the large-diameter portion 311 may increase as it moves away from the first surface 10a. The diameter of the porous body 40 may also increase as it moves away from the first surface 10a. In this case as well, the cylindrical member 30 has excellent mechanical strength and is resistant to thermal shock, so it is less likely to break even if the temperature of the environment in which the sample holder 1 is used changes. Therefore, the sample holder 1 has excellent durability.

[0058] (Fifth Embodiment) Figure 7A is a cross-sectional view showing an example of the configuration of the cylindrical member 30 and porous body 40 according to the fifth embodiment. Figures 7B to 7D and 8 are cross-sectional views showing another example of the configuration of the cylindrical member 30 and porous body 40 according to the fifth embodiment.

[0059] A space 60 may be located between the first part 41 and the second part 42. In the direction in which the first part 41 and the second part 42 are aligned (here, in the Z-axis direction), a space 60 may be located between the first part 41 and the second part 42.

[0060] For example, as shown in Figure 7A, the first portion 41 may have a first recess in the central part of the surface facing the second portion 42 in a plan view. The second portion 42 may have a second recess in the portion of the surface facing the first portion 41 that faces the first recess. The space 60 may be the space sandwiched between the first recess and the second recess. That is, the space 60 may be located between the central part of the first portion 41 in a plan view and the central part of the second portion 42 in a plan view, in the direction in which the first portion 41 and the second portion 42 are aligned. In other words, the outer edge of the first portion 41 and the outer edge of the second portion 42 may be in contact. Specifically, the outer edge of the surface of the first portion 41 facing the second portion 42 may be in contact with the outer edge of the surface of the second portion 42 facing the first portion 41.

[0061] It should be noted that the example in Figure 7A is not limited to the first recess of the first portion 41 and the second recess of the second portion 42. For example, if only the first recess is present, the space 60 may be the space sandwiched between the first recess of the first portion 41 and the opposing surfaces of the first portion 41 of the second portion 42. Alternatively, if only the second recess is present, as shown in Figure 8, the space 60 may be the space sandwiched between the opposing surface of the second portion 42 of the first portion 41 and the second recess of the second portion 42.

[0062] Furthermore, as shown in Figure 7B, the second portion 42 may have a third recess on its outer edge in a plan view of the surface facing the first portion 41. The space 60 may be the space sandwiched between the surface of the first portion 41 facing the second portion 42 and the third recess of the second portion 42. That is, the space 60 may be located between the outer edge of the first portion 41 in a plan view and the outer edge of the second portion 42 in a plan view in the direction in which the first portion 41 and the second portion 42 are aligned. In other words, the central portion of the first portion 41 and the central portion of the second portion 42 may be in contact. Specifically, the central portion of the surface of the first portion 41 facing the second portion 42 may be in contact with the central portion of the surface of the second portion 42 facing the first portion 41.

[0063] Furthermore, not limited to the example in Figure 7B, the first portion 41 may have a fourth recess on its outer edge on the surface facing the second portion 42. The space 60 may be the space sandwiched between the third recess and the fourth recess. In this case, the second portion 42 does not have to have the third recess. That is, the space 60 may be the space sandwiched between the fourth recess and the surface of the second portion 42 facing the first portion 41.

[0064] Furthermore, as shown in Figures 7C and 7D, the first portion 41 and the second portion 42 do not have to be in contact. That is, the space 60 may be a space sandwiched between the surface of the first portion 41 facing the second portion 42, the surface of the second portion 42 facing the first portion 41, and the circumferential surface of the cylindrical member 30. In this case, as shown in Figure 7D, the third through hole 31 of the cylindrical member 30 may have a step. The first portion 41 may be supported by such a step.

[0065] In this way, the presence of a space 60 between the first part 41 and the second part 42 allows for the distribution of stress applied to the first part 41 and the second part 42. Furthermore, since gas can flow more freely in the space 60 compared to the contact area between the first part 41 and the second part 42, the pressure (gas pressure) caused by the gas flow rate at the contact area can be reduced. As the operating temperature of the sample holder 1 increases, the gas pressure also increases, so the effect is more pronounced in high-temperature environments.

[0066] Furthermore, as shown in Figures 7B and 8, the contact between the outer edge of the first portion 41 and the outer edge of the second portion 42 provides the sample holder 1 with superior mechanical strength. Also, as shown in Figure 7A, the contact between the central portion of the first portion 41 and the central portion of the second portion 42 ensures that even if the gas temperatures differ between the first portion 41 and the second portion 42, the contact portion between the first portion 41 and the second portion 42 does not come into contact with the cylindrical member 30. Therefore, thermal stress caused by the temperature difference in the gas is less likely to be applied to the cylindrical member 30. Moreover, as shown in Figures 7C and 7D, if the first portion 41 and the second portion 42 are not in contact, thermal stress is less likely to occur even if there is a temperature difference in the gas between the first portion 41 and the second portion 42, as described above.

[0067] As shown in Figure 8, the reaction layer 70 may be located near the interface between the outer edge of the first portion 41 and the outer edge of the second portion 42. Such a reaction layer 70 may, for example, contain a glass component contained in the cylindrical member 30. By having a reaction layer 70 in this way, the gas flows around the reaction layer 70, i.e., through the space 60, so that stress is less likely to be applied to the cylindrical member 30.

[0068] Although Figures 7A to 7D and Figure 8 show an example where the cross-sectional shape of space 60 is rectangular, the cross-sectional shape of space 60 is not limited to this. For example, the cross-sectional shape of space 60 may be circular or elliptical.

[0069] (Sixth Embodiment) Figure 9 is a cross-sectional view showing an example of the configuration of the sample holder 1 according to the sixth embodiment. As shown in Figure 9, the cylindrical member 30 may be positioned across the ceramic body 10 and the base plate 20. Specifically, the cylindrical member 30 may be positioned from inside the second through hole 21 of the base plate 20 to inside the first through hole 11 of the ceramic body 10. The porous body 40 may similarly be positioned from inside the second through hole 21 to inside the first through hole 11.

[0070] With this configuration, even if gas leaks from between the first portion 41 and the second portion 42 of the porous body 40, the gas remains inside the cylindrical member 30, making it difficult for the gas to flow into the bonding layer 50 between the ceramic body 10 and the base plate 20. Therefore, the sample holder 1 according to this embodiment has excellent heat uniformity because the temperature around the bonding layer 50 does not drop locally.

[0071] Furthermore, this technology can also take the following configurations: (1) A sample holder comprising: a ceramic body having a sample holding surface and a first through-hole; a base plate supporting the ceramic body and having a second through-hole connected to the first through-hole; a cylindrical member located inside at least one of the first through-hole and the second through-hole and having a third through-hole connected to the first through-hole; and a porous body located inside the third through-hole, wherein the porous body includes a first portion and a second portion located along the direction of alignment between the ceramic body and the base plate, and the first portion and the second portion have different porosity. (2) The sample holder according to (1), wherein the second portion is located further from the sample holding surface than the first portion, and the first portion has a lower porosity than the second portion. (3) The sample holder according to (1) or (2), wherein the porous body has a three-dimensional network structure. (4) The sample holder according to any one of (1) to (3), wherein the third through-hole has a large-diameter portion in which the porous body is located and a small-diameter portion located further from the sample holding surface than the large-diameter portion and having a smaller diameter than the large-diameter portion. (5) The sample holder according to any one of (1) to (4), wherein a space is located between the first portion and the second portion. (6) The sample holder according to (5), wherein the outer edge of the first portion and the outer edge of the second portion are in contact. (7) The sample holder according to any one of (1) to (6), wherein the thickness of the cylindrical member in the portion where the first portion is located is greater than the thickness of the portion where the second portion is located. (8) The sample holder according to any one of (1) to (7), wherein the thickness of the cylindrical member gradually increases along the direction of alignment. (9) The sample holder according to any one of (1) to (8), wherein the cylindrical member and the porous body are located from the inside of the second through hole to the inside of the first through hole.

[0072] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Indeed, the embodiments described above can be embodied in a variety of forms. Furthermore, the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0073] 1 Sample holder 10 Ceramic body 10a First surface 10b Second surface 11 First through hole 12 Electrode 20 Base plate 20a Third surface 20b Fourth surface 21 Second through hole 30 Cylindrical member 31 Third through hole 40 Porous body 41 First section 42 Second section 43 Third section 50 Bonding layer 60 Space 70 Reaction layer 311 Large diameter section 312 Small diameter section

Claims

1. A sample holder comprising: a ceramic body having a sample-holding surface and a first through-hole; a base plate supporting the ceramic body and having a second through-hole connected to the first through-hole; a cylindrical member located inside at least one of the first and second through-holes and having a third through-hole connected to the first through-hole; and a porous body located inside the third through-hole, wherein the porous body includes a first portion and a second portion located along the direction of alignment between the ceramic body and the base plate, and the first portion and the second portion have different porosity.

2. The sample holder according to claim 1, wherein the second portion is located further from the sample holding surface than the first portion, and the first portion has a lower porosity than the second portion.

3. The sample holder according to claim 1 or 2, wherein the porous body has a three-dimensional network structure.

4. The sample holder according to any one of claims 1 to 3, wherein the third through-hole has a large-diameter portion in which the porous body is located, and a small-diameter portion located further from the sample holding surface than the large-diameter portion and having a smaller diameter than the large-diameter portion.

5. The sample holder according to any one of claims 1 to 4, wherein a space is located between the first part and the second part.

6. The sample holder according to claim 5, wherein the outer edge of the first portion and the outer edge of the second portion are in contact.

7. The sample holder according to any one of claims 1 to 6, wherein the thickness of the cylindrical member in the portion where the first portion is located is greater than the thickness of the portion where the second portion is located.

8. The sample holder according to any one of claims 1 to 7, wherein the thickness of the cylindrical members gradually increases along the direction of arrangement.

9. The sample holder according to any one of claims 1 to 8, wherein the cylindrical member and the porous body are located extending from the inside of the second through-hole to the inside of the first through-hole.

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