Sample holder

Abstract

A sample holder according to one embodiment comprises a ceramic body, a base member, a bonding material, and a first conductive film. The ceramic body has a first surface, which is a sample holding surface, and a second surface that is positioned on the reverse side of the first surface. In addition, the ceramic body has an internal electrode. The base member is conductive. The bonding material is positioned between the ceramic body and the base member. The first conductive film has a lower volume resistivity than the ceramic body, and is positioned so as to extend from at least a part of the outer surface of the ceramic body to at least a part of the outer surface of the base member.

Description

Sample holder

[0001] SUMMARY OF THE INVENTION The disclosed embodiments relate to a sample holder.

[0002] The electrostatic chuck has a ceramic body having an internal electrode and a base member, and attracts and holds a semiconductor wafer (hereinafter referred to as a wafer) on the upper surface of the ceramic body by applying a DC voltage to the internal electrode. The ceramic body and the base member are bonded together, and therefore a bonding material is located between the ceramic body and the base member.

[0003] For example, U.S. Patent No. 6,277,949 discloses an electrostatic chuck featuring a conductive path to ground that allows excess surface charge to be discharged to ground, thereby reducing wafer sticking due to surface charge collection.

[0004] Special Publication No. 2013-542590

[0005] A sample holder according to one aspect of the embodiment includes a ceramic body, a base member, a bonding material, and a first conductive film. The ceramic body has a first surface that is a sample support surface and a second surface located opposite the first surface. The ceramic body also has an internal electrode. The base member is conductive. The bonding material is located between the ceramic body and the base member. The first conductive film has a lower volume resistivity than the ceramic body and is located across at least a portion of the outer surface of the ceramic body and at least a portion of the outer surface of the base member.

[0006] FIG. 1A is a perspective view schematically showing the configuration of a sample holder according to the first embodiment. FIG. 1B is a cross-sectional view schematically showing the sample holder according to the first embodiment. FIG. 2A is a view schematically showing conductive paths of a sample holder according to a reference example. FIG. 2B is a view schematically showing conductive paths of a sample holder according to the first embodiment. FIG. 3 is a cross-sectional view schematically showing a sample holder according to the second embodiment. FIG. 4 is a side view schematically showing a sample holder according to the third embodiment. FIG. 5 is a side view schematically showing a sample holder according to the fourth embodiment. FIG. 6 is a side view schematically showing a sample holder according to the fifth embodiment. FIG. 7 is a side view schematically showing another example of the sample holder according to the fifth embodiment. FIG. 8 is a side view schematically showing a sample holder according to the sixth embodiment. FIG. 9 is a side view schematically showing another example of the sample holder according to the sixth embodiment. FIG. 10 is a side view schematically showing a sample holder according to the seventh embodiment. FIG. 11 is a cross-sectional view schematically showing a sample holder according to the eighth embodiment. FIG. 12 is a cross-sectional view schematically showing another example of the sample holder according to the eighth embodiment. FIG. 13 is a cross-sectional view schematically showing another example of the sample holder according to the eighth embodiment. FIG. 14 is a cross-sectional view schematically showing another example of the sample holder according to the eighth embodiment. FIG. 15 is a cross-sectional view schematically showing a sample holder according to the ninth embodiment. FIG. 16A is an enlarged cross-sectional view of a chamfered portion of a sample holder according to the tenth embodiment. FIG. 16B is an enlarged cross-sectional view of another example of the chamfered portion of a sample holder according to the tenth embodiment. FIG. 17 is a cross-sectional view schematically showing a sample holder. FIG. 18 is a cross-sectional view schematically showing a sample holder. FIG. 19 is a cross-sectional view schematically showing a sample holder.

[0007] Hereinafter, embodiments of the sample holder disclosed in the present application will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to the embodiments shown below. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from reality. Furthermore, the dimensional relationships and ratios may differ between the drawings.

[0008] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc.

[0009] Electrostatic chucks have been proposed that feature a conductive path to ground. However, if the end of the conductive path penetrates into the outer periphery of the interface between the ceramic body and the base member, the outer periphery of the interface is prone to change in the direction of charge movement, making it susceptible to heating and stress concentration. As a result, the bonding material near the outer periphery of the interface is prone to peeling, which reduces the thermal uniformity of the electrostatic chuck.

[0010] Therefore, it is desired to realize a sample holder that can solve the above problems and maintain excellent thermal uniformity, which will make it possible to stabilize the thermal uniformity of the sample holder.

[0011] <First embodiment> Fig. 1A is a perspective view schematically showing the configuration of a sample holder according to a first embodiment, and Fig. 1B is a cross-sectional view schematically showing the sample holder according to the first embodiment.

[0012] As shown in FIGS. 1A and 1B, the sample holder 100 includes a ceramic body 10, a base member 20, a bonding material 30, and a first conductive film 40.

[0013] The ceramic body 10 is a member formed by forming a ceramic-containing raw material into a disk shape and firing it. The ceramic body 10 utilizes electrostatic force to attract and hold a sample, such as a wafer. The ceramic body 10 contains, for example, aluminum nitride (AlN) as a main component. In the present disclosure, the main component is, for example, a material that accounts for 50 mass % or more of the material. The ceramic body 10 may also contain a ceramic other than aluminum nitride, such as aluminum oxide (Al ２ O ３ ) or yttria (Y ２ O ３ ) may be contained as a main component.

[0014] The ceramic body 10 has a first surface 10a serving as a sample support surface, a second surface 10b located opposite the first surface 10a, and an outer surface 10c connecting the first surface 10a and the second surface 10b. In this embodiment, the outer surface 10c is a side surface of the ceramic body 10. The ceramic body 10 has an internal electrode 11. The internal electrode 11 is connected to a power source 12. A sample is attracted and held on the first surface 10a by electrostatic force generated by application of a DC voltage from the power source 12 to the internal electrode 11. Examples of materials that can be used for the internal electrode 11 include metals such as platinum, tungsten, and molybdenum. However, the material of the internal electrode 11 is not limited to these. A heater electrode (not shown) may be located inside the ceramic body 10 to adjust the temperature of the sample.

[0015] The base member 20 is a disk-shaped member. The base member 20 is a conductive member and is electrically connected to ground. 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 a ceramic such as silicon carbide and a metal such as aluminum. However, the material of the base member 20 is not limited to these.

[0016] The base member 20 has a third surface 20a, a fourth surface 20b located opposite the third surface 20a, and an outer surface 20c connecting the third surface 20a and the fourth surface 20b. In this embodiment, the outer surface 20c is a side surface of the base member 20. The base member 20 may have a flow path through which a liquid or gas heat exchange medium flows. The base member 20 may function as a cooling member that cools members around the base member 20 by adjusting the temperature of the heat exchange medium flowing through the flow path. The base member 20 may be, for example, a heat exchanger. The base member 20 may also serve as, for example, a high-frequency electrode.

[0017] The bonding material 30 is located between the ceramic body 10 and the base member 20. The bonding material 30 may bond the ceramic body 10 and the base member 20. The bonding material 30 may be an insulating adhesive such as silicone that bonds the second surface 10b of the ceramic body 10 and the third surface 20a of the base member 20 together.

[0018] The first conductive film 40 is located from at least a portion of the outer surface 10c of the ceramic body 10 to at least a portion of the outer surface 20c of the base member 20. In the example shown in FIGS. 1A and 1B , the first conductive film 40 is located on a portion of the outer surface 10c of the ceramic body 10 from the first surface 10a to the second surface 10b, and is further located on a portion of the outer surface 20c of the base member 20. This causes a portion of the bonding material 30 to be covered by the first conductive film 40. However, the location of the first conductive film 40 is not limited thereto. For example, the first conductive film 40 may be located on the outer surface 10c of the ceramic body 10 from below the first surface 10a to at least a portion of the outer surface 20c of the base member 20. The first conductive film 40 may be located up to the fourth surface 20b, as long as it covers at least a portion of the outer surface 20c of the base member 20. The first conductive film 40 shown in FIGS. 1A and 1B shows an example in which both the width in the circumferential direction and the length in the thickness direction of the ceramic body 10 and the base member 20 are uniform.

[0019] The first conductive film 40 is made of diamond-like carbon (DLC), silicon carbide (SiC), titanium nitride (TiN), or boron carbide (B ４ C). When the first conductive film 40 is diamond-like carbon, diamond-like carbon is harder than silicon carbide, titanium nitride, or boron carbide, and therefore, particle generation from the ceramic body 10 can be reduced. As a result, the sample holder 100 can be applied to semiconductor manufacturing equipment. The first conductive film 40 may be formed by plasma CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition), ion plating, or sputtering.

[0020] The conductive paths of the sample holder 100 according to the first embodiment will be described in comparison with the conductive paths of the sample holder according to the reference example with reference to Figures 2A and 2B. Figure 2A is a diagram schematically showing the conductive paths of the sample holder according to the reference example. Figure 2B is a diagram schematically showing the conductive paths of the sample holder 100 according to the first embodiment. Note that the internal electrodes 11 and the power source 12 are omitted from Figures 2A and 2B. The conductive paths are indicated by arrows.

[0021] In recent years, the amount of charge transfer from the conductive path to the base member 20 has increased due to increases in the size and diameter of the ceramic body 10, as well as an increase in the DC voltage applied to the internal electrode 11. In addition, there is a demand for increasing the temperature of the ceramic body 10 that functions as an electrostatic chuck, which has further increased the stress caused by the difference in thermal expansion at the outer peripheral edge of the boundary between the ceramic body 10 and the base member 20.

[0022] In the sample holder 900 according to the reference example, a conductive film 90 having a volume resistivity relatively lower than that of the ceramic body 10 covers the ceramic body 10 from the first surface 10a to the outer periphery of the interface between the ceramic body 10 and the base member 20. In this configuration, when the application of a DC voltage to the internal electrode 11 is stopped, the electric charge stored on the first surface 10a of the ceramic body 10 flows through the conductive film 90 in a short time, as indicated by the arrows in FIG. 2A . The direction of charge movement then changes at the outer periphery of the interface between the ceramic body 10 and the base member 20. Thus, the temperature rises and stress concentrates at the outer periphery of the interface where the direction of charge movement changes. As a result, if the bonding material 30 located near the outer periphery of the interface peels off, this can cause a decrease in the thermal uniformity of the sample holder 900.

[0023] 2B , the volume resistivity of the first conductive film 40 is also lower than the volume resistivity of the ceramic body 10. For example, when the ceramic body 10 is made of aluminum nitride, the volume resistivity of the ceramic body 10 is 3×10 ９ ~3 x 10 １０ Furthermore, for example, when the base member 20 is made of aluminum, the volume resistivity of the base member 20 is 1×10 －５ ~1 x 10－６ The volume resistivity of the first conductive film 40 is, for example, 1×10 ３ ~1 x 10 ８ It is Ω·cm.

[0024] The first conductive film 40 extends from at least a portion of the outer surface 10c of the ceramic body 10 to at least a portion of the outer surface 20c of the base member 20. In this configuration, when the application of DC voltage to the internal electrode 11 is stopped, the charge stored on the first surface 10a travels along the first conductive film 40, as indicated by the arrows in FIG. 2B , through the interface between the ceramic body 10 and the base member 20, and is discharged through the base member 20. Thus, the direction of charge movement is minimal at the outer periphery of the boundary between the ceramic body 10 and the base member 20. Therefore, the outer periphery of the boundary between the ceramic body 10 and the base member 20 is less susceptible to heating and stress concentration. As a result, the sample holder 100 maintains excellent thermal uniformity because the bonding material 30 located near the outer periphery of the interface is less likely to peel off. In other words, the sample holder 100 has stable thermal uniformity. Furthermore, since the electric charge charged on the first surface 10a moves in a short time across the first conductive film 40 from the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20, the sample holder 100 can easily detach the sample from the ceramic body 10.

[0025] <Second embodiment> Fig. 3 is a cross-sectional view schematically showing a sample holder according to a second embodiment. In the sample holder 100 according to the second embodiment, the first conductive film 40 may be positioned so as to cover the entire periphery of the outer surface 10c of the ceramic body 10, on at least a part of the outer surface 10c of the ceramic body 10. Fig. 3 is a cross-sectional view of an example in which the first conductive film 40 is positioned so as to cover the entire periphery of the outer surface 10c of the ceramic body 10.

[0026] Charges charged on the first surface 10a of the ceramic body 10 while current is being applied to the internal electrode 11 are transferred from the entire circumference of the outer surface 10c of the ceramic body 10 along the first conductive film 40, which covers the entire circumference of at least a portion of the outer surface 10c of the ceramic body 10. Therefore, heat generated during charge transfer is dispersed around the entire circumference of the outer surface 10c of the ceramic body 10. This dispersion of heat, without any concentrated areas, allows the sample holder 100 to maintain thermal uniformity for a long period of time. Furthermore, charges charged on the first surface 10a of the ceramic body 10 are transferred in a short time along the first conductive film 40 from the entire circumference of the outer surface 10c of the ceramic body 10. This allows the sample holder 100 to easily detach a sample from the ceramic body 10.

[0027] As shown in Figure 3, a first distance a from the internal electrode 11 to the first surface 10a in a first direction, which is the thickness direction of the ceramic body 10 and the base member 20, may be smaller than a second distance b from the internal electrode 11 to the first conductive film 40 in a second direction perpendicular to the first direction.

[0028] By making the first distance a smaller than the second distance b, the sample holder 100 can increase the adsorptive force of the sample and also facilitate the transfer of the electric charge stored on the first surface 10a of the ceramic body 10 from the first surface 10a to the outer surface 10c of the ceramic body 10. This allows the sample holder 100 to promote the discharge of the electric charge stored on the first surface 10a and improve the ease of detachment of the sample.

[0029] Third Embodiment Fig. 4 is a side perspective view schematically showing a sample holder according to a third embodiment. As shown in Fig. 4, in the sample holder 100 according to the third embodiment, the first conductive film 40 is positioned so as to extend from the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20 and surround the outer surface 10c and the outer surface 20c. In the illustrated example, the first conductive film 40 extends from below the first surface 10a of the ceramic body 10 to the second surface 10b and further to below the third surface 20a of the base member 20, surrounding the outer surface 10c and the outer surface 20c. As a result, the bonding material 30 is covered with the first conductive film 40.

[0030] When current is applied to the internal electrode 11, the electric charge stored on the first surface 10a of the ceramic body 10 travels from the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20 and along the first conductive film 40 located around the ceramic body 10. Therefore, heat generated during the charge transfer is dispersed from the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20 and around the ceramic body 10. This dispersion of heat without any concentrated areas allows the sample holder 100 to maintain thermal uniformity for a long period of time. Furthermore, the electric charge stored on the first surface 10a of the ceramic body 10 travels from the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20 and around the ceramic body 10 in a short burst. This allows the sample holder 100 to easily detach a sample from the ceramic body 10.

[0031] As shown in the illustrated example, the first conductive film 40 does not have to reach the first surface 10 a of the ceramic body 10 , and does not have to reach the fourth surface 20 b of the base member 20 .

[0032] <Fourth embodiment> Fig. 5 is a side perspective view schematically showing a sample holder according to a fourth embodiment. As shown in Fig. 5, in the sample holder 100 according to the fourth embodiment, the first conductive film 40 may be located from the outer surface 10c below the first surface 10a of the ceramic body 10 and above the internal electrode 11 to the outer surface 20c of the base member 20, and may also be located around the outer surface 20c. In the example shown, the first conductive film 40 extends around the outer surface 20c to below the third surface 20a of the base member 20.

[0033] By positioning the surrounding region of the first conductive film 40 on the outer surface 10c of the ceramic body 10 closer to the first surface 10a than the internal electrode 11, the sample holder 100 can easily release the charge that is mainly charged between the internal electrode 11 and the first surface 10a to the first conductive film 40.

[0034] Fifth Embodiment Fig. 6 is a side perspective view schematically showing a sample holder according to a fifth embodiment. As shown in Fig. 6, in the sample holder 100 according to the fifth embodiment, the first conductive film 40 may be positioned so as to extend from the upper end of the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20 and surround the outer surface 10c. In the illustrated example, the first conductive film 40 surrounds the outer surface 10c from the first surface 10a to the second surface 10b of the ceramic body 10 and further surrounds the outer surface 20c below the third surface 20a of the base member 20.

[0035] When a current is applied to the internal electrode 11, the electric charge is most highly charged on the first surface 10a of the ceramic body 10. In the fifth embodiment, the outer surface 10c of the ceramic body 10 is completely covered with the first conductive film 40 along the first surface 10a side. This allows the sample holder 100 to more easily release the electric charge that is most highly charged on the first surface 10a to the first conductive film 40.

[0036] 7 is a side perspective view schematically showing another example of the sample holder according to the fifth embodiment. As shown in FIG. 7, the lower end 40l of the first conductive film 40 may be curved and wavy. By lengthening the edge surface distance of the lower end 40l of the first conductive film 40 in this manner, the sample holder 100 can easily distribute stress in the first conductive film 40, making it difficult for the first conductive film 40 to peel off.

[0037] Sixth Embodiment Fig. 8 is a side perspective view schematically illustrating a sample holder according to a sixth embodiment. As shown in Fig. 8, in the sample holder 100 according to the sixth embodiment, the first conductive film 40 is positioned around the ceramic body 10, extending from the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20. Furthermore, the first conductive film 40 may have multiple extensions 40u extending from the first conductive film 40 in the surrounding region to partially reach the first surface 10a. The multiple extensions 40u may extend from the first conductive film 40 at intervals in the circumferential direction of the ceramic body 10. Heat generated during charge emission is easily dispersed throughout the ceramic body 10 through the extensions 40u, thereby improving the thermal uniformity of the sample holder 100.

[0038] 9 is a side perspective view schematically showing another example of the sample holder according to the sixth embodiment. As shown in Fig. 9, the first conductive film 40 may be located on the outer surface 10c of the ceramic body 10 closer to the first surface 10a than the internal electrodes 11. In this case, the first conductive film 40 may also have a plurality of extensions 40u extending from the first conductive film 40 in the surrounding region partially to the first surface 10a.

[0039] 10 is a side perspective view that schematically shows a sample holder according to a seventh embodiment. As shown in Fig. 10, the sample holder 100 according to the seventh embodiment may have a second conductive film 41 that is located on the first surface 10a and has a volume resistivity lower than that of the ceramic body 10 and higher than that of the first conductive film 40. The volume resistivity of the second conductive film 41 is, for example, 1 x 10 ８ ~1 x 10 ９ The second conductive film 41 may be located on the entire surface of the first surface 10a, or may be located on only a part of the first surface 10a.

[0040] The second conductive film 41 has a volume resistivity lower than that of the ceramic body 10 and higher than that of the first conductive film 40. Therefore, while current is passing through the internal electrode 11, charge easily flows to the second conductive film 41, which has a volume resistivity lower than that of the ceramic body 10. As a result, the sample holder 100 can easily attract the sample to the first surface 10a. Furthermore, after current is stopped passing through the internal electrode 11, the sample holder 100 can easily transfer the charge on the first surface 10a from the second conductive film 41 to the first conductive film 40, which has a volume resistivity lower than that of the second conductive film 41. This allows the sample holder 100 to further shorten the time required to attach and detach the sample.

[0041] The second conductive film 41 is made of diamond-like carbon (DLC), silicon carbide (SiC), titanium nitride (TiN), or boron carbide (B ４C). When the second conductive film 41 is diamond-like carbon, diamond-like carbon is harder than silicon carbide, titanium nitride, or boron carbide, and therefore, particle generation from the ceramic body 10 can be reduced. As a result, the sample holder 100 can be applied to semiconductor manufacturing equipment. The second conductive film 41 may be formed by plasma CVD, PVD, ion plating, or sputtering.

[0042] The first conductive film 40 and the second conductive film 41 may be made of the same material. Because the first conductive film 40 and the second conductive film 41 are made of the same material, there is no difference in thermal expansion, and they are unlikely to peel off from the ceramic body 10. This makes the sample holder 100 resistant to deterioration over time even with repeated use, and allows samples to be stably attached and detached over a long period of time.

[0043] The first conductive film 40 and the second conductive film 41 may be formed so as to have a difference in crystallinity, such as a difference in grain size. This allows the first conductive film 40 and the second conductive film 41 to have different volume resistivities due to the difference in crystallinity. However, without being limited to this, the first conductive film 40 and the second conductive film 41 may have different volume resistivities due to at least one of a difference in crystallinity and a difference in thickness.

[0044] Eighth Embodiment Fig. 11 is a cross-sectional view schematically showing a sample holder according to an eighth embodiment. Figs. 12 to 14 are cross-sectional views schematically showing other examples of the sample holder according to the eighth embodiment.

[0045] 11 to 14 , in the sample holder 100 according to the eighth embodiment, the thickness of the first conductive film 40 may have a portion that becomes thinner in a first direction, which is the thickness direction of the ceramic body 10 and the base member 20. The first direction is a direction perpendicular to the first surface 10 a of the ceramic body 10.

[0046] The first conductive film 40 shown in FIG. 11 has a first portion 40a that covers the outer surface 10c of the ceramic body 10 to a portion of the outer surface 20c of the base member 20, and a second portion 40b that extends from the first portion 40a in a first direction and covers a portion of the outer surface 20c of the base member 20. In the first portion 40a, the thickness of the first conductive film 40 is constant in the first direction. In the second portion 40b, the thickness of the first conductive film 40 continuously decreases in the first direction. In other words, in the first portion 40a, the side surface of the first conductive film 40 is flat, whereas in the second portion 40b, the side surface of the first conductive film 40 is inclined. As a result, the first conductive film 40 gradually becomes thinner toward the tip on the outer surface 20c of the base member 20. In the first conductive film 40 shown in FIG. 11, the boundary between the first portion 40a and the second portion 40b is near the outer surface 20c of the base member 20.

[0047] The first conductive film 40 shown in Figure 12 has a first portion 40a that covers from the outer surface 10c of the ceramic body 10 to the side surface of the bonding material 30, and a second portion 40b that extends from the side surface of the bonding material 30 in a first direction and covers up to a portion of the outer surface 20c of the base member 20. In the first portion 40a, the thickness of the first conductive film 40 is constant in the first direction. In the second portion 40b, the thickness of the first conductive film 40 continuously decreases in the first direction. In the first conductive film 40 shown in Figure 12, the boundary between the first portion 40a and the second portion 40b is near the side surface of the bonding material 30.

[0048] 13 includes a first portion 40a that covers the outer surface 10c of the ceramic body 10 to a portion of the outer surface 20c of the base member 20, and a second portion 40b that extends in a first direction from the first portion 40a and covers a portion of the outer surface 20c of the base member 20. The thickness of the first conductive film 40 continuously decreases in the first direction in both the first portion 40a and the second portion 40b. The inclination of the side surface of the first conductive film 40 in the second portion 40b is greater than the inclination of the side surface of the first conductive film 40 in the first portion 40a. The boundary between the first portion 40a and the second portion 40b is near the outer surface 20c of the base member 20.

[0049] The thickness of the first conductive film 40 has a portion that gradually becomes thinner in a first direction. In the illustrated example, the first conductive film 40 becomes thinner in two stages: a first portion 40a that becomes continuously thinner, and a second portion 40b that becomes continuously thinner and more rapidly thinner than the first portion 40a.

[0050] 14 covers the outer surface 10c of the ceramic body 10 to a portion of the outer surface 20c of the base member 20. The thickness of the first conductive film 40 decreases continuously and uniformly in the first direction. The first conductive film 40 may cover the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20 up to the fourth surface 20b of the base member 20.

[0051] The thinner the first conductive film 40, the higher the resistance of the first conductive film 40 and the more likely it is to generate heat. Therefore, the portion of the first conductive film 40 where the thickness becomes thinner in the first direction, which is the thickness direction of the ceramic body 10 and the base member 20, is more likely to generate heat. This allows the sample holder 100 to distribute the heat-generating portions of the first conductive film 40. Furthermore, by having the first conductive film 40 have portions where the thickness becomes thinner, the sample holder 100 can impart a gradient to the amount of charge transfer to the ceramic body 10 and the base member 20, thereby improving the stress relaxation effect of the first conductive film 40.

[0052] Furthermore, since the thickness of the first conductive film 40 gradually decreases in the first direction, the resistance of the first conductive film 40 gradually increases in the first direction. Therefore, the first conductive film 40 gradually becomes more likely to generate heat in the portions where the resistance gradually increases in the first direction. This allows the sample holder 100 to distribute the heat-generating portions of the first conductive film 40, further enhancing the stress relaxation effect of the first conductive film.

[0053] The slope of the side surface of the first conductive film 40 does not have to be continuous. For example, the side surface of the first conductive film 40 may not be sloped, and the thickness of the first conductive film 40 may have a step between the first portion 40 a and the second portion 40 b.

[0054] Ninth Embodiment Fig. 15 is a cross-sectional view schematically illustrating a sample holder according to a ninth embodiment. As shown in Fig. 15, in a sample holder 100 according to the ninth embodiment, the ceramic body 10 has a through hole 50 penetrating the first surface 10a and the second surface 10b. Furthermore, the through hole 50 penetrates the bonding material 30 and the third surface 20a and the fourth surface 20b of the base member 20. The sample holder 100 also has a third conductive film 42 positioned to cover at least a portion of the inner surface of the through hole 50 and having a volume resistivity lower than that of the ceramic body 10. The third conductive film 42 covers the inner surface of the through hole 50 formed in the ceramic body 10 and a portion of the inner wall of the through hole 50 formed in the base member 20. This also covers the inner surface of the through hole 50 formed in the bonding material 30. However, this is not a limitation, and the third conductive film 42 may cover the entire inner surface of the through hole 50.

[0055] The electric charge stored on the first surface 10a of the ceramic body 10 moves along the first conductive film 40 and the third conductive film 42. The route through which the electric charge is released from the first surface 10a is expanded from only the first conductive film 40 to the first conductive film 40 and the third conductive film 42. This enables the sample holder 100 to shorten the time required for discharging the electric charge, further shorten the time required for desorption of the sample, and further stabilize the temperature uniformity.

[0056] The first surface 10a of the ceramic body 10 may have a second conductive film 41 connected to the first conductive film 40 and the third conductive film 42. This increases the route for discharging electric charges from the first surface 10a from only the first conductive film 40 to the first conductive film 40, the second conductive film 41, and the third conductive film 42. This enables the sample holder 100 to further shorten the time required for discharging electric charges, further shorten the time required for attaching and detaching the sample, and further stabilize the thermal uniformity.

[0057] The first conductive film 40 and the third conductive film 42 may be made of the same material. Because the first conductive film 40 and the third conductive film 42 are made of the same material, there is no difference in thermal expansion, and they are unlikely to peel off from the ceramic body 10. This makes the sample holder 100 resistant to deterioration over time even with repeated use, and allows samples to be stably attached and detached over a long period of time.

[0058] <Tenth embodiment> Fig. 16A is an enlarged cross-sectional view of a chamfered portion of a sample holder according to the tenth embodiment. Fig. 16B is an enlarged cross-sectional view of another example of a chamfered portion of a sample holder according to the tenth embodiment. As shown in Figs. 16A and 16B, in a sample holder 100 according to the tenth embodiment, the ceramic body 10 may have a chamfered portion 10d between the first surface 10a and the outer surface 10c. The chamfered portion 10d may be a rounded surface.

[0059] The first conductive film 40 is located from the outer surface 10c of the ceramic body 10 to the chamfered portion 10d. The first conductive film 40 may gradually become thinner from the chamfered portion 10d toward the first surface 10a. In the example of Fig. 16A, the sample holder 100 does not have the second conductive film 41 on the first surface 10a. On the other hand, in the example of Fig. 16B, the sample holder 100 has the second conductive film 41 on the first surface 10a. In this case, the first conductive film 40 may gradually become thicker or thinner from the chamfered portion 10d toward the first surface 10a, or may have the same thickness.

[0060] The first conductive film 40 is located along the chamfered portion 10d from the outer surface 10c of the ceramic body 10. This allows the electric charge stored on the first surface 10a of the ceramic body 10 to easily move from the chamfered portion 10d and the outer surface 10c of the ceramic body 10 toward the outer surface 20c of the base member 20. This allows the sample holder 100 to promote the movement of the electric charge stored on the first surface 10a and improve the ease of detaching the sample.

[0061] (Other Examples of Sample Holders) Sample holders 100A to 100C will be described with reference to FIGS. 17 to 19. FIGS. 17 to 19 are cross-sectional views showing sample holders in schematic form. In the sample holders 100 according to the first to tenth embodiments, the ceramic body 10, bonding material 30, and base member 20 have the same diameter, and are different in shape from the sample holders 100A to 100C shown in FIGS. 17 to 19. However, the configuration of the sample holders 100 according to the first to tenth embodiments can also be applied to the sample holders 100A to 100C shown in FIGS. 17 to 19.

[0062] The sample holder 100A may have a portion where the diameter of the ceramic body 10 and the diameter of the base member 20 are different. In the sample holder 100A shown in Fig. 17, the diameter of the base member 20 on the third surface 20a side of the step portion 20d is smaller than the diameter of the base member 20 on the fourth surface 20b side of the step portion 20d. The diameter of the base member 20 on the third surface 20a side of the step portion 20d is the same as the diameter of the ceramic body 10. The outer surface 20c of the base member 20 includes the side surface of the base member 20 and the surface of the step portion 20d.

[0063] The first conductive film 40 is positioned on a surface extending from at least a portion of the outer surface 10 c along the outer surface 20 c of the base member 20 to at least a portion of the outer surface 20 c that is closer to the fourth surface 20 b than the stepped portion 20 d. In the illustrated example, the first conductive film 40 is positioned over the entire outer surface 10 c of the ceramic body 10 and the outer surface 20 c of the base member 20.

[0064] The electric charge stored on the first surface 10a travels in a straight line along the outer surface 10c of the ceramic body 10 and the side surface of the bonding material 30 in a first direction, which is the thickness direction of the ceramic body 10, to the outer surface 20c of the base member 20, including the surface of the stepped portion 20d, and is discharged through the base member 20. Because the first conductive film 40 covers the entire surface from the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20, a temperature rise is unlikely to occur at the outer peripheral edge of the interface between the ceramic body 10 and the base member 20, and stress is alleviated. This stabilizes the thermal uniformity of the sample holder 100A. Furthermore, the sample holder 100A can promote the discharge of the electric charge stored on the first surface 10a, thereby improving the ease of sample attachment and detachment.

[0065] In the sample holder 100B, the diameter of the ceramic body 10 and the diameter of the base member 20 may be different. In the sample holder 100B shown in FIG. 18 , the diameter of the base member 20 is larger than the diameter of the ceramic body 10. In the sample holder 100B, the third surface 20a of the base member 20 is in contact with the bonding material 30, except for a surface 20a1 of the third surface 20a that is not in contact with the bonding material 30 on the periphery. The first conductive film 40 is located from at least a part of the outer surface 10c of the ceramic body 10, along the surface 20a1 of the third surface 20a that is not in contact with the bonding material 30, to at least a part of the outer surface 20c of the base member 20. The outer surface 20c of the base member 20 includes the side surface of the base member 20 and the surface 20a1 of the third surface 20a that is not in contact with the bonding material 30.

[0066] The first conductive film 40 extends from at least a portion of the side surface of the ceramic body 10 along the surface 20a1 of the third surface 20a that does not contact the bonding material 30 to at least a portion of the outer surface 20c of the base member 20. As a result, electric charge stored on the first surface 10a travels in a straight line along the outer surface 10c of the ceramic body 10 and the side surface of the bonding material 30 in the first direction, moves to the outer surface 20c of the base member 20, including the surface 20a1, and is discharged through the base member 20. Because the first conductive film 40 covers the entire surface from the outer surface 10c of the ceramic body 10 to the outer surface 20c of the base member 20, temperature rise is unlikely to occur at the outer peripheral edge of the interface between the ceramic body 10 and the base member 20, and stress is alleviated. This stabilizes the thermal uniformity of the sample holder 100B. Furthermore, the sample holder 100B promotes discharge of electric charge stored on the first surface 10a, thereby improving the ease of sample attachment and detachment.

[0067] 19 , in the sample holder 100C, the diameters of the ceramic body 10 and the base member 20 may be different from the diameter of the bonding material 30. In the illustrated example, the diameters of the ceramic body 10 and the base member 20 are the same. The diameter of the bonding material 30 may be smaller than the diameters of the ceramic body 10 and the base member 20. In this case, the first conductive film 40 is located from at least a part of the outer surface 10 c of the ceramic body 10 to at least a part of the outer surface 20 c of the base member 20, along the recess in the side surface of the bonding material 30.

[0068] Further advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0069] The present technology can take the following configurations: (1) A sample holder comprising: a ceramic body having a first surface as a sample support surface and a second surface opposite the first surface, and having an internal electrode; a conductive base member; a bonding material positioned between the ceramic body and the base member; and a first conductive film having a volume resistivity lower than that of the ceramic body, the first conductive film being positioned from at least a portion of the outer surface of the ceramic body to at least a portion of the outer surface of the base member. (2) The sample holder described in (1), in which the first conductive film is positioned covering the entire periphery of the outer surface of the ceramic body on at least a portion of the outer surface of the ceramic body. (3) The sample holder described in (1) or (2), in which the first conductive film is positioned from the outer surface of the ceramic body to the outer surface of the base member and surrounding the periphery. (4) The sample holder described in (3), in which the circumferential region of the outer surface of the ceramic body of the first conductive film is positioned closer to the first surface than the internal electrode. (5) The sample holder according to (3) or (4), wherein the first conductive film is located in a circumferential region on the outer surface of the ceramic body across the first surface. (6) The sample holder according to any one of (1) to (5), further comprising a second conductive film having a volume resistivity lower than that of the ceramic body and higher than that of the first conductive film, the second conductive film being located on the first surface. (7) The sample holder according to (6), wherein the first conductive film and the second conductive film are made of the same material. (8) The sample holder according to (6) or (7), wherein at least one of the first conductive film and the second conductive film is made of diamond-like carbon. (9) The sample holder according to any one of (1) to (8), wherein the thickness of the first conductive film has a portion that becomes thinner in a first direction, which is the thickness direction of the ceramic body and the base member. (10) The sample holder according to (9), wherein the thickness of the first conductive film has a portion that gradually becomes thinner in the first direction. (11) The sample holder according to (10), wherein the ceramic body has a through hole penetrating the first surface and the second surface, and the ceramic body is provided with a third conductive film positioned so as to cover at least a part of the inner surface of the through hole and having a volume resistivity lower than that of the ceramic body.(12) The sample holder according to (11), wherein the first conductive film and the third conductive film are made of the same material. (13) The sample holder according to (4) or (5), wherein a first distance from the internal electrode to the first surface in a first direction that is a thickness direction of the ceramic body and the base member is smaller than a second distance from the internal electrode to the first conductive film in a second direction that is perpendicular to the first direction. (14) The sample holder according to (4) or (5), wherein the ceramic body has a chamfered portion between the first surface and the outer surface, and the first conductive film is located along the chamfered portion from the outer surface of the ceramic body.

[0070] REFERENCE SIGNS LIST 10 ceramic body 10a first surface 10b second surface 10c outer surface 10d chamfered portion 11 internal electrode 20 base member 20a third surface 20b fourth surface 20c outer surface 30 bonding material 40 first conductive film 41 second conductive film 42 third conductive film 50 through-hole 100, 100A, 100B, 100C sample holder

Claims

1. A sample holder comprising: a ceramic body having a first surface that is a sample holding surface and a second surface located opposite the first surface, and having an internal electrode; a conductive base member; a bonding material located between the ceramic body and the base member; and a first conductive film that has a volume resistivity lower than that of the ceramic body, wherein the first conductive film is located across at least a portion of the outer surface of the ceramic body and at least a portion of the outer surface of the base member.

2. The sample holder according to claim 1, wherein the first conductive film is positioned over the entire periphery of the outer surface of the ceramic body on at least a portion of the outer surface of the ceramic body.

3. A sample holder according to claim 1 or claim 2, wherein the first conductive film is positioned across and around the outer surface of the ceramic body and the outer surface of the base member.

4. A sample holder according to claim 3, wherein the first conductive film has a circumferential region on the outer surface of the ceramic body that is positioned closer to the first surface than the internal electrode.

5. A sample holder according to claim 3 or 4, wherein the first conductive film is positioned over the first surface in a circumferential region on the outer surface of the ceramic body.

6. A sample holder according to any one of claims 1 to 5, comprising a second conductive film having a volume resistivity lower than that of the ceramic body and higher than that of the first conductive film, the second conductive film being located on the first surface.

7. A sample holder according to claim 6, wherein the first conductive film and the second conductive film are made of the same material.

8. A sample holder according to claim 6 or 7, wherein at least one of the first conductive film and the second conductive film is made of diamond-like carbon.

9. A sample holder according to any one of claims 1 to 8, wherein the thickness of the first conductive film has a portion that becomes thinner in a first direction, which is the thickness direction of the ceramic body and the base member.

10. A sample holder according to claim 9, wherein the thickness of said first conductive film has a portion that gradually becomes thinner in said first direction.

11. A sample holder according to any one of claims 1 to 5, wherein the ceramic body has a through hole penetrating the first surface and the second surface, and is provided with a third conductive film positioned so as to cover at least a portion of the inner surface of the through hole and having a volume resistivity lower than that of the ceramic body.

12. The sample holder according to claim 11, wherein the first conductive film and the third conductive film are made of the same material.

13. A sample holder as described in claim 4 or claim 5, wherein a first distance from the internal electrode to the first surface in a first direction, which is the thickness direction of the ceramic body and the base member, is smaller than a second distance from the internal electrode to the first conductive film in a second direction perpendicular to the first direction.

14. A sample holder according to claim 4 or claim 5, wherein the ceramic body has a chamfered portion between the first surface and the outer surface, and the first conductive film is positioned along the chamfered portion from the outer surface of the ceramic body.

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