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

Sample holder

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

[0002] There are sample holders for holding samples such as semiconductor wafers to be plasma processed. Such sample holders are constructed by bonding a ceramic plate having a sample support surface to a metal cooling member.

[0003] Another proposed sample holder structure involves placing a composite material with a thermal expansion coefficient relatively close to that of the ceramic plate between a ceramic plate and a cooling member, bonding the composite material to the cooling member with an adhesive, and bonding the composite material to the ceramic plate with metal (see, for example, Patent Document 1).

[0004] JP 2017-126640 A

[0005] A 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 being arranged in this order: the ceramic plate, the heat-resistant member, and the base member. The heat-resistant member has a smaller coefficient of thermal expansion than the ceramic plate, and is not bonded to the ceramic plate.

[0006] FIG. 1 is a perspective view schematically showing the configuration of a sample holder according to an embodiment. FIG. 2 is a cross-sectional view schematically showing the sample holder shown in FIG. 1. FIG. 3 is a cross-sectional view schematically showing a sample holder according to Alternative Embodiment 1. FIG. 4 is a cross-sectional view schematically showing a sample holder according to Alternative Embodiment 2. FIG. 5 is an enlarged view of region A shown in FIG. 4. FIG. 6 is a view showing an example of the external configuration of each convex portion shown in FIG. 5. FIG. 7 is a view showing another example of the external configuration of each convex portion shown in FIG. 5. FIG. 8 is a cross-sectional view schematically showing a sample holder according to Alternative Embodiment 3. FIG. 9 is a cross-sectional view schematically showing a sample holder according to Alternative Embodiment 4. FIG. 10 is a view showing an example of a coating pattern using a coating layer according to Alternative Embodiment 4. FIG. 11 is a view showing another example of a coating pattern using a coating layer according to Alternative Embodiment 4. FIG. 12 is a cross-sectional view schematically showing a sample holder according to Alternative Embodiment 5. FIG. 13 is a plan view perspective view of the ceramic plate shown in FIG. 12, viewed from the second surface side.

[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] <Embodiment> Fig. 1 is a perspective view showing a structure of a sample holder according to an embodiment, and Fig. 2 is a cross-sectional view showing the sample holder shown in Fig. 1.

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

[0011] The ceramic plate 10 is a member made by forming a ceramic-containing raw material into a substantially circular disk shape and firing it. The ceramic plate 10 utilizes electrostatic force to attract and hold a sample, such as a semiconductor wafer. The ceramic plate 10 is made of, for example, aluminum oxide (Al ２ O ３ ), aluminum nitride (AlN), yttria (Y ２ O ３ ) as its main ingredient.

[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. That is, the first surface 10a serves as a sample support surface for holding the sample.

[0013] An electrostatic attraction electrode is located inside the ceramic plate 10. The ceramic plate 10 may also incorporate, for example, a heater electrode for heating the ceramic plate 10. These electrodes may be made of metals such as platinum, tungsten, or molybdenum.

[0014] The ceramic plate 10 is fixed to the base member 20 via a fixing member 40. For ease of explanation, the fixing member 40 is not shown in FIG. 1 . The fixing member 40 may be, for example, a bolt or a clamp. 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, i.e., on the opposite side of the heat-resistant member 30 from the ceramic plate 10. 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 device, and causes the sample holder 100 to function as a semiconductor holder that holds samples such as semiconductor wafers.

[0016] The base member 20 is a substantially cylindrical 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 a ceramic 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 for cooling the ceramic plate 10 that is heated by the plasma processing of 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 for flowing a liquid or gas heat exchange medium.

[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 thermal expansion coefficient smaller than that of the ceramic plate 10. Since the thermal expansion coefficient of the heat-resistant member 30 is smaller than that of the ceramic plate 10, deformation of the heat-resistant member 30 due to temperature differences in the thickness direction can be reduced even when the heat-resistant member 30 is heated to, for example, 300°C or higher. The heat-resistant member 30 may be made of, for example, cordierite or glass.

[0019] The heat-resistant member 30 is located between the ceramic plate 10 and the base member 20 without being bonded to the ceramic plate 10 .

[0020] If the heat-resistant member 30 and the ceramic plate 10 are bonded together with a bonding material or the like, warping of the heat-resistant member 30 and the ceramic plate 10 may occur due to a difference in thermal expansion between the heat-resistant member 30 and the ceramic plate 10. If warping occurs due to a 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 non-uniform, and the heat transfer between the first surface 10a of the ceramic plate 10, i.e., the sample support surface, and the base member 20 becomes non-uniform in the in-plane direction, thereby impairing the uniform temperature distribution within the surface of the sample holder 100.

[0021] In contrast, by not joining the heat-resistant member 30, which has a smaller thermal expansion coefficient than the ceramic plate 10, to the ceramic plate 10, the heat-resistant member 30 and the ceramic plate 10 slide more easily than when the heat-resistant member 30 and the ceramic plate 10 are joined, thereby reducing warping caused by the difference in thermal expansion between the heat-resistant member 30 and the ceramic plate 10. This reduces unevenness in heat transfer between the heat-resistant member 30 and the base member 20, thereby reducing unevenness in the in-plane direction in heat transfer between the sample support surface and the base member 20, thereby improving the in-plane thermal uniformity of the sample holder 100.

[0022] Furthermore, the ceramic plate 10 is fixed to the base member 20 via the fixing member 40, and thus the heat-resistant member 30 is sandwiched between the ceramic plate 10 and 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 when the heat-resistant member 30 is not joined to the ceramic plate 10 and the base member 20.

[0023] 3 is a cross-sectional view schematically showing a sample holder according to another embodiment 1. The sample holder 100 shown in FIG.

[0024] The bonding material 50 is located between the heat-resistant member 30 and the base member 20. The bonding material 50 bonds the heat-resistant member 30 and the base member 20. Bonding the heat-resistant member 30 and the base member 20 with the bonding material 50 reduces warping of the heat-resistant member 30 due to thermal cycles compared to when the heat-resistant member 30 and the base member 20 are not bonded. This reduces unevenness in heat transfer between the ceramic plate 10 and the heat-resistant member 30, further reducing unevenness in the in-plane direction in heat transfer between the sample support surface and the base member 20, thereby further improving the in-plane thermal uniformity of the sample holder 100.

[0025] Furthermore, by bonding the heat-resistant member 30 and the base member 20 with the bonding material 50, it is possible to reduce misalignment between the heat-resistant member 30 and the base member 20.

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

[0027] FIG. 4 is a cross-sectional view schematically illustrating a sample holder according to another embodiment 2. In the sample holder 100 shown in FIG. 4 , the heat-resistant member 30 has, on its surface facing the ceramic plate 10, multiple protrusions 31 (an example of first protrusions) that contact the ceramic plate 10 and spaces 32 (an example of first spaces) located around each protrusion 31. The multiple 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. The multiple protrusions 31 and spaces 32 in the heat-resistant member 30 can reduce the contact area between the heat-resistant member 30 and the ceramic plate 10. This allows the ceramic plate 10 to slide more easily relative to the heat-resistant member 30, thereby mitigating stress caused by differential expansion and contraction between the heat-resistant member 30 and the ceramic plate 10 during thermal cycling.

[0028] The space 32 is located around each protrusion 31 and 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. That is, the space 32 may serve as a flow path 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) through a gas inlet 321. The gas inlet 321 penetrates the base member 20, the bonding material 50, and the heat-resistant member 30 and communicates with the space 32. Introducing the heat transfer gas into the space 32 allows the heat transfer gas to be delivered to the second surface 10b of the ceramic plate 10, improving 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 described with reference to Fig. 5 and Fig. 6. Fig. 5 is an enlarged view of area A shown in Fig. 4. Fig. 6 is a view showing an example of the external configuration of each protrusion shown in Fig. 5.

[0030] 5 and 6 , the side surface of each protrusion 31 may be tapered so that its width narrows toward the ceramic plate 10. In other words, each protrusion 31 may be tapered so that its width narrows toward the top of the protrusion 31. By tapering each protrusion 31, 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. This makes it easier for the ceramic plate 10 to slide relative to the heat-resistant member 30, thereby further alleviating stress caused by differential expansion and contraction between the heat-resistant member 30 and the ceramic plate 10 due to thermal cycles.

[0031] 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 face 32a of the space 32. This allows the end face 31a of each protrusion 31 to be in uniform contact with the ceramic plate 10 in the in-plane direction, thereby equalizing heat transfer from the ceramic plate 10 to the multiple protrusions 31. Furthermore, a smaller surface roughness Ra of the end face 31a of each protrusion 31 that contacts the ceramic plate 10 allows the ceramic plate 10 to slide more easily relative to the heat-resistant member 30, thereby further reducing stress caused by differential expansion and contraction between the heat-resistant member 30 and the ceramic plate 10 during thermal cycling. Furthermore, a larger surface roughness Ra of the bottom face 32a of the space 32 allows the surface area of ​​the bottom face 32a of the space 32 to be larger. This, for example, can promote heat exchange between the heat-transfer gas and the heat-resistant member 30 when a heat-transfer gas is introduced into the space 32.

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

[0033] The grooves 311 may extend in a direction from an end surface 31 a of each protrusion 31 that contacts the ceramic plate 10 toward a bottom surface 32 a of the space 32 on the side surface of each protrusion 31. This causes the flow direction of the heat transfer gas introduced into the space 32 to intersect with the extension 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] The extending direction of the grooves 311 is not limited to the direction shown in Fig. 7. The grooves 311 may extend in any direction on the side surface of each protrusion 31.

[0035] 7 shows the case where the grooves 311 are provided on the side surfaces of the respective convex portions 31, but instead of the grooves 311, protrusions may be provided on the side surfaces of the respective convex portions 31. Furthermore, both the grooves 311 and protrusions may be provided on the side surfaces of the respective convex portions 31.

[0036] FIG. 8 is a cross-sectional view schematically illustrating a sample holder according to another embodiment 3. In the sample holder 100 shown in FIG. 8 , the ceramic plate 10 has, on its surface facing the heat-resistant member 30, i.e., the second surface 10b, multiple 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. The multiple protrusions 11 and spaces 12 can be formed, for example, by blasting the second surface 10b of the ceramic plate 10. The multiple protrusions 11 and spaces 12 on the ceramic plate 10 reduce the contact area between the heat-resistant member 30 and the ceramic plate 10. This allows the ceramic plate 10 to slide easily relative to the heat-resistant member 30, thereby reducing stress caused by differential expansion and contraction between the heat-resistant member 30 and the ceramic plate 10 during thermal cycling.

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

[0038] The space 12 is located around each protrusion 11 and between the ceramic plate 10 and the heat-resistant member 30. The space 12 has a depth corresponding to the height of each protrusion 11. A heat transfer gas, such as helium, may be introduced into the space 12. That is, the space 12 may serve as a flow path for the heat transfer gas. In this case, for example, the heat transfer gas may be introduced into the space 12 from a gas supply mechanism (not shown) through a gas inlet 121. The gas inlet 121 penetrates the base member 20, the bonding material 50, and the heat-resistant member 30 and communicates with the space 12. Introducing the heat transfer gas into the space 12 allows the heat transfer gas to be delivered to the second surface 10b of the ceramic plate 10, improving heat transfer between the heat-resistant member 30 and the ceramic plate 10 via the space 32.

[0039] Fig. 9 is a cross-sectional view schematically showing a sample holder according to another embodiment 4. The sample holder 100 shown in Fig. 9 further includes a coating layer 60 (an example of the first intermediate layer, the second intermediate layer, and the 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 facing the ceramic plate 10.

[0041] The coating layer 60 may have a smaller 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. The coating layer 60 may also have a lower electrical resistance than the ceramic plate 10. For example, diamond-like carbon (DLC) or silicon carbide (SiC) may be used as the coating layer 60. When the coating layer 60 has a small 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 the heat-resistant member 30 and the ceramic plate 10 is reduced, thereby reducing particle generation from the heat-resistant member 30 and the ceramic plate 10. When the coating layer 60 has a high hardness, even when a 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, the wear of the heat-resistant member 30 is reduced, thereby reducing particle generation 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 support surface, can be released to the coating layer 60, thereby reducing the deterioration of the sample releasability caused by the residual charge on the ceramic plate 10. Furthermore, the coating layer 60 may have an electrical resistance lower than that of the heat-resistant member 30. This makes it even easier for the charge remaining on the sample support surface to release.

[0042] Here, the details of the coating layer 60 will be further described with reference to Fig. 10 and Fig. 11. Fig. 10 is a diagram showing an example of a coating aspect of the coating layer according to Alternative Embodiment 4. Fig. 11 is a diagram showing another example of a coating aspect of the coating layer according to Alternative Embodiment 4. Figs. 10 and 11 correspond to enlarged views of region B shown in Fig. 9.

[0043] 10, the coating layer 60 may be positioned so as to cover only the end surface 31a (see FIG. 6) of each protrusion 31 that comes into contact with the ceramic plate 10. This makes it possible to prevent a reduction in the cross-sectional area of ​​the space 32, which serves as a flow path for the heat transfer gas, when the heat transfer gas is introduced into the space 32, for example.

[0044] 11 , the coating layer 60 may be positioned so as to cover the end faces 31 a (see FIG. 6 ) of each protrusion 31 that come into contact with the ceramic plate 10, the side faces of each protrusion 31, and the bottom faces 32 a of the spaces 32. This allows the coating layer 60 to cover the entire surface of the heat-resistant member 30 that faces the ceramic plate 10, making it easier for charge remaining on the first surface 10 a of the ceramic plate 10, i.e., the sample-support surface, to escape to the coating layer 60.

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

[0046] FIG. 13 is a planar perspective view of the ceramic plate 10 shown in FIG. 12 , viewed from the second surface 10b. As shown in FIG. 13 , the second electrodes 14, 14 are, for example, comb-like electrodes in which one second electrode 14 and the other second electrode 14 are alternately and finely arranged. The second electrodes 14, 14 having such a shape can attract and hold not only conductors and semiconductors but also insulators by applying a gradient force generated by applying a positive voltage to one second electrode 14 and a negative voltage 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 fixed to the base member 20 via a fixing member 40.

[0047] Since the entire surface of the ceramic plate 10, including the central portion, is adhered to the heat-resistant member 30, deformation of the first surface 10a, which is the sample support surface, is reduced, and temperature uniformity within the sample support surface is less likely to decrease. Furthermore, compared to when the outer periphery of the ceramic plate 10 is mechanically fixed, deformation of the first surface 10a, which is the sample support surface, is reduced, which makes it less likely for the sample to peel off from the sample support surface or for the sample processing accuracy to decrease. Thus, the sample holder 100 according to the fifth embodiment can withstand use in high-temperature environments while reducing deformation of the sample support surface.

[0048] 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.

[0049] REFERENCE SIGNS LIST 10 ceramic plate 10a first surface 10b second surface 11 convex portion 12 space 13 first electrode 14 second electrode 20 base member 30 heat-resistant member 31 convex portion 31a end surface 32 space 32a bottom surface 40 fixing member 50 bonding material 60 coating layer 100 sample holder 311 groove

Claims

1. Ceramic plate and A heat-resistant member; A base member. the ceramic plate, the heat-resistant member, and the base member are arranged in this order; The heat-resistant member has a smaller thermal expansion coefficient than the ceramic plate and is not joined to the ceramic plate.

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

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

4. 2. The sample holder according to claim 1, wherein the heat-resistant member has a plurality of first protrusions in contact with the ceramic plate and first spaces positioned around the first protrusions.

5. 5. The sample holder according to claim 4, wherein the side surface of said first protrusion is tapered so that the width of said side surface narrows toward said ceramic plate.

6. 6. The sample holder according to claim 4, wherein a surface roughness of an end face of said first protrusion which comes into contact with said ceramic plate is smaller than a surface roughness of a bottom face of said first space.

7. The sample holder according to claim 4 , wherein a heat transfer gas is introduced into the first space.

8. The sample holder according to claim 5 , wherein the side surface of the first convex portion has at least one of a projection and a groove.

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

10. 2. The sample holder according to claim 1, wherein the ceramic plate has a plurality of second protrusions in contact with the heat-resistant member and second spaces positioned around the second protrusions.

11. The sample holder according to claim 10 , wherein a heat transfer gas is introduced into the second space.

12. a first intermediate layer between the heat-resistant member and the ceramic plate; 2. The sample holder of claim 1, wherein the first intermediate layer has a coefficient of friction smaller than that of the heat-resistant member.

13. a second intermediate layer between the heat-resistant member and the ceramic plate; 2. The sample holder according to claim 1, wherein the second intermediate layer has a hardness greater than that of the heat-resistant member.

14. a third intermediate layer between the heat-resistant member and the ceramic plate; 2. The sample holder according to claim 1, wherein the third intermediate layer has an electrical resistance lower than that of the ceramic plate.

15. The ceramic plate has an electrostatic attraction electrode therein, 2. The sample holder according to claim 1, wherein the heat-resistant member is attracted to the ceramic plate by the electrostatic attraction electrode.