Wafer mounting stage and its manufacturing method

Abstract

This invention provides a wafer mounting stage and its manufacturing method, which prevents cracking in the ceramic substrate and makes the connecting member less prone to detachment. The electrostatic chuck of this invention comprises: a first ceramic substrate having a wafer mounting surface on its upper surface; a second ceramic substrate disposed on the lower surface side of the first ceramic substrate; a metal bonding layer that bonds the lower surface of the first ceramic substrate to the bonding surface of the second ceramic substrate; a connecting member having an upper base and a lower base, and embedded in the second ceramic substrate with the upper base in contact with the metal bonding layer; and a power supply terminal electrically connected to the lower base of the connecting member. The connecting member has a portion whose cross-sectional area increases from the upper base side towards the lower base side when cut along a surface parallel to the upper base.

Description

TECHNICAL FIELD

[0001] The present application relates to a wafer placement table and a manufacturing method thereof. BACKGROUND

[0002] Conventionally, a wafer placement table in which a metal joining layer joining ceramic substrates to each other is used as an electrode is known. For example, Patent Literature 1 discloses an electrostatic chuck in which a metal joining layer is used as an RF electrode.

[0003] [Related Art Literature]

[0004] [Patent Literature]

[0005] [Patent Literature 1] Japanese Patent Application Publication No. 2018-006737 SUMMARY

[0006] Problems to be Solved by the Invention

[0007] Such an electrostatic chuck is manufactured, for example, as follows. That is, first, a first ceramic substrate having a wafer placement surface and a second ceramic substrate in which a connecting member is embedded are produced. Next, one surface of the second ceramic substrate is subjected to grinding processing to expose one surface of the connecting member, and a ground surface is formed. Then, a surface of the first ceramic substrate on the opposite side of the wafer placement surface is joined to the ground surface of the second ceramic substrate via a metal joining layer. Therefore, if the adhesion of the second ceramic substrate to the connecting member is low, the second ceramic substrate can be cracked due to a load at the time of grinding processing. In addition, the connecting member can be detached from the second ceramic substrate due to a load at the time of grinding processing.

[0008] The present application is made to solve such a problem, and its main object is to prevent cracks in a ceramic substrate at the time of manufacturing and to prevent a connecting member from being easily detached.

[0009] Means for Solving the Problems

[0010] The wafer placement table of the present application includes:

[0011] a first ceramic substrate having a wafer placement surface on an upper surface;

[0012] a second ceramic substrate disposed on a lower surface side of the first ceramic substrate;

[0013] a metal joining layer joining a lower surface of the first ceramic substrate to an upper surface of the second ceramic substrate;

[0014] a connecting member having an upper bottom and a lower bottom, which is embedded in the second ceramic substrate in a state in which the upper bottom is in contact with the metal joining layer; and

[0015] a power supply terminal electrically connected to the lower bottom of the connecting member,

[0016] The connecting member has a portion in which a cross-sectional area of the connecting member when cut along a plane parallel to the upper bottom increases from the upper bottom side toward the lower bottom side.

[0017] In the wafer boat, the connecting member embedded in the second ceramic base has a portion in which a cross-sectional area of the connecting member when cut along a plane parallel to the upper bottom increases from the upper bottom toward the lower bottom. Therefore, for example, compared with a case where the connecting member has a cylindrical shape, the area of the side surface of the connecting member increases, and thus the contact area of the second ceramic base with the connecting member increases, and the adhesion of the second ceramic base to the connecting member improves. Thus, even if a process of polishing a surface of the second ceramic base in which the metal joining layer is formed to expose the upper bottom of the connecting member is included in the manufacture of the wafer boat, a crack is less likely to occur in the second ceramic base. In addition, even if a load is applied to the connecting member in this process, since the side surface of the connecting member is caught on the second ceramic base, the connecting member is less likely to fall off.

[0018] In addition, in the present specification, "upper" and "lower" do not indicate absolute positional relationships, but indicate relative positional relationships. Therefore, depending on the orientation of the wafer boat, "upper" and "lower" can become "lower" and "upper", or "left" and "right", or "front" and "back".

[0019] In the wafer boat of the present application, the second ceramic base can have a hole for inserting the power supply terminal into the lower surface of the second ceramic base, and the side surface of the power supply terminal can be joined to the side surface of the hole. In this way, the side surface of the power supply terminal is fixed to the side surface of the hole of the second ceramic base, and thus the connecting member is less likely to fall off from the second ceramic base together with the power supply terminal.

[0020] In the wafer boat of the present application, the connecting member can be a member in which a plurality of metal meshes are stacked. In this way, even if the wafer boat is heated or cooled, since the connecting member is made of a metal mesh and thus easily expands and contracts, and ceramic enters the gaps of the meshes, the coefficient of thermal expansion approaches that of the second ceramic base. Therefore, a crack is less likely to occur in the second ceramic base.

[0021] In the wafer boat of the present application, the connecting member can have a shape in which a cross-sectional area of the connecting member when cut along a plane parallel to the upper bottom increases from the upper bottom toward the lower bottom. In this way, the connecting member has a relatively simple shape, and thus the connecting member can be easily manufactured. In this case, the connecting member can have a shape of a truncated cone, a shape of a hemisphere, or a shape in which the side surface is recessed inward compared with the shape of the truncated cone. In this way, the connecting member has a simple shape, and thus the connecting member can be easily manufactured.

[0022] The wafer mounting table manufacturing method of the present application includes:

[0023] (a) a step of preparing a first ceramic base having a wafer mounting surface on an upper surface and a second ceramic base in which a connecting member having an upper bottom and a lower bottom is embedded;

[0024] (b) a step of grinding the second ceramic base to expose the upper bottom of the connecting member, thereby forming a joining surface; and

[0025] (c) a step of metal joining the lower surface of the first ceramic base and the joining surface of the second ceramic base,

[0026] The connecting member embedded in the second ceramic base prepared in the step (a) has a portion in which a cross-sectional area when the connecting member is cut along a plane parallel to the upper bottom increases from the upper bottom side toward the lower bottom side.

[0027] In the wafer mounting table manufacturing method, the connecting member embedded in the second ceramic base prepared in the step (a) has a portion in which a cross-sectional area when the connecting member is cut along a plane parallel to the upper bottom increases from the upper bottom side toward the lower bottom side. Therefore, for example, compared with a case where the connecting member has a cylindrical shape, the area of the side surface of the connecting member increases, and thus the contact area between the second ceramic base and the connecting member increases, and the adhesion between the second ceramic base and the connecting member improves. Therefore, when the second ceramic base is ground in the step (b) to expose the upper bottom of the connecting member, thereby forming a joining surface, it is difficult to cause a crack in the second ceramic base. In addition, even if a load is applied to the connecting member in this step (b), since the side surface of the connecting member is caught in the second ceramic base, the connecting member is not easily detached. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a perspective view of the electrostatic chuck 10.

[0029] Figure 2 is an A-A sectional view of Figure 1

[0030] Figure 3 is an enlarged view of the B portion of Figure 2

[0031] Figure 4 is an explanatory view showing an example of a manufacturing method of the electrostatic chuck 10.

[0032] Figure 5 is a sectional view of the connecting member 120.

[0033] Figure 6 is a sectional view of the connecting member 220.

[0034] Figure 7 ​​This is a sectional view of the connecting member 320.

[0035] Figure 8 This is a sectional view of the connecting member 420.

[0036] Figure 9 This is a sectional view of the connecting member 520.

[0037] Figure 10 This is a sectional view of the connecting member 620.

[0038] Symbol Explanation

[0039] 10: Wafer stage; 11: First ceramic substrate; 11a: Wafer mounting surface; 11b: Bonding surface; 12: Second ceramic substrate; 12a: Bonding surface; 12b: Lower surface; 12c: Upper surface; 13: Metal bonding layer; 14: Resistance heating element; 20, 120, 220, 320, 420, 520, 620: Connecting components; 20a, 220a, 320a, 420a, 520a, 620a: Upper base; 20b, 220b, 320b, 4... 20b, 520b, 620b: Bottom layer; 28: Dielectric layer; 30: Power supply terminal; 30s: Side surface; 30t: End face; 31: Terminal end face bonding layer; 32: Terminal side bonding layer; 33: Hole; 33s: Side surface; 41: Ceramic powder; 42: Metal solder; 51: First ceramic molded body; 52: Second ceramic molded body; 53: Metal bonding material; 70: Laminated body; 420c, 520c, 620c: Partial; M1~M6: Metal mesh; W: Wafer. Detailed Implementation

[0040] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a 3D view of the electrostatic chuck 10. Figure 2 yes Figure 1 AA section view, Figure 3 yes Figure 2 An enlarged view of part B.

[0041] The electrostatic chuck 10 is an example of the wafer mounting stage of the present invention, and includes a first ceramic substrate 11, a second ceramic substrate 12, a metal bonding layer 13, a connecting member 20, and a power supply terminal 30.

[0042] The first ceramic substrate 11 is a disk-shaped plate made of ceramic (e.g., alumina, aluminum nitride) with the same diameter as the silicon wafer W to be subjected to plasma processing. The diameter of the first ceramic substrate 11 is not particularly limited, and can be, for example, 250–350 mm. The upper surface of the first ceramic substrate 11 is the wafer mounting surface 11a. A resistive heating element 14 is embedded in the first ceramic substrate 11. The resistive heating element 14 is composed of a material mainly composed of elements or compounds (carbides, etc.) of W, Mo, Ti, Si, and Ni, a combination thereof, or a mixture thereof with the raw materials of the first ceramic substrate 11. The resistive heating element 14 is patterned using a one-stroke drawing method, with wiring extending across the entire surface of the first ceramic substrate 11. The resistive heating element 14 heats up when a voltage is applied, thereby heating the wafer W. The area with the wiring of the resistive heating element 14 is circular when viewed from above and is located on a surface parallel to the wafer mounting surface 11a. In addition, the term "parallel" means that, apart from the case of perfect parallelism, even if they are not perfectly parallel, they are considered parallel as long as they are within the tolerance range.

[0043] The second ceramic substrate 12 is disposed on the side of the first ceramic substrate 11 opposite to the wafer mounting surface 11a (lower surface). The second ceramic substrate 12 has the same shape as the first ceramic substrate 11 and is formed of ceramic made of the same material as the first ceramic substrate 11. A connecting member 20 is embedded in the second ceramic substrate 12.

[0044] The metal bonding layer 13 bonds the lower surface of the first ceramic substrate 11 to the upper surface of the second ceramic substrate 12. Therefore, the lower surface of the first ceramic substrate 11 is referred to as the bonding surface 11b, and the upper surface of the second ceramic substrate 12 is referred to as the bonding surface 12a. The metal bonding layer 13 is, for example, made of an Al-containing material such as an Al-Si-Mg or Al-Mg system material. The thickness of the metal bonding layer 13 is not particularly limited, but is preferably 1 to 300 μm, more preferably 50 to 150 μm. Furthermore, it is preferable that the outer periphery of the metal bonding layer 13 does not extend beyond the outer periphery of the first ceramic substrate 11. The metal bonding layer 13 is formed, for example, by TCB (Thermal Compression Bonding). Here, TCB refers to a known method in which a metal bonding material is sandwiched between two components to be bonded, and the two components are pressure-bonded at a temperature below the solidus temperature of the metal bonding material. In this embodiment, the metal bonding layer 13 is used as an electrostatic electrode. The region from the bonding surface 11b of the first ceramic substrate 11 to the wafer mounting surface 11a (the entire first ceramic substrate 11) functions as a dielectric layer 28. When a DC voltage is applied to this metal bonding layer 13, the wafer W mounted on the wafer mounting surface 11a is adsorbed and fixed to the wafer mounting surface 11a. When the DC voltage is released, the adsorption and fixation of the wafer W to the wafer mounting surface 11a is released.

[0045] The connecting member 20 has an upper base 20a and a lower base 20b, and is embedded in the second ceramic substrate 12 with the upper base 20a in contact with the metal bonding layer 13. The shape of the connecting member 20 has a portion where the cross-sectional area when the connecting member 20 is cut along a plane parallel to the upper base 20a increases from the upper base 20a side to the lower base 20b side. In this embodiment, the shape of the connecting member 20 is such that the cross-sectional area increases from the upper base 20a to the lower base 20b, specifically a frustum-cone shape. The connecting member 20 is, for example, a block (bulk body) made of a mixed material in which ruthenium alloy (e.g., RuAl) is added to tungsten carbide, or a metal such as Mo. The surface area of ​​the upper base 20a of the connecting member 20 is preferably 50% to 98% of the surface area of ​​the lower base 20b.

[0046] One end face 30t of the power supply terminal 30 is electrically connected to the lower bottom 20b of the connecting member 20, and the other end face is connected to an external DC power source (not shown). The power supply terminal 30 is formed of a metal such as Ni or Mo, and is inserted into a hole 33 (see reference) formed on the lower surface 12b of the second ceramic substrate 12. Figure 4 The end face 30t of the power supply terminal 30 is joined to the lower bottom 20b of the connecting member 20 via the terminal end face bonding layer 31. The terminal end face bonding layer 31 is a layer containing ceramic particles and metal solder, with the metal solder entering the gaps between the ceramic particles. Alumina ceramic particles and aluminum nitride ceramic particles are preferred as ceramic particles. The terminal end face bonding layer 31 fills the gaps between the ceramic particles with metal solder, thus electrically connecting the power supply terminal 30 to the connecting member 20. The side surface 30s of the power supply terminal 30 is joined to the side surface 33s of the hole 33 via the terminal side surface bonding layer 32. The terminal side surface bonding layer 32 is a layer formed of metal solder. Au-Ni solder, Al solder, Ag solder, etc., are preferred as metal solder.

[0047] Next, use Figure 4 The manufacturing method of the electrostatic chuck 10 is described. Figure 4 This is an explanatory diagram illustrating an example of a manufacturing method for the electrostatic chuck 10.

[0048] First, a first ceramic substrate 11 having a wafer mounting surface 11a and a resistive heating element 14 embedded therein, and a second ceramic substrate 12 having a connecting member 20 embedded therein, are prepared. Specifically, as follows... Figure 4As shown in (a), a first ceramic molded body 51 (the precursor of the first ceramic substrate 11) in the shape of a disc with an embedded resistive heating element 14 and a second ceramic molded body 52 (the precursor of the second ceramic substrate 12) in the shape of a disc with an embedded connecting member 20 are manufactured. This process is referred to as process (1). In process (1), the first ceramic molded body 51 and the second ceramic molded body 52 are manufactured by a molding process, etc. Here, "molding process" refers to a method of injecting a ceramic slurry containing ceramic raw material powder and a molding agent into a molding mold, and molding the ceramic slurry by causing a chemical reaction of the molding agent in the molding mold, thereby obtaining a molded body. As a molding agent, for example, isocyanate and polyol may be included, and molding is carried out by a carbamate reaction. Next, as Figure 4 As shown in (b), the first ceramic molded body 51 and the second ceramic molded body 52 are hot-pressed and fired while applying pressure in the thickness direction to produce the first ceramic substrate 11 and the second ceramic substrate 12. This process is referred to as process (2). These processes (1) and (2) correspond to process (a) in the manufacturing method of the wafer mounting stage of the present invention.

[0049] Next, as Figure 4 As shown in (c), a hole 33 is formed on the lower surface 12b of the second ceramic substrate 12 to expose the lower bottom 20b of the connecting member 20 embedded in the second ceramic substrate 12. This process is referred to as process (3). In process (3), the hole 33 is formed by grinding, cutting, and sandblasting. It should be noted that in process (3), the load applied to the connecting member 20 when the hole 33 is formed in the second ceramic substrate 12 is small, so the connecting member 20 is not easy to fall off the second ceramic substrate 12.

[0050] Next, insert the power supply terminal 30 into the hole 33. Specifically, as follows: Figure 4 As shown in (d), the second ceramic substrate 12 is arranged with the hole 33 facing upwards. With ceramic powder 41 composed of multiple ceramic particles and metal solder 42 disposed on the lower bottom 20b of the connecting member 20, the power supply terminal 30 is inserted into the hole 33. This process is referred to as process (4). In process (4), the ceramic powder 41 can be, for example, alumina ceramic, aluminum nitride ceramic, etc. In addition, in process (4), the metal solder 42 can be Au-Ni solder, Al solder, Ag solder, etc.

[0051] Next, the power supply terminal 30 is connected to the connecting member 20. Specifically, firstly, the second ceramic substrate 12 is heated to a temperature above the melting point of the solder 42, causing the solder 42 to melt. The molten solder 42 penetrates into the ceramic powder 41 and fills the gaps between the ceramic particles of the ceramic powder 41, and enters between the side surface 30s of the power supply terminal 30 and the side surface 33s of the hole 33. Then, cooling is performed to solidify the solder 42. Thus, as Figure 4 As shown in (e), a terminal end face bonding layer 31 is formed by the metal solder 42 entering the gaps between the ceramic particles, and a terminal side bonding layer 32 is formed by the metal solder 42. Thus, the end face 30t of the power supply terminal 30 is bonded to the lower bottom 20b of the connecting member 20, and the side surface 30s of the power supply terminal 30 is bonded to the side surface 33s of the hole 33. This process is referred to as process (5). In process (5), the side surface 30s of the power supply terminal 30 is fixed to the side surface 33s of the hole 33 in the second ceramic substrate 12. Therefore, it is possible to prevent the connecting member 20 from detaching from the second ceramic substrate 12 along with the power supply terminal 30.

[0052] Next, after arranging the second ceramic substrate 12 with the hole 33 facing downwards, as follows... Figure 4 As shown in (f), the upper surface 12c of the second ceramic substrate 12 is ground to expose the upper bottom 20a of the connecting member 20, forming a mating surface 12a. This process is referred to as process (6). Process (6) corresponds to process (b) in the manufacturing method of the wafer mounting stage of the present invention. The connecting member 20 has a portion whose cross-sectional area increases from the upper bottom 20a side to the lower bottom 20b side when the connecting member 20 is cut along a surface parallel to the upper bottom 20a. In this embodiment, the shape of the connecting member 20 is such that its cross-sectional area increases from the upper bottom 20a side to the lower bottom 20b side; specifically, it is a frustum-shaped cone. Therefore, compared to the case where the connecting member 20 is cylindrical, the contact area between the second ceramic substrate 12 and the connecting member 20 is increased, and the fit between the second ceramic substrate 12 and the connecting member 20 is improved. Therefore, in process (6), it is less likely for cracks to form in the second ceramic substrate 12. In addition, even if a load is applied to the connecting member 20 in process (6), it is not easy to fall off because the side of the connecting member 20 is stuck on the second ceramic substrate 12.

[0053] Then, metal bonding is performed on the bonding surface 11b of the first ceramic substrate 11 opposite to the wafer mounting surface 11a and the bonding surface 12a of the second ceramic substrate 12. Specifically, firstly, as Figure 4As shown in (g), a flat metal bonding material 53 with the same diameter as the second ceramic substrate 12 is placed on the bonding surface 12a of the second ceramic substrate 12, and the first ceramic substrate 11 is placed on it in such a way that the bonding surface 11b of the first ceramic substrate 11 contacts the metal bonding material 53. In this way, a laminate 70 is formed in which the metal bonding material 53 is sandwiched between the first ceramic substrate 11 and the second ceramic substrate 12. This process is called process (7). In process (7), Al-Mg based bonding materials and Al-Si-Mg based bonding materials can be used as the metal bonding material 53. Next, the laminate 70 is pressurized at a temperature below the solidus temperature of the metal bonding material 53 (for example, above the temperature after subtracting 20°C from the solidus temperature and below the solidus temperature) to perform TCB bonding between the first ceramic substrate 11 and the second ceramic substrate 12, and then restored to room temperature. As a result, the metal bonding material 53 becomes the metal bonding layer 13, and an electrostatic chuck 10 is obtained. This process is called process (8). These steps (7) and (8) correspond to step (c) in the manufacturing method of the wafer stage of the present invention.

[0054] Next, an example of using the electrostatic chuck 10 of this embodiment will be described. A wafer W is placed on the wafer mounting surface 11a of the electrostatic chuck 10. By applying a voltage between the metal bonding layer 13 and the wafer W, the wafer W is attracted to the wafer mounting surface 11a by electrostatic force. In this state, plasma CVD film deposition or plasma etching is performed on the wafer W. Alternatively, the temperature of the wafer W is controlled to a constant level by heating the wafer W by applying a voltage to the resistive heating element 14, or by cooling the wafer W by circulating a coolant in a coolant path of a cooling plate (not shown) bonded to the electrostatic chuck 10.

[0055] According to the electrostatic chuck 10 of this embodiment described above, the connecting member 20 embedded in the second ceramic substrate 12 has a portion whose cross-sectional area increases from the upper bottom 20a side to the lower bottom 20b side when the connecting member 20 is cut along a surface parallel to the upper bottom 20a. Therefore, for example, compared to the case where the connecting member 20 is cylindrical, the area of ​​the side surface of the connecting member 20 is larger, thus increasing the contact area between the second ceramic substrate 12 and the connecting member 20, and improving the tightness of the fit between the second ceramic substrate 12 and the connecting member 20. Therefore, when manufacturing the electrostatic chuck 10, even if a process is included in which the surface of the second ceramic substrate 12 where the connecting member 20 is embedded is ground to expose the upper bottom 20a of the connecting member 20, cracks are less likely to occur in the second ceramic substrate 12. In addition, even if a load is applied to the connecting member 20 in this process, it is less likely to fall off because the side surface of the connecting member 20 is engaged with the second ceramic substrate 12.

[0056] Furthermore, the second ceramic substrate 12 has a hole 33 for inserting the power supply terminal 30 into the lower surface of the second ceramic substrate 12, and the side of the power supply terminal 30 engages with the side 33s of the hole 33. In this way, since the side 30s of the power supply terminal 30 is fixed to the side 33s of the hole 33 in the second ceramic substrate 12, it is possible to prevent the connecting member 20 from detaching from the second ceramic substrate 12 together with the power supply terminal 30.

[0057] Furthermore, the shape of the connecting member 20 is such that when the connecting member 20 is cut along a plane parallel to the upper base 20a, the cross-sectional area increases from the upper base 20a toward the lower base 20b (in this case, a frustum shape), thus the connecting member 20 can be easily manufactured.

[0058] It should be noted that the present invention is not limited to any of the above embodiments. As long as it falls within the technical scope of the present invention, it can be implemented in various ways.

[0059] For example, in the above embodiment, a connecting member 20 made of a metal block (bulk body) is used to connect the power supply terminal 30 to the metal bonding layer 13, but it is not limited to this. For example, such as Figure 5 As shown, a connecting member 120 can also be formed by stacking multiple layers (6 layers in this case) of metal meshes M1 to M6 with different diameters from the power supply terminal 30 side in descending order of diameter, connecting the power supply terminal 30 to the metal bonding layer 13. In this way, even if the electrostatic chuck 10 is heated or cooled, the connecting member 20, being made of metal mesh, easily expands and contracts, allowing the ceramic to enter the gaps between the metal meshes M1 to M6, thus its coefficient of thermal expansion is close to that of the second ceramic substrate 12. Therefore, cracks are less likely to form in the second ceramic substrate 12. It should be noted that... Figure 5 In this document, the same symbols are used for the same constituent elements as in the above-described embodiments, and the descriptions are omitted.

[0060] In the electrostatic chuck 10 of the above embodiment, a frustum-shaped connecting member 20 is used, but it is not limited to this. For example, as Figure 6 As shown, the shape of the connecting member 220 can also be set as a frustum-shaped hemispherical structure where the cross-sectional area increases from the upper bottom 220a side to the lower bottom 220b side when the connecting member 220 is cut along a plane parallel to the upper bottom 220a. (Or a shape where the hemisphere is cut along two planes parallel to the bottom surface.) Alternatively, as shown... Figure 7 As shown, the shape of the connecting member 320 can also be set as a cone-shaped volcano (the shape of a truncated cone with its side surface concave inwards) where the cross-sectional area of ​​the connecting member 320 when cut along a plane parallel to the upper base 320a increases from the upper base 320a side towards the lower base 320b side. Alternatively, as... Figure 8As shown, it can also be a barrel shape with a portion 420c where the cross-sectional area of ​​the connecting member 420 increases from the upper bottom 420a side towards the lower bottom 420b side when cut along a surface parallel to the upper bottom 420a. Or, as shown... Figure 9 As shown, it can also be a shape with a portion 520c where the cross-sectional area of ​​the connecting member 520 increases from the upper base 520a side towards the lower base 520b side when cut along a surface parallel to the upper base 520a. (A shape where the side of a cylinder is recessed inwards.) Or, as shown... Figure 10 As shown, it can also be a shape with a portion 620c where the cross-sectional area of ​​the connecting member 620 increases from the upper bottom 620a side towards the lower bottom 620b side when cut along a surface parallel to the upper bottom 620a (a shape that bulges below the side of a pipa-shaped container). Figures 6-10 In this document, the same symbols are used for the same components as in the embodiments described above, and their descriptions are omitted. Compared to the case where the connecting members are cylindrical, the side surface areas of the connecting members 220, 320, 420, 520, and 620 are larger. Therefore, even if a process is included in which the lower surface 12b of the second ceramic substrate 12 is ground to expose the upper bottoms 220a, 320a, 420a, 520a, and 620a, cracks are less likely to occur in the second ceramic substrate 12. Furthermore, even if a load is applied to the connecting members 220, 320, 420, 520, and 620 in this process, they are less likely to detach because their side surfaces are held in place by the second ceramic substrate 12.

[0061] In the above embodiment, the metal bonding layer 13 is used as an electrostatic electrode, but it is not limited to this. For example, it can also be used as a grounding electrode. In this case, the metal bonding layer 13 can also be grounded, and the electrostatic electrode can be embedded in the first ceramic substrate 11 in a manner parallel to the resistive heating element 14.

[0062] In the above embodiment, the end face 30t of the power supply terminal 30 is joined to the bottom 20b of the connecting member 20 via a terminal side bonding layer 32 composed of ceramic powder 41 and metal solder 42, but this is not a limitation. For example, the terminal side bonding layer 32 may not contain ceramic powder 41 but be composed of metal solder 42. In this case, in step (4), metal solder 42 is provided on the bottom 20b of the connecting member 20 without ceramic powder 41, and in this state, the power supply terminal 30 is inserted into the hole 33. Similarly to the above embodiment, after melting the metal solder 42, it is cooled and solidified.

[0063] In the above-described embodiments, when manufacturing the electrostatic chuck 10, after connecting the power supply terminal 30 to the connecting member 20, the upper surface 12c of the second ceramic substrate 12 is ground to form a mating surface 12a, and the first ceramic substrate 11 and the second ceramic substrate 12 are joined together, but this is not a limitation. For example, after grinding the upper surface 12c of the second ceramic substrate 12 to form the mating surface 12a, a hole 33 may be provided on the lower surface 12b to connect the power supply terminal 30 to the connecting member 20, and the first ceramic substrate 11 and the second ceramic substrate 12 may be metal-bonded. Alternatively, the upper surface 12c of the second ceramic substrate 12 may be ground to form the mating surface 12a, and the first ceramic substrate 11 and the second ceramic substrate 12 may be metal-bonded, and then a hole 33 may be formed on the lower surface 12b to connect the power supply terminal 30 to the connecting member 20.

[0064] In the above embodiments, RF electrodes may also be embedded in the first ceramic substrate 11 or the second ceramic substrate 12. RF electrodes are electrodes used when generating plasma.

Claims

1. A wafer table comprising: a first ceramic base having a wafer placement surface on an upper surface; a second ceramic base disposed on a lower surface side of the first ceramic base; a metal joining layer joining a lower surface of the first ceramic base and an upper surface of the second ceramic base; a connecting member having an upper bottom and a lower bottom, the connecting member being embedded in the second ceramic base with the upper bottom in contact with the metal joining layer; and a power supply terminal electrically connected to the lower bottom of the connecting member, the connecting member having a portion in which a cross-sectional area of the connecting member when cut along a plane parallel to the upper bottom increases from the upper bottom side toward the lower bottom side, the connecting member being a member in which a plurality of metal meshes are laminated or a block of a mixed material in which a ruthenium alloy is added to tungsten carbide, the second ceramic base having a hole for inserting the power supply terminal into a lower surface of the second ceramic base, a side surface of the power supply terminal being joined to a side surface of the hole, the connecting member having a shape in which a cross-sectional area of the connecting member when cut along a plane parallel to the upper bottom increases from the upper bottom toward the lower bottom, the connecting member having a conical frustum shape, a hemi-spherical frustum shape, or a shape in which a side surface is recessed inward compared to the conical frustum shape.

5. A method of manufacturing a wafer table, comprising: (a) a step of preparing a first ceramic base having a wafer placement surface on an upper surface and a second ceramic base in which a connecting member having an upper bottom and a lower bottom is embedded, the connecting member being a member in which a plurality of metal meshes are laminated or a block of a mixed material in which a ruthenium alloy is added to tungsten carbide; (b) a step of grinding the second ceramic base to expose the upper bottom of the connecting member and form a joining surface; and (c) a step of metal joining a lower surface of the first ceramic base and the joining surface of the second ceramic base, the connecting member embedded in the second ceramic base in the step (a) having a portion in which a cross-sectional area of the connecting member when cut along a plane parallel to the upper bottom increases from the upper bottom side toward the lower bottom side. ​ ​ ​ ​ ​ ​ ​ 2. The wafer boat of claim 1, wherein, ​ ​ 3. The wafer boat of any of claims 1 or 2, wherein, ​ 4. The wafer boat of claim 3, wherein, ​ ​ ​ ​ ​ ​

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