Ceramic assembly and electrostatic chuck device

Abstract

A ceramic composite having a pair of ceramic plates stacked in the thickness direction, a buffer layer disposed between the pair of ceramic plates, a strip-shaped heater portion disposed between the pair of ceramic plates and within a groove portion provided in at least one of the pair of ceramic plates, wherein the side surface of the heater portion and the side wall surface of the groove portion face each other with a gap interposed therebetween, and the buffer layer is made of an insulating material having a coefficient of thermal expansion greater than that of the ceramic material constituting the pair of ceramic plates, and at least a portion overlaps with the gap when viewed in the thickness direction.

Description

Technology Field

[0001] The present invention relates to a ceramic assembly and an electrostatic chuck device.

[0002] The present application claims priority based on Japanese patent application No. 2023-143425 filed on September 5, 2023, and incorporates the contents thereof herein. Background Technology

[0003] In semiconductor manufacturing processes, an electrostatic chuck device is used to support a semiconductor wafer in a vacuum environment. The electrostatic chuck device places a plate-shaped sample, such as a semiconductor wafer, on a mounting surface and generates an electrostatic force between the plate-shaped sample and an internal electrode to adsorb and fix the plate-shaped sample. In such an electrostatic chuck device, it is known that a heater unit is embedded inside a ceramic assembly on which the mounting surface is formed, and the mounting surface is heated by said heater unit (e.g., Patent Document 1). Prior art literature

[0004] Japanese Patent Publication No. Hei 9-82786 The problem to be solved

[0005] With the recent increase in high temperatures in semiconductor manufacturing processes, electrostatic chucks are required to control the mounting surface to a high and uniform temperature. For this reason, it is considered necessary to utilize a configuration in which the heater section is densely arranged relative to the mounting surface. Generally, the heater section is placed within a groove of one of a pair of ceramic plates and sandwiched between them. However, if the heater section is densely arranged, the strength of the region between the heater sections within the ceramic plates becomes insufficient, making the ceramic plates susceptible to damage. Furthermore, gaps may occur between the ceramic plate with the groove and its pair, posing challenges regarding the temperature uniformity of the mounting surface and the reliability of the electrostatic chuck.

[0006] One of the objectives of the present invention is to provide a highly reliable ceramic assembly and an electrostatic chuck device that can suppress damage to the ceramic plates even when the heater portion is densely arranged and has no gaps between the ceramic plates. means of solving the problem

[0007] The present invention includes the inventions of [1] to

[11] below.

[0008] It is also desirable to combine two or more of the following inventions as needed.

[0009] [1] A ceramic composite having a pair of ceramic plates stacked in the thickness direction, a buffer layer disposed between the pair of ceramic plates, and a band-shaped heater portion disposed between the pair of ceramic plates and within a groove portion provided in at least one of the pair of ceramic plates, wherein the side of the heater portion and the side wall of the groove portion face each other with a gap between them, and the buffer layer is made of an insulating material having a coefficient of thermal expansion greater than that of the ceramic material constituting the pair of ceramic plates, and at least a portion of which overlaps with the gap when viewed in the thickness direction.

[0010] [2] The width dimension of the gap in the opening of the above-mentioned groove is greater than the thickness dimension of the portion of the buffer layer that is sandwiched between the pair of ceramic plates, as described in [1].

[0011] [3] A ceramic composite described in [1] or [2], wherein the ratio of the thermal expansion coefficient of the insulating material to the thermal expansion coefficient of the ceramic material is 1.1 or greater and 2.0 or less.

[0012] [4] A ceramic composite described in any one of [1] to [3], wherein the width dimension of the heater portion is at least twice the distance between the groove portions in which the heater portion is placed.

[0013] [5] A ceramic composite described in any one of [1] to [4], wherein a portion of the buffer layer is disposed in the gap above.

[0014] [6] A ceramic composite described in any one of [1] to [5], wherein the side wall surface of the groove portion has an inclined surface that is inclined in a direction that increases the width dimension of the groove portion as it faces the opening side of the groove portion in the depth direction of the groove portion.

[0015] [7] The width dimension of the above inclined surface is greater than the thickness dimension of the portion of the buffer layer that is sandwiched between the pair of ceramic plates, as described in [6].

[0016] [8] The inner wall surface of the groove portion has, in addition to a pair of side walls, a bottom wall surface facing the opening side of the groove portion, and a pair of curved surfaces located at the boundary between the side walls and the bottom wall surface and smoothly connecting the side walls and the bottom wall surface, as described in any one of [1] to [7].

[0017] [9] The radius of curvature of the above curved surface is greater than the thickness of the above buffer layer, [8] of the ceramic composite.

[0018]

[10] A ceramic composite described in any one of [1] to [9], wherein the thickness dimension of the heater portion is greater than the depth dimension of the groove portion.

[0019]

[11] An electrostatic chuck device having a ceramic assembly described in any one of [1] to

[10] . Effects of the invention

[0020] According to one aspect of the present invention, a ceramic composite and an electrostatic chuck device are provided that can suppress damage to the ceramic plate even when the heater portion is densely arranged. Brief explanation of the drawing

[0021] [Fig. 1] Fig. 1 is a schematic cross-sectional view showing an electrostatic chuck device of one embodiment. [Fig. 2] Fig. 2 is a partial enlarged view showing an example of a pair of ceramic plates of an electrostatic chuck member (ceramic composite) of one embodiment, and is a schematic diagram showing the appearance before integration. [Fig. 3] Fig. 3 is a partial enlarged view showing an example of a pair of ceramic plates of an electrostatic chuck member (ceramic composite) of one embodiment, and is a schematic diagram showing the appearance after integration. [Fig. 4] Fig. 4 is a partial enlarged view showing an example of a pair of ceramic plates of an electrostatic chuck member (ceramic composite) of Variant Example 1, and is a schematic diagram showing the appearance before integration. [Fig. 5] Fig. 5 is a partial enlarged view showing an example of a pair of ceramic plates of an electrostatic chuck member (ceramic composite) of Variant Example 1, and is a schematic diagram showing the appearance after integration. [Fig. 6] Fig. 6 is a partial cross-sectional view showing an example of an electrostatic chuck member (ceramic bond) of Variant Example 2. [Fig. 7] Fig. 7 is a partial cross-sectional view showing an example of an electrostatic chuck member (ceramic bond) of Variant Example 3. Specific details for implementing the invention

[0022] Hereinafter, preferred examples of each embodiment of the electrostatic chuck device of the present invention will be described with reference to the drawings. In addition, in all of the following drawings, the dimensions or proportions of each component may be shown differently to make the drawings easier to view.

[0023] Furthermore, the following description is intended to provide a more detailed explanation of the intent of the invention and, unless specifically designated, does not limit the invention. For example, unless specifically limited, conditions such as materials, quantities, types, numbers, sizes, shapes, locations, and ratios may be changed, added, or omitted as necessary.

[0024] In addition, the Z-axis is illustrated in each drawing. In this specification, the Z-axis represents the thickness direction of the ceramic plates (11, 12) described later. In this specification, the Z-axis is assumed to extend in the up-and-down direction, and the direction in which the arrow of the Z-axis points is the upper side, and the opposite side is the lower side, and each part of the electrostatic chuck device (1) is described. In addition, the up-and-down direction in this specification is used solely for the purpose of simplifying the explanation and does not limit the posture when using the electrostatic chuck device (1).

[0025] FIG. 1 is a cross-sectional schematic diagram showing an electrostatic chuck device (1) of the present embodiment.

[0026] The electrostatic chuck device (1) comprises an electrostatic chuck member (ceramic composite) (2) having a mounting surface (2s) for mounting a wafer (sample) (W), a base (3) that supports the electrostatic chuck member (2) from the opposite side of the mounting surface (2s), a plurality of first power supply terminals (16A), and a plurality of second power supply terminals (16B). Additionally, a focus ring surrounding the wafer (W) may be disposed on the outer periphery of the upper surface of the electrostatic chuck member (2). Furthermore, a flow path for flowing a cooling medium, etc., may be provided in the base (3).

[0027] In the electrostatic chuck device (1), a gas passage (19) is provided. The gas passage (19) has a first gas hole (19a), a second gas hole (19b), and a connecting passage (19c). The connecting passage (19c) is located inside the electrostatic chuck member (2) and extends along the planar direction of the mounting surface (2s). The connecting passage (19c) is provided in the second bonding layer (11e) described later. The first gas hole (19a) extends downward from the connecting passage (19c) and is connected to the introduction portion of the heat transfer gas (not shown) at the lower part of the base (3). An insulator (18) is provided around the portion of the first gas hole (19a) that passes through the base (3). The second gas hole (19b) extends upward from the connecting passage (19c) and opens to the mounting surface (2s). The first gas hole (19a) and the second gas hole (19b) are connected to each other via a connecting passage (19c). A heating gas flows through the gas passage (19). The heating gas is a cooling gas, such as He. The heating gas is supplied to the mounting surface (2s) through the gas passage (19) and cools the wafer (W) mounted on the mounting surface (2s). The number and location of the gas passage (19) are selected arbitrarily.

[0028] The electrostatic chuck member (2) is disc-shaped or approximately disc-shaped. The electrostatic chuck member (2) has a pair of ceramic plates (11, 12), an electrostatic adsorption electrode (13), a buffer layer (25), and a heater part (20). The pair of ceramic plates (11, 12) are stacked in the thickness direction. In the following description, when distinguishing between the pair of ceramic plates (11, 12), the one located on the upper side is called the first ceramic plate (11), and the other located on the lower side is called the second ceramic plate (12). The mounting surface (2s) of the electrostatic chuck member (2) is provided on the first ceramic plate (11).

[0029] The first ceramic plate (11) is a circular plate shape when viewed in planar view. An electrostatic adsorption electrode (13) is provided inside the first ceramic plate (11). The first ceramic plate (11) has a mounting surface (2s) facing upward and a first opposing surface (11f) facing downward. On the mounting surface (2s), for example, a plurality of protrusions (not shown) are formed at predetermined intervals. The mounting surface (2s) supports a wafer (W) at the leading edge of the plurality of protrusions. The first opposing surface (11f) faces the second ceramic plate (12).

[0030] The first ceramic plate (11) has a first plate portion (11a), a second plate portion (11b), a third plate portion (11c), a first bonding layer (11d), and a second bonding layer (11e). The first plate portion (11a), the second plate portion (11b), and the third plate portion (11c) are plate-shaped with the Z-axis direction as the thickness direction. The first plate portion (11a), the second plate portion (11b), and the third plate portion (11c) are stacked in this order in the thickness direction from the upper side toward the lower side.

[0031] Between the first plate portion (11a) and the second plate portion (11b), a first bonding layer (11d) and an electrostatic adsorption electrode (13) are disposed. The first bonding layer (11d) is provided to surround the perimeter of the electrostatic adsorption electrode (13). The first bonding layer (11d) bonds the first plate portion (11a) and the second plate portion (11b). The electrostatic adsorption electrode (13) extends in layers along a plane orthogonal to the thickness direction (Z-axis direction) of the first ceramic plate (11). Thus, the electrostatic adsorption electrode (13) is embedded inside the first ceramic plate (11).

[0032] A second bonding layer (11e) is disposed between the second plate portion (11b) and the third plate portion (11c). The second bonding layer (11e) bonds the second plate portion (11b) and the third plate portion (11c). A passage (19c) of the gas flow path (19) is provided in the second bonding layer (11e). Additionally, a bias electrode surrounded by the second bonding layer (11e) may be disposed between the second plate portion (11b) and the third plate portion (11c).

[0033] The first ceramic plate (11) of the present embodiment is formed by applying an unsintered paste constituting an electrostatic adsorption electrode (13), a first bonding layer (11d), and a second bonding layer (11e) between a first plate part (11a), a second plate part (11b), and a third plate part (11c) which are sintered bodies formed by pre-sintering, respectively, stacking them in the thickness direction, and hot-pressing them under high temperature and high pressure to form an integrated structure.

[0034] The first plate portion (11a), the second plate portion (11b), the third plate portion (11c), the first bonding layer (11d), and the second bonding layer (11e) constituting the first ceramic plate (11) are made of ceramic material. That is, the first ceramic plate (11) is made of ceramic material. The ceramic material constituting the first ceramic plate (11) can be arbitrarily selected, but for example, an aluminum oxide (Al2O3) sintered body, an aluminum nitride (AlN) sintered body, an aluminum oxide (Al2O3)-silicon carbide (SiC) composite sintered body, etc. are suitably used. In this embodiment, the first plate portion (11a), the second plate portion (11b), the third plate portion (11c), the first bonding layer (11d), and the second bonding layer (11e) are composed of a material of the same composition. However, the first plate (11a), the second plate (11b), the third plate (11c), the first bonding layer (11d), and the second bonding layer (11e) do not have to be composed of materials of the same composition and may be composed of materials different from each other.

[0035] The electrostatic adsorption electrode (13) is preferably a composite of an insulating material and a conductive material. The insulating material included in the electrostatic adsorption electrode (13) is not particularly limited, but is preferably at least one selected from the group consisting of aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (Si3N4), yttrium(III) oxide (Y2O3), yttrium aluminum garnet (YAG), and SmAlO3. The conductive material can be arbitrarily selected.

[0036] A first power supply terminal (16A) is connected to the electrostatic adsorption electrode (13). The first power supply terminal (16A) applies voltage to the electrostatic adsorption electrode (13). By applying voltage, the electrostatic adsorption electrode (13) generates an electrostatic adsorption force that supports a plate-shaped sample on the mounting surface (2s). The first power supply terminal (16A) penetrates the second plate portion (11b), the third plate portion (11c), the buffer layer (25), the second ceramic plate (12), and the base (3). A tubular insulator (18) for insulation is mounted on a part of the outer surface of the first power supply terminal (16A). The insulator (18) insulates the first power supply terminal (16A) and the base (3) from each other.

[0037] The second ceramic plate (12) is a circular plate in a planar view. The second ceramic plate (12) has a second opposing surface (12f) facing upward. The second opposing surface (12f) is opposite to the first opposing surface (11f) of the first ceramic plate (11) in the vertical direction.

[0038] A groove (15) is provided in the second opposing surface (12f). The groove (15) of this embodiment has a uniform width and a uniform depth over its entire length. However, the width and depth of the groove (15) do not necessarily have to be uniform. A strip-shaped heater portion (20) is accommodated in the groove (15). A strip-shaped shape may, for example, mean a shape that is long and thin with a constant width. The heater portion (20) may have all parts continuous. The overall pattern shape of the heater portion (20) in a planar view can be arbitrarily selected, and for example, it may be a shape that is serpentine to fit inside a circle. The heater portion (20) is placed within an area that overlaps with the mounting surface (2s) in a planar view, but is not limited to this example. The groove (15) is formed with a pattern shape approximately equivalent to the pattern shape of the heater portion (20). Also, the width dimension of the groove (15) is slightly larger than the width dimension of the heater portion (20). Additionally, a plurality of grooves (15) may be provided on the second opposing surface (12f). In this case, a heater portion (20) is individually disposed in each groove (15).

[0039] In this embodiment, a case is described in which the groove portion (15) is provided only on the second ceramic plate (12) and not on the first ceramic plate (11). However, the groove portion (15) may be provided on at least one of the pair of ceramic plates (11, 12). That is, the groove portion may be provided only on the first opposing surface (11f) of the first ceramic plate (11) and may not be provided on the second ceramic plate (12). In addition, the groove portion may be provided on both the first opposing surface (11f) and the second opposing surface (12f) of the pair of ceramic plates (11, 12). In this case, the groove portions provided on the pair of ceramic plates (11, 12) have the same shape and overlap each other when viewed in the thickness direction.

[0040] The second ceramic plate (12) is made of a ceramic material. As the ceramic material constituting the second ceramic plate (12), for example, an aluminum oxide (Al2O3) sintered body, an aluminum nitride (AlN) sintered body, an aluminum oxide (Al2O3)-silicon carbide (SiC) composite sintered body are suitably used. In this embodiment, the second ceramic plate (12) is composed of the same material as the first ceramic plate (11). However, the second ceramic plate (12) may be composed of a material different from that of the first ceramic plate (11). Also, the second ceramic plate (12) of this embodiment is composed of a single sintered body. However, the second ceramic plate (12) may be composed by stacking and joining a plurality of sintered bodies in the thickness direction. In this case, the plurality of sintered bodies may be composed of different ceramic materials.

[0041] The heater portion (20) is located between the first ceramic plate (11) and the second ceramic plate (12). The heater portion (20) is placed within a groove (15) provided in the second ceramic plate (12). The heater portion (20) has a strip-like shape, and the thickness direction of the heater portion (20) coincides with the thickness direction of the pair of ceramic plates (11, 12).

[0042] The heater section (20) is composed of a resistance heating element. The type of resistance heating element, the shape, and the manufacturing method of the heater section (20) are arbitrarily selected. The heater section (20) is preferably manufactured by processing the entire outline of a non-magnetic metal thin plate, such as an Inconel (registered trademark) thin plate, titanium thin plate, tungsten (W) thin plate, molybdenum (Mo) thin plate, etc., into a desired heater shape by photolithography or laser processing, for example, a shape formed by meandering a strip-shaped conductive thin plate, into an annular shape. In this embodiment, the heater section (20) is arranged meanderingly between a pair of ceramic plates (11, 12). The heater section (20) generates heat when an electric current flows.

[0043] A second power supply terminal (16B) is connected to both ends in the longitudinal direction of the heater section (20). The second power supply terminal (16B) supplies current to the heater section (20). The second power supply terminal (16B) extends downward from the heater section (20). The second power supply terminal (16B) penetrates the second ceramic plate (12) and the base (3). A tubular insulating insulator (18) is mounted on a part of the outer surface of the second power supply terminal (16B). The insulator (18) insulates the second power supply terminal (16B) and the base (3) from each other.

[0044] A buffer layer (25) is placed between a pair of ceramic plates (11, 12). The buffer layer (25) joins the pair of ceramic plates (11, 12). Also, the buffer layer (25) joins the first ceramic plate (11) and the heater part (20).

[0045] The buffer layer (25) is made of an insulating material. For this reason, even when the buffer layer (25) is brought into contact with the heater part (20), no current flows through the buffer layer (25). The insulating material constituting the buffer layer (25) is made of an insulating material having a greater coefficient of thermal expansion than the ceramic material constituting the pair of ceramic plates (11, 12). As the insulating material constituting the buffer layer (25), for example, high-purity alumina (Al2O3) can be suitably employed. The coefficient of thermal expansion of high-purity alumina is 7.1 × 10⁻⁶. -6 / K~8.2×10 -6 It is approximately / K. Meanwhile, the coefficient of thermal expansion of the aluminum oxide (Al2O3)-silicon carbide (SiC) composite sintered body that can be used in a pair of ceramic plates (11, 12) is 4.6×10⁻⁶ -6 / K~5.2×10 -6 It is approximately / K. When using these in combination, care is taken so that each coefficient of thermal expansion satisfies the relationship described above. In addition, as a buffer layer (25), other examples include a coefficient of thermal expansion of 8.0×10 -6 / K~13.4×10 -6 Silicon oxide (SiO2) with a value of approximately / K may also be used.

[0046] As described above, the first ceramic plate (11) has a plurality of members (first plate part (11a), second plate part (11b), third plate part (11c), first bonding layer (11d), and second bonding layer (11e)), and these members may be composed of different ceramic materials. The coefficient of thermal expansion of the insulating material constituting the buffer layer (25) must be greater than the coefficient of thermal expansion of the ceramic material of the part of the first ceramic plate (11) that contacts the buffer layer (25) (i.e., the third plate part (11c)). Also, the second ceramic plate (12) may also have a plurality of members. When the second ceramic plate (12) is composed of multiple members made of different ceramic materials, the thermal expansion coefficient of the insulating material constituting the buffer layer (25) must be greater than the thermal expansion coefficient of the ceramic material in the part of the member constituting the second ceramic plate (12) that is in contact with the buffer layer (25).

[0047] The buffer layer (25) of the present embodiment is sintered in a process of integrating the first ceramic plate (11) and the second ceramic plate (12) by hot pressing under high temperature and high pressure. In this process, for example, first, a buffer layer (25) in the form of an unsintered paste is applied to the first opposing surface (11f) of the first ceramic plate (11). The procedure for applying the paste of the buffer layer (25) to the first opposing surface (11f) can be arbitrarily selected and may be performed using a brush, spatula, trowel, etc., or may be performed by screen printing. Subsequently, the first opposing surface (11f) is positioned to face the second opposing surface (12f) of the second ceramic plate (12), which has a heater portion (20) placed within the groove portion (15), and the first ceramic plate (11) and the second ceramic plate (12) are laminated in the thickness direction. Next, a pair of ceramic plates (11, 12) are hot-pressed under high temperature and high pressure to be integrated. The conditions of the hot press are selected arbitrarily. By undergoing this process, the buffer layer (25) is bonded to the entire surface of the first opposing surface (11f). Additionally, the buffer layer (25) is bonded to the portion of the second opposing surface (12f) other than the groove (15) and to the upper surface of the heater portion (20).

[0048] FIGS. 2 and FIGS. 3 are partial enlarged views of a pair of ceramic plates (11, 12) in the vicinity of the heater portion (20), FIG. 2 shows the appearance before integration, and FIG. 3 shows the appearance after integration. In addition, the cross-sections shown in FIGS. 2 and FIG. 3 are cross-sections perpendicular to the longitudinal direction of the heater portion (20).

[0049] As shown in FIG. 2, the groove (15) of the present embodiment has a cross-section that is approximately rectangular. The groove (15) has an opening (15a) that opens upward. The opening (15a) is covered by the first opposing surface (11f) of the first ceramic plate (11). The inner wall surface of the groove (15) has a bottom wall surface (15b) and a pair of side walls (15c). The bottom wall surface (15b) faces the opening side of the groove (15). The pair of side walls (15c) each extend upward from both ends in the width direction of the bottom wall surface (15b). The pair of side walls (15c) face each other in the width direction of the groove (15).

[0050] The cross-sectional shape of the heater portion (20) is approximately rectangular. The heater portion (20) has an upper surface (20a), a lower surface (20b), and a pair of side surfaces (20c). The pair of side surfaces (20c) extend along the thickness direction of the pair of ceramic plates (11, 12) and connect the upper surface (20a) and the lower surface (20b).

[0051] As shown in FIG. 3, after integration, the upper surface (20a) of the heater part (20) is covered by a cushioning layer (25). The lower surface (20b) of the heater part (20) comes into contact with the bottom wall surface (15b) of the groove part (15). As shown in FIG. 2, in this embodiment before the heater part (20) is embedded in the electrostatic chuck member (2), that is, before the hot press, the thickness dimension (t2a) of the heater part (20) is greater than the depth dimension (t1) of the groove part (15). Because of this, the upper surface (20a) of the heater part (20) before being embedded in the electrostatic chuck member (2) is located above the second opposing surface (12f).

[0052] As shown in FIG. 3, the heater portion (20) is inserted between a pair of ceramic plates (11, 12) and is deformed by being pressed and crushed in the thickness direction of the pair of ceramic plates (11, 12). Because of this, the thickness dimension (t2b) of the heater portion (20) after being embedded in the electrostatic chuck member (2) becomes smaller than the thickness dimension (t2a) before being embedded (see FIG. 2). Also, the thickness dimension (t2b) of the heater portion (20) after being embedded in the electrostatic chuck member (2) becomes slightly larger than the depth dimension (t1) of the groove portion (15) (see FIG. 2). That is, in this embodiment, the thickness dimensions (t2a, t2b) of the heater portion (20) are larger than the depth dimension (t1) of the groove portion (15) both before and after being embedded in the electrostatic chuck member (2). According to the present embodiment, during hot pressing, the heater part (20) is inserted into a pair of ceramic plates (11, 12) and compressed in the thickness direction, thereby deforming. As a result, the force applied between the pair of ceramic plates (11, 12) during hot pressing can be received by the heater part (20), and the force applied between the grooves of the second opposing surface (12f) is reduced. As a result, damage to the pair of ceramic plates (11, 12) during hot pressing can be suppressed.

[0053] As shown in FIG. 2, the width dimension (W4) of the heater portion (20) is smaller than the width dimension (W2) of the groove portion (15). The heater portion (20) is positioned approximately in the center of the width dimension (W2) of the groove portion (15). The side (20c) of the heater portion (20) faces the side wall surface (15c) of the groove portion (15) with a gap (G) interposed therebetween. That is, within the groove portion (15), a gap (G) is provided on both sides in the width direction of the heater portion (20). The gap (G) extends along the side (20c) of the heater portion (20). The width dimensions (d1) of the gap (G) located on both sides in the width direction of the heater portion (20) are approximately equal to each other. The width dimension (W4) of the heater portion (20) is, for example, 1 mm or more and 6 mm or less. Also, the width dimension (d1) of the gap (G) is, for example, 100 μm or more and 300 μm or less. In addition, the width dimensions (W4, d1) of the heater part (20) and the gap (G) can be selected arbitrarily and are not limited to these values.

[0054] In the present specification, the gap (G) refers to the area between the side (20c) of the heater part (20) and the side wall surface (15c) of the groove part (15), and an inclusion such as a buffer layer (25) may be placed in the said area. That is, the gap (G) does not necessarily mean a space where nothing is placed.

[0055] In the present specification, the width dimension refers to a dimension in the width direction. Also, the width direction refers to a direction orthogonal to both the length direction of the target part (heater part (20), groove part (15), gap (G), etc.) and the thickness direction (Z-axis direction) of the ceramic plate (11, 12).

[0056] The buffer layer (25) has a first region (25a) sandwiched between the first opposing surface (11f) and the second opposing surface (12f), a second region (25b) disposed between the first opposing surface (11f) and the upper surface (20a) of the heater part (20), and a third region (25c) located between the first region (25a) and the second region (25b). The third region (25c) is a region that overlaps with the gap (G) when viewed in the thickness direction of a pair of ceramic plates (11, 12) and penetrates into the gap (G). That is, at least a portion (in this embodiment, the third region (25c)) of the buffer layer (25) overlaps with the gap (G) when viewed in the thickness direction.

[0057] As shown in FIG. 3, according to the present embodiment, a buffer layer (25) is disposed between a pair of ceramic plates (11, 12). The buffer layer (25) is sandwiched between a pair of ceramic plates (11, 12) in a non-sintered state and is sintered when the pair of ceramic plates (11, 12) are hot-pressed to form an integral. Because of this, the buffer layer (25) absorbs the irregularities even if there are slight irregularities on the surface of the first opposing surface (11f) and the second opposing surface (12f) of the pair of ceramic plates (11, 12). As a result, the buffer layer (25) can suppress the application of a large local force to the first opposing surface (11f) and the second opposing surface (12f) of the ceramic plates (11, 12), or conversely, the formation of a gap. As a result, when undergoing hot pressing, damage and gaps can be suppressed near the interface of a pair of ceramic plates (11, 12), thereby increasing the uniformity of the temperature of the mounting surface (2s) of the electrostatic chuck member (2).

[0058] The buffer layer (25) is sandwiched between the members in the first region (25a) and the second region (25b) during hot pressing and pushed out toward the gap (G) in the third region (25c). That is, the third region (25c), which is part of the buffer layer (25), is placed in the gap (G) of the present embodiment. For this reason, even if the uncured buffer layer (25) is applied to the first opposing surface (11f) of the first ceramic plate (11) with a uniform thickness as shown in FIG. 2, the buffer layer (25) after hot pressing is difficult to have a uniform thickness as shown in FIG. 3. In the present embodiment, the thickness of the first region (25a) and the second region (25b) of the buffer layer (25) is, for example, 10 μm or more and 200 μm or less. Additionally, as described above, the upper surface (20a) of the heater part (20) in the state before burial shown in FIG. 2 is located above the second opposing surface (12f). Because of this, the thickness dimension of the second region (25b) becomes smaller than the thickness dimension of the first region (25a).

[0059] According to the present embodiment, a gap (G) is provided between the side (20c) of the heater part (20) and the side wall surface (15c) of the groove part (15). Additionally, the buffer layer (25) has a third region (25c) that overlaps with the gap (G) when viewed in the thickness direction. Furthermore, the thermal expansion coefficient of the insulating material constituting the buffer layer (25) is greater than the thermal expansion coefficient of the ceramic material constituting the pair of ceramic plates (11, 12). Because of this, when the pair of ceramic plates (11, 12) are hot-pressed to form an integral, the insulating material of the first region (25a) and the second region (25b) expands and extends toward the third region (25c), and the insulating material of the third region (25c) is pushed out into the gap (G). Accordingly, when heating and pressurizing, a portion of the pressure applied to the pair of ceramic plates (11, 12) escapes toward the third region (25c), thereby reducing the pressure applied to the first opposing surface (11f) and the second opposing surface (12f). As a result, damage to the pair of ceramic plates (11, 12) can be suppressed. Because of this, the proportion of the groove (15) when viewed in the thickness direction of the electrostatic chuck member (2) can be widened, the heater portion (20) can be densely arranged inside the electrostatic chuck member (2), and the mounting surface (2s) can be controlled to a high temperature and a uniform temperature, thereby providing an electrostatic chuck member (2).

[0060] According to the present embodiment, the buffer layer (25) has a greater coefficient of thermal expansion than the ceramic plates (11, 12). Thus, when a pair of ceramic plates (11, 12) are integrated by hot pressing, the buffer layer (25) expands more thermally than the ceramic plates (11, 12) to fill the space between the pair of ceramic plates (11, 12), thereby suppressing the occurrence of a gap between the ceramic plates (11, 12). Furthermore, a portion of the buffer layer (25) can escape into the gap (G) between the side (20c) of the heater part (20) and the side wall surface (15c) of the groove part (15). Because of this, the buffer layer (25) does not apply excessive stress between the ceramic plates (11, 12) due to thermal expansion. That is, according to the present embodiment, by making the coefficient of thermal expansion of the buffer layer (25) greater than that of the ceramic plates (11, 12) and arranging them to overlap the gap (G) when viewed in the thickness direction, it is possible to suppress the occurrence of a gap between the ceramic plates (11, 12) and suppress the application of excessive stress between the ceramic plates (11, 12). That is, according to the present embodiment, a highly reliable electrostatic chuck member (2) can be provided that suppresses damage to the ceramic plates (11, 12) and the gap between the ceramic plates (11, 12).

[0061] In this embodiment, the width dimension (W4) of the heater portion (20) is preferably at least twice the distance (W1) between the groove portions (15) where the heater portion (20) is placed. By making the width dimension (W4) of the heater portion (20) larger than the distance (W1) between the groove portions (15), the area occupied by the groove portion (15) on the second opposing surface (12f) increases. Because of this, it becomes possible to densely arrange the heater portion (20) on the mounting surface (2s) when viewed in the thickness direction, while the area of ​​the second opposing surface (12f) decreases, making it easier for damage to occur to a pair of ceramic plates (11, 12) during hot pressing. In the electrostatic chuck member (2) of the present embodiment, the load applied to the first opposing surface (11f) and the second opposing surface (12f) of a pair of ceramic plates (11, 12) is reduced by the action of the buffer layer (25). Because of this, even if the width dimension (W4) of the heater part (20) is more than twice the distance (W1) between the groove parts (15), damage to the pair of ceramic plates (11, 12) can be suppressed. According to the present embodiment, by making the width dimension (W4) of the heater part (20) more than twice the distance (W1) between the groove parts (15), it becomes possible to control the mounting surface (2s) to a sufficiently high temperature and a uniform temperature, and also to suppress damage to the pair of ceramic plates (11, 12) by the action of the buffer layer (25). The width dimension (W4) may be 2.5 times or more, 3 times or more, 4 times or more, with respect to the distance (W1), as needed.

[0062] In the electrostatic chuck member (2) of the present embodiment, a gap (G) is provided between the side (20c) of the heater part (20) and the side wall surface (15c) of the groove part (15). Because of this, the amount of heat transferred from the heater part (20) to the pair of ceramic plates (11, 12) in the part corresponding to the gap (G) is locally lowered, and there is a concern that the temperature of the mounting surface (2s) will be lowered in the part overlapping with the gap (G) when viewed in the thickness direction. The inventors carefully examined this concern and found that when the distance (H) (see FIG. 1) from the heater part (20) to the mounting surface (2s) is sufficiently large relative to the width dimension (d1) of the gap (G), the non-uniformity of the temperature of the mounting surface (2s) caused by the gap (G) hardly occurs. More specifically, if the distance (H) (see FIG. 1) from the heater part (20) to the mounting surface (2s) is 10 times or more with respect to the width dimension (d1) of the gap (G), the influence of the gap (G) on the temperature uniformity of the mounting surface (2s) can be ignored. The distance (H) may, if necessary, be 15 times or more, 20 times or more, 30 times or more with respect to the width dimension (d1).

[0063] As shown in FIG. 3, in this embodiment, the width dimension (d1) of the gap (G) in the opening (15a) of the groove (15) is preferably larger than the thickness dimension (t3) of the portion (first region (25a)) that is sandwiched between a pair of ceramic plates (11, 12) of the buffer layer (25). By making the width dimension (d1) of the gap (G) wider than the thickness dimension (t3) of the first region (25a), it becomes easier to sufficiently push the buffer layer (25) into the gap (G) by the pressure received in the first region (25a). That is, it becomes easier to release the force received in the first region (25a) to the third region (25c). As a result, it becomes easier to reduce the load received by the pair of ceramic plates (11, 12) in the portion in contact with the first region (25a), thereby suppressing damage to the pair of ceramic plates (11, 12).

[0064] As described above, the thermal expansion coefficient (α) of the insulating material constituting the buffer layer (25) of the present embodiment 25 (to be defined as) the coefficient of thermal expansion (α) of the ceramic material constituting a pair of ceramic plates (11, 12). 11 is greater than (α 25 ≥α 11 Also, the coefficient of thermal expansion α of the ceramic material constituting a pair of ceramic plates (11, 12). 11 Regarding the thermal expansion coefficient α of the insulating material constituting the buffer layer (25). 25 The ratio α 25 / α 11 It is preferable that it be between 1.1 and 2.0 (1.1≤α 25 / α 11 Ratio of coefficients of thermal expansion α ≤2.0). 25 / α 11 If this is excessively large, the shear stress generated at the interface between the buffer layer (25) and the first ceramic plate (11) and at the interface between the buffer layer (25) and the second ceramic plate (12) when thermal expansion occurs increases, and there is a risk that the bonding between the members at the interface will become unstable. Meanwhile, the ratio α of the coefficient of thermal expansion 25 / α 11 If this is excessively small, there is a concern that the function of releasing pressure acting between a pair of ceramic plates (11, 12) into the gap (G) due to the thermal expansion of the buffer layer (25) may not function sufficiently. Ratio α of the coefficient of thermal expansion 25 / α 11 By setting it to the range described above, the load applied to a pair of ceramic plates (11, 12) during hot pressing can be reduced while stabilizing the bonding between the members. Also, the ratio α of the coefficients of thermal expansion 25 / α 11 For the same reason, it is more desirable that it be between 1.3 and 1.7 (1.3≤α 25 / α 11 ≤1.7). The above ratio may be 1.2 or more and 1.8 or less, or 1.4 or more and 1.6 or less, as needed.

[0065] The electrostatic chuck member (2) of the present embodiment is formed by processing a pair of pre-sintered ceramic plates (11, 12) to form a groove (15), placing a heater part (20) within the groove (15), and joining the ceramic plates (11, 12) by a hot press. According to the present embodiment, compared to the case where the heater part (20) is formed when stacking uncured green sheets (unfired flexible ceramic substrates) and the heater part (20) is embedded inside the green sheets by sintering them, it is easier to form the heater part (20) with a uniform width and thickness over the entire length. Therefore, according to the present embodiment, compared to the case where green sheets are used, the resistance value of the heater part (20) can be made uniform along the length direction, and consequently, the amount of heat generated by the heater part (20) can be made uniform along the length direction. In addition, according to the present embodiment, in order to integrate the pre-sintered ceramic plates (11, 12), it is easy to suppress non-uniformity in plate thickness due to sintering, and compared to the case where a green sheet is used, it is also possible to suppress non-uniformity in the distance from the heater part (20) to the mounting surface (2s). That is, according to the electrostatic chuck member (2) of the present embodiment, compared to the case where an electrostatic chuck member with a built-in heater part is formed using a green sheet, the temperature of the mounting surface (2s) can be adjusted with high precision.

[0066] In addition, each dimension of the heater portion (20) and the groove portion (15) of the present embodiment can be confirmed by cutting the electrostatic chuck member (2) in the thickness direction and observing the cross-section. It is preferable to confirm the pattern of the heater portion (20) within the electrostatic chuck member (2) by non-destructive inspection such as ultrasonic inspection from the thickness direction, and to measure each of these dimensions by cutting the cross-section along the width direction of the heater portion (20).

[0067] (Variation Example 1)

[0068] FIGS. 4 and FIGS. 5 are partial cross-sectional views showing an electrostatic chuck member (102) of Variant Example 1 that can be employed in the above-described embodiment, FIG. 4 shows the appearance before integration, and FIG. 5 shows the appearance after integration. In addition, the cross-sections shown in FIGS. 4 and FIG. 5 are cross-sections perpendicular to the longitudinal direction of the heater part (20).

[0069] The electrostatic chuck member (102) of this modified example has a different configuration of the buffer layer (125) compared to the embodiment described above. In addition, in the description of each embodiment described below, components of the same form as those in the previously described embodiment are given the same reference numerals and their descriptions are omitted.

[0070] As shown in FIG. 4, the buffer layer (125) of the present modified example is applied to the second ceramic plate (12) in a non-sintered paste state and sintered while sandwiched between the first ceramic plate (11) and the second ceramic plate (12). A groove (15) is formed on the second opposing surface (12f) of the second ceramic plate (12). The non-sintered buffer layer (125) is applied not only to the second opposing surface (12f) but also to the inner wall surface of the groove (15). Accordingly, a portion of the buffer layer (125) is formed along the inner surface of the groove (15).

[0071] As shown in FIG. 5, the buffer layer (125) of the present modified example has a first region (125a) sandwiched between the first opposing surface (11f) and the second opposing surface (12f), a second region (125b) disposed between the bottom wall surface (15b) of the groove portion (15) and the bottom surface (20b) of the heater portion (20), and a third region (125c) located between the first region (125a) and the second region (125b). The third region (125c) extends along the side wall surface (15c) of the groove portion (15). The third region (125c) is disposed within the gap (G). That is, in the present modified example as well, at least a portion (the third region (125c) of the present modified example) of the buffer layer (125) overlaps with the gap (G) when viewed in the thickness direction.

[0072] According to the present variation, when a pair of ceramic plates (11, 12) are integrated by hot pressing in the same manner as the above-described embodiment, the insulating material of the first region (125a) and the second region (125b) expands and extends toward the third region (125c), and the insulating material of the third region (125c) expands in the gap (G). Accordingly, when heating and pressurizing, a portion of the pressure applied to the pair of ceramic plates (11, 12) escapes toward the third region (125c), thereby reducing the pressure applied to the first opposing surface (11f) and the second opposing surface (12f). This allows for the suppression of damage to the pair of ceramic plates (11, 12) during the hot pressing process.

[0073] In addition, according to the present modification, the third region (125c) is positioned along the side wall surface (15c) of the groove (15), thereby filling in a portion of the gap (G) between the side wall surface (15c) of the groove (15) and the side surface (20c) of the heater (20). This allows the air layer provided inside the electrostatic chuck member (102) to be reduced, making it easier to increase the uniformity of the temperature of the mounting surface (2s).

[0074] Additionally, the buffer layer (125) may have a region located between the heater portion (20) and the first opposing surface (11f), in addition to the first region (125a), the second region (125b), and the third region (125c). Also, the buffer layer (125) may have a portion of any one of the first region (125a), the second region (125b), and the third region (125c) omitted.

[0075] (Variation Example 2)

[0076] FIG. 6 is a partial cross-sectional view showing an electrostatic chuck member (202) of variant example 2 that can be employed in the above-described embodiment. Compared to the above-described embodiment, the shape of the groove portion (215) of the electrostatic chuck member (202) of this variant example is mainly different.

[0077] In the same manner as the above-described embodiment, a groove (215) is provided on the second opposing surface (212f) of the second ceramic plate (212) of the present variation. A heater portion (20) is disposed in the groove (215). The groove (215) of the present variation has a cross-section that is approximately trapezoidal. The groove (215) has an opening (215a) that is covered by the first ceramic plate (11). The inner wall surface of the groove (215) has a bottom wall surface (215b) and a pair of side walls (215c). The bottom wall surface (215b) faces the opening side of the groove (215). The pair of side walls (215c) each extend upward from both ends in the width direction of the bottom wall surface (215b). A pair of side walls (215c) face each other in the width direction of the groove (215).

[0078] In this modified example, a pair of side wall surfaces (215c) are separated from each other as they face upward. That is, the side wall surface (215c) has an inclined surface (215t) that slopes in a direction that increases the width dimension of the groove (215) as it faces the opening side of the groove (215) in the depth direction of the groove (215). The inclined surface (215t) of this modified example is provided throughout the depth direction of the side wall surface (215c). The angle of the inclined surface relative to the bottom wall surface can be arbitrarily selected, for example, 40 degrees or more and less than 90 degrees, 50 degrees or more and less than 80 degrees, or 60 degrees or more and less than 70 degrees.

[0079] Here, the portion between the grooves (215) in the second ceramic plate (212) is called a wall portion (215w). According to this modified example, the width dimension of the wall portion (215w) is increased as it faces away from the first ceramic plate (11) in the thickness direction. Because of this, when a pair of ceramic plates (11, 212) are integrated in a hot press process, it becomes possible to support the force received from the upper surface of the wall portion (215w) at the lower portion of the wall portion (215w). In addition, the wall portion (215w) can disperse the force received from the first ceramic plate (11) on the upper surface to both sides in the width direction by extending the inclined surface (215t) outward in the width direction, thereby suppressing the localized application of pressure. This allows for the suppression of damage to the second ceramic plate (212) during the hot press process.

[0080] The width dimension (W3) of the inclined surface (215t) is smaller than the width dimension (d1) of the gap (G). Because of this, the heater portion (20) within the groove portion (215) is prevented from resting on the inclined surface (215t). Additionally, it is preferable that the width dimension (W3) of the inclined surface (215t) is larger than the thickness dimension (t3) of the portion (first region (25a)) that is inserted between a pair of ceramic plates (11, 212) of the buffer layer (25). In this way, by securing a sufficiently large width dimension (W3) of the inclined surface (215t), the effect of dispersing the force applied to the wall portion (215w) by the inclined surface (215t) is sufficiently secured, thereby preventing damage to the second ceramic plate (212).

[0081] In addition, in the electrostatic chuck member (202) of the present modified example, the buffer layer (25) acts in the same way as in the above-described embodiment to suppress damage to a pair of ceramic plates (11, 212) during the hot press process. Also, in the present modified example, the width dimension (d1) of the gap (G) in the opening (215a) of the groove portion (215) is larger than the thickness dimension (t3) of the first region (25a), and damage to a pair of ceramic plates (11, 212) can be effectively suppressed.

[0082] (Variation Example 3)

[0083] FIG. 7 is a partial cross-sectional view showing an electrostatic chuck member (302) of variant example 3 that can be employed in the above-described embodiment. Compared to the above-described embodiment, the shape of the groove portion (315) of the electrostatic chuck member (302) of this variant example is mainly different. In addition, in the electrostatic chuck member (302) of this variant example, the cushioning layer (25) acts in the same way as in the above-described embodiment to suppress damage to a pair of ceramic plates (11, 312) during the hot press process.

[0084] In the same manner as the above-described embodiment, a groove (315) is provided on the second opposing surface (312f) of the second ceramic plate (312) of the present variation. A heater portion (20) is disposed in the groove (315). The groove (315) of the present variation has an opening (315a) that is covered by the first ceramic plate (11). The inner wall surface of the groove (315) has a bottom wall surface (315b), a pair of side walls (315c), and a pair of curved surfaces (315d). The bottom wall surface (315b) faces upward. The pair of side walls (315c) face each other in the width direction of the groove (315).

[0085] The curved surface (315d) is located at the boundary between the side wall surface (315c) and the bottom wall surface (315b). The curved surface (315d) smoothly connects the side wall surface (315c) and the bottom wall surface (315b). The curved surface (315d) of this modified example is curved with a constant radius of curvature (R). According to this modified example, the width dimension of the wall portion (315w) is increased as it faces away from the first ceramic plate (11) in the thickness direction. Because of this, when a pair of ceramic plates (11, 312) are integrated in a hot press process, it becomes possible to support the force received from the upper surface of the wall portion (315w) at the lower part of the wall portion (315w). Additionally, the wall portion (315w) is extended outward in the width direction at the curved surface (315d) located at the bottom, thereby dispersing the force received from the first ceramic plate (11) on the upper surface to both sides in the width direction, so that localized pressure can be suppressed. This prevents damage to the second ceramic plate (312) during the hot press process.

[0086] The radius of curvature (R) of the curved surface (315d) is smaller than the width dimension (d1) of the gap (G). Because of this, the heater portion (20) within the groove portion (315) is prevented from resting on the curved surface (315d). Additionally, it is preferable that the radius of curvature (R) of the curved surface (315d) is larger than the thickness dimension (t3) of the portion (first region (25a)) that is sandwiched between a pair of ceramic plates (11, 312) of the buffer layer (25). In this way, by securing a sufficiently large radius of curvature (R) of the curved surface (315d), the effect of dispersing the force applied to the wall portion (315w) by the curved surface (315d) is sufficiently secured, thereby preventing damage to the second ceramic plate (312). Additionally, in this modified example, although the case where the radius of curvature (R) of the curved surface (315d) is uniform was described, when the radius of curvature (R) of the curved surface (315d) changes continuously along the depth direction of the groove (315), it is preferable that all radii of curvature (R) are larger than the thickness dimension (t3) of the first region (25a).

[0087] Although embodiments and variations of the present invention have been described above, each component and combination thereof in the embodiments and variations is merely an example, and as described above, addition, omission, substitution, and other modifications of components are possible within the scope of the spirit of the present invention. Furthermore, the present invention is not limited by the embodiments.

[0088] For example, the buffer layer (125) of deformation example 1 may be applied to the electrostatic chuck member (202, 302) having the groove portion (215, 315) of deformation examples 2 and 3. Also, the curved surface (315d) of deformation example 3 may be applied to the groove portion (215) having the inclined surface (215t) of deformation example 2.

[0089] In the above-described embodiments and variations thereof, the above-described configuration is applied over the entire length of the heater portion (20) and the groove portion (15, 215) in which the heater portion (20) is received. However, the above-described configuration may be adopted in at least a part of the heater portion (20) and the groove portion (15, 215), and in that case, the effect of suppressing damage to the vicinity of the corresponding part can be obtained. Explanation of the symbols

[0090] 1… Electrostatic chuck device 2, 102, 202, 302… Electrostatic chuck member (ceramic assembly) 11… First ceramic plate, 11a… First plate portion 11b… Second plate portion 11c… Third plate portion 11d… First bonding layer 11e… Second bonding layer 11f… First opposing surface 12, 212, 312… Second ceramic plate 12f… Second opposing surface 13… Electrostatic adsorption electrode 15, 215, 315… Groove portion 15a, 215a, 315a… Opening portion 15b, 215b, 315b… Bottom wall surface 15c, 215c, 315c… Side wall surface 16A… First power supply terminal 16B… Second power supply terminal 18… Insulator 19… Gas flow path 19a… First gas hole 19b… Second gas hole 19c… Conduit 20… Heater section 20a… Upper surface of heater section 20b… Lower surface of heater section 20c… ​​Side surface of heater section 25, 125… Buffer layer 25a, 125a… First region of buffer layer 25b, 125b… Second region of buffer layer 25c, 125c… Third region of buffer layer 215t… Inclined surface 215w, 315w… Wall section 315d… Curved surface d1, W2, W3, W4… Width dimension G… Gap H, W1… Distance R… Radius of curvature t1… Depth dimension t3, t2a, t2b… Thickness dimension W… Wafer Z… Thickness direction

Claims

Claim 1 A ceramic composite having a pair of ceramic plates stacked in the thickness direction, a buffer layer disposed between the pair of ceramic plates, a strip-shaped heater portion disposed between the pair of ceramic plates and within a groove portion provided in at least one of the pair of ceramic plates, wherein the side surface of the heater portion and the side wall surface of the groove portion face each other with a gap interposed therebetween, and the buffer layer is made of an insulating material having a coefficient of thermal expansion greater than that of the ceramic material constituting the pair of ceramic plates, and at least a portion overlaps with the gap when viewed in the thickness direction. Claim 2 A ceramic composite according to claim 1, wherein the width dimension of the gap in the opening of the groove is larger than the thickness dimension of the portion of the buffer layer that is sandwiched between the pair of ceramic plates. Claim 3 A ceramic composite according to claim 1, wherein the ratio of the thermal expansion coefficient of the insulating material to the thermal expansion coefficient of the ceramic material is 1.1 or more and 2.0 or less. Claim 4 A ceramic composite according to claim 1, wherein the width dimension of the heater portion is at least twice the distance between the groove portions in which the heater portion is disposed. Claim 5 A ceramic composite according to claim 1, wherein a portion of the buffer layer is disposed in the gap. Claim 6 A ceramic composite according to claim 1, wherein the side wall surface of the groove portion has an inclined surface that is inclined in a direction that increases the width dimension of the groove portion as it faces the opening side of the groove portion in the depth direction of the groove portion. Claim 7 In claim 6, the width dimension of the inclined surface is greater than the thickness dimension of the portion of the buffer layer sandwiched between the pair of ceramic plates. Claim 8 A ceramic composite according to claim 1, wherein the inner wall surface of the groove portion has, in addition to a pair of side walls, a bottom wall surface facing the opening side of the groove portion and a pair of curved surfaces located at the boundary between the side walls and the bottom wall surface and smoothly connecting the side walls and the bottom wall surface. Claim 9 In claim 8, the radius of curvature of the curved surface is greater than the thickness of the buffer layer, in a ceramic composite. Claim 10 A ceramic composite according to claim 1, wherein the thickness dimension of the heater portion is greater than the depth dimension of the groove portion. Claim 11 An electrostatic chuck device having a ceramic assembly described in any one of claims 1 to 10.

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