Ceramic joined body and electrostatic chuck device

Abstract

This ceramic joined body comprises a first ceramic plate and a second ceramic plate that are laminated in a thickness direction, and a belt-form heater part that is positioned between the first ceramic plate and the second ceramic plate. The second ceramic plate is provided with a plurality of groove parts in which the heater part is accommodated and which are arranged in a width direction, and a wall part that is positioned between the groove parts and projects to the bottom wall surface of the groove parts. The distal-end surface of the wall part is positioned on the width-direction outer side of the groove parts with respect to the bottom wall surface.

Description

Ceramic bonded body and electrostatic chuck device

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

[0002] Electrostatic chucks are used in semiconductor manufacturing processes to hold semiconductor wafers in a vacuum environment. The electrostatic chucks place a plate-shaped sample, such as a semiconductor wafer, on a mounting surface, and generate an electrostatic force between the plate-shaped sample and an internal electrode to attract and fix the sample. Known electrostatic chucks include a heater embedded in a ceramic bonded body on which the mounting surface is formed, and the heater heats the mounting surface (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 9-82786

[0004] In recent semiconductor manufacturing processes, there has been an increasing demand for etching with a high aspect ratio. To achieve this, the temperature of the coolant used to cool the wafer needs to be lowered. However, lowering the coolant temperature increases the coolant's viscosity, potentially leading to temperature variations due to the flow path. This necessitates localized heating of areas where the temperature is too low. Meanwhile, as wafer processing becomes increasingly finer, a high etching selectivity ratio is required. However, achieving the required etching selectivity can sometimes be achieved with insufficient etching energy alone. To address this deficiency, a heater built into the ceramic bonded body can be used to increase the temperature of the processed substrate (plate-shaped sample) and provide additional energy. Therefore, there is a need to heat the support surface of an electrostatic chuck device to a higher temperature and maintain a uniform temperature. To meet these requirements, a heater can be precisely positioned relative to the support surface. For example, the heater is placed in a groove in one of a pair of ceramic plates and then sandwiched between the two plates. However, it has been found that if the heater portions are arranged closely on the mounting surface, the strength of the areas of the ceramic plate arranged between the heater portions may be insufficient, making the ceramic plate more susceptible to serious damage.

[0005] An object of the present invention is to provide a ceramic bonded body and an electrostatic chuck device in which damage to the ceramic plate is suppressed.

[0006] The present invention includes the following items [1] to

[11] . Two or more of the following items [1] to

[11] may be preferably combined as necessary. [1] A ceramic joined body comprising: a first ceramic plate and a second ceramic plate stacked in a thickness direction; and a strip-shaped heater portion located between the first ceramic plate and the second ceramic plate, wherein the second ceramic plate has a plurality of grooves aligned in a width direction thereof and a plurality of wall portions located between adjacent grooves and protruding from bottom wall surfaces of the grooves, the heater portion is housed in the grooves, and the wall portions have tip surfaces located outward of the bottom wall surface in the width direction of the grooves. [2] The ceramic bonded body according to [1], wherein the groove has a sidewall surface, the sidewall surface having a first region extending in the thickness direction and a second region located closer to the first ceramic plate than the first region and connected to the tip surface, the second region inclining outward in the width direction of the groove as it approaches the first ceramic plate. [3] The ceramic bonded body according to [2], wherein the second region is a curved surface whose inclination angle with respect to the thickness direction increases as it approaches the first ceramic plate, and the second region is smoothly connected to the first region and the tip surface. [4] The ceramic bonded body according to [1] or [2], wherein the dimension of the tip surface in the width direction is 2500 μm or less. [5] The ceramic bonded body according to any one of [1] to [4], further comprising a buffer layer disposed between the first ceramic plate and the second ceramic plate. [6] The ceramic bonded body according to [5], wherein a side surface of the heater portion and a side wall surface of the groove face each other via a gap, the buffer layer is made of an insulating material having a thermal expansion coefficient larger than that of the ceramic material constituting the first ceramic plate and the second ceramic plate, and at least a portion of the buffer layer overlaps with the gap as viewed from the thickness direction. [7] The ceramic bonded body according to [6], wherein a dimension of the gap in the width direction at an opening of the groove is larger than a thickness dimension of a portion of the buffer layer sandwiched between the first ceramic plate and the second ceramic plate.[8] The ceramic bonded body according to [6] or [7], wherein a ratio of a thermal expansion coefficient of the insulating material constituting the buffer layer to a thermal expansion coefficient of the ceramic material constituting the first ceramic plate and the second ceramic plate is 1.1 or more and 2.0 or less. [9] The ceramic bonded body according to any one of [6] to [8], wherein a dimension in the width direction of the heater portion is at least twice a dimension in the width direction of the tip surface.

[10] The ceramic bonded body according to any one of [6] to [9], wherein a part of the buffer layer is disposed in the gap.

[11] The ceramic bonded body according to any one of [6] to

[10] , wherein the sidewall surface of the groove has a first region extending in the thickness direction and a second region located closer to the first ceramic plate than the first region and connected to the tip surface, the second region inclining outward in the width direction of the groove as it approaches the first ceramic plate, and the width dimension of the second region is larger than the thickness dimension of a portion of the buffer layer sandwiched between the first ceramic plate and the second ceramic plate.

[12] The ceramic bonded body according to

[11] , wherein the sidewall surface of the groove has a third region located at a boundary between the first region and the bottom wall surface and smoothly connecting the first region and the bottom wall surface.

[13] The ceramic bonded body according to

[12] , wherein the radius of curvature of the third region is larger than the thickness dimension of a portion of the buffer layer sandwiched between the first ceramic plate and the second ceramic plate.

[14] The ceramic bonded body according to any one of [6] to

[13] , wherein a thickness dimension of the heater portion is larger than a thickness dimension of a portion of the buffer layer sandwiched between the first ceramic plate and the second ceramic plate.

[15] The ceramic bonded body according to any one of [1] to

[14] , wherein the heater portion is made of a thin metal plate.

[16] An electrostatic chuck device having the ceramic bonded body according to any one of [1] to

[15] .

[0007] According to one aspect of the present invention, there are provided a ceramic bonded body and an electrostatic chuck device in which damage to the ceramic plate is suppressed.

[0008] FIG. 1 is a schematic cross-sectional view illustrating a preferred example of an electrostatic chuck device according to an embodiment of the present invention. FIG. 2 is a partially enlarged view illustrating an example of a pair of ceramic plates of an electrostatic chuck member (ceramic bonded body) according to an embodiment of the present invention during manufacture, showing the state before integration. FIG. 3 is a partially enlarged view illustrating an example of a pair of ceramic plates of an electrostatic chuck member (ceramic bonded body) according to an embodiment of the present invention, showing the state after integration. FIG. 4 is a diagram schematically illustrating an example of a bonded portion between a first ceramic plate and a second ceramic plate according to an embodiment. FIG. 5 is a schematic partial cross-sectional view illustrating an example of an electrostatic chuck member according to Modification 1. FIG. 6 is a schematic partial cross-sectional view illustrating an example of an electrostatic chuck member according to Modification 2. FIG. 7 is a schematic partial cross-sectional view illustrating an example of an electrostatic chuck member according to Modification 3. FIG. 8 is a schematic partial cross-sectional view illustrating an example of an electrostatic chuck member according to Modification 4. FIG. 9 is a diagram schematically illustrating a bonded portion between a first ceramic plate and a second ceramic plate according to a comparative example.

[0009] The present invention provides a ceramic bonded body including a first ceramic plate and a second ceramic plate stacked in the thickness direction, and a strip-shaped heater portion positioned between the first ceramic plate and the second ceramic plate. The second ceramic plate has a plurality of grooves arranged in the width direction and accommodating the heater portion. Wall portions are located between the grooves and protrude from bottom walls of the grooves, and the leading ends of the walls are positioned outside the grooves in the width direction relative to the bottom walls. This invention also provides an electrostatic chuck device including the ceramic bonded body. Preferred embodiments of the electrostatic chuck device of the present invention will be described below with reference to the drawings. Note that in all of the drawings, the dimensions and proportions of the components may be changed as appropriate to make the drawings easier to understand. Note that the present embodiments are specifically described to facilitate understanding of the spirit of the invention and, unless otherwise specified, do not limit the present invention. For example, unless otherwise specified, conditions such as materials, positions, quantities, types, numbers, values, sizes, shapes, and proportions may be changed, added, or omitted as necessary. Among the embodiments and modified examples described below, preferred examples may be exchanged or shared with each other.

[0010] The Z axis is also shown in each figure. In this specification, the Z axis indicates the thickness direction of ceramic plates 11 and 12, which will be described later. In this specification, the Z axis extends in the vertical 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 the respective parts of the electrostatic chuck device 1 will be described. Note that the vertical direction in this specification is used merely to simplify the description, and does not limit the posture of the electrostatic chuck device 1 during use.

[0011] 1 is a schematic cross-sectional view showing a preferred example of an electrostatic chuck device 1 according to this embodiment. The electrostatic chuck device 1 includes an electrostatic chuck member (ceramic bonded body) 2 having a mounting surface 2s on which a wafer (sample) W is mounted, a base 3 supporting the electrostatic chuck member 2 from the side opposite the mounting surface 2s, a plurality of first power supply terminals 16A, and a plurality of second power supply terminals 16B. A focus ring surrounding the wafer W may be disposed on the outer periphery of the upper surface of the electrostatic chuck member 2.

[0012] The electrostatic chuck device 1 is provided with a gas flow path 19. The gas flow path 19 has a first gas hole 19a, a second gas hole 19b, and a communication path 19c. The communication path 19c is located inside the electrostatic chuck member 2 and extends along the planar direction of the mounting surface 2s. The communication path 19c is provided in a second bonding layer 11e (described later). The first gas hole 19a extends downward from the communication path 19c and is connected to an inlet for a heat transfer gas (not shown) at the lower end portion 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 communication path 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 the communication path 19c. A heat transfer gas flows through the gas flow path 19. The heat transfer gas is, for example, a cooling gas such as He. The heat transfer gas is supplied to the mounting surface 2s through the gas flow passage 19 and cools the wafer W mounted on the mounting surface 2s.

[0013] The electrostatic chuck member 2 is disk-shaped. The electrostatic chuck member 2 includes a pair of ceramic plates 11, 12, an electrostatic attraction electrode 13, a buffer layer 25, and a heater section 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 upper one will be referred to as the first ceramic plate 11 and the lower one will be referred to as the second ceramic plate 12. A mounting surface 2s of the electrostatic chuck member 2 is provided on the first ceramic plate 11.

[0014] The first ceramic plate 11 has a circular plate shape in a plan view. An electrostatic attraction 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. For example, a plurality of protrusions (not shown) are formed at predetermined intervals on the mounting surface 2s. The mounting surface 2s supports the wafer W at the tips of the plurality of protrusions. The first opposing surface 11f faces the second ceramic plate 12.

[0015] The first ceramic plate 11 includes 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 portions whose thickness direction is the Z-axis direction. The first plate portion 11a, the second plate portion 11b, and the third plate portion 11c are stacked in this order from top to bottom in the thickness direction.

[0016] A first bonding layer 11d and an electrostatic attraction electrode 13 are disposed between the first plate portion 11a and the second plate portion 11b. The first bonding layer 11d is provided so as to surround the electrostatic attraction electrode 13. The first bonding layer 11d bonds the first plate portion 11a and the second plate portion 11b together. The electrostatic attraction electrode 13 extends in a layered form along a plane perpendicular to the thickness direction (Z-axis direction) of the first ceramic plate 11. As a result, the electrostatic attraction electrode 13 is embedded inside the first ceramic plate 11.

[0017] 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 communication passage 19c for the gas flow passage 19 is provided in the second bonding layer 11e. 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.

[0018] The first ceramic plate 11 of the present embodiment is formed, for example, by applying unsintered pastes constituting the electrostatic attraction electrode 13, the first bonding layer 11 d, and the second bonding layer 11 e between the first plate portion 11 a, the second plate portion 11 b, and the third plate portion 11 c, which are sintered and formed in advance, respectively, and then stacking these in the thickness direction to form a laminate, which is then integrated by hot pressing under high temperature and high pressure.

[0019] The first ceramic plate 11 is made of a ceramic material, which includes 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. In other words, the first ceramic plate 11 is made of a ceramic material. Examples of the ceramic material that makes up the first ceramic plate 11 include aluminum oxide (Al ２ O ３ ) sintered body, aluminum nitride (AlN) sintered body, aluminum oxide (Al ２ O ３ A sintered body of silicon carbide (SiC) composite is preferably 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 made of materials having the same composition. However, two or more or all of 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 may be made of different materials.

[0020] The electrostatic attraction electrode 13 is a composite of an insulating material and a conductive material. The insulating material contained in the electrostatic attraction electrode 13 is not particularly limited, but may be, for example, aluminum oxide (Al ２ O ３ ), aluminum nitride (AlN), silicon nitride (Si ３ N ４), yttrium (III) oxide (Y ２ O ３ ), yttrium aluminum garnet (YAG) and SmAlO ３ The conductive material is preferably at least one selected from the group consisting of, but is not particularly limited to, molybdenum carbide (Mo ２ It is preferable that the material is at least one selected from the group consisting of molybdenum (Mo), tungsten carbide (WC), tungsten (W), tantalum carbide (TaC), tantalum (Ta), silicon carbide (SiC), carbon black, carbon nanotubes, and carbon nanofibers.

[0021] A first power supply terminal 16A is connected to the electrostatic chucking electrode 13. The first power supply terminal 16A applies a voltage to the electrostatic chucking electrode 13. When a voltage is applied to the electrostatic chucking electrode 13, an electrostatic chucking force is generated that holds the plate-shaped sample on the mounting surface 2s. The first power supply terminal 16A penetrates the second plate portion 11b, the second bonding layer 11e, the third plate portion 11c, the buffer layer 25, the second ceramic plate 12, and the base 3. A cylindrical insulating insulator 18 is attached to a portion of the outer periphery of the first power supply terminal 16A. The insulator 18 insulates the first power supply terminal 16A from the base 3.

[0022] The second ceramic plate 12 of this embodiment has a circular plate shape in a plan view. The second ceramic plate 12 has a second opposing surface 12 f facing upward. The second opposing surface 12 f faces the first opposing surface 11 f of the first ceramic plate 11 in the up-down direction.

[0023] A plurality of grooves 15 are provided on the second opposing surface 12f. The grooves 15 are formed by any method, such as milling, laser processing, or sandblasting. The plurality of grooves 15 are aligned along the width direction of the groove. For example, the plurality of grooves 15 may extend in an arc shape in the circumferential direction of the second ceramic plate 12 and be aligned in the radial direction of the second ceramic plate 12. In this embodiment, the plurality of grooves 15 may be portions of a single groove or portions of different grooves. That is, the internal spaces of the plurality of grooves 15 may be connected to each other or may be isolated from each other. It is preferable that the number of grooves and the number of heater units are the same, but this is not limited to this example.

[0024] In this embodiment, the width and depth of each of the grooves 15 are uniform over the entire length. However, the width and depth of each of the grooves 15 do not necessarily have to be uniform. Also, in this embodiment, the width and depth of each of the grooves 15 are the same as each other. However, the width and depth of each of the grooves 15 do not necessarily have to be the same as each other.

[0025] The groove portion 15 accommodates a strip-shaped heater portion 20. The heater portion 20 is located between the first ceramic plate 11 and the second ceramic plate 12. In a plan view, the groove portion 15 is formed in a pattern shape that is substantially the same as the pattern shape of the heater portion 20. The width dimension of the groove portion 15 is slightly larger than the width dimension of the heater portion 20. When multiple groove portions 15 are portions of multiple grooves, heater portions 20 may be disposed individually in each of the multiple groove portions 15. For example, when multiple grooves that are not connected to each other are formed, multiple heater portions 20 may be disposed in each groove. The pattern shape of the heater portion 20 may be selected arbitrarily.

[0026] In this embodiment, the groove 15 is provided only in the second ceramic plate 12, which is the lower of the pair of ceramic plates 11 and 12. However, the groove 15 may be provided in at least one of the pair of ceramic plates 11 and 12. That is, the groove 15 may be provided only in the first opposing surface 11f of the first ceramic plate 11, and not in the second ceramic plate 12. Alternatively, the groove 15 may be provided in both the first opposing surface 11f and the second opposing surface 12f of the pair of ceramic plates 11 and 12. In this case, the grooves 15 provided in the pair of ceramic plates 11 and 12 have the same shape and overlap each other when viewed in the thickness direction. In this case, the heater unit is disposed within the space formed by the overlapping groove 15 of the first ceramic plate 11 and the groove 15 of the second ceramic plate 12. In this case, the heater unit may be disposed in one or both of the opposing grooves 15, and a buffer layer, described later, may also be disposed as necessary.

[0027] The second ceramic plate 12 has wall portions 17 located between adjacent groove portions 15 arranged in the width direction. The wall portions 17 are portions of the second ceramic plate 12 located between adjacent groove portions 15. The wall portions 17 protrude toward the first ceramic plate 11 relative to the bottom wall surfaces 15b of the groove portions 15. The wall portions 17 separate adjacent groove portions 15 in the width direction. The wall portions 17 extend in a rib-like manner along the length of the groove portions 15. The wall portions 17 have a tip surface 17a facing the first ceramic plate 11. The tip surface 17a extends along a plane perpendicular to the thickness direction of the second ceramic plate 12. The tip surface 17a is joined to the first opposing surface 11f of the first ceramic plate 11 via a buffer layer 25.

[0028] The second ceramic plate 12 is made of a ceramic material. Examples of the ceramic material that constitutes the second ceramic plate 12 include aluminum oxide (Al ２ O ３ ) sintered body, aluminum nitride (AlN) sintered body, aluminum oxide (Al ２ O ３A silicon carbide (SiC) composite sintered body or the like is preferably used. In this embodiment, the second ceramic plate 12 is made of the same material as the first ceramic plate 11. However, the second ceramic plate 12 may be made of a material different from that of the first ceramic plate 11. Furthermore, the second ceramic plate 12 in this embodiment is made of a single sintered body. However, the second ceramic plate 12 may be made by stacking and bonding multiple sintered bodies in the thickness direction. In this case, the multiple sintered bodies may be made of different ceramic materials.

[0029] The heater portion 20 is located between the first ceramic plate 11 and the second ceramic plate 12. The heater portion 20 is disposed in a groove portion 15 formed in the second ceramic plate 12. The heater portion 20 has a strip-like shape whose thickness direction coincides with the thickness direction of the pair of ceramic plates 11, 12. The number of heater portions 20 can be selected arbitrarily.

[0030] The heater unit 20 is composed of an arbitrarily selected resistance heating element. That is, the heater unit 20 generates heat when a current flows through it. The heater unit 20 of this embodiment is manufactured by processing, for example, a non-magnetic metal thin plate, such as an Inconel (registered trademark) thin plate, a titanium thin plate, a tungsten (W) thin plate, or a molybdenum (Mo) thin plate, into a desired heater shape, for example, a meandering strip-shaped conductive thin plate with an overall circular outline, using a method such as photolithography or laser processing. The heater unit 20 of this embodiment is arranged between the pair of ceramic plates 11 and 12 so as to have a meandering shape.

[0031] In the electrostatic chuck member 2 of this embodiment, the heater portion 20 is formed from a thin metal plate. However, the heater portion 20 may be formed from a composite of an insulating material and a conductive material, similar to the electrostatic attraction electrode 13. In this case, the heater portion 20 is formed by disposing unsintered paste for the heater portion in the groove 15 and sintering it in the groove 15 when the pair of ceramic plates 11 and 12 are integrated by hot pressing. By using a composite of an insulating material and a conductive material for the heater portion 20, stress applied from the heater portion 20 to the ceramic plates 11 and 12 when the ceramic plates 11 and 12 are integrated by hot pressing can be reduced, thereby suppressing damage to the pair of ceramic plates 11 and 12 during manufacturing. However, when a composite of an insulating material and a conductive material is used for the heater portion 20, precise temperature control over a wide range from low to high temperatures is difficult due to, for example, the difficulty of passing a large current through the heater portion 20. According to the electrostatic chuck member 2 of the present embodiment, by forming the heater portion 20 from a thin metal plate, it is possible to provide an electrostatic chuck member 2 that can precisely control the temperature of the mounting surface 2 s over a wide range. Furthermore, by forming the heater portion 20 from a thin metal plate, a load is likely to be applied to the pair of ceramic plates 11, 12 during manufacturing, but by adopting a shape of the groove portion 15 described below, damage to the pair of ceramic plates 11, 12 can be suppressed.

[0032] Second power supply terminals 16B are connected to both longitudinal ends of the heater section 20. The second power supply terminals 16B pass current through the heater section 20. The second power supply terminals 16B extend downward from the heater section 20. The second power supply terminals 16B penetrate the second ceramic plate 12 and the base 3. A cylindrical insulating insulator 18 is attached to part of the outer periphery of the second power supply terminal 16B. The insulator 18 insulates the second power supply terminal 16B from the base 3.

[0033] In this embodiment, the buffer layer 25 is disposed between the pair of ceramic plates 11 and 12. The buffer layer 25 bonds the pair of ceramic plates 11 and 12. The buffer layer 25 also bonds the first ceramic plate 11 and the heater portion 20.

[0034] The buffer layer 25 is made of an insulating material selected arbitrarily. Therefore, even if the buffer layer 25 is in contact with the heater portion 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 thermal expansion coefficient greater than that of the ceramic material constituting the pair of ceramic plates 11 and 12. The insulating material constituting the buffer layer 25 is, for example, high-purity alumina (Al ２ O ３ The thermal expansion coefficient of high-purity alumina is 7.1 × 10 －６ / K~8.2 x 10 －６ On the other hand, aluminum oxide (Al O ... ２ O ３ The thermal expansion coefficient of the silicon carbide (SiC) composite sintered body is 4.6 × 10 －６ / K~8.1 x 10 －６ When these are combined, consideration is given to ensuring that the respective thermal expansion coefficients satisfy the above-mentioned relationship. －６ ~13.4 x 10 －６ Silicon oxide (SiO ２ ) can also be adopted.

[0035] As described above, the first ceramic plate 11 has multiple components (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), and these components may be made of different ceramic materials. The thermal expansion coefficient of the insulating material making up the buffer layer 25 is only required to be greater than the thermal expansion coefficient of the ceramic material of the portion of the components making up the first ceramic plate 11 that contacts the buffer layer 25 (i.e., the third plate portion 11c). The second ceramic plate 12 may also have multiple components. When the second ceramic plate 12 is made up of multiple components made of different ceramic materials, the thermal expansion coefficient of the insulating material making up the buffer layer 25 is only required to be greater than the thermal expansion coefficient of the ceramic material of the portion of the components making up the second ceramic plate 12 that contacts the buffer layer 25.

[0036] In this embodiment, the buffer layer 25 is sintered by a process in which the first ceramic plate 11 and the second ceramic plate 12 are integrated by hot pressing under high temperature and high pressure. In this process, the buffer layer 25 is first applied in an unsintered paste form to the first opposing surface 11f of the first ceramic plate 11. The procedure for applying the buffer layer 25 paste to the first opposing surface 11f can be arbitrarily selected, and may be performed using a brush, spatula, trowel, or screen printing. Next, the first opposing surface 11f is placed opposite the second opposing surface 12f of the second ceramic plate 12, with the heater portion 20 positioned in the groove portion 15, and the first ceramic plate 11 and the second ceramic plate 12 are stacked in the thickness direction. Next, the pair of ceramic plates 11 and 12 are integrated by hot pressing under high temperature and high pressure. Through this process, the buffer layer 25 is bonded to the entire first opposing surface 11f. The buffer layer 25 is bonded to the tip surface 17a of the wall portion 17 of the second opposing surface 12f, and to the upper surface of the heater portion 20. The base 3 of this embodiment is preferably provided with a flow path therein for circulating a coolant as needed. Examples of the coolant flowing through the flow path include water, He gas, and N ２ Gas, fluorine-based inert liquid, etc. may be used. The base 3 may be fixed to the second ceramic plate 12 by an adhesive (adhesive layer). Examples of adhesives include, but are not limited to, acrylic resins, silicone resins, and epoxy resins. For example, the material forming the bonding portion (adhesive layer) may be an inorganic metal. In such a case, when the entire bonding portion is taken as 100 volume %, the bonding portion is preferably an alloy containing 50 volume % to 99.98 volume % of Al or Ag and 0.02 volume % to 40 volume % of at least one metal selected from the group consisting of Ti, Zr, and Hf.

[0037] 2 and 3 are enlarged partial views of the pair of ceramic plates 11, 12 near the heater portion 20, with Fig. 2 showing the state before integration and Fig. 3 showing the state after integration. The cross sections shown in Fig. 2 and 3 are cross sections perpendicular to the longitudinal direction of the heater portion 20.

[0038] As shown in Figure 2, the groove portion 15 of this embodiment has a substantially rectangular cross section. The groove portion 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 groove portion 15 also has inner wall surfaces, namely a bottom wall surface 15b and a pair of side wall surfaces 15c. The bottom wall surface 15b faces the opening side of the groove portion 15. The bottom wall surface 15b extends along a plane perpendicular to the thickness direction of the second ceramic plate 12. The side wall surfaces 15c also serve as side surfaces of the wall portion 17.

[0039] The pair of side wall surfaces 15c extend upward from both widthwise ends of the bottom wall surface 15b and face each other in the width direction of the groove portion 15. The side wall surface 15c has a first region 15ca and a second region 15cb that are aligned in the thickness direction of the second ceramic plate 12.

[0040] The first region 15ca is continuous with the bottom wall surface 15b and extends in the thickness direction of the second ceramic plate 12. In this embodiment, the first region 15ca is perpendicular to the bottom wall surface 15b.

[0041] The second region 15cb is located closer to the first ceramic plate 11 than the first region 15ca. The second region 15cb is provided in the opening 15a of the groove 15. The second region 15cb is continuous at its lower end with the first region 15ca. The second region 15cb is also continuous at its upper end with the tip surface 17a of the wall 17.

[0042] The second region 15cb is inclined toward the outer side of the groove 15 in the width direction as it approaches the first ceramic plate 11. That is, the second region 15cb is inclined toward the outer side of the groove 15 in the width direction as it approaches the first ceramic plate 11. Therefore, the second region 15cb is inclined with respect to the thickness direction of the second ceramic plate 12. In this embodiment, the second region 15cb is a curved surface whose inclination angle with respect to the thickness direction increases as it approaches the first ceramic plate 11. This allows the second region 15cb to smoothly connect to the first region 15ca and the tip surface 17a. In this way, the second region 15cb may have a shape with rounded corners or form a gently curved surface. Note that the inclination angle with respect to the thickness direction in the first region 15ca is 0°.

[0043] Here, the effects of providing the second region 15cb will be specifically described with reference to FIGS. 4 and 9 . FIG. 4 is a diagram schematically illustrating the bonded portion between the first ceramic plate 11 and the second ceramic plate 12 of this embodiment. FIG. 9 is a diagram for comparison, and is a diagram schematically illustrating the bonded portion between the first ceramic plate 911 and the second ceramic plate 912 of a comparative embodiment to explain the advantages of this embodiment. Note that in the following description based on FIGS. 4 and 9 , the buffer layer will be omitted to simplify the effects. However, even when a buffer layer is interposed between the first ceramic plate and the second ceramic plate, similar stresses act between the first ceramic plate and the second ceramic plate in this embodiment and the comparative embodiment.

[0044] 9, a second ceramic plate 912 of the comparative embodiment is provided with a groove 915 and a wall 917, similar to the embodiment. The groove 915 has a bottom wall 915b and a pair of side wall 915c as inner wall surfaces. In this comparative embodiment, the side wall 915c is perpendicular to the bottom wall 915b over the entire thickness direction. The opposing side wall 915c are parallel to each other.

[0045] The leading end surface 917a of the wall portion 917 is a flat surface formed along a plane perpendicular to the thickness direction of the second ceramic plate 912. However, the leading end surface 917a has a slight inclination and irregularities on a microscopic level. As a result, when the first ceramic plate 911 and the second ceramic plate 912 are joined by hot pressing, the leading end surface 917a and the first opposing surface 911f do not make surface-to-surface contact but make localized contact. In particular, we will describe a case where the leading end surface 917a is inclined, resulting in "partial contact" in which the leading end surface 917a makes contact with the first opposing surface 911f at its widthwise end. In the comparative example shown in FIG. 9 , the leading end surface 917a makes contact with the first opposing surface 911f at contact point P, which is located at the left end in FIG. 9 .

[0046] When the first ceramic plate 911 and the second ceramic plate 912 of this comparative configuration are joined by hot pressing, thermal stress resulting from differences in shape, such as "uneven contact," occurs between the first ceramic plate 911 and the second ceramic plate 912. As shown in Fig. 9, for example, a widthwise stress toward the right in Fig. 9 is applied to the contact portion between the first ceramic plate 911 and the second ceramic plate 912, and the wall portion 917 is deformed by a small displacement Δ in the shear direction.

[0047] Furthermore, missing portions of crystal grains of the material (hereinafter referred to as cracks C) may occur on the sidewall surface 915c of the groove portion 915. Such cracks C alone do not have any effect on the performance of the electrostatic chuck member 902. However, the cracks C may become the starting points for cracks in the ceramic plate 12. A force F directed toward the contact point P is applied to the cracks C in FIG. 9 due to the thermal stress generated between the tip surface 917a and the first opposing surface 911f.

[0048] As shown in FIG. 9 , the force F can be expressed as a resultant force of an upward peeling shear stress Fa, which is a component in the thickness direction, and a horizontal stress Fb, which is a component in the width direction. In this comparative example, the contact point P is located almost directly above the crack C. Therefore, the angle between the force F and the upward peeling shear stress Fa is extremely small relative to the angle between the force F and the horizontal stress Fb. As a result, the upward peeling shear stress Fa is sufficiently larger than the horizontal stress Fb. The upward peeling shear stress Fa is a stress applied in a direction that widens the crack C, and this makes it easier for a crack originating from the crack C to propagate toward the interior of the wall portion 917. That is, in the electrostatic chuck member 902 of the comparative example, if a one-sided contact occurs between the tip surface 917a and the first opposing surface 911f, a crack is more likely to propagate toward the interior of the wall portion 917.

[0049] 4 and 5, when the leading end surface 17a of the wall portion 17 has a microscopic inclination, a portion of the leading end surface 17a may "contact unevenly" with the first opposing surface 11f. Also, in the groove portion 15 of this embodiment, a crack C may occur on the side wall surface 15c. Furthermore, in this embodiment, when the crack C and the uneven contact occur, thermal stress occurs between the leading end surface 17a and the first opposing surface 11f during the process of joining the first ceramic plate 11 and the second ceramic plate 12 by hot pressing, and a force F is applied to the crack C toward the contact point P.

[0050] However, in this embodiment, a second region 15cb is provided at the upper end of the side wall surface 15c. As a result, the leading edge surface 17a is offset outward in the width direction of the groove 15 relative to the bottom wall surface 15b, i.e., the leading edge surface 17a is positioned away from the bottom wall surface 15b in a plan view. Therefore, in this embodiment, as shown in FIG. 4, the upward peel shear stress Fa, which is the vertical component of the force F, is smaller than in the comparative embodiment shown in FIG. 9. On the other hand, the horizontal stress Fb, which is the horizontal component of the force F, is larger than in the comparative embodiment.

[0051] That is, according to this embodiment, it is possible to reduce the component (upward peel shear stress Fa) that propagates a crack originating from the crack C, thereby suppressing the crack from propagating inside the wall portion 17. This makes it possible to provide an electrostatic chuck member 2 that suppresses damage to the ceramic plates 11, 12. If a crack occurs inside the wall portion 17, the second ceramic plate 12 cannot support the first ceramic plate 11 at the wall portion 17, and distortion of the mounting surface 2s is likely to occur. Furthermore, since the crack makes it difficult for heat to be transmitted in the thickness direction of the second ceramic plate 12, the thermal uniformity of the mounting surface 2s may be deteriorated. According to this embodiment, it is possible to improve the thermal uniformity of the mounting surface 2s while suppressing distortion of the mounting surface 2s.

[0052] The widthwise distance d2 from the bottom wall surface 15b to the tip surface 17a (the width dimension W3 of the second region 15cb) is preferably 10% or more of the width dimension W1 of the tip surface 17a, and preferably 20% or more combined. If necessary, it may be 30% or more, 50% or more, 70% or more, or 90% or more. By making the distance d2 10% or more of the width dimension W1 of the tip surface 17a, even when the width of the tip surface 17a is narrowed and the surface pressure applied to the tip surface 17a is increased, the ratio of the widthwise distance from the crack C on the side wall surface 15c to the contact point P to the thicknesswise distance can be maintained within a preferred range, thereby further reducing the upward peel shear stress Fa. For the same reason, the widthwise distance d2 from the bottom wall surface 15b to the tip surface 17a is preferably 50 μm or more.

[0053] In this embodiment, the second region 15cb has a curved surface whose inclination angle with respect to the thickness direction increases toward the first ceramic plate 11, smoothly connecting to the first region 15ca and the tip surface 17a. Therefore, the second region 15cb does not form a discontinuous step at the boundary between the first region 15ca and the tip surface 17a, thereby preventing cracks C from forming at these boundaries. The radius of curvature R1 of the second region 15cb in this embodiment may be uniform or may vary throughout the entire second region 15cb. Furthermore, the radius of curvature R1 of the second region 15cb is preferably equal to or greater than the maximum crystal grain size of the ceramic material constituting the second ceramic plate 12 at any position in the second region 15cb. By setting the radius of curvature R1 of the second region 15cb to be equal to or greater than the maximum crystal grain size of the ceramic material, it is possible to prevent the formation of cracks C in the second region 15cb, which are the starting points of cracks due to the loss of crystal grains in the second region 15cb. Note that the maximum crystal grain size contained in the ceramic material is generally less than five times the average grain size of the particles contained in the ceramic material. Therefore, it is preferable that the radius of curvature R1 of the second region 15cb be equal to or greater than five times the average grain size of the ceramic material constituting the second ceramic plate 12. For example, in the case of Al constituting the second ceramic plate 12, ２ O ３When the average crystal grain size of the particles is 5 μm, the radius of curvature R1 of the second region 15cb is preferably 25 μm or more.

[0054] The second region 15cb of this embodiment can be formed by, for example, forming the groove 15 and then performing any suitable process, such as buffing, brushing, or sandblasting, to process and smoothly curve the corner between the side wall surface 15c and the tip surface 17a of the groove 15. In a typical electrostatic chuck member, the opening of the groove 15 is not chamfered solely for the purpose of removing cracks C. This is because even if cracks C of a grain size occur, they have little effect on the performance of the electrostatic chuck member unless they develop into cracks. Furthermore, the "damage to the ceramic plates 11, 12" suppressed by the electrostatic chuck member 2 of this embodiment does not refer to the cracks C that typically occur in ceramic plates, but rather to cracks that originate from the cracks C and extend across the wall portion 17. The process of forming the second region 15cb is not intended simply to remove the cracks C, but rather to suppress the occurrence of cracks originating from the remaining cracks C.

[0055] In this embodiment, the second region 15cb is curved. However, the second region 15cb may extend linearly. The second region 15cb may be flat instead of curved. Even in this case, the tip surface 17a can be positioned outside the bottom wall surface 15b in the width direction of the groove portion 15, thereby suppressing the progression of cracks originating from the crack C. In this case, the angle formed by the second region 15cb and the first region 15ca can be selected arbitrarily, and may be, for example, 100° or more and less than 180°, 120° or more and 170° or less, or 140° or more and 160° or less.

[0056] 2 and 3, the cross-sectional shape of the heater section 20 in the width direction is rectangular or approximately rectangular. The heater section 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 to connect the upper surface 20a and the lower surface 20b.

[0057] In this embodiment, the upper surface 20a of the heater portion 20 is covered with the buffer layer 25. The lower surface 20b of the heater portion 20 is in contact with the bottom wall surface 15b of the groove portion 15. As shown in Fig. 2, before integration, the thickness dimension t2a of the heater portion 20 before being embedded between the ceramic plate 11 and the electrostatic chuck member 2 by integration is larger than the depth dimension t1 of the groove portion 15. Therefore, the upper surface 20a of the heater portion 20 before being embedded is located above the tip surface 17a.

[0058] In this embodiment, as shown in FIG. 3 , when the heater portion 20 is integrated, it is sandwiched between the pair of ceramic plates 11 and 12 and is therefore deformed so as to be crushed in the thickness direction of the pair of ceramic plates 11 and 12. Therefore, the thickness dimension t2b of the heater portion 20 after embedding is smaller than the thickness dimension t2a (see FIG. 2 ) before embedding. Furthermore, the thickness dimension t2b of the heater portion 20 after embedding in the electrostatic chuck member 2 is slightly larger than the depth dimension t1 (see FIG. 2 ) of the groove portion 15. That is, in this embodiment, the thickness dimensions t2a and t2b of the heater portion 20 are larger than the depth dimension t1 of the groove portion 15 both before and after embedding by integration. Regarding the thickness of the buffer layer 25, the thickness between the first opposing surface 11f and the tip surface 17a (the thickness of the first portion 25a described below) is larger than the thickness between the heater portion 20 and the first opposing surface 11f (the thickness of the second portion 25b described below). According to this embodiment, during integration processing such as hot pressing, the heater portion 20 is sandwiched between the pair of ceramic plates 11 and 12 and compressed and deformed in the thickness direction. This allows the heater portion 20 to withstand the force applied between the pair of ceramic plates 11 and 12 during hot pressing, thereby reducing the force applied to the wall portion 17. This prevents damage to the pair of ceramic plates 11 and 12 during hot pressing. Note that the thickness dimensions t2a and t2b of the heater portion 20 before and after integration processing do not necessarily need to be greater than the depth dimension t1 of the groove portion 15. For example, even if the thickness dimensions t2a and t2b of the heater portion 20 are the same as or slightly smaller than the depth dimension t1 of the groove portion 15, the force applied to the wall portion 17 can be reduced by the effect of the buffer layer 25.

[0059] In this embodiment, the width W1 of the tip surface 17a of the wall portion 17 is preferably 100 μm or more and 2500 μm or less. If necessary, it may be 300 μm or more and 2100 μm or less, 500 μm or more and 1800 μm or less, or 700 μm or more and 1500 μm or less. By setting the width W1 of the tip surface 17a to 2500 μm or less, the proportion of the second opposing surface 12f occupied by the tip surface 17a can be reduced, and conversely, the proportion occupied by the groove portion 15 can be increased. This makes it easier to arrange the heater portion 20 densely when viewed from the thickness direction. Furthermore, in this embodiment, the width W1 of the wall portion 17 (W1 + W3 + W3) can be set to 500 μm or more, thereby ensuring the rigidity of the wall portion 17. The width can be selected as needed, and may be, for example, 700 μm or more, 1000 μm or more, 1500 μm or more, 2000 μm or more, 3000 μm or more, or 5000 μm or more.

[0060] As shown in FIG. 2 , the width W4 of the heater portion 20 is smaller than the width W2 of the groove portion 15 (the distance between adjacent tip surfaces 17a across the groove portion). The heater portion 20 is disposed approximately in the center of the width W2 of the groove portion 15. The side surface 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, gaps G are provided on both sides of the heater portion 20 in the width direction. The gaps G extend along the side surface 20c of the heater portion 20. The widths d1 of the gaps G on both sides of the heater portion 20 in the width direction are substantially equal to each other. The width W4 of the heater portion 20 is, for example, 1 mm or more and 6 mm or less. It may also be 2 mm or more and 5 mm or less, or 3 mm or more and 4 mm or less. The width d1 of the gap G is, for example, 100 μm or more and 300 μm or less. It may be 130 μm or more and 270 μm or 160 μm or more and 230 μm or more, etc. The width dimensions W4 and d1 of the heater portion 20 and the gap G are not limited to these values.

[0061] In this specification, the gap G refers to the region between the side surface 20c of the heater portion 20 and the side wall surface 15c of the groove portion 15, and an intervening material such as a buffer layer 25 may be disposed in this region. In other words, the gap G does not necessarily refer only to a space where nothing is disposed.

[0062] In this specification, the width dimension refers to the dimension in the width direction, which is the direction perpendicular to both the length direction of the target portion (heater portion 20, groove portion 15, gap G, etc.) and the thickness direction (Z-axis direction) of ceramic plates 11 and 12.

[0063] The buffer layer 25 has a first portion 25a sandwiched between the first opposing surface 11f of the first ceramic plate and the tip surface 17a of the wall portion 17, a second portion 25b disposed between the first opposing surface 11f and the upper surface 20a of the heater portion 20, and a third portion 25c located between the first portion 25a and the second portion 25b in the width direction. The third portion 25c is a region that overlaps with and penetrates into the gap G when viewed from the thickness direction of the pair of ceramic plates 11, 12. That is, at least a portion of the buffer layer 25 (the third portion 25c in this embodiment) overlaps with the gap G when viewed from the thickness direction. While the thicknesses of the first portion 25a and the second portion 25b are constant or nearly constant when viewed from the cross section, the thickness of the third portion 25c is not constant because it protrudes toward the space in the gap G.

[0064] As shown in FIG. 3 , in this embodiment, a buffer layer 25 is disposed between the pair of ceramic plates 11 and 12. As shown in FIG. 2 , the buffer layer 25 is sandwiched between the pair of ceramic plates 11 and 12 in an unsintered state and then sintered when the pair of ceramic plates 11 and 12 are hot-pressed together. Therefore, even if slight irregularities exist on the first opposing surfaces 11 f and the leading end surfaces 17 a of the pair of ceramic plates 11 and 12, the buffer layer 25 can absorb these irregularities. This prevents localized application of large forces to the first opposing surfaces 11 f and the leading end surfaces 17 a of the ceramic plates 11 and 12 and, conversely, prevents gaps from being formed. As a result, damage and gaps can be prevented from being formed at or near the interface between the pair of ceramic plates 11 and 12 during hot pressing, thereby improving the temperature uniformity of the mounting surface 2 s of the electrostatic chuck member 2.

[0065] Note that providing buffer layer 25 prevents point contact between tip surface 17 a and first opposing surface 11 f at contact point P (see FIG. 4 ) during hot pressing, and therefore stress concentration at the contact portion between tip surface 17 a and first opposing surface 11 f is reduced, but stress concentration cannot be completely prevented. For this reason, even when buffer layer 25 is interposed between tip surface 17 a and first opposing surface 11 f, it is preferable to position tip surface 17 a on the outer side in the width direction of groove portion 15 with respect to bottom wall surface 15 b of groove portion 15 to suppress the progression of cracks.

[0066] During hot pressing, the buffer layer 25 is sandwiched between the upper and lower members at its first and second portions 25a and 25b, and its third portion 25c is extruded toward the gap G. In other words, in this embodiment, the third portion 25c, which is a part of the buffer layer 25, is disposed in the gap G. The thickness of the third portion 25c is greater than the thicknesses of the first and second portions 25a and 25b. Therefore, even if the unsintered 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 unlikely to have a uniform thickness, as shown in FIG. 3. In this embodiment, the thickness of the first and second portions 25a and 25b of the buffer layer 25 is, for example, 10 μm to 200 μm. It may also be 30 μm to 150 μm or 50 μm to 100 μm. 2 is located above the tip end surface 17a, the thickness of the second portion 25b of the buffer layer 25 is smaller than the thickness of the first portion 25a.

[0067] According to this embodiment, a gap G is provided between the side surface 20c of the heater portion 20 and the sidewall surface 15c of the groove portion 15. Furthermore, the buffer layer 25 has a third portion 25c that overlaps the gap G when viewed in the thickness direction. Additionally, 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. Therefore, when the pair of ceramic plates 11, 12 are integrated by hot pressing, the insulating material of the first portion 25a and the second portion 25b expands and spreads toward the third portion 25c, and the insulating material of the third portion 25c is extruded into the gap G. When viewed in the cross-sectional direction, a portion of the third portion 25c enters the gap G. Due to this extrusion, a portion of the pressure applied to the pair of ceramic plates 11, 12 during heating and pressurization is released toward the third portion 25c, thereby reducing the pressure applied to the first opposing surface 11f and the tip surface 17a. As a result, it is possible to suppress damage to the pair of ceramic plates 11, 12. Therefore, it is possible to increase the proportion of the groove portion 15 when viewed from the thickness direction of the electrostatic chuck member 2, and it is possible to provide an electrostatic chuck member 2 that can precisely arrange the heater portion 20 inside the electrostatic chuck member 2 and control the mounting surface 2 s to a high and uniform temperature.

[0068] According to this embodiment, the buffer layer 25 has a larger thermal expansion coefficient than the ceramic plates 11 and 12. As a result, when the pair of ceramic plates 11 and 12 are integrated by hot pressing, the buffer layer 25 thermally expands more than the ceramic plates 11 and 12, filling the gap between the pair of ceramic plates 11 and 12 and preventing a gap from being formed between the ceramic plates 11 and 12. Meanwhile, a portion of the buffer layer 25 can escape to the gap G between the side surface 20 c of the heater portion 20 and the side wall surface 15 c of the groove portion 15. Therefore, the buffer layer 25 does not apply excessive stress between the ceramic plates 11 and 12 due to thermal expansion. That is, according to this embodiment, the buffer layer 25 has a larger thermal expansion coefficient than the ceramic plates 11 and 12, and is disposed so that a portion of the buffer layer 25 overlaps the gap G when viewed from the thickness direction. This prevents a gap from being formed between the ceramic plates 11 and 12 and prevents excessive stress from being applied between the ceramic plates 11 and 12. That is, according to this embodiment, it is possible to provide a highly reliable electrostatic chuck member 2 that suppresses damage to the ceramic plates 11 and 12 and the occurrence of gaps between the ceramic plates 11 and 12 .

[0069] In this embodiment, the width W4 of the heater portion 20 is preferably larger than the width W1 of the tip surface 17a of the wall portion 17, and more preferably at least twice as large. It may be three times, four times, or five times as large. Increasing the width W4 of the heater portion 20 relative to the width W1 of the tip surface 17a increases the area occupied by the groove portion 15 on the second opposing surface 12f. Increasing the area occupied by the heater portion 20 allows the heater portion 20 to be densely arranged on the mounting surface 2s when viewed in the thickness direction. However, this reduces the area of ​​the tip surface 17a, making the pair of ceramic plates 11, 12 more susceptible to damage during hot pressing. However, in the electrostatic chuck member 2 of this embodiment, the buffer layer 25 acts to reduce the load applied to the first opposing surface 11f and the tip surface 17a of the pair of ceramic plates 11, 12. Furthermore, by disposing the tip surface 17a on the outside of the groove in the width direction of the groove with respect to the bottom wall surface 15b of the groove 15, the progression of cracks into the wall 17 is suppressed. Therefore, even if the width of the heater portion 20 is more than twice the width dimension W1 of the tip surface 17a, damage to the pair of ceramic plates 11, 12 can be suppressed. According to this embodiment, by making the width dimension W4 of the heater portion 20 more than twice the width dimension W1 of the tip surface 17a, it is possible to control the temperature of the mounting surface 2s to a sufficiently high and uniform temperature, and further, it is possible to suppress damage to the pair of ceramic plates 11, 12 due to the action of the buffer layer 25. It is not necessary that the width dimension W4 of the heater portion 20 is larger than the width dimension W1 of the tip end face 17a at all points, and in order to improve the thermal uniformity of the mounting surface 2s, there may be some points where the width dimension W4 of the heater portion 20 is the same as the width dimension W1 of the tip end face 17a, or there may be some points where W1 is larger than W4, as long as this does not affect the effects of the present invention. In other words, the heater portion 20 may include a portion where W4<W1.

[0070] As described above, in this embodiment, the side wall surface 15c of the groove 15 is provided with a second region 15cb that slopes outward in the width direction toward the first ceramic plate 11. This allows the wall 17 to distribute the force that its tip surface 17a receives from the first ceramic plate 11 to both sides in the width direction, thereby preventing localized pressure. This reduces damage to the second ceramic plate 12 during the hot pressing process. The width W3 of the second region 15cb of the groove 15 is preferably larger than the thickness t3 of the portion (first portion 25a) of the buffer layer 25 sandwiched between the pair of ceramic plates 11 and 12. By ensuring a sufficiently large width W3 of the second region 15cb, the second region 15cb effectively distributes the force applied to the wall 17, thereby reducing damage to the second ceramic plate 12.

[0071] In the electrostatic chuck member 2 of this embodiment, a gap G is provided between the side surface 20 c of the heater portion 20 and the side wall surface 15 c of the groove portion 15. Therefore, there is a concern that the amount of heat transferred from the heater portion 20 to the pair of ceramic plates 11, 12 will be locally reduced in the area corresponding to the gap G, resulting in a decrease in the temperature of the mounting surface 2 s in the area overlapping the gap G when viewed in the thickness direction. The inventors conducted extensive research to address this concern and found that when the distance H (see FIG. 1 ) from the heater portion 20 to the mounting surface 2 s is sufficiently larger than the width d1 of the gap G, temperature non-uniformity on the mounting surface 2 s due to the gap G hardly occurs. More specifically, when the distance H (see FIG. 1 ) from the heater portion 20 to the mounting surface 2 s is 10 times or more the width d1 of the gap G, the effect of the gap G on the temperature uniformity of the mounting surface 2 s can be ignored. Therefore, it is preferable that the distance H from the heater portion 20 to the mounting surface 2s is 10 times or more the width dimension d1 of the gap G. The ratio may be 20 times or more, 30 times or more, or 50 times or more as needed.

[0072] As shown in FIG. 3 , in this embodiment, the width dimension d1 of the gap G at the opening 15a of the groove 15 is preferably larger than the thickness dimension t3 of the portion (first portion 25a) of the buffer layer 25 sandwiched between the pair of ceramic plates 11 and 12. By making the width dimension d1 of the gap G larger than the thickness dimension t3 of the first portion 25a, the buffer layer 25 can be easily pushed into the gap G by the pressure received by the first portion 25a. In other words, the force received by the first portion 25a can be easily released to the third portion 25c. This makes it easier to reduce the load received by the pair of ceramic plates 11 and 12 at the portion where the buffer layer 25 contacts the first portion 25a, thereby suppressing damage to the pair of ceramic plates 11 and 12. For example, depending on the need, the width dimension d1 of the gap G may be 1.1 times or more, 2 times or more, 5 times or more, 7.5 times or more, 8.5 times or more, 10 times or more, 12 times or more, or 15 times or more of the thickness dimension t3 of the first portion 25a.

[0073] As described above, the thermal expansion coefficient (α ２５ ) is the thermal expansion coefficient (α １１ It is preferable that the value is equal to or greater than (α ２５ ≧α １１ Furthermore, the thermal expansion coefficient α of the ceramic material constituting the pair of ceramic plates 11 and 12 １１ The thermal expansion coefficient α of the insulating material constituting the buffer layer 25 ２５ The ratio α ２５ / α １１ may be 1.03 or more and 2.0 or less, and is preferably 1.1 or more and 2.0 or less (1.1≦α ２５ / α １１ ≦2.0). The ratio of the thermal expansion coefficients α ２５ / α １１ If the ratio α of the thermal expansion coefficients is too large, the shear stress generated at the interface between the buffer layer 25 and the first ceramic plate 11 and the interface between the buffer layer 25 and the second ceramic plate 12 when thermal expansion occurs becomes large, which may cause the bonding between the members at the interface to become unstable. ２５ / α１１ If the ratio α of the thermal expansion coefficients is too small, the pressure acting between the pair of ceramic plates 11 and 12 due to the thermal expansion of the buffer layer 25 may not be sufficiently released to the gap G. ２５ / α １１ By setting the ratio α of the thermal expansion coefficients in the above range, the load applied to the pair of ceramic plates 11 and 12 during hot pressing can be reduced while stabilizing the bonding between the members. ２５ / α １１ For the same reason, α is more preferably 1.2 or more and 1.8 or less, and further preferably 1.3 or more and 1.7 or less (1.3≦α ２５ / α １１ ≦1.7).

[0074] The electrostatic chuck member 2 of this embodiment is formed by forming a groove 15 in one of a pair of pre-sintered ceramic plates 11, 12, placing a heater portion 20 in the groove 15, and then hot-pressing the ceramic plates 11, 12 together. A buffer layer 25 is optionally provided on the inner surface of one of the ceramic plates before hot-pressing. This embodiment makes it easier to form the heater portion 20 with a uniform width and thickness along its entire length, compared to when uncured green sheets (unfired flexible ceramic substrates) are stacked and the heater portion 20 is embedded in the stack by sintering the green sheets. Therefore, this embodiment makes it possible to achieve a uniform resistance value of the heater portion 20 along its length, which results in a uniform heat generation amount of the heater portion 20 along its length, compared to when green sheets are used. Furthermore, according to this embodiment, since the pre-sintered ceramic plates 11 and 12 are integrated, it is easy to suppress variations in plate thickness due to sintering, and it is also possible to suppress variations in the distance from the heater portion 20 to the mounting surface 2s compared to when a green sheet is used. That is, according to the electrostatic chuck member 2 of this embodiment, it is possible to adjust the temperature of the mounting surface 2s with higher precision compared to when a green sheet is used to form an electrostatic chuck member with a built-in heater portion.

[0075] The dimensions of the heater portion 20, the groove portion 15, and the like in this 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 in the electrostatic chuck member 2 from the thickness direction by a non-destructive test such as an ultrasonic test, and then cut the heater portion 20 at a cross section along the width direction to measure the dimensions.

[0076] 5 is a partial cross-sectional view showing an electrostatic chuck member 102 according to Modification 1, which can be employed in the above-described embodiment. In the following description of each modification, the same components as those in the embodiment already described are denoted by the same reference numerals, and description thereof will be omitted.

[0077] As shown in FIG. 5 , the electrostatic chuck member 102 of this first modification differs from the above-described embodiment in that it does not include the buffer layer 25. In the electrostatic chuck member 102 of this first modification, the first ceramic plate 11 and the leading end surface 17 a of the wall portion 17 are in direct contact with each other. Therefore, compared to when the buffer layer 25 is provided, point contact occurs between the leading end surface 17 a and the first opposing surface 11 f during hot pressing, making it easier for cracks to propagate. However, in this modification, as in the above-described embodiment, the leading end surface 17 a of the wall portion 17 is positioned outside the bottom wall surface 15 b of the groove portion 15 in the width direction, thereby suppressing the propagation of cracks originating from the crack C compared to the electrostatic chuck member 902 of the conventional structure shown in FIG. 9 .

[0078] 6 is a partial cross-sectional view showing an electrostatic chuck member 202 according to Modification 2 that can be used in the above-described embodiment. The electrostatic chuck member 202 of this modification differs from the above-described embodiment mainly in the shape of the sidewall surface 215c of the groove 215. The electrostatic chuck member 202 of this modification does not have a second region.

[0079] Similar to the above-described embodiment, the second ceramic plate 212 of this second modification has a plurality of grooves 215 and wall portions 217 positioned between the grooves 215. The heater portion 20 is disposed in the grooves 215. As shown in FIG. 6 , the wall portions 217 of this second modification have a trapezoidal or substantially trapezoidal cross section. Therefore, the side wall surfaces 215c of the grooves 215 are inclined from the bottom wall surface 215b toward the first ceramic plate 11 and outward in the width direction of the grooves throughout the entire area. When viewed from the cross section, the inclination angle of the side wall surfaces 215c of the grooves 215 is constant or nearly constant. The angle (interior angle) formed by the side wall surfaces 215c and the tip surface 217a can be arbitrarily selected, but may be, for example, 95° to 170°, 110° to 160°, or 120° to 140°.

[0080] According to the second modification, similarly to the above-described embodiment, the tip surface 217a of the wall portion 217 can be positioned on the outer side of the bottom wall surface 215b in the width direction of the groove portion 15. This increases the width direction distance from the crack C on the side wall surface 215c to the contact point P, thereby further reducing the upward peel shear stress Fa.

[0081] 7 is a partial cross-sectional view showing an electrostatic chuck member 302 according to Modification 3 that can be used in the above-described embodiment. The electrostatic chuck member 302 according to Modification 3 differs from the above-described embodiment mainly in the shape of the sidewall surface 315c of the groove 315.

[0082] Similar to the above-described embodiment, the second ceramic plate 312 of the third modified example is provided with a plurality of grooves 315 and wall portions 317 located between the grooves 315. The heater portion 20 is disposed in the grooves 315. In this embodiment, the side wall surface 315c of the groove 315 has a third region 315cc in addition to the first region 315ca and the second region 315cb similar to those in the above-described embodiment.

[0083] The first region 315ca and the second region 315cb of this third modification have the same configuration as those of the above-described embodiment. The first region 315ca extends in the thickness direction. The second region 315cb is located closer to the first ceramic plate 11 than the first region 315ca and is continuous with the tip surface 317a. Furthermore, the second region 315cb curves and slopes outward in the width direction of the groove as it approaches the first ceramic plate 11. Furthermore, the width dimension W3 of the second region 315cb is larger than the thickness dimension t3 of the portion of the buffer layer 25 sandwiched between the first ceramic plate 11 and the second ceramic plate 312. As in the above-described embodiment, in this modification, by ensuring a sufficiently large width dimension W3 of the second region 315cb, the second region 315cb can sufficiently disperse the force applied to the wall portion 317, thereby suppressing damage to the second ceramic plate 312.

[0084] As shown in FIG. 7 , the third region 315cc of the third modification is located at the boundary between the first region 315ca and the bottom wall surface 315b, smoothly connecting the first region 315ca and the bottom wall surface 315b. The third region 315cc of the third modification is curved with a constant radius of curvature R2. The wall portion 317 of the third modification gradually increases in width toward the base end in the thickness direction. This allows the base end of the wall portion 317 to effectively support the force received from the distal end surface 317a of the wall portion 317 when the pair of ceramic plates 11 and 312 are integrated in a hot press process. Furthermore, the wall portion 317 curves and expands toward the outside in the width direction of the wall portion in the third region 315cc located at the base end. This allows the force received from the first ceramic plate 11 to be distributed to both sides in the width direction on the upper surface, thereby suppressing localized pressure. This can prevent damage to the second ceramic plate 312 during the hot pressing process.

[0085] The radius of curvature R2 of the third region 315cc is preferably larger than the thickness t3 of the portion (first portion 25a) of the buffer layer 25 sandwiched between the pair of ceramic plates 11 and 312. By ensuring a sufficiently large radius of curvature R2 of the third region 315cc, the third region 315cc can sufficiently disperse the force applied to the wall portion 317, thereby suppressing damage to the second ceramic plate 312. In the third modification, the radius of curvature R2 of the third region 315cc is uniform. However, if the radius of curvature R2 of the third region 315cc continuously changes along the depth direction of the groove 315, it is preferable that all of the varying radii of curvature R2 be smaller than the thickness t3 of the first portion 25a.

[0086] 8 is a partial cross-sectional view showing an electrostatic chuck member 402 according to Modification 4 that can be used in the above-described embodiment. The electrostatic chuck member 402 according to Modification 4 differs from the above-described embodiment mainly in the shape of the side wall surface 415c of the groove portion 415.

[0087] Similar to the above-described embodiment, the second ceramic plate 412 of this fourth modification has multiple grooves 415 and wall portions 417 located between the grooves 415. The heater portion 20 is disposed in the grooves 415. Similar to the above-described embodiment, the side wall surface 415c of this fourth modification has a first region 415ca and a second region 415cb. Similar to the above-described embodiment, the second region 415cb is a curved surface whose inclination angle with respect to the thickness direction increases toward the first ceramic plate 11. The radius of curvature of the second region 415cb may be uniform or may vary. The width dimension W1 of the tip surface 417a may be 30% or less of the distance d2 (W3), 20% or less, 10% or less, or 5% or less. When viewed from a cross section, the second region 415cb may be the apex of a curved surface (convex portion) formed by two opposing second regions 415cb.

[0088] 8 , in the fourth modification, the second regions 415cb of the two side wall surfaces 415c, located on one side and the other side of the wall portion 417 in the width direction, are smoothly connected to each other at the tip surface 417a of the wall portion 417. In this case, the width dimension of the tip surface 417a of the wall portion 417 is sufficiently small. Even with this configuration, the tip surface 417a can be positioned outward in the width direction of the groove portion 415 relative to the bottom wall surface 415b of the groove portion 415, thereby suppressing the progression of a crack originating from a crack C occurring in the side wall surface 415c.

[0089] While the embodiments and modifications of the present invention have been described above, the configurations and combinations thereof in the embodiments and modifications are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments.

[0090] In the above-described embodiment and its modified examples, the above-described configuration is applied over the entire length of the heater and the groove in which the heater is housed. However, it is sufficient if the above-described configuration is adopted in at least a portion of the heater and the groove. In this case, it is possible to obtain the effect of suppressing damage in the vicinity of the portion corresponding to the above-described configuration.

[0091] 1 Electrostatic chuck device 2, 102, 202, 302, 402, 902 Electrostatic chuck member (ceramic bonded body) 2s Mounting surface 3 Base 11, 12 Ceramic plate 11, 911 First ceramic plate 11a First plate portion 11b Second plate portion 11c Third plate portion 11d First bonding layer 11e Second bonding layer 11f, 911f First opposing surface 12, 212, 312, 412, 912 Second ceramic plate 12f Second opposing surface 13 Electrostatic attraction electrode 15, 215, 315, 415, 915 Groove portion 15a Opening 15b, 215b, 315b, 415b, 915b Bottom wall surface 15c, 215c, 315c, 415c, 915c Side wall surface 15ca, 315ca, 415ca First region 15cb, 315cb, 415cb Second region 16A First power supply terminal 16B Second power supply terminal 17, 217, 317, 417, 917 Wall portion 17a, 217a, 317a, 417a, 917a Tip surface 18 Insulator 19 Gas flow path 19a First gas hole 19b Second gas hole 19c Communication path 20 Heater portion 20a Upper surface 20b Lower surface 20c Side surface 25 Buffer layer 25a First portion 25b Second portion 25c Third portion 315cc Third region C Crack d1 Width dimension d2 Distance F Force Fa Upward peel shear stress Fb Horizontal stress G Gap H Distance P Contact point R1, R2 Radius of curvature t1 Depth dimension t3, t2a, t2b Thickness dimension W Wafer W1 Width dimension of tip surface W2 Width dimension of groove W3 Width dimension of second region W4 Width dimension of heater section Z Z axis α １１ , α ２５ Thermal expansion coefficient Δ Displacement

Claims

1. A ceramic joint comprising: a first ceramic plate and a second ceramic plate stacked in the thickness direction; and a band-shaped heater portion located between the first ceramic plate and the second ceramic plate, wherein the second ceramic plate has a plurality of groove portions aligned in the width direction thereof, and a plurality of wall portions located between adjacent groove portions and protruding from a bottom wall surface of the groove portions, the heater portion is housed in the groove portions, and the wall portions have a tip surface that is located outside the groove portions in the width direction relative to the bottom wall surface.

2. A ceramic joined body as described in claim 1, wherein the groove portion has a side wall surface, the side wall surface having a first region extending in the thickness direction, and a second region located closer to the first ceramic plate than the first region and connected to the tip surface, the second region inclining toward the outside in the width direction of the groove portion as it approaches the first ceramic plate.

3. A ceramic joined body as described in claim 2, wherein the second region is a curved surface whose inclination angle with respect to the thickness direction increases toward the first ceramic plate, and which is smoothly connected to the first region and the tip surface.

4. The ceramic joint according to claim 1, wherein the dimension of said tip surface in said width direction is 2500 μm or less.

5. The ceramic joint body according to claim 1, further comprising a buffer layer disposed between the first ceramic plate and the second ceramic plate.

6. A ceramic joint as described in claim 5, wherein a side surface of the heater portion and a side wall surface of the groove portion face each other via a gap, and the buffer layer is made of an insulating material having a larger thermal expansion coefficient than the ceramic material constituting the first ceramic plate and the second ceramic plate, and at least a portion of the buffer layer overlaps with the gap when viewed in the thickness direction.

7. A ceramic joint as set forth in claim 6, wherein the width dimension of the gap at the opening of the groove is greater than the thickness dimension of a portion of the buffer layer that is sandwiched between the first ceramic plate and the second ceramic plate.

8. A ceramic joint as described in claim 6, wherein the ratio of the thermal expansion coefficient of the insulating material constituting the buffer layer to the thermal expansion coefficient of the ceramic material constituting the first ceramic plate and the second ceramic plate is 1.1 or more and 2.0 or less.

9. A ceramic joined body according to claim 6, wherein the dimension of said heater portion in said width direction is at least twice the dimension of said tip end surface in said width direction.

10. The ceramic joined body according to claim 6, wherein a part of the buffer layer is disposed in the gap.

11. A ceramic joint as described in claim 6, wherein the side wall surface of the groove has a first region extending in the thickness direction and a second region located closer to the first ceramic plate than the first region and connected to the tip surface, the second region inclining outward in the width direction of the groove as it approaches the first ceramic plate, and the width dimension of the second region is larger than the thickness dimension of a portion of the buffer layer sandwiched between the first ceramic plate and the second ceramic plate.

12. The ceramic joined body according to claim 11, wherein the side wall surface of the groove has a third region located at the boundary between the first region and the bottom wall surface and smoothly connecting the first region and the bottom wall surface.

13. A ceramic joint as set forth in claim 12, wherein the radius of curvature of the third region is greater than the thickness dimension of a portion of the buffer layer that is sandwiched between the first ceramic plate and the second ceramic plate.

14. The ceramic joined body according to claim 6, wherein the thickness of the heater portion is greater than the thickness of a portion of the buffer layer that is sandwiched between the first ceramic plate and the second ceramic plate.

15. The ceramic joined body according to claim 1, wherein the heater portion is made of a thin metal plate.

16. An electrostatic chuck device comprising the ceramic bonded body according to any one of claims 1 to 15.