Ceramic joined body and electrostatic chuck device

Abstract

This ceramic joined body comprises: a pair of ceramic plates laminated in a thickness direction; a buffer layer positioned between the pair of ceramic plates; and a belt-shaped heater part that is located between the pair of ceramic plates and is disposed in a groove part that is disposed in at least one of the pair of ceramic plates. A side surface of the heater part and a side wall surface of the groove part face each other with a gap therebetween. The buffer layer comprises an insulating material having a coefficient of thermal expansion larger than that of the ceramic material constituting the pair of ceramic plates, and, when viewed in the thickness direction, at least a portion of the buffer layer overlaps with the gap.

Description

Ceramic bonded body and electrostatic chuck device

[0001] This application claims priority to Japanese Patent Application No. 2023-143425, filed September 5, 2023, the contents of which are incorporated herein by reference.

[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] With the recent trend toward higher temperatures in semiconductor manufacturing processes, electrostatic chuck devices are required to maintain a high and uniform temperature on the mounting surface. To this end, a configuration in which the heater unit is densely arranged relative to the mounting surface is considered. The heater unit is typically located in a groove in one of a pair of ceramic plates and sandwiched between the pair of ceramic plates. However, dense arrangement of the heater unit results in insufficient strength in the region of the ceramic plate located between the heater units, making the ceramic plate more susceptible to damage. Furthermore, gaps may occur between the grooved ceramic plate and its mating ceramic plate, posing challenges to the temperature uniformity of the mounting surface and the reliability of the electrostatic chuck.

[0005] An object of the present invention is to provide a highly reliable ceramic bonded body and electrostatic chuck device in which damage to the ceramic plates can be suppressed even when heater portions are densely arranged and there are no gaps between the ceramic plates.

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

[11] . It is also preferable to combine two or more of the following inventions as necessary. [1] A ceramic bonded body comprising a pair of ceramic plates stacked in a thickness direction, a buffer layer disposed between the pair of ceramic plates, and a strip-shaped heater portion located between the pair of ceramic plates and disposed in a groove formed in at least one of the pair of ceramic plates, wherein a side surface of the heater portion faces a sidewall surface of the groove via a gap, and the buffer layer is made of an insulating material having a thermal expansion coefficient larger than that of the ceramic material constituting the pair of ceramic plates, and at least a portion of the buffer layer overlaps the gap as viewed from the thickness direction. [2] The ceramic bonded body according to [1], wherein a width dimension of the gap at an opening of the groove is larger than a thickness dimension of a portion of the buffer layer sandwiched between the pair of ceramic plates. [3] The ceramic bonded body according to [1] or [2], wherein a 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. [4] The ceramic bonded body according to any one of [1] to [3], wherein a width dimension of the heater portion is at least twice the distance between the groove portions in which the heater portions are arranged. [5] The ceramic bonded body according to any one of [1] to [4], wherein a part of the buffer layer is arranged in the gap. [6] The ceramic bonded body according to any one of [1] to [5], wherein a side wall surface of the groove portion has an inclined surface that inclines in a direction in which the width dimension of the groove portion increases toward the opening side of the groove portion in the depth direction of the groove portion. [7] The ceramic bonded body according to [6], wherein a width dimension of the inclined surface is larger than a thickness dimension of a portion of the buffer layer that is sandwiched between the pair of ceramic plates. [8] The ceramic bonded body according to any one of [1] to [7], wherein the inner wall surface of the groove has, in addition to the pair of side wall surfaces, a bottom wall surface facing the opening of the groove, and a pair of curved surfaces located at boundaries between the side wall surfaces and the bottom wall surface and smoothly connecting the side wall surfaces and the bottom wall surface. [9] The ceramic bonded body according to [8], wherein a radius of curvature of the curved surfaces is larger than a thickness of the buffer layer.

[10] The ceramic bonded body according to any one of [1] to [9], wherein a thickness dimension of the heater portion is greater than a depth dimension of the groove portion.

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

[10] .

[0007] According to one aspect of the present invention, there are provided a ceramic bonded body and an electrostatic chuck device that can suppress damage to a ceramic plate even when heater portions are densely arranged.

[0008] FIG. 1 is a cross-sectional schematic diagram illustrating an electrostatic chuck device according to an embodiment. 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, the view being a schematic diagram illustrating the pair of ceramic plates before being integrated. 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, the view being a schematic diagram illustrating the pair of ceramic plates after being integrated. FIG. 4 is a partially enlarged view illustrating an example of a pair of ceramic plates of an electrostatic chuck member (ceramic bonded body) according to a first modification, the view being a schematic diagram illustrating the pair of ceramic plates before being integrated. FIG. 5 is a partially enlarged view illustrating an example of a pair of ceramic plates of an electrostatic chuck member (ceramic bonded body) according to the first modification, the view being a schematic diagram illustrating the pair of ceramic plates after being integrated. FIG. 6 is a partially cross-sectional view illustrating an example of an electrostatic chuck member (ceramic bonded body) according to a second modification. FIG. 7 is a partially cross-sectional view illustrating an example of an electrostatic chuck member (ceramic bonded body) according to a third modification.

[0009] Preferred examples of each embodiment of the electrostatic chuck device of the present invention will be described below with reference to the drawings. In all of the following drawings, the dimensions and ratios of each component may be displayed differently as appropriate to make the drawings easier to understand. The following explanations are provided to provide a more detailed explanation for a better understanding of the gist of the invention, and do not limit the present invention unless otherwise specified. For example, unless otherwise specified, conditions such as materials, quantities, types, numbers, sizes, shapes, positions, and ratios may be changed, added, or omitted as necessary.

[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 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. The base 3 may also be provided with a flow path for flowing a cooling medium or the like.

[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 passages 19 to cool the wafer W mounted on the mounting surface 2s. The number and positions of the gas flow passages 19 can be selected arbitrarily.

[0013] The electrostatic chuck member 2 has a disk or approximately disk shape. 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 unit 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 with their thickness direction aligned in 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 11d, and the second bonding layer 11e between the first plate portion 11a, the second plate portion 11b, and the third plate portion 11c, which are sintered bodies formed in advance, stacking them in the thickness direction, and hot pressing them under high temperature and high pressure to integrate them.

[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. The first ceramic plate 11 is made of a ceramic material. The ceramic material for the first ceramic plate 11 can be selected arbitrarily, but may be, for example, 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)-based 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, 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 do not have to be made of materials having the same composition, and may be made of materials different from each other.

[0020] The electrostatic attraction electrode 13 is preferably 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 It is preferable that the conductive material is at least one selected from the group consisting of: The conductive material can be selected arbitrarily.

[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, it generates an electrostatic chucking force that holds the 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 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 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 groove 15 is provided on the second opposing surface 12f. In this embodiment, the groove 15 has a uniform width and a uniform depth throughout 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. The strip-shaped shape may refer to, for example, a long, thin shape with a constant width. The entire heater portion 20 may be continuous. The overall pattern shape of the heater portion 20 in a planar view can be selected arbitrarily, and may, for example, be a meandering shape that fits within a circle. The heater portion 20 is disposed 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 in a pattern shape substantially identical to the pattern shape of the heater portion 20. The width dimension of the groove 15 is slightly larger than the width dimension of the heater portion 20. Note that multiple grooves 15 may be provided on the second opposing surface 12f. In this case, a heater portion 20 is individually disposed in each groove portion 15 .

[0024] In this embodiment, a case will be described in which the groove portion 15 is provided only in the second ceramic plate 12 and not in the first ceramic plate 11. However, the groove portion 15 may be provided in at least one of the pair of ceramic plates 11, 12. That is, the groove portion 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 portion may be provided in 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 in the pair of ceramic plates 11, 12 have the same shape and overlap each other when viewed in the thickness direction.

[0025] 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 ３ A 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.

[0026] 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.

[0027] The heater unit 20 is composed of a resistance heating element. The type of resistance heating element, the shape of the heater unit 20, and the manufacturing method thereof are arbitrarily selected. The heater unit 20 is preferably manufactured by processing 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, into a circular shape with an overall contour such as a meandering strip-shaped conductive thin plate, using photolithography, laser processing, or the like. In this embodiment, the heater unit 20 is disposed in a meandering manner between a pair of ceramic plates 11 and 12. The heater unit 20 generates heat when a current flows through it.

[0028] 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.

[0029] 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 together.

[0030] The buffer layer 25 is made of an insulating material. 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 ~ 5.2 × 10 －６ When these are used in combination, 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.

[0031] 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.

[0032] In this embodiment, the buffer layer 25 is sintered in a process in which the first ceramic plate 11 and the second ceramic plate 12 are integrated by hot pressing at high temperature and high pressure. In this process, for example, first, the buffer layer 25 in an unsintered paste state is applied 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 selected arbitrarily, 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 unit 20 disposed in the groove 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, 12 are integrated by hot pressing at high temperature and high pressure. The hot pressing conditions can be selected arbitrarily. Through this process, the buffer layer 25 is bonded to the entire first opposing surface 11f. The buffer layer 25 is bonded to the portion of the second opposing surface 12 f other than the groove portion 15 and the upper surface of the heater portion 20 .

[0033] 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.

[0034] 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 inner wall surface of the groove portion 15 has 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 pair of side wall surfaces 15c extend upward from both ends of the bottom wall surface 15b in the width direction. The pair of side wall surfaces 15c face each other in the width direction of the groove portion 15.

[0035] The heater section 20 has a substantially rectangular cross-sectional shape. The heater section 20 has an upper surface 20 a, a lower surface 20 b, and a pair of side surfaces 20 c. The pair of side surfaces 20 c extend along the thickness direction of the pair of ceramic plates 11, 12 and connect the upper surface 20 a and the lower surface 20 b.

[0036] 3, after integration, 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 contacts the bottom wall surface 15b of the groove portion 15. As shown in FIG. 2, in this embodiment before the heater portion 20 is embedded in the electrostatic chuck member 2, i.e., before hot pressing, the thickness dimension t2a of the heater portion 20 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 in the electrostatic chuck member 2 is located above the second opposing surface 12f.

[0037] As shown in FIG. 3 , the heater portion 20 is sandwiched between the pair of ceramic plates 11 and 12 and is therefore deformed by being 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 being embedded in the electrostatic chuck member 2 is smaller than the thickness dimension t2a (see FIG. 2 ) before being embedded. Furthermore, the thickness dimension t2b of the heater portion 20 after being embedded 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 being embedded in the electrostatic chuck member 2. According to this embodiment, the heater portion 20 is sandwiched between the pair of ceramic plates 11 and 12 and is compressed and deformed in the thickness direction during hot pressing. This allows the heater portion 20 to receive the force applied between the pair of ceramic plates 11 and 12 during hot pressing, thereby reducing the force applied between the grooves of the second opposing surface 12 f, thereby preventing damage to the pair of ceramic plates 11 and 12 during hot pressing.

[0038] 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 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. The width d1 of the gap G is, for example, 100 μm or more and 300 μm or less. The widths W4 and d1 of the heater portion 20 and the gap G can be selected arbitrarily and are not limited to these values.

[0039] 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 to a space in which nothing is disposed.

[0040] 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.

[0041] 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 section 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 from the thickness direction of the pair of ceramic plates 11, 12 and penetrates into the gap G. That is, at least a portion of the buffer layer 25 (the third region 25c in this embodiment) overlaps with the gap G when viewed from the thickness direction.

[0042] As shown in FIG. 3 , in this embodiment, a buffer layer 25 is disposed between the pair of ceramic plates 11 and 12. The buffer layer 25 is sandwiched between the pair of ceramic plates 11 and 12 in an unsintered state and is sintered when the pair of ceramic plates 11 and 12 are hot-pressed together. Therefore, even if slight irregularities exist on the surfaces of the first opposing surface 11 f and the second opposing surface 12 f of the pair of ceramic plates 11 and 12, the buffer layer 25 absorbs these irregularities. This prevents localized application of large forces to the first opposing surface 11 f and the second opposing surface 12 f of the ceramic plates 11 and 12 and, conversely, prevents gaps from being formed. As a result, damage and gap formation near the interface between the pair of ceramic plates 11 and 12 during hot pressing can be suppressed, thereby improving the temperature uniformity of the mounting surface 2 s of the electrostatic chuck member 2.

[0043] During hot pressing, the buffer layer 25 is sandwiched between the members in the first region 25a and the second region 25b and extruded toward the gap G in the third region 25c. That is, in this embodiment, the third region 25c, which is a part of the buffer layer 25, is disposed in the gap G. 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 thicknesses of the first region 25a and the second region 25b of the buffer layer 25 are, for example, 10 μm or more and 200 μm or less. As described above, the upper surface 20a of the heater section 20 before embedding shown in FIG. 2 is located above the second opposing surface 12f. Therefore, the thickness of the second region 25b is smaller than the thickness of the first region 25a.

[0044] 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. The buffer layer 25 also has a third region 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 and 12. Therefore, when the pair of ceramic plates 11 and 12 are integrated by hot pressing, the insulating material in the first region 25a and the second region 25b expands and spreads toward the third region 25c, forcing the insulating material in the third region 25c into the gap G. Accordingly, during heating and pressurization, a portion of the pressure applied to the pair of ceramic plates 11 and 12 is released 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 and 12 can be suppressed. As a result, the proportion of the groove portion 15 when the electrostatic chuck member 2 is viewed from the thickness direction can be increased, the heater portion 20 can be precisely arranged inside the electrostatic chuck member 2, and an electrostatic chuck member 2 can be provided that can control the mounting surface 2s to a high and uniform temperature.

[0045] 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 generated 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, by making the thermal expansion coefficient of the buffer layer 25 larger than that of the ceramic plates 11 and 12 and arranging the buffer layer 25 so as to overlap the gap G when viewed in the thickness direction, it is possible to prevent a gap from being generated between the ceramic plates 11 and 12 and prevent 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 generation of gaps between the ceramic plates 11 and 12 .

[0046] In this embodiment, the width dimension W4 of the heater portion 20 is preferably at least twice the distance W1 between the grooves 15 in which the heater portion 20 is disposed. By making the width dimension W4 of the heater portion 20 larger than the distance W1 between the grooves 15, the area occupied by the grooves 15 on the second opposing surface 12f is increased. This allows the heater portion 20 to be densely arranged on the mounting surface 2s when viewed in the thickness direction, but reduces the area of ​​the second opposing surface 12f, making the pair of ceramic plates 11, 12 more susceptible to damage during hot pressing. 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 second opposing surface 12f of the pair of ceramic plates 11, 12. Therefore, even if the width dimension W4 of the heater portion 20 is at least twice the distance W1 between the grooves 15, 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 at least twice the distance W1 between the groove portions 15, it becomes possible to control the temperature of the mounting surface 2s to be sufficiently high and uniform, and furthermore, it becomes possible 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, or 4 times or more the distance W1, as necessary.

[0047] 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 have conducted extensive research to address this concern and have 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. The distance H may be 15 times or more, 20 times or more, or 30 times or more the width dimension d1, as needed.

[0048] As shown in Figure 3, in this embodiment, the width dimension d1 of the gap G at the opening 15a of the groove portion 15 is preferably larger than the thickness dimension t3 of the portion (first region 25a) of the buffer layer 25 sandwiched between the pair of ceramic plates 11, 12. By making the width dimension d1 of the gap G larger than the thickness dimension t3 of the first region 25a, the buffer layer 25 can be easily pushed into the gap G by the pressure received by the first region 25a. In other words, the force received by the first region 25a can be easily released to the third region 25c. This makes it easier to reduce the load received by the pair of ceramic plates 11, 12 at the portions in contact with the first region 25a, thereby suppressing damage to the pair of ceramic plates 11, 12.

[0049] As described above, the thermal expansion coefficient (α ２５ ) is the thermal expansion coefficient (α １１ is larger 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 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 / α １１ If the ratio α 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 １１By 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, it is more preferable that α is 1.3 or more and 1.7 or less (1.3≦α ２５ / α １１ ≦1.7), and the ratio may be 1.2 or more and 1.8 or less, or 1.4 or more and 1.6 or less, as required.

[0050] The electrostatic chuck member 2 of this embodiment is formed by forming grooves 15 in a pair of pre-sintered ceramic plates 11 and 12, placing the heater portion 20 in the grooves 15, and joining the ceramic plates 11 and 12 by hot pressing. This embodiment facilitates the formation of the heater portion 20 with a uniform width and thickness along its entire length, compared to when the heater portion 20 is formed during lamination of uncured green sheets (unfired flexible ceramic substrates) and then sintering the green sheets to embed the heater portion 20. Therefore, this embodiment allows the heater portion 20 to have a uniform resistance along its length, compared to when green sheets are used, and as a result, the heater portion 20 generates a uniform amount of heat along its length. Furthermore, this embodiment integrates the pre-sintered ceramic plates 11 and 12, which facilitates the suppression of variations in plate thickness due to sintering. This also reduces variations in the distance from the heater portion 20 to the mounting surface 2s, compared to when green sheets are used. That is, according to the electrostatic chuck member 2 of this embodiment, the temperature of the mounting surface 2s can be adjusted with higher precision than when a heater-integrated electrostatic chuck member is formed using a green sheet.

[0051] 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 measure these dimensions by checking 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 cutting the heater portion 20 at a cross section along the width direction.

[0052] 4 and 5 are partial cross-sectional views showing an electrostatic chuck member 102 according to a first modification that can be employed in the above-described embodiment, with Fig. 4 showing the state before integration and Fig. 5 showing the state after integration. Note that the cross sections shown in Figs. 4 and 5 are cross sections perpendicular to the longitudinal direction of the heater portion 20.

[0053] The electrostatic chuck member 102 of this modified example is different from the above-described embodiment in the configuration of the buffer layer 125. In the following description of each embodiment, the same components as those in the already-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0054] 4 , the buffer layer 125 of this modified example is applied in an unsintered paste state to the second ceramic plate 12 and sintered while sandwiched between the first ceramic plate 11 and the second ceramic plate 12. Grooves 15 are formed on the second opposing surface 12f of the second ceramic plate 12. The unsintered buffer layer 125 is applied not only to the second opposing surface 12f but also to the inner wall surfaces of the grooves 15. Therefore, a portion of the buffer layer 125 is formed along the inner side surfaces of the grooves 15.

[0055] 5, the buffer layer 125 of this modification 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 15 and the lower surface 20b of the heater 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 15. The third region 125c is disposed within the gap G. That is, in this modification as well, at least a portion of the buffer layer 125 (the third region 125c of this modification) overlaps with the gap G when viewed in the thickness direction.

[0056] According to this modification, as in the above-described embodiment, when the pair of ceramic plates 11, 12 are integrated by hot pressing, the insulating material in the first region 125a and the second region 125b expands and spreads toward the third region 125c, and the insulating material in the third region 125c expands in the gap G. Accordingly, during heating and pressurization, a portion of the pressure applied to the pair of ceramic plates 11, 12 is released toward the third region 125c, and the pressure applied to the first opposing surface 11f and the second opposing surface 12f is reduced. This makes it possible to prevent damage to the pair of ceramic plates 11, 12 during the hot pressing process.

[0057] Furthermore, according to this modification, the third region 125c is disposed along the side wall surface 15c of the groove portion 15, thereby filling a part of the gap G between the side wall surface 15c of the groove portion 15 and the side surface 20c of the heater portion 20. This makes it possible to reduce the size of the air layer provided inside the electrostatic chuck member 102, and makes it easier to improve the temperature uniformity of the mounting surface 2s.

[0058] The buffer layer 125 may have a region located between the heater unit 20 and the first opposing surface 11 f, in addition to the first region 125 a, the second region 125 b, and the third region 125 c. The buffer layer 125 may be configured such that any part of the first region 125 a, the second region 125 b, and the third region 125 c is omitted.

[0059] 6 is a partial cross-sectional view showing an electrostatic chuck member 202 according to Modification 2 that can be employed in the above-described embodiment. The electrostatic chuck member 202 according to this modification differs from the above-described embodiment mainly in the shape of the groove 215.

[0060] As in the above-described embodiment, a groove 215 is provided on the second opposing surface 212f of the second ceramic plate 212 in this modified example. A heater unit 20 is disposed in the groove 215. The groove 215 in this modified example has a substantially trapezoidal cross section. 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 wall surfaces 215c. The bottom wall surface 215b faces the opening side of the groove 215. The pair of side wall surfaces 215c extend upward from both ends of the bottom wall surface 215b in the width direction. The pair of side wall surfaces 215c face each other in the width direction of the groove 215.

[0061] In this modification, the pair of side wall surfaces 215c are spaced apart from each other as they extend upward. That is, the side wall surfaces 215c have inclined surfaces 215t that are inclined in a direction that increases the width of the groove 215 as they extend toward the opening of the groove 215 in the depth direction of the groove 215. In this modification, the inclined surfaces 215t are provided over the entire depth direction of the side wall surfaces 215c. The angle of the inclined surfaces relative to the bottom wall surface can be selected arbitrarily, and examples include 40 degrees or more and less than 90 degrees, 50 degrees or more and 80 degrees or less, and 60 degrees or more and 70 degrees or less.

[0062] Here, the portions of the second ceramic plate 212 between the grooves 215 are referred to as wall portions 215w. According to this modification, the width of the wall portions 215w increases as they move away from the first ceramic plate 11 in the thickness direction. Therefore, when the pair of ceramic plates 11, 212 are integrated in the hot-pressing process, the force received from the upper surface of the wall portions 215w can be supported by the lower end of the wall portions 215w. Furthermore, the inclined surfaces 215t of the wall portions 215w extend outward in the width direction, distributing the force received from the first ceramic plate 11 on the upper surface to both sides in the width direction and preventing the pressure from being applied locally. This reduces damage to the second ceramic plate 212 during the hot-pressing process.

[0063] The width dimension W3 of the inclined surface 215t is smaller than the width dimension d1 of the gap G. This prevents the heater unit 20 in the groove 215 from climbing up onto the inclined surface 215t. Furthermore, the width dimension W3 of the inclined surface 215t is preferably larger than the thickness dimension t3 of the portion (first region 25a) of the buffer layer 25 that is sandwiched between the pair of ceramic plates 11 and 212. By ensuring that the width dimension W3 of the inclined surface 215t is sufficiently large, the inclined surface 215t can sufficiently disperse the force applied to the wall portion 215w, thereby preventing damage to the second ceramic plate 212.

[0064] In the electrostatic chuck member 202 of this modified example, the buffer layer 25 also functions in the same manner as in the above-described embodiment to suppress damage to the pair of ceramic plates 11, 212 during the hot pressing process. In this modified example, the width dimension d1 of the gap G at the opening 215a of the groove portion 215 is larger than the thickness dimension t3 of the first region 25a, and therefore damage to the pair of ceramic plates 11, 12 can be effectively suppressed.

[0065] 7 is a partial cross-sectional view showing an electrostatic chuck member 302 according to a third modification that can be used in the above-described embodiment. The electrostatic chuck member 302 of this modification differs from the above-described embodiment mainly in the shape of the groove 315. In the electrostatic chuck member 302 of this modification, the buffer layer 25 also functions in the same manner as in the above-described embodiment to suppress damage to the pair of ceramic plates 11, 12 during the hot pressing process.

[0066] As in the above-described embodiment, a groove 315 is provided on the second opposing surface 312f of the second ceramic plate 312 of this modified example. A heater unit 20 is disposed in the groove 315. The groove 315 of this modified example has an opening 315a 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 wall surfaces 315c, and a pair of curved surfaces 315d. The bottom wall surface 315b faces upward. The pair of side wall surfaces 315c face each other in the width direction of the groove 315.

[0067] 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. In this modification, the curved surface 315d is curved with a constant radius of curvature R. According to this modification, the width of the wall portion 315w increases as it moves away from the first ceramic plate 11 in the thickness direction. This allows the lower end of the wall portion 315w to support the force received from the upper surface of the wall portion 315w when the pair of ceramic plates 11, 312 are integrated in the hot pressing process. Furthermore, the curved surface 315d located at the lower end of the wall portion 315w extends outward in the width direction, distributing the force received from the first ceramic plate 11 on the upper surface to both sides in the width direction and preventing localized pressure. This reduces damage to the second ceramic plate 312 during the hot pressing process.

[0068] The radius of curvature R of the curved surface 315d is smaller than the width dimension d1 of the gap G. This prevents the heater unit 20 in the groove 315 from climbing up onto the curved surface 315d. The radius of curvature R of the curved surface 315d is preferably larger than the thickness dimension t3 of the portion (first region 25a) of the buffer layer 25 sandwiched between the pair of ceramic plates 11 and 312. By ensuring a sufficiently large width dimension W3 of the curved surface 315d, the curved surface 315d can sufficiently disperse the force applied to the wall portion 315w, thereby suppressing damage to the second ceramic plate 312. In this modification, the case where the radius of curvature R of the curved surface 315d is uniform has been described. However, when the radius of curvature R of the curved surface 315d continuously changes along the depth direction of the groove 315, it is preferable that all radii of curvature R be smaller than the thickness dimension t3 of the first region 25a.

[0069] 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 as mentioned above, additions, omissions, substitutions, and other modifications of the configurations are possible within the scope of the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments.

[0070] For example, the buffer layer 125 of Modification 1 may be applied to the electrostatic chuck members 202 and 302 having the grooves 215 and 315 of Modifications 2 and 3. Furthermore, the curved surface 315d of Modification 3 may be applied to the groove 215 having the inclined surface 215t of Modification 2.

[0071] In the above-described embodiment and its modified examples, the above-described configuration is described as being applied over the entire length of the heater section 20 and the groove section 15, 215 that accommodates the heater section 20. However, it is sufficient if the above-described configuration is adopted in at least a part of the heater section 20 and the groove section 15, 215, and in that case, the effect of suppressing damage to the vicinity of the relevant portion can be obtained.

[0072] REFERENCE SIGNS LIST 1...electrostatic chuck device 2, 102, 202, 302...electrostatic chuck member (ceramic bonded body) 11...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 attraction electrode 15, 215, 315...groove portion 15a, 215a, 315a...opening 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...Communicating path 20...Heater portion 20a...Upper surface of heater portion 20b...Lower surface of heater portion 20c...Side surface of heater portion 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 portion 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

1. A ceramic joint comprising: a pair of ceramic plates laminated in a thickness direction; a buffer layer disposed between the pair of ceramic plates; and a band-shaped heater portion located between the pair of ceramic plates and disposed in a groove portion provided in at least one of the pair of ceramic plates, wherein a side surface of the heater portion and a side wall surface of the groove 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 pair of ceramic plates, and at least a portion of the buffer layer overlaps with the gap when viewed in the thickness direction.

2. The ceramic joined body according to claim 1, wherein a width dimension of the gap at an opening of the groove is greater than a thickness dimension of a portion of the buffer layer that is sandwiched between the pair of ceramic plates.

3. The ceramic joint according to claim 1, wherein the ratio of the thermal expansion coefficient of said insulating material to the thermal expansion coefficient of said ceramic material is 1.1 or more and 2.0 or less.

4. The ceramic joined body according to claim 1, wherein a width dimension of said heater portion is at least twice the distance between said groove portions in which said heater portion is arranged.

5. The ceramic joined body according to claim 1, wherein a part of the buffer layer is disposed in the gap.

6. A ceramic joined body as set forth in claim 1, wherein a side wall surface of the groove has an inclined surface that inclines in a direction that increases the width dimension of the groove as it approaches the opening side of the groove in the depth direction of the groove.

7. A ceramic joined body according to claim 6, wherein the width dimension of said inclined surface is greater than the thickness dimension of the portion of said buffer layer that is sandwiched between said pair of ceramic plates.

8. A ceramic joint as described in claim 1, wherein the inner wall surface of the groove has, in addition to the pair of side wall surfaces, a bottom wall surface facing the opening side of the groove, and a pair of curved surfaces located at the boundaries between the side wall surfaces and the bottom wall surface and smoothly connecting the side wall surfaces and the bottom wall surface.

9. The ceramic joint according to claim 8, wherein the radius of curvature of the curved surface is greater than the thickness of the buffer layer.

10. The ceramic joined body according to claim 1, wherein the thickness of said heater portion is greater than the depth of said groove portion.

11. An electrostatic chuck device comprising the ceramic bonded body according to any one of claims 1 to 10.

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