Holding member

Abstract

To provide a holding member capable of suppressing the occurrence of cracks due to thermal expansion of a via at a connection point between a pad arranged in a through hole of a planar electrode and the via connected thereto.SOLUTION: A holding member 2 includes: a ceramic tabular member 10 having a mounting surface 11 on which a semiconductor wafer W to be held is placed; a heater electrode 60 provided inside the tabular member 10, a driver electrode 70 provided inside the tabular member 10 and having through holes 72 penetrating in a Z-axis direction; a first via 81 provided extending from the heater electrode 60 toward the through hole 72; a second via 82 provided extending from the through hole 72 toward an opposite side of the heater electrode 60; a pad 80 provided inside the through hole 72 and electrically connecting the first via 81 and the second via 82; and reinforcing portions 14 provided between the pad 80 and the driver electrode 70. Therein the first via 81 and the second via 82 are arranged so as not to overlap when viewed in the Z-axis direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a holding member for holding an object. [Background technology]

[0002] In semiconductor manufacturing processes, a holding member is used to hold a semiconductor wafer. Such a holding member is used, for example, in an electrostatic chuck heater. Patent Document 1, for example, discloses a ceramic heater as an example of this type of electrostatic chuck heater. This ceramic heater includes a resistance heating element (heater electrode) and a planar electrode provided within a ceramic plate (plate-shaped member). A power supply path to the resistance heating element (heater electrode) includes a first via extending from the resistance heating element toward a through hole in the planar electrode, a second via extending from the through hole toward the opposite side of the resistance heating element, and a connecting portion (pad) provided within the through hole to electrically connect the first via and the second via. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7202326 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned ceramic heater, when the ceramic plate is fired, the first and second vias thermally expand, causing thermal stress to act on the connection points with the connecting portions (pads). Furthermore, because the first and second vias connected to the connecting portions (pads) are aligned in a straight line in the thickness direction, thermal stress acts on almost the same locations in the first and second vias. In other words, thermal stress is concentrated and acts on the connection points between the vias and the connecting portions (pads). Therefore, cracks may occur at the connection points between the first vias and the connecting portions (pads) and the connection points between the second vias and the connecting portions (pads).

[0005] Therefore, the present disclosure has been made to solve the above-mentioned problems, and aims to provide a retaining member that can suppress the occurrence of cracks caused by thermal expansion of the via at the connection point between a pad placed in a through hole of a planar electrode and a via connected to it. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present disclosure is to a ceramic plate-shaped member having a mounting surface on which an object to be held is placed; a heater electrode provided inside the plate-shaped member; a planar electrode provided inside the plate-like member and having a through hole penetrating in a thickness direction; a first via provided from the heater electrode toward the through hole; a second via provided from the through hole toward the opposite side of the heater electrode; a pad provided inside the through hole and electrically connecting the first via and the second via; a reinforcing portion provided between the pad and the planar electrode; and The first via and the second via are arranged so as not to overlap each other when viewed in the thickness direction.

[0007] In this holding member, the first via and the second via are arranged offset so as not to overlap when viewed in the thickness direction. This allows the connection point between the first via and the pad and the connection point between the second via and the pad to be offset. Therefore, when the first via and the second via thermally expand, the thermal stress acting on the connection point with the pad acts on different locations for the first via and the second via, preventing the thermal stress from concentrating at one point. Therefore, it is possible to suppress the occurrence of cracks due to thermal expansion at the connection point between the first via and the pad and the connection point between the second via and the pad.

[0008] Furthermore, a reinforcing portion is provided between the pad and the planar electrode (inside the through hole), which increases the bonding strength between the plate-like members located on both sides of the planar electrode. Therefore, even if the first and second vias are offset, deformation of the pad in the thickness direction due to the thermal expansion of the first and second vias can be suppressed. This reduction in the pad's resistance to deformation in the thickness direction also suppresses the occurrence of cracks due to thermal expansion at the connection points between the first and pad vias and the second vias.

[0009] In the above-mentioned holding member, The reinforcing portion is preferably formed in a ring shape and made of ceramics with a grain size of 5 μm or less.

[0010] By forming the reinforcing part from ceramics with a small particle size of 5 μm or less, the contact area between the reinforcing part and the plate-like member can be increased, thereby further increasing the bonding strength between the reinforcing part and the plate-like members located on both sides of the planar electrode.

[0011] In any of the above-mentioned holding members, The reinforcing part is formed in a ring shape and has a density of 2.5 g / cm 3 It is preferable that the ceramic material be one of the above.

[0012] In this way, the reinforcement part has a density of 2.5 g / cm 3 By using the above ceramics, the density of the reinforcing portion increases, which increases the contact area between the reinforcing portion and the plate-like member, thereby further increasing the bonding strength between the reinforcing portion and the plate-like members located on both sides of the planar electrode.

[0013] In any of the above-mentioned holding members, The area of ​​the reinforcing part is 1 mm 2 It is preferable that this is equal to or greater than this.

[0014] The area of ​​the reinforced part is 1 mm 2If the area of ​​the reinforcing portion is less than 1 mm, the contact area between the reinforcing portion and the plate-like member is small, and there is a risk that the bonding strength between the reinforcing portion and the plate-like members located on both sides of the planar electrode cannot be increased. 2 By doing so, it is possible to ensure the contact area between the reinforcing portion and the plate-like member required for increasing the bonding strength, thereby sufficiently increasing the bonding strength between the reinforcing portion and the plate-like members located on both sides of the planar electrode.

[0015] In any of the above-described holding members, The ratio (S1 / S2) of the area S1 of the reinforcing portion to the area S2 of the pad is preferably 20 or less.

[0016] Here, the larger the area of ​​the reinforcing portion, the stronger the bonding strength between the reinforcing portion and the plate-like members located on both sides of the planar electrode. However, as the reinforcing portion becomes larger, the temperature difference between the reinforcing portion and areas other than the reinforcing portion increases, which can cause the reinforcing portion to become a temperature singularity on the mounting surface, resulting in a deterioration of the temperature distribution.

[0017] Therefore, by setting the size of the reinforcing portion so that the ratio (S1 / S2) of the area S1 of the reinforcing portion to the area S2 of the pad is 20 or less, it is possible to ensure sufficient bonding strength while preventing deterioration of the temperature distribution on the mounting surface.

[0018] In any of the above-mentioned holding members, The second via preferably has a portion extending in a direction substantially perpendicular to the thickness direction.

[0019] The second via often has a longer dimension in the thickness direction than the first via. In such cases, the second via, which has a longer dimension in the thickness direction than the first via, experiences greater thermal expansion than the first via, increasing the risk of cracks occurring at the connection point with the pad. Therefore, by providing the second via with a portion that extends in a direction approximately perpendicular to the thickness direction, it is possible to reduce the thermal stress that occurs at the connection point between the second via and the pad when the second via thermally expands. Therefore, it is possible to further suppress the occurrence of cracks due to thermal expansion at the connection point between the second via and the pad.

[0020] And as an electrostatic chuck, Any one of the holding members described above; an electrostatic electrode provided inside the plate-shaped member and configured to generate an electrostatic attraction force for fixing the object to the placement surface; a base member joined to a surface opposite to the mounting surface; It is preferable that the holding member and the base member are joined together by a bonding layer.

[0021] Such an electrostatic chuck can suppress the occurrence of cracks at the connection points between the first via and the pad, the second via and the pad, thereby improving the reliability of the electrostatic chuck and enabling accurate temperature control of an object held on the mounting surface. [Effects of the Invention]

[0022] According to the present disclosure, a holding member can be provided that can suppress the occurrence of cracks caused by thermal expansion of the via at the connection point between the pad placed in the through hole of the planar electrode and the via connected to it. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic perspective view of an electrostatic chuck according to an embodiment; [Figure 2] 3 is a schematic configuration diagram of an XZ cross section of a holding member according to an embodiment. FIG. [Figure 3] FIG. 3 is a diagram showing the shape of a heater electrode. [Figure 4] FIG. 2 is a diagram showing the shape of a driver electrode. [Figure 5] FIG. 3 is an enlarged view of part A shown in FIG. 2. [Figure 6] 10 is a diagram showing an XY cross section of a reinforcing portion and a pad. FIG. [Figure 7] FIG. 10 is a diagram showing the results of a durability test of the examples. [Figure 8] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] A holding member according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, a case where the holding member according to the present disclosure is applied to an electrostatic chuck used in a semiconductor manufacturing apparatus such as a film forming apparatus (such as a CVD film forming apparatus or a sputtering film forming apparatus) or an etching apparatus (such as a plasma etching apparatus) will be described.

[0025] 1 to 6, an electrostatic chuck 1 according to this embodiment will be described. The electrostatic chuck 1 according to this embodiment is a device that attracts and holds a semiconductor wafer W (object) by electrostatic attraction, and is used, for example, to fix the semiconductor wafer W in a vacuum chamber of a semiconductor manufacturing device. As shown in FIG. 1, the electrostatic chuck 1 includes a holding member 2, a base member 20, and a bonding layer 30 that bonds the holding member 2 and the base member 20 together.

[0026] In the following description, for convenience of explanation, X, Y, and Z axes are defined as shown in Fig. 1. Here, the Z axis is the axis in the axial direction of the electrostatic chuck 1 (the up-down (vertical) direction in Fig. 1) and is an example of the "thickness direction" in the present disclosure. The X and Y axes are axes in the radial (horizontal) direction of the electrostatic chuck 1.

[0027] 1, the holding member 2 is a disk-shaped member and has a plate-shaped member 10 made of ceramics. The plate-shaped member 10 has an upper surface, that is, a mounting surface 11 on which a semiconductor wafer W is placed, and a lower surface 12 provided on the opposite side of the mounting surface 11 in the thickness direction (Z-axis direction) of the plate-shaped member 10.

[0028] Although various ceramics are used as the ceramic, it is preferable to use ceramics whose main component is, for example, aluminum oxide (alumina, Al2O3) or aluminum nitride (AlN) from the viewpoint of strength, wear resistance, plasma resistance, etc. The main component here means the component with the highest content (for example, a component with a volume content of 90 vol% or more).

[0029] The diameter of the plate-shaped member 10 is, for example, about 150 mm to 350 mm. The thickness of the plate-shaped member 10 is, for example, about 2 mm to 60 mm. The thermal conductivity of the plate-shaped member 10 is preferably in the range of 10 W / mK to 50 W / mK (more preferably, 18 W / mK to 30 W / mK).

[0030] 2, such a plate-like member 10 has therein a chuck electrode 50, a heater electrode 60, and a driver electrode 70. The chuck electrode 50 is an example of an "electrostatic electrode" in the present disclosure, and the driver electrode 70 is an example of a "planar electrode" in the present disclosure.

[0031] The chuck electrode 50 has, for example, a substantially circular shape when viewed in the Z-axis direction, and is made of a conductive material (for example, tungsten or molybdenum). The chuck electrode 50 is disposed over almost the entire area of ​​the mounting surface 11 (slightly smaller than the mounting surface 11) when viewed in the Z-axis direction. When a voltage is applied to the chuck electrode 50, an electrostatic attraction (adsorption force) is generated over the entire area of ​​the mounting surface 11, and the semiconductor wafer W is attracted and fixed to the mounting surface 11 by this electrostatic attraction.

[0032] The heater electrode 60 is an electrode for uniformly heating the entire mounting surface 11, and is patterned, for example, spirally as viewed in the Z-axis direction. This heater electrode 60 is configured of a linear heating resistor made of a metal material (e.g., tungsten, molybdenum, etc.) that generates heat when a voltage is applied and a current flows. In this embodiment, as shown in FIG. 3, the heater electrode 60 is configured by arranging heating resistors 100 patterned to match the shape of each heating zone in each heating zone that is virtually divided into a circular zone and an annular zone (or an arc-shaped zone) on the inside and outside of the plate-like member 10 as viewed in the Z-axis direction. Pad portions 101, 102 are formed on both ends of the heating resistor 100.

[0033] The driver electrode 70 is an electrode for supplying power to the heater electrode 60, and as shown in FIG. 4, includes conductor patterns 70a and 70b patterned to have predetermined regions parallel to the plane (XY plane). In this embodiment, the driver electrode 70 includes a set of conductor patterns: a circular conductor pattern 70a and an annular conductor pattern 70b. The conductor patterns may have other shapes (e.g., semicircular, arc-shaped, or fan-shaped). The number of conductor patterns is not limited to two (one set) and may be four or more (two sets). Each of the conductor patterns 70a and 70b of the driver electrode 70 is provided with a through-hole 72 penetrating in the Z-axis direction. The driver electrode 70 is formed of a conductive material (e.g., tungsten, molybdenum, etc.).

[0034] A power supply path is formed inside the plate-like member 10, electrically connecting the heater electrode 60 and the driver electrode 70 and supplying power to the heater electrode 60. The power supply path is made up of the driver electrode 70 and a plurality of vias and pads. In this embodiment, for example, as shown in FIG. 2, the power supply path to the heater electrode 60 is made up of the driver electrode 70, first to fourth vias 81 to 84 that extend linearly in the Z-axis direction (the vertical direction in the figure), and a pad 80 arranged in the through-hole 72.

[0035] The first to fourth vias 81 to 84 are rod-shaped conductive members extending in the Z-axis direction within the plate-shaped member 10, and are made of a conductive material such as tungsten or molybdenum. The pad 80 is a conductor pattern formed in a circular shape when viewed in the Z-axis direction, and is made of a conductive material such as tungsten or molybdenum.

[0036] The first via 81 is provided from the heater electrode 60 toward the through hole 72, with one end connected to the heater electrode 60 (pad portion 101) and the other end connected to the upper surface of the pad 80. The second via 82 is provided from the through hole 72 toward the opposite side from the heater electrode 60, with one end connected to the lower surface of the pad 80 and the other end exposed at the lower surface 12 of the plate-like member 10. In this way, the first via 81 and the second via 82 are electrically connected via the pad 80, and the other end of the second via 82 is connected to an external power supply (not shown).

[0037] The first via 81 and the second via 82, which are electrically connected via the pad 80, are arranged offset so as not to overlap when viewed in the Z-axis direction. Note that "arranged offset so as not to overlap when viewed in the Z-axis direction" means that the central axes of the first via 81 and the second via 82 do not overlap (do not coincide) when viewed in the Z-axis direction, but it is preferable that the vias are arranged apart so that the outer periphery of the first via 81 and the outer periphery of the second via 82 do not intersect when viewed in the Z-axis direction.

[0038] The third via 83 is provided between the heater electrode 60 and the driver electrode 70, with one end connected to the heater electrode 60 (pad portion 102) and the other end connected to the driver electrode 70. The fourth via 84 is provided from the driver electrode 70 toward the lower surface 12, with one end connected to the driver electrode 70 and the other end exposed at the lower surface 12. The other end of the fourth via 84 is connected to ground.

[0039] Here, as shown in Figures 5 and 6, a ring-shaped reinforcing portion 14 is provided around the pad 80. This reinforcing portion 14 is disposed in the through-hole 72, that is, between the pad 80 and the driver electrode 70. The reinforcing portion 14 is made of ceramics with a particle size of 5 µm or less. The density of the ceramics forming the reinforcing portion 14 is 2.5 g / cm3. 3 It would be better if it was more than that.

[0040] The area S1 of the reinforcing portion 14 is 1 mm 2 As described above, the ratio (S1 / S2) of the area S1 of the reinforcing portion 14 to the area S2 of the pad 80 is equal to or less than 20. The areas S1 and S2 are the areas in the XY cross section of the driver electrode 70, and can be measured by cutting the driver electrode 70 along the XY plane perpendicular to the Z-axis direction.

[0041] 1, the base member 20 is disposed on the opposite side of the plate-like member 10 from the mounting surface 11. The base member 20 is formed, for example, in a cylindrical shape. The base member 20 is formed, for example, from a metal (for example, aluminum or an aluminum alloy), but may be formed from a material other than metal.

[0042] 1 and 2, the base member 20 has an upper surface 21 and a lower surface 22 provided on the opposite side to the upper surface 21 in the thickness direction (i.e., the Z-axis direction) of the base member 20. The upper surface 21 of the base member 20 is thermally connected to the lower surface 12 of the plate-like member 10 via a bonding layer 30.

[0043] The base member 20 is formed with a coolant flow path (not shown) for flowing a coolant (e.g., a fluorine-based inert liquid, water, etc.). By flowing the coolant through this coolant flow path, the base member 20 is cooled, and the plate-like member 10 is cooled via the bonding layer 30. This allows the semiconductor wafer W held on the mounting surface 11 to be cooled.

[0044] 1 and 2, the bonding layer 30 is disposed between the lower surface 12 of the plate-shaped member 10 and the upper surface 21 of the base member 20, and bonds the plate-shaped member 10 and the base member 20 in a heat-transferable manner. The bonding layer 30 is made of a resin adhesive such as a silicone resin, an acrylic resin, or an epoxy resin.

[0045] In the electrostatic chuck 1 having such a configuration, the semiconductor wafer W is attracted and fixed to the mounting surface 11 by the electrostatic force generated by the chuck electrode 50, and various processes are performed on the semiconductor wafer W while the temperature of the semiconductor wafer W is controlled by the heater electrode 60. If the temperature of the semiconductor wafer W is not controlled accurately, the accuracy of the processes will decrease. Therefore, in order to control the temperature of the semiconductor wafer W accurately, it is important to supply power to the heater electrode 60 accurately, and it is required that the power supply path to the heater electrode 60 is free of defects such as cracks.

[0046] Here, the holding member 2 is formed by firing ceramics. During firing, the vias 81-84 thermally expand, causing thermal stress to act on both ends of the vias (connections with the pads and electrodes). If the first and second vias connected to the pads are aligned in the Z-axis direction as in the conventional example, the thermal stress acts on approximately the same location in the first and second vias at the connection between the pad and the vias, resulting in concentrated thermal stress at the connection between the first and second vias and the pad. This may result in cracks occurring at the connection between the first via and the pad and at the connection between the second via and the pad.

[0047] Therefore, in the holding member 2 of this embodiment, the first via 81 and the second via 82 connected to the pad 80 arranged in the through hole 72 of the driver electrode 70 are arranged so as to be offset so as not to overlap when viewed in the Z-axis direction. Therefore, the connection portion between the first via 81 and the pad 80 and the connection portion between the second via 82 and the pad 80 are offset. In other words, on the top and bottom surfaces of the pad 80, the connection portions between the first via 81 and the second via 82 are positioned so as not to overlap when viewed in the Z-axis direction.

[0048] As a result, when the first via 81 and the second via 82 thermally expand, the thermal stress acting on the connection portion with the pad 80 acts on different locations for the first via 81 and the second via 82. This prevents the thermal stress from concentrating at one point. This makes it possible to suppress the occurrence of cracks due to thermal expansion of the vias in the connection portion between the first via 81 and the pad 80 and the connection portion between the second via 82 and the pad 80. As a result, power can be supplied to the heater electrode 60 with high precision.

[0049] In the electrostatic chuck 1, a ring-shaped reinforcing portion 14 is provided between the pad 80 and the driver electrode 70 within the through hole 72. This allows the reinforcing portion 14 to increase the bonding strength between the plate-like members 10 located on both the upper and lower sides of the driver electrode 70. Therefore, even if the first via 81 and the second via 82 are arranged offset from each other, deformation of the pad 80 in the thickness direction (Z-axis) due to the influence of thermal expansion of the first via 81 and the second via 82 can be suppressed. Such suppression of deformation of the pad 80 also suppresses the occurrence of cracks due to thermal expansion of the vias 81 and 82 at the connection portion between the first via 81 and the pad 80 and the connection portion between the second via 82 and the pad 80.

[0050] The reinforcing portion 14 is made of ceramics with a particle size of 5 μm or less. This increases the contact area between the reinforcing portion 14 and the plate-like member 10, thereby further increasing the bonding strength between the reinforcing portion 14 and the plate-like members 10 located on both the upper and lower sides of the driver electrode 70. Furthermore, the density of the ceramics forming the reinforcing portion 14 is set to 2.5 g / cm 3 By doing so, the density of the reinforcing portion 14 increases, and it is possible to increase the contact area between the reinforcing portion 14 and the plate-like member 10. This makes it possible to further increase the bonding strength between the reinforcing portion 14 and the plate-like members 10 located on both the upper and lower sides of the driver electrode 70.

[0051] Here, if the area S1 of the reinforcing portion 14 is too small, it may not be possible to increase the bonding strength between the reinforcing portion 14 and the plate-like members 10 located on both the upper and lower sides of the driver electrode 70. On the other hand, if the area S1 of the reinforcing portion 14 is too large, the temperature difference between the reinforcing portion 14 and the area other than the reinforcing portion 14 becomes large, which may cause the area of ​​the reinforcing portion 14 to become a temperature singularity on the mounting surface 11, resulting in a deterioration of the temperature distribution. Therefore, it is necessary to set the area S1 of the reinforcing portion 14 to an appropriate size so that the necessary and sufficient bonding strength is obtained and temperature singularities do not occur.

[0052] Therefore, a plurality of test pieces (Examples 1 to 5) were prepared for each Example, each having a different combination of the area S1 of the reinforcing portion 14 and the area S2 of the pad 80, and a durability test was conducted. The test results are shown in FIG. 7. In FIG. 7, the test results "◯" indicate that no cracks occurred in any of the plurality of test pieces, and "△" indicate that very small cracks occurred in some of the plurality of test pieces. The durability test involved repeating a heat-to-cool cycle 3,000 times, in which the temperature of the mounting surface was heated from 30°C to 120°C, and then cooled to 30°C after reaching 120°C.

[0053] In each example, the respective areas are as follows: (1) In Example 1, the area S1 of the reinforcing portion 14 is 3.7 mm 2 , the area S2 of the pad 80 is 1.8 mm 2 , the area ratio S1 / S2 is 2.1. (2) In Example 2, the area S1 of the reinforcing portion 14 is 20 mm 2 , the area S2 of the pad 80 is 1.8 mm 2 , the area ratio S1 / S2 is 11.1. (3) In Example 3, the area S1 of the reinforcing portion 14 is 5.0 mm 2 , the area S2 of the pad 80 is 0.25 mm 2 , the area ratio S1 / S2 is 20. (4) In Example 4, the area S1 of the reinforcing portion 14 is 8.0 mm 2 , the area S2 of the pad 80 is 0.25 mm 2 , the area ratio S1 / S2 is 32. (5) In Example 5, the area S1 of the reinforcing portion 14 is 0.7 mm 2 , the area S2 of the pad 80 is 0.7 mm 2 , the area ratio S1 / S2 is 1.0.

[0054] As can be seen from the test results shown in FIG. 7, the results for Examples 1 to 4 were "◯", meaning that no cracks occurred in any of the multiple test pieces. In contrast, the result for Example 5 was "△", meaning that very small cracks occurred in some of the multiple test pieces. In this way, when the area S1 of the reinforcing portion 14 is small (0.7 mm in Example 5), 2 ), it was confirmed that cracks occurred. This is because the contact area between the reinforcing portion 14 and the plate-like member 10 is small, and the bonding strength between the reinforcing portion 14 and the plate-like member 10 located on both sides of the driver electrode 70 cannot be sufficiently ensured.

[0055] Therefore, in this embodiment, the area S1 of the reinforcing portion 14 is set to 1 mm 2 The above settings are made. This makes it possible to ensure the contact area between the reinforcing portion 14 and the plate-like member 10 required to increase the bonding strength between the reinforcing portion 14 and the plate-like members 10 located on both sides of the driver electrode 70. Therefore, it is possible to sufficiently increase the bonding strength between the reinforcing portion 14 and the plate-like members 10 located on both sides of the driver electrode 70. As a result, it is possible to suppress the occurrence of cracks in the connection portions between the pad 80 and the vias 81, 82 due to thermal expansion of the vias 81, 82.

[0056] Here, if the reinforcing portion 14 becomes large, the temperature difference between the reinforcing portion 14 and the area other than the reinforcing portion 14 becomes large, which may cause the area directly above the reinforcing portion 14 on the mounting surface 11 to become a temperature singularity point, resulting in a deterioration in the temperature distribution.

[0057] In Examples 1 to 4, for which the results were "○", as the ratio (S1 / S2) of the area S1 of the reinforcing portion 14 to the area S2 of the pad 80 increased, the temperature difference between the area directly above the reinforcing portion 14 and other areas on the mounting surface 11 increased, and in Example 4, an unacceptable temperature difference occurred.

[0058] Therefore, in this embodiment, the size of the reinforcing portion 14 is set so that the ratio (S1 / S2) of the area S1 of the reinforcing portion 14 to the area S2 of the pad 80 is equal to or less than 20. This makes it possible to prevent deterioration of the temperature distribution on the mounting surface 11 while ensuring the necessary and sufficient bonding strength.

[0059] In this manner, in this embodiment, in order to limit the size of the reinforcing portion 14, the area S1 of the reinforcing portion 14 is set to 1 mm 2 In addition to the above, the area ratio (S1 / S2) of the area S1 to the area S2 of the pad 80 is set to be equal to or less than 20. This makes it possible to suppress the occurrence of cracks at the connection portions between the pad 80 and the vias 81, 82 due to thermal expansion of the vias 81, 82, and to prevent deterioration of the temperature distribution on the mounting surface 11.

[0060] Next, a modified example of the electrostatic chuck (holding member) will be described with reference to Fig. 8. In this modified example, as shown in Fig. 8, the shape of the second via 82 is different from that of the above embodiment. That is, the second via 82 in the modified example has a portion that extends in a direction (XY plane direction: horizontal direction in the figure) that is approximately perpendicular to the thickness direction of the plate-shaped member 10 (Z-axis direction: vertical direction in the figure). In other words, the second via 82 in the modified example does not extend in a straight line in the Z-axis direction, but has a shape that is partially bent.

[0061] Generally, the dimension of the second via 82 in the Z-axis direction is often longer than that of the first via 81 (see FIG. 2). In such a case, the second via 82, which has a dimension longer in the Z-axis direction than the first via 81, will have a larger thermal expansion than the first via 81, and therefore there is a higher risk of cracks occurring at the connection point with the pad 80.

[0062] Therefore, in this modification, the second via 82 is provided with a portion that extends in the XY plane (horizontal) direction, which is approximately perpendicular to the Z-axis (vertical) direction. As a result, the portion of the second via 82 that extends in the Z-axis direction and is connected to the pad 80 is shortened. By shaping the second via 82 in this way, it is possible to reduce the thermal stress that occurs at the connection point between the second via 82 and the pad 80 when the second via 82 thermally expands. Therefore, in this modification, it is possible to further suppress the occurrence of cracks due to thermal expansion at the connection point between the second via 82 and the pad 80.

[0063] As described above, according to the electrostatic chuck 1 of this embodiment, the first via 81 and the second via 82 connected to the pad 80 are arranged at a position offset from each other so as not to overlap when viewed in the Z-axis direction. This allows the connection point between the first via 81 and the pad 80 and the connection point between the second via 82 and the pad 80 to be offset from each other. Therefore, when the first via 81 and the second via 82 thermally expand, the thermal stress acting on the connection point with the pad 80 acts on different positions for the first via 81 and the second via 82, preventing the thermal stress from concentrating at one point. As a result, the occurrence of cracks due to thermal expansion can be suppressed at the connection point between the first via 81 and the pad 80 and the connection point between the second via 82 and the pad 80.

[0064] Furthermore, since reinforcing portion 14 is provided between pad 80 and driver electrode 70 (inside through hole 72), this reinforcing portion 14 can increase the bonding strength between the plate-like members located on both the upper and lower sides of driver electrode 70. Therefore, even if first via 81 and second via 82 are arranged with a shift, deformation of pad 80 in the Z-axis direction due to the influence of thermal expansion of first via 81 and second via 82 can be suppressed. This suppression of deformation of pad 80 in the Z-axis direction also suppresses the occurrence of cracks due to thermal expansion at the connection point between first via 81 and pad 80 and the connection point between second via 82 and pad 80.

[0065] As described above, the electrostatic chuck 1 of the present embodiment can suppress the occurrence of cracks at the connection points between the first via 81 and the pad 80, and between the second via 82 and the pad 80. This improves the reliability of the electrostatic chuck 1, and also enables accurate temperature control of the semiconductor wafer W held on the mounting surface 11.

[0066] It should be noted that the above-described embodiments are merely examples and do not limit the present disclosure in any way, and various improvements and modifications are possible without departing from the spirit and scope of the present disclosure. For example, in the above-described embodiments, the present disclosure is applied to an electrostatic chuck, but the present disclosure is not limited to electrostatic chucks and can be applied to any holding device that holds an object on the surface of a plate-like member.

[0067] In addition, in the modified example, the second via 82 has a portion extending in the XY plane direction substantially perpendicular to the Z-axis direction, but the first via 81 may also have a portion extending in the XY plane direction in the same manner. [Explanation of symbols]

[0068] 1. Electrostatic chuck 2. Retaining member 10 Plate-shaped member 11 Placement surface 14 Reinforcement 60 heater electrode 70 Driver Electrode 72 through holes 80 pads 81 First Via 82 Second Via W Semiconductor wafer

Claims

1. a ceramic plate-shaped member having a mounting surface on which an object to be held is placed; a heater electrode provided inside the plate-shaped member; a planar electrode provided inside the plate-like member and having a through hole penetrating in a thickness direction; a first via provided from the heater electrode toward the through hole; a second via provided from the through hole toward an opposite side to the heater electrode; a pad provided inside the through hole and electrically connecting the first via and the second via; a reinforcing portion provided between the pad and the planar electrode; and The first via and the second via are arranged so as not to overlap each other when viewed in the thickness direction. A holding member characterized by:

2. 2. The holding member according to claim 1, The reinforcing portion is formed in a ring shape and is made of ceramics with a grain size of 5 μm or less. A holding member characterized by:

3. 2. The holding member according to claim 1, The reinforcing portion is formed in a ring shape and has a density of 2.5 g / cm ３ Composed of the above ceramics A holding member characterized by:

4. 2. The holding member according to claim 1, The area of ​​the reinforcing portion is 1 mm ２ That's all A holding member characterized by:

5. The holding member according to claim 4, The ratio (S1 / S2) of the area S1 of the reinforcing portion to the area S2 of the pad is 20 or less. A holding member characterized by:

6. 2. The holding member according to claim 1, The second via has a portion extending in a direction substantially perpendicular to the thickness direction. A holding member characterized by:

7. A holding member according to any one of claims 1 to 4 and 6; an electrostatic electrode provided inside the plate-shaped member and configured to generate an electrostatic attraction force for fixing the object to the placement surface; a base member joined to a surface opposite to the mounting surface; a bonding layer that bonds the holding member and the base member together Electrostatic chuck characterized by:

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