Holding device

Abstract

To provide a holding device capable of improving joint strength of a plate-like member and a base member.SOLUTION: In an electrostatic chuck 1 which has a plate-like member 10 having a holding surface 11 and a lower surface 12 provided on an opposite side to the holding surface 11, a base member 20 having an upper surface 21 and a lower surface 22 provided on an opposite side to the upper surface 21, and a joint layer 30 which is arranged between the lower surface 12 and the upper surface 21 and joins the plate-like member 10 and the base member 20, and holds a semiconductor wafer W on the holding surface 11 of the plate-like member 10, the joint layer 30 has a joint material 32 containing metal as a main component and a metal member 31 having a plurality of holes in communication with each other, the joint material 32 enters into at least a part of the holes of the metal member 31, and the metal member 31 has a high density region R1 and a low density region R2 when being viewed from an arrangement direction of the plate-like member 10 and the base member 20.SELECTED DRAWING: Figure 3

Description

Technical Field

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[0001] The present disclosure relates to a holding device for holding an object.

Background Art

[0002] As a holding device for holding an object, there is known one having a holding member (plate-like member), a base member, and a bonding layer for bonding the holding member and the base member. Among this type of holding device, there is one in which the holding member and the base member are bonded using a bonding layer provided with a bonding material containing a metal having a low surface tension. For example, in the electrostatic chuck (holding device) described in Patent Document 1, a mesh member having a high thermal conductivity is provided in the bonding layer for bonding an insulating member (plate-like member) and a base (base member).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above holding device, since there is a difference in thermal expansion between the plate-like member and the base member, the amount of dimensional deformation in each case when the temperature rises / falls is different, and a difference occurs in the radial dimension during thermal expansion / contraction. Therefore, if the radial dimensional difference generated between the two members during thermal expansion / contraction is large, there is a risk that the bonding layer will be damaged during thermal expansion / contraction. And in the above holding device, since the bonding layer is provided with a mesh member, the mesh member inhibits the deformation of the bonding material during thermal expansion / contraction, so there is a problem that the bonding layer is easily damaged.

[0005] Therefore, this disclosure has been made to solve the above-mentioned problems, and aims to provide a holding device that can improve the bonding strength between a plate-shaped member and a base member while preventing damage to the bonding layer including the bonding material. [Means for solving the problem]

[0006] One form of this disclosure made to solve the above problem is: A plate-shaped member having a first surface and a second surface provided on the opposite side of the first surface, A base member having a third surface and a fourth surface provided on the opposite side of the third surface, It has a bonding layer disposed between the second surface and the third surface to join the plate-like member and the base member, In a holding device for holding an object on the first surface of the plate-shaped member, The bonding layer comprises a bonding material mainly composed of metal and a metal member having a plurality of holes communicating with each other. The joining material is inserted into at least a portion of the hole in the metal member. The metal member is characterized in that, when viewed from the direction of arrangement between the plate-shaped member and the base member, it has a high-density region and a low-density region.

[0007] In this way, by providing a metal member having multiple interconnected holes in the bonding layer, the bonding material, which is mainly composed of metal, enters at least a portion of the holes in the metal member. As a result, the bonding material spreads throughout the entire bonding interface between the plate-shaped member and the base member and the bonding layer, while preventing the bonding material from flowing out from between the plate-shaped member and the base member. This allows the bonding material to be retained in the bonding layer, thereby suppressing a decrease in the bonding strength between the plate-shaped member and the base member. The main component of the bonding material refers to the component that accounts for 50% or more of the total weight of the bonding material.

[0008] Here, the metal member has both high-density regions (low porosity) and low-density regions (high porosity). Note that the high-density region includes cases where the porosity is zero. In the high-density region, the joining material can be held (retained) better than in the low-density region, and the thickness of the joining material can be kept constant without variation. This is because the thickness changes less in the high-density region, and it is less affected by heating and pressurizing during joining. On the other hand, in the low-density region, the deformation of the joining material can be avoided.

[0009] Therefore, in the bonding layer, by forming low-density regions of metal members in areas where there is a large dimensional difference between the plate-shaped member and the base member during thermal expansion / contraction, and forming high-density regions of metal members in areas where it is undesirable for the bonding material to leak out from between the plate-shaped member and the base member, it is possible to improve the bonding strength of the bonding layer while preventing damage to the bonding layer due to thermal expansion / contraction.

[0010] In the above-described holding device, The bonding layer has through holes that penetrate in the thickness direction, Preferably, the high-density region is formed around the through-hole.

[0011] As a result, the bonding material is retained in high-density areas, preventing it from flowing into the through-hole. Therefore, if the through-hole is a terminal hole, the occurrence of insulation failure due to leakage of bonding material into the through-hole can be suppressed. If the through-hole is a lift pin hole, the occurrence of malfunction of the lift pin due to leakage of bonding material into the through-hole can be suppressed. Furthermore, if the through-hole is a gas hole that supplies inert gas to the first surface, the blockage of the through-hole due to leakage of bonding material into the through-hole can be suppressed. In this way, the occurrence of insulation failure, malfunction, and blockage of through-holes in the retaining device can be suppressed, thereby preventing loss of function of the retaining device.

[0012] In any of the above-mentioned holding devices, Preferably, the high-density region is formed in the central portion of the bonding layer.

[0013] As a result, the density of the metal members is higher in the central part of the joint layer than in the outer peripheral part located outside the central part. Therefore, in the central part where the density of the metal members is higher, the joint material is less likely to flow out from between the plate-shaped member and the base member, thereby improving the joint strength of the joint layer. On the other hand, in the outer peripheral part where the radial dimensional difference between the plate-shaped member and the base member is large during thermal expansion / contraction, the density of the metal members is lower, so it is possible to avoid hindering the deformation of the joint material. Thus, damage to the joint layer during thermal expansion / contraction can be prevented.

[0014] In any of the above-mentioned holding devices, The bonding layer has through holes that penetrate in the thickness direction, The high-density region includes a first high-density region formed around the through hole and a second high-density region formed in the central part of the bonding layer. It is preferable that the density of the metal member in the first high-density region is higher than that in the second high-density region.

[0015] Thus, when high-density regions are formed around the through-hole and in the central part of the joint layer, increasing the density of the metal member around the through-hole compared to the central part improves the joint strength of the joint layer, while also ensuring that the thickness of the joint layer (jointing material) is consistent across products and preventing the joining material from flowing into the through-hole.

[0016] In any of the above-mentioned holding devices, The heat transfer coefficient of the metal member is preferably 1 / 4 to 3 times that of the bonding material.

[0017] The overall heat conduction in the bonded layer is determined by the combination of the metal component and the bonding material. Therefore, if the heat transfer coefficient of the metal component is less than 1 / 4 times that of the bonding material, the overall heat conductivity of the bonded layer will decrease, which may reduce the uniformity of the heat distribution on the first surface.

[0018] On the other hand, when the heat transfer coefficient of the porous body becomes greater than three times the heat transfer coefficient of the bonding material, most of the heat conduction in the bonding layer is carried out through the metal member. Therefore, the shape of the metal member is transferred to the temperature distribution on the first surface, and there is a risk that the heat uniformity on the first surface will deteriorate.

[0019] Therefore, by setting the heat transfer coefficient of the metal member to 1 / 4 to 3 times the heat transfer coefficient of the bonding material, an appropriate heat conductivity can be ensured for the entire bonding layer, so that the temperature distribution on the first surface can be made uniform. Preferably, the heat transfer coefficient of the metal member is set to 1 to 2 times the heat transfer coefficient of the bonding material. Thereby, the heat conductivity of the entire bonding layer can be appropriately increased, and the heat uniformity of the temperature distribution on the first surface can be improved.

Advantages of the Invention

[0020] According to the present disclosure, it is possible to provide a holding device that can improve the bonding strength between the plate-like member and the base member while preventing damage to the bonding layer including the bonding material.

Brief Description of the Drawings

[0021] [Figure 1] It is a schematic perspective view of the electrostatic chuck of the first embodiment. [Figure 2] It is a partial cross-sectional view of the electrostatic chuck of the first embodiment. [Figure 3] It is a plan view showing a metal member (bonding layer). [Figure 4] It is an enlarged view of part A shown in FIG. 3. [Figure 5] It is a diagram showing an example of a combination of a metal member and a bonding material. [Figure 6] It is a diagram showing a modification in the first embodiment. [Figure 7] It is a plan view showing a metal member (bonding layer) in the second embodiment. [Figure 8] It is a diagram showing a modification in the second embodiment. [Modes for carrying out the invention]

[0022] The holding device, which is an embodiment of the present disclosure, will be described in detail with reference to the drawings. In this embodiment, for example, an electrostatic chuck used in semiconductor manufacturing equipment such as a film deposition apparatus (CVD film deposition apparatus, sputtering film deposition apparatus, etc.) and an etching apparatus (plasma etching apparatus, etc.) will be given as an example.

[0023] [First Embodiment] First, the electrostatic chuck 1 of the first embodiment will be described with reference to Figures 1 to 4. The electrostatic chuck 1 of this embodiment is a device that attracts and holds a semiconductor wafer W (object) by electrostatic attraction, and is used, for example, to fix a semiconductor wafer W in a vacuum chamber of a semiconductor manufacturing apparatus. As shown in Figure 1, the electrostatic chuck 1 has a plate-shaped member 10, a base member 20, and a bonding layer 30 that joins the plate-shaped member 10 and the base member 20.

[0024] In the following explanation, for the sake of clarity, the XYZ axes are defined as shown in Figure 1. Here, the Z axis is the axial axis of the electrostatic chuck 1 (vertical direction in Figure 1), and the X and Y axes are the radial axes of the electrostatic chuck 1. Note that the Z axis direction is an example of the "arrangement direction of plate-like members and base members" and the "thickness direction" as described in this disclosure.

[0025] As shown in Figure 1, the plate-shaped member 10 is a circular member made of ceramics. Various ceramics can be used, but from the viewpoint of strength, wear resistance, plasma resistance, etc., it is preferable to use ceramics mainly composed of aluminum oxide (alumina, Al2O3) or aluminum nitride (AlN). Here, "main component" means the component with the highest content (for example, a component with a volume content of 90 vol% or more).

[0026] Furthermore, the diameter of the plate-shaped member 10 is, for example, about 150 to 350 mm. The thickness of the plate-shaped member 10 is, for example, about 1 to 6 mm. The thermal conductivity of the plate-shaped member 10 is preferably in the range of 10 to 200 W / mK.

[0027] As shown in Figures 1 and 2, the plate-shaped member 10 includes a holding surface 11 for holding the semiconductor wafer W, and a lower surface 12 provided on the opposite side of the holding surface 11 in the thickness direction (direction coinciding with the Z-axis direction) of the plate-shaped member 10. The holding surface 11 is an example of the "first surface" of this disclosure, and the lower surface 12 is an example of the "second surface" of this disclosure.

[0028] As shown in Figure 2, the plate-shaped member 10 is equipped with a chuck electrode 40 inside. The chuck electrode 40 is, for example, approximately circular in shape when viewed in the Z-axis direction and is made of a conductive material (for example, tungsten or molybdenum). Power is supplied to the chuck electrode 40 from an external power source (not shown), which generates an electrostatic attraction (adsorption force). This electrostatic attraction causes the semiconductor wafer W to be attracted and fixed to the holding surface 11 of the plate-shaped member 10.

[0029] Furthermore, a recess 13 is formed on the lower surface 12 of the plate-shaped member 10. The end portion 15a of an electrode terminal 15, which supplies power from an external power source (not shown) to internal electrodes such as a chuck electrode 40, is located in this recess 13. Through holes 16 and 17 are also formed in the plate-shaped member 10. The through hole 16 penetrates the plate-shaped member 10 in the Z-axis direction, and a lift pin 18 is inserted into it. The through hole 17 serves as a gas channel through which an inert gas (e.g., helium gas) supplied between the holding surface 11 and the semiconductor wafer W when the semiconductor wafer W is held on the holding surface 11 flows.

[0030] As shown in Figure 1, the base member 20 has an upper surface 21 and a lower surface 22 provided on the opposite side of the upper surface 21 in the thickness direction (i.e., the Z-axis direction) of the base member 20, and is formed in a cylindrical shape. The base member 20 is preferably made of metal (for example, aluminum or an aluminum alloy, etc.), but may be made of a material other than metal.

[0031] The diameter of the base member 20 is, for example, about 180 mm to 350 mm. The thickness of the base member 20 (dimension in the Z-axis direction) is, for example, about 20 mm to 50 mm. The thermal conductivity of the base member 20 (assuming aluminum) is preferably in the range of 100 to 250 W / mK (preferably about 230 W / mK).

[0032] The base member 20 has a refrigerant channel (not shown) for flowing a refrigerant (for example, a fluorine-based inert liquid or water). As a result, the plate-shaped member 10 is cooled via the bonding layer 30, and the semiconductor wafer W held by the plate-shaped member 10 is cooled.

[0033] The base member 20 has through holes 25, 26, and 27 formed therein. As shown in Figure 2, each of the through holes 25, 26, and 27 penetrates the base member 20 in the Z-axis direction. An electrode terminal 15 is inserted through through hole 25, a lift pin 18 is inserted through through hole 26, and through hole 27 serves as a gas passage for inert gas.

[0034] As shown in Figure 1, the bonding layer 30 is positioned 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. The lower surface 12 of the plate-shaped member 10 and the upper surface 21 of the base member 20 are thermally connected via this bonding layer 30. The bonding layer 30 comprises a metal member 31 having a plurality of holes communicating with each other, and a bonding material 32 mainly composed of metal.

[0035] The metal member 31 is positioned between the lower surface 12 of the plate-shaped member 10 and the upper surface 21 of the base member 20. The metal member 31 is a substantially circular, planar mesh member, and is woven to form a mesh using multiple wires, for example, made of molybdenum (Mo). As a result, multiple interconnected holes are formed in the metal member 31. Note that the metal member 31 is not limited to a mesh member, but may also be a porous material or a mesh structure material. The material forming the metal member 31 is not limited to molybdenum, but may also be made from tungsten (W), aluminum (Al), titanium (Ti), or alloys thereof.

[0036] The metal member 31 (joint layer 30) has through holes 35, 36, and 37 that penetrate in the thickness direction (Z-axis direction). Through hole 35 connects the recess 13 of the plate-shaped member 10 with the through hole 25 of the base member 20. Through hole 36 connects the through hole 16 of the plate-shaped member 10 with the through hole 26 of the base member 20. Through hole 37 connects the through hole 17 of the plate-shaped member 10 with the through hole 27 of the base member 20.

[0037] As a result, in the electrostatic chuck 1, terminal holes for which electrode terminals 15 are positioned are formed by the recess 13 and the through holes 35 and 25. Lift pin holes for which lift pins 18 are positioned are formed by the through holes 16, 36, and 26. Gas holes for which inert gas flows are formed by the through holes 17, 37, and 27. In this embodiment, the metal member 31 (bonding layer 30) is provided with seven through holes 35 (part of the terminal holes), three through holes 36 (part of the lift pin holes), and two through holes 37 (part of the gas holes), as shown in Figure 3, for example.

[0038] As shown in Figures 3 and 4, the metal member 31 has a high-density region R1 and a low-density region R2. The high-density region R1 is a region with a higher density than the other regions (regions other than the high-density region R1), and the low-density region R2 is a region with a lower density than the high-density region R1. In this embodiment, the high-density region R1 is formed around the through holes 35, 36, and 37, and the low-density region R2 is formed elsewhere. In other words, most of the metal member 31 is the low-density region R2, and the area around the through holes 35, 36, and 37 is the high-density region R1. In this embodiment, the high-density region R1 is formed with a mesh member of, for example, 50 mesh, and the low-density region R2 is formed with a mesh member of, for example, 20 mesh. Figure 4 shows an example of the area around one through hole 36, but the structure around the other through holes 35, 36, and 37 is the same as the structure shown in Figure 4.

[0039] The bonding material 32 is a bonding material mainly composed of metal. The main component of the bonding material refers to the component that accounts for 50% or more of the total weight of the bonding material. The main component of the bonding material is identified using an energy-dispersive X-ray spectrometer (EDS) of a scanning electron microscope (SEM). As the bonding material 32, for example, a bonding material mainly composed of metal such as indium (In), tin (Sn), gold-tin (AuSn), or alloys thereof can be used. Such a bonding material 32 is located in the bonding layer 30 on both the plate-shaped member 10 side and the base member 20 side of the metal member 31, and penetrates at least some of the multiple pores in the metal member 31. In this embodiment, the weight ratio of indium to the total weight of the bonding material 32 is 100%.

[0040] Therefore, in the bonding layer 30, the bonding material 32 spreads throughout the entire bonding interface between the plate-shaped member 10 and the base member 20 and the bonding layer 30, while preventing the bonding material 32 from flowing out from between the plate-shaped member 10 and the base member 20. As a result, the bonding material 32 is retained in the bonding layer 30, and a decrease in the bonding strength between the plate-shaped member 10 and the base member 20 can be suppressed.

[0041] Here, the thermal conductivity in the bonding layer 30 is determined by the combination of the metal member 31 and the bonding material 32. Therefore, if the thermal conductivity of the bonding material 32 is low, it is better if the thermal conductivity of the metal member 31 is high. However, if the mesh opening of the metal member 31 is large (for example, 3 mm or more), or if the wire diameter of the mesh is large (for example, 3 mm or more), the difference in thermal conductivity between the high-density region R1 and the low-density region R2 of the metal member 31 becomes large, which may reduce the uniformity of heat distribution on the holding surface 11.

[0042] Therefore, it is preferable that the heat transfer coefficient of the metal member 31 is 1 / 4 to 3 times the heat transfer coefficient of the bonding material 32 (heat transfer coefficient ratio of 25% to 300%). It is advisable to select a combination of the metal member 31 and the bonding material 32 so that such a heat transfer coefficient ratio is achieved. If the heat transfer coefficient of the metal member 31 is less than 1 / 4 of the heat transfer coefficient of the bonding material 32, the thermal conductivity in the bonding layer 30 will be low, which may reduce the uniformity of the heat on the holding surface 11. On the other hand, if the heat transfer coefficient of the metal member 31 is greater than three times that of the bonding material 32 (for example, if the bonding material is indium (heat transfer coefficient: 82 W / m·K) and the metal member is silver (heat transfer coefficient: 429 W / m·K) (heat transfer coefficient ratio: 523%)), then most of the heat conduction in the bonding layer 30 will occur through the metal member 31. As a result, the shape of the metal member 31 will be transferred to the temperature distribution on the holding surface 11, which may reduce the uniformity of the heat on the holding surface 11.

[0043] By selecting a combination of metal member 31 and bonding material 32 such that the heat transfer coefficient of metal member 31 is in the range of 1 / 4 to 3 times (heat transfer coefficient ratio of 25% to 300%), more preferably in the range of 1 to 2 times (heat transfer coefficient ratio of 25% to 300%), an appropriate thermal conductivity can be ensured for the entire bonding layer 30, thereby enabling a uniform temperature distribution on the holding surface 11. In this embodiment, since the metal member 31 is molybdenum (heat transfer coefficient: 138 W / m·K) and the bonding material 32 is indium (heat transfer coefficient: 82 W / m·K), the heat transfer coefficient ratio is 168%.

[0044] The combination of metal member 31 and bonding material 32 is not limited to molybdenum and indium; for example, as shown in Figure 5, it may be tungsten and indium, aluminum and indium, titanium and tin, molybdenum and tin, tungsten and tin, etc. By using such a combination, an appropriate thermal conductivity can be ensured for the entire bonding layer 30, thereby making the temperature distribution on the holding surface 11 uniform.

[0045] Here, when the electrostatic chuck 1 is used, the temperature rises and falls. Therefore, due to the difference in thermal expansion between the plate-shaped member 10 and the base member 20, the amount of dimensional deformation of each differs when the temperature rises and falls, resulting in a difference in radial dimensions during thermal expansion and contraction. Therefore, if the radial dimensional difference between the two members during thermal expansion and contraction is large, there is a risk that the bonding layer 30 will be damaged during thermal expansion and contraction. Furthermore, since the bonding layer 30 is equipped with a metal member 31, if the metal member 31 hinders the deformation of the bonding material 32 during thermal expansion and contraction, the risk of damage to the bonding layer 30 increases.

[0046] Therefore, in the electrostatic chuck 1 of this embodiment, a high-density region R1 and a low-density region R2 are provided in the metal member 31. That is, in the electrostatic chuck 1, the density is increased around the through holes 35, 36, and 37 of the metal member 31 to form a high-density region R1. This high-density region R1 can hold (retain) the bonding material 32 better than the low-density region R2. As a result, the flow of bonding material 32 into the through holes 35, 36, and 37 can be suppressed. This suppresses the occurrence of insulation failures in the terminal holes due to leakage of bonding material 32 into the through hole 35. It also suppresses the occurrence of malfunctions of the lift pin 18 due to leakage of bonding material 32 into the through hole 36. Furthermore, it suppresses the blockage of the gas hole due to leakage of bonding material 32 into the through hole 37. Therefore, since the occurrence of insulation failures, malfunctions, and blockages of through holes can be suppressed in the electrostatic chuck 1, the loss of function of the electrostatic chuck 1 can be suppressed.

[0047] Here, a 50-mesh mesh member was used as an example for the high-density region R1 around the through holes 35, 36, and 37 of the metal member 31. However, as shown in Figure 6, the high-density region R1 can also be formed from a metal body that is not a mesh member (i.e., has no holes: zero porosity). This reliably prevents the bonding material 32 from flowing into the through holes 35, 36, and 37. A metal member having such a high-density region R1 with zero porosity and a low-density region R2 with 20 mesh can be easily manufactured by etching.

[0048] Furthermore, in the high-density region R1, the thickness of the metal member 31 changes little, and it is less susceptible to the effects of heating and pressurizing during joining, so the thickness of the joining material 32 (joining layer 30) can be kept constant without variation. On the other hand, in the low-density region R2, the deformation of the joining material 32 can be avoided.

[0049] Furthermore, in the electrostatic chuck 1, a high-density region R1 is formed around the numerous through holes 35, 36, and 37 formed in the bonding layer 30, so that the thickness of the bonding layer 30 can be kept constant without variation, and the bonding strength of the bonding layer 30 can be improved. In addition, a low-density region R2 is formed outside the area around the through holes 35, 36, and 37, so that damage to the bonding layer 30 due to thermal expansion / contraction during use can be prevented. Therefore, according to the electrostatic chuck 1 of this embodiment, it is possible to improve the bonding strength of the bonding layer 30 while preventing damage to the bonding layer 30 due to thermal expansion / contraction. Preferably, there is a difference of 20% or more between the porosity of the high-density region R1 and the porosity of the low-density region R2.

[0050] Furthermore, in the electrostatic chuck 1, the combination of the metal member 31 and the bonding material 32 is determined such that the heat transfer coefficient of the metal member 31 is 1 / 4 to 3 times that of the bonding material 32 (heat transfer coefficient ratio of 25% to 300%). This ensures an appropriate thermal conductivity for the entire bonding layer 30 and allows for a uniform temperature distribution on the holding surface 11.

[0051] As described above, according to the electrostatic chuck 1 of this embodiment, a high-density region R1 is formed around the through holes 35, 36, and 37 of the metal member 31, and a low-density region R2 is formed elsewhere. This allows the plate-shaped member 10 and the base member 20 to be joined by a high-quality metal joint using the joining layer 30, thereby preventing damage to the joining layer 30 due to thermal expansion / contraction while improving the joining strength of the joining layer 30.

[0052] [Second Embodiment] Next, a second embodiment will be described. In the second embodiment, the basic configuration is the same as in the first embodiment, but the formation regions of the high-density region R1 and the low-density region R2 in the metal member 31 differ from those in the first embodiment. Therefore, components similar to those in the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted as appropriate, and the differences from the first embodiment will be the focus of the description.

[0053] As shown in Figure 7, in the electrostatic chuck of the second embodiment, a high-density region R1b is formed in the central part of the metal member 31 (bonding layer 30), and a low-density region R2 is formed in the outer peripheral part of the metal member 31 (bonding layer 30) (outside the high-density region R1). Furthermore, a high-density region R1a is formed around the through holes 35, 36, and 37. Since the composition of the high-density region R1a is the same in all cases, Figure 7 shows an enlarged example of the area around one of the through holes 37. The high-density region R1a has a higher density than the high-density region R1b. In this embodiment, for example, the high-density region R1a is formed of a metal body, the high-density region R1b is formed of a 50-mesh mesh member, and the low-density region R2 is formed of a 20-mesh mesh member. Note that the high-density region R1a is an example of the "first high-density region" of this disclosure, and the high-density region R1b is an example of the "second high-density region" of this disclosure.

[0054] As described above, in the electrostatic chuck of the second embodiment, the central portion (high-density region R1b) of the metal member 31 (joining layer 30) has a higher density than the outer portion (low-density region R2). Therefore, the bonding strength of the joining layer 30 can be improved in the high-density region R1b where the density of the metal member 31 is increased. In addition, since the low-density region R2 is formed in the outer portion where the radial dimensional difference between the plate-shaped member 10 and the base member 20 becomes large during thermal expansion / contraction, it is possible to avoid hindering the deformation of the joining material 32. Therefore, it is possible to prevent damage to the joining layer 30 during thermal expansion / contraction.

[0055] Furthermore, since the densest region R1a is formed around the through holes 35, 36, and 37, it is possible to prevent the joining material 32 from flowing into the through holes 35, 36, and 37. In addition, since the densest regions R1a and R1b are formed around and in the center of the numerous through holes 35, 36, and 37, the joining material is less susceptible to the effects of heating and pressurizing during joining, and the thickness of the joining material 32 can be kept constant without variation. With such a joining layer 30, the plate-shaped member 10 and the base member 20 can be joined by high-quality metal joining. Preferably, the densest region R1a is formed to a size of 1 mm to 5 mm from the outer edge of the through holes 35, 36, and 37.

[0056] In the above embodiment, the example given was that the density in the low-density region R2 is constant. However, the density in the low-density region R2 may be changed to decrease gradually or continuously towards the outside. For example, as shown in Figure 8, the low-density region R2a can be formed with a 20-mesh mesh member, and the low-density region R2b outside of the low-density region R2a can be formed with a 10-mesh mesh member. This makes it possible to further prevent the deformation of the bonding material 32 from being hindered in the outer peripheral portion where the radial dimensional difference between the plate-shaped member 10 and the base member 20 is larger during thermal expansion / contraction, thereby preventing damage to the bonding layer 30 during thermal expansion / contraction.

[0057] It should be noted that the above embodiments are merely illustrative and do not limit this disclosure in any way, and various improvements and modifications are possible without departing from the gist of the invention. For example, in the above embodiments, the case in which the weight ratio of indium to the total weight of the bonding material 32 is 100% is illustrated, but the weight ratio of indium is not limited to this, and it is sufficient if the weight ratio to the total weight of the bonding material 32 is 50% or more.

[0058] Furthermore, in the above embodiment, a case in which the density in the low-density region R2 is changed in two stages was illustrated, but the density change in the low-density region R2 may be in three or more stages. Also, the density change in the low-density region R2 is not limited to being changed in steps, but can also be changed continuously. Moreover, the low-density region R2b (the outermost part of the bonding layer 30) can be composed only of the bonding material 32 without providing a mesh member in this region. [Explanation of symbols]

[0059] 1. Electrostatic Chuck 10 Plate-shaped member 11 Holding surface 12 Bottom side 20 Base members 21 Top side 22 Bottom side 30 Bonding layer 31 Metal components 32 Bonding material 35 Through hole 36 Through holes 37 Through hole R1 high density area R1a high density area R1b high density area R2 low density region W Semiconductor wafer

Claims

1. A plate-shaped member having a first surface and a second surface provided on the opposite side of the first surface, A base member having a third surface and a fourth surface provided on the opposite side of the third surface, It has a bonding layer disposed between the second surface and the third surface to join the plate-like member and the base member, In a holding device for holding an object on the first surface of the plate-shaped member, The bonding layer comprises a bonding material mainly composed of metal and a metal member having a plurality of holes communicating with each other. The joining material is inserted into at least a portion of the hole in the metal member. The metal member has a high-density region and a low-density region when viewed from the direction of arrangement between the plate-shaped member and the base member. A holding device characterized by the following features.

2. In the holding device described in claim 1, The bonding layer has through holes that penetrate in the thickness direction, The high-density region is formed around the through hole. A holding device characterized by the following features.

3. In the holding device described in claim 1, The high-density region is formed in the central part of the bonding layer. A holding device characterized by the following features.

4. In any one of the holding devices described in claim 1 to claim 3, The bonding layer has through holes that penetrate in the thickness direction, The high-density region includes a first high-density region formed around the through hole and a second high-density region formed in the central part of the bonding layer. The first high-density region has a higher density of the metal member than the second high-density region. A holding device characterized by the following features.

5. In the holding device described in claim 1, The heat transfer coefficient of the metal member is 1 / 4 to 3 times that of the joining material. A holding device characterized by the following features.

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