Holding device

Abstract

To provide a technique suppressing warpage of a tabular part in a retainer for holding an object.SOLUTION: A retainer includes: a tabular part formed in a tabular shape; an inorganic substrate which is bonded to the tabular part, is mainly composed of an inorganic material, and has lower thermal conductivity than the tabular part; a tabular cooling part which is placed on an opposite side of the inorganic substrate to the tabular part; and a joint part which is located between the inorganic substrate and the cooling part and joins the inorganic substrate and the cooling part. When a thickness of the inorganic substrate is t (mm) and a Young's modulus of the inorganic substrate is k (GPa), t×k≤10 (GPa-mm) is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a holding device for holding an object. [Background technology]

[0002] Electrostatic chucks, for example, are used as holding devices for holding objects such as wafers during semiconductor manufacturing. The electrostatic chuck includes a plate-shaped portion on which the object is placed, a cooling portion for cooling the plate-shaped portion, and a joining portion for joining the plate-shaped portion and the cooling portion. When an electrostatic chuck is used in a high-temperature process, for example, at 250°C or higher, the joining portion formed with a silicone adhesive or the like can deteriorate due to heat and peel off. To address this issue, a technique has been proposed in which an inorganic substrate is inserted between the plate-shaped portion and the joining portion to thermally protect the joining portion (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-048445 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the technology described in Patent Document 1 can prevent the plate-shaped portion from peeling off from the cooling portion, warping of the plate-shaped portion has not been fully considered. In a configuration in which an inorganic substrate is inserted between the plate-shaped portion and the joining portion, if the thermal expansion coefficients of the plate-shaped portion and the inorganic substrate differ, warping may occur on the surface of the plate-shaped portion when the plate-shaped portion and the inorganic substrate are joined together or due to temperature changes in the holding device.

[0005] Such a problem is not limited to electrostatic chucks, but is a common problem with holding devices such as heater devices, susceptors, and mounting tables for vacuum devices such as CVD (chemical vapor deposition), PVD (physical vapor deposition), and PLD (pulsed laser deposition).

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a technique for suppressing warping of a plate-shaped portion in a holding device that holds an object. [Means for solving the problem]

[0007] The present invention has been made to solve the above-mentioned problems, and can be realized in the following forms.

[0008] (1) According to one aspect of the present invention, there is provided a holding device for holding an object, the holding device comprising: a plate-shaped portion; an inorganic substrate made primarily of an inorganic material and having a lower thermal conductivity than the plate-shaped portion, joined to the plate-shaped portion; a plate-shaped cooling portion disposed on the opposite side of the inorganic substrate from the plate-shaped portion; and a joining portion disposed between the inorganic substrate and the cooling portion and joining the inorganic substrate to the cooling portion, wherein t×k≦10 (GPa mm) is satisfied, where t (mm) is the thickness of the inorganic substrate and k (GPa) is the Young's modulus of the inorganic substrate.

[0009] The thinner the inorganic substrate, the smaller the temperature difference in the thickness direction of the inorganic substrate, and the smaller the force pulling the plate-shaped portion inward, thereby suppressing warping of the plate-shaped portion. However, if the inorganic substrate is too thin, its function as a heat insulating board will be reduced. The lower the Young's modulus of the inorganic substrate, the softer it is, and the smaller the force acting on the plate-shaped portion can be. By setting the product (t × k) of the thickness t of the inorganic substrate and the Young's modulus k within the above range, the balance between the thickness and Young's modulus of the inorganic substrate can suppress warping of the plate-shaped portion.

[0010] (2) In the holding device of the above embodiment, the thickness of the inorganic substrate may be 0.15 mm or more and 0.5 mm or less. By setting the thickness of the inorganic substrate within this range, appropriate thermal insulation can be obtained, the joints can be thermally protected, and warping of the plate-shaped portion can be further suppressed. Furthermore, the heat transferred to the cooling portion can be reduced, and the surface temperature of the plate-shaped portion can be prevented from overcooling. Therefore, if the holding device has a heater, heating of the plate-shaped portion by the heater can be suppressed, and the power consumption of the heater can be reduced. Furthermore, since the heat transferred to the cooling portion can be reduced, the uniformity of the in-plane temperature distribution of the plate-shaped portion can be improved.

[0011] (3) In the holding device of the above embodiment, the absolute value of the difference between the thermal expansion coefficient of the material constituting the plate-like portion and the thermal expansion coefficient of the inorganic material constituting the inorganic substrate may be 7 (ppm / K) or less. Even in this case, when the plate-like portion is heated, the force generated in the direction toward the center or the outside of the circle in a plan view can be reduced, thereby suppressing warping.

[0012] (4) In the holding device of the above embodiment, the thickness of the plate-shaped portion may be 2 mm or more and 10 mm or less. This allows, for example, chucking electrodes and heater wiring to be disposed in the inner layer of the plate-shaped portion, or an inert gas-filled layer to be formed on the surface layer. Furthermore, the thickness of the plate-shaped portion can further suppress warping of the plate-shaped portion. Furthermore, by setting the thickness of the plate-shaped portion within the above range, it is possible to suppress the occurrence of cracks during the manufacturing of the plate-shaped portion, as well as the occurrence of gaps, voids, and the like within the plate-shaped portion.

[0013] The present invention can be realized in various forms, for example, in the form of a semiconductor manufacturing apparatus including a holding device, a manufacturing method for a holding device, a method for forming an inorganic substrate, and the like. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view schematically illustrating an external configuration of an electrostatic chuck according to an embodiment. [Figure 2]FIG. 2 is an explanatory view schematically showing an XZ cross-sectional configuration of the electrostatic chuck. [Figure 3] 3 is an explanatory diagram showing the planar configuration of a first surface side of a plate-shaped portion. FIG. [Figure 4] 2 is an explanatory diagram illustrating an enlarged schematic XZ cross-sectional configuration of an end portion of the electrostatic chuck. FIG. [Figure 5] FIG. 1 is a diagram showing the product of the thickness and Young's modulus of an inorganic substrate. [Figure 6] FIG. 10 is a diagram showing changes in warpage of a plate-shaped member-inorganic substrate assembly. [Figure 7] FIG. 10 is a diagram showing the maximum temperature of the joint when the surface of the plate-shaped part is heated to 250° C. [Figure 8] FIG. 1 is a graph showing the relationship between the thickness of an inorganic substrate (Young's modulus: 20 GPa) and the warpage of a bonded body and the maximum temperature of a bonded portion. [Figure 9] FIG. 1 is a graph showing the relationship between the thickness of an inorganic substrate (Young's modulus: 30 GPa), the warpage of a bonded body, and the maximum temperature of a bonded portion. [Figure 10] FIG. 1 is a graph showing the relationship between the thickness of an inorganic substrate (Young's modulus 10 GPa), the warpage of a bonded body, and the maximum temperature of a bonded portion. [Figure 11] FIG. 10 is a diagram showing the power consumption required to heat the first surface of the plate-shaped portion to 250°C. [Figure 12] 10 is a diagram showing the relationship between the difference in thermal expansion coefficient between the plate-shaped portion and the inorganic substrate and the warpage of the bonded body. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Embodiment> FIG. 1 is a perspective view schematically illustrating the external configuration of an electrostatic chuck 10 according to an embodiment. FIG. 2 is an explanatory diagram schematically illustrating the XZ cross-sectional configuration of the electrostatic chuck 10. In FIGS. 1 and 2, mutually orthogonal X, Y, and Z axes are shown to identify directions. In FIG. 2, the positive Y-axis direction is the direction toward the back of the page. For convenience, in this specification, the positive Z-axis direction is referred to as the upward direction and the negative Z-axis direction is referred to as the downward direction, but the electrostatic chuck 10 may actually be installed in an orientation different from these orientations. The electrostatic chuck 10 according to this embodiment is also referred to as a "holding device."

[0016] The electrostatic chuck 10 is a device that attracts and holds an object (e.g., a wafer W) by electrostatic attraction, and is used, for example, to fix the wafer W in a vacuum chamber of a semiconductor manufacturing device. The electrostatic chuck 10 includes a plate-shaped member 100 and a cooling member 200 that are arranged in a vertical direction (Z-axis direction), an inorganic substrate 300 that is arranged between the plate-shaped member 100 and the cooling member 200 and functions as a heat insulator, and a bonding member 400 that bonds the inorganic substrate 300 and the cooling member 200. The bonded assembly of the plate-shaped member 100 and the inorganic substrate 300 is also referred to as a plate-shaped member-inorganic substrate bonded assembly 310, or simply as the bonded assembly 310.

[0017] The plate-shaped member 100 is a plate-shaped member having a first surface S1 and a second surface S2, which is the reverse side of the first surface S1. Specifically, the plate-shaped member 100 includes a first plate-shaped member 110 (FIG. 1) having a substantially circular, flat first surface S1, and a second plate-shaped member 120 (FIG. 1) having a substantially circular, flat second surface S2 (FIG. 2) with a larger diameter than the first plate-shaped member 110. The plate-shaped member as a whole expands in a stepped manner downward (in the negative Z-axis direction). In this embodiment, the first surface S1 of the plate-shaped member 100 functions as a mounting surface on which a wafer W is placed. The plate-shaped member 100 is a dense body primarily composed of ceramics (e.g., alumina, aluminum nitride, etc.) known as fine ceramics or new ceramics. In this specification, the phrase "mainly comprising" or "mainly comprising" a specific component means that the content of the specific component is 50% by volume or more. In other embodiments, the plate-shaped portion 20 may be formed mainly from a material other than ceramic, such as a resin such as polyimide, or transparent glass.

[0018] The diameter of the first surface S1 of the first plate-shaped portion 110 is, for example, approximately 50 mm to 500 mm (usually approximately 200 mm to 350 mm). In this specification, when a numerical range is indicated using "to", it is assumed that the range includes both the lower limit value and the upper limit value unless otherwise specified. For example, the expression "10 to 20" includes both the lower limit value of "10" and the upper limit value of "20". In other words, "10 to 20" has the same meaning as "10 or more and 20 or less".

[0019] An attraction electrode 130 (FIG. 2) made of a conductive material (e.g., tungsten, molybdenum, etc.) is disposed inside the plate-shaped portion 100. The shape of the attraction electrode 130 as viewed in the Z-axis direction is, for example, substantially circular. When a voltage is applied to the attraction electrode 130 from a power source (not shown), an electrostatic attraction force is generated, and the wafer W is attracted and fixed to the first surface S1 of the plate-shaped portion 100 by this electrostatic attraction force.

[0020] Furthermore, inside the plate-shaped portion 100, a heater 140 (FIG. 2) having a spiral shape as viewed in the Z-axis direction is arranged below the chucking electrode 130 (on the negative Z-axis side). In this embodiment, the heater 140 is a metallized layer made of tungsten, molybdenum, or the like. The shape of the heater 140 is not limited to this embodiment and may be, for example, a disk shape. In other embodiments, the plate-shaped portion 100 may not include the heater 140.

[0021] 3 is an explanatory diagram showing the planar configuration of the first surface S1 side of the plate-shaped portion 100. FIG. 4 is an explanatory diagram showing an enlarged schematic XZ cross-sectional configuration of the end portion of the electrostatic chuck 10. As shown in the figure, a gas filling portion 112 having a circular recessed shape in plan view is formed on the first surface S1 of the plate-shaped portion 100. The gas filling portion 112 has a plurality of cylindrical protrusions 114 standing on the bottom surface. The upper surfaces (surfaces facing the positive direction of the Z axis) of the protrusions 114 constitute the first surface S1. In other words, the height position of the upper surfaces of the protrusions 114 substantially coincides with the height position of the end portion of the first plate-shaped portion 110.

[0022] 4, the electrostatic chuck 10 has a gas flow passage 500, which is a through-hole that penetrates the electrostatic chuck 10 in the stacking direction (Z-axis direction). The gas flow passage 500 is a hole for supplying an inert gas (e.g., helium gas) for cooling the wafer W to the gas filling section 112. Note that the gas flow passage 500 preferably has a plurality of outlets on the bottom surface of the gas filling section 112 in order to uniformly supply the inert gas to the gas filling section 112.

[0023] In the electrostatic chuck 10 of this embodiment, when a wafer is attracted to the first surface S1, an inert gas is supplied to the gas filling portion 112 of the first plate-shaped portion 110 through the gas flow path 500. By flowing the inert gas between the electrostatic chuck 10 and the wafer W, the wafer W can be cooled or heated in combination with a heater, thereby controlling the temperature of the wafer W during processing.

[0024] The electrostatic chuck 10 in this embodiment has a gas filling portion 112, and since the gas filling portion 112 is filled with an inert gas, the inert gas is uniformly distributed between the electrostatic chuck 10 and the wafer W, and the electrostatic chuck 10 can hold the wafer W while maintaining a uniform temperature distribution of the wafer W. In addition, since the gas filling portion 112 is provided with a plurality of protrusions 114, the remaining time of the attracting force after the voltage applied to the attracting electrode 130 is removed can be shortened.

[0025] The thickness of the plate-shaped portion 100 is not particularly limited, but is preferably 2 mm or more and 10 mm or less. In this embodiment, the chucking electrode 130 and the heater 140 are provided in the inner layer of the plate-shaped portion 100, and the gas filling portion 112 is formed in the surface layer of the plate-shaped portion 100, so the thickness is preferably 2 mm or more. In order to suppress warping of the plate-shaped portion 100, a moderate thickness is necessary, but 10 mm or less is preferable. This is because forming the plate-shaped portion 100 thicker than 10 mm increases the possibility of cracks, internal gaps, voids, etc. occurring.

[0026] The cooling unit 200 is a plate-like member having a substantially circular, flat shape and a larger diameter than the plate-like unit 100. The cooling unit 200 may contain at least one metal selected from the group consisting of aluminum, magnesium, molybdenum, titanium, tungsten, and nickel. Among the above-mentioned metals, molybdenum, titanium, and tungsten have relatively small thermal expansion coefficients. Therefore, using at least one of these metals to construct the cooling unit 200 is desirable because it minimizes the difference in thermal expansion coefficient between the cooling unit 200 and the plate-like unit 100. In this specification, the term "thermal expansion coefficient" refers to the "linear expansion coefficient." Furthermore, magnesium has a relatively small Young's modulus. Therefore, using magnesium to construct the cooling unit 200 is desirable because it reduces thermal stress generated in the cooling unit 200. Furthermore, aluminum has a relatively high thermal conductivity, is easy to process, and is inexpensive. Therefore, using aluminum to construct the cooling unit 200 is desirable because it increases the cooling efficiency of the cooling unit 200 for the plate-like unit 100 and the wafer W and reduces the manufacturing cost of the electrostatic chuck 10. From the viewpoint of suppressing manufacturing costs while increasing the cooling efficiency of the cooling part 200, it is desirable that the metal content in the cooling part 200 is high, and it is desirable that the cooling part 200 be mainly composed of metal. For example, it is desirable that the cooling part 200 contains 90 mass % or more of aluminum, which is highly versatile (for example, being made of an aluminum alloy such as A6061 or A5052). However, the cooling part 200 may also contain components other than metal, such as ceramic. The diameter of the cooling part 200 is, for example, about 220 mm to 550 mm (usually 220 mm to 350 mm), and the thickness of the cooling part 200 is, for example, about 20 mm to 40 mm.

[0027] A coolant flow path 210 ( FIG. 2 ) is formed inside the cooling unit 200. When a wafer W held on the plate-shaped portion 100 of the electrostatic chuck 10 is processed using plasma, heat is input from the plasma to the wafer W, causing the temperature of the wafer W to rise. When a coolant (e.g., a fluorine-based inert liquid or water) flows through the coolant flow path 210 formed in the cooling unit 200, the cooling unit 200 is cooled. The plate-shaped portion 100 is cooled by heat transfer between the cooling unit 200 and the plate-shaped portion 100 via the bonding portion 400 and the inorganic substrate 300, and the wafer W held on the first surface S1 of the plate-shaped portion 100 is cooled. This allows temperature control of the wafer W. In other embodiments, the cooling unit may not have a coolant flow path formed therein, and may be cooled from the outside.

[0028] The inorganic substrate 300 is a plate-like member having a substantially circular, flat shape with a diameter equal to that of the second surface S2 of the plate-like member 100. The inorganic substrate 300 is a plate-like member primarily composed of an inorganic material and having a lower thermal conductivity than the plate-like member 100. Because the inorganic substrate 300 has a lower thermal conductivity than the plate-like member 100, it functions as a heat insulator. Examples of inorganic materials that can be used include natural minerals primarily composed of alumina, silica, etc., and ceramics known as fine ceramics or new ceramics. In other words, the term "inorganic material" encompasses both ceramics and natural minerals. In this embodiment, the inorganic substrate 300 is a dense body. In other embodiments, a porous body can be used as the inorganic substrate 300. In this embodiment, the inorganic substrate 300 is bonded to the plate-like member 100 by the following method. For example, an uncured sheet-like inorganic substrate having adhesive properties may be bonded to the plate-like member 100 by thermocompression bonding, or an uncured inorganic substrate may be formed by applying a paste-like inorganic binder having adhesive properties to the plate-like member 100, followed by thermocompression bonding. After thermocompression bonding, the inorganic substrate is cured while being integrated with the plate-shaped member 100. In other embodiments, the inorganic substrate 300 may be bonded to the plate-shaped member 100 with, for example, an adhesive containing an inorganic material as a main component.

[0029] The thickness t (mm) and Young's modulus k (GPa) of the inorganic substrate 300 satisfy the following. t×k≦10(GPa·mm) The thinner the inorganic substrate 300, the smaller the temperature difference in the thickness direction of the inorganic substrate 300, and the smaller the force pulling the plate-shaped portion 100 inward, thereby suppressing warping of the plate-shaped portion 100. However, if the inorganic substrate 300 is too thin, its function as a heat insulating plate is reduced. Furthermore, the lower the Young's modulus of the inorganic substrate 300, the softer it is, thereby reducing the force acting on the plate-shaped portion 100. By setting the product of the thickness and Young's modulus of the inorganic substrate 300 within the above range, the balance between the thickness and Young's modulus of the inorganic substrate 300 can suppress warping of the plate-shaped portion. As a result, the adhesion of the wafer W is improved, wafer wobble and tilt are suppressed, and a decrease in etching accuracy can be suppressed. Furthermore, the uniformity of the temperature distribution within the surface of the wafer W can be improved.

[0030] The thickness t of the inorganic substrate 300 can be measured by the following method. The electrostatic chuck 10 is cut using a cutting machine along a cut plane perpendicular to the first surface S1 (for example, the XZ plane in FIG. 1), and the cross section is observed and measured using a magnifying glass or microscope capable of measuring length. Here, the cut plane passes through the center of the first surface S1. The center of the cross section (corresponding to the center of the second surface S2), the ends, and a position between these (radius / 2) are observed within a range of 1.5 mm in width, and the thicknesses of the convex and concave portions in each range are measured, and the average value is calculated to determine the thickness of the inorganic substrate 300.

[0031] The Young's modulus of the inorganic substrate 300 can be measured by the following method. A sample is cut out in the shape specified in JIS K6911. Using a known tensile tester, predetermined portions of both ends of the sample are held and the load is measured while pulling at a rate of 5 mm / min. The tensile stress (Pa) is calculated by dividing the load by the cross-sectional area of ​​the sample. Strain is measured with a strain gauge. In a graph with the horizontal axis representing strain (%) and the vertical axis representing stress (Pa), the slope near the origin is calculated and taken as Young's modulus.

[0032] The inorganic substrate 300 can be produced by, for example, blending a silane compound such as tetramethoxysilane or tetraethoxysilane with a filler such as alumina or silica powder or glass fiber, and then heating and compressing the silane compound such as tetramethoxysilane or tetraethoxysilane while subjecting it to hydrolysis and condensation polymerization, solidifying it, and shaping it into a plate. Alternatively, the inorganic substrate 300 can be produced by blending alumina or silica powder or glass fiber with a glass powder (also called glass frit) as a filler, and then heating it to a temperature at which the glass powder softens and flows, and compressing it to form it into a plate. The Young's modulus of the inorganic substrate 300 can be adjusted by changing the amount of filler or glass fiber blended.

[0033] The thickness of the inorganic substrate 300 is not particularly limited, but is preferably 0.15 mm or more and 0.5 mm or less. Furthermore, 0.2 mm or more and 0.4 mm or less is more preferable. As mentioned above, the thinner the inorganic substrate 300, the more warping of the plate-like portion 100 can be suppressed; however, if it is too thin, its function as a heat insulating plate is reduced. By making the inorganic substrate 300 thicker than 0.15 mm, the temperature rise of the bonding portion 400 can be suppressed. For example, if the bonding portion 400 is primarily composed of a silicone adhesive, the temperature of the bonding portion 400 can be kept below 200°C, for example, thereby suppressing deterioration of the silicone adhesive. Furthermore, by making the inorganic substrate 300 thicker than 0.15 mm, the heat transfer to the cooling portion 200 can be reduced, preventing the surface temperature of the plate-like portion 100 from being overcooled. This suppresses heating of the plate-like portion 100 by the heater, thereby reducing the power consumption of the heater 140. Furthermore, since the heat transferred to the cooling section 200 can be reduced, the uniformity of the in-plane temperature distribution of the plate-shaped section 100 can be improved. Furthermore, if the thickness of the inorganic substrate 300 is set to 0.5 mm or less, the temperature difference in the thickness direction of the inorganic substrate 300 can be reduced, and the force pulling the plate-shaped section 100 inward can be reduced, thereby suppressing warping of the plate-shaped section 100. In other words, the temperature rise of the bonding section 400 and the warping of the plate-shaped section 100 can be suppressed in a balanced manner.

[0034] Although the thermal expansion coefficient of the inorganic material constituting the inorganic substrate 300 is not particularly limited, it is preferable that the absolute value of the difference between the thermal expansion coefficient of the material constituting the plate-like portion 100 and the thermal expansion coefficient of the inorganic material constituting the inorganic substrate 300 is 7 (ppm / K) or less. When the absolute value of the difference in the thermal expansion coefficient between the material constituting the plate-like portion 100 and the inorganic material constituting the inorganic substrate 300 is within the above range, it is possible to reduce the force generated in the direction toward the center or the outside of the circle in a planar view when the plate-like portion 100 is heated, thereby suppressing warping.

[0035] The thermal expansion coefficient can be measured by the following method. A known thermal expansion measurement device (e.g., Rigaku Corporation TMA8311) can be used. A sample is cut to a size of 18 mm long, 3 mm wide, and 4 mm thick. A compressive load of 100 mN is applied in the longitudinal direction, and the change in length is measured while the temperature is raised to 400°C at a rate of 10°C / min in a nitrogen atmosphere with a nitrogen flow rate of 100 ml / min. The thermal expansion coefficient between 260°C and 40°C can be measured by subtracting the length at 40°C from the length at 260°C and dividing the result by the original length and the temperature difference of 220°C.

[0036] The thermal expansion coefficient can be adjusted by changing the amount of filler or glass fiber, and can be reduced by increasing the amount of amorphous silica or glass fiber, especially E-glass.

[0037] The thermal conductivity of the inorganic material constituting the inorganic substrate 300 is not particularly limited, but is preferably 1.8 W / mK or less, and more preferably 0.9 W / mK or less. By setting the thermal conductivity of the inorganic material constituting the inorganic substrate 300 within the above range, heat conduction from the plate-shaped portion 100 to the bonding portion 400 can be further suppressed, thereby further suppressing temperature increases at the bonding portion 400. For example, when the bonding portion 400 is formed from an adhesive whose main component is silicone, setting the thermal conductivity of the inorganic material to 1.8 W / mK or less can suppress the maximum temperature at the bonding portion 400 to 200°C or less. Furthermore, setting the thermal conductivity of the inorganic material to 0.9 W / mK or less can suppress the maximum temperature at the bonding portion 400 to 190°C or less, thereby further improving reliability. Here, the thermal conductivity is the thermal conductivity at room temperature (20°C).

[0038] Thermal conductivity can be calculated from thermal diffusivity using the laser flash method. The density used in the calculation is measured using the Archimedes method. The sample can be molded individually or cut from a holding device, and the results will be the same.

[0039] The thermal conductivity of the inorganic substrate 300 can be adjusted by changing the amount of filler or glass fiber added. Thermal conductivity increases with an increase in alumina, and decreases with an increase in silica. When using silica, amorphous silica has a greater effect on reducing thermal conductivity than crystalline silica, and when the same amount is added by volume, amorphous silica can reduce thermal conductivity more effectively than crystalline silica.

[0040] The thermal conductivity of the plate-shaped portion 100 cannot be changed as greatly as that of the inorganic substrate 300, but it can be adjusted by changing the amount of silica or magnesia added as a sintering aid. Increasing the amount of silica decreases the thermal conductivity, while increasing the amount of magnesia increases the thermal conductivity.

[0041] The warpage of the plate-shaped portion-inorganic substrate assembly 310 can be measured using a general shape measuring device, such as a laser or optical three-dimensional measuring machine or an image measuring machine.

[0042] The bonding part 400 is a substantially circular, flat, plate-like member having the same diameter as the inorganic substrate 300, and bonds the inorganic substrate 300 and the cooling part 200. The bonding part 400 is formed from an adhesive, and for example, an adhesive containing an organic substance such as acrylic or polyimide, or silicone as a main component can be used.

[0043] Silicone adhesives can be prepared, for example, by mixing polydimethylsiloxane with a crosslinker, a silane coupling agent, a curing catalyst, and a filler. The filler can be at least one of alumina, silica, aluminum nitride, boron nitride, carbon black, graphite, carbon nanotubes, silicon carbide, silicon nitride, iron oxide, and magnesium oxide. Sheet- or varnish-type silicone adhesives can be used to bond the inorganic substrate 300 and the cooling unit 200. When used in sheet form, the silicone adhesive is cut to a predetermined shape and then attached to the inorganic substrate 300 integrated with the plate-like unit 100 and the cooling unit 200 in a vacuum. Furthermore, the inorganic substrate 300 integrated with the plate-like unit 100 and the cooling unit 200 can be bonded to each other by bonding them together in a vacuum using the silicone adhesive and curing the adhesive at a temperature of 100°C or higher. When a varnish-like silicone adhesive is used, it is applied to the cooling part 200 by screen printing, and then bonded to the inorganic substrate 300 integrated with the plate-like part 100 in a vacuum, and cured at a temperature of 100° C. or higher, thereby bonding the inorganic substrate 300 and the cooling part 200. Here, a resin wall may be formed on the cooling part 200 to prevent outflow.

[0044] The thickness of the joint 400 is not particularly limited, but is preferably 200 μm to 800 μm. A thinner joint 400 is better in terms of heat dissipation, but if it is too thin, it will not be possible to alleviate the difference in thermal expansion between the plate-like portion 100 and the cooling portion 200. If the thickness of the joint 400 is within the above range, it will be possible to properly dissipate heat and also to alleviate the difference in thermal expansion between the plate-like portion 100 and the cooling portion 200.

[0045] The thermal conductivity of the joint 400 is not particularly limited, but is preferably 0.2 to 1.5 W / (m·K). While a high thermal conductivity of the joint 400 is preferable, adding a large amount of thermally conductive filler (e.g., alumina, aluminum nitride, boron nitride, etc.) to increase the thermal conductivity makes the joint hard and difficult to stretch, which may cause breakage due to temperature changes or reduce the ability to relax stress caused by the temperature difference between the plate-like part 100 and the cooling part 200. Setting the thermal conductivity of the joint 400 within the above range ensures stress relaxation ability and enables efficient heat conduction.

[0046] The method for manufacturing the electrostatic chuck 10 is not particularly limited, but for example, the electrostatic chuck 10 can be manufactured by the following method. First, a ceramic green sheet containing alumina as its main component is prepared by a conventional method. A heater, an adsorption electrode, vias, and air holes are formed on the ceramic green sheet. Multiple ceramic green sheets are stacked and thermocompression bonded together, and then fired at 1400°C to 1600°C in a reducing atmosphere to obtain a ceramic substrate (plate-shaped portion).

[0047] The inorganic substrate used is a dense inorganic substrate obtained by impregnating glass wool with an inorganic binder solution, drying, and curing. The inorganic binder solution is prepared by mixing a metal alkoxide solution containing silica and alumina as its main components, silica and alumina filler, an organic solvent, and polysiloxane. The Young's modulus, thermal conductivity, thermal expansion coefficient, and thickness of the inorganic substrate are adjusted using the methods described above.

[0048] The inorganic substrate is cut to a predetermined size, drilled, coated with an inorganic binder containing a silane coupling agent over the entire surface, and bonded to the plate-like part by thermocompression. At this time, the inorganic substrate after impregnated with the inorganic binder solution may be dried only, cut to a predetermined size, drilled, and then thermocompressed to the plate-like part, thereby simultaneously curing and bonding.

[0049] Next, the assembly of the plate-shaped portion and inorganic substrate and the cooling portion are bonded together using a silicone adhesive to obtain a holding device. Specifically, the silicone adhesive is made by mixing polydimethylsiloxane containing curable functional groups with a crosslinking agent, a silane coupling agent, a curing catalyst, and a filler. Alumina and aluminum nitride are used as fillers. A sheet-like silicone adhesive is used for bonding. After molding the silicone adhesive into a sheet, a portion is cured at a temperature below 100°C and cut to the desired shape. After that, the inorganic substrate integrated with the plate-shaped portion and the cooling portion are bonded together in a vacuum using the sheet-like silicone adhesive, and the adhesive is cured at a temperature above 100°C to obtain a holding device.

[0050] As described above, according to the electrostatic chuck 10 of this embodiment, the product (t×k) of the thickness t and Young's modulus k of the inorganic substrate 300 is 10 (GPa·mm) or less, and therefore, the balance between the thickness and Young's modulus of the inorganic substrate 300 can suppress warping of the plate-shaped portion 100. As a result, the adsorption of the wafer W is improved, wobbling and tilting of the wafer are suppressed, and a decrease in etching accuracy can be suppressed. In addition, the uniformity of the temperature distribution within the surface of the wafer W can be improved. [Example]

[0051] The present invention will be explained in more detail with reference to examples. Fig. 5 is a diagram showing the product of the thickness t and Young's modulus k of the inorganic substrate 300, and Fig. 6 is a diagram showing the results of a simulation of changes in warpage of the plate-like portion-inorganic substrate assembly 310 as the product of the thickness t and Young's modulus k of the inorganic substrate 300 changes. Fig. 6 shows the warpage of the plate-like portion-inorganic substrate assembly 310 for the combinations of the thickness and Young's modulus of the inorganic substrate 300 shown in Fig. 5. Fig. 6 shows the results of a simulation performed under the assumption that the thermal expansion coefficient of the constituent material of the plate-like portion 100 is 6.8 ppm / K, the thermal expansion coefficient of the constituent material of the inorganic substrate 300 is 11 ppm / K, and the absolute value of the difference between the thermal expansion coefficients of the constituent material of the plate-like portion 100 and the inorganic substrate 300 is 4.2 ppm / K. In the simulations shown in Figures 5 and subsequent figures, the plate-shaped portion 100, inorganic substrate 300, and bonding portion 400 all have a radius of 180 mm, the cooling portion 200 has a radius of 180 mm, and the bonding portion 400 is made of a silicone-based adhesive. In the examples, the plate-shaped portion 100 is a circular plate with no steps on its outer periphery. In other words, the first plate-shaped portion 110 and the second plate-shaped portion 120 have the same diameter. The results of these simulations tend to be consistent with experimental results using a 210 mm square rectangular sample. In the examples, a paper titled "Evaluation of Stress and Deformation in Printed Circuit Boards Using Multilayer Beam Theory," published in Transactions of the Japan Society of Mechanical Engineers, Vol. 59, No. 563, pp. 1777-1782, was used as a reference. Plates with different thermal conductivities were bonded together, and the stresses generated in each layer and the warpage of the bonded structure as the temperature changed were simulated.

[0052] As shown in FIG. 6 , the higher the Young's modulus k of the inorganic substrate 300, the greater the warpage of the plate-like member-inorganic substrate assembly 310. Furthermore, the thicker the thickness t of the inorganic substrate 300, the greater the warpage of the plate-like member-inorganic substrate assembly 310. In FIG. 6 , multiple cells with warpage of 50 μm or less are surrounded by a bold line. If the warpage exceeds 50 μm, it becomes difficult to adsorb the wafer W. Even if the wafer W is adsorbed, it may be unsteady or tilted, resulting in reduced etching accuracy. In other words, it is preferable to maintain warpage at 50 μm or less. In FIG. 5 , multiple cells corresponding to FIG. 6 are surrounded by a bold line. As shown in FIG. 5 , when the product of the thickness t (mm) and Young's modulus k (GPa) of the inorganic substrate 300 is 10 (GPa·mm) or less, the warpage of the plate-like member-inorganic substrate assembly 310 is 50 μm or less. 5 and 6, it can be seen that by setting the product of the thickness t (mm) and the Young's modulus k (GPa) of the inorganic substrate 300 to 10 (GPa mm) or less, warping of the plate-like portion-inorganic substrate assembly 310 is suppressed, and the wafer W can be adsorbed well.

[0053] FIG. 7 is a diagram showing the maximum temperature of the bonding portion 400 when the surface (first surface S1) of the plate-shaped portion 100 is heated to 250°C. As shown in the figure, the maximum temperature of the bonding portion 400 when the surface (first surface S1) of the plate-shaped portion 100 is heated and a 90°C refrigerant is supplied to the cooling portion, and the surface (first surface S1) of the plate-shaped portion 100 is heated to 250°C is simulated by changing the thermal conductivity of the inorganic substrate 300. The temperature of each portion is calculated based on the thermal resistance (m 2 The simulation was performed using a one-dimensional equation for steady-state heat conduction, in which the amount of heat passing through all layers from the plate-shaped portion to the chiller is constant. The temperature of the bonding portion 400 is the temperature of the fourth surface S4 (FIG. 2) that contacts the inorganic substrate 300. In the example shown in FIG. 7, the thickness t of the inorganic substrate 300 is 0.3 mm, and the Young's modulus k of the inorganic substrate 300 is 20 GPa, satisfying t×k≦10 (GPa·mm).

[0054] In FIG. 7, a temperature of the bonding portion 400 below 190°C is indicated by "◎", a temperature between 190°C and 200°C is indicated by "◯", and a temperature of 200°C or higher is indicated by "X". In this example, the bonding portion 400 is made of an adhesive whose main component is silicone. Silicone may deteriorate or peel if its temperature exceeds 200°C, so the evaluation was performed using 200°C as the reference temperature. As shown in FIG. 7, a thermal conductivity of the inorganic substrate 300 of 1.8 W / mK or less is preferable because it can suppress the maximum temperature of the bonding portion 400 to 200°C or less. A thermal conductivity of the inorganic substrate 300 of 0.9 W / mK or less is even more preferable because it can suppress the maximum temperature of the bonding portion 400 to 190°C or less. As described above, the material that mainly constitutes the bonding portion 400 is not limited to silicone. However, even when the bonding portion 400 is constituted by an adhesive whose main component is another material, such as an organic material such as acrylic or polyimide, it is preferable to set the thermal conductivity of the inorganic substrate 300 to 1.8 W / mK or less, because this allows the maximum temperature of the bonding portion 400 to be appropriately suppressed.

[0055] FIG. 8 is a graph showing the relationship between the thickness of the inorganic substrate 300 (Young's modulus 20 GPa) and the warpage of the bonded body 310 and the maximum temperature of the bonded portion 400. In the example shown in FIG. 8, the thickness t of the inorganic substrate 300 increases as the sample number increases from Sample 11 to Sample 17, but the other configurations (including physical properties) are the same for each sample. In the example shown in FIG. 8, the bonding temperature when bonding the inorganic substrate 300 to the plate-shaped portion 100 is 170°C, and the temperature after cooling is 20°C (room temperature). The simulation shows the warpage of the bonded body 310 (plate-shaped portion-inorganic substrate bonded body 310) when cooled from the bonding temperature of 170°C to room temperature. In addition, the maximum temperature of the fourth surface S4 of the bonded portion 400 when the temperature of the first surface S1 of the plate-shaped portion 100 in the electrostatic chuck 10 reaches 250°C is simulated and is shown as "bonded portion temperature" in FIG. 8. In the examples shown in FIGS. 9 and 10, which will be described later, simulations were performed under similar conditions and evaluations were performed using similar criteria.

[0056] 8, similarly to Fig. 7, the temperature of the joint 400 is evaluated as "◎" when it is less than 190°C, "◯" when it is 190°C or more and less than 200°C, and "×" when it is 200°C or more. Furthermore, the warpage of the joined body 310 is evaluated as "◎" when it is less than 40 μm, "◯" when it is 40 μm or more and less than 50 μm, and "×" when it is 50 μm or more.

[0057] 8, the Young's modulus k of the inorganic substrate 300 is 20 GPa, and Samples 11 to 16 satisfy t×k≦10 (GPa·mm), while Sample 17 does not satisfy t×k≦10 (GPa·mm). As shown in the figure, Samples 11 to 16, which satisfy t×k≦10 (GPa·mm), were able to suppress the warpage of the bonded body 310 to 50 μm or less.

[0058] As shown in the figure, when the thickness of the inorganic substrate 300 is 0.5 mm or less, the warpage of the bonded body 310 is 50 μm or less (Samples 11 to 16). As described above, when the warpage of the bonded body 310 is 50 μm or less, the electrostatic chuck 10 can adsorb the wafer W well, and etching can be performed well. Furthermore, when the thickness of the inorganic substrate 300 is 0.15 mm or more, the maximum temperature of the bonded portion 400 is 200°C or less (Samples 12 to 17). As described above, when the temperature of the bonded portion 400 is 200°C or less, deterioration and peeling of the bonded portion 400 can be suppressed. Furthermore, because the heat transferred from the plate-shaped portion 100 to the cooling portion 200 is reduced, heating of the first surface S1 of the plate-shaped portion 100 by the heater 140 can be suppressed, and the power consumption of the heater 140 can be reduced. Furthermore, the heat transferred from the plate-shaped portion 100 to the cooling portion 200 is reduced, which improves the uniformity of the in-plane temperature distribution of the plate-shaped portion 100. In this way, when the thickness of the inorganic substrate 300 is set to 0.15 mm or more and 0.5 mm or less, warping of the bonded body 310 can be suppressed and heat transfer from the plate-shaped portion 100 to the cooling portion 200 can be suppressed, which is preferable.

[0059] It is more preferable to set the thickness of the inorganic substrate 300 to 0.2 mm or more and 0.4 mm or less, since this makes it possible to suppress the maximum temperature of the bonding portion 400 to approximately 190°C and to suppress the warpage of the bonded body 310 to 40 μm or less.

[0060] FIG. 9 is a diagram showing the relationship between the thickness of the inorganic substrate 300 (Young's modulus 30 GPa), the warpage of the bonded body 310, and the maximum temperature of the bonded portion 400. The examples shown in FIG. 9, from sample 21 to sample 27, are similar to the example shown in FIG. 8 in that the thickness t of the inorganic substrate 300 increases as the sample number increases, but the other configurations (including physical properties) are the same for each sample. The samples shown in FIG. 9 have a larger Young's modulus of the inorganic substrate 300 than the sample shown in FIG. 8, with the Young's modulus being 30 GPa. That is, samples 21 to 27 shown in FIG. 9 are harder than samples 11 to 17 (FIG. 8).

[0061] 9, the Young's modulus k of the inorganic substrate 300 is 30 GPa, and Samples 21 to 25 satisfy t×k≦10 (GPa·mm), while Samples 26 to 29 do not satisfy t×k≦10 (GPa·mm). As shown in the figure, Samples 21 to 25, which satisfy t×k≦10 (GPa·mm), were able to suppress the warpage of the bonded body 310 to 50 μm or less.

[0062] As shown in the figure, when the thickness of the inorganic substrate 300 is 0.33 mm or less, the warpage of the bonded body 310 can be reduced to 50 μm or less (Samples 21 to 25). Furthermore, when the thickness of the inorganic substrate 300 is 0.15 mm or more, the maximum temperature of the bonded portion 400 is reduced to 200°C or less (Samples 22 to 29). Thus, when the thickness of the inorganic substrate 300 is 0.15 mm or more and 0.33 mm or less, the warpage of the bonded body 310 can be suppressed and heat transfer from the plate-like portion 100 to the cooling portion 200 can be suppressed, which is preferable. When the thickness of the inorganic substrate 300 is 0.3 mm or more and 0.33 mm or less, the maximum temperature of the bonded portion 400 can be suppressed to 190°C or less, which is even more preferable.

[0063] FIG. 10 is a diagram showing the relationship between the thickness of the inorganic substrate 300 (Young's modulus 10 GPa), the warpage of the bonded body 310, and the maximum temperature of the bonded portion 400. The examples shown in FIG. 10, from sample 31 to sample 37, are similar to the example shown in FIG. 8, in that the thickness t of the inorganic substrate 300 increases as the sample number increases, but the other configurations (including physical properties) are the same for each sample. The samples shown in FIG. 10 have a smaller Young's modulus of the inorganic substrate 300 than the sample shown in FIG. 8, with a Young's modulus of 10 GPa. That is, samples 31 to 37 shown in FIG. 10 are softer than samples 11 to 27 (FIG. 8).

[0064] 10, the Young's modulus k of the inorganic substrate 300 is 10 GPa, and t×k≦10 (GPa·mm) is satisfied in all of Samples 31 to 37. As shown in the figure, Samples 31 to 37 that satisfy t×k≦10 (GPa·mm) were able to suppress the warpage of the bonded body 310 to 50 μm or less.

[0065] As shown in the figure, when the thickness of the inorganic substrate 300 is 0.6 mm or less, the warpage of the bonded body 310 is 50 μm or less (Samples 31 to 37). Furthermore, when the thickness of the inorganic substrate 300 is 0.15 mm or more, the maximum temperature of the bonded portion 400 is 200°C or less (Samples 32 to 37). Thus, when the thickness of the inorganic substrate 300 is 0.15 mm or more and 0.6 mm or less, the warpage of the bonded body 310 can be suppressed and the transfer of heat from the plate-like portion 100 to the cooling portion 200 can be suppressed, which is preferable. When the thickness of the inorganic substrate 300 is 0.3 mm or more and 0.6 mm or less, the maximum temperature of the bonded portion 400 can be suppressed to 190°C or less, which is more preferable.

[0066] As shown in FIGS. 8 to 10 , the thicker the inorganic substrate 300, the greater the warpage of the bonded body 310. This is because, as the inorganic substrate 300 becomes thicker, the temperature difference between the front and back surfaces of the inorganic substrate 300 becomes greater, which increases strain during expansion and contraction due to temperature changes and generates greater forces. Furthermore, the thinner the inorganic substrate 300, the higher the maximum temperature of the bonded portion 400. Furthermore, the greater the Young's modulus of the inorganic substrate 300, the greater the warpage of the bonded body 310. By satisfying the relationship (thickness t × Young's modulus k≦10 (GPa·mm)) for the inorganic substrate 300, warpage of the bonded body 310 can be suppressed. Furthermore, by setting the thickness of the inorganic substrate 300 to 0.15 mm or more and 0.5 mm or less, the temperature rise in the bonded portion 400 and deterioration of the bonded portion 400 can be suppressed.

[0067] FIG. 11 is a graph showing the power consumption required to heat the first surface S1 of the plate-shaped member 100 to 250°C. As shown in the figure, the plate-shaped member 100 is heated while a 90°C refrigerant is supplied to the cooling unit to heat the surface (first surface S1) of the plate-shaped member 100 to 250°C. The power consumption of the electrostatic chuck 10 is simulated by varying the thickness of the inorganic substrate 300. In the example shown in FIG. 11, the Young's modulus k of the inorganic substrate 300 is 20 GPa. Samples 41 to 46 satisfy t×k≦10 (GPa·mm), while Sample 47 does not satisfy t×k≦10 (GPa·mm). In FIG. 11, power consumption of less than 7000 W is evaluated as "Good" and power consumption of 7000 W or more is evaluated as "Poor." The evaluation criteria are generally determined based on the upper limit of the power that can be supplied from a power source.

[0068] As shown in the figure, sample 41 has an inorganic substrate 300 with a thickness of 0.1 mm, and power consumption was 7000 W or more. If the inorganic substrate 300 is thin, heat is transferred to the cooling unit 200, and even when heated by the heater 140, the temperature of the first surface S1 of the plate-shaped member 100 does not increase easily, resulting in high power consumption. From the viewpoint of power consumption, the thickness of the inorganic substrate 300 is preferably 0.15 mm or more.

[0069] FIG. 12 illustrates the relationship between the difference in thermal expansion coefficient between the plate-shaped portion 100 and the inorganic substrate 300 and the warpage of the bonded body 310. In FIG. 12, the difference between the thermal expansion coefficient of the constituent material of the plate-shaped portion 100 and the thermal expansion coefficient of the constituent material of the inorganic substrate 300 is displayed as the "difference in thermal expansion coefficient." The simulation conditions were the same as those in the examples of FIGS. 7 to 11. When the bonded body has a positive warpage, it is convex toward the plate-shaped portion 100 (convex toward the positive Z-axis direction in FIG. 2). When the bonded body has a negative warpage, it is convex toward the inorganic substrate 300 (convex toward the negative Z-axis direction in FIG. 2). In FIG. 12, as in FIG. 8, the absolute value of the warpage of the bonded body 310 is evaluated as "◎" when it is less than 40 μm, "◯" when it is 40 μm or more but less than 50 μm, and "×" when it is 50 μm or more. In the example shown in FIG. 12, all of Samples 41 to 49 satisfy the relationship: thickness t of the inorganic substrate 300 × Young's modulus k≦10 (GPa·mm).

[0070] As shown in the figure, when the absolute value of the difference in thermal expansion coefficients is 7 ppm / K or less (Samples 42 to 49), the absolute value of the warpage of the bonded body 310 is 50 μm or less, which is preferable. In Samples 47 to 49, the warpage of the bonded body 310 alone is convex toward the inorganic substrate 300 (convex in the negative Z-axis direction in FIG. 2). When the bonded body 310 is bonded to the cooling unit 200 by the bonding unit 400 to form an electrostatic chuck 10, the cooling unit 200 often has a higher thermal expansion coefficient than the bonded body 310. Therefore, a force that causes the bonded body 310 to become convex toward the plate-like member 100 (convex in the positive Z-axis direction in FIG. 2) due to temperature changes is often generated. Therefore, it is preferable that the warpage of the bonded body 310 alone is convex toward the inorganic substrate 300 (convex in the negative Z-axis direction in FIG. 2), because this suppresses warpage when the electrostatic chuck 10 is formed. That is, a difference in thermal expansion coefficients of -6 ppm / K or more and less than 0 ppm / K is more preferable.

[0071] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0072] In the above embodiment, an example is shown in which an object is held on the first surface S1 of the plate-shaped portion 100, but it is also possible to bond another ceramic substrate onto the plate-shaped portion 100 and hold the object on top of that.

[0073] In the above embodiment, an electrostatic chuck is used as an example of the holding device, but the holding device is not limited to an electrostatic chuck. For example, the holding device may be configured as a heater device, susceptor, or mounting table for a vacuum device such as CVD, PVD, or PLD (Pulsed Laser Deposition).

[0074] In the above embodiment, the holding device is provided with a stack of plate-like members having a substantially circular planar shape, but the planar shape is not limited to the above embodiment. For example, the holding device may have a rectangular or polygonal planar shape.

[0075] The present disclosure is not limited to the above-described embodiments, examples, and modifications, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

[0076] The present disclosure can also be realized as the following application examples. [Application example 1] A holding device for holding an object, a plate-shaped portion formed in a plate shape; an inorganic substrate that is mainly composed of an inorganic material and has a lower thermal conductivity than the plate-shaped portion, and is joined to the plate-shaped portion; a plate-shaped cooling part disposed on the opposite side of the inorganic substrate from the plate-shaped part; a joining portion disposed between the inorganic substrate and the cooling portion and joining the inorganic substrate and the cooling portion; Equipped with When the thickness of the inorganic substrate is t (mm) and the Young's modulus of the inorganic substrate is k (GPa), t×k≦10(GPa·mm) characterized in that holding device. [Application example 2] The holding device according to Application Example 1, The thickness of the inorganic substrate is 0.15 (mm) or more and 0.5 (mm) or less. holding device. [Application example 3] The holding device according to Application Example 1 or Application Example 2, The absolute value of the difference between the thermal expansion coefficient of the material constituting the plate-shaped portion and the thermal expansion coefficient of the inorganic material constituting the inorganic substrate is 7 (ppm / K) or less. holding device. [Application example 4] The holding device according to any one of Application Examples 1 to 3, The thickness of the plate-shaped portion is 2 mm or more and 10 mm or less. holding device. [Explanation of symbols]

[0077] 10...Electrostatic chuck 20...Plate-shaped part 100...Plate-shaped part 110...First plate-shaped portion 112...Gas filling section 114...Protrusion 120...Second plate-shaped portion 130...Adsorption electrode 140...Heater 200...Cooling section 210... refrigerant flow path 300...Inorganic substrate 310... Plate-shaped portion-inorganic substrate assembly (assembly) 400…Joint part 500...Gas flow path S1...Side 1 S2...Side 2 S4...Side 4

Claims

1. A holding device for holding an object, a plate-shaped portion formed in a plate shape; an inorganic substrate that is mainly composed of an inorganic material, has a lower thermal conductivity than the plate-shaped portion, and is joined to the plate-shaped portion; a plate-shaped cooling part disposed on the opposite side of the inorganic substrate from the plate-shaped part; a joining portion disposed between the inorganic substrate and the cooling portion and joining the inorganic substrate and the cooling portion; Equipped with When the thickness of the inorganic substrate is t mm and the Young's modulus of the inorganic substrate is kGPa, t×k≦10GPa・mm and The thickness of the plate-shaped portion is 2 mm or more and 10 mm or less, the inorganic substrate is a dense body having a Young's modulus of 10 GPa or more and 30 GPa or less; a warpage of a plate-like portion-inorganic substrate joint in which the plate-like portion and the inorganic substrate are joined together is 50 μm or less; holding device.

2. 2. The holding device of claim 1, The thickness of the inorganic substrate is 0.15 mm or more and 0.5 mm or less. holding device.

3. 3. The holding device according to claim 1 or 2, the absolute value of the difference between the thermal expansion coefficient of the material constituting the plate-like portion and the thermal expansion coefficient of the inorganic material constituting the inorganic substrate is 7 ppm / K or less; holding device.

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