JP2017174853A - Manufacturing method of holding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of exfoliation on the interface, or the like, of a bonding layer and a member to be bonded, in a holding device.SOLUTION: A holding device includes a ceramic plate, a composite plate formed of a composite material of ceramic and a first aluminum alloy having a solid phase line temperature Ts1 (°C) and a liquid phase line temperature Tl1 (°C), and a bonding layer for bonding the ceramic plate and composite plate. A manufacturing method of a holding device includes a step of preparing a foil material of the second aluminum alloy having a solid phase line temperature Ts2 (°C) (Ts2≤Ts1-40), a step of placing the foil material between the ceramic plate and composite plate, and a step of forming a bonding layer by heating the ceramic plate and composite plate and foil material, while compressing, in a temperature range between a lower limit temperature Tmin (Tmin=Ts1-30) and an upper limit temperature Tmax (Tmax is lower one of Ts1+30 and Tl1), thereby melting at least a part of the foil material.SELECTED DRAWING: Figure 4

Description

  The technology disclosed in this specification relates to a method of manufacturing a holding device that holds an object.

  For example, in a semiconductor manufacturing apparatus, an electrostatic chuck is used as a holding device that holds a wafer. The electrostatic chuck has a configuration in which, for example, a plate-shaped ceramic plate and a plate-shaped base plate are bonded by a bonding layer. The electrostatic chuck has an internal electrode, and attracts the wafer to the surface of the ceramic plate (hereinafter referred to as “adsorption surface”) by using electrostatic attraction generated by applying a voltage to the internal electrode. And hold.

  If the temperature distribution of the wafer held on the electrostatic chuck becomes non-uniform, the accuracy of each process (film formation, etching, exposure, etc.) on the wafer will be reduced. Performance is required. Therefore, when the electrostatic chuck is used, the temperature of the adsorption surface of the ceramic plate can be controlled by heating with a heater provided inside the ceramic plate or cooling by supplying a refrigerant to the refrigerant flow path formed in the base plate. Done.

  The electrostatic chuck is subjected to a thermal cycle during use. In general, since the base plate is often made of metal, the difference in coefficient of thermal expansion between the ceramic plate and the base plate is relatively large. Therefore, when the electrostatic chuck is exposed to a thermal cycle, a difference in thermal expansion occurs repeatedly between the ceramic plate and the base plate, and peeling occurs at the interface between the bonding layer and the member to be bonded (ceramic plate and base plate). May occur. When such delamination occurs, the heat transfer between the base plate and the ceramic plate decreases at the delamination location, and the cooling effect of the ceramic plate by the refrigerant supplied to the refrigerant flow path formed in the base plate is reduced. There is a risk that the uniformity of the temperature distribution on the adsorption surface of the ceramic plate will decrease.

  2. Description of the Related Art Conventionally, a technique for joining a ceramic plate and a base plate with a joining layer containing an organic adhesive having a relatively high elastic deformation capability is known. In this technology, the difference in thermal expansion between the ceramic plate and the base plate can be mitigated by the bonding layer having a relatively high elastic deformation capability, and peeling occurs at the interface between the bonding layer and the member to be bonded. Can be suppressed.

  In addition, a technique is known in which a base plate is formed of a composite material in which a metal is infiltrated into porous ceramics, and the ceramic plate and the base plate are brazed and joined with a metal brazing material (see, for example, Patent Document 1). According to this technique, by making the thermal expansion coefficient of the base plate close to the thermal expansion coefficient of the ceramic plate, the difference in thermal expansion between the ceramic plate and the base plate can be reduced. The occurrence of peeling at the interface or the like can be suppressed.

JP-A-11-163109

  In recent years, along with diversification of semiconductor processes, electrostatic chucks are sometimes used in an environment of higher temperature than conventional (for example, 250 ° C. or more), and in such cases, electrostatic chucks have a larger temperature difference. Exposed to the thermal cycle. In the technique using the bonding layer including the organic adhesive described above, when the electrostatic chuck is exposed to a higher temperature, the organic adhesive included in the bonding layer reaches the decomposition temperature, and the bonding layer and the bonded member There is a possibility that peeling occurs at the interface or the like. Further, in the technique of brazing and joining the base plate and the ceramic plate formed of the composite material described above, although the heat resistance of the bonding layer is improved, the elastic deformation capability of the bonding layer is relatively low. When exposed to a large number of thermal cycles, peeling may occur at the interface between the bonding layer and the member to be bonded due to the difference in thermal expansion between the ceramic plate and the base plate.

 Such a problem is not limited to the bonding of the ceramic plate and the base plate, but is common to bonding of the ceramic plate and other members constituting the electrostatic chuck. Such a problem is not limited to an electrostatic chuck that holds a wafer using electrostatic attraction, and includes a ceramic plate and another member bonded to the ceramic plate, and an object on the surface of the ceramic plate. This is a problem common to the holding device that holds the.

  In this specification, the technique which can solve the subject mentioned above is disclosed.

  The technology disclosed in the present specification can be realized as, for example, the following forms.

(1) A method for manufacturing a holding device disclosed in the present specification includes a plate-shaped ceramic plate having a first surface and a second surface opposite to the first surface, and a third surface And is arranged such that the third surface faces the second surface of the ceramic plate, and ceramics, a solidus temperature Ts1 (° C.) and a liquidus temperature Tl1 ( And a ceramic plate disposed between the ceramic plate and the composite plate, a composite plate formed of a composite material with a first aluminum alloy having a temperature of 1 ° C.), a heater disposed inside the ceramic plate, and the ceramic plate. And a bonding layer for bonding the composite plate, and in a method of manufacturing a holding device for holding an object on the first surface of the ceramic plate, the solidus temperature Ts2 (° C.) (where Ts2 ≦ Ts1-40) A step of preparing a foil material formed of a second aluminum alloy, a step of arranging the foil material between the ceramic plate and the composite plate, the ceramic plate, the composite plate, and the foil material, Is heated in a temperature range not lower than the lower limit temperature Tmin (where Tmin = Ts1-30) and not higher than the upper limit temperature Tmax (where Tmax is the lower of Ts1 + 30 and Tl1). And forming the bonding layer by melting at least a part thereof. When the heating temperature is lower than the lower limit temperature Tmin, that is, when the heating temperature is lower than the solidus temperature Ts1-30 ° C. of the first aluminum alloy included in the composite plate, the second aluminum alloy is formed. The liquid phase generated in the foil material does not sufficiently diffuse into the first aluminum alloy of the composite plate, and the bonding strength by the bonding layer is lowered. Conversely, the heating temperature is higher than the upper limit temperature Tmax, that is, the heating temperature is higher than the solidus temperature Ts1 + 30 ° C. of the first aluminum alloy contained in the composite plate, or the liquid phase of the first aluminum alloy When the temperature is higher than the linear temperature Tl1, the first aluminum alloy in the composite plate flows out, and there is a possibility that a gap is formed in the composite plate or the composite plate is deformed. Even if the heating temperature is not less than the lower limit temperature Tmin and not more than the upper limit temperature Tmax, the difference between the solidus temperature Ts1 of the first aluminum alloy and the solidus temperature Ts2 of the second aluminum alloy is less than 40 ° C. If it exists, the quantity of the liquid phase which arises at the time of heating and pressurizing will decrease, the mutual reactivity will become poor, and the joint strength by a joining layer will become low. According to this manufacturing method, the first aluminum alloy and the second aluminum alloy are appropriately selected from the viewpoint of the solidus temperature Ts, and the heating temperature is appropriately set, so that the bonding strength by the bonding layer is obtained. It is possible to suppress the occurrence of delamination on the joint surface even when exposed to a thermal cycle with a large temperature difference. Further, a gap is formed inside the composite plate or the composite plate is deformed. Can be suppressed.

(2) In the manufacturing method of the holding device, the pressurization in the step of forming the bonding layer may be performed in a pressure range of 0.1 MPa or more and 15 MPa or less in vacuum. According to the method for manufacturing the holding device, when the pressure is lower than 0.1 MPa, a gap that is not bonded between the members is generated when the surface of the member is wavy, and the initial bonding strength may be reduced. On the other hand, if the pressure is higher than 15 MPa, the ceramic plate may be cracked or the composite plate may be deformed. By setting the pressure within the above range, it is possible to suppress a decrease in initial bonding strength and to suppress the occurrence of cracks in the ceramic plate and deformation of the composite plate.

(3) In the manufacturing method of the holding device, the second aluminum alloy contains aluminum (Al) as a main component, copper (Cu) of 3.0 wt% or more and 5.0 wt% or less, and 0.3 wt%. As described above, 2.0 wt% or less of magnesium (Mg) and 0.1 wt% or more and 1.0 wt% or less of manganese (Mn) are contained, and the first aluminum alloy is mainly made of aluminum (Al). It is good also as a structure which contains 5.0 wt% or more and 20 wt% or less of silicon (Si) as a component. According to the manufacturing method of the holding device, the second aluminum alloy and the first aluminum alloy can be selected so as to satisfy Ts2 ≦ Ts1-40, the bonding strength by the bonding layer can be strengthened, Even if it is exposed to a thermal cycle with a large temperature difference, it is possible to suppress the occurrence of peeling at the joint surface.

(4) In the method for manufacturing the holding device, the upper limit temperature Tmax may be the lowest temperature among Ts1 + 30, Tl1, and the liquidus temperature Tl2 of the second aluminum alloy. According to the method for manufacturing the holding device, when the heating temperature is higher than the liquidus temperature Tl2 of the second aluminum alloy, the amount of the liquid phase generated in the foil material formed of the second aluminum alloy becomes excessive. Flowing out, particularly at the outer periphery, the bonding strength by the bonding layer is lowered. When the heating temperature is lower than the liquidus temperature Tl2 of the second aluminum alloy, the bonding strength by the bonding layer can be strengthened, and peeling occurs at the bonding surface even when exposed to a thermal cycle with a large temperature difference. Can be suppressed.

(5) In the manufacturing method of the holding device, the composite plate may have a refrigerant flow path. According to the method for manufacturing the holding device, even if the holding device is exposed to a thermal cycle with a large temperature difference, it is possible to suppress the occurrence of peeling at the joint surface. It is possible to suppress the occurrence of a situation in which the cooling effect of the ceramic plate by the refrigerant supplied to the refrigerant flow path formed in the composite plate is lowered and the temperature distribution on the first surface of the ceramic plate is reduced. It can suppress that a uniformity falls.

  The technology disclosed in the present specification can be realized in various forms, for example, in the form of a holding device, an electrostatic chuck, a heater, a vacuum chuck, a manufacturing method thereof, and the like. Is possible.

1 is a perspective view schematically showing an external configuration of an electrostatic chuck 100 in the present embodiment. It is explanatory drawing which shows roughly the XZ cross-sectional structure of the electrostatic chuck 100 in this embodiment. It is explanatory drawing which shows roughly the XY cross-sectional structure of the electrostatic chuck 100 in this embodiment. It is a flowchart which shows the manufacturing method of the electrostatic chuck 100 in this embodiment. It is explanatory drawing which shows the result of performance evaluation. It is explanatory drawing which shows the kind of aluminum alloy used for performance evaluation. It is explanatory drawing which shows an example of the measurement result of the solidus temperature Ts of an aluminum alloy.

A. Embodiment:
A-1. Configuration of the electrostatic chuck 100:
FIG. 1 is a perspective view schematically showing an external configuration of the electrostatic chuck 100 in the present embodiment, and FIG. 2 is an explanatory diagram schematically showing an XZ sectional configuration of the electrostatic chuck 100 in the present embodiment. FIG. 3 is an explanatory diagram schematically showing an XY cross-sectional configuration of the electrostatic chuck 100 according to the first embodiment. 2 shows an XZ cross-sectional configuration at the position II-II in FIG. 3, and FIG. 3 shows an XY cross-sectional configuration at the position III-III in FIG. In each figure, XYZ axes orthogonal to each other for specifying the direction are shown. In this specification, for convenience, the positive direction of the Z-axis is referred to as the upward direction, and the negative direction of the Z-axis is referred to as the downward direction. However, the electrostatic chuck 100 is actually installed in a direction different from such a direction. May be.

  The electrostatic chuck 100 is a device that attracts and holds an object (for example, a wafer W) by electrostatic attraction, and is used, for example, to fix the wafer W in a vacuum chamber of a semiconductor manufacturing apparatus. The electrostatic chuck 100 includes a ceramic plate 10 and a base plate 20 that are arranged in a predetermined arrangement direction (in this embodiment, the vertical direction (Z-axis direction)). The ceramic plate 10 and the base plate 20 are configured such that the lower surface of the ceramic plate 10 (hereinafter referred to as “ceramic side bonding surface S2”) and the upper surface of the base plate 20 (hereinafter referred to as “base side bonding surface S3”) are arranged in the arrangement direction. It arrange | positions so that it may oppose. The electrostatic chuck 100 further includes a bonding layer 30 disposed between the ceramic side bonding surface S2 of the ceramic plate 10 and the base side bonding surface S3 of the base plate 20. The base plate 20 corresponds to the composite plate in the claims, the ceramic side bonding surface S2 of the ceramic plate 10 corresponds to the second surface in the claims, and the base side bonding surface S3 of the base plate 20 is This corresponds to the third surface in the claims.

  The ceramic plate 10 is, for example, a circular flat plate member, and is formed of ceramics. The diameter of the ceramic plate 10 is, for example, about 50 mm to 500 mm (usually about 200 mm to 350 mm), and the thickness of the ceramic plate 10 is, for example, about 2 mm to 10 mm.

Various ceramics can be used as the material for forming the ceramic plate 10. From the viewpoint of strength, wear resistance, plasma resistance, and the relationship with the material for forming the base plate 20 described later, for example, aluminum oxide (alumina , Al ₂ O ₃ ) or ceramics mainly composed of aluminum nitride (AlN) are preferably used. In addition, the main component here means a component having the largest content ratio (weight ratio).

  A pair of internal electrodes 40 formed of a conductive material (for example, tungsten or molybdenum) is provided inside the ceramic plate 10. When a voltage is applied to the pair of internal electrodes 40 from a power source (not shown), an electrostatic attractive force is generated, and the wafer W causes the upper surface of the ceramic plate 10 (hereinafter referred to as an “attracting surface S1”) by the electrostatic attractive force. It is fixed by adsorption. The adsorption surface S1 of the ceramic plate 10 corresponds to the first surface in the claims.

  In addition, a heater 50 made of a resistance heating element formed of a conductive material (for example, tungsten or molybdenum) is provided inside the ceramic plate 10. When a voltage is applied to the heater 50 from a power source (not shown), the ceramic plate 10 is heated by the heat generated by the heater 50, and the wafer W held on the suction surface S1 of the ceramic plate 10 is heated. Thereby, the temperature control of the wafer W is realized. As shown in FIG. 3, the heater 50 is arranged substantially concentrically, for example, as viewed in the Z direction in order to warm the adsorption surface S <b> 1 of the ceramic plate 10 as uniformly as possible.

  The base plate 20 is, for example, a circular flat plate-like member having the same diameter as the ceramic plate 10 or a larger diameter than the ceramic plate 10 and is formed of a composite material composed of ceramics and an aluminum alloy. The diameter of the base plate 20 is, for example, about 220 mm to 550 mm (usually about 220 mm to 350 mm), and the thickness of the base plate 20 is, for example, about 20 mm to 40 mm.

  Various composite materials can be used as a material for forming the base plate 20, and an aluminum alloy containing aluminum as a main component is melted and pressed into porous ceramics containing silicon carbide (SiC) as a main component. Preferably, a composite material is used. The aluminum alloy contained in the composite material may contain Si (silicon) or Mg (magnesium), or may contain other elements as long as the properties are not affected.

The coefficient of thermal expansion of the base plate 20 can be adjusted by adjusting the volume ratio of the ceramics of the composite material that is the forming material of the base plate 20 and the aluminum alloy. The difference from the coefficient of thermal expansion can be reduced. For example, the ceramic plate 10 is formed of ceramics mainly composed of alumina (Al ₂ O ₃ ), and the base plate 20 is formed of a composite material obtained by infiltrating an aluminum alloy into ceramics mainly composed of silicon carbide (SiC). If the volume ratio of ceramics to aluminum alloy in the composite material is adjusted to a range of 80:20 to 55:45, the absolute value of the difference between the thermal expansion coefficient of the base plate 20 and the thermal expansion coefficient of the ceramic plate 10 Is preferably 2.0 × 10 ⁻⁶ (/ ° C.) or less.

  A coolant channel 21 is formed inside the base plate 20. When a refrigerant (for example, a fluorine-based inert liquid or water) flows through the refrigerant flow path 21, the base plate 20 is cooled, and heat transfer between the base plate 20 and the ceramic plate 10 via the bonding layer 30 is performed. The ceramic plate 10 is cooled, and the wafer W held on the suction surface S1 of the ceramic plate 10 is cooled. Thereby, the temperature control of the wafer W is realized.

  The bonding layer 30 is formed of an aluminum alloy containing aluminum as a main component, and bonds the ceramic plate 10 and the base plate 20 together. The thickness of the bonding layer 30 is, for example, about 0.03 mm to 1 mm. The aluminum alloy that is the material for forming the bonding layer 30 may contain Cu (copper), Mg (magnesium), Mn (manganese), Si (silicon), or other elements within a range that does not affect properties and the like. May be included.

  In the following description, in order to distinguish between an aluminum alloy contained in a composite material that is a forming material of the base plate 20 and an aluminum alloy that is a forming material of the bonding layer 30, the former is referred to as an aluminum alloy AA1 for a composite material. The latter may be referred to as joining aluminum alloy AA2. The aluminum alloy for composite material AA1 corresponds to the first aluminum alloy in the claims, and the bonding aluminum alloy AA2 corresponds to the second aluminum alloy in the claims.

Here, the solidus temperature Ts of the aluminum alloy (temperature at which the solid phase and the liquid phase coexist) and the liquidus temperature Tl (the liquid phase and the solid phase coexist from the liquid state). The temperature at which the state shifts to a different state depends on the composition of the aluminum alloy. In the present embodiment, the joining aluminum alloy AA2 and the joining aluminum alloy AA2 are set so that the solidus temperature Ts2 (° C.) of the joining aluminum alloy AA2 is 40 ° C. or more lower than the solidus temperature Ts1 (° C.) of the composite aluminum alloy AA1. The composition of the composite aluminum alloy AA1 is selected. That is, in the electrostatic chuck 100 of the present embodiment, the following condition C1 is satisfied.
Condition C1: Ts2 ≦ Ts1-40

A-2. Method for manufacturing electrostatic chuck 100:
Next, a method for manufacturing the electrostatic chuck 100 in the present embodiment will be described. FIG. 4 is a flowchart showing a method for manufacturing the electrostatic chuck 100 according to the present embodiment. First, the ceramic plate 10 and the base plate 20 are prepared (S110). As described above, the ceramic plate 10 is formed of ceramics, and the base plate 20 is formed of a composite material composed of ceramics and an aluminum alloy AA1 for composite materials. In addition, since the ceramic board 10 and the base board 20 can be manufactured with a well-known manufacturing method, description of a manufacturing method is abbreviate | omitted here.

  Next, a foil material of a joining aluminum alloy AA2 which is a material for forming the joining layer 30 is prepared (S120). As described above, in the present embodiment, the compositions of the composite aluminum alloy AA1 and the joining aluminum alloy AA2 are selected so that the condition C1 is satisfied. Next, the prepared foil material of the joining aluminum alloy AA2 is disposed between the ceramic plate 10 and the base plate 20 (S130).

  Next, the laminated body of the ceramic plate 10 and the base plate 20 through the foil material of the joining aluminum alloy AA2 is placed in a hot press furnace and heated while being pressurized in a vacuum (S140). Thereby, the foil material of the joining aluminum alloy AA2 is melted to form the joining layer 30, and the ceramic plate 10 and the base plate 20 are joined by the joining layer 30. This heating / pressure bonding is also called brazing, and the foil material of the joining aluminum alloy AA2 is also called brazing material.

  The pressure in this heating / pressurizing bonding (hereinafter referred to as “bonding pressure BP”) is preferably set within a range of 0.1 MPa or more and 15 MPa or less. When the bonding pressure BP is set to 0.1 MPa or more, it is possible to suppress a gap that is not bonded between the members to be bonded even when the surface of the member to be bonded (the ceramic plate 10 or the base plate 20) has a wave or the like. It is possible to suppress a decrease in the initial bonding strength. Moreover, when the joining pressure BP is set to 15 MPa or less, it is possible to suppress the cracking of the ceramic plate 10 and the deformation of the base plate 20.

Further, the temperature in the heating / pressurizing joining (hereinafter referred to as “joining temperature BT”) is set within the range of the lower limit temperature Tmin or more and the upper limit temperature Tmax or less. Specifically, the lower limit temperature Tmin of this temperature range is a temperature 30 ° C. lower than the solidus temperature Ts1 (° C.) of the composite aluminum alloy AA1. The upper limit temperature Tmax of this temperature range is a temperature 30 ° C. higher than the solidus temperature Ts1 (° C.) of the aluminum alloy AA1 for composite material and the liquidus temperature Tl1 (° C.) of the aluminum alloy AA1 for composite material. The lower one. That is, in the present embodiment, the junction temperature BT is set so that the following condition C2 is satisfied.
Condition C2: Tmin ≦ BT ≦ Tmax
(However, Tmin = Ts1-30, and Tmax is the lower of Ts1 + 30 and Tl1.)

  After the heating and pressure bonding in S140, post-processing (polishing of the outer periphery and upper and lower surfaces, formation of terminals, etc.) is performed as necessary. With the above manufacturing method, the electrostatic chuck 100 having the above-described configuration is manufactured.

A-3. Performance evaluation:
The performance evaluation described below was performed on the electrostatic chuck 100 having the above-described configuration. FIG. 5 is an explanatory diagram showing the results of performance evaluation.

A-3-1. For each example and each comparative example:
As shown in FIG. 5, in the performance evaluation, the electrostatic chucks 100 of Examples 1 to 9 and Comparative Examples 1 to 4 were used. The electrostatic chuck 100 of each example and each comparative example is common in the following points.
(Configuration of ceramic plate 10)
・ Material: Ceramics mainly composed of alumina (Al ₂ O ₃ ) ・ Diameter: 350 mm
・ Thickness: 4mm
(Configuration of base plate 20)
・ Material: Composite material in which aluminum alloy AA1 for composite material mainly composed of aluminum is infiltrated into porous ceramics composed mainly of silicon carbide (SiC) ・ Diameter: 350 mm
・ Thickness: 35mm
(Configuration of bonding layer 30)
-Material: Foil material of aluminum alloy AA2 for joining mainly composed of aluminum-Thickness of foil material: 50-70 µm
(Joining method between ceramic plate 10 and base plate 20)
The laminated body of the ceramic plate 10 and the base plate 20 through the foil material of the joining aluminum alloy AA2 is placed in a hot press furnace, and joined by heating and pressurizing in a vacuum.

  On the other hand, as shown in FIG. 5, the electrostatic chuck 100 of each example and each comparative example includes a composition of the aluminum alloy AA2 for bonding and the aluminum alloy AA1 for composite material, and a composite material that is a forming material of the base plate 20. The ratio of the volume of the aluminum alloy to the total volume (hereinafter referred to as “aluminum alloy ratio”) is different from the bonding temperature BT and the bonding pressure BP.

(Composition of aluminum alloy AA2 for bonding and aluminum alloy AA1 for composite material)
FIG. 6 is an explanatory diagram showing the types of aluminum alloys used for performance evaluation. FIG. 6 shows the composition (weight%), the solidus temperature Ts (° C.), and the liquidus temperature Tl (° C.) for each type of aluminum alloy (aluminum alloys A to D) used for performance evaluation. Is shown. As shown in FIG. 6, the aluminum alloys A to D have different compositions, and as a result, the solidus temperature Ts (° C.) and the liquidus temperature Tl (° C.) are different from each other.

  The solidus temperature Ts and the liquidus temperature Tl of each aluminum alloy were measured by DSC measurement (differential scanning calorimetry). FIG. 7 is an explanatory view showing an example of the measurement result of the solidus temperature Ts of the aluminum alloy. FIG. 7 shows a chart obtained by performing DSC analysis on the aluminum alloy C shown in FIG. As shown in FIG. 7, the initial fall point of the endothermic peak (the lowest temperature peak when multiple endothermic peaks are confirmed) of the chart obtained when the temperature of the solid-state aluminum alloy is raised Was determined as the solidus temperature Ts (553 ° C. for aluminum alloy C). Similarly, the solidus temperature Ts was measured for other aluminum alloys. Similarly, for the liquidus temperature Tl, the exothermic peak of the chart obtained when the temperature of the liquid phase aluminum alloy is lowered (the highest temperature peak when a plurality of exothermic peaks are confirmed). The temperature at the initial rising point was specified as the liquidus temperature Tl.

  As shown in FIG. 5, in the electrostatic chucks 100 of Examples 1 to 6 and Comparative Examples 3 and 4, the aluminum alloy A is used as the bonding aluminum alloy AA2, and the aluminum alloy D is used as the composite aluminum alloy AA1. It was. Therefore, in these examples and comparative examples, the solidus temperature Ts1 (575 ° C.) of the aluminum alloy AA1 for composites (aluminum alloy D) and the solidus temperature Ts2 of the aluminum alloy AA2 for bonding (aluminum alloy A) ( 510 ° C.) was 65 ° C. Further, in the electrostatic chucks 100 of Examples 8 and 9, the aluminum alloy A was used as the bonding aluminum alloy AA2, and the aluminum alloy C was used as the composite aluminum alloy AA1. Therefore, in these Examples, the solidus temperature Ts1 (553 ° C.) of the aluminum alloy AA1 (aluminum alloy C) for composite material and the solidus temperature Ts2 (510 ° C.) of the aluminum alloy AA2 for bonding (aluminum alloy A). The difference was 43 ° C. In the electrostatic chuck 100 of Example 7, the aluminum alloy B was used as the bonding aluminum alloy AA2, and the aluminum alloy D was used as the composite aluminum alloy AA1. Therefore, in this example, the solidus temperature Ts1 (575 ° C.) of the aluminum alloy AA1 (aluminum alloy D) for composite material and the solidus temperature Ts2 (532 ° C.) of the aluminum alloy AA2 for bonding (aluminum alloy B) The difference was 43 ° C. As described above, in the electrostatic chucks 100 of Examples 1 to 9 and Comparative Examples 3 and 4, the joining aluminum alloy AA2 and the composite aluminum alloy are satisfied so that the above-described condition C1 (Ts2 ≦ Ts1-40) is satisfied. AA1 was selected.

  On the other hand, in the electrostatic chuck 100 of Comparative Example 1, the aluminum alloy C was used as the bonding aluminum alloy AA2, and the aluminum alloy D was used as the composite aluminum alloy AA1. Therefore, in this comparative example, the solidus temperature Ts1 (575 ° C.) of the aluminum alloy AA1 (aluminum alloy D) for composite material and the solidus temperature Ts2 (553 ° C.) of the aluminum alloy AA2 for bonding (aluminum alloy C) The difference was 22 ° C. In the electrostatic chuck 100 of Comparative Example 2, the aluminum alloy D was used as both the bonding aluminum alloy AA2 and the composite aluminum alloy AA1. Therefore, in this comparative example, the difference between the solidus temperature Ts1 of the composite aluminum alloy AA1 and the solidus temperature Ts2 of the joining aluminum alloy AA2 was 0 ° C. Thus, in the electrostatic chucks 100 of Comparative Examples 1 and 2, the joining aluminum alloy AA2 and the composite aluminum alloy AA1 were selected so that the above-described condition C1 (Ts2 ≦ Ts1-40) was not satisfied. .

(About aluminum alloy ratio)
As shown in FIG. 5, in all the examples and comparative examples except Example 4, the aluminum alloy ratio of the composite material that is the forming material of the base plate 20 was 30 (%). Moreover, in Example 4, the aluminum alloy ratio of the composite material which is a forming material of the base plate 20 was 40 (%).

(About junction temperature BT)
As shown in FIG. 5, in Examples 1 and 3 to 8, the bonding temperature BT was 550 ° C. In Examples 2 and 9 and Comparative Examples 1 and 2, the bonding temperature BT was 580 ° C. Therefore, in Examples 1 to 9 and Comparative Examples 1 and 2, the difference (BT-Ts1) between the bonding temperature BT and the solidus temperature Ts1 of the composite aluminum alloy AA1 is -30 ° C or higher and 30 ° C or lower. It is. In Examples 1 to 9 and Comparative Examples 1 and 2, since the aluminum alloy C or D is used as the composite aluminum alloy AA1, the bonding temperature BT is equal to the liquidus temperature Tl1 of the composite aluminum alloy AA1. (603 ° C or 584 ° C). Thus, in Examples 1-9 and Comparative Examples 1 and 2, the junction temperature BT was set so that the above-described condition C2 was satisfied.

  On the other hand, in Comparative Example 3, the bonding temperature BT was 630 ° C. Therefore, in Comparative Example 3, the difference (BT−Ts1) between the bonding temperature BT and the solidus temperature Ts1 of the composite aluminum alloy AA1 is 30 ° C. or higher. In Comparative Example 3, since the aluminum alloy D is used as the composite aluminum alloy AA1, the bonding temperature BT is higher than the liquidus temperature Tl1 (584 ° C.) of the composite aluminum alloy AA1. In Comparative Example 4, the bonding temperature BT was 520 ° C. Therefore, in Comparative Example 4, the difference (BT−Ts1) between the bonding temperature BT and the solidus temperature Ts1 of the composite aluminum alloy AA1 is −30 ° C. or less. Thus, in Comparative Examples 3 and 4, the junction temperature BT was set so that the above-described condition C2 was not satisfied.

(About bonding pressure BP)
As shown in FIG. 5, in all the examples and comparative examples except Example 6, the bonding pressure BP was set to a value within the range of 0.1 MPa or more and 15 MPa or less. On the other hand, in Example 6, the bonding pressure BP was set to 0.05 MPa.

A-3-2. Evaluation method:
(Evaluation of initial bonding state)
As an evaluation of the initial bonding state, immediately after the production of the electrostatic chuck 100 of the example and the comparative example, an appearance inspection, an ultrasonic flaw detection inspection of the bonding surface, and an in-plane temperature difference inspection were performed. In the appearance inspection, it was confirmed whether the base plate 20 was deformed or aluminum alloy flowed out of the base plate 20. In the ultrasonic flaw inspection, it was determined whether or not there is an unjoined portion on the joint surface based on the reflection level of the ultrasonic wave from the joint surface. In the in-plane temperature difference inspection, the heater 50 arranged inside the ceramic plate 10 is energized to set the adsorption surface S1 of the ceramic plate 10 to 250 ° C., and a 80 ° C. refrigerant flows through the refrigerant flow path 21 of the base plate 20. In this state, the temperature of a plurality of points on the adsorption surface S1 of the ceramic plate 10 was measured using a radiation thermometer, and the presence or absence of hot spots (points higher than the average temperature of each point of the adsorption surface S1 by 10 ° C.) was confirmed. . In general, in the state where there is no separation or gap in the joint between the ceramic plate 10 and the base plate 20, the temperature at each point of the adsorption surface S1 is within the average temperature ± 5 ° C., but there is no separation or gap in the joint. When this occurs, the heat transfer between the base plate 20 and the ceramic plate 10 decreases at that portion, and a hot spot is generated on the adsorption surface S1. The initial temperature distribution on the adsorption surface S1 depends on the design of the heater 50 (control of the amount of heat generated by the location of the heater 50, individual control by making the heater 50 multi-zoned), and the design of the refrigerant flow path 21 of the base plate 20. It is possible to control by optimizing the above.

(Regarding evaluation of bonding state after thermal cycling)
Evaluation of the bonding state after the thermal cycle was performed as follows. In order to create a thermal cycle environment, the electrostatic chuck 100 of the example or the comparative example is installed in the evaluation chamber, and the heater 50 is turned on / off while supplying an 80 ° C. chiller to the refrigerant flow path 21 of the base plate 20. Repeated alternately. Specifically, the temperature at a plurality of points on the adsorption surface S1 of the ceramic plate 10 is measured using a radiation thermometer, and the maximum value of the temperature measurement values at each point (hereinafter referred to as “maximum point temperature HT”). When the temperature increased to 250 ° C., the heater 50 was turned off, and when the highest point temperature HT of the suction surface S1 decreased to 100 ° C., the control to turn the heater 50 on was repeated 1000 cycles. Thereafter, the presence or absence of a new hot spot that did not exist in the initial state was confirmed on the suction surface S1. Moreover, in order to check whether the uniformity of the temperature distribution on the adsorption surface has deteriorated, although not so much as a hot spot is generated, the ceramic plate 10 is subjected to an initial state and a point when the thermal cycle is repeated 1000 times. The temperature difference ΔT, which is the difference between the highest value (maximum point temperature HT) and the lowest value (hereinafter referred to as “lowest point temperature LT”) among the temperature measurement values at each point of the adsorption surface S1, was calculated. Then, the difference between the temperature difference ΔT when the thermal cycle was repeated 1000 times and the temperature difference ΔT in the initial state was calculated as the temperature difference change amount Ct.

A-3-3. Evaluation results:
As shown in FIG. 5, in Examples 1 to 9, in the initial state, no abnormality was observed in the appearance inspection and the ultrasonic flaw detection inspection, and it was determined as acceptable (◯). Moreover, there was no hot spot and the bonding state was good. Further, even after 1000 thermal cycles, no new hot spots were generated, and the temperature difference change Ct was smaller than 2 ° C., and a good bonding state was maintained.

  In Example 6, in the initial state, no abnormality was observed in the appearance inspection and there were no hot spots, but it was confirmed in the ultrasonic flaw inspection that there was an unjoined portion in a very small region. In Example 6, since the bonding pressure BP is as low as 0.05 MPa, the undulations on the surface of the ceramic plate 10 and the base plate 20 are not sufficiently relaxed, and a gap is generated and an unbonded portion is generated. it is conceivable that. However, since the size of the unjoined portion was small and the region where the unjoined portion was confirmed was as small as 5% or less of the entire joint surface, it was determined as acceptable (◯). Further, even after 1000 heat cycles, no new hot spots were generated, and the temperature difference change amount Ct was smaller than 5 ° C., and a good bonding state was generally maintained.

  On the other hand, in Comparative Examples 1 and 2, no abnormality was confirmed in the initial state, but after 1000 thermal cycles, the occurrence of a new hot spot was confirmed, and the temperature difference change amount Ct was also greater than 10 ° C. A good bonding state was not maintained. In Comparative Examples 1 and 2, the difference (Ts1−Ts2) between the solidus temperature Ts1 of the composite aluminum alloy AA1 and the solidus temperature Ts2 of the joining aluminum alloy AA2 is less than 40 ° C. (that is, as described above). Condition C1 is not satisfied). Therefore, in Comparative Examples 1 and 2, when the bonding temperature BT is set within the range of the solidus temperature Ts1 ± 30 ° C. of the aluminum alloy AA1 for composites according to the above-described condition C2, during the heating and pressure bonding, The amount of the liquid phase generated in the aluminum alloy AA1 for composite material and the aluminum alloy AA2 for bonding decreases, and the bonding strength decreases by reducing the reactivity between each other, and a good bonding state is obtained after 1000 thermal cycles. It is thought that it was not maintained.

  Further, in Comparative Example 3, the aluminum alloy AA1 for composite material flows out from the porous ceramic skeleton of the composite member after heating and pressure bonding, and a number of voids are generated in the composite member. ). In Comparative Example 3, the bonding temperature BT is higher than the solidus temperature Ts1 (° C.) + 30 ° C. of the aluminum alloy AA1 for composite material (that is, the above-described condition C2 is not satisfied). For this reason, in Comparative Example 3, the aluminum alloy AA1 for composite material became a large amount of liquid phase during heating and pressure bonding, and could not stay in the skeleton of the porous ceramic, but flowed out to the surface of the porous ceramic. it is conceivable that. In such a state, a large number of gaps are formed in the base plate 20, and when the base plate 20 is pressurized, it is greatly deformed, so that it cannot be put into practical use.

  In Comparative Example 4, no abnormality was confirmed in the initial state, but after 1000 heat cycles, the occurrence of a new hot spot was confirmed, and the temperature difference change amount Ct was also larger than 10 ° C. The bonded state was not maintained. In Comparative Example 4, the bonding temperature BT is as low as the solidus temperature Ts1 (° C.) − 30 ° C. of the aluminum alloy AA1 for composite material (that is, the above-described condition C2 is not satisfied). Therefore, in Comparative Example 4, the liquid phase generated in the bonding aluminum alloy AA2 is difficult to diffuse into the composite aluminum alloy AA1, the bonding strength is reduced, and a good bonding state is maintained after 1000 thermal cycles. It is thought that there was not.

  From the performance evaluation results described above, the joining aluminum alloy AA2 and the composite aluminum alloy AA1 are selected so as to satisfy the above-described condition C1, and the joining temperature BT is set so as to satisfy the above-described condition C2. In addition, the ceramic plate 10 and the base plate 20 of the electrostatic chuck 100 can be firmly bonded by the bonding layer 30, and even when exposed to a thermal cycle with a large temperature difference, it is possible to prevent peeling or the like from occurring on the bonding surface. Further, it was confirmed that it is possible to suppress the formation of a gap in the base plate 20 and the deformation of the base plate 20.

  Further, from the performance evaluation results described above, when the bonding pressure BP is set to 0.1 MPa or more, even when there is a undulation or the like on the surface of the member, a gap that is not bonded between the members is suppressed, and the initial bonding strength It was confirmed that it can suppress that falls.

  In Examples 1 to 9, an aluminum alloy A or B is used as the bonding aluminum alloy AA2, and an aluminum alloy D or C is used as the composite aluminum alloy AA1. Referring to the compositions of aluminum alloys A to D shown in FIG. 6, as aluminum alloy AA2 for bonding, aluminum (Al) as a main component, and 3.0 wt% or more and 5.0 wt% or less of copper (Cu) and Aluminum alloy containing 0.3 wt% or more and 2.0 wt% or less of magnesium (Mg) and 0.1 wt% or more and 1.0 wt% or less of manganese (Mn) When an aluminum alloy containing aluminum (Al) as a main component and containing silicon (Si) of 5.0 wt% or more and 20 wt% or less is used as AA1, the above-described condition C1 (Ts2 ≦ Ts1-40) is satisfied. I can say that. In addition, it is preferable that content of silicon (Si) of aluminum alloy AA2 for joining is 3.0 wt% or less.

  In the performance evaluation described above, in any of the examples and comparative examples, the bonding temperature BT is equal to or lower than the liquidus temperature Tl2 (° C.) of the bonding aluminum alloy AA2, but the bonding temperature BT is assumed to be the bonding aluminum alloy AA2. When the temperature is higher than the liquidus temperature Tl2 (° C.), the amount of the liquid phase in the joining aluminum alloy AA2 becomes excessive at the time of heating and pressurizing joining, and the joining aluminum alloy AA2 flows out, particularly in the outer peripheral portion. The bonding strength due to 30 is considered to be low. Therefore, the bonding temperature BT is preferably equal to or lower than the liquidus temperature Tl2 (° C.) of the bonding aluminum alloy AA2.

In the above-described performance evaluation, in any of the examples and comparative examples, the ceramic plate 10 is formed of ceramics mainly composed of alumina (Al ₂ O ₃ ), and the base plate 20 is composed mainly of silicon carbide (SiC). The ceramic material is made of a composite material in which an aluminum alloy is infiltrated, and the volume ratio of the aluminum alloy in the composite material is in the range of 20 to 45%. If the electrostatic chuck 100 has such a configuration, it is possible to suppress the occurrence of peeling at the interface between the bonding layer 30 and the members to be bonded (the ceramic plate 10 and the base plate 20).

A-4. Effects of this embodiment:
As described above, the electrostatic chuck 100 according to the present embodiment includes the ceramic plate 10, the base plate 20, the heater 50, and the bonding layer 30. The ceramic plate 10 is a plate-like member having an adsorption surface S1 and a ceramic side bonding surface S2 opposite to the adsorption surface S1. The base plate 20 is a plate-like member having a base-side bonding surface S3, and is arranged so that the base-side bonding surface S3 faces the ceramic-side bonding surface S2 of the ceramic plate 10. The base plate 20 is formed of a composite material of ceramics and an aluminum alloy AA1 for composite material having a solidus temperature Ts1 (° C.) and a liquidus temperature Tl1 (° C.). The heater 50 is disposed inside the ceramic plate 10. The bonding layer 30 is disposed between the ceramic plate 10 and the base plate 20 and bonds the ceramic plate 10 and the base plate 20.

  Moreover, the manufacturing method of the electrostatic chuck 100 of the present embodiment includes a step of preparing a foil material formed of the joining aluminum alloy AA2 having a solidus temperature Ts2 (° C.) (where Ts2 ≦ Ts1-40). The step of disposing the foil material between the ceramic plate 10 and the base plate 20, and the lower limit temperature Tmin (where Tmin = Ts1-30) while pressing the ceramic plate 10, the base plate 20 and the foil material. ) Above, the step of forming the bonding layer 30 by melting at least a part of the foil material by heating in the temperature range below the upper limit temperature Tmax (where Tmax is the lower of Ts1 + 30 and Tl1). Is provided. When the bonding temperature BT is lower than the lower limit temperature Tmin, that is, the solidus temperature of the composite aluminum alloy AA1 included in the base plate 20 is lower than Ts1-30 ° C., the bonding aluminum alloy AA2 is formed. The liquid phase generated in the foil material does not sufficiently diffuse into the composite aluminum alloy AA1 of the base plate 20, and the bonding strength by the bonding layer 30 is lowered. On the contrary, the bonding temperature BT is higher than the upper limit temperature Tmax, that is, the height exceeds the solidus temperature Ts1 + 30 ° C. of the aluminum alloy AA1 for composite material included in the base plate 20, or the liquid of the aluminum alloy AA1 for composite material When the phase line temperature is higher than Tl1, the composite aluminum alloy AA1 in the base plate 20 flows out, and there is a possibility that a gap is formed in the base plate 20 or the base plate 20 is deformed. Even when the bonding temperature BT is not less than the lower limit temperature Tmin and not more than the upper limit temperature Tmax, the difference between the solidus temperature Ts1 of the composite aluminum alloy AA1 and the solidus temperature Ts2 of the bonding aluminum alloy AA2 is 40 ° C. If it is less than this, the amount of the liquid phase generated during the heating and pressure bonding is reduced, the mutual reactivity becomes poor, and the bonding strength by the bonding layer 30 is lowered. According to the manufacturing method of the electrostatic chuck 100 of the present embodiment, the aluminum alloy AA1 for composite material and the aluminum alloy AA2 for bonding are appropriately selected from the viewpoint of the solidus temperature Ts, and the bonding temperature BT is appropriately set. By setting, the bonding strength by the bonding layer 30 can be strengthened, and it is possible to suppress the occurrence of delamination on the bonding surface even when exposed to a thermal cycle with a large temperature difference. As a result, the base plate 20 and the ceramic plate 10 can be prevented from being deteriorated in heat transfer and the uniformity of the temperature distribution on the adsorption surface S1 of the ceramic plate 10 can be suppressed, and a gap can be formed inside the base plate 20. Or the base plate 20 can be prevented from being deformed.

  Moreover, in the manufacturing method of the electrostatic chuck 100 of this embodiment, it is preferable that a heating and pressurizing joining is performed in a pressure range of 0.1 MPa or more and 15 MPa or less in a vacuum. When the bonding pressure BP is lower than 0.1 MPa, a gap that is not bonded between the members occurs when the surface of the member is wavy, and the initial bonding strength may be reduced. Further, if the bonding pressure BP is higher than 15 MPa, the ceramic plate 10 may be cracked or the base plate 20 may be deformed. By setting the bonding pressure BP in the above range, it is possible to suppress the initial decrease in bonding strength and to suppress the cracking of the ceramic plate 10 and the deformation of the base plate 20.

  The joining aluminum alloy AA2 is mainly composed of aluminum (Al), 3.0 wt% or more and 5.0 wt% or less copper (Cu), and 0.3 wt% or more and 2.0 wt% or less magnesium (Cu). Mg) and 0.1 wt% or more and 1.0 wt% or less of manganese (Mn), and the aluminum alloy AA1 for composite material is mainly composed of aluminum (Al) and is 5.0 wt% or more and 20 wt%. % Or less of silicon (Si) is preferably contained. If it does in this way, aluminum alloy AA2 for joining and aluminum alloy AA1 for composite materials can be selected so that the above-mentioned conditions C1 (Ts2 <= Ts1-40) may be satisfied, and the joint strength by joining layer 30 will be strengthened. It is possible to suppress the occurrence of peeling at the joint surface even when exposed to a thermal cycle with a large temperature difference.

  The upper limit temperature Tmax of the bonding temperature BT is preferably the lowest temperature among Ts1 + 30, Tl1, and the liquidus temperature Tl2 of the bonding aluminum alloy AA2. When the joining temperature BT is higher than the liquidus temperature Tl2 of the joining aluminum alloy AA2, the amount of the liquid phase generated in the foil material formed by the joining aluminum alloy AA2 becomes excessive and flows out, particularly in the outer peripheral portion. The bonding strength due to becomes low. When the bonding temperature BT is lower than the liquidus temperature Tl2 of the bonding aluminum alloy AA2, the bonding strength by the bonding layer 30 can be strengthened, and peeling occurs at the bonding surface even when exposed to a thermal cycle with a large temperature difference. Can be suppressed.

B. Variations:
The technology disclosed in the present specification is not limited to the above-described embodiment, and can be modified into various forms without departing from the gist thereof. For example, the following modifications are possible.

  The material which forms each member in the said embodiment is an example to the last, and each member may be formed with another material. For example, the combination of the composition of the composite aluminum alloy AA1 and the composition of the bonding aluminum alloy AA2 in the above embodiment is merely an example, and can be changed to any combination as long as the condition C1 is satisfied.

  In the above embodiment, the refrigerant flow path 21 is formed inside the base plate 20, but the refrigerant flow path 21 is not inside the base plate 20 but on the surface of the base plate 20 (for example, the base plate 20 and (Between the bonding layers 30). Moreover, in the said embodiment, although the bipolar system with which a pair of internal electrode 40 was provided in the inside of the ceramic board 10 was employ | adopted, the monopolar system in which the one internal electrode 40 was provided in the inside of the ceramic board 10 is used. It may be adopted.

  Further, the method of manufacturing the electrostatic chuck 100 in the above embodiment is merely an example, and various modifications can be made. For example, the bonding temperature BT in the method for manufacturing the electrostatic chuck 100 of the above embodiment is merely an example, and can be changed to any temperature as long as the condition C2 is satisfied.

  The present invention also relates to a ceramic in an electrostatic chuck comprising a ceramic plate, a base plate formed of metal, and an intermediate plate disposed between the ceramic plate and the base plate and formed of the composite material described above. It can also be applied to the joining of a plate and an intermediate plate. In this case, the intermediate plate corresponds to the composite plate in the claims.

  In addition, the present invention is not limited to the electrostatic chuck 100 that holds the wafer W using electrostatic attraction, but includes other ceramic plates and base plates, and other holding devices that hold an object on the surface of the ceramic plates. (For example, it is applicable also to a vacuum chuck, a heater, etc.).

10: Ceramic plate 20: Base plate 21: Refrigerant flow path 30: Bonding layer 40: Internal electrode 50: Heater 100: Electrostatic chuck

Claims (5)

A plate-like ceramic plate having a first surface and a second surface opposite to the first surface;
A plate having a third surface, the third surface being arranged so as to oppose the second surface of the ceramic plate, ceramics, solidus temperature Ts1 (° C.) and liquidus temperature A composite plate formed of a composite material with a first aluminum alloy having Tl1 (° C.);
A heater disposed inside the ceramic plate;
A bonding layer disposed between the ceramic plate and the composite plate and bonding the ceramic plate and the composite plate;
A method of manufacturing a holding device for holding an object on the first surface of the ceramic plate,
Preparing a foil material formed of a second aluminum alloy having a solidus temperature Ts2 (° C.) (where Ts2 ≦ Ts1-40);
Disposing the foil material between the ceramic plate and the composite plate;
While pressurizing the ceramic plate, the composite plate, and the foil material, the lower limit temperature Tmin (however, Tmin = Ts1-30) or more and the upper limit temperature Tmax (where Tmax is the lower of Ts1 + 30 and Tl1) or less. Forming the bonding layer by melting at least a part of the foil material by heating in a temperature range of
A method for manufacturing a holding device. In the manufacturing method of the holding device according to claim 1,
The method for manufacturing a holding device is characterized in that the pressurization in the step of forming the bonding layer is performed in a pressure range of 0.1 MPa to 15 MPa in vacuum. In the manufacturing method of the holding device according to claim 1 or 2,
The second aluminum alloy has aluminum (Al) as a main component, copper (Cu) of 3.0 wt% or more and 5.0 wt% or less, and magnesium (Mg) of 0.3 wt% or more and 2.0 wt% or less. ), And 0.1 wt% or more and 1.0 wt% or less of manganese (Mn),
The first aluminum alloy contains aluminum (Al) as a main component and contains 5.0 wt% or more and 20 wt% or less of silicon (Si). In the manufacturing method of the holding device according to any one of claims 1 to 3,
The upper limit temperature Tmax is the lowest temperature among Ts1 + 30, Tl1, and the liquidus temperature Tl2 of the second aluminum alloy. In the manufacturing method of the holding device according to any one of claims 1 to 4,
A method of manufacturing a holding device, wherein the composite plate is formed with a refrigerant flow path.

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