Patent Publication Number: US-2021183679-A1

Title: Method for manufacturing holding device and holding device

Description:
TECHNICAL FIELD 
     The technique disclosed in the present specification relates to a method for manufacturing a holding device. 
     BACKGROUND ART 
     An example of a known holding device is an electrostatic chuck which attracts and holds a wafer by means of electrostatic attraction force. The electrostatic chuck includes a ceramic member, a base member, a joining portion joining the ceramic member and the base member together, and a chuck electrode provided in the ceramic member. The electrostatic chuck attracts and holds a wafer on a surface (hereinafter referred to as an “attracting surface”) of the ceramic member by utilizing electrostatic attraction force generated as a result of application of a voltage to the chuck electrode. 
     Since the accuracy of various processes (film formation, etching, etc.) performed on the wafer held on the attracting surface of the electrostatic chuck may degrade unless the temperature of the wafer is maintained at a desired temperature, the electrostatic chuck needs to have the ability to control the temperature distribution of the wafer. 
     Conventionally, there has been known an electrostatic chuck in which a resin for adjustment whose heat conductivity differs from that of the joining portion is embedded in a surface of the ceramic member opposite the attracting surface at a position determined in accordance with the temperature distribution of the attracting surface (see, for example, Patent Documents 1 and 2). 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2016-1757 
     Patent Document 2: Japanese Patent Application Laid-Open (kokai) No. 2013-247342 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     A method for manufacturing an electrostatic chuck in which a ceramic member and a base member are joined together via a joining portion may involve a deviation of the temperature distribution of an attracting surface of the ceramic member from a desired distribution due to an unintentional production-related variation, for example, in the case where the heat conductivity and/or heat capacity of the ceramic member or the base member changes inside the member, the case where a heater electrode provided in the ceramic member has a heat generation distribution, the case where the flow rate of a coolant (for example, a fluorine-based inert liquid, water, or the like) flowing through a coolant channel of the base member becomes nonuniform, or the case where the ceramic member inclines in relation to the base member. Since each of a production line, a production apparatus, etc. has unintended characteristics, even when a resin for adjustment is embedded in the joining portion as in the above-described conventional electrostatic chuck manufacturing method, possibly, an overall deviation of the temperature distribution of the attracting surface cannot be suppressed sufficiently, although a partial deviation of the temperature distribution of the attracting surface can be suppressed. 
     Notably, such a problem is a common problem that occurs not only in the method for manufacturing the electrostatic chuck but also in a method for manufacturing a holding device (for example, a heating device, a vacuum chuck, or the like) which includes a ceramic member and a base member joined together. 
     The present specification discloses a technique capable of solving the above-described problem. 
     Means for Solving the Problems 
     The technique disclosed in the present specification can be embodied in the following modes. 
     (1) A holding device manufacturing method disclosed in the present specification is a method for manufacturing a holding device comprising a ceramic member having a first surface and a second surface located opposite the first surface, a base member having a third surface and a fourth surface located opposite the third surface and disposed such that the third surface is located on a side toward the first surface of the ceramic member, and a joining portion disposed between the first surface of the ceramic member and the third surface of the base member and joining the ceramic member and the base member together, the holding device holding an object on the second surface of the ceramic member. The holding device manufacturing method comprises the steps of: preparing a first joined body which includes a pre-machining ceramic member which is the ceramic member before formation of the second surface thereon and has the first surface and a fifth surface located opposite the first surface and approximately parallel to the first surface, the base member, and the joining portion disposed between the first surface of the pre-machining ceramic member and the third surface of the base member and joining the pre-machining ceramic member and the base member together, the joining portion of the first joined body increasing in thickness in a first direction in which the first surface and the third surface face each other via the joining portion, from one end side toward the other end side of the joining portion in a second direction approximately perpendicular to the first direction; and machining the fifth surface of the pre-machining ceramic member in the first joined body. In a method for manufacturing the holding device including the ceramic member and the base member joined together via the joining portion, the temperature distribution of the second surface of the ceramic member may deviate from a desired distribution due to the unintended characteristics of each of a production line, a production apparatus, etc. In contrast, in the present holding device manufacturing method, the first joined body in which the pre-machining ceramic member and the base member are joined together via the joining portion such that the first surface of the pre-machining ceramic member inclines in relation to the third surface of the base member is intentionally prepared. As a result, it is possible to prevent the overall temperature distribution of the second surface from deviating from a desired distribution due to the unintended characteristics of each of the production line, the production apparatus, etc.
 
(2) In the above-described holding device manufacturing method, the first joined body may be prepared by applying a joining agent to at least one of the first surface of the pre-machining ceramic member and the third surface of the base member such that its thickness in the first direction increases from the one end side toward the other end side in the second direction, disposing the first surface of the pre-machining ceramic member and the third surface of the base member to face each other via the joining agent, and curing the joining agent to form the joining portion. In the present holding device manufacturing method, the joining agent is applied to the first surface of the pre-machining ceramic member or the third surface of the base member in advance such that the thickness of the joining agent increases from one end side toward the other end side. Thus, according to the present holding device manufacturing method, the direction of inclination of the pre-machining ceramic member in relation to the base member can be adjusted to a desired direction.
 
(3) In the above-described holding device manufacturing method, the first joined body may be prepared by applying loads to portions of the joining portion located on the one end side and the other end side, respectively, in the second direction such that the load allied to the portion on the one end side is larger than the load allied to the portion on the other end side, wherein the application of the loads is performed at least before the curing of the joining agent, in the course of the curing of the joining agent, or after the curing of the joining agent. According to the present holding device manufacturing method, it is possible to reliably join the base member and the ceramic member together in a state in which the ceramic member is inclined in relation to the base member, while adjusting the direction of inclination of the ceramic member in relation to the base member to a desired direction.
 
(4) In the above-described holding device manufacturing method, the first joined body may be prepared by disposing a joining agent between the first surface of the pre-machining ceramic member and the third surface of the base member, and applying loads to portions of the joining portion located on the one end side and the other end side, respectively, in the second direction such that the load allied to the portion on the one end side is larger than the load allied to the portion on the other end side, wherein the application of the loads is performed at least before the curing of the joining agent, in the course of the curing of the joining agent, or after the curing of the joining agent. According to the present holding device manufacturing method, it is possible to reliably join the base member and the ceramic member together in a state in which the ceramic member is inclined in relation to the base member.
 
(5) The above-described holding device manufacturing method may comprise the steps of preparing a second joined body by joining the pre-machining ceramic member and the base member via a provisional joining portion and measuring a temperature distribution of the fifth surface) of the pre-machining ceramic member in the second joined body; and separating from each other the pre-machining ceramic member and the base member in the second joined body and joining the pre-machining ceramic member and the base member via a joining agent such that the first surface of the pre-machining ceramic member inclines, in relation to the third surface of the base member, to a direction determined on the basis of the measured temperature distribution, whereby the first joined body is prepared. According to the present holding device manufacturing method, the controllability of the temperature distribution of the second surface of the ceramic member (for example, heat equalization performance) can be improved by inclining the pre-machining ceramic member, in relation to the base member, to a direction determined on the basis of the measured temperature distribution of the second joined body formed by joining the pre-machining ceramic member and the base member together via the provisional joining portion.
 
(6) A holding device disclosed in the present specification comprises: a ceramic member having a first surface and a second surface located opposite the first surface; a base member having a third surface and a fourth surface located opposite the third surface and disposed such that the third surface is located on a side toward the first surface of the ceramic member; and a joining portion disposed between the first surface of the ceramic member and the third surface of the base member and joining the ceramic member and the base member together, the holding device being adapted to hold an object on the second surface of the ceramic member. The holding device comprises a conductor provided in the ceramic member and disposed on an imaginary plane; over the entirety of the joining portion, the joining portion increases in thickness in a first direction in which the first surface and the third surface face each other via the joining portion, from one end side toward the other end side of the joining portion in a second direction approximately perpendicular to the first direction; and the distance between the second surface and the imaginary plane on which the conductor is disposed decreases from the one end side toward the other end side of the conductor in the second direction. In the present holding device, since the heat conductivity of the joining portion is low, the temperature of a portion of the second surface of the ceramic member, which portion corresponds to a relatively thick portion of the joining portion, can be increased. Also, the temperature of the portion corresponding to the relatively thick portion of the joining portion can be increased more effectively, because the distance between the second surface of the ceramic member and the conductor is relatively short.
 
(7) In the above-described holding device manufacturing method, the conductor may be a heater electrode.
 
     Notably, the technique disclosed in the present specification can be embodied in various forms. For example, the technique can be embodied as an electrostatic chuck, a heater device (e.g., a CVD heater), a vacuum chuck, other holding devices in which a ceramic member and a base member are joined together, and methods for manufacturing these devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view schematically showing the external structure of an electrostatic chuck  100  in an embodiment. 
         FIG. 2  is an explanatory view schematically showing the XZ cross-sectional structure of the electrostatic chuck  100  in the embodiment. 
         FIG. 3  is a flowchart showing a method for manufacturing the electrostatic chuck  100  in the embodiment. 
         FIG. 4  is a pair of explanatory views showing the temperature distribution and XZ cross-sectional structure of a second joined body  100 P and the temperature distribution and XZ cross-sectional structure of a first joined body  100 Q. 
         FIG. 5  is an explanatory view schematically showing a step of forming the first joined body  100 Q (first forming method) in the method for manufacturing the electrostatic chuck  100 . 
         FIG. 6  is an explanatory view schematically showing a step of forming the first joined body  100 Q (second forming method) in the method for manufacturing the electrostatic chuck  100 . 
         FIG. 7  is an explanatory view schematically showing the step of a modification of the first forming method. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     A. Embodiment 
     A-1. Structure of Electrostatic Chuck  100 : 
       FIG. 1  is a perspective view schematically showing the external structure of an electrostatic chuck  100  in the present embodiment, and  FIG. 2  is an explanatory view schematically showing the XZ cross-sectional structure of the electrostatic chuck  100  in the present embodiment. Mutually orthogonal X, Y, and Z axes for designating directions are shown in these figures. In the present specification, a positive Z-axis direction is referred to as an upward direction, and a negative Z-axis direction is referred to as a downward direction, for the sake of convenience. However, in actuality, the electrostatic chuck  100  may be disposed with an orientation different from such an orientation. 
     The electrostatic chuck  100  is a device which attracts and holds an object (e.g., a wafer W) by electrostatic attraction force and is used to fix the wafer W, for example, in a vacuum chamber of a semiconductor manufacturing apparatus. The electrostatic chuck  100  includes a ceramic member  10  and a base member  20  which are arranged in a predetermined arrangement direction (the vertical direction (the Z axis direction) in the present embodiment). The ceramic member  10  and the base member  20  are arranged such that the lower surface of the ceramic member  10  (hereinafter referred to as the “ceramic-side joining surface S 2 ”) and the upper surface of the base member  20  (hereinafter referred to as the “base-side joining surface S 3 ”) face each other in the arrangement direction and sandwich a joining portion  30 , which will be described later. Namely, the base member  20  is disposed such that the base-side joining surface S 3  of the base member  20  is located on the side toward the ceramic-side joining surface S 2  of the ceramic member  10 . The electrostatic chuck  100  further includes the joining portion  30  disposed between the ceramic-side joining surface S 2  of the ceramic member  10  and the base-side joining surface S 3  of the base member  20 . The vertical direction (the Z-axis direction) corresponds to the first direction in the claims; the ceramic-side joining surface S 2  corresponds to the first surface in the claims; and the base-side joining surface S 3  corresponds to the third surface in the claims. 
     The ceramic member  10  is a plate-like member having, for example, a circular flat shape and is formed of a ceramic material. The diameter of the ceramic member  10  is, for example, about 50 mm to about 500 mm (generally about 200 mm to about 350 mm), and the thickness of the ceramic member  10  is, for example, about 1 mm to about 10 mm. 
     Various ceramic materials may be used to form the ceramic member  10 . However, from the viewpoint of, for example, strength, wear resistance, and plasma resistance, it is preferred to use a ceramic material which contains aluminum oxide (alumina, Al 2 O 3 ) or aluminum nitride (AlN) as a main component. Notably, the term “main component” used herein means a component whose content ratio (weight ratio) is the largest. 
     A pair of internal electrodes  40  formed of an electrically conductive material (for example, tungsten, molybdenum, or the like) are disposed in the ceramic member  10 . When a voltage is applied from a power source (not shown) to the pair of internal electrodes  40 , electrostatic attraction force is generated, and the wafer W is attracted and fixed to the upper surface (hereinafter referred to as the “attracting surface S 1 ”) of the ceramic member  10  by the electrostatic attraction force. The attracting surface S 1  corresponds to the second surface in the claims. 
     A heater electrode  50  composed of a resistance heating element containing an electrically conductive material (for example, tungsten, molybdenum, or the like) is disposed in the ceramic member  10 . When a voltage is applied from a power source (not shown) to the heater electrode  50 , the heater electrode  50  generates heat. As a result, the ceramic member  10  is heated, and the wafer W held on the attracting surface S 1  of the ceramic member  10  is heated. Thus, control of the temperature of the wafer W is realized. The heater electrode  50  is formed into, for example, an approximately concentric shape as viewed in the Z direction so as to heat the attracting surface S 1  of the ceramic member  10  as evenly as possible. 
     The base member  20  is a plate-like member having, for example, a circular flat shape. The base member  20  has a diameter equal to or larger than the diameter of the ceramic member  10  and is formed of, for example, a material whose heat conductivity is higher than the heat conductivity of the ceramic material used to form the ceramic member  10  (for example, a metal (such as aluminum or an aluminum alloy)). The diameter of the base member  20  is, for example, about 220 mm to about 550 mm (generally about 220 mm to about 350 mm), and the thickness of the base member  20  is, for example, about 20 mm to about 40 mm. 
     A coolant channel  21  is formed in the base member  20 . When a coolant (such as a fluorine-based inert liquid or water) is circulated through the coolant channel  21 , the base member  20  is cooled. When the cooling of the base member  20  is performed together with the heating of the ceramic member  10  by the above-described heater electrode  50 , the temperature of the wafer W held on the attracting surface S 1  of the ceramic member  10  is maintained constant by virtue of heat transfer between the ceramic member  10  and the base member  20  through the bonding portion  30 . Further, in the case where heat from plasma enters the electrostatic chuck  100  during a plasma process, the electric power applied to the heater electrode  50  is adjusted, whereby the temperature control of the wafer W is realized. 
     The bonding portion  30  contains a joining agent (adhesive) such as a silicone-based resin, an acrylic-based resin, or an epoxy-based resin and joins the ceramic member  10  and the base member  20  together. The thickness of the bonding portion  30  is, for example, 0.1 mm to 1 mm. Notably, the structure of the vicinity of a region where the ceramic member  10  and the joining portion  30  are in contact with each other, etc. will be described next. 
     A-2. Structure of the vicinity of a region where the ceramic member  10  and the joining portion  30  are in contact with each other, etc.: 
     In the present specification, for the sake of convenience, the X-axis direction will be referred to as the left-right direction, and the Y-axis direction will be referred to as the near-far direction. The left-right direction corresponds to the second direction in the claims. 
     As shown in  FIG. 2 , over the entirety of the joining portion  30 , the thickness of the joining portion  30  in the vertical direction (the Z-axis direction) increases continuously from one end toward the other end of the joining portion  30  in the left-right direction (the X-axis direction). In other word, in an arbitrary cross section approximately perpendicular to the near-far direction (the Y-axis direction), the thickness of the joining portion  30  in the vertical direction increases continuously from the left end toward the right end of the joining portion  30 . Notably, the difference between the thickness (D 1 ) of the thinnest portion of the joining portion  30  and the thickness (D 2 ) of the thickest portion of the joining portion  30  is preferably 20 μm to 100 μm, more preferably, 30 μm to 60 μm. It is not preferred that the difference in thickness in the joining portion  30  is excessively small or excessively large. Namely, when the difference in thickness in the joining portion  30  is excessively small, the sloping of the joining portion  30  may be buried in a variation in the thickness of the joining portion  30  itself in the vertical direction, and the temperature increasing effect by the joining portion  30  may not be expected. Meanwhile, when the the difference in thickness in the joining portion  30  is excessively large, the temperature of the ceramic member  10  on the outer peripheral side may increase excessively, and the strength of the joining portion  30  may decrease due to stress concentration at a specific location. Notably, in the present specification, the term “continuously” means that the joining portion  30  does not have a step. Therefore, the term “continuously” encompasses not only the case where the joining portion  30  has a straight surface (flat surface), but also the case where the joining portion  30  has, for example, a curved surface or a smooth undulation. 
     In the present embodiment, the base-side joining surface S 3  of the base member  20  is a flat surface approximately parallel to a lower surface S 4  of the base member  20 . Meanwhile, the ceramic-side joining surface S 2  of the ceramic member  10  is a flat surface sloping in relation to the lower surface S 4  of the base member  20 . Namely, the ceramic-side joining surface S 2  is a sloping flat surface sloping such that the distance between the sloping flat surface and the base-side joining surface S 3  increases continuously from the left end toward the right end of the joining portion  30 . In other words, in an arbitrary cross section of the electrostatic chuck  100  approximately perpendicular to the near-far direction (the Y-axis direction), the ceramic-side joining surface S 2  is a sloping straight line sloping such that the distance between the sloping straight line and the base-side joining surface S 3  increases continuously from the left end toward the right end of the ceramic member  10 . The attracting surface S 1  of the ceramic member  10  is a flat surface approximately parallel to the lower surface S 4  of the base member  20 . Therefore, the ceramic-side joining surface S 2  is a sloping flat surface sloping such that the distance between the sloping flat surface and the attracting surface S 1  decreases continuously from the left end toward the right end of the ceramic member  10 . The lower surface S 4  of the base member  20  corresponds to the fourth surface in the claims. 
     In the present embodiment, the heater electrode  50  is disposed on a first imaginary plane L 1  approximately parallel to the ceramic-side joining surface S 2 . Therefore, the distance between the attracting surface S 1  and the first imaginary plane L 1  on which the heater electrode  50  is disposed decreases continuously from the left end side toward the right end side of the heater electrode  50 . Notably, in the present embodiment, the internal electrodes  40  are disposed on a second imaginary plane L 2  approximately parallel to the ceramic-side joining surface S 2 . 
     A-3. Method for Manufacturing the Electrostatic Chuck  100 : 
       FIG. 3  is a flowchart showing a method for manufacturing the electrostatic chuck  100  in the present embodiment.  FIG. 4  is a pair of explanatory views showing the temperature distribution and XZ cross-sectional structure of a second joined body  100 P, which will be described later, and the temperature distribution and XZ cross-sectional structure of a first joined body  100 Q, which will be described later. The XY planar structure of the second joined body  100 P is shown in an upper section of  FIG. 4(A) , and the XZ cross-sectional structure of the second joined body  100 P is shown in a lower section of  FIG. 4(A) . The XY planar structure of the first joined body  100 Q is shown in an upper section of  FIG. 4(B) , and the XZ cross-sectional structure of the first joined body  100 Q is shown in a lower section of  FIG. 4(B) . 
     (Step of Preparing the Second Joined Body  100 P): 
     First, the second joined body  100 P is prepared (S 110 ). As shown in  FIG. 4(A) , the second joined body  100 P is a composite formed by joining a pre-machining ceramic member  10 P and the base member  20  via a provisional joining portion  30 P. The pre-machining ceramic member  10 P is the above-described ceramic member  10  before being subjected to machining. Specifically, the pre-machining ceramic member  10 P is the same as the ceramic member  10  except the point that a pre-machining surface S 1 P which will become the attracting surface S 1  after the machining is approximately parallel to the ceramic-side joining surface S 2 . The pre-machining ceramic member  10 P and the base member  20  can be manufactured by known manufacturing methods. For example, the pre-machining ceramic member  10 P is manufactured by the following method. Namely, a plurality of ceramic green sheets (for example, alumna green sheets) are prepared, and processes, such as printing with metallization ink for forming the internal electrodes  40 , the heater electrode  50 , etc., are performed on the ceramic green sheets. Subsequently, the ceramic green sheets are stacked and are bonded together through thermocompression bonding. The resultant ceramic green laminate is cut into pieces having a predetermined disk-like shape, which are then fired, and polishing or the like is finally performed on the fired pieces, whereby the pre-machining ceramic member  10 P is manufactured. Notably, the pre-machining surface SiP corresponds to the fifth surface in the claims. 
     (Step of Temperature Distribution Measurement): 
     Next, for the pre-machining surface SiP of the pre-machining ceramic member  10 P in the second joined body  100 P, the temperature distribution in a planar direction approximately perpendicular the vertical direction (the Z-axis direction) is measured (S 120 ). At that time, it is preferred to measure the temperature distribution of the pre-machining surface SiP in a state in which the second joined body  100 P is used. The temperature distribution of the pre-machining surface SiP is measured, for example, in a state in which electric power is supplied to the internal electrodes  40  and the heater electrode  50  provided in the pre-machining ceramic member  10 P and a coolant is supplied to the coolant channel  21  formed in the base member  20 . The measurement of the temperature distribution can be performed through use of, for example, an infrared radiation thermometer or a wafer with a thermocouple. 
     As shown in the upper section of  FIG. 4(A) , the results of the temperature distribution measurement in S 120  show that, on the pre-machining surface SiP of the second joined body  100 P, a temperature singular point S 1 A (temperature singular region) of high temperature is present on the left end side of the pre-machining ceramic member  10 P, and a temperature singular point S 1 B of low temperature is present on the right end side of the pre-machining ceramic member  10 P. The temperature singular points S 1 A and S 1 B may appear due to, for example, the characteristics of a production line, a production apparatus, etc. for the electrostatic chuck  100 . 
     (Step of Forming the First Joined Body  100 Q): 
     Next, the pre-machining ceramic member  10 P and the base member  20  in the second joined body  100 P are separated from each other, and then the first joined body  100 Q is formed (S 130 ). The first joined body  100 Q is obtained by again joining the pre-machining ceramic member  10 P and the base member  20  together and is the same as the second joined body  100 P except the point that the pre-machining ceramic member  10 P is disposed to incline in relation to the base member  20 . Namely, the first joined body  100 Q is a composite formed by joining the pre-machining ceramic member  10 P and the base member  20  via the joining portion  30  such that the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P inclines in relation to the base-side joining surface S 3  of the base member  20 . 
     In the step of S 130 , after the pre-machining ceramic member  10 P and the base member  20  in the second joined body  100 P are separated from each other, the pre-machining ceramic member  10 P and the base member  20  are joined together via a joining agent such that the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P inclines, in relation to the base-side joining surface S 3  of the base member  20 , to a direction determined on the basis of the temperature distribution of the pre-machining surface S 1 P measured in S 120 , whereby the first joined body  100 Q is formed (S 130 ). The direction determined on the basis of the temperature distribution of the pre-machining surface S 1 P measured in S 120  refers to, for example, the direction to which the ceramic-side joining surface S 2  inclines such that the pre-machining surface S 1 P has a desired temperature distribution (for example, the temperature becomes approximately uniform in the planar direction). In the example of  FIG. 4 , as shown in  FIG. 4(B) , the pre-machining ceramic member  10 P is joined to the base member  20  while being inclined to a direction such that the distance between the ceramic-side joining surface S 2  and the base-side joining surface S 3  increases from the left end toward the right end of the pre-machining ceramic member  10 P. As a result, the thickness (in the vertical direction (the Z-axis direction)) of the joining portion  30  in the first joined body  100 Q increases continuously from the left end toward the right end of the joining portion  30 , over the entirety of the joining portion  30 . Therefore, at the left end side of the pre-machining ceramic member  10 P, since a part of the joining portion  30 , which part is present between the pre-machining ceramic member  10 P and the base member  20 , has a relatively small thickness, the amount of heat transfer from the pre-machining ceramic member  10 P to the base member  20  is relatively large. Meanwhile, at the right end side of the pre-machining ceramic member  10 P, since a part of the joining portion  30 , which part is present between the pre-machining ceramic member  10 P and the base member  20 , has a relatively large thickness, the amount of heat transfer from the pre-machining ceramic member  10 P to the base member  20  is relatively small. Therefore, in the first joined body  100 Q, the temperature difference in the pre-machining surface S 1 P is reduced, whereby occurrence of the temperature singular point S 1 A and the temperature singular point S 1 B are suppressed. 
     Here, a first forming method and a second forming method for forming the first joined body  100 Q will be described as examples.  FIG. 5  is an explanatory view schematically showing a step of forming the first joined body  100 Q (first forming method) in the method for manufacturing the electrostatic chuck  100 .  FIG. 6  is an explanatory view schematically showing a step of forming the first joined body  100 Q (second forming method) in the method for manufacturing the electrostatic chuck  100 . 
     (1) First Forming Method: 
     In the first forming method, a joining agent  30 X 1  is applied to at least one of the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P and the base-side joining surface S 3  of the base member  20  in such a manner that the joining agent  30 X 1  has a sloping shape; i.e., a sloping upper portion  31 , and the first joined body  100 Q is formed by joining the pre-machining ceramic member  10 P and the base member  20  by utilizing the joining agent  30 X 1  having a sloping shape. Specifically, as shown in  FIG. 5 , the joining agent  30 X 1  is applied to the base-side joining surface S 3  of the base member  20  in such a manner that the thickness of the joining agent  30 X 1  in the vertical direction (the Z-axis direction) increases continuously or stepwise from the left end side toward the right end side of the base member  20 . Namely, the joining agent  30 X 1  has a sloping surface such that, as viewed in the near-far direction (the Y-axis direction), the upper portion  31  slopes in relation to the base-side joining surface S 3  of the base member  20 . The joining agent  30 X 1  is, for example, in the form of paste and has a viscosity which allows the joining agent  30 X 1  to maintain the shape after being applied. 
     Subsequently, the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P and the base-side joining surface S 3  of the base member  20  are bonded together via the joining agent  30 X 1 . At that time, since the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P comes into contact with the sloping upper portion  31  of the joining agent  30 X 1 , the pre-machining ceramic member  10 P is disposed to incline to a predetermined direction in relation to the base member  20 . A curing process for curing the joining agent  30 X 1  is performed in a state in which the pre-machining ceramic member  10 P and the base member  20  are bonded together, whereby the above-described joining portion  30  is formed, and the first joined body  100 Q is formed. 
     As described above, in the first forming method, the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P is guided by the upper portion  31  of the joining agent  30 X 1  applied to the base-side joining surface S 3  of the base member  20 , and, as a result, the pre-machining ceramic member  10 P and the base member  20  are bonded together such that the ceramic-side joining surface S 2  inclines to the predetermined direction in relation to the base-side joining surface S 3 . Thus, according to the first forming method, the direction of inclination of the pre-machining ceramic member  10 P in relation to the base member  20  can be adjusted to a desired direction, unlike the case where the joining agent is applied to the base-side joining surface S 3  of the base member  20  such that the thickness of the joining agent becomes uniform. 
     (2) Second Forming Method: 
     In the second forming method, the first joined body  100 Q is formed by bonding the pre-machining ceramic member  10 P and the base member  20  together via a joining agent  30 X 2  and applying different loads to at least one of the pre-machining ceramic member  10 P and the base member  20 . Specifically, as shown in  FIG. 6(A) , the joining agent  30 X 2  is applied to at least one of the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P and the base-side joining surface S 3  of the base member  20 . For example, the thickness of the joining agent  30 X 2  in the vertical direction (the Z-axis direction) is approximately uniform over the entire joining agent  30 X 2 . 
     Next, the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P and the base-side joining surface S 3  of the base member  20  are bonded together via the joining agent  30 X 2  (see  FIG. 6(A) ). Subsequently, an external force is applied to at least one of the pre-machining ceramic member  10 P and the base member  20  such that the load in vertical direction (the Z-axis direction) applied to a left end side of the joining agent  30 X 2  becomes larger than the load in vertical direction (the Z-axis direction) applied to a right end side of the joining agent  30 X 2 . For example, as shown in  FIG. 5(B) , a jig  200  having a sloping lower surface  202  is prepared, and the lower surface  202  of the jig  200  is pressed against the pre-machining surface S 1 P of the pre-machining ceramic member  10 P of the second joined body  100 P. As a result, a left-hand-side portion of the joining agent  30 X 2  is squeezed more greatly as compared with a right-hand-side portion of the joining agent  30 X 2 , so that the pre-machining ceramic member  10 P is disposed to incline in relation to the base member  20 . A curing process for curing the joining agent  30 X 2  is performed in a state in which the pre-machining ceramic member  10 P and the base member  20  are bonded together, whereby the above-described joining portion  30  is formed, and the first joined body  100 Q is formed. 
     (Step of Machining the Pre-Machining Surface S 1 P of the Pre-Machining Ceramic Member  10 P): 
     After formation of the first joined body  100 Q, the pre-machining surface S 1 P of the pre-machining ceramic member  10 P in the first joined body  100 Q is machined (S 140 ). In the present embodiment, the pre-machining surface S 1 P is machined to decrease the inclination angle of the pre-machining surface S 1 P in relation to the lower surface S 4  of the base member  20 . As a result, the pre-machining surface S 1 P becomes the attracting surface S 1  approximately parallel to the lower surface S 4  of the base member  20 . Notably, the machining of the pre-machining surface S 1 P can be performed relatively simply by, for example, polishing or blasting. After completion of the machining of the pre-machining surface S 1 P, a surface treatment is performed, for example, a plurality of protrusions are formed on the pre-machining surface S 1 P, or a seal band is formed on the pre-machining surface S 1 P. As a result of performance of the above-described steps, manufacture of the electrostatic chuck  100  having the above-described structure is completed. Notably, even when the inclination angle of the pre-machining surface S 1 P is changed or protrusions are formed, the influence on the temperature distribution of the attracting surface S 1  of the electrostatic chuck  100  is relatively small. The reason for this is as follows. The heat conductivity of the ceramic material used to form the ceramic member  10  is higher than the heat conductivity of the material used to form the joining portion  30 . Therefore, even when the variation of the distance between the attracting surface S 1  and the heater electrode  50  changes due to machining of the pre-machining surface S 1 P, its influence on the temperature distribution is small as compared with the variation of the thickness of the joining portion  30 . 
     A-4. Effects of the Present Embodiment: 
     As described above, in the method for manufacturing electrostatic chuck  100  of the present embodiment, the first joined body  100 Q in which the pre-machining ceramic member  10 P and the base member  20  are joined together via the joining portion  30  such that the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P inclines in relation to the base-side joining surface S 3  of the base member  20  is intentionally prepared. As a result, it is possible to prevent the overall temperature distribution of the attracting surface S 1  from deviating from a desired distribution due to the unintended characteristics of a production line, a production apparatus, etc. Also, the temperature distribution of the attracting surface S 1  can be controlled by a relatively simple method of changing the inclination angle of the ceramic member  10  in relation to the base member  20 . 
     B. Modifications 
     The technique disclosed in the present specification is not limited to the embodiment described above and may be modified into various forms without departing from the scope of the invention. For example, the following modifications are possible. 
     The structure of the electrostatic chuck  100  in each of the above-described embodiments is a merely example and can be modified variously. For example, the electrostatic chuck  100  may be configured such that at least one of the heater electrode  50  and the internal electrodes  40  is not provided in the ceramic member  10 . This is because the controllability of the temperature distribution of the attracting surface S 1  may be required in such a configuration. Also, the electrostatic chucks  100  may have, for example, a structure in which a metal, a ceramic material, a resin, or the like is disposed between the ceramic member  10  and the base member  20  or a structure in which, separately from the heater electrode  50  disposed in the ceramic member  10 , a heater is disposed between the ceramic member  10  and the base member  20 . In the above-described embodiment, the heater electrode  50  is exemplified as a conductor. However, the conductor is not limited thereto, and any of other conductors, such as a resistor for temperature measurement, may be disposed in the ceramic member  10 . 
     In the above-described embodiment, the ceramic-side joining surface S 2  is not limited to a flat surface and may be, for example, a sloping curved surface sloping such that the distance between the ceramic-side joining surface S 2  and the base-side joining surface S 3  increases from the left end toward the right end of the joining portion  30 . In other words, in an arbitrary cross section of the electrostatic chuck  100  approximately perpendicular to the near-far direction (the Y-axis direction), the ceramic-side joining surface S 2  may be a sloping curved line sloping such that the distance between the sloping curved line and the base-side joining surface S 3  increases from the left end toward the right end of the ceramic member  10 . 
     The method for manufacturing the electrostatic chuck  100  in each of the above-described embodiments is a mere example and may be modified in various ways. For example, in the first forming method of the step of forming the first joined body  100 Q (S 130  of  FIG. 3 ) in the above-described embodiment, a joining agent may be applied to the ceramic-side joining surface S 2  of the pre-machining ceramic member  10 P or to both the ceramic-side joining surface S 2  and the base-side joining surface S 3  of the base member  20  in such a manner that the thickness of the joining agent in the vertical direction (the Z-axis direction) increases from the left end side toward the right end side of the pre-machining ceramic member  10 P or the base member  20 . 
       FIG. 7  is an explanatory view schematically showing the step of a modification of the first forming method. In  FIG. 7 , constituent elements identical to those of  FIG. 5  are denoted by the same reference numerals, and only constituent elements different from those of  FIG. 5  are denoted by different reference numerals. The base member  20   a  shown in  FIG. 7  is the same as the base member  20  of the above-described embodiment except the point that the base member  20   a  has a plurality of through holes  22  extending through the base member  20   a  in the vertical direction. The through holes  22  communicate with, for example, a gas passage and a lift pin insertion hole (both of which are not shown in the drawing) formed in the pre-machining ceramic member  10 P in a state in which the pre-machining ceramic member  10 P and the base member  20   a  are joined together. In the case where holes (e.g., the through holes  22 ) open to the base-side joining surface S 3  are formed in the base-side joining surface S 3  of the base member  20   a , it is preferred to dispose annular dam portions  60  on the base-side joining surface S 3  such that the dam portions  60  surround the openings of the respective through holes  22  as viewed in the vertical direction (the Z-axis direction). The dam portions  60  are formed of, for example, the same material as the joining agent  30 X 3  and has been subjected to a curing process beforehand before the joining agent  30 X 3  is applied to the base-side joining surface S 3 . As a result, it is possible to prevent the joining agent  30 X 3  from entering the through holes  22  and causing clogging or the like when the pre-machining ceramic member  10 P and the base member  20   a  are joined together. In the present modification, the plurality of dam portions  60  include a first dam portion  62  and a second dam portion  64  whose lengths in the vertical direction differ from each other. Specifically, the length (in the vertical direction) of the first dam portion  62  located on the left side is shorter than the length (in the vertical direction) of the second dam portion  64  located on the right side. As a result, as shown in  FIG. 7 , when the pre-machining ceramic member  10 P and the base member  20   a  are joined together, the pre-machining ceramic member  10 P can be precisely inclined to a predetermined direction in relation to the base member  20   a  by the first dam portion  62  and the second dam portion  64 , which are harder than the joining agent  30 X 3 . Notably, when a curing process is performed on the joining agent  30 X 3 , the joining agent  30 X 3  and the dam portions  60  are integrated, whereby the joining portion  30  is formed. 
     In the second forming method of the step of forming the first joined body  100 Q (S 130  of  FIG. 3 ) of the above-described embodiment, loads different from each other may be applied to the right end side and left end side portions of the second joined body  100 P without using the jig  200 . In an example load application method, a weight may be placed on the second joined body  100 P so as to apply a load to the joining agent  30 X 2 . In another example load application method, a vice (C clamp or the like) is used to sandwich the second joined body  100 P and the base member  20  to thereby apply a load to the joining agent  30 X 2 . In the second forming method, the joining agent  30 X 2  applied to, for example, the base-side joining surface S 3  of the base member  20  may have a sloping shape similar to that of the joining agent  30 X 1  used in the first forming method. When the joining agent  30 X 2  has a sloping shape, in the second forming method, it is possible to prevent the inclination direction of the pre-machining ceramic member  10 P in relation to the base member  20  from deviating from the desired direction. In the above-described embodiment, the load application timing in the second forming method is before curing of the joining agent  30 X 2 . However, the load may be applied during the process for curing the joining agent  30 X 2  or after the process for curing the joining agent  30 X 2 . 
     The process performed in the step of machining the pre-machining surface S 1 P of the pre-machining ceramic member  10 P (S 140  of  FIG. 3 ) in the above-described embodiment is not limited to the machining for changing the inclination angle of the pre-machining surface S 1 P. For example, a plurality of protrusions may be formed on the pre-machining surface S 1 P, or surface treatment may be performed on the pre-machining surface S 1 P. 
     In the above-described embodiment, the pre-machining ceramic member  10 P and the base member  20  are joined together (S 130 ) in such a manner that the pre-machining ceramic member  10 P inclines, in relation to the base member  20 , to a direction determined on the basis of the temperature distribution of the pre-machining surface S 1 P measured in S 120 . However, the pre-machining ceramic member  10 P and the base member  20  may be joined together in such a manner that the pre-machining ceramic member  10 P inclines to a predetermined direction in relation to the base member  20  without measuring the temperature distribution of the pre-machining surface SiP in the second joined body  100 P. This is because, in some cases, the position on the pre-machining surface SiP of the first joined body  100 Q at which the temperature singular point appears can be predicted beforehand from the characteristics of the production line, the production apparatus, etc. for the electrostatic chuck  100 . In such a case, it is sufficient to join the pre-machining ceramic member  10 P to the base member  20  such that the pre-machining ceramic member  10 P inclines to a predetermined direction determined on the characteristics of the process of the production line, the production apparatus, etc. without measuring the temperature distribution of the pre-machining surface SiP of the first joined body  100 Q. 
     The present invention can be applied not only to the electrostatic chuck  100 , which holds the wafer W by using electrostatic attraction force, but also to other holding devices (a vacuum chuck or the like) and manufacturing methods therefor. 
     DESCRIPTION OF REFERENCE NUMERALS 
       10 : ceramic member  10 P: pre-machining ceramic member  20 ,  20   a : base member  21 : coolant channel  22 : through hole  30 : joining portion  30 P: provisional joining portion  30 X 1 ,  30 X 2 ,  30 X 3 : joining agent  31 : upper portion  40 : internal electrode  50 : heater electrode  60 : dam portion  62 : first dam portion  64 : second dam portion  100 : electrostatic chuck  100 P: second joined body  100 Q: first joined body  200 : jig  202 : lower surface L 1 : first imaginary plane L 2 : second imaginary plane S 1 : attracting surface S 1 A, S 1 B, S 1 C: temperature singular point S 1 P: pre-machining surface S 2 : ceramic-side joining surface S 3 : base-side joining surface S 4 : lower surface W: wafer