Patent Publication Number: US-2022223438-A1

Title: Holding device

Description:
TECHNICAL FIELD 
     A technique disclosed in this specification relates to a holding device that holds an object. 
     BACKGROUND ART 
     A known heating device (also called a “susceptor”) heats an object (for example, a semiconductor wafer) to a predetermined temperature (for example, approximately 400 to 800° C.) while holding the object. The heating device is used, for example, as a part of a semiconductor manufacturing apparatus, such as a film deposition apparatus (a CVD film deposition apparatus, a sputtering film deposition apparatus, etc.) and an etching apparatus (a plasma etching apparatus, etc.). 
     Typically, a heating device includes a plate-like member and a tubular member. The plate-like member is a plate-shaped member having a surface (hereinbelow, a “holding surface”) substantially perpendicular to a predetermined direction (hereinbelow, a “first direction”) and a surface (hereinbelow, a “back surface”) on the side opposite to the holding surface. The tubular member (also called a “shaft”) is a tube-shaped member extending in the first direction and is joined to the back surface of the plate-like member at an end on one side in the first direction. A heater electrode, which is a resistive heating element, is provided inside the plate-like member. When a voltage is applied to the heater electrode, the heater electrode generates heat, and an object held on the holding surface of the plate-like member is heated. 
     The heating device further includes a connecting member (also called an “adapter”) disposed on the other side (the side opposite to the side facing the plate-like member) of the tubular member in the first direction. The connecting member is a member via which the tubular member is connected to another member (for example, a vacuum chamber). The connecting member is made of a metal material, such as, for example, aluminum. 
     The tubular member and the connecting member of the heating device are joined together with a fastening member, such as a bolt (for example, see Patent Literature 1). More specifically, a flange portion is formed at an end of the tubular member on the side facing the connecting member, and the flange portion has a through-hole. As a result of the fastening member being inserted through the through-hole in the flange portion and being screwed into a hole formed in the surface of the connecting member on the side facing the tubular member, the tubular member and the connecting member are joined together. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. H10-298767 
     SUMMARY OF INVENTION 
     Technical Problem 
     Typically, the tubular member of the heating device is made of ceramic, which is easy to chip. Hence, if there is a slight inclination between the tubular member and the connecting member in fastening the two members together with a fastening member, the connecting member may come into contact with a portion near the outer edge line of the end face (the face facing the connecting member) of the tubular member, and the portion near the outer edge line may chip. 
     Note that this problem is not specific to heating devices, but is common among typical holding devices that have a plate-like member, a ceramic tubular member, and a connecting member and hold an object on the surface of the plate-like member. 
     This specification discloses a technique capable of solving the above-described problem. 
     Solution to Problem 
     The technique disclosed in this specification can be implemented, for example, in the aspects below. 
     (1) A holding device disclosed in this specification includes: a plate-like member having a first surface substantially perpendicular to a first direction, and a second surface on a side opposite to the first surface; and a tubular member extending in the first direction, made of ceramic, joined to the second surface of the plate-like member at an end of the tubular member on one side in the first direction, and having a flange portion at an end of the tubular member on the other side in the first direction, the flange portion projecting in a direction substantially perpendicular to the first direction and having a first through-hole extending in the first direction. The holding device holds an object on the first surface of the plate-like member. The holding device further includes a connecting member disposed on the other side of the tubular member in the first direction, the connecting member having a hole in a third surface, which is an end face of the connecting member on the one side in the first direction, into which a fastening member inserted through the first through-hole in the flange portion is to be screwed. A portion of a fourth surface, which is an end face of the tubular member on the other side in the first direction, is in contact with the third surface of the connecting member. A specific portion, which is a portion in an outer edge line of the fourth surface of the tubular member, the portion overlapping a minimum virtual circle covering the fourth surface, is not in contact with the third surface of the connecting member. 
     The outer edge line portion of the fourth surface (the end face on the side facing the connecting member) of the tubular member described above is a portion where chipping of the tubular member due to contact with the connecting member is likely to occur when there is a slight inclination between the tubular member and the connecting member in fastening the tubular member and the connecting member together with the fastening member. In particular, in the outer edge line of the fourth surface of the tubular member, the specific portion (i.e., the extreme outer circumferential portion of the outer edge line), which is a portion overlapping the minimum virtual circle covering the fourth surface, is a portion where the above-described chipping is most likely to occur. As described above, in this holding device, the specific portion in the outer edge line of the fourth surface of the tubular member is not in contact with the third surface of the connecting member. Hence, in this holding device, even when there is a slight inclination between the aforementioned two members, it is possible to prevent or reduce contact between the specific portion in the outer edge line of the fourth surface of the tubular member and the connecting member. As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member. 
     (2) In the above-described holding device, the entirety of the outer edge line of the fourth surface of the tubular member may not be in contact with the third surface of the connecting member. This configuration can more reliably prevent or reduce the occurrence of chipping of the tubular member. 
     (3) In the above-described holding device, the third surface of the connecting member has a portion overlapping the specific portion in the outer edge line of the fourth surface of the tubular member, as viewed in the first direction, and the third surface of the connecting member and the specific portion in the outer edge line of the fourth surface of the tubular member may be spaced from each other in the first direction. This configuration can prevent or reduce the occurrence of chipping of the tubular member, regardless of the size relationship between the outside diameter of the flange portion of the tubular member and the outside diameter of the connecting member. 
     (4) The above-described holding device may further include a spacer disposed on the one side of the flange portion in the first direction and having a second through-hole that communicates with the first through-hole in the flange portion and through which the fastening member is inserted. A portion of a fifth surface, which is an end face of the flange portion on the one side in the first direction, may be in contact with a sixth surface, which is an end face of the spacer on the other side in the first direction, and the entirety of an outer edge line of the fifth surface of the flange portion may not be in contact with the sixth surface of the spacer. In a form in which the tubular member and the connecting member are fastened together via the spacer, the above-described outer edge line portion of the fifth surface (the end face on the side facing the spacer) of the flange portion of the tubular member is a portion where chipping of the tubular member due to contact with the spacer is likely to occur when there is a slight inclination between the spacer and the tubular member. In the above-described configuration, the entirety of the outer edge line of the fifth surface of the flange portion of the tubular member is not in contact with the sixth surface of the spacer. Hence, with the above-described configuration, even when there is a slight inclination between the aforementioned two members, it is possible to prevent or reduce contact between the outer edge line portion of the fifth surface of the flange portion of the tubular member and the spacer. As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member. 
     (5) In the above-described holding device, the flange portion of the tubular member may have a plurality of the first through-holes, and the connecting member may have a plurality of the holes into which a plurality of the fastening members inserted through the plurality of the first through-holes in the flange portion are to be screwed. With this configuration, in fastening together the tubular member and the connecting member with the plurality of fastening members, a slight inclination is likely to occur between the tubular member and the connecting member due to variation in the fastening force of the fastening members, and thus, the above-described chipping is likely to occur. However, in this holding device, because the specific portion in the outer edge line of the fourth surface of the tubular member is not in contact with the third surface of the connecting member, it is possible to prevent or reduce contact between the specific portion in the outer edge line of the fourth surface of the tubular member and the connecting member. As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member. 
     (6) The above-described holding device may further include the fastening member. With this configuration, in the holding device having the fastening member for fastening together the tubular member and the connecting member, it is possible to prevent or reduce contact between the specific portion in the outer edge line of the fourth surface of the tubular member and the connecting member. As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member. 
     (7) The above-described holding device may further include an internal electrode provided inside the plate-like member. With this configuration, in the holding device having the internal electrode provided inside the plate-like member, it is possible to prevent or reduce contact between the specific portion in the outer edge line of the fourth surface of the tubular member and the connecting member. As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member. 
     Note that the technique disclosed in this specification may be implemented in various aspects and may be implemented in aspects of, for example, heating devices, holding devices, and methods for manufacturing those devices. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view schematically illustrating an external configuration of a heating device  100  according to this embodiment. 
         FIG. 2  is an explanatory diagram schematically illustrating a sectional configuration of the heating device  100  according to this embodiment. 
         FIG. 3  is an explanatory diagram illustrating a configuration of a lower surface S 4  of a tubular member  20 . 
         FIG. 4  is an explanatory diagram illustrating a sectional configuration of the tubular member  20 . 
         FIG. 5  is an explanatory diagram illustrating a configuration of an upper surface S 3  of a connecting member  80 . 
         FIG. 6  is an explanatory diagram illustrating a sectional configuration of the connecting member  80 . 
         FIG. 7  is an explanatory diagram illustrating a configuration of lower surfaces S 6  of spacers  90 . 
         FIG. 8  is an explanatory diagram illustrating a sectional configuration of the spacers  90 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. Embodiment: 
     A-1. Configuration of Heating Device  100 : 
       FIG. 1  is a perspective view schematically illustrating an external configuration of a heating device  100  according to this embodiment, and  FIG. 2  is an explanatory diagram schematically illustrating a sectional configuration of the heating device  100  according to this embodiment.  FIG. 2  illustrates an XZ sectional configuration of the heating device  100  at positions II-II in  FIGS. 3 to 8  described below. In each drawing, XYZ axes perpendicular to one another for specifying the directions are indicated. In this specification, for convenience&#39;s sake, a positive Z-axis direction will be called an upper direction, and a negative Z-axis direction will be called a lower direction. However, in practice, the heating device  100  may be installed in a direction different from such a direction. 
     The heating device  100  is a device that heats an object (for example, a semiconductor wafer W) to a predetermined temperature (for example, approximately 400 to 800° C.) while holding the object and is also called a susceptor. The heating device  100  is used, for example, as a part of a semiconductor manufacturing apparatus, such as a film deposition apparatus (a CVD film deposition apparatus, a sputtering film deposition apparatus, etc.) and an etching apparatus (a plasma etching apparatus, etc.). The heating device  100  is an example of a holding device in CLAIMS. 
     As illustrated in  FIGS. 1 and 2 , the heating device  100  includes a plate-like member  10 , a tubular member  20 , and a connecting member  80 . 
     The plate-like member  10  is a substantially circular plate-like member having a surface (hereinbelow, a “holding surface S 1 ”) substantially perpendicular to a predetermined direction (in this embodiment, the Z-axis direction) and a surface (hereinbelow, a “back surface S 2 ”) on the side opposite to the holding surface S 1 . The plate-like member  10  is made of ceramic, such as aluminum nitride (AlN) or alumina (A 1   2 O 3 ). The diameter of the plate-like member  10  is, for example, approximately from 100 mm to 500 mm, and the thickness (the length in the upper-lower direction) of the plate-like member  10  is, for example, approximately from 3 mm to 20 mm. The holding surface S 1  of the plate-like member  10  is an example of a first surface in CLAIMS, the back surface S 2  is an example of a second surface in CLAIMS, the Z-axis direction is an example of a first direction in CLAIMS, the upper side in the Z-axis direction is an example of one side in the first direction in CLAIMS, and the lower side in the Z-axis direction is an example of the other side in the first direction in CLAIMS. 
     The tubular member  20  is a substantially circular tube-shaped member extending in the predetermined direction (Z-axis direction). The tubular member  20  is made of ceramic, such as aluminum nitride or alumina, like the plate-like member  10 . In this embodiment, the tubular member  20  has an upper flange portion  22  projecting in a direction (hereinbelow, a “plane direction”) perpendicular to the Z-axis direction at the end thereof on the upper side (the side facing the plate-like member  10 ), and a lower flange portion  23  projecting in the plane direction at the end thereof on the lower side (the side facing the connecting member  80 ). The upper flange portion  22  and the lower flange portion  23  are formed over the entirety of the tubular member  20  in the circumferential direction. Note that, in the description below, the portion of the tubular member  20  other than the upper flange portion  22  and the lower flange portion  23  will be called a body part  21 . The outside diameter of the body part  21  of the tubular member  20  is, for example, approximately from 30 mm to 90 mm, and the height (the length in the upper-lower direction) of the tubular member  20  is, for example, approximately from 100 mm to 300 mm. The lower flange portion  23  is an example of a flange portion in CLAIMS. 
     The plate-like member  10  and the tubular member  20  are arranged such that the back surface S 2  of the plate-like member  10  and an upper surface S 3  of the tubular member  20  face each other in the upper-lower direction. The tubular member  20  is joined to the central portion of the back surface S 2  of the plate-like member  10  via a joint part  30  made of a known joining material. 
     As illustrated in  FIG. 2 , a heater electrode  50 , which is a heating resistor, is provided inside the plate-like member  10 . The heater electrode  50  is made of, for example, a material containing metal, such as tungsten or molybdenum. In this embodiment, the heater electrode  50  forms a substantially concentrically extending linear pattern, as viewed in the Z-axis direction. The ends of the linear pattern of the heater electrode  50  are located near the center of the plate-like member  10 , and the ends are connected to the upper ends of via conductors  52 . A pair of recesses  12  are formed in the back surface S 2  of the plate-like member  10 , and conductive feeding electrodes (electrode pads)  54  are provided at the positions of the recesses  12 . In this embodiment, the feeding electrodes  54  are substantially circular as viewed in the Z-axis direction and are made of a material containing tungsten (for example, a mixed material of tungsten and aluminum nitride). The lower ends of the via conductors  52  are connected to the feeding electrodes  54 . As a result, the heater electrode  50  and the feeding electrodes  54  are electrically connected to each other through the via conductors  52 . 
     The tubular member  20  has a through-hole  24  extending over the overall length of the tubular member  20  in the Z-axis direction. The through-hole  24  accommodates a plurality of terminal members  70 . The terminal members  70  are, for example, substantially cylindrical members as viewed in the Z-axis direction and are made of a material containing nickel (Ni) (for example, pure nickel or an alloy containing nickel (for example, Kovar)). The upper ends of the terminal members  70  are joined to the feeding electrodes  54  through a metal brazing material  56  (for example, gold solder). 
     When a power supply (not shown) applies a voltage to the heater electrode  50  through the terminal members  70 , the feeding electrodes  54 , the via conductors  52 , and the like, the heater electrode  50  generates heat, and an object (for example, a semiconductor wafer W) held on the holding surface S 1  of the plate-like member  10  is heated to a predetermined temperature (for example, approximately 400 to 800° C.). 
     The connecting member  80  is a member disposed below the tubular member  20  and via which the tubular member  20  is attached to another member (for example, a vacuum chamber (not shown)). The connecting member  80  has, for example, a substantially cylindrical shape extending in the predetermined direction (Z-axis direction) and is made of, for example, a metal material, such as aluminum. The connecting member  80  and the tubular member  20  are arranged such that the upper surface S 3  of the connecting member  80  and the lower surface S 4  of the tubular member  20  face each other in the Z-axis direction and are joined to each other with a plurality of bolts  99 , as described below. The connecting member  80  has a through-hole  84  communicating with the through-hole  24  in the tubular member  20 . The terminal members  70  mentioned above are disposed in a space formed by the through-hole  24  in the tubular member  20  and the through-hole  84  in the connecting member  80 . The upper surface S 3  of the connecting member  80  is an example of a third surface in CLAIMS, and the lower surface S 4  of the tubular member  20  is an example of a fourth surface in CLAIMS. 
     Note that, as illustrated in  FIGS. 3 to 6  described below, the body part  21  of the tubular member  20  has a plurality of through-holes  26  extending in the Z-axis direction, and the connecting member  80  has a plurality of through-holes  86  extending in the Z-axis direction and communicating with the through-holes  26  in the tubular member  20 . The spaces (the spaces extending in the Z-axis direction) formed by the through-holes  26  in the tubular member  20  and the through-holes  86  in the connecting member  80  are used as, for example, gas flow paths to which an inert gas, such as nitrogen or argon, is supplied to form an air curtain (not shown) surrounding the holding surface S 1  of the plate-like member  10 , the semiconductor wafer W, and the like, or are used as a space for accommodating a high-frequency body (not shown) connected to a high-frequency electrode (not shown) disposed in the plate-like member  10 . 
     A- 2 . Detailed Configuration of Joint Part between Tubular Member  20  and Connecting Member  80  and Vicinity Thereof: 
     Next, a detailed configuration of a joint part between the tubular member  20  and the connecting member  80  and the vicinity thereof in the heating device  100  according to this embodiment will be described.  FIG. 3  is an explanatory diagram illustrating a configuration of the lower surface S 4  of the tubular member  20 ,  FIG. 4  is an explanatory diagram illustrating a sectional configuration of the tubular member  20 ,  FIG. 5  is an explanatory diagram illustrating a configuration of the upper surface S 3  of the connecting member  80 ,  FIG. 6  is an explanatory diagram illustrating a sectional configuration of the connecting member  80 ,  FIG. 7  is an explanatory diagram illustrating a configuration of lower surfaces S 6  of spacers  90 , described below, and  FIG. 8  is an explanatory diagram illustrating a sectional configuration of the spacers  90 .  FIG. 4  illustrates an XY sectional configuration of the tubular member  20  at a position IV-IV in  FIG. 2 ,  FIG. 6  illustrates an XY sectional configuration of the connecting member  80  at a position VI-VI in  FIG. 2 , and  FIG. 8  illustrates an XY sectional configuration of the spacers  90  at a position VIII-VIII in  FIG. 2 . 
     As described above, the tubular member  20  has the lower flange portion  23  projecting in the plane direction at the lower end thereof (see  FIGS. 2 to 4 ). The lower flange portion  23  is formed over the entirety of the tubular member  20  in the circumferential direction. In this embodiment, the lower flange portion  23  has eight through-holes  25  arranged at substantially equal intervals in the circumferential direction. The through-holes  25  formed in the lower flange portion  23  are holes through which the bolts  99  are to be inserted. Note that, in this embodiment, the through-holes  25  formed in the lower flange portion  23  are not closed holes, but holes (cut-away portions) that are open in the outer circumferential surface of the lower flange portion  23 . Specifically, in this specification, through-holes formed in a member and extending in a direction include, in addition to closed holes that are not open in the outer circumferential surface of the member around the direction, holes (cut-away portions) that are open in the outer circumferential surface. The through-holes  25  are examples of a first through-hole in CLAIMS, and the bolts  99  are examples of a fastening member in CLAIMS. 
     As illustrated in  FIGS. 5 and 6 , the connecting member  80  has eight bolt holes  85  that are open in the upper surface S 3 . The bolt holes  85  are arranged at substantially equal intervals in the circumferential direction. A plurality of the bolts  99  inserted through the through-holes  25  in the lower flange portion  23  of the tubular member  20  are screwed into the bolt holes  85  in the connecting member  80  (see  FIG. 2 ). As a result, the tubular member  20  and the connecting member  80  are joined together. The bolt holes  85  are examples of a hole provided in the connecting member  80  in CLAIMS. 
     As illustrated in  FIGS. 5 and 6 , a substantially circular-ring-shaped recess (groove)  88  surrounding the through-hole  84  is formed in the upper surface S 3  of the connecting member  80 , and an O ring  89  is disposed in the recess  88  (see  FIG. 2 ). To avoid complications in the drawings, in  FIGS. 5 and 6 , the O ring  89  is simply illustrated as a one-dot chain line. Because of the presence of the O ring  89 , the space formed by the through-hole  84  is sealed. In this embodiment, the recess  88  is continuously formed at positions where the through-holes  86  are formed, and the O ring  89  has a shape surrounding the through-holes  86 . As a result, the spaces formed by the through-holes  86  are also sealed. 
     The heating device  100  according to this embodiment further has two spacers  90  disposed above the lower flange portion  23  of the tubular member  20  (see  FIG. 2 ). As illustrated in  FIGS. 7 and 8 , each spacer  90  is a substantially semicircular-arc-shaped plate-like member, as viewed in the Z-axis direction, and is formed of, for example, a metal material, such as aluminum. The two spacers  90  are arranged such that the two spacers  90  together form a substantially circular shape, as viewed in the Z-axis direction. The two spacers  90  forming a pair and arranged in this manner have eight through-holes  95  (that is, four through-holes  95  in each spacer  90 ) arranged at substantially equal intervals in the circumferential direction. The through-holes  95  communicate with the through-holes  25  provided in the lower flange portion  23  of the tubular member  20 , and the bolts  99  are inserted therethrough (see  FIG. 2 ). The two spacers  90  are in contact with the upper surface S 5  of the lower flange portion  23  and also with bearing surfaces of the bolts  99  and serve as washers. The through-holes  95  are examples of a second through-hole in CLAIMS. 
     (Relationship between Lower Surface S 4  of Tubular Member  20  and Upper Surface S 3  of Connecting Member  80 ) 
     In the heating device  100  according to this embodiment, projections and recesses are formed on the upper surface S 3  of the connecting member  80 . As a result, a portion of the lower surface S 4  of the tubular member  20  is in contact with the upper surface S 3  of the connecting member  80 , and the remaining portion of the lower surface S 4  of the tubular member  20  is not in contact with the upper surface S 3  of the connecting member  80 . This point will be described in detail below. 
     As illustrated in  FIGS. 3 and 4 , an outer edge line Lx of the lower surface S 4  of the tubular member  20  includes portions (hereinbelow, “outer circumferential portions Lx 1 ”) overlapping a minimum virtual circle VC covering the lower surface S 4  and portions (portions constituting the inner circumferential surfaces of the through-holes  25  and, hereinbelow, “inside portions Lx 2 ”) other than the outer circumferential portions Lx 1 . In the outer edge line Lx of the lower surface S 4  of the tubular member  20 , the outer circumferential portions Lx 1  are portions defining the extreme outer circumferential surface of the lower flange portion  23 , and the inside portions Lx 2  are portions defining the inner circumferential surfaces of the through-holes  25 . Note that, in order to show the positional relationship between the outer edge line Lx of the lower surface S 4  of the tubular member  20  and the connecting member  80 ,  FIGS. 5 and 6  illustrate the position of the outer edge line Lx as viewed in the Z-axis direction by a dashed line. The outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20  are examples of a specific portion in CLAIMS. 
     As illustrated in  FIGS. 5 and 6 , in the heating device  100  according to this embodiment, the outside diameter of the upper surface S 3  of the connecting member  80  is larger than the outside diameter of the lower surface S 4  of the tubular member  20 . Hence, the upper surface S 3  of the connecting member  80  has a portion overlapping the outer edge line Lx (the outer circumferential portions Lx 1  and the inside portions Lx 2 ) of the lower surface S 4  of the tubular member  20 , as viewed in the Z-axis direction. 
     As illustrated in  FIGS. 2, 5, and 6 , the upper surface S 3  of the connecting member  80  has a recess (a portion dented downward)  87 . The recess  87  includes a belt-like outer circumferential portion  87   a  having a substantially uniform width over the entire outer circumference of the upper surface S 3  of the connecting member  80 , as viewed in the Z-axis direction, and substantially semicircular inside portions  87   b  extending inward from the outer circumferential portion  87   a  toward the positions where the bolt holes  85  are formed. As illustrated in  FIGS. 5 and 6 , when viewed in the Z-axis direction, the entire outer circumferential portions Lx 1  of the outer edge line Lx of the lower surface S 4  of the tubular member  20  overlap the outer circumferential portion  87   a  of the recess  87  formed in the upper surface S 3  of the connecting member  80 . Hence, the entire outer circumferential portions Lx 1  are spaced from the upper surface S 3  of the connecting member  80  in the Z-axis direction and are not in contact with the upper surface S 3 . Meanwhile, when viewed in the Z-axis direction, although some portions of the inside portions Lx 2  of the outer edge line Lx of the lower surface S 4  of the tubular member  20  overlap the outer circumferential portion  87   a  of the recess  87 , the remaining portions do not overlap the outer circumferential portion  87   a  of the recess  87 . However, the remaining portions overlap the inside portions  87   b  of the recess  87 . Hence, the overall inside portions Lx 2  are also spaced from the upper surface S 3  of the connecting member  80  in the Z-axis direction and are not in contact with the upper surface S 3 . From the description above, in the heating device  100  according to this embodiment, the entire outer edge line Lx of the lower surface S 4  of the tubular member  20  is spaced from the upper surface S 3  of the connecting member  80  in the Z-axis direction and is not in contact with the upper surface S 3 . 
     (Relationship between Upper Surface S 5  of Lower Flange Portion  23  of Tubular Member  20  and Lower Surfaces S 6  of Spacers  90 ) 
     In the heating device  100  according to this embodiment, the lower surfaces S 6  of the spacers  90  have projections and recesses. As a result, a portion of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  is in contact with the lower surfaces S 6  of the spacers  90 , and the remaining portion of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  is not in contact with the lower surfaces S 6  of the spacers  90 . This point will be described in detail below. The upper surface S 5  of the lower flange portion  23  of the tubular member  20  is an example of a fifth surface in CLAIMS, and the lower surfaces S 6  of the spacers  90  are examples of a sixth surface in CLAIMS. 
     As illustrated in  FIG. 2 , the side surface of the lower flange portion  23  of the tubular member  20  is parallel to the Z-axis direction. Hence, as illustrated in  FIGS. 3 and 4 , an outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  is aligned with the outer edge line Lx of the lower surface S 4  of the tubular member  20 , as viewed in the Z-axis direction. More specifically, the outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  includes portions (hereinbelow, “outer circumferential portions Ly 1 ”) overlapping a minimum virtual circle VC covering the upper surface S 5  and portions (hereinbelow, “inside portions Ly 2 ” constituting the inner circumferential surfaces of the through-holes  25 ) other than the outer circumferential portions Ly 1 . In the outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20 , the outer circumferential portions Ly 1  are portions defining the extreme outer circumferential surface of the lower flange portion  23 , and the inside portions Ly 2  are portions defining the inner circumferential surfaces of the through-holes  25 . In order to show the positional relationship between the outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  and the spacers  90 ,  FIGS. 7 and 8  illustrate the position of the outer edge line Ly as viewed in the Z-axis direction by a dashed line. 
     As illustrated in  FIGS. 7 and 8 , in the heating device  100  according to this embodiment, the outside diameter of an area formed by the lower surfaces S 6  of the two spacers  90  is larger than the outside diameter of the upper surface S 5  of the lower flange portion  23  of the tubular member  20 . Hence, the lower surfaces S 6  of the spacers  90  have portions overlapping the outer edge line Ly (the outer circumferential portions Ly 1  and the inside portions Ly 2 ) of the upper surface S 5  of the lower flange portion  23  of the tubular member  20 , as viewed in the Z-axis direction. 
     As illustrated in  FIGS. 2, 7, and 8 , the lower surfaces S 6  of the spacers  90  have recesses (portions dented upward)  97 . The recesses  97  include belt-like outer circumferential portions  97   a  having a substantially uniform width over the entire outer circumferences of the lower surfaces S 6  of the spacers  90  as viewed in the Z-axis direction, and substantially rectangular inside portions  97   b  extending inward from the outer circumferential portions  97   a  toward the positions where the through-holes  95  are formed. As illustrated in  FIGS. 7 and 8 , when viewed in the Z-axis direction, the entire outer circumferential portions Ly 1  in the outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  overlap the outer circumferential portions  97   a  of the recesses  97  formed in the lower surfaces S 6  of the spacers  90 . Hence, the entire outer circumferential portions Ly 1  are spaced from the lower surfaces S 6  of the spacers  90  in the Z-axis direction and are not in contact with the lower surfaces S 6 . Meanwhile, when viewed in the Z-axis direction, although some portions of the inside portions Ly 2  of the outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  overlap the outer circumferential portions  97   a  of the recesses  97 , the remaining portions do not overlap the outer circumferential portions  97   a  of the recesses  97 . However, the remaining portions overlap the inside portions  97   b  of the recesses  97 . Hence, the overall inside portions Ly 2  are also spaced from the lower surfaces S 6  of the spacers  90  in the Z-axis direction and are not in contact with the lower surfaces S 6 . From the description above, in the heating device  100  according to this embodiment, the entire outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  is spaced from the lower surfaces S 6  of the spacers  90  in the Z-axis direction and is not in contact with the lower surfaces S 6 . 
     A- 3 . Advantages of this Embodiment: 
     As has been described above, the heating device  100  according to this embodiment is a holding device including: the plate-like member  10  having the holding surface S 1  extending substantially perpendicular to the Z-axis direction, and the back surface S 2  on the side opposite to the holding surface S 1 ; and the tubular member  20  extending in the Z-axis direction and made of ceramic. The holding device holds an object on the holding surface S 1  of the plate-like member  10 . The tubular member  20  is joined to the back surface S 2  of the plate-like member  10  at the upper end thereof and has the lower flange portion  23  projecting in the plane direction at the lower end thereof. The lower flange portion  23  has the through-holes  25  extending in the Z-axis direction. The heating device  100  according to this embodiment further includes the connecting member  80  disposed below the tubular member  20 . The connecting member  80  has the bolt holes  85  that are open in the upper surface S 3  of the connecting member  80 . The bolt holes  85  are to be screwed with the bolts  99  inserted through the through-holes  25  in the lower flange portion  23  of the tubular member  20 . In the heating device  100  according to this embodiment, a portion of the lower surface S 4  of the tubular member  20  is in contact with the upper surface S 3  of the connecting member  80 , and, in the outer edge line Lx of the lower surface S 4  of the tubular member  20 , the outer circumferential portions Lx 1 , which are portions overlapping the minimum virtual circle VC covering the lower surface S 4 , are not in contact with the upper surface S 3  of the connecting member  80 . 
     The outer edge line Lx portion of the lower surface S 4  (the end face on the side facing the connecting member  80 ) of the tubular member  20  described above is a portion where chipping of the tubular member  20  due to contact with the connecting member  80  is likely to occur when there is a slight inclination between the tubular member  20  and the connecting member  80  in fastening together the tubular member  20  and the connecting member  80  with the bolts  99 . In particular, in the outer edge line Lx of the lower surface S 4  of the tubular member  20 , the outer circumferential portions Lx 1  (i.e., the extreme outer circumferential portions of the outer edge line Lx), which are portions overlapping the minimum virtual circle VC covering the lower surface S 4 , are portions where the above-described chipping is most likely to occur. As described above, in the heating device  100  according to this embodiment, the outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20  are not in contact with the upper surface S 3  of the connecting member  80 . Hence, in the heating device  100  according to this embodiment, even when there is a slight inclination between the aforementioned two members, it is possible to prevent or reduce contact between the outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20  and the connecting member  80 . As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member  20 . 
     In the heating device  100  according to this embodiment, the entire outer edge line Lx of the lower surface S 4  of the tubular member  20  is not in contact with the upper surface S 3  of the connecting member  80 . Hence, in the heating device  100  according to this embodiment, it is possible to more reliably prevent or reduce the occurrence of chipping of the tubular member  20 . 
     In the heating device  100  according to this embodiment, the upper surface S 3  of the connecting member  80  has a portion overlapping the outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20 , as viewed in the Z-axis direction, and the upper surface S 3  of the connecting member  80  and the outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20  are spaced from each other in the Z-axis direction. Hence, in the heating device  100  according to this embodiment, it is possible to prevent or reduce the occurrence of chipping of the tubular member  20 , regardless of the size relationship between the outside diameter of the lower flange portion  23  of the tubular member  20  and the outside diameter of the connecting member  80 . 
     The heating device  100  according to this embodiment further includes the spacers  90  disposed above the lower flange portion  23  of the tubular member  20 . The spacers  90  have the through-holes  95 . The through-holes  95  in the spacers  90  are holes that communicate with the through-holes  25  in the lower flange portion  23  of the tubular member  20  and through which the bolts  99  are inserted. In the heating device  100  according to this embodiment, a portion of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  is in contact with the lower surfaces S 6  of the spacers  90 , and the entire outer edge line Ly of the upper surface S 5  of the lower flange portion  23  is not in contact with the lower surfaces S 6  of the spacers  90 . In a form in which the tubular member  20  and the connecting member  80  are fastened together using the spacers  90 , the outer edge line Ly portion of the above-described upper surface S 5  (the end face on the side facing the spacers  90 ) of the lower flange portion  23  of the tubular member  20  is a portion where chipping of the tubular member  20  due to contact with the spacers  90  is likely to occur when there is a slight inclination between the spacers  90  and the tubular member  20 . As described above, in the heating device  100  according to this embodiment, the entire outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  is not in contact with the lower surfaces S 6  of the spacers  90 . Hence, in the heating device  100  according to this embodiment, even when there is a slight inclination between the aforementioned two members, it is possible to prevent or reduce contact between the outer edge line Ly portion of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  and the spacers  90 . As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member  20 . 
     In the heating device  100  according to this embodiment, the lower flange portion  23  of the tubular member  20  has the plurality of through-holes  25 , and the connecting member  80  has the plurality of bolt holes  85  into which the plurality of bolts  99  inserted through the plurality of through-holes  25  in the lower flange portion  23  of the tubular member  20  are to be screwed. Hence, in the heating device  100  according to this embodiment, in fastening together the tubular member  20  and the connecting member  80  with the plurality of bolts  99 , a slight inclination between the tubular member  20  and the connecting member  80  is likely to occur due to variation in the fastening force of the bolts  99 , and thus, the above-described chipping is likely to occur. However, in the heating device  100  according to this embodiment, as described above, because the outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20  are not in contact with the upper surface S 3  of the connecting member  80 , even when there is a slight inclination between the aforementioned two members, it is possible to prevent or reduce contact between the outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20  and the connecting member  80 . As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member  20 . 
     The heating device  100  according to this embodiment further includes the bolts  99 . Hence, according to the heating device  100  of this embodiment, in the heating device  100  having the bolts  99  for fastening together the tubular member  20  and the connecting member  80 , it is possible to prevent or reduce contact between the outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20  and the connecting member  80 . As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member  20 . 
     The heating device  100  according to this embodiment further includes the heater electrode  50 , which is an internal electrode provided inside the plate-like member  10 . Hence, according to the heating device  100  of this embodiment, in the heating device  100  having the internal electrode provided inside the plate-like member  10 , it is possible to prevent or reduce contact between the outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20  and the connecting member  80 . As a result, it is possible to prevent or reduce the occurrence of chipping of the tubular member  20 . 
     B. Modification: 
     The technique disclosed in this specification is not limited to the above-described embodiment, but may be modified in various forms within a scope not departing from the spirit thereof, and, for example, the following modification is possible. 
     The configuration of the heating device  100  according to the above-described embodiment is merely an example, and various modifications are possible. For example, in the above-described embodiment, although the entire outer edge line Lx of the lower surface S 4  of the tubular member  20  is not in contact with the upper surface S 3  of the connecting member  80 , it is also possible to configure such that the outer circumferential portions Lx 1  in the outer edge line Lx are not in contact with the upper surface S 3  of the connecting member  80 , and (at least a portion of) the inside portions Lx 2  are in contact with the upper surface S 3  of the connecting member  80 . 
     In the above-described embodiment, although a configuration is realized in which the outer circumferential portions Lx 1  in the outer edge line Lx of the lower surface S 4  of the tubular member  20  are not in contact with the upper surface S 3  of the connecting member  80  due to the provision of the recess  87  in the upper surface S 3  of the connecting member  80 , this configuration may be realized by making the outside diameter of the upper surface S 3  of the connecting member  80  smaller than the outside diameter of the lower surface S 4  of the tubular member  20 . 
     In the above-described embodiment, although the entire outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  is not in contact with the lower surfaces S 6  of the spacers  90 , it is also possible to configure such that the outer circumferential portions Ly 1  of the outer edge line Ly are not in contact with the lower surfaces S 6  of the spacers  90 , and (at least a portion of) the inside portions Ly 2  are in contact with the lower surfaces S 6  of the spacers  90 . It is also possible to configure such that the entire outer edge line Ly of the upper surface S 5  of the lower flange portion  23  of the tubular member  20  is in contact with the lower surfaces S 6  of the spacers  90 . It is also possible to configure such that the heating device  100  does not have the spacers  90 . 
     In the above-described embodiment, although the lower flange portion  23  of the tubular member  20  has the plurality of through-holes  25 , and the connecting member  80  has the plurality of bolt holes  85  into which the plurality of bolts  99  inserted through the plurality of through-holes  25  in the lower flange portion  23  of the tubular member  20  are to be screwed, it is also possible to configure such that the lower flange portion  23  of the tubular member  20  has one through-hole  25 , and the connecting member  80  has one bolt hole  85  into which one bolt  99  inserted through the one through-hole  25  in the lower flange portion  23  of the tubular member  20  is to be screwed. 
     In the above-described embodiment, although the heating device  100  has the heater electrode  50  serving as the internal electrode provided inside the plate-like member  10 , the heating device  100  may have another electrode (f o r example, an RF electrode) serving as the internal electrode provided inside the plate-like member  10 . 
     The materials for forming the respective members constituting the heating device  100  according to the above-described embodiment are merely examples, and the respective members may be made of other materials. For example, in the above-described embodiment, although the plate-like member  10  is made of ceramic, the plate-like member  10  may be made of a material other than ceramic (for example, metal, such as aluminum or an aluminum alloy). In the above-described embodiment, although the connecting member  80  and the spacers  90  are made of metal, the connecting member  80  and the spacers  90  may be made of materials other than metal. 
     In the heating device  100  according to the above-described embodiment, although the through-holes  26  in the tubular member  20  and the through-holes  86  in the connecting member  80  are formed to define a space to be used as a gas flow path for supplying purge gas or as a space for accommodating a high-frequency body, these holes may be omitted, or a hole for defining another space may be additionally formed. 
     The technique disclosed in this specification may be applied not only to heating devices, but also to other holding devices that have a plate-like member, a ceramic tubular member, and a connecting member and hold an object on a surface of the plate-like member. 
     REFERENCE SIGNS LIST 
       10  plate-like member,  12  recess,  20  tubular member,  21  body part,  22  upper flange portion,  23  lower flange portion,  24  through-hole,  25  through-hole,  26  through-hole,  30  joint part,  50  heater electrode,  52  via conductor,  54  feeding electrode,  56  metal brazing material,  70  terminal member,  80  connecting member,  84  through-hole,  85  bolt hole,  86  through-hole,  87  recess,  87   a  outer circumferential portion,  87   b  inside portion,  88  recess,  89  O ring,  90  spacer,  95  through-hole,  97  recess,  97   a  outer circumferential portion,  97   b  inside portion,  99  bolt,  100  heating device, Lx 1  outer circumferential portion, Lx 2  inside portion, Lx outer edge line, Ly 1  outer circumferential portion, Ly 2  inside portion, Ly outer edge line, S 1  holding surface, S 2  back surface, S 3  upper surface, S 4  lower surface, S 5  upper surface, S 6  lower surface, VC virtual circle, W semiconductor wafer