Abstract:
A bearing ( 12 ) being a recessed section that receives a spindle ( 20 ) is provided in a lower surface ( 10 B) of a susceptor ( 10 ). The bearing ( 12 ) has a tapers from the lower surface ( 10 B) towards an upper surface ( 10 A). A gap ( 12 B) is provided in an side wall ( 12 A) of the bearing ( 12 ), further on the outside of the bearing ( 12 ) than a fitting surface ( 12 X) between the bearing ( 12 ) and the spindle ( 20 ) in the horizontal direction. As a result, reduction in the fitting force between the susceptor bearing and the spindle can be suppressed and susceptor temperature reduction in the vicinity of the bearing can also be suppressed.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a susceptor provided with a base member having a recessed portion. 
       BACKGROUND ART 
       [0002]    Conventionally, in performing treatment where a film made of silicon carbide, gallium arsenite, a composite metal oxide (for example, YBa 2 Cu 3 O 7 ) or the like is formed on a surface of a wafer, a wafer holder for holding the wafer (hereinafter referred to as “susceptor”) is used. 
         [0003]    Here, as a reactor which houses the susceptor, there has been known a vertical-type reactor which is configured such that a reactive gas flows from an upper direction to a lower direction, and the susceptor is rotated at a high speed about a rotary shaft (spindle) along a vertical direction. The susceptor is provided with a bearing which receives the spindle, and the susceptor is fitted on the spindle due to its own weight (see Patent Literature 1, for example). 
       CITATION LIST 
     Patent Literature 
       [0004]    Patent Literature 1: JP 2004-525056 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    In the above-mentioned configuration, the susceptor rotates at a high speed and hence, a fitting strength between the bearing of the susceptor and the spindle is important. On the other hand, in view of the transfer of heat from the susceptor to the spindle, it is also necessary to take into account lowering of a temperature of the susceptor in the vicinity of the bearing. 
         [0006]    The present invention has been made to overcome the above-mentioned problem, and it is an object of the present invention to provide a susceptor which can suppress lowering of a temperature of the susceptor in the vicinity of the bearing while suppressing lowering of a fitting strength between a bearing of the susceptor and a spindle. 
       Solution to Problem 
       [0007]    A susceptor according to a first aspect has an upper surface on which a wafer is placed and a lower surface arranged on a side opposite to the upper surface, and configured to be rotated about a spindle which extends in a vertical direction. A bearing formed of a recessed section receiving the spindle is formed on the lower surface. The bearing has a shape where the bearing is tip-narrowed toward the upper surface from the lower surface. A gap is formed in an side wall of the bearing such that the gap projects toward the outside of the bearing from a fitting surface between the bearing and the spindle in a horizontal direction perpendicular to the vertical direction. 
         [0008]    The gap may project more toward the outside of the bearing than an opening portion formed on a lowermost end of the bearing in a horizontal direction. 
         [0009]    A bottom surface corresponding to a upper end surface of the bearing may have a convex shape projecting downward. 
         [0010]    A bottom surface corresponding to a upper end surface of the bearing may have a concave shape recessed upward. 
       Advantageous Effects of Invention 
       [0011]    The present invention provides a susceptor which can suppress lowering of a temperature of the susceptor in the vicinity of the bearing while suppressing lowering of a fitting strength between a bearing of the susceptor and a spindle. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a view illustrating a susceptor  10  according to a first embodiment of the present invention. 
           [0013]      FIG. 2  is a view illustrating the susceptor  10  according to the first embodiment of the present invention. 
           [0014]      FIG. 3  is a view illustrating the susceptor  10  according to a first modification of the present invention. 
           [0015]      FIG. 4  is a view illustrating the susceptor  10  according to a second modification of the present invention. 
           [0016]      FIG. 5  is a view illustrating the susceptor  10  according to a third modification of the present invention. 
           [0017]      FIG. 6  is a view illustrating the susceptor  10  according to another third modification of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0018]    Hereinafter, a susceptor according to an embodiment of the present invention will be described with reference to the drawings. Note that, in the following description of the drawings, same or similar reference signs denote same or similar elements and portions. 
         [0019]    It is to be noted that the drawings are schematic and the dimensions or ratios are different from actual values. Accordingly, specific dimensions and the like should be determined by taking the following description into consideration. Needless to say, a relationship or a ratio of mutual dimensions may differ among the drawings. 
       SUMMARY OF EMBODIMENT 
       [0020]    The susceptor according to the embodiment has an upper surface on which a wafer is placed and a lower surface arranged on a side opposite to the upper surface, and is configured to be rotated about a spindle which extends in a vertical direction. A bearing which is a recessed portion for receiving the spindle is formed on the lower surface. The bearing has a shape where the bearing is tip-narrowed toward the upper surface from the lower surface, that is, a tapered shape. A gap is formed in an side wall of the bearing such that the gap projects toward the outside of the bearing from a fitting surface between the bearing and the spindle in a horizontal direction perpendicular to the vertical direction. 
         [0021]    In this embodiment, the bearing has the shape where the bearing is tip-narrowed toward the upper surface from the lower surface, that is, a tapered shape. Accordingly, lowering of a fitting strength between the bearing of the susceptor and the spindle can be suppressed. On the other hand, on the side wall of the bearing, the gap is formed more outside of the bearing than the fitting surface between the bearing and the spindle in the horizontal direction. Accordingly, a contact area between the bearing and the spindle is decreased and hence, the transfer of heat from the susceptor to the spindle can be suppressed whereby lowering of a temperature of the susceptor in the vicinity of the bearing can be suppressed. 
       First Embodiment 
     (Configuration of Susceptor) 
       [0022]    Hereinafter, a susceptor according to a first embodiment is described.  FIG. 1  and  FIG. 2  are views showing the susceptor  10  according to the first embodiment.  FIG. 1  is a view showing a main surface (upper surface) of the susceptor  10 .  FIG. 2  is a view schematically showing a portion of a cross section (cross section taken along a line A-A) of the susceptor  10 . 
         [0023]    As shown in  FIG. 1  and  FIG. 2 , the susceptor  10  has an upper surface  10 A on which a wafer is placed, and a lower surface  10 B arranged on a side opposite to the upper surface  10 A. The susceptor  10  is configured to be rotated about a spindle  20  (rotary shaft) extending along a vertical direction. The susceptor  10  is configured to be heated by a heater  30  from a side of the lower surface  10 B. 
         [0024]    The susceptor  10  is made of a carbon base material. The susceptor  10  may not be covered by a SiC film or the like. The susceptor  10  may be made of quartz glass. The susceptor  10  may have a circular disc shape, for example. 
         [0025]    Recessed portions  11  respectively holding a wafer are formed on the upper surface  10 A. Since the movement of the wafer is suppressed by a side wall of the recessed portion  11 , even when the susceptor  10  is rotated, the wafers are held on the upper surface  10 A. 
         [0026]    A bearing  12  which is a recessed portion for receiving the spindle  20  is formed on the lower surface  10 B. The bearing  12  has a shape where the bearing  12  is tip-narrowed from the lower surface  10 B to the upper surface  10 A, that is, a tapered shape. In other words, the bearing  12  has a tapered shape corresponding to a distal end portion of the spindle  20 . 
         [0027]    The spindle  20  is made of metal having higher thermal conductivity than a material for forming the susceptor  10 , for example. The spindle  20  has a shape where the spindle  20  is gradually narrowed toward a distal end of the spindle  20 , that is, a tapered shape. For example, the spindle  20  has a circular columnar shape, and a distal end portion of the spindle  20  has a tapered conical trapezoidal shape, that is, a frustoconical shape. 
         [0028]    As described above, the bearing  12  has a shape corresponding to the distal end of the spindle  20 . By inserting the spindle  20  into the bearing  12 , the spindle  20  is fitted in the bearing  12 . The susceptor  10  is fitted on the spindle  20  by the own weight of the susceptor  10 . Ideally, it is preferable that the bearing  12  and the distal end of the spindle  20  have shapes which completely correspond to each other. However, from a viewpoint of a problem on working accuracy of the bearing  12  or the like, there may be a case where it is difficult to apply working to the bearing  12  and the spindle  20  such that the shape of the bearing  12  and the shape of distal end portion of the spindle  20  completely correspond to each other. In such a case, it is preferable to make the size of the bearing  12  and the size of the distal end portion of the spindle  20  completely agree with each other on a lower end side of the bearing  12  (large end fitting). 
         [0029]    Although the heater  30  is not particularly limited, for example, the heater  30  is formed of an electrically-heated wire having a vortex-shaped pattern. 
         [0030]    In the first embodiment, a gap  12 B is formed in the side wall  12 A of the bearing  12  such that the gap  12 B projects toward the outside of the bearing  12  from a fitting surface  12 X between the bearing  12  and the spindle  20  in a horizontal direction perpendicular to a vertical direction. In this embodiment, the fitting surface  12 X indicates a surface of the side wall  12 A of the bearing  12  which is in contact with the spindle  20 . From a viewpoint of fitting strength between the susceptor  10  (bearing  12 ) and the spindle  20 , it is preferable that the side wall  12 A (fitting surface  12 X) of the bearing  12  be a flat surface. 
         [0031]    It is preferable that the gap  12 B project more toward the outside of the bearing  12  than an opening portion  12 Y formed on a lowermost end of the bearing  12  in a horizontal direction. Further, it is preferable that the gap  12 B be formed on an uppermost end (bottom surface side) of the bearing  12 . It is preferable that the gap  12 B project in all azimuths in the horizontal direction. That is, the gap  12 B has a circular annular shape around the spindle  20 . 
       (Operation and Advantageous Effects) 
       [0032]    In the first embodiment, the bearing  12  has the shape where the bearing  12  is tip-narrowed toward the upper surface  10 A from the lower surface  10 B, that is, a tapered shape. Accordingly, lowering of a fitting strength between the bearing  12  of the susceptor  10  and the spindle  20  can be suppressed. On the other hand, the gap  12 B is formed in the side wall  12 A of the bearing  12  such that the gap  12 B projects toward the outside of the bearing  12  from the fitting surface  12 X between the bearing  12  and the spindle  20  in the horizontal direction. Accordingly, a contact area between the bearing  12  and the spindle  20  is decreased and hence, the transfer of heat from the susceptor  10  to the spindle  20  can be suppressed whereby lowering of a temperature of the susceptor  10  in the vicinity of the bearing  12  can be suppressed. 
       First Modification 
       [0033]    A first modification of the first embodiment is described hereinafter. The description is made hereinafter mainly with respect to points which make the first modification differ from the first embodiment. 
         [0034]    Although not particularly described in the first embodiment, in the first modification, as shown in  FIG. 3 , a bottom surface  12 C of a bearing  12  has a convex shape projecting downward. With such a configuration, even when an upper end surface of the spindle  20  reaches the bottom surface  12 C, a contact area between the upper end surface of the spindle  20  and the bottom surface  12 C is decreased and hence, the transfer of heat from the susceptor  10  to the spindle  20  can be suppressed. Since the upper end surface of the spindle  20  reaches the bottom surface  12 C, the rotation of the susceptor  10  becomes stable. 
       Second Modification 
       [0035]    A second modification of the first embodiment is described hereinafter. The description is made hereinafter mainly with respect to points which make the second modification differ from the first embodiment. 
         [0036]    Although not particularly described in the first embodiment, in the second modification, as shown in  FIG. 4 , a bottom surface (upper end surface)  12 C of a bearing  12  has a concave shape recessed upward. With such a configuration, even when an upper end surface of the spindle  20  reaches the bottom surface  12 C, a contact area between the upper end surface of the spindle  20  and the bottom surface  12 C is decreased and hence, the transfer of heat from the susceptor  10  to the spindle  20  can be suppressed. Since the upper end surface of the spindle  20  reaches the bottom surface  12 C, the rotation of the susceptor  10  becomes stable. 
       Third Modification 
       [0037]    A third modification of the first embodiment is described hereinafter. The description is made hereinafter mainly with respect to points which make the third modification differ from the first embodiment. 
         [0038]    In the first embodiment, the side wall  12 A of the bearing  12  is a flat surface. However, the embodiment is not limited to such a configuration. To be more specific, the side wall  12 A of the bearing  12  may have a stepped shape as shown in  FIG. 5 . Alternatively, as shown in  FIG. 6 , the side wall  12 A of the bearing  12  may have a convex shape which projects toward the inside of the bearing  12 . 
       Other Embodiments 
       [0039]    Although the present invention has been described in conjunction with the above-mentioned embodiments, it should not be construed that the description and the drawings which form a part of this disclosure limit the present invention. Various substitute embodiments, examples and techniques to carry out the present invention will become apparent to those who are skilled in the art from this disclosure. 
         [0040]    In this embodiment, the gap  12 B is formed on the uppermost end (bottom surface side, that is, the upper end surface side) of the bearing  12 . However, the embodiment is not limited to such a configuration. The gap  12 B may be formed in the middle portion between the lowermost end of the bearing  12  and the uppermost end of the bearing  12 . 
         [0041]    In this embodiment, the gap  12 B projects in all azimuths in a horizontal direction. However, the embodiment is not limited to such a configuration. The gap  12 B may project in only some azimuths in the horizontal direction. 
         [0042]    Although not particularly described in the embodiment, it is sufficient that the fitting surface  12 X between the bearing  12  and the spindle  20  account for 80% or more of an area of a portion of a side surface of the spindle  20  inserted into the inside of the bearing  12 . In other words, it is sufficient that the gap  12 B have a size which satisfies such a condition. 
         [0043]    In this embodiment, the distal end portion of the spindle  20  has a tapered conical trapezoidal shape, that is, a frustoconical shape, and the bearing  12  has a shape corresponding to the distal end portion of the spindle  20 . However, the distal end portion of the spindle  20  may have a tapered triangular pyramidal trapezoidal shape, that is, a triangular frustopyramidal shape or a tapered pyramidal trapezoidal shape, that is, a frustopyramidal shape. In such cases, it is needless to say that the bearing  12  has a shape corresponding to the distal end portion of the spindle  20 . 
         [0044]    It should be noted that the present application claims priority to Japanese Patent Application No. 2013-177762, filed on Aug. 29, 2013, the entire contents of which are incorporated by reference herein. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               10  SUSCEPTOR 
               11  RECESSED PORTION 
               12  BEARING 
               12 A SIDE WALL 
               12 B GAP 
               12 C BOTTOM SURFACE (UPPER END SURFACE) 
               12 X FITTING SURFACE 
               12 Y OPENING PORTION 
               20  SPINDLE 
               30  HEATER