JP6428358B2 - Epitaxial growth apparatus and susceptor support shaft - Google Patents

Description

  The present invention relates to an epitaxial growth apparatus for vapor-phase growing an epitaxial film on the surface of a semiconductor wafer, and a susceptor support shaft for supporting a susceptor on which a semiconductor wafer is placed in the apparatus from below.

  An epitaxial wafer is obtained by vapor-phase-growing an epitaxial film on the surface of a semiconductor wafer. For example, when crystal integrity is more required or a multilayer structure with different resistivity is required, an epitaxial silicon wafer is produced by vapor-phase growth (epitaxial growth) of a single crystal silicon thin film on a silicon wafer. To do.

For manufacturing an epitaxial wafer, for example, a single wafer epitaxial growth apparatus is used. Here, a general single wafer epitaxial growth apparatus will be described with reference to FIG. As shown in FIG. 6, the epitaxial growth apparatus 200 has a chamber 10 including an upper dome 11, a lower dome 12, and a dome mounting body 13, and the chamber 10 defines an epitaxial film forming chamber. The chamber 10 is provided with a gas supply port 15 and a gas discharge port 16 for supplying and discharging the reaction gas at positions opposite to the side surfaces thereof. On the other hand, a susceptor 20 on which the silicon wafer W is placed is disposed in the chamber 10. The susceptor 20 is supported by the susceptor support shaft 30 from below. The susceptor support shaft 30 includes a main column 32 and three arms 34 (one not shown) extending radially from the main column 32 at equal intervals, and three support pins 38 (1) at the tip of the arm. One is not shown), and the outer peripheral portion of the lower surface of the susceptor 20 is fitted and supported. The susceptor 20 has three through holes (one is not shown), and the three arms 34 have one through hole. The lift pins 40 are inserted into the through holes of these arms and the through holes of the susceptor. The lower end portion of the lift pin 40 is supported by the lifting shaft 50. When supporting the semiconductor wafer W carried into the chamber 10, placing the semiconductor wafer W on the susceptor 20, and carrying out the epitaxial wafer after vapor phase growth out of the chamber 2, the lift shaft 50 The lift pin 40 moves up and down while sliding with the through hole of the arm and the through hole of the susceptor, and the semiconductor wafer W is moved up and down at its upper end.

  Patent Document 1 describes a technique in which a cylindrical member is provided in a through hole provided in the first arm of the susceptor support shaft as described above, and thereby guides the lifting and lowering movement of the lift pin.

JP 2003-1000085 A

  As described above, in the epitaxial growth apparatus, it is essential to raise and lower the lift pins. When the lift pins support the semiconductor wafer, the lift pins come into contact with the portion where the lift pins on the back side of the semiconductor wafer come into contact with the lift pins, and the contact between the upper ends of the lift pins is maintained. ) Occurred.

  In addition, during the lifting and lowering operation of the lift pin, the lift pin slides with the wall surface defining the through hole of the susceptor, and as a result, dust is generated from the lift pin. Since this dust becomes particles and adheres to the surface of the epitaxial film and degrades the quality of the epitaxial wafer, suppression thereof has been desired.

  It is considered that a stable lifting movement of the lift pin is necessary to suppress the degree of soot and the generation of dust. However, since the improvement of stability is insufficient only by the lift pin guide technology using the cylindrical member as in Patent Document 1, sliding with the wall surface that defines the through hole of the susceptor of the lift pin cannot be avoided. Cannot be suppressed. Further, the tubular member must be welded to the first arm as a separate member from the first arm, and the tubular member may be detached from the arm after a long period of use. Therefore, a technique that replaces the tubular member is desired.

  Then, in view of the said subject, this invention aims at providing the susceptor support shaft and epitaxial growth apparatus which can implement | achieve the stable raising / lowering motion of a lift pin.

The gist configuration of the present invention for solving the above-described problems is as follows.
(1) An epitaxial growth apparatus for vapor-phase growing an epitaxial film on the surface of a semiconductor wafer,
A chamber;
A susceptor having three or more through-holes and mounting the semiconductor wafer inside the chamber;
A susceptor support shaft for supporting the susceptor from below,
A main pillar disposed substantially coaxially with the center of the susceptor;
Three or more first arms extending radially from the main pillar below the periphery of the susceptor and having first through holes;
A second arm having the same number as the number of the first arms, extending radially from the main pillar below the peripheral edge of the susceptor and extending above the first arm, and having a second through hole;
Support pins of the same number as the number of the first arms that connect the tips of the first arm and the second arm that overlap in the vertical direction and directly support the susceptor;
A susceptor support shaft having
It has an upper end and a lower end, is inserted into the through-hole of the susceptor, and is moved up and down so that the semiconductor wafer is attached to and detached from the susceptor while the semiconductor wafer is supported by the upper end. 3 or more lift pins,
A lifting shaft that lifts and lowers the lift pin while supporting the lower end of the lift pin;
Each of the lift pins is inserted through the first through hole of the first arm and the second through hole of the second arm, which overlap in the vertical direction.

  (2) The epitaxial growth apparatus according to (1), wherein the diameter and the position of the first through hole and the second through hole are set so that the inclination of the lift pin with respect to the vertical direction is 0.8 degrees or less.

  (3) In the above (1) or (2), the distance from the lower surface of the first arm to the upper surface of the second arm is 10 mm or more and 30 mm or less at the position of the first through hole and the second through hole. The epitaxial growth apparatus described.

(4) A susceptor support shaft for supporting the susceptor from below in an epitaxial growth apparatus for vapor-phase growing an epitaxial film on the surface of the semiconductor wafer placed on the susceptor,
A main pillar disposed substantially coaxially with the center of the susceptor;
Three or more first arms extending radially from the main pillar below the periphery of the susceptor and having first through holes;
A second arm having the same number as the number of the first arms, extending radially from the main pillar below the peripheral edge of the susceptor and extending above the first arm, and having a second through hole;
Support pins of the same number as the number of the first arms that connect the tips of the first arm and the second arm that overlap in the vertical direction and directly support the susceptor;
Have
The susceptor support shaft, wherein the first through hole and the second through hole provided in the first arm and the second arm that overlap in the vertical direction are provided at the same position in the vertical direction.

  According to the susceptor support shaft and the epitaxial growth apparatus of the present invention, stable lifting movement of the lift pin can be realized.

It is a schematic diagram of the epitaxial growth apparatus 100 by one Embodiment of this invention, and shows the state (at the time of vapor phase growth) where the lift pin 40 descend | falls with respect to the susceptor 20. FIG. 1 is a schematic diagram of an epitaxial growth apparatus 100 according to an embodiment of the present invention, showing a state in which lift pins 40 are raised with respect to a susceptor 20 and supporting a semiconductor wafer W. FIG. (A) is an exploded perspective view of the susceptor 20, and (B) is an exploded perspective view of the susceptor support shaft 30. 4A is an exploded perspective view of the lift pin 40, and FIG. 4 is a schematic diagram showing a positional relationship among a susceptor 20, a susceptor support shaft 30, a lift pin 40, and a lifting shaft 50. FIG. It is a schematic diagram of the conventional epitaxial growth apparatus 200, and shows the state (during vapor phase growth) in which the lift pins 40 are lowered with respect to the susceptor 20.

  With reference to FIGS. 1 and 2, an epitaxial growth apparatus 100 according to an embodiment of the present invention will be described. A susceptor support shaft 30 according to an embodiment of the present invention included in the epitaxial growth apparatus 100 will be described with reference to FIGS.

(Epitaxial growth equipment)
The epitaxial growth apparatus 100 shown in FIGS. 1 and 2 is also shown in the chamber 10, the susceptor 20 also shown in FIG. 3A, the susceptor support shaft 30 also shown in FIG. 3B, and FIG. 4A. It has three lift pins 40A, 40B, and 40C, and a lifting shaft 50 that is also shown in FIG.

(Chamber)
The chamber 10 includes an upper dome 11, a lower dome 12, and a dome mounting body 13, and the chamber 10 defines an epitaxial film forming chamber. The chamber 10 is provided with a gas supply port 15 and a gas discharge port 16 for supplying and discharging the reaction gas at positions opposite to the side surfaces thereof.

(Susceptor)
The susceptor 20 is a disk-shaped member on which the semiconductor wafer W is placed inside the chamber 10. Referring also to FIG. 3A, the susceptor 20 has three through holes 22A, 22B, and 22C that penetrate the front and rear surfaces in the vertical direction at equal intervals of 120 ° in the circumferential direction. Lift pins 40A, 40B, and 40C, which will be described later, are inserted through the through holes 22A, 22B, and 22C, respectively. Each through hole is positioned concentrically so as to support a back surface region of the semiconductor wafer W having a radius of 50% or more with a lift pin. The susceptor 20 has a thickness of about 20 to 40 mm, and can use carbon graphite (graphite) as a base material and a surface coated with silicon carbide (SiC: Vickers hardness 2,346 kgf / mm ² ). . On the surface of the susceptor 20, a counterbore part (not shown) for accommodating and placing the semiconductor wafer W is formed.

(Susceptor support shaft)
The susceptor support shaft 30 supports the susceptor 20 from below in the chamber 10, and as shown in FIG. 3B, the main pillar 32, the three first arms 34A, 34B, 34C, 3 There are two second arms 36A, 36B, 36C and three support pins 38A, 38B, 38C. The main pillar 32 is disposed substantially coaxially with the center of the susceptor.

The first arms 34A, 34B, and 34C have first through holes 35A, 35B, and 35C that extend radially from the main pillar 32 below the periphery of the susceptor 20 and penetrate in the vertical direction. The second arms 36A, 36B, and 36C extend radially from the main pillar 32 below the peripheral edge of the susceptor 20 and above the first arms 34A, 34B, and 34C, respectively, and pass through the second arms in the vertical direction. Through holes 37A, 37B, 37C are provided. In the present specification, the “periphery of the susceptor” means a region outside the susceptor radius by 80% or more from the susceptor center. The support pins 38A, 38B, and 38C connect the tips of the first arms 34A, 34B, and 34C and the second arms 36A, 36B, and 36C that overlap in the vertical direction, and directly support the susceptor 20. That is, the support pins 38A, 38B, and 38C support the rear surface peripheral edge portion of the susceptor. The first through holes 35A, 35B, and 35C and the second through holes 37A, 37B, and 37C are provided at the same position in the vertical direction, and lift pins 40A, 40B, and 40C, which will be described later, are respectively inserted therethrough. The characteristic part of this embodiment is the structure of such a susceptor support shaft 30, and the technical significance thereof will be described later.

The susceptor support shaft 103 is preferably made of quartz (Vickers hardness 1,103 kgf / mm ² ), and more preferably made of synthetic quartz. However, the tip portions of the support pins 38 </ b> A, 38 </ b> B, 38 </ b> C are preferably made of the same silicon carbide as the susceptor 20.

(Lift pin)
As shown in FIG. 4A, the lift pins 40A, 40B, and 40C include straight body portions 44A, 44B, and 44C that are respectively inserted into the through holes 22A, 22B, and 22C of the susceptor 20, and the straight body portions 44A and 44B. , 44C and the through holes 22A, 22B, and 22C have upper end portions 42A, 42B, and 42C that are larger in diameter and lower end portions 46A, 46B, and 46C, respectively. The lift pins 40A, 40B, and 40C are respectively provided in the first through holes 35A, 35B, and 35C of the first arm, the second through holes 37A, 37B, and 37C of the second arm, and the through holes 22A, 22B, and 22C of the susceptor 20, respectively. It is inserted. The lift pins 40A, 40B, and 40C are moved up and down by a lift shaft 50, which will be described later, so that the semiconductor wafer W (back surface region having a radius of 50% or more) is supported by the upper end portions 42A, 42B, and 42C. The wafer W can be attached to and detached from the susceptor 20. Details of this operation will be described later. The lift pins 40A, 40B, and 40C are generally formed by coating a carbon graphite base material with silicon carbide, similarly to the susceptor 20.

(Elevating shaft)
As shown in FIG. 4B, the elevating shaft 50 defines a hollow that accommodates the main column 32 of the susceptor support shaft 30, and a main column 52 that shares the rotation axis with the main column 32, and the main column 52. The three support posts 54A, 54B, 54C branch off at the front ends of the lift pins, and the lower ends 46A, 46B, 46C of the lift pins are respectively supported by the front ends of the support posts 54A, 54B, 54C. The lifting shaft 50 is preferably made of quartz. When the elevating shaft 50 moves up and down along the main pillar 32 of the susceptor support shaft 30, the lift pins 40A, 40B, and 40C can be raised and lowered.

(Heating lamp)
The heating lamps 14 are disposed in the upper region and the lower region of the chamber 10, and generally, a halogen lamp or an infrared lamp that has a high temperature raising / lowering speed and excellent temperature controllability is used.

(Epitaxial wafer manufacturing procedure)
Next, a series of operations of carrying in the semiconductor wafer W into the chamber 10, vapor phase growth of the epitaxial film onto the semiconductor wafer W, and carrying out the manufactured epitaxial wafer out of the chamber 10 are shown in FIGS. 1 and 2. Will be described with reference to FIG.

  The semiconductor wafer W carried into the chamber 10 moves the lift pins 40A, 40B, 40C (40B not shown in FIGS. 1 and 2) toward the upper side of the susceptor 20, and the upper ends 42A, 42B, 42C of the lift pins. Is brought into contact with the back surface of the semiconductor wafer W, and the semiconductor wafer W is temporarily supported by lift pins 40A, 40B, and 40C. The lift pins 40A, 40B, and 40C are moved upward and downward through the lift shaft 50 that supports the lower ends 46A, 46B, and 46C.

  Next, by raising the susceptor support shaft 30, the susceptor 20 is moved to the position of the semiconductor wafer W, and the semiconductor wafer W is placed on the susceptor 20. In this state, the upper end portions 42A, 42B, and 42C of the lift pins are accommodated in the through holes 22A, 22B, and 22C of the susceptor. Thereafter, the semiconductor wafer W is heated to a temperature of 1000 ° C. or higher by the heating lamp 14 while a reactive gas is supplied from the gas supply port 15 into the chamber 10 to vapor-phase grow an epitaxial film having a predetermined thickness. An epitaxial wafer is manufactured. During vapor phase growth, the susceptor support shaft 30 is rotated about the main column 32 as a rotation axis, thereby rotating the susceptor 20 and the semiconductor wafer W thereon.

  Thereafter, the susceptor 20 is lowered by lowering the susceptor support shaft 30. This lowering is performed until the lift pins 40A, 40B, 40C are supported by the lift shaft 50 and protrude from the susceptor 20, and the manufactured epitaxial wafer is supported by the lift pins 40A, 40B, 40C. Then, a carrier blade (not shown) is introduced into the chamber 10 and the lift pins 40A, 40B, 40C are lowered to place the epitaxial wafer on the carrier blade. Thus, the epitaxial wafer is transferred from the lift pins 40A, 40B, and 40C to the transfer blade. Thereafter, the epitaxial wafer is carried out of the chamber 10 together with the transfer blade.

  In the present embodiment, the first through holes 35A, 35B, and 35C and the second through holes 37A, 37B, and 37C are provided at the same vertical position, that is, the hole center coincides with the vertical direction, and the lift pin 40A is provided here. , 40B, 40C are respectively inserted. When the lift pins 40A, 40B, and 40C move up and down, they slide with the wall surfaces that define the first through holes 35A, 35B, and 35C and the second through holes 37A, 37B, and 37C. Thus, by having a plurality of arms at the overlapping positions in the vertical direction, it is possible to realize a stable lifting movement of the lift pins as compared with the conventional case where there is only one arm in the vertical direction.

  As a result, at the conveyance temperature (600 to 900 ° C.), the lift pins 40A, 40B, and 40C do not slide with the wall surfaces that define the through holes 22A, 22B, and 22C of the susceptor when the lift pins 40A and 40C move up and down. As a result, dust generation from the lift pins 40A, 40B, and 40C can be suppressed, and the quality of the epitaxial film can be improved. Further, since the lift pins 40A, 40B, and 40C are moved up and down stably, the degree of pin marks on the back surface of the epitaxial wafer caused by the contact of the lift pins 40A, 40B, and 40C is suppressed.

  In addition, since a plurality of arms are provided at overlapping positions in the vertical direction, the strength of the susceptor support shaft 30 is improved and thermal deformation is suppressed. As a result, the susceptor 20 is prevented from wavy and eccentric when the susceptor 20 is rotated (vapor phase growth), and the film thickness uniformity of the epitaxial film is improved.

  In order to prevent sliding between the lift pin and the wall surface defining the through hole of the susceptor, it is conceivable to sufficiently increase the diameter of the through hole of the susceptor. However, in that case, heat transfer from the susceptor to the semiconductor wafer is hindered, and the uniformity of the film thickness of the epitaxial film is impaired. Therefore, in this embodiment, for example, the difference between the hole diameters of the through holes 22A, 22B, and 22C of the susceptor and the peripheral diameters of the straight body portions 44A, 44B, and 44C of the lift pins without excessively increasing the hole diameter of the through hole of the susceptor. Is preferably set to 0.5 mm or more and 0.6 mm or less.

In order to reduce the vertical tilt of the lift pin with respect to the vertical direction during vapor phase growth (high temperature state), it is desirable to design in consideration of the difference in thermal expansion coefficient between the susceptor 20 and the susceptor support shaft 30. Specifically, before vapor phase growth (normal temperature state), the center positions of the first through holes 35A, 35B, 35C and the second through holes 37A, 37B, 37C of the susceptor support shaft are set to the through holes 22A, 22B of the susceptor. , 22C is preferably positioned outwardly within a range of 0.10 mm to 0.35 mm. In other words, rather than the distance from the center of the susceptor to the centers of the through holes 22A, 22B, and 22C, the distance from the center of the main pillar to the centers of the first through holes 35A, 35B, and 35C and the second through holes 37A, 37B, and 37C. It is preferable to lengthen the distance within a range of 0.10 mm to 0.35 mm. As a result, at the time of vapor phase growth (high temperature state), the center positions of the first through holes 35A, 35B, 35C and the second through holes 37A, 37B, 37C of the susceptor support shaft and the through holes 22A, 22B, Since the center position of 22C substantially coincides with the vertical direction, the inclination of the lift pin with respect to the vertical direction can be set to 0.8 degrees or less, and the sliding between the wall surface defining the through-hole of the susceptor and the lift pin is more reliable. Can be prevented.

  From the viewpoint of reducing the inclination of the lift pin with respect to the vertical direction, the diameters of the first through holes 35A, 35B, and 35C and the second through holes 37A, 37B, and 37C of the susceptor susceptor support shaft and the straight body portions 44A and 44B of the lift pins. , 44C is preferably 0.5 mm or more and 0.6 mm or less.

  Further, as shown in FIG. 5, the distance D from the lower surface of the first arm 34A to the upper surface of the second arm 36A at the position of the first through hole 35A and the second through hole 37A should be 10 mm or more and 30 mm or less. preferable. When the distance D is less than 10 mm, there is a possibility that the function of regulating the lifting and lowering of the lift pins in the vertical direction cannot be obtained sufficiently. When the distance D exceeds 30 mm, the lengths of the support pins 38A, 38B, and 38C that come into contact with the susceptor and the lengths of the lift pins 40A, 40B, and 40C become longer during the epitaxial growth process, and the support pins and the lift pins are extended from the susceptor. There is a possibility that the amount of heat conduction to the surface increases and the soaking of the susceptor is hindered, and the epitaxial film thickness to be grown becomes non-uniform.

In the present embodiment, the example in which the two arms are provided in the overlapping position in the vertical direction has been described. However, the present invention is not limited to this, and three or more arms may be provided. Moreover, although the example which extends three arms at equal intervals in the direction branched from the main pillar 32 was shown, this invention is not limited to this, You may branch four or more.

(Invention example)
An epitaxial silicon wafer was manufactured using the epitaxial growth apparatus shown in FIGS. Here, as the susceptor, the surface of the carbon substrate coated with SiC was used. Further, a boron-doped silicon wafer having a diameter of 300 mm was used as the substrate of the epitaxial wafer.

  In the manufacture of the epitaxial wafer, first, trichlorosilane gas as a source gas was supplied at a temperature of 1150 ° C., and silicon coating was applied to the surface of the susceptor. Next, the silicon wafer was introduced into the chamber and placed on the susceptor using lift pins. Subsequently, hydrogen gas was supplied at 1150 ° C. to perform hydrogen baking, and then an epitaxial silicon film was grown at 1150 ° C. by 4 μm to obtain an epitaxial silicon wafer. 100 epitaxial silicon wafers were manufactured under the same conditions. Here, trichlorosilane gas was used as the source gas, diborane gas was used as the dopant gas, and hydrogen gas was used as the carrier gas.

  The diameter and position of the first through hole and the second through hole of the susceptor support shaft were set so that the inclination of the lift pin during the vapor phase growth with respect to the vertical direction was 0.6 degrees. The distance D from the lower surface of the first arm to the upper surface of the second arm was 30 mm.

(Comparative example)
Using the epitaxial growth apparatus shown in FIG. 6, 100 epitaxial silicon wafers were manufactured under the same conditions as in the invention example.

[Surface quality]
About the epitaxial wafer manufactured by the invention example and the comparative example, the surface of the epitaxial film was observed in a DCO mode (Dark Field Composite Oblique mode) using a surface inspection device (KLA-Tencor: Surfscan SP-2). The number of LPD (Light Point Defect) of 0.25 μm or more was examined. From this measurement result, it is possible to evaluate the generation state of particles due to dust generation. As a result, it was 0.22 pieces / wafer in the comparative example, whereas it was 0.10 pieces / wafer in the inventive example.

[Backside quality]
For the epitaxial wafers manufactured in the inventive example and the comparative example, using a surface inspection device (KLA-Tencor: Surfscan SP-2), the back surface is observed in the DCO mode, and the set value of the laser reflection in the lift pin contact area The area (pin mark intensity) of the region having the above scattering intensity was measured, and wrinkles due to lift pins on the back surface of the epitaxial wafer were evaluated. As a result, the average value was 0.72 mm ² in the comparative example, whereas the average value was 0.58 mm ^{2 in the} invention example.

  The present invention provides a susceptor support shaft and an epitaxial growth apparatus that can realize a stable lifting movement of lift pins, and therefore can be suitably applied to the manufacture of an epitaxial semiconductor wafer.

DESCRIPTION OF SYMBOLS 100 Epitaxial growth apparatus 10 Chamber 11 Upper dome 12 Lower dome 13 Dome attachment body 14 Heating lamp 15 Gas supply port 16 Gas exhaust port 20 Susceptor 22A, 22B, 22C Through-hole 30 Susceptor support shaft 32 Main pillar 34A, 34B, 34C 1st arm 35A, 35B, 35C First through hole 36A, 36B, 36C Second arm 37A, 37B, 37C Second through hole 38A, 38B, 38C Support pin 40A, 40B, 40C Lift pin 42A, 42B, 42C Upper end (head)
44A, 44B, 44C Straight body part 46A, 46B, 46C Lower end part 50 Lifting shaft 52 Main pillar 54A, 54B, 54C Post W Semiconductor wafer

Claims (4)

An epitaxial growth apparatus for vapor-phase growing an epitaxial film on the surface of a semiconductor wafer,
A chamber;
A susceptor having three or more through-holes and mounting the semiconductor wafer inside the chamber;
A susceptor support shaft for supporting the susceptor from below,
A main pillar disposed substantially coaxially with the center of the susceptor;
Three or more first arms extending radially from the main pillar below the periphery of the susceptor and having first through holes;
A second arm having the same number as the number of the first arms, extending radially from the main pillar below the peripheral edge of the susceptor and extending above the first arm, and having a second through hole;
Support pins of the same number as the number of the first arms that connect the tips of the first arm and the second arm that overlap in the vertical direction and directly support the susceptor;
A susceptor support shaft having
It has an upper end and a lower end, is inserted into the through-hole of the susceptor, and is moved up and down so that the semiconductor wafer is attached to and detached from the susceptor while the semiconductor wafer is supported by the upper end. 3 or more lift pins,
A lifting shaft that lifts and lowers the lift pin while supporting the lower end of the lift pin;
Each of the lift pins is inserted through the first through hole of the first arm and the second through hole of the second arm, which overlap in the vertical direction.   The epitaxial growth apparatus of Claim 1 which sets the hole diameter and position of a said 1st through-hole and a said 2nd through-hole so that the inclination with respect to the perpendicular direction of the said lift pin may be 0.8 degrees or less.   3. The epitaxial growth apparatus according to claim 1, wherein a distance from a lower surface of the first arm to an upper surface of the second arm is 10 mm or more and 30 mm or less at the position of the first through hole and the second through hole. A susceptor support shaft for supporting the susceptor from below in an epitaxial growth apparatus for vapor-phase growth of an epitaxial film on the surface of a semiconductor wafer placed on the susceptor;
A main pillar disposed substantially coaxially with the center of the susceptor;
Three or more first arms extending radially from the main pillar below the periphery of the susceptor and having first through holes;
A second arm having the same number as the number of the first arms, extending radially from the main pillar below the peripheral edge of the susceptor and extending above the first arm, and having a second through hole;
Support pins of the same number as the number of the first arms that connect the tips of the first arm and the second arm that overlap in the vertical direction and directly support the susceptor;
Have
The susceptor support shaft, wherein the first through hole and the second through hole provided in the first arm and the second arm that overlap in the vertical direction are provided at the same position in the vertical direction.