Patent Publication Number: US-2022230896-A1

Title: Substrate processing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application Nos. 2021-007698 filed on Jan. 21, 2021 and 2021-097486 filed on Jun. 10, 2021, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a substrate processing apparatus. 
     BACKGROUND 
     In a depressurization drying apparatus, it is proposed to weld reinforcement ribs to extend in a direction intersecting adjacent edge portions of a chamber cover having a quadrilateral shape, so as to suppress deformation of the chamber cover during depressurization, thereby suppressing separation or the like of the welded portion (Patent Document 1). In addition, as a substrate processing apparatus for processing a substrate (hereinafter, also referred to as a “wafer”) in a substrate processing system, a substrate processing apparatus which processes four wafers in one chamber at the same time is known (Patent Document 2). 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Laid-Open Patent Publication No. 2009-041790 
         Patent Document 2: Japanese Laid-Open Patent Publication No. 2019-220509 
       
    
     SUMMARY 
     According to one embodiment of the present disclosure, there is provided a substrate processing apparatus including: a vacuum processing container; and a rotation arm including a rotary axis disposed at a central portion of the vacuum processing container, wherein, in the rotation arm, a rotation cylinder having a hollow interior constitutes the rotary axis, and a hollow portion of the rotation cylinder constitutes an exhaust path of the vacuum processing container. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure. 
         FIG. 1  is an exploded perspective view illustrating an example of a configuration of a substrate processing apparatus according to an embodiment of the present disclosure. 
         FIG. 2  is a view illustrating an example of a positional relationship between a processing space and a rotation arm at a standby position. 
         FIG. 3  is a view illustrating an example of the positional relationship between the processing space and the rotation arm at a wafer holding position. 
         FIG. 4  is a view illustrating an example of a moving path of wafers in the substrate processing apparatus of the present embodiment. 
         FIG. 5  is a view illustrating an example of an exhaust path of the substrate processing apparatus of the embodiment. 
         FIG. 6  is a schematic cross-sectional view illustrating an example of a configuration of the substrate processing apparatus of the embodiment. 
         FIG. 7  is an exploded perspective view illustrating an example of a configuration of a substrate processing apparatus according to Modification 1. 
         FIG. 8  is a partial enlarged view illustrating an example of a cross section of the vicinity of a joined exhaust port according to Modification 2. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of a substrate processing apparatus according to the present disclosure will be described in detail based on the drawings. The technology disclosed herein is not limited by the following embodiments. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments. 
     In the substrate processing apparatus that processes four wafers in one chamber at the same time as described above, a joined exhaust path in which exhaust paths from respective wafer processing spaces are joined with each other is provided in the central portion (central region) of the substrate processing apparatus. When a rotation arm is provided in the central portion of the chamber in order to transfer wafers among the respective processing spaces, the exhaust paths are provided in the outer peripheries of the respective processing spaces and are joined with each other at the lower portion of the chamber, thereby causing an increase in the volume of the chamber and the complication in exhaust path. In addition, in this configuration, since a beam cannot be installed in the central portion of the chamber, the central portion of the chamber in the vacuum atmosphere may be deformed by the atmospheric pressure, which may affect the process performance in each processing space. Thus, it is desired to achieve both the installation of the rotation mechanism of the rotation arm in the central portion of a vacuum processing container (chamber), and the simplification of an exhaust path. Further, it is desired to suppress the deformation of the vacuum processing container 
     [Configuration of Substrate Processing Apparatus] 
       FIG. 1  is an exploded perspective view illustrating an example of a configuration of a substrate processing apparatus according to an embodiment of the present disclosure. In the present embodiment, descriptions will be made on an example in which a substrate processing apparatus  2  illustrated in  FIG. 1  is applied to, for example, a film forming apparatus which performs plasma chemical vapor deposition (CVD) on a wafer W. The substrate processing apparatus  2  is an example of a process module and a vacuum processing apparatus. As illustrated in  FIG. 1 , the substrate processing apparatus  2  includes a processing container (vacuum container)  20  having a rectangular shape in a plan view. The processing container  20  is configured to maintain the interior thereof in a vacuum atmosphere. That is, the processing container  20  is an example of a vacuum processing container. The processing container  20  is configured by closing a top open portion with a gas supplier  4  and a manifold  36  to be described later. In  FIG. 1 , internal partition walls and the like are omitted such that a relationship between the processing spaces S 1  to S 4  and a rotation arm  3  can be easily understood. The processing container  20  is provided with two carry-in/out ports  21  arranged in a Y direction in a side surface thereof connected to a vacuum transfer chamber (not illustrated). The carry-in/out ports  21  are opened and closed by gate valves (not illustrated). 
     A plurality of processing spaces S 1  to S 4  are provided inside the processing container  20 . Stages  22  are disposed in the processing spaces S 1  to S 4 , respectively. The stages  22  are movable vertically, so that the stages  22  move upward when wafers W are processed, and move downward when wafers W are transferred. A transfer space T is provided below the processing spaces S 1  to S 4 , to be connected to the processing spaces S 1  to S 4  for transferring wafers W by the rotation arm  3 . The transfer space T below the processing spaces S 1  and S 2  is connected to each of the carry-in/out ports  21 , and wafers W are carried in/out between the processing container and the vacuum transfer chamber by a substrate transfer mechanism (not illustrated). In order to collectively transfer two wafers W to the substrate processing apparatus  2 , a substrate holder of the substrate transfer mechanism is configured to hold, for example, two wafers W at the same time. 
     The respective stages  22  of the processing spaces S 1  to S 4  are arranged in a two-row and two-column layout when viewed from the above. The layout has different dimensions for row and column intervals. That is, a pitch Py, which is a pitch in the Y-direction between the stages  22  (row interval), and a pitch Px 1 , which a pitch in an X-direction between the stages  22  (column interval), have a relationship of Py&gt;Px 1 . 
       FIG. 2  is a view illustrating an example of a positional relationship between the processing spaces and the rotation arm at a standby position.  FIG. 3  is a view illustrating an example of the positional relationship between the processing space and the rotation arm at a wafer holding position. As illustrated in  FIGS. 2 and 3 , the rotation arm  3  includes four end effectors  32  capable of holding wafers W to be placed on the stages  22 , respectively, and a base member  33  having a rotation axis at the center position of the two-row and two-column layout. The four end effectors  32  are connected to the base member  33  to form an X shape. That is, the rotation arm  3  includes the same number of end effectors  32  as the number of processing spaces S 1  to S 4 . The X shape of the rotation arm  3  has a configuration in which the dimension in the Y direction corresponding to the row interval of the X shape and the dimension in the X direction corresponding to the column interval of the X shape differ from each other at the wafer holding position illustrated in  FIG. 3 . 
     At the standby position illustrated in  FIG. 2 , each end effector of the rotation arm  3  is disposed between two of the processing spaces S 1  to S 4 , so that the rotation arm  3  does not disrupt the vertical movement of each stage  22 .  FIG. 2  illustrates a state in which wafers W are placed on the stages  22 , respectively. A description will be made of the movement of the rotation arm  3  when the wafers W are transferred such that the wafers W in the first column and the wafers W in the second column are interchanged from this state, that is, when the wafers W in the processing spaces S 1  and S 2  are transferred to the processing spaces S 3  and S 4 , and the wafers W in the processing spaces S 3  and S 4  are transferred to the processing spaces S 1  and S 2 . 
     First, respective stages  22  are moved to delivery positions in the transfer space T at the lower side, and lift pins  26  (to be described later) provided on the respective stages  22  are raised to lift the wafers W. Subsequently, the rotation arm  3  is rotated clockwise by about 30 degrees to insert respective end effectors  32  between the stages  22  and the wafers W as illustrated in  FIG. 3 . Subsequently, the lift pins  26  are lowered to place the wafers W on respective end effectors  32 . Subsequently, the rotation arm  3  is rotated clockwise by 180 degrees to transfer the wafers W to holding positions on respective stages  22 . When the respective stages  22  raise the lift pins  26  to receive the wafers W, the rotation arm  3  is rotated counterclockwise by about 30 degrees to move to the standby position. In this way, the wafers W can be transferred by the rotation arm  3  such that the wafers W in the first column and the wafers W in the second column are interchanged with each other. Therefore, for example, when different processes are repeated in the processing spaces S 1  and S 2  and the processing spaces S 3  and S 4  (e.g., when a film forming process and an annealing process are repeated), the time required to transfer the wafers W can be reduced. 
       FIG. 4  is a view illustrating an example of wafer movement paths in the substrate processing apparatus of the present embodiment. In  FIG. 4 , the movement paths when the wafers W are transferred from the vacuum transfer chamber to the interior of the substrate processing apparatus  2  will be described. First, by a substrate transfer mechanism (not illustrated) of the vacuum transfer chamber, as illustrated by a path F 1 , at the delivery positions of the transfer space T under the processing spaces S 1  and S 2  corresponding to the stages  22  in the same column, two wafers W are simultaneously loaded into respective stages  22 . The respective stages  22  of the processing spaces S 1  and S 2  raise the lift pins  26  to receive the wafers W. 
     Subsequently, the rotation arm  3  is rotated clockwise from the standby position by about 30 degrees, the end effectors  32  are inserted between the stages  22  located at the delivery positions under the processing spaces S 1  and S 2  and the wafers W, respectively, and the lift pins  26  are lowered to place the wafers W on the respective end effectors  32 . When the wafers W are placed, the rotation arm  3  is rotated clockwise by 180 degrees as illustrated by a path F 2  to transfer the wafers W onto the stages  22  located at the delivery positions (the holing positions of the rotation arm  3 ) of the transfer space T under the processing spaces S 3  and S 4 . When the stages  22  located at the delivery positions under the processing spaces S 3  and S 4  raise the lift pins  26  to receive the wafers W, respectively, the rotation arm  3  is rotated counterclockwise by about 30 degrees to move to the standby position. In this state, no wafers W are placed on the stages  22  of the processing spaces S 1  and S 2 , but the wafers W are placed on the stages  22  of the processing spaces S 3  and S 4 . Subsequently, as illustrated by the path F 1 , two wafers W are simultaneously loaded into respective stages  22  at the delivery positions located under the processing spaces S 1  and S 2  by the substrate transfer mechanism of the vacuum transfer chamber, and the wafers W are placed on the stages  22  of the processing spaces S 1  and S 2 , whereby the wafers W are placed on all of the stages  22  of the processing spaces S 1  to S 4 , respectively. 
     Similarly, during unloading, the wafers W placed on the stages  22  located at the delivery positions under the processing spaces S 1  and S 2  are first transferred to the vacuum transfer chamber by the substrate transfer mechanism. Subsequently, the wafers W placed on the stages  22  located at the delivery positions under the processing spaces S 3  and S 4  are transferred by the rotation arm  3  to the stages  22  located at the delivery positions under the processing spaces S 1  and S 2 . Subsequently, the wafers W placed on the stages  22  located at the delivery positions under the processing spaces S 1  and S 2  are transferred to the vacuum transfer chamber by the substrate transfer mechanism. In this way, by using the substrate transfer mechanism capable of simultaneously transferring two wafers W and the rotation arm  3 , the wafers W can be loaded into and unloaded from the processing spaces S 1  to S 4 . 
     When the rotation arm  3  transfers the wafers W, the deviations of the wafers W from the stages  22  of a transfer destination may be detected, and the stages  22  may be finely moved in the XY plane to correct the deviation of the wafers W. In this case, the substrate processing apparatus  2  includes a deviation detection sensor configured to detect a deviation of each wafer W at each of rotationally symmetric positions within the row interval or the column interval, on the rotation trajectory of the wafers W held by the rotation arm  3 . In the example of  FIG. 4 , sensors  31   a  and  31   b  are provided between the processing spaces S 1  and S 2  and between the processing spaces S 3  and S 4 , respectively, within the row interval. 
     Each of the sensors  31   a  and  31   b  is, for example, a set of two optical sensors, which are arranged on a straight line in the X direction that passes through the center of the substrate processing apparatus  2 , that is, the center position of the two-row and two-column layout. This is to make the direction of expansion of the processing container  20  caused by a thermal expansion the same in the two sensors, thereby reducing an error. The arrangement positions of the sensors  31   a  and  31   b  are not limited to the X direction as long as the positions are on a straight line passing through the center of the substrate processing apparatus  2 . The substrate processing apparatus  2  detects deviation amounts of the wafers W by comparing front and rear edges of the wafers W detected by the sensors  31   a  and  31   b  with output results of an encoder (not illustrated) provided in the rotation arm  3 . 
     In the example of  FIG. 4 , a position P 24  represents a state in which the rear edge of the wafer W passes through the sensor  31   b  when the wafer W is transferred from the processing space S 2  to the processing space S 4 , and a position P 42  represents a state in which the rear edge of the wafer W passes through the sensor  31   a  when the wafer W is transferred from the processing space S 4  to the processing space S 2 . The substrate processing apparatus  2  may finely move the stages  22  within the XY plane according to a detected deviation amount to correct the deviations of the wafers W. That is, the substrate processing apparatus  2  adjusts the deviations such that the wafers W are located at the centers of the processing spaces S 1  to S 4 , respectively, when the stages  22  are raised. The term “finely” used herein refers to about 5 mm or less. 
       FIG. 5  is a view illustrating an example of exhaust paths of the substrate processing apparatus in the present embodiment.  FIG. 5  illustrates a case in which the processing container  20  is viewed from above in the state in which the gas supplier  4  (to be described later) is removed. As illustrated in  FIG. 5 , a manifold  36  is arranged in the center of the substrate processing apparatus  2 . The manifold  36  includes a plurality of exhaust paths  361 , which are connected to the processing spaces S 1  to S 4 , respectively. Each exhaust path  361  is connected to a hole  351  in a thrust nut  35  (to be described later) below the center of the manifold  36 . Each exhaust path  361  is connected to an annular flow path  363  in each of the guide members  362  provided above the processing spaces S 1  to S 4 . That is, the gas in the processing spaces S 1  to S 4  is exhausted to a joined exhaust port  205  (to be described later) via the flow path  363 , the exhaust paths  361 , and the hole  351 . 
       FIG. 6  is a schematic cross-sectional view illustrating an example of a configuration of the substrate processing apparatus of the present embodiment. The cross section of  FIG. 6  corresponds to the cross section of the substrate processing apparatus  2  taken along line A-A in  FIG. 5 . The four processing spaces S 1  to S 4  are configured in the same manner as one another, and are formed between the stages  22 , on which the wafers W are respectively placed, and the gas suppliers  4  disposed to face the stages  22 . In other words, in the processing container  20 , the stage  22  and the gas supplier  4  are provided for each of the four processing spaces S 1  to S 4 .  FIG. 6  illustrates the processing spaces S 1  and S 3 . Hereinafter, the processing space S 1  will be described as an example. 
     The stage  22  also serves as a lower electrode, is made of, for example, a metal or aluminum nitride (AlN) in which a metal mesh electrode is embedded, and is formed in a flat column shape. The stage  22  is supported by a support member  23  from the bottom side. The support member  23  is formed in a cylindrical shape, extends vertically downward, and penetrates a bottom  27  of the processing container  20 . A lower end portion of the support member  23  is located outside the processing container  20  and connected to a rotational driving mechanism  600 . The support member  23  is rotated by the rotational driving mechanism  600 . The stage  22  is configured to be rotatable with the rotation of the support member  23 . An adjustment mechanism  700  is provided at the lower end portion of the support member  23  to adjust the position and inclination of the stage  22 . The stage  22  is configured to be capable of being raised and lowered between a processing position and a delivery position using the support member  23  by the adjustment mechanism  700 . In  FIG. 6 , the stage  22  located at the delivery position is indicated by a solid line, and the stage  22  located at the processing position is indicated by a broken line. In addition, at the delivery position, the end effector  32  is inserted between the stage  22  and the wafer W to receive the wafer W from the lift pins  26 . The processing position is a position when substrate processing (e.g., a film forming process) is performed, and the delivery position is a position at which the wafer W is delivered to and from a substrate transfer mechanism (not illustrated) or the end effector  32 . 
     A heater  24  is embedded in each stage  22 . The heater  24  heats each wafer W placed on the stage  22  to, for example, about 60 degrees C. to 600 degrees C. In addition, the stage  22  is connected to a ground potential. 
     In addition, the stage  22  is provided with a plurality of (e.g., three) pin through-holes  26   a , and the lift pins  26  are arranged inside these pin through-holes  26   a , respectively. The pin through-holes  26   a  are provided to penetrate the stage  22  from a placement surface (upper surface) of the stage  22  to a rear surface (bottom surface) opposite to the placement surface. The lift pins  26  are slidably inserted into the respective pin through-holes  26   a . Upper ends of the lift pins  26  are suspended at placement-surface sides of the pin through-holes  26   a . That is, the upper ends of the lift pins  26  have a diameter larger than those of the pin through-holes  26   a , and recesses having a diameter and a thickness larger than those of the upper ends of the lift pins  26  are formed at the upper ends of the pin through-holes  26   a  to be capable of accommodating the upper ends of the lift pins  26 , respectively. As a result, the upper ends of the lift pins  26  are engaged with the stage  22  and suspended at the placement-surface sides of the pin through-holes  26   a , respectively. In addition, the lower ends of the lift pins  26  protrude from the rear surface of the stage  22  toward the bottom  27  of the processing container  20  so as to be capable of coming into contact with a lifting mechanism (not illustrated). 
     In the state in which the stage  22  is raised to the processing position, the upper ends of the lift pins  26  are received in the recesses at the placement-surface sides of the pin through-holes  26   a , respectively. In this state, when the stage  22  is lowered to the transfer position and the lift pins  26  are raised by the lifting mechanism (not illustrated), the upper ends of the lift pins  26  protrude from the placement surface of the stage  22 . 
     The gas supplier  4  is provided in a ceiling portion of the processing container  20  and above the stage  22  via a guide member  362  made of an insulating member. The gas supplier  4  has a function as an upper electrode. The gas supplier  4  includes a lid  42 , a shower plate  43  forming a facing surface provided to face the placement surface of the stage  22 , and a gas flow chamber  44  formed between the lid  42  and the shower plate  43 . A gas supply pipe  51  is connected to the lid  42 , and gas ejection holes  45  penetrating the shower plate  43  in the thickness direction are arranged vertically and horizontally in the shower plate  43  such that the gas is ejected toward the stage  22  in the form of a shower. 
     Each gas supplier  4  is connected to a gas supply system  50  via a gas supply pipe  51 . The gas supply system  50  includes, for example, sources of a reaction gas (a film forming gas), a purge gas, and a cleaning gas, which are processing gases, a pipe, a valve V, a flow rate adjuster M, and the like. The gas supply system  50  includes, for example, a cleaning gas source  53 , a reaction gas source  54 , a purge gas source  55 , valves V 1  to V 3  provided in the pipes of respective gas sources, and flow rate adjusters M 1  to M 3 . 
     The cleaning gas source  53  is connected to a cleaning gas supply path  532  via the flow rate adjuster M 1 , the valve V 1 , and a remote plasma unit (RPU)  531 . The cleaning gas supply path  532  branches into four systems at the downstream side of the RPU  531  to be connected to each gas supply pipe  51 . Valves V 11  to V 14  are provided for respective branched pipes at the downstream side of the RPU  531 . The respective valves V 11  to V 14  are opened during cleaning. For the sake of convenience in illustration, only the valves V 11  and V 14  are illustrated in  FIG. 6 . 
     The reaction gas source  54  and the purge gas source  55  are connected to a gas supply path  52  via the flow rate adjusters M 2  and M 3 , respectively, and the valves V 2  and V 3 , respectively. The gas supply path  52  is connected to the gas supply pipe  51  via the gas supply pipe  510 . In  FIG. 7 , the gas supply path  52  and the gas supply pipe  510  collectively illustrate respective supply paths and respective supply pipes corresponding to respective gas suppliers  4 . 
     A radio-frequency power supply  41  is connected to the shower plate  43  via a matcher  40 . The shower plate  43  has a function as an upper electrode facing the stage  22 . When radio-frequency power is applied between the shower plate  43 , which is the upper electrode, and the stage  22 , which is the lower electrode, it is possible to plasmarize a gas supplied from the shower plate  43  to the processing space S 1  (a reaction gas in this example) by capacitive coupling. 
     Next, the exhaust paths from the processing spaces S 1  to S 4  to the joined exhaust port  205  will be described. As illustrated in  FIGS. 5 and 6 , the exhaust paths pass through respective exhaust paths  361  from the annular flow paths  363  in respective guide members  362  provided above the processing spaces S 1  to S 4 , and are directed to a joined exhaust port  205  via a junction portion and the hole  351  below the center of the manifold  36 . The exhaust paths  361  have, for example, a circular cross section. 
     Around each of the processing spaces S 1  to S 4 , a guide member  362  used for exhaust is provided to surround each of the processing spaces S 1  to S 4 . The guide member  362  is, for example, an annular body, which is provided to surround a region around the stage  22  located at the processing position with an interval from the stage  22 . The guide member  362  is configured to form therein a flow path  363  having, for example, a rectangular vertical cross section and an annular shape in a plan view. In  FIG. 5 , the processing spaces S 1  to S 4 , the guide members  362 , the exhaust paths  361 , and the manifold  36  are schematically illustrated. 
     The guide members  362  form slit-shaped slit exhaust ports  364 , which are open toward respective processing spaces S 1  to S 4 . In this way, the slit exhaust ports  364  are formed in the side peripheral portions of respective processing spaces S 1  to S 4  in the circumferential direction. The exhaust paths  361  are connected to the flow paths  363 , and the processing gas exhausted from the slit exhaust ports  364  is allowed to flow toward the junction portion and the hole  351  below the center of the manifold  36 . 
     As illustrated in  FIG. 5 , the set of processing spaces S 1  and S 2  and the set of processing spaces S 3  and S 4  are arranged rotationally symmetrically by 180 degrees around the manifold  36  when viewed from the above. As a result, processing-gas flow paths extending from respective processing spaces S 1  to S 4  to the hole  351  via the slit exhaust ports  364 , the flow paths  363  in the guide members  362 , and the exhaust paths  361  are formed rotationally symmetrically by 180 degrees to surround the hole  351 . 
     The hole  351  is connected to the exhaust pipe  61  via the joined exhaust port  205  inside a thrust pipe  341  of a biaxial vacuum seal  34  arranged in the central portion of the processing container  20 . The exhaust pipe  61  is connected to a vacuum pump  62  constituting a vacuum exhaust mechanism via a valve mechanism  7 . One vacuum pump  62  is provided in, for example, one processing container  20 , and the exhaust pipes at the downstream sides of respective vacuum pumps  62  are joined and are connected to, for example, a factory exhaust system. 
     The valve mechanism  7  opens and closes the processing-gas flow path formed in each exhaust pipe  61 , and includes, for example, a casing  71  and an opening/closing part  72 . A first opening  73  connected to the exhaust pipe  61  located at the upstream side is formed in the upper surface of the casing  71 , and a second opening  74  connected to the exhaust pipe  61  located at the downstream side is formed in the side surface of the casing  71 . 
     The opening/closing part  72  includes, for example, an opening/closing valve  721  formed to have such a size as to close the first opening  73 , and a lifting mechanism  722  provided outside the casing  71  so as to raise and lower the opening/closing valve  721  inside the casing  71 . The opening/closing valve  721  is configured to be capable of being raised and lowered between a closing position (indicated by the alternating long and short dash line in  FIG. 6 ) at which the first opening  73  is closed and an opening position (indicated by the solid line in  FIG. 6 ) displaced below the first and second openings  73 . When the opening/closing valve  721  is located at the closing position, the downstream end of the joined exhaust port  205  is closed, and the exhaust of the interior of the processing container  20  is stopped. In addition, when the opening/closing valve  721  is located at the opening position, the downstream end of the joined exhaust port  205  is opened and the interior of the processing container  20  is exhausted. 
     Next, the biaxial vacuum seal  34  and the thrust nut  35  will be described. The biaxial vacuum seal  34  includes a thrust pipe  341 , bearings  342  and  344 , a rotor  343 , a main body  345 , magnetic fluid seals  346  and  347 , and a direct drive motor  348 . 
     The thrust pipe  341  is a non-rotating central axis and receives a thrust load applied to the upper center of the substrate processing apparatus  2  via the thrust nut  35 . That is, the thrust pipe  341  receives a vacuum load applied to the central portion of the substrate processing apparatus  2  when the interiors of the processing spaces S 1  to S 4  become a vacuum atmosphere, thereby suppressing the deformation of the upper portion of the substrate processing apparatus  2 . The thrust pipe  341  has a hollow structure, and the interior of the thrust pipe  341  forms the joined exhaust port  205 . The upper surface of the thrust pipe  341  is in contact with the bottom surface of the thrust nut  35 . In addition, the inner surface of the upper portion of the thrust pipe  341  and the outer surface of a convex portion at the inner peripheral side of the thrust nut  35  are sealed by an O-ring (not illustrated). The lower surface of the thrust pipe  341  is fixed to the main body  345  by bolts (not illustrated). 
     The outer peripheral side surface of the thrust nut  35  has a screw structure, and the thrust nut  35  is screwed to a partition wall of the central portion of the processing container  20 . The manifold  36  is provided above the central portion of the processing container  20 . The thrust load is received by the manifold  36 , the partition wall in the central portion of the processing container  20 , the thrust nut  35 , and the thrust pipe  341 . The lower surface of the manifold  36  is brought into partial contact with the upper surface of the thrust nut  35 . 
     The bearing  342  is a radial bearing that holds the rotor  343  at the side of the thrust pipe  341 . The bearing  344  is a radial bearing that holds the rotor  343  at the side of the main body  345 . The rotor  343  is arranged concentrically with the thrust pipe  341  and is a rotation axis in the center of the rotation arm  3 . In addition, the base member  33  is connected to the rotor  343 . When the rotor  343  rotates, the rotation arm  3 , that is, the end effectors  32  and the base member  33 , rotates. 
     The main body  345  accommodates therein the bearings  342  and  344 , the rotor  343 , the magnetic fluid seals  346  and  347 , and the direct drive motor  348 . The magnetic fluid seals  346  and  347  are arranged at the inner peripheral side and the outer peripheral side of the rotor  343 , and seal the processing spaces S 1  to S 4  from the outside. The direct drive motor  348  is connected to the rotor  343 , and drives the rotor  343  to rotate the rotation arm  3 . Further, the main body  345  is fixed to the bottom portion  27  (bottom surface) of the processing container  20  by bolts (not illustrated), and the thrust load applied to the thrust pipe  341  is received by the processing container  20  via the main body  345 . 
     In other words, the rotor  343  is an example of a rotation cylinder having a hollow interior, and corresponds to the outer cylinder of the biaxial vacuum seal  34 , which is an example of a coaxial magnetic fluid seal. The rotor  343  is disposed at a location equidistant from each of the processing spaces S 1  to S 4 . Meanwhile, the thrust pipe  341  is disposed in the hollow portion at the inner periphery side of the rotor  343 , and the joined exhaust port  205  inside the thrust pipe  341  is an example of the exhaust path and corresponds to the inner cylinder of the biaxial vacuum seal  34 . The upper surface of the thrust pipe  341  is fixed to the partition wall in the central portion of the processing container  20 , that is, the upper wall of the processing container  20  via the thrust nut  35 . That is, the thrust pipe  341  supports the manifold  36  against the bottom wall (the bottom portion  27 ) of the processing container  20 , via the partition wall in the central portion of the processing container  20  and the thrust nut  35 . 
     In this way, in the biaxial vacuum seal  34 , the thrust pipe  341 , which is the non-rotating central axis as a first axis, serves as a gas exhaust pipe while supporting the load of the upper portion of the processing container  20 , and the rotor  343  as a second axis serves to rotate the rotation arm  3 . 
     [Modification 1] 
     In the embodiments described above, the rotation arm  3  is rotated clockwise by 180 degrees to transfer the wafer W in the processing space S 1  to the processing space S 3  and to transfer the wafer W in the processing space S 2  to the processing space S 4 . However, the rotation arm  3  may be divided into two arms which may rotate independently from each other. This embodiment will be described as Modification 1. 
       FIG. 7  is an exploded perspective view illustrating an example of a configuration of a substrate processing apparatus in Modification 1. As illustrated in  FIG. 7 , a substrate processing apparatus  2   a  of Modification 1 includes rotation arms  3   a  and  3   b , instead of the rotation arm  3  of the embodiment. Although not illustrated, the substrate processing apparatus  2   a  includes a triaxial vacuum seal, instead of the biaxial vacuum seal  34 . Since the configuration of the substrate processing apparatus  2   a  of Modification 1 is the same as that of the substrate processing apparatus  2  of the embodiment, except for the rotation arms  3   a  and  3   b  and the triaxial vacuum seal that drives the rotation arms  3   a  and  3   b , descriptions thereof will be omitted. 
     The rotation arm  3   a  includes two end effectors  32   a  capable of holding wafers W to be placed on two stages  22  (the set of processing spaces S 1  and S 3  or the set of processing spaces S 2  and S 4 ), respectively, which are rotationally symmetric with respect to the center position of the two-row and two-column layout, among the stages  22 , and a base member  33   a  the rotation axis of which is located at the center position of the two-row and two-column layout. The two end effectors  32   a  are connected to the base member  33   a  to be rotationally symmetric with each other, that is, to be linearly arranged. 
     Similarly to the rotation arm  3   a , the rotation arm  3   b  includes two end effectors  32   b  capable of holding wafers W to be placed on the two stages  22  (the set of processing spaces S 1  and S 3  or the set of processing spaces S 2  and S 4 ), respectively, which are rotationally symmetric with respect to the center position of the two-row two-column layout, among the stages  22 , and a base member  33   b , the rotation axis of which is located at the center position of the two-row and two-column layout. The two end effectors  32   b  are connected to the base member  33   b  to be rotationally symmetric with each other, that is, to be linearly arranged. 
     The triaxial vacuum seal is an example of a coaxial magnetic fluid seal in which a rotation axis corresponding to the rotor  343  of the biaxial vacuum seal  34  is divided into two first and second rotation cylinders rotatable independently of each other. The first and second rotation cylinders are arranged coaxially with the thrust pipe  341 . The second rotation cylinder is disposed outside the first rotation cylinder. That is, the first rotation cylinder is an example of a first outer cylinder of the triaxial vacuum seal, and the second rotation cylinder is an example of a second outer cylinder of the triaxial vacuum seal. 
     In the substrate processing apparatus  2   a , for example, the rotation arm  3   a  is connected to the first rotation cylinder, and the rotation arm  3   b  is connected to the second rotation cylinder. As a result, the rotation arms  3   a  and  3   b  are rotatable independently of each other. That is, by rotating the rotation arms  3   a  and  3   b  at different rotation angles, it is possible to transfer wafers W between adjacent processing spaces (reactors) even when the pitches Px and Py of the stages  22  are different from each other. That is, in the substrate processing apparatus  2   a , wafers W can be transferred, for example, from the processing space S 1  to the processing space S 2 , from the processing space S 2  to the processing space S 3 , from the processing space S 3  to the processing space S 4 , or from the processing space S 4  to the processing space S 1 . 
     [Modification 2] 
     In the embodiment described above, the inner wall of the thrust pipe  341  serves as the wall surface of the joined exhaust port  205 . However, a gas pipe having a heater may be provided inside the thrust pipe  341 . This embodiment will be described as Modification 2. 
       FIG. 8  is a partial enlarged view illustrating an example of a cross section of the vicinity of the joined exhaust port in Modification 2. As illustrated in  FIG. 8 , in Modification 2, a gas pipe  352  is provided inside the thrust pipe  341 . That is, the gas pipe  352  is the innermost cylinder disposed more inward of the thrust pipe  341  that corresponds to the inner cylinder of the coaxial magnetic fluid seal. The gas pipe  352  has a hollow structure, and the interior of the gas pipe  352  forms the joined exhaust port  205 . A sheet-shaped heater  353  is provided on the outer side surface of the gas pipe  352 . The gas pipe  352  does not rotate like the thrust pipe  341 . The upper outer periphery side of the gas pipe  352  is in contact with the inner periphery side of the thrust nut  35 . A space between the outer surface of the upper portion of the gas pipe  352  and the inner peripheral surface of the thrust nut  35  is sealed by an O-ring (not illustrated). The lower portion of the gas pipe  352  is in contact with the upper portion of the exhaust pipe  61  via a heat insulator (not illustrated), and is sealed by an O-ring (not illustrated). 
     The heater  353  uniformly heats the gas pipe  352  to a temperature of, for example, 180 degrees C. By performing the heating control of the gas pipe  352  using the heater  353 , the adhesion of deposits to the inner wall of the gas pipe  352  (facing the joined exhaust port  205  side) can be suppressed. The heater  353  is provided with a plurality of control regions to be able to heat only portions desired to be heated. When heating the gas pipe  352 , the heater  353  also heats the thrust pipe  341  by radiation. Since the temperature of the thrust pipe  341  rises due to the radiation heating by the heater  353 , the adhesion of deposits to the surface (outer surface) of the thrust pipe  341  facing the processing spaces S 1  to S 4  may be suppressed. 
     That is, in Modification 2, one axis of the rotor  343  among the three axes is rotatable, and the two axes of the thrust pipe  341  and the gas pipe  352  are fixed, at the center of the processing container  20 . The gas pipe  352  and the heater  353  in Modification 2 may be combined with the triaxial vacuum seal of Modification 1 to implement four axes. In this case, in the central portion of the processing container  20 , among the four axes, the two axes of the first and second rotation cylinders that correspond to the rotation arms  3   a  and  3   b  are rotatable, and the other two axes of the thrust pipe  341  and the gas pipe  352  are fixed. 
     In addition, in the above-described embodiments, the direct drive motor  348  is used as a method of driving the rotor  343  in the biaxial vacuum seal  34 , but the present disclosure is not limited thereto. For example, the rotor  343  may be provided with a pulley and may be driven using a timing belt from a motor provided outside the biaxial vacuum seal  34 . A gear driving may be used by fitting a gear provided in the rotor  343 , which is the outer cylinder, with a gear of a motor provided outside. Similarly, in the method of driving the first and second rotation cylinders in the triaxial vacuum seal, any of the driving by the direct drive motor, the driving by the timing belt, and the driving by the gear may be used. 
     As described above, according to the embodiments of the present disclosure, the substrate processing apparatus  2  includes the vacuum processing container (the processing container  20 ) and the rotation arm  3  having a rotation axis located at the center (central region) of the vacuum processing container. In the rotation arm  3 , the rotation cylinder having a hollow interior (the rotor  343 ) constitutes the rotary axis, and the hollow portion of the rotation cylinder constitutes an exhaust path (the joined exhaust port  205 ) of the vacuum processing container. As a result, it is possible to achieve both the installation of the rotation mechanism of the rotation arm  3  (the rotor  343  and the direct drive motor  348 ) in the central portion of the vacuum processing container and the simplification of the exhaust path. 
     In addition, according to the embodiments, the rotation cylinder is configured with the outer cylinder (the rotor  343 ) of the coaxial magnetic fluid seal (the biaxial vacuum seal  34 ), and the exhaust path is configured with the inner cylinder (the thrust pipe  41 ) of the coaxial magnetic fluid seal. As a result, it is possible to achieve both the installation of the rotation mechanism of the rotation arm  3  in the central portion of the vacuum processing container and the simplification of the exhaust path. 
     According to the embodiments, the rotation cylinder is configured with the outer cylinder of the coaxial magnetic fluid seal, and the exhaust path is configured with the innermost cylinder (the gas pipe  352 ) disposed more inward of the inner cylinder of the coaxial magnetic fluid seal. As a result, the adhesion of deposits to the inner cylinder of the coaxial magnetic fluid seal can be suppressed. 
     According to the embodiments, the rotation cylinder includes the first and second rotation cylinders, the outer cylinder includes the first outer cylinder and the second outer cylinder disposed outside the first outer cylinder, the first rotation cylinder is configured with the first outer cylinder, and the second rotation cylinder is configured with the second outer cylinder. As a result, even when the pitches Px and Py of the plurality of processing spaces (reactors) are different from one another, wafers W can be transferred between adjacent processing spaces. 
     According to the embodiments, the first and second outer cylinders are rotatable independently of each other. As a result, even when the pitches Px and Py of the plurality of processing spaces (reactors) are different from one another, wafers W can be transferred between adjacent processing spaces. 
     According to the embodiments, the lower end of the inner cylinder is fixed to the bottom wall of the vacuum processing container, and the upper end of the inner cylinder is fixed to the upper wall of the vacuum processing container. As a result, the deformation of the vacuum processing container can be suppressed. The bottom wall and the upper wall to which the inner cylinder is fixed are not limited strictly to the bottom wall and the upper wall. For example, in addition to a case in which the inner cylinder is fixed directly to the bottom wall and the upper wall, a case in which the inner cylinder is indirectly fixed to the bottom wall and the upper wall via an intermediate member between the inner cylinder and the bottom wall/the upper wall may also be included as long as the load of the upper wall is supported by the bottom wall via the inner cylinder. 
     According to the embodiments, the plurality of processing spaces S 1  to S 4  are formed inside the vacuum processing container, and the rotation axis is disposed at a location equidistant from each of the plurality of processing spaces S 1  to S 4 . As a result, wafers W can be transferred among the processing spaces S 1  to S 4  using the rotation arm  3 . 
     According to the embodiments, the rotation arm  3  includes the end effectors  32  capable of holding the same number of wafers W as that of the plurality of processing spaces S 1  to S 4 . As a result, the wafers W in the respective processing spaces S 1  to S 4  can be transferred at the same time. 
     According to the embodiments, the vacuum processing container includes the exhaust manifold (the manifold  36 ) for connecting the plurality of processing spaces S 1  to S 4  to the exhaust path, and the inner cylinder of the coaxial magnetic fluid seal supports the exhaust manifold against the bottom wall. As a result, the deformation of the vacuum processing container can be suppressed. 
     According to the embodiments, the rotation cylinder rotates when the outer cylinder of the coaxial magnetic fluid seal is driven by the direct drive motor  348 . As a result, the driving part of the rotation arm  3  can be miniaturized. 
     According to the embodiments, the innermost cylinder is heated by the heater  353 . As a result, the adhesion of deposits to the inner wall of the gas pipe  352  can be suppressed. 
     According to the embodiments, the inner cylinder is heated by the heater  353  through radiation. As a result, the adhesion of deposits to the surface of the inner cylinder (the thrust pipe  341 ) that faces the processing spaces S 1  to S 4  can be suppressed. 
     According to the embodiments, the lower end of the innermost cylinder is fixed to the exhaust pipe  61  of the exhaust path, and the upper end of the innermost cylinder is fixed to the upper wall of the vacuum processing container. As a result, the adhesion of deposits in the exhaust path (the joined exhaust port  205 ) up to the exhaust pipe  61  can be suppressed. 
     According to the present disclosure, it is possible to achieve both installation of a rotation mechanism of a rotation arm in a central portion of a vacuum processing container and simplification of an exhaust path. 
     It should be understood that the embodiments disclosed herein are illustrative and are not limiting in all aspects. The above-described embodiments may be omitted, replaced, or modified in various forms without departing from the scope and spirit of the appended claims. 
     For example, in the embodiments described above, an example in which the substrate processing apparatus  2  is an apparatus that performs a plasma CVD process as substrate processing has been described, but the technique disclosed herein may be applied to any apparatus that performs other substrate processing such as plasma etching.