Patent Publication Number: US-2023141856-A1

Title: In-vacuum twin-arm robot

Description:
TECHNICAL FIELD 
     The present invention relates to a twin-arm robot that transports wafers in a vacuum space. 
     BACKGROUND ART 
     Conventionally, a twin-arm robot for wafer transportation is known, which picks up and transports wafers from wafer storage devices, processing devices, etc. PTL 1 discloses this type of twin-arm substrate transfer apparatus. 
     The twin-arm substrate transfer apparatus of PTL 1 comprises a drive section, an upper arm, a first forearm, and a second forearm. One end of the upper arm is rotatably connected to the drive section. The first forearm and the second forearm are connected to the upper arm and can be rotated with respect to the upper arm. 
     CITATION LIST 
     Patent Literature 
     PTL 1: U.S. Pat. No. 7,578,649 
     SUMMARY OF THE INVENTION 
     Problem to Be Solved by the Invention 
     In the configuration of the above PTL 1, a second support shaft to which the second forearm is fixed is provided within the first hollow support shaft to which the first forearm is fixed. Therefore, when the end-effectors mounted on the first forearm and the second forearm are equipped with sensors, etc., it is difficult to place harnesses, etc. for output/input of electrical signals inside the twin-arm substrate transfer apparatus. 
     The present invention has been made in view of the circumstances described above, and its purpose is to provide an in-vacuum twin arm robot that can effectively utilize internal space. 
     Solution to the Problem and Effect 
     Problems to be solved by the present invention are as described above, and next, means for solving the problems and effects thereof will be described. 
     According to the first aspect of the present invention, an in-vacuum twin-arm robot having the following configuration is provided. That is, this in-vacuum twin-arm robot is used to transport substrates in a sealed vacuum space. The in-vacuum twin-arm robot comprises a base arm, a first arm, a second arm, a first hand, and a second hand. The base arm can move vertically and can rotate. The first arm can rotate with respect to the base arm. The second arm can rotate with respect to the base arm. The first hand can rotate with respect to the first arm, and the first hand holds and transports a substrate. The second hand can rotate with respect to the second arm, and the second hand holds and transports a substrate. The first arm and the second arm are rotatably mounted on a leading end of the base arm via a joint shaft formed hollow. An angle of the first hand with respect to the first arm and an angle of the second hand with respect to the second arm can be changed independently of each other. 
     This allows for efficient use of the internal space of the joint shaft. Therefore, it can realize miniaturization of the in-vacuum twin-arm robot. In addition, by the independent drive of the two hands, it can realize a variety of movements of the in-vacuum twin-arm robot. 
     According to the second aspect of the present invention, an in-vacuum twin-arm robot having the following configuration is provided. That is, this in-vacuum twin-arm robot is used to transport substrates in a sealed vacuum space. The in-vacuum twin-arm robot comprises a base arm, a first arm, a second arm, a first hand, and a second hand. The base arm can move vertically and can rotate. The first arm can rotate with respect to the base arm. The second arm can rotate with respect to the base arm. The first hand can rotate with respect to the first arm, and the first hand holds and transports a substrate. The second hand can rotate with respect to the second arm, and the second hand holds and transports a substrate. The first arm and the second arm are rotatably mounted on a leading end of the base arm via a joint shaft formed hollow. A length of the base arm is greater than a length of the first arm and greater than a length of the second arm. 
     This allows for efficient use of the internal space of the joint shaft. Therefore, it can realize miniaturization of the in-vacuum twin-arm robot. In addition, the access distance for the robot is greater, allowing it to flexibly adapt to the layout of the surrounding chamber. 
     Effect of the Invention 
     The invention provides an in-vacuum twin-arm robot that can effectively utilize internal space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic plan view showing a semiconductor processing facility equipped with an in-vacuum twin-arm robot according to one embodiment of the present invention. 
         FIG.  2    is a diagonal view showing a configuration of the in-vacuum twin-arm robot. 
         FIG.  3    is a partial cross-sectional view showing an inside of the in-vacuum twin-arm robot. 
         FIG.  4    is a plan view showing a movement of the in-vacuum twin-arm robot. 
         FIG.  5    is a plan view showing a movement of the in-vacuum twin-arm robot. 
         FIG.  6    is a plan view showing a movement of the in-vacuum twin-arm robot. 
         FIG.  7    is a plan view showing a movement of the in-vacuum twin-arm robot. 
     
    
    
     EMBODIMENT FOR CARRYING OUT THE INVENTION 
     Next, an embodiment of the present invention will be described with reference to drawings.  FIG.  1    is a schematic plan view showing a semiconductor processing system  100  equipped with an in-vacuum twin-arm robot  1  according to one embodiment of the present invention.  FIG.  2    is a diagonal view showing a configuration of the in-vacuum twin-arm robot  1 .  FIG.  3    is a partial cross-sectional view showing the inside of the in-vacuum twin-arm robot  1 . 
     The semiconductor processing system  100  shown in  FIG.  1    applies various predetermined processes to a wafer  10 , which is an object to be processed in the system. The wafer  10  may be any of the following: raw materials of the wafer  10 , semi-finished products undergoing processing, and finished products that have been processed. The wafer  10  in this embodiment is disc-shaped, but is not limited to this. 
     Various process treatments applied to the wafer  10  may include, for example, cleaning, film deposition, resist coating, exposure, development, etching, impurity implantation, impurity activation, resist stripping, and others. 
     The semiconductor processing system  100  mainly includes a storage unit  101 , a processing unit  102 , and a control unit (robot controller)  103 . 
     The storage unit  101  includes an in-vacuum twin-arm robot  1 , a plurality of load ports  2 , and a plurality of storage devices  3 . In this embodiment, the storage unit  101  includes six load ports  2  and storage devices  3 . However, this is an example, and the number of load ports  2  and storage devices  3  can be increased or decreased as necessary. In the following description, the in-vacuum twin-arm robot  1  included by the storage unit  101  may be referred to as storage-side robot  1   a.    
     In the storage unit  101 , a space sealed against the external environment is formed. The interior of the space is filled with a predetermined gas. This gas can be, for example, nitrogen gas. Because the amount of this gas filled is quite small, the interior of the storage unit  101  is in a substantial vacuum. 
     The storage-side robot  1   a  is configured as a horizontal articulated robot, for example. The storage-side robot  1   a  is used for transferring the wafers  10 . This transfer includes carrying the wafers  10  into and out of the storage device  3 . The storage-side robot  1   a  is arranged in a storage preparation chamber  30  formed in the storage unit  101 . The specific configuration of this in-vacuum twin-arm robot  1  (storage-side robot  1   a ) will be described later. 
     The load ports  2  are provided on the outside of the walls that make up the storage preparation chamber  30 . In this embodiment, the six load ports  2  are arranged to surround the storage preparation chamber  30  in three directions. Each load port  2  includes an opening/closing door  2   a  that can be opened and closed to the storage preparation chamber  30 . The storage device  3  is set in each load port  2 . 
     The storage device  3  can store a plurality of wafers  10  in a vertically stacked manner. The storage device  3  is configured as a FOUP, for example. FOUP is an abbreviation for Front Opening Unified Pod. The storage device  3  includes a lid that can be opened and closed, which is not shown. 
     The opening and closing of the lid of the storage device  3  is linked to the opening and closing of the opening/closing door  2   a  of the load port  2 . When the lid of the storage device  3  and the opening/closing door  2   a  of the load port  2  are opened, the interior space of the storage device  3  and the interior space of the storage preparation chamber  30  are connected to each other. In this state, the in-vacuum twin-arm robot  1  can hold the wafer  10  and carry it in and out of the storage device  3 . The opening and closing of the lid of the storage device  3  and the opening/closing door  2   a  of the load port  2  are controlled, for example, by the control unit  103 . 
     In the processing unit  102 , a space sealed against the external environment is formed. As in the storage unit  101 , this space is filled with a small amount of the predetermined gas. Thus, the interior of the processing unit  102  is in a substantial vacuum. 
     The processing unit  102  includes the in-vacuum twin-arm robot  1  and a plurality of processing devices  4 . In the following description, the in-vacuum twin-arm robot  1  included by the processing unit  102  may be referred to as process-side robot  1   b.    
     The process-side robot  1   b  has the same configuration as the storage-side robot  1   a . The process-side robot  1   b  is arranged in the approximate center of the processing preparation chamber  40  formed in the processing unit  102 . 
     The processing device  4  performs at least one of the above process treatments on the wafer  10 . This processing is performed in a vacuum. 
     Between the storage unit  101  and the processing unit  102 , a plurality of PASS chambers  5  are provided. The PASS chamber  5  functions as a stage for passing the wafer  10 . The number of PASS chambers  5  is two in this embodiment. However, this is not limited to this, and the number of PASS chambers  5  can be increased or decreased as necessary. 
     Each PASS chamber  5  includes a first door  51  and a second door  52 . The first door  51  can open and close to the storage preparation chamber  30 . When the first door  51  is opened, the PASS chamber  5  and the storage preparation chamber  30  are connected to each other. The second door  52  can open and close to the processing preparation chamber  40 . When the second door  52  is opened, the PASS chamber  5  and the processing preparation chamber  40  are connected to each other. The opening and closing of the first door  51  and the second door  52  are controlled by the control unit  103 . 
     With the storage preparation chamber  30  and the PASS chamber  5  spatially connected, the storage-side robot  1   a  can transport the wafers  10  between the PASS chamber  5  and the storage preparation chamber  30 . With the processing preparation chamber  40  and the PASS chamber  5  spatially connected, the process-side robot  1   b  can transport the wafers  10  between the PASS chamber  5  and the processing preparation chamber  40 . 
     The control unit  103  is configured as, for example, a known computer. This computer includes an arithmetic unit such as a CPU, and a memory unit including HDD, ROM, RAM, and the like. The memory unit stores, for example, programs for controlling the in-vacuum twin-arm robot  1  and various control information. The arithmetic unit controls the opening/closing movement of the opening/closing door  2   a  of the load port  2 , the lid of the storage device  3 , the first door  51  and the second door  52  of the PASS chamber  5 , etc. by executing the program stored in the storage unit. Furthermore, the arithmetic unit of the control unit  103  controls the movements of the in-vacuum twin-arm robot  1 . The control unit that controls the in-vacuum twin-arm robot  1  can be provided separately from the control unit  103 . 
     The configuration of the in-vacuum twin-arm robot  1  is then described in detail with reference to  FIG.  2    and  FIG.  3   .  FIG.  2    is the diagonal view showing an example of the configuration of the in-vacuum twin-arm robot  1 .  FIG.  3    is the cross-sectional view illustrating the internal structure of the in-vacuum twin-arm robot  1 . 
     As shown in  FIG.  2   , the in-vacuum twin-arm robot  1  includes mainly a base  11 , a base arm  12 , a first arm  13 , a second arm  14 , a first hand  15 , and a second hand  16 . 
     The base  11  serves as a base member to support a plurality of arms and hands included by the in-vacuum twin-arm robot  1 . The base  11  is fixed, for example, to a wall or bottom plate comprising the storage preparation chamber  30  (processing preparation chamber  40 ). The base  11  is provided with an elevation shaft  17 . 
     The elevation shaft  17  is provided to be elevated and lowered along its axis. The elevation shaft  17  is elevated and lowered, for example, by an elevation drive source (not shown) provided inside the base  11 . The base arm  12  is connected to an upper end of the elevation shaft  17 . 
     In the following description, when the base arm  12 , the first arm  13 , and the second arm  14  are extended in a straight line, an end of each arm on a side near the elevation shaft  17  is referred to as “base end” and an end of each arm on a side far from the elevation shaft  17  is referred to as “leading end”. 
     The base arm  12  is configured as an elongated member that extends in a horizontal straight line. One end (base end) of the base arm  12  in the longitudinal direction is fixed to the upper end of the elevation shaft  17 . The base arm  12  and the elevation shaft  17  are rotatably supported around an axis (vertical axis) of the elevation shaft  17 . The first arm  13  and the second arm  14  are arranged at the other end (leading end) of the base arm  12  in the longitudinal direction. 
     The rotational movement of the base arm  12  is performed, for example, by a base arm drive unit  12   a  provided at the lower end of the elevation shaft  17 . The base arm drive unit  12   a  includes, for example, an electric motor, a gear box, and the like. The power from the base arm drive unit  12   a  is transmitted to the base arm  12  via the elevation shaft  17 . 
     The configuration in which the base arm  12  is elevatable and rotatable with respect to the base  11  is not limited to the above configuration. For example, the base arm  12  also can be rotatably supported relative to the elevation shaft  17 , and the elevation shaft  17  may be configured to only elevate and lower with respect to the base  11 . 
     In  FIG.  1   , the length of the base arm  12  of the process-side robot  1   b  and the length of the storage-side robot  1   a  are depicted as being equal. However, in reality, the base arm  12  of the process-side robot  1   b  is longer than the base arm  12  of the storage-side robot  1   a . Thus, the access distance by the base arm  12 , the first arm  13 , and the second arm  14  realized by the process-side robot  1   b  can be longer than that of the storage-side robot  1   a .  FIG.  3    shows an example that the length L 1  of the base arm  12  is longer than the length L 2  of the first arm  13  and longer than the length L 2  of the second arm  14  (L 1 &gt;L 2 ). The longer accessible distance allows the wafers  10  to be transported between locations farther away from each other without the need for a special configuration such as a mechanism to move the base  11  horizontally. 
     The left side of  FIG.  1    shows an example where the number of load ports  2  arranged around the storage-side robot  1   a  is six. Four of the six load ports  2  are arranged in two pairs facing each other. The distance between the opposing load ports  2  in each pair is equal among the pairs. 
     The right side of  FIG.  1    shows an example where the number of the processing devices  4  arranged around the process-side robot  1   b  is ten. Eight of the ten processing devices  4  are arranged in four pairs facing each other. The distance between the opposing processing devices  4  in each pair is equal among the pairs. 
     As shown in  FIG.  1   , in the plan view, the load ports  2  or the processing devices  4  are lined up to form three sides of a rectangle, and the robot  1  is arranged approximately in the center of the rectangle. This layout has the advantage of utilizing factory space more efficiently than a layout in which the load ports  2  or processing devices  4  are lined up to form a circle. 
     In particular, by the process-side robot  1   b  , the length L 1  of the base arm  12  is longer than the length L 2  of the first arm  13  and longer than the length L 2  of the second arm  14 . Thus, the access distance can be increased. 
     Therefore, the process-side robot  1   b  can appropriately handle the case where a relatively large number of source/destination location of transportation are arranged. 
     As shown in  FIG.  3   , the base arm  12  is formed into a hollow shape. The base arm  12  of this embodiment is formed so that its vertical dimension (thickness) is smaller than the first arm  13  and the second arm  14 , which will be described later. In the inner wall of the base arm  12  is provided with a rigid metal (not shown). This increases the mechanical strength of the base arm  12 . 
     This configuration allows the in-vacuum twin-arm robot  1  to be compactly formed in the height direction. Therefore, the semiconductor processing system  100  can be made compact overall. In addition, since the thickness of the base arm  12  is small, the reference height at which the first arm  13  and the second arm  14  are mounted (i.e., the height of the top surface of the base arm  12 ) can be lowered. As a result, the access height of the first hand  15  and the second hand  16  (described later) mounted respectively to the first arm  13  and the second arm  14  can be lowered. 
     The first arm  13  is configured as an elongated member that extends in a horizontal straight line. One end (the base end) of the first arm  13  in the longitudinal direction is mounted on the leading end of the base arm  12 . The first arm  13  is supported to rotate around an axis (vertical axis) parallel to the elevation shaft  17 . The first hand  15  is mounted to the other end (the leading end) of the first arm  13  in the longitudinal direction. 
     As shown in  FIG.  3   , the first arm  13  has a predetermined thickness and is formed into a hollow shape. A first arm gear box  13   a  is provided inside the first arm  13 . An electric motor and reduction gear, which are not shown, are installed inside the first arm gear box  13   a . The first arm gear box  13   a  can rotate the first arm  13  with respect to the base arm  12  by the driving force of the electric motor. 
     A first hand gear box  15   a  is provided inside the first arm  13 . An electric motor and reduction gear, which are not shown, are installed inside the first hand gear box  15   a . The first hand gear box  15   a  can rotate the first hand  15  with respect to the first arm  13  by a driving force of the electric motor. 
     Like the first arm  13 , the second arm  14  is configured as an elongated member that extends in a horizontal straight line. The second arm  14  is provided above the first arm  13 . One end (the base end) of the second arm  14  in the longitudinal direction is mounted on the base end of the first arm  13  (the leading end of the base arm  12 ). The second arm  14  is supported to rotate around an axis (vertical axis) parallel to the elevation shaft  17 . The second hand  16  is mounted on the other end (the leading end) of the second arm  14  in the longitudinal direction. 
     As shown in  FIG.  3   , the second arm  14  has a predetermined thickness and is formed into a hollow shape. A second arm gear box  14   a  is provided inside the second arm  14 . The configuration of the second arm gear box  14   a  is the same as that of the first arm gear box  13   a . The second arm gear box  14   a  can rotate the second arm  14  with respect to the base arm  12  by a driving force of an electric motor. 
     A second hand gear box  16   a  is provided inside the second arm  14 . The configuration of the second hand gear box  16   a  is the same as that of the first hand gear box  15   a . The second hand gear box  16   a  can rotate the second hand  16  with respect to the second arm  14  by a driving force of an electric motor. 
     As shown in  FIG.  2    and  FIG.  3   , the first arm  13  and the second arm  14  are connected to the base arm  12  via an elbow shaft (joint shaft)  18 . The elbow shaft  18  is parallel to the elevation shaft  17 . The elbow shaft  18  is formed in a hollow cylindrical shape. 
     As shown in  FIG.  3   , magnetic fluid seals  6  are provided at predetermined locations on an outer circumference of the elbow shaft  18 . These predetermined locations are, for example, the connection points between the elbow shaft  18  and each of the base arm  12 , the first arm  13 , and the second arm  14  respectively. This allows the interior space of the in-vacuum twin-arm robot  1  to be sealed. Thus, air inside the in-vacuum twin-arm robot  1  can be prevented from leaking to the outside (storage preparation chamber  30  or processing preparation chamber  40 ). 
     As shown in  FIG.  3   , a first gear  13   b  and a second gear  14   b  as transmission members are mounted on the outer circumference of the elbow shaft  18 . The first gear  13   b  is used to transmit a driving force from the electric motor (not shown) included by the first arm gear box  13   a  to the first arm  13 . The second gear  14   b  is used to transmit a driving force from the electric motor (not shown) included by the second arm gear box  14   a  to the second arm  14 . In other words, the first gear  13   b  and the second gear  14   b  constitute a drive transmission mechanism that transmits the driving force from the electric motor to the first arm  13  and the second arm  14 . The drive transmission mechanism is not limited to the use of gears, but can also be, for example, a belt. In this case, a pulley as a transmission member is mounted on the outer circumference of the elbow shaft  18 . 
     Specifically, the first gear  13   b  is fixed to the outer circumference of the elbow shaft  18 . The first gear  13   b  meshes with the output gear (not shown) provided by the first arm gear box  13   a . Since the first arm gear box  13   a  is fixed to the first arm  13 , the first arm  13  rotates with respect to the first gear  13   b  (elbow shaft  18 ) by the driving of the motor in the first arm gear box  13   a.    
     The second gear  14   b  is fixed to the outer circumference of the elbow shaft  18 . The second gear  14   b  meshes with the output gear (not shown) provided by the second arm gear box  14   a . Since the second arm gear box  14   a  is fixed to the second arm  14 , the second arm  14  rotates with respect to the second gear  14   b  (elbow shaft  18 ) by the driving of the motor in the second arm gear box  14   a.    
     As shown in  FIG.  2    etc., the first hand  15  is formed in a shape branched into two branches. The wafer  10  can be held at each of tip ends of the branches the first hand  15 . Thus, the first hand  15  can hold two wafers  10  at the same time. The first hand  15  can simultaneously transfer the wafers  10  to each of the two storage devices  3  adjacent to each other or each of the two PASS chambers  5  adjacent to each other. 
     The first hand  15  can hold and can release the holding of the wafer  10 . The wafer  10  can be held by the first hand  15  in various ways, such as by placing the wafer  10  on the first hand  15  or by clamping the wafer  10  by the first hand  15 . 
     The second hand  16  is also configured in the same way as the first hand  15  and can hold two wafers  10  at the same time. 
     The first hand  15  is rotatably mounted on the leading end of the first arm  13 . The first hand  15  is arranged above the first arm  13  and adjacent to the first arm  13 . 
     A gear (not shown) is fixed to the first hand  15 . This gear meshes with an output gear (not shown) provided by the first hand gear box  15   a . Since the first hand gear box  15   a  is fixed to the first arm  13 , the first hand  15  rotates with respect to the first arm  13  by the driving of the motor in the first hand gear box  15   a.    
     The second hand  16  is rotatably mounted on the leading end of the second arm  14 . The second hand  16  is arranged below the second arm  14  and adjacent to the second arm  14 . 
     The second hand  16  rotates with respect to the second arm  14  by the driving of the second hand gear box  16   a . Since this configuration is substantially the same as the configuration in which the first hand  15  is driven by the first hand gear box  15   a , the explanation is omitted. 
     As described above, in this embodiment of the in-vacuum twin-arm robot  1 , the second arm  14 , the second hand  16 , the first hand  15 , and the first arm  13  are arranged in order from top to bottom. This configuration allows the first hand  15  and the second hand  16  to be arranged close to each other in the height direction. Therefore, for example, when two wafers  10 , which are located adjacent to each other in the vertical direction, are respectively taken out while switching the two hands and transported, the elevating distance of the elevation shaft  17  can be extremely shortened. Therefore, the operating efficiency of the in-vacuum twin-arm robot  1  can be improved. 
     In this embodiment of the in-vacuum twin-arm robot  1 , electric motors for driving the elevation shaft  17 , the base arm  12 , the first arm  13 , the second arm  14 , the first hand  15 , and the second hand  16  are provided respectively. The drive of each electric motor is independently controlled by the control unit  103 . That is, the elevation shaft  17 , the base arm  12 , the first arm  13 , the second arm  14 , the first hand  15 , and the second hand  16  are driven independently by controlling of the control unit  103 . 
     This allows for greater freedom of movement of the first hand  15  and the second hand  16 . For example, the in-vacuum twin-arm robot  1  can be flexibly adapted to either the six-chamber layout shown on the left side of  FIG.  1    or the ten-chamber layout shown on the right side. 
     In the processing unit  102  shown on the right side of  FIG.  1   , in the plan view, ten processing devices  4  are arranged in four, two, and four to form three sides of an elongated rectangle. The processing device  4  located in the corner of the rectangle is relatively far from the base  11 . 
     In this process-side robot  1   b  , which is located in the processing unit  102 , the length L 1  of the base arm  12  is longer than the length L 2  of the first arm  13  and longer than the length L 2  of the second arm  14 . In the process-side robot  1   b  , the base arm  12 , the first arm  13 , the second arm  14 , the first hand  15 , and the second hand  16  are driven independently of each other. 
     By the above configuration, even in the ten-chamber layout as described above and without a mechanism such as a moving shaft for moving the base  11  of the process-side robot  1   b  , the only one process-side robot  1   b  can move and transfer the wafer  10  to each processing device  4 . As a result, the equipment cost for the process-side robot  1   b  can be greatly reduced. In addition, the process-side robot  1   b  can swap the wafers  10  as workpieces without performing the swapping operation described later. Therefore, the wafers  10  can be swapped at high speed, and the throughput of processing can be improved. 
     Each of the first hand  15  and the second hand  16  is equipped with electrical components not shown, such as mapping sensors, cameras, etc. The in-vacuum twin-arm robot  1  includes a wiring harness  9  to provide electrical connections to these components. The wiring harness  9  includes power cables that supply power to the electrical components, signal cables that transmit input or output signals, and the like. 
     As shown in  FIG.  3   , this wiring harness  9  passes through the inside of the elevation shaft  17 , the base arm  12 , the elbow shaft  18 , and the first arm  13  or the second arm  14  to the first hand  15  or the second hand  16 . 
     In the in-vacuum twin-arm robot  1 , air flows in the internal space through which the wiring harness  9  passes. For example, when the processing device  4  performs processing at high temperatures, the process-side robot  1   b  , which transports the wafers  10 , may also become hot. However, by circulating air inside the in-vacuum twin-arm robot  1 , the temperature of the in-vacuum twin-arm robot  1  can be prevented from becoming excessively high. As a result, the wiring harness  9 , which is relatively easily affected by heat, can be passed through the interior space of the in-vacuum twin-arm robot  1 . 
     Here, the layout for driving the first arm  13  and the second arm  14  independently will be described. 
     If the first arm gear box  13   a  and the second arm gear box  14   a  are arranged in the base arm  12 , a drive transmission path (typically, a transmission shaft) to transmit the output of each gear box to the first arm  13  and the second arm  14  would need to be arranged in the elbow shaft  18 . Moreover, in order to drive each of the two arms independently, the transmission shaft needs to be, for example, doubly structured. 
     In this regard, in the in-vacuum twin-arm robot  1 , the first arm gear box  13   a  and the second arm gear box  14   a  are provided inside the first arm  13  and the second arm  14 . Therefore, the transmission of power to drive the first arm  13  and the second arm  14  is completed only by each gear box meshing with the first gear  13   b  and the second gear  14   b  fixed on the outer periphery of the elbow shaft  18 . Therefore, in this embodiment, there is no need to place a transmission shaft inside the elbow shaft  18 . 
     This allows for a larger internal space in the elbow shaft  18 . This space margin allows the wiring harness  9  to be placed in the elbow shaft  18  with some slack. This slack allows the wiring harness  9  to easily absorb the twisting when the first arm  13  and the second arm  14  rotate. As a result, the durability of the wiring harness  9  can be improved. 
     Next, the movement when the storage-side robot  1   a  accesses the PASS chamber  5  will be briefly described with reference to  FIGS.  4  to  7   .  FIGS.  4  to  7    are plan views of the movement of the in-vacuum twin-arm robot  1 . 
     In the plan view of  FIG.  4   , the first hand  15  is not shown because it is directly below the second hand  16  and overlaps exactly. 
       FIG.  4    shows the state of the second hand  16  just before it begins to move into the PASS chamber  5 . As shown in  FIG.  4   , the second hand  16  is positioned so that it is facing straight into the PASS chamber  5 . 
     In  FIG.  4   , the first hand  15  is in the same posture as the second hand  16 , and the first arm  13  is in the same posture as the second arm  14 . Thus, although the first arm  13  and the first hand  15  do not appear in  FIG.  4   , they are located directly below the second arm  14  and the second hand  16 . 
     Consider the case where the second hand  16  is moved in a straight line to advance into the PASS chamber  5  from the state shown in  FIG.  4   . In this case, as shown in  FIGS.  5  to  7   , the control unit  103  causes the first arm  13  and the first hand  15  to rotate following the rotation of the base arm  12 , the second arm  14  and the second hand  16  for realizing such a movement. 
     Specifically, the base arm  12  rotates clockwise as appropriate in  FIG.  4   . The second arm  14  rotates accordingly in conjunction with the rotation of the base arm  12  so that the leading end of the second arm  14  approaches the PASS chamber  5  side in a linear trajectory. The second hand  16  rotates appropriately so that the second hand  16  maintains a straight orientation toward the PASS chamber  5  even if the orientation of the second arm  14  changes. The above allows the second hand  16  to move in a straight line while maintaining the orientation of the second hand  16 . When the leading end of the second hand  16  reaches the PASS chamber  5 , the advancing movement is complete. 
     During the advancing process of the second hand  16  described above, the position of the leading end of the base arm  12  changes in an arc. As shown in  FIGS.  5  to  7   , the first arm  13  and the first hand  15 , which do not perform the advancing movement, rotate correspondingly with the rotation of the base arm  12 . 
     As shown in  FIGS.  5  to  7   , as the base arm  12  rotates, the angle between the base arm  12  and the first arm  13  changes so that the angle gradually increases. As the base arm  12  rotates, the angle between the first arm  13  and the first hand  15  changes so that the angle gradually decreases. 
     This movement allows the first arm  13  and the first hand  15  to be folded compactly, and their moving range can be kept within the range of the chain line circle shown in  FIGS.  4  to  7   . This allows the in-vacuum twin-arm robot  1  to be set up even in the storage preparation chamber  30 , which is a relatively small space, and be capable of accessing the storage devices  3  and the PASS chamber  5 . 
     The folded state means, for example, that the angle between the first arm  13  and the first hand  15  is 90° or less. However, it is not limited to this. 
     During the operation from  FIG.  4    to  FIG.  7   , the first hand  15  is bent at a large angle relative to the first arm  13 . Thus, at least a portion of the first hand  15  is, in the plan view (in other words, when viewed along the axis of the elbow shaft  18 ), overlapping the base arm  12 . 
     As described above, the control unit  103  independently drives each of the base arm  12 , the first arm  13 , the second arm  14 , the first hand  15 , and the second hand  16 . This allows the complex movement described above to be achieved. 
       FIG.  7    shows that the second hand  16  has completed its advancing movement and is ready to perform the transferring to the PASS chamber  5 . After transferring the wafer  10 , the second hand  16  performs a retreat movement. In this retreat movement, the base arm  12 , the first arm  13 , the second arm  14 , the first hand  15 , and the second hand  16  move in exactly the opposite way as in the above-mentioned advancing movement. The above allows the system to return to the state shown in  FIG.  4   . 
     The above is an example of moving the second hand  16  into and out of the PASS chamber  5 , instead of the second hand  16 , the first hand  15  can move into and out of the PASS chamber  5  from the state shown in  FIG.  4   . In this case, the operation of the first hand  15  and the second hand  16  in the above description are interchanged. 
     In summary, the state shown in  FIG.  4    is a state in which the first hand  15  can advance/retract relative to the PASS chamber  5 , while the second hand  16  can advance/retract relative to the PASS chamber  5 . Therefore, it can be said that the state shown in  FIGS.  4    is a base state common to both the first hand  15  and the second hand  16 . 
     Any of the first hand  15  and the second hand  16  can be advanced into the PASS chamber  5  from the state shown in  FIG.  4   . The control unit  103  controls each part so that when one of the first hand  15  and the second hand  16  is advanced, the other hand is rotated in a folded state (non-advanced state). The control unit  103  controls each part so that when one of the hands that is advancing retracts for returning to the original state ( FIG.  4   ), the other hand in the folded state rotates in the opposite direction for returning to the original state ( FIG.  4   ). 
     Thus, the storage-side robot  1   a  can access the PASS chamber  5  by the first hand  15  and the second hand  16  sequentially without requiring a special operation such as switching the accessing hand (swapping operation). Therefore, the access movement by each hand can be performed continuously, and the operating efficiency of the in-vacuum twin-arm robot  1  can be improved. 
     When the storage-side robot  1   a  accesses the storage preparation chamber  30  (storage device  3 ) located above, left, or below in  FIG.  4   , it also can operate in substantially the same manner as when accessing the PASS chamber  5  described above. 
     As described above, in this embodiment of the in-vacuum twin-arm robot  1 , a transmission shaft to the first arm  13  and the second arm  14  is not provided in the elbow shaft  18 . Therefore, the elbow shaft  18  can be formed thin. Thus, this can prevent interference between the elbow shaft  18  and the first hand  15 , even when the first hand  15  is bent strongly against the first arm  13 , as shown in  FIG.  7   , for example. Similarly, interference between the elbow shaft  18  and the second hand  16  can be prevented, even when the second hand  16  is bent strongly against the second arm  14 . Therefore, the range of movement can be made compact. 
     As described above, the in-vacuum twin-arm robot  1  of this embodiment is used to transport the wafers  10  in the sealed vacuum space (storage preparation chamber  30  or processing preparation chamber  40 ). The in-vacuum twin-arm robot  1  includes the base arm  12 , the first arm  13 , the second arm  14 , the first hand  15 , and the second hand  16 . The base arm  12  can move vertically and can rotate. The first arm  13  can rotate with respect to the base arm  12 . The second arm  14  can rotate with respect to the base arm  12 . The first hand  15  can rotate with respect to the first arm  13 , and the first hand  15  holds and transports the wafer  10 . The second hand  16  can rotate with respect to the second arm  14 , and the second hand  16  holds and transports the wafer  10 . The first arm  13  and the second arm  14  are rotatably mounted on the leading end of the base arm  12  via the elbow shaft  18  formed hollow. The angle of the first hand  15  with respect to the first arm  13  and the angle of the second hand  16  with respect to the second arm  14  can be changed independently of each other. 
     This allows for efficient use of the internal space of the elbow shaft  18 . Therefore, it can realize miniaturization of the in-vacuum twin-arm robot  1 . In addition, by the independent drive of the first hand  15  and the second hand  16 , it can realize a variety of movements of the in-vacuum twin-arm robot  1 . 
     At the in-vacuum twin-arm robot  1 , the length L 1  of the base arm  12  is longer than the length L 2  of the first arm  13  and longer than the length L 2  of the second arm  14 . 
     Thus, this allows a greater access distance for the in-vacuum twin-arm robot  1 . 
     At the in-vacuum twin-arm robot  1 , the base arm  12 , the first arm  13 , the second arm  14 , the first hand  15 , and the second hand  16  are each driven independently. 
     Thus, this allows complex operations to be realized by independent driving of each part, thereby reducing operation time, etc. 
     At the in-vacuum twin-arm robot  1 , the outer circumference of the elbow shaft  18  is provided with the first gear  13   b  and the second gear  14   b . The first gear  13   b  and the second gear  14   b  constitute the drive transmission mechanism that transmits the driving force to drive the first arm  13  and the second arm  14 . 
     Thus, it is not necessary to arrange the transmission shafts of the first arm  13  and the second arm  14  inside the elbow shaft  18 , ensuring a larger interior space of the elbow shaft  18 . 
     At the in-vacuum twin-arm robot  1 , the harness  9  to the first hand  15  and the second hand  16  pass through the inside of the elbow shaft  18 . 
     Thus, for example, when the first hand  15  and the second hand  16  are equipped with electrical components such as sensors, it is possible to easily secure the installation space of the harness  9  connected to these electrical components. 
     At the in-vacuum twin-arm robot  1 , the base arm  12 , the first arm  13 , and the second arm  14  are formed hollow. The interior space of each of the base arm  12 , the first arm  13 , and the second arm  14  is sealed against the storage preparation chamber  30  or processing preparation chamber  40 . Air flows through the interior space. 
     Thus, the in-vacuum twin-arm robot  1  can be cooled by the flowing air. 
     At the in-vacuum twin-arm robot  1 , the first arm gear box that drives the first arm  13  and the first hand gear box that drives the first hand  15  are located inside the first arm  13 . The second arm gear box that drives the second arm  14  and the second hand gear box that drives the second hand  16  are located inside the second arm  14 . 
     Thus, it is not necessary to arrange the gear box in the base arm  12 . Therefore, the base arm  12  can be formed thinner and the minimum access height of each hand can be lowered. 
     The in-vacuum twin-arm robot  1  includes the control unit  103 . The control unit  103  controls movements of each of the base arm  12 , the first arm  13 , the second arm  14 , the first hand  15 , and the second hand  16 . The control unit  103  controls, from the state of  FIG.  4   , to advance one of the first hand  15  and the second hand  16  (for example, the second hand  16 ) to the PASS chamber  5  and, in conjunction with its advancing, to rotate the other arm and hand (for example, the first arm  13  and the first hand  15  in  FIG.  7   ) in a folded state. In the state of  FIG.  4   , the first arm  13  and the second arm  14  are in the same posture and the first hand  15  and the second hand  16  are in the same posture. 
     Thus, when one of the first hand  15  and the second hand  16  is extended, the other arm and hand are rotated without being straightened, which makes the in-vacuum twin-arm robot  1  can operate in the narrow storage preparation chamber  30  or the narrow processing preparation chamber  40 . 
     At the in-vacuum twin-arm robot  1 , the control unit  103  controls one of the first hand  15  and the second hand  16  (for example, the second hand  16  in  FIG.  7   ), that is advancing to the PASS chamber  5 , to retract for returning to the state in  FIG.  4    and, in conjunction with its retracting, to rotate the other arm and hand (for example, the first arm  13  and the first hand  15  in  FIG.  7   ) in a folded state for returning to the state in  FIG.  4   . 
     Thus, the first hand  15  and the second hand  16  can continuously access operations without the swapping operation of the hand. Therefore, the operation efficiency of the in-vacuum twin-arm robot  1  can be improved. 
     Although the preferred embodiment of the present invention has been described above, the configurations described above may be modified as follows, for example. 
     The control unit that controls the various parts of the in-vacuum twin-arm robot  1  can also be located inside the base  11 . 
     The first hand  15  may be provided adjacent to the lower side of the first arm  13 . The second hand  16  may be provided adjacent to the upper side of the second arm  14 . 
     When any one of the first hand  15  and the second hand  16  is advanced/retracted in a straight line, the other hand and arm can maintain their posture and rotate in conjunction with the rotation of the base arm  12 . 
     The layout of the load ports  2  around the storage-side robot  1   a  and the layout of the processing devices  4  around the process-side robot  1   b  are not limited to those shown in  FIG.  1   . For example, ten load ports  2  may be arranged around the storage-side robot  1   a  in substantially the same arrangement as the processing devices  4 . 
     The present invention can also be applied to a robot for transporting substrates other than the wafers  10  (for example, glass plates). 
     DESCRIPTION OF THE REFERENCE NUMERALS 
       1  in-vacuum twin-arm robot 
       12  base arm 
       13  first arm 
       14  second arm 
       15  first hand 
       16  second hand 
       18  elbow shaft (joint shaft) 
       30  storage preparation chamber (vacuum space) 
       40  processing preparation chamber (vacuum space)