Patent Publication Number: US-2022223447-A1

Title: Substrate transfer apparatus, substrate transfer method, and substrate processing system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Japanese Patent Application No. 2021-002579 filed on Jan. 12, 2021, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a substrate transfer apparatus, a substrate transfer method, and a substrate processing system. 
     BACKGROUND 
     For example, in a semiconductor manufacturing process, when a semiconductor wafer, which is a substrate, is processed, a substrate processing system including a plurality of processing chambers, a vacuum transfer chamber connected to the processing chambers, and a substrate transfer apparatus disposed in the vacuum transfer chamber is used. 
     As such a substrate transfer apparatus, a transfer robot having an articulated arm structure has been conventionally used (see, e.g., Japanese Laid-open Patent Publication No. 2017-168866). However, a technique using a transfer robot has a problem such as gas intrusion from a vacuum seal or limitation of movement of the transfer robot. Therefore, a substrate transfer apparatus (see, e.g., Japanese Laid-open Patent Publication No. 2018-504784) using a planar motor utilizing magnetic levitation is suggested as a technique capable of solving the above-described problem. 
     SUMMARY 
     The present disclosure provides a substrate transfer apparatus, a substrate transfer method, and a substrate processing system capable of transferring a substrate to a transfer position in a processing chamber with high positioning accuracy using a planar motor. 
     To this end, a substrate transfer apparatus for transferring a substrate is disclosed. The apparatus comprises: a transfer unit including a substrate holder configured to hold a substrate, and a base having therein a magnet and configured to move the substrate holder; a planar motor including a main body, a plurality of electromagnetic coils disposed in the main body, and a linear driver configured to supply a current to the electromagnetic coils, and magnetically levitate and linearly drive the base; a substrate detection sensor configured to detect the substrate when the substrate held by the substrate holder passes by; and a transfer controller configured to calculate an actual position of the substrate held by the substrate holder based on detection data of the substrate detection sensor, calculate correction values for a logical position that has been set, and correct a transfer position of the substrate based on the correction values. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and features of the present disclosure will become apparent from the following description of embodiments, given in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic plan view showing a substrate processing system according to a first embodiment; 
         FIG. 2  is a cross-sectional view for explaining a transfer unit and a planar motor in an example of a substrate transfer apparatus; 
         FIG. 3  is a perspective view for explaining a driving principle of a planar motor; 
         FIG. 4  is a side view for explaining a wafer detection sensor; 
         FIG. 5  is a block diagram for explaining a control system of the substrate transfer apparatus; 
         FIG. 6  is a plan view showing a logical center of a wafer on an end effector and a physical center of a wafer that is actually placed on the end effector; 
         FIG. 7  is a flowchart showing an example of a wafer transfer sequence executed by a transfer controller; 
         FIGS. 8A and 8B  are plan views showing a transfer unit in another example of the substrate transfer apparatus; and 
         FIG. 9  is a side view showing a transfer unit in another example of the substrate transfer apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a schematic plan view showing a substrate processing system according to an embodiment. 
     A substrate processing system  100  of the present embodiment continuously performs processing on a plurality of substrates. The substrate processing is not particularly limited, and may include various treatments such as film formation, etching, ashing, cleaning, and the like. The substrate is not particularly limited. However, in the following description, a case where a semiconductor wafer (hereinafter, simply referred to as “wafer”) is used as the substrate will be described as an example. 
     As shown in  FIG. 1 , the substrate processing system  100  is a cluster structure (multi-chamber type) system, and includes a plurality of processing chambers  110 , a vacuum transfer chamber  120 , load-lock chambers  130 , an atmosphere transfer chamber  140 , a substrate transfer apparatus  150 , and a controller  160 . 
     The vacuum transfer chamber  120  has a rectangular planar shape. The inside of the vacuum transfer chamber  120  is depressurized to a vacuum atmosphere. A plurality of processing chambers  110  are connected to two opposing walls on long sides of the vacuum transfer chamber  120  through gate valves G. Further, two load-lock chambers  130  are connected to one wall on a short side of the vacuum transfer chamber  120  through gate valves G 1 . The atmosphere transfer chamber  140  is connected to the sides of the two load-lock chambers  130 , which sides are opposite to the sides connected to the vacuum transfer chamber  120 , through gate valves G 2 . In  FIG. 1 , the arrangement direction of the processing chambers  110  is defined as the X direction, and the direction orthogonal to the X direction is defined as the Y direction. 
     The substrate transfer apparatus  150  in the vacuum transfer chamber  120  loads and unloads the wafer W, which is a substrate, into and from the processing chambers  110  and the load-lock chambers  130 . The substrate transfer apparatus  150  includes a transfer unit  20  having an end effector  50  that is a wafer holder that actually holds the wafer W, and wafer detection sensors  60 . The substrate transfer apparatus  150  will be described in detail later. 
     By opening the gate valves G, the communication between the processing chambers  110  and the vacuum transfer chamber  120  is allowed and the wafer W can be transferred therebetween by the substrate transfer apparatus  150 . By closing the gate valves G, the communication therebetween is blocked. By opening the gate valves G 1 , the communication between the load-lock chambers  130  and the vacuum transfer chamber  120  is allowed and the wafer W can be transferred by the substrate transfer apparatus  150 . By closing the gate valves G 1 , the communication therebetween is blocked. 
     Each of the processing chambers  110  has a placement table  111  on which the wafer W is placed, and desired processing (film formation, etching, ashing, cleaning or the like) is performed on the wafer W placed on the placement table  111  in a state where the inner atmosphere of the processing chamber  110  is depressurized to a vacuum atmosphere. 
     Each of the load-lock chambers  130  has therein a placement table  131  on which the wafer W is placed, and the pressure in each load-lock chamber  130  is controlled between an atmospheric pressure and a vacuum level at the time of transferring the wafer W between the atmospheric transfer chamber  140  and the vacuum transfer chamber  120 . 
     The atmospheric transfer chamber  140  is set to an atmospheric atmosphere. For example, a downflow of clean air is formed in the atmospheric transfer chamber  140 . Further, a load port (not shown) is disposed on a wall surface of the atmosphere transfer chamber  140 . A carrier (not shown) accommodating wafers W or an empty carrier is connected to the load port. The carrier may be, e.g., a front opening unified pod (FOUP) or the like. 
     Further, an atmospheric transfer device (not shown) for transferring the wafer W is disposed in the atmospheric transfer chamber  140 . The atmospheric transfer device takes out the wafer W accommodated in the load port (not shown) and places it on the placement table  131  of the load-lock chamber  130 , or takes the wafer W placed on the placement table  131  of the load-lock chamber  130  and accommodates it in the load port. By opening the gate valves G 2 , the communication between the load-lock chambers  130  and the atmospheric transfer chamber  140  is allowed and the wafer W can be transferred by the atmospheric transfer device. By closing the gate valves G 2 , the communication therebetween is blocked. 
     The controller  160  is a computer, and includes a main controller having a CPU, an input device, an output device, a display device, and a storage device (storage medium). The main controller controls operations of individual components of the substrate processing system  100 . For example, the main controller controls the processing of the wafer W in each processing chamber  110 , the opening/closing of the gate valves G, G 1  and G 2 , and the like. The main controller controls the individual components based on a processing recipe that is a control program stored in the storage medium (hard disk, optical disk, semiconductor memory, or the like) built in the storage device. 
     Further, in the present embodiment, the controller  160  controls a transfer controller  70  which is a part of the substrate transfer apparatus  150 . The transfer controller  70  will be described later together with the substrate transfer apparatus  150  to be described later. 
     Next, an example operation of the substrate processing system  100  will be described. Here, an operation of processing the wafer W accommodated in the carrier attached to the load port in the processing chamber  110  and accommodating the wafer W in an empty carrier attached to the load port will be described as an example of the operation of the substrate processing system  100 . The following operations are executed based on the processing recipe of the controller  160 . 
     First, the wafer W is taken out from the carrier connected to the load port by the atmospheric transfer device (not shown) in the atmospheric transfer chamber  140 . Then, the gate valve G 2  is opened so that the wafer W is loaded into the load-lock chamber  130  in an atmospheric atmosphere. Then, the gate valve G 2  is closed, and the load-lock chamber  130  into which the wafer W has been loaded is set to a vacuum state corresponding to that of the vacuum transfer chamber  120 . Next, the corresponding gate valve G 1  is opened so that the wafer W in the load-lock chamber  130  is taken out by the end effector  50  of the transfer unit  20  and, then, the gate valve G 1  is closed. Next, the gate valve G corresponding to one of the processing chambers  110  is opened, and the wafer W is loaded into that processing chamber  110  by the end effector  50  and placed on the placement table  111 . Thereafter, the end effector  50  is retracted from the processing chamber  110 , and the gate valve G is closed. Then, processing such as film formation or the like is performed in the processing chamber  110 . 
     After the processing in the processing chamber  110  is completed, the corresponding gate valve G is opened, and the end effector  50  of the transfer unit  20  takes out the wafer W from the processing chamber  110 . Then, the gate valve G is closed, and the gate valve G 1  is opened so that the wafer W held by the end effector  50  is transferred to the load-lock chamber  130 . Thereafter, the gate valve G 1  is closed, and the load-lock chamber  130  into which the wafer W has been loaded is set to an atmospheric atmosphere. Then, the gate valve G 2  is opened, and the wafer W is taken out from the load-lock chamber  130  by an atmospheric transfer device (not shown). The wafer W is accommodated in the carrier of the load port (all not shown). 
     The above processes are simultaneously performed on a plurality of wafers W, and all the wafers W in the carrier are processed. 
     Although the case of parallel transfer in which one wafer W is transferred to one of the processing chambers  110  by the substrate transfer apparatus  150  and another wafer W is transferred to another processing chamber  110  at the same time has been described, the present disclosure is not limited thereto. For example, serial transfer in which one wafer W is sequentially transferred to the multiple processing chambers  110  may be performed. 
     Example of Substrate Transfer Apparatus 
     Next, an example of the substrate transfer apparatus will be described in detail with reference to  FIGS. 2 to 5  in addition to  FIG. 1 .  FIG. 2  is a cross-sectional view for explaining a transfer unit and a planar motor in an example of a substrate transfer apparatus.  FIG. 3  is a perspective view for explaining a driving principle of a planar motor.  FIG. 4  is a side view for explaining a wafer detection sensor.  FIG. 5  is a block diagram for explaining a control system of the substrate transfer apparatus. 
     As shown in  FIG. 1 , the substrate transfer apparatus  150  includes a planar motor (linear unit)  10 , a transfer unit  20 , a wafer detection sensor  60 , and a transfer controller  70 . 
     The planar motor (linear unit)  10  linearly drives the transfer unit  20 . The planar motor (linear unit)  10  includes a main body  11  that constitutes a bottom wall  121  of the vacuum transfer chamber  120 , a plurality of electromagnetic coils  12  arranged throughout in the main body  11 , and a linear driver  13  for linearly driving the transfer unit  20  by supplying a current to each of the plurality of electromagnetic coils  12 . The linear driver  13  is controlled by a planar motor controller  72  of the transfer controller  70 . A magnetic field is generated by supplying a current to the electromagnetic coils  12 . 
     The transfer unit  20  has the end effector  50  that is a wafer holder for holding the wafer W, and a base  30 . Although one transfer unit  20  is illustrated in the drawing, two or more transfer units  20  may be provided. 
     As shown in  FIG. 3 , the base  30  has therein a plurality of permanent magnets  35  and is driven by the planar motor (linear unit)  10 . The end effector  50  is moved as the base  30  is driven. By setting the direction of the current supplied to the electromagnetic coils  12  of the planar motor (linear unit)  10  to a direction such that the magnetic field generated by the current repels the permanent magnets  35 , the base  30  is magnetically levitated from the surface of the main body  11 . By stopping the supply of the current to the electromagnetic coils  12 , the levitation of the base  30  is stopped and the base  30  is placed on the bottom surface of the vacuum transfer chamber  120 , i.e., on the surface of the main body  11  of the planar motor  10 . Further, by individually controlling the current supplied from the linear driver  13  to the electromagnetic coils  12  using the planar motor controller  72 , it is possible to move the base  30  along the surface of the planar motor  10  and control the position of the base  30  in a state where the base  30  is magnetically levitated. Further, the amount of levitation can be controlled by controlling the current. 
     The wafer detection sensor  60  has two sensor elements  61  disposed at portions in the vacuum transfer chamber  120  corresponding to the wafer loading/unloading port of each processing chamber  110 . As shown in  FIG. 4 , the sensor element  61  has, e.g., a light emitting element  61   a  and a light receiving element  61   b  arranged in a vertical direction, and constitutes an optical sensor. The wafer W is detected when the wafer W passes through the space between the light emitting element  61   a  and the light receiving element  61   b . As shown in  FIG. 5 , the wafer detection sensor  60  has a measurement part  62  that receives and measures a signal from the sensor element  61 . 
     The transfer controller  70  includes a calculator  71  and the above-described planar motor controller  72 . The calculator  71  acquires a signal from the measurement part  62  of the wafer detection sensor  60 , calculates an actual position of the wafer W on the end effector  50 , and calculates correction values from the logical position of the wafer position based on the calculation result. The planar motor controller  72  corrects the transfer position of the wafer W on the placement table  111  of the processing chamber  110  based on the correction values, and controls the linear driver  13  to transfer the wafer W to the corrected transfer position. 
     In the substrate transfer apparatus  150  configured as described above, the base  30  is magnetically levitated by generating magnetic field that repels the permanent magnets  35  by controlling the current supplied from the linear driver  13  of the planar motor (linear unit)  10  to the electromagnetic coils  12  using the planar motor controller  72 . The amount of levitation at this time can be controlled by controlling the current. 
     By individually controlling the current supplied from the linear driver  13  to the electromagnetic coils  12  in a state where the base  30  is magnetically levitated, it is possible to move the base  30  along the surface of the main body  11  of the planar motor  10  (the bottom surface of the vacuum transfer chamber  120 ), and control the position of the base  30 . Accordingly, the transfer unit  20  can be moved and rotated. 
     In the case of loading the wafer W into the processing chamber  110  by the transfer unit  20 , the base  30  is moved to locate the end effector  50  at a position corresponding to the processing chamber  110  in a state where the wafer W placed on the end effector  50 . Then, the gate valve G is opened, and the base  30  is further moved to insert the end effector  50  into the processing chamber  110 . Accordingly, the wafer W is delivered to the placement table  111  in the processing chamber  110 . 
     At this time, the transfer controller  70  controls the position of the base  30  based on the pre-obtained position data, and transfers the wafer W to a target position on the placement table  111  in the processing chamber  110 . However, the wafer W may be placed on the end effector  50  while being deviated from a preset position. 
     Specifically, as shown in  FIG. 6 , the transfer controller  70  sets a logical center O 1  as a center position of the wafer W placed on the end effector  50 , and controls a position of a center M of the base  30  that is a linear driving center based on the logical center O 1 . However, a position of a physical center O 2  of the wafer W actually placed on the end effector  50  may be deviated from the position of the logical center O 1 . The example of  FIG. 6  shows a state in which the physical center O 2  of the wafer W placed on the end effector  50  is deviated from the logical center O 1  by the amount of x in the X direction and the amount of y in the Y direction. 
     In the linear driving using the planar motor  10 , the central axis used by the conventional transfer robot is not used, so that it is not possible to perform transfer correction with the central axis as a reference point. Therefore, when the wafer W is placed in a deviated position on the end effector  50 , the wafer W is placed in a position deviated from a transfer target position on the placement table  111  even if the transfer controller  70  controls the transfer position of the wafer W. 
     As described above, the substrate transfer using the planar motor solves the problem of the technique using the transfer robot, such as gas intrusion from the vacuum seal or limitation of the movement of the transfer robot. However, recently, due to a growing demand for miniaturization of devices, the demand for placement accuracy of the substrate (wafer) on the placement table in the processing chamber is increasing in order to improve uniformity and characteristics. The processing of the substrate (wafer) includes high-temperature processing and low-temperature processing. In that case, the positional misalignment of the substrate on the end effector tends to be large due to the difference in thermal expansion. Therefore, the positional misalignment with respect to the transfer target position occurs due to the positional misalignment of the substrate on the end effector. 
     Therefore, in the present embodiment, the sensor elements  61  of the wafer detection sensor  60  are disposed at portions in the vacuum transfer chamber  120  corresponding to the wafer loading/unloading port of each processing chamber  110 , and the position of the wafer W is detected by the sensor elements  61  at the time of transferring the wafer on the end effector  50  to the placement table  111  in the processing chamber  110 . Then, based on the detection data, the calculator  71  of the transfer controller  70  calculates the actual position of the wafer W on the end effector  50 , and calculates the correction values from the logical position of the wafer position based on the calculation result. The planar motor controller  72  corrects the transfer position of the wafer W on the placement table  111  in the processing chamber  110  based on the correction values. Then, the linear driver  13  is controlled to transfer the wafer W to the corrected transfer position. 
       FIG. 7  shows an example of a sequence executed by the transfer controller  70  in that case. 
     First, a command for center coordinates (X,Y) of the wafer W corresponding to the transfer target position is given to the linear driver  13  (step ST 1 ). The transfer target position indicates a position on the placement table  111  in the processing chamber  110 . 
     Next, the linear driver  13  is operated based on the command (step ST 2 ). Accordingly, the base  30  of the transfer unit  20  is moved, and the wafer W on the end effector  50  is transferred. Specifically, the wafer W held by the end effector  50  is transferred in the X direction to a position corresponding to a target processing chamber  110 , and transferred in the Y direction toward the target processing chamber  110 . 
     Next, the wafer W is detected by the wafer detection sensor  60  (step ST 3 ). Specifically, the two sensor elements  61  detect the wafer W passing therebetween, and the detection signal is measured by the measurement part  62 . 
     Next, the physical center position O 2  of the wafer W on the end effector  50  is calculated based on the detection data of the wafer detection sensor  60 , and the correction values (x,y) from the logical center O 1  are calculated (step ST 4 ). 
     Next, the center coordinates of the wafer W corresponding to the transfer position of the wafer W are corrected to (X+x, Y+y) based on the correction values (x,y) (step ST 5 ). The linear driver  13  is transfer-controlled based on the corrected transfer position. 
     Accordingly, the wafer W can be transferred with high positioning accuracy to a preset transfer position on the placement table  111  in the processing chamber  110 . 
     The wafer detection sensor  60  (the sensor elements  61 ) is disposed in each processing chamber  110 , and the same position correction is performed whenever the wafer W is transferred to each processing chamber  110 . 
     Such position correction can be performed in the same manner regardless of whether the wafers W are transferred in parallel or serial. 
     Another Example of Substrate Transfer Apparatus 
     Next, another example of the substrate transfer apparatus will be described. This example is different from the above example in the configuration of the transfer unit.  FIGS. 8A and 8B  are plan views showing the transfer unit of the substrate transfer apparatus of this example.  FIG. 9  is a side view showing the transfer unit of the substrate transfer apparatus of this example.  FIGS. 8A and 8B  show different states of the transfer unit. 
     A transfer unit  20 ′ of this example has two bases  31  and  32 , a link mechanism (links  41  and  42 ), and the end effector  50 . 
     Similarly to the base  30  of the above example, the bases  31  and  32  have therein a plurality of permanent magnets  35  (see  FIG. 3 ), and the end effector  50  is moved via the link mechanism (the links  41  and  42 ). By setting the direction of the current supplied to the electromagnetic coils  12  of the planar motor (linear unit)  10  to the direction such that the magnetic field generated by the current repels the permanent magnets  35 , the bases  31  and  32  are magnetically levitated from the surface of the main body  11 . 
     The links  41  and  42  constituting the link mechanism connect the two bases  31  and  32  with the end effector  50 . Specifically, one end of the link  41  is rotatably connected to the base  31  via a vertical rotation shaft  43 . The other end of the link  41  is rotatably connected to the end effector  50  via a vertical rotation shaft  45 . One end of the link  42  is rotatably connected to the base  32  via a vertical rotation shaft  44 . The other end of the link  42  is rotatably connected to the end effector  50  via a vertical rotation shaft  46 . 
     Further, the link mechanism may be configured to be moved while adjusting a link angle. For example, the link mechanism may include an angle co-adjusting mechanism (not shown) for adjusting an angle formed by the extension direction of the end effector  50  (direction orthogonal to a line that connects the rotation shafts  45  and  46 ) and an angle formed by the extension direction of the end effector  50  and the link  42  to be the same. The angle co-adjusting mechanism (not shown) includes, e.g., a gear, a belt, or the like. Accordingly, the link mechanism can extend and contract while maintaining the direction of the end effector  50  by changing the gap between the rotation shafts  43  and  44  (i.e., the gap between the bases  31  and  32 ). 
     In this example, the end effector  50  is connected to the link mechanism (links  41  and  42 ). By connecting the two bases  31  and  32  with the end effector  50  via the link mechanism (links  41  and  42 ), the end effector  50  can be located at a retracted position shown in  FIG. 8A  and an extended position shown in  FIG. 8B . 
     In other words, at the retracted position shown in  FIG. 8A , the distance between the bases  31  and  32  is D 1 , and an extension distance H 1  of the end effector  50  is uniquely determined. Further, at the extended position shown in  FIG. 8B , the distance between the bases  31  and  32  is D 2 , and the extension distance H 2  of the end effector  50  is uniquely determined. 
     The gap between the bases  31  and  32  is the gap between the reference position of the base  31  and the reference position of the base  32 . In this example, the gap between the bases  31  and  32  is the gap between the rotation shafts  43  and  44 . The extension distance is the distance between a straight line that connects the rotation shaft  43  of the base  31  with the rotation shaft  44  of the base  32  and the center of the wafer W placed on the end effector  50 . If necessary, stoppers  47  and  48  for limiting the rotation angles of the links  41  and  42 , respectively, are provided. 
     In the transfer unit  20 ′ configured as described above, the bases  31  and  32  are magnetically levitated by generating the magnetic field that repels the permanent magnets  35  by controlling the current supplied from the linear driver  13  of the planar motor (linear unit)  10  to the electromagnetic coils  12  using the planar motor controller  72 . By individually controlling the current supplied to the electromagnetic coils  12  in a state where the bases  31  and  32  are magnetically levitated, it is possible to move the bases  31  and  32  along the surface of the main body  11  of the planar motor  10  (the bottom surface of the vacuum transfer chamber  120 ), and control the positions of the bases  31  and  32 . Accordingly, the transfer unit  20 ′ can be moved and rotated. 
     Further, the extension distance of the end effector  50  can be changed by controlling the current supplied to the electromagnetic coils  12  such that the gap between the bases  31  and  32  becomes a desired gap. For example, in the case of accessing the processing chamber  110  or the load-lock chamber  130 , the gap between the bases  31  and  32  is reduced to increase the extension distance of the end effector  50  as shown in  FIG. 8B . Accordingly, the end effector  50  can be inserted into the processing chamber  110  or the load-lock chamber  130  in a state where the bases  31  and  32  are located on the surface of the main body  11  of the planar motor  10  (the bottom surface of the vacuum transfer chamber  120 ). Further, in the case of moving and rotating the transfer unit  20 ′ in the vacuum transfer chamber  120 , for example, the gap between the bases  31  and  32  is increased to reduce the extension distance of the end effector  5  as shown in  FIG. 8A . Accordingly, the end effector  50  holding the wafer W can be positioned close to the bases  31  and  32 , and the misalignment of the wafer W that is being transferred can be reduced by suppressing sagging and vibration of the link mechanism (the links  41  and  42 ). 
     In this example as well as the above example, the sensor elements  61  of the wafer detection sensor  60  are disposed at the portions in the vacuum transfer chamber  120  corresponding to the wafer loading/unloading port of each processing chamber  110 , and the position of the wafer W is detected by the sensor element  61  at the time of transferring the wafer W on the end effector  50  to the placement table  111  of the processing chamber  110 . Then, based on the detection data, the calculator  71  of the transfer controller  70  calculates the position of the wafer W on the actual end effector, and calculates the correction values from the logical position of the wafer position based on the calculation result. The planar motor controller  72  corrects the transfer position of the wafer W on the placement table  111  of the processing chamber  110  based on the correction values, and controls the linear driver  13  to transfer the wafer W to the corrected transfer position. 
     Accordingly, the wafer W can be transferred with high positioning accuracy to a preset transfer position on the placement table  111  in the processing chamber  110 . 
     Other Applications 
     While the embodiments of the present disclosure have been described, the embodiments of the present disclosure are illustrative in all respects and are not restrictive. The above-described embodiments may be omitted, replaced, or changed in various forms without departing from the scope of the appended claims and the gist thereof. 
     For example, in the above embodiment, the transfer unit of the substrate processing system has one base or two bases. However, the transfer unit may have three or more bases. Further, in the case of providing the link mechanism between the base and the end effector, an articulated link mechanism may be used, or combination of a link mechanism displaced in a horizontal direction and a link mechanism displaced in a height direction may be used. 
     Further, in the above embodiment, the target transfer position of the wafer is set on the placement table of the processing chamber, but the target transfer position of the wafer is not limited thereto. 
     Further, in the above embodiment, the optical sensor in which the sensor element has the light emitting element and the light receiving element was used as the wafer detection sensor. However, the present disclosure is not limited thereto. 
     Further, although the case in which the semiconductor wafer (wafer) is used as the substrate has been described, the substrate is not limited to the semiconductor wafer, and may be another substrate such as a flat panel display (FPD) substrate, a quartz substrate, a ceramic substrate, or the like. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.