Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a Continuation of U.S. patent application Ser No. 12/182,239 filed on Jul. 30, 2008, which claims the priority from Japanese Patent Application No. 2007-201533 filed on Aug. 2, 2007, the entire disclosure of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present disclosure relates to a position detecting method for performing a position alignment of a transfer point of a transfer arm holding and transferring a substrate. 
       BACKGROUND OF THE INVENTION 
       [0003]    For example, in a manufacturing process of semiconductor devices, a photolithography process is performed by a coating and developing system including a plurality of apparatuses such as a resist coating apparatus, a developing apparatus, a heat treating apparatus and the like. The coating and developing system has a transfer mechanism for transferring a wafer to each of the apparatuses. 
         [0004]    The transfer mechanism has a transfer arm for holding the wafer thereon, and, for example, the transfer arm moves three-dimensionally in forward-backward, left-right, and up-down directions to transfer the wafer to each apparatus. 
         [0005]    However, in case that the wafer is not transferred to a preset position in each apparatus, the delivery of the wafer or processing of the wafer may not be performed properly, for example. For this reason, when starting the coating and developing system, for example, it is checked whether or not the transfer arm has transferred the wafer to the preset position. In the event that the wafer is not transferred to the right position, the transfer point of the transfer arm is adjusted. 
         [0006]    Patent Document 1 discloses an example method for adjusting the transfer position, wherein the method involves the steps of holding a trajectory-detecting wafer having a CCD camera by the transfer arm; transferring the trajectory-detecting wafer by the transfer arm; and detecting a transfer stop position of the transfer arm by the CCD camera. 
         [0007]    [Patent Document 1] Japanese Patent Laid-open Publication No. 2003-243479 
         [0008]    However, an optical apparatus such as the CCD camera needs to have a sufficient thickness in a vertical direction due to the necessity of an adjusting mechanism of a focus, a focal length or the like. For this reason, as for an apparatus having a transfer port with a reduced opening size due to the influence of a recent miniaturization, it is impossible to load the trajectory-detecting wafer into the apparatus, and to adjust the position thereof properly, either. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    In view of the foregoing, the present disclosure provides a position detecting method capable of properly performing a position alignment of a transfer point of a transfer arm. 
         [0010]    In accordance with one aspect of the present invention, there is provided a position detecting method for performing position alignment of a transfer point of a transfer arm which holds and transfers a substrate body. The method includes: detecting electrostatic capacitances in relation with a reference object for position alignment by a plurality of electrostatic capacitance detecting electrodes provided on a surface of the substrate body; communicating with each electrostatic capacitance detecting electrode and controlling a detection of each electrostatic capacitance detecting electrode; and calculating coordinates (x, y) of the reference object with respect to the substrate body based on a preset relationship between electrostatic capacitance values of multiple electrostatic capacitance detecting electrodes and a position of the reference object with respect to the substrate body. 
         [0011]    The method may further include: prior to detecting electrostatic capacitances, holding the substrate body and moving the substrate body to the transfer point by the transfer arm. 
         [0012]    The method may further include: after calculating coordinates (x, y) of the reference object, calculating an amount of correction required to adjust the transfer point of the transfer arm to a proper position based on the calculated coordinates (x, y) of the reference object. 
         [0013]    The method may further include: after calculating an amount of correction, adjusting the transfer point of the transfer arm based on the calculated amount of correction. 
         [0014]    The method may further include: when detecting electrostatic capacitances, controlling a guard wiring covering the electrostatic capacitance detecting electrode to have the same potential as that of the electrostatic capacitance detecting electrode. 
         [0015]    The method may further include: when detecting electrostatic capacitances, blocking an external electric field with respect to an electrical signal transmitted from the electrostatic capacitance detecting electrode. 
         [0016]    The method may further include: amplifying the electrostatic capacitance detected by the electrostatic capacitance detecting electrode. 
         [0017]    The method may further include: transmitting wirelessly the electrostatic capacitance detected by the electrostatic capacitance detecting electrode to a controller. 
         [0018]    The method may further include: holding and rotating the substrate body at the transfer point of the transfer arm; and measuring acceleration of the substrate body by an acceleration sensor while the substrate body is being rotated. Further, the method may include: measuring humidity of an atmosphere around the substrate body by a humidity sensor. Further, the method may include: measuring temperature of an atmosphere around the substrate body by a temperature sensor. 
         [0019]    It may be possible that the substrate body is provided with a plurality of electrical conduction paths perforated from a rear surface to a front surface of the substrate body, and each electrostatic capacitance detecting electrode is connected to a control circuit for controlling the detection of each electrostatic capacitance detecting electrode through the electrical conduction paths. Further, it may be possible that the plurality of electrical conduction paths are formed in a peripheral portion of the substrate body. Further, it may be possible that the plurality of electrical conduction paths are arranged annularly in the peripheral portion of the substrate body, and the electrostatic capacitance detecting electrodes are disposed in a central portion of the rear surface of the substrate body in comparison with the electrical conduction paths, and wirings connecting the electrostatic capacitance detecting electrodes with the electrical conduction paths are formed in the rear surface of the substrate body in a radial pattern. 
         [0020]    It may be possible that an amplifier circuit for amplifying a signal of the electrostatic capacitance detected by the electrostatic capacitance detecting electrode is provided on each wiring connecting each electrostatic capacitance detecting electrode with a control circuit for controlling the detection of each electrostatic capacitance detecting electrode, and the amplifier circuit is disposed on a front surface of the substrate body. Further, it may be possible that each wiring, connecting each electrostatic capacitance detecting electrode with the amplifier circuit, and each of the electrostatic capacitance detecting electrodes are covered with a guard wiring which can be maintained at the same potential as that of the wiring or the electrostatic capacitance detecting electrode. 
         [0021]    It may be possible that the electrostatic capacitance detecting electrodes are also provided at a position supported by the transfer arm on a rear surface of the substrate body. Further, it may be possible that the electrostatic capacitance detecting electrodes are formed by a photolithography process. Further, it may be possible that the electrostatic capacitance detecting electrodes are formed by a screen printing process. 
         [0022]    In accordance with the present disclosure, it is possible to properly perform the position alignment of the transfer point of the transfer arm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The disclosure may best be understood by reference to the following description taken in conjunction with the following figures: 
           [0024]      FIG. 1  provides a schematic view of a substrate processing system; 
           [0025]      FIGS. 2A and 2B  provide a side view and a plan view to illustrate a schematic configuration of a processing apparatus, respectively; 
           [0026]      FIG. 3  presents a perspective view of a position detecting wafer; 
           [0027]      FIG. 4  offers a perspective view of a rear surface of the position detecting wafer; 
           [0028]      FIG. 5  illustrates an electrostatic capacitance detecting electrode and a wiring covered with a guard wiring; 
           [0029]      FIG. 6  illustrates distances between electrostatic capacitance detecting electrodes of the position detecting wafer and a front surface of a mounting table; 
           [0030]      FIG. 7  illustrates a state in which the transfer arm is loaded into the processing apparatus; 
           [0031]      FIG. 8  shows a position of a center hole with respect to the center point of the position detecting wafer; 
           [0032]      FIG. 9  offers a perspective view of the position detecting wafer provided with an acceleration sensor on a front surface thereof; 
           [0033]      FIG. 10  offers a perspective view of the position detecting wafer provided with the acceleration sensor, a humidity sensor and a temperature sensor on the front surface thereof; 
           [0034]      FIG. 11A  shows locations of supporting portions of the transfer arm, and  FIG. 11B  illustrates locations of electrostatic capacitance detecting electrodes of the position detecting wafer; and 
           [0035]      FIG. 12  offers a perspective view of the rear surface of the position detecting wafer on any place of which electrical conduction paths are arranged. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.  FIG. 1  provides a schematic configuration view of a substrate processing system  1  to which a position detecting wafer is applied as a position detecting jig in accordance with the embodiment of the present invention. 
         [0037]    For example, the substrate processing system  1  includes a plurality of processing apparatuses  10  for processing a wafer W and a transfer mechanism  11  for transferring the wafer W to the processing apparatuses  10 . 
         [0038]    For example, the transfer mechanism  11  has a transfer arm  20 . The transfer arm  20  has a front end substantially having, for example, a C shape. A plurality of supporting portions  20   a  is installed at inner portions of the C-shaped part of the transfer arm  20 , and the wafer W can be sustained on these supporting portions  20   a . The transfer arm  20 , for example, can move back and forth along a rail  22  installed on a base  21 . For example, the base  21  is attached to a rail  23  extending in vertical direction, and the rail  23  is attached to a rail  24  extending in left and right directions. With this structure, the transfer arm  20  can move three-dimensionally in forward and backward, left and right, and up and down directions. Therefore, while supporting the wafer W by the transfer arm  20 , the transfer mechanism  11  advances the transfer arm  20  into each processing apparatus  10  and transfers the wafer W to a preset position within the processing apparatus  10 . 
         [0039]    Furthermore, the transfer position of the wafer W by the transfer arm  20  is controlled by an external controller  30  which controls the movement of the transfer arm  20 . 
         [0040]    The processing apparatus  10  includes, for example, a mounting table  41  for mounting the wafer W thereon in a processing chamber  40  as illustrated in  FIG. 2A . For example, as illustrated in  FIG. 2B , a central hole  42  is provided on a center portion of the top surface of the mounting table  41  to be used as a reference object for position alignment. In this embodiment, for example, a proper transfer position of the wafer W is the center portion of the mounting table  41 , and the wafer W needs to be transferred so that its center aligns with the central hole  42 . Further, a transfer port  43  through which the wafer W is loaded and unloaded by the transfer arm  20  is provided in a sidewall of the processing chamber  40 . 
         [0041]    Now, the structure of a position detecting wafer S will be explained.  FIG. 3  is a perspective view of the position detecting wafer S. The position detecting wafer S may be formed in the same shape and size as the product wafer W, for example, and can be transferred by the transfer arm  20 . The position detecting wafer S is made of, for example, ceramic, silicon or resin in which a wiring pattern or a hole can be easily formed. 
         [0042]    The position detecting wafer S is provided with an electrostatic capacitance detecting sensor  50  for detecting an electrostatic capacitance between the reference object for position alignment and the wafer S. The electrostatic capacitance detecting sensor  50  has a control circuit  51  on the front surface of the wafer S and has a plurality of electrostatic capacitance detecting electrodes  52  on the rear surface of the wafer S, as illustrated in  FIG. 4 . 
         [0043]    For example, the electrostatic capacitance detecting electrodes  52  are placed on the center portion of the position detecting wafer S column-wise and row-wise in a grid pattern as illustrated in  FIG. 4 . Each electrostatic capacitance detecting electrode  52  is, for example, rectangular-shaped and has a diameter, for example, less than that of the reference object (the central hole  42  in this embodiment) which generates the electrostatic capacitance. Also, the interval between the neighboring electrostatic capacitance detecting electrodes  52  is smaller than the diameter of the central hole  42 . 
         [0044]    In the peripheral portion of the position detecting wafer S, there is provided a plurality of electrical conduction paths  60  which is vertically perforated from the rear surface to the front surface of the wafer. These electrical conduction paths  60  are arranged annularly in the peripheral portion of the position detecting wafer S. Each electrostatic capacitance detecting electrode  52  is connected to corresponding one of the electrical conduction paths  60  via a wiring  61  extended in diametric direction of the position detecting wafer S. That is, a plurality of wirings  60  connecting the electrostatic capacitance detecting electrodes  52  to the electrical conduction paths  60  is formed on the rear surface of the position detecting wafer S in a radial pattern. 
         [0045]    Each wiring  61  and each electrostatic capacitance detecting electrode  52  are surrounded by a guard wiring  62  as illustrated in  FIG. 5 . Further, the wiring  61  is extended to a portion in the front surface of the position detecting wafer S, and the portion is also surrounded by the guard wiring  62 . For example, the guard wiring  62  is controlled by the control circuit  51  to have the same potential as that of the wiring  61  or the electrostatic capacitance detecting electrode  52  when detecting the electrostatic capacitance. Therefore, it is possible to block an external electric field or the like with respect to an electrical signal transmitted through the wiring  61  or the electrostatic capacitance detecting electrode  52 , and, thus, a parasitic capacitance can be removed. 
         [0046]    The components placed on the rear surface of the position detecting wafer S, such as the electrostatic capacitance detecting electrodes  52 , the wirings  61  and the guard wirings  62  are formed by a photolithography process in which film formation, exposure, development and etching are performed repeatedly. Further, since the electrostatic capacitance detecting electrodes  52 , the wirings  61  and the guard wirings  62  are formed by the photolithography process, the rear surface of the position detecting wafer S can be formed to be flat. 
         [0047]    As illustrated in  FIG. 3 , a plurality of wirings  70  connecting the electrical conduction paths  60  in the peripheral portion with the control circuit  51  in the center portion of the wafer S is formed on the front surface of the position detecting wafer S in a radial pattern. Each wiring  70  is provided with an amplifier circuit  71  which amplifies a signal of electrostatic capacitance detected by the electrostatic capacitance detecting electrode  52 . The amplifier circuits  71  are placed adjacent to the electrical conduction paths  60 . The above-described guard wirings  62  are also provided around the wirings  70  between the amplifier circuits  71  and the electrical conduction paths  60 . 
         [0048]    The control circuit  51  is formed, for example, on a circuit board A installed on the center portion of the position detecting wafer S. The control circuit  51  transceiver a signal of voltage or the like to/from each electrostatic capacitance detecting electrode  52  and detects an electrostatic capacitance generated between the electrostatic capacitance detecting electrode  52  and the reference object. On the circuit board A, a wireless circuit  80  allowing the control circuit  51  to communicate with an external controller  30  wirelessly is installed. In addition, a power supply for the electrostatic capacitance detecting electrodes  52 , the control circuit  51 , the guard wirings  62  and the wireless circuit  80  and the like is installed at the circuit board A of the position detecting wafer S. 
         [0049]    For example, the controller  30  receives an electrostatic capacitance signal of each of the electrostatic capacitance detecting electrodes  52  from the position detecting wafer S, and specifies, based on those electrostatic capacitance signals, the position of the central hole  42 , i.e., the reference object with respect to the position detecting wafer S. For example, the controller can specify coordinates of the central hole  42  with respect to the position detecting wafer S based on a previously recognized relationship between the electrostatic capacitance value detected by each electrostatic capacitance detecting electrode  52  and the position of the central hole with respect to the position detecting wafer S. As illustrated in  FIG. 6 , if positional relationships between the plurality of electrostatic capacitance detecting electrodes  52  and the central hole  42  are different, a distance D between two poles, i.e., between each electrostatic capacitance detecting electrode  52  and the top surface of the mounting table  41  having the central hole  42  becomes changed, so that an electrostatic capacitance therebetween is varied (electrostatic capacitance (C)=Eo·B/D (Eo represents a dielectric constant between the two poles, and B refers to an area of the electrostatic capacitance detecting electrode)). Based on the relationships, it is possible to specify the position corresponding to the central hole  42  within the position detecting wafer S by detecting the electrostatic capacitance of the plurality of electrostatic capacitance detecting electrodes  52  in the surface of the position detecting wafer S. 
         [0050]    Furthermore, the controller  30  calculates an amount of correction required to locate the transfer arm  20  to the proper position based on the specified coordinates of the central hole  42  to thereby adjust the transfer position of the transfer arm  20 . 
         [0051]    Hereinafter, a process of adjusting the transfer position of the transfer arm  20 , which is performed by using the position detecting wafer S having the above-mentioned configuration, will be explained. 
         [0052]    First, the position detecting wafer S is held on the transfer arm  20 . Next, in accordance with current transfer position set by the controller  30 , the transfer arm  20  is advanced into the processing chamber  40  from the transfer port  43  of the processing apparatus  10  and is stopped at a transfer position, i.e., a location above the central portion of the mounting table  41  as illustrated in  FIG. 7 . After that, according to instructions from the controller  30 , the electrostatic capacitance detecting sensors  50  of the position detecting wafer S are operated, so that an electrostatic capacitance generated between each of the electrostatic capacitance detecting electrodes  52  and the top surface of the mounting table  41  having the central hole  42  is detected. 
         [0053]    At this time, an electrostatic capacitance signal detected by each of the electrostatic capacitance detecting electrodes  52  is amplified by the amplifier circuit  71  and then transmitted to the control circuit  51 . The control circuit  51  receives the electrostatic capacitance signal from each electrostatic capacitance detecting electrode  52 , and these electrostatic capacitance signals are transmitted wirelessly to the controller  30  by the wireless circuit  80 . As illustrated in  FIG. 8 , the controller  30  calculates the coordinates (x, y) of the central hole  42  with respect to the center point E of the position detecting wafer S based on the preset relationship between the electrostatic capacitance value of each electrostatic capacitance detecting electrode  52  and the position of the central hole  42  with respect to the position detecting wafer S. 
         [0054]    From the calculated coordinates of the central hole  42 , a deviation amount (x, y) between the center point E of the position detecting wafer S and the central hole  42  is calculated, and based on the calculated deviation amount, the transfer position of the transfer arm  20  is adjusted. 
         [0055]    In accordance with the above-described embodiment, the position detecting wafer S has the electrostatic capacitance detecting sensor  50 , and the plurality of electrostatic capacitance detecting electrodes  52  is installed on the rear surface of the position detecting wafer S, and the control circuit  51  is installed on the front surface thereof. Since this position detecting wafer S uses the electrostatic capacitance detecting electrodes  52  and the control circuit  51 , which can be made very thin, instead of using the conventional optical apparatus, the total thickness of the position detecting wafer S can be reduced. Therefore, the position detecting wafer S can be loaded even into a thin type processing apparatus  10  having a narrow transfer port  43 , and it is also possible to properly adjust the transfer position of the transfer arm  20  in the processing apparatus  10 . Furthermore, since the electrostatic capacitance detecting electrodes  52  are installed on the rear surface and the control circuit  51  is installed on the front surface, it is possible to freely set the number, the shape and the position of the electrostatic capacitance detecting electrodes  52  depending on a reference object for position alignment. Therefore, it is possible to detect the position of the reference object with a high accuracy, which in turn makes it possible to adjust the position of the transfer arm  20  with a high accuracy. 
         [0056]    Meanwhile, if the control circuit and the electrostatic capacitance detecting electrodes were installed on the same surface, an electric field generated by the control circuit would affect an electric field around the electrostatic capacitance detecting electrodes. In accordance with the present embodiment, however, since the control circuit  51  and the electrostatic capacitance detecting electrodes  52  are installed on the different surfaces, the electric field generated by the control circuit  51  is prevented from affecting the electric field around the electrostatic capacitance detecting electrodes  52 , and therefore it is possible to detect the electrostatic capacitance between the electrostatic capacitance detecting electrodes  52  and the reference object with a higher accuracy. As a result, it is possible to carry out the detection of the reference object position by the position detecting wafer S with a higher accuracy. In addition, in the present embodiment, since the amplifier circuit  71  or the wireless circuit  80  is installed on the front surface of the position detecting wafer S, the detection of the reference object position can be carried out with a higher accuracy. 
         [0057]    Furthermore, in accordance with the present embodiment, since only the thin electrostatic capacitance detecting electrodes  52  are disposed on the rear surface of the position detecting wafer S while disposing the relatively thick control circuit  51  and so forth on the front surface thereof, a flatness of the entire rear surface of the position detecting wafer S becomes high. Therefore, for example, it becomes easy to horizontally maintain the position detecting wafer S on the transfer arm, and, as a result, the detection of the electrostatic capacitance between the plurality of the electrostatic capacitance detecting electrodes  52  and the reference object can be carried out with a higher accuracy, thereby making it possible to detect the reference object position more stably and accurately. 
         [0058]    Furthermore, since the electrical conduction paths  60  are formed in the peripheral portion of the position detecting wafer S, in which hole formation can be carried out easily, it is relatively easy to connect the electrostatic capacitance detecting electrodes  52  on the rear surface with the control circuit  51  on the front surface by wiring. Also, since the electrical conduction paths  60  are annularly formed in the peripheral portion of the position detecting wafer S, and the electrostatic capacitance detecting electrodes  52  are formed in the central portion thereof, and the wirings  61  connecting the electrical conduction paths  60  and the electrostatic capacitance detecting electrodes  52  are formed in the radial pattern, it is possible to properly implement the wiring of the plurality of the electrostatic capacitance detecting electrodes  52 . Also, even if the number of the electrostatic capacitance detecting electrodes  52  increases, it is possible to wire them in a relatively simple pattern, so that a great increase of manufacturing costs for the position detecting wafer S can be suppressed. 
         [0059]    Since the amplifier circuits  71  are installed on the position detecting wafer S, it is possible to detect even a signal indicating a minute change in the electrostatic capacitance. Therefore, position detection can be performed with a higher accuracy. Furthermore, since the amplifier circuits  71  are installed on the front surface of the position detecting wafer S, freedom in arranging the electrostatic capacitance detecting electrodes  52  on the rear surface is still ensured. 
         [0060]    Since the guard wirings  62  are installed around the electrostatic capacitance detecting electrodes  52  and the wirings  61 , it is possible to prevent a signal flowing through the wiring  61  or the electrostatic capacitance detecting electrode  52  from being affected by an external electric field, so that parasitic capacitance can be eliminated. As a result, it is possible to detect even a signal indicating a minute change in the electrostatic capacitance, so that position detection can be carried out with a higher accuracy. 
         [0061]    Since the wireless circuit  80  is installed on the front surface of the position detecting wafer S, it is possible to wirelessly transmit detection results of the electrostatic capacitance from the electrostatic capacitance detecting sensor  50  to the controller  30 . Also, it is possible to wirelessly transmit operation instructions from the controller  30  to the position detecting wafer S. Therefore, it is possible to perform the position alignment without having to consider, for example, wiring of the transfer arm  20  which transfers the wafer W to a narrow space. 
         [0062]    In the above-described embodiment, since the electrostatic capacitance detecting electrodes  52  in the rear surface of the position detecting wafer S are formed by the photolithography process, it is possible to form the electrostatic capacitance detecting electrode  52  very thin. Thus, the flatness of the entire rear surface of the position detecting wafer S improves. Accordingly, for example, it becomes easier to horizontally support the position detecting wafer S on the transfer arm  20 . As a result, the detection of the reference object position by the plurality of electrostatic capacitance detecting electrodes  52  can be performed more stably and accurately. 
         [0063]    Furthermore, since the electrostatic capacitance detecting electrodes  52 , the wiring  61  and the guard wiring are all formed by the photolithography process, a flatness of the entire rear surface of the position detecting wafer S becomes higher. With this configuration, for example, it becomes easier to horizontally maintain the position detecting wafer S on the transfer arm  20 . As a result, the detection of the reference object position can be performed more stably and accurately. Further, if the flatness of the rear surface of the position detecting wafer S is sufficiently high, it is possible to horizontally maintain the position detecting wafer S even on, for example, a fork-shaped transfer arm which supports the entire rear surface of the position detecting wafer S. Further, the position detecting wafer S is also useful in the case, for example, where the rear surface of the position detecting wafer S is vacuum-attracted. If the processing apparatus  10  to which the position detecting wafer S is transferred is, for example, a resist coating apparatus, a developing apparatus or the like, provided commonly within the apparatus is a spin chuck for vacuum-attracting the rear surface of the position detecting wafer S. Even in this case, since the flatness of the rear surface of the position detecting wafer S is sufficiently high, it is possible for the spin chuck to vacuum-attract the position detecting wafer S horizontally thereto. Furthermore, for example, as illustrated in  FIG. 9 , while the position detecting wafer S vacuum-attracted to the spin chuck is being rotated, the acceleration in the center portion of the position detecting wafer S can be measured by an acceleration sensor  100  installed thereon and a relative position of the center portion of the position detecting wafer S with respect to the center portion of the spin chuck can be detected. Further, in such case, after detecting the position of the reference object by detecting the electrostatic capacitance through the electrostatic capacitance detecting electrodes  52 , the relative position of the center portion of the position detecting wafer S with respect to the center portion of the spin chuck can be successively detected. Therefore, two kinds of the position detection can be carried out by one position detecting wafer S so that it is not necessary for the position detecting wafer S to be loaded and unloaded, and it is possible to drastically shorten an adjusting time of the processing apparatus  10 . In accordance with this embodiment, it is possible for the position detecting wafer S to exert advantageous effects especially when the flatness of a specific portion (e.g., the portion vacuum-attracted to the spin chuck as described above) of the rear surface of the position detecting wafer S is required. 
         [0064]    As illustrated in  FIG. 10 , for example, a humidity sensor  110  may be additionally provided on the front surface of the position detecting wafer S of the above-described embodiment. The humidity sensor  110  is installed on the circuit board A, and is capable of measuring the humidity of the atmosphere around the position detecting wafer S. Here, if the humidity of the atmosphere around the position detecting wafer S is changed, the electrostatic capacitance detected by the electrostatic capacitance detecting electrodes  52  is also changed accordingly. In this embodiment, it is possible to compensate the electrostatic capacitance detected by the electrostatic capacitance detecting electrodes  52  based on the humidity measured by the humidity sensor  110 . It may be possible that such compensation is performed by the control circuit  51  of the position detecting wafer S or by the controller  30  after the wireless circuit  80  transmits the humidity measured by the humidity sensor  110  to the controller  30 . In such case, for example, even if the humidity of the atmosphere around the position detecting wafer S is changed, it is possible to detect the electrostatic capacitance between the electrostatic capacitance detecting electrode  52  and the reference object more accurately and to detect the position of the reference object more precisely. Further, a temperature sensor  120  may be additionally provided on the front surface of the position detecting wafer S may as illustrated in  FIG. 10 , for example. The temperature sensor  120  is installed on the circuit board A, and is capable of measuring the temperature of the atmosphere around the position detecting wafer S. Further, it is possible to set an alarm device (not shown) to give an alarm when a specific temperature is measured by the temperature sensor  120 , for example. By this setting, if the specific temperature is set to be lower than the temperature where devices such as the control circuit  51  of the position detecting wafer S or the like can be damaged, the devices can be prevented from being damaged by the occurrence of the alarm. Further, in the above-described embodiment, the acceleration sensor  100 , the humidity sensor  110  and the temperature sensor  120  are provided on a single position detecting wafer S, but it may be possible to install at least one sensor thereon. 
         [0065]    In the above-described embodiment, the electrostatic capacitance detecting electrodes  52  on the rear surface of the position detecting wafer S may be also provided at portions in contact with the transfer arm  20  which supports the wafer S. For example, as illustrated in  FIG. 11A , when supporting portions  20   a  of the transfer arm  20  are installed so as to support four peripheral positions of the position detecting wafer S, the electrostatic capacitance detecting electrodes  52  are installed at each of positions corresponding to the supporting portions  20   a , as illustrated in  FIG. 11B . Further, each of the electrostatic capacitance detecting electrodes  52  is connected with the control circuit  51  on the front surface of the position detecting wafer S as stated above. 
         [0066]    In this case, while the position detecting wafer S is being supported by the transfer arm  20  during the position adjustment, for example, the electrostatic capacitance between each of the electrostatic capacitance detecting electrodes  52  and the corresponding one of the supporting portions  20   a  is detected. Based on the detected electrostatic capacitance, it is determined whether or not the position detecting wafer S is supported by the transfer arm  20  at a proper position and in a proper direction. For example, after the detection value of the electrostatic capacitance is compared to a preset proper value, it is determined whether or not the position detecting wafer S is properly supported on the four supporting portions  20   a  and whether the direction of the position detecting wafer S in θ direction is proper. Therefore, while adjusting position, it can be checked whether or not the position detecting wafer S is supported by the transfer arm  20  at the proper position and in the proper direction, so that it is possible to check the positional relationship between the position detecting wafer S and the transfer arm  20 . As a result, since the position alignment of the position detecting wafer S to the reference object is conducted after its position to the transfer arm  20  is adjusted first, it is possible to detect the position of the transfer point of the transfer arm  20  more accurately by the position detecting wafer S. 
         [0067]    In the foregoing embodiments, the electrical conduction paths  60  are arranged annularly in the peripheral portion of the position detecting wafer S. However, for example, as illustrated in  FIG. 12 , it may be possible to arrange the electrical conductions paths  60  in any portions of the position detecting wafer S. For example, the electrostatic capacitance detecting electrodes  52  are placed in any place depending on the position of the reference object, in lieu of on the center portion of the rear surface of the position detecting wafer S column-wise and row-wise in a grid pattern as described in the foregoing embodiments. Further, the arrangement position of the devices such as the control circuit  51 , the amplifier circuit  71 , the wireless circuit  80  or the circuit board A on the front surface of the position detecting wafer S is not limited to the center portion of the front surface of the position detecting wafer S as described in the foregoing embodiments. In accordance with this embodiment, it may be possible to arrange the electrical conduction paths  60  in any place depending on the arrangement of the electrostatic capacitance detecting electrodes  52 , the control circuit  51  or the like. Specifically, since it is possible to set the interval between the electrical conduction paths  60  to be greater than the interval between the neighboring electrostatic capacitance detecting electrodes  52 , degree of freedom in arranging the electrical conduction paths  60  improves. 
         [0068]    It may be possible to form a protective film made of an insulating material on the rear surface of the position detecting wafer S of the foregoing embodiments. The protective film is formed to cover the electrostatic capacitance detecting electrodes  52 , the wirings  61  and the guard wirings  62  so as to prevent a possible metal contamination of the electrostatic capacitance detecting electrodes  52 . Further, the electrostatic capacitance detecting electrodes  52  can be prevented from being damaged even if they are used many times. 
         [0069]    In the foregoing embodiments, the components placed on the rear surface of the position detecting wafer S, such as the electrostatic capacitance detecting electrodes  52 , the wirings  61  and the guard wirings  62  are formed by a photolithography process, but it may be possible to form such components by a screen printing process. Here, the screen printing process includes the steps of filling engraved pattern holes in a screen plate with ink, transcribing the engraved pattern into an imaging object and forming a certain pattern in the imaging object. In this embodiment, by using a screen plate formed with certain patterns corresponding to the electrostatic capacitance detecting electrodes  52 , the wirings  61  and the guard wirings  62 , the patterns are transcribed into the rear surface of the position detecting wafer S by using, e.g., silver ink or epoxy ink. After this process, the electrostatic capacitance detecting electrodes  52 , the wirings  61  and the guard wirings  62  are formed on a certain place of the rear surface of the position detecting wafer S. By this screen printing process, it is possible to make the rear surface of the position detecting wafer S flat. Therefore, it becomes easier to horizontally maintain the position detecting wafer S by the transfer arm  20 , so that it is possible to detect the position of the reference object more stably and accurately. By this screen printing process, it is possible to obtain substantially the same effects as obtained by the above-described embodiments using the photolithography process. 
         [0070]    The above description of the present invention is provided for the purpose of illustration, and it would be understood by those skilled in the art that various changes and modifications may be made without changing technical conception and essential features of the present invention. Thus, it is clear that the above-described embodiments are illustrative in all aspects and do not limit the present invention. 
         [0071]    For example, the number, the size, the shape or the position of the electrostatic capacitance detecting electrodes  52  on the rear surface of the position detecting wafer S can be properly selected depending on the reference object for position alignment. Further, the position or the number of the amplifier circuits  71  or the control circuit on the front surface of the position detecting wafer S shall not be limited to the above-described examples. Furthermore, the position or the number of the electrical conduction paths  60  in the position detecting wafer S shall not be limited to the above-described examples, either. Also, the reference object is not limited to the central hole  42 , and it may be any object as long as it has a prominence or a depression. In the above-described embodiment, though the position detected by the position detecting wafer S is a position on the horizontal plane, the position detecting wafer S may detect a vertical position as well. In addition, it may be possible to install any other circuits having other functions to adjust the position on the front surface of the position detecting wafer S. Furthermore, in the above-described embodiment, though the position detecting jig is of the wafer type, it may be of a substrate type having another shape, e.g., a rectangular shape. 
         [0072]    The present invention has many advantages when it is used to properly perform the position alignment of the transfer point of the transfer arm even in an apparatus having a thin transfer port. 
         [0073]    The scope of the present invention is defined by the following claims rather than by the detailed description of the embodiment. It shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

Technology Category: 5