Abstract:
A wafer processing apparatus on which a pod having an opening is detachably mounted is provided with a door unit and a mapping unit provided with a transmitting type sensor having an emitter and a detector forming a slot therebetween. The emitter and the detector are moved toward the opening in the pod and are plunged into the interior of the pod after a door is opened by the door unit, and the slot between the emitter and the detector crosses an end portion of a wafer to thereby detect the presence or absence of the wafer. Thereby, a mechanism portion liable to produce dust which may adhere to the wafer and cause the contamination thereof can be disposed separately from the pod.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a wafer processing apparatus including a wafer mapping apparatus having a function of detecting the presence or absence of a wafer. Also, this invention particularly relates to a wafer processing apparatus for detecting the presence or absence of a wafer on each shelf of a rack (shelves) on which the wafer is placed and which is provided in the interior of a clean box for keeping a wafer in a good condition for use in a semiconductor product, a product related to an electronic part, an optical disc product or the like during the manufacture thereof.  
           [0003]    2. Related Background Art  
           [0004]    In recent years, in a wafer processing process in the manufacture of a semiconductor product or the like which requires a high degree of cleanness, there has been adopted a technique which does not an entire room relating to the treating process into a highly clean environment. In this technique, a small space (hereinafter referred to as minienvironment) kept highly clean is provided in each wafer processing apparatus in a wafer manufacturing process. This aims at keeping a small space only in the wafer processing apparatuses and a container (hereinafter referred to as the pod) for keeping the wafer in a good condition during the movement among those wafer processing apparatuses at a high degree of cleanness. Thereby, facility investment and facility maintenance expenses required when the entire room relating to the wafer treating process is kept in a highly clean environment are curtailed to thereby obtain the same effect as keeping the entire room relating to the wafer processing process in a highly clean environment and realize an efficient production process.  
           [0005]    In the pod, there are disposed a rack having shelves on each of which a wafer is placed. In these shelves, wafers are contained in such a state that a shelf is allotted to a wafer. The wafers placed on the shelves are moved in each wafer processing apparatus with the movement of the pod. In some cases, however, there occurs a wafer which does not satisfy a predetermined standard in the processing process of each wafer processing apparatus, and the wafer which does not satisfy the predetermined standard is removed from the shelf in the pod. Accordingly, at the initial stage of the manufacture, each shelf of the rack (shelves) is filled with the wafer, but as each processing step of the wafer processing apparatus progresses, the number of shelves in the pod on which the wafer is absent increases.  
           [0006]    The wafer processing apparatus automatically effects the treatment of the wafer and therefore usually it is provided with a wafer transport robot (hereinafter simply referred to as the transport robot). The transport robot gains access to a shelf of the rack in the pod, transports the wafer and executes the wafer processing process. Although a wafer to be processed is absent on that shelf, if the transport robot gains access to that shelf on which the wafer is absent in order to transport the wafer, there will occur a useless movement process from after the transport robot gains access to that shelf until it returns to its original position. Further, as such a useless movement process increases, the amount of processed wafers is reduced as a whole. So, it becomes necessary to detect the presence or absence of the wafer on each shelf of the rack in the pod in each wafer processing apparatus to thereby judge in which shelf of the shelves in the pod in each wafer processing apparatus a wafer is contained and in which shelf a wafer is not contained (mapping).  
           [0007]    The detection of the presence or absence of the wafer for mapping will now be described with reference to FIG. 1 and FIGS. 7A and 7B to  9  of the accompanying drawings. FIG. 1 shows the whole of wafer processing apparatus  50 . The wafer processing apparatus chiefly includes a load port portion  51  and a minienvironment portion  52 . The load port portion  51  and the minienvironment  52  are partitioned by a partition  55  and a cover  58 . A stand  53  is disposed on the load port portion  51 . A pod  2  can be placed on and fixed to the stand  53 . The stand  53  is movable on the load port portion  51  toward or away from the minienvironment  52  side. The interior of the minienvironment  52  is kept at a high degree of cleanness to process a wafer  1 . The robot arm  54  of a transport robot for effecting the transport of the wafer  1  is provided in the minienvironment  52 . The pod  2  has an opening portion in one surface thereof, and includes a box-shaped main body portion  2   a  having a cavity space for containing the wafer  1  therein, and a lid  4  for sealing the opening portion. A shelf having a plurality of shelves is disposed in the main body portion  2   a.  The wafer  1  can be placed on each of the plurality of shelves. Each of the shelves is disposed with a predetermined spacing from the shelf adjacent thereto so that adjacent wafers  1  may not contact with each other.  
           [0008]    An access opening  10  is formed in the minienvironment  52  on the load port portion  51  side. The position at-which the access opening  10  in the minienvironment  52  is disposed is a position at which the pod  2  fixed onto the stand  53  is right opposed to the opening portion of the pod  2  when it is moved on the load port portion  51  toward the minienvironment  52  side so as to become proximate to the access opening  10 .  
           [0009]    [0009]FIGS. 7A and 7B are enlarged views of an opener  3  in a conventional wafer processing apparatus. The opener  3  is provided near the access opening  10  inside the minienvironment  52 . The opener  3  includes a door  6  and a door arm  42  of an elongated shape. A bar extending perpendicularly to the lengthwise direction of the door arm  42  is disposed at one end of the door arm  42 . On the other hand, a fixing member  46  having a through-hole is attached to the door  6 , and the bar provided at one end of the door arm  42  extends through this hole in the door  6 , whereby the door  6  is pivotably fixed to the door arm  42 . The other end of the door arm  42  is formed with a hole. The door arm  42  is rotatably supported by this hole being coupled to a hole at the tip end of a rod  37  which is a portion of an air-driven type cylinder  31  by a pivot  40 . A through-hole is formed between the aforementioned one end and the other end of the door arm  42 , and a pin extends through this hole and a hole in a fixing member  39  fixed to the support member  60  of a movable portion  56  to thereby constitute a fulcrum  41 . Accordingly, the door arm  42  is pivotable about the fulcrum  41  by the expansion and contraction of the rod  37  by the driving of the cylinder  31 . The fulcrum  41  of the door arm  42  is fixed to the support member  60  provided on an upwardly and downwardly movable portion  56 . The door  6  has holding ports  11   a  and  11   b,  and can hold the lid  4  of the pod  2  by vacuum absorption. The opener  3  is mounted on the movable portion  56  vertically movable to move up and down the door arm  42  and the door  6  together with each other. The movable portion  56  is vertically movable along the wall surface of the minienvironment  52 .  
           [0010]    Accordingly, when the processing of the wafer is to be effected, the pod  2  is first disposed on the stand  53  so as to approach the access opening  10 , and the lid  4  is held by the door  6 . When the rod of the cylinder  31  is then contracted, the door arm  42  is moved about the fulcrum  41  so as to move away from the access opening  10 . By this movement, the door  6  is pivotally moved with the lid  4 , and the lid  4  is detached from the pod  2 . Thereafter, the movable portion  56  is moved downwardly and the lid  4  is transported to a predetermined retracted position.  
           [0011]    In the detection of the wafers  1  on the shelves of the rack in the pod  2 , it becomes necessary for a detector to scan each shelf at least once while sweeping along a direction in which the wafers  1  are stacked, to thereby effect the detection of the wafers  1 . To effect this sweeping movement for detecting the wafers  1 , various methods are conceivable. For example, there is a method of providing a detector on a portion of the robot arm  54  and moving the detector by this robot arm  54  to thereby execute the detecting operation. The robot arm  54 , however, is a device originally prepared to effect the transport of the wafer  1 , and if the robot arm  54  is to effect the detection of the wafer, the robot arm  54  cannot perform the transporting operation for the wafers  1  during the detecting operation, and this leads to the disadvantage that the amount of treated wafers  1  is reduced.  
           [0012]    As another method, there is a method of providing a detector on a portion of an opening and closing device for the lid  4  of the pod  2  and detecting the wafer  1  by the detector during the unsealing of the lid  4 . FIGS. 7A and 7B show an apparatus adopting this method. In this apparatus, there is provided a mapping frame  5  comprised of a frame member disposed so as to-surround the door  6 . A pair of bar-like members  13   a  and  13   b  are disposed on the upper portion of the mapping frame  5 . A transmitting type sensor  9  as a detector is mounted on the tip end of each of these bar-like members  13   a  and  13   b.  The transmitting type sensor  9  forms a pair by an emitter  9   a  and a detector  9   b.  FIG. 8 is a view of the mapping frame  5  of this apparatus as it is seen from its upper side. As shown in this figure, these bar-like members  13   a  and  13   b  have their respective one end fixed for the pivotal movement about shafts  36   a  and  36   b  on the mapping frame  5 , and are rotated by cylinders  34   a  and  34   b  disposed also on the mapping frame  5  and can evolve so as to protrude from the mapping frame  5  toward the interior of the pod  2 . That is, when the detecting operation for the wafer  1  is not executed, the bar-like members  13   a  and  13   b  are contained so as to be within the width of the mapping frame  5  along the axis of the frame of the mapping frame  5  (a bar-like member  13   c  and a bar-like member  13   d ). When the detection of the wafer  1  is to be effected, the bar-like member  13   c  and the bar-like member  13   d  are rotated by nearly 90 degrees about shafts  36   a  and  36   b,  respectively, by a cylinder  34   a  and a cylinder  34   b  and the bar-like members  13   a  and  13   b  evolve toward the wafer  1 . In this state, the emitter  9   a  attached to the tip end of the bar-like member  13   a  and the detector  9   b  attached to the tip end of the bar-like member  13   b  become opposed to each other. When the bar-like members  13   a  and  13   b  evolve so as to protrude from the mapping frame  5 , slots are formed between the emitter  9   a  and the detector  9   b.  The emitter  9   a  and the detector  9   b  are mounted so that the edge portion of the wafer  1  may be located between these slots. Also, the mapping frame  5  is mounted on the movable portion  56  so as to be moved up and down with the door  6 . Further, the mapping frame  5  is supported also by the rod of another cylinder  43  so as to be movable up and down discretely from the door  6 .  
           [0013]    Reference is now had to FIG. 9 to describe the mapping of a wafer processing apparatus having the wafer mapping function. To carry out mapping in this apparatus, the pod  2  is disposed on the stand  53  so as to be proximate to the access opening  10 , and the lid  4  is held by the door  6 . When the rod of the cylinder  31  is contracted, the door arm  42  is moved about the fulcrum  41  so as to separate from the access opening  10 . Then the door  6  is pivotally moved with the lid  4  and the lid  4  is detached from the pod  2 . Here, when the emitter  9   a  and the detector  9   b  have evolved, the rod of the cylinder  32  is contracted to a preparatory position in which it becomes insertable into the interior of the pod  2  (a position located from the edge of the opening in the pod  2  to the vertically lower side which is the inner side of the pod  2 ) to thereby move down the mapping frame  5 . After the mapping frame  5  has been moved down to the preparatory position, the cylinder  34   a  and the cylinder  34   b  are actuated to thereby evolved the emitter  9   a  and the detector  9   b.  Thereupon, the emitter  9   a  and the detector  9   b  become inserted into the interior of the pod  2 . In this state, as shown in FIG. 8, when the wafer  1  is seen from a direction perpendicular to the surface of the wafer  1 , there is brought about such a positional relation that the wafer  1  exists in the slot between the emitter  9   a  and the detector  9   b.  When here, the movable portion  56  is moved down, the mapping frame  5  is moved down with the door  6 , and the slot between the emitter and the detector crosses the end portion of the wafer  1  to be located when the wafer  1  exists on each of the shelves. The emitter  9   a  and the detector  9   b  can scan each shelf of the shelves which sweeping along the direction in which the wafers  1  are stacked, to thereby detect the presence or absence of the wafers  1  and effect mapping.  
           [0014]    The above-described method, however, has suffered from the following problems.  
           [0015]    (1) The emitter  9   a  and the detector  9   b  disposed on the mapping frame  5 , in order to prevent them from interfering with the pod  2 , are designed to be capable of evolving so as to be rotated by the cylinders  34   a  and  34   b  and protrude from the mapping frame  5  toward the interior of the pod  2 . The evolving mechanism, including such an air cylinder, is generally liable to produce dust. Further, in this structure, it is necessary that the cylinder  34   a  and the cylinder  34   b  be disposed in proximity to the pod  2 . This leads to the problem that the dust produced from the cylinder  34   a  and the cylinder  34   b  adheres to the wafer  1  and causes the contamination of the wafer  1 .  
           [0016]    (2) Also, an air-driven type cylinder is used in the operation of opening and closing the door  6 , the operation of moving up and down the door  6  and the operation of moving up and down the mapping frame  5 . This is for obtaining a force necessary to appropriately crush a seal provided on the lid  4  of the pod  2  to keep the degree of cleanness in the pod. If a driving device for opening and closing the lid is a motor, a great load corresponding to a moment comprising the distance from the fulcrum  41  to the door  6  multiplied by a force necessary to appropriately crush this seal becomes necessary, and this leads to a disadvantageous problem. Accordingly, a driving device for pivotally moving the door  6  and a driving device for retracting the door  6  to a predetermined position are made discrete from each other, and both of them are air-driven type cylinders. In the mapping operation, however, the air-driven type cylinder poses the problem that there cannot be generated a reference signal indicative of the distance over which the emitter  9   a  and the detector  9   b  are actually moved, for contrasting with a signal generated when the slot between the emitter  9   a  and the detector  9   b  crosses the wafer  1 , cannot be generated.  
           [0017]    (3) Also, in the opening and closing apparatus of the type as previously described which is provided with a linear motor and in which the opener  3  is opened in a horizontal direction with the door  6 , there is the problem that the production of dust from the linear motor cannot be prevented.  
         SUMMARY OF THE INVENTION  
         [0018]    It is an object of the present invention to provide a wafer processing apparatus in which a mechanism for evolving and containing a transmitting type sensor need not be disposed in proximity to a wafer and dust produced from the wafer processing apparatus to evolve and contain the transmitting type sensor during the evolving and containing operation for the transmitting type sensor can be prevented from contaminating the wafer.  
           [0019]    It is another object of the present invention to provide a wafer processing apparatus on which a pod is detachably mounted, having an access port through which a wafer is put in and out, the pod having a box having an opening, shelves for taking custody of wafers, and a lid for separably covering the opening, the wafer processing apparatus detecting whether the wafer is present on each of the shelves, the wafer processing apparatus comprising: a door unit including a door capable of holding the lid and for covering the access port; a door arm for pivotally supporting the door near one end thereof; the door arm being supported for pivoted movement about a first fulcrum disposed on a door arm supporting member disposed near the other end of the door arm by the door arm supporting member; and a door opening and closing driver for rotating the door arm about the first fulcrum; a mapping unit including a transmitting type sensor having an emitter and a detector; a mapping frame for holding the emitter and the detector so as to protrude toward the access port, the emitter and the detector being disposed in face-to-face relationship with each other, a slot being formed between the emitter and the detector; a mapping frame arm for supporting the mapping frame near one end thereof, the mapping frame arm being supported for pivotal movement about a second fulcrum disposed on a mapping frame arm supporting member disposed near the other end of the mapping frame arm by the mapping frame arm supporting member; and a mapping frame driver for rotating the mapping frame arm about the second fulcrum; and a movable portion for supporting the door arm supporting member and the mapping frame arm supporting member, and moving the door unit and the mapping frame; wherein the emitter and the detector are moved toward the access port and the opening and are plunged into the pod after the door is opened with the lid by the door unit, and by the movable portion, the slot between the emitter and the detector crosses an end portion of a wafer to be located when a wafer is present on each of the shelves. 
       
    
    
       [0020]    The above and other objects of the invention will appear more fully hereinafter from the consideration of the following description taken in connection with the accompanying drawings wherein one example is illustrated by way of example.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 generally shows a wafer processing apparatus to which the present invention is applied.  
         [0022]    [0022]FIG. 2A is an enlarged view of the vicinity of the opener of a wafer processing apparatus according to the present embodiment as it is seen from a side thereof.  
         [0023]    [0023]FIG. 2B is an enlarged view of the vicinity of the opener of the wafer processing apparatus according to the present embodiment as it is seen from the inside of a minienvironment.  
         [0024]    [0024]FIG. 3A is a front view of the movable portion of the opener of a wafer processing apparatus according to Embodiment 1 as it is seen from a load port side.  
         [0025]    [0025]FIG. 3B is a view of the movable portion of the opener of the wafer processing apparatus according to Embodiment 1 as it is seen from a side thereof.  
         [0026]    [0026]FIG. 4 is a view showing the sequence of the mapping of a wafer, and shows a state when the mapping preparation has been completed.  
         [0027]    [0027]FIG. 5 is a view showing the sequence of the mapping of the wafer, and shows a state when the mapping operation has been completed.  
         [0028]    [0028]FIG. 6 is a view showing the sequence of the mapping of the wafer, and shows a state when all of the mapping and the opening operation of a lid have been completed.  
         [0029]    [0029]FIG. 7A is an enlarged view of the vicinity of the opener of a conventional wafer processing apparatus as it is seen from a side thereof.  
         [0030]    [0030]FIG. 7B is an enlarged view of the vicinity of the opener of the conventional wafer processing apparatus as it is seen from the inside of a minienvironment.  
         [0031]    [0031]FIG. 8 shows the transmitting type sensor portion of the conventional wafer processing apparatus.  
         [0032]    [0032]FIG. 9 shows the details of the operation of a mapping frame provided with the transmitting type sensor of the conventional wafer processing apparatus.  
         [0033]    [0033]FIG. 10 shows the arrangement of the emitter and the detector of the transmitting type sensor with regard to the wafer placed on a shelf. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
       [0034]    Embodiment 1 will hereinafter be described with reference to the drawings.  
         [0035]    [0035]FIG. 1 shows the whole of a wafer processing apparatus  50 . The wafer processing apparatus  50  is comprised chiefly a load port portion  51  and a minienvironment  52 . In the minienvironment  52  of the wafer processing apparatus  50 , in order to exhaust dust and keep a high degree of cleanness, a constant air flow is produced from the upper portion toward the lower portion of the minienvironment  52  by a fan (not shown) provided in the upper portion of the minienvironment  52 . Thus, the dust is always exhausted downwardly.  
         [0036]    The load port portion  51  and the minienvironment  52  are comparted by a partition  55  and a cover  58 . A stand  53  for placing a pod  2  thereon is installed on the load port portion  51 , and can be moved on the load port portion  51  toward or away from the minienvironment  52 .  
         [0037]    The pod  2  is provided with a main body  2   a  which is a box having a space for containing a wafer  1  therein and provided with an opening, and a lid  4  for detachably closing the opening. In the main body  2   a,  there is disposed a rack having shelves arranged in a predetermined direction. In the present embodiment, this predetermined direction is a vertical direction. A wafer can be placed on each of the shelves. The interior of the minienvironment  52  is kept at a high degree of cleanness to treat the wafer  1 .  
         [0038]    An access opening  10  somewhat larger than the lid  4  of the pod  2  is formed in the minienvironment  52  on the load port portion  51  side. An opener  3  for opening and closing the lid  4  of the pod  2  is provided on a side of the access opening  10  which is the interior of the minienvironment.  52 . Also, the robot arm  54  of a transport robot is provided in the interior of the minienvironment  52 . After the lid  4  of the pod  2  is opened, the robot arm  54  puts in and out the wafer  1  contained in the pod  2  through an opening in the pod  2  and the access opening  10  to thereby effect predetermined treatment.  
         [0039]    The opener  3  will be described here with reference to FIGS. 2A and 2B. FIG. 2A is a magnified view of the load port portion  51 , the pod  2 , the opener  3  and the lid  4  in FIG. 1, and FIG. 2B is a view of the portions shown in FIG. 2A as they are seen from the inside of the minienvironment  52 . The opener  3  is provided with a door  6  and a mapping frame  5 . The door  6  is a plate-shaped member of a size which can cover the access opening  10 , and the surface thereof is provided with holding portions  11   a  and  11   b  which are vacuum intake holes. A surface located on the pod  2  side when the door  6  covers the access opening  10  is such a flat surface as can closely contact with the lid  4 . A fixing member  46  having a hole is attached to the door  6 . It is fixed by a pivot shaft  45  which is provided on the upper end of a door arm  42  pivotally extending through this hole. A hole is formed in the lower end of the door arm  42 , and the door arm  42  is coupled and rotatably supported by a pivot shaft  40  extending through that hole and a hole in the tip end of a rod  37  which is a portion of an air-driven type door opening and closing cylinder  31  which is a driving device for opening and closing the door.  
         [0040]    A mapping frame  5  is a structure comprising a frame member disposed along the access opening  10  and so as to surround the periphery of the door  6 . The mapping frame  5  is mounted on the upper ends of a mapping frame arm  12   a  and a mapping frame arm  12   b  extending long in the frame member under it. Holes are formed in the lower ends of the mapping frame arm  12   a  and the mapping frame arm  12   b,  and a pivot shaft  44  extends through those holes and a hole in the tip end of a rod  38  which is a portion of an air-driven type mapping frame driving cylinder  35  which is a mapping frame driving device, whereby the two mapping frame arms are coupled together and rotatably supported. The mapping frame arm  12   a  and the mapping frame arm  12   b  extend symmetrically and in parallel to each other along the center axis of the mapping frame  5  and in a vertical direction to equally support a load. A rod  47  perpendicular to each of the mapping frame arm  12   a  and the mapping frame arm  12   b  is mounted between the upper ends and lower ends of the mapping frame arm  12   a  and the mapping frame arm  12   b.  A fixing member  39  which is a fulcrum supporting portion of a shape extending perpendicularly from a support member  60  is disposed on the support member  60 . The fixing member  39  has a through-hole parallel to the support member  60 . A bearing (not shown) is disposed in the through-hole in the fixing member  39 , and the outer ring of the bearing is fitted to the inner wall of the through-hole, and the inner ring of the bearing pivotally supports the rod  47 . Thereby, the rod  47  constitutes a fulcrum  41  in a state in which it is contained in the through-hole in the fixing member  39 .  
         [0041]    This fulcrum  41  is constituted as a coaxial fulcrum serving as the fulcrum of the mapping frames  12   a  and  12   b  and the fulcrum of the door arm in common. That is a discrete through-hole is formed between the upper end and lower end of the door arm  42 . The rod  47  extends through this through-hole and constitutes the fulcrum  41 .  
         [0042]    The door arm  42  is pivotally movable about the fulcrum  41  by the expansion and contraction of the rod  37  by the driving of the cylinder  31 . The fulcrum  41  of the door arm  42  is fixed to the support member  60  provided on an upwardly and downwardly movable portion  56 . The door  6  has holding ports  11   a  and  11   b,  and can hold the lid  4  of the pod  2  by vacuum absorption. The door arm  42  is disposed so as to be substantially vertical when the door  6  is urged against the access opening  10  (hereinafter referred to as waiting state), and the door arm  42  is rotated, whereby the door  6  is moved away from the wall surface of the minienvironment  52 .  
         [0043]    By the expansion and contraction of the rod  38  by the driving of the mapping frame driving cylinder  35 , the mapping frame arm  12  is pivotally movable about the fulcrum  41 . That is, the mapping frame arm  12  is also fixed to the support member  60  provided on the upwardly and downwardly movable portion  56 . The mapping frame  5  is disposed so as to be inclined with separating from the wall surface of the minienvironment  52  when the door  6  is in its waiting state. That is, in this state, the mapping frame arm  12   a  and the mapping frame arm  12   b  are supported in a state in which they are inclined so as to have a certain angle with respect to the door arm  42 , and the upper portion of the mapping frame  5  is spaced apart by a predetermined distance from the wall surface of the minienvironment  52 . On the other hand, when from this waiting state, the mapping frame  5  rotates the mapping frame arm  12   a  and the mapping frame arm  12   b  in a direction to abut against the wall surface of the minienvironment  52 , the mapping frame  5  substantially abuts against the wall surface of the minienvironment  52 . A sensor supporting bar  13   a  and a sensor supporting bar  13   b  are fixed to a frame member disposed in the upper portion of the mapping frame  5  so as to protrude toward the wall surface of the minienvironment  52 . The emitter  9   a  and detector  9   b  of transmitting type sensor  9  which is a first transmitting type sensor are attached to the tip ends of the sensor supporting bar  13   a  and the sensor supporting bar  13   b,  respectively, in opposed relationship with each other and so as to form a slot therebetween.  
         [0044]    The wafer processing apparatus  50  is provided with a movable portion  56  for moving up and down the opener  3 . FIG. 3A is a view of the movable portion  56  of the opener  3  as it is seen from the load port portion  51  side, and FIG. 3B is a view taken along the arrow X of FIG. 3A. The movable portion  56  is provided with an air-driven type rodless cylinder  33  for effecting vertical movement and a support member  60 , and is disposed below the underside of the pod  2  so as to be downstream of the pod  2  with respect to an air flow. The fixing member  39 , the air-driven type cylinder  31  and the cylinder  35  are mounted on the support member  60 . The movable portion  56  is provided on the load port portion  51  side, and supports the opener  3  on the minienvironment  52  side from a slot  57  formed in a partition  55  by the door arm  42 , the mapping frame arm  12   a  and the mapping frame arm  12   b.  The slot  57  is formed with the direction of movement of the movable portion  56 , i.e., in the case of the present embodiment, the vertical direction, as the lengthwise direction. The load port portion  51  and the minienvironment  52  are partitioned by a cover  58  so that the degree of cleanness in the minienvironment  52  may not be lowered by the slot  57 . Further, a limiter  59  for preventing the overrun of the opener  3  when the opener  3  is moved down is provided below a partition  55 . The partition  55  is provided with the rodless cylinder  33 , a guide  61   a  and a guide  61   b  along the slot  57 . The movable portion  56  effects upward and downward movement along the guide  61   a  and the guide  61   b  by the rodless cylinder  33 . A timing plate  7  is provided sideways of the movable portion  56  along the rodless cylinder  33 .  
         [0045]    The timing plate  7  is a plate-shaped member extending in a direction along the rodless cylinder  33 , and has in the lengthwise direction thereof index means disposed at predetermined intervals. In the present embodiment, the timing plate has notches as the index means having a certain width and disposed at predetermined intervals to form an uneven portion  12 . The member of the uneven portions corresponds to the number of the shelves of the wafer arranging shelf in the pod, and the uneven portions are disposed so that when the movable portion comes to any shelf, a notch corresponds thereto without fail. In the movable portion  56  on the timing plate  7  side, a transmitting type sensor  8  which is a second transmitting type sensor is fixed onto the lateral partition  55 . The emitter and detector of the transmitting type sensor  8  are disposed in opposed relationship with each other and slots are formed therebetween. The emitter and detector of the transmitting type sensor  8  are disposed so that the uneven portions  12  provided with notches at predetermined intervals provided on the timing plate  7  may be interposed among the slots of the transmitting type sensor  8 , and the uneven portions  12  of the timing plate  7  can be detected in conformity with the movement of the movable portion  56 .  
         [0046]    A transmitting type sensor  62  is provided on the support member.  60  of the movable portion  56 , and a limiter  64  is provided on the partition  55  near the lower side of the slot  57 . Design is made such that when a protruding portion  62  intercepts light from the limiter  64 , a stop signal is outputted to the movable portion and the movement of the whole of the opener  3  is stopped.  
         [0047]    Reference is now had to FIGS. 2A and 2B and FIGS.  4  to  6  to describe how the detection of the wafer  1  for the mapping of the wafer  1  is effected on the basis of these constructions. FIGS. 2A and 2B show a waiting state, FIG. 4 shows a state in which the lid  4  is opened and closed and the mapping frame  5  is operated, FIG. 5 shows a state in which the detection of the wafer  1  has been completed, and FIG. 6 shows a state in which the mapping frame  5  has been returned to the waiting state after the completion of the detection of the wafer  1 .  
         [0048]    Wafers  1  which have satisfied the treatment standard of pre-treatment are contained in the shelf in the pod  2  which has terminated the preceding treating process, while on the other hand, wafers  1  which have not satisfied the standard are eliminated from the process at the stage of the pre-treatment. In the shelf for the wafers  1 , there are mixedly present shelves on which the wafers  1  are present and shelves on which the wafers  1  are not present. The pod  2  in this state, as shown in FIGS. 2A and 2B, is placed on the stand  53  on the minienvironment  52  and is moved so as to approach the access opening  10 .  
         [0049]    In this state, the opener  3  is in the waiting state. That is, the rod  37  of the cylinder  31  for opening and closing the door is in its most expanded state and the door arm  42  is in a state in which it urges the door  6  against the access opening  10  about the fulcrum  41  to thereby cover the access opening. In the present embodiment, in this state, the arm  42  is in its vertically erect state. On the other hand, the rod  38  of the mapping frame driving cylinder  35  is in its most contracted state and the mapping frame arms  12   a  and  12   b  are in a state in which they act to pull the mapping frame  5  apart from the wall surface of the minienvironment  52  about the fulcrum  41 . That is, in the present embodiment, the mapping frame arms  12   a  and  12   b  are in an oblique state at a certain angle with respect to the door arm  42 .  
         [0050]    [0050]FIG. 4 shows a state in which the pod  2  becomes proximate to the access opening  10  and the door  6  holds the lid  4 . When the pod  2  becomes proximate to the access opening  10 , the lid  4  of the pod  2  comes into close contact with the door  6 , and the door  6  effects the holding of the lid  4  of the pod  2  from holding portions  11   a  and  11   b  by vacuum suction. When the door  6  holds the lid  4 , the cylinder  31  for opening and closing the door works to contract the rod  37 . Thereupon the door arm  42  pulls a pivot shaft  40  provided on the end portion of the door arm  42  toward a support base  60  side, and is pivotally moved by the fulcrum  41  so as to pull the door  6  apart from the access opening  10  in accordance with the principle of the lever, and opens the lid  4  from the pod  2 .  
         [0051]    Assuming that the mapping frame arms  12  are pivotally moved after the lid  4  has been opened, the movable portion  56  is slightly moved down to a position on which the upper end of the mapping frame  5  enters the position of the access opening  10 . After the termination of this downward movement, the mapping frame arms  12  actually start their pivotal movement. That is, the mapping frame arms  12  are pivotally moved until the rod  38  of the mapping frame driving cylinder  35  is expanded and the mapping frame  5  substantially abuts against the periphery of the access opening  10 . Thereupon the transmitting type sensor  9  attached to the upper side of the mapping frame  5  comes out of the access opening  10  and is inserted into the pod  2 . At this point of time, the emitter  9   a  and the detector  9   b,  like the conventional transmitting type sensor  9  as shown in FIG. 8, constitute a slot which is a detection space with the wafer  1  lying on a straight line linking the emitter  9   a  and the detector  9   b  together.  
         [0052]    When in this state., the movable portion  56  is vertically moved, mapping is executed. That is, the opener  3  is moved down to a position shown in FIG. 5 by the rodless cylinder  33 . The emitter  9   a  and the detector  9   b  are moved down in a direction perpendicular to the surface of the wafer  1  with the movable portion  56  and the opener  3  and therefore, when the wafer  1  is present on a shelf of the shelves, light emitted from the emitter  9   a  is intercepted, and when the wafer  1  is absent on the shelf, the light of the emitter  9   a  is not intercepted.  
         [0053]    If design is made such that the detector  9   b  generates a non-transmission signal when it is interrupted by the wafer  1 , and the detector  9   b  generates a transmission signal when it is not interrupted by the wafer  1 , it can be judged that when the non-transmission signal is detected, the wafer  1  is present, and it can be judged that when the transmission signal is detected, the wafer  1  is absent. Further, as will hereinafter be described, general judgment is effected with a signal indicative of the position of the wafer  1  added thereto.  
         [0054]    The emitter and detector of the transmitting type sensor  8  are disposed so as to have interposed therebetween the uneven portions  12  which are cut-aways at predetermined intervals which are index means provided on the timing plate  7  and therefore, when the movable portion  56  is moved down, the transmitting type sensor  8  is also moved down therewith and detects the uneven portions  12  of the timing plate  7 . Design is made such that when at this time, the transmitting type sensor  8  passes a notched portion, the light from the emitter of the transmitting type sensor  8  is not intercepted, but is sensed by the detector to thereby generate a transmission signal, and when the transmitting type sensor  8  passes an un-notched portion, the light from the emitter of the transmitting type sensor  8  is intercepted and is not detected by the detector to thereby generate a non-transmission signal. Accordingly, if the uneven portions  12  of the timing plate  7  are preset so that the point of time at which the emitter and detector of the transmitting type sensor  9  pass each shelf of the shelves in the pod  2  and point of time at which the emitter and detector of the transmitting type sensor  8  pass the notched portion may correspond to each other, the transmission or non-transmission signal detected by the transmitting type sensor  8  is indicative of the signal of a shelf of the shelves which the transmitting type sensor  9  actually passes. If this is compared with the result of the detection of the transmission or non-transmission signal detected as a result of the transmitting type sensor  9  having its light intercepted by the wafer  1  and when the transmitting type sensor  8  detects a signal corresponding to a shelf of the shelves, the transmitting type sensor  9  has its light intercepted, it can be judged that the wafer  1  is present on that shelf, and if at that time, the transmitting type sensor  9  has its light not intercepted, it can be judged that the wafer  1  is absent on that shelf. This detecting operation is executed for all wafers  1 , and when the detection terminating position of the opener  3  shown in FIG. 5 is reached, the detecting operation is completed.  
         [0055]    Of course, an un-notched portion can also be index means having a certain width and disposed at predetermined intervals.  
         [0056]    Thereafter, the rod  38  of the cylinder  35  for opening and closing the mapping frame is again contracted, whereupon the mapping frame arms  12  are pivotally moved and the mapping frame  5  is moved away from the access opening  10 . When the rod  38  is most contracted the movement of the mapping frame  5  is completed. The movable portion  56  is then moved to the lowest point, thus opening the lid  4  and completely a series of detecting operations for the mapping of the wafer  1 . This state is the state shown in FIG. 5.  
         [0057]    As described above, the emitter and detector of the transmitting type sensor  9  are fixed to the mapping frame, and provision is made of the mapping frame arms  12  and the mapping frame driving cylinder which are means for pivotally moving the mapping frame  5 , and further these devices are provided on the movable portion  56  sufficiently spaced apart from the access opening  10 , whereby it has become unnecessary to provide a device for performing the evolving operation of the transmitting type sensor near the wafer  1 .  
         [0058]    Also, by utilizing the timing plate  7  and the transmitting type sensor  8 , a synchronizing signal corresponding to a shelf of the shelves in the pod  2  can be easily generated and therefore, even if a drive motor is not used as a driving device, the accurate mapping of the wafer  1  becomes possible. If the timing plate  7  is thus utilized, an air-driven type cylinder which cannot generate a signal can be utilized for the mapping of the wafer  1 .  
         [0059]    While in the present embodiment, the shelves are disposed so as to be arranged vertically and the movable portion  56  is vertically moved up and down and the mapping frame  5  is a structure comprising a frame member disposed along the access opening  10  and so as to surround the door  6 , the same effect is achieved as long as the direction in which the shelves are arranged and the direction in which the movable portion  56  is moved are substantially the same and the mapping frame  5  has a member on which a pair of transmitting type sensors  9  can be disposed so that a line linking the pair of transmitting type sensors  9  together on the starting point side of the movement of the movable portion  56  may cross the semiconductor wafer placed on a shelf of the shelves. That is, the mapping frame can achieve a similar effect if as in the present embodiment, the shelves are disposed so as to be arranged vertically and a pair of transmitting type sensors  9  can be disposed above the door so that when the movable portion  56  is vertically moved up and down, a line linking the pair of transmitting type sensors  9  together may cross the semiconductor wafer placed on a shelf of the shelves.  
         [0060]    Also, while in the present embodiment, the fulcrum of the door arm  42  and the fulcrum of the mapping frame  5  are made common to each other by the fulcrum  41 , a similar effect will be achieved even if the two fulcrums are made discrete from each other. That is, an effect similar to that of the present invention will be achieved even if different fulcrums are provided as a first fulcrum to be provided on the door arm  42  and a second fulcrum to be provided on the mapping frame.  
         [0061]    While in the present embodiment, the movable portion  56 , the fulcrum  41 , the cylinder  31  for opening and closing the door and the mapping frame driving cylinder  35  are made integral with one another, they need not always be made integral with one another in obtaining the effect of the present invention. A similar effect will be achieved as long as these mechanisms are disposed downstream of the pod  2  with respect to the air flow.  
         [0062]    Furthermore, in theory, the emitter  9   a  and the detector  9   b  can be arranged so that the light beam (a center of the light beam) from the emitter  9   a  to the detector  9   b  is parallel to the surface of the wafer placed on each shelf. In practice, however, as shown in Fig. 10 , the emitter  9   a  and the detector  9   b  should be arranged with an angle to the surface of the wafer placed on each shelf. This is because the light beam from the emitter  9   a  diffusely reflects by the surface of the wafer on a shelf. That is, in order to avoid the diffuse reflection, the emitter  9   a  and the detector  9   b  may be arranged so that the light beam from the emitter  9   a  to the detector  9   b  is inclined with an angle to the surface of the wafer placed on each shelf. Preferably, the angle should be substantially 1 degree.  
         [0063]    An actual solid angle of the light beam from the emitter  9   a  is about 2 degree. If the emitter  9   a  and the detector  9   b  are arranged so that the light beam from the emitter  9   a  to the detector  9   b  is parallel to the surface of the wafer placed on each shelf, the light beam diffusely reflects on the surface of the wafer and reach the detector  9   b  even though the direct light beam from the emitter  9   a  is blocked by the wafer. In this case, ever though the wafer should be detected, the detector  9   b  cannot detect the wafer since the detector receives the diffuse reflection from the wafer. Therefore, if the emitter  9   a  and the detector  9   b  are arranged with an angle of about 1 degree to the surface of the wafer placed on each shelf, it can avoid causing the diffuse reflection from the wafer.  
       Second Embodiment  
       [0064]    In Embodiment 1, a magnetic fluid seal is disposed in such a state in which the rod  47  extends through the opposite end portions of the through-hole in the fixing member  39 , whereby dust produced from the pivotally movable portion can be prevented from being outputted to the outside to thereby further prevent the contamination by the dust. Embodiment 2 will hereinafter be described.  
         [0065]    Magnetic fluid seals  48   a  and  48   b  attached to the opposite end portions of the through-hole in the fixing member  39  in such a state that the rod  47  extends therethrough. Each of the magnetic fluid seal  48   a  and the magnetic fluid seal  48   b  is of structure in which a magnetic member (e.g., a ferrite magnet) is sandwiched between two annular thin plates. Further, when a magnetic fluid is interposed between these plates, this magnetic fluid is held between these plates by the magnetic force of the ferrite magnet, and the held magnetic fluid is held in the gap with respect to an object to be sealed by surface tension. As a result, film of the magnetic fluid is forcibly forced on the magnetic fluid seals to thereby achieve sealing. In the present apparatus, film of oil including a magnetic material is disposed so as to be formed between the peripheral surface of the rod  47  and the magnetic fluid seals  48   a  and  48   b.  Thereby, dust produced from the rod  47  which is a rotary shaft constituting the fulcrum  41  can be prevented.  
         [0066]    Of course, Embodiment 2 can be applied to Embodiment 1, and can be applied not only to the fulcrum  41  for opening and closing the mapping frame  5  and the door  6 , but also to the whole of the pivotally movable portion. Accordingly, the magnetic fluid seal can be applied to the whole of the pivotally movable portion in spite of the fact that in the wafer processing apparatus, there is an air flow flowing from the upper portion toward the lower portion of the apparatus and that the first fulcrum and the second fulcrum are located below the underside of the pod.  
         [0067]    While the invention has particularly been shown and described with respect to the preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details can be made therein without departing from the spirit and scope of the invention.