Abstract:
A wafer carrying system includes an intermediate cassette device having a plurality of wafer support holders, a robot arm device to carry wafers, an aligner unit to align the wafers, and a wafer feed and storage cassette. The wafers held by the robot arm device are transferred to the aligner unit are aligned in the intermediate cassette device, and are then directly delivered from the aligner unit to the wafer support holders of the intermediate cassette device.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention broadly relates to a wafer carrying system, and in particular, to a wafer carrying system including an intermediate cassette device having a plurality of wafer support holders, a robot arm device for carrying a wafer, an aligner unit for aligning the wafer, and a wafer feed and storage cassette, and to a carrying method thereof.  
           [0002]    Conventionally, as shown in FIG. 1, a wafer  101  is carried once from a wafer cassette  104  to an aligner unit  102  by a robot arm  105 , and then, the aligned wafer  101  is carried to an intermediate cassette (shuttle)  103 .  
           [0003]    More specifically, the wafer  101  is aligned by the aligner unit  102  separately located from the intermediate cassette  103  to appropriately set the rotational position of the wafer  101  using a mark such as an orientation flat (a notch), and then, the wafer  101  is loaded on the intermediate cassette  103 . Herein, it is to be noted that numeral  105  denotes a main cassette (a vacuum cassette) while numeral  106  denotes an unloading cassette (a shuttle).  
           [0004]    For example, when the wafer  101  is carried from the wafer cassette  104 →to the intermediate cassette  103 , the carrying path is: the wafer cassette  104 →(carriage by the robot arm  105 )→the aligner unit  102 →(carriage by the robot arm  105 )→the intermediate cassette  103 ; and thus two carriages by the robot are necessary.  
         SUMMARY OF THE INVENTION  
         [0005]    It is therefore an object of this invention to provide a wafer carrying system which is capable of carrying each wafer in single operation of a robot device, and which is capable of shortening the changing time of a treated wafer with an untreated wafer, and a carrying method thereof.  
           [0006]    According to an aspect of the present invention, a wafer carrying system comprises an intermediate cassette device having a plurality of wafer support holders, a robot arm device to carry the wafer, an aligner unit to align the wafer, and a wafer feed and storage cassette.  
           [0007]    With such a structure, the wafer held by the robot arm device is transferred to the aligner unit, and aligned in the intermediate cassette device, and then, directly delivered from the aligner unit to a plurality of wafer support holders of the intermediate cassette device.  
           [0008]    The aligner unit has a positioner, and the wafer is centered by the positioner and transferred to a wafer holding and rotating part by the vertical movement of the wafer holding and rotating part of the aligner unit or the positioner.  
           [0009]    Further, the wafer is centered by the positioner on the aligner unit in which the positioner is provided in a concentric manner, is transferred to the wafer holding and rotating part of the aligner unit, and is delivered to a next process by the vertical movement of the whole aligner unit.  
           [0010]    The center of the aligner unit and the wafer loading center of the intermediate cassette device are disposed substantially concentrically with each other.  
           [0011]    The aligner unit is horizontally moved to the intermediate cassette device so that the center of the aligner unit and the wafer loading center of the intermediate cassette device are disposed substantially concentrically with each other.  
           [0012]    The intermediate cassette device is horizontally moved to the aligner unit so that the center of the aligner unit and the wafer loading center of the intermediate cassette device are disposed substantially concentrically with each other.  
           [0013]    The center of the positioner of the aligner unit and the center of the wafer holding and rotating part of the aligner are disposed concentrically with each other in the perpendicular direction.  
           [0014]    The aligner unit can be vertically raised/lowered, and wafers are successively loaded from an upper end stage to a lower end stage of a plurality of wafer support holders of the intermediate cassette device by the raising/lowering operation of the aligner unit.  
           [0015]    The aligner unit is disposed on the wafer-loading-center locus on a wafer insertion path of the intermediate cassette device, and the aligner unit is horizontally moved to receive the wafer from the robot arm device.  
           [0016]    The aligner unit is horizontally moved to receive the wafer from the robot arm device, and the intermediate cassette device is vertically moved to deliver the wafer.  
           [0017]    The plurality of wafer support holders of the intermediate cassette device have an open-bottom cavity part, and the aligner unit can be vertically raised/lowered within this cavity part.  
           [0018]    The positioner and the wafer holding and rotating part of the aligner unit can be vertically raised/lowered within the open-bottom cavity part of the plurality of wafer support holders of the intermediate cassette device.  
           [0019]    The intermediate cassette device can be vertically raised/lowered, and the wafers are successively loaded on the plurality of wafer support holders of the intermediate cassette device from the aligner unit from an upper stage to a lower stage by the raising/lowering operation of the intermediate cassette device.  
           [0020]    The aligner unit is disposed on the horizontal moving line of the intermediate cassette device or on a wafer-loading-center locus during the rotation by the shuttle drive, the wafer is delivered by horizontally moving the intermediate cassette device, and the aligner unit is vertically moved.  
           [0021]    The intermediate cassette device is horizontally moved to deliver the wafer, and the intermediate cassette device is vertically moved.  
           [0022]    The wafer is delivered from the robot arm device to the aligner unit, the position of which can be changed by vertical movement, and the aligner unit or the intermediate cassette is vertically moved to receive and load the wafer.  
           [0023]    The robot arm device is vertically moved during the carriage of the wafer from the feed and storage cassette, and the wafer is delivered to the aligner unit, the position of which can be changed by vertical movement, and the aligner unit or the intermediate cassette is vertically moved to receive and load the wafer.  
           [0024]    The carried and loaded wafers are aligned successively from a slot stage of the upper-stage wafer support holder of the intermediate cassette device, and are reloaded on the same slot stage of the wafer support holder.  
           [0025]    A sensor to detect the mark such as the orientation flat of the wafer is installed in an inclined manner on the aligner unit.  
           [0026]    The untreated wafer is automatically carried into a vacuum treatment chamber from a vacuum container, and the treated wafer is automatically carried out of the vacuum treatment chamber to the vacuum container.  
           [0027]    The main cassette device is stored in a sealed box for continuous transfer into the vacuum treatment chamber.  
           [0028]    The feed and storage cassette device is stored in a sealed box for continuous transfer into a clean room.  
           [0029]    The aligner unit can be advanced into a holding part of the main cassette device, and the main cassette device or the aligner unit is vertically moved to receive the wafer from the aligner unit.  
           [0030]    The robot arm device is horizontally movable between a plurality of the feed and storage cassettes.  
           [0031]    According to another aspect of the present invention, a wafer carrying system comprises a wafer carrying device to collectively deliver a plurality of wafers between a plurality of wafer holding shelves in a vacuum cassette device provided in a treatment device in a vacuum chamber, including a wafer-loading shuttle device and a wafer-unloading shuttle device disposed at the side of the vacuum cassette device.  
           [0032]    The shuttle devices include shuttle cassettes having a plurality of wafer support holders corresponding to a plurality of the wafer holding shelves of the vacuum cassette device.  
           [0033]    In this event, the shuttle cassette is movable between a delivery position to deliver the wafers to/from the cassette device and a waiting position distant therefrom.  
           [0034]    Each of the plurality of wafer holds shelves holding the wafer in each center area. The plurality of wafer support holders supports each wafer at positions on both sides in the diameter direction and away from the center area.  
           [0035]    Under this circumstance, an aligner unit is disposed in a carrying path to the shuttle device. Further, the wafer held by a robot arm device is transferred to the aligner unit in the shuttle device, which is the intermediate cassette device. In this condition, the wafers are aligned, and directly delivered from the aligner unit to the wafer support holders of the shuttle device, which is the intermediate cassette device.  
           [0036]    According to still another aspect of the present invention, a wafer carrying method for a wafer carrying system includes an intermediate cassette device having a plurality of wafer support holders, a robot arm device to carry a wafer, an aligner unit to align the wafer, and a wafer feed and storage cassette, and delivering the wafer to the wafer support holder after the wafer is aligned, the method comprising the steps of: taking out the wafer from the feed and storage cassette by the robot arm device to the intermediate cassette device; transferring the held wafer to the wafer support device of the intermediate cassette device; transferring the wafer to the aligner unit and aligning the wafer; and directly delivering the aligned wafer to the wafer support holder of the intermediate cassette device in the aligner unit.  
           [0037]    More specifically, the orientation flat (a notch) alignment of a wafer (this operation is hereinafter referred to as “aligning”) to be transferred to a swing-type cassette referred to as a vacuum cassette (hereinafter referred to as “shuttle”) to collectively transfer silicon wafers is implemented in an aligner unit which can be raised/lowered in the shuttle (hereinafter referred to as “elevator-type (raising/lowering-type) aligner unit” in a device to carry treated and untreated silicon wafers out of/into a vacuum container in a device to treat works (the silicon wafers) in a vacuum chamber such as an ion implanter.  
           [0038]    The carrying time of the wafer to the shuttle can be improved, thereby improving the wafer treatment capacity per unit time. For example, when the wafer is carried from the wafer cassette to the shuttle, the cassette is carried in the order of: the cassette→(carriage by the robot arm device)→the aligner unit→the intermediate cassette; and thus the carriage by the robot can be completed in single operation.  
           [0039]    The shuttle and the aligner unit are conventionally located separately from each other; however, space in the device can be saved by disposing them together.  
           [0040]    In accordance with the present invention, the loading time taking several minutes (for thirteen wafers) in a conventional system is substantially halved in an example of handling thirteen 12-inch wafers.  
           [0041]    The carriage by the robot can be completed in single operation when an elevator-type aligner unit is used in carrying wafers to the shuttle. The robot which completes the carriage of the wafer to the aligner unit can fetch the next wafer without waiting for the aligning operation, and the carrying capacity of the robot can be improved.  
           [0042]    In addition, the wafer can be aligned at each position of the shuttle by the elevator-type aligner unit. Further, carriage of one wafer by a robot device can be completed in single operation.  
           [0043]    Still further, the changing time of a treated wafer and an untreated wafer can be shortened, and the wafer carrying system can be saved in space. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0044]    [0044]FIG. 1 is a view of a conventional wafer carrying system;  
         [0045]    [0045]FIG. 2 is an overall schematic view of a wafer carrying system according to a first embodiment of this invention;  
         [0046]    [0046]FIGS. 3A and 3B show the construction of a main cassette (a vacuum cassette) and an intermediate cassette, and the delivery state of a wafer, respectively;  
         [0047]    [0047]FIGS. 4A and 4B show a detailed construction of the intermediate cassette, wherein FIG. 4A is a plan view and FIG. 4B is a sectional view;  
         [0048]    [0048]FIG. 5 is a view of an orientation-flat sensor provided on an aligner unit;  
         [0049]    [0049]FIGS. 6A to  6 F show the aligning positioning operation of the wafer carrying system of this invention;  
         [0050]    [0050]FIG. 7 is a view of the wafer carrying system according to a second embodiment of this invention;  
         [0051]    [0051]FIG. 8 is a view of the wafer carrying system according to a third embodiment of this invention;  
         [0052]    [0052]FIG. 9 is a view of a wafer carrying system according to a fourth embodiment of this invention; and  
         [0053]    [0053]FIG. 10 is a view of a wafer carrying system according to a fifth embodiment of this invention.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0054]    (First Embodiment)  
         [0055]    A first embodiment of this invention will be described with reference to the drawings.  
         [0056]    The overall construction of a wafer carrying system of this invention will be described with reference to FIG. 2.  
         [0057]    As shown in FIG. 2, the wafer carrying system collectively delivers thirteen wafers to/from, for example, thirteen wafer holding shelves in a main cassette device (a vacuum cassette)  20  provided on a vacuum container  10  in a batch-treatment-type ion implanter, and includes an intermediate cassette (a wafer-loading shuttle device)  30  and a wafer-unloading cassette device (a shuttle device)  40  which are disposed on either side of the main cassette  20 . In this case, only a part of the vacuum container  10  is shown in the figure.  
         [0058]    The intermediate cassette  30  and the wafer-unloading cassette  40  have thirteen wafer support holders corresponding to the thirteen wafer holding shelves. With such a structure, the intermediate cassette  30  and the wafer-unloading cassette  40  are turnable between a delivery position to deliver the wafers to/from the main cassette  20  and a waiting position away therefrom.  
         [0059]    The first embodiment includes a handling device  50  for removing thirteen untreated wafers one-by-one from a wafer feed cassette  60  and delivering them to the intermediate cassette  30  which is at the waiting position, and for receiving thirteen treated wafers one-by-one from the wafer-unloading cassette device  40  in the waiting position and delivering them to the wafer feed cassette  60 . The handling device  50  is horizontally movable along a rail  70 .  
         [0060]    The main cassette device  20  has thirteen wafer holding shelves  21  as shown in FIGS. 3A and 3B, and each wafer holding shelf  21  holds a wafer  22  at a plurality of points in its center area. The main cassette device  20  can be inserted in/removed from the vacuum container  10 , and the plurality of wafers  22  are delivered with the main cassette device  20  outside the vacuum container  10 .  
         [0061]    As illustrated in FIGS. 3A and 3B, the thirteen wafer holding shelves  21  in the main cassette device  20  are vertically movable by a given distance. When the thirteen untreated wafers  22  are collectively delivered from the intermediate cassette device  30  to the main cassette device  20 , the thirteen wafer holding shelves  21  are initially at a position which is lowered by the given distance, and then raised by the given distance when the thirteen wafer support holders are at the delivery position. Thus, the thirteen untreated wafers can be collectively received.  
         [0062]    Thus, the intermediate cassette device  30  can collectively deliver thirteen wafers (untreated)  22  to the main cassette device  20 . Herein, numeral  23  denotes a wafer treatment chamber. In the wafer treatment chamber  23 , ions are implanted in the wafers  22  using an ion implanter (not shown).  
         [0063]    The above-described structure is completely the same for the wafer-unloading cassette device  40 , and thus, the illustration and description thereof will be omitted. When a plurality of treated wafers  22  are collectively delivered from the main cassette device  20  to the wafer-unloading cassette device  40 , thirteen wafer holding shelves  21  are initially at a position which is raised by the given distance, and are then lowered by the given distance when thirteen wafer support holders are at the delivery position. Thus the thirteen treated wafers can be collectively delivered to thirteen wafer support holders.  
         [0064]    Meanwhile, the handling device  50  of the known art (disclosed in, for example, Japanese Unexamined Patent Publication No. H03-154791) is utilized, and the illustration and description thereof will be thus omitted.  
         [0065]    Then, the general operation of this carrying system will be described briefly.  
         [0066]    (1) Thirteen untreated wafers  22  are loaded on the intermediate cassette device  30  in the waiting state by the handling device  50 .  
         [0067]    (2) When the ion implantation is completed in the vacuum container  10 , the main cassette device  20 , to which the treated wafers  22  are shifted, is raised from the vacuum container  10 .  
         [0068]    (3) To receive the treated wafers  22 , the wafer-unloading cassette device  40  is turned to the wafer delivery position.  
         [0069]    (4) The main cassette device  20  is lowered by a given distance (10 mm here) to deliver the treated wafers  22  to the wafer-unloading cassette device  40 .  
         [0070]    (5) The wafer-unloading cassette device  40  receives the treated wafers  22 , and is turned to the original waiting position. The treated wafers  22  are thus collectively carried out of the main cassette device  20 .  
         [0071]    (6) After the wafer-unloading cassette device  40  is turned to the waiting position, the intermediate cassette device  30 , which is in the waiting state in (1) above, is turned to the delivery position of the wafers  22 .  
         [0072]    (7) The main cassette device  20  is raised by 10 mm, and receives the untreated wafers  22  from the intermediate cassette device  30 .  
         [0073]    (8) The intermediate cassette device  30  is turned to the original waiting position.  
         [0074]    (9) The main cassette device  20  receiving the untreated wafers  22  is stored in the vacuum container  10 , and the untreated wafers  22  are shifted from the main cassette device  20  to the ion implantation position, and the ion implantation is started.  
         [0075]    (10) The handling device  50  shifts the treated wafers  22  in the wafer-unloading cassette device  40  to the wafer feed cassette  60 , and loads the untreated wafers  22  in the intermediate cassette  30  from a new wafer feed cassette  60 .  
         [0076]    Subsequently, an elevator-type (raising/lowering-type) aligner unit  300  will be described with reference to FIGS. 4A and 4B.  
         [0077]    The elevator-type aligner unit  300  comprises a wafer holding and rotating part  31 , a positioner  32 , an orientation-flat (notch) detection part  33 , and a raising/lowering drive part  34 .  
         [0078]    The wafer holding and rotating part  31  holds the reverse side of the wafer, and rotates the wafer. It can rotate the wafer in the forward direction and in the reverse direction to detect the orientation flat (notch). Under this circumstance, the wafer is held by a vacuum chuck.  
         [0079]    The positioner  32  is disposed so that the center of the wafer and the rotation center of the wafer holding and rotating part  31  are concentric to each other, and is of a shape which does not interfere with a robot hand in centering the wafer only by loading the wafer.  
         [0080]    The orientation-flat (notch) detection part  33  contains a transmission-type sensor, as shown in FIGS. 4A, 4B and  5 , so as not to interfere with the wafer on the intermediate cassette (shuttle)  30  during the aligning to detect the position of the orientation flat (notch) while the wafer is rotated.  
         [0081]    The raising/lowering drive part  34  shown in FIG. 4B can be raised/lowered in a vertical direction. If the wafer in the wafer cassette is projected towards the front and carried by the robot, the wafer can be located on the proximally shifted protruding position. To prevent this, a protrusion sensor  35  to detect the protrusion is provided. This protrusion sensor  35  includes an optical sensor of the transmission type, the reflection type or the limited reflection type, or other electric or mechanical precision-positioning sensors.  
         [0082]    Subsequently, description will be made about the positional relationship to the intermediate cassette device (shuttle)  30  with reference to FIGS. 4A and 4B.  
         [0083]    The intermediate cassette device  30  is gate-shaped, and the elevator-type aligner unit  300  is located between the intermediate cassette device (shuttle)  30 . The elevator-type aligner unit  300  is installed so that the center of the positioner  32  and the wafer center of the intermediate cassette device  30  are perpendicularly concentric with each other. Successively, description will be made about the aligning and positioning operations of this invention with reference to FIG. 6A to  6 F.  
         [0084]    (1) The elevator-type aligner unit  31  waits at the wafer aligning position of the highest stage of the intermediate cassette device (shuttle)  30 , with the positioner  32  in a lowered state, as illustrated in FIG. 6A.  
         [0085]    (2) An untreated wafer in the intermediate cassette device  30  is loaded on the wafer holding and rotating part  31  by the handing robot  50 . After loading the wafer, the handing robot  50  fetches the next wafer in the cassette.  
         [0086]    In this event, the next wafer is waited for with the positioner  32  in a lowered condition, and when the next wafer is carried, the positioner  32  is raised to receive the wafer. Alternatively, if the interval between the wafers is large in the intermediate cassette (shuttle)  30 , and a clearance (a space) between the wafer and the positioner  32  is sufficient, the next wafer is waited for with the positioner  32  in the raised state, and the wafer carried from the handing robot  50  can be received directly by the positioner  32 . In both cases, the operation is then moved to the operation in (4) below, as illustrated in FIG. 6B.  
         [0087]    (3) The positioner  32  is raised to center the wafer, as illustrated in FIG. 6C.  
         [0088]    (4) The positioner  32  of the wafer holding and rotating part  31  is lowered, and the wafer is held by the wafer holding and rotating part  31 , as illustrated in FIG. 6C.  
         [0089]    (5) The wafer holding and rotating part  31  is rotated together with the wafer, the orientation flat (notch) is detected, and the rotation is stopped at the required position, as illustrated in FIG. 6D.  
         [0090]    (6) The vacuum chuck is turned OFF. The aligner unit  31  is lowered by 13 mm, and the wafer on the vacuum chuck is delivered to the intermediate cassette (load shuttle)  30 . At the same time, the stopping position of this aligner unit  31  becomes the aligning position of the second wafer, as illustrated in FIG. 6E.  
         [0091]    (7) The second wafer is loaded on the chuck. The wafers are treated successively from the upper stage by repeating this process.  
         [0092]    (8) When the aligning of the wafer on the lowest stage is completed, the aligner unit  31  is lowered to a position to avoid interference with the rotational motion of the intermediate cassette (shuttle)  30 , as illustrated in FIG. 6F.  
         [0093]    (9) The intermediate cassette (shuttle)  30  is rotated to the main cassette device (vacuum cassette)  20  to deliver the wafers.  
         [0094]    (10) The intermediate cassette (shuttle)  30  returns to the original position in an empty state.  
         [0095]    (11) The operation is repeated from the operation in (1).  
         [0096]    (Second Embodiment)  
         [0097]    Referring to FIG. 7, description will be made about a second embodiment of this invention.  
         [0098]    In the second embodiment, as shown in FIG. 7, an aligner unit  600  is horizontally moved to the intermediate cassette device  30  so that the center of the aligner unit  600  and the center of the intermediate cassette device  30  are located substantially concentric with each other.  
         [0099]    With such a structure, this aligner unit  600  is horizontally moved by a horizontal-movement cylinder  610 . During the aligning operation, the wafer is sucked by the vacuum chuck to the aligner unit  600 .  
         [0100]    (Third Embodiment)  
         [0101]    Referring to FIG. 8, description will be made about a third embodiment of this invention.  
         [0102]    In the third embodiment, as shown in FIG. 8, the intermediate cassette device  30  is horizontally moved to an aligner unit  700  so that the center of the aligner unit  700  and the wafer loading center of the intermediate cassette device  30  are located substantially concentric with each other. During the aligning operation, the wafer is sucked by the vacuum chuck to the aligner unit  700 .  
         [0103]    (Fourth Embodiment)  
         [0104]    Referring to FIG. 9, description will be made about a fourth embodiment of this invention.  
         [0105]    In the fourth embodiment, the aligner unit is disposed on the wafer-loading-center locus on a wafer insertion path of the intermediate cassette device  30 , and the aligner unit is horizontally moved to receive the wafer from the robot arm  50 .  
         [0106]    The aligner unit is horizontally moved to receive the wafer from the robot arm  50 , and the intermediate cassette device  30  is vertically moved to deliver the wafer.  
         [0107]    (Fifth Embodiment)  
         [0108]    Referring to FIG. 10, description will be made about a fifth embodiment of this invention.  
         [0109]    In the fifth embodiment, an aligner unit  900  can advance into a holding part of the main cassette device  20 , and the main cassette device  20  or the aligner unit  900  is vertically moved to receive the wafer from the aligner unit  900 .  
         [0110]    In the fifth embodiment, no intermediate cassette  30  is present, and the main cassette device  20  receives the wafer directly from the aligner unit  900  via the robot arm device  50 .  
         [0111]    (Other Embodiments)  
         [0112]    While this invention has thus far been disclosed in conjunction with several embodiments thereof, it will be readily possible for those skilled in the art to put this invention into practice in the various other manners.  
         [0113]    For example, in other embodiments, an aligner unit may be installed on the wafer feed cassette  60  shown in FIG. 2.  
         [0114]    In the above-described embodiments, the aligner unit includes the positioner, and the wafer is centered by this positioner.  
         [0115]    However, in other embodiments, the wafer may be centered by providing the positioner not on the aligner unit itself, but independently on another part (for example, a shuttle shelf).