Abstract:
An apparatus for transferring a container stored with a workpiece (for example, a semiconductor wafer container) between manufacturing stations includes: a manufacturing station that includes a generally horizontal support platform; one or more guides for guiding a vehicle; a vehicle configured to travel on one or more guides to a position below support platform; and a vertical translation unit attached to one of the manufacturing station and the vehicle that vertically translates the container between a lowered position beneath the support platform and a raised position above the support platform. In this configuration, the apparatus can provide a relatively narrow work bay while still allowing sufficient room for a worker. Also, because the vehicle can operate below the level of the manufacturing stations, there is no need for special mounting on the ceiling of the factory.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to a manufacturing system for semiconductor wafers, and more particularly to a transfer apparatus for transferring a container of wafers between processing devices.  
         BACKGROUND OF THE INVENTION  
         [0002]    When being manufactured, semiconductor devices are typically subjected to a variety of processes such as photolithography, deposition, etching and a thin-film formation. In order to perform the foregoing processes, often a plurality of wafers (usually 25 wafers) are transferred while loaded within a container. The container retaining the wafers therein is transferred between processing stations manually by an operator or by an unmanned automatic transfer system.  
           [0003]    To keep up with advancing technology, wafer diameter is being increased from 8 to 12 inches. The 12-inch wafer has a larger footprint area than that of an 8-inch wafer; a container of 25 wafers weighs about 20 kgs, thus rendering manual transfer quite laborious. Therefore, it is understandable that a mass process line which uses the 12-inch wafer increasingly would desirable employ an unmanned transfer system.  
           [0004]    Containers retaining wafers therein have typically employed an open wafer cassette for 8 inch wafers, but, recently, a closed-type container known as a front open unified pod (hereinafter referred to as a “FOUP”) has been employed. A FOUP can be effective in preventing contamination which arises during the transfer process of wafers. FOUPs have been customary for use with unmanned transfer systems.  
           [0005]    Two general types of automated transfer systems are known: an overhead transfer or overhead conveyor (hereinafter referred to as “OHT” or “OHC”); and an automatic guided vehicle system (“AGV” or “RGV”). These are described below.  
           [0006]    The OHT (or OHC) system, as shown in FIG. 1, utilizes the space above the processing stations to transfer FOUPs. An OHT system is formed such that linear rails  18   a  and  18   b  are installed on the ceiling of a processing facility and hangers  22   a  and  22   b  are mounted to the linear rails  18   a  and  18   b . A FOUP  20   a  is suspended under hanger  22   a  and is positioned to be moved along linear rail  18   a  and is loaded on a FOUP index  16   a  (i.e., a load port) of a designated processing device. Also, a FOUP  20   b  is positioned on a FOUP index  16   b  to be drawn upwardly therefrom and moved over another designated processing device along linear rail  18   b . An exemplary OHT system has been proposed in U.S. Pat. No. 5,927,472 entitled “Conveyor Transfer Unit.” In an OHT system, because the upper space of FOUP indices  16   a  and  16   b  is utilized for movement of the FOUPs between processing stations, an interval W 1  between the load ports FOUP indices or a width B 1  of the bays can be relatively small to assist in space compactness or space utilization of the facility.  
           [0007]    However, the OHT system installed on the ceiling of a clean room bay can be disadvantageous. First, a powerful structural member should be installed on the ceiling due to the weight of a 12 inch wafer FOUP; also, the weight may necessitate the installation of safety devices. Second, when considering that the general height of the clean room is approximately 4 m, the installation height of the OHT system is sufficient that a ladder may be required for performing maintenance or to inspect the FOUP. Third, if an electric power source fails or is otherwise non-operational, it is very difficult for an operator to manually transfer the heavy FOUP from that height. Fourth, the typical distance between the FOUP index and the OHT is large enough to require considerable time for loading/unloading of the FOUP. The above-described problems may be sufficient to adversely impact or even negate the advantages, i.e., compactness of the facility, of the OHT system.  
           [0008]    As shown in FIG. 2, an AGV system transfers FOUPs  20   a  and  20   b  from automatic guidance vehicles  32   a  and  32   b  having a multi-axial joints. The vehicles  22   a  and  22   b  load/unload FOUPs  20   a  and  20   b  onto/from FOUP indices  16   a  and  16   b  of the designated processing device. An exemplary AGV system has been proposed in U.S. Pat. No. 5,332,013 entitled “Unmanned Conveying Device in Clean Room.” 
           [0009]    However, the AGV system has some drawbacks. First, the width W 2  of the bay shown in FIG. 2 includes load ports  16   a  and  16   b  of the devices on opposed sides within the bay, a space which allows (a) two AGVs to execute the loading/unloading operations by being positioned in parallel with each other and (b) a worker moving space between two AGVs. As such, additional space is required beyond that needed for an OTH system. Second, the simultaneous operation by the worker and transfer robot, i.e., AGV, within the bay can increase safety risk. Third, because of the use of multi-axial robot, the AGV is large (or heavy), such that the traveling speed may be limited. Fourth, in case of a 12-inch wafer, the transportable number of the FOUPs per AGV is limited due to the size thereof; this can increase capital costs, as the cost of each AGV is is typically high.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention can address some of the shortcomings of the prior art. As a first aspect, the present invention is directed to an apparatus for transferring a container stored with a workpiece (for example, a semiconductor wafer container) between manufacturing stations. The apparatus comprises: a manufacturing station that includes a generally horizontal support platform; one or more guides for guiding a vehicle; a vehicle configured to travel on one or more guides to a position below support platform; and a vertical translation unit attached to one of the manufacturing station and the vehicle that vertically translates the container between a lowered position beneath the support platform and a raised position above the support platform. In this configuration, the apparatus can provide a relatively narrow work bay while still allowing sufficient room for a worker. Also, because the vehicle can operate below the level of the manufacturing stations, there is no need for special mounting on the ceiling of the factory.  
           [0011]    In one embodiment, the vertical translation unit is attached to the vehicle, and the support platform includes a cut-out portion through which the vehicle can raise the container. The cut-out portion may be a window within an otherwise solid platform, or can be the space between two arms of a substantially U-shaped member. In some embodiments, retractable pins are present that enable the container to pass through the cut-out portion when the pins are retracted and prevent passage of the container (i.e., the pins support the container from below) when the pins are extended.  
           [0012]    As a second aspect, the present invention is directed to a method for transferring a container that stores semiconductor wafers between manufacturing stations. The method comprises the steps of: transporting a vehicle loaded with a container to a predetermined location below a horizontal support platform of a manufacturing station, the movement of the vehicle being controlled by guides; raising the container to a raised position above the support platform; and capturing the container at an operating elevation located below the raised position. Like the aforementioned apparatus, the method enables the transfer of the container in a relatively narrow space and operations can occur below the level of the wafer inlet.  
           [0013]    As a third aspect, the present invention is directed to an apparatus for transferring a container that utilizes a horizontal conveyor upon which the container is conveyed. The apparatus comprises: a horizontal conveyor positioned adjacent and below the wafer inlet of each processing station and extending in a horizontal x-direction; a vertical conveyor positioned adjacent the wafer inlet of each processing station and being configured to convey the wafer container substantially vertically along a z-axis between a position on the horizontal conveyor and the wafer inlet; and a controller operably associated with the horizontal and vertical conveyors to control the position of the wafer container. In a preferred embodiment, the apparatus also includes a y-axis conveyor to transport the container from a raised position into the wafer inlet.  
           [0014]    The z-axis conveyor may include a pair of vertically-oriented screws that serve to raise a pair of gripping arms, a pair of hydraulic piston units that raise the gripping arms by extending their piston rods, or a retractable suction head.  
           [0015]    As a fourth aspect, the present invention is directed to method of loading a container utilizing the horizontal conveyor noted above. This method comprises the steps of: conveying the wafer container along a horizontal x-axis to a position below a wafer inlet and adjacent a loading apparatus associated with the processing station; conveying gripping arms of the loading apparatus to a lowered position below the wafer container; gripping the wafer container with the gripping arms; and raising the wafer container to a raised position at a level at least as high as the wafer inlet. In a preferred embodiment, the method includes the step of conveying the container along the y-axis to insert the container in the wafer inlet. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The above objects and other advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:  
         [0017]    [0017]FIG. 1 is an end view of a conventional OHT or OHC system transferring wafer containers;  
         [0018]    [0018]FIG. 2 is an end view of a conventional AGV system transferring wafer containers;  
         [0019]    [0019]FIG. 3 is a schematic perspective view of an unmanned transfer system installed a manufacturing bay according to a preferred embodiment of the present invention;  
         [0020]    [0020]FIG. 4 is an end section view taken along line A-A of FIG. 3 for illustrating the installation position of the FOUP index, guide rails and transport shuttle;  
         [0021]    [0021]FIG. 5A is a perspective view of a FOUP index and transport shuttle according to a first embodiment of the present invention.  
         [0022]    [0022]FIG. 5B is a front section view of the transport shuttle and FOUP index of FIG. 5A taken along line B-B therein;  
         [0023]    [0023]FIG. 5C is a top section view taken along line C-C of FIG. 5B;  
         [0024]    [0024]FIG. 6A is a perspective view of another embodiment of a FOUP index and transport shuttle according to a second embodiment of the present invention;  
         [0025]    [0025]FIG. 6B is a front section view taken of the transport shuttle and FOUP index of FIG. 6A taken along line B-B thereof;;  
         [0026]    [0026]FIG. 7A is an end section view of a transport shuttle of the present invention provided with a support stand in the form of a vertical double step;  
         [0027]    [0027]FIG. 7B is a top section view of the shuttle of FIG. 7A;  
         [0028]    [0028]FIG. 8A is a schematic perspective view of a manufacturing bay of the present invention showing the transfer of a FOUP from one manufacturing station to another;  
         [0029]    [0029]FIG. 8B is a front view of a transport shuttle loaded with a FOUP with the transport shuttle lifting the FOUP to a height above the FOUP index;  
         [0030]    [0030]FIG. 8C is a partial front view of the shuttle and FOUP of FIG. 8B with the FOUP being lowered through the FOUP index;  
         [0031]    [0031]FIG. 8D is a front view of the shuttle of FIG. 8C loaded with a FOUP in a lowered position;  
         [0032]    [0032]FIG. 8E is a front section view of the FOUP index of FIG. 8B with its retaining pins extended;  
         [0033]    [0033]FIG. 9 is a flow chart for illustrating the sequential procedure of the process of loading a transport shuttle;  
         [0034]    [0034]FIG. 10A is a schematic perspective view of a manufacturing bay showing the transfer of a FOUP from one manufacturing station to another;  
         [0035]    [0035]FIG. 10B is a front section view of a FOUP index with its retaining pins in their retracted positions;  
         [0036]    [0036]FIG. 10C is a front view of a transport shuttle loaded with a FOUP with the transport shuttle lifting the FOUP to a height above a FOUP index and the retaining pins retracted;  
         [0037]    [0037]FIG. 10D is a front view of the transport shuttle loaded with a FOUP of FIG. 10C with the FOUP being lowered onto the FOUP index, which has its retaining pins extended;  
         [0038]    [0038]FIG. 10E is a front view of the transport shuttle and FOUP index of FIG. 10B with the FOUP index loaded and the transport shuttle in a lowered position;  
         [0039]    [0039]FIG. 11 is a flow chart for illustrating the sequential procedure of the process of unloading a transport shuttle;  
         [0040]    [0040]FIGS. 12A, 12B and  12 C are plan view of exemplary guide rail arrangements;  
         [0041]    [0041]FIG. 13 is an end view of a semiconductor manufacturing line equipped with an auto-guided conveying device for conveying a wafer carrier according to the present invention;  
         [0042]    [0042]FIG. 14 is an end view of the auto guided conveying device of FIG. 13 for conveying the wafer carrier;  
         [0043]    [0043]FIG. 15 is a front view of the auto guided conveying device shown in FIG. 13;  
         [0044]    FIGS.  16  is a perspective view of the vertical conveyer according to preferred embodiment of the present invention shown in FIG. 13;  
         [0045]    [0045]FIG. 17 is a block diagram illustrating the control function of the auto guided conveying device shown in FIG. 13;  
         [0046]    [0046]FIG. 18 is a perspective view showing another embodiment of the semiconductor manufacturing line of the present invention equipped with the auto guided conveying device for conveying the wafer carrier of FIG. 13;  
         [0047]    [0047]FIG. 19 is an end view of an auto guided conveying device for conveying the wafer carrier according to another embodiment of the present invention; and  
         [0048]    [0048]FIG. 20 is a front view of the auto guided conveying device for conveying the wafer carrier shown in FIG. 19. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0049]    The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown and described. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like components throughout.  
         [0050]    Referring now to the drawings, FIG. 3 illustrates an overall manufacturing system  50  that employs a transfer system  70  according to a preferred embodiment of the present invention. Within the facility  50 , bays  122   a  and  122   b  provide space for a series of transfer shuttles  110  and working space for an operator. At the ends of the bays  122   a  and  122   b , a plurality of stockers  102  are located; the stockers  102  (only one is illustrated herein) store containers, e.g., FOUPs  120 ,  120   a ,  120   b  and  120   c , that retain the workpiece such as wafers. Processing devices  100 ,  100   a ,  100   b ,  100   c ,  100   d ,  100   e  and  110   f  are installed along the lengths of the bays  122   a ,  122   b.    
         [0051]    Guide rails  108 ,  108   a ,  108   b  and  108   c  extend along parallel paths on the floors of the bays  122   a  and  122   b  in front of the processing devices  100 ,  100   a ,  100   b ,  100   c ,  100   d ,  100   e  and  100   f . The guide rails  108 ,  108   a ,  108   b  and  108   c  are positioned below a load port  106  (also known as an “index”) of each processing device. Each index  106  is configured to receive a device or container (a “FOUP”) that contains workpiece-like wafers. Exemplary guide rails include raised tracks, magnetic tape or the like. When magnetic tape is employed as the guide rail, it may be installed onto the bottom surface of the bay  122   a  along the traveling path under the load port. Alternatively, if a raised track is employed, (as is shown in FIG. 4 at  108 ), the bottom plane of the bay  122   a  may be slightly recessed along the traveling path to form a trench, and the track is installed within the trench as the guide rail  108 . The floor of the clean room in a semiconductor factory is typically formed of grating; in such an instance, the grating is slightly recessed.  
         [0052]    The arrangement of the guide rails  108  can be varied depending on the configuration of the facility  50 . For example, as shown in FIG. 12A, the guide rails  108   d  may be installed to form separate tracks along both border sides of bays on which shuttles  110  reciprocate. Alternatively, as shown in FIGS. 12B and 12C, guide rails  108  may be installed to form a closed loop along both border sides of the bays (guide rails  108   e ) or along the edges of the sides of the bays arranged in an “H” shape (guide rails  108   f ).  
         [0053]    Referring back to FIG. 3, a plurality of transport shuttles  110 ,  110   a ,  110   b ,  110   c,    110   d,    110   e,    110   f  and  110   g  are positioned on the guide rail  108 . The transport shuttles respectively transmit their own position information, state information, and so on to a central control system  200  via wireless communication. The central control system  200  controls the travel and and loading/unloading operation of the shuttles. When the guide rail  108  is installed as an open loop, the transport shuttle linearly reciprocates between both ends of the guide rail  108 . When the guide rail  108  is constructed as a closed loop, e.g., a circular loop, the transport shuttle may change direction to negotiate arcuate sections of the closed loop as well as traveling along a rectilinear path.  
         [0054]    [0054]FIG. 4 illustrates the installation of a FOUP in a processing device  100 . First, a FOUP  120  in the stocker  102  is transferred to the FOUP index  106  thereof and transferred onto the transfer shuttle  110 . The loaded transfer shuttle  110  moves to one of several processing devices which contains photolithography equipment, deposition equipment, etching equipment, or the like. After the shuttle  110  loaded with the FOUP  120  has moved under the FOUP index  106  of the processing device  100  and loaded the FOUP  120  onto the FOUP index  106  (as will be described in detail below), a transfer robot  104  in the transfer chamber of the processing device  100  transfers wafers in the FOUP  120  to the load lock  103 , where the processing device  100  acts on the wafers. After completing the process in the processing device  100 , the transfer robot  104  returns the processed wafers from the load lock  103  to the FOUP  120  (as it is still positioned on the FOUP index  106 ). Both the above-described operation within the processing device and the operation of the transport shuttle  110  and loading/unloading operation of the FOUP  120  outside the processing device  100  are controlled via the wire/wireless communication with central control system  200 .  
         [0055]    Referring now to FIGS. 5A and 5B, the transport shuttle  110  illustrated therein has a plurality of wheels  135  for rolling motion along the guide rails  108 , a transmitting/receiving unit  150  for wirelessly communicating with the central control unit  200 , and a control unit  132  for supplying the position information or traveling information thereof via transmitting/receiving unit  150  to the central control system  200 . The form of the transport shuttle  110  may be varied depending on the configuration of the guide rails  108 . For example, if the guide rail  108  is a track, the transport shuttle  110 , as shown in FIG. 4 or FIGS. 5A and 5B, has a slide block  134  fitted onto the track  108  along the lower portion of the body thereof. In contrast, if magnetic tape is employed as the guide rail  108 , the transport shuttle  110  should be equipped with sensing means (not shown) capable of recognizing the traveling path by sensing a magnetic field formed by the magnetic tape. Alternatively, controlling the movement of the transport shuttles  110  by a GPS (Global Positioning System) may permit the omission of the guide rail entirely.  
         [0056]    Still referring to FIGS. 5A to  5 C, the transport shuttle  110  also has a lifting member  111  which performs the vertical motion for loading/unloading the FOUP  120  onto/from the FOUP index  106 . The lifting member  111  may take various forms. As shown in FIGS. 5A and 5B, in one embodiment the lifting member  111  is a foldable arm assembly driven by a motor. Included as parts of the lifting member are a support stand  114   a  for loading the FOUP  120  thereon, a motor  130 , a pair of worm gear assemblies  114   c  and  114   d  rotatably coupled on the shaft of the motor  130 , and a foldable arm assembly member  114   b  having lower end portions engaged with the pair of gear assemblies  114   c  and  114   d , upper end portions coupled to the support stand  114   a , and a center portion cross-coupled by a hinge. The length of the lower end portion of arm assembly  114   b  coupled to the gear assemblies  114   c  and  114   d  is increased or decreased in accordance with the rotative direction of the motor  130 . By moving the lower end portion of the assembly  114   b , the horizontal level of the support stand  114   a  descends or ascends.  
         [0057]    A second embodiment of the lifting member  111  (see FIGS. 6A and 6B) utilizes a hydraulic driving mechanism. The lifting member  111  according to the above system is formed by a support stand  114   a  for placing the FOUP  120  thereon, and a hydraulic cylinder assembly  115  coupled to allow an upper end portion thereof to suspend the support stand  114   a . The hydraulic cylinder assembly  115  has a hydraulic cylinder  160 , a valve  162  for controlling the fluid injection into the hydraulic cylinder  160 , a fluid tank  168  for storing the fluid, and a hydraulic pump  164  for controlling the fluid flow between the fluid tank  168  and the hydraulic cylinder  160 . The lifting member may be further augmented with a hinge-coupled foldable arm assembly  170   a ,  170   b  for assisting the horizontal balance of the support stand  114   a . For reference, a controlling unit  132   a  and a transmitting/receiving unit  150   a  are shown in the drawings, in which the former is provided for controlling the opening/closing valve  162  or the operation of the hydraulic pump  164 , while the latter cooperates with the wireless transmission/reception with the central control system  200  as stated above. According to the foregoing construction, the controlling portion  132   a  controls the operation of hydraulic pump  164  and valve  162  based upon the loading/unloading information supplied via transmitting/receiving portion  150   a  to permit hydraulic cylinder  160  to move vertically.  
         [0058]    Referring again to FIGS.  5 A- 5 C, the FOUP index  106  should be configured such that the loading/unloading of the FOUP  120  is executed by the vertical motion of the lifting member  111 . The FOUP index  106  has a rectangular ring-like supporting member  107  that is attached to the front wall of an entrance chamber to the processing device  100  and horizontally protrudes toward the bay  122   a . The supporting member  107  has a center window  109  which allows the FOUP  120  to pass therethrough. Also, a plurality of supporting pins  116   a ,  116   b ,  116   c ,  116   d  protrude into and retract from the window  109  of the supporting member  107  to support the FOUP  120 .  
         [0059]    The supporting pins  116   a ,  116   b ,  116   c ,  116   d  are retracted during unloading/loading so as not to interfere with the movement of the FOUP  120  as it passes through the supporting member  107 . The width and length dimensions of the window  109  of the supporting member  107  are larger than that of the FOUP  120  to allow the FOUP  120  to pass therethrough when the supporting pins  116   a ,  116   b ,  116   c ,  116   d  retract. Also, even when the supporting pins  116   a ,  116   b ,  116   c ,  116   d  are extended, the support stand  114   a  preferably has dimensions capable of passing through the window  107  without striking the extended supporting pins  116 .  
         [0060]    The mechanism for controlling the extension and retraction of the supporting pins  116   a ,  116   b ,  116   c  and  116   d  may be embodied by using mechanical or electro-magnetic principles in several different ways. FIG. 5 illustrates, as one exemplary case, supporting pins  116   a ,  116   b ,  116   c ,  116   d  of a solenoid-driving system. Metallic supporting pins  116   a ,  116   b ,  116   c  and  116   d  are magnetically retracted toward the supporting member  107  by solenoids  138   a ,  138   b ,  138   c  and  138   d . The pins  116   a ,  116   b ,  116   c ,  116   d  are extended to their original positions by springs  136   a ,  136   b ,  136   c  and  136   d , which extend in the absence of any magnetization force supplied by the solenoids  138   a ,  138   b ,  138   c ,  138   d.    
         [0061]    Another embodiment of the present invention is illustrated in FIGS. 6A and 6B. In this embodiment, the FOUP index  106   f  is a U-shaped member with supporting arms  106   a  and an open center portion  109   a . The supporting arms  106   a  are pivotally mounted to the front side wall of the entrance chamber. Motors  140   a  and  140   b  permit the supporting arms  106   a  to rotate between a lowered position, in which they are parallel with the front side wall of the entrance chamber, and a raised position, in which they horizontally protrude toward the bay side. Movement between these positions corresponds with the up and down motion of the lifting member  111 . A width D 2  of the gap between the supporting arms  106   a  is narrower than a width D 3  of the container  120  and wider than a width D 1  of the support stand  114   a . Upon the driving of motors  140   a ,  140   b , the supporting arms  106   a  pivot to the lowered position as not to hinder the up and down motion of the lifting member when the lifting member ascends or descends under the state of loading FOUP  120  onto support stand  114   a ; otherwise, the supporting arms  106   a  horizontally protrude by being rotated by the motors  140   a ,  140   b  to the raised position.  
         [0062]    [0062]FIGS. 7A and 7B illustrate an embodiment of a transport shuttle  110   b  equipped with a vertically stacked support stand. The transport shuttle  110   b  includes a transmitting/receiving unit  150   b , a controlling unit  132   b  and a slide block  134  that engages the vehicle  110   b  with a rail  108 , each of which carry out the same function as those of the above-stated embodiment. As a characteristic feature, the lifting member  180  of the transport shuttle  110   b  has two support stands  184  and  186  that are vertically stacked, and an auxiliary plate  182  integrally coupled with the support stands  184  and  186  and a gear train  189  arranged along one corner at a prescribed interval. In addition, the lifting member  180  of the transport shuttle  110   b  includes a motor  130   b  for generating a rotative force under the control of control unit  132   b , and a chain  188  brought into engagement with the gear train  189  of the auxiliary plate  182  to transmit the rotative force of the motor  130   b  to the auxiliary plate  182 . Typically, since facility  100  or  102  is formed to have two FOUP indices at right and left sides, two FOUPs can be loaded or unloaded per visit once when the support stand has the illustrated and described vertically stacked structure, with the consequence of further increasing the efficiency of the operation.  
         [0063]    Additionally, the FOUP index  106   b , as shown in FIG. 7B, preferably adopts the U-shape illustrated in FIGS. 6A and 6B, which can facilitate the interaction of the FOUP index  106   b  with the ascending of the auxiliary plate  182 . Supporting pins  116   e ,  116   f ,  116   g  and  116   h  are constructed to extend and retract by the reciprocal action of springs  136   e ,  136   f ,  136   g  and  136   h  and solenoids  138   e,    138   f,    138   g  and  138   h  as described above.  
         [0064]    The loading process of a FOUP  120  will be described with reference to FIGS. 8A, 8B,  8 C,  8 D and  8 E and FIG. 9. “Loading” refers to the operation of transferring the FOUP  120  to be subjected to processing from a wafer storing device, i.e., the stocker  102 , or a processing device  100 , onto a shuttle  110 , or refers to the operation of transferring the FOUP completely-processed in the processing device  100  to the stocker  102  from the processing device  100 .  
         [0065]    The loading operation is performed as follows. First, a selected transport shuttle  110  under the duty-off state is moved to the right bottom of the FOUP index  106   b  of the facility  102  which requests the shuttle  110 . In performing this action, the central control system  200  determines which transport shuttle  110  is to respond to the above traveling request. The central control system  200  analyzes individual position information supplied from the plurality of transport shuttles  110  and transfer request information, including information about the departure and arrival positions supplied from the facility  102  which requests the operation, and thereby selects a single transport shuttle for responding to the transfer request (typically the shuttle  110  capable of responding the most efficiently). Thereafter, the central control system  200  provides information regarding the position of the facilities and the operation to be performed, (i.e., loading operation or unloading operation) to the selected transport shuttle  110 . The transport shuttle  110  that receives the foregoing movement and operation instruction is moved along guide rail  108  to a position below the FOUP index  106   b  of the facility that requests the operation (FIG. 8A, steps S 10 , S 11 , S 12 , S 13 , S 14 , S 15  and S 16 ).  
         [0066]    Once in position below the FOUP index  106   b  of the facility  102 , the transport shuttle  110  raises the lifter  114  to slightly lift the container  120  positioned on the FOUP index  106  to an elevated position (FIG. 8B, step S 18 ). Then, the solenoids  138   a ,  138   b ,  138   c  and  138   d  are magnetically activated to retract the supporting pins  116   a ,  116   b ,  116   c  and  116   d  that support the container  120  to a position inside of the supporting member  106   a  (in the case of the FOUP index according to the embodiments shown in FIGS. 6 a  and  6   b , the motor  140   a  is driven to rotate the supporting member  106   a  downwardly to be parallel with the front side wall of the entrance chamber). Thereafter, the lifter  114  lowers to place the FOUP  120  on the transport shuttle  110  (FIGS. 8C and 8D, steps S 20  and S 22 ). Thereafter, the solenoids  138   a ,  138   b ,  138   c  and  138   d  are deactivated (or the motor  140   a  is stopped) to return the supporting pins  116   a ,  116   b ,  116   c  and  116   d  or the supporting member  106   a  to their original positions (FIG. 8E, step S 24 ).  
         [0067]    Referring now to FIGS. 10A, 10B,  10 C,  10 D and  10 E and FIG. 11, the process of unloading a FOUP  120  will be described. “Unloading” refers an operation in which, conversely to loading, the FOUP  120  to be subjected to the processing operation is transferred from a transport shuttle  110  to a processing device  100 , or in which a completely-processed FOUP  120  is transferred from a transport shuttle  110  to a stocker  102 .  
         [0068]    Initially, the transport shuttle  100  with the FOUP  120  is moved to a position below the the FOUP index  106   b ′ of a facility  100  designated by the central control system  200  (FIG. 10A, step S 26 ).  
         [0069]    After confirming the arrival of the transport shuttle  110 , the FOUP index  106   b ′ magnetically activates the solenoids  138   a ,  138   b ,  138   c ,  138   d , thereby retracting the supporting pins  116   a ,  116   b ,  116   c  and  116   d  (or, in the case of the FOUP index according to the embodiment shown in FIGS. 6A and 6B, the supporting arms  106   a ,  106   b  are rotated to their lowered position). (FIG. 10B, step S 28 ). Subsequently, the lifter  114  vertically raises the FOUP support stand  114   a  loaded with the FOUP  120  thereon to an elevated position that is slightly higher than the horizontal level of the FOUP index  106   b ′ (FIG. 10C, step S 30 ). After this operation, the solenoids are deactivated, thereby extending the supporting pins  116   a ,  116   b ,  116   c  and  116   d  to their original positions (or power is supplied to the motor  140   a  to place the supporting member  106   a  in its original lowered position) (FIG. 10D, step S 32 ). Finally, the lifter  114  descends to allow the FOUP  120  to be loaded on the FOUP index  106   b ′ supported by the supporting pins  116   a ,  116   b ,  116   c  and  116   d  (FIG. 10E, step S 34 ).  
         [0070]    Hereinafter, another embodiment of the present invention will be described. FIGS. 13 and 14 show a semiconductor manufacturing line  200  equipped with an auto guided conveying device for conveying the wafer carrier according to the present invention. A bay B 3  is installed in a clean room to provide the working space for the auto guided conveying device and the operator. A plurality of stockers for storing containers having wafers, such as FOUPs, or wafer processing equipment  201  are installed on both sides of the bay B 3  in line with each other. The wafer processing equipment  201  includes an inlet chamber  202  formed at a front center portion thereof with a wafer inlet  204  and a process chamber  208  having a load lock  210 . A conveying robot  206  is installed in the inlet chamber  202 . The conveying robot  206  receives a wafer from a wafer carrier  400  installed at the wafer inlet  204  and transfers the wafer to the loadlock  210 , or transfers the wafer from the load lock  210  to the wafer carrier  400 .  
         [0071]    A sliding roller conveyer  300  is installed at a bottom of the bay B 3 . The to sliding roller conveyer  300  is positioned at a space formed below a FOUP index  502  which protrudes forwardly from the wafer processing equipment  201 . The height of the sliding roller conveyer  300  is lower than the height of the wafer inlet  204  in such a manner that, when one wafer carrier  400  resides in the wafer inlet  204 , another wafer carrier  400   a  can be passed without making contact with the waiting wafer carrier  400 .  
         [0072]    A vertical conveyer  500  is installed between the inlet chamber  202  and the sliding roller conveyer  300  that can move the wafer carrier  400  conveyed by the conveyer up to the wafer inlet  204 . The vertical conveyer  500  has a pair of gripping arms  502  which move vertically along the vertical conveyer  500 . Accordingly, the depth of the vertical conveyer  500  is relatively small as compared with a conventional FOUP index. Since the wafer carrier supporter is not present in this embodiment, the bay B 3  has sufficient space for use.  
         [0073]    As shown in FIG. 15, the wafer carrier  400  has projections  402  protruding from both sides thereof. The projections  402  are supported by supporting brackets  504  of gripping arms  502 . With this configuration, the undersides of the projections can be horizontally maintained.  
         [0074]    The vertical conveyer  500  has a rectangular housing  506  with a working space  508  therein. The working space  508  extends from a conveying surface  302  of the conveyer  300  to the wafer inlet  204 . The gripping arms  502  are installed at both side walls  508   a  of the working space  508 , and the gripping arms  502  and the wafer carrier  400  are conveyed within the working space  508 .  
         [0075]    Referring now to FIG. 16, one half of the symmetrically-formed vertical conveyer  500  is illustrated. As shown in FIG. 16, a conveying screw  510 , which is a z-axis (vertical) conveying device, extends vertically along an inner surface of the housing  506 . A guiding member  512  is installed in parallel to the conveying screw  510 . The guiding member  512  comprises a smooth rod and guides a block  514  such that the block  514  can slide thereon when the block  514  moves up and down. The block  514  is cooperatively threaded to the conveying screw  510  so that the block  514  moves up when the conveying screw  510  rotates in a forward direction and moves down when the conveying screw  510  rotates in a reverse direction.  
         [0076]    The conveying screw  510  rotates in forward and reverse directions when driven by a motor (not shown). A driving/driven gear combination can be installed between a rotating shaft of the motor and the conveying screw  510  so as to reduce the moving speed of the moving member  514 .  
         [0077]    The gripping arm  502  is fixed to an inner side of the block  514 . Accordingly, the gripping arm  502  also moves when the block  514  moves up and down. The gripping arm  502  protrudes beneath the projection  402  of the wafer carrier  400 , which is conveyed from the front portion of the wafer processing device through the conveyer  300 . The gripping arm  502  includes a y-axis (horizontal) conveying device  518 , such as a conveying screw, for conveying the wafer carrier  400  in a y-axis direction and a y-axis block  520  which is conveyed in the y-axis direction by the y-axis conveying device  518 . The y-axis block  520  has a supporting bracket  504  for supporting the projection  402  of the wafer carrier  400 . A motor and a gear box  516  installed at a rear portion of the gripping arm  502  rotate the y-axis conveying device  518 . Through the rotation of the y-axis conveying device  518 , the y-axis block  520  moves in the forward and backward directions. The supporting bracket  504  attached to the y-axis block  520  moves in the forward and backward directions within the length of the gripping arm  502  so that the supporting bracket  504  is positioned below the projection  402  of the wafer carrier  400 .  
         [0078]    The control function of the auto guided conveying device  200  is shown in FIG. 17. A controller  522  of the auto guided conveying device  200  controls the movement of the wafer carrier  400  of the conveyer  300  through a motor CM, a pulse generator for detecting the rotational speed of the motor CM and an encoder PG. In addition, the controller  522  is connected to vertical conveyers  500  installed in the wafer processing equipment  201  so as to control the conveying of the FOUP.  
         [0079]    A wafer carrier detector WCD is installed at a front portion of the wafer processing equipment  201  so as to detect the wafer carrier  400  when the wafer carrier  400  reaches a predetermined position. When the wafer carrier  400  is not detected, the y-axis moving member  520  is positioned at a rear position and the gripping arm  502  is positioned at an uppermost position through a z-axis motor ZM and y-axis motor YM. The rear position is detected by a rear detector RD and the uppermost position is detected by an upper detector UD.  
         [0080]    When the wafer carrier  400  is detected by the wafer carrier detector WCD, the y-axis block  520  moves down to a lowest position by using a lowest position detector DD. When the wafer carrier  400  reaches the lowest position, the y-axis block  520  moves up to a front position by using a front detector FD.  
         [0081]    As the y-axis block  520  moves to the front position, the wafer carrier  400  positioned in the front position is engaged by the gripping arm  502 . When this occurs, the z-axis motor ZM rotates in the reverse direction so that the gripping arm  502  moves up to the uppermost position. When the gripping arm  502  reaches the uppermost position, the y-axis block  520  is moved so as to convey the wafer carrier  400  to the rear position.  
         [0082]    The downward movement of the wafer carrier  400  is carried out by reversing to the aforementioned upward movement of the wafer carrier  400 .  
         [0083]    Referring now to FIG. 18, another embodiment of the semiconductor manufacturing line  600  equipped with the auto guided conveying device for conveying a wafer carrier is illustrated therein. In FIG. 18, two wafer inlets  601  and two vertical conveyers  602  are installed on one device  603 . According to this embodiment, two vertical conveyers  602  can be alternatively or simultaneously operated so that the speed of the up/down operation of the wafer carrier  604  can be increased twofold.  
         [0084]    Referring now to FIGS. 19 and 20, an auto guided conveying device  700  for conveying a wafer carrier  400  according to another embodiment of the present invention is illustrated. In this embodiment, an upper portion of the wafer carrier  400  is gripped by using a vacuum suction head  544 . Accordingly, space for a vertical conveyer is not required at a lower center area in front of the processing station so that the space of the bay can be efficiently used.  
         [0085]    The housing  541  of the vertical conveyer  540  is installed on an upper front portion of the wafer inlet. A gripping rod  542  extending from a bottom surface of the housing  541  is provided with the vacuum suction head  544 . The vacuum suction head  544  applies suction to an upper surface of the wafer carrier  400  so as to pick up the wafer carrier  400 . The gripping rod  542  can be installed in the housing such that it can moves in the y-axis (horizontal) direction.  
         [0086]    While the present invention has been described in detail with reference to the preferred embodiment thereof, it should be understood to those skilled in the art that various changes, substitutions and alterations can be made hereto without departing from the scope of the invention as defined by the appended claims.  
         [0087]    For example, the z-axis conveying device can be constructed with a linear motor having a stator rail and a rotor or with a hydraulic or pneumatic cylinder and a piston rod. When the z-axis conveying device is constructed by a linear motor, the gripping arm or gripping rod can be fixed to the rotor. When the z-axis conveying device is constructed with a hydraulic cylinder and a piston rod, the gripping arm can be fixed to an end portion of the piston rod.  
         [0088]    The structure of the y-axis conveying device can be variously changed in the same manner as the z-axis conveying device. The structures of the y-axis conveying device and the z-axis conveying device can be formed by combining the above elements or by combining various reciprocating mechanisms.  
         [0089]    As described above, the present invention can utilize airtight characteristics of the FOUP. A non-airtight wafer container (i.e., open-type wafer cassette) is may be undesirable due to its being vulnerable to contaminating material, as the transferring operation is performed at the lower portion of the FOUP index.  
         [0090]    As can be seen from the foregoing, the present invention allows the guide rail to be placed along the lower portion of a FOUP index to enhance the approach and stability with respect to the processing device of the operation. The multi-axial robot having been required in the AGV system is unnecessary; the simple lifter that is capable of performing vertical motion can simplify the apparatus. Because the transport shuttle travels by utilizing the lower space of the FOUP index, the width of the bays can be reduced to improve the device compactness or space utilization while lowering the maintenance cost. Furthermore, a working space capable of providing simultaneous operation with the worker can enable the execution of manual operations in case of a state of emergency, such as electrical power failure or interrupted operation.  
         [0091]    While the present invention has been particularly shown and described with reference to particular embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the appended claims.