Abstract:
A mount base is adapted to be fixed to a partition wall which is disposed between a stockyard for temporarily storing a wafer carrier which houses a wafer and a wafer processing device for processing the wafer. A wafer transfer window is provided on the mount base. A carrier stage has a table horizontally extended from a lower edge of the wafer transfer window and a carrier plate disposed on the table so as to support the wafer carrier and movable so as to transfer the wafer carrier to the processing device. A buffer stage has a buffer plate horizontally disposed below the table so as to temporarily store the wafer carrier.

Description:
The present application claims priority from Japanese Patent Application No. 2006-230357, filed on Aug. 28, 2006. 
     BACKGROUND 
     The present invention relates to a load port device that is disposed in front of a processing device for performing a wafer processing and that carries out an opening/closing operation of a cover of a wafer carrier and a sending/receiving operation of a wafer housed in the wafer carrier in a semiconductor fabrication apparatus. 
     Referring to the drawings according to the invention, first, a semiconductor fabrication apparatus (hereinafter, simply referred to as “a fabrication apparatus”) and a front-end apparatus (hereinafter, referred to as “an EFEM”) will be described, and subsequently a related-art load port device will be described.  FIG. 7  is a longitudinal sectional view illustrating a fabrication apparatus.  FIG. 9  is an overall perspective view illustrating a related-art load port device F′. In a semiconductor fabrication factory, a carrier conveyance system conveys a plurality of wafers W housed in a wafer carrier (hereinafter, simply referred to as “a carrier”)  30  to facilities in production lines by a carrier unit. FOUP (Front Opening Unified Pod) is frequently used as the carrier. As shown in  FIG. 7 , a fabrication apparatus for receiving the wafer W by a carrier unit and performing a wafer processing includes the EFEM having a stockyard R 1 , and a processing device R 3 . The EFEM which includes an external load port L, the stockyard processing device R 3 . The EFEM which includes an external load port L, the stockyard R 1  and an enclosure R 2  is installed on the front side of the processing device R 3 . The carrier  30  that is conveyed from the carrier conveyance system and to be transferred to the stockyard R 1  of the fabrication apparatus is placed on the external load port L. As shown in  FIG. 7 , the external load port L is placed outside the stock yard R 1 . In the stockyard R 1 , a plurality of carrier installation shelves S on which the carrier  30  is placed and a carrier transfer device T 1  are disposed. Further, the enclosure R 2  is a front chamber of the processing device R 3 . An FFU (Fan Filter Unit) and a wafer conveyance robot T 2  are provided in the enclosure R 2 . In the enclosure R 2 , highly clean air is sent out by the FFU. Thus, the wafer W is prevented from being contaminated with particles before a wafer processing. 
     In the fabrication apparatus, the related-art load port device F′ is an internal load port device that is mounted in the front side of a wall member P by means of a bolt  81  or the like, which isolates the stockyard R 1  from the enclosure R 2  that is a front chamber of the processing device R 3 . Hereinafter, the internal load port device will be called “a load port device” and distinguished from the external load port L. As shown in  FIG. 9 , the related-art load port device F′ includes a mount base  1  that has a rectangular plate shape and is mounted on the wall member P, a wafer transfer window  2  that is provided on the mount base  1 , and a carrier stage C that is disposed on a substantial lower end of the wafer transfer window  2  and places the carrier  30  thereon. The carrier stage C is disposed so as to be parallel to the stockyard R 1  that is in a front side of the wall member P, and the front side is a front side of the load port device F′. In the same front side, an elevation mechanism U 2  of a mapping device M for detecting an existence or non-existence of the wafer W housed in the carrier  30  in each stair is disposed below one side of the carrier stage C. The rear side of the load port device F′ is disposed in the enclosure R 2 . In the same rear side, a cover opening/closing unit N for carrying out an opening/closing operation of a cover  32  of the carrier  30  by detaching and attaching the cover  32  therefrom and thereto, an elevation mechanism U 1  of the cover opening/closing unit N, and the mapping device M are disposed. Further, a support member  1   a  is attached to both ends of the mount base  1 . 
     When the carrier  30  housing the wafer W is conveyed to the fabrication apparatus, the carrier  30  is received in the external load port L and then temporarily stored in the stockyard R 1  by the carrier transfer device T 1 . When a non-processed wafer W is supplied to the processing device R 3  in accordance with a wafer processing status of the processing device R 3 , the carrier  30  stored in the stockyard R 1  is first transferred onto a carrier plate  11  of the carrier stage C of the load port device F′ by the transfer device T 1 , and then the carrier plate  11  moves toward the wafer transfer window  2 . Subsequently, the cover  32  of the carrier  30  is opened by the cover opening/closing unit N of the load port device F′ and then the wafer W in the carrier  30  is conveyed to the processing device R 3  so as to perform a wafer processing thereon. After the wafer processing ends, the wafer W is again housed in the carrier  30  from the processing device R 3 , the cover  32  of the carrier  30  is closed, and then the carrier plate  11  moves away from the wafer transfer window  2 . Subsequently, the carrier  30  is transferred from the carrier stage C to the external load port L or a carrier installation shelf S in the stockyard R 1 . The carrier  30  transferred to the external load port L is conveyed from the fabrication apparatus to proceed to the next process by the carrier conveyance system. The carrier  30  transferred to the carrier installation shelf S is also transferred to the external load port L at any time. Similarly, the carrier  30  is conveyed from the fabrication apparatus to proceed to the next process. The load port device F′ for carrying out a sending operation of the carrier  30  and a receiving operation of the carrier  30  at the same time and the carrier transfer device T 1  are disclosed in Patent Document 1. In addition, a carrier interface device including an open/close mechanism of the carrier  30  is disclosed, for example, in Patent Document 2. 
     In a case where the wafer W is supplied to the processing device R 3  in accordance with the wafer processing status of the processing device R 3 , it is more effective in terms of cost and time to supply the carrier  30  temporarily stored in the stockyard R 1  from the stockyard R 1  to the processing device R 3  on demand than to supply the carrier  30  housing the wafer W from outside to the fabrication apparatus on demand. In order to improve an operation rate of the fabrication apparatus and to process a lot of wafer W, it is necessary to ensure storing spaces as many as the number of the wafers W or storing spaces for the carriers  30  housing the wafer W. However, since the fabrication apparatus is in a clean room, it is not possible to arbitrarily increase storing spaces for the wafer W within a limited space of the clean room. For this reason, in the past, it was a task to increase a reception capacity of the wafer W in the clean room, particularly in the stockyard R 1 , that is, a reception capacity of the carrier. 
     Patent Document 1: Japanese Patent Publication No. 2003-51527A 
     Patent Document 2: Japanese Patent Publication No. 10-303271A 
     SUMMARY 
     It is therefore an object of the invention to increase a reception capacity of a wafer carrier in a stockyard of a semiconductor fabrication apparatus. 
     In order to achieve the above objects, according to an aspect of the invention, there is provided a load port device comprising: 
     a mount base adapted to be fixed to a partition wall which is disposed between a stockyard for temporarily storing a wafer carrier which houses a wafer and a wafer processing device for processing the wafer; 
     a wafer transfer window provided on the mount base; 
     a carrier stage having:
         a table horizontally extended from a lower edge of the wafer transfer window; and   a carrier plate disposed on the table so as to support the wafer carrier and movable so as to transfer the wafer carrier to the processing device; and       

     a buffer stage having a buffer plate horizontally disposed below the table so as to temporarily store the wafer carrier. 
     As described above, since one of functions of the load port device is to open and close a cover of the wafer carrier placed on the carrier stage, the load port device was not used as a reception space of the wafer carrier. However, according to the aspect the invention, additional one wafer carrier can be placed thereon by mounting a buffer stage on the load port device, and thus a reception capacity of the wafer carrier in the stockyard increases. For this reason, the number of non-processed wafers supplied to the processing device increases. As a result, it is not necessary to convey the wafer carrier one by one by means of a conveyance system in order to supply the wafer carrier to the stockyard in the fabrication apparatus in accordance with a wafer processing status. Accordingly, a conveyance frequency can be decreased. Further, since the buffer stage is provided right below the table, a distance when transferring the wafer carrier from the buffer plate of the buffer stage to the carrier plate of the carrier stage is shorter than that when transferring the wafer carrier from a normal carrier installation shelf in the stockyard thereto. As a result, a transfer efficiency of the wafer carrier is improved. Accordingly, mounting the buffer stage on the load port device leads to an increase of an operation rate of the fabrication apparatus, an efficiency of a wafer processing and an improvement of a wafer production. In the load port device according to the aspect of the invention, since thickness of the carrier stage and depth of devices such as the elevation mechanism of the mapping device disposed below the carrier stage are smaller than those of a related-art load port device, a sufficient space in which the wafer carrier can be placed is ensured. Accordingly, the buffer stage can be mounted on the load port device according to the aspect of the invention. 
     The carrier plate may be movable between a first position and a second position which is nearer to the wafer transfer window than the first position; 
     the carrier plate may be provided with a plurality of first positioning pins operable to position the wafer carrier relative to the carrier plate and a first hand insertion space so as to prevent interference with a transfer hand of a carrier transfer device for transferring the wafer carrier by supporting the wafer carrier so as to attach and detach the wafer carrier to and from the carrier plate; 
     the buffer plate may be provided with a plurality of second positioning pins operable to position the wafer carrier relative to the buffer plate and a second hand insertion space so as to prevent interference with the transfer hand of the carrier transfer device; and 
     when the carrier plate is positioned in the first position, the first positioning pins may be situated at the same position with the second positioning pins as viewed from the top and the first hand insertion space are situated at the same position with the second positioning pins as viewed from the top. 
     When the wafer carrier is transferred onto the carrier stage, the carrier plate is located at a maximum recession position from the transfer window of the load port device in reciprocation directions to and from the processing device. With the above-described configuration, the second positioning pins and the second hand insertion space formed on the buffer plate have the same configuration as the first positioning pins and the first hand insertion space formed on the carrier plate, and the second positioning pins and the second hand insertion space are disposed at the same positions as the first positioning pins and the first hand insertion space as viewed from the top in a case where the carrier plate is at the maximum recession position (the first position) from the wafer transfer window. As a result, when the wafer carrier is transferred from the buffer carrier plate onto the carrier plate at the recession position (the first position), an operation range in three dimension of the carrier transfer device can be simply set. That is, in the operation range of the transfer arm of the carrier transfer device, regarding a height direction, it is only necessary to set a distance between the buffer plate and the carrier plate at the first position. Regarding the reciprocation direction to and from the processing device, it is only necessary to set a distance between a point when the transfer arm of the carrier transfer device shortens to a maximum recession position from each of the plates and a position when the transfer arm lengthens to insert the transfer hand in the hand insertion space of each of the plates. A distance in a transverse direction perpendicular to the reciprocation directions can be set to a fixed value. As a result, the wafer carrier can be effectively transferred from the buffer stage to the carrier stage. 
     The buffer plate may be disposed substantially at the same height with a load port which is placed outside the stockyard. 
     The wafer carrier conveyed from the semiconductor fabrication apparatus by the carrier conveyance system is placed on a load port which is placed outside the stockyard. This load port is an external load port disposed on the most front side of the semiconductor fabrication apparatus. With the above-described configuration, when the wafer carrier is transferred from the external load port to the stockyard so as to temporarily store the wafer carrier, even though the transfer arm of the carrier transfer device is slightly lifted up in a height direction so as to fit the positioning pins of the buffer plate to positioning pedestals formed on the bottom surface of the wafer carrier, the wafer carrier is transferred to the buffer plate just by operating the transfer arm in the reciprocation direction relative to the processing device. For this reason, a transfer distance of the wafer carrier transferred to the buffer plate is shorter than that of the wafer carrier transferred to the carrier installation shelf in the stockyard. As a result, the wafer carrier can be effectively transferred to the stockyard. 
     The load port device may further comprises: 
     a mapping device; 
     an elevator disposed below the carrier stage and operable to move the mapping device in a vertical direction; and 
     a cover covering the elevator. 
     With the above-described configuration, the cover is mounted below the carrier stage so as to cover the elevator of the mapping device. As a result, mounting the cover mounted below the carrier stage results in a good appearance of the load port device. Moreover, the wafer carrier is prevented from interfering with the elevator due to a malfunction or the like of the carrier transfer device, thereby protecting the wafer carrier and the elevator. 
     According to the invention, one additional wafer carrier can be placed on a load port device on which a buffer stage is mounted. For this reason, a reception capacity of a wafer carrier in a stockyard increases. Thus, it is not necessary to convey the wafer carrier one by one to the stockyard in a fabrication apparatus by a wafer carrier conveyance system in accordance with a wafer processing status. As a result, a transfer frequency can be decreased. In addition, since a buffer stage is formed right below a table, a transferring distance of the wafer carrier between the buffer plate of the buffer stage and the carrier plate of the carrier stage is shorter than that between a carrier installation shelf in the stockyard and the carrier plate. As a result, a transfer efficiency of the wafer carrier is improved. Therefore, mounting the buffer stage on the load port device leads to an increase of an operation rate of the fabrication apparatus, an efficiency of a wafer processing, and an improvement of a wafer production. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
         FIG. 1  is an overall perspective view illustrating a load port device F; 
         FIG. 2  is a front view illustrating the load port device F; 
         FIG. 3  is a sectional view illustrating the load port device F taken along Line A 1 -A 1  in  FIG. 2 ; 
         FIG. 4  is a sectional view illustrating the load port device F taken along Line A 2 -A 2  in  FIG. 2 ; 
         FIG. 5  is a view illustrating a front side of the load port device F mounted on a wall member P and a shelf S on which a carrier is mounted; 
         FIG. 6  is a sectional view illustrating the load port device F taken along Line A 3 -A 3  in  FIG. 5 ; 
         FIG. 7  is a longitudinal sectional view illustrating a fabrication apparatus; 
         FIG. 8  is a perspective view illustrating the load port device F in the state where a carrier  30  is placed on a buffer plate  21  of a buffer stage B by a carrier transfer device T 1 ; and 
         FIG. 9  is an overall perspective view illustrating a related-art load port device F′. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, an embodiment of the invention will be described in detail with reference to the drawings. In addition, the same reference numerals are given to the same components as those in BACKGROUND section. Repetitive explanations for those will be omitted and characteristics of the invention will be described. 
     First, a configuration of a load port device F according to the invention will be described with reference to  FIGS. 1 to 4 . The load port device F is an internal load port mounted in front of a wall member P isolating a stockyard R 1  from an enclosure R 2  that is a front chamber of a processing device R 3 . The load port device F will be described separately from an external load port L.  FIG. 1  is an overall perspective view illustrating a load port device F.  FIG. 2  is a front view illustrating the load port device F.  FIG. 3  is a sectional view illustrating the load port device F taken along Line A 1 -A 1  in  FIG. 2 .  FIG. 4  is a sectional view illustrating the load port device F taken along Line A 2 -A 2  in  FIG. 2 . As shown in  FIG. 1 , the load port device F includes a mount base  1  with a thick rectangular plate shape, a transfer window  2  formed on an upper part of the mount base  1 , a carrier stage C disposed in reciprocation directions X (hereinafter, referred to as “direction X”) of a carrier plate  11  to and from a processing device R 3  in a lower edge of the wafer transfer window  2 , and a buffer stage B formed so as to protrude to the front side thereof below a table  18  of the carrier stage C. In a front side of the load port device F, an elevation mechanism U 2  of a mapping device M and a cover  3  covering the elevation mechanism U 2  are disposed. In a rear side of the load port device F, a cover opening/closing unit N, an elevation mechanism U 1 , and the mapping device M are disposed. A lower space of the carrier stage C is a space used to place a carrier on the buffer stage B. Since the elevation mechanism U 2  of the mapping device M protrudes from a surface of the mount base  1 , the cover  3  is provided to protect the elevation mechanism U 2  of the mapping device M by covering the same. The cover  3  is classified into three cover members  3   a ,  3   b , and  3   c  (where it will be described in detail below). Further, in the load port device F, each attachment member  80  is fixed to an upper end and a lower end of the mount base  1  by the use of an installation assisting piece  82 . Then, the load port device F is configured so as to be mounted on a wall member P as below. After the load port device F is fitted into a load port device space Pb formed on a wall member P, both ends of each of the attachment members  80  in a transverse direction Y (hereinafter, referred to as “a direction Y”) are fixed to the wall member P by the use of a bolt  81  or the like. 
     As shown in  FIGS. 1 and 2 , the carrier stage C includes a carrier plate  11 , a table  18  formed on the lower edge of the wafer transfer window  2  and constituted by a pair of plate support members  18   a  and  18   b  with a different length formed in parallel to the front side of the mount base  1 , a pair of guides  16  and a pair of guide rails  17  formed so as to slide in the X direction, and a slide drive unit  12 . A pair of guide rails  17  are laid down in the X direction of the table  18  and the guide  16  is mounted on the guide rail  17 . In the embodiment, the slide drive unit  12  is attached to one side surface of the support  18   b  disposed on one side of the table  18 . In the carrier plate  11 , a movable region part (in the embodiment, a front side of a front right side) of a transfer arm  71  is cut out so as not to allow the transfer arm  71  of a carrier transfer device T 1  to interfere with the carrier stage C. For this reason, in the table  18  supporting the carrier plate  11 , the plate support member  18   a  on the movable region side is configured to be shorter in size than the plate support member  18   b  on the other side. Further, in the carrier plate  11 , a hand insertion space  14  with a triangular shape is formed at the substantial center of the carrier plate  11  so as to insert a transfer hand  72  with a triangular shape of the carrier transfer device T 1  therein. Positioning pins  13  fitted into positioning pedestals  31  formed on positions corresponding to three apexes with a triangular shape on a bottom surface of the carrier  30  and a seating sensor  15  for detecting whether the carrier  30  is placed is attached to a circumference of the carrier plate  11  forming the hand insertion space  14  so as to correspond to three apexes of the hand insertion space  14  with a triangular shape. Additionally, reference numeral  19  is a locker for securely maintaining the carrier  30  in its positioned state. 
     The buffer stage B will be described with reference to  FIGS. 1 ,  3 , and  8 .  FIG. 8  is a perspective view illustrating the load port device F in the state where the carrier  30  is placed on a buffer plate  21  of the buffer stage B by the carrier transfer device T 1 . The buffer stage B includes the buffer plate  21 , a strengthening plate  22 , and positioning pins  23 . The buffer plate  21  is formed in a shape in which a thin plate with a substantial rectangular shape and a pair of side walls erecting from the side end to the lower side are included. The buffer plate  21  is fixed thereto so as to be connected to the lower end of the cover member  3   a  and a support member  1   a , and covers an upper part of the cover member  3   b . The upper surface of the buffer plate  21  is similar in shape to the carrier plate  11  of the carrier stage C. A hand insertion space  24  with a substantial triangular shape to which the transfer hand  72  with a triangular shape of the carrier transfer device T 1  is inserted is formed thereon. Further, when the carrier transfer device T 1  places the carrier  30  on the buffer plate  21 , a movable region part (in the embodiment, a front side of the front right side) of the transfer arm  71  on the buffer plate  21  is cut out so as not to allow the transfer arm  71  to interfere with the buffer plate  21 . The strengthening plate  22  formed of a thin plate with a predetermined width is attached to a circumference of the buffer plate  21  forming the hand insertion space  24  so as to enclose the circumference of the buffer plate  21  at a predetermined width. The positioning pins  23  fitted to the positioning pedestals  31  on the bottom surface of the carrier  30  are fixed to the circumference of the buffer plate  21  through the strengthening plate  22  so as to correspond to three apexes of the hand insertion space  24  with a triangular shape, which is the same configuration as the positioning pins  13  on the carrier plate  11 . The positioning pins  23  of the buffer plate  21  and the hand insertion space  24  have the same configuration as the positioning pins  13  on the carrier plate  11  and the hand insertion space  14 . When the carrier plate  11  is at a maximum recession position from the wafer transfer window  2 , on an XY plane (in a top view), the positioning pins  23  and the hand insertion space  24  are disposed at the same positions as the positioning pins  13  of the carrier plate  11  and the hand insertion space  14 . 
     A shape of the hand insertion space  24  of the buffer plate  21  does not necessarily correspond to that of the transfer hand  72  of the carrier transfer device T 1  as long as the transfer hand  72  does not interfere with the buffer plate  21 . However, the transfer hand  72  mounted with the carrier  30  may be inserted in the hand insertion space  24  when the shapes do not correspond with each other. Accordingly, it is necessary to take a relationship between a shape of the hand insertion space  24  and an arrangement of the positioning pins  23  into consideration so that a position of the carrier  30  does not change on the XY plane (in a top view) when the carrier  30  is locked thereto by the positioning pins  23  and when the carrier  30  inserted in the hand insertion space  14  of the carrier plate  11  is locked thereto by the positioning pins  13 . 
     The cover opening/closing unit N and the elevation mechanism U 1  will be described with reference to  FIGS. 2 to 4 . As shown in  FIG. 4 , the cover opening/closing unit N is disposed on the rear side of the load port device F. The lower end of a main body  41  constituting the cover opening/closing unit N is guided by a guide rail  45  and thereby allowed to reciprocate in the X direction. As shown in  FIGS. 2 and 4 , a locking claw mechanism  42  and a sucking disk mechanism  43  are provided on a front side (one side corresponding to the rear side of the mount base  1 ) of the main body  41  so as to attach or detach the cover  32  of the carrier  30 . A driving motor, a mechanical mechanism, and the like for moving the cover opening/closing unit N in the X direction and for attaching or detaching the cover  32  are accommodated in a box member  46  attached to the rear side of the main body  41 . In addition, as shown in  FIGS. 3 and 4 , the elevation mechanism U 1  of the cover opening/closing unit N is installed at the center of the lower end of the cover opening/closing unit N on the rear side of the mount base  1  and accommodated in a cover  44 . 
     Next, the mapping device M and the elevation mechanism U 2  thereof will be described with reference to  FIGS. 2 to 4 . As shown in  FIG. 2 , the elevation mechanism U 2  includes the following members. That is, the elevation mechanism U 2  includes a ball screw  55  disposed on the lower part (in the embodiment, the lower part of a front right side) of one side of the carrier stage C, brackets  52  rotatably supporting the upper end and the lower end of the ball screw  55 , a stepping motor  56  connected to the lower end of the ball screw  55  through a coupling  57 , a nut member  53  elevating along the ball screw  55  when the ball screw  55  rotates by operating the stepping motor  56 , a connection member  54  connecting the nut member  53  to a guide  61 , and a guide rail  58  guiding an elevation of the guide  61  with the nut member  53  elevating. An opening  59  that is parallel to the guide rail is formed on the mount base  1  so as to be positioned between the guide rail  58  and the support member  1   a . As shown in  FIG. 3 , a sectional view of the guide  61  is a substantial L shape in which a member  61   a  is perpendicular to a member  61   b . The member  61   b  is inserted into the opening  59  and then a portion of the member  61   b  protruding to the rear side of the mount base  1  is connected to the mapping frame  62 . Further, the member  61   a  on the front side of the mount base  1  is connected to the connection member  54 . Since the elevation mechanism U 2  has the above-described configuration, the elevation mechanism U 2  does not largely protrude to the front side of the mount base  1 . Accordingly, a space for placing the carrier  30  thereon is formed below the carrier stage C. As shown in  FIG. 4 , the mapping device M includes a mapping mechanism (not shown), a mapping frame  62 , and a mapping head  63 . The mapping head  63  is attached to the upper end of the mapping frame  62  so as to have a cantilever shape in a Y direction. The mapping mechanism is disposed on the mapping head  63 . The mapping head  63  is disposed just above the box member  46  of the cover opening/closing unit N. 
     The cover  3  has a shape in which side walls erects by a predetermined length from both side ends of a thin plate with a rectangular shape and covers the mount base  1  below the table  18  of the carrier base C. The cover  3  includes three members, that is, the cover member  3   a  covering a part from a position right below the table  18  of the carrier stage C to a position of an upper surface of the buffer plate  21  of the buffer stage B, the cover member  3   b  covering a part right below the buffer plate  21  of the buffer stage B as many as a predetermined length, and the cover member  3   c  covering a part from a position of the lower end of the cover member  3   b  to a position of the lower end of the mount base  1  when viewed from the front side of the mount base  1 . A height (that is, a length in the X direction from the mount base  1  to the cover member  3   a ) of the cover member  3   a  is designed so as not to allow the cover member  3   a  to interfere with any one of the elevation mechanism U 2  of the mapping device M and the cover  32  placed on the buffer plate  21 . For this reason, the carrier  30  is prevented from interfering with the elevation mechanism U 2  due to a malfunction or the like of the carrier transfer device T 1 . As a result, it is possible to protect the carrier  30  and the elevation mechanism U 2 . A height (that is, a length in the X direction from the mount base  1  to the cover member  3   b ) of the cover member  3   b  is designed so as not to allow the cover member  3   b  to interfere with the stepping motor  56  of the elevation mechanism U 2 . Since the height of the cover member  3   b  is larger than that of the cover member  3   a , the cover member  3   b  is formed so as to protrude to the front side more than the cover member  3   a . For this reason, the cover member  3   b  having the above-described shape can upwardly support an installation part of the buffer plate  21  on the mount base  1 . As a result, the buffer plate  21  can be effectively strengthened. A height of the cover member  3   c  can be freely designed. However, a height of the cover member  3   c  is substantially set to be large so as not to allow the cover member  3   c  to interfere with the stepping motor  56  of the elevation mechanism U 2 . Alternatively, in consideration of a heat from the stepping motor  56  at the time of an operation of thereof, a part corresponding to the stepping motor  56  is cut out and then the stepping motor  56  is allowed to protrude from the cover member  3   c  so as not to allow the cover member  3   c  to interfere with the stepping motor  56 . In the cover member  3   c  according to the embodiment, the height of the cover member  3   c  is the same as that of the cover member  3   a , but formed in a protruding shape in which the stepping motor  56  protrudes from the cover member  3   c  by cutting out the cover member  3   c  along the shape of the stepping motor  56 . 
     Next, a fabrication apparatus on which the load port device F is installed will be described with reference to  FIGS. 4 to 7 .  FIG. 5  is a view illustrating a front side of the load port device F mounted on the wall member P and a shelf S on which the carrier is placed.  FIG. 6  is a sectional view illustrating the load port device F taken along Line A 3 -A 3  in  FIG. 5 . The load port device F is disposed so as to allow a protruding direction of the carrier stage C to be disposed in the stockyard R 1 . The load port device F is fitted to a load port mount space Pb formed on the wall member P isolating the stockyard R 1  from the enclosure R 2  and fixed to the wall member P by the use of the bolt  81  or the like. That is, the front side of the load port device F is disposed on the side of the stockyard R 1  and the rear side thereof is disposed on the side of the enclosure R 2 . One or more of the load port devices F are attached to the wall member P depending on a size of the fabrication apparatus in the Y direction. In the embodiment, as shown in  FIG. 5 , two load port devices F are installed. Further, in the related-art fabrication apparatus, the same number of the external load ports L as the load port devices F are provided. The carrier transferring operation from the external load port L to the carrier stage C of the load port device F is carried out in the same line as a reciprocation direction X relative to the processing device R 3 . In the drawings, Pa denotes a frame of the fabrication apparatus. 
     The carrier installation shelf S disposed in the stockyard R 1  will be described with reference to  FIGS. 5 and 6 . The carrier installation shelf S is a shelf for placing the carrier  30  thereon when the carrier  30  placed on the external load port L is received in the stockyard R 1 . The carrier installation shelf S is attached to the wall member P. Each of the carrier installation shelves S is installed at a predetermined interval on each of the upper part and the lower part of the load port device F attached to the wall member P within a height of the fabrication apparatus. In the carrier installation shelf S according to the embodiment, two carrier installation shelves S are provided on the upper part of each of the two load port device F and one carrier installation shelf S is provided on the lower part thereof while being attached to the wall member P. The carrier installation shelves S installed in each row thereof are sequentially denoted by S 1 , S 2 , and S 3  from the top thereof. In each of carrier installation shelves S 1 , S 2 , and S 3 , positioning pins  91  for locking the carrier  30  fitted to the positioning pedestals  31  and a hand insertion space (not shown) are formed. In the load port device F and the carrier installation shelves S 1 , S 2 , and S 3  disposed in the same row, when the carrier mounted on the transfer hand  72  of the carrier transfer device T 1  is placed onto any one of the carrier installation shelves S 1 , S 2 , and S 3  by the positioning pins  91  after insertion into the hand insertion space, a position of the carrier on the XY plane (in a top view) corresponds to a position where the carrier is placed on the carrier plate  11  when the carrier plate  11  is at a maximum recession position from the wafer transfer window  2 . In addition, a seating pin  92  is formed on each of the carrier installation shelves S 1 , S 2 , and S 3 . When the carrier  30  is placed on the carrier installation shelf S, the bottom surface of the carrier  30  is allowed to come in contact with the seating pin  92 . As a result, stability of the carrier  30  placed thereon is ensured. 
     The carrier transfer device T 1  will be described with reference to  FIG. 8 . The carrier transfer device T 1  is disposed in the stockyard R 1 . The carrier transfer device T 1  includes an elevation mechanism  77  fixed to an inner surface of one side wall of the stockyard R 1  and disposed in a Z direction of a height of the fabrication apparatus, a rail  75  having one end fixed to the elevation mechanism  77  and disposed in the Y direction, a horizontal movement mechanism  76  fixed to the rail  75  and sliding on the rail  75 , the transfer arm  71  rotatably fixed to the horizontal movement mechanism  76 , and the transfer hand  72  rotatably attached to a front end of the transfer arm  71 . The transfer arm  71  includes a unit  71   a  and a unit  71   b . One end of the unit  71   a  is fixed to the horizontal movement mechanism  76  so as to rotate by the use of a rotation shaft  78  and the other end thereof is connected to one end of the unit  71   b  through a rotation shaft  74 . The other end of the unit  71   b  is connected to the transfer hand  72 . Each locking pin  73  is attached to each apex on the transfer hand  72  with a triangular shape. The locking pins  73  on three positions are disposed so as to correspond to the positioning pedestals on three positions that are disposed on three apexes with a triangular shape on the bottom surface of the carrier  30 . 
     Next, a procedure when transferring the carrier  30  that is conveyed to the fabrication apparatus and then temporarily stored in the buffer stage B to the carrier stage C with reference to  FIGS. 7 and 8 . In the embodiment, two load port devices F are installed, but focusing on one of them, a transferring operation from the external load port L that is disposed on the same line in the X direction of the load port device F to the load port device F will be described. First, the carrier  30  conveyed from the fabrication apparatus is received in the external load port L attached to a front side of the fabrication apparatus so as to allow the cover  32  of the carrier  30  to face an entrance of the fabrication apparatus. The rail  75  fitted to the horizontal movement mechanism  76  is elevated and then stopped at a predetermined height by the elevation mechanism  77  constituting the carrier transfer device T 1 . Subsequently, the horizontal movement mechanism  76  slides on the rail  75  in the Y direction and then stopped at a position of the external load port L. The transfer arm  71  lengthens by rotating each of the unit  71   a , the unit  71   b , and the transfer hand  72  so as to insert the transfer hand  72  below the bottom surface of the carrier  30  placed on the external load port L. The transfer arm  71  and the transfer hand  72  are slightly lifted up so as to fit the locking pins  73  of the transfer hand  72  to the positioning pedestals  31  at three positions on the bottom surface of the carrier  30 . Subsequently, the transfer arm  71  is slightly lifted up so as to securely support the lower part of the carrier  30  by the use of the transfer hand  72 . Subsequently, the transfer arm  71  shortens by rotating each of the unit  71   a , the unit  71   b , and the transfer hand  72  so as to recede from the external load port L. Subsequently, the transfer arm  71  lengthens by rotating each of the unit  71   a , the unit  71   b , and the transfer hand  72  so as to allow the carrier  30  to move in the X direction to the buffer stage B of the load port device F while the cover  32  of the carrier  30  faces the front side. At this time, three dimensional (XYZ) direction positions of the horizontal movement mechanism  76  should be fixed. Subsequently, the lengthened transfer arm  71  inserts the transfer hand  72  supporting the carrier  30  slightly above the hand insertion space  24  of the buffer plate  21 . The transfer arm  71  is slightly lifted down so as to fit the positioning pins  23  of the buffer plate  21  to the positioning pedestals  31  on the bottom surface of the carrier  30 . At this time, in the grooves formed on the positioning pedestals  31 , the locking pins  73  of the transfer hand  72  are fitted into the inside of the grooves and the positioning pins  23  of the buffer plate  21  are fitted into the outside of the grooves so as not to interfere with each other. Subsequently, when the transfer arm  71  is lifted down so as to completely detach the locking pins  73  of the transfer hand  72  from the positioning pedestals  31 , the carrier  30  is placed on the buffer plate  21  in the state where the positioning pins  23  are fitted to the positioning pedestals  31 . Finally, the transfer arm  71  shortens by rotating each of the unit  71   a , the unit  71   b , and the transfer hand  72  so as to allow the transfer hand  72  to recede from the hand insertion space  24 . 
     Next, a procedure when transferring the carrier  30  placed on the buffer plate  21  onto the carrier plate  11  of the carrier stage C will be described. First, the transfer arm  71  moves from a present position of the transfer arm  71  of the carrier transfer device T 1  to the front side of the carrier  30  by operating the elevation mechanism  77  and the horizontal movement mechanism  76 . The transfer arm  71  lengthens by rotating each of the unit  71   a , the unit  71   b , and the transfer hand  72 . The transfer hand  72  is inserted into the hand insertion space  24  of the buffer plate  21  so as to be positioned slightly lower than the buffer plate  21 . Subsequently, the locking pins  73  of the transfer hand  72  are fitted into the positioning pedestals  31  on the bottom surface of the carrier  30  by slightly lifting up the transfer hand  72 . At this time, in the grooves of the positioning pedestals  31 , the locking pins  73  are fitted into the inside of the grooves and the positioning pins  23  of the buffer plate  21  are fitted into the outside of the grooves so as not to interfere with each other. Subsequently, the positioning pins  23  are completely detached from the positioning pedestals  31  by slightly lifting up the transfer hand  72 , so that the lower part of the carrier  30  is completely supported by the transfer hand  72 . The transfer arm  71  shortens by rotating each of the unit  71   a , the unit  71   b , and the transfer hand  72  and allows the carrier  30  to move backward in the X direction so as to completely recede from the buffer stage B. 
     Subsequently, the elevation mechanism  77  lifts up the rail  75  so as to reach the height of the carrier plate  11  of the carrier stage C, and then lifts up the transfer arm  71 . At this time, the carrier plate  11  slides to a maximum recession position from the wafer transfer window  2  by the slide mechanism  12 . Subsequently, the transfer arm  71  lengthens by rotating each of the unit  71   a , the unit  71   b , and the transfer hand  72 , and allows the carrier  30  to move forward in the X direction, so that the transfer hand  72  supporting the carrier  30  is inserted into the hand insertion space  14  of the carrier plate  11  so as to be slightly higher than the plate  11 . The transfer hand  72  is allowed to slightly move down so that the positioning pins  13  on the carrier plate  11  are fitted into the positioning pedestals  31  on the bottom surface of the carrier  30 . At this time, in the grooves of the positioning pedestals  31 , the locking pins  73  of the transfer hand  72  are fitted into the inside of the grooves and the positioning pins  13  are fitted into the outside of the grooves so as not to interfere with each other. When the transfer hand  72  is lifted down, the positioning pins  13  are securely fitted into the positioning pedestals  31  and the locking pins  73  of the transfer hand  72  are detached from the positioning pedestals  31 . Accordingly, the carrier  30  is placed on the carrier plate  11  so as to insert the positioning pins  13  into the positioning pedestals  31 . Finally, as the transfer arm  71  shortens by rotating each of the unit  71   a , the unit  71   b , and the transfer hand  72 , the transfer hand  72  thereby recedes in the X direction. The carrier plate  11  on which the carrier  30  is placed moves toward the wafer transfer window  2  until the cover  32  of the carrier  30  comes in contact with the wafer window  2  by means of the slide mechanism  12 . 
     The above-described procedure is the same as a procedure when transferring the carrier  30  from the external load port L to the carrier installation shelves S 1 , S 2 , and S 3 . Accordingly, when the carrier  30  conveyed to the external load port L is stored in the stockyard R 1 , in each load port device F, one additional space for placing the carrier  30  thereon increases in addition to the carrier installation shelves S 1 , S 2 , and S 3  by attaching the buffer stage B to the load port device F. For this reason, a reception capacity of the carrier in the limited space of the stockyard R 1  increases. Additionally, in the load port device F, the buffer stage B is formed right below the table  18  of the carrier stage C. As a result, a distance when transferring the carrier  30  from the buffer plate  21  of the buffer stage B to the carrier plate  11  of the carrier stage C is shorter than that when transferring from the carrier installation shelves S 1 , S 2 , and S 3  in the stockyard R 1 . Further, a height of the external load port L is almost the same as that of the buffer plate  21 . Accordingly, when the buffer stage B in the stockyard R 1  is empty and the carrier  30  is transferred from the external load port L, a carrier moving distance when transferring the carrier  30  to the buffer stage B is shorter than that when transferring the carrier  30  to the carrier installation shelves S 1 , S 2 , and S 3 . As a result, work efficiency is improved. 
     When the carrier  30  is placed on the carrier plate  11  and then the carrier  30  moves forward to a position of coming in contact with the wafer transfer window  2 , the processing device R 3  performs a wafer processing to the wafer W housed in the carrier  30  according to the known procedure. That is, a cover of the carrier  30  is first opened by an operation of the cover opening/closing unit N, and then the cover opening/closing unit N and the cover  32  are lifted down by the elevation mechanism U 1 . Subsequently, the mapping device M is lifted down by the elevation mechanism U 2  while detecting the wafer W housed in the carrier  30  in a form of multi stairs. After the detection, the wafer W is taken out by the wafer transfer robot T 2  and then conveyed to the processing device R 3  to be processed. The plurality of sheets of the wafer W conveyed to the processing device R 3  is received in a wafer board V in a form of multi stairs and the wafer W is subjected to a chemical process every wafer board V. When the process ends, the wafer transfer robot T 2  returns a processed wafer W′ received in the wafer board V to the carrier  30  to be housed therein. Subsequently, the mapping device M is lifted up while detecting the wafer W′ housed in the carrier  30 . After the detection, the cover  32  of the carrier  32  that is lifted down along with the cover opening/closing unit N is lifted up so as to be attached to the opening of the carrier  30 . Subsequently, the carrier plate  11  slides from the wafer transfer window  2  and thereby the carrier  30  recedes from the wafer transfer window  2 . 
     When the carrier  30  recedes from the wafer transfer window  2  in the X direction and reaches the maximum recession position, the carrier  30  is transferred from the carrier plate  11  to the external load port L by the carrier transfer device T 1  or the carrier  30  is temporarily stored in the buffer plate  21  of the buffer stage B or the carrier installation shelf S and then transferred to the external load port L. The carrier  30  transferred to the external load port L is conveyed from the fabrication apparatus to proceed to the next process by the carrier conveyance system. When the carrier  30  is temporarily stored in the buffer stage B from the carrier stage C and then transferred to the external load port L, it may take a reverse procedure that is totally different from the above-described procedure in which the carrier  30  is transferred from the external load port L to the buffer stage B and then the carrier stage C. 
     The buffer stage B according to the invention is attached to the load port device F, but may be attached to the external load port L. Accordingly, a storage space of the carrier  30  is provided even in the outside of the fabrication apparatus. Therefore, a high reception capacity of the carrier  30  can be effectively ensured in the clean room.