Abstract:
An apparatus for holding a substrate includes a shelf capable of holding the substrate; a body which encloses the shelf, the body having an open side; and an outer door frame pivotally coupled to the body and defining an opening. The apparatus also includes an inner door which fits into the opening. The body&#39;s open side is substantially covered by the inner door and by the outer door frame when the inner door and outer door frame are in closed positions. The apparatus can include a double hinge for pivotally coupling the outer door frame to the body. It can also include a bolt that is movably attached to the inner door, so that the inner door has a locked position in which the bolt extends into the frame and an unlocked position in which the bolt retracts from the frame.

Description:
TECHNICAL FIELD 
     This invention relates to apparatus for transport and storage of semiconductor substrates. 
     BACKGROUND 
     A front opening unified pod (FOUP) is a container for transporting and storing semiconductor substrates. A FOUP combines a cassette and a boat box for holding cassettes. It has shelves for holding substrates, an outer box-shaped pod body having five sides, and a door for sealing the pod body&#39;s sixth side. The frame is slightly larger, both in terms of width and length, than the pod body. The door is bolted into the frame, and the frame is fused to the pod body. The pod body, shelves, and door are made of plastic. Typically, to open the door, keys need to be inserted into a lock assembly in the door. 
     In use, a single FOUP is placed in a loading station of a semiconductor processing tool, flush against a tool door having two keys. The tool door, attached to an arm, opens the FOUP door by turning the keys in the FOUP door, thus opening bolts that attach the FOUP door to the FOUP body. The tool door pulls on the FOUP door with a vacuum, pulls the FOUP door away from the FOUP pod body, and lowers the FOUP door, thereby exposing wafers inside the FOUP. After a wafer is removed from the FOUP for processing and is processed, the wafer is returned to the FOUP. 
     The FOUP door cannot be opened without a tool door, unless one has two keys manufactured, inserts the keys into the FOUP door by hand, turns the keys simultaneously, and pulls the door off. This option is undesirable because opening the FOUP door outside a FOUP station can expose the wafers inside the FOUP to a relatively unclean environment. 
     The door of a FOUP is generally opened in ultra-clean system environments, e.g. Class 1, to avoid contaminating wafers inside the FOUP. Sometimes, however, wafers may be exposed to less clean environments. For example, during a lithography process, a wafer may be removed from a FOUP in a Class 1 environment and fed by a track to a scanner. The wafer is processed and returned to the FOUP pod via the track. If, however, the wafer is rejected by the scanner, it is not returned to the FOUP. Instead, it is transferred to an open wafer cassette, e.g., a Crystalpak®, with other rejected wafers. A Crystalpak®, manufactured by Entegris, Inc., is a plastic cassette in which wafers are shipped by a wafer manufacturer. A Crystalpak® has 13 slots for holding 13 300 mm wafers and has a height of 18 centimeters (cm). On the other hand, a FOUP currently used in industry has 25 slots for holding 25 300 mm wafers and is twice the height of a Crystalpak®, e.g., 36 cm. A Crystalpak® can be placed inside a scanner, and rejected wafers can be moved into the Crystalpak®. The scanner&#39;s loading arm is stationery and the wafer carrier moves during loading and unloading. The configuration does not provide sufficient range of motion for loading and unloading wafers to/from a FOUP, but it is sufficient for, e.g., a Crystalpak®. The wafer cassette is then removed from the scanner, and the wafers in the boat are transferred to another FOUP. The wafers in the wafer boat are thus exposed to a less clean atmosphere than that of the processing equipment, such as Class 10 instead of Class 1. This exposure can contaminate the wafers, increasing defect densities. The wafers in the system environment cannot be placed directly into a second FOUP if the system has only one port for a FOUP. Further, a FOUP cannot be placed inside the processing tool because of constraints imposed by the method of opening the front door, such as the requirement that a tool door be used for opening the FOUP door. Finally, a FOUP may not physically fit inside a tool, even in the FOUP&#39;s closed position. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A-1B are schematic drawings of a door-in-door front opening unified pod. 
     FIG. 2 is a frontal view of a door-in-door in a locked position. 
     FIG. 3 is a frontal view of a door-in-door in an unlocked position. 
     FIGS. 4-7 are cross-sectional views of a door-in-door front opening unified pod illustrating some embodiments, with the door in various positions. 
    
    
     DESCRIPTION 
     A FOUP is described, having thirteen slots for holding thirteen wafers. Its door configuration enables it to be placed inside a processing tool and opened by a currently available FOUP handler, as well as to be opened and closed without a FOUP handler. 
     Referring to FIGS. 1A-1B, a door-in-door front opening unified pod  10 , hereinafter referred to as “DIDFOUP,” has a cube-shaped pod body  12 . Pod body  12  has a top side  14 , a bottom side  16 , first and second lateral sides  18 ,  20 , and a back side  22 . A door-in-door  24  is sized to close a front side  25  of pod body  12 . Door-in-door  24  has a frame  26  and an inner door  28 . 
     Frame  26  is movably attached to first and second lateral sides  18 ,  20  by first and second double hinges  30 ,  32 , respectively. First ends  34 ,  36  of double hinges  30 ,  32  are pivotally secured to frame  26  by hinge bolts  38 ,  40 , respectively. Second ends  42 ,  44  of double hinges  30 ,  32  are pivotally secured to first and second lateral sides  18 ,  20 , respectively, by hinge bolts  46 ,  48 . In its closed position, frame  26  is further secured against pod front side  25  by first and second latches  50 ,  52 . First and second latches  50 ,  52  are attached to first and second sides  58 ,  60  of frame  26 . First and second latch receptacles  54 ,  56  are located on first and second lateral sides  18 ,  20  of pod body  12 . When frame  26  is positioned against pod front side  25 , first and second latches  50 ,  52  can be manipulated to close by hooking onto latch receptacles  54 ,  56 . First and second latches  50 ,  52  can thus to prevent accidental opening of frame  26 . 
     Inner door  28  is sized to fit in an opening  64  defined by an inner perimeter  65  of frame  26 . In its closed position, inner door  28  is secured by four bolts  66 ,  68 ,  70 ,  72  protruding into frame  26 . 
     Pod body  12  contains a wafer support structure  74  having a plurality of shelves  76  (represented by dotted lines in FIGS.  1 A and  1 B), for example, thirteen shelves  76 . Each shelf  76  is sized to hold a semiconductor wafer (not shown), such as a round silicon wafer having a diameter of 300 mm. Each shelf  76  is a horizontal ridge extending along first and second lateral sides  18 ,  20  and back side  22 . Each shelf  76  is formed by, e.g., injection molding as an integral part of first and second lateral sides  18 ,  20  and back side  22 . 
     Pod body  12  has a height H 1  of, e.g., 18 centimeters (cm) and a depth D 1  of, e.g., 32 cm. Frame  26  has a height H 2  of, e.g., 21 cm. 
     Each of the plurality of shelves  76  has a thickness T 1  of, e.g., 0.3 cm. Each one of the plurality of shelves  76  is a distance D 3 , e.g., 0.4 cm from a proximate shelf  76 . Shelves  76 , therefore, have a pitch of 0.7 cm, equal to the sum of T 1  and D 3 . 
     Pod body  12  and each of the plurality of shelves  76  are made of a plastic material. 
     Referring also to FIG. 2, inner door  28  has first and second keyed locking mechanisms  80 ,  82 . Here, first and second locking mechanisms  80 ,  82  are shown in a locked position in which bolts  66 ,  68 ,  70 ,  72  extend into frame  26 . First and second keyed locking mechanisms  80 ,  82  have similar structures. To avoid redundancy, only first locking mechanism  80  will be described in detail, with the implication that second keyed locking mechanism has an analogous construction. First keyed locking mechanism  80  has a plate  84  defining a keyhole  86 . Plate  84  and keyhole  86  are located on an external side of inner door  28 . First and second locking rods  88 ,  90  are positioned within inner door  28  and are encased by inner door  28 . First and second locking rods  88 ,  90  are pivotally attached at their respective first ends  92 ,  94  to plate  84  by first and second rod bolts  96 ,  98 . Respective second ends  100 ,  102  of first and second locking rods  88 ,  90  are slidably attached by first and second roller bolts  104 ,  106  to first and second cams  108 ,  110 . First and second cams  108 ,  110  define first and second grooves  112 ,  114  to which first and second roller bolts  104 ,  106  are slidably coupled. First keyed locking mechanism  80  controls positioning of two bolts  66 ,  72  by controlling the positioning of first and second cams  108 ,  110  to which two bolts  66 ,  72  are attached. As shown (FIG.  2 ), when first keyed locking mechanism  80  is in a locked position, bolts  66 ,  72  extend into frame  26 . Bolts  66 ,  72 , along with bolts  68 ,  70  that are similarly configured in second keyed locking mechanism  82 , thus secure inner door  28  within frame  26 . 
     Referring also to FIG. 3, first keyed locking mechanism  80  is moved to an unlocked position when a key (not shown) is inserted into keyhole  86  and the key is turned counterclockwise. Turning the key also rotates plate  84  counterclockwise, thus moving first keyed locking mechanism  80  from a locked position to an unlocked position. When plate  84  rotates counterclockwise, it moves first and second locking rods  88 ,  90  as follows. First end  92  of first locking rod  88  moves upwardly counterclockwise, rotating about first rod bolt  96 . At the same time, second end  100  of first locking rod  88  also moves upwardly counterclockwise, with first roller bolt  104  sliding along groove  112 . While moving upwards, second end  100  also moves cam  108  upwards and lifts bolt  66  out of frame  26 . Meanwhile, first end  94  of second locking rod  90  moves downwardly counterclockwise, rotating about second rod bolt  98 . At about the same time, second end  102  of second locking rod  90  moves downwardly counterclockwise, with second roller bolt  106  sliding along groove  114 . While moving downward, second end  102  also moves cam  110  downwards and retracts bolt  72  down from frame  26 . 
     Second keyed locking mechanism  82  is similarly moved to an unlocked position. When both first and second keyed locking mechanisms  80 ,  82  are in their respective unlocked positions, bolts  66 ,  68 ,  70 , and  72  are withdrawn from frame  26 . Inner door  28  is then free to be removed from frame  26  by, e.g., a tool door (not shown). 
     Referring to FIG. 4, in its fully closed position, inner door  28  is locked in frame  26  (FIG.  2 ), and frame  26  is closed flush with front side  25  of pod body  12 . Latch  52  secures frame  26  against front side  25  and prevents frame  26  from opening. An o-ring  150  is fitted into front side  25  to ensure a tight seal between pod body  12  and frame  26 , thus preventing contaminants from entering pod body  12 . Bolts  68 ,  72  secure inner door  28  in frame  26 . 
     Referring to FIG. 5, latch  50  and latch  52  (not shown) are manually opened to allow frame  26  and inner door  28  to be raised. To open latch  50 , hook portion  152  of latch  50  is released by hand from latch receptacle  54  of latch  50 . Frame  26  is then free to move upward and away from front side  25  of pod body  12  in the direction of arrow A. 
     Referring to FIG. 6, frame  26  is lifted further away from front side  25  and further toward top side  14  of pod body  12 . Double hinge  32  moves in a counterclockwise direction, as indicated by arrow B, as frame  26  is lifted away from front side  25 . Double hinge  32  enables frame  26  to be moved from a closed position to an open position. Double hinge  32  provides a full range of motion for frame  26 . 
     Referring to FIG. 7, in its fully open position, frame  26  rests in a flat position on top side  14  of pod body  12 . Here, pod front side  25  is open, and wafers (not shown) can be placed on—or removed from—shelves  76 . Shelves  76  have a length L 1  of 30.5 cm. 
     In use, pod front side  25  can be opened in one of two ways. Referring to FIGS. 1A,  2 , and  3 , first and second keyed locking mechanisms  80 ,  82  can be moved to their respective unlocked positions by a key (not shown) inserted into keyholes  86 ,  83  and turned to unlock bolts  66 ,  68 ,  70 ,  72 , i.e. retract them from frame  26 . Inner door  28  can then be pulled away from pod body  12  and removed by a tool door (not shown). A slightly positive pressure is provided at the loading station to the tool, and thus any wafers inside pod body  12  are exposed to the clean atmosphere of the tool. The DIDFOUP can therefore be used with currently available FOUP stations for loading wafers into processing tools. 
     Alternatively, referring to FIGS. 1A,  1 B, and  4 - 7 , latches  50 ,  52  can be opened manually, allowing frame  26  to be lifted away from pod front side  25  and onto pod body top side  14 . Providing access to pod front side  25  manually is desirable when, for example, the DIDFOUP is used with a tool that does not have a FOUP interface. Pod front side  25  can also be opened manually if there is a need to access wafers inside pod body  12  without a machine, such as in the case of wafer recovery. 
     Wafers can be transferred from a thirteen-slot DIDFOUP to a conventional twenty-five slot FOUP by use of a wafer handling tool, such as a lot splitter, for example the SPP300mm_F01, manufactured by RECIF, based in Aussone, France. 
     The invention is not limited to the specific embodiments described above. For example, shelves for supporting wafers can be formed independently of pod sides and inserted into the pod body. The shelves can be made of a material different from that of the pod body. 
     Other embodiments not described herein are also within the scope of the following claims.