Abstract:
A wafer container comprising a base and a cover that nest together. The cover includes tabs on a lower portion that engage notches on the frame. The cover can be combined with the base without indexing to a precise opening on the frame. A handle on the cover enables an operator to easily rotate the container into a locked position. A ribbed pattern on the exterior surface of the frame enables the wafer container to be stacked with another wafer container.

Description:
FIELD OF THE INVENTION 
   The invention relates to a wafer container for handling wafers between processing stations or for transporting wafers outside a production facility. 
   BACKGROUND OF THE INVENTION 
   Conventional wafer containers have two sections: a cover and a base. One such container is described in U.S. Pat. No. 6,237,771 (Haq). Haq discloses a cover and a base with receiving apertures. It is essential that the projections align with the receiving apertures to allow the container to be properly locked. 
   Once the projections align with the apertures, the two sections of the wafer container can be locked into place. If the top section is not properly aligned, the cover will have to be lifted and reinserted into the correct position. It is also difficult to observe in the Haq container whether the cover is engaging correctly to the base. 
   When a container is not properly locked it affects the stability of a stack of wafer containers. An improperly closed container may cause a stack of wafer containers to unnecessarily shift in position. It is also time consuming for an operator to remove covers from within a stack of containers to determine which container is responsible for the instability. Moreover, most wafer containers lack a gripping area that allows an operator to easily grip the cover for removal. 
   A need exists for a wafer container that has increased stability during stacking, a gripping area, and that is not constrained to specific angles when the top section (cover) engages to the base. A need also exists for a wafer container that allows an operator to easily observe if the two sections have correctly engaged to each other. 
   SUMMARY OF THE INVENTION 
   The present invention concerns a wafer container comprising a base having a cylindrical wall structure and a frame. On the frame are notches that extend to an edge of the frame. Tabs extend from a cylindrical cover to engage with the notches on the frame thereby forming a closed wafer container. 
   Another embodiment of the invention concerns a stackable wafer container comprising a base and a cover that lock into a closed position. The base includes a pattern on an exterior region that is contoured to mate with an upper surface of the cover of a second wafer container. 
   Yet another embodiment of the invention is directed to a wafer container that is provided with a gripping area on the cover that facilitates the disassembly of the two sections of the container. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the disassembled wafer container. 
       FIG. 2  is a perspective view of the cover as it is being rotated into the base of the container. 
       FIG. 3  illustrates a top view of the base of the present invention. 
       FIG. 4  illustrates a side view of the assembled wafer container. 
       FIG. 5  illustrates a planar bottom view of the base of  FIG. 3 . 
       FIG. 6  illustrates a simplified sectional view of a stack of wafer containers. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   To solve the above problems, the wafer container of the present invention was developed.  FIG. 1  is a perspective view of the two sections of the wafer container of the present invention.  FIG. 1  illustrates a cylindrical cover  15  that has a deck  20  near its open end. The deck  20  has chamfered corners  18  on which tabs  23  are attached. Cover  15  has a diameter that is greater than the diameter of the circumference defined by wall structure  71  of base  30 . This allows cover  15  to nest onto walls  71 A- 71 D of the base. Walls  71 A- 71 D extend from a substantially square-shaped frame  27 . Within frame  27  are open edges  41  cut out on more than one corner region  35 . Corner regions  35  include a corner and a portion of the frame walls,  27 A and  27 B, adjacent each corner as shown in  FIG. 1 . Each open edge, or notch  41 , engages with a corresponding tab  23  to form a closed container. 
   To secure wafers within wafer container  100 , cover  15  is lowered onto base  30 . Cover  15  is rotated clockwise as shown in  FIG. 2  until tabs  23  engage with notches  41  at corner regions  35  of base  30 . Tabs  23  can engage the base from any angle and need not be indexed to a specific spot as in the prior art. In  FIG. 2  notches  41 - 1  and  41 - 2  are shown at specific locations on corner regions  50 . However, notches  41  can instead be placed at a different location of the corner region  35 . 
     FIG. 3  illustrates a top view of the base, wherein notches are located on frame walls  27 B,  29 B,  31 B and  33 B. Notch  41 - 1  can instead appear on frame wall  27 A, that is at a 90° angle to frame wall  27 B. Similarly, notches  41 - 2 ,  41 - 3 , and  41 - 4  can be placed on walls  29 A,  31 A and  33 A respectively instead on the frame walls shown in  FIG. 3 . Of course, if notches  41 - 1 ,  41 - 2 ,  41 - 3 , and  41 - 4  appear on frame walls,  27 A,  29 A,  31 A and  33 A respectively, the cover of wafer box  100  will be rotated counterclockwise to engage the tabs with notches  41 . 
     FIG. 4  illustrates the assembled wafer container  100 . On cover  15  a raised handle  58  is shown. Handle  58  enables an operator to grip the cover to lock the two sections  15  and  30  into place. In addition, handle  58  may be rotated in a counterclockwise direction to disengage the tabs from notches  41 , thereby unlocking the cover when the notches  41  are in the position illustrated in  FIG. 3 . In an unlocked position, cover  15  is simply lifted from base  30  to insert, inspect or remove the contents therein. 
   Wall structure  71  preferably has at least one lateral opening  44  perpendicular to the horizontal plane of base  30 . Lateral openings  44  facilitate an operator&#39;s access to the wafers and any other contents stored within wafer container  100 . Additional contents may include separator sheets to prevent dust from accumulating and to prevent scratches to wafer surfaces. The separators may be for example thin disks constructed of paper or foam, and/or a carbon impregnated material. In addition, a plastic insert, foam, or sponge material may be used to fill any empty space of a container that is not filled to capacity. However, the present invention excludes the use of any foamed padding that is attached to cover  15  or walls  27 A- 27 D. 
   Cover  15  is configured to nest with the wall structure  71  of base  30 . When cover  15  and base  30  are nested together, there is a limited clearance between wall structure  71  and cover  15 . The wall structure thereby constrains the contents of the wafer box  100  to limit movement of the wafers  10  during shipment and handling. 
   The containers of the present invention are also stackable.  FIG. 5  illustrates the exterior bottom surface of base  30 . Base  30  has multiple locations at which it can align to the top of a second container. These locations comprise parallel longitudinal areas  32  that traverse the planar exterior surface of frame  27 . Although a single pair of longitudinal ribs in the form of an “=” sign would suffice for stacking purposes, it is preferred to provide multiple parallel longitudinal areas  32  on frame  27 . In either case, ribs  37  are symmetrical along each axis that extends through the space that lies between ribs  37 . 
   In a preferred embodiment, longitudinal area  32  is a cross-shaped pattern  32  that receives handle  58  when the container is in a locked orientation. Ribs  37  of a second container  200  mate with handle  58  of container  100  as shown in  FIG. 6 . When the cover of container  100  is misaligned with the base of container  200 , base  34  is rotated no more than 90° until the two containers are aligned to each other in stacking formation. Accordingly, handle  58  will reside in either the longitudinal space  32 A between ribs  37  or the longitudinal space  32 B between ribs  37 . In this manner, the base from a second container  200  can be stacked on the cover of a first container  100 . 
   In a preferred embodiment, the height of ribs  37  is greater than the height of handle  58 . More specifically, pattern  32  is defined by ribs  37  that are between approximately 0.60 and 0.70 inches in height and between approximately 0.075 and 0.085 inches in width. In a more preferred embodiment, ribs  37  have a height of approximately 0.65 inches and a thickness of approximately 0.080 inches. These dimensions ensure that the ribs do not contact the upper planar surface  19  of handle  58  during stacking. In addition, the planar space between ribs  32 A and  32 B does not contact handle  58  either when covered containers  100  and  200  are stacked together. Containers stacked in accordance with the present invention are maintained in a stable position for shipping and do not rotate out of position. 
   The containers of the present invention are preferably manufactured with a standard injection molding process. Suitable manufacturing materials for the present invention include conductive, thermoplastic, non-conductive, and insulated plastic. In addition, the wafer containers can be fabricated from material that has electrostatic dissipating properties. 
   The specific examples provided above are intended to be illustrative of the invention only. It should be apparent to those skilled in the art that various features of the invention may be modified without departing from the spirit and scope of the invention. It is therefore the intent that the scope of the invention is to be defined by the appended claims.