Abstract:
Improvements in a semiconductor wafer container including improvements in side protection to the wafers, improved cover design to minimize rotation, a simplified top cover orientation mechanism and an improved bottom holding mechanism for automation. The side protection to the wafers is with multiple staggered inner and outer walls. The improved cover design improves alignment of the top and bottom housings and minimizes rotation of the housings in transit or motion. The housings have a recessed tab ramp feature with bi-directional locking that also increases the rigidity of the containment device when the two housings are assembled. The improved bottom holding mechanism for automation is an integrated feature that is molded into the bottom housing and not assembled in a secondary operation. The molded integration reduces tolerance errors that are present in assembling multiple pieces and joining multiple pieces.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not Applicable 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0004]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0005]    1. Field of the Invention 
         [0006]    This invention relates to improvements in a container for the transportation of semiconductor wafers. More particularly, the present wafer container includes improvements in side protection to the wafers, improved cover design to minimize rotation, a simplified top cover orientation mechanism and an improved bottom holding mechanism for automation. 
         [0007]    2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
         [0008]    In the processing of semiconductor wafers the typically must be transported either between processes or to other facilities. The semiconductor wafers are fragile and damage to the surface of the wafers can make the wafer useless for the intended purpose. Because of the high potential for damage to the wafer the semiconductors must be packaged and transported to minimize harm. In transportation, multiple semiconductor wafers are stacked into a transportation container. There have been a number of containment products and patents have been sold and patented to try and minimize damage to these silicon wafers. Exemplary examples of patents covering these products are disclosed herein. 
         [0009]    U.S. Pat. No. 6,193,068 issued Feb. 27, 2001 to Lee Lewis et al., and U.S. Pat. No. 6,341,695 issued Jan. 29, 2002 to Lee Lewis et al., disclose a containment device for retaining semiconductor wafers. This patent discloses two concentric walls on the top and bottom housings that nest to protect the semiconductor wafers. Double walls were designed to protect the wafers from the direct transmission of forces that may contact the outer wall. While the nesting walls provide protection from side impacts they do not provide flexibility to absorb and cushion a side impact or drop. The combination of an outer wall and a gap provide the protection. Damage may also occur if the force is such that the outer wall flexes enough to interfere with the inner wall, thereby damaging the wafers. That can cause the semiconductor wafers to shift and scratch. 
         [0010]    U.S. Patent Publication Number US2009/0095650 that was published on Apr. 16, 2009 to James D. Pylant et al., discloses a wafer container with staggered wall structure. In this published application the design is limited by the amount overlap of the inner and outer walls by the design of its staggered walls. The walls were limited to 5% overlap, with 95 percent of the outer wall not located in adjoining angular sectors. This and other top cover rotation locating mechanisms use either an inner surface of a feature on the top cover or an exterior surface of a feature on the top cover to secure the top cover in place and prevent rotation. 
         [0011]    U.S. Pat. No. 6,550,619 issued Apr. 22, 2003 to Gregory W. Bores et al., discloses a shock resistant variable load tolerant wafer shipper. This patent uses four inner tapers walls with a variable amount of cushions placed between the semiconductor wafers to pack and cushion the semiconductor wafer. While this patent allows for a variable amount of semiconductor wafers to be packed within the shipper the cushioning relies on the variable amount of cushions placed between the semiconductor wafers to reduce damage. 
         [0012]    U.S. Pat. No. 7,040,487 issued on May 9, 2006 to Michael Zabka et al., discloses a protective shipper with a corrugates inner containment lip. The corrugated inner lip provides multiple surfaces for the edges if the semiconductor wafers to make contact with, but because the edges are corrugated the tangential walls of the corrugation limit the flexing of the inner lips. 
         [0013]    Some semiconductor wafer containers use a rotation locking design where the locating mechanism with an exclusive inner surface or exterior surface do not securely capture the wall that they are adjacent to in both directions of rotation. These features only stop rotation in only one direction. The features must rely on a sister feature to stop rotation in the opposite direction which is generally located farther away and allows for more manufacturing tolerance to build up since it is located at a greater distance. These deficiencies result in larger gaps between the plus and minus rotational limiting surfaces, thereby leading to more rotational movement. 
         [0014]    There are a number of prior designs that use top cover orientation features with differing wall engagement angles or large latches as opposed to small slots. The new feature in this proposed wafer container allows improved orientation that is not found in the prior art. 
         [0015]    There are a number of different holding and clamping features in wafer shipping containers. All of these prior designs rely on multiple parts to create a clamping lip. These designs have several drawbacks including but not limited to the parts not being rigid with respect to the bottom assembly because they must be sonic welded, bonded or snapped together and that secondary parts or assembly operations are more expensive to produce. 
         [0016]    The engagement of latches that secure the top and bottom housings together have a number of limitations. Specifically, prior art latches provide a raised straight slope ramp. The raise straight sloped surface is susceptible to damage and also, the straight slope does not provide an ideal self gripping to engage between the top and bottom housings. The top cover orientation features use differing wall engagement angles or large latches as opposed to small slots as presented in this pending application. 
         [0017]    What is needed is a semiconductor wafer container with improvements in side protection to the wafers, improved cover design to minimize rotation, a simplified top cover orientation mechanism and an improved bottom holding mechanism for automation. This pending application satisfies these requirements with novel improvements in the identified areas. 
       BRIEF SUMMARY OF THE INVENTION 
       [0018]    It is an object of the semiconductor wafer container that has an overlapping double wall. The wall structure comprises multiple outer walls and multiple inner walls. The overlapping double containment wall increases semiconductor wafer protection during impact or shipping. Each inner wall shares a minimal percentage of a common angular sector with each adjacent outer wall. The inner wall is generally very stiff and does not absorb and cushion the wafers if the container is dropped or subject to impact. On the bottom assembly, the inner walls and outer walls are positioned in an offset and overlapping configuration provides maximum protection to the semiconductor wafers. 
         [0019]    It is an object of the semiconductor wafer container to improve alignment of the top cover with the base. The alignment system includes reference tabs that are received by the cover and a visual identifier for guiding an operator in the proper alignment of the two halves of the container. The top cover orientation features prevent improper installation of the top cover to the bottom member. The top cover orientation feature is incorporated into the top cover that mates with the features of the double locking location feature. This orientation feature prevents installation of the top cover in plus or minus 90 degree locations about the central axis. 
         [0020]    It is an object of the semiconductor wafer container to provide an improved locking mechanism for securing two halves of a wafer container together. The bottom half comprises a wall structure perpendicular to the base. The wall structure comprises segmented inner and outer walls, where each portion of the wall structure has a distinctive arc length. The arc length of each inner wall does not completely overlap with the arc length of any outer wall. 
         [0021]    It is an object of the semiconductor wafer container to provide an improved engagement feature for the locking tabs. These improved tabs include a cover for a wafer container that engages to a base. The cover includes one or more notches, each having a ramp that easily receive latches from the base. 
         [0022]    It is another object of the semiconductor wafer container to incorporate bi-directional rotation locking feature(s). These features improve orienting, the top member on the bottom member that decreases the amount of top cover rotation and movement with respect to the bottom member. This feature creates a double locking location that securely locates and locks the top cover in place during top cover assembly. The bi-directional rotation locking feature is located on both sides of the perpendicular top cover surfaces of a single wall on both the interior and the exterior simultaneously. This improvement provides bi-directional locking of the captured surface decreases the amount of top cover rotation and movement with respect to the bottom member and increases the rigidity of the containment device when the members are assembled. 
         [0023]    It is still another object of the semiconductor wafer container to include an improved holding and clamping feature to allow for automated machinery to latch onto and hold the bottom member and secure it firmly to the machinery nesting locations. This mechanism is comprised of a single piece feature that is molded into the bottom member. The holding and clamping feature on the bottom member improves equipment interface where these containers are used. The feature is a holding mechanism to allow for automated machinery to latch onto and hold the bottom member and secure it firmly to the machinery nesting locations. 
         [0024]    It is still another object of the semiconductor wafer container to include an improved curved latch recess for improved closure and retention of the containment device latches. In the improved latch and latch recess the height of the latch is equal to or lower than the inner wall structure. This allows equipment to interface with the bottom member of the container without interference with the equipment and latch height. A curvature on the mating surface provides superior holding and self centering and gripping during handling and after impact. This recessed feature also protects the mating surface from damage when the top cover is disassembled from the bottom member. The latch recess and curved surface also provides increased latch retention and container integrity during impact or shipping. This includes a lowered latch equal to or less than the inner wall height. 
         [0025]    Various objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0026]      FIG. 1  shows a perspective exploded view of the wafer container with a plurality of wafers disposed between the two wafer container halves. 
           [0027]      FIG. 2  shows a top view of the bottom housing with the overlapping rib wall pattern. 
           [0028]      FIG. 3  shows a detailed perspective view of the overlapping inner rib walls. 
           [0029]      FIG. 4  shows a top view of the bi-directional locking feature in the bottom housing. 
           [0030]      FIG. 5  shows a perspective view of the bi-directional locking feature on the bottom housing. 
           [0031]      FIG. 6  shows a perspective view of the bi-directional locking feature on the top housing. 
           [0032]      FIG. 7  shows an inside plan view of the top housing showing the orientation features. 
           [0033]      FIG. 8  shows inside plan view of the bottom housing showing the orientation features. 
           [0034]      FIG. 9  shows a detail perspective view of the orientation key in the top housing. 
           [0035]      FIG. 10  shows a detail perspective view without the orientation key in the top housing 
           [0036]      FIG. 11  shows a detail perspective view of the clearance for the orientation key in the bottom housing. 
           [0037]      FIG. 12  shows a detail perspective view of the interference for the orientation key in the bottom housing. 
           [0038]      FIG. 13  shows a top perspective view of the bottom housing. 
           [0039]      FIG. 14  shows a detailed perspective view of the hold down latch. 
           [0040]      FIG. 15  shows a perspective cross section of the hold down latch. 
           [0041]      FIG. 16  shows a perspective view of the top and bottom latch tab engaged. 
           [0042]      FIG. 17  shows a side view of the bottom latch tab. 
           [0043]      FIG. 18  shows a sectional view of the latch engaged between the top and bottom housings. 
           [0044]      FIG. 19  shows a detailed view of the engaged between the top and bottom housings. 
           [0045]      FIG. 20  shows a perspective view of the top and bottom housings in an open exploded view for reference of the internal components. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0046]      FIG. 1  shows a perspective exploded view of the wafer container with a plurality of wafers disposed between the two wafer container clam shells. A plurality of semiconductor wafers  20 ,  21  and  22  are shown between the top  50  and bottom  100  housing with wafer separators  25 . The inside base surface  102  extends to the outside of the base surface  103  where the bottom housing has a ribbed pattern  101  that supports the bottom of the bottom most semiconductor wafer  20  and provides increased structural strength to the fairly plainer base surface  102  and  103 . Both the top  50  and the bottom housings  100  have essentially planar rectangular or square bases. A plurality of inner rib walls  110  and  111  of the bottom housing  100  protect the semiconductor wafers from shifting side damage. These walls can flex to cushion side impact. They are formed in a segmented pattern in the bottom housing. The segmented ribs are shown and described in more detail with  FIG. 2 . A second set of segmented outer ribs  112  and  113  exist outside of the inner rib walls  110  and  111 . The rib walls exist in an overlapped  120  and  121  pattern to prevent debris from passing directly through the segmented ribs. 
         [0047]      FIG. 2  shows a top view of the bottom housing with the overlapping rib wall pattern. Note that some features, such as bottom ribs, have been deleted from the bottom surface  102  and  103  and the overlapping ribs have been moved slightly to improve clarity of the overlapping rib features being discussed herein.  FIG. 3  shows a detailed perspective view of the overlapping inner rib walls. While in  FIGS. 2 and 3  only one section of overlapping ribs is identified, the overlapping condition exists in eight places in the bottom housing  100 . While the preferred embodiment shows four inner rib walls  110 - 113  and four outer rib walls  114 - 117  it is contemplated that a greater or lesser number of overlapping can be used. In  FIGS. 2 and 3  the overlap  120  is labeled, and in the preferred embodiment the overlap angle is between 5 and 15 degrees, but prototypes have been made using an overlap angle  120  of 7.5 degrees. The ribs  110 - 117  are arc segments that extend perpendicular from the essentially planar base  102  and  103 . These angles are variable based upon the height of the rib, the material, the thickness of the rib, the desired cushion and the distance between the inner and outer ribs. In general the distance between the inner and outer ribs is controlled based upon the annular rib in the top clam shell housing. 
         [0048]    The overlapping double wall provides maximum protection from shock or impact to the exterior of the containment device by positioning the inner and outer wall in an offset and overlapping configuration as to increase the protection of the semiconductor wafers from direct transmission forces by increasing the amount of flex movement allowed by the outer wall. Increasing the flex tolerance of the outer wall increases the overall shock absorbing ability of the containment device. This design also allows for a greater percentage of “wrap” around the semiconductor wafer and therefore minimize lateral shift into the gaps between inner wall segments. Segmenting the inner wall makes it more flexible and thus able to absorb and cushion the wafers if the container is dropped or subject to impact. 
         [0049]    As shown in  FIGS. 1 and 3 . The outer rib walls  114 - 117  need not be the same height as the inner rib  110 - 113  walls. In some cases, the lowered exterior wall allows for greater top cover deflection during impact before it touches the inner wall. The image in the figures shows the exterior rib walls  114 - 117  at approximately ⅔rds the height of the inner rib walls  110 - 113  as shown in  FIG. 1 . 
         [0050]      FIG. 4  shows a top view of the bi-directional locking feature in the bottom housing  100 .  FIG. 5  shows a perspective view of the bi-directional locking feature on the bottom housing  100 .  FIG. 6  shows a perspective view of the bi-directional locking feature on the top housing  50 . Starting with  FIG. 6  the circular rib  51  is shown extending from the planar base of the top housing  50 . A “U” shaped rib extends from the circular rib  51  to the outer edge  55  of the top housing  50  and around to join back with the circular rib  51 . This “U” shaped rib can exist in a variety of shapes to provide a key to ensure that it locks into only one of four possible orientations with the bottom housing  100 . This “U” shaped rib that extends to the outer edge  55  has an inside face  53  and an outside face  52 . Where the “U” shaped rib joins with the outer edge  55  there is an outside protection and support rib  54 . 
         [0051]    A pair of securing ribs consisting of an outer locking rib  131  and an inner locking rib  132  on the bottom housing  100  are configured to engage onto the opposing sides of the inside face  53  and an outside face  52  of the “U” shaped rib when the “U” shaped rib is engaged into the locking cavity  130 . Circular lock rib  133  is configured to fit within cavity  56  on the top housing  50  along with the inner lock rib  132 . When the rib defined by items  52 / 53  is engaged into the locking cavity  130  these features improve orienting, the top housing  50  on the bottom housing  100  that decreases the amount of top cover  50  rotation and movement with respect to the bottom member  100 . This feature creates a double locking location that securely locates and locks the top cover  50  in place during top cover assembly. The bi-directional rotation locking further increases the rigidity of the containment device when the members are assembled. The “U” shaped and is shown in an approximate orthogonal relationship to three sides of the bottom housing  100 . While only one location of the bi-directional lock is shown and described in detail, the feature exists on all four sides of the top and bottom housings. 
         [0052]      FIG. 7  shows an inside plan view of the top housing showing the orientation features and  FIG. 8  shows inside plan view of the bottom housing showing the orientation features.  FIG. 9  shows a detail perspective view of the orientation key in the top housing.  FIG. 10  shows a detail perspective view without the orientation key in the top housing.  FIG. 11  shows a detail perspective view of the clearance for the orientation key in the bottom housing.  FIG. 12  shows a detail perspective view of the interference for the orientation key in the bottom housing. For perspective, the area&#39;s  90 ,  91 ,  92  and  93  are shown enlarged and in perspective in  FIGS. 9 ,  10 ,  11  and  12  to show the orientation tab  60  and how in allows or blocks seating of the top and bottom housings  50  and  100 . 
         [0053]    In  FIG. 9  the orientation rib  60  is shown extending essentially normal from the circular rib  51  at a particular distance  62  from the corner of the “U” shaped rib  54  and  57 . In  FIG. 10  the orientation rib is not present in area  61  in the corner of the “U” shaped rib  54  and  58 . Now refer to  FIGS. 11 and 12  to see where the orientation rib  60  would be blocked or bypassed by the details. In  FIG. 11  the dimension  106  between the corner radius of curved lock rib  133  and the inner lock rib  132  is shorter than the distance  107  between the curved lock rib  134  and the inner lock rib  132  in  FIG. 12 . Upon placement of the top housing onto the bottom in an out of proper orientation arrangement the longer circular block rib  134  would interfere with the orientation rib  60 . In the correct orientation the shorter circular lock rib  133  would clear the orientation tab  60 . 
         [0054]    From  FIG. 7 , a total of four orientation tabs are shown to allow the housings to sit flat on the orientation tabs when the housings are not properly aligned. The orientation tabs  60  prevent improper assembly of said top housing and said bottom housing members from being installed 90 degrees out of alignment. 
         [0055]      FIG. 13  shows a top perspective view of the bottom housing.  FIG. 14  shows a detailed perspective view of the hold down latch.  FIG. 15  shows a perspective cross section of the hold down latch. In views  13  and  15  some parts of the circular ribs  110 ,  111 ,  114  and  115  are visible to help to provide a visual orientation for the pocket  80  and latch features. The bottom housing  100  has an undercut hold down recessed pocket  80  with a latch surface tab  81  for a retention mechanism to hold the housing in automated assembly. The latch surface is formed in a molding process with the molding of said bottom housing  100 . The latch surface  81  is located at a height that is equal to or lower than the planar bottom surface  103  of said bottom housing  100 . The latch surface  81  further has an angled or curved entry surface  82 . The pocket further has at least two essentially vertical side walls  83  to self center said bottom housing on said retention mechanism. 
         [0056]    The height of the latch is equal to or lower than the inner wall structure to allow equipment to interface with the bottom member of the container without interference with the equipment and recess pocket  80  and the latch surface  81 . This recessed feature also protects the mating surface from damage when the top cover is disassembled from the bottom member. In  FIGS. 13 and 15  housing latches  70 ,  71  and  72  are shown. These latches secured the top and bottom housings together. 
         [0057]    In  FIGS. 13 and 15  a plurality of bearing ribs  85  are shown. These ribs are configured to distribute the load from a bottom housing stacked on top of the top housing. Looking briefly at  FIG. 18 , it can be seen that the annular lip  87  of the bottom housing  100  is placed at a different dimension from the annular lip  86  of the top housing  50 . This allows the housings to stack or nest. When stacking multiple wafer containers together the weight of the container when filled with wafers is significant. Some wafer containers are enclosed in a protective plastic bag, and when the stacked bearing surface is small this creates a high bearing load which damages or punctures the protective bag. Calculation and testing has identified that multiple bearing surfaces  85  of greater than 2.25 mm 2  each with more than 4 bearing ribs  85  per quadrant will adequately protect the containers from damage and will also prevent the protective plastic bags from being punctured or damaged. 
         [0058]      FIG. 16  shows a perspective view of the top and bottom latch tab engaged.  FIG. 17  shows a side view of the bottom latch tab.  FIG. 18  shows a sectional view of the latch engaged between the top and bottom housings.  FIG. 19  shows a detailed view of the engaged between the top and bottom housings. The bottom housing  100  has at least one latch that engages in a corresponding notch  75  located on the top housing  50 . 
         [0059]    The top surface  74  of said latch  70  is located at a height  76  that is below the top surface of said at least one rib  141 . The height  76  of the latch  70  is equal to or lower than the inner wall  141  structure. This allows equipment to interface with the bottom member of the container without interference with the equipment and latch height. This further reduces the possibility of damage to the latch  70  if the bottom housing  100  is dragged on a surface. In the preferred embodiment there are four latches  70  and four corresponding notches  75  located in each corner region of said top housing  50  or said bottom  100  housing, but as few as one or two are contemplate as well as four or more latches.  FIG. 19  shows that the notch  70  has a curve entry ramp  77  and a recess  78  that elevates the latch  70  above said entry ramp  77  and lowers said latch  70  into the recess  78  to retain the latch  70  in the recess  78 . When the latch(s) are secured the top of the inner rib wall  111  is tightly engaged and captured on the corresponding surface  84  of the top housing  50 . The notch  75  is located in a latch pocket  140  that protects the latch  70  during handling and impact. 
         [0060]      FIG. 20  shows a perspective view of the top and bottom housings in an open exploded view for reference of the internal components. This view provides a view into the open cavity of the top housing  50  and the bottom housing  100  without obstruction of the semiconductor wafers. 
         [0061]    Thus, specific embodiments of a semiconductor wafer container have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims.