Patent Publication Number: US-2006000747-A1

Title: Shipping container for integrated circuit wafers

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a container for shipping a stacked array of integrated circuit wafers such as semiconductor wafers. More particularly, the present invention relates to horizontal-type wafer shipping containers that may be reused a number of times.  
      2. Description of the Related Art  
      A variety of shipping containers are known for shipping and storing integrated circuit wafers. Typically, these containers are intended to provide a stable support for shipping and handling a number of wafers simultaneously. The containers are also intended to provide sufficient protection to substantially reduce the likelihood of breakage of the wafers, which are typically brittle. It is also desirable for wafer shipping containers to protect the wafers from contamination from airborne particulates and an excessive accumulation of static electricity.  
      Two general types of reusable shipping containers are in common use for shipping integrated circuit wafers. One type of shipping container has a chamber with internal structure for retaining an array of disc-shaped wafers in an aligned row. This type of shipping container is known as a “vertical shipper” or “front opening shipping box”. The other type of shipping container is known as a “HWS” or “horizontal wafer shipper” and has a chamber for retaining a plurality of wafers in a stacked array, with separators between the wafers and foam cushions placed above and below the stacked array for cushioning.  
      Shipping containers for integrated circuit wafers are often constructed to be used in conjunction with automated equipment that unloads each wafer from the container when needed for use. For example, some front opening shipping boxes have a bottom surface that is adapted to be releasably received onto a “load port” in a manufacturing assembly line. The load port typically has a clamp, such as an “L”-shaped pin or a “T”-shaped pin, that pivots to engage an overhang or other structure attached to the bottom of the container in order to retain the container in place. Once the shipping container is clamped onto the load port, a robot arm or other automated device removes the wafers from the shipping container in sequential fashion.  
      In many instances, the bottom sections of wafer shipping containers are provided with a series of cavities that are precisely positioned in a standardized, predetermined arrangement. These cavities are known as “information pad holes” or “info pad holes” and often comprise four circular cavities or recesses that are arranged in a generally “V”-shaped pattern. Some or all of the cavities are then filled with snap-in plastic plugs according to a pre-defined set of rules that provide information relating to the identity or use of the wafers in that container. In particular, the user may select certain cavities to be filled by plugs in order to provide information such as the type of wafers in the container, or a desired location where the wafers are to be used in a particular manufacturing line.  
      As an example, a shipping container with four info pad holes may be provided with one plug that fills a certain one of the four holes. In turn, the desired load port is arranged with three projections for reception in the unfilled cavities. If, for example, the three projections correspond to the arrangement of the three unfilled cavities, the shipping container will rest flatly against the upper surface of the load port. On the other hand, if the shipping container cannot be flatly received on the load port due to contact of projections against plugs mounted in one of the three cavities, the user is thereby tacitly informed that the selected shipping container is not the proper container for use at that particular load port.  
      While the horizontal wafer shipping containers described above have been deemed satisfactory by many, there is a continuing need to improve the state of the art with respect to such containers. In particular, features that provide additional protection for the wafers and facilitate use of the shipping container are especially desirable.  
     SUMMARY OF THE INVENTION  
      The present invention relates to a horizontal wafer shipping container that is constructed to provide enhanced protection against contaminates for integrated circuit wafers received in the container. The container includes an upper section with a continuous depending wall having a lower edge portion, and a lower section in contact with a seal. The seal contacts the lower edge portion when the lower section and the upper section are assembled together.  
      The present invention also relates to a shipping container for integrated circuit wafers, wherein a lower section of the container includes a plurality of cavities that receive info pad plugs. At least one of the info pad plugs includes an adhesive for connecting the plug to the lower section.  
      In more detail, the present invention is directed in one aspect to a shipping container for integrated circuit wafers. The shipping container comprises a lower section including a base and a wall extending upwardly from the base. The base and the wall of the lower section define a chamber for receiving a plurality of integrated circuit wafers. The base includes a shoulder that extends next to the wall of the lower section along a path that lies in a flat reference plane. The shipping container also comprises an upper section including a top and a wall depending from the top. The wall of the upper section extends continuously along a path that is adjacent the periphery of the top and has a lower edge portion. The lower edge portion extends along a path that lies in a flat reference plane and is adjacent the shoulder when the lower section and the upper section are assembled together. The shipping container also includes a seal that is in contact with the lower edge portion and the shoulder when the lower section and the upper section are assembled together.  
      The present invention is also directed in another aspect to a shipping container for integrated circuit wafers. The container comprises an upper section including a top and a wall depending from the top. The shipping container also comprises a lower section releasably connected to the upper section. The lower section includes a base and a wall extending upwardly from the base. The base and the wall of the lower section define a chamber for receiving a plurality of integrated circuit wafers. The lower section additionally includes a plurality of cavities for receiving info pad plugs. The shipping container also comprises at least one info pad plug received in one of the cavities. At least one info pad plug comprises a body and an adhesive for connecting the body to the lower section.  
      These and other aspects are described in more detail in the description that follows and are illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exploded perspective view of a shipping container for integrated circuit wafers according to one embodiment of the invention, looking in a direction toward the side and top of the container;  
       FIG. 2  is an inverted perspective view of the shipping container shown in  FIG. 1 , wherein the container is illustrated in assembled view, and looking at the container toward its bottom surface and back side;  
       FIG. 3  is a plan view of a lower section of the shipping container shown in  FIGS. 1 and 2 ;  
       FIG. 4  is an enlarged side cross-sectional view taken across a portion of the shipping container illustrated in  FIGS. 1-3 ;  
       FIG. 5  is a bottom view of the lower section of the shipping container depicted in  FIG. 3 ; and  
       FIG. 6  is an enlarged side cross-sectional view taken across a portion of the lower section of the shipping container. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A shipping container for integrated circuit wafers according to one embodiment of the present invention is illustrated in  FIGS. 1-6  and is broadly designated by the numeral  10 . The shipping container  10  is of the type generally known as a “horizontal wafer shipper” or “coin stack shipper”, and includes a lower section  12  and an upper section  14  that may be releasably connected to the lower section  12  when desired.  
      In more detail, the lower section  12  includes a base  16  having an overall, generally octagonal configuration in plan view as shown in  FIG. 3 , although other shapes are also possible. The base  16  extends in a horizontal reference plane, and has a bottom surface  44  ( FIG. 5 ) for reception onto a load port as will be described in more detail below.  
      The lower section  12  also includes a wall  18  that extends upwardly from the base  16 . As depicted in  FIG. 3 , the wall  18  extends along a circular path adjacent the periphery of the base  16 . A portion of the wall  18  is omitted to provide an access opening  20 . Although the embodiment shown in  FIGS. 1-6  includes only one access opening  20 , it should be understood in this regard that additional access openings may be provided as well.  
      The base  16  includes a shoulder  21  that is located radially outwardly from the wall  18 . A groove  24  is disposed on the shoulder  24  and extends along a circular path that is concentric with the path of the wall  18 .  
      A seal  26  is received in the groove  24 . The seal  26  extends along a circular path in a flat reference plane parallel to the plane of extension of the base  16 . The seal  26  may comprise an O-ring made of, for example, silicone rubber or other elastomeric materials. Alternatively, the seal  26  may be constructed of other gasket materials such as a resilient polymeric foam having a durometer in the range of about 10 A to about 60 A, and more preferably about 30 A. The use of foam materials is presently preferred because such materials are reduced in volume when compressed, in contrast to other materials that are displaced when compressed. However, other materials may also be used, including a molded polymer with a thermally activated foaming agent, a gel (preferably a UV-curable crosslinkable gel), a tacky adhesive or a hollow tube.  
      The seal  26  has sufficient memory to recover its original shape when relaxed, and yet is sufficiently flexible to ensure that the seal  26  conforms to the shape of the groove  24  when compressed. The seal  26  as shown in the drawings has a circular cross-sectional configuration, although other cross-sectional configurations (such as rectangular, square or wedge-shaped) are possible as well. Preferably, the cross-sectional configuration of the seal  26  matches the cross-sectional configuration of the groove  24 . For example, in the exemplified embodiment shown in the drawings (see, e.g.,  FIG. 5 ) the seal  26  and the groove  24  in areas of contact with each other have matching, partially circular shapes in cross-section.  
      The upper section  14  includes a top  28  having a flat configuration. Optionally, the top  28  includes a locater or index mark  29  ( FIG. 1 ) that serves to inform the user of the location of the underlying opening  20  when the container  10  is closed. A wall  30  depends from the top  28  and extends continuously along a path adjacent the periphery of the top  28 . In plan view, the top  28  and the side of the wall  30  present an octagonal configuration that matches the octagonal shape of the lower section  12 . The wall  30  also has a generally cylindrical inner surface that matches and complementally receives the cylindrical shape of the outer surface of the wall  18 . Although not shown in the drawings, the upper section  14  includes an inner protrusion that fits within a notch  31  positioned along the top of the wall  18  of the lower section  12 , in order to ensure that the upper section  14  and the lower section  12  are properly oriented with respect to each other when the container  10  is closed.  
      The wall  30  includes a lower edge portion  32  that extends along a path lying in a flat reference plane. The lower edge portion includes a pair of ribs  22 , each of which extends along a circular path that is concentric with the inner surface of the wall  30 . When the upper section  14  and the lower section  12  are assembled together as shown in  FIG. 2 , the ribs  22  extend over the groove  24  in overlying relation and press against the seal  26 . Each of the ribs  22  contacts the seal  26  along a continuous circular path in order to provide a barrier that hinders the transmission of moisture, airborne particulates and/or other contaminates to areas within the container  10 . Preferably, the ribs  22  and the seal  26  are constructed so that an air gap is present between the seal  26  and the lower edge portion  32  in the region between the ribs  22  when the container  10  is closed, to facilitate opening of the container  10  and detachment of the sections  12 ,  14  when desired.  
      The construction of the container  10  with respect to the shoulder  21 , the seal  26  and the ribs  22  is a particular advantage, in that the seal  26  contacts the ribs  22  and the groove  24  in flat, parallel reference planes. Certain prior art horizontal wafer shipping containers, such as shipping containers similar to the container described in U.S. Pat. No. 6,193,090, were provided with a gasket or seal that extended along an undulating path including portions following along the periphery of one or more access openings. As a result, this gasket was relatively expensive to construct. By contrast, the present invention enables the use of a relatively inexpensive seal, such as a flat foam gasket made by a stamping process from a flat sheet of foam material. Moreover, the overall length of the seal is considerably less than the overall length of the prior art gasket, resulting in fewer areas where the integrity or sealing tightness of the seal could be compromised.  
      The base  16  and the wall  18  of the lower section  12  together partially define a chamber  34  for receiving a stacked array of integrated circuit wafers such as semiconductor wafers. The wafers are not shown in the drawings, but generally resemble thin disks of material having a diameter smaller than the inner diameter of the wall  18 . The wafers are preferably separated by circular sections of resilient packaging material such as polymeric sheet material. Preferably, circular sections of foam material are provided in the chamber  34  above and below the stack of wafers and compressed when the container  10  is closed to provide cushioning.  
      The container  10  also includes four latches  36  having a generally overall, U-shaped configuration. Each latch  36  has two end portions with apertures  38  ( FIG. 1 ) that have a somewhat oval-shaped configuration. Each aperture  38  is releasably received in snap-fit relation on a tab  40  ( FIGS. 1 and 2 ) that is integrally connected to the base  16  of the lower section  12 .  
      When the sections  12 ,  14  are assembled together, a middle portion of each latch  36  is received in a notch  42  ( FIG. 1 ) that is provided on the upper section  14 . The latches  36  are made of a resilient material that can be slightly deformed or stretched as needed to fit in the respective notch  42  in snap-fit relation. An example of a suitable resilient material is Hytrel brand elastomer from Dupont, preferably having a durometer in the range of about 30 D to about 60 D, and more preferably about 40 D. As the latches  36  are received in the notches  42 , the sections  12 ,  14  are preferably urged together with sufficient force to compress the seal  26  in order to ensure complete, sealing contact with both of the ribs  22  as well as the bottom of the groove  24 . Other latches are also possible, such as the general type of latches found on luggage, including toggle lever-assisted latches.  
      A total compression force on the sections  12 ,  14  of preferably less than about 30 pounds, and more preferably less than about 10 pounds, is needed to compress the seal  26  sufficiently to close the container  10  and latch the latches  36 . Preferably, the ribs  22  each have a generally “U” or “V”-shaped cross-sectional configuration that tapers to a lowermost, slightly rounded edge. This edge provides local regions where the seal  26  is sufficiently compressed and helps to avoid the need of compressing larger regions of the seal  26 , which might otherwise require a higher compression force to close the container  10 . For example, with a low density foam material having a density in the range of two pounds to six pounds per cubic foot, a compression force of approximately 5.5 to 8.5 pounds will be needed to close the container  10  and latch the latches  36 , when at least part of the cross-sectional area of the seal is compressed to a 25% compression.  
      The base  16  includes a bottom surface  44  (see, e.g.,  FIGS. 2 and 5 ). Four info pad cavities or holes  46  are provided in the bottom surface  44 , although a greater or smaller number of cavities may be provided as well. The cavities  46  extend upwardly into the base  16  a limited distance. As depicted in the exemplary embodiment shown in  FIG. 6 , each cavity  46  includes two contiguous portions, comprising a lower, larger diameter, generally cylindrical portion and an upper, smaller diameter, generally cylindrical portion that is concentric with the lower cylindrical portion. An annular shoulder or ledge  48  extends in a horizontal reference plane that also defines a boundary between the lower cylindrical portion and the upper cylindrical portion.  
      Optionally, one or more info pad plugs  50  are received in the info pad cavities  46 . In the accompanying drawings, one plug  50  is shown, although other plugs may be provided as well. The presence and placement pattern of the plugs  50  in the holes  46  provides information relating to the type of wafers in the chamber  34 .  
      Preferably, each plug  50  comprises a polymeric body  52  and an adhesive  54  for connecting the body  52  to the ledge  48 . Preferably, the adhesive  54  is a high tack pressure sensitive adhesive. Preferably, the adhesive  54  has sufficient strength to reliably retain the plug  50  in the hole  46  during normal shipping, handling and manufacturing operations, but also enables the plug  50  to be removed from the hole  46  without undue effort when desired. Optionally, a lever-type hand tool may be used to pry the plug  50  from the hole  46  to facilitate disengagement of the plug  50  from the shoulder  48 . An example of a suitable plug  50  is “Bumpon” brand bumper, no. SJ-5763, from 3M Company.  
      The container also includes a clamping plate  56  ( FIGS. 1 and 2 ; omitted in  FIG. 5 ) that is releasably coupled to the bottom surface  44  of the lower section  12  by four self-tapping screws. Alternatively, an adhesive may be used to connect the clamping plate  56  to the bottom surface  44 . The clamping plate  56  includes a central opening  58  as well as a curved, outwardly extending lip  60  that extends along one side of the clamping plate  56 . The opening  58  and the lip  60  are provided for releasable connection to a center pin or latch pin of the loading port in order to releasably couple the container  10  to the loading port as desired.  
      As illustrated in  FIGS. 2 and 5 , the lower section  12  also includes three recesses  62  that serve to align the container  10  to the loading port. Additionally, a recess  64  is provided for receiving an RFID transponder tag. Preferably, the recess  64  has structure such as inwardly extending, resilient polymeric wall sections that deform slightly to receive the RFID transponder tag and snugly retain the same until removal is desired. An example of a suitable transponder tag is “TIRIS” 32 mm glass transponder tag, no. RI-TRP-DR2B, from Texas Instruments.  
      The lower section  12  also includes two finger-gripping recesses  66  that extend along opposite sides of the base  16 . Each recess  66  includes four side-by-side, parallel channels that are all inclined upwardly as the center of the base  16  is approached. The upward inclination of the channels facilitates gripping of the container  10  and helps to ensure that the container  10 , when loaded with wafers, is not inadvertently dropped.  
      Preferably, the sections  12 ,  14  are integrally made using a polymeric material in a blow molding process. Suitable polymeric materials include olefinic materials such as polypropylene copolymer and high density polyethylene. Optionally, a static dissipative material such as carbon particles or fibers (including nanotubes) can be added to the polymeric material to enhance static dissipative properties to the container  10 . Additional information regarding the construction of the sections  12 ,  14  is set out in the aforementioned U.S. Pat. No. 6,193,090 which is expressly incorporated by reference herein.  
      The embodiments described above exemplify the present invention, and other constructions are possible. Accordingly, the invention should not be deemed limited to the particular embodiments mentioned above, but instead only by a fair scope of the claims that follow along with their equivalents.