Abstract:
A front opening wafer container suitable, for large diameter wafers, 300 mm and above, utilizes a removable robotic flange that attaches vertically, without separate fasteners, using detents having resilient bending members that extend vertically to attach to an upwardly extending flange on the top wall of the container portion. A multiplicity of upwardly and outwardly extending strengthening ribs extend upwardly from the top wall of the container portion and extend along the top wall toward the left and right sides and the back side of the container portion, ad each of all four sides of the attachment flange. A further locking piece or core may be inserted and retained at the neck of the robotic flange to lock the resilient deflectable portions in their retention position. The locking piece further may be secured in place with a detent mechanism formed by part of the core and flanges.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of U.S. patent application Ser. No. 13/880,710, filed Jul. 1, 2013, which is a § 371 of International Patent Application No. PCT/US2011/056915, filed Oct. 19, 2011, which claims the benefit of U.S. Provisional Application No. 61/394,751, filed Oct. 19, 2010, all of which are hereby incorporated by reference herein in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Integrated circuits such as computer chips are manufactured from silicon wafers. The silicon wafers need to be maintained in extremely clean and contamination free environments during their transport and in between manufacturing process steps. Additional, required or desirable characteristics of containers to transport and/or store semiconductor wafers include light weight, rigidity, cleanliness, limited gaseous emissions, and cost effective manufacturability. The containers provide hermetic or close to hermetic isolation of wafers when the containers are closed. Simply stated, such containers need to keep the wafers clean, uncontaminated, and undamaged. 
         [0003]    Plastic containers have been used for decades for transporting and storing wafers in-between process steps. Selected polymer materials provide adequate characteristics. Such containers have highly controlled tolerances for interfacing with processing equipment as well as the equipment/robots that transport the containers. Moreover, it is desirable in such plastic containers to utilize components that are attachable and removable without using metallic fasteners such as screws. Metal fasteners cause particle generation when inserted and removed. 
         [0004]    Driven by cost efficiencies and improved manufacturing capabilities, the size of wafers utilized in manufacturing semiconductors has been increasing. Now several fabrication facilities utilize 300 mm wafers. As the size of wafers has increased and the density of the circuits has increased making the circuits susceptible to smaller and smaller particles and other contaminants. Thus, as the wafers have increased in size, the containers have increased in size as well; the requirements of keeping the wafers clean and contaminant free have become more stringent due to the wafers being more susceptible to smaller particles and other contaminants, containers have increased in size. Additionally, carriers need to maintain their capabilities under the rigors of robotic handling which includes lifting the carrier by the robotic flange positioned at the top of the container. 
         [0005]    Front opening wafer containers have become the industry standard for transporting and storing large diameter 300 mm wafers. 
         [0006]    In such wafer containers the front door is latchable to a container portion and closes a front access opening through which the wafers are robotically inserted and removed. When the container is fully loaded with wafers the door is inserted into the door frame of the container portion and latched thereto. When seated the cushions on the door then provide upward, downward, and inward constraint. 
         [0007]    A problem discovered in fabricating front opening plastic containers for holding and/or transporting larger wafers, for example 300 mm containers, is that the expanses of plastic utilized on the top, bottom, sides, front, and back of the container may flex due to the increased weight of the wafer load. Particularly, when the container is picked up by the robotic flange affixed to the top of the container. The flexing can compromise the sealing of the door to door frame by distorting the shape of the door frame, essentially elongating it in the vertical direction. Also, the flexing can affect the container to wafer engagement, more particularly, the constraints that the wafer supports provide to the wafers is altered. 
         [0008]    It is conventional wisdom in 300 mm wafer containers to avoid using metal in any fashion. Interlocking flanges with are used for attachment of accessories such as robotic flanges and side handles. Plastic leaf springs that are part of the engaging components and that form detents are utilized to retain the components, such as robotic flanges in place. See U.S. Pat. No. 6,010,008, owned by the owner of this application, and incorporated herein by reference. Such robotic flanges extend in the z direction utilizing flanges extending also in the z direction. The detents operate only to maintain the cooperating structures and stay properly positioned on the flanges without carrying any appreciable loading through the detent structures, for example the resiliently bendable portion of such detents extend in the z direction and bend about an axis in the x direction. Thus, the direct loading on the robotic flange to container portion connection is primarily in the y direction and is carried through the horizontally extending flanges. When such containers are fully loaded and robotically supported by the robotic flange, stress analysis studies confirms that the primary stresses are found on the top and sides adjacent the flanges as opposed to the back side and front side. From a structural perspective, it would be preferable to better distribute the load carrying forces more uniformly on the back of the carrier portion to minimize deflection issues. 
         [0009]    This problem has been addressed to some extent by utilizing robotic flanges that effectively saddle the container portion and extend down the sides of the containers such that the load of the wafers is not transferred totally through the side walls of the carrier, see U.S. Pat. No. 7,347,329 assigned to the owner of the instant application and incorporated herein by reference. 
         [0010]    The semiconductor industry is now moving toward utilizing larger, 450 mm diameter wafers. The larger diameter wafers, although providing cost efficiencies, also provide increased fragility, greater weight, and present undiscovered issues associated with handling and storing the larger wafers in containers made of plastic. The flexing and corresponding problems associated with the expanses of plastic on the top, bottom, sides, front, and back are exacerbated. 
         [0011]    With the significant leaps in the size of processed wafers, new issues and problems arise that were not present with smaller sized wafers. Many standards for 450 mm wafers, such as the number of wafers in containers and the spacing between wafers, may very well remain the same as 300 mm wafer container standards due to existing equipment compatibilities and cost pressures. And, of course, as wafers get larger in diameter, they correspondingly get heavier. A wafer container that holds the same number of 450 mm wafers as is provided in standardized 300 mm containers is expected to weigh approximately 40 pounds. At this weight, manual handling starts to become more difficult. 
         [0012]    Using comparable thicknesses of polymer walls for a larger container may not provide sufficient structural rigidity of the container. That is, the container would be expected to be less dimensionally stable under loading, transfer and shipping due to the greater dimensions and greater expanses of polymer. Thickening the walls and adding significant strengthening structure would further increase the weight of 450 mm wafer containers. 
         [0013]    Moreover, conventional 300 mm wafer containers are typically injection molded. It is anticipated that it will be difficult to adequately control the dimensions of larger containers utilizing comparable injection molding practices and comparable or larger wall thicknesses. Currently 300 mm wafer containers generally utilize the shell as the principal structural member for positioning components that interface with wafers and outside equipment, namely the wafer supports and the kinematic coupling machine interface. 
         [0014]    In addition, the open interior volume will significantly increase as will the area of the open front that sealingly receives the door. This suggests more difficult sealing issues between the door and the container portion. 
         [0015]    Wafers of larger dimensions will also have significantly greater sag which will make them more susceptible to damage during handling and transport and require unique support not required for smaller wafers. This greater sag presents challenges in maintaining the desired spacing between wafers while still allowing placement and removal of the wafers robotically by robotic arms. 
         [0016]    Accordingly, it would be desirable to develop front opening configurations for 450 mm wafer containers that have design attributes for minimizing wafer sag and minimizing weight of the container. In addition, configurations providing improved sealing characteristics for the doors would be desirable. Moreover, configurations providing enhanced wafer support to accommodate storing of 450 mm wafers in wafer containers as well during robotic handling of the wafers would be desirable. 
       SUMMARY OF THE INVENTION 
       [0017]    In an embodiment of the invention, a front opening wafer container suitable, for large diameter wafers, 300 mm and above, utilizes a removable robotic flange that attaches vertically, without separate fasteners, using detents having resilient bending members that extend vertically to attach to an upwardly extending flange on the top wall of the container portion. In embodiments of the invention, a multiplicity of upwardly and outwardly extending strengthening ribs extend upwardly from the top wall of the container portion and extend along the top wall toward the left and right sides and the back side of the container portion, at each of all four sides of the attachment flange. In embodiments of the invention, the flange on the top wall has four sides, a front, a back, a left side, and a right side with each side having at least one a detent mechanism that actuates to capture the robotic flange with a downward placement of the neck of the robotic flange to engage the upwardly extending flange and to deflect resilient deflectable portions of the detent mechanisms horizontally from a retention position to a deflected position where the lifting flange may be installed and removed. In embodiments of the invention, a further locking piece may be inserted and retained at the neck of the robotic flange to lock the resilient deflectable portions in their retention position. In embodiments of the invention, a multiplicity of upwardly and outwardly extending strengthening ribs extend from the top wall of the container portion adjacent to each of all four sides of the attachment flange. The ribs may be aligned normally to each side of the attachment flange and may continue to extend from the top side down the walls to or towards the bottom of the container portion. 
         [0018]    It has been discovered through stress analysis that the deflection caused by the loading on the sides of the robotic attachment flange, as opposed to the back side can cause a significant inward outward deflection of the back wall of the wafer container. This deflection can be reduced by more than 75% by utilizing the back side of the attachment flange to share the load when the container is lifted by the robotic flange. Thus, a feature and advantage of the invention is a container portion where the deflection of the back wall is minimized by a robotic lifting flange that is structurally connected to the attachment flange at the front, back, and sides of the attachment flange such that weight of the container is shared by all four sides of the attachment flange. 
         [0019]    Some embodiments include a front opening wafer container for large 450 mm diameter wafers. The wafer container including a container portion having a top wall, bottom wall, right side wall, left side wall, rear wall and door frame defining a front opening. The wafer container also including an upwardly extending flange on the top wall having a plurality of sides in a rectangular shape as well as an attachment flange operably attached to an upwardly extending flange. Further the wafer container has a multiplicity of upwardly and outwardly extending strengthening ribs that extend upwardly from the top wall of the container portion and extend along the top wall toward the left and right side walls and the back side wall of the container portion from the sides of the upwardly extending flange. 
         [0020]    In other embodiments, a front opening wafer container for large diameter wafers, is disclosed. In these embodiments, the wafer contain includes a container portion having a top wall, a pair of sidewalls, a back wall, bottom wall and a door frame defining a front opening. The container also has an upwardly extending flange on the top wall of the container portion and a removable robotic flange that attaches vertically, without separate fasteners, using detents having resilient bending members that extend vertically to attach to the upwardly extending flange on the top wall of the container portion. 
         [0021]    Other embodiments are directed to a front opening wafer container for large diameter wafers including a container portion, an attachment flange, and a multiplicity of strengthening ribs. The container portion having a top wall, bottom wall, right side wall, left side wall, rear wall and front opening. The attachment flange with four sides, operably attached to the top wall. Finally, the multiplicity of ribs include a multiplicity of upwardly and outwardly extending strengthening ribs extending from the top wall of the container portion adjacent to each of the four sides of the attachment flange, the ribs aligned normally to each of the four sides of the attachment flange and further extend from the top side down the right and left side walls towards the bottom of the container portion. 
         [0022]    In yet other embodiments, the invention includes a robotic flange including a frame portion adapted to engage in vertical attachment to a top port on the top of a substrate container with a plurality of vertically-disposed cantilevered snaps and further contains a plurality of flexible spring members in its interior and an internal portion that includes detents that engage with the flexible spring members on the interior of the frame portion to secure the internal portion into place. 
         [0023]    An embodiment of the invention further includes a method of attaching a robotic flange. The method includes providing a frame portion adapted to engage in vertical attachment to the top of a substrate container. It further includes lowering the frame portion vertically into place within a port on the top of the substrate container, snapping into place the frame portion with detents, and securing an interlocking core piece within the frame portion. 
         [0024]    Other embodiments include a front opening wafer container for large diameter wafers. Such containers include a container portion, an attachment flange and a supplemental distortion minimization structure. Specifically, the container portion generally includes a top wall, a bottom wall, a right side wall, a left side wall, and a rear wall. The attachment flange is operably attached to the top wall and the supplemental distortion minimization structure is at least partially surrounding container for minimizing wafer container distortion under loading conditions. 
         [0025]    It is a feature and advantage of embodiments of the invention that the robotic flange is attached without separate fasteners such as screws or the like. 
         [0026]    It is a feature and advantage of embodiments of the invention that the attachment of the flange by way of detent mechanisms on all four sides are locked in with a single interlocking core. 
         [0027]    It is a feature and advantage of embodiments of the invention that the loading through the robotic flange assembly when lifted by the robotic flange is more evenly distributed to the back wall of the wafer container which minimizes the deflection of the back wall and thereby provides more secure wafer constraint during such transport. 
         [0028]    It is a feature and advantage of embodiments of the invention that the leaf springs extend vertically, in the same direction as the load carrying direction, allowing additional structural ribbing rearwardly of the attachment flange. Where the robotic flange slides on horizontally as in prior art wafer containers, such ribs are precluded or substantially precluded. The additional structural ribbing facilitates the load spreading more evenly between the sides and the back. 
         [0029]    It is noted that certain aspects of the invention herein, namely the robotic flange features and components, may be utilized for other substrates containers beyond 450 mm wafers and 300 mm wafers. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  is a perspective of a front opening wafer container according to the invention. 
           [0031]      FIG. 2  is an exploded view of the top of a front opening wafer container and a robotic flange assembly according to the invention herein. 
           [0032]      FIG. 3  is a perspective view of an automation flange according to the invention herein. 
           [0033]      FIG. 4  is a perspective view of an interlocking core according to the invention herein. 
           [0034]      FIG. 5  is a cross sectional illustrating assembly steps of a robotic flange according to the invention herein. 
           [0035]      FIG. 6  is a cross sectional illustrating assembly associated with Fig. 
           [0036]      FIG. 7  is a cross sectional illustrating assembly associated with  FIGS. 5 and 6 . 
           [0037]      FIG. 8  is a cross sectional illustrating assembly associated with  FIGS. 5, 6, and 7   
           [0038]      FIG. 9  is a cross sectional illustrating assembly associated with  FIGS. 5-8  and taken at line  9 - 9  of  FIG. 1 . 
           [0039]      FIG. 10  is a further exploded view of the top of a front opening wafer container and a robotic flange assembly according to the invention herein. 
           [0040]      FIG. 11  is a perspective of a fully assembled front opening wafer container according to the invention. 
           [0041]      FIG. 12  is a perspective of a fully assembled front opening wafer container according to the invention. 
           [0042]      FIG. 13  is a perspective of a container portion of a front opening wafer container according to the invention. 
           [0043]      FIG. 14  is a perspective of a container portion of a front opening wafer container according to the invention. 
           [0044]      FIG. 15  is a perspective of a container portion of a front opening wafer container having a supplemental distortion minimization structure according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0045]    Referring to the figures, a front opening wafer container  20  is illustrated and comprises generally a container portion  22 , having a top wall  23 , a pair of right and left side walls  24 ,  25 , a back wall  26 , a bottom wall  27 , a door frame  28  defining a front opening  29 , and a front door  30  configured to close the open front. The door has a pair of key holes  36 ,  38  that access latch mechanisms  42  located inside the door housing  44 . The door has an outside surface  50 , a periphery  54 , and an inside surface  56 . Slots  60  are positioned on the periphery and allow latching tabs  64  or tips to extend and retract from the door to engage and disengage recesses  70  on the inside surface of the door frame. A seal or gasket  72  follows the circumference of the door and engages with the door frame to sealingly close the door when the latches are actuated. 
         [0046]    An automation or robotic flange assembly  76  is positioned on the top side  78  of the container portion. The robotic flange or attachment flange  150  is generally comprised of a frame portion  152  and an interlocking core  120 . The robotic flange  150  attaches vertically into a receiver  77  configured as a socket  80  defined by a vertically upwardly extending flange  81  formed of ribbing  82 , including at least four sides  99 , laid out in a rectangular shape. The upwardly extending flange  81  and ribbing integral with and extending from the top wall  23  has apertures  84  for receiving catch nubs or hooks  86  on leaf springs  88 , configured as downwardly extending cantilevered snaps  89 , that extend downwardly from a base  90  of the flange. The leaf springs and hooks together with the cooperating rib with opening constitute a detent mechanism  91 . The flange base has four sides  92 ,  93 ,  94 ,  95  each with two of the cantilevered snaps. Robotic lifting shelves  98  extend outwardly at all four sides of the base for engagement by a lifting robot. Notably the leaf springs extend vertically, in the same direction as the load carrying direction and they flex or resiliently bend horizontally, to engage and disengage from the receiver. 
         [0047]    Referring to  FIGS. 5-9 , wedge shaped surfaces  104 , that provides a taper on the end of the leaf springs allow the flange to be inserted with one single motion. The frame portion  152  of the flange  150  is placed within the receiver  77  or port  156 , is pushed downward to deflect the leaf springs inwardly, see  FIG. 7 , as the tapered surfaces engage the engagement surfaces  110  on the receiver. When the nubs then reach the apertures or recesses, see  FIG. 8 , they snap into said apertures or recesses. The interlocking core  120  then is pushed into the recess defined by the interior  122  of the frame portion of the flange to secure the nubs in the apertures. Notably, referring to  FIG. 2 , the flange has a four spring members  130  that deflect outward by engagement with the catches  134  of the core as the core is being pushed down and then snap over the top of the catches to secure the core in place. 
         [0048]    The components may generally be injected molded from polymers typically used for semiconductor wafers. For example, polycarbonates, fluoropolymers, polyetheretherketone. 
         [0049]    In  FIG. 10 , a further exploded view of a robotic flange  150  is depicted in an embodiment of the invention. The robotic flange  150  is shown here to include a flange frame portion  152  and an internal portion or interlocking core  120 . The internal portion  120  includes detents or catches  134  that engage with flexible tabs or spring members  130  on the interior of the frame portion  152  to secure the internal portion  120  into place. The frame portion  152  is mounted to a top port  156  defined on the top wall  23  of the container  22 . More specifically, to the sides  99  of the upwardly extending flange  81 . The frame portion  152  includes protrusions in the form of cantilevered snaps  89  that extend into the top port  156  with angled surfaces that cause the protrusions  89  to deflect inward as the frame portion  152  slides into the top port  156 . Barbs or detents on the protrusions  89  clip into recesses or apertures  84  when the frame portion  152  is in place. 
         [0050]      FIGS. 11 and 12  depict a fully assembled wafer container  20 , including the container portion  22 , front door  30 , and other features. Specifically, opposite perspective views are shown in which the fully assembled robotic flange  150  is depicted residing in the top port  156  on the top wall  23  of the container  22 . Further, the front door  30  is shown in the door frame  28  of the front opening  29 . At the bottom of the container  20  is a horizontally-disposed base plate  200  that is mounted proximate the bottom wall  27  of the housing on the exterior of the container  20 . At each of the two sides of the container, are horizontally disposed conveyor rails  202 . These conveyor rails are double horizontal conveyor rails which may be used by equipment, such as forklifts that may be used to manipulate the wafer containers. A set of short ribs  204  below the back portion of the conveyor rails  202  on either side of the container provide a lead in feature for automation entering from the backside of the carrier. 
         [0051]      FIGS. 13 and 14  depict top perspective and bottom perspective views of the container portion  22 . As noted above, the container design is equipped with a rib design surrounding the container to minimize distortion. These ribs  210  are especially useful in minimizing distortion of the top wall  23  of the container during load carrying conditions. Such distortion may occur at either the forklift conveyor rails  202  or at the robotic flange  150 . 
         [0052]    As seen in these figures, a plurality of vertically-raised, spaced-apart, parallel rib members extend from two side walls of the engagement surfaces  110  all the way around the container  22  in a generally continuous fashion. This continuous path around the top wall, side walls, and bottom wall defines the full circumference or perimeter of the container  22 . Although the double horizontal conveyor rails  202  cross the path of these ribs, the ribs continue through these features and should be considered uninterrupted. The conveyor rails  202  found on either sidewall, further provide some linear stiffness along the container length as well. The ribs  210  may extend in other directions from the flange and may be the same or different in terms of size and structure. Some embodiments may have more than 15 spaced apart ribs. Some embodiments may have between 10 and 15 spaced apart ribs. Some embodiments may have fewer than 10 spaced apart ribs. Some embodiments have 7 to 10 ribs. Further, some embodiments include evenly spaced ribs of 4 to 6 ribs on a side or 7 to 10 ribs on a side of the attachment flange  150 . Ribs  210  may be of various sizes and dimensions. In some embodiments, the ribs  210  may be converging structures. For example, in some embodiments the ribs will have a width of 3.9 mm at the base and 2.2 mm at their tips. Accordingly, each of the ribs  210  will have an average thickness of between 3.9 and 2.2 mm. 
         [0053]    The ribs  202  may generally extend upwardly and outwardly from the wall container and extend toward the right, left, front and back sidewalls of the container. The ribs  210  may preferably run transverse in the x direction across the bottom and top walls  23  and  27  of the container and may run vertically in the Y direction on the side walls  24  and  25 . The ribs may have rounded corners  226  at each of the corners of the container  22 . 
         [0054]    Although spaced apart ribs, as shown, are one means for minimizing distortion in the loading condition, various other repeating rib or related pattern or structural members may be possible as well. 
         [0055]      FIG. 15  depicts a further alternative embodiment to the rib structure seen the previous figures. Specifically, the container  22  shown is surrounded by an exoskeleton  230  to minimize distortion under loading. This exoskeleton  230  may take on various shapes. For example, in some embodiments, the exoskeleton will comprise a secondary wall which extends like a saddle around the housing walls. This secondary set of walls may surround the top wall and side walls in some embodiments. In some embodiments, the secondary walls may surround the bottom surface of the container as well. In some embodiments the exoskeleton is integrally formed with the container portion. In other embodiments the exoskeleton may separately but closely coupled with the container walls. It is contemplated that the secondary walls of the exoskeleton may surround open and accessible central cavities to the outside environment, or alternatively be fully closed structures. 
         [0056]    In some embodiments, the exoskeleton may be fixed integrally and continuously against the outside surfaces of the container  22 . In other embodiments, the exoskeleton may only be fixed at locations  250  adjacent the bottom wall or at locations  260  at the corners of the container as well as locations  270  at the portion of the container adjacent the robotic flange  150 . Alternatively, the exoskeleton may be attached at spaced apart locations along the perimeter of the exoskeleton. 
         [0057]    It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with an enabling disclosure for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof. 
         [0058]    The embodiments above are intended to be illustrative and not limiting. Additional embodiments are within the claims. Although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. 
         [0059]    Various modifications to the invention may be apparent to one of skill in the art upon reading this disclosure. For example, persons of ordinary skill in the relevant art will recognize that the various features described for the different embodiments of the invention can be suitably combined, un-combined, and re-combined with other features, alone, or in different combinations, within the spirit of the invention. Likewise, the various features described above should all be regarded as example embodiments, rather than limitations to the scope or spirit of the invention. Therefore, the above is not contemplated to limit the scope of the present invention.