Abstract:
A wafer container and improved door. The wafer container door has a latch mechanism cover adapted to retain and guide the latch mechanism components. The latch mechanism cover is form fitted to the latch mechanism components and may have apertures, creating a cover with an open architecture. The open architecture is of benefit for making the area under the mechanism cover more easily cleanable.

Description:
This application claims the benefit under 35 U.S.C 119(e) of U.S. Provisional Application No. 60/349,708, filed Jan. 16, 2002. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to wafer containers and more particularly it relates to sealable wafer enclosures having doors with latch mechanisms. 
     BACKGROUND OF THE INVENTION 
     Processing of semi-conductor wafers into finished electronic components typically requires many processing steps where the wafers must be handled and processed. The wafers are very valuable, and are extremely delicate and easily damaged by physical and electrical shocks. In addition, successful higher yield processing requires the utmost in cleanliness, freedom from particulates and other contaminants. As a result, specialized containers or carriers have been developed for use during processing, handling and transport of wafers. These containers protect the wafers from physical and electrical hazards, and are sealable to protect the wafers from contaminants. Such wafer carriers or containers generally comprise an enclosure having a number of wafer holding shelves inside. One side of the container is open for access, and is closed by a door. The door has a latch mechanism to securely retain and seal it in place. Normally, the latch mechanism is enclosed to protect it from damage and accidental actuation. 
     Although wafer enclosures are used in clean environments, undesirable contaminants accumulate on and in the enclosure over time. Particulate contaminants are generated through frictional contact between parts of the enclosure and in the operation of loading and unloading wafers from the enclosure. Accordingly, an important characteristic for wafer containers is that they must be thoroughly cleanable to ensure that process cleanliness is maintained. Cleaning is generally accomplished with a liquid solution, and the parts are dried afterward with compressed air or other gas. 
     Latch mechanism enclosures present particular problems in efficient cleaning of wafer carriers. In prior art carriers, such as those shown in U.S. Pat. No. 5,915,562 to Nyseth and Krampotich, and U.S. Pat. No. 5,957,292 to Mikkelsen, et. al. for example, each of which are fully incorporated herein by reference, the latch mechanisms are located in cavities in the door that are covered by flat panels. Although such enclosure helps to isolate and contain particle generation from the latch mechanism itself, access to the latch mechanism area for cleaning and drying is limited. In addition, relatively large cavities with correspondingly large interior surface areas are formed around the latch components. The combination of limited access with large surface areas and volumetric areas makes it generally infeasible to effectively clean and dry the mechanism area with the enclosure in place. Also, large cavities may retain a correspondingly larger amount of particulate or other contaminant material. As a result, at least partial disassembly of the mechanism enclosure is necessary. This can be a tedious, labor-intensive process that can introduce process inefficiencies and delays. Accordingly, a mechanism enclosure that allows increased access to the mechanism components and that offers a reduced surface area inside the enclosure is desirable. 
     One way of reducing the interior surface area of the latch enclosure is to exclude unnecessary areas by conforming the enclosure to the latch components it protects. A wafer carrier door having a latch mechanism cover that more closely conforms to the contour of the latch mechanism was disclosed in PCT Application No. WO 01/04022 A1. The disclosed mechanism cover does not cover the entire latch cavity, but rather covers only the latch arms, the motion translation mechanism and a portion of the manual handle. The disclosed mechanism cover conforms to the contour of the latching arms for only a portion of one side of the latching arms. Thus, there are significant areas unnecessarily captured under the mechanism cover, particularly the areas between the latching arms and door margins. These areas remain difficult to clean and dry with the mechanism cover in place. 
     Moreover, manufacturing, and subsequent assembly, and disassembly of wafer carrier doors is sometimes complicated by previous designs of the latch mechanisms and latch mechanism covers. Typically, the latch mechanism components are retained and guided by structures formed in the door chassis. The mechanism cover merely serves to cover the latching components in such designs, and does not typically function to guide or laterally retain the components. It is generally necessary to form retaining and guide structures for latch components on the door chassis itself in such designs. These structures may be difficult to form, add complexity to the door chassis, and may complicate the assembly and disassembly process. 
     What is needed is an improved wafer container and door that overcomes the difficulties presented by the prior art designs. 
     SUMMARY OF THE INVENTION 
     The present invention is a wafer container and improved door. The door has a latch mechanism cover that retains and guides the latch mechanism components. The latch mechanism cover may be form fitted to the shape of the latch mechanism, thus minimizing the surface area of the door chassis captured under the mechanism cover, and thereby reducing the amount of particulates and other contaminants retained in the structure of the door. The retaining and guiding function of the latch mechanism cover may eliminate the need for guiding and retaining structures on the door chassis, thereby simplifying manufacture, assembly and disassembly of the door. Moreover, the latch mechanism cover may have a plurality of apertures for providing cleaning access to areas underneath. 
     Thus, the invention generally includes a wafer container and door. The door generally includes a door chassis with at least one latch mechanism. The latch mechanism has at least one slidable latch arm. A latch mechanism cover disposed over the latch mechanism, and the cover includes a panel portion substantially covering the latch mechanism and having an inner surface confronting the latch mechanism. A pair of spaced-apart guide portions projects from the inner surface of the panel portion adjacent the latch arm. The latch arm is longitudinally slidably disposed between the guide portions, which are adapted to slidably guide and locate the latch arm. 
     An object and advantage of the invention is a latch mechanism cover that provides protection for the latch mechanism parts. 
     Another object and advantage of the invention is a latch mechanism cover that retains and guides the latch mechanism parts. 
     Another object and advantage of the invention is a latch mechanism cover that allows cleaning and drying of area under the cover while the cover remains in place. 
     Yet another object and advantage of the invention is to provide a latch mechanism cover with apertures forming an open architecture mechanism cover that improves cleanability of the portions of the door located under the mechanism cover. 
     Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a wafer container and door; 
     FIG. 2 is an enlarged perspective view of a wafer container door according to the present invention; 
     FIG. 3 is a perspective view of the latch mechanism cover of the present invention from an exterior view; and 
     FIG. 4 is a perspective view of the latch mechanism cover of the present invention from an interior view. 
     FIG. 5 is a perspective view of a further embodiment of a latch mechanism cover of the present invention from an exterior view; and 
     FIG. 6 is a perspective view of the latch mechanism cover of FIG. 5 from an interior view. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The accompanying Figures depict embodiments of the wafer container of the present invention, and features and components thereof. Any references to front and back, right and left, top and bottom, upper and lower, and horizontal and vertical are intended for convenience of description, not to limit the present invention or its components to any one positional or spacial orientation. Any dimensions specified in the attached Figures and this specification may vary with a potential design and the intended use of an embodiment of the invention without departing from the scope of the invention. 
     Referring first to FIG. 1, a wafer container  10  is depicted seated on automatic processing equipment  12 . Wafer container  10  has an enclosure portion  14 , constructed of polycarbonate plastic, and having a top  16 , a bottom  18 , a pair of opposing sides  20 ,  22 , and a back  24 . A door  26  completes the enclosure by enclosing the open front  28  of enclosure portion  14 , fitting into door recess  30 . Wafer supports  32  are provided to support semi-conductor wafers (not depicted) within the enclosure  14 . Kinematic coupling  34 , mounted to the exterior surface of enclosure bottom  18  is provided to facilitate automated handling of the container during use and to provide a reference datum for locating the wafers in the housing during processing. Robotic lifting flange  36  is mounted on the exterior surface of enclosure top  16  and is provided to facilitate automated handling and transport of container  10  during use. 
     Referring to FIG. 2, the wafer carrier door  26  of the present invention is depicted. Door  26  generally includes a door chassis  38 , latch mechanisms  40 ,  42 , and latch mechanism covers  44 ,  46 . FIG. 2 also designates, for reference purposes, the relative directions of x-y-z coordinates as applied to the wafer carrier door  26 . Any reference herein to movement or constraint of components in an x-axis direction, a y-axis direction, or a z-axis direction, or to rotation about an x-axis, a y-axis or a z-axis, relates to these coordinate axes. The y-axis is oriented top to bottom on door  26  as installed on the container  10 , the x-axis is oriented perpendicular to the y-axis and side-to-side on door  26  as installed on the container  10 , and the z-axis is perpendicular to both the x-axis and the y-axis and is oriented perpendicular with the plane formed by door  26  when installed on container  10 . 
     Door chassis  38  may be formed from any material suitable for a wafer carrier, such as polycarbonate plastic, and generally includes a planar body portion  48  forming a door exterior surface  50 . Recesses  52 ,  54 , may be provided in door chassis  38  for receiving latch mechanisms  40 ,  42 . 
     Latch mechanisms  40 ,  42 , each generally include an actuating portion  56 , and one or more laterally slidable latch arms  58 . Although actuating portion  56  is depicted herein as a rotating cam member, any other suitable member or mechanism capable of imparting a linear sliding motion to latch arms  58  may be also be used, including a rack and pinion mechanism such as depicted in PCT Application No. WO 01/04022 A1. Further details of a cam operated latching mechanism suitable for use with the present invention are disclosed in co-pending U.S. patent applications Ser. Nos. 10/307,894, 10/317,023, and 10/318,374, each commonly owned by the owners of the present invention, and each hereby fully incorporated by reference herein. 
     In the depicted embodiment, latching arms  58  each have a cam follower portion  60  engaged with the periphery  62  of cam member  64  at cam portion  66 . Each of latching arms  58  has a latching portion  68  at the end opposite from cam follower portion  60 . When a key (not shown) is inserted into key slot  70  and rotated, cam follower portion  60  slides along cam portion  66 . Due to the shape of cam member  64 , latching arms  58  are translated radially in the y-axis direction, extending or retracting latching portions  68  through latch openings  72 . Latching portions  68  are received by latch receptacles  74  in the wafer container  10 , allowing the door  26  to be secured in place. 
     Referring now to FIGS. 2-4, an embodiment of the latch mechanism cover  44  of the present invention is depicted. Although, for simplicity, the following description refers only to latch mechanism cover  44 , the description may be assumed to apply to either latch mechanism cover  44 ,  46  as depicted in FIG.  2 . FIG. 3 depicts latch mechanism cover  44  as viewed from the exterior of the door  26 , and FIG. 4 depicts latch mechanism cover  44  from the interior of the door  26 . Latch mechanism cover  44  generally includes a panel portion  76  and projecting guide portions  78 . Latch mechanism cover  44  may also include a perimeter frame  80  for attaching the cover  44  to door chassis  38 . Key opening  82  may be provided to enable a key to be inserted into key slot  70 . 
     As depicted, panel portion  76  is substantially coextensive with, and covers, latch mechanism  40 . Projecting guide portions  78 , depicted here in the form of ribs  84 , extend downwardly adjacent latch arms  58 . Although depicted here as ribs  84 , it will be readily appreciated that guide portions  78  may be provided in a variety of other forms according to the invention, including a plurality of projecting posts or other structures. Each projecting guide portion  78  may have one or more bearing surfaces  86  in slidable contact with latch arm  58 . These bearing surfaces  86  serve to guide and locate latch arm  58 , as well as constrain lateral movement of latch arm  58  in the x-axis direction. Inner surface  88  of panel portion  76  confronts latch arm  58  and may also have a portion in slidable contact with latch arm  58 . Thus, panel portion  76  serves to retain and constrain movement of latch arm  58  in the z-axis direction. The projecting guide portions  78 , together with inner surface  88  of panel portion  76 , define a channel  90  for each latch arm  58 . 
     Panel portion  76  includes a center portion  92  covering the actuating portion  56  of latch mechanism  40 . Center portion  92  has an inner surface  94  confronting actuating portion  56  of latch mechanism  40 , including cam member  64 . Bearing portion  96  may slidably contact cam member  64 , retaining cam member  64  in place and preventing movement in the z-axis direction. Downwardly projecting rib  98  may be provided at the periphery of center portion  92  to form an actuating mechanism enclosure  100 . This actuating mechanism enclosure  100 , together with channels  90 , forms a substantially complete latch enclosure  104  for latch mechanism  40 . This latch enclosure  104  is essentially form-fitted to the shape of the latch mechanism  40 . 
     Of course, it will be appreciated that latch mechanism  40  may take a variety of alternative forms and configurations, including varying types of actuating mechanisms as set forth above, as well a single, or any other number, of latching arms. The latch mechanism cover of the present invention may be applied to any such alternative configurations. 
     Referring again to FIGS. 2-4, perimeter frame  80  may be provided to attach mechanism cover  44  to door chassis  38 . In another aspect of the invention, perimeter frame  80 , together with latch enclosure  104 , defines a plurality of apertures  106 . The apertures  106  provide access for cleaning substantially all areas of door chassis  38  covered by latch mechanism cover  44 , as well as, latch mechanism  40  itself. With apertures  106 , or without perimeter frame  80 , latch mechanism cover  44  has an open architecture. This open architecture design opens up the latch enclosure areas and provide easier access for cleaning and drying of the portions of door  26  located under the latch mechanism cover  44 . It is preferable that the apertures  106  have an aggregate area of at least a majority of the aggregate area under latch mechanism cover  44  not disposed substantially directly over latch mechanism  40 . In a preferred embodiment the apertures may be at least 2 inches square in area. 
     Referring to FIGS. 2,  4 , and  5 , a further embodiment of the latch mechanism cover  44  is disclosed. In this embodiment, a latch enclosure portion  108  is substantially coextensive with, and is form-fitted over, latch mechanism  40 . The latch enclosure portion  108  is defined by perimeter frame  80  and recessed portions  110 . The recessed portions  110  have an inner surface  112  that is disposed closer to door chassis  38  than inner surface  114  of latch enclosure portion  108  when latch mechanism cover  44  is attached to door chassis  38 . Significantly, the recessed portions  110  are formed from solid material and do not have apertures in this embodiment. As depicted, ribs  84  may be provided to guide and retain the latch mechanism components as described previously. As an alternative, recessed portions  110  may be sufficiently recessed so that an inner surface of side portions  116  of latch enclosure portion  108  may be positioned to guide and laterally retain latch arms  58 . 
     Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of the invention. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.