Abstract:
A substrate container is generally comprised of a cover, a base, a latching mechanism, and a substrate retention system. Substrate container has corners with flanges disposed at the corners. Each flange has a hole there through to enhance shock absorption capability by the container, and thus provide greater protection to the substrate.

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application No. 60/765,038, filed Feb. 3, 2006, which is incorporated herein in its entirety by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to containers and, in particular, this invention relates to containers for storing and transporting substrates such as semiconductor wafers and masks. 
     BACKGROUND 
     Semiconductor components, such as single semiconductors and integrated circuits, are made using semiconductor wafers. To this end, relatively fragile masks (or reticles) are used to determine dimensions and locations of the structures in the final product. These masks are generally in the form of a substantially planar substrate. During manufacture, small particles of foreign material may settle upon the masks or substrate, hence damaging the mask or the product being manufactured or otherwise interfering with the manufacturing process. These foreign particles are present in the environments in which masks are stored and transported. Because of the fragile nature of masks and the necessity to prevent adherence of foreign particles to the masks, containers are used. These containers serve the dual purpose of protecting the masks from damage and providing a dust-free microenvironment. Similar containers are also used to store and transport other substrates, such as semiconductor wafers and magnetic storage disks. 
     Because of the fragile nature of such substrates, they can be damaged even when enclosed in such a container if the container is dropped or otherwise roughly handled. As such, a container that can absorb such an impact itself to prevent damage to the substrates contained inside is desirable. 
     SUMMARY OF THE INVENTION 
     The invention as depicted in a preferred embodiment is a shock absorbing substrate container. A substrate container is generally comprised of an openable and closeable container with a plurality of corners, a substrate constraint inside the container and a latch. Shock absorbing fingers are positioned at corners of the container and are deflectable or frangible to absorb impacts at the corners. Substrate container can be configured with curved flanges disposed around container and preferably at corners. Each flange has a thinned portion or an aperture there through for providing the flange with desired shock absorbing characteristics. In a preferred embodiment four flanges at four corners will have four apertures defining a finger supported at two ends at apex of each corner. 
     An advantage of a preferred embodiment is enhanced shock absorption capability by the container, and thus greater substrate protection. If a container is dropped on its side, the holes in flanges allow flanges to deform and/or fracture, increasing the time of impact and absorbing a greater portion of the energy of the impact. The impact energy that is transmitted inside the package can then be further absorbed by pads and cushions supporting the substrates, thereby providing optimal substrate protection. 
     Another advantage and feature of a preferred embodiment is that the enhanced shock absorbing capabilities provide greater resistance to the container opening, that is, less shock or energy is imparted to the latch mechanism lessening the likelihood of it opening. 
     Another advantage of a preferred embodiment is ease of manufacture. Flanges and apertures can simply be incorporated into existing molds for containers, thus providing increased shock absorption without increasing the cost and difficulty of manufacture. 
     Another advantage and feature of preferred embodiments is that the flanges with apertures can be configured to be frangible, fracturing upon impact providing an uneraseable record of the impact. In some instances, the fracturable feature can be intentionally fractured to ineraseably indicate another occurrence other than impact, for example a single use, or a washing, a repair, or some other event of significance. In embodiments wherein the impact record is to be preserved, the fracturable portion of the container can have other shapes than apertured flanges. Thus, an embodiment of the invention is a method for ineraseably recording an event relating to a substrate container comprising the step of intentional fracturing a readily frangible portion of a substrate container. Said frangible area can be on a corner flange or other suitable area. 
     A feature and advantage of preferred embodiments is that a method of manufacturing a shock absorbing container is provided wherein the container has a corner positioned flange and an aperture therein for allowing deformation or fracturing upon impact with said corner. 
     A feature and advantage of preferred embodiments is that a method of modifying a container with a flanges in order to provide improved impact resistance with said flanges is provided and comprises adding holes to said flanges for allowing improved deformation and shock absorption capabilities at said flanges. 
     A feature and advantage of the invention is that a method of providing protection to masks in use and storage in semiconductor fabrication facilities is provided wherein a mask container with apertured flanged corners is utilized to contain and store masks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of the inside of an opened shock absorbing substrate container according to an embodiment of the present invention. 
         FIG. 2  is a top view of the outside of an opened shock absorbing substrate container according to an embodiment of the present invention. 
         FIG. 3   a  is a partial view of a shock absorbing substrate container according to an embodiment of the present invention. 
         FIG. 3   b  is a partial view of a shock absorbing substrate container according to an embodiment of the present invention. 
         FIG. 3   c  is a cross-sectional view of a apertured flange according to an embodiment of the present invention. 
         FIG. 4  is a perspective view of a shock absorbing substrate container according to an embodiment, of the present invention. 
         FIG. 5  is a perspective view of a shock absorbing substrate container according to an embodiment of the present invention. 
         FIG. 6  is a perspective view of a shock absorbing substrate container according to an embodiment of the present invention. 
         FIG. 7  is a perspective view of a shock absorbing substrate container according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-3   a , one embodiment of a shock absorbing substrate container of the instant invention is depicted generally at  100  and includes an upper member such as a lid  102 , a lower member such as a base  104 , a hinge  106 , and a latching mechanism  108 . The substrate in the embodiment is a mask or reticle for manufacturing semiconductors. In other embodiments the substrate may be semiconductor wafers or magnetic disks. 
     The lid  102 , in turn, has a shell  114  with a generally planar top  116 , opposed front and back sides  118  and  120  and opposed lateral sides  122  and  124 , thereby defining a lid cavity  126 . Disposed within the lid cavity  126  are longitudinally inclined raised surfaces  128  and  130  and laterally opposed mask cushions  132  and  134 . The mask cushions are part of a restraint system  147  for the mask. 
     The base  104  has a shell  136  having a generally planar bottom  138 , opposed front and back sides  140  and  142 , and generally opposed lateral sides  144  and  146 , thereby defining a base cavity  148 . The restraint system  147  for the substrate, that is the mask, further comprises posts  150 ,  152 ,  154 , and  156  that extend from the bottom  138  proximate the four corners of the base cavity  148  and define a substrate placement position  149  or pocket. Laterally opposed inclined raised surfaces  158  and  160  are at the lateral sides  144  and  146 , respectively. 
     A rim  162  is defined at the periphery of the lid  102  and a ledge  164  is defined at a periphery of the base  104 . The rim  162  sealingly contacts the ledge  164  when the container  100  is closed. The ledge  164  can include four flange portions  110  located at each of the corners of the base  104 . Each flange portion  110  further includes a hole or aperture  112  there through as can be seen in  FIG. 3 . Holes  112  are preferably not obstructed by the lid  102  when the container  100  is closed. 
     In use, a substrate, such as a mask, is placed in the base cavity  148  so as to be confined therein by the posts  150 ,  152 ,  154 ,  156 . 
     Holes  112  and flanges  110  are disposed on base  104  in order to absorb the shock if container  100  is dropped on its side, thereby protecting any substrates contained therein from damage. When the force from a drop is imparted on container  100 , hole  112  allows flange  100  to deform  112 , thereby extending the impact time and effectively absorbing the brunt of the impact. This results in reduced force being passed on to the interior of the container  100 , which may be absorbed by the cushions  132 ,  134  in the lid and resiliency in the posts leaving the substrates undamaged. In addition, muted force is transmitted to the latching mechanism  108 , lessening the likelihood that the container  100  will pop open upon impact. 
     Holes  112  must be large enough and configured to permit flanges  110  to deform or fracture upon impact. However, if holes  112  are too large, flanges  110  will deform too easily and/or be unable to support the weight of the container and contents which would not be desirable in many cases. Preferably, the shortest distance from the perimeter of the hole to the perimeter of the flange is smaller than the radius of the hole or half the distance across the aperture for non circular holes. In preferred embodiments, the thickness of the material from the boundary of the hole  112  to the outer periphery  113  of the flange is in the range of 0.030 inches to 0.400 inches. In a more preferred embodiment, the thickness of the material from the hole to the outer periphery of the flange is 0.050 to 0.300 inches. The hole  112  size and shape can vary, depending on the size of the flanges  110  and the weight and size of the container  100 , as necessary to provide the proper amount of deformation upon loading such as by a drop of the container. In preferred embodiments the radius of the hole when circular ranges from 0.125 inches to 0.300 inches. In other embodiments the hole can have a length dimension where it is non-circular of up to about an inch. For example a curved slot of 0.100 to 0.200 inches wide could follow the curved corner periphery. In preferred embodiments the flange is an integral portion of the container, conveniently the base portion but also the cover or lid is suitable. In certain cases it may be desirable to have multiple apertures at each flange. In the preferred embodiments, the apertures serve no purpose other than effectuating and enhancing the shock absorption capability of the container when receiving impacts at said corners. Referring to  FIGS. 3   a ,  3   b , and  3   c , note that the apertures can be open or closed. “Closed” being where aperture has a continuous perimeter or boundary  180  that does not extend to the outer periphery  184  of the flange as shown in  FIG. 3   a . “Open” being where the boundary of the aperture does extend to the periphery of the flange as shown in  FIG. 3   b.    
     Also note that in preferred embodiments the flange is horizontally extending (in the x-y axis) and extends from a vertical wall  188  (substantially parallel to the z axis) of the container. The flange is preferable of uniform thickness except at the periphery  113  where the thickness may increase at the peripheral lip  189 . Referring to  FIG. 3   c , in a preferred embodiments the portion of the edge of the flange that is apertured compared to the distance from the inside perimeter of the aperture to the outer periphery of the flange is at lease about 50% and preferably about at least 70% of the corner where the aperture is closed measured through a line taken where the aperture is closest to the flange periphery. This may or may not be at the apex  192  of the corner of the flange. Stated in other terms, b/(a+b) is at least about 0.5 and preferably about at least 0.7. Moreover, taken at a line through the widest part of the aperture, the portion of the horizontal flange extending outwardly from the vertical wall  188  that is apertured compared to the entire distance is preferably at least 40%, and more preferably at least about 60%. In other words, b/c is preferably at least 0.4 and more preferably at least about 0.6. 
     Referring to  FIGS. 3   a  and  3   b , the aperture  112  and the periphery  113  in the flange define at least one either resilient or frangible elongate finger member  195 . The finger  195  is illustrated as integrally connected to the flange at both ends  197 ,  198  of the finger. Where the aperture is open, a second elongate finger member  196  may be defined. Depending on the material and specific configuration, these fingers can be designed to either fracture or bend upon impact. In a preferred embodiment, the fingers have a width, identified with the letter a in  FIG. 3   c , measured in a direction parallel to the plane of the flange (the x-y plane), and a height, measured in the direction transverse to the plane of the flange and designated with the letter d, that is in the z direction. In a preferred embodiment, the width dimension is less than the height dimension at the point of minimal width or at the apex of the corner. 
     Although described with respect to one specific container configuration, it will be appreciated by one of skill in the art that a shock absorbing substrate container according to the present invention can be created by taking any similar substrate container configuration and adding flanges and creating holes there through. A container for storing masks that can be easily modified according to the present invention is disclosed in co-pending application Ser. No. 11/364,812, which is hereby incorporated by reference. 
     Referring to  FIGS. 4-7 , there can be seen various other shock absorbing substrate containers according to embodiments of the present invention. In  FIG. 4 , a substrate shipper, for semiconductor wafers is illustrated. This shock absorbing package  200  includes an upper member  202  and a lower member  204  that define an interior region in which substrates can be stored. Such a container is described in U.S. Pat. No. 4,793,488 owned by the owner of the instant invention. Said patent is incorporated herein by reference. An H-bar wafer cassette may be the support system for the substrates, that is, the wafers. Upper member  202  and lower member  204  can be sealingly connected by a latching mechanism  206 . Package  200  further includes flanges  208  with apertures  210  there through to absorb the impact if the package  200  is dropped. 
     Referring to  FIG. 5 , a shock absorbing container  300  includes a shell  302  that can contain substrates. The container is typically known as a FOUP which is an acronym for front opening unified pod. Such a container is illustrated in U.S. Pat. No. 5,944,194 and is owned by the owner of the instant invention. Said patent is incorporated herein by reference. Container  300  is sealable with a door  304  and a latching mechanism  306 . The support system for the substrates therein comprises a series of shelves and wafer restrainst on the inside of a front door. Container  300  further includes flanges  308  with apertures there through  310  to absorb the impact if the container  300  is dropped. 
     Depicted in  FIG. 6  is a shock absorbing substrate carrier  400  including a cassette  402  for container substrates, a top cover  404 , and a bottom cover  406 . The substrates for this type of shipper are magnetic disks and such a shipper is illustrated in U.S. Pat. No. 6,902,059, owned by the owner of the instant invention. Said patent is incorporated herein by reference. The support system for substrates in this embodiment comprises a series of teeth defining slots and a disk “cushion” on the top cover. A latching mechanism  408  can seal the top cover  404  and bottom cover  406  to the cassette  402 . Carrier  400  further includes flanges  410  with apertures there through  412  to absorb the impact if the carrier  400  is dropped. 
     Referring to  FIG. 7 , a shock absorbing substrate carrier  500  is depicted. Carrier  500  includes a container portion  502  that is sealable with a door  504 . Carrier  500  further includes a flanged portion  506  that includes a plurality of apertures  508  there through to absorb the impact if the carrier  500  is dropped. 
     Substrate container may be injection molded, though one of skill in the art will recognize that other processes can be used. Any existing substrate container mold can be easily modified to impart the flanges and holes of the present invention to provide a shock absorbing substrate container. Alternatively, holes may be created by a separate process after the base is molded. 
     Suitable materials for the substrate container include acrylonitrile-butadiene-styrene (ABS), optionally with a static dissipative property, e.g., StatPro 435™ available from Entegrisr, Inc. the owner of the instant invention. However, a person of ordinary skill in the art will routinely substitute other polymers for specific applications. Polypropylenes and polycarbonates are examples. 
     Because numerous modifications of this invention may be made without departing from the spirit thereof, the scope of the invention is not to be limited to the embodiments illustrated and described. Rather, the scope of the invention is to be determined by the appended claims and their equivalents.