Abstract:
A container for creating a microenvironment is disclosed. The container includes a shell, a door and a plurality of supports having a unique design which are used to securely retain items, such as silicon wafers, in a spaced apart parallel relationship. The supports are removable. An electrical path is provided to ground the supports. Kinematic coupling structures are also provided for positioning the container on a surface so as to, for example, properly align the door with the port of a wafer processing tool.

Description:
Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No. 5,944,194. The reissue applications are application Ser. No. 11/351,214 (the present application), which is a continuation of application Ser. No. 10/310,069, filed Dec. 4, 2002, now issued as U.S. Reissue Pat. No. RE41,231, which is a continuation of application Ser. No. 09/943,098, filed Aug. 30, 2001, now issued as U.S. Reissue Pat. No. RE38,221, all of which are reissues of U.S. Pat. No. 5,944,194. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to a package for an item. More particularly, the present invention relates to a package specifically designed to isolate from contamination materials used in the manufacture of electronic semiconductor components and circuits. Such packages are particularly well suited for substrates, wafers, memory disks, photomasks, flat panel displays, liquid crystal displays, and the like. 
     II. Description of the Prior Art 
     Various containers have been used for centuries to transport items from one place to another. Such containers have, for example, been used to provide a way to confine items in a space for efficient storage. Such containers also provide an easy way of handling items. Another important function provided by packages and containers is protection. 
     Substrates used in the manufacture of semiconductor circuits, rigid memory disks, photomasks, liquid crystal displays, and flat panel displays can be extremely sensitive. Effective steps must be taken to protect such items from damage by moisture, particles, static electricity, or the like. Steps must also be taken to protect the articles from damage caused by vibration and shock within the package. Similarly, steps must be taken to prevent outgassing and the generation of particles which will occur if the items stored in the package scrape, rub, or impact various surfaces within the package. 
     This combination of problems makes designing a suitable package very difficult. Such problems are only compounded by the environment in which such packages are typically used. 
     Suitable packaging for use in connection with the storage and transport of wafers, memory disks, photomasks, liquid crystal display panels and flat panel displays tend to be very expensive. It is highly desirable that such packaging be reusable and have durable construction. Also, such packaging must be capable of being readily and thoroughly cleaned. Finally, when the package is used in connection with the manufacture of semiconductors, it must be readily adaptable for use with robotic handling and automated manufacturing equipment. 
     Empak, Inc., has made a number of suitable packages in the past for use in the processing and transport of such items. Examples of such packages are shown in U.S. Pat. No. 5,273,159 and U.S. Pat. No. 5,423,422. While such package designs have proven to be highly effective in conjunction with smaller items, the designs, for a variety of reasons, are not suitable for storage and transport of items having outside dimensions in the range of 300 mm or more. 
     SUMMARY OF THE INVENTION 
     Suitable containers for use with wafers, photomasks, memory disks, liquid crystal display panels and flat panel displays must meet several important design criteria. They must be light weight to make manual and robotic handling tasks easier. The internal volume of the container should be minimized to reduce storage space requirement and increase storage density. The height of the container should be minimized to allow for improved stacking of the containers. The amount of polymer surface area surrounding the items during transport and storage should be minimized to reduce inorganic and organic contaminants as well as the negative affects of outgassing of the polymer. 
     Containers built in accordance with the present invention meet the design criteria set forth above. Such containers also provide several other unique advantages. First, tolerance build-up is minimized by means of locating the container about item center lines, thereby increasing the positional accuracy of the items stored in such containers. This enhances effective insertion and removal of the items from the container using robotic equipment. Second, the containers reduce the risk of damage caused by static electricity. This is achieved in one preferred embodiment by providing a conductive path to ground from static dissipative internal item supports to the container&#39;s external kinematic coupling plate which is used to position the container on various pieces of equipment. Third, the containers of the present invention are designed to be wet-cleaned with or without disassembly. Fourth, since the containers of the present invention can have an integral design which does not require a separate carrier, the containers can remain associated with a specific lot of items. This enables workers in the factory to better track a lot and, therefore, reduces the chance of processing errors. Fifth, the integral design, by eliminating the need for a separate cassette, minimizes the number of packaging components required to be kept in inventory and the space such components take up. Sixth, the integral design eliminates the need to accurately position a removable cassette in the container and lock it in place. Finally, the integral design can be manufactured using fewer and smaller parts, thereby reducing manufacturing costs. 
     It is therefore an object of the present invention to provide an isolation container which will provide protection against contamination by particles or moisture. 
     Another object of the present invention to provide a container which protects the items stored therein from damage due to shock and vibration and from damage due to the item scraping, rubbing, or impacting various surfaces of the container. 
     A further object of the invention is to provide such a container which is reusable and easily cleaned. 
     Still another object of the invention is to provide such a container which has interior structures which are not susceptible to wear or generation of particles which could contaminate the contents of the package. 
     Yet another object of the invention is to provide such a container which is highly effective when used in conjunction with automated processing or handling equipment. 
     Still another object of the invention is to provide a structure which can easily be handled, manipulated and transported by humans. 
     These and other objects are accomplished by providing a container having a shell with an opening for insertion and removal of the items, a door designed to effectively seal the opening, a plurality of item-retaining structures within the shell which securely hold the items and retain them in spaced apart relation from each other, a kinematic coupler plate to assist in aligning the container with the port of equipment used to process the items in a factory, and ergonomically designed handles which can be effectively used either manually or through robotic means. In order to reduce contamination by particles inside the container, the item supports are made of a high-temperature resistant, conductive material. The item supports are also grounded to the exterior of the container as described in detail below. The entire container is structured to maximize the support and protection offered to the items, maximize ease of handling, and reduce, to the extent possible, the height and weight of the container. 
     A better understanding of the invention will be deserved from reading the description of the preferred embodiment set forth below in conjunction with the drawings. While the description and drawings specifically relate to a microenvironment pod for silicon wafers, the invention described is also well suited for other applications, such as the storage and transport of photomasks, rigid memory disks, liquid crystal display panels, flat panel displays, or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a container shell made in accordance with the invention; 
         FIG. 2  is a top plan view of the container shell; 
         FIG. 3  is a cross-section of the container through line A-A in  FIG. 2 ; 
         FIG. 4  is a cross-section of the container through line B-B in  FIG. 2 ; 
         FIG. 5  is a side view of the container incorporating the present invention; 
         FIG. 6  is a cross-section of the container through line C-C in  FIG. 5 ; 
         FIG. 7  is a view of the container from the side opposite the door; 
         FIG. 8  is a drawing of the kinematic coupler plate; 
         FIG. 9  is a cross-section of the kinematic coupler plate through line D-D in  FIG. 8 ; 
         FIG. 10  is a cross-section of the kinematic coupler plate through line E-E in  FIG. 8 ; 
         FIG. 11  is a cross section of the kinematic coupler plate through line F-F in  FIG. 8 ; 
         FIG. 12  is a prospective view of one of the ergonomic handles used in the design; 
         FIG. 13  is an end view of the handle; 
         FIG. 14  is a cross-section of the handle through line G-G in  FIG. 13 ; 
         FIG. 15  is a plan view of the door of the container in the closed position with respect to the container&#39;s shell; 
         FIG. 16  is a perspective view of a cushion which can be attached to the inside surface of the door to help support and retain items stored in the container in the proper position during storage and transport; and 
         FIG. 17  is a cross section showing two opposing dividers and a wafer. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in  FIG. 1 , the container of the present invention has an exterior shell  10 . The exterior shell  10  has six sides  12 ,  14 ,  16 ,  18 ,  20  and  22 . 
     Side  12  comprises a door frame  6  having a pair of opposing end portions  7  and a pair of side portions  8 . Sides  14  and  16  of the exterior shell  10  are defined generally by straight walls extending from the opposite end portions  7  of the door frame  6 . Wall  18  extends between walls  14  and  16  and is in the shape of a partial cylinder. The radius of curvature of wall  18  is generally the same as the radius of curvature of the wafer to be stored in the container. Top and bottom walls  20  and  22  complete the shell. Walls  20  and  22  have a generally flat surface  24  and a reinforcement member  26  projecting outwardly from the flat surface  24 . Reinforcement member  26  prevents warpage of the container and especially walls  20  and  22 . Reinforcement members  26  have four legs  28 ,  30 ,  32  and  34 . Extending across wall  18  between the two legs  30  is a cross-brace  31 . In a similar fashion, cross-brace  33  extends between the two legs  32 . Cross-braces  31  and  33  can be used to support the exterior shell  10  on a flat surface if it is positioned so that wall  18  is down. 
     Also shown in  FIG. 1  is a kinematic coupling plate  40 .  FIGS. 1-5  and  8 - 11  show the structure of the kinematic coupling plate in greater detail. This plate is secured to wall  20  by a plurality of mounting posts  42  (see  FIG. 5 ). Three separate coupling grooves  44 ,  45  and  46  are formed into the kinematic coupling plate  40 . These grooves are designed to mate with posts on the processing equipment (not shown) to align the access opening  8  with a port on the processing equipment. As best shown in  FIG. 10 , the grooves  44 ,  45  and  46  are Y-shaped to include a narrow, deeper, center channel  47  and wider, less deep, upper channel  48  which serves to catch and direct the alignment post of the processing equipment into the center channel  47  to achieve proper alignment. Proper alignment results when the three alignment posts on the processing equipment (not shown) mate with the center channel  47  of the grooves  44 ,  45  and  46 . 
     The kinematic coupling plate  40  is made of a conductive material. It is also designed to include a pair of screw receiving members  49 . As explained below, members  49  each receive a screw which is used to electrically couple the kinematic coupling plate  40  to the wafer supports  60  located inside the container. This electrical coupling creates a path by which the wafer supports can be grounded to dissipate any electrical charge on the wafers or wafer supports and, thus, prevent damage to the wafers caused by static electricity. 
       FIG. 1  also shows a pair of handles  50 . These handles are located at the center of gravity of the container. The handles are ergonomically designed so they are easily gripped from a variety of angles by the human hand. The design of the handles  50  allows them to be effectively grasped by robotic handling equipment. 
     More specifically, each handle  50  includes a support column  51  which joins the handle  50  to the shell  10  and a wider gripping member  52 . The gripping member  52  has an exterior shape which permits it to be comfortably grasped by a human hand. The gripping member  52  also has a recessed channel formed in its end. Channel  53  is generally straight, but includes a notch  54 . The channel  53  and notch  54  are present to be engaged by gripping members of a robotic arm. As such, the container is designed for easy, efficient and safe handling by humans or robots. 
       FIGS. 3 ,  4  and  6  show some of the interior structure of the shell  10  not visible in  FIG. 1 . For example,  FIGS. 3 and 4  show wafer supports  60  and  62  which cooperate to hold up to thirteen wafers  80 . Typically, twelve of the wafers  80  are product wafers and one is a test wafer. The wafer supports  60  and  62  are all made of a material which is electrically conductive and resistant to high temperatures. The wafer supports  60  and  62 , as shown, each have fourteen wafer dividers  65 . A wafer edge receiving channel  66  is formed between each pair of dividers  65 . The channels on wafer support  60  cooperate with the channels on wafer support  62  to hold the wafers  80  in a parallel spaced apart registration as shown in  FIGS. 3 and 4 . Those skilled in the art will recognize that the wafer supports  60  and  62  can be modified to hold more wafers (for example, 25) or fewer wafers (for example, 7) without deviating from the present invention. Likewise, the wafer supports  60  and  62  could also be dimensioned to retain something other than a wafer or to retain wafers of differing sizes. 
     In the preferred embodiment shown in the drawings, each of the channels  66  is especially formed to retain 300 mm wafers. The back side of each channel is curved in the circumferential direction (e.g. the direction of the circumference of the wafer  80 ) and in the transverse direction (e.g., the direction across the thickness of the wafer  80 ). The curvature of the backside of each channel  66  is approximately the same radius of curvature as the outside edge of the 300 mm wafers  80 , in both the circumferential and transverse directions. Providing the same radius of curvature along the circumferential direction presents contact between the channel&#39;s back side and the edge of the wafer  80  along an arc rather than merely at a point. 
     Significant advantages are provided by shaping the wafer divider  65  as shown in  FIG. 17 . The wafer dividers have a continuously varying slope such that gravity helps center the wafer  80  in the middle of the carrier. With this style of wafer divider  65 , the wafer always rests on a portion of the wafer divider that has a finite slope, so edge contact is guaranteed. Further, if for any reason the wafer is moved off of dead center, one edge is raised more quickly than the other edge is lowered. Thus, for carriers where the wafers are transported horizontally, gravity may be used to help center the wafer with this support. Once centered, the wafer&#39;s vertical location is precisely defined. As the carrier is moved from one location to the next, small levels of vibration may help to center the wafer in the carrier, thus improving the horizontal positional accuracy of the wafers as well as the vertical positional accuracy. 
     An additional benefit of the wafer design, as shown in  FIG. 17 , is that it presents the lowest possible cross-section for a given support strength. The divider  65  presents an area of interference for the wafer  80  as it is inserted into and removed from the carrier. Thin dividers are preferred because there is less chance of a wafer  80  hitting the divider and causing particles to be generated. On the other hand, the divider  65  must be thick enough to support the wafer  80  and to avoid deflection over the life of the container. In light of these conflicting requirements, the divider design has a continuously varying angle as shown in  FIG. 17 . 
     In the preferred embodiment, a pair of screws  64  are provided. One of the screws  64  is used to form a conductive path between the wafer support  60  and the conductive kinematic coupling plate  40 . The other screw  64  is used to provide a conductive path between wafer support  62  and the kinematic coupling plate  40 . This arrangement provides the advantage of grounding the wafer supports  60  and  62  via screws  64  and the kinematic coupling plate  40  so that the wafer supports  60  and  62  have no electrical charge. The walls of the shell  10  are not grounded and have a slightly negative charge which will cause particles in the container to migrate and attach themselves to the walls of the container where they can do no harm to the wafers. So that the screws  64  do not ground the exterior shell  10 , it may be desirable to line the bores in the shell  10  through which the screws  64  pass with an insulative material. 
     To close the access opening  8  of the shell  10 , a door  90  is provided. The door  90  is shaped and dimensioned to fit within the door frame  6 . When in place, the door engages the door frame  6  to seal the container. Likewise, the outer edge of door frame  6  can be used to form a seal around the access opening  8  between the door frame  6  and the port of a tool used to process semiconductor wafers  80 . The risk of contamination is reduced if such a seal is created before the door  90  is opened. When such a seal is created, the door  90  can safely be opened so that the wafers  80  can be withdrawn from the shell  10 , through the port and into the tool for processing without substantial risk of contamination. Typically, a plurality of latches (not shown) to hold the door in the closed position will be provided. Also, a flexible gasket or ring can be provided between the door  90  and frame  6  to ensure complete sealing between the door  90  and frame  6 . 
     The door  90  can be provided with a wafer cushion  92 . As shown in  FIG. 16 , cushion  92  has a pair of rigid rails  93  and  94  and a plurality of deformable cross-members  95 . Thirteen deformable cross-members  95  are shown in  FIG. 16 . Each cross-member  95  has a pair of dividers  96 . Each divider  96  is aligned with a divider  97  on rigid rail  93  and a divider  98  on rigid rail  94 . Thus, as the door  90  is closed, the wafers  80  engage the channels formed by the dividers  96 ,  97  and  98 . Cross-members  95  will deform until the edges of wafers  80  also engage the rigid rails  93  and  94 . Even if the wafers  80  are jarred during transport, contact with and support by cushion  92  is not lost because of the deformable cross-members  95 . 
     The inclusion of such a wafer cushion  92  on the door  90  yields three areas of support for the wafers  80 , thereby reducing movement and vibration of the wafers  80  during transport. Supporting the wafers  80  in three areas reduces damage to the wafers due to scraping, rubbing or impacting surfaces within the container. It also limits generation of particles due to such scraping, rubbing or impacting. Finally, means can be provided on the exterior door for kinematically coupling the door  90  to another surface. This can be a series of three grooves (not shown) similar to those shown in kinematic coupling plate  40  which mate with projections on the surface or three projections on the door  90  which mate with grooves on the surface. 
     Although the present invention has been illustrated and described with reference to the preferred embodiment thereof, the invention may also be used in conjunction with the transport and storage of liquid crystal displays, flat panel displays, photomasks, rigid memory disks, substrates, and the like. Also, various components of the invention may be constructed so that they are removable and replaceable to extend the life of the container. This is certainly true of the wafer supports  60  and  62  and wafer cushion  92  which can be removed and replaced with supports or cushions more ideally suited for other items to be held in the container. It should be understood, therefore, that the illustrations and descriptions provided herein are not intended to be limiting and that numerous modifications can be made within the scope of this invention and the claims set forth below.