Abstract:
A bridge loadport is described comprising a tool interface, an advance plate assembly, a port plate, and a port door. The tool interface extends vertically and is configured to substantially cover one end of a process tool. The advance plate assembly is supported on the front side of the tool interface and is configured to support a front-opening unified pod (pod). The port plate extends vertically, covering an upper portion of the tool interface. An aperture having a size and shape that substantially matches a size and shape of a door of a pod is formed in the port plate. The port door has a port door actuator and a port door face attached to the port door actuator. In one embodiment, the port door face is movable with respect to the port door actuator along a ling perpendicular to the aperture.

Description:
CLAIM FOR PRIORITY 
       [0001]    This Application claims benefit of earlier-filed and co-pending U.S. Provisional Patent Application 60/819,603 filed on Jul. 10, 2006, and entitled, “Bridge load port with variable lot size capability,” which is incorporated herein by reference in its entirety. 
         [0002]    This Application is a continuation-in-part of related U.S. patent application Ser. No. 11/599,020, filed Nov. 13, 2006, and entitled, “Load Port Door With Simplified FOUP Door Sensing and Retaining Mechanism,” which is also incorporated herein by reference in its entirety. 
     
     BACKGROUND 
       [0003]    During semiconductor manufacturing, semiconductor wafers and other substrates may undergo a plurality of process steps, each of which are performed by a specialized process tool. Pods are used to convey substrates from one tool to another. An exemplary type of pod is referred to as a front-opening unified pod (FOUP). Each pod is capable of transporting a number of substrates of a specific size. For example, for wafers having a diameter of 300 mm, a conventional FOUP has a capacity of 25 wafers, and can therefore carry 25 or fewer 300 mm wafers at a time. The pods are designed to maintain a protected internal environment to keep the wafers free of contamination, e.g., by particulates in the air outside the pod. 
         [0004]    A lot size is the number of substrates being processed as a group. A pod having a maximum capacity of 25 substrates is appropriate for a lot size of 25, since each 25-substrate lot can be kept together during processing and conveyed from one tool to another in a single pod. However, some fabricators are moving to reduce their lot size for a variety of reasons. Storing a 10-substrate lot in a pod designed for 25 substrates can be space-inefficient, resulting in a greatly reduced storage density. In a fabrication facility where floor space can be precious, it may be desirable to increase the storage density by storing the substrate lots in smaller size pods, each having a smaller maximum capacity e.g., 8 or 10 substrates each. However, each pod is designed specifically to interface with a particular load port in each tool and each load port is correspondingly designed to fit a standard 25-substrate pod. Therefore, simply resizing the pod would result in an incompatibility between the pod and the load port. A redesign of the load port is possible so that the load port can then accommodate the smaller-capacity pod, however, this is an expensive proposition which may not provide compatibility with future lot size changes. 
         [0005]    In the semiconductor industry, as wafer sizes increase, the number of devices formed into each wafer increases, improving yield per wafer. Wafer sizes have been steadily increasing since the early 1960s from 10 mm to the now common 300 mm diameter size. Many fabricators are transitioning or are planning to transition to a new 450 mm diameter standard. As with the change in lot size, accommodating this change in wafer diameter is expensive, requiring new tools, new pods, new load ports, and new conveyances. It would be desirable to provide a flexible load port capable of being easily and cheaply reconfigured to accommodate multiple size wafers. 
         [0006]      FIGS. 1 and 2  show a conventional load port  10  configured to interface with a standard 300 mm, 25-wafer pod  70  (shown in  FIG. 2 ). Load port  10  includes a tool interface  20 . Typically, tool interface  20  is in conformance with the standard for Box Opener/Loader-to-Tool Standard Interface (BOLTS), commonly referred to as a BOLTS interface or a BOLTS plate. Tool interface  20  includes an aperture  22  surrounded by a recessed shoulder  24 . Aperture  22  is occluded by a port door  30 . Port door  30  forms a proximity seal with aperture  22  to prevent contaminates from migrating to the interior of process tool  40 . A proximity seal takes advantage of a positive interior pressure that is maintained by process tool  40 , and provides a small amount of clearance, e.g., about 1 mm, between the parts forming the proximity seal, allowing air to escape process tool  40  and sweep away any particulates from the sealing surfaces. 
         [0007]    Load port  10  also includes an advance plate assembly  50  having an advance plate  52 . Registration pins  54  mate with corresponding slots or recesses in the bottom support  72  of pod  70 . Advance plate assembly  50  has an actuator (not shown) that slides advance plate  52  between the retracted position shown and an advanced position that is proximate tool interface  20 . 
         [0008]    Port door  30  is moved from the closed position shown in  FIGS. 1 and 2  to an open position. In the closed position, port door  30  substantially occludes aperture  22  of tool interface  20 . Port door  30  is moved from the closed position by mechanism  32  which translates port door  30  to the right (as viewed in  FIG. 2 ) and then down to the open position. In the open position, aperture  22  and the interior of pod  70  remains substantially unobstructed by port door  30 . The front surface  34  of port door  30  includes a pair of latch keys  60 . Latch keys  60  include a post  62  and a crossbar  64 , and are configured to rotate on the axis of post  62 . Latch keys  60  are inserted into corresponding latch key receptacles (not shown) of the pod door  74  as pod  70  is advanced towards the port door  30  by advance plate assembly  50 . Latch keys  60  are rotated on the axis of post  62 , interacting with a mechanism (not shown) internal to pod door  74 , causing latches to disengage from lip  76  of pod  70 . An example of a door latch assembly within a pod door adapted to receive and operate with latch keys is disclosed in U.S. Pat. No. 4,995,430, entitled “Sealable Transportable Container Having Improved Latch Mechanism,” which is incorporated herein by reference. Another example is presented in U.S. Pat. No. 6,502,869, issued on Jan. 7, 2003 to Rosenquist et al., also incorporated herein by reference. 
         [0009]    In addition to disengaging pod door  74  from the pod  70 , rotation of the latch keys  60  locks the keys in their respective latch key receptacles, thereby coupling the pod door  74  to the port door  30 . A conventional load port includes two latch keys  60 , each of which pairs are structurally and operationally identical to each other. Once the latches are disengaged, port door  30  may be retracted thereby removing pod door  74  from pod  70 . 
         [0010]    Alignment pins  34  ensure a degree of alignment between port door  30  and pod door  74 , so that pod door  74  will be sufficiently aligned with aperture  22  to pass through aperture and be stowed in the interior of process tool  40 . However, these alignment pins may not always be sufficiently precise to ensure alignment between pod door  74  and lip  76  of pod  70  when replacing pod door  74 , particularly if any amount of shifting has occurred between pod door  74  and port door  30 . Accordingly, it is common practice to provide a vacuum system (not shown) for retaining pod door  74  against port door  30  and prevent any relative movement between the two. The U.S. Pat. No. 6,502,869 mentioned above describes an alternative mechanism to prevent relative movement between the port door and the pod door. In that system, the latch keys are biased in a rearward direction after engaging the pod door, thereby compressing the pod door between the back of the latch keys and the pod door, the friction between pod door  74  and port door  30  preventing any relative movement. 
       SUMMARY 
       [0011]    Broadly speaking, the present invention addresses a desire to make load ports easily reconfigurable to accommodate pods of varying capacities and sizes these needs by providing a bridge loadport as described hereinbelow. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below. 
         [0012]    In one embodiment, a bridge loadport is provided. The bridge load port includes a tool interface, an advance plate assembly, a port plate, and a port door. The tool interface extends vertically and is configured to substantially cover one end of a process tool. The advance plate assembly is supported on the front side of the tool interface and is configured to support a front-opening unified pod (pod). The port plate extends vertically, covering an upper portion of the tool interface. An aperture having a size and shape that substantially matches a size and shape of a door of a pod is formed in the port plate. The port door has a port door actuator and a port door face attached to the port door actuator. The port door face is movable with respect to the port door actuator along an axis that is perpendicular to the aperture. The port door actuator includes a latch key extending from a front of the port door actuator through the port door face and from a front of the port door face. 
         [0013]    In another embodiment, a method for loading a pod to a load port of a process tool is provided. The method includes mounting the pod onto an advance plate of an advance plate assembly, the advance plate being in a retracted position. The advance plate is advanced from the retracted position to an advanced position. In the advanced position, the pod forms a proximity seal with a port plate of the load port. A latch key is extended from a port door into a latch key receptacle of a door of the pod, which is latched to a lip of the pod. The extending causes a port door face to engage the door of the pod, the port door face being biased by a spring against the door of the pod. The latch key is rotated, causing the door of the pod to disengage from the lip of the pod. The port door is then moved to an open position, the moving causing the door of the pod to be removed from a front opening of the pod and allowing substantially unobstructed access to an interior of the pod. 
         [0014]    In yet another embodiment, a load port is provided that includes a port plate, and a port door. The port plate includes an aperture having a size and shape that substantially matches a size and shape of a door of a pod, the pod having a selected maximum capacity and being capable of holding substrates of a selected diameter. The port door has a port door actuator and a port door face attached to the port door actuator. The port door may be positioned in a closed position in which the port door face substantially occludes the aperture in the port plate and an open position in which the aperture is substantially unobstructed by the port door. The port door actuator includes a latch key extending from a front of the port door actuator through the port door face and from a front of the port door face. The latch key extends from the front side of the tool interface when the port door is in the closed position. 
         [0015]    In yet another embodiment, a method for operating a load port of a process tool is provided. The method includes selecting a pod size of a pod for transporting substrates to and from a process tool. The pod size has a capacity defined as a maximum number of substrates that the pod can contain at one time, and a substrate dimension, the substrate dimension being a size of each of the substrates that the pod can contain. A port plate is selected from among a plurality of port plates. Each of the plurality of port plates has an aperture corresponding to a differing pod size. The selected port plate has an aperture corresponding to a size of the front opening of the pod of the selected pod size. The selected port plate is attached to a tool interface of a load port. A port door face is selected from among a plurality of port door faces of differing sizes. The selected port door face has a shape corresponding to a front surface of a door of the pod of the selected pod size. The selected port door face is attached to the port door actuator. 
         [0016]    The advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, and like reference numerals designate like structural elements. 
           [0018]      FIGS. 1 and 2  are isometric and profile views showing a conventional load port configured to interface with a standard 300 mm, 25-wafer pod. 
           [0019]      FIG. 3  shows an isometric view of an exemplary bridge loadport. 
           [0020]      FIGS. 4A and 4B  show embodiments of a load port for the bridge loadport of  FIG. 3 . 
           [0021]      FIGS. 5 ,  6 ,  7 , and  8  show schematic representations of the loadport of  FIG. 4B  in various stages of operation. 
           [0022]      FIG. 9  shows a schematic representation of a control system for the bridge loadport of  FIG. 3 . 
           [0023]      FIGS. 10A ,  10 B,  10 C, and  10 D show the bridge loadport of  FIG. 3  in various configurations. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well known process operations and implementation details have not been described in detail in order to avoid unnecessarily obscuring the invention. 
         [0025]      FIG. 3  shows an exemplary bridge loadport  100  having a tool interface  120  having a generally vertically extending plate. In one embodiment, tool interface  120  conforms to an industry standard BOLTS interface, and is configured to substantially cover one end of a process tool, such as process tool  40  shown in  FIG. 1 . Bridge loadport  100  also includes an advance plate assembly  150  having an advance plate  152  for mounting a pod as described in further detail below. Advance plate assembly  150  includes an elevator mechanism  156  configured to raise and lower advance plate  152  for purposes that will be made clear below with reference to  FIGS. 10A-10D . In one embodiment, elevator mechanism  156  is implemented using a linear actuator, such as a belt drive, lead screw, or other servo actuator as would occur to those skilled in the art. In addition, advance plate assembly  150  includes an internal actuator for moving the advance plate  152  from a retracted position, which is spaced from tool interface  120  to an advanced position, proximate tool interface  120 . 
         [0026]    Bridge loadport  100  also includes a load port  105  having a port plate  140 . Port plate  140  defines an aperture  142  that is shown substantially occluded by port door face  132  of port door  130 . In one embodiment, port plate  140  is attached to a frame (not visible in  FIG. 3 ) of bridge loadport  100  using a releasable attaching means such as a plurality of screws or one or more latches. A partial cross section view of loadport  105  is shown in  FIG. 4A . It can be seen here that port plate  140  is attached to frame  145  by screws  147 . In addition, port door face  132  is retained to port door actuator  136  by a coupling. In one embodiment, the coupling simply fixes port door face  132  to port door actuator  136  in the absence of springs  134 . For example, the coupling could include a plurality of screws, latches, clips, etc. In another embodiment, the coupling allows for relative movement between port door face  132  and port door actuator  136 . In this embodiment, the coupling could include one or more alignment means which permit relative movement only in the direction perpendicular to the plane of the port door face. 
         [0027]    Such alignment means may be formed by the axial shafts of the two latch keys  160 , in combination with corresponding surfaces in the port door, or additional alignment means (not shown) may be provided such as a linear bearing, alignment pins, etc., to ensure port door face smoothly moves with one degree of freedom along a single axis perpendicular to port door actuator  130 , substantially preventing rotational movement or translational movements along other axes. The additional alignment means can also include a catch for retaining port door face  132  to port door  136 . In either embodiment, the coupling may be cooperative with any of a plurality of port door faces of differing sizes and shapes, depending on the size of pod  70 . 
         [0028]    Although represented as helical springs, springs  134  may be implemented in any suitable fashion, and may, for example, be formed integrally with port door face  132  or port door actuator  136 . Port door face, e.g., may be made from a suitable plastic material, wherein at least the front surface is formed from a material sufficiently stiff to meet flatness standards promulgated for process tool interface port doors by Semiconductor Equipment and Materials International (SEMI). In one embodiment, port door face  132  includes an extended rim  138 , shaped to improve the air flow and resulting proximity seal between port door face  132  and aperture  142  of port plate  140 . 
         [0029]    Pod  70  includes an interior space  73  enclosed by a pod door  74 . Pod door  74  includes, for each latch key  160 , a latch key receptacle  80  (only one being visible in  FIG. 4A ) having an internal shoulder  82 . In  FIG. 4A , pod  70  is mounted to a support  75  capable of moving left and right to advance pod  70  to port plate  140  for loading and to retract pod  70  from port plate  140  for unloading.  FIG. 4B  shows a second embodiment wherein pod  70  is mounted to an advance plate  152 , which is moved left and right by advance plate assembly  150 , which is shown in more detail in  FIG. 3 . 
         [0030]      FIGS. 5-8  show various stages of operation of load port  105 . It should be noted that these operations apply both to the embodiments of  FIG. 4A  and  FIG. 4B . In  FIG. 5 , the pod support, in this case advance plate  152 , is moved to the advanced position, thereby bringing front flange  79  of pod  70  to port plate  140 . In one embodiment, front flange  70  is brought sufficiently close to port plate  140  to form a proximity seal therewith. 
         [0031]    In one embodiment, port door actuator  136  moves forward after pod  70  is moved to the advanced position, the forward movement of port door actuator  136  causing springs  134  to compress and latch keys  160  to be extended into latch key receptacles  80 . In another embodiment, port door actuator  36  is moved into the forward position prior to or during the advance of pod  70 . In either case, latch keys  160  are inserted into latch key receptacles  80  and springs  134  are in a compressed state, biasing port door face  132  into engagement with pod door  74 . The movement of port door actuator is effectuated by mechanism  135  shown by way of example in  FIG. 4A . Mechanism  135  is capable of moving port door  130  on a Y and a Z axis, the Y-axis being left and right as viewed in  FIG. 5 , and the Z-axis being up and down. 
         [0032]    In  FIG. 6 , latch key  160  is rotated 90° to unlatch the pod door from the pod. Port door actuator  136  includes an actuator mechanism (not shown) such as a servo or solenoid causing latch key  160  to rotate. Rotation of latch key  160  interacts with an internal mechanism (not shown) in pod door  74 . The internal mechanism causes pod door latches to retract from slots (not shown) formed in lip  76  of pod  70 , thereby releasing pod door  74  from pod  70 . Such a mechanism is described in more detail in U.S. Pat. Nos. 4,995,430 and 6,502,869, previously incorporated herein by reference. In addition, the rotation of latch keys  160  cause the pod door  74  to be coupled to port door  30 , due to interference between cross bar  164  (see  FIG. 4A ) and internal shoulder  82  of pod door  74 . 
         [0033]    In  FIG. 7 , port door  130  is shown moved a small distance away from aperture  142 , allowing springs  13  to decompress slightly. In the position shown in  FIG. 7 , the back edges of cross bar  164  ( FIGS. 4A ,  4 B,  5 ) of latch key  160  just engage internal shoulders  82  of latch key receptacles  80  formed in pod door  74 . Note that springs  134  remain in a compressed state, exerting a force against port door face  132 , which in turn is pressed against pod door  74 . Resulting friction between port door face  132  and pod door  74  ensures that there is no relative movement between pod door  74  and port door face  132 . Port door actuator  136  continues to move in a rearward direction from the position shown in  FIG. 7 , as shown in  FIG. 8 , wherein pod door  74  is removed entirely away from pod  70 . From this position, port door  30 , along with pod door  74 , may move down using an actuator such as actuator  132  shown in  FIG. 4A . Once port door  30  is moved down, access to substrates  78  in pod  70  becomes substantially unobstructed either by pod door  74  or port door  30 . 
         [0034]    Replacement of pod door  74  can be achieved by performing, in reverse, the steps described above with reference to  FIGS. 4B through 8 . Specifically, port door actuator  130  is moved forward from the position shown in  FIG. 8  until pod door  74  is positioned within pod lip  76 , as shown in  FIG. 7 . Then, port door actuator  130  continues its forward movement until cross bar  164  of latch key  160  disengages from internal shoulder  82  in latch key receptacle  80 , as shown in  FIG. 6 . Then, the latch key is rotated 90° to a vertical position shown in  FIG. 5 , causing the pod door  74  to engage lip  76  of pod  70 . Then, advance plate  152  retracts to the retracted position shown in  FIG. 4B , and optionally, port door actuator  136  moves to a retracted position. 
         [0035]      FIG. 9  shows an exemplary control system  190  for controlling the operations of bridge loadport  100 , described above with reference to  FIGS. 3-8 . Control system  190  includes a control unit  192  which is in communication with an external control system  195 . In one embodiment, external control system  195  may provide load and unload directives to control unit  192 , in response to which control unit  192  operates bridge loadport  100  to load and unload a pod. Advance plate assembly  150  (or other support system such as support  75  shown in  FIG. 4A ) includes an advance actuator  153  for moving the pod  70  between the retracted and advanced positions described previously. Advance plate assembly  150  may include a pod sensor  155  that detects a presence of a pod on the advance plate. For example, pod sensor  155  may be implemented using a microswitch or a proximity sensor to detect when a pod is properly mounted on advance plate  152 . Pod sensor  155  may further be adapted to sense the particular type or configuration of pod which has been placed on the loadport, or the loadport control unit  192  may receive a signal from the external control system  195  conveying such information. 
         [0036]    Upon receiving a “load” directive from external control system  195 , control unit  192  detects whether a pod is mounted by way of pod sensor  155 , then causes advance plate  152  to move to the advanced position (shown, e.g., in  FIG. 5 ) by activating advance actuator  153 . Control unit  192  also actuates port door mechanism  132  (shown in  FIG. 4A ) to cause the port door actuator  136  to move forward so that the latch keys  160  extend into latch key receptacles  80  as shown in  FIG. 5 . Control unit  192  then causes port door actuator  136  to rotate the latch keys  160  to disengage pod door  74  from outer lip  76  of pod  70 . Control unit  192  then actuates port door mechanism  32  to cause port door  30  to move from the closed position to the open position described above. These operations are performed substantially in reverse upon receipt by control unit  190  of an “unload” directive from external control system  195 . In one embodiment, control unit  192  also operates elevator  156  shown in  FIG. 3 , to raise and lower advance plate assembly  150 , for reasons that will be made clear in the discussion below referencing  FIGS. 10A-10D . 
         [0037]    Bridge loadport  100  described above may be easily reconfigured for different size pods by replacing port plate  140  and port door face  132 .  FIGS. 10A-10D  show exemplary configurations. In  FIG. 10A , bridge loadport  100  includes a port plate  140 ′ having an aperture  142 ′ sufficiently tall and wide to accommodate a large capacity pod designed to contain a maximum of 25 450 mm wafers. In  FIG. 10B , bridge loadport  100  includes a port plate  140 ″ having an aperture  142 ″ sufficiently tall and wide to accommodate a low capacity pod designed to contain a maximum of 10 wafers 450 mm wafers. Since a pod of this capacity has a lower profile, advance plate assembly  150  is lifted from the position shown in  FIG. 10A  to ensure alignment between the pod door and port door face  132  and between latch keys  160  and the latch key receptacles formed on the pod. 
         [0038]    Advance plate assembly  150  may be lifted by elevator  156  shown by way of example in  FIG. 3 . In one embodiment, elevator  156  is manually operated, e.g., by using a manually operated vertically adjustable support or by manually removing advance plate assembly  150  from a first location on and reattaching advance plate assembly  150  to load port  100  at a different elevation. In another embodiment, elevator  156  is automatically adjusted in response to signals from control unit  192  ( FIG. 9 ). 
         [0039]    In  FIG. 10C , bridge loadport  100  includes a port plate  140 ′″ having an aperture  142 ′″ sized to correspond with a low capacity pod designed to contain a maximum of 10 wafers each 300 mm in diameter. Since these wafers have a smaller diameter, the pod used to transport them is not as wide, and therefore aperture  142 ′″ is not as wide as the apertures  142 ′ and  142 ″ shown in  FIGS. 10A and 10B , respectively.  FIG. 10D  shows a bridge loadport  100  configured to cooperate with a standard 25 300 mm wafer, pod, substantially as shown in  FIG. 3 , but presented again here for comparison with configurations in  FIGS. 10A-10C . 
         [0040]    While  FIGS. 10A through 10D  show by way of example, pods and loadports configured for receiving and storing semiconductor wafers, other substrate types, such as magnetic media, LCD panels, etc., can be received and stored using loadports and pods as described above. It should also be recognized that various mechanisms, aside from the spring-biased door face described above with reference to  FIGS. 4-8 , may be used to retain a pod door to the port door. For example, suction means, or the twist and pull latch key mechanism described in the above-mentioned U.S. Pat. No. 6,502,869. The interchangeable port plates and port door faces allows easy reconfiguration of a load port that is initially configured to receive pods of a first size to be subsequently configured to receive pods of a second size, wherein the first and second pod sizes can differ with respect to a lot size difference, a substrate dimension difference, or both. 
         [0041]    Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.