Patent Publication Number: US-7594789-B2

Title: Overhead transfer flange and support for suspending a substrate carrier

Description:
This application is a continuation of and claims priority to U.S. patent application Ser. No. 10/764,820, filed Jan. 26, 2004, which claims priority to U.S. Provisional Application Ser. No. 60/443,153, filed Jan. 27, 2003. Each of these applications is hereby incorporated by reference herein in its entirety for all purposes. 
   CROSS REFERENCE TO RELATED APPLICATIONS 
   The present application is related to the following commonly-assigned, co-pending U.S. patent applications, each of which is hereby incorporated by reference herein in its entirety: 
   U.S. patent application Ser. No. 10/650,310, filed Aug. 28, 2003 and titled “System For Transporting Substrate Carriers”; 
   U.S. patent application Ser. No. 10/650,312, filed Aug. 28, 2003 and titled “Method and Apparatus for Using Substrate Carrier Movement to Actuate Substrate Carrier Door Opening/Closing”; 
   U.S. patent application Ser. No. 10/650,481, filed Aug. 28, 2003 and titled “Method and Apparatus for Unloading Substrate Carriers from Substrate Carrier Transport Systems”; 
   U.S. patent application Ser. No. 10/650,479, filed Aug. 28, 2003 and titled “Method and Apparatus for Supplying Substrates to a Processing Tool”; 
   U.S. Patent Application Ser. No. 60/407,452, filed Aug. 31, 2002 and titled “End Effector Having Mechanism For Reorienting A Wafer Carrier Between Vertical And Horizontal Orientations”; 
   U.S. Patent Application Ser. No. 60/407,337, filed Aug. 31, 2002, and titled “Wafer Loading Station with Docking Grippers at Docking Stations”; 
   U.S. patent application Ser. No. 10/650,311, filed Aug. 28, 2003 and titled “Substrate Carrier Door having Door Latching and Substrate Clamping Mechanism”; 
   U.S. patent application Ser. No. 10/650,480, filed Aug. 28, 2003 and titled “Substrate Carrier Handler That Unloads Substrate Carriers Directly From a Moving Conveyor”; 
   U.S. Provisional Application Ser. No. 60/443,087, filed Jan. 27, 2003 and titled “Methods and Apparatus for Transporting Wafer Carriers”; 
   U.S. Provisional Application Ser. No. 60/443,001, filed Jan. 27, 2003, and titled “Systems and Methods for Transporting Wafer Carriers Between Processing Tools”; and 
   U.S. Provisional Application Ser. No. 60/443,115, filed Jan. 27, 2003, and titled “Apparatus and Method for Storing and Loading Wafer Carriers”. 

   FIELD OF THE INVENTION 
   The present invention relates generally to semiconductor device manufacturing, and more particularly to an overhead transfer flange of a substrate carrier and a support for suspending the substrate carrier via the overhead transfer flange. 
   BACKGROUND OF THE INVENTION 
   Semiconductor devices are made on substrates, such as silicon substrates, glass plates, etc., for use in computers, monitors, and the like. These devices are made by a sequence of fabrication steps, such as thin film deposition, oxidation or nitridization, etching, polishing, and thermal and lithographic processing. Although multiple fabrication steps may be performed in a single processing station, substrates typically must be transported between processing stations for at least some of the fabrication steps. 
   Substrates generally are stored in cassettes or pods (hereinafter referred to collectively as “substrate carriers”) for transfer between processing stations and other locations. Although substrate carriers may be carried manually between processing stations, the transfer of substrate carriers is typically automated. For instance, automatic handling of a substrate carrier may be performed by a robot, which lifts the substrate carrier by means of an end effector. As one example, end effectors have been proposed that lift a substrate carrier by engaging a flange provided at the top of the substrate carrier. One known type of end effector includes a support plate and fingers extending downwardly and inwardly from the support plate to define a “T”-shaped slot. The slot may be moved horizontally over and around the carrier flange. Pins may be provided that protrude upwardly from the end effector fingers to mate with detents provided on the flange. 
   Successful transport and transfer of substrate carriers requires that a substrate carrier position be controlled with a high degree of precision. It is desirable to provide a substrate carrier support and an overhead transfer flange that together facilitate proper substrate carrier positioning. 
   SUMMARY OF THE INVENTION 
   In a first aspect of the invention, a first apparatus is provided for use in supporting a substrate carrier. The first apparatus includes an overhead transfer flange adapted to couple to a substrate carrier body and an overhead carrier support. The overhead transfer flange has a first side and a second side opposite the first side that is wider than the first side. 
   In a second aspect of the invention, a substrate carrier is provided. The substrate carrier includes (1) a substrate carrier body adapted to support one or more substrates; and (2) an overhead transfer flange coupled to the substrate carrier body and adapted to couple to an overhead carrier support. The overhead transfer flange has a first side and a second side opposite the first side that is wider than the first side. 
   In a third aspect of the invention, a second apparatus is provided for use in supporting a substrate carrier. The second apparatus includes an overhead carrier support adapted to suspend a substrate carrier via an overhead transfer flange. The overhead carrier support has a first side and a second side opposite the first side that is wider than the first side. Numerous other aspects, as are methods and systems in accordance with these and other aspects of the invention. 
   Other features and aspects of the present invention will become more fully apparent from the following detailed description of exemplary embodiments, the appended claims and the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective elevational view of a portion of an overhead transfer conveyor, as the overhead transfer conveyor transports a first and a second carrier; 
       FIG. 2  is a perspective elevational view, exploded along the in-line direction, of the assembly of the overhead carrier support and the overhead transfer flange shown in  FIG. 1 ; 
       FIG. 3  is a bottom plan view, of the exploded assembly of the overhead carrier support and the overhead transfer flange shown in  FIG. 2 ; 
       FIG. 4  is a bottom plan view of the exploded assembly of the overhead carrier support and the overhead transfer flange shown in  FIG. 2 ; 
       FIGS. 5 and 6  are perspective views of respective portions of the first blade receiver of the overhead carrier support, and of the first blade of the overhead transfer flange (including cross-sections); 
       FIGS. 7-8  are simple cross-sectional views of the same portions of the overhead carrier support and the overhead transfer flange; 
       FIG. 9  is a perspective cut-away view of a portion of the overhead transfer conveyor of  FIG. 1  utilizing the inventive coupling between the overhead carrier support and the overhead transfer flange, wherein an object, present in the path through which the overhead transfer conveyor carries a carrier, strikes the carrier; 
       FIGS. 10-12  are cross-sectional views of respective portions of the first blade receiver of the overhead carrier support, and the first blade of the overhead transfer flange, which depict a decoupling process that results in a carrier dislodging from the overhead transfer conveyor of  FIG. 1 ; 
       FIG. 13  is a cross sectional view of a portion of the first blade receiver of the overhead carrier support and of the first blade of the overhead transfer flange illustrating an alternative embodiment of such components; 
       FIG. 14  is a perspective view of a plurality of shelves configured to support substrate carriers via an overhead transfer flange in accordance with the present invention; and 
       FIG. 15  is a perspective view of the shelves of  FIG. 14  wherein the top shelf supports a substrate carrier via its overhead transfer flange. 
   

   DETAILED DESCRIPTION 
   The present invention provides an overhead transfer flange for a substrate carrier and a corresponding overhead support for supporting the carrier via the overhead transfer flange. The substrate carrier may be a single substrate carrier adapted to store only one substrate or a multiple substrate carrier adapted to store a plurality of substrates. In one aspect, the overhead support is adapted such that the support provides a capture window (for capturing the overhead transfer flange) that varies from a wider window to a narrower window in a direction in which the overhead transfer flange can approach the support. In a second aspect the overhead transfer flange and overhead support are adapted such that when the overhead transfer flange is supported by the overhead support, the overhead transfer flange is prevented from moving relative to the overhead support in any direction except vertically. In a further aspect the overhead transfer flange and overhead support are adapted such that if a substrate carrier supported thereby is impacted in a direction opposite to the direction in which the carrier is traveling, the carrier&#39;s overhead transfer flange will decouple from the overhead support, allowing the carrier to fall. 
   Each of these aspects is considered inventive on its own, however, in at least one embodiment the overhead transfer flange and overhead support may embody each of the aspects described above. The figures and the following description thereof provide a specific configuration that embodies each of the inventive aspects identified above. The configuration of  FIGS. 1-12 , is merely exemplary and it will be understood that alternative configurations may be designed that function in accordance with the invention. 
     FIG. 1  is a perspective elevational view of a portion  101  of an overhead transfer conveyor  103 , as the overhead transfer conveyor  103  transports a first and a second carrier  105   a ,  105   b  in a first in-line direction  107  along a moveable track  109  of the overhead transfer conveyor  103 . An inventive first overhead carrier support  111   a  of the overhead transfer conveyor  103  supports the first carrier  105   a  via an inventive first overhead transfer flange  113   a  fixed to and centered above the first carrier  105   a , and an inventive second overhead carrier support  111   b  of the overhead transfer conveyor  103  supports the second carrier  105   b  via an inventive second overhead transfer flange  113   b  fixed to and centered above the second carrier  105   b . Other positions of the overhead transfer flanges  113   a ,  113   b  relative to the substrate carriers  105   a ,  105   b  may be employed. 
     FIG. 2  is a perspective elevational view, exploded along the in-line direction  107 , of the assembly of the overhead carrier support  111   a  and the overhead transfer flange  113   a  shown in  FIG. 1 . The overhead carrier support  111   a  comprises a support plate  115  and a coupling clamp  117  fixed atop the support plate  115  and adapted to securely couple the overhead carrier support  111   a  to the moveable track  109  of the overhead transfer conveyor  103 . The overhead carrier support  111   a  further includes a flexible hanger  119 , also fixed atop the support plate  115 , and adapted to provide additional support for the overhead carrier support  111   a  along the moveable track  109 . A first blade receiver  121   a  is fixed below a first side  123   a  of the support plate  115 , and a second blade receiver  121   b  is fixed below a second side  123   b  of the support plate  115 , opposite the first side  123   a . The various components of the overhead carrier support  111   a  may be coupled together using any suitable coupling mechanism (e.g., screws, bolts, adhesives, etc.). All or a portion of the components of the overhead carrier support  111   a  may be integrally formed. 
   The overhead transfer flange  113   a  comprises a flange plate  125  adapted to attach to a carrier (e.g., the first carrier  105   a  ( FIG. 1 )) via a suitable fastening mechanism such as fastener holes  127  or the like. A first blade  129   a  extends down from a first side  131   a  of the flange plate  125 , and a second blade  129   b  (obscured in  FIG. 2  but see  FIG. 3 ) extends down from a second side  131   b  of the flange plate  125 . A stiffening extension  133  extends down from a third side  131   c  of the flange plate  125 . 
   As will be explained further below, the first blade receiver  121   a  is adapted to receive the first blade  129   a , and the second blade receiver  121   b  is adapted to receive the second blade  129   b . And as will be also explained further below, the support plate  115 , the first blade receiver  121   a , and the second blade receiver  121   b  of the overhead carrier support  111   a  define an overhead flange capture window  137  through which the overhead transfer flange  113   a  is adapted to pass prior to the first and second blade receivers  121   a ,  121   b  of the overhead carrier support  111   a  receiving the respective first and second blades  129   a ,  129   b  of the overhead transfer flange  113   a.    
     FIG. 3  is a bottom plan view of the exploded assembly of the overhead carrier support  111   a  and the overhead transfer flange  113   a  shown in  FIG. 2 . The overhead carrier support  111   a  and the overhead transfer flange  113   a  are aligned along a vertical plane  135  coinciding with a centerplane  135 A of the overhead carrier support  111   a  and a centerplane  135 B of the overhead transfer flange  113   a . Referring to  FIG. 1 , the vertical plane  135  is preferably aligned with the vertically-oriented moveable track  109  of the overhead transfer conveyor  103 , however other orientations (e.g., at an angle, or parallel but offset) can also be provided in accordance with the present invention. 
   The overhead flange capture window  137  appears as a line in the view of  FIG. 3 . The overhead carrier support  111   a  is adapted to permit the overhead transfer flange  113   a  to advance toward the overhead carrier support  111   a  from the relative position of the overhead transfer flange  113   a  shown in the view of  FIG. 3  and through the overhead flange capture window  137 . 
   The first blade receiver  121   a  is oriented at a first angle  139   a  to the centerplane  135 A of the overhead carrier support  111   a , and the second blade receiver  121   b  is oriented at a second angle  139   b  to the centerplane  135 A of the overhead carrier support  111   a . Preferably, the first angle  139   a  and the second angle  139   b  are equivalent so that the second blade receiver  121   b  mirrors the first blade receiver  121   a  from across the centerplane  135 A of the overhead carrier support  111   a . In one embodiment, a third angle  141  between the first blade receiver  121   a  and the second blade receiver  121   b  is about 60 degrees. Other angles may be employed (e.g., including angles as small as about 10-20 degrees). As will be apparent, the selection of the extent of the third angle  141  is related to other aspects of the geometry of the overhead carrier support  111   a  and the overhead transfer flange  113   a , as will be explained below. 
   The first blade  129   a  is oriented at a fourth angle  139   c  to the centerplane  135 B of the overhead transfer flange  113   a , and the second blade  129   b  is oriented at a fifth angle  139   d  to the centerplane  135 B of the overhead transfer flange  113   a . Preferably, the fourth angle  139   c  and the fifth angle  139   d  are equivalent so that the second blade  129   b  mirrors the first blade  129   a  from across the centerplane  135 B of the overhead transfer flange  113   a . In one embodiment, a sixth angle  143  between the first blade  129   a  and the second blade  129   b  is about 60 degrees. Other angles may be employed. For proper interaction between the overhead carrier support  111   a  and the overhead transfer flange  113   a , the third angle  141  and the sixth angle  143  are preferably substantially equivalent. 
     FIG. 4  is a bottom plan view of the exploded assembly of the overhead carrier support  111   a  and the overhead transfer flange  113   a  shown in  FIG. 2 .  FIG. 4  is similar to  FIG. 3  except that the overhead transfer flange  113   a  has advanced from the position relative to the overhead carrier support  111   a  (see phantom outline) that is occupied in the view of  FIG. 3 , passed through the overhead flange capture window  137 , and is shown in a nested position with respect to the overhead carrier support  111   a . In this nested position, the first and second blades  129   a ,  129   b , which together substantially form a cropped “V” shape or a cropped chevron, are in close spaced relation with the respective first and second blade receivers  121   a ,  121   b  (which also substantially form a cropped “V” shape or a cropped chevron), but are not yet mated with the same. This may be referred to as a staging position for the overhead transfer flange  113   a.    
   Although advancement of the overhead transfer flange  113   a  through the overhead flange capture window  137  may be employed to mate the overhead transfer flange  113   a  with the overhead carrier support  111   a , the present invention provides, and the discussion below explains, that the overhead transfer flange  113   a  also can be raised up from below the overhead carrier support  111   a  to assume the nesting position of  FIG. 4  (rather than approaching with a horizontal component). A continuation of the in-line advancement similar to that shown in  FIG. 4  can then take place for the first blade  129   a  and the second blade  129   b  of the overhead transfer flange  113   a  to respectively mate with and be securely supported by the first blade receiver  121   a  and the second blade receiver  121   b  of the overhead carrier support  111   a . Section V-V as depicted in  FIG. 4  is representative of the cross-sections cut normal to the first blade receiver  121   a  and the first blade  129   a  as shown and described below with reference to  FIGS. 5-12 . 
     FIGS. 5 and 6  are perspective views of respective portions of the first blade receiver  121   a  of the overhead carrier support  111   a , and of the first blade  129   a  of the overhead transfer flange  113   a  (including cross-sections), and  FIGS. 7-8  are simple cross-sectional views of the same portions of the overhead carrier support  111   a  and the overhead transfer flange  113   a .  FIGS. 5-8  depict the coupling process that results in the first blade receiver  121   a  and the second blade receiver  121   b  (not shown) of the overhead carrier support  111   a  supporting the first blade  129   a  and the second blade  129   b  (not shown) of the overhead transfer flange  113   a.    
   During the coupling process depicted in  FIGS. 5-8 , the first blade receiver  121   a  (shown coupled to, and below, the support plate  115  of the overhead transfer flange  113   a ) and the first blade  129   a  move relative to each other, and the second blade receiver  121   b  (not shown) and the second blade  129   b  (not shown) also move relative to each other. As between each respective pairing of blade and blade receiver, the relative motion is substantially similar, except that a relative motion between the second blade receiver  121   b  (not shown) and the second blade  129   b  (not shown) will tend to be the reverse of, or the mirror-image of, the relative motion between the first blade receiver  121   a  and the first blade  129   a  shown in  FIGS. 5-8  and  FIGS. 10-12 . As such,  FIGS. 5-8  and  FIGS. 10-12  illustrate only the relative motion between the first blade receiver  121   a  and the first blade  129   a , with the relative motion of the other blade-blade receiver pairing being understood to be the mirror image of the same. 
   In  FIGS. 5-8 , as well as in  FIGS. 10-12 , the support plate  115  and first blade receiver  121   a  are shown as two pieces, coupled together. However, the support plate  115  and the first blade receiver  121   a  may be a single piece. 
   Referring to  FIG. 5 , a first receiving surface  121   aa  of the first blade receiver  121   a  is preferably planar, and is adapted to slidably communicate with a first blade surface  129   aa  (obscured) of the first blade  129   a , also preferably planar, in conjunction with the first blade receiver  121   a  mating with the first blade  129   a . A second receiving surface  121   ab  (obscured) of the first blade receiver  121   a  is also preferably planar, and is adapted to contact a first blade edge  129   ab  of the first blade  129   a . In at least one embodiment of the invention, the first blade edge  129   ab  is adapted to settle into the first blade receiver  121   a  by the force of gravity and achieve contact with an extended vertex  121   ac  of the first blade receiver  121   a , defined by the intersection between the first blade receiver&#39;s first receiving surface  121   aa  and the first blade receiver&#39;s second receiving surface  121   ab . The first receiving surface  121   aa  of the first blade receiver  121   a  is also adapted to achieve contact with the first blade edge  129   ab  if necessary. An elongated lip  121   ad  of the first blade receiver  121   a  is preferably located at a right most extent  121   ae  of the first blade receiver  121   a . Other locations of the lip  121   ad  may be employed. 
   The first blade  129   a  of the overhead transfer flange  113   a  is shown in  FIG. 5  in a convenient staging position relative to the first blade receiver  121   a  of the overhead carrier support  111   a  as shown and described above with reference to  FIG. 4 , the view being that of section V-V, as indicated in  FIG. 4 . One reason why this staging position is convenient is because the first blade  129   a  is close to a lodging position within the first blade receiver  121   a , requiring only to be urged toward the first blade receiver  121   a  in the in-line direction  107  (see  FIG. 1 ) and lowered with respect to the first blade receiver  121   a  to achieve such lodging. Another reason why the staging position shown is convenient is that the first blade  129   a  can reach the position from multiple staging position access directions (e.g., a first staging position access direction  145   a , a second staging position access direction  145   b , etc.). 
   The first staging position access direction  145   a  is the horizontal access direction as shown and described with reference to  FIG. 4  above. If sufficient in-line spacing exists between successive carrier supports (e.g., between the first carrier  105   a  and the second carrier  105   b  of  FIG. 1 ) along the conveyor (e.g., the overhead transfer conveyor  103  of  FIG. 1 ), the first staging position access direction  145   a  can easily be accommodated, and has the advantage of continuity and simplicity, since a simple continuation of motion of the overhead transfer flange  113   a  in the in-line direction  107  (see  FIG. 1 ), past the staging position shown, is required to place the first blade  129   a  directly above a lodging position within the first blade receiver  121   a.    
   The second staging position access direction  145   b  is a practical alternative to the first staging position access direction  145   a  when carriers are closely spaced along the conveyor (e.g., as closely spaced as the first carrier  105   a  and the second carrier  105   b  are along the moveable track  109  of the overhead transfer conveyor  103  as shown in  FIG. 1 ). The second staging position access direction  145   b  is a vertical access direction, and it takes advantage of the fact that the chevron formed by the first blade  129   a  and the second blade  129   b  can nest closely behind the chevron formed by the first blade receiver  121   a  and the second blade receiver  121   b  without the blades coming in contact with the blade receivers  121   a ,  121   b.    
   Because the chevron formed by the first blade  129   a  and the second blade  129   b  can nest behind the chevron formed by the first blade receiver  121   a  and the second blade receiver  121   b , the overhead transfer flange  113   a  can rise up from below the overhead carrier support  111   a  and move upwards past the first blade receiver lip  121   ad  and past the rightmost extent  121   ae  of the first blade receiver  121   a , such that the first blade  129   a  rises above the first blade receiver  121   a  from behind the first blade receiver  121   a  (e.g., behind in the in-line direction  107 ) to reach the convenient staging position shown in  FIGS. 4 and 5 . The second staging position access direction  145   b  has the advantage of introducing the overhead transfer flange  113   a  to the overhead transfer conveyor  103  at a position along the length of moveable track  109  of the overhead transfer conveyor  103  that is very close to the position at which the overhead carrier support  111   a  will support the overhead transfer flange  113   a , so that only a minimum of in-line, lateral motion between the overhead transfer flange  113   a  and the overhead carrier support  111   a  is required to enable the overhead transfer flange  113   a  to lodge in the overhead carrier support  111   a . For example, during raising of the overhead transfer flange  113   a , a footprint of the overhead transfer flange  113   a  may overlap a footprint of the overhead carrier support  111   a.    
   Referring to  FIG. 6 , the first blade receiver  121   a , the first blade surface  129   aa , and the rightmost extent  121   ae  of the first blade receiver  121   a , all described above with reference to  FIG. 5 , are shown. The overhead transfer flange  113   a  has begun to move in the in-line direction  107  (see  FIG. 4 ) such that relative motion between the overhead transfer flange  113   a  and the overhead carrier support  111   a  is occurring. Specifically the overhead transfer flange  113   a  has moved toward the overhead carrier support  111   a  such that the first blade edge  129   ab  is now directly above the first blade receiver lip  121   ad , and is aligned with the rightmost extent  121   ae  of the first blade receiver  121   a.    
   A first clearance  147   a  exists between the first blade edge  129   ab  of the first blade  129   a  and the lip  121   ad  of the first blade receiver  121   a . In one embodiment of the invention, the first clearance  147   a  is preferably about 3 mm or less, and more preferably about 1.5 mm or less. Other clearances may be employed in addition, a second clearance  147   b  exists between the flange plate  125  ( FIG. 2 ) of the overhead transfer flange  113   a  and the support plate  115  of the overhead carrier support  111   a . In one embodiment of the invention, the second clearance  147   b  is also preferably about 3 mm or less, and more preferably about 1.5 mm or less. Other clearances may be employed. It is preferable to keep clearances such as the first clearance  147   a  and the second clearance  147   b  at a minimum since space in the clean room of a typical semiconductor device manufacturing facility can be exceptionally expensive. 
   It should be noted that when the overhead transfer flange  113   a  approaches the overhead carrier support  111   a  along the in-line direction  107  (see  FIG. 1 ) the first blade  129   a  does not approach the first blade receiver  121   a  directly (e.g., parallel to the cross sections of  FIG. 5 ) such that a particular point along the first blade  129   a  (e.g., point  129   aba  along the first blade edge  129   ab  of the first blade  129   a , as shown in  FIG. 6 ) will pass in a normal direction to the first blade receiver  121   a  and over a corresponding point (e.g., point  121   ada  along the first blade receiver lip  121   ad , as shown in  FIG. 6 ) on the first blade receiver lip  121   ad . Rather, a combination of normal convergence between the first blade  129   a  and the first blade receiver  121   a  (e.g., the “line” of the first blade edge  129   ab  remains parallel with the “line” of the first blade receiver lip  121   ad  while advancing toward the same) and lateral, relative motion between the first blade  129   a  and the first blade receiver  121   a  (e.g., the first blade edge point  129   aba  moving laterally past the first blade receiver lip point  121   ada ) will occur as the overhead transfer flange  113   a  advances toward the overhead carrier support  111   a  in the in-line direction  107  (see  FIG. 1 ). 
   As such the respective points (not separately shown) along the overhead transfer flange  113   a  and the overhead carrier support  111   a  at which the cross-sections of  FIGS. 5-8  and  FIGS. 10-12  are taken are not all to be presumed to be those of cross-sections V-V of  FIG. 4  but should instead be presumed to change from figure to figure according to the distance between the overhead transfer flange  113   a  and the overhead carrier support  111   a , (e.g., cross sectional views taken at points on the overhead transfer flange  113   a  and on the overhead carrier support  111   a  close to that of section V-V of  FIG. 4 ), without necessarily affecting the manner in which the overhead transfer flange  113   a  and the overhead carrier support  111   a  are depicted therein. 
   Referring to  FIG. 7 , the overhead transfer flange  113   a  has moved further relative to the overhead carrier support  111   a  such that the first blade edge  129   ab  is directly above the first blade receiver&#39;s extended vertex  121   ac . With the overhead transfer flange  113   a  in this position relative the overhead carrier support  111   a , the first blade  129   a  can be allowed to drop relative to the first blade receiver  121   a  along a vertical path  149   a  such that the first blade edge  129   ab  can achieve linear contact with the first blade receiver&#39;s extended vertex  121   ac.    
   Alternatively, the first blade  129   a  can be urged further toward the first blade receiver  121   a  along a horizontal path  149   b  in the same horizontal plane, resulting in linear contact between the first blade edge  129   ab  and the first blade receiver&#39;s second receiving surface  121   ab . As yet another alternative, the first blade  129   a  can be moved through a sloping path  149   c  having both horizontal and vertical components to achieve a similar result as that achieved via the sloping path  149   c . The sloping path  149   c  in particular can be achieved by allowing the overhead transfer flange  113   a  to lower or drop onto the overhead carrier support  111   a  after the contribution of an initial horizontal velocity component. 
   As an example, the overhead transfer flange  113   a  (e.g., the first carrier  105   a  of which the overhead transfer flange  113  is a part) can be propelled horizontally at the same speed as the moveable track  109  of the overhead transfer conveyor  103  (e.g., by an arrangement of motorized rollers providing a horizontal conveying surface or by any other means). The horizontal speed of the first carrier  105  may be increased, causing the overhead transfer flange  113   a  to “close” with the overhead carrier support  111   a  and the first carrier  105   a  (and the overhead transfer flange  113   a  attached thereto) may be lowered or dropped relative to the overhead carrier support  111   a.    
   A curved path similar to the sloping path  149   c  can begin when the lateral position of the overhead transfer flange  113   a  relative to the overhead carrier support  111   a  is as shown in  FIG. 6 , or even before the first blade edge  129   ab  clears the first blade receiver lip  121   ad , as shown in  FIG. 5 , provided the overhead transfer flange  113   a  passes over the first blade receiver lip  121   ad  without striking the first blade receiver lip  121   ad , and contacts the first blade receiver&#39;s first receiving surface  121   aa , the first blade receiver&#39;s second receiving surface  121   ab , or the first blade receiver&#39;s extended vertex  121   ac.    
   Referring to  FIG. 8 , the overhead transfer flange  113   a  is shown supported by the first blade receiver  121   a , with the first blade  129   a  being lodged within the overhead carrier support  111   a . The first blade edge  129   ab  is in linear contact with the first blade receiver&#39;s extended vertex  121   ac , and the first blade  129   a  is in planar contact with the first blade receiver&#39;s first receiving surface  121   aa.    
   As an example, just prior to the first blade edge  129   ab  achieving linear contact with the first blade receiver&#39;s extended vertex  121   ac , the first blade  129   a  may have slid downward and rightward, with the first blade edge  129   ab  sliding atop and in linear contact with the first blade receiver&#39;s second receiving surface  121   ab . In one embodiment of the invention, the first blade receiver&#39;s second receiving surface  121   ab  is preferably oriented at about a 25-degree to a 30-degree angle to the vertical plane. Such an inclination ensures that the first blade  129   a  will travel expeditiously downward from the point of contact of the first blade edge  129   ab  with the first blade receiver&#39;s second receiving surface  121   ab . Other angles may be employed. 
   Alternatively, the first blade  129   a  may have slid downward and leftward, with the first blade surface  129   aa  sliding atop and in planar contact with the first blade receiver&#39;s first receiving surface  121   aa . In at least one embodiment of the invention, the first blade receiver&#39;s first receiving surface  121   aa  is preferably oriented at about a 25-degree to a 30-degree angle to the vertical plane. Other angles may be employed. 
   While the first blade  129   a  is seated within the first blade receiver  121   a  (and the second blade  129   b  is seated within the second blade receiver  121   b  (see FIGS.  4 - 5 )), the overhead transfer flange  113   a  is advantageously restricted in both lateral directions and in the rearward direction (e.g., opposite the in-line direction  107  (see  FIG. 1 )) by the obstacle to the first blade surface  129   aa  posed by the first blade receiver&#39;s first receiving surface  121   aa . In at least one embodiment of the invention, the blade and receiving surfaces are preferably flat and have complementary orientations with regard to the vertical to ensure close mating communication between the first blade surface  129   aa  and the first blade receiver&#39;s first receiving surface  121   aa . As previously noted, the second blade receiver restricts lateral motion in the same manner. Non-flat surfaces also may be employed. 
   At the same time the overhead transfer flange  113   a  is advantageously restricted in the forward direction (e.g., the in-line direction  107  (See  FIG. 1 )) by the obstacle to the first blade edge  129   ab  posed by the first blade receiver&#39;s second receiving surface  121   ab . The first blade edge  129   ab  may be somewhat rounded (e.g., a sharp corner that is broken, a radiused edge, a truncated cone, etc.) to ensure smooth sliding between the first blade edge  129   ab  and the first blade receiver&#39;s second receiving surface  121   ab  whenever the first blade edge  129   ab  and the first blade receiver&#39;s second receiving surface  121   ab  are caused to slidably communicate. 
   It should be noted, however, that communication between the first blade edge  129   ab  and the first blade receiver&#39;s second receiving surface  121   ab  is expected to occur almost exclusively during the process of depositing the overhead transfer flange  113   a  upon the overhead carrier support  111   a . That is, once the first blade edge  129   ab  is lodged within the first blade receiver&#39;s extended vertex  121   ac , and the first carrier  105   a  (see  FIG. 1 ) is being transported in the in-line direction  107  by the overhead transfer conveyor  103 , there may be relatively little likelihood of the first carrier  105   a  being subjected to a force tending to urge the overhead transfer flange  113   a  forward relative the overhead carrier support  111   a . As will be explained further below, and with reference to  FIGS. 9-12 , it is more likely that the overhead transfer flange  113   a  will be subjected to forces tending to urge it laterally, or forces tending to urge it rearwardly, or a combination of such forces. 
     FIG. 9  is a perspective cut-away view of a portion of the overhead transfer conveyor  103  utilizing the inventive coupling between the overhead carrier support  111   a  and the overhead transfer flange  113   a  to carry the first carrier  105   a  in the in-line direction  107 . An object  151 , present in the path through which the overhead transfer conveyor  103  carries the first carrier  105   a , strikes a corner  105   aa  of the first carrier  105   a . The object  151  may be a piece of machinery such as a robot that has moved away from its intended path due to a programming error, misplaced equipment or any other object. Many other objects or items may be placed, either intentionally or unintentionally, in positions near the overhead transfer conveyor  103  such that a collision with the first carrier  105   a  may take place at the first carrier corner  105   aa.    
   Collisions with the first carrier  105   a  may also be caused by objects (not separately shown) striking the bottom, side, top or rear of the first carrier  105   a . It would be unexpected for an object to strike the first carrier  105   a  from behind, since the moveable track  109  of the overhead transfer conveyor  103  preferably carries substrate carriers at a high rate of speed in the in-line direction  107 . 
   An advantage of the overhead carrier support  111   a  and the overhead transfer flange  113   a  of the present invention is that the first carrier  105   a  can predictably and controllably dislodge from the overhead transfer conveyor  103  when subjected to a rearward or lateral force of a predetermined amount, such as, for example, 3 pounds or more, or preferably 5 pounds or more. That is, in one embodiment of the invention, if the first carrier  105   a  is struck by a force of 1 or 2 pounds, directed toward the first carrier  105   a  from the front or side, the overhead transfer flange  113   a  preferably remains within the overhead carrier support  111   a  so that the first carrier  105   a  continues to be carried by the overhead transfer conveyor  103  in the in-line direction  107 . However, if the first carrier  105   a  is struck by a force of 7 or 8 pounds, directed toward the first carrier  105   a  from the front or side, the overhead transfer flange  113   a  preferably dislodges from the overhead carrier support  111   a  and falls downward away from the overhead transfer conveyor  103  and away from the other substrate carriers being carried by the overhead transfer conveyor  103 . 
   As described above and with respect to  FIG. 1 , when the first carrier  105   a  is being carried by the overhead transfer conveyor  103  along the moveable track  109  in the in-line direction  107 , lateral relative movement, front-to-rear relative movement, and rear-to-front relative movement on the part of the overhead transfer flange  113   a  relative to the overhead carrier support  111   a  is restricted, and in the normal operation of the overhead transfer conveyor  103 , such movement is essentially prevented. Downward movement of the overhead transfer flange  113   a  relative to the overhead carrier support  111   a  is similarly restricted. Upward motion of the overhead transfer flange  113   a  relative to the overhead carrier support  111   a  however is generally unrestricted. 
   The object  151  depicted in  FIG. 9  is likely to subject the first carrier  105   a  to lateral and rearward forces which will vary depending on the speed of the overhead transfer conveyor  103  in the in-line direction  107 , the angle at which the first carrier  105   a  strikes the object  151 , and the width of the first carrier  105   a  (e.g., the distance from the moveable track  109  at which the collision between the object  151  and the first carrier  105   a  takes place). The overhead carrier support  111   a , however, preferably restricts twisting and translating motion of the overhead transfer flange  113   a  in the horizontal plane. As such, in order to prevent damage to the moveable track  109  of the overhead transfer conveyor  103 , the horizontal forces resulting from the collision should be somehow redirected. 
   As viewed from the front of the overhead transfer flange  113   a  in the in-line direction  107 , the first blade receiver&#39;s first receiving surface  121   aa  ( FIG. 5 ) tilts backward, and the horizontally cropped chevron formed by the first blade receiver&#39;s first receiving surface  121   aa  and its counterpart surface (not shown) on the second blade receiver  121   b  (see  FIG. 2 ) increases from a narrow aspect near the front of the overhead transfer flange  113   a  to a wider aspect near the rear of the overhead transfer flange  113   a . This combination of two backward-tilting surfaces forming a rear-outward tapering chevron provides that the mating surface (e.g., the first blade surface  129   aa  and its counterpart surfaces (not shown) on the second blade  129   b  (see  FIG. 2 ) may “ride” upward and rearward with regard to the overhead transfer flange  113   a , sliding along and in mating communication with their corresponding support surfaces as they ride. 
   In operation, the chevron-shaped arrangement of rearward and upward tilting surfaces just described, cooperates with rearward and lateral impact forces to which the first carrier  105   a  may be subjected (e.g., during a collision) to cause the overhead transfer flange  113   a  of the first carrier  105   a  to move upward and rearward relative to the overhead carrier support  111   a  of the overhead transfer conveyor  103 . The overhead transfer flange  113   a  may dislodge from the overhead carrier support  111   a , and thereby cause the first carrier  105   a  to fall from the overhead transfer conveyor  103 . This cooperation is explained below and with reference to  FIGS. 10-12 . 
     FIGS. 10-12  are cross-sectional views of respective portions of the first blade receiver  121   a  of the overhead carrier support  111   a , and the first blade  129   a  of the overhead transfer flange  113   a , which views depict the decoupling process that results in the first carrier  105   a  dislodging from the overhead transfer conveyor  103 . Referring to  FIG. 10 , the force F 1  is applied to the overhead transfer flange  113   a  normal to the direction in which the first blade  129   a  extends as shown in  FIGS. 5 and 6 , and is a force derived from an impact between the first carrier  105   a  and the object  151  as shown in  FIG. 10 . 
   If not for the obstacle posed by the first blade receiver&#39;s first receiving surface  121   aa  to the lateral motion of the first blade  129   a  of the overhead transfer flange  113   a , the force F 1  would urge the first blade  129   a  away from the first blade receiver  121   a  in a lateral direction within the horizontal plane in which the overhead transfer flange  113   a  is shown to reside in  FIG. 8 . However, because the first blade receiver&#39;s first receiving surface  121   aa  blocks direct lateral movement of the overhead transfer flange  113   a  due to the planar communication between the first blade receiver&#39;s first receiving surface  121   aa  and the first blade surface  129   aa , the overhead transfer flange  113   a  reacts to the force F 1  by the first blade surface  129   aa  sliding or “riding” upwards and rearward with respect to the overhead carrier support  111   a  as a whole. 
   As described above, rearward motion of the overhead transfer flange  113   a  relative to the overhead carrier support  111   a  means that the point (not shown) on the overhead transfer flange  113   a  at which the cross section of  FIG. 10  is taken, moves into the page as the first blade surface  129   aa  slides upward along the first blade receiver&#39;s first receiving surface  121   aa , and that cross-sections of the overhead transfer flange  113   a  in  FIGS. 10-12  are taken at different points of the overhead transfer flange  113   a.    
   Referring again to  FIG. 10 , in response to the force F 1 , the first blade surface  129   aa  of the first blade  129   a  rides up the first blade receiver&#39;s first receiving surface  121   aa  of the overhead carrier support  111   a  in direction  153 , which is aligned with the slope  155  of the first blade receiver&#39;s first receiving surface  121   aa . Because the first blade surface  129   aa  of the overhead transfer flange  113   a  and the first blade receiver&#39;s first receiving surface  121   aa  are in planar communication, and because complementary surfaces (not shown) on the other side of the overhead transfer flange  113   a  operate at the same time, the overhead transfer flange  113   a  can tend to retain, as it rises, the horizontal orientation it assumed while being carried by the overhead carrier support  111   a  along the overhead transfer conveyor  103  (see  FIG. 8 ) prior to the impact between the first carrier  105   a  and the object  151  (see  FIG. 9 ). In addition, the above-described arrangement of cooperating surfaces may cause the centerplane (not shown) of the overhead transfer flange  113   a  to remain roughly aligned with the moveable track  109  of the overhead transfer conveyor  103  as the overhead transfer flange  113   a  rises and moves rearward relative to the overhead carrier support  111   a.    
   Referring to  FIG. 11 , the overhead transfer flange  113   a  has been fully dislodged from the overhead carrier support  111   a  and is in upward projectile motion, as shown by projectile motion path  157 , departing from the slope  155  of the first blade receiver&#39;s first receiving surface  121   aa . The overhead transfer flange  113   a  is now no longer restricted in its vertical motion and may pass downward and away from the overhead carrier support  111   a.    
   The overhead transfer flange  113   a  is shown in  FIG. 11  to have risen such that the first blade edge  129   ab  has at least achieved a clearance  147   c  with respect to the first blade receiver&#39;s extended vertex  121   ac , which coincides with the height of the first blade receiver lip  121   ad  above the first blade receiver extended vertex  121   ac . As such, the first blade edge  129   ab  can pass above the first blade receiver lip  121   ad  without risk of the first blade  129   a  striking the first blade receiver  121   a . The clearance  147   c  is preferably about 3 mm, it being noted that the extent of the clearance  147   c  is to be selected based in part on the desired breakaway force, which in this embodiment is about 5 pounds, as described above. Should the desired breakaway force be less than 5 pounds, a lesser clearance  147   c  may be selected, and vice-versa. For example, in another embodiment of the invention, a force of up to 20 pounds may be required to dislodge the first carrier  105   a  from the overhead transfer conveyor  103 . In such embodiments, a larger clearance  147   c  may be desired (e.g., about 0.5 inches in one embodiment). 
   Referring to  FIG. 12 , the overhead transfer flange  113   a  has passed rearward, downward and away from the overhead carrier support  111   a , with the progression of points on the first blade edge  129   ab  describing the remainder of the projectile motion path  157 . The first carrier  105   a  (see  FIG. 9 ) may now be caught in a net or other similar mechanism for gentle collection of the first carrier  105   a  after the impact with the object  151  (see  FIG. 9 ). 
   The foregoing description discloses only exemplary embodiments of the invention; modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, the overhead carrier support lila and the overhead transfer flange  113   a  may be formed from any suitable material (e.g., materials that slide freely and exhibit long term wear resistance). Exemplary materials for the overhead carrier support and/or the overhead transfer flange include metals (e.g., stainless steel, aluminum, etc.), plastics (e.g., polycarbonate, polyethelene, other ultra high molecular weight or high density plastics, nylon, PTFE, etc.), or other similar materials. Plastic components may be molded or otherwise fabricated. 
     FIG. 13  is a cross sectional view of a portion of the first blade receiver  121   a  of the overhead carrier support  111   a  and of the first blade  129   a  of the overhead transfer flange  113   a  illustrating an alternative embodiment of such components. With reference to  FIG. 13 , both the right most extent  121   ae  of the first blade receiver  121   a  and the first blade edge  129   ab  of the first blade  129   a  are angled at about 45 degrees from vertical (although other angles may be employed). Such a configuration provides a larger capture window for the overhead transfer flange  113   a  than when the right most extent  121   ae  and the first blade edge  129   ab  are not angled. Also, when angled, these surfaces may slide relative to one another when misaligned and may assist in capture of the overhead transfer flange  113   a  by the overhead carrier support  111   a.    
   While the overhead carrier support  111   a  and the overhead transfer flange  113   a  have been described herein primarily for use with overhead transport systems, it will be understood that the overhead carrier support  111   a  (or portions thereof) may be employed to support and/or position a substrate carrier having the overhead transfer flange  113   a  at any other location. For example, the overhead carrier support  111   a  (or portions thereof) may be used for supporting and/or positioning substrate carriers within stockers, substrate carrier cleaners, local storage buffers that are part of a processing tool, batch process tools such as a furnace or a wet clean station, etc. 
     FIG. 14  is a perspective view of a plurality of shelves  175   a - b  configured to support substrate carriers via an overhead transfer flange in accordance with the present invention. More or fewer than two shelves may be employed. Each shelf  175   a - b  includes a support surface  177   a - b  having blade receivers  121   a ,  121   b  coupled thereto (or formed therein). The shelves  177   a - b  thus forms overhead carrier supports that may support substrate carriers having overhead transfer flanges such as the overhead transfer flange  113   a  ( FIGS. 1-12 ). The angles/dimensions of the blade receivers  121   a ,  121   b  may be, for example, similar to those described previously. The shelves  177   a - b  may be mounted at any location at which a substrate carrier is to be supported (e.g., within stockers, substrate carrier cleaners, local storage buffers that are part of a processing tool, batch process tools, etc.). In one or more embodiments of the invention, the shelf  175   a  and/or  175   b  may be moveable. For example, the shelf  175   a  and/or  175   b  may be used to dock or undock a substrate carrier to/from a loadport of a processing tool. 
     FIG. 15  is a perspective view of the shelves  175   a - b  of  FIG. 14  wherein the top shelf  175   a  supports a substrate carrier  179  via its overhead transfer flange  113   a . The substrate carrier  179  may be a single substrate carrier or adapted to house multiple substrate carriers. As will be apparent, use of the blade receivers  121   a ,  121   b  and the overhead transfer flange  113   a  allows substrate carriers to be stacked with a high packing density and stored on and removed from storage shelves with relatively few movements. 
   The overhead transfer flange  113   a  may be employed with open substrate containers or trays. The blade receivers of an overhead carrier support may be angled from front to back of the overhead carrier support (relative to horizontal); and/or the blade edges of an overhead transfer flange may be angled from front to back of the overhead transfer flange (relative to horizontal). 
   Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.