Dual cassette load lock

Abstract

A workpiece loading interface is included within a workpiece processing system which processes workpieces, typically wafers, in a vacuum. The workpiece loading interface includes two separate chambers. Each chamber may be separately pumped down. Thus, while a first cassette of wafers, from a first chamber is being accessed, a second cassette of wafers may be loaded in the second chamber and the second chamber pumped down. Each chamber is designed to minimize intrusion to a clean room. Thus a door to each chamber has a mechanism which, when opening the door, first moves the door slightly away from an opening in the chamber and then the door is moved down parallel to the chamber. After the door is opened, a cassette of wafers is lowered through the opening in a motion much like a drawbridge. The cassette may be pivoted within the chamber when the position from which wafers are accessed from the cassette differs from the position from which the cassette is lowered out of the chamber.

1 - 4 . (canceled)  
   
   
       5 . In a work piece processing system, a method for closing and sealing a chamber, comprising: 
 a) providing a chamber having an opening formed through a surface of the chamber adapted to allow work pieces to be received from outside the chamber and a door adapted to seal against the surface so as to close the opening;    b) moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface; and    c) moving the door linearly horizontally a distance toward the opening so as to cause the door to contact and seal against the surface of the chamber and close the opening.    
   
   
       6 . The method of  claim 5 , further comprising: 
 providing a carriage, the carriage being horizontally stationary and adapted to move parallel to the chamber surface, and a link between the door and the carriage, the link permitting linear horizontal movement of the door.    
   
   
       7 . The method of  claim 6 , wherein providing a carriage, the carriage being horizontally stationary and adapted to move parallel to the chamber surface, and a link between the door and the carriage, the link permitting linear horizontal movement of the door comprises: 
 providing a four-bar linkage comprising the carriage, the door, and a link between the carriage and the door.    
   
   
       8 . The method of  claim 6 , wherein providing a carriage, the carriage being horizontally stationary and adapted to move parallel to the chamber surface, and a link between the door and the carriage, the link permitting linear horizontal movement of the door comprises: 
 providing a rail, oriented parallel to the chamber surface, along which the carriage is adapted to move and which is adapted to substantially prevent horizontal motion of the carriage.    
   
   
       9 . The method of  claim 8 , wherein providing a rail along which the carriage is adapted to move and which is adapted to limit horizontal motion of the carriage comprises: 
 providing a rail fixedly coupled to the chamber.    
   
   
       10 . The method of  claim 6 , further comprising providing an abutment adapted to limit parallel motion of the door while the link converts parallel motion of the carriage into linear horizontal motion of the door.  
   
   
       11 . The method of  claim 10 , wherein providing an abutment adapted to limit parallel motion of the door while the link converts parallel motion of the carriage into linear horizontal motion of the door comprises: 
 providing an abutment adapted to contact a portion of the door and thereby block further motion of the door parallel to the chamber as the carriage continues to move parallel to the chamber.    
   
   
       12 . The method of  claim 11 , wherein providing an abutment adapted to contact a portion of the door and thereby block further motion of the door parallel to the chamber as the carriage continues to move parallel to the chamber comprises: 
 providing an abutment along which the door portion is adapted to move while moving linearly horizontally.    
   
   
       13 . The method of  claim 12 , further comprising providing an extensible spring coupled between the carriage and the door portion adapted to bias the door portion against the abutment as the carriage continues to move parallel to the chamber.  
   
   
       14 . The method of  claim 10 , wherein providing an abutment adapted to limit parallel motion of the door while the link converts parallel motion of the carriage into linear horizontal motion of the door comprises: 
 providing an abutment fixedly coupled to the chamber.    
   
   
       15 . The method of  claim 6 , wherein moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface comprises: 
 urging the carriage along a rail oriented parallel to the chamber surface so as to cause the door to move parallel to the chamber surface.    
   
   
       16 . The method of  claim 6 , wherein moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface comprises: 
 biasing the link so as to cause the link to retract the door linearly horizontally so as to provide a friction-preventing gap between the door and the chamber surface during parallel motion of the door.    
   
   
       17 . The method of  claim 5 , further comprising: 
 d) causing a portion of the door to contact and move linearly horizontally against an abutment.    
   
   
       18 . The method of  claim 17 , wherein causing a portion of the door to contact and move linearly horizontally against an abutment is performed after moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface; and is performed during moving the door linearly horizontally a distance toward the opening so as to cause the door to contact and seal against the surface of the chamber and close the opening.  
   
   
       19 . The method of  claim 5 , further comprising: 
 d) after performing moving the door linearly horizontally a distance toward the opening so as to cause the door to contact and seal against the surface of the chamber and close the opening, opening and unsealing the chamber by moving the door linearly horizontally a distance away from the opening so as to cause the door to break contact with and unseal from the surface of the chamber, and then again moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface.    
   
   
       20 . A door assembly for opening and closing an opening through which a chamber receives and discharges work pieces, comprising: 
 a door adapted to close and seal an opening through which a chamber receives and discharges work pieces;    a horizontally stationary carriage; and    a link coupled between the door and the horizontally stationary carriage so as to permit linear horizontal movement of the door toward or away from the opening.    
   
   
       21 . The door assembly of  claim 20 , wherein the door, the carriage, and the link comprise a four-bar linkage.  
   
   
       22 . The door assembly of  claim 20 , wherein the carriage is adapted to move parallel to a chamber surface through which the opening is formed, and wherein the link is adapted to convert parallel motion of the carriage into linear horizontal motion of the door toward or away from the opening.  
   
   
       23 . The door assembly of  claim 22 , further comprising an abutment, and wherein a portion of the door is adapted to contact and move against the abutment, and wherein the door is supported by the carriage such that the door is adapted to move with the carriage parallel to the chamber surface sufficiently to cause the door portion to contact the abutment.  
   
   
       24 . The door assembly of  claim 23 , wherein the abutment is fixedly coupled to the chamber.  
   
   
       25 . The door assembly of  claim 23 , wherein the abutment is adapted to block the door from moving further parallel to the chamber surface while the door portion contacts the abutment, and wherein the door portion is adapted to move linearly horizontally against the abutment while the carriage continues to move parallel to the chamber.  
   
   
       26 . The door assembly of  claim 25 , further comprising a spring coupled between the carriage and the door portion and adapted to bias the door portion against the abutment while the carriage continues to move parallel to the chamber surface.  
   
   
       27 . The door assembly of  claim 26 , wherein the door is supported by the carriage such that the door is adapted to move with the carriage parallel to the chamber surface, and further comprising a spring coupled between the carriage and the door portion and adapted to bias the link, and wherein the link is adapted when biased by the spring to retract the door linearly horizontally so as to provide a friction-preventing gap between the door and the chamber surface during said parallel motion of the door.  
   
   
       28 . The door assembly of  claim 27 , wherein the door portion is a panel fixedly extending from a side of the door.  
   
   
       29 . The door assembly of  claim 20 , wherein the door is supported by the carriage such that the door is adapted to move with the carriage parallel to the chamber surface, and further comprising a spring coupled between the carriage and the door and adapted to bias the link, and wherein the link is adapted when biased by the spring to retract the door linearly horizontally so as to provide a friction-preventing gap between the door and the chamber surface during said parallel motion of the door.  
   
   
       30 . The door assembly of  claim 22 , further comprising a horizontally-stationary rail oriented parallel to the chamber surface along which the carriage is adapted to move.  
   
   
       31 . The door assembly of  claim 30 , wherein the rail is fixedly coupled to the chamber.