Lift pin alignment and operation methods and apparatus

Abstract

A lifting mechanism includes a plurality of lift pins which may be driven separately and independently upward to engage an alignment surface of the chamber using ambient atmospheric pressure as the chamber is evacuated by a pump. In the illustrated embodiment, each lift pin includes a piston which is exposed to the internal chamber pressure on one side of the piston, and is exposed to the external ambient pressure on the other side of the piston. As the pump evacuates the chamber, the internal chamber pressure decreases, causing each lift pin piston to drive the associated lift pin upward. Once all the lift pins have securely engaged the alignment surface, the lift pins may be clamped to a linking mechanism to permit a motor to actuate the lift pins during processing operations.

1 . A method of aligning workpiece lift pins in a semiconductor processing chamber, comprising: 
 driving a plurality of lift pins using ambient atmospheric pressure to engage an alignment surface in said chamber.    
   
   
       2 . The method of  claim 1  wherein each lift pin includes a piston adapted for slidable vertical movement and exposed to internal chamber pressure on a first side of said piston, each lift pin further including a bellows which encloses a second side of said piston to define a piston chamber vented to the exterior of said processing chamber so that piston second side is exposed to ambient atmospheric pressure, and wherein said driving includes evacuating said chamber to reduce said internal chamber pressure on said first side of said piston relative to said ambient atmospheric pressure on said second side of said piston to drive said piston of said lift pin upward toward said engagement surface of said chamber.  
   
   
       3 . The method of  claim 1  wherein said processing chamber has a bottom wall which defines a plurality of apertures, and each lift pin includes a lift finger secured to a shaft adapted for slidable vertical movement in a processing chamber bottom wall aperture and wherein said driving includes driving each lift pin shaft upward through a chamber bottom wall aperture.  
   
   
       4 . The method of  claim 1  further comprising releasably coupling each lift pin to a motor-driven linking member after each lift pin engages said alignment surface.  
   
   
       5 . The method of  claim 4  further comprising driving said linking member upward prior to releasably coupling each lift pin to said linking member.  
   
   
       6 . The method of  claim 5  wherein said driving includes controlling said motor which is adapted to apply an upward force on said linking member in response to said motor controlling, and controlling pressure to a pressure cylinder adapted to apply a downward force on said linking member in response to said pressure controlling.  
   
   
       7 . The method of  claim 4  wherein said releasable coupling includes clamping each said lift pin to said linking member.  
   
   
       8 . The method of  claim 7  wherein said clamping includes clamping a floating joint of each lift pin to said linking member.  
   
   
       9 . The method of  claim 8  wherein said clamping includes clamping a clamp to a cylindrically shaped clamping surface of each floating joint wherein said clamping surface has a length to diameter ratio of at least 1.  
   
   
       10 . The method of  claim 9  wherein said ratio is at least 1.5.  
   
   
       11 . The method of  claim 1  wherein said driving includes driving a spherically-shaped engagement surface of said lift pin to engage said alignment surface.  
   
   
       12 . The method of  claim 1  wherein said plurality of lift pins of said driving consists of four lift pins.  
   
   
       13 - 16 . (canceled)  
   
   
       17 . A method of elevating a workpiece in a semiconductor processing chamber, comprising: 
 driving a plurality of lift pins engaging a workpiece in a vertical direction, wherein said driving includes controlling a motor adapted to selectively apply one of an upward force and a downward force on said lift pins in response to said motor controlling, and controlling pressure to a pressure cylinder adapted to apply a downward force on said lifting pins in response to said pressure controlling.    
   
   
       18 . The method of  claim 17  wherein each lift pin includes a piston disposed in said processing chamber for vertical sliding motion, and said driving further includes applying ambient atmospheric pressure on one side of each lift pin piston and applying processing chamber internal pressure on the other side of each lift pin piston.  
   
   
       19 . The method of  claim 18  wherein the pressure to said pressure cylinder is controlled at a first value when said motor applies an upward force and is controlled at a second value when said motor applies a downward force.  
   
   
       20 . The method of  claim 19  wherein said second value is greater than said first value.  
   
   
       21 . The method of  claim 20  wherein said first value is approximately 10 pounds per square inch and said second value is approximately 20 pounds per square inch.  
   
   
       22 . The method of  claim 18  wherein pistons of said plurality of lift pins are linked by a linking member and said motor applies a force on said lift pins by applying a force on said linking member, and said pressure cylinder applies a downward force on said lift pins by applying a downward force on said linking member.  
   
   
       23 - 26 . (canceled)  
   
   
       27 . A method of assembling a lift pin, comprising: 
 placing a flat surface of a piston shaft on a first supporting surface;    placing a flat surface of a flange member on a second support surface; and    permanently attaching a bellows to said piston shaft and to said flange member.    
   
   
       28 . The method of  claim 27  wherein said attaching includes welding.