Workpiece chuck

Abstract

A workpiece chuck includes an upper assembly on which can be mounted a flat workpiece such as a semiconductor wafer. A lower assembly is mountable to a base that supports the chuck. A non-constraining attachment means such as vacuum, springs or resilient washers applied to the chuck holds the upper assembly to the lower assembly, the lower assembly to the base and can hold the wafer to the top surface of the upper assembly. By holding the chuck together by non-constraining means, the chuck layers can move continuously relative to each other under expansion forces caused by temperature effects, such that mechanical stresses on the chuck and resulting deformation of the chuck and workpiece over temperature are substantially eliminated. A plurality of support members including inclined surfaces provided between an upper and lower portion of the chuck maintain the top surface of the chuck and any workpiece mounted thereon at a constant height over temperature.

What is claimed is:  
     
         1 . A chuck for supporting a workpiece comprising: 
 an upper portion on which the workpiece can be mounted;    a lower portion by which the chuck can be mounted to a base; and    a temperature control device for altering the temperature of the workpiece, said temperature control device having a housing made of a cast material, an upper surface of said housing being coated with a hard material to prevent the cast material from rubbing off of the housing and onto a chuck layer in contact with the top surface.    
     
     
         2 . The chuck of  claim 1  wherein the hard material comprises a hard anodize.  
     
     
         3 . The chuck of  claim 1  wherein the temperature control device comprises a heat sink.  
     
     
         4 . A method of supporting a workpiece with a chuck comprising: 
 providing an upper portion on which the workpiece can be mounted;    providing a lower portion by which the chuck can be mounted to a base;    providing a temperature control device for altering the temperature of the workpiece, said temperature control device having a housing made of a cast material; and    coating an upper surface of said housing with a hard material to prevent the cast material from rubbing off of the housing and onto a chuck layer in contact with the top surface.    
     
     
         5 . The method of  claim 4  wherein the hard material comprises a hard anodize.  
     
     
         6 . The method of  claim 4  wherein the temperature control device comprises a heat sink.