Low temperature chuck for plasma processing systems

Abstract

A wafer chuck assembly includes a puck, a shaft and a base. The puck includes an electrically insulating material that defines a top surface of the puck; a plurality of electrodes are embedded within the electrically insulating material. The puck also includes an inner puck element that forms one or more channels for a heat exchange fluid, the inner puck element being in thermal communication with the electrically insulating material, and an electrically conductive plate disposed proximate to the inner puck element. The shaft includes an electrically conductive shaft housing that is electrically coupled with the plate, and a plurality of connectors, including electrical connectors for the electrodes. The base includes an electrically conductive base housing that is electrically coupled with the shaft housing, and an electrically insulating terminal block disposed within the base housing, the plurality of connectors passing through the terminal block.

We claim: 
     
         1 . A wafer chuck assembly, comprising:
 a puck comprising:
 an electrically insulating material defining a top surface of the puck; 
 a plurality of electrodes embedded within the electrically insulating material; 
 an inner puck element that forms one or more channels for a heat exchange fluid, the inner puck element being in thermal communication with the electrically insulating material; and 
 an electrically conductive plate disposed proximate to the inner puck element; 
   a shaft comprising:
 an electrically conductive shaft housing that is electrically coupled with the plate; and 
 a plurality of connectors, comprising electrical connectors for the electrodes; and 
   a base comprising:
 an electrically conductive base housing that is electrically coupled with the shaft housing; and 
 an electrically insulating terminal block disposed within the base housing, the plurality of connectors passing through the terminal block. 
   
     
     
         2 . The wafer chuck assembly of  claim 1 , the terminal block comprising polyether ether ketone. 
     
     
         3 . The wafer chuck assembly of  claim 1 , the connectors further comprising one or more connectors for a thermocouple or a resistance temperature detector. 
     
     
         4 . The wafer chuck assembly of  claim 1 , the connectors further comprising one or more fluid conduits. 
     
     
         5 . The wafer chuck assembly of  claim 4 , at least one of the one or more fluid conduits being configured to provide a heat transfer gas, the top surface defining channels for the heat transfer gas to spread between the top surface and a bottom surface of a wafer. 
     
     
         6 . The wafer chuck assembly of  claim 1 , each of the electrical connectors for the plurality of electrodes comprising an inner conductor, an insulating layer about the inner conductor, a ground tube about the insulating layer, and a ceramic tube about the ground tube. 
     
     
         7 . The wafer chuck assembly of  claim 1 , further comprising a wafer processing system in which the wafer chuck assembly is disposed. 
     
     
         8 . The wafer chuck assembly of  claim 7 , wherein the wafer processing system comprises:
 a process chamber bounded by one or more chamber walls, and   one or more power supplies;   wherein the wafer chuck assembly is disposed such that at least the puck is within the process chamber; and   the one or more power supplies couple with the plurality of electrodes and at least one of the one or more chamber walls to provide:
 an RF voltage between the electrodes and the at least one of the one or more chamber walls; and 
 a DC voltage differential across the electrodes, for electrostatically clamping a wafer to the top surface. 
   
     
     
         9 . The wafer chuck assembly of  claim 8 ,
 further comprising a DC probe that extends through the top surface of the puck,   the connectors further comprising a connector for the DC probe.   
     
     
         10 . The wafer chuck assembly of  claim 9 , wherein a power supply of the one or more power supplies adjusts a DC offset between at least one of the electrodes and the at least one of the one or more chamber walls in response to a signal from the DC probe. 
     
     
         11 . The wafer chuck assembly of  claim 1 , further comprising a connective element disposed between the inner puck element and the electrically insulating material. 
     
     
         12 . The wafer chuck assembly of  claim 11 , the connective element comprising aluminum silicon carbide. 
     
     
         13 . The wafer chuck assembly of  claim 1 , wherein the electrically conductive base housing defines one or more channels for the heat exchange fluid. 
     
     
         14 . A method of plasma processing, comprising:
 stabilizing temperature of a chuck by flowing a heat exchange fluid through an inner puck element of the chuck, the chuck having an electrically insulating top surface in thermal communication with the inner puck element;   loading a workpiece onto the chuck;   providing a DC voltage differential across two spatially separated electrodes embedded in the electrically insulating top surface, to clamp the workpiece to the chuck;   providing process gases in a chamber surrounding the chuck; and   providing an RF voltage between a conductive plate beneath the chuck, and one or more walls of the chamber, to ignite a plasma from the process gases.   
     
     
         15 . The method of plasma processing of  claim 14 , further comprising flowing a heat transfer gas through the top surface into channels defined by the top surface, wherein the channels allow the heat transfer gas to spread between the top surface and the workpiece. 
     
     
         16 . The method of plasma processing of  claim 14 , wherein stabilizing temperature of the chuck comprises stabilizing temperature of the top surface within a temperature range of 20 C to 150 C. 
     
     
         17 . The method of plasma processing of  claim 14 , wherein stabilizing temperature of the chuck further comprises stabilizing temperature of a connective element comprising aluminum silicon carbide disposed between the inner puck element and the top surface, such that a thermal mass of the chuck rapidly stabilizes a temperature of the workpiece after loading. 
     
     
         18 . The method of plasma processing of  claim 14 , further comprising adjusting a DC offset between at least one of the electrodes and the at least one of the one or more walls of the chamber, in response to a signal from a DC probe that extends through the top surface. 
     
     
         19 . A semiconductor wafer, processed as the workpiece according to the method of plasma processing of  claim 14 . 
     
     
         20 . The method of plasma processing of  claim 14 , further comprising flowing the heat exchange fluid through a base that is in thermal communication with a shaft housing of a shaft that supports the chuck, the shaft being in thermal communication with the conductive plate such that the heat exchange fluid stabilizes temperature of the base, the shaft housing and the conductive plate.