Patent ID: 8546267

Claim:
A method of processing a workpiece in a plasma reactor having an electrostatic chuck for supporting the workpiece within a reactor chamber, comprising: circulating a coolant through a refrigeration loop that includes inner and outer zone evaporators inside respective inner and outer zones of said electrostatic chuck, while pressurizing inner and outer zones of a workpiece-to-chuck interface with a thermally conductive gas; sensing conditions in said chamber including inner and outer zone temperatures near said workpiece; obtaining a next scheduled change in RF heat load on said workpiece and using thermal modeling to estimate respective changes in thermal conditions of the coolant in said inner and outer zone evaporators, respectively, that would hold temperatures measured in said inner and outer electrostatic chuck zones, respectively, nearly constant by compensating for said next scheduled change in RF heat load; making said respective changes in thermal conditions of the coolant in said inner and said outer zone evaporators prior to a time of said next scheduled change.