Patent ID: 8329586

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 an evaporator inside said electrostatic chuck, while pressurizing a workpiece-to-chuck interface with a thermally conductive gas; sensing conditions in said chamber including temperature near said workpiece; simulating heat flow through said electrostatic chuck in a thermal model of said chuck based upon said conditions; obtaining a next scheduled change in RF heat load on said workpiece and using said model to estimate a change in thermal conditions of the coolant in said evaporator that would hold said temperature nearly constant by compensating for said next scheduled change in RF heat load; making said change in thermal conditions of the coolant in said evaporator at a selected time prior to the scheduled time of said next scheduled change, said selected time and said scheduled time being separated by a time difference corresponding to the thermal propagation delay through said electrostatic chuck.