Patent ID: 8337660

Claim:
A plasma reactor, for processing a workpiece, comprising: a reactor chamber; an electrostatic chuck within said chamber having a top surface for supporting a workpiece and having indentations in said top surface that form enclosed gas flow channels whenever covered by a workpiece resting on said top surface; thermal control apparatus thermally coupled to said electrostatic chuck; an RF plasma bias power generator coupled to apply RF power to said electrostatic chuck; a pressurized gas supply of a thermally conductive gas; a controllable gas valve coupling said pressurized gas supply to said indentations to facilitate filling said channels with said thermally conductive gas for heat transfer between a backside of a workpiece and said electrostatic chuck at a heat transfer rate that is a function of the pressure against the backside of the workpiece of the thermally conductive gas; a workpiece temperature control loop comprising: (a) a workpiece temperature probe in said electrostatic chuck; and (b) a first controller for controlling the backside gas pressure, said first controller coupled to an output of said workpiece temperature probe and responsive to a difference between the output of said workpiece temperature probe and a specified desired workpiece temperature, said first controller governing said gas valve in response to a difference between the output of said workpiece temperature probe and said desired workpiece temperature; an electrostatic chuck temperature control loop comprising: (a) an electrostatic chuck temperature probe in said electrostatic chuck and arranged to sense a temperature of said electrostatic chuck; (b) a second controller for controlling the thermal control apparatus, the second controller coupled to an output of said electrostatic chuck temperature probe and responsive to a difference between said output of said electrostatic chuck temperature probe and a desired electrostatic chuck temperature probe and a desired electrostatic chuck temperature; wherein said thermal control apparatus comprises: (a) an evaporator inside said electrostatic chuck and having a thermal transfer medium inlet and a thermal transfer medium outlet; (b) a compressor coupled at least indirectly to said outlet of said evaporator; (c) a condenser coupled to an outlet of said compressor; and (d) an expansion valve coupled between an output of said condenser and said inlet of said evaporator.