Patent ID: 8034180

Claim:
A method of controlling the temperature of a workpiece supported on a top surface of a workpiece support in an RF coupled plasma reactor, comprising: placing coolant in a flow channel that is thermally coupled to said workpiece support; supplying a thermally conductive gas between the backside of said workpiece and the workpiece support top surface to establish a backside gas pressure; providing a first temperature sensor thermally coupled to said workpiece support and a second temperature sensor thermally coupled to said workpiece; determining whether a change in thermal condition of said workpiece is a first type of change having a first rate of change not exceeding a rate limited by a thermal mass of said workpiece support or a second type of change having a second rate of change exceeding said first rate of change; causing or responding to said first type of change in thermal condition of said workpiece by monitoring a temperature of said workpiece support through said first temperature sensor, and changing the thermal conditions of said coolant in said flow channel so as to reduce a difference between the output of said first temperature sensor and a target workpiece support temperature; causing or responding to said second type of change in thermal condition of said workpiece by monitoring the temperature of said workpiece through said second temperature sensor, and changing the pressure of said thermally conductive gas so as to reduce a difference between the output of said second temperature sensor and a target workpiece temperature.