Patent ID: 8092639
Filing Date: 2012-01-10
Classification: F25B,H01J,H01L,H05H

Abstract:
1. A plasma reactor, comprising: a reactor chamber and an electrostatic chuck having a surface for holding a workpiece inside said chamber; a backside gas pressure source coupled to said electrostatic chuck for applying a thermally conductive gas under a selected pressure into a workpiece-surface interface formed whenever a workpiece is held on said surface; an evaporator inside said electrostatic chuck and a refrigeration loop having an expansion valve for controlling flow of coolant through said evaporator; a temperature sensor in said electrostatic chuck; a memory storing a schedule of changes in RF power or workpiece temperature; a thermal model capable of simulating heat transfer between said evaporator and said surface based upon measurements from said temperature sensor; a first control processor coupled to said thermal model and to said memory and governing said backside gas pressure source in response to a prediction from said model of a change in said selected pressure that would compensate for the effect of the next scheduled change in RF power or implement the next scheduled change in workpiece temperature.