Voltage control sensor and control interface for radio frequency power regulation in a plasma reactor

Abstract

A plasma reactor system with controlled DC bias for manufacturing semiconductor wafers and the like. The reactor system includes a plasma chamber, a plasma generating coil and a chuck including a chuck electrode. The chuck supports a workpiece within the chamber. The plasma reactor system further includes a pair of generators, one of which supplies a radio frequency signal to the plasma generating coil. The second generator delivers a RF signal which to the chuck electrode and acts to control DC bias at the workpiece. Peak voltage sensor circuitry and set point signal circuitry controls the power output of the generator, and a matching network coupled between the generator and the first electrode matches the impedance of the RF signal with the load applied by the plasma. DC bias determines the energy with which plasma particles impact the surface of a workpiece and thereby determines the rate at which the process is performed. This DC bias forms at the surface of the workpiece upon generation of a plasma in the plasma chamber and is affected by the RF signal applied to the chuck electrode. Since power losses within the match network are variable and unpredictable, the peak voltage at the electrode can not be consistently maintained by simply applying a predetermined generator output. By monitoring the peak voltage at the electrode and generating a corresponding control signal to control the generator, a consistent DC bias and corresponding process rate can be maintained.