Patent ID: 8872525
Filing Date: 2014-10-28
Classification: H01J

Abstract:
1. A method of measuring a self bias DC voltage on a semiconductor wafer in a plasma chamber comprising: generating a plasma in the region between a top electrode and a top surface of an electrostatic chuck in a plasma chamber including applying one or more RF signals to one or both of the top electrode and the electrostatic chuck, wherein the semiconductor wafer is supported on the top surface of an electrostatic chuck; developing the self bias DC voltage on the semiconductor wafer; oscillating a vibrating electrode to produce a variable capacitance, the vibrating electrode being located within the electrostatic chuck; developing an electrical current in a sensor circuit connected to the vibrating electrode; measuring an output voltage across a sampling resistor in the sensor circuit; and applying a second DC potential to the vibrating electrode to nullify the output voltage; wherein the second DC potential is equal to the self bias DC voltage on the semiconductor wafer.