Patent ID: 8909365

Claim:
A method comprising: obtaining a radio frequency (RF) voltage signal from an RF sensing mechanism via a high impedance path, the RF voltage signal having multiple RF frequencies associated with multiple RF generators, the multiple frequencies including a first frequency and a second frequency, said RF sensing mechanism is an RF rod, wherein said RF rod is proximate to a component of an electrostatic chuck (ESC) subsystem, wherein the component is outside a region having plasma when formed in a plasma chamber, wherein the RF rod is used for sensing said RF voltage signal, said RF rod providing said RF voltage signal to a capacitor divider network; processing said RF voltage signal to generate a plurality of signals, one of the signals in said plurality of signals having the first frequency and another one of the signals in said plurality of signals having the second frequency; applying a transfer function to the signal having the first frequency and the other signal having the second frequency to derive a wafer potential; and providing the wafer potential as a control signal to control at least a subsystem of said plasma processing system.