Patent ID: 8404598

Claim:
A method of etching a dielectric layer on a substrate, comprising: generating a plasma by pulsing a first RF source signal having a first duty cycle; applying a second RF bias signal having a second duty cycle to the plasma, wherein an RF frequency of the first RF signal is about 162 MHz and an RF frequency of the second RF signal is about 13.56 MHz or about 60 MHz, or wherein an RF frequency of the first RF signal is about 60 MHz and an RF frequency of the second RF signal is about 13.56 MHz; applying a third RF bias signal having a third duty cycle and an RF frequency of about 2 MHz to the plasma, wherein the first, second, and third signals are synchronized; adjusting a phase variance between the first RF source signal and at least one of the second or third RF bias signals to control at least one of plasma ion density non-uniformity in the plasma or charge build-up on the dielectric layer; and etching the dielectric layer with the plasma.