Patent ID: 8222155

Claim:
A method for selectively etching a substrate in a plasma processing system that includes an electrode, the substrate including a first layer formed of a first material having a first ion energy threshold for etching and a second layer formed of a second material having a second ion energy threshold for etching, said second ion energy threshold being greater than said first ion energy threshold, the method comprising: coupling said electrode to said substrate; providing a bias RF signal to said electrode to produce an ion energy distribution; and configuring a bias frequency of said bias RF signal such that a mean ion energy value of said ion energy distribution is between said first ion energy threshold and said second ion energy threshold and that a first difference between said first ion energy threshold and said mean ion energy value of said ion energy distribution is greater than a second difference between said second ion energy threshold and said mean ion energy value of said ion energy distribution, wherein said plasma processing system represents an inductively coupled plasma processing system.