US Patent 9666447 Method for selectivity enhancement during dry plasma etching

A method of etching a layer on a substrate is described. The method includes disposing a substrate having a heterogeneous layer composed of a first material and a second material in a processing space of a plasma processing system, wherein the heterogeneous layer has an initial upper surface exposing the first material and the second material to a plasma environment in the processing space, and performing a modulated plasma etching process to selectively remove the first material at a rate greater than removing the second material. The modulated plasma etching process includes a modulation cycle that preferentially reacts an etchant with the first material during a first phase of the modulation cycle, and differentially adheres a passivant on the second material relative to the first material during a second phase of the modulation cycle.