Patent ID: 6916746

Claim:
A method for etching a feature in a dielectric layer through an etch mask over a substrate, comprising: performing a gas-modulated cyclic process for more than three cycles, wherein each cycle comprises: performing a protective layer forming phase using first gas chemistry with a deposition gas chemistry, wherein the protective layer forming phase is performed in about 0.0055 to 7 seconds for each cycle, comprising; providing the deposition gas; and forming a plasma from the deposition gas; and performing an etching phase for etching the feature into the dielectric layer through the etch mask using a second gas chemistry using a reactive etching gas chemistry, where the first gas chemistry is different than the second gas chemistry, wherein the etching phase is performed in about 0.005 to 14 seconds for each cycle, comprising: providing a reactive etching gas; and forming a plasma from the reactive etching gas.