METHOD FOR PLASMA ETCHING USING PERIODIC MODULATION OF GAS CHEMISTRY

摘要

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