Method for selectively etching with reduced aspect ratio dependence

A method for selectively etching an etch layer with respect to a mask with isolated and dense regions in a processing chamber, comprising:

• providing an etch process comprising a plurality of etch cycles, wherein each etch cycle comprises:
• providing a deposition phase, comprising:
• providing a flow of a deposition phase gas into the processing chamber comprising a fluorocarbon or hydrofluorocarbon containing gas and an oxygen containing gas with a fluorocarbon or hydrofluorocarbon to oxygen ratio;
• providing a RF power, wherein the RF power transforms the deposition phase gas into a plasma;
• and
• stopping the deposition phase;
• and
• providing an etch phase, comprising:
• providing a flow of an etch phase gas into the processing chamber comprising a fluorocarbon or hydrofluorocarbon containing gas and an oxygen containing gas with a fluorocarbon or hydrofluorocarbon to oxygen ratio that is different than the fluorocarbon or hydrofluorocarbon to oxygen ratio of the deposition phase gas;
• providing a RF power, wherein the RF power transforms the etch phase gas into a plasma;
• and
• stopping the etch phase.