A method for etching features into a silicon substrate disposed below a mask in a plasma processing chamber is provided. The silicon substrate is etched through the mask comprising a plurality of cycles, wherein each cycle comprises a sidewall deposition phase and an etch phase. The sidewall deposition phase comprises providing a flow of sidewall inorganic deposition phase gas comprising a silicon containing compound gas and at least one of oxygen, nitrogen or NOx, into the plasma processing chamber, forming a plasma from the sidewall deposition phase gas in the plasma processing chamber, and stopping the flow of the sidewall deposition gas into the plasma processing chamber. The etch phase comprises, providing a flow of an etching gas comprising a halogen component, forming a plasma from the etching gas in the plasma processing chamber, and stopping the flow of the etching gas.