Nitride open etch process based on trifluoromethane and sulfur hexafluoride

摘要

A nitride etch process particularly useful when integrated with a silicon trench etch needing a sloping silicon surface adjacent to the interface between the silicon and an oxide layer intermediate the silicon and nitride. The nitride etch process is a plasma process having an etching gas mixture of sulfur hexafluoride (SF6) and trifluoromethane (CHF3) although nitrogen or oxygen may be added for additional controls. The trifluoromethane is believed to create a polymer passivation on the sidewalls of the hole being etched which, when the etch reaches the oxide-silicon interface, protects the interface and underlying silicon. The nitride etch may proceed through the oxide or a separate fluorocarbon-based oxide etching step may be performed before a bromine-based etch of the silicon starts.