Method for removing silicon nitride material

摘要

A etchant recipe including a mixed gas of one of a CHxFy group and CO gas is used to etch a silicon nitride layer by plasma etching so as to form a thin polymer layer to protect a silicon layer under the silicon nitride layer from over-etching. Then a soft etching is performed to remove the thin polymer. The etchant recipe is, for example, used in forming a contact opening on a gate of a MOS transistor, on which a silicon nitride layer is formed.