Methods of selectively etching silicon nitride

Abstract

Embodiments of the present disclosure are directed to selective etching processes. The processes include an etching chemistry (a plasma of a fluorine-containing precursor and a first gas mixture), and a passivating chemistry (a plasma of a sulfur-containing precursor and a second gas mixture). In some embodiments, the sulfur-containing precursor and the second gas mixture are present in a ratio of sulfur-containing precursor to second gas mixture in a range of from 0.01 to 5. The methods include etching a substrate having a plurality of alternating layers of silicon oxide and silicon nitride thereon and a trench formed through the plurality of alternating layers. The silicon nitride layers are selectively etched relative to the silicon oxide layers at an etch selectivity of greater than or equal to 500:1.