An exemplary method for laterally etching silicon nitride can include flowing a fluorine-containing precursor and an oxygen-containing precursor into a remote plasma region of a semiconductor processing chamber. The method can include forming a plasma in a remote plasma region to produce plasma emissions of fluorine-containing precursors and oxygen-containing precursors. The method can also include flowing a plasma emission into the processing region of the semiconductor processing chamber. The substrate may be disposed in the processing region and may include a trench formed through a stacked layer including alternating layers of silicon nitride and silicon oxide. The method may also include laterally etching the layer of silicon nitride from the sidewalls of the trench while substantially maintaining the layer of silicon oxide. The layer of silicon nitride can be etched laterally by less than 10 nm from the trench sidewalls. [Selection] Figure 5
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