Halogen-free etching of silicon nitride

A semiconductor processing method comprising:

• providing a hydrogen-containing precursor to a processing region of a semiconductor processing chamber, wherein a substrate is disposed on a substrate support within the processing region, wherein a layer of silicon-and-oxygen-containing material is disposed on the substrate, and wherein a layer of silicon-and-nitrogen-containing material is disposed on the layer of silicon-and-oxygen-containing material;
• forming plasma effluents of the hydrogen-containing precursor;
• and
• contacting the layer of silicon-and-nitrogen-containing material with plasma effluents of the hydrogen-containing precursor, wherein the contacting selectively etches a portion of the layer of silicon-and-nitrogen-containing material relative to the layer of silicon-and-oxygen-containing material, and wherein the substrate is characterized by a temperature of less than or about −50° C. 18. The semiconductor processing method of claim 17, further comprising:
• providing helium with the hydrogen-containing precursor to the processing region. 19. The semiconductor processing method of claim 17, wherein the processing region is maintained halogen-free. 20 The semiconductor processing method of claim 1, wherein the plasma effluents are formed at a plasma power of greater than or about 1,000 W.