Methods of selectively etching silicon

A method comprising:

• flowing a precursor comprising one or more of an interhalogen, a halogen-containing species, a pseudohalogen species, a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species and one or more of an amine, a phosphine, a glycol, or an acid, or a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species and a sulfur-containing species, into a semiconductor processing chamber containing a substrate;
• forming an activated species of the precursor;
• exposing the substrate to the activated species;
• and
• etching the substrate, the substrate having a plurality of alternating layers of silicon and silicon germanium thereon, wherein the silicon layers are selectively etched relative to the silicon germanium layers.

A method comprising:

• flowing a precursor comprising one or more of an interhalogen, a halogen-containing species, a pseudohalogen species, a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species and one or more of an amine, a phosphine, a glycol, or an acid, or a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species and a sulfur-containing species, into a semiconductor processing chamber containing a substrate;
• forming an activated species of the precursor;
• exposing the substrate to the activated species;
• and
• etching the substrate, the substrate having a plurality of alternating layers of silicon and silicon germanium thereon, and alternating silicon oxide layers and silicon nitride layers in contact with the alternating silicon layers and silicon germanium layers, wherein the silicon layers are selectively etched relative to the silicon oxide layers and the silicon nitride layers.