Improved methods for chemically etching silicon are provided herein. In some embodiments, a method of etching a silicon material includes: (a) exposing the silicon material to a halogen-containing gas; (b) evacuating the halogen-containing gas from the semiconductor processing chamber; (c) exposing the silicon material to an amine vapor to etch a monolayer of the silicon material; (d) evacuating the amine vapor from the semiconductor processing chamber and; (e) optionally repeating (a)-(d) to etch the silicon material to a predetermined thickness.