A method of selectively dry etching silicon from patterned heterogeneous structures is described. The method optionally includes a plasma process prior to a remote plasma etch. The plasma process may use a biased plasma to treat some crystalline silicon (e.g. polysilicon or single crystal silicon) to form amorphous silicon. Subsequently, a remote plasma is formed using a hydrogen-containing precursor to form plasma effluents. The plasma effluents are passed into the substrate processing region to etch the amorphous silicon from the patterned substrate. By implementing biased plasma processes, the normally isotropic etch may be transformed into a directional (anisotropic) etch despite the remote nature of the plasma excitation during the etch process.