Conventional methods of semiconductor fabrication and processing typically
utilize three gas (e.g., HBr, Cl2 and O2) and four gas (e.g.,
HBr, Cl2, O2 and CF4) chemistries to perform gate
etching in plasma process chambers. However, the silicon to resist selectivity
achieved by these chemistries is limited to about 3:1. The present invention concerns
a plasma source gas comprising SF6 and one or more fluorine-containing
gases selected from C3F6, C4F8, C5F8,
CH2F2, CHF3, and C4F6 (e.g.,
SF6 and C4F8), allowing the use of a two gas etch
chemistry that provides enhanced silicon to photoresist selectivity in gate etching processes.
