INTERACTIVE EFFECTS IN THE REACTIVE ION ETCHING OF SIGE ALLOYS

Reactive ion etching (RIE) of epitaxial, strained Si1-xGex alloys, x less-than-or-equal-to 0.20, in fluorine-, chlorine-, and bromine-based low-pressure plasmas has been investigated. The SiGe etch rates increase for each etchant with Ge concentration, e.g., for fluorine-based RIE (CF4 and SF6) the etch rate of a Si80Ge20 alloy is congruent-to 2x that of elemental Si. Analysis shows that the etch rate increase is not accounted for by the greater rate of gasification of Ge atoms alone but that the presence of Ge atoms in the SiGe alloy increases the rate of Si etch product formation.