HIGH-RESOLUTION REACTIVE ION ETCHING AND DAMAGE EFFECTS IN THE SI/GEXSI1-X SYSTEM

The reactive ion etching characteristics of epitaxial GexSi1-x(x less-than-or-equal-to 0.25) alloys in SF6/O2/He and SiCl4/Cl2/He plasmas have been studied. A high-resolution patterning process for Ge0.25Si0.75 using SiCl4/Cl2/He as a dry etch gas mixture has been developed. The etch rate and etch profile of Ge0.25Si0.75 are found to be strongly influenced by the substrate temperature and the oxygen content in the SF6/02/He gas mixture. Conductance measurements of dry etched narrow wires in a Si/Ge0.2Si0.8 two-dimensional hole gas at 4.2 K reveal less sidewall damage for gas mixture SiCl4/Cl2 compared with SF6/O2/He, SiCl4/Cl2/He, and SF6/02. Scattering in the condUCting wires is studied using weak localization theory.