OPTICAL-PROPERTIES OF REACTIVE-ION-ETCHED SI SI1-XGEX HETEROSTRUCTURES/

A patterning technology for fabrication of nanometer structures in Si/ SiGe heterosystems is developed. The method pursued here combines high -resolution electron-beam lithography with reactive-ion-etching patter n transfer. A modified SF6/O-2 dry-etching process is optimized by var ying the gas mixture to achieve the required anisotropy, Photoluminesc ence measurements are carried out on uniformly etched samples to deter mine the influence of the reactive-ion-etching process on the optical properties. Etch process induced surface modifications drastically alt er the electrical surface potentials. They are identified by laser des orption. These modifications are partially removed by low-temperature postannealing steps. A qualitative model is presented to explain the o bserved effects. With this optimized technology, SiGe wires with later al widths from 4 mu m down to 25 nm are fabricated. Photoluminescence has been detected for structures as small as 600 nm. (C) 1996 American Vacuum Society.