Thermal stability of highly Sb-doped molecular beam epitaxy silicon grown at low temperatures: Structural and electrical characterization

Abstract

The structural and electrical properties of highly Sb-doped molecular beam epitaxy grown silicon have been investigated as function of rapid thermal annealing (RTA) temperature. Doping levels of 3×1020 cm−3 were obtained using low temperature epitaxy (LTE) performed at a growth temperature of 300 °C. Ion channeling and transmission electron microscopy (TEM) measurements showed that the as-grown samples were of very high quality. The combination of Hall-effect profiling and Rutherford backscattering spectroscopy revealed an electrically active Sb fraction of 0.8. Short time RTA processing improved the electron mobility and the activation: RTA at 600 °C for 10 s yielded unity activation and RTA at 800 °C gave mobilities matching phosphorus doped bulk values, thus significantly exceeding previously reported values for highly doped LTE material. A degradation of the crystalline quality was observed for higher RTA temperatures: RTA at 1000 °C for 10 s reduced both the Sb-substitutional fraction and electrical activation to 0.6 due to precipitation of Sb, and lead to the formation of a high density of dislocation loops as observed by TEM. A large fraction of the precipitates decorated these dislocation loops. Mesa isolated diodes were fabricated to evaluate the use of LTE material for device production. Current–voltage measurements on these diodes revealed high quality junctions with low reverse currents and near-ideal forward characteristic.