SiGe Synthesis by Ge Ion Implantation

Abstract

We report here the successful synthesis of SiGe by Ge ion implantation into Si-on-insulator (SOI) substrates. The fundamental principle for our SiGe synthesis is a chemical reaction preference by nature; oxygen molecules preferentially combine with Si atoms rather than Ge atoms since the formation energy of SiO2 is lower than GeO/GeO2, and the chemical bond strength of SiO2 is higher. This phenomenon consequently retards the diffusion of implanted Ge ions from the desired area, offering them sufficient time and chances to homogeneously unite with Si atoms and curing implantation damage during O2 gas annealing. Thus, the result is practical synthesis of SiGe that can flexibly create various Ge concentrations along with high crystalline quality. Ge ions with a dose of 1017 cm-2 are implanted at 100 keV into 193-nm-thick top Si layers of SOIs at room temperature. The Ge-implanted samples are subsequently annealed at 1100 or 1200 °C in an O2 gas ambient for 5 to 180 min. It is found that the implanted Ge ions mostly remain in the desired area during O2 gas annealing. An apparent increase in Ge concentration and a significant decrease in defect density by increasing annealing time are also observed. A theoretical basis and useful simulation for this material synthesis method are presented in this study, being supported by evidential experimental data and comparison of theoretical calculation and measured values.