Low-temperature doped and undoped epitaxial silicon and silicon(1-x) germanium(x) growth

Doped and undoped silicon homoepitaxy and Si{dollar}rmsb{lcub}1-x{rcub}Gesb{lcub}x{rcub}{dollar}-on-Si heteroepitaxy have been achieved by Photo-enhanced Chemical Vapor Deposition (PCVD) and cold-wall Ultra High Vacuum Chemical Vapor Deposition (UHVCVD) using disilane (Si{dollar}rmsb2Hsb6{dollar}), silane (SiH{dollar}sb4{dollar}), digermane (Ge{dollar}rmsb2Hsb6{dollar}) and germane (GeH{dollar}sb4{dollar}) as the reactant gases. Crystalline Si and Si{dollar}rmsb{lcub}1-x{rcub}Gesb{lcub}x{rcub}{dollar} films were obtained at substrate temperatures from 250{dollar}spcirc{dollar}C to 600{dollar}spcirc{dollar}C. The growth mechanism and film quality of intrinsic Si, B or P-doped films and Si{dollar}rmsb{lcub}1-x{rcub}Gesb{lcub}x{rcub}{dollar} alloys using SiH{dollar}sb4{dollar} and Si{dollar}rmsb2Hsb6{dollar} were comparatively studied. It was also found that the "phosphine (PH{dollar}sb3{dollar}) poisoning effect" resulting in growth rate reduction and crystallinity degradation in Si{dollar}rmsb2Hsb6{dollar} CVD is not as serious as in SiH{dollar}sb4{dollar} CVD. A model for the PH{dollar}sb3{dollar} poisoning effect was developed to explain the growth rate reduction in SiH{dollar}sb4{dollar} CVD with high PH{dollar}sb3{dollar} flux. A growth kinetic model was developed to predict the growth rate of undoped Si for various reactant gas partial pressures and substrate temperatures. The adsorption coefficient for Si{dollar}rmsb2Hsb6{dollar} was found to be about 10 times higher than that of SiH{dollar}sb4{dollar}. The model can also predict the Ge mole fraction in Si{dollar}rmsb{lcub}1-x{rcub}Gesb{lcub}x{rcub}{dollar} alloys and B or P doping concentrations in the Si films. In this study, Si{dollar}rmsb2Hsb6{dollar} was found to be a better Si precursor compared to SiH{dollar}sb4{dollar} under the same growth conditions.