Initial growth characteristics of germanium on silicon in LPCVD using germane gas

The growth characteristics in the initial stage of Ge epitaxy on the Si(1 0 0) epitaxial buffer layer have been investigated by ultraclean LPCVD at 350°C using GeH₄ at 0.2 and 12 Pa with H₂ or Ar as a carrier gas. When H₂ was used as a carrier gas, an incubation period was found (about 12 min at 0.2 Pa), during which Ge nuclei were formed on Si. After the incubation period layer growth of Ge film began. In the case where Ar was used as a carrier gas, the incubation period was drastically reduced without any apparent change in the layer growth rate. The nucleus size was larger and the nucleus density was lower in the case of H₂ as carrier gas. These growth characteristics are believed to be caused by the suppression of adsorption and/or decomposition of GeH₄ on the H-terminated Si surface in the case of H₂.