Selective germanium epitaxial growth on silicon using CVD technology with ultra-pure gases

Low pressure chemical vapor deposition (LPCVD) experiments of Ge are presented. The results show that Ge epitaxy is possible by the LPCVD technique at low temperatures, if high-purity reactive gases and ultrahigh vacuum (UHV) compatible CVD equipment is used. Epitaxial films can be grown for several deposition parameter combinations. At low GeH₄ pressures facet formation can be observed, which originates from a stepflow dominated growth mechanism. At higher partial pressures plain surfaces are obtained due to dangling bond dependent growth, which is verified in a comparison between several Si substrate orientations. Ge CVD reveals perfect Si/SiO₂ selectivity and can, therefore, be used as a contact hole filling method as shown by Ge plugs in contact holes.