Nucleation control of silicon-germanium on silicon oxide for selective epitaxy and polysilicon formation in ultraclean low-pressure CVD

Nucleation processes on Si oxide and epitaxial growth on Si for Si-Ge deposition have been investigated by ultraclean low-pressure CVD using SiH₄ and GeH₄ gases. It is found that, with GeH₄ addition, the deposition rate on Si increases and the nucleation rate decreases, and the degree of nucleation strongly depends on the Si oxide material. High selective Si-Ge epitaxy has been realized between Si and Si oxide at temperatures as low as 550°C. Moreover, it is suggested that control of the grain size of the deposited polysilicon film on Si oxide is possible by the Si-Ge nuclei.