Influence of strain and initial reactions on epitaxial SiGe growth

Heteroepitaxial growths of SiGe (0 – 40%) on fully relaxed SiGe virtual substrate (VS) with various Ge content (0 – 44%) are investigated to clarify the influence of strain and the initial surface on the SiGe growth. The deposition is performed using H 2 -SiH 4 -GeH 4 based chemical vapor deposition (CVD) on planarized SiGe substrates, achieved by chemical mechanical polishing (CMP). The CMP interface is separated from the heteroepitaxial interface by depositing a homoepitaxial SiGe buffer layer on the SiGe VS, followed by a top heteroepitaxial SiGe growth. No relaxation of the top SiGe is confirmed for all combinations of the top SiGe and the SiGe buffers. With increasing tensile strain, an increase in the Ge content and a decrease in the growth rate are observed. The increase in the Ge content is more pronounced for the top SiGe growth with higher Ge content. It seems the surface reaction of SiH 4 on the SiGe growth front is reduced by higher tensile strain. The top SiGe with higher Ge content shows higher interface pile-up of Ge, and the pile-up is pronounced on the SiGe buffer with higher Ge content as well as higher growth temperature, indicating non-equilibrium reaction at the initial stage of the SiGe growth. These results obtained here enable precise control of heteroepitaxial SiGe growth by CVD.