Study of Si–Ge Interdiffusion in Laser Recrystallization of Ge Epitaxial Film on Si Substrate

Direct epitaxial growth of germanium (Ge) film on silicon (Si) substrate (GOSS) holds great potential in micro-electronics and optoelectronics. However, due to the 4.2% lattice mismatch between Si and Ge, it is difficult to directly obtain high quality Ge by epitaxy on Si substrate. Laser recrystallization technology provides a simple, efficient and low-cost way to improve the crystal quality of epitaxial Ge film grown on Si substrate. This technology is essentially a process of thermally induced phase transformation. By controlling the laser process parameters, epitaxial film of a certain thickness is melted, so that lattice rearrangement and recrystallization are achieved, and high-quality thin Ge/Si can be prepared. Laser recrystallization is a high temperature thermal process, and Si–Ge interdiffusion may detrimentally occur. In this paper, the mechanism of Si–Ge interdiffusion is discussed. Based on Fick's law of diffusion, a numerical model for Si–Ge interdiffusion of GOSS is established. On this basis, the process simulation of thermal annealing and laser recrystallization Si–Ge interdiffusion is carried out by Sentaurus Process simulation. The results show that compared with the traditional thermal annealing, the Si–Ge interdiffusion of Ge on Si almost does not occur in the process of laser recrystallization. By reasonably controlling the process parameters of laser recrystallization, the thin Ge film near the Si–Ge interface does not melt, which can not only improve the crystal quality of Ge epitaxial layer, but also effectively avoid the Si–Ge interdiffusion in the process of laser recrystallization. Through this research, we have aimed at predicting and control the Si–Ge interdiffusion, providing an important technical reference for the preparation of high quality GOSS by laser recrystallization technology.