Analysis of intrinsic stress in and microstructure of Si thin films using molecular dynamics

The microstructure of silicon thin films deposited onto the (001) surface of silicon substrates and the intrinsic stress present in them were studied using three-dimensional molecular dynamics simulation. The Tersoff potential was used to represent the interaction among the silicon atoms. Simulation results show that such thin films have crystalline structures at deposition temperatures T/T_m>0.45 (T : absolute temperature, T_m: melting temperature) while they are amorphous at T/T_m<0.45. The pair correlation function and bond-angle distribution for amorphous silicon obtained from our simulations agreed well with experimental results. The simulation results show that the tensile stress in amorphous silicon films increases and that the variations in stress caused by the difference in the positions at which deposited atoms impinge become larger when the substrate temperature decreases. It was verified that the intrinsic stress in silicon thin films depends strongly on the microstructure of the films.