The model of solid phase crystallization of amorphous silicon under elastic stress

Solid phase crystallization of an amorphous silicon (a-Si) film stressed by a Si₃N₄ cap was studied by laser Raman spectroscopy. The a-Si films were deposited on Si₃N₄ (50 nm)/Si(100) substrate by rf sputtering. The stress in an a-Si film was controlled by thickness of a Si₃N₄ cap layer. The Si₃N₄ films were also deposited by rf sputtering. It was observed that the crystallization was affected by the stress in a-Si films introduced by the Si₃N₄ cap layer. The study suggests that the elastic stress increases with crystallization due to the smaller elastic modulus of a-Si with respect to crystalline silicon (c-Si). It is most reasonable to think that the elastic stress does not relax and that the elastic energy increased with crystallization because the elastic modulus of a-Si is smaller than that of c-Si. The experimental data was fitted by this model and the difference of the enthalpy ΔH_ac between a-Si and c-Si which is the latent heat of crystallization obtained by the fitting showed good coincidence with the previously reported value.