Control of polycrystalline silicon structure by the two-step deposition method

Polycrystalline silicon (poly-Si) films are obtained at temperatures below 400 degrees C by the catalytic chemical vapor deposition (Cat-CVD), often called "hot-wire CVD" method, using two-step deposition (TSD). In TSD, the substrate temperature is changed during deposition from the initial step for a short time of 200 s to the second step of 820 s. A comparative study on the structural properties of Cat-CVD poly-Si films prepared by the TSD method and those of the films prepared by conventional method was carried out using Raman spectroscopy, atomic force microscopy, reflection high-energy electron diffraction and transmission electron microscopy observation. It is found that the surface morphology, grain structure and thickness of the amorphous Si incubation layer are all correlated, and the structures are changed by TSD method.