Substrate temperature dependence of the roughness evolution of HWCVD a-Si:H studied by real-time spectroscopic ellipsometry

The surface roughness of HWCVD deposited a-Si:H films has been monitored as a function of the film thickness for substrate temperatures between 70 and 450 °C using real-time spectroscopic ellipsometry. Information on the microstructural evolution of the a-Si:H films has been deduced from the data and different growth phases in this microstructural evolution are discussed in terms of the underlying surface processes such as nucleation and initial growth, surface smoothening and roughening processes, and surface diffusion. From the data, it is concluded that, for the specific conditions studied, the best material properties are obtained at ∼ 250–350 °C.