I n s i t u spectroscopic ellipsometry study of the growth of microcrystalline silicon

High sensitivity, high-energy resolution, and the capability to obtain data in situ make ellipsometry a useful tool for addressing a number of problems in thin-film deposition processes. Dielectric functions ε̃=ε1−i ε2 of glow-discharge-produced microcrystalline silicon films (μc-Si) are determined by using spectroscopic ellipsometry (SE). ε2 spectra present a shoulder near 4.2 eV which corresponds to the E2 optical transition observed in crystalline silicon. This peak is not observed in amorphous silicon spectra. c-Si is described as a mixture of amorphous phase, microcrystallites, and voids. The choice of the microcrystalline reference phase is discussed in particular by comparing the microcrystallite volume fraction determined from SE and x-ray measurements. Strong variations in the nature of the material are observed during growth: the density deficiency and the surface roughness both increase as functions of film thickness up to 0.4–0.5 μm.