In situ spectroscopic ellipsometry study of the growth of microcrystalline silicon

摘要

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 ϵ~=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.