INTERRELATION OF BOND CONFIGURATION AND OPTICAL PROPERTIES OF μc-SiC THIN FILMS BY SPECTROSCOPIC ELLIPSOMETRY

摘要

Amorphous (a-SiC:H) and microcrystalline (μc-SiC:H) thin films have been deposited by plasma enhanced chemical vapor deposition (PECVD) using He-diluted SiF_4-CH_4-H_2 r.f. plasmas. Gas flow rates have been varied to deposit films with different carbon content and microstructure. Their microstructure and optical properties have been investigated by spectroscopic ellipsometry in the energy range 1.5 - 5.0 eV. Ellipsometric spectra have been analyzed in terms of the Bruggeman effective medium approximation and the tetrahedron model to determine the film microstructure and carbon-bond configurations Correlation between bonding configuration and optical properties of films has been studied as a function of total carbon content and microstructre The optical gap was found to increase with carbon content and microcrystallinity. A chemical model for the amorphous-to-microcrystalline transition of the alloys based on the deposition/etching competition operated by atomic hydrogen and fluorine is proposed.