MICROSTRUCTURAL CHARACTERIZATION OF ION-ASSISTED SIO2 THIN-FILMS BY VISIBLE AND INFRARED ELLIPSOMETRY

The complex dielectric function of SiO2 films deposited on silicon sub strates by electron-beam evaporation under ion bombardment is determin ed by infrared ellipsometry between 700 and 5000 cm(-1) Analysis of th e absorption band associated with the Si-O-Si stretching mode at about 1040 cm(-1), the water absorption band at about 3300 cm(-1), and know ledge of the visible refractive index determined by Visible ellipsomet ry (in situ and after venting to atmosphere) enable us to model the co mplex structure of the films, as a densified silica matrix with pores. Depending on the ion assistance conditions, the pores are either most ly connected (allowing water penetration) or largely isolated (no wate r adsorption). The refractive index of the silica matrix, the pore vol ume fraction and the pore water filling rate are evaluated as a functi on of the assistance conditions. (C) 1998 American Vacuum Society. [S0 734-2101(98)10704-2].