Optical properties of PECVD TEOS-SiO2 Films

Abstract

A plasma enhanced chemical vapor deposition (PECVD) system was utilized to deposit silicon dioxide thick film using vapor TEOS (Si(OC2H5)4) and oxygen. And the refractive index of SiO2 film was modified by adding vapor TMP (P(OCH3)3) for doping phosphorous. The p-doped SiO2, with its refractive index higher than the SiO2 buffer layer, could be used as the light transmitting core layer. The thickness and the refractive index were measured by means of prism couple system. Fourier transform infrared spectrometer, FTIR, was also used to understand the bonding characteristics and help improving the optical properties. By Marcatili's method, an optimal range of relative refractive index between core layer and cladding layer could be calculated. On this basis, a ridge-type of waveguide could be designed, and the distribution of light inside the waveguide could be simulated using Beam PROP software. In combining the photolithography and etching process to fabricate an optical waveguide structure, the light propagation loss could be measured by direct couple method. A single mode waveguide with sharp sidewall and smooth interface could be fabricated successfully.