Fabrication of high index contrast waveguide stacks for biosensing and other applications require nanometer scale thickness control. Nanoscale dielectric films from electron-beam evaporation can be difficult to obtain due to the resulting porosity and poor stoichiometry of the films. An alternative approach is the reactive deposition of the film from a metal source in the presence of oxygen ions. Using spectroscopic ellipsometry, we have shown that greater control over thickness and index of refraction of silicon dioxide depositions can be obtained through reactive depositions as compared to depositions from SiO2 dielectric source material itself. Through Fourier Transform Infrared Spectroscopy (FT-IR), the Si-O in-phase stretching peak at 1078 cm-1 can be traced, allowing us to determine the stoichiometry of the film.
The effects of performing depositions of aluminum oxide dielectric source material in the presence of oxygen ions has also been investigated. Through the use of the oxygen ion source, greater control over index of refraction and optical losses has been observed. By controlling ion source parameters, the aluminum oxide films’ index of refraction can be engineered within a range of 1.58 to 1.64, and waveguide losses can be reduced to as low as 2.0 dB/cm.