Optical and surface analysis of DC-reactive sputtered AlN films

Abstract

A set of aluminium nitride (AlN), thin films were prepared by DC-reactive magnetron sputtering. The deposition parameters, such as substrate temperature, sputtering gas composition and plasma current were varied. Spectroscopic ellipsometry, XPS, RBS, XRD, SEM, AFM and FTIR techniques were utilized to study the relationship between film properties and preparation conditions. We observed that the optical and surface properties have a strong dependence on the deposition rate. All prepared films present a composition close to AlN stoichiometry, even for nitrogen to argon gas concentrations below 1:2. The near surface of AlN films exposed to atmosphere was primarily composed of Al 2O 3 while the bulk was AlN with some minor contamination of oxygen and carbon. The thickness of the oxide layer was reduced when higher plasma current and lower nitrogen concentration were used. Deposits prepared at 400 °C presented the best refractive index and deposition rate, for both utilized plasma currents.