Optimization of plasma-enhanced chemical vapor deposition silicon oxynitride layers for integrated optics applications

Silicon oxynitride $(SiO_{x}N_{y}:H)$ layers were grown from 2% $SiH_{4}/N_{2}$ and $N_{2}O$ gas mixtures by plasma-enhanced chemical vapor deposition (PECVD). Layer properties such as refractive index, deposition rate, thickness non-uniformity and hydrogen bond content were correlated to the relevant deposition parameters including radio frequency power, chamber pressure, total gas flow, substrate temperature and $N_{2}O/SiH_{4}$ gas flow ratio. As a result, optimized $SiO_{x}N_{y}:H$ layers could be produced over a wide index range (1.46–1.70) with good thickness uniformity and sufficiently high deposition rate. With a refraction index non-uniformity < 5 × $10^{− 4}$ a thickness non-uniformity could be obtained below 1% over a 70 × 70 mm2 area of a 100 mm wafer at a deposition rate > 50 nm/min. The material composition and the optical properties of the $SiO_{x}N_{y}:H$ layers were characterized by spectroscopic ellipsometry, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared spectroscopy and prism coupler techniques. A simple atomic valence model is found to describe the measured atomic concentrations for PECVD silicon oxynitride layers.