Structural, compositional and optical properties of PECVD silicon nitride layers

We have investigated the correlation between the various plasma-enhanced chemical vapour deposition (PECVD) process parameters on the structural, compositional and optical properties of SiNx layers. The investigated process parameters are gas composition, radio frequency power and its frequency and deposition temperature. We also investigated SiON and ammonia-free SiNx layers. Refractive index, thickness, residual stress, structure and composition of the dielectric layers were determined using interferometry, wafer bowing, scanning electron microscopy, Fourier transform infra-red and secondary ion mass spectrometry measurements. SiNx films can be deposited to be almost stress-free with relatively low concentration of hydrogen (10 to 19% of atomic H). SiNx layers have the potential to cover a wide range of refractive indices (1.8-2.1) with possible extension down to 1.40 through various SiON layers.