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 SiN _x layers. The investigated process parameters are gas composition, radio frequency power and its frequency and deposition temperature. We also investigated SiON and ammonia-free SiN _x 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. SiN _x films can be deposited to be almost stress-free with relatively low concentration of hydrogen (10 to 19% of atomic H). SiN _x 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.