Low-stress and Long-term Stable a-SiNx:H Films Deposited by ICP-PECVD

Based on a systematic variation of the gas flow ratio of silane (SiH4) and nitrogen (N2), amorphous hydrogenated silicon nitride (a-SiNx:H) thin films are synthesized with an inductively coupled plasma enhanced chemical vapour deposition (ICP-PECVD) technique offering a low (< 50 MPa) film stress in combination with a negligible drift behaviour. Most recently, two dominating regimes were identified, characterized by either high, but stable compressive stress or low stress, but with a strong drift behaviour. A rapid change in chemical composition at the transition point promotes the oxidation of the layer in the latter case causing the drift, and is confirmed by the corresponding change of the refractive index n, as well as FT-IR (Fourier-Transform Infrared Spectroscopy) and XPS (X-ray Photoelectron Spectroscopy) measurements.