We examined the chemical, structural, mechanical and optical properties of amorphous hydrogenated silicon nitride thin films deposited by hot-wire chemical vapour deposition using SiH4, NH3 and H-2 gases at total flow rates below 33 sccm. Time of flight secondary ion mass spectroscopy reveal that the film surfaces consist of predominantly Si with hydrogenated SixNyOz species. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy corroborate on the N/Si ratio. Electron energy loss spectroscopy discloses that the thickness of the nitrogen rich oxidized interface between the SiNx films and the c-Si substrate decrease with an enhancing NH3 flow rate. By varying the NH3 flow rate, dense SiNx films can be realized with hydrogen content between 16 and 9 at.%, a refractive index between 3.5 and 1.9 and optical band gap ranging from 2 to 4.5 eV. The SiNx film stress is compressive for N/Si <0.4 and tensile for higher N/Si > 0.55. Mechanisms relating the HWCVD conditions and the film structure and properties are proposed. (C) 2013 Elsevier B.V. All rights reserved.