Silicon nitride layers (SiNx:H) are widely used in the photovoltaics field as antireflection coating and to passivate multicrystalline silicon solar cells. With this aim, we have developed a plasma-assisted chemical vapour deposition reactor using microwave remote plasma (2.45 GHz). Effect of gas flow rate, microwave power and substrate temperature on the layers is presented. Refractive index varies between 1.7 to 3 in the sample as grown, with a deposition rate up to 40 nm/min. The temperature was observe to have no influence on the deposition rate, and the optical properties of the layers are very stable towards rapid thermal annealing at high temperature (850°C). This is attributed to the low hydrogen content of the layers, as revealed by FTIR analysis.