The lifetime of InGaAs/AlGaAs high power lasers increased significantly when silicon nitride (SiN) films deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) technique were used as optical coatings for the emitting facet of the lasers. Precleaning of the surfaces to be coated, and the stable low stress in the film have been found to be highly valuable for these lasers. The films were deposited at a low temperature (90degreesC) from a mixture of Ar, N-2, and SiH4 as precursors. Rutherford backscattering spectroscopy and nuclear reaction analysis measurements reveal that the composition of the film is 48 atom % Si, 32 atom % N, and 20 atom % H. The most important properties of the films are low intrinsic stress and a negligible hysteresis in the dependence of stress on temperature upon thermal cycling. The stress measurements indicate that all hydrogen atoms in the films are chemically bonded. (C) 2003 The Electrochemical Society.