Using an electron cyclotron resonance plasma compact source, we have studied the deposition of silicon nitride films at low deposition temperature (<300 degrees C) and low microwave power (<250 W). Nitrogen plasma and pure silane have been used as gas precursors. We report on the effect of the main process parameters on the composition and properties of the films. We show that each experimental parameter has an optimal range of values or a threshold value necessary to obtain films with high dielectric quality. For a deposition temperature of 300 degrees C, the best films exhibit a resistivity of 10(15) Omega cm and a soft breakdown field (at 10(-9) A cm(-2)) of 3 MV cm(-1). The physicochemical properties of the films are close to those of stoichiometric silicon nitride: N/Si ratio of 1.33, optical index value of 2 at 3 eV and etch rate of 10 Angstrom/min. Moreover, we observed strong correlations between the physicochemical and the electrical properties of the deposited films, over the entire range of process parameters.