Plasma deposition of SiN on silicon substrates in a microwave (2.45 GHz) electron cyclotron resonance SiH4/N2/He, in the ratio 4/10/10, discharge has been investigated as a function of rf (40 MHz) self‐biasing of the sample. Low levels of rf bias (0–10 W) were investigated and are reported in this letter. The effect of bias was measured for the deposited films with respect to refractive index, etch rate in BHF, Si—H bonding, and the intrinsic film stress. All depositions were conducted at or near room temperature to evaluate the effect of the applied rf bias on film density. All parameters examined indicated that low levels of rf bias help prepare a high quality, dense film at very low substrate temperatures.