Low temperature silicon nitride CVD process

Thermal CVD process for forming Si3N4-type films on substrates by reaction of gaseous NF3 with gaseous disilane at a temperature in the range of 250 DEG -500 DEG C., at pressures of 0.1-10 Torr. The mole ratio of NF3 to silane is in the range of 0.5-3.0 and the reaction zone is preferably isothermal (T controlled to within +5 DEG C.). The resulting films have RI's in the range of 1.4 to 3.0. The process parameters can be controlled to dope the film with H and/or F, or to create zones of differing properties within the film. The process does not cause radiation damage, metal migration, stored charge dissipation or high levels of impurities. Control of distance between adjacent wafers and wafer-to-wall spacing combined with laminar gas flow gives excellent film thickness uniformity, on the order of below about +/-5% across the wafer face, both within (across) wafers and from wafer to wafer (batch uniformity).