A silicon nitride membrane growth process has been characterized. The films were grown by LPCVD on 100 mm diameter silicon substrates using ammonia and dichlorosilane as reactant gases. The films were grown using a range of gas ratios at three different temperatures. The film composition was determined by elastic recoil detection. The silicon-nitrogen absorption bands were characterized by FTIR spectroscopy. The photon transmission of the films was measured in the visible region from 350 – 850 nm, and in the x-ray region for photon energies from 1000 to 3000 eV. The film stresses were determined using the wafer bow technique. An increase in the silicon content of the films was observed for increased dichlorosilane gas flow and for increasing growth temperatures. The increased silicon content of the films is correlated to a decrease in the tensile stress and a decrease in the optical transmission of the films.