The effect of diluent gas and rapid thermal annealing on the properties of plasma-deposited silicon nitride films

Abstract

The effects of diluent gases on the deposition rate, content of hydrogen bonds, etch rate, refractive index and fixed charge density of plasma-enhanced chemical vapour deposition silicon nitride films have been studied for various gas compositions. Post-rapid thermal annealing (RTA) of as-grown films was also performed in the temperature range 500-1100°C. From the results of optical emission spectroscopy it is suggested that metastable N2 molecules can contribute to silicon nitride film formation as an extra nitrogen source. Metastable N2 molecules may enhance the dissociation of other feed gases. Lower refractive index, higher deposition rate and higher NH bond density were obtained for silicon nitride films grown in N2 diluent as compared with films grown in H2 diluent. As the RTA temperature was increased, the content of hydrogen bonds was reduced and the film density increased. Hence the etch rate of silicon nitride films in buffered HF solution decreased with increasing RTA temperature. A minimum value of fixed charge density was obtained at the RTA temperature of 900°C for all the films investigated. ？ 1992.