Silicon Nitride Films by Reactive Sputtering

Silicon nitride films (from 500 to 7500A in thickness) have been deposited on silicon and silicon dioxide by reactive sputtering of a silicon cathode in a N2 glow discharge. Both d-c and rf sputtering have been investigated. Physical and chemical properties of silicon nitride films prepared by sputtering were examined in reference to the process variables. The rate of deposition was aDDroximately proportional to the square root of rf power density. Film den-sity increased with power density, and decreased with gas pressure. Opt imum gas pressure was in the range 3-10 x 10-3 Torr. Higher pressures resulted in less dense and electronically leaky films. Dielectric constant and etch rate in HF solution appeared to correlate well with film density. Residual pres-sure higher than I-2 x 10-6 Torr was found to have a most detrimental effect. Argon and nitrogen gas mixtures resulted in excess silicon incorporation in the deposited nitride films. Silicon dioxide has for the past several years bee