Mechanical and etching properties of dual ion beam deposited hydrogen-freesilicon nitride films

Hydrogen-free silicon nitride (SiNx) with x varying from 0 to 1.3 were prep ared by sputtering a Si target with concurrent nitrogen ion (N-2(+)) assist at an energy of 250 eV. The value of x saturated at 1.3 when the assist N- 2(+) beam current was higher than 25 mA. As x increases from 0 to 13, the h ardness of the films increases from 12.2 to 21.5 GPa, the elastic modulus i ncreases from 191 to 256 GPa, the friction coefficient drops from 0.65 to 0 .37, the compressive stress rises from -0.52 to -1.4 GPa, and the etching r ate in buffered hydrofluoric acid increases. from a negligible small value to 7 mn min(-1) . Potassium hydroxide does not attack the film at any compo sition. Ion assist resulted in peening and densification of the film struct ure, causing the SiN1.3 films to have high hardness, high stability against oxidation in air, and great compressive stress. Ion bombardment also gener ated defects, thus giving rise to the moderate etching rate of SiN1.3 in BH F. The good mechanical and etching properties suggest that dual ion beam de position SiN, films are potentially useful materials in microelectromechani cal devices applications. (C) 2001 American Vacuum Society.