Intrinsic stress in A1N prepared by dual-ion-beam sputtering

Abstract

The intrinsic stress of AIN, prepared by dual-ion-beam sputtering, has been investigated as a function of deposition temperature and nitrogen ion energy. The results show that the stress is compressive over the temperature range 75–700°C with a maximum value of -28×10 9 dyn cm -2 at 75°C. The stress decreases gradually with increasing deposition temperature up to T d/ T m = 0.33 and then decreases sharply for higher temperatures. These results are similar to those reported for evaporated and r.f. sputtered metal films and appears to be a general result independent of the sign of the stress. The temperature dependence is interpreted in terms of the annealing of a strained layer and grain growth models. The results show that the compressive stress is due to the bombardment of the condensing film by energetic particles. Calculations indicate that the most energetic particles are of the order of 160 eV, originating as neutralized back-reflected argon neutrals. The nitrogen ions from the auxiliary gun do not appear to contribute materially to the intrinsic stress. Evaporation of aluminum, while simultaneously bombarding the film with an independent source, indicates that a saturation stress condition is established above a normalized energy of about 50 eV atom −1.