Characteristics of ion-beam-sputtered thin films

Abstract

Thin films of Au, Si, Al, NiFe, Ta, and W have been prepared by ion beam sputtering, and physical properties have been compared with films deposited by rf sputtering, and electron beam evaporation. In general, films of a given material appeared to be comparable for the properties measured, independent of deposition method. In the ion beam sputtering system, the effects of deposition rates are studied as a function of the accelerating voltage of the ion beam, and of the angle created by the target tilt and the path of the ion beam. Deposition rates generally leveled off at an accelerating voltage of 750 V; and for several materials, a peak in deposition rate was observed at a target-beam angle of 30°. The magnetic properties of ion-beam-sputtered NiFe films are compared before and after annealing in vacuum at 350°C for 30 minutes. Annealing produced a small drop in the resistivity of these films, with a corresponding increase in the magnetoresistive effect, Δρ/ρ. Electron microprobe measurements indicate no significant incorporation of ionizing gas in the films. Ion-beam-sputtered thin films appear to be as good as films deposited by the other techniques discussed, and have shown a distinct advantage for use in liftoff processes. Since ion beam deposition occurs in a field-free region, heating effects due to electron bombardment of the substrate are minimal. Photoresist images are not degraded, and subsequent lift-off is facilitated.