INTERNAL-STRESS AND ADHESION OF RF-SPUTTERED MGO FILMS ON GLASS SUBSTRATES

Magnesium oxide films from 50 nm to 1 μm thick were prepared on glass substrated by an r.f. magnetron sputtering technique. The effects of the introduction of oxygen in the sputtering gas and the substrate bias on the internal stress and the film adhesion were studied. The tribological characteristics were examined with a new scratch tester (microtribometer). Sputtering in 100% Ar yielded films of strong compressive internal stress and weak cohesion, i.e. the films were scratched into small pieces at light loads. As the concentration of oxygen in the sputtering gas was increased, the internal stress was relieved and the adhesion strength increased. Flaky fragments of broken films were observed. By contrast, a negative substrate bias resulted in a strongly compressive internal stress. Although the film structure became homogeneous, it was not possible to obtain thick films without crack generation.