STRESS MEASUREMENTS AND CALCULATIONS FOR VACUUM-DEPOSITED MGF2 FILMS

Previous in situ measurements of the intrinsic stress in thin crystalline dielectric films have been interpreted in terms of a stress mechanism due to forces at the grain boundaries. The same stress interpretations were given for metal films by Hoffman and coworkers several years ago. In the present work it is shown that the tensile stress is a decreasing function of impurity concentration in the MgF2 films. A similar decrease occurs through water vapour adsorption. Assuming that the impurity is located mainly on the crystallite surface, as with adsorbed water molecules, this effect can also be interpreted using the grain boundary model which predicts a decreasing tensile stress with increasing crystal size. The results of stress measurements of MgF2 films deposited onto heated substrates support this prediction. © 1979.