ON THE THEORY OF THERMAL-STRESSES IN A THIN-FILM ON A CERAMIC SUBSTRATE

It is generally recognized that thermal stresses in thin films are pri marily responsible for morphological changes in thin films, including hillocks, whiskers, and void or pit formations, which present serious problems of reliability in microelectronics. In the present paper, the analytical theory of thermal stresses is constructed under some natur al simplifying assumptions. The latter include that of the thermoelast ic or thermoelastic-plastic behavior of the materials of a film and su bstrate after depositing the film and cooling the composite system to an operational temperature. The closed system of governing partial dif ferential equations for thermal stresses in a thin film is derived for any in-plane shape of the film. Some particular problems are solved i n an explicit form and the implication of the solutions for the predic tion of hillocks is discussed. Numerical and physical experiments are planned to verify the theory.