Stresses evolution at high temperature (200°C) in Copper/Alumina (Cu/Al2O3) stack

This paper presents the temperature influence on the adhesion of a copper thin film deposited on an alumina substrate. 5μm and 20 μm thicknesses of copper films were deposited by RF sputtering and characterized. Simulation and mechanical characterizations were realized. Results obtained by Stoney stresses and by Von Mises Stress show stresses relaxation after first annealing and their stabilization for following annealing cycles (200°C). Stress values obtained are lower than the elastic stress on the copper layer which corroborate SEM analysis where copper films present absence of cracks after an annealing at 200°C during one hour. On the other hand, an experimental critical stress characterization has been performed. Results show that critical stress increase with the increasing temperature and decreasing with the copper thickness.