Note that samole C has a uniform death profile. We have found that sanple A and also similarly prepared films having titanium or chromium layers have similar solute depth profiles after annealing. This uniform copper depth profile is expected from calculations of the diffusion length of copper in aluminum which is about 4.8pm under our annealing conditions. In contrast, the copper profile of sample E exhibits a linear gradient from about 1.9wt% at the surface to
3.O wt% at the metal/oxide interface. It has been suggested that this condition can occur
under conditions of high deposition rates where the substrate temperature is high
enough for the formation of theta phase CuAl2 particles during the deposition7 A summary
of the annealing conditions and RBS data is presented in Table II.