Solid state diffusion of Cu from copper containing films into a chemical vapor deposited (CVD) Al film was evaluated as a method to dope the CVD Al with Cu atoms to enhance its electromigration resistance. CVD Cu and PVD Al-1.5 wt% Cu thin films were used as the copper sources. Thin film stacks consisting of CVD Al/CVD Cu and PVD Al-Cu/CVD Al were deposited onto unpatterned silicon dioxide films as well as silicon dioxide films patterned with 0.6-micron diameter by 1.2-micron deep via holes. Samples were annealed for 0, 5, 15, or 60 minutes at 360, 390, or 420 degrees Celsius. Backscatter electron microscopy was used to image theta phase (Al@sub 2@Cu) precipitates inside vias. The number of precipitates and fraction of via cross-sectional area covered by the precipitates were used to estimate the amount of Cu present in the vias. These results are compared to Rutherford backscatter spectrometry and Auger electron depth profiling analyses of samples with films deposited onto unpatterned substrates.