The use of passivation metals to protect Cu from interacting with polyamic acid precursor has been investigated by means of cross‐sectional transmission electron microscopy, Rutherford backscattering spectroscopy, and resistivity measurements. Palladium or platinum, each 100 nm in thickness, was electron‐beam evaporated onto Cu surface. Although not a good diffusion barrier against Cu outdiffusion, these metals can still effectively inhibit the Cu‐polyamic acid interactions and, consequently, prevent the formation of Cu oxide precipitates in the polymer film. The trade‐off is that, since Pd and Pt both diffuse into Cu and form solid solution alloys, the resistivity of Cu is raised significantly due to the enhanced electron‐impurity scattering. In contrast, Cr serves both as a passivation metal and a good diffusion barrier without raising Cu resistivity. This is probably due to the lack of mutual solubility between Cr and Cu.