Thin layers of Ta and Cr deposited onto plasma-deposited silicon dioxide (SiO2) and silicon nitride (SiN) surfaces promote adhesion of Cu to the underlying insulating surfaces. In this paper, the peel adhesion strength of the Ta and Cr layers to the reactive ion etched (RIE) and Ar-sputtered insulating surfaces is measured after Cu deposition. Peel tests, which provide a measure of the adhesion strength of the metallic (Cu + Ta or Cr) layer to the insulators, indicate that both Ta and Cr adhere better to SiN than to SiO2. Cohesive failure of the peel strip occurred for the Ta/SiN system rather than failure at the interface. The freshly exposed surfaces of the peeled metallic strip and the underlying insulator, which represent the locus of adhesion failure, were analyzed by X-ray photoelectron spectroscopy (XPS). Characterization of the chemistry at the surfaces and their relationship to adhesion is discussed.