Interfacial reactions of Ta with a Si-O-C low-dielectric constant (low-k) material and Cu/Ta/Si-O-C multilayers are investigated using x-ray photoelectron spectroscopy (XPS) and cross-sectional transmission electron microscopy (TEM). Data indicate that Ta deposition on the low-k substrate results in the initial formation of Ta oxide and TAC. Subsequent deposition of Ta eventually results in the formation of a metallic Ta overlayer at 300 K. The thickness of the. initial Ta oxide/TaC-containing layer varies with the Ta deposition rate. At a deposition rate of similar to1 Angstrom min(-1), no metallic Ta is observed, even after 32 min sputter deposition time. In contrast, a film of roughly the same thickness, obtained after 15 s deposition at a rate of similar to2 Angstrom s(-1), is predominantly metallic Ta. Sputter deposition rates, derived from XPS data., are in agreement with film thicknesses derived from cross-sectional TEM data. Heating of Ta/low-k films in UHV results in no significant changes (as detected by XPS) up to 800 K. Cu deposited by sputter deposition onto a low-k surface covered with metallic Ta exhibits conformal growth, whereas 3d islanding is observed on a surface where TaC and Ta oxide are present. Cu diffusion into the bulk substrate is not observed at temperatures below 800 K in UHV. (C) 2003 American Vacuum Society.