© 2014 Elsevier B.V. All rights reserved. In this study X-ray photoelectron spectroscopy (XPS) has been used to characterize manganese silicate Cu diffusion barrier layer formation on a range of ultralow-κ (ULK) carbon doped oxide (CDO) layers. Ultra-thin Si and Mn oxide films were deposited in order to provide accurate binding energy (BE) references for the Si 2p and O 1s core levels of the dielectric materials. The results indicate that there is a strong correlation between carbon content in the CDO films and the BE position of both the Si 2p and O 1s core level peaks. Furthermore, it has been shown that the full width half maximum (FWHM) of these peaks are significantly larger than those observed in SiO2 leading to complications in the analysis and identification of barrier layer formation on these low-κ substrates. In a separate experiment, the deposition and high temperature annealing of thin fully oxidized Mn layers (MnOy, where y ≥ 1) on these ULK CDO substrates suggests the formation of an interface layer consistent with MnSiO3 based on analysis of both the O 1s and Mn 2p core level spectra. It is also shown that the use of oxidized Mn films tend to minimize the formation of Mn carbide within the barrier layer region in agreement with previous studies on other CDO substrates.