Electrical bias-temperature stress measurements were performed on copper oxide/SiO2/silicon metal-oxide-semiconductor capacitors to measure the oxygen partial pressure dependence of the copper ion transport rates through the SiO2 layer. Both copper(1) oxides (Cu2O) and copper(II) oxides (CuO) were investigated, and copper oxide film stoichiometry was characterized by glancing incidence x-ray diffraction and x-ray photoelectron spectroscopy. At relatively high oxygen pressures, copper ion transport is observed for both Cu2O/SiO2/Si and CuO/SiO2/Si, and the activation energies are comparable. Under reduced oxygen pressures and vacuum, the copper ion flux is reduced for both copper oxides. In vacuum, the activation energy for copper transport from CuO layers is reduced by approximately 0.7 eV compared to the apparent activation barrier at high oxygen pressures, and the copper transport signals for Cu2O are below the detection limit of the experiment. A study of copper transport rates for both CuO and Cu2O electrode layers shows that the copper ion flux increases with increasing oxygen pressure, with an oxygen pressure dependence close to p(O2)(1/2). (c) 2006 American Vacuum Society.