Secondary ion mass spectroscopy (SIMS) and electrical measurements have been used to investigate the mechanism of copper transport in dielectric materials. Vacuum bias-temperature-stress (BTS) measurements on circular metal-oxide-semiconductor (MOS) capacitor structures show no sign of copper diffusion at temperatures up to 300 degreesC with electric fields up to 0.5 MV/cm. In contrast, measurements on samples oxidized via ambient gases or pure oxygen show significant copper transport through SiO2 based dielectric materials. The results suggest a mechanism where oxidized copper is a source of copper ions that are transported through the dielectric layer via diffusion and drift. After transport through the oxide, the copper crosses the SiO2/Si interface and diffuses into the silicon substrate, which acts as a sink for copper. An analytical model provides an apparent activation energy of 1.8 eV for the diffusion coefficient, and an exponential field dependence with a multiplier of 5.6 x 10(-7) cm. A more rigorous model based on a one-dimensional solution of the drift-diffusion equation and Poisson's equation is also developed to fit the flux data. The model reveals that a unique activation energy cannot be assigned due to uncertainty about the chemical-physics at the Cu/SiO2 interface. (C) 2004 Elsevier B.V. All rights reserved.