Copper oxidation, ionization, and penetration into a low-k polymer, SiLK-D (TM), are studied here. It is demonstrated by exposure to an oxidizing plasma and subsequent bias-temperature-stress experiments that an increase in the content of reactive or weakly bound oxygen at the SiLK-D (TM) surface in contact with the copper leads to the oxidation of the copper and injection of the copper into the polymer. The oxidation and injection are driven by the applied external electric field. X-ray photoelectron spectroscopy has been used to characterize the surface oxygen content on as-deposited (low oxygen content, the reference) and oxygen plasma treated films (high surface oxygen content). Capacitors were fabricated on both materials and bias temperature stress tests were done for several O-2 plasma exposure times and for external electric fields of 1, 0.5, and 0.1 MV/cm to detect copper ionization and injection. With an electric field of only 0.1 MV/cm, copper injection was not detectable even though oxygen at the SiLK-D (TM) surface had been increased by exposure to oxygen plasma. (c) 2006 American Vacuum Society.