Oxidation Kinetics of Cu Thin Films in Air at 100°C to 300°C

Oxidation of Ti-Cu thin films was studied in air at 100°C to 300°C by three independent techniques: conductance change, weight gain, and in-depth profiling by ion sputtering Auger electron spectroscopy. X-ray diffraction was also used to confirm the oxide stoichiometry. Three evaporated Cu thicknesses (45 nm, 118 nm, and 528 nm) and one plated thickness (587 nm) were evaluated. The results from this study are the following. 1) The oxide grows with a time dependence of t^1/2as determined by conductivity and weight gain techniques. 2) The oxide stoichiometry is Cu2O as determined by Auger profiling and X-ray diffraction, and corroborated by weight gain. 3) The Auger technique indicated reasonable agreement with the conductivity data when comparable samples were studied. 4) Arrhenius plots made from the conductivity and weight gain data established the activation energy for the oxidation of the thicker Cu (528 am) as 1.0 to 1.3eV. 5) Auger profiles on the thick films indicated no Ti at the top surface of the Cu. 6) Preliminary information on the conductor stability and end-of-life requirements of the Ti-Cu metallization system have been established. Calculations indicate less than 1 mum of film is lost during high temperature stabilization (e.g., 4 hours at 300°C). It takes more than 40 years at 50°C to oxidize 250 nm of Cu.