ELECTROCHEMISTRY OF CHEMICAL-VAPOR-DEPOSITED TUNGSTEN FILMS WITH RELEVANCE TO CHEMICAL-MECHANICAL POLISHING

The electrochemical behavior of chemically vapor deposited tungsten fi lms in solutions of interest to tungsten chemical mechanical polishing has been investigated using de potentiodynamic polarization, Linear p olarization, and Tafel methods. It was found that in the absence of an oxidizer, the tungsten surface was passivated most effectively at aci dic pH values. At pH 2 or 4, a WO2/WO3 duplex oxide layer of less than 50 Angstrom thickness was detected over the tungsten layer by x-ray p hotoelectron spectroscopy. The oxide layer formed at pH 2 was much thi cker, and had better passivity compared to the oxide formed at pH 4. A ddition of H2O2 at pH 2 or 4 resulted in a dramatic increase in tungst en dissolution.