Study of interface impurity sputtering in partially ionized beam deposition of Cu on Si

Cu thin films have been deposited on Si(111) substrate using partially ionized deposition technique in which the self-ions, i.e., the ions derived from the depositing materials themselves, are being used to concurrently bombard the substrate surface during thin film growth. The ion percentage in the deposition beam is in the range from 0% to 5% with the ion energy varying between a few eV and several keV. The Si(111) substrates are chemically cleaned by a RCA cleaning process before loading into the vacuum chamber of deposition. No in situ cleaning of the substrate surface is performed prior to deposition. A reduction of impurities such as oxygen, carbon, and hydrogen at the Cu/Si interface is observed as a function of the ion bombardment parameters using secondary-ion mass spectrometry. The estimates of the sputtering cross section of oxygen, carbon and hydrogen at the Cu/Si interface by Cu ions and their energy dependence are discussed in the framework of mechanisms of the impurity sputtering by low-energy ions.