Microstructural comparisons of ultrathin Cu films deposited by ion-beam and dc-magnetron sputtering

We report and contrast both the electrical resistance and the microstructure of copper thin films deposited in an oxygen-containing atmosphere by ion-beam and dc-magnetron sputtering. For films with thicknesses of 5 nm or less, the resistivity of the Cu films is minimized at oxygen concentrations ranging from 0.2% to 1% for dc-magnetron sputtering and 6%-10% for ion-beam sputtering. Films sputtered under both conditions show a similar decrease of interface roughness with increasing oxygen concentration, although the magnetron-deposited films are smoother. The dc-magnetron-produced films have higher resistivity, have smaller Cu grains, and contain a higher concentration of cuprous oxide particles. We discuss the mechanisms leading to the grain refinement and the consequent reduced resistivity in both types of films. © 2005 American Institute of Physics.