Initial Growth of Cu Films Fabricated by Sputtering and Evaporation.

Microstructural changes in the initial growth stage of Cu films fabricated by sputtering and evaporation are discussed. During and after deposition, the amplitude V of surface acoustic waves (SAWs) propagated on the piezoelectric substrate through the films deposited on it, and the electrical sheet resistivity of the films, Rsq, were measured. The surface morphology of the films was examined by using an atomic force microscope. As a result, it was found that (1) the critical thicknesses dp, at which the islands of a film begin to percolate, and dc, at which the film becomes two-dimensionally continuous, are smaller in sputter-deposited films than in evaporated ones; (2) the surface roughness of sputter-deposited films is smaller than that of evaporated films; and (3) microstructural change that increases the average inter-island spacing is harder to achieve in sputter-deposited films than in evaporated ones.