Surface roughness analysis of electrodeposited Cu

Cu films were electrodeposited with mass transport controlled using a rotating disc electrode (RDE), and imaged with an atomic force microscope (AFM). The length-dependent roughness w(l,t)w(l,t) of these films follows a power law of the form w∝lHtβlocw∝lHtβloc for small length-scales l, with the local roughness exponent, βloc, varying from 0 to 0.5 depending on the experimental conditions. It was found that contrary to previous work βloc is not simply a function of the ratio of the current j to its diffusion-limited value jL. Focused ion beam (FIB) imaging was used as a new method of characterizing the film roughness. FIB images confirmed the existence of small βloc values for films for which the AFM data could have been unreliable. FIB is a particularly powerful method for characterizing high roughness films.