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SCALING OF THE ROUGHNESS OF Cu FILMS ELECTRODEPOSITED AT CURRENT DENSITY FAR FROM THE LIMITING CURRENT DENSITY
Manon Lafouresse and Walther Schwarzacher
H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, UK
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The roughness, w, of electrodeposited Cu films follows a power law of the form
w ~ lHtßloc for small
length-scale l, with the local exponent ßloc varying from 0 (normal scaling) to 0.5
(anomalous scaling). Cu films were electrodeposited
galvanostatically with mass transport controlled using a Rotating Disc Electrode (RDE) in an attempt to find which
parameter influences the value of ßloc. The deposition current density, j, was set to be far from the diffusion
limited current density, jl, with j/jl = 0.1-0.2. The films were then imaged with Atomic Force Microscopy (AFM)
and Focussed Ion Beam (FIB). The value of ßloc was found to depend strongly on the potential. The roughness of high
thickness films (up to 20 microns) was measured thanks to the FIB images and a transition from anomalous scaling to
normal scaling was detected as the thickness of the films increased.
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