Scanning probe studies of electromigration in gold films
Abstract
Scanning Probe Microscopy (SPM) has been used to study electromigration (EM) and surface diffusion rates in electroplated Au films. Scanning probe studies of EM in 4 $\mu$m wide by 1 $\mu$m thick electroplated Au wires reveal substantial changes in surface morphology due to current stressing. Both hillock growth and void formation have been observed in-situ. Changes in surface morphology caused by electromigration can be quantitatively described from the scanning probe images and new techniques for studying mass flow due to electromigration are now possible. A novel technique which combines the well established theory of Sinusoidal Profile Decay (SPD) with SPM is introduced which allows surface-self diffusion rates at small length scales ($\sim$ 100nm wavelengths and $\sim$ 20 nm amplitudes) to be measured. The validity of a continuum based model used to describe surface diffusion at these length scales is tested. Direct experimental observations of terraces forming during profile decay show clear evidence that atomistic diffusion effects are occurring during SPD. Comparison of experiments performed by pure annealing to those due to current stressing show that the surface diffusion rate is $\sim$ 3 times larger during current stressing. The results provide evidence for enhanced surface diffusion due to electromigration.
Degree
Ph.D.
Advisors
Reifenberger, Purdue University.
Subject Area
Condensation|Materials science
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