Electrochemistry-enabled atomic layer deposition of copper: Investigation of the deposit growth rate and roughness

Electrochemical atomic layer deposition (e-ALD) presents a low-cost, environmentally friendly and scalable approach for the atomically precise fabrication of semiconductor interconnect materials. In the present work, growth rate and roughness evolution during e-ALD of copper (Cu) were analyzed using anodic stripping coulometry, atomic force microscopy, and diffusion-reaction modeling. Through considerations of the unsteady-state diffusional transport of species and their associated surface electrochemical reactions, a semianalytical e-ALD process model is developed. The model enables quantification of the e-ALD growth rate and the deposit surface roughness as a function of various e-ALD process parameters, i.e., electrolyte composition and deposition time. Model predictions are compared with experimental data and good agreement is noted. The model is used to develop guidelines for the selection of optimal process parameters that enable e-ALD of Cu with minimal roughness evolution and a deposit growth rate close to one monolayer-per-cycle. Published by the AVS.