Cu Electrodeposition on Resistive Substrates in Alkaline Chemistry: Effect of Current Density and Wafer RPM

A wafer-scale wet alkaline seed electrodeposition process directly on resistive substrates, such as PVD RuTa and CVD Co films as thin as 2 and 5 nm respectively, is studied. The effect of the directly plated stack composition and thicknesses, plating waveform, rotation speed and applied current on the plating rate and morphology of the deposited copper is reported. The alkaline deposition process is directly compared to the acid deposition process on the resistive RuTa substrate, while the thin Co films undergo to dissolution in acidic chemistries. In the case of the alkaline chemistry, since the deposition is less mass transport dependent and less sensitive to preferential nucleation due to terminal effect, the presence of Cu complexing agents results in a more uniform distribution of the Cu ions along the wafer surface translating in a higher throwing power with respect to acid plating baths. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3576121] All rights reserved.