Rapid screening of plating additives for bottom-up metallization of nano-scale features

Abstract

An improved test for rapid determination of the efficacy of additives systems for use in bottom-up copper metallization of micro- and nano-scale features is introduced as a replacement for the classical injection technique. The conventional injection test is based on measuring the polarization response to the injection of an additive into a solution in which a rotating disk electrode is plated at a moderate constant current density of about 10 mA cm−2. The inaccurate assumptions underlying this test and its limitations are discussed. The modified screening technique introduced here is based on the recognition that bottom-up metallization of micro- and nano-scale features is carried out at a constant overpotential where the current density at the inhibited regions of the feature is significantly lower, on the order of 1 mA cm−2. A single polarization measurement at this low current density in an electrolyte containing the tested suppressors is suggested. The suppressors exhibiting the largest overpotentials are considered promising and should be selected for further characterization.