Leveler effect and oscillatory behavior during copper electroplating

Abstract

The electrochemical behavior of levelers was studied and compared for two commercial Cu plating chemistries in an effort to correlate the electrochemical behaviors with their impacts on bottom-up filling, impurity incorporation, and grain structures. While a strong complexing between leveler and accelerator resulted in a leveler-sensitive bottom-up filling rate and low impurity level in the deposit, a traditional non-interacting leveler showed little impact on the filling performance and yielded a high impurity incorporation. An oscillatory behavior was reported for the strongly-interacting leveler chemistry during galvanostatic plating, this oscillation manifested itself in both the potential and impurity incorporation. High impurity incorporation is known to inhibit the Cu grain growth; a laminated structure with alternating layers of big and fine Cu grains was obtained by annealing the Cu films plated with the oscillatory behavior. © 2012 The Electrochemical Society. All right reserved.