Electrodeposition of Cu on Ta-based layer II: Cu Electrodeposition on Cu/Ta bilayers

Abstract

Ta substrates covered with nominal thicknesses of 1, 2.5, and 5 nm physical vapor deposited (PVD) Cu seed were employed as substrates for Cu electrodeposition. Electroplating a thin, uniform Cu film on Cu seed less than 5 nm in thickness is problematic using a typical acid electrolyte. A basic electrolyte was seen to be successful in electrodepositing a thin, continuous Cu film on all these substrates. Polarization curves show the nucleation of Cu from this electrolyte is influenced by the PVD Cu seed thickness, with the 5 nm Cu seed exhibiting behavior similar to that obtained on thick PVD Cu seed. Chronoamperometry and SEM suggest that the presence of the PVD Cu on the Ta surface significantly affects the Cu nucleation process. High electrodeposited particle densities are achievable with the basic electrolyte on Cu PVD seeds <5 nm in nominal thickness. © 2007 The Electrochemical Society.