Characterization of Electroless-Plated Cu Film over Pd Catalytic Layer Formed by an Ionized Cluster Beam

Abstract

A continuous electroless-plated Cu film only 10 nm thick was successfully deposited on a TaN barrier over a 1-nm-thick Pd catalytic layer formed by ionized cluster beam deposition. Secondary ion mass spectrometry (SIMS) analyses for the electroless-plated Cu films on the 20-nm and 1-nm ionized cluster beam (ICB)–Pd layers showed that the Pd metal had diffused into the Cu and caused a high electrical resistivity of Cu interconnect. The electrical resistivity of Cu interconnects formed by electroless plating on an ICB-deposited Pd catalyst layer decreased with decreasing thickness of the ICB–Pd layer. At an ICB–Pd layer thickness of 1-nm, the electrical resistivity of the overlying Cu interconnect was . Moreover, the deposited film has adhesion strength as high as that of sputtered Cu on TaN, even for the case of the 1-nm-thick Pd catalyst layer. A uniform and continuous 10-nm-thick Cu seed layer was formed by electroless plating over a 1-nm-thick Pd layer, and subsequent Cu electroplating filled all high-aspect-ratio via holes without the appearance of voids.