Highly adhesive electroless Cu layer formation using an ultra thin ionized cluster beam (ICB)-Pd catalytic layer for sub-100 nm Cu interconnections

A continuous electroless-plated Cu film of only 10 nm in thickness was successfully deposited on a TaN barrier over a 1 nm-thick Pd catalytic layer formed by ionized cluster beam deposition. The electrical resistivity of the Cu interconnection was found to decrease as the Pd layer thickness was reduced, to as low as 2.1 muOmega.cm at a Pd thickness of 1 nm. 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 10nm-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.