Effect of Ar and He/H-2 (5%) plasma treatments on the electrical properties of the Cu/SiLK damascene structures for multilevel interconnect technology have been investigated. It was found that the Kelvin via resistances of the samples treated using the two kinds of plasma have no significant difference when the vias in the structures is more than 0.24 Vim in diameter. However, the via resistance of He/H-2-treated samples is much lower than that of Ar-plasma-treated samples when the vias is reduced to 0.22 mum and below. It was also found that the line-line leakage current has no obvious difference for both the Ar- and He/H-2-Plasma-treated samples. By increasing the applied voltage to the comb structures, the leakage current undergoes an abrupt rise at 3 MV/cm for the Ar-plasma-treated samples, but at 2 MV/cm for the He/H-2-treated samples. After annealing at 350 degreesC for 1 h under N-2 ambient, the line-line leakage current increases significantly from 3 x 10(-12) to 5 x 10(-9) A for the samples with He/H-2 Plasma treatment, but no obvious change was observed for the samples with Ar plasma treatment. The Fourier transform infrared spectroscopy results indicated that a new Si-H peak appears in the samples treated using the He/H-2 (5%) plasma, which is likely related to the differences observed in the breakdown voltages and the leakage current after annealing. (C) 2004 Elsevier B.V. All rights reserved.