Optimizing the composition of a TaSiN barrier layer is presented. The stress in a copper seed layer decreases markedly with the increase of Si composition in the barrier. A resistivity of 2.8 muOmega-cm is obtained when a TaN barrier layer (Si composition: 0) is used. This resistivity decreases with increasing composition of Si in the TaSiN barrier layer and reaches a minimum of 2.3 muOmega-cm in an as-deposited 300 nm thick copper layer on a TaSiN barrier containing 0.06 Si. Resistivity of 1.92 and 1.82 muOmega-cm can be obtained in 300 and 500 nm thick copper layers, respectively, after annealing. (C) 2004 The Electrochemical Society.