Abstract: A method includes forming a first conductive feature in a first dielectric layer. A second dielectric layer is formed over the first conductive feature and the first dielectric layer. An opening is formed in the second dielectric layer. The opening exposes a top surface of the first conductive feature. The top surface of the first conductive feature includes a first metallic material and a second metallic material different from the first metallic material. A native oxide layer is removed from the top surface of the first conductive feature. A surfactant soaking process is performed on the top surface of the first conductive feature. The surfactant soaking process forms a surfactant layer over the top surface of the first conductive feature. A first barrier layer is deposited on a sidewall of the opening. The surfactant layer remains exposed at the end of depositing the first barrier layer.