Abstract: The invention relates to an electrolyte used in connection with the deposition of a gold-tin alloy on an electroplatable substrate. This solution generally includes water; stannous and/or stannic tin ions, a complexing agent to render the stannous and/or stannic tin ions soluble, complexed gold ions, and an alloy stabilizing agent that includes ethoxylated compounds with phosphate ester functional group, brightening additives based on ethoxylated phosphate esters and alkali metal fatty acids dipropionates. The brighteners may be used alone or in conjunction with each other to achieve beneficial synergistic effect. The alloy stabilizing agent is present in an amount sufficient to stabilize the composition of the gold-tin deposit over a usable current density range. The solution has a pH of between 2 and 10 and the gold ions and tin ions are present in relative amounts sufficient to provide a deposit having a gold content less than 90% by weight and a tin content greater than 10% by weight.

Abstract: A method for forming a quaternary alloy film of Co—W—P—Au for use as a diffusion barrier layer on a copper interconnect in a semiconductor structure and devices formed incorporating such film are disclosed. In the method, a substrate that has copper conductive regions on top is first pre-treated by two separate pre-treatment steps. In the first step, the substrate is immersed in a H2SO4 rinsing solution and next in a solution containing palladium ions for a length of time sufficient for the ions to deposit on the surface of the copper conductive regions. The substrate is then immersed in a solution that contains at least 15 gr/l sodium citrate or EDTA for removing excess palladium ions from the surface of the copper conductive regions.