Electrochemical Study of the Mechanism of Ag(W) Electroless Deposition

We present an electrochemical study of the mechanism of silver-tungsten, Ag(W), thin film electroless deposition from the solutions that are used for micro-systems-metallization applications. Ag(W) electroless films were deposited on palladium-activated surface of thin silicon dioxide layers on silicon substrates from ammonia-acetic or benzoate silver complex based solutions at room temperature using hydrazine hydrate as a reducing agent. These solution compositions have been investigated. The adsorption mechanism of tungsten incorporation into Ag coating on the positively charged silver surface was proposed and its co-deposition with silver due to interfacial catalytic interaction between tungsten and silver ions in form of Ag 2 W 2 O 7 was shown. The kinetics of the Ag(W) electroless deposition process was analyzed by mixed potential theory. It was shown that the anodic charge-transfer reaction for ammonia-acetic solution and the diffusion of reduced silver ions to substrate for benzoate complex have controlled this process.