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 Ag2 W2 O7 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.