Novel highly conductive silver-tungsten thin films electroless deposited from benzoate solution for microelectronic applications

In this study we present the results of electroless deposition of silver-tungsten (Ag-W) films on SiO2, suitable for applications in microelectronics and ultralarge-scale integration technology. The thin-film composition and resistivity was studied as a function of the bath formulation. The optimal parameters (temperature, pH) and composition of aqueous solution for the deposition of Ag-W thin films with minimum resistivity were defined. It was shown that elevated temperature of the deposition bath results in impairment of solution stability and causes the Ag-W film resistivity to increase. Thin-film morphology was studied using scanning electron microscopy and optical microscopy. Ag-W electrical properties as a function of film deposition rate, composition, and structure were discussed. Novel Ag-W layers with improved properties, such as electrical resistivity and surface coverage, are presented in this work. The highest concentration of tungsten in Ag-W deposits was similar to2.1 atom % with oxygen concentration about 4 atom %. Resistivity of 150 nm thick Ag-W films reaches a value of similar to4 muOmega cm, and it is similar to6 muOmega cm for layers thinner than 60 nm. These films can be applied as both barrier and capping layers for corrosion protection of Ag. The possibility of reducing Ag-W film resistivity using vacuum annealing is demonstrated. (C) 2003 The Electrochemical Society.