Electroless-deposited Ag-W films for microelectronics applications

Abstract Thin Ag–W films, with a tungsten concentration of up to 3.2 at.% and a thickness in the range 20–300 nm, were directly deposited on Si(100) substrate by the electroless (auto-catalytic) method. The deposition characteristics and the thin film electrical and physical properties were studied as a function of the bath composition. The role of tungsten in the silver matrix was studied via measurements of the film microhardness and thermal stability as a function of the thin film composition. Ag–W films thicker than 200 nm had a shiny appearance with good reflectivity and their specific electrical resistivity was 2 μΩ cm. The specific resistivity of films increased with decreasing thickness. Exposure of electroless silver films to air at 200°C for a few h causes them to tarnish severely and their sheet resistance to significantly increase, while similar Ag–W films were not affected under the same conditions. Therefore, we assume that silver–tungsten films can be used for applications that require reliable conducting thin films, such as packaging and interconnects for microelectronics.