Abstract
Tungsten nuclei, for the subsequent electroless deposition of nickel, were formed of a water‐based tungsten‐rich microlithographic resist consisting of phosphotungstic acid and polyvinyl alcohol (PVA). Spinning the aqueous resist solution at 4000 RPM yields a pinhole‐free 103 Å thick negative resist film, containing ∼60 weight percent (w/o) tungsten. Exposure (≤100 mJ cm−2) of the resists to 254 nm light, postbaking and developing in an aqueous developer produces 0.3 μm features. Removal of the PVA at 400°C in air leaves a tungsten oxide film, with grains that are small enough to allow moderate temperature (450°C) furnace, or ambient temperature plasma hydrogen reduction to tungsten metal. The resulting patterned film, of 
thickness, consists of fine ≤0.05 μm tungsten grains. After palladium‐activation, the grains are selective nucleation sites for electroless deposition of nickel. 2000 Å thick nickel deposits on patterned nucleating films with 1 μm features did not show opens or shorts and had sharply defined boundaries. Because of the PVA's wetting ability, the spun aqueous resist also coats walls of vertical, 1 μm deep, 1 μm diam via holes. Upon processing, the wall‐coatings are converted into metallic tungsten nuclei. Palladium activation, followed by electroless deposition of nickel, produces nickel plugs in the vias. When nickel is deposited on small‐grained nuclei, the nickel grains are also small and the metal, growing from the wall inbound, fills the vias completely.