Decrease in Electrical Resistivity of W Films on GaAs Substrates after High-Temperature Annealing

A specific decrease in the electrical resistivity of W films on GaAs substrates was found after annealing above 800°C in Ar. A decrease in the concentration of oxygen in sputter-deposited W films (0.2 µm thick) with a diffusion of Ga and As atoms from GaAs substrates into the films was also observed after annealing using AES and SIMS measurements. The decrease in the resistivity could be explained by a remarkable W grain growth by applying the Mayadas and Shatzkes grain boundary scattering theory. The grain growth was accompanied by the release of oxygen from the films. Depth-distribution profiles of Ga, As, and O in W/GaAs structures suggest two processes for the release. One is a pile-up of the oxygen which forms Ga-oxide on a W film surface. The other is the evaporation of oxygen from the surface in the form of As-oxide.