WSix formation in W–Si multilayers

The formation of WSix phases from multiple thin layers of W and Si was investigated. Tungsten and silicon thin films of ~5 nm thickness were deposited sequentially onto GaAs substrates by dc magnetron sputtering from elemental targets. The total film thickness was ~300 nm. The W and Si layer thickness, and thus the overall composition of the films, was controlled by adjusting the power applied to the two sputtering targets. The films examined in this work had nominal compositions in the range WSi2–WSi0.48.The multilayered structure was subjected to rapid thermal annealing at 900 °C. The extent of the reaction, the grain size, and the crystal structure of the silicides were determined using transmission electron microscopy and X-ray diffraction. For WSix films with [Formula: see text], the silicides had the βW structure and were relatively large grained, ~450 nm, while for x > 0.52, the film contained the W5Si3 phase and consisted of grains ~45 nm in diameter.Schottky contacts were of good quality for [Formula: see text], with a barrier height (ϕ) of 0.7 V and an ideality factor (n) of 1.15. Schottky contacts with higher silicon concentrations were poor.The WSix (x = 0.52) Schottky contact has been successfully incorporated into a self-aligned gate field-effect transistor.