Thermal Stability and Oxidation Resistance of W, TiW, W(N) and TiW(N) Thin Films Deposited on Si

The thermal stability and oxidation resistance of ∼100-nm-thick W, TiW, W(N) and TiW(N) thin films deposited on Si substrate by rf magnetron sputtering were investigated by X-ray diffraction, resistivity measurement, X-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. All films showed good thermal stability against rapid thermal annealing in nitrogen (RTN) at 800°C for 1 min, except the W(N) film which decomposed to W and N2 at 800°C. The films also exhibited differences in oxidation resistance against rapid thermal annealing in oxygen (RTO). Both W and W(N) films were significantly oxidized at temperatures above 450 and 500°C, respectively, while TiW and TiW(N) films showed much better oxidation resistance up to temperatures of 750 and 650°C, respectively. In general, nitridized films, i.e., W(N) and TiW(N), exhibit better resistance against oxidation than metallic films. However, TiW films exhibit better oxidation resistance than nitridized films at RTO temperatures ≧600°C due to a change in surface oxide formation from a uniform oxide to a Ti-rich oxide. Once the films were completely oxidized, they were peeled off.