Atomic Layer Deposition of Tungsten(III) Oxide Thin Films from W2(NMe2)6 and Water:  Precursor-Based Control of Oxidation State in the Thin Film Material

The atomic layer deposition of W2O3 films was demonstrated employing W2(NMe2)6 and water as precursors with substrate temperatures between 140 and 240 °C. At 180 °C, surface saturative growth was achieved with W2(NMe2)6 vapor pulse lengths of ≥2 s. The growth rate was about 1.4 Å/cycle at substrate temperatures between 140 and 200 °C. Growth rates of 1.60 and 2.10 Å/cycle were observed at 220 and 240 °C, respectively. In a series of films deposited at 180 °C, the film thicknesses varied linearly with the number of deposition cycles. Time-of-flight elastic recoil analyses demonstrated stoichiometric W2O3 films, with carbon, hydrogen, and nitrogen levels between 6.3 and 8.6, 11.9 and 14.2, and 4.6 and 5.0 at. %, respectively, at substrate temperatures of 160, 180, and 200 °C. The as-deposited films were amorphous. Atomic force microscopy showed root-mean-square surface roughnesses of 0.7 and 0.9 nm for films deposited at 180 and 200 °C, respectively. The resistivity of a film grown at 180 °C was 8500 microhm cm.