Low pressure chemical vapor deposition of molybdenum oxides from molybdenum hexacarbonyl and oxygen

Thin films of molybdenum oxides were deposited at 300-500 °C and 200-1014 m Torr (26.6-135 Pa) from Mo(CO)₆, O₂, and H₂O using an inductively heated low pressure chemical vapor deposition system. Two oxygen gas flow rates of 5 and 15 sccm were used. α-MoO₃ films were deposited at temperatures of 425-450 °C, pressures of 660-1014 m Torr (88.0-135 Pa), with an O₂ flow rate of 5 sccm; and at 450-500 °C, 300-500 m Torr (40.0-66.7 Pa), with an O₂ flow rate of 5 sccm. The polycrystalline films were deposited on silicon (100) wafers and exhibited preferred orientations. Gas phase decomposition of the precursor was significant with temperatures ≫400 °C and pressures ≫600 m Torr (88.0 Pa), with an O₂ flow rate of 15 sccm. Owing to decomposition of the precursor in the gas phase and low gas velocities, the films decreased in thickness in the direction of flow. Thermodynamic equilibrium calculations indicated that α-MoO₃ was the most stable phase for all deposition conditions. However, α-MoO₃ was deposited only at high temperatures and pressures. A quadratic model of α-MoO₃ formation was developed using experimental design for the 5 sccm deposition data as a function of temperature and pressure. Both parameters were significant in the formation of α-MoO₃ films. The films were characterized using X-ray diffraction and X-ray photoelectron, Auger, and laser Raman spectroscopies.