Date of Award
Doctor of Philosophy
Chemical and Biological Engineering
Glenn L. Schrader
Thin films of molybdenum oxides were produced on silicon substrates from Mo(CO)[subscript]6 and O[subscript]2 using both a low pressure and plasma enhanced chemical vapor deposition (LPCVD and PECVD). The substrates were heated using a SiC coated graphite susceptor which was inductively coupled to a 200-450 kHz radio-frequency (RF) generator and using a Macor resistive heater. The process variables investigated were temperature, 250-530°C; pressure, 100-1014 mtorr; Mo(CO)[subscript]6 flow rate, 0.56-6.7 mg/min; O[subscript]2 flow rate, 5-15 sccm; H[subscript]2O flow rate of 0.0-0.53 sccm; and RF current, 22-34 amps;Thermodynamic equilibrium calculations were conducted on the system using a computer program, Solgasmix-PV. The calculations indicated that [alpha]-MoO[subscript]3 was the most stable phase for all deposition conditions. [alpha]-MoO[subscript]3 films formed under LPCVD conditions at temperatures greater than 350°C and pressures of 300 mtorr or more depending upon the reactor geometry and the heater used during deposition. The [alpha]-MoO[subscript]3 films were oriented and had a columnar or platelet structure. At lower temperatures under LPCVD conditions reduced molybdenum oxides, MoO[subscript]2 and Mo[subscript]4O[subscript]11, were produced. A quadratic model was developed of the formation of LPCVD [alpha]-MoO[subscript]3 as a function of temperature and pressure. The film uniformity and composition were strongly influenced by transport processes;At high RF currents, the RF generator created an inductively coupled Ar-O[subscript]2 plasma in the system when using the Macor heater. Films deposited under PECVD conditions were oriented [alpha]-MoO[subscript]3; the PECVD films had lower deposition rates and were produced at lower temperatures than LPCVD [alpha]-MoO[subscript]3 films. The deposits contained little carbon (<1%). A model of the [alpha]-MoO[subscript]3 formation as a function of the process variables was developed using experimental design and regression analysis. The model indicated that the process variables act synergistically on the [alpha]-MoO[subscript]3 formation. The films were characterized using profilometry, x-ray diffraction and x-ray photoelectron, Fourier transform infrared, Auger and laser Raman spectroscopy.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Jeffrey Scott Cross
Cross, Jeffrey Scott, "Low pressure and plasma enhanced chemical vapor deposition of molybdenum oxide films " (1992). Retrospective Theses and Dissertations. 10105.