Date of Award

1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

First Advisor

Gregory L. Griffin

Abstract

TiO$\sb2$ thin films have been prepared by the thermal decomposition of titanium tetra-isopropoxide (TTIP) in two low pressure chemical vapor deposition (LPCVD) reactors. The two reactors are the vertical tube hot-wall reactor and the stagnation point flow single-wafer cold-wall reactor. The effects of TTIP partial pressure, substrate temperature, gas flow rate, and reactor pressure on the growth rate of TiO$\sb2$ film were examined. Aerosol formation, wall effects, the effect of water content, and the effect of reactor geometry were also investigated. The experiments were performed in the substrate temperature range 225-400$\sp\circ$C, inlet TTIP partial pressure range $6.4\times10\sp{-4}$ $-$ 0.4 torr, reactor pressure range 1.5-8 torr, and gas flow rate range 12-192 sccm. Growth rates up to 5 $\mu$m/h were obtained. The TiO$\sb2$ films were characterized by X-ray diffraction and scanning electron microscopy. Only anatase TiO$\sb2$ films were obtained under the present experimental conditions. The morphology of TiO$\sb2$ films varies with the reactor used. A two-dimensional model for reactor transport and kinetic mechanism has been developed. A homogeneous gas phase reaction mechanism was utilized in the model. Aerosol formation in the gas phase was considered. To save computation time, simplified flow models were used in the modeling. The model equations were solved using a control volume based finite difference method. The model predictions of growth rates and uniformity of TiO$\sb2$ films agree well with the experimental results. Addition of multi-component diffusion coefficients and thermal diffusion in the model are recommended to improve the model predictions.

Pages

274

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