TEOS surface chemistry on SiO{sub 2} at CVD temperatures and pressures

We have developed a significantly improved understanding of thermal TEOS (tetraethylorthosilicate, Si(OCH{sub 2}CH{sub 3}){sub 4}) surface chemistry at CVD (chemical vapor deposition) temperatures and pressures. This was accomplished using GCMS (gas chromatography-mass spectroscopy) and FTIR (Fourier transform infrared spectroscopy) to examine how TEOS reaction rates are influenced by factors critical to the heterogeneous reaction. This included determining the TEOS pressure dependence, testing if reaction by-products inhibit TEOS decomposition, evaluating functional groups on the SiO{sub 2} surface as potential reaction sites, and establishing the functional group coverage dependencies. Our results show that TEOS decomposition rates are first-order in TEOS pressure and independent of the surface reaction by-products and the relative coverages of siloxane bridges (Si-O-Si) and hydroxyls on SiO{sub 2}. These conclusions suggest that a precise knowledge of functional group coverages on SiO{sub 2} is not essential for modeling thermal TEOS decomposition rates at 1000K. In the absence of gas-phase reactions, growth rates should be directly proportional to TEOS pressure. Therefore, it is likely that non-uniform SiO{sub 2} depositions observed in thermal TEOS CVD are due to depletion of TEOS in the gas-phase and/or thermal gradients on the surface