Fluorine-enhanced oxidation of polycrystalline silicon and application to thin-film transistor fabrication

The kinetics of the fluorinated oxidation of polycrystalline silicon thin films has been investigated and compared to the (100) single-crystal silicon case. The growth of silicon dioxide was performed at oxidation temperatures down to 650 °C in dry ambients, which was made possible by fluorine-induced oxidation enhancement; growth rates in the presence of fluorine additions approach those of wet oxidation. Silicon dioxide films grown on polycrystalline silicon were found to be thicker by about 10%–20% compared to films grown on (100) single-crystal silicon oxidized under the same conditions. The application of fluorinated gate oxides in the fabrication of n-channel polycrystalline silicon thin-film transistors was found to improve the effective electron mobility.