Thermal oxide of polycrystalline silicon on steel foil as a thin-film transistor gate dielectric

The gate dielectric of polycrystalline silicon thin-film transistors on steel foil substrates was grown by direct thermal oxidation. The silicon dioxide was formed on the polysilicon channel layer by dry oxidation for 40 min at 950 degreesC. Self-aligned sources and drains were ion implanted. The thin-film transistors have electron mobilities of similar to 30 cm(2).V-1 s(-1) in both the linear and saturated regimes, off currents of 35 pA/mum, and on/off current ratios of similar to 10(6). The thin-film transistors function even though they are processed at 950 degreesC separated from steel by only 0.5 mum of SiO2, and at room temperature may be under compressive strain as high as 1%. The implementation of conventional high-temperature fabrication techniques makes polycrystalline silicon on steel foil a strong contender for flexible electronic backplanes. (C) 2001 American Institute of Physics.