High-Mobility Amorphous-Silicon MUS Transistors

Process conditions for gate oxide formation in amorphous-silicon MOS transistors have been investigated systematically. It was found that the n + micro-crystal silicon layer just above the active transistor region should be removed before the gate oxidation at 250°C. Annealings in nitrogen ambient just after the oxidation and in hydrogen ambient after gate electrode evaporation were also effective. The highest field-effect mobility measured by the transistor fabricated under the optimum process conditions was about 4.8 cm 2 /Vs. Dynamic response characteristics have also been evaluated.