Stability of low-temperature amorphous silicon thin film transistors formed on glass and transparent plastic substrates

This article describes the formation of amorphous silicon thin film transistors (TFTs) on glass and flexible transparent plastic substrates using rf plasma enhanced chemical vapor deposition and a maximum processing temperature of 110 °C. Silane diluted with hydrogen was used for the preparation of the amorphous silicon, and SiH4/NH3/N2 or SiH4/NH3/N2/H2 mixtures were used for the deposition of the silicon nitride gate dielectric. The amorphous silicon nitride layers were characterized by transmission infrared spectroscopy and current-voltage measurements; the plastic substrates were 10 mil thick (0.25 mm) polyethylene terephthalate sheets. Transistors formed using the same process on glass and plastic showed linear mobilities ranging from 0.1 to 0.5 cm2/V s with ION/IOFF ratios⩾107. To characterize the stability of the transistors on glass, n- and p-channel transconductances were measured before and after bias stressing. Devices formed at 110 °C show evidence of charge trapping near the a-Si/SiNx interfa...

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