Integration of amorphous and polycrystalline silicon thin-film transistors through selective crystallization of amorphous silicon

Selective exposure of a hydrogenated amorphous silicon ~a-Si:H! film to a room-temperature hydrogen plasma using a patterned masking layer and a subsequent anneal at 600 °C, results in patterned polycrystalline and amorphous silicon regions. However, most of the hydrogen in the amorphous silicon is lost, leading to severe degradation in its properties. In this letter, we report the rehydrogenation of amorphous silicon films following this anneal to give a-Si:H thin-film transistors with a mobility as high as 1.2 cm/V s and ON/OFF current ratios of ;10. This process was used to integrate amorphous and polycrystalline silicon transistors on a single substrate with only one more lithography and processing step than that required for a single type of transistor. © 1999 American Institute of Physics. @S0003-6951~99!03340-9#