Polysilicon thin-film transistors with channel length and width comparable to or smaller than the grain size of the thin film

Poly-Si thin-film transistors (TFTs) with channel dimensions (width W, and length L) comparable to or smaller than the grain size of the poly-Si film were fabricated and characterized. The grain size of the poly-Si film was enhanced by Si ion implantation followed by a low-temperature anneal and was typically 1 to 3 mu m in diameter. A remarkable improvement was observed in the device characteristics as the channel dimensions decreased to W=L=2 mu m. On the other hand, TFTs with submicrometer channel dimensions were characterized by an extremely abrupt switching in their I/sub D/ versus V/sub GS/ characteristics. The improvement was attributed to a reduction in the effect of the grain boundaries and to the effect of the device's floating body.< >