Poly-Si thin-film transistors 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 μm in diameter. A remarkable improvement was observed in the device characteristics as the channel dimensions decreased to W = L = 2 μm. On the other hand, TFT's with submicrometer channel dimensions were characterized by an extremely abrupt switching in their ID versus VGS 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.
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