Channel Thickness Effect on High-Frequency Performance of Poly-Si Thin-Film Transistors

In this letter, we present the high-frequency performances of polycrystalline silicon (poly-Si) thin-film transistors (TFTs) with a nominal gate length of 0.22 μm. Owing to the short gate length and adoption of salicide process, cutoff frequency (f
_T
) of 17 GHz and maximum oscillation frequency of ~ 21 GHz are obtained. The result suggests that the poly-Si TFT technology is applicable to RF integrated circuits up to 2 GHz. In addition, we also investigate the effects of channel thickness on the high-frequency characteristics of poly-Si TFTs. We find that the variation of f
_T
with channel thickness is mainly due to the change in transconductance.