Novel Symmetric Vertical-Channel Ni-Salicided Poly-Si Thin-Film Transistors With High ON/OFF-Current Ratio

Abstract

We have successfully fabricated the symmetric vertical-channel Ni-salicided polycrystalline silicon thin-film transistors (VSA-TFTs) for the first time. The transfer characteristics of VSA-TFTs show a sharp turning between subthreshold and ON state. The OFF-state currents can be improved by a modified overetching of oxide, equivalent dual-gate structure, and n(+) floating-region length. The ON-state currents can be enhanced by Ni-salicidation. The VSA-TFTs display a good subthreshold swing of 220 mV/dec, steep mobility increase (field-effect mobility of 76 cm(2)/ V . s), and large ON/OFF-current ratio of more than 109 (I(OFF) = 4 x 10 (14), I(ON) = 7 x 10 (5), and W(mask)/L(mask) = 10 mu m/3 mu m).