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

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 10
⁹
(
I
_OFF
= 4 × 10
^-14
,
I
_ON
= 7 × 10
^-5
, and
W
_mask
/
L
_mask
= 10 μm/3 μm).