A Novel Poly-Si TFT with T-Shaped Gate and Air Spacers
|關鍵字:||T型閘極;多晶矽;薄膜電晶體;空氣邊襯;射頻元件;T-shaped gate;poly silicon;thin film transistor;air spacer;RF device|
In this thesis, a novel poly-Si thin-film transistor (TFT) with T-gate and air spacers is proposed and demonstrated with a new process scheme which ingeniously makes use of a highly selective etching to laterally remove the bottom n+ poly-Si in a p+ poly-Si/n+ poly-Si stack and form the T-gate. This T-gate process is simple and can be readily implemented in conventional fabrication flow. In order to further reduce the parasitic resistances, we also introduce Ni self-aligned silicidation (SALICEDE) process in the fabrication. In addition, owing to the shadowing effect of the T-gate, sidewall air spacers can be obtained after the deposition of the passivation oxide. The results confirm that the silicided T-gate can significantly reduce the parasitic gate resistance, while air spacers can reduce the parasitic capacitances between gate and source/drain (S/D). Furthermore, the lateral etching shortens the channel length of the T-gate devices to 96nm, greatly improving the current drive and transconductance. As a consequence, the cut-off frequency (fT) of the T-gate poly-Si TFTs reaches 12.4GHz, which is two times higher than that of the conventional devices. In the meantime, maximum oscillation frequency (fMAX) also receives a great improvement owing to the reduced gate resistance with the T-gate.
|Appears in Collections:||Thesis|