Gate Field Plate Structure for Subthreshold Swing Improvement of Si Line-Tunneling FETs
Gate Field Plate Structure for Subthreshold Swing Improvement of Si Line-Tunneling FETs
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用于改善硅线隧道 FET 亚阈值摆幅的栅极场板结构
DOI：
10.1109/access.2019.2928692
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发表时间：
2019
期刊：
影响因子：
3.9
通讯作者：
Liu Yang
中科院分区：
文献类型：
--
作者：
Wang Xiangzhan;Tang Zhouquan;Cao Lei;Li Jingchun;Liu Yang
隧道场效应晶体管（tfet）由于其独特的带对带隧道操作而在超低功耗应用中有很大的应用前景。然而，这些硅基隧道器件的导通电流明显低于mosfet。此外，高-<inline-formula> < text -math符号="LaTeX">$\kappa $ </ text -math></inline-formula>电介质用作栅极绝缘体或间隔体，以提高ttfet的隧道场强度；这通常会导致条纹诱导的势垒降低和阈下特性的恶化。本文提出了一种栅极场板型TFET （GFP-TFET）结构，以增强驱动电流并抑制条纹势垒降低引起的电流扭结。通过大量的器件模拟，详细研究了栅极场极板对TFET性能的影响。栅极氧化物和栅极场极板氧化物可用于定制电场线，以增加隧道结处的电场。同时，采用功函数较高的金属作为场极板电极，降低了边缘场浓度。因此，电场强度在栅极边缘附近减小，而在通道内增大。GFP-TFET以降低截止频率为代价，表现出高驱动电流和低亚阈值特性。优化参数后的GFP-TFET结构具有<inline-formula> < text -math符号="LaTeX">$10^{3}\乘以$ </ text -math></inline-formula>的通态电流。最小亚阈值振荡从146.3 mV/dec下降到21.4 mV/dec， ON/OFF电流比从<inline-formula> < text -math notation="LaTeX">$10^{7}$ </ text -math></inline-formula>增加到<inline-formula> < text -math notation="LaTeX">$10^{13}$ </ text -math></inline-formula>。
Tunnel field-effect transistors (TFETs) are promising for use in ultralow-power applications owing to their distinct band-to-band tunneling operation. However, the ON-state current of these Si-based tunnel devices is considerably lower than that of MOSFETs. Furthermore, a high-<inline-formula> <tex-math notation="LaTeX">$\kappa $ </tex-math></inline-formula> dielectric is used as a gate insulator or spacer to increase the TFET’s tunneling field strength; this usually causes fringe-induced barrier lowering and deterioration of its subthreshold characteristics. Here, in this paper, a gate field plate TFET (GFP-TFET) structure is proposed to enhance the driving current and suppress the current kink induced by fringe-induced barrier lowering. A detailed investigation into the effects of a gate field plate on TFET performance was conducted with the help of extensive device simulations. The gate oxide and gate field plate oxide could be used to tailor the electric field lines to increase the electric field in the tunnel junction. Meanwhile, the fringing field concentration was reduced by using a metal with a relatively high work function as the field plate electrode. Thus, the electric field strength decreased near the gate edge and increased in the channel. The GFP-TFET exhibited high driving current and low subthreshold characteristics at the cost of a reduction in cutoff frequency. A GFP-TFET structure with optimized parameters had a <inline-formula> <tex-math notation="LaTeX">$10^{3}\times $ </tex-math></inline-formula> higher ON-state current compared with a normal silicon tunnel FET. The minimum subthreshold swing decreased from 146.3 to 21.4 mV/dec and the ON/OFF current ratio increased from <inline-formula> <tex-math notation="LaTeX">$10^{7}$ </tex-math></inline-formula> to <inline-formula> <tex-math notation="LaTeX">$10^{13}$ </tex-math></inline-formula> compared with a normal TFET.
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3.1
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