碩士 / 國立臺灣大學 / 電子工程學研究所 / 103 / Since Moore’s law was proposed in 1965, transistor numbers have been increased from thousands to billions on a single chip. While the size of the transistor is scaling, the operating frequency is also enhanced from MHz toward THz. To maintain the scaling path and benefit from both price and performance boosting, short channel effects (SCEs) must be solved in each generation. To suppress SCEs, except for improving gate oxides, it can be achieved by 3D structures, i.e. fin field-effect transistors (FinFETs).
In this thesis, we focus on suppressing SCEs in the Si FinFET and the InGaAs Metal-Oxide-Semiconductor high-electron-mobility transistor (MOSHEMT). Also we investigate the radio frequency electronic characteristics of HEMT.
Firstly, we show the influence of fin structure on mainstream Si FinFET. Compared with planar MOSFET, FinFET is superior not only in the SCEs control but also in the on-state current under same footprint. The off-state performance is improved from off-state leakeage current larger than threshold current definition to DIBL = 78 mV/V, as the fin width (WFin) shrinking from 200 to 30 nm. The on-state current increases from 179 to 422 μA/μm, as the fin height (HFin) increasing from 30 to 110 nm.
Secondly, we investigate the gate recess and the fin structure effect in the InGaAs MOSHEMT which is regarded as next generation n-channel transistor. In planar devices, as the barrier thickness decreases from 302 to 158 Å, the on/off ratio increases from 1 to 6 orders, but the on-state current decreases from 373 to 95 μA/μm. In 3D devices, as the fin width decreases from 6 to 2 μm, threshold voltage increases from -4 to -2 V, but the on-state current decreases from 192 to 1.29 μA/μm. The barrier thickness and the fin width need further optimization to achieve superior both on-state and off-state performance.
Thirdly, we investigate the radio frequency electronic characteristic of HEMT by building the small signal model. The cut-off frequency (fT) increases from 1.32 to 11.54 GHz, as gate length (LG) decreases from 10 to 2 μm. The fT increases from 10.77 to 11.54 GHz, as the gate to source/drain distance (LGS/LGD) decreases from 20 to 5 μm. In the future, we are planing on shrinking LG, LGS/LGD and further investigating of the influence of the gate width and the multi-gate structure via different effective gate width, the gate width times the gate number, in order to obtain the optimized layout to enhance the cut-off frequency.
| Identifer | oai:union.ndltd.org:TW/103NTU05428088 |
| Date | January 2015 |
| Creators | Tzu-Kuan Wu, 吳子寬 |
| Contributors | Chao-Hsin Wu, 吳肇欣 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 93 |
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