Threshold voltage modulation of AlGaN/GaN MIS-FinFETs with sub-60 mV/decade subthreshold swing

• Main Authors: Dai, Quan, Kim, Ryun-Hwi, Lee, Jun-Hyeok, Kim, Jeong-Gil, Thingujam, Terirama, Kang, Seung-Hyeon, Ahn, Woo-Hyun, Kim, Eun-Jin, Lee, Jung-Hee
• Format: Conference Proceeding
• Language: English
• Subjects: AlGaN/GaN; Aluminum gallium nitride; Aluminum oxide; Dielectrics; Logic gates; MIS-FinFET; Modulation; normally-off; sub-60 mV/dec; Threshold voltage; Wide band gap semiconductors
• ISSN: 2472-9132
• DOI: 10.1109/EUROSOI-ULIS49407.2020.9365447

In this work, threshold voltage modulation realized by adjusting fin width and dielectric layer were investigated through MIS-FinFETs. As fin width decreases from 120 to 30 nm, threshold voltage shifts toward positive direction and finally becomes positive value while maintaining SS smaller than 60 mV/dec. The phenomenon of achieving sub-60 mV/dec characteristics were illustrated by simulation and the concept of effective channel length. As for dielectric layer, by 20 nm-thick SiO 2 dielectric layer, device with fin width of 90 nm exhibits a threshold voltage of −0.5 V with SS as small as 50 mV/dec. Even when fin width is 30 nm, drain leakage is still not small enough when VG = 0, which indicates that the gate is not able to totally deplete the fin structure. In order to further increase threshold voltage and enhance the gate controllability, by 10 nm-thick Al 2 O 3 dielectric layer, a threshold voltage of 2 V is achieved when fin width is 40 nm with SS as small as 52 mV/dec due to the higher dielectric constant and thinner thickness of Al 2 O 3 compared with SiO 2 . Therefore, by the modulation of fin width, dielectric layer type, and dielectric thickness, threshold voltage can be carefully designed according to the application requirements while maintaining SS below 60 mV/dec.