Novel Channel-First Fishbone FETs With Symmetrical Threshold Voltages and Balanced Driving Currents Using Single Work Function Metal Process

• Published in: IEEE transactions on electron devices 2022-11, Vol.69 (11), p.1-7
• Main Authors: Cao, Lei, Zhang, Qingzhu, Luo, Yanna, Gu, Jie, Gan, Weizhuo, Lu, Peng, Yao, Jiaxin, Xu, Haoqing, Zhao, Peng, Luo, Kun, Wu, Yongqin, Bu, Weihai, Wu, Zhenhua, Yin, Huaxiang
• Format: Article
• Language: English
• Subjects: CAD; Computer aided design; Fishbone FETs; nano-fins; nanosheets (NSs); Silicon germanides; single work function metal (sWFM); Threshold voltage; Work functions; wrapped spacers
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2022.3206179

In this article, one feasible fabrication appro-ach for novel fishbone FETs using the channel-first and single work function metal (sWFM) processes is proposed and investigated by 3-D technical computer-aided design (TCAD) simulations. Through a small modification on the fabrication process of general gate-all-around (GAA) nanosheet FETs (NSFETs), the special fishbone-like channel composed of vertically stacked Si NSs and sandwiched SiGe nano-fins is experimentally demonstrated by the channel-first process. The simulated electrical characteristics show that the width of the nano-fins should be within 5 nm for a better gate control. Unlike traditional NSFETs, symmetrical threshold voltages ( \textit{V}_{\text{th}} s) for n-type and p-type fishbone FETs can be achieved by using a sWFM, and \Delta \textit{V}_{\text{th}} is optimized by 99.26% compared with that of NSFETs. Meanwhile, it is also found that the SiGe nano-fins contribute more driving current for p-type devices. Therefore, the proposed fishbone FETs with sWFM not only exhibit significantly enhanced driving current but also provide good balance between the performances of n-type and p-type fishbone FETs with a little extra process cost.