An improved subthreshold swing expression accounting for back-gate bias in FDSOI FETs. (April 2023)

• Record Type: Journal Article
• Authors: Han, Hung-Chi; Jazaeri, Farzan; Zhao, Zhixing; Lehmann, Steffen; Enz, Christian
• Is Part Of: Solid-state electronics. Volume 202(2023)
• Publication Date: 2023-04
• Subjects: Double-gate -- FDSOI -- Gate coupling -- Interface states -- MOSFET -- Subthreshold swing; Semiconductors -- Periodicals; Semiconducteurs -- Périodiques; 621.38152
• DOI: 10.1016/j.sse.2023.108608
• Languages: English
• ISSNs: 0038-1101

Abstract

Abstract: In a MOSFET transistor, the subthreshold swing defines the switching efficiency, and the associated slope factor, or so-called body factor, is a critical parameter in charge-based models. However, in an advanced Fully-Depleted Silicon-On-Insulator (FDSOI) process, the slope factor is influenced by a strong back gate coupling due to a thin buried oxide (BOX). A conventional constant expression cannot describe the slope factor at various back-gate voltages. Therefore, this paper proposes a general slope factor expression for front- and back-gate transfer characteristics of long-channel FDSOI MOSFETs in a strong gate coupling. The proposed expression is a continuous function of the surface potential difference between the front and back sides, which explains the slope factor behavior versus the back-gate voltage. Besides, the systematic study is presented for the front/back interface states. The proposed model is applied to evaluate the down-scaling of FDSOI technologies in terms of the gate-coupled slope factor. The scaling in the buried oxide layer degrades the front slope factor, which a thinner channel or a reverse body bias can compensate for at the cost of a higher vertical electric field. Compared to the SiO2, the application of high- κ dielectric for the buried oxide layer shows a better stand to the degraded slope factor by the interface states. Highlights: The model is proposed for subthreshold swing and slope with strong gate coupling. The reverse body bias shows the efficient enhancement on the subthreshold swing. The proposed model gives insight into the down-scaling of FDSOI technology.