Record 60.3 mV/dec Subthreshold Swing and >20% Performance Enhancement in Gate-All-Around Nanosheet CMOS Devices Using O₃-Based Quasi-Atomic Layer Etching Treatment Technique
Renjie Jiang, Guanqiao Sang, Lei Cao, Jiaxin Yao, Kun‐Lin Yang, Yihong Lu, Xuexiang Zhang, Peng Wang, Junjie Li, Xinyu He, Na Zhou, Yadong Zhang, Zhaohao Zhang, C.C. Zhang, Lianlian Li, Q. Li, Jie Li, Qingzhu Zhang, Huaxiang Yin, Jun Luo, Bowen Dai
Abstract
To overcome the critical channel interface issues in gate-all-around (GAA) devices that are induced by germanium (Ge) residue on the nanosheet (NS) channels, a precise quasi-atomic layer etching (qALE) technique based on O3 was developed in this work. This technique has a self-limited oxidation thickness of 6.1 Å and is able to remove the residual Ge atoms. The improved interface quality leads to a 99% reduction in the interface state density (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D} _{\textit {it}}$ </tex-math></inline-formula>) and a reduction in the current density (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J} _{g}$ </tex-math></inline-formula>) of two orders of magnitude. Therefore, the GAA devices fabricated using this method achieve a record low subthreshold swing (SS) of 60.3 mV/dec, with the maximum reduction in the SS reaching up to 21% when compared with that of unprocessed devices after a two-cycle qALE treatment. Moreover, the treatment also results in an enhancement of more than 20% in the on-current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\textit {on}}$ </tex-math></inline-formula>) and a 66.7% reduction in the off-current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\textit {off}}$ </tex-math></inline-formula>). These results and the proposed method provide effective technical guidance for improving the interface characteristics, leakage characteristics, and performance of future mass-produced GAA NS field-effect transistors.