Improvement of Selective Quasi Atomic Layer Etching of SiGe/Si by Plasma Surface Modification for Fishbone FET Fabrication

Abstract

Gate-all-around field effect transistors (GAAFETs), including nanosheet (NS) and nanowire (NW) structures, are crucial for the advancement of novel logic devices. One significant challenge in GAA NS is the electrical performance mismatch between NMOS and PMOS drive currents, which stems from the different mobility of holes and electrons. In this study, an innovative Fishbone FET structure with nanoscale dimensions integrating SiGe nano-fins and Si nanosheet is experimentally fabricated. This structure addresses the performance mismatch between NMOS and PMOS in GAAFETs, and enhances the driving capability of the device by increasing the number of effective channels. The Fishbone FET channel is fabricated using dry quasi-atomic layer etching (quasi-ALE), which has emerged as a promising candidate for accurately controlling the etching depth of the SiGe layer. Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), and X-ray Photoelectron Spectroscopy (XPS) are employed to systematically investigate various process phenomena and interfacial reaction mechanisms associated with quasi-ALE. The findings show that etching per cycle is ≈0.27 nm, and the etching process involves a two-step self-limiting reaction. This novel channel structure fabrication approach is expected to serve as an important reference for optimizing the channel in GAAFETs.