High performance GAA SNWT with a triangular cross section: Simulation and experiments

Abstract

In this paper, we present a gate-all-around silicon nanowire transistor (GAA SNWT) with a triangular cross section by simulation and experiments. Through the TCAD simulation, it was found that with the same nanowire width, the triangular cross-sectional SNWT was superior to the circular or quadrate one in terms of the subthreshold swing, on/off ratio, and SCE immunity, which resulted from the smallest equivalent distance from the nanowire center to the surface in triangular SNWTs. Following this, we fabricated triangular cross-sectional GAA SNWTs with a nanowire width down to 20 nm by TMAH wet etching. This process featured its self-stopped etching behavior on a silicon (1 1 1) crystal plane, which made the triangular cross section smooth and controllable. The fabricated triangular SNWT showed an excellent performance with a large Ion/Ioff ratio (~107), low SS (85 mV/dec), and preferable DIBL (63 mV/V). Finally, the surface roughness mobility of the fabricated device at a low temperature was also extracted to confirm the benefit of a stable cross section.