Electrical Behavior at Cryogenic Temperature of the Radiation-Tolerant Hourglass MOS Transistor

Abstract

This article presents experimental $I_{d}$ - $V_{gs}$ measurements and an analysis of the electrical characteristics of a MOS (Metal-Oxide-Semiconductor) transistor featuring a novel gate geometry referred to as the hourglass shape. This new transistor was designed to increase total ionizing radiation (TID) tolerance without modifying the manufacturing process. Experiments were conducted using a test chip with individual transistors, under temperature sweeps down to 3.6 K. Key performance metrics—including threshold voltage, subthreshold swing, and zero temperature coefficient (ZTC)—were compared against those of a conventional rectangular transistor used as a reference and a diamond transistor with similar geometry, and fabricated on the same chip. The experimental results show that the hourglass-shaped transistor presents a 27.17% reduction in normalized power consumption compared to the rectangular transistor, while the reduction is 3.61% compared to the diamond-shaped transistor. Additionally, the hourglass transistor presents a normalized increment of 115% and 10.4% in current difference with respect to the rectangular and diamond transistor, respectively across the evaluated temperature range. This study highlights the improved current efficiency of the hourglass design while maintaining lower power consumption under cryogenic conditions. The enhanced thermal stability, the stability of threshold voltage ( $V_{th}$ ) and subthreshold swing (SS) shifts and energy efficiency of the proposed device across a wide temperature range are also shown.