Comprehensive Analysis of Distinct TID Effects on SGT MOSFETs at On/Off States and Radiation Hardening Strategies

This study investigates the mechanisms of total-ionizing-dose (TID) degradation in split-gate trench (SGT) MOSFETs, considering both the on-state and off-state operations. The degradation shows as the drain-induced barrier lowering (DIBL) effect at the on-state and charge imbalance at the off-state, respectively. Charges in the interpoly oxide (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>IPOX</roman></sub>) are involved in both states. On the one hand, during the on-state, a significant portion of charges are deposited at the gate oxide (GOX) and the head of the IPOX, modifying the potential near the channel, which promotes P-body punchthrough and exacerbates threshold voltage shifts (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\vert\Delta \textit{V}_{\text{th}}\vert$</tex-math></inline-formula>). Consequently, the DIBL effect intensifies, leading to an increase in leakage current and subsequent deterioration of breakdown voltage (BV) and capacitance. On the other hand, at the off-state, charges in the trench oxide (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>TROX</roman></sub>) are more pronounced. The interaction between <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>TROX</roman></sub> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>IPOX</roman></sub> creates a severe charge imbalance, which primarily contributes to BV degradation at the off-state. To mitigate these degradation effects, several targeted hardening technologies have been developed, enabling the successful fabrication of high-performance SGT MOSFETs with robust <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\vert \Delta \textit{V}_{\text{th}}\vert$</tex-math></inline-formula> and BV under varying TID exposure conditions.