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

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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 (QIPOX) 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 (Δ Vₜₕ). 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 (QTROX) are more pronounced. The interaction betweenQTROXandQIPOXcreates 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 robustΔ Vₜₕand BV under varying TID exposure conditions.