Total Ionizing Dose Effects in 30-V Split-Gate Trench VDMOS

In this article, the total ionizing dose (TID) effect is investigated in the 30-V split-gate trench (SGT) Vertical double diffused MOSFET (VDMOS). The complex trench structure, including gate oxide, split-gate oxide, and isolation oxide, is carefully studied to reveal the degradation mechanisms. Due to the multioxidation and annealing processes, the trench structure suffers serious oxide defeats. The analytical result shows a larger trapping efficiency (fot) compared to the planar gate technology, leading to significant Vth shifts and subthreshold leakage. Meanwhile, irradiation-induced trapped charges in the split-gate oxide have a great influence on the electric field profile in bulk, which gives rise to breakdown voltage (BV) degradation. The experimental result shows that BV presents a gradient descent and drops to as low as 14 V at 100 krad(Si). Through TCAD simulation and analytical calculation, these TID responses are evaluated, and three approaches have been proposed for the radiation hardness of SGT VDMOS.