Gate Oxide Breakdown in P-Channel Split-Gate Trench VDMOS Induced by Total Ionizing Dose Effects Under High Gate Bias

This study elucidates the permanent gate oxide breakdown mechanism in P-channel split-gate trench vertical double-diffused MOSFETs (P-channel SGT VDMOS) under the synergistic effect of ⁶⁰Co-γ irradiation and elevated gate bias (VG), representing a critical reliability concern previously less explored in aerospace power device research. Specifically, concurrent exposure to VG of 15 V and ⁶⁰Co-γ irradiation at a total ionizing dose (TID) of 200 krad with a dose rate of 50 rad/s was analyzed to reveal the underlying breakdown mechanism. This failure manifests through abrupt gate current surges exceeding 100 mA, along with a threshold voltage (V_th) shift beyond the normal operating range. Experimental and simulation analyses confirm that elevated VG accelerates both the accumulation of oxide charges (N_ot) generated by irradiation accumulation and the generation of interface traps (N_it). This process generates an electric field distortion surpassing SiO2 critical breakdown strength of 1×10⁷ V/cm. Crucially, the post irradiation immediate measurement (PIM) demonstrates that the superposition of applied bias fields and radiation-induced electric fields establishes percolation pathways within the gate oxide.Under combined stress conditions of a 15 V V_G and 200 krad TID, these pathways trigger permanent gate oxide breakdown. These findings provide essential design guidance for suppressing gate oxide failure in aerospace power systems.