Breakdown Voltage Instability Mechanism and Improving Ruggedness in Trench Field Plate Power MOSFET

Breakdown voltage instability mechanism of Trench Field Plate Power MOSFET was studied. We found that breakdown voltage (BVDSS) shifts obeyed power-law time dependence by analysis of time dependent BCDss shifts. Furthermore, stress / suspend measurements revealed that BVDss shift repeated increase / recovery behaviors. These results were discussed by Si-II bond dissociation Reaction-Diffusion (R-D) model as well as hot carrier degradation and negative bias temperature instability (NBTI) in conventional MOSFET. TCAD simulations suggested that positively charged traps at bottom of trench caused the BVDss instability. Therefore, we believe that Si-II bond dissociation at trench bottom Si/SiO2 interface was induced by hot carriers. Based on these findings, improvement of BVDss stability by trench bottom electric field optimization was demonstrated.