Predicting worst-case charge buildup in power-device field oxides

Existing models for worst-case charge buildup in silicon dioxide are applied to single- and two-level field plate termination structures in n-channel power MOSFETs. It is shown that the field-collapse model, when properly applied to these termination structures, provides excellent agreement between experimental and simulation worst-case breakdown-voltage degradation results. Nonuniform charge buildup in the termination structure field oxide is identified, and two methods of doing device simulation that take the nonuniformity into account are introduced. Finally, simple analytical models are presented that enable the nonuniform charge distribution to be calculated for any field-plate structure.>