Modelling the 3-D Charge-Sharing in Field-Plate Power MOSFETs With Circular Layouts

The state-of-the-art field-plate (FP) power MOSFETs are mostly based on a stripe cell pattern. Few attentions were paid to their circular/hexagonal cell patterns. In this article, analytical models are developed to compare the performances between stripe and circular cell patterns for the first time. The proposed models offer a physical insight into the 3-D charge-sharing effect and also a design formula for circular FP power MOSFETs. Numerical results are well consistent with the proposed models. It is revealed through the model that the circular structure with a silicon shell has the best breakdown ability as well as improved trade-off relationship between breakdown voltage (BV) and specific on-resistance. The static performance limit for the circular structure is calculated. Due to the unique 3-D charge-sharing effect, the specific on-resistance for circular structure rated above 100 V can be reduced by more than 50% when compared with the stripe structure.