Influence of interconnections onto the breakdown voltage of planar high-voltage p-n junctions

The influence of a high-voltage interconnection onto the blocking capability of a resurf diode is determined by solving the 2-D Poisson equation. By adding a metal interconnection which crosses the space-charge region, the breakdown voltage is reduced, depending on the distance between the interconnection and the semiconductor surface. If the distance is 5 mu m, the breakdown voltage is decreased 38%, but if the distance is as low as 3 mu m, the breakdown voltage is decreased by 54%. To compensate for the effect of the interconnection two different methods are discussed. By optimizing the doping concentration of the p/sup -/layer in front of the p-n junction the influence of the interconnection can be reduced to 18% and 37%, respectively. The second method uses floating metal rings positioned in the oxide film between the semiconductor and the interconnection. If the rings are optimally positioned, the influence of the interconnection can be reduced from 54% to only 16%. It is shown that a variation of the lateral gap between the metal rings influences the shielding effectiveness.<
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