Impact of Interface Charge on the Electrostatics of Field-Plate Assisted RESURF Devices

A systematic study on the effects of arbitrary parasitic charge profiles, such as trapped or fixed charge, on the 2-D potential distribution in the drain extension of reverse-biased field-plate-assisted reduced surface field (RESURF) devices is presented. Using TCAD device simulations and analytical means, the significance of the so-called characteristic or natural length λ is highlighted with respect to the potential distribution and related phenomena in both ideal (virgin) and nonideal (degraded) extensions. Subsequently, a novel and easy-to-use charge-response method is introduced that enables calculation of the potential distribution for an arbitrary parasitic charge profile once the peak potential and lateral fall-off (∝λ) caused by a single unit charge has been determined. This can be used for optimizing and predicting the performance, also after hot carrier injection, of RESURF power devices.