Electrical characterisation of vertical vapor phase doped (VPD) RESURF MOSFETs

Publications on the optimisation of vertical RESURF MOSFETs typically only address the drift region. The drift region resistance decreases strongly with pitch size, potentially offering extremely low specific resistances when moving to smaller pitch sizes. However, at a certain pitch, one will have decreased the drift region component such that other contributions will start to play a dominant role and need to be taken into account when optimising such devices. Recently, the first vertical RESURF MOSFETs, manufactured using a trench etch and vapor phase doping (VPD) process, were presented with pitch size down to 4 μm. Based on the electrical characterisation of these devices, we evaluate the various contributions to the overall specific resistance and their effect on the attainable figure-of-merits (FOMs) of vertical RESURF devices with DMOS layout at such small pitch.