The effect of static charge imbalance on the on state behavior of the superjunction power MOSFET: CoolMOS

The effect of static charge imbalance on the forward blocking voltage (FBV) of a superjunction power MOSFET designed for 600 V is investigated with device simulation. It is observed that the presence of the conduction channel and carriers in the drift region in the on state effectively changes the charge balance in the device. As a result, the BV changes substantially with the applied gate voltage. The variation of FBV as function of gate voltage V/sub GS/ is obtained by device simulation, for three cases of superjunction (SJ) drift layer doping variations (i) N/sub a/ = N/sub d/, (ii) N/sub a/ > N/sub d/, (iii) N/sub d/ > N/sub a/. Representative potential contours are also shown for illustration.