30V sub-micron shallow junction planar-MOSFET for DC-DC converters

We present sub-micron shallow p-base planar-DMOSFETs (DMOS: double diffused MOSFET type) for DC-DC converter applications. The shallow junction depth is quite useful to reduce the device on-resistance. It was found that the gate-drain feedback charge can effectively be reduced by adopting a very narrow and shallow JFET region with very high JFET donor concentration, based on the charge compensation theory. An experimental planar DMOSFET with p-base depth of 0.8 μm exhibited a breakdown voltage of 34 V, an Ron*Qgd of 14.9 mΩnC, and good UIS capability. This is the best value ever reported for a 30 V planar DMOSFET structure.