An improved on-resistance high voltage LDMOS with junction field plate

Abstract

An improved breakdown voltage LDMOS with reduced specific on-resistance is proposed and its mechanism is investigated. The LDMOS is characterized by a junction-type field plate (JFP) and an N + floating layer (NFL) in the p-substrate. First, the linear doped JFP not only modulates the surface electric field (E-field) distribution of the drift region to make it more uniform and thus increases the breakdown voltage (BV), but also employs the P region in the JFP to deplete the N-drift region in the off-state, and hence increases the drift region doping (N d ) and decreases the specific on-resistance (R s, on ). Second, the NFL is equal-potential in the lateral direction in the off-state, and it thus optimizes the E-field distributions at the source side and drain side; furthermore, the NFL in the p-sub introduces an additional PN junction in the vertical, both of which further improve the BV. Compared with a conventional LDMOS, the JFP NFL LDMOS increases the BV by 63.6% and reduces the R s, on by 47.2%.