Super junction LDMOS with step field oxide layer

Abstract

A novel step-oxide super junction-lateral double-diffused metal-oxide-semiconductor field-effect transistor (SOSJ-LDMOS) structure is proposed and optimised which allows the high breakdown voltage (BV) and low-specific on-resistance (R on,sp). The proposed structure overcomes the effect of thick field oxide formed by shallow trench isolation process in conventional buffer layer SJ-LDMOS (N-buffered SJ-LDMOS), effectively enhancing the performance of the SJ-LDMOS. Thanks to the SO layer, a new electric field peak has been introduced in the surface electric field distribution, which makes the lateral surface electric field uniform in the off-state. Moreover, due to the thinner oxide layer, in the on-state the majority of electron current is accumulated near the top surface under the field plate and the thinner oxide layer also provides a wider current flowing path. In the virtue of integrated systems engineering (ISE) simulation, not only has the BV of SOSJ-LDMOS been increased, but also the R on,sp has been reduced simultaneously compared with the N-buffered SJ-LDMOS in the same drift length. In addition, when SOSJ-LDMOS and N-buffered LDMOS are at the same BV, the R on,sp of SOSJ-LDMOS is decreased by 26.3-38.9%, compared with the N-buffer SJ-LDMOS.