Study on Reverse Recovery of a P-pillar Tunable Super-Junction MOSFET*

Abstract

In this paper, a novel bubble-shift super junction (SJ) MOSFET structure is proposed, and its main static electrical parameters and reverse recovery characteristics are simulated by TCAD software tool. By designing the P-pillar ion implantation windows with a certain offset, the bubble-shift SJ-MOSFET contains a curved pillar region in the upper half of the P-pillar. In the reverse recovery test of the proposed bubble-shift SJ-MOSFET, the peak reverse recovery current (I rrm ) is reduced from 16.04 A to 15.21 A, and the current drop rate (di/dt) is reduced from 1587 A/μs to 815 A/μs. Correspondingly, the proposed device achieves a better reverse recovery characteristic while sacrificing a small fraction of the drain-source breakdown voltage (BV) and drain-source special on-resistance (R on,sp ). Compared with the BV of 700 V and the R on,sp of 9 mΩ·cm 2 of the benchmark SJ-MOSFET. The proposed device has a BV of 650 V and a R on,sp of 12.4 mΩ·cm 2 . Mechanistically, the non-uniform depletion of the curved P-pillar reduces the carrier extraction rate, thereby prolonging the reverse current drop time (t f ) and increasing the softness factor (S) of the bubble-shift SJ-MOSFET.