Improvement of reverse blocking performance in vertical power MOSFETs with Schottky-drain-connected semisuperjunctions

To enhance the reverse blocking capability with low specific on-resistance, a novel vertical metal-oxide-semiconductor field-effect transistor (MOSFET) with a Schottky-drian (SD) and SD-connected semisuperjunctions (SD-D-semi-SJ), named as SD-D-semi-SJ MOSFET is proposed and demonstrated by two-dimensional (2D) numerical simulations. The SD contacted with the n-pillar exhibits the Schottky-contact property, and that with the p-pillar the Ohmic-contact property. Based on these features, the SD-D-semi-SJ MOSFET could obviously overcome the great obstacle of the ineffectivity of the conventional superjunctions (SJ) or semisuperjunctions (semi-SJ) for the reverse applications and achieve a satisfactory trade-off between the reverse breakdown voltage (BV) and the specific on-resistance (R_onA). For a given pillar width and n-drift thickness, there exists a proper range of n-drift concentration (N), in which the SD-D-semi-SJ MOSFET could exhibit a better trade-off of R_onA-BV compared to the predication of SJ MOSFET in the forward applications. And what is much valuable, in this proper range of N, the desired BV and good trade-off could be achieved only by determining the pillar thickness, with the top assist layer thickness unchanged. Detailed analyses have been carried out to get physical insights into the intrinsic mechanism of R_onA-BV improvement in SD-D-semi-SJ MOSFET. These results demonstrate a great potential of SD-D-semi-SJ MOSFET in reverse applications.