A semi-superjunction MOSFET with P-type Bottom Assist Layer

A new Semi-Superjunction Vertical Double-diffusion MOSFET (Semi-SJ MOSFET) with P-type Bottom Assist Layer (P-BAL) is proposed. The P-BAL is introduced upon the N-Stop substrate and embedded in the n-BAL, on the one hand, another reverse biasing PN junction J(P-BAL/N-stop) at the bottom substrate is formed, which helps to deplete the n-BAL along the longitudinal direction and changes the shapes of the electric field distribution. On the other hand, another Semi-SJ structure is formed by the P-BAL and n-BAL, the transverse electric field in n-BAL part is enhanced, and this indicates that the trade-off between breakdown voltage (BV) and on-state resistance (R-on,R-sp) has been optimized due to the improvement of BV. As results show, in the proposed MOSFET, the BV (i.e., 1097 V) is improved 25% higher than that of the conventional Semi-SJ structure (i.e., 877 V) and the proposed does negligible disadvantage to the R-on,R-sp (i.e., the proposed with a R-on,R-sp of 59 m Omega cm(2) and the conventional MOSFET with a R-on,R-sp of 56 m Omega cm(2)). (C) 2015 Elsevier Ltd. All rights reserved.