A novel LDMOS with circular drift region for uniform electric field distribution

Abstract

In this paper, a lateral double diffused MOS which features a circular drift region (Cir-LDMOS) is proposed and investigated by numerical simulation. The circular drift region in Cir-LDMOS introduces a curvature effect on the electric field, which can neutralize the effect of ionized dopants on electric field and optimize the electric field distribution. Our investigations prove that the Cir-LDMOS can achieve uniform electric field distribution when the drift region doping concentration (Ndrift) is appropriate designed to balance with the curvature effect of electric field. Moreover, it is found that the curvature effect of the electric field in Cir-LDMOS is proportional to the critical electric field (Ec) and is inversely proportional to the radius of curvature. Since the curvature effect of electric field is proportional to Ec, the Cir-LDMOS exhibits a larger Ndrift as well as better performance in the field of wide bandgap semiconductor materials. Our simulation results show that, for silicon carbide (SiC), the performance of Cir-LDMOS is better than that of LDMOS based on reduced surface electric field techniques and can reach the one-dimensional SiC limit. Therefore, this work revealed the affecting factors of curvature effect of electric field and proposed a promising LDMOS structure for wide bandgap semiconductor materials.