Theoretical Analyses of Complete 3-D Reduced Surface Field LDMOS With Folded-Substrate Breaking Limit of Superjunction LDMOS

A new theory of lateral double-diffused MOS (LDMOS) by the folded-silicon substrate field-effect (FSLDMOS) with the complete 3-D REduced SURface Field (RESURF) is proposed in this paper for the first time. The analytical model for the relationship between the breakdown voltage (BV) and the specific ON-resistance ( $R_{\rm \mathrm{\scriptscriptstyle ON},sp}$ ) of FSLDMOS is obtained, which breaks the limit relationship of the superjunction (SJ) LDMOS by applying three kinds of methods, including the additional electric-field modulation effect, majority carrier accumulation, and increasing the effective conduction paths simultaneously. In the analytical model, the influence of the structural parameters of the folded-drift and electric field modulation coefficients is considered. Besides, the optimal doping concentration of the folded-drift region for FSLDMOS is derived, which can give guidance for the dose of the folded-drift region. The results indicate that a new analytical expression for the relationship between the BV and $R_{\mathrm{\scriptscriptstyle ON},\text {sp}}$ is obtained, which breaks the limit relationship of the SJ LDMOS by the complete 3-D RESURF. All analytical results are well verified by the simulation results conducted by ISE-TCAD, showing the validity of the presented model.