Novel Constant Surface Concentration Depletion Mechanism and Its Experiments in Homogenization field LDMOS

Abstract

A novel constant surface concentration depletion (CSD) mechanism for the homogenization field (HOF) LDMOS is proposed and experimentally demonstrated in this paper. Because the depletion of the HOF LDMOS is independent on the P-substrate, the surface doping concentration of the HOF LDMOS can keep constant and thus the total doping dose of the N-drift region can increase with the junction and trench depths. Based on the CSD mechanism, a CSD HOF LDMOS with 15 μm trench depth was designed and experimentally fabricated. The doping dose of the N-drift region is increased up to 8 × 1012 cm-2. As a results, a measured low specific on-resistance Ron,sp of 15.6 mΩ·cm2 was observed under a breakdown voltage VB of 420 V, realizing a high figure of merit FOM = VB2 / Ron,sp of 11.3 MW/cm2 and a reduction of 53.3% compared with the theoretical limit of the triple RESURF technology under the same VB. Ron,sp of the CSD HOF LDMOS also realizes a reduction of 20.8% when compared with that of the best-in-class HOF LDMOS.