A novel substrate Voltage-assisted RESURF technique in SOI LDMOS with a heavily doped drift region

Abstract

A novel substrate voltage-assisted (SVA) reduced surface field (RESURF) technique in SOI lateral double-diffused Metal-Oxide-Semiconductor (LDMOS) with a heavily doped drift region is proposed. Without any additional masks and processes, an external control circuit is designed to adaptively control the substrate voltage in the technique. The co-simulation based on TCAD and the circuit is implemented to explore the mechanism of the SVA RESURF technique. In the off-state, a negative bias is applied to the substrate, which induces positive charges to compensate for the heavily doped ionizing acceptors in the drift region. The breakdown voltage is improved and remains at the same level as the conventional RESURF device. In the on-state, a zero bias is applied to the substrate, and heavy doping in the drift region can achieve low specific on-resistance compared to the RESURF device with a lightly doped drift region. As a result, the proposed technique reconstructs the charge balance and the conventional RESURF condition. The simulation results show reduced specific on-resistance, low drain leakage current, large saturation current, high transconductance and cut-off frequency, decreased turn-on/off characteristics and improved FOM and BFOM compared with the conventional RESURF technique. Furthermore, an analytical model is developed to optimize the substrate voltage for the maximum breakdown voltage in the external control circuit design of the proposed technique.