A novel high-voltage device structure with an N+ ring in substrate and the breakdown voltage model

Abstract

A novel high-voltage device structure with a floating heavily doped N+ ring embedded in the substrate is reported, which is called FR LDMOS. When the N+ ring is introduced in the device substrate, the electric field peak of the main junction is reduced due to the transfer of the voltage from the main junction to the N+ ring junction, and the vertical breakdown characteristic is improved significantly. Based on the Poisson equation of cylindrical coordinates, a breakdown voltage model is developed. The numerical results indicate that the breakdown voltage of the proposed device is increased by 56% in comparison to conventional LDMOS.