Electrostatic Discharge Sensing of Concentric Circles of Poly2 with Different Potentials and Discrete High-voltage P-well Modulation on Circular Ultrahigh-voltage N-channel Laterally Diffused MOSFET Devices

In this paper, we present N-channel laterally diffused MOSFET (nLDMOS) devices for electrostatic discharge (ESD) contact-mode sensors in ultrahigh voltage (UHV) applications. These circular UHV nLDMOS devices have concentric circles of poly-layer 2 (Poly2) with different potential configurations and a discrete high-voltage P-well (HVPW) in the drift region. The Poly2 on the drift region is made of polysilicon to reduce the peak electric field in the drift region, thereby reducing the on-resistance. When the Poly2 was connected to the positive VDD potential, the trigger voltage of the device decreased due to the change in the interface electric field in the drift region; thus, this device more easily triggered conduction than the Poly2 grounded type. We used five radial methods to insert the HVPW into the drift region and evenly distributed it into two, four, eight, 16, and 32 equal partitions. When the Poly2 was grounded and the HVPW layer of the drift region was divided into 32 partitions, it had the highest secondary breakdown current of 3.56 A. This is because the more uniform the distribution of the superjunction (SJ), the higher the ability of the component to discharge the ESD current. Therefore, changing the potential of Poly2 changes the electric field distribution and affects the trigger voltage. Adding an HVPW SJ structure in the drift region will increase the on-resistance, thus improving the discharging current capability.