ESD-ability of Circular nLDMOS Transistors of UHV by Super-junction Length Modulation and Concentration Gradient

In this paper, circular nLDMOS devices of the ultra-high voltage (UHV) with drain-side super-junction (SJ) structures were formed in the drift region by using the HVPW and HVNW layers. The length of the SJ was adjusted by the length of the HVPW layer. On the other hand, the drain-side of some of nLDMOS devices were designed with different SJ concentration gradients by the HVPW layer discretization. The purpose was generating the size-gradient depletion and making the device not only having the higher breakdown voltage, but also a better ESD-ability. Eventually, the HBM value of these embedded SJ designs in an UHV nLDMOS device was increased from 1500V to the largest value 4000V.