Impact of Drain-Side nWell Engineering on ESD Robustness in 0.35μm LV MOSTs

Abstract

A multi-finger nMOST is widely used as an electrostatic discharge (ESD) protection device especially in the input/output pads. However, the contact-spiking leakage phenomenon in an MOST are seriously impacted the ESD capability. Therefore, one drain-side engineering is investigated in this paper, i.e., by adding a negative-type well (nWell) structure in the drain-side of device, hoping to avoid contact-spiking issues to enhance ESD reliability. The nWell width variations will be explored the influence on snapback parameters of ESD devices in a 0.35μm 3.3V low voltage (LV) process. However, after a systematic analysis, it is found that adding an nWell structure in the drain-side will lower ESD capability (It2 value) about 24% for this process. And, as compared with the original reference DUT, adding any nWell in the drain-side will make the Vh value slightly decreasing about 1%.