The Effect of the P-Substrate Connection on the HBM Robustness of P-type ESD Device

Although the p-substrate connection of p-type ESD device does not have any impact on the device's It2 while connecting the p-substrate to the ground degrades the human-body model (HBM) robustness of the device significantly. From the experiment results, adding N-type buried layer (NBL) to p-type ESD device can have the device HBM robustness invariant to the p-substrate connection. Based on the T-CAD simulations, the effect of the p-substrate connection on the HBM robustness of p-type ESD device is revealed in this paper. As HBM raises up the potential of the whole region of p-type ESD device after the onset of zapping for a while and then the high potential region of the device decreases with decreasing HBM current if the p-substrate is grounded, resulting in the current crowding. On the contrary, the high potential region of p-type ESD device does not decrease with decreasing HBM current if the p-substrate is floating or NBL is added to the device, resulting in the uniform current distribution.