ESD protection for the tolerant I/O circuits using PESD implantation

In this paper, we propose an electrostatic discharge (ESD) solution with cascode structure for deep-submicron integrated circuits technology to enhance its ESD robustness. Using the added boron implantation (we call "PESD" implantation here) at the drain side of the stacked n-type metal-oxide semiconductor (NMOS), the long-base parasitic NPN (i.e., emitter, base and collector in the bipolar transistor are n-type, p-type, and n-type, respectively) bipolar transistor in the cascode NMOS structure can be easily triggered by the Zener breakdown mechanism at the drain side under ESD stress conditions. Based on UMC 0.25 μ process, this method provides a significant improvement in the cascode ESD performance.