Design and analysis of different trigger techniques for ESD clamp circuit in 0.5-µm 5 V/18 V CDMOS process

Abstract

In this work, gate-driven, substrate-triggered and gate-substrate-triggered techniques for both 5V NMOS-based and 18V NLDMOS-based power clamps under electrostatic discharge (ESD) stress were investigated in details. Schematics of the three trigger designs were depicted and their physical mechanisms were studied at first. To verify and make comparisons of their performance, they were fabricated in a standard 0.5-μm 5V/18V CDMOS process and characterized by transmission line pulse (TLP) test system, respectively. Experimental results show that 5V NMOS-based power clamp with substrate-triggered technique has the lowest trigger voltage (∼8.37V) and the highest failure current (∼3.58A), and 18V gate-substrate-triggered design based on NLDMOS has low trigger voltage (∼34.02V) and greatest robustness (It2=3.32A). Therefore, as for low-voltage NMOS-based ESD power clamps, substrate-triggered design obtains the most superior ESD protection performance; but for high-voltage power clamps, gate-substrate-triggered technique can make NLDMOS actualize uniform current conduction and better ESD robustness.