Investigation of the gate-driven effect and substrate-triggered effect on ESD robustness of CMOS devices

The gate-driven effect and substrate-triggered effect on electrostatic discharge (ESD) robustness of CMOS devices are measured and compared in this paper. The operation principles of gate-grounded design, gate-driven design, and substrate-triggered design on CMOS devices for ESD protection are explained clearly by energy-band diagrams. The relations between ESD robustness and the devices with different triggered methods are also explained by transmission line pulsing (TLP) measured results and energy-band diagrams. The turn-on mechanisms of nMOS devices with triggered methods are further verified using the emission microscope (EMMI) photographs of the nMOS devices under current stress. The experimental results confirm that the substrate-triggered design can effectively and continually improve ESD robustness of CMOS devices better than the gate-driven design. The human body model (HBM) ESD level of nMOS with a W/L of 400 μm/0.8 μm in a silicided CMOS process can be improved from the original 3.5 kV to over 8 kV by using the substrate-triggered design. The gate-driven design cannot continually improve the ESD level of the device in the same deep-submicron CMOS process