Electrostatic discharge protection design for mixed-voltage CMOS

Abstract—A new electrostatic discharge (ESD) protection cir-cuit, using the stacked-nMOS triggered silicon controlled rectifier (SNTSCR) as the ESD clamp device, is designed to protect the mixed-voltage I/O buffers of CMOS ICs. The new proposed ESD protection circuit, which combines the stacked-nMOS structure with the gate-coupling circuit technique into the SCR device, is fully compatible to general CMOS processes without causing the gate-oxide reliability problem. Without using the thick gate oxide, the experimental results in a 0.35- m CMOS process have proven that the human-body-model ESD level of the mixed-voltage I/O buffer can be successfully increased from the original 2 kV to 8 kV by using this proposed ESD protection circuit. Index Terms—Electrostatic discharge (ESD), ESD protection circuit, mixed-voltage I/O buffer, silicon controlled rectifier (SCR). I