ESD protection design for mixed-voltage I/O buffer by using stacked-NMOS triggered SCR device

A new ESD protection circuit, by 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 IC´s. Without using the thick gate oxide, the experimental results in a 0.35-mum 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 become > 8 kV by using this new proposed ESD protection circuit.