ESD protection design for low trigger voltage and high latch-up immunity

An embedded silicon-controlled rectifier (SCR) protection structure is proposed with a compatible CMOS layout. It first turns on like a gate-coupled NMOSFET, and then provides second-snapback conduction by a parasitic SCR. As compared with a conventional gate-ground NMOS transistor, the trigger voltage and the human body mode (HBM) test immunity are both greatly improved. Also, this cell is latch-up resistant, both the holding voltage and the turn-on current are adjustable and greatly raised than those of a conventional SCR device.