Stacked-NMOS triggered silicon-controlled rectifier for ESD protection in high/low-voltage-tolerant I/O interface

Abstract

A stacked-NMOS triggered silicon-controlled rectifier (SNTSCR) is proposed as the electrostatic discharge (ESD) clamp device to protect the mixed-voltage I/O buffers of CMOS ICs. This SNTSCR device is fully compatible to general CMOS processes without using the thick gate oxide to overcome the gate-oxide reliability issue. ESD robustness of the proposed SNTSCR device with different layout parameters has been investigated in a 0.35-mum CMOS process. The HBM ESD level of the mixed-voltage I/O buffer with the stacked-NMOS channel width of 120 mum can be obviously improved from the original similar to2 kV to be greater than 8 kV by this SNTSCR device with a device dimension of only 60 mum/0.35 mum.