A Zener-diode-activated ESD protection circuit for sub-micron CMOS processes

A Zener-diode-activated electrostatic discharge (ESD) protection circuit is implemented in a 0.5 μm CMOS process. This ESD circuit uses a substrate p-n-p transistor with its base connected to a Zener diode to discharge the electrostatic energy. The Zener diode implementation utilizes a silicide block capability to avoid short circuits in the active area. Its performance has been tested by the human body model and a high-speed ESD test. Its latchup-free characteristic makes it an ideal circuit for ESD protection of I/O pads, ESD clamping between power rails, poly-antenna effect protection, and overshoot attenuation