Input/output electrostatic discharge protection circuit for an integrated circuit

摘要

An Input/Output (I/O) circuit (11) for an integrated circuit including Electrostatic Discharge Protection (ESD) circuitry is disclosed. A Silicon Controlled Rectifier SCR (30) is triggered by a transistor (36) which is scaled to an output transistor (24) of the I/O circuit (11) to shunt an ESD event. The SCR (30) couples between a pad (12) and a power supply line VSS. The transistor (36) is disabled. The triggering mechanism is voltage breakdown of the transistor (36) due to an ESD event. The SCR protection mechanism is process independent since the triggering mechanism is formed similarly to the output transistor (24) and thus breaks-down similarly. Zener diodes (26-29) are coupled to gates of the I/O circuit (11) and between the power supply lines. A phosphorous doping less than 5.0 E18 per cubic centimeter is used to form the cathode of zener diodes (26-29).