Electrostatic discharge protection circuit

摘要

An electrostatic discharge (ESD) protection circuit formed on a P-type substrate. The ESD protection circuit is disposed between a bonding pad and an internal circuit formed on a P-type substrate, and has a P-type metal-oxide semiconductor (PMOS) and an N-type metal-oxide semiconductor (NMOS). The PMOS has a first doped regionformed below a P<+> guard ring of the PMOS and a well pick-up of the PMOS. The NMOS has second doped regionformed below a N<+> guard ring of the NMOS and a well pick-up of the NMOS. An equivalent zener diode is formed on the P-type substrate. A breakdown of the equivalent zener diode restricts the PMOS or the NMOS from producing a snapback breakdown.