Esd power clamp for silicon-on-insulator (soi) and finfet processes lacking parasitic esd diode

Abstract

An Electro-Static-Discharge (ESD) protection circuit uses Silicon-On-Insulator (SOI) transistors with buried oxide but no parasitic substrate diode useable for ESD protection. A filter voltage is generated by a resistor and capacitor. When a VDD-to-VSS ESD positive pulse occurs, the filter voltage passes through an n-channel pass transistor and inverted to drive a gate of a big SOI transistor that shunts ESD current. A second path is used for a VSS-to-VDD ESD positive pulse. The filter voltage passes through a p-channel pass transistor to the gate when the positive ESD pulse is applied to VSS. The big SOI transistor can connect between VDD and VSS for a power clamp, and the gates of the n-channel and p-channel pass transistors connect to VDD. A small diode may be added between VDD and VSS to generate a small triggering current to activate grounded-gate transistors near I/O pads for full-chip Pad-based ESD protection.