Electrostatic discharge suppression circuit employing trench capacitor

摘要

An enhanced electrostatic discharge suppression circuit is disclosed for protecting integrated circuit chips from electrostatic discharges or other potentially damaging voltage transients on an input/output pad. The suppression circuit includes a discharge circuit, electrically coupled to the input/output pad, having a diode comprising a diffusion in a substrate well formed in a substrate. The diffusion is connected to the input/output pad of the integrated circuit. A capacitor is locally provided to couple the substrate well to the substrate. The capacitor is sized to maintain the diode in a forward-bias mode during the electrostatic discharge event, thereby facilitating dissipating of the electrostatic discharge. The capacitor comprises a trench capacitor, which depending upon the configuration, may function as a guard ring for the discharge circuit. Certain beneficial parasitic effects are also discussed in association with integration of a trench capacitor into the suppression circuit.