Drain-extended MOS ESD protection structure

US6624487B1 · kind B1 · utility

Assignee

• TEXAS INSTRUMENTS INCORPORATED · US

Inventors

• Keith E. Kunz · Bryan, US
• Charvaka Duvvury · Plano, US
• Dan M. Mosher · Plano, US

Key dates

• Filing date: Jun 5, 2002
• Grant date: Sep 23, 2003
• Expiry date: Jun 5, 2022

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10D89/811

Abstract

A protection structure (30; 30′; 30″) for safely conducting charge from electrostatic discharge (ESD) at a terminal (IN) is disclosed. The protection structure (30; 30′; 30″) includes a pair of drain-extended metal-oxide-semiconductor (MOS) transistors (32, 34). In a pump transistors (32), the gate electrode (45) overlaps a portion of a well (42) in which the drain (44) is disposed, to provide a significant gate-to-drain capacitance. The drains of the transistors (32, 34) are connected together and to the terminal (IN), while the gates of the transistors (32, 34) are connected together. The source of one transistor (32) is connected to a guard ring (50), of the same conductivity type as the substrate (40) within which the channel region of the other transistors (34) is disposed. An ESD event received at the terminal (IN) is thus coupled to the gate of the transistors (32, 34), causing conduction to the substrate (40) via the guard ring (50), and turning on a parasitic bipolar transistor at the other transistor (34), safely conducting the ESD current. One alternative structure (30′) includes a junction capacitor (65) coupled between the terminal (IN) an…