Method of forming a zener diode

US6645802B1 · kind B1 · utility

Assignee

• XILINX, INC. · US

Inventors

• Sheau-Suey Li · Cupertino, US
• Shahin Toutounchi · Pleasanton, US
• Michael J. Hart · Palo Alto, US
• Xin Wu · Fremont, US
• Daniel Gitlin · Palo Alto, US

Key dates

• Filing date: Jun 8, 2001
• Grant date: Nov 11, 2003
• Expiry date: Oct 8, 2021

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S438/983

Abstract

An ESD protection circuit includes a bipolar transistor, a resistor, and a zener diode formed on and within a semiconductor substrate. The resistor extends between the base and emitter regions of the transistor so that voltage developed across the resistor can turn on the transistor. The zener diode is formed in series with the resistor and extends between the base and collector regions of the transistor. Thus configured, breakdown current through the zener diode, typically in response to an ESD event, turns on the transistor to provide a nondestructive discharge path for the ESD. The zener diode includes anode and cathode diffusions. The cathode diffusion extends down into the semiconductor substrate in a direction perpendicular to the substrate. The anode diffusion extends down through the cathode diffusion into the semiconductor substrate. The anode diffusion extends down further than the cathode diffusion so that the zener diode is arranged vertically with respect to the substrate. The cathode diffusion can be formed using two separate diffusions, one of which extends deeper into the substrate than other.