Method of making a power diode with high reverse voltage rating

US4960731A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Richard Spitz · Reutlingen, DE
• Vesna Biallas · Reutlingen, DE

Key dates

• Filing date: Apr 27, 1989
• Grant date: Oct 2, 1990
• Expiry date: Apr 27, 2009

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S438/92
• WIPO field: Semiconductors
• WIPO sector: Electrical engineering

Abstract

In making a power diode with high reverse voltage rating, corrosion of the silicon wafer surface by gettering substances is avoided by employing two different diffusion steps. In the first step, boron and phosphorus are respectively applied to opposing major surfaces of the disk-shaped semiconductor body (10) and driven into it by heating to a predetermined temperature. Gettering is employed to increase the charge carrier lifetime and thereby reduce the forward voltage drop of the diode. The gettering is carried out in a second diffusion step at a diffusion temperature sufficiently reduced with respect to the diffusion temperature of the first step to avoid significantly affecting the depth of diffusion of the doping substances into the semiconductor body.