Process for anisotropic etching of silicon plates

US5071510A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Guenther Findler · Stuttgart, DE
• Horst Muenzel · Reutlingen, DE

Key dates

• Filing date: Sep 24, 1990
• Grant date: Dec 10, 1991
• Expiry date: Sep 24, 2010

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S438/958
• WIPO field: Semiconductors
• WIPO sector: Electrical engineering

Abstract

Electrochemical etching of silicon wafers or plates, on the front side of which a monocrystalline epitaxy layer is provided having a doping of a type opposite to the doping of the remainder of the silicon plate, so as to provide a pn or np junction, is performed with an organic photo film material of negative type and polyisoprene base serving as a passivating layer on the previously etched and metallized front (epitaxy) side. The film layer is held in place with the help of an adhesion promoting silane compound and covers the entire front side including the portions previously masked with silicon nitride or oxide. It is dried and hardened before exposure to the etchant which is used to etch the rear side of the plate until the etchant reaches the pn junction, where a small voltage bias applied to the junction from the front side assures an etch-stop. Etchants containing tetraalkylammonium hydroxide in water solution or in water-free form are preferred, with various additives as inhibitors, complexing agents and/or wetting agents.