The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 16, 1999
Filed:
Jul. 16, 1996
Adrianus W Ludikhuize, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
In many circuits in which a current is switched off, a high voltage appears at the drain electrode of a transistor, in particular in the case of an inductive load. When a lateral high-voltage DMOST is used, such a high voltage may lead to instability in the transistor characteristics or may even damage the transistor. To avoid this problem, the drain of a high-voltage LDMOST is locally provided with a strongly doped n-type zone 18, 21 (in the case of an n-channel transistor) which extends, seen from the surface, down into the semiconductor body to a greater depth than does the source zone 8, so that a pn-junction is formed at a comparatively great depth in the semiconductor body having a breakdown voltage that is lower than the BV.sub.ds of the transistor without this zone. The energy stored in the inductance may thus be drained off through breakdown of the pn-junction. This breakdown is separated from the normal current path of the transistor owing to the comparatively great depth of the pn-junction, so that the robustness of the transistor is improved. This deep zone in the drain may be formed, for example, by a buried layer at the boundary between an epitaxial layer and the substrate.