Browse Prior Art Database

Suppression of a Parasitic SCR by Ion Implantation

IP.com Disclosure Number: IPCOM000086073D
Original Publication Date: 1976-Jul-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Kroell, KE: AUTHOR

Abstract

Between merged integrated circuit elements, such as an NPN transistor and a Schottky diode, a parasitic silicon-controlled rectifier (SCR) or thyristor effect resulting from an NPNP zone sequence may occur during operation. A cross-sectional view of two such element structures is shown in the figure.

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Suppression of a Parasitic SCR by Ion Implantation

Between merged integrated circuit elements, such as an NPN transistor and a Schottky diode, a parasitic silicon-controlled rectifier (SCR) or thyristor effect resulting from an NPNP zone sequence may occur during operation. A cross- sectional view of two such element structures is shown in the figure.

Initially, the existence of region 1 shall be ignored. The usual planar transistor structure comprises, for example, a substrate 2 with subcollector region 3 on which a collector (epitaxial) region 4 with base and emitter zones 5 and 6, respectively, is superimposed. E and B are the emitter and base contacts. The Schottky diode in the form of metal electrode 7 is merged with transistor collector zone 4 in a manner generally known per se. Regions 8 serve to isolate the transistor/diode structure produced by conventional isolation diffusion or recessed oxidation.

The above NPNP zone sequence can be divided into the NPN transistor and a parasitic, lateral PNP transistor, whose emitter is formed by the Schottky diode (electrode), whose base is formed by epitaxial layer 4, and whose collector is formed by base 5 of the vertical NPN transistor.

This lateral PNP transistor behaves as follows: when the Schottkv diode is forward biased, it emits minority carriers (holes) into N conducting epitaxial layer 4, whereby these minority carriers are collected in part by base zone 5 of the NPN transistors. The SCR is then able to fi...