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Nondestructive Localization of Collector Emitter Pipes

IP.com Disclosure Number: IPCOM000083209D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Bohg, A: AUTHOR

Abstract

The method serves to localize pipes within individual transistors, without etching parts of the transistor structure.

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Nondestructive Localization of Collector Emitter Pipes

The method serves to localize pipes within individual transistors, without etching parts of the transistor structure.

Fig. 1 is a cross-sectional view of a typical bipolar transistor with a pipe, i.e., an undesirable current path between emitter E and collector C. Collector C, base B and emitter E are contacted by point contacts under a light microscope.

Fig. 2 shows the electrical conditions arising when the method is used in connection with an NPN transistor with a pipe. The C)B diode is reverse biased at a voltage VCB. As emitter E is connected to collector C via the pipe, and the E/B breakdown voltage BVEB is essentially below the C/B breakdown voltage, breakdown on the transistor surface occurs via the E/B diode.

A separately controllable voltage source for the E/B diode is so adjusted that when it is used in connection with voltage VCB, a current Ipipe flows through the pipe from C to E, thus a potential gradient is set up over the length of the pipe. This potential gradient keeps emitter E slightly below E/B breakdown voltage BVEB.

Additionally, recombination current Irec flows across the C/B diode, causing an avalanche breakdown on the respective point of the pipe. This process is linked with the emission of white light and permits the defect being localized with light-microscopic precision. The metallization on the emitter contact has to be removed beforehand.

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