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Improving Power Transistor Second Breakdown Capacity

IP.com Disclosure Number: IPCOM000082637D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 84K

Publishing Venue

IBM

Related People

Anantha, NG: AUTHOR [+3]

Abstract

One method of improving device structures, in order to enhance the reversed biased second breakdown capacity of power transistors, is to decrease the power transistor base resistance near the center of emitter fingers.

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Improving Power Transistor Second Breakdown Capacity

One method of improving device structures, in order to enhance the reversed biased second breakdown capacity of power transistors, is to decrease the power transistor base resistance near the center of emitter fingers.

When power transistors are connected in a switching circuit with an inductive load, the simultaneous presence of a high base-collector junction voltage and high collector and emitter currents, increases the chance of reverse biased second breakdown near the center of emitter fingers.

One way of lowering the base resistance is to add a highly doped base region under the center of the emitter finger, which will allow enlargement of the effective emitter area, and thus reduce the emitter current density.

Fig. 1 shows a conventional power transistor with a high voltage-high current capability. When used in switching, only a very small emitter area is effective. The emitter contact metal is 6, emitter 8, base 10, base contact metal 12, high- resistivity collector 14, low resistivity collector 16, and collector contact metal is
18.

Fig. 2 shows the emitter fingers 20 and emitter contact metal 6', and Fig. 3 is a top view of the emitter fingers 20.

Fig. 4 shows fewer emitter fingers with each finger 20' having a larger width because of the finger configuration of highly doped base region 22 underneath the concentric emitter finger configuration 20', which reduces the base resistance in those areas.

Anot...