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Ring-Shaped Subcollector Reach-Through Contact for Vertical PNP Transistor

IP.com Disclosure Number: IPCOM000036845D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Pelella, MM: AUTHOR

Abstract

The forward-biased operating range of vertical bipolar PNPs in complementary technologies is limited due to a four-terminal thyristor breakover voltage or latch-up that occurs when the N+ and P subcollector junction becomes conductive. This self-biasing latch-up or breakover voltage phenomenon can be pushed-out and/or avoided by incorporating a ring-shaped subcollector reach-through contact, as shown in Fig. 1.

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Ring-Shaped Subcollector Reach-Through Contact for Vertical PNP Transistor

The forward-biased operating range of vertical bipolar PNPs in complementary technologies is limited due to a four-terminal thyristor breakover voltage or latch-up that occurs when the N+ and P subcollector junction becomes conductive. This self-biasing latch-up or breakover voltage phenomenon can be pushed-out and/or avoided by incorporating a ring-shaped subcollector reach- through contact, as shown in Fig. 1.

In normal complementary transistor devices with vertical PNPs, a reach- through collector contact is provided by a single, highly doped contact region. However, due to variations and limitations in obtaining low sheet Rho resistances of the subcollector, the subcollector region becomes highly resistive. This high resistivity causes a larger voltage drop to occur within these regions and causes the reverse- biased isolation to become forward-biased.

In order to better maintain the reverse-biased junction/isola

(Image Omitted)

tion, a ring-shaped collector reach-through contact region collector (C) can be formed surrounding the base region, as shown in Fig. 1. This design reduces the resistivity of the collector by reducing the distance or the number of squares the majority carriers (holes) have to travel through the high resistance subcollector. This also allows the collector current to spread out in all four directions thus reducing the total collector resistance by several orders...