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Bipolar Transistors With a High Mobility Base

IP.com Disclosure Number: IPCOM000041198D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Chu, WK: AUTHOR [+2]

Abstract

A technique is described whereby the operational performance of bipolar NPN transistors is increased through the incorporation of controlled impurities into the base region of the transistor. Elements, such as germanium and boron, introduced into the base region of the transistor under controlled conditions, decrease the base resistance and the base transit time of the conductive carriers. The result is an improved operational performance of the transistor.

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Bipolar Transistors With a High Mobility Base

A technique is described whereby the operational performance of bipolar NPN transistors is increased through the incorporation of controlled impurities into the base region of the transistor. Elements, such as germanium and boron, introduced into the base region of the transistor under controlled conditions, decrease the base resistance and the base transit time of the conductive carriers. The result is an improved operational performance of the transistor.

In prior art, decreasing the switching time of high performance bipolar NPN transistors has been primarily the result of a reduction of the size of the transistor and an increase in the conductivity of the base contact, by using a narrow base. Typically, size reduction decreases the collector capacitance and the narrower base reduces the base transit time. Reducing the base width, so as to shorten the transit time, must be compensated by increasing the base doping in order to preserve the same sheet resistance of the internal base regions.

A limiting factor to scaling to a smaller and smaller base width is the decrease in mobility which occurs as impurity concentration increases. This causes a super-linear increase in the base dopant required to maintain the same base resistance. The maximum dopant concentration in the base is limited, therefore the minimum base width is also limited. Instead of attempting to continue to reduce the size of the base width, the conce...