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Annular Emitter Lateral PNP Transistor

IP.com Disclosure Number: IPCOM000048448D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Muggli, RA: AUTHOR

Abstract

This lateral PNP transistor is characterized by a higher Beta characteristic and higher level injection current onset by maximizing the ratio of emitter perimeter to emitter bottom area in a structure that has an increased active area.

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Annular Emitter Lateral PNP Transistor

This lateral PNP transistor is characterized by a higher Beta characteristic and higher level injection current onset by maximizing the ratio of emitter perimeter to emitter bottom area in a structure that has an increased active area.

The active area of a lateral transistor is the vertical peripheral area around the emitter. This active area is increased over the conventional transistor in this arrangement by making the emitter in annular form, whereby the inner and outer peripheral areas are both effective. The transistor comprises a P- substrate 10 having an N+ base subcollector 12 therein. An N epitaxial layer 14 is grown over the substrate and the subcollector, and P isolation is diffused into the epitaxial layer to delineate the transistor. An N+ base reach-through 18 is diffused down to the subcollector 12. Also, diffused in the epitaxial layer 14 is an emitter 22 in annular form within which one collector 24 is diffused and about which an annular collector 26 is also diffused.

This arrangement allows more emitter perimeter and therefore a larger active area for a given amount of horizontal area, which minimizes the ratio and gives higher beta and higher emitter current for the onset of high level injection.

In the figure, the horizontal area of the emitter A(H) is L(E) times W(E). This horizontal area is an inactive area and reduces the Beta and F(T). The vertical area of the emitter is the active area and must face...