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Emitter Base Diffusion Process

IP.com Disclosure Number: IPCOM000077275D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Ponsolle, JA: AUTHOR [+2]

Abstract

In this process a base diffusion having a very high surface concentration with a low junction depth is followed by an emitter diffusion and base drive-in process, which minimizes crystalline defects in the base region.

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Emitter Base Diffusion Process

In this process a base diffusion having a very high surface concentration with a low junction depth is followed by an emitter diffusion and base drive-in process, which minimizes crystalline defects in the base region.

In device fabrication, it is noted that boron diffused into a silicon semiconductor induces defects. These defects will subsequently, during the emitter diffusion, provide sites for the emitter impurity to penetrate the device to greater depths than is desired.

In this process, the boron base diffusion is made with a very high-surface concentration and a low depth, as indicated by the dotted profile 10. The profile and diffusion depth can be controlled by the vapor pressure of the boron and the temperature of the diffusion. Subsequently, an emitter diffusion is made with an impurity having a higher surface concentration and ultimately a depth greater than the initial base diffusion, as indicated by profile 12. The emitter diffusion is used to drive the base impurity into the wafer to the desired depth, as indicated by profile 14. Profile 16 is included to indicate the subcollector profile. When the emitter-base diffusion is controlled in the aforementioned manner, the active base region of the transistor is below the initial base diffusion and, therefore, below the region of the initial high diffusion where defects are likely to cause crystalline defects.

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