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Planar Transistor Process without Post Emitter Diffusion Thermal Reoxidation

IP.com Disclosure Number: IPCOM000093054D
Original Publication Date: 1967-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Barson, F: AUTHOR [+4]

Abstract

The use of a thermal reoxidation step following the emitter phosphorus diffusion is conventional in fabricating planar silicon NPN transistors. However, semiconductor devices, made with high surface concentration phosphorus diffusions followed by the usual thermal reoxidation, result in a relatively low current gain beta devices as compared to a low surface concentration phosphorus diffusion process followed by reoxidation. The high surface concentration diffusion process is the most desirable of the two processes because it yields a higher speed semiconductor device. Therefore, there has had to be a compromise between maximum speed and maximum current gain beta in the production of semiconductor devices.

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Planar Transistor Process without Post Emitter Diffusion Thermal Reoxidation

The use of a thermal reoxidation step following the emitter phosphorus diffusion is conventional in fabricating planar silicon NPN transistors. However, semiconductor devices, made with high surface concentration phosphorus diffusions followed by the usual thermal reoxidation, result in a relatively low current gain beta devices as compared to a low surface concentration phosphorus diffusion process followed by reoxidation. The high surface concentration diffusion process is the most desirable of the two processes because it yields a higher speed semiconductor device. Therefore, there has had to be a compromise between maximum speed and maximum current gain beta in the production of semiconductor devices.

The elimination of the thermal reoxidation step, and the substitution for it of either the adjustment of the emitter junction depth by control of the emitter diffusion itself, an inert atmosphere drive-in, a controlled slow thermal oxidation or a nonthermal silicon oxide deposition after the high surface concentration phosphorus diffusion, produces semiconductor devices having both high current gain beta and high speed.

The reason for the inferior current gain characteristic of post-emitter diffusion thermal reoxidation in the high surface concentration process is the dislocations. The latter result at the edge of the emitter and extend beyond the diffusion front as a consequence of str...