Browse Prior Art Database

Making High Beta and Low Beta Transistors on the same Chip

IP.com Disclosure Number: IPCOM000077175D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Tsui, F: AUTHOR

Abstract

This method allows normal high-beta as well as wide-base low-beta transistors to be formed on the same chip, which is required for certain very high-density bipolar memory cell circuits.

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Making High Beta and Low Beta Transistors on the same Chip

This method allows normal high-beta as well as wide-base low-beta transistors to be formed on the same chip, which is required for certain very high- density bipolar memory cell circuits.

Using this method, a normal NPN transistor is formed, as in conventional processes, on P- substrate 1, by N+ buried layer subcollector 2, P+ base diffusion 5 and N+ emitter diffusion 10; whereas a wide-base low-beta transistor is made by introducing a P+ diffusion 3 in N+ subcollector 2 prior to the growth of epitaxial layer 6. This same P+ diffusion, when applied to regions 4 around subcollector 2 and joined later by subsequent P+ diffusion in regions 7 around epitaxial regions 8, provides an isolation which has little lateral diffusion. With this method of isolation the fabrication of high high-beta and low-beta transistors on the same chip does not require more steps than the fabrication of high-beta transistors only. The low-beta transistors have emitters 9 of normal depths and wide bases containing no excessively high impurity-concentration gradients. Emitter-contacting or low-breakdown voltage problems will therefore not arise.

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