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Browse Prior Art Database

Recessed Oxide Isolation Method

IP.com Disclosure Number: IPCOM000086432D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 82K

Publishing Venue

IBM

Related People

Ko, W: AUTHOR

Abstract

Recessed silicon dioxide for dielectric isolation of bipolar integrated circuits is extensively used in the art. For an example of such recessed oxide, attention is directed to U. S. Patent 3,858,231. Publications by G. T. Galyon, Vol. 18, No. 6, November 1975, pp. 1854 and 1855, and A. W. Chang et al, Vol. 18, No. 2, July 1975, pp. 380 and 381, of the IBM Technical Disclosure Bulletin, describe methods of forming recessed oxide wherein impurities are introduced into the trench in the silicon, in which the recessed oxide is to be formed prior to oxidation to form the oxide.

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Recessed Oxide Isolation Method

Recessed silicon dioxide for dielectric isolation of bipolar integrated circuits is extensively used in the art. For an example of such recessed oxide, attention is directed to U. S. Patent 3,858,231. Publications by G. T. Galyon, Vol. 18, No. 6, November 1975, pp. 1854 and 1855, and A. W. Chang et al, Vol. 18, No. 2, July 1975, pp. 380 and 381, of the IBM Technical Disclosure Bulletin, describe methods of forming recessed oxide wherein impurities are introduced into the trench in the silicon, in which the recessed oxide is to be formed prior to oxidation to form the oxide.

The present method represents a modification of these methods which minimizes emitter-collector short circuits along the isolation periphery. The process employs a boron diffusion in the isolation trenches to prevent emitter- collector shorts and a bottom boron implantation to provide the isolation between the device cells. The method permits emitter abutting against oxide isolation.

As shown in Fig. 1, the bipolar structure is fabricated with a p-substrate and a conventional n+ buried subcollector diffused region. A lightly doped n-type epitaxial layer of about 2 microns is then grown on the silicon slice. The slice is then oxidized to about 800 - 2000 Angstroms of SiO(2) and then coated with silicon nitride. The silicon oxide and nitride are then patterned using photoresist mask 11, and the oxide and the isolation trenches 10 are etched.

The slice is then doped with boron in the isolation trenches 10, for example, by BBr(3) deposition from a boron s...