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Browse Prior Art Database

Recessed Oxide Isolated Integrated Circuits

IP.com Disclosure Number: IPCOM000088238D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 41K

Publishing Venue

IBM

Related People

Jambotkar, CG: AUTHOR

Abstract

In the integrated-circuit field, recessed silicon dioxide has been widely used to laterally, dielectrically isolate integrated circuits. Silicon nitride, usually in the form of a composite layered structure of silicon dioxide covered with silicon nitride, is generally used in defining the active and passive regions as well as the recessed oxide regions in such integrated circuits. When such silicon dioxide-silicon nitride composites are used in connection with recessed silicon dioxide, the structure is subject to a problem known as the "bird's beak" problem.

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Recessed Oxide Isolated Integrated Circuits

In the integrated-circuit field, recessed silicon dioxide has been widely used to laterally, dielectrically isolate integrated circuits. Silicon nitride, usually in the form of a composite layered structure of silicon dioxide covered with silicon nitride, is generally used in defining the active and passive regions as well as the recessed oxide regions in such integrated circuits. When such silicon dioxide- silicon nitride composites are used in connection with recessed silicon dioxide, the structure is subject to a problem known as the "bird's beak" problem.

This problem is discussed in some detail in U. S. Patent 3,966,514. Unlike the method in this patent which attempts to eliminate or minimize the "bird's beak" problem, the present approach does not attempt to affect the "bird's beak" structure. Rather, it lives with it. It does so by the recognition that once the recessed silicon dioxide regions are formed, together with their attendant "bird's beaks", the edges of the recessed silicon dioxide regions, which are to abut and thereby define either contact openings or subsequent regions of introduced impurities, are never again subjected to a thermal oxidation wherein a surface silicon dioxide layer is grown. In such cases, where the silicon dioxide must be grown in portions of such openings, the critical edges of the openings which are to abut and define contacts for regions of introduced impurities must be masked with silicon nitride during any such oxidation.

An example of this approach will be given with reference to the diagrammatic representations of Figs. 1A - 5A, of which Figs. 1B - 5B are sections along the lines shown. Commencing with a structure shortly after the recessed oxide regions 10 (Fig. 1A) are formed, laterally defining pockets in epitaxial layer 11, silicon nitride layer 12, which has been used to define the regions of re...