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Isolation of N and P Regions in Recessed Oxide Semiconductor Structure

IP.com Disclosure Number: IPCOM000082242D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Antipov, I: AUTHOR

Abstract

This is a solution to the surface inversion problems of P-type regions, which come in contact with the recessed oxide isolation (ROI) of semiconductor bipolar transistor structures. The P-type regions tend to invert to N type. The process involves the selective doping of the well and sidewalls of the recess to prevent the joinder of various isolated regions, in particular, N type emitter-to-collector shorts and P type base-to-isolation shorts.

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Isolation of N and P Regions in Recessed Oxide Semiconductor Structure

This is a solution to the surface inversion problems of

P-type regions, which come in contact with the recessed oxide isolation (ROI) of semiconductor bipolar transistor structures. The P-type regions tend to invert to N type. The process involves the selective doping of the well and sidewalls of the recess to prevent the joinder of various isolated regions, in particular, N type emitter-to-collector shorts and P type base-to-isolation shorts. The process involves the following steps:
(1) Form the recessed regions, which separate the active

regions in the semiconductor substrate, by

conventional methods;
(2) Deposit a solid N-type diffusant such as As

doped oxide into the recess to substantially

cover the entire recess;
(3) Evaporate a mask material, such as Cr, into

the recess so as to cover the well of the

recess, but not the sidewalls;
(4) Remove the N-doped oxide from the sidewalls;
(5) Subsequently remove the Cr mask, leaving the

doped oxide in the well of the recess;
(6) Remove the doped oxide from the center of

the well, thereby leaving patches of the

doped oxide around the well;
(7) Diffuse P-type impurities into the exposed

center region of the well and the sidewalls

of the recess;
(8) Simultaneously drive N-type impurities in

between these two regions, the source of the

impurities being the remaining patches of the

doped oxide; and
(9) Complete the ROI deposition in the standard

mann...