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Browse Prior Art Database

Elimination of Bird's Beak in ROI Process

IP.com Disclosure Number: IPCOM000052908D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Ho, AP: AUTHOR [+3]

Abstract

The density and planarity of devices fabricated by the recessed oxide isolation (ROI) process is negatively impacted by the formation of the ""bird's beak'' during the ROI oxide growth, as shown by the Fig. 1, wherein the ROI is 10, silicon body 11, thin thermally grown silicon dioxide 12 and silicon nitride 13. The bird's beak can be prevented with an extra masking process in which a narrow strip of silicon nitride (about 2 microns wide) is deposited directly on the silicon surface. This prevents oxygen diffusion under the silicon nitride, and hence formation of the bird's beak. Alternatively, a self-aligned process can achieve the same goal without the use of the extra masking step.

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Elimination of Bird's Beak in ROI Process

The density and planarity of devices fabricated by the recessed oxide isolation (ROI) process is negatively impacted by the formation of the ""bird's beak'' during the ROI oxide growth, as shown by the Fig. 1, wherein the ROI is 10, silicon body 11, thin thermally grown silicon dioxide 12 and silicon nitride 13. The bird's beak can be prevented with an extra masking process in which a narrow strip of silicon nitride (about 2 microns wide) is deposited directly on the silicon surface. This prevents oxygen diffusion under the silicon nitride, and hence formation of the bird's beak. Alternatively, a self-aligned process can achieve the same goal without the use of the extra masking step.

The process is as follows:

1) Standard process through epitaxial reoxidation,(1600 angstroms oxide) layer 14 and deposition of silicon nitride (1000 angstroms) layer 15 and silicon dioxide (1000 angstroms) layer 16 on silicon body 17, as shown in Fig. 2.

2) Deposit photoresist, expose and develop to form openings therein where the ROI is to be formed. Reactive ion etch (RIE) through the oxide-nitride-oxide layer to the silicon surface. Strip the photoresist, resulting in the Fig. 3 structure.

3) Deposit 2500 angstroms layer of silicon nitride layer 18, as shown in Fig.


4.

4) Blanket RIE off the 2500 angstroms silicon nitride. This leaves a 2500 angstroms nitride on the sidewalls, as seen in Fig. 5.

5) RIE the exposed silicon at 19 using the...