Browse Prior Art Database

Polysilicon Trench Isolation

IP.com Disclosure Number: IPCOM000048592D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Antipov, I: AUTHOR

Abstract

Since oxidation of deep trenches and oxidation of ROI (recessed oxide isolation) can lead to the generation of oxidation stacking faults, in some cases, to improve density, it is desirable to use P+ polysilicon directly for isolation, especially if polysilicon-filled trenches are made very narrow, and heat cycles thereafter are minimized.

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Polysilicon Trench Isolation

Since oxidation of deep trenches and oxidation of ROI (recessed oxide isolation) can lead to the generation of oxidation stacking faults, in some cases, to improve density, it is desirable to use P+ polysilicon directly for isolation, especially if polysilicon-filled trenches are made very narrow, and heat cycles thereafter are minimized.

A preferred process is the following:
1. Mask defined subcollector diffusion 1/oxidation.
2. Epi layer 2 deposition/oxidation. (No P autodoping.)
3. Either use E-beam photolithography, or use following

steps to define very narrow isolation trenches.

a. CVD (chemically vapor deposit) about 1 micrometer

SiO(2)3.

b. RIE (reactive ion etch) isolation trenches 4 in SiO(2).

c. Again, CVD about 1 micrometer SiO(2).

d. RIE in SiO(2) isolation trenches to produce shoulders

5, shrinking oxide opening below mask capability from

2.5 micrometers to 1.5 micrometers, as shown in Fig. 1.
4. RIE deep narrow isolation trenches 6 in Si (Fig. 2).
5. CVD polysilicon 7 to refill trenches 6. Planarize by

RIE (Fig. 3).
6. Diffuse P+ isolation into exposed polysilicon trenches 7.

Since diffusion into polysilicon is very fast, diffusion into

single crystal 8 will be shallow (Fig. 4).
7. Oxidize to form layer 9 (optionally, remove all oxide prior

to oxidation).

The completing device processing is done in a standard manner using the P base diffusion to make contact to isolation. To minimize heat cycles thereafter, the applicati...