Browse Prior Art Database

Dielectric Isolation

IP.com Disclosure Number: IPCOM000085245D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Aboaf, JA: AUTHOR [+2]

Abstract

Dielectric isolation is one of the steps in the processing of bipolar or field-effect transistor (FET) devices. A trench is etched in the silicon wafer using silicon dioxide and silicon nitride films as a mask. During oxidation, the silicon oxides not only deep into the trench, but also sideways under the silicon nitride film lifting that film and forming a "bird's beak". Loss of planarity occurs as shown in Fig. 1 because the edge of the silicon nitride is lifted by about 4000 Angstroms.

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Dielectric Isolation

Dielectric isolation is one of the steps in the processing of bipolar or field- effect transistor (FET) devices. A trench is etched in the silicon wafer using silicon dioxide and silicon nitride films as a mask. During oxidation, the silicon oxides not only deep into the trench, but also sideways under the silicon nitride film lifting that film and forming a "bird's beak". Loss of planarity occurs as shown in Fig. 1 because the edge of the silicon nitride is lifted by about 4000 Angstroms.

The following is a step-by-step sequence wherein the silicon nitride film is not lifted above the surface of the silicon. 1. Silicon dioxide-silicon nitride, 10, 11, window opening

(Fig. 2A).

2. Etching of silicon trench 12 (Fig. 2B).

3. Removal of silicon dioxide-silicon nitride 10, 11.

Redisposition of silicon dioxide-silicon nitride 13, 14 on

the whole surface (Fig. 2C).

4. Window opening as shown in Fig. 2D.

5. Oxidation to form dielectric isolation 15 (Fig. 2E).

This approach is different from the conventional one in that it includes two extra steps, 3 and 4 above.

The advantage of this process where buttingof emitter in bipolar devices is necessary, are (1) no loss of real estate occurs, and (2) no difficulty should result because of nonuniform SiO(2) thickness at the surface.

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