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Anisotropic Etching of Silicon Nitride

IP.com Disclosure Number: IPCOM000040495D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Dhong, SH: AUTHOR [+4]

Abstract

Improved selectivity and diminished mask undercutting are achieved in plasma chemical etching of silicon nitride on silicon dioxide or polysilicon by supplying excessive oxidant to a low fluorine fluorohydrocarbon atmosphere. Etch rate ratios of 8-10:1 of silicon nitride on silicon dioxide, 18-20:1 for silicon nitride on polysilicon, and 1:1 for silicon nitride on photoresist are obtained by maintaining carbon dioxide as approximately 75% of the total gas flow. An example of reactive ion etching process conditions is as follows: Methyl fluoride 10 sccm. Carbon dioxide 30 sccm. Electrode water cooled Pressure 50 mtorr. Power 100 watts Power density 0.88 watts/in.

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Anisotropic Etching of Silicon Nitride

Improved selectivity and diminished mask undercutting are achieved in plasma chemical etching of silicon nitride on silicon dioxide or polysilicon by supplying excessive oxidant to a low fluorine fluorohydrocarbon atmosphere. Etch rate ratios of 8-10:1 of silicon nitride on silicon dioxide, 18-20:1 for silicon nitride on polysilicon, and 1:1 for silicon nitride on photoresist are obtained by maintaining carbon dioxide as approximately 75% of the total gas flow. An example of reactive ion etching process conditions is as follows: Methyl fluoride 10 sccm.

Carbon dioxide 30 sccm.

Electrode water cooled

Pressure 50 mtorr.

Power 100 watts

Power density 0.88 watts/in.2 An etch rate of 250 Ao/minute is obtained with these conditions. The excess carbon dioxide acts as a passive etching barrier to minimize the ion-enhanced etching of the silicon dioxide. Simultaneously, the sides of features, where recombinant concentration is greatest, have slower etch rates than the surfaces, making etching anisotropic.

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