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Low Temperature Photoresist Mask Etching of Silicon Nitride

IP.com Disclosure Number: IPCOM000078538D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Dolgov, I: AUTHOR [+2]

Abstract

Silicon nitride may be etched under relatively mild conditions by employing an ammonium bifluoride and water solution as the etchant, and standard negative or positive photoresist material as the etchant resist.

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Low Temperature Photoresist Mask Etching of Silicon Nitride

Silicon nitride may be etched under relatively mild conditions by employing an ammonium bifluoride and water solution as the etchant, and standard negative or positive photoresist material as the etchant resist.

Unless the silicon nitride has been freshly deposited, surface pretreatment is required before etching. The pretreatment comprises cleaning the surface of the silicon nitride in a strongly oxidizing medium, such as a 9:1 mixture of sulfuric and nitric acids. The cleaned surface is purged of moisture, for example, by placing in a vacuum oven for at least thirty minutes at 200 degrees C or by applying a silizane material such as HMDS, spin drying, applying a fluorocarbon material such as FREON*, spin drying, and then baking in an oven at 160 degrees C.

Immediately after drying the cleaned surface, conventional photoresist procedures are carried out for selectively masking the silicon nitride to be etched. The masked silicon nitride is etched in a solution of ammonium bifluoride (NH(4)HF(2)) in deionized water. The formal concentration should be in the range 0.5+/- 0.05, to yield an etch rate of approximately 75 angstroms per minute at 90 degrees C. For resist materials that tend to flow at the aforementioned temperature, the temperature may be reduced to 80 degrees C with a corresponding reduction in etch rate of approximately 30 angstroms per minute. * Trademark of E. I. du Pont de Nemours & Co.

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