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Browse Prior Art Database

Selective Etch of Silicon Nitride Films

IP.com Disclosure Number: IPCOM000073774D
Original Publication Date: 1971-Feb-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Doo, VY: AUTHOR

Abstract

Selective etching of cleanly defined areas of silicon nitride Si(3)N(4) films can be accomplished by utilizing a phospho-silicate glass reaction with silicon nitride at elevated temperatures to convert the nitride into a silicate that is readily etchable by standard silicon dioxide etching techniques. As shown, silicon nitride is deposited in a conventional manner on thermal silicon dioxide layer formed on a silicon substrate. A layer of phospho-silicate glass P(2)O(5)- SiO(2) is deposited on top of the silicon nitride layer which is to be etched. The glass layer is removed by a conventional photo-etch process at those locations where the underlying silicon nitride is to remain. Next, a thin layer of pyrolytic oxide is deposited over the entire wafer. The wafer is annealed at temperatures of about 800 to 1000 degrees C.

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Selective Etch of Silicon Nitride Films

Selective etching of cleanly defined areas of silicon nitride Si(3)N(4) films can be accomplished by utilizing a phospho-silicate glass reaction with silicon nitride at elevated temperatures to convert the nitride into a silicate that is readily etchable by standard silicon dioxide etching techniques. As shown, silicon nitride is deposited in a conventional manner on thermal silicon dioxide layer formed on a silicon substrate. A layer of phospho-silicate glass P(2)O(5)- SiO(2) is deposited on top of the silicon nitride layer which is to be etched. The glass layer is removed by a conventional photo-etch process at those locations where the underlying silicon nitride is to remain. Next, a thin layer of pyrolytic oxide is deposited over the entire wafer. The wafer is annealed at temperatures of about 800 to 1000 degrees C. During annealing, the phospho-silicate glass converts the immediately adjacent silicon nitride into a silicate having a high etching rate in buffered hydrogen fluoride solution. Upon application of such solution, windows are opened in the silicon nitride and in the underlying oxide only in those locations where the nitride is converted into a silicate. Phosphorus is prevented from diffusing into the silicon wafer during the etching of the converted nitride by the thermal silicon dioxide layer which separates the silicon nitride from the wafer.

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