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Removal With O2 of Leaked Photoresist From Wafer Backside Prior to Plasma Etching of Silicon Nitride

IP.com Disclosure Number: IPCOM000041275D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Carey, ER: AUTHOR [+3]

Abstract

In device fabrication, low pressure chemical vapor deposited (LPCVD) silicon nitride is deposited on both sides of the substrate. Prior to further processing, the backside silicon nitride must be removed. This is accomplished by protecting the substrate device side with photoresist and then etching the backside silicon nitride in a CF4 plasma. When applying the photoresist to the device side, a small quantity of photoresist is splashed on the substrate backside. Since photoresist will not etch appreciably in a CF4 plasma, this residual resist will not allow the underlying silicon nitride to be etched in these areas. The solution is to first process the coated substrates in an 02 plasma or "flash strip" cycle which removes the small quantity of residual backside resist.

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Removal With O2 of Leaked Photoresist From Wafer Backside Prior to Plasma Etching of Silicon Nitride

In device fabrication, low pressure chemical vapor deposited (LPCVD) silicon nitride is deposited on both sides of the substrate. Prior to further processing, the backside silicon nitride must be removed. This is accomplished by protecting the substrate device side with photoresist and then etching the backside silicon nitride in a CF4 plasma. When applying the photoresist to the device side, a small quantity of photoresist is splashed on the substrate backside. Since photoresist will not etch appreciably in a CF4 plasma, this residual resist will not allow the underlying silicon nitride to be etched in these areas. The solution is to first process the coated substrates in an 02 plasma or "flash strip" cycle which removes the small quantity of residual backside resist. The "flash strip" operation is completed using a faraday cage which surrounds the substrates. The faraday cage reduces the strip rate of photoresist such that the thick coat of protective photoresist on the device side remains intact. The backside nitride is then etched in CF4 plasma followed by an asher strip operation to remove the device side photoresist. The process sequence is diagrammed in the figure.

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