| 摘要 |
In a process using a hot phosphoric acid etchant ( 12 ) to etch silicon nitride on a semiconductor wafer ( 15 ) submerged in a tank ( 11 ) of the etchant ( 12 ), a recirculating path is established for the etchant ( 12 ). A porous filter ( 35 ) is coated with silicon nitride and installed in the recirculating path. As the etchant ( 12 ) in the recirculating path flows through the porous filter ( 35 ), the silicon nitride on the porous filter ( 35 ) dissolves into the etchant ( 12 ). In the tank ( 11 ), the silicon nitride dissolved in the etchant ( 12 ) significantly suppresses the etch of silicon dioxide on the semiconductor wafer ( 15 ), thereby enhancing the etch selectivity of the process. Monitoring and maintaining the concentration of the silicon nitride in the etchant ( 12 ) stabilizes the etch selectivity of the process.
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