Abstract: An etch apparatus. The etch apparatus includes a tank coupled to a recirculating path that includes a dissolver. The dissolver includes a porous carbon matrix filter coated with silicon nitride. An etchant from the tank circulates through the recirculating path and performs a selective etching of a structure in the tank in contact with the etchant. The structure includes silicon nitride on a pad layer that includes silicon dioxide. The selective etching is characterized by the silicon nitride on the pad layer being selectively etched by the etchant relative to an etching by the etchant of the silicon dioxide. The etch apparatus further includes: means for dissolving the silicon nitride coated on the filter into the etchant at a controlled dissolution rate sufficient to cause the selective etching; and means for coating the silicon nitride onto the filter to facilitate the selective etching.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: An apparatus and method for screening packets at an interface between a local site and an external network. A heuristic profiler ascribes a hierarchical value to each address on the external network based at least on prior activity associated with the address and a filter selectively passes packets from the external network to the site on the basis, at least, of the hierarchical value ascribed to the source address associated with each packet.

Abstract: A computer program product and method for screening packets at an interface between a local site and an external network. A heuristic profiler scrutinizes a candidate packet and calculates a value characterizing the IP source of the packet on the basis of prior encounters with the IP source as maintained in a hashed history table entry. A filter selectively passes packets from the external network to the site on the basis, at least, of the value ascribed to the source relative to a current threshold value determined on the basis of bandwidth usage.