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Aerosol reactors have been developed that enable synthesis of nanoparticles with tightly controlled size and structure. This presentation will discuss the reactor technology that has enabled production of silicon-nanoparticle-based floating gate memory devices. The nanoparticles consist of a crystalline core of silicon encased within a silica shell in order to prevent direct electrical communication between nanoparticles when they are incorporated into the floating gate of the device. The nanoparticles are produced by pyrolytic decomposition of silane gas, leading to nucleation of silicon nanoparticles in the first stage of a multistage aerosol reactor. Two methods for production of the silica shell have been demonstrated: (i) chemical vapor deposition of silica on silicon core, and (ii) partial thermal oxidation of the silicon nanoparticle. Core-shell aerosol nanoparticles produced by the latter route in a quartz reactor were transported directly to a thermophoretic deposition chamber for deposition on a wafer. A clean system was developed in which the aerosol reactor was located adjacent to a clean room in which the deposition tool and wafer handling facilities were located. Wafers processed through this system were then transported to an industrial fab where conventional lithography was used to fabricate the floating gate memories. Initial devices were made on 200 mm using a deposition tool that produced a range of areal concentrations ranging from submonolayer to multilayer. Subsequent developments have focused on shortening the deposition times with high throughput aerosol reactors and a second generation 300 mm thermophoretic deposition tool that produces uniform areal densities. |