Reversible floating-gate memory

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Abstract
Reversible memory behavior is reported for an insulated gate structure, in which charge is stored on a polysilicon gate. This gate is floating between layers of silicon dioxide (SiO2) and silicon nitride (Si3N4). The floating gate is charged negatively by hot carrier injection through the SiO2, from an avalanche plasma in the underlying silicon. This charge can then be removed by applying a positive voltage between an external gate and the silicon substrate. The positive voltage causes electrons to flow through the nitride layer. Both charge states are remembered when external bias voltages are removed. The importance of circuit configuration during charging is discussed, and improvements of injection efficiency for a favorable configuration are described.