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This letter studies the nonvolatile memory characteristics of polycrystalline-silicon thin-film transistors with a silicon-oxide-nitride-oxide-silicon (SONOS) structure. As the device was programmed, significant trap-assisted gate-induced drain leakage current was observed due to the extra programmed electrons trapped in the nitride layer which lies above the gate-to-drain overlap region. In order to suppress the leakage current and thereby avoid signal misidentification, we utilized band-to-band hot hole injection into the nitride layer. Because the injected hot holes can remain in the nitride layer after repeated Fowler-Nordheim erase and program operations, this method can exhibit good sustainability in such a SONOS-TFT memory device.
Date of Publication: Aug. 2009