Suppression of anomalous leakage current in tunnel oxides by fluorine implantation to realize highly reliable flash memory

By analyzing charge retention characteristics, we found that a flash memory with a critical tunnel oxide thickness has cells with anomalous threshold voltage (V/sub th/) lowering. We proposed a model where the traps near the poly-Si gate/tunnel oxide interface generate anomalous leakage current in the voltage range of 0-1 V, and the trapping/detrapping of electrons into the traps dominates the V/sub th/ distribution. We succeeded in suppressing the anomalous leakage current of the tunnel oxide by fluorine implantation into the Si substrate.