Non-uniform current flow through thin oxide after Fowler-Nordheim current stress

Non-uniform current flow after Fowler-Nordheim current stress has been discussed. In a large thin oxide area, there are certain fixed spot areas which can trap electrons easily, and Fowler-Nordheim tunnel current is reduced at the spot areas. Enlargement of the stress induced leakage current due to trapped holes could happen at all spot areas with the same probability, but the spot areas are replaced easily by additional Fowler-Nordheim current stress. Each phenomenon occurs with very low probability. Using a 2M bit NOR flash EEPROM test array, non-uniform current flow occurring in a large area has been clarified by tracking all cell behavior individually.