FLASH MEMORY HAVING PRE-DETECTION FOR DATA LOSS TO PREVENT DATA RETENTION ERRORS IN NON-VOLATILE MEMORY DEVICE

摘要

PURPOSE: A flash memory having pre-detection for data loss to prevent data retention errors in a non-volatile memory device is provided to enhance the efficiency and the productivity by detecting and correcting weakly programmed cells. CONSTITUTION: A plurality of non-volatile memory cells are provided. A unit for reading a selected cell by comparing the performance of the selected cell with the performance of a reference cell is provided. A first read state is obtained by reading the selected cell with the reference cell biased to a first value(65). A second read state is obtained by reading the selected cell with the reference cell biased to a second value greater than the first value(70). The selected cell is flagged as a weakly programmed and high cell if said first and second read states do not match(75). A third read state is obtained by reading the selected cell with the reference cell biased to a third value less than the first value(80). The selected cell is flagged as a weakly programmed and low cell if the first and third read states do not match(85). The selected cell is refreshed if the selected cell is weakly programmed(90).