A NON-VOLATILE MEMORY HAVING A BIAS ON THE SOURCE ELECTRODE FOR HCI PROGRAMMING

摘要

Each cell (60, 62, 64, 66) of a memory (10) is programmed by first using a source bias that is typically effective for programming the cells (60-66). If a cell (60-66) is not successfully programmed in the first attempt, that is typically because a number of cells (60-66) on the same column (74, 78) as that of the cell (60-66) that did not successfully program have a relatively low threshold voltage, a low enough threshold voltage that these memory cells (60-66) are biased, even with grounded gates, to be conductive. The vast majority of the cells (60-66) do not have this problem, but it is common for there to be a few memory cells (60-66) that do have this low threshold voltage characteristic. To overcome this, a different source bias is applied during subsequent programming attempts. Thus, the vast majority of the cells (60-66) are programmed at the faster programming condition, and only the few that need it are programmed using the slower approach.