Temporary lock-out is provided while programming a group of non-volatile
memory cells to more accurately program the memory cells. After
successfully verifying that the threshold voltage of a memory cell has
reached the level for its intended state, it is possible that the
threshold voltage will subsequently decrease to below the verify level
during additional iterations of the programming process needed to
complete programming of other memory cells of the group. Memory cells are
monitored (e.g., after each iteration) to determine if they fall below
the verify level after previously verifying that the target threshold
voltage has been reached. Cells that pass verification and then
subsequently fail verification can be subjected to further programming.
For example, the bit line voltage for the memory cell of interest may be
set to a moderately high voltage to slow down or reduce the amount of
programming accomplished by each subsequent programming pulse. In this
manner, a memory cell that falls out of verification can be placed back
in the normal programming flow without risking over-programming of the
cell.