Systems for Coarse/Fine Program Verification in Non-Volatile Memory Using Different Reference Levels for Improved Sensing

摘要

Coarse/fine programming of non-volatile memory is provided in which memory cells are programmed at a first rate of programming prior to reaching a coarse verify level for their intended state and a second rate of programming after reaching the coarse verify level but before reaching the final verify level for their intended state. Large sub-threshold swing factors associated with smaller memory cells can affect the accuracy of sense operations, particularly when sensing at a fine verify level after sensing at a coarse verify level without pre-charging the bit line between the different sensings. Different reference potentials are utilized when sensing at a coarse verify level and a final verify level. The different between the reference potentials can compensate for any discharge of the bit line during the coarse level sensing.