Negative word line enabled pre-boosting strategy to improve nand program performance

Abstract

To improve programming performance in NAND memory, while maintaining programming accuracy and reducing program disturb, the channel pre-charge phase before a programming pulse can be eliminated. Instead, a read recovery phase after the program verify directly discharges a selected word line from the verify voltage to a negative word line voltage, with non-selected word lines being directly discharged from the read bypass voltage to the negative word line voltage. From the negative word line voltage, the word lines are then ramped up to ground and then on the bias levels of the following programming pulse. These conditions can drive electrons from the charge storage region of the selected memory cell, resulting in a high degree of channel boosting and much less program disturb. Variations of the technique can be applied to NAND memory operable in a sub-block mode where it can be difficult to use the typical channel pre-charge.