Hole channel pre-charge to enable large-volume in-place data sanitization of non-volatile memory

Abstract

In NAND memory, data sanitization allows a relatively small unit of data (e.g., less than a block) to be effectively destroyed by increasing threshold voltages of memory cells from their programmed threshold voltage to the highest threshold state. To reduce the amount of disturb on memory cells not selected for data sanitization, prior to applying a program voltage to a target word line, a hole based pre-charge operation is performed. More specifically, for NAND strings having a memory cell selected for data sanitation, prior to applying a programming pulse to the corresponding word line, a soft erase operation is performed. After biasing the memory cells and select gates of the NAND strings to a low voltage, a soft erase voltage pulse is applied to the source lines and bit line to pre-charge the NAND string channels with holes.