The Effect of Adjacent Bit-Line Cell Interference on Random Telegraph Noise in nand Flash Memory Cell Strings

摘要

The effect of adjacent bit-line (BL) cell interference on BL current fluctuation $(Delta I_{rm BL} = hbox{high} I_{rm BL} - hbox{low} I_{rm BL})$ due to random telegraph noise (RTN) in floating-gate nand Flash cell strings is characterized. It was found that the electron current density $(J_{e})$ of a read cell can be appreciably different depending on the position in the channel width direction because of the interference from adjacent BL cells. The interference can be controlled by the state (program or erase) of the adjacent cells. We verified that $Delta I_{rm BL}$ due to RTN increases as a high-$J_{rm e}$ position is controlled to be close to a trap position in 32-nm nand Flash memory strings. Finally, it was also shown that the adjacent cell interference affects not only $Delta I_{rm BL}$ but also the ratio of capture and emission time constants $[ln(tau_{c}/tau_{e})]$.