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

The effect of adjacent bit-line (BL) cell interference on BL current fluctuation (ΔIBL= highIBL- lowIBL) due to random telegraph noise (RTN) in floating-gate nand Flash cell strings is characterized. It was found that the electron current density (Je) 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 ΔIBLdue to RTN increases as a high-Jeposition 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 ΔIBLbut also the ratio of capture and emission time constants [ln(τc/τe)].