Effect of Adjacent Bit-Line Cell Interference on Low Frequency Noise in NAND Flash Memory Cell Strings

Abstract

The effect of adjacent bit-line (BL) interference on low frequency in 26 nm NAND flash memory was characterized. With the program (P) and erase (E) states of adjacent cells, current fluctuation (deltaI(BL)) and corner frequency (f(c)) of Lorentzian spectrum were changed. DeltaI(BL) due to RTN ranges from approximately 67.3 nA to approximately 45.9 nA with 4 different modes (P/P, P/E, E/P, E/E) of the state of adjacent cells and f(c) ranges from 48 Hz to 89 Hz. Using measured deltaI(BL) and extracted capture (tau(c)) and emission times (tau(e)) with 4 different modes, we calculated tau and f(c), and extracted the position of a trap in the channel width direction with deltaI(BL) and simulated data. The calculated data showed excellent agreement with measured spectra. Finally, we prepared energy band diagrams in P/P and P/E modes using 3-D device simulation and clarified the effect of adjacent bit-line cell interference. The control gate bias is slightly higher in P/P mode than P/E mode, and then trap energy in P/P mode is relatively lower than that in P/E mode, resulting in shorter capture time in P/P mode.