Analysis of Clockwise and Counter-Clockwise Hysteresis Characteristics in 3-D NAND Flash Memory Cells

The origin of two different hysteresis phenomena observed in a few cells of 3-D NAND flash memory with a tube-type poly-Si body was analyzed. To identify the origin, we analyzed the capture and emission property of charges in two different trap sites by measuring devices at various temperature conditions and using fast I-V measurement. It was found that the clockwise hysteresis property is originated from the traps in the tunneling oxide butted to tube-type poly-Si body and the counter-clockwise hysteresis property is originated from the traps in the high- k blocking dielectric. Although the number of abnormal cells with a large hysteresis is much smaller than that of the normal cells, it is confirmed by pulse measurement that these abnormal cells can produce large threshold voltage variations.