The Effects of Taper-Angle on the Electrical Characteristics of Vertical NAND Flash Memories

The effects of taper angle of the string and the number of layers on the electrical characteristics of vertical NAND flash memories are investigated. Simulation results show that the transconductance and the threshold voltage distribution over the position of the cell along the string depend on taper angle and the number of layers. There is a taper angle that minimizes the spread of threshold voltage, and hence, the impact of the random telegraph noise and this angle depends on the number of layers. These results will be helpful in designing the vertical NAND flash memories.