Investigation of the Effect of Grain for Vertically Stacked NAND Flash Memory with a Poly-GaAs Channel

The cell characteristics of a vertically stacked NAND (V-NAND) flash memory with a poly-GaAs channel are investigated for the effect of grain using a three-dimensional simulation method, and they are compared to V-NAND with a poly-silicon channel. Under the same physical conditions, it is confirmed that the initial status of the V-NAND flash memory with a poly-GaAs channel shows a higher drain current and higher threshold voltage, which provides a better feasibility to improve the V-NAND flash memory. Due to the grain, V-NAND flash memory with a poly-GaAs channel shows more degradation in cell characteristics as the grain length decreases and the trap density in the grain boundary increases, compared to the V-NAND with a poly-silicon channel. Here, we explain that the higher energy band diagram in the poly-GaAs channel causes these results. The values of the trap density and grain length in the poly-GaAs channel are very important; the trap density should be maintained at a value less than 9e–13 cm^–2eV^–1 and the grain length should be maintained at a value more than 50 nm in order to obtain better cell characteristics compared to the V-NAND with a poly-Si channel.