Improvement of cell characteristics using controlling the current path in 3D NAND flash

Abstract

In vertical-NAND (V-NAND) flash memory, the effect of current path change according to the program state was analyzed. A new memory structure in which a heavily doped polysilicon layer is added around a typical V-NAND channel was proposed, and electrical characteristics were observed through simulations. As a result, it was confirmed that the electrical characteristics such as Vth and S.S of V-NAND can be changed and that the current path can be adjusted. Through an experiment to change the doping concentration of the added doping area, there was a sudden change in the current path at 5.0 × 1017 cm–3 and 5.2 × 1017 cm–3 during boron doping. The change of the current path was observed at this rapidly changing point, and the device characteristics could be dramatically improved if the current path was changed by adding an extra doping region. Additionally, the effects of program operating voltage conditions and doping type changes on V-NAND operation were analyzed.