A Novel Double-Density Hemi-Cylindrical (HC) Structure to Produce More than Double Memory Density Enhancement for 3D NAND Flash

A novel hemi-cylindrical (HC) 3D NAND Flash architecture is demonstrated for the first time. HC 3D NAND squeezes the gate-all-around (GAA) hole in one direction, followed by a slit cut to split the GAA device to produce twin cells. It creates ~ 2.6 times of memory density increase than standard GAA 3D NAND at the same stacking layer. Both experimental and simulation results clarify that the "non-local" effect of channel potential can essentially "smooth" the non-uniform curvature effect thus the HC 3D NAND device possesses regular P/E window characteristics even it is not a regular shape of GAA. Good 100K PE cycling endurance and post 10K-cycled 150C retention are demonstrated. HC 3D NAND structure has potential to further scale 3D NAND device in lateral dimension, with the advances of processing technologies.