Highly Manufacturable 7^th Generation 3D NAND Flash Memory with COP structure and Double Stack Process

A novel 3D NAND Flash memory device with 17X WL (Word line) layers has been successfully developed. COP(Cell Over Peripheral) Structure has been applied, improving tR and tPROG by 11% and 20%, respectively. Compared with our previous product(6 ^th generation), the bit density is increased by 70% through cell volume scaling and COP structure. Several breakthrough processes have been successfully combined to achieve this new structure. Double stack process, low stress W(tungsten), MSE(Multi Step Etch), and channel hole side-wall butting etc. In addition, the double stack process was applied to significantly improve the channel hole profile. As a result, better cell operation characteristics were achieved.