3D VG-Type NAND Flash Memories

Abstract

Solid State Disk applications have been the main drivers for the cost reduction of NAND Flash memory. Technology scaling limits have been almost reached and new directions were investigated for a decade. 3D NAND appeared as the most promising and short term viable solution to the scaling problem. 3D NAND offers the possibility to keep scaling memory density beyond 2D NAND 1z nm technology and opens new landscapes if the technology hurdles can be definitely overcome. Additionally Multi bit per cell technology is applicable to 3D NAND as well; therefore, the storage capacity growth trend is not going to meet the inflection point soon. Big Data storage demand remains certainly the driver for the rapidity of 3D NAND to become industry mainstream.With respect to the flat 2D NAND Flash, three-dimensional architectures demand a more challenging approach to deal with process, design architectures, parasitic effects, testing. At the time of writing this chapter, 3D technology is moving into production inside solid state storage solutions; however, those NAND chips aren't commercially available as raw components. 3D NAND chips are used by vertically integrated manufacturers and few partners to build the storage systems under a strict control on the usage. Technology solutions are still diversified among the few players in the 3D arena and no unique mainstream solution is emerged yet.In this chapter the principal architectural pieces of 3D NAND will be reviewed putting the focus on one of them: VG-Type, Vertical Gate 3D NAND.