Pipe-shaped BiCS flash memory with 16 stacked layers and multi-level-cell operation for ultra high density storage devices

Abstract

We propose pipe-shaped bit cost scalable (P-BiCS) flash memory which consists of pipe-shaped NAND strings folded like a u-shape instead of the straight-shape. P-BiCS flash technology achieves a highly reliable memory film of which the program and erase (P/E) operation is managed by Fowler-Nordheim (FN) tunneling, that is originated by the strong curvature effect of its small pipe radius, a low resistance source line by the layered metal wirings and a tightly controlled diffusion profile for the select-gate (SG) transistor due to low thermal budget. The effective 1-bit cell area of 0.00082 mum2 and its functionality are successfully demonstrated using the 32 Gbit test chip with the 3-dimensionally 16 stacked layers and the multi-level-cell (MLC) operation by 60 nm P-BiCS flash technology.