A 128Gb 1-bit/Cell 96-Word-Line-Layer 3D Flash Memory to Improve the Random Read Latency With tProg = 75 μs and tR = 4 μs

Abstract

A 128-Gb 1-bit/cell 3-D flash memory chip has been developed with 96-word-line-layer technology. A novel chip floorplan architecture with less time constants of wordline and bitline realizes fast read access time. A newly introduced program sequence achieves for higher reliability with less read-retry even after write/erase cycles. External VPP supply (12 V), current mode reference distribution, and auto temperature code refresh are also adopted to boost the performance of the chip. A new duty cycle corrector succeeds in obtaining wider unit interval of the DQS. Consequently, the proposed chip has a read access latency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4~\mu \text{s}$ </tex-math></inline-formula> and a program time of 75 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> , which is 12–13 and 4–5 times faster than conventional 3-D flash memory with the same technology [Maejima <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> , (2018)]. The random read latency (tRRL) is estimated to be less than 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> , which enables in the reduction of total read access time of solid state drive (SSD) system.