SK Hynix calls the architecture 4D-NAND, apparently for marketing reasons. The company started shipping samples to NAND controller IC makers in November for them to develop their products.
Micron (see Micron ships 176-layer 3D-NAND flash ) and SK Hynix have overtaken Yangtze Memory Technologies Co. Ltd. (Wuhan, China), which briefly took a lead in the technology (see China's YMTC takes lead in 3D-NAND memory ).
SK Hynix 176-layer 3D-NAND is based on charge-trap flash – which in the context of 3D-NAND simplifies design from floating-gate flash – and places the peripheral logic circuitry for the memory underneath the 3D-stack to minimize footprint.
This allows the bit productivity to be improved by 35 percent compared to the previous generation with the differentiated cost competitiveness. The read speed of cell is increased by 20 percent over the previous generation adopting two-division cell array selection technology. The data transfer speed also has been improved by 33 percent to 1.6Gbps adopting speed-up technology without increasing the number of processes.
The 176-layer 3D-NAND will be deployed in solid-state disk drives (SSDs) for mobile applications in the middle of 2021 before expanding into consumer and enterprise SSDs.
The problems that going to more layers incurs include a reduction in cell current, channel hole twisting and stack misalignment. To overcome these challenges SK Hynix took multiple steps: interlayer height reduction, layer variable timing control and ultra-precise alignment.
The technology will be used to develop a 176-layer, 1Tbit 3D-NAND flash memory, SK Hynix said.
The annual market for NAND flash memories is set to grow from 431.8 billion gigabytes in 2020 to 1.366 trillion gigabytes in 2024, according to market analyst Omdia. This represents a compound annual growth rate in the bit supply of 33.4 percent.
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