As the world’s largest supplier of 3D NAND, Samsung is constantly increasing the bit density and capacities of its solid state drives. At the China Flash Memory Market Summit, the company said the capacity of a single SSD can grow to 1 petabyte (PB, or 1,024 terabytes), but of course that would take time.
According to a report by A&SMag, Samsung expects 3D NAND to continue unabated in both physical and logical scaling. This means that the size of NAND flash cells will decrease and the number of layers will increase, allowing each layer to store more data. Samsung is also anticipating more advanced storage technologies for 3D NAND ICs. Physical, logical and storage innovations will increase the capacity of a drive to one petabyte within the next decade, Samsung said at the event.
Giant SSDs are a tradition at Samsung.
Samsung has long delivered some of the highest capacity SSDs in the industry. The company was among the first to mass-produce a 15.36TB drive in 2016 and launched a 3D-TLC-based 30.72TB product in 2017. Samsung also unveiled a 64TB SSD in 2019 and a prototype 128TB SSD based on 3D QLC NAND in 2021, but these devices haven’t entered mass production yet. These are expensive enterprise SSDs. With halfway affordable consumer SSDs, eight terabytes per SSD is currently the limit.
Unlike some of its industry peers, Samsung is adopting a more conservative approach to 3D QLC NAND memory and is currently exploring ways to bring QLC technology into the mainstream through controller advancements. However, Samsung acknowledges that physically scaling (shrinking the size of NAND cells and increasing the number of NAND layers) to around 1,000 layers per 3D NAND device alone will not be enough to rapidly increase flash memory bit density.
After Quad Level Cell (QLC) comes Penta, Hexa and Octa
Unlike Samsung, Kioxia (formerly Toshiba) has been particularly vocal about NAND’s logical scaling. In 2019, Kioxia was the first 3D NAND manufacturer to talk about developing a PLC 3D NAND (Penta Level Cell) memory capable of storing 5 bits per cell (bpc). The Kioxia team of scientists and engineers then demonstrated a working 3D HLC (hexa-level cell) 3D NAND memory that stores 6 bpc in 2021. The company even suggested that 8 bpc octa-level cell (OLC) 3D NAND memory might be possible.
To store six bits per cell, the NAND cell requires 64 voltage states, while an 8-bit-per-cell 3D NAND memory requires 256 voltage states. Increasing the number of bits per cell presents several challenges to manufacturers.
On the one hand, they have to find suitable materials that are able to store 64 or 256 states of stress without interfering with each other. On the other hand, they must be able to produce such materials in large quantities. Likewise, when designing 3D NAND memory, they also need to consider temperatures as higher bit densities increase the temperature of the memory chips. Last but not least, the development of 3D HLC and 3D OLC NAND memories requires extremely complex ECC algorithms and powerful controllers. However, these can be expensive enough to outweigh the logical scaling benefits of 3D NAND.
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