Kioxia is sample shipping 2 terabit NAND chips, the highest capacity NAND chips available.
They have a QLC (4bits/cell) design and use Kioxia’s BiCS 8 218-layer flash node architecture. Compared to the prior BiCS 6 generation, with 162 layers, the new chip has scaled its cells down in size both laterally and vertically. An intervening BiCS 7 generation was abandoned in favor of BiCS 8. Kioxia says that a stack of 16 x 2 Tb dies will provide 4 TB of capacity in a single package. Such a package is available with a size of 11.5 x 13.5 mm and height of 1.5 mm.
Kioxia CTO Hideshi Miyajima said in a statement: “With its industry-leading high bit density, high speed data transfer, and superior power efficiency, the 2 Tb QLC product will offer new value for rapidly emerging AI applications and large storage applications demanding power and space savings.”
Pure Storage CEO Charles Giancarlo added: ”We have a long-standing flash 2 Tb QLC flash memory products to enhance the performance and efficiency of our all-flash storage solutions. Pure’s unified all-flash data storage platform is able to meet the demanding needs of artificial intelligence as well as the aggressive costs of backup storage. Backed by Kioxia technology, Pure Storage will continue to offer unmatched performance, power efficiency, and reliability, delivering exceptional value to our customers.”
Pure Storage is shipping a 75 TB Direct Flash Module, its proprietary SSD, and has a 150 TB version coming. Giancarlo suggests Pure Storage will use Kioxia’s 2 Tb QLC chips.
Most commercial off-the-shelf SSDs top out at 61.44 TB currently, with Solidigm and Samsung shipping such products in QLC designs. Samsung has hinted that a >100TB version could be coming.
Kioxia’s chip has its separately manufactured logic component directly bonded to the NAND cell array in a CBA (CMOS Bonded to Array) architecture. The chip’s interface speed is 3.6 Gbps.
We’re told that the 2 Tb chip has a bit density approximately 2.3 times higher and a write power efficiency approximately 70 percent higher than Kioxia’s current fifth-generation (BiCS 5 112-layer) QLC device, which has the highest capacity in Kioxia’s product lineup.
We think that both Kioxia and its NAND foundry joint venture partner Western Digital will use the 2 Tb QLC dies to offer new SSDs with better price/capacity than current products and also new, higher-capacity SSDs, exceeding 100TB.
Kioxia also added a performance-optimized 1 Tb QLC memory device to its portfolio. Compared to the 2 Tb QLC chip, the faster 1Tb QLC die offers around 30 percent faster sequential write performance and near 15 percent improvement in read latency. The 1 Tb QLC chip will be deployed in high performance applications, including client SSDs and mobile devices.
Competitors have also exceeded 200 3D NAND layers, with Micron at 232, Samsung at 236, SK hynix at 238, and YMTC at 232. SK hynix subsidiary Solidigm is at 192 layers and hasn’t indicated what layer count is coming next.
Bootnote
Samsung revealed it was working on a 1 Tb NAND chip in November 2022, with a 236-layer, TLC (3bits/cell) design. Now, 18 months later, we have a 2 Tb chip with fewer layers, and a QLC (4bits/cell) design from Kioxia.
