128-layer 3D NAND QLC, production begins in China

128-layer 3D NAND QLC, production begins in China

128-layer 3D NAND QLC

Yangtze Memory Technologies (YMTC) is reportedly now deploying consumer-grade 128-layer, QLC-based NANDs produced with proprietary 3D Xtacking technology. The move is seen as important for China to reduce its reliance on imports of high-tech and semiconductors, and the company is beginning to penetrate the market through consumer-oriented solutions that will be deployed in Chinese smartphones and notebooks. The goal is to leverage the explosive growth in capacity requirements for storage applications, as well as emerging and expanding technologies such as 5G.

Credit: YMTC Tech Insights Teardown PCIe 4.0 SSD Asgard's 1TB AN4, which is the first commercial application of this technology. According to YMTC COO Cheng Weihua, this is the result of the volume production achieved with the 128-layer design. For now, Xtacking 2.0 technology is being used in the production of 512Gb 128-layer TLC die, as well as the 128-layer QLC 3D NAND itself. The company plans to switch to its Xstacking 3.0 design in the second half of 2022, with production capacity peaking by then. Xstacking 2.0 by YMTC is based on the expansion of NAND flash memory on the Z axis by connecting two wafers produced separately: one of these takes care of the NAND array itself, while the other contains the CMOS circuits (as a page buffer , column decoders, charge pumps, global datapaths and voltage generators / selectors).

The Xstacking technology underlying the production process has been well received by the industry. The company achieved 92% higher bit density (8.48 Gb / mm2, 512 Gb) than die produced with xStacking 1.0 (4.42 Gb / mm2, 256 Gb), showing that YMTC has a solid plan future for the technology roadmap. Perhaps more surprising is that YMTC achieved higher density levels (8.48) than Samsung (6.91), Micron (7.76) and Sk hynix (8.13). However, YMTC brought its 128-layer process to market later than the aforementioned manufacturers.

Credit: Tech Insights Credit: Tech Insights The launch comes in the wake of a reported delay on the volume production capabilities of the 128-layer NAND QLC, with the company citing unsatisfactory yields as the deciding factor in advancing the quantity produced. At the moment it is not clear whether the company has already overcome these difficulties and is now on schedule with its 100,000 wafers per month. However, its presence only in consumer-oriented solutions, sacrificing the high turnover of professional and server-related applications, indicates a conservative estimate of the company's progress in terms of performance.

China's YMTC has started mass production of 128-layer 3D NAND memory

Why it matters: China has been trying to bolster its semiconductor industry for years in an effort to become self-sufficient and more competitive on the global market. Development has been slow on the CPU side of things, but it looks like the country's NAND champion is quickly closing the gap on flash storage when compared to industry giants like Samsung, Micron, and SK Hynix.

Back in July, Chinese media outlets reported that Yangtze Memory Technologies Co (YMTC) was getting ready for mass manufacturing of 128-layer 3D NAND memory, which is considered the pinnacle of domestic flash memory development and key to addressing the high demand for consumer-grade solid-state storage in the region.

The Wuhan-based company may be China's NAND champion, but it's a relatively small player in the grand scheme of things. For reference, Intel, Micron, Kioxia, Samsung, SK Hynix, and Western Digital account for a combined 97 percent of the NAND market, so it won't be easy for YMTC to compete with these memory giants. It also doesn't help that parent company Tsinghua Unigroup has been having financial difficulties and is currently looking for a generous cash infusion to stay afloat.

According to a report from Tech Insights, YMTC has indeed started mass-producing the new memory chips. The IP and tech intelligence firm managed to take a closer look at Asgard's new AN4 1-terabyte SSD, which is based on the YMTC's 128-layer NAND. Although the Chinese company calls it '3D NAND,' it should be noted that a more accurate term would be 2.5D NAND, as it leverages Xstacking 2.0 hybrid bonding technology to essentially glue together two separate dies -- one for the TLC NAND array and another for the CMOS peripheral circuitry.

That said, the new SSD is no slouch, with sequential read speeds of up to 7,500 megabytes per second and write speeds of up to 5,500 megabytes per second. As you may have guessed, the Asgard is a PCIe 4.0 SSD, and these speeds are achieved over an x4 interface thanks to the InnoGrit IG5236 controller. This is the same controller used in the Plextor M10P SSD, and coupled with YMTC's 128-layer NAND, it can achieve over 1.2 million IOPS in 4K read workloads and 900,000 in 4K write workloads.

NAND TechnologyYMTC 128L XtackingSamsung 128L V-NANDMicron 128L CuA CTFSK Hynix 128L 4D PUCDeviceAsgard AN4 1TBSamsung EVO 870 1TBCrucial BX500 480GBSK Hynix Gold P31 1TBCapacity per die512 Gb512 Gb512 Gb512 GbDie size60.42 sq. mm74.09 sq. mm66.02 sq. mm63 sq. mmMemory density8.48 Gb per sq. mm6.91 Gb per sq. mm7.76 Gb per sq. mm8.13 Gb per sq. mm

It's also worth noting that YMTC's new 128-layer NAND memory has almost double the density of previous designs based on the initial version of its Xstacking tech. More importantly, the 8.48 Gb per square millimeter in storage density is higher than that achieved by Samsung, Micron, and SK Hynix using comparable 128-layer TLC NAND designs. These companies have largely moved on to more advanced designs, but it looks like China is quickly closing the gap.

YMTC has also been working on a successor to Xstacking 2.0, which will allow the company to make high-capacity QLC 3D NAND memory with a capacity of 1.33 Tb per die. However, development on 128-layer QLC NAND has been slow, and the company says it has yet to achieve better yields needed for mass manufacturing of the new memory chips. In the meantime, YMTC is scrambling to increase production to 100,000 wafer starts per month by the end of the year and is not affected by the recent energy crunch in China.

Overall, this development is much more impressive than what's been going on with x86 and Arm-based CPU development in the region. That said, Zhaoxin's x86 processors are slowly creeping into consumer products, and Huawei's HiSilicon subsidiary has been quietly pushing its custom Arm-based Kunpeng silicon to both consumers and data center clients. As for YMTC, it has an extensive list of clients, mainly Chinese phone makers and SSD manufacturers. With its new 128-layer NAND, the Wuhan-based chipmaker intends to attack the data center market in the near future.

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