Production Volume Remains Small
The author is an analyst of NH Investment & Securities. He can be reached at hwdoh@nhqv.com. -- Ed.
Chinese memory maker YMTC has started selling SSDs, the first products it has sold since being established in 2016. However, the burden on NAND supply is likely to be limited as production volume remains small.
YMTC starts selling SSD products
Last week, Chinese memory maker YMTC held a presentation to launch its new SSDs, which are based on its in-house Xtacking technology. Under the brand name Zhitai, the drives will be sold at JD.com and other retailers for RMB369 for the 256GB version and RMB529 for the 512GB version. That said, consumers are currently unable to purchase the drives as they are out of stock—we believe that the firm’s production quantity is limited.
YMTC has yet to achieve high production yields. The company planned to expand its capacity from 15K wpm at the beginning of the year to 40K by 3Q20. The memory maker first announced its 128-layer QLC product in April. The recent product release is meaningful as it is the first product that the firm has launched since being established in 2016. From a long-term perspective, NAND supply/demand may be burdened.
YMTC’s technology has edge in terms of bit density, but disadvantage in terms of yield
Xtacking is a technique that makes peripheral circuits on a separate wafer and then attaches the wafer with memory array wafer via hybrid bonding. Of note, hybrid bonding technology was developed by Xperi. Recently, TSMC and other manufacturers started applying the technology to next-generation packaging (SoIC). YMTC claims that its NAND I/O speeds reach 3.0Gbps through Xtacking, which is similar to DRAM DDR4.
YMTC connects the memory M1 line and aluminum interconnect layer via TSV through array stack and silicon substrate, enabling more memory density. The firm’s 64-layer NAND bit density is 4.40Gb/mm2, which is higher than Samsung Electronics’ 3.42Gb/mm2. However, Xtacking is more complex in that it uses two wafers and a hybrid bonding process. Therefore, in terms of cost and yield, competing technology is more efficient.