Yangtze Memory Technologies (YMTC), China's largest 3D NAND memory maker, filed a lawsuit against Micron Technology for patent infringement on Thursday, November 9, in a California court. The legal battle involves eight U.S. patents related to 3D NAND technology that cover multiple basic aspects of how modern flash memory works and is manufactured. The lawsuit could be a part of YMTC's efforts to get removed from the U.S. government's blacklist, or it could be a part of the larger China-U.S. tensions.

The lawsuit alleges that Micron used the patented tech, the cornerstone of YMTC's Xtacking technology , in its 128- and 176-layer 3D NAND products. Tthe lack of publicly available information for YMTC somewhat lowers the public view of the legal action (we discovered the lawsuit at TechNews.TW ).

Here is the list of YMTC's patents that it alleges Micron has infringed:

• US10,950,623 covers methods for building 3D NAND memory chips, essential for the layered architecture that these chips utilize.
• US11,501,822 focuses on the management of non-volatile storage devices, crucial for maintaining data without power.
• US10,658,378 and US10,937,806 both deal with through-silicon via (TSV) technology, a fundamental tech for 3D NAND memory in general.
• US10,861,872 describes a 3D NAND manufacturing technology.
• US11,468,957 covers architectural and operational aspects of NAND memory.
• TUS11,600,342 is focused on methods for reading data from 3D NAND flash memory, another critical aspect of flash memory in general.
• US10,868,031 is about techniques for stacking memory cells in multi-layered 3D NAND chips, another key aspect of 3D NAND in general.

The extensive nature of the lawsuit filed in California may be a sign of YMTC's backlash for inclusion it into the U.S. Entity List (which cost it an increase in CapEx around $7 billion ), which severely cut the company's access to advanced wafer fab equipment. This legal action follows China's ban on Micron products in May over alleged cybersecurity concerns, though China has recently signaled a thaw in relations with Micron .

As with all patent disputes, the legal battle between YMTC and Micron could take years to work its way through the courts. YMTC's patents cover a wide range of basic NAND technology, but multiple companies, like Western Digital, SK hynix, Samsung, and Kioxia, also use similar architectures. This could make the patents difficult to defend in court.