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Micron claims the YMTC patents used to sue it were Micron's to begin with
Micron's new lawsuit says YMTC built its patents on Micron know-how, and it names eight former Micron engineers who became inventors on them. If a court accepts that, YMTC's infringement suits against Micron turn first on who owns the patents.
The Engineer · Build desk
What happened
- Micron says it began to uncover the scheme after YMTC sued it for patent infringement in California in November 2023, when several asserted patents named former Micron engineers as inventors.
- According to the complaint, the departing engineers cited personal or family reasons for resigning and left their LinkedIn profiles without their new YMTC roles.
- YMTC, the complaint alleges, had the hires patent standard essential inventions or ones closely resembling their Micron work, so its portfolio would overlap other 3D NAND makers' patents.
- The know-how went into YMTC's manufacturing from its 64-layer 3D NAND onward, Micron alleges, and into its memory products and patent portfolio.
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Why it matters
- constraint An ownership ruling would reach every jurisdiction where YMTC asserts these patents at once, while a non-infringement defence has to be won court by court.
- exposure Any YMTC patent listing a former Micron employee as inventor is open to the same challenge, and the inventor names are printed on the patents for anyone to check.
- precedent If the theory holds, an incumbent sued by a newcomer outside the memory cross-licensing deals has a counter that goes after title to the patents before infringement is argued.
The complaint lists former Micron employees who became inventors on YMTC patents, among them Hongbin Zhu, Jun Liu, Yushi Hu, Qian Tao, Changhyun Lee, Daesik Song, Wenxi Zhou and Hua Tan [14]. That is eight names in Tom's Hardware's account [1]. If Micron's version is right, YMTC kept these hires quiet everywhere except the inventor lines of patents it planned to sue with.
For three of them the complaint sets out the case directly. "For example, these individuals include Daesik Song, Wenxi Zhou, and Hua Tan," the complaint says. "Each of these employees owed Micron contractual obligations to keep trade secrets confidential, had access to certain of the Micron Trade Secrets further described below while employed at Micron, and on information and belief, each joined YMTC shortly after leaving Micron." [10] The same passage says each one regularly accessed trade secrets held on servers in Boise, in Micron's technical materials for its test and production nodes [11].
According to Micron, the engineers' confidentiality terms continued after they left. Those terms barred them from using, disclosing or possessing Micron's confidential information [5]. The joining dates are pleaded "on information and belief" [10]. In a complaint, that phrase marks a fact the filer believes and has not yet proved.
Micron's answer to YMTC's suits goes to title. Micron says YMTC's campaign relies largely on patents granted to former Micron employees [2]. It argues those patents belong to Micron and so cannot be used against it [9]. In Micron's telling, the overlap with other 3D NAND makers' patents is what made YMTC's portfolio usable in court, and that overlap came from Micron's own work [3]. A court that accepts the argument would settle ownership before it ever compared Micron's chips to the patent claims [9].
Incumbents rarely fight this way. Tom's Hardware notes that the large DRAM and NAND makers hold broad cross-licensing agreements. Those deals exist to head off patent wars that could end in injunctions stopping fab operations [7]. The report says the arrangement does not seem to cover YMTC and CXMT, both founded in 2016, and that both are increasingly suing Micron in various courts [8].
The complaint also gives Micron's reason for not looking sooner. It says Micron did not investigate where its former employees went and "had no reason to suspect YMTC itself" because "YMTC did not have any material market share in the industry" [6].
These are allegations in a complaint Micron filed this month [1]. Tom's Hardware's report does not include a response from YMTC. A shared name on an inventor line shows who filed a patent. It does not show what the inventor copied. In my view the ownership claim stands or falls on whether Micron can match specific YMTC patent claims to specific trade secrets the named engineers accessed in Boise [11].
What to watch
- YMTC's answer to the complaint, and whether it disputes that the named engineers' YMTC patents draw on Micron work.
- Whether the courts hearing YMTC's infringement suits, including the California case filed in November 2023, pause or take up the ownership question first.
- Whether Micron ties specific YMTC patent claims to specific trade secrets the engineers accessed on its Boise servers.