TL;DR
- Theft Allegations: Micron has sued Chinese memory rival YMTC, alleging former Micron employees supplied confidential Micron technology that became patents used against Micron.
- Patent Ownership: The Idaho complaint seeks ownership of four named U.S. patents, injunctions and damages over alleged misuse of engineering work.
- German Orders: Micron appealed two Munich injunctions aimed at stopping infringement of YMTC’s utility models, registered rights protecting technical inventions.
U.S. memory maker Micron has sued Chinese rival Yangtze Memory Technologies (YMTC), alleging that former Micron engineers helped turn confidential engineering work into YMTC patents later used to sue Micron. The Idaho complaint seeks ownership of four named U.S. patents, arguing that their inventors had already assigned Micron rights to the inventions while working for Micron.
Filed on Sept. 15, 2026, the complaint also names Hongbin Zhu, a former Micron process engineer in Boise. The case combines claims about confidential manufacturing and circuit technology with patent-ownership claims and alleged breaches of Zhu’s employment agreements.
From Confidential Work to Patent Ownership
Micron bases its case on two obligations it says engineers accepted while working for the company. Their confidentiality agreements barred disclosure or misuse of protected information after departure. Their invention-assignment agreements gave Micron rights to inventions developed during their employment, which is the basis for its demand that YMTC transfer patent ownership.
The complaint alleges that at least 20 employees moved from Micron to YMTC over a few years. Micron says some cited family reasons for leaving and omitted their new jobs from LinkedIn, while YMTC’s small early market presence gave Micron little reason to suspect misuse of its technology. It says YMTC’s November 2023 patent lawsuit in California prompted an investigation that identified former Micron engineers among the patents’ inventors.
Daesik Song was a principal design engineer at Micron’s San Jose campus. Micron says he worked on low-power DRAM circuits that move data into and out of memory, particularly for mobile computing. It identifies a confidential presentation he prepared in 2016.
According to Micron, the work became subject matter of YMTC’s U.S. Patent No. 10,707,851, which names Song as an inventor and stems from applications filed in 2019. Micron alleges that Song retained or disclosed confidential information after leaving and that YMTC encouraged or accepted its use. Its ownership claim rests on the additional assertion that Song had already assigned the relevant invention to Micron while employed there.
The same patent was among the eight rights YMTC asserted in an Oct. 6, 2025 lawsuit in Texas against Micron, two other Micron entities and Avnet. Micron says investigating that action exposed Song’s role in the patent. The Idaho complaint asks the court to recognize Micron’s ownership of the patent, or alternatively a share of it, and transfer legal title from YMTC.
Three other expressly named ownership claims concern patents attributed to Zhu. Micron says he developed the relevant inventions while working on its manufacturing processes and was bound by an earlier assignment agreement. It identifies a patent family filed in 2018, after his September 2017 departure. Zhu is also accused of breaching both his confidentiality and invention-assignment agreements.
Micron also seeks damages and recovery of profits from the alleged misuse, or royalties as an alternative. Its filing leaves the dollar amount to be proved at trial.
Why Chip-Manufacturing Recipes Matter
Much of the alleged confidential work concerns 3D NAND, the flash-storage chips used in solid-state drives (SSDs), phones and other devices. Stacking memory cells vertically increases storage capacity within a smaller footprint. Making those stacks requires precise control of high-aspect-ratio holes, openings that are deep relative to their width. The memory structures have to remain uniform throughout the stack as more layers are added.
The complaint describes eight groups of alleged trade secrets. Six concern fabrication: protective coatings that guide hole etching, removal of temporary layers, connections between stacked sections, control of hole shape, cleaning after pillar etching, and shaping the bottoms of memory pillars. These operations help form working memory structures while avoiding defects. Micron alleges that the protected information lies in particular materials, equipment settings, sequences and process conditions.
A protective coating, called a hard mask, illustrates the claimed value. It shields some areas while chemicals or plasma carve holes through exposed parts of the stack. Micron says its confidential choices govern the mask’s composition, dimensions and removal. Another alleged process removes temporary silicon-nitride layers so conducting material can take their place; Micron says its chemical and equipment choices reduce defects and processing time. It argues that access to its secrets could save a rival months or years of development and millions of dollars.
The other two groups reach beyond fabrication recipes. One concerns changing the voltage used to read NAND cells according to the percentage of bits successfully read. The other concerns the input-output circuit designs illustrated by Song’s work. Micron alleges that the information supported YMTC’s 64-layer, 128-layer and 232-layer NAND generations and later devices, as well as patent filings. Detailed recipe parameters are redacted in the public complaint.
A Rival with a Different Manufacturing Approach
In September 2021, TechInsights researcher Dr. Jeongdong Choe examined a YMTC 128-layer chip taken from an Asgard SSD. His comparison included a Micron chip with the same 128-layer generation and capacity of 512 gigabits (Gb) per die, the individual silicon chip.
The sampled YMTC memory die measured 60.42 square millimeters, compared with 66.02 square millimeters for Micron’s. YMTC’s Xtacking design paired the memory-array die with a separately fabricated logic die, which contains circuitry controlling the memory. The two were bonded together.
In September 2021, SemiAnalysis argued that separate fabrication helped YMTC reach 128 layers. Memory arrays and control circuitry have different manufacturing requirements, it explained, so producing them separately avoided compromises involved in building both on one wafer, as Micron and other rivals did.
Micron Appeals German Injunctions
YMTC has also obtained court victories in German proceedings. JUVE Patent reported two Munich injunctions after judges found two German utility models valid and infringed. Utility models are registered rights protecting technical inventions. Micron appealed both decisions.
Such injunctions seek to stop or prevent infringement, which can include offering or selling products using the protected inventions. The specific products covered and enforcement status of the two Munich orders remain unclear.
The German rulings were reported as issued on Sept. 18, three days after the Idaho complaint. The two utility models cover structural features in 3D NAND memory chips. Three other Munich cases were adjourned.
Micron also filed a Munich patent-infringement action against YMTC in mid-July 2026. Its parallel cases also reach other businesses: Lexar and Apacer, providers of digital storage products, are defendants in European proceedings brought by Micron.
