Background
Yangtze Memory Technologies Co., Ltd. (YMTC), the Chinese state-backed NAND flash memory manufacturer, has been at the center of geopolitical and commercial tension with American chipmakers for years. In October 2022, the U.S. Department of Commerce added YMTC to the Entity List, effectively barring most U.S. companies from exporting advanced semiconductor equipment and technology to it without a license. Against that backdrop, Micron Technology and YMTC are engaged in cross-IPR litigation at the PTAB — each challenging the other’s patents while also competing fiercely in the global NAND flash memory market.
U.S. Patent No. 10,879,164 covers an electrostatic discharge (ESD) bus architecture for integrated circuits. ESD protection is a foundational concern in chip design: without it, static electricity can destroy semiconductor devices during manufacture or use. The ‘164 patent covers a specific bus topology that uses bonding wires to connect discontinuous ESD bus segments to pad groups, eliminating the need for “filler cells” in the chip layout and enabling more flexible, area-efficient chip designs. While YMTC is best known for its 3D NAND XtackingTM architecture, the ‘164 patent reflects the company’s growing investment in a broad semiconductor IP portfolio covering circuit-design fundamentals that apply across many chip types.
Micron filed IPR2025-00118 in November 2024, challenging the validity of the ‘164 patent on obviousness grounds. During the institution phase in 2025, Micron made an unusual argument: that YMTC’s Entity List status and national security considerations should prevent PTAB from instituting or continuing the review. The Board rejected that argument in a June 2025 institution decision (“Micron’s National Security Arguments Fall Flat at PTAB”), found a reasonable likelihood that some claims were unpatentable, and instituted the IPR for a full trial on the merits.
The Court’s Holding
In its June 9, 2026 Final Written Decision, the PTAB panel found that Micron had failed to prove any of the challenged claims unpatentable. YMTC’s U.S. Patent No. 10,879,164 survives the IPR with all challenged claims intact.
Micron’s invalidity theory rested on obviousness — that a person of ordinary skill in the art would have combined the prior art references cited in the petition to arrive at the claimed ESD bus structure. The PTAB panel found Micron’s obviousness case insufficient. While the full reasoning will be available in the decision document, PTAB rejections of IPR obviousness arguments at the final written decision stage typically turn on: (1) the motivation to combine the specific references in the specific way claimed; (2) a reasonable expectation of success from that combination; or (3) secondary considerations such as commercial success or industry skepticism that support the patent’s non-obviousness. In this case, Micron did not carry its burden of proof on at least one of those elements.
Key Takeaways
- National security arguments do not provide a basis for shielding an IPR from PTAB institution or terminating an ongoing review. The Board’s earlier rejection of Micron’s national security defense — and its survival through the Final Written Decision — confirms this limitation.
- Cross-IPR warfare (where companies petition to invalidate each other’s patents simultaneously) is an increasingly common defensive strategy in high-stakes semiconductor IP disputes. The outcome here favors YMTC in this round, but the broader Micron-YMTC patent battle continues across multiple proceedings.
- YMTC is actively building and enforcing U.S. patent rights across a range of semiconductor technologies, not just NAND architecture. Companies competing with YMTC need to monitor its growing IP portfolio.
- Micron may appeal this Final Written Decision to the Federal Circuit, which will give the court another opportunity to address PTAB obviousness analysis standards in semiconductor patent cases.
Why It Matters
The Micron-YMTC dispute sits at the intersection of patent law and U.S.-China semiconductor competition. YMTC’s Entity List status bars it from directly importing advanced U.S. manufacturing equipment, but it does not prevent YMTC from holding U.S. patents or enforcing them at the PTAB. A successful defense of a U.S. patent by a Chinese Entity-List company is a notable outcome that underscores the separation between export control law and IP law — two regulatory frameworks that operate on different principles even when aimed at the same foreign competitor.
For the semiconductor industry, the ruling also signals that the PTAB treats cross-IPR litigation between geopolitical rivals on standard patent-law merits, without importing national security policy considerations into the obviousness analysis. Companies filing IPRs against Entity-List patents should expect exactly this outcome: the Board will evaluate the prior art and the claim language, not the geopolitical context.