PTAB challenges

Proceedings overview

There is one AIA trial proceeding on file for US Patent 6888181. This proceeding, IPR2025-01082, was terminated before a final decision. This gives a defendant a neutral defensive posture as no claims were invalidated or sustained by the PTAB.

IPR2025-01082 — Taiwan Semiconductor Manufacturing Company Limited v. Marlin Semiconductor Ltd

• Type: Inter Partes Review
• Filed: 2025-08-08
• Status: Terminated (as of 2026-05-13)
• Judge panel: Not publicly available due to early termination.
• Petition grounds: The petition challenged claims 1-10 of U.S. Patent No. 6,888,181 as unpatentable under 35 U.S.C. § 103(a) over the combination of U.S. Patent No. 6,413,802 (Hu) and U.S. Patent No. 6,727,546 (Andry).
• Institution decision: Not instituted. The PTAB issued an Order denying institution on February 10, 2026, finding that the Petitioner, Taiwan Semiconductor Manufacturing Company Limited, had not demonstrated a reasonable likelihood of prevailing with respect to at least one challenged claim as required by 35 U.S.C. § 314(a).
• Final Written Decision: Not applicable; the proceeding was terminated prior to a Final Written Decision.
• Settlement / termination: The proceeding was terminated on May 13, 2026, subsequent to the denial of institution. The termination is a procedural action following the non-institution of the IPR.
• Appeal: Not applicable; there was no Final Written Decision to appeal.
• Defensive value: The denial of institution means that the specific arguments and prior art (Hu and Andry) presented by Taiwan Semiconductor Manufacturing Company Limited were deemed insufficient by the PTAB to establish a reasonable likelihood of invalidating claims 1-10. This makes an IPR-based defense using these specific grounds harder, as the PTAB has already reviewed and rejected them for institution. However, it does not prevent a different petitioner from challenging the patent on different grounds or a district court from finding the patent invalid.

Strategic summary

Currently, all claims of US6888181 (claims 1-10) remain UNTESTED in the sense that they have not been subjected to a full IPR trial and final written decision. While an IPR petition challenging all claims (1-10) was filed by Taiwan Semiconductor Manufacturing Company Limited, the PTAB denied institution of the trial. This means the Board did not proceed to an inter partes review.

The estoppel landscape under § 315(e)(2) applies to grounds "raised or reasonably could have been raised." In this case, since institution was denied, the petitioner (Taiwan Semiconductor Manufacturing Company Limited) and its privies would likely be estopped from challenging claims 1-10 on the specific grounds presented in the petition (i.e., over Hu in view of Andry). However, they would not be estopped from raising different prior art grounds against the patent. For any other defendant, all prior-art grounds remain available, as they are not subject to the estoppel from this non-instituted IPR. There is no pattern of aggressive PTAB appeals or defensive aggregator involvement observed from this single, non-instituted proceeding.

Recommended next steps

If you are a defendant facing assertion of US6888181 today, the IPR2025-01082 proceeding did not result in any claims being canceled. The denial of institution indicates that the specific combination of prior art (Hu and Andry) was not found sufficiently strong by the PTAB to warrant a full trial. This does not preclude challenging the patent through other means or with different prior art.

You should review the PTAB's Order denying institution for IPR2025-01082, available at the USPTO PTAB Decisions portal, to understand the specific reasons why institution was denied. This will help inform whether alternative prior art or arguments could be more successful in a new IPR petition or district court litigation.

Given that no claims have been invalidated by the PTAB, the patent owner's position regarding the patentability of claims 1-10 against the specific art cited in IPR2025-01082 is strengthened for that particular set of arguments. If considering an IPR, a thorough prior art search for new and stronger invalidity grounds would be essential.