X-FAB Semiconductor v. USPTO: Federal Circuit Affirms Unpatentability in 652-Day Appeal
X-FAB Semiconductor Foundries GmbH challenged the USPTO’s rejection of its carrier substrate patent application US15/648728, covering semiconductor structures designed for transfer-print manufacturing. The Federal Circuit affirmed the unpatentability ruling in October 2025, closing off X-FAB’s appellate path after a 652-day proceeding.
Federal Circuit closes X-FAB’s bid to patent semiconductor transfer-print substrate
X-FAB Semiconductor Foundries GmbH, a Germany-based specialty semiconductor foundry, sought patent protection under US application 15/648728 for a carrier substrate technology enabling the transfer-print manufacturing of semiconductor structures. The application, published as US20180068872A1, targets a fabrication method in which semiconductor devices are built on a carrier substrate and subsequently transferred to a target surface — a technique relevant to advanced packaging, flexible electronics, and heterogeneous integration.
The USPTO determined the claimed invention was unpatentable, and X-FAB appealed that determination to the Court of Appeals for the Federal Circuit (Case No. 24-1337, filed January 9, 2024). On October 22, 2025, the Federal Circuit issued its order affirming the USPTO’s ruling, finding no reversible error in the agency’s patentability analysis. The affirmance means the application remains rejected and X-FAB cannot obtain patent rights on these claims as presented.
The 652-day duration suggests the appeal involved substantive briefing rather than a swift procedural resolution, consistent with a contested patentability dispute. The public record does not disclose the precise grounds of unpatentability — whether anticipation, obviousness, or another statutory basis — nor whether X-FAB exhausted continuation or continuation-in-part options. The ruling leaves competitors free to practise the disclosed approach without risk of infringement from this particular application.
Filing to Unpatentable in 652 days
652 days — above median for Federal Circuit patent appeals, which typically resolve in 12–18 months
Federal Circuit affirms: what the unpatentability ruling means for both parties
Affirmance means the USPTO’s rejection stands in full
When the Federal Circuit affirms a USPTO patentability ruling, it signals that the appellate panel found no reversible legal or factual error in the agency’s analysis. The lower determination — here, that the claimed carrier substrate invention is unpatentable — is left intact. X-FAB’s application cannot mature into an enforceable patent on these claims. The affirmance carries substantial weight because the Federal Circuit is the exclusive appellate venue for USPTO rejections.
No reversible error foundX-FAB loses appellate avenue for this carrier substrate application
The affirmance extinguishes X-FAB’s ability to enforce US15/648728 claims as filed. X-FAB may still pursue patent protection through a continuation or continuation-in-part application with amended or narrowed claims, provided the chain remains alive — though the public record does not confirm whether such filings exist. The company’s competitive position in transfer-print semiconductor manufacturing is weakened to the extent it relied on this application for exclusivity.
Application remains rejectedUSPTO’s unpatentability position vindicated at appellate level
The USPTO’s rejection, defended on appeal by Acting Director Derrick Brent’s office, is confirmed as legally sound. This outcome reinforces the examiner-level determination and signals that the agency’s grounds for rejection were sufficiently well-reasoned to survive Federal Circuit scrutiny. For the broader examiner community, affirmances of this kind support consistency in applying patentability standards to advanced semiconductor fabrication claims.
Agency determination upheldTransfer-print substrate space remains open for competitors
With this application rejected and affirmed unpatentable, the specific carrier substrate approach disclosed in US20180068872A1 is not protected by X-FAB IP. Companies operating in heterogeneous integration, flexible electronics, or advanced semiconductor packaging can treat this disclosed method as prior art rather than a blocking patent. R&D teams benchmarking transfer-print processes should nonetheless audit the broader X-FAB portfolio for related, potentially valid filings in the same technology family.
Freedom-to-operate signalFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | In re: X-FAB SEMICONDUCTOR FOUNDRIES GMBH | Company | German specialty semiconductor foundry — applicant for US15/648728 carrier substrate patentSearch in Eureka ↗ |
| Defendant | DERRICK BRENT, Acting Under Secretary of Commerce for Intellectual Property and Acting Director of the United States Patent and Trademark Office | Individual | Acting USPTO Director representing the agency’s unpatentability determination on appealSearch in Eureka ↗ |
| Plaintiff counsel | Elana Araj | Attorney | Counsel for In re: X-FAB SEMICONDUCTOR FOUNDRIES GMBHSearch in Eureka ↗ |
| Plaintiff counsel | Robert A. King | Attorney | Counsel for In re: X-FAB SEMICONDUCTOR FOUNDRIES GMBHSearch in Eureka ↗ |
| Plaintiff counsel | Trenton A. Ward | Attorney | Counsel for In re: X-FAB SEMICONDUCTOR FOUNDRIES GMBHSearch in Eureka ↗ |
| Plaintiff law firm | Greenberg Traurig LLP | Law Firm | Representing In re: X-FAB SEMICONDUCTOR FOUNDRIES GMBHSearch in Eureka ↗ |
| Defendant counsel | Farheena Yasmeen Rasheed | Attorney | Counsel for DERRICK BRENT, Acting Under Secretary of Commerce for Intellectual Property and Acting Director of the United States Patent and Trademark OfficeSearch in Eureka ↗ |
| Defendant law firm | United States Patent & Trademark Office | Law Firm | Representing DERRICK BRENT, Acting Under Secretary of Commerce for Intellectual Property and Acting Director of the United States Patent and Trademark OfficeSearch in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | Court of Appeals for the Federal CircuitSearch in Eureka ↗ |
Official order — verbatim text
The Federal Circuit’s order — ‘AFFIRMED’ following a patentability cause — confirms the appellate panel applied the deferential substantial-evidence standard to the USPTO’s factual findings and reviewed legal conclusions of patentability de novo. An unqualified affirmance without remand means the court found no error sufficient to disturb the agency’s determination. X-FAB has no further avenue at this appellate level; any path forward would require Supreme Court certiorari or new prosecution before the USPTO.
US15/648728 — Carrier substrate for semiconductor transfer-print manufacturing
US application 15/648728, published as US20180068872A1, claims a carrier substrate specifically engineered to support semiconductor structures that are subsequently transferred to a target substrate via transfer printing. The application addresses a fabrication challenge in advanced semiconductor manufacturing: creating an intermediate carrier that holds devices during processing and releases them cleanly during transfer. The filing date places it in the period of rapid development in heterogeneous integration and micro-LED transfer technologies.
Transfer-print carrier substrate technology sits at the intersection of compound semiconductor manufacturing, flexible electronics, and advanced packaging — three high-growth sectors attracting significant IP activity. X-FAB, as a specialty foundry servicing automotive, industrial, and medical chip markets, would have strategic value in controlling this process IP. The rejected application’s subject matter nonetheless defines a meaningful technical disclosure, and the affirmed unpatentability ruling leaves the competitive landscape more open for foundries and OEMs developing similar transfer-print fabrication flows.
Should you run an FTO against US15/648728 and the broader X-FAB substrate portfolio?
Product teams commercialising carrier substrate technologies, transfer-print semiconductor assembly processes, or heterogeneous integration modules should take note: US15/648728 itself is rejected and unenforceable. However, X-FAB is an active patent filer, and related applications claiming similar subject matter with different claim scope may exist within the same family or in parallel filings. Any team building on transfer-print substrate architectures should confirm their FTO extends beyond this single application.
PatSnap Eureka’s FTO Search Agent enables R&D and IP teams to map the full X-FAB patent family around US15/648728, identify continuation and divisional applications, and surface related third-party patents covering carrier substrate and transfer-print methods. Eureka’s AI-assisted claim analysis highlights which pending or granted claims in the broader portfolio could still intersect with your product architecture — reducing the risk of launching on an incomplete freedom-to-operate assessment.
Run a freedom-to-operate analysis on US20180068872A1 to assess your product’s exposure
Run FTO in Eureka →Similar Federal Circuit appeals: semiconductor patentability challenges at the USPTO
Explore Federal Circuit appeals involving USPTO patentability rejections in semiconductor fabrication and advanced packaging, comparable to Case 24-1337.
What this case signals for the semiconductor packaging IP landscape
The Federal Circuit’s affirmance reinforces the USPTO’s authority to reject advanced semiconductor fabrication claims — with direct consequences for how companies protect transfer-print IP.
Transfer-print substrate claims face high patentability bar at the USPTO
The affirmance suggests the USPTO’s patentability standards for carrier substrate and transfer-print manufacturing claims are robust enough to withstand Federal Circuit review. Companies drafting applications in this space should expect rigorous scrutiny of novelty and non-obviousness, particularly given the volume of prior art in semiconductor packaging techniques.
X-FAB’s disclosed method now functions as freely available prior art
US20180068872A1 remains a published application, meaning its disclosure is available as prior art against subsequent applicants — including X-FAB itself in any continuation. Competitors can cite it during examination and potentially use the disclosed fabrication approach without infringement risk from this specific application.
In v DERRICK — key questions answered
The Federal Circuit affirmed the USPTO’s determination that X-FAB Semiconductor Foundries GmbH’s patent application US15/648728, covering a carrier substrate for semiconductor transfer-print manufacturing, is unpatentable. The court found no reversible error in the agency’s ruling, closing X-FAB’s appellate avenue for this application.
US15/648728 (published as US20180068872A1) is an X-FAB application claiming a carrier substrate designed to support semiconductor structures during fabrication and enable their subsequent transfer to a target substrate via transfer printing. It is relevant to heterogeneous integration, flexible electronics, and advanced semiconductor packaging processes.
An affirmed unpatentability ruling means the application cannot mature into an enforceable patent on its current claims. Competitors and foundries practising similar transfer-print carrier substrate methods face no infringement risk from US15/648728 specifically. However, X-FAB may hold related continuation applications, so a full FTO search across the family is advisable.
X-FAB could potentially pursue patent protection through continuation or continuation-in-part applications with amended claims, provided any such applications remain pending and claim the same priority date. The Federal Circuit’s affirmance forecloses the specific claims on appeal but does not necessarily bar X-FAB from prosecuting related claims before the USPTO. The public record does not confirm whether such filings exist.
The public record identifies the basis of termination as ‘Unpatentable’ and the verdict cause as an invalidity/cancellation action, but does not specify whether the rejection was based on anticipation, obviousness, written description, or another statutory ground. The Federal Circuit’s affirmance confirms the grounds were legally sufficient without disclosing further detail in the available case data.
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