SK hynix Asks a California Court to Declare That Its HBM and DRAM Products Do Not Infringe Eight Former TSMC Patents Held by Mago Barca IP.

The parties and the patents

The case is SK hynix Inc. v. Longhorn IP LLC, No. 3:26-cv-11609 (N.D. Cal.). The complaint describes SK hynix Inc. as a Korean company based in Icheon, South Korea, and SK hynix America Inc. as its wholly owned California subsidiary based in San Jose, California. It describes Longhorn IP as a Texas patent licensing company based in Plano, Texas, and MBIP as a Texas affiliate of Longhorn IP at the same location. The eight patents are U.S. Patents 7,932,608 and 8,390,125 (each titled Through-Silicon Via Formed With a Post Passivation Interconnect Structure), 9,177,914 and 9,530,690 (Metal Pad Structure Over TSV to Reduce Shorting of Upper Metal Layer), 9,984,971 (Methods of Forming Metal Pad Structures Over TSVs to Reduce Shorting of Upper Metal Layers), 8,334,170 (Method for Stacking Devices), 11,410,877 (Source/Drain Contact Spacers and Methods of Forming Same), and 9,570,324 (Method of Manufacturing Package System). The complaint says TSMC and MBIP signed a patent assignment agreement covering these patents on March 28, 2025.

How the dispute arose, according to the complaint

The complaint traces the patents to agreements between TSMC and Longhorn IP. It says a Longhorn IP affiliate, Katana, sued TSMC in the Western District of Texas in December 2019 (No. 6:19-cv-00695), and that the March 2020 settlement included a collaboration agreement under which TSMC assigned five patents to another affiliate, Trenchant. SK hynix filed a declaratory judgment suit against Longhorn IP and its affiliates in the Northern District of California on July 5, 2022 (No. 5:22-cv-03915), and SK hynix and Trenchant entered into a patent license on October 18, 2022. TSMC sued Longhorn IP in that district in August 2023 for breach of the collaboration agreement (No. 5:23-cv-04265), and the complaint says that case settled in November 2024 with a renewed agreement. It alleges, on information and belief, that MBIP was formed on January 10, 2025 to acquire the TSMC patents.

According to the complaint, a June 11, 2025 letter alleged that SK hynix and its affiliates infringe the '608, '170, '125, '690, '971, and '877 patents and offered to discuss license terms. Letters from MBIP's outside counsel followed on October 13, 2025, May 6, 2026 (adding the '914 patent), and May 28, 2026 (adding the '324 patent). The parties met by videoconference on October 13, 2025 and January 14, April 14, June 23, and August 12, 2026. The complaint says SK hynix denied infringement throughout and concluded that further talks would be unproductive.

The claims and the non-infringement theories

Claim 1 of the '608 patent covers an integrated circuit structure with a through-silicon via (TSV) extending into a semiconductor substrate, a pad over the substrate spaced apart from the TSV, and an interconnect structure electrically connecting the TSV and the pad, with an upper portion formed on the pad that extends to electrically connect the TSV and a lower portion outside the TSV that is adjacent to and directly contacts the pad. The complaint says the accused HBM products do not have a claimed interconnect structure separate from a pad.

Claim 1 of the '914 patent covers a semiconductor die for bonding with another die, with a through substrate via (TSV) formed in a substrate of the die and a slotted metal pad formed directly over the TSV, where the pad's top surface area is larger than the TSV's, the pad has a plurality of metal bars in a first direction, and the slots between the bars are filled with a dielectric material to form dielectric bars. The complaint says SK hynix's HBM3, HBM3E, HBM4, and HBM4E products do not have a slotted metal pad with the claimed dielectric bars.

Claim 1 of the '324 patent covers a method of manufacturing a package system: forming a first interconnect structure over a first surface of a first substrate; forming at least one first through silicon via (TSV) structure in that substrate; disposing the substrate over a carrier with the first surface facing the carrier; depositing a molding compound material over the carrier and around the substrate; forming at least one through via in the molding compound material, offset from the substrate in a direction parallel to the first surface; forming a second interconnect structure over a second surface of the substrate; removing the carrier to expose the first interconnect structure; and disposing a first integrated circuit over the first surface, electrically coupled with the TSV structure through the first interconnect structure and connecting bumps. The complaint says the defendants accused SK hynix HBM "for use in advanced 2.5D package architectures," that SK hynix does not make, use, or sell any 2.5D package products and so does not perform the claimed method steps, and that, to the extent the defendants contend TSMC performs those steps, TSMC is licensed under the March 28, 2025 assignment agreement.

The complaint says the defendants accused SK hynix DRAM devices of infringing at least claim 1 of the '877 patent, and that the accused HBM and DRAM products "use a different manufacturing process that neither requires nor includes the claimed contact etch stop layer."

For the seven patents other than the '324 patent, the complaint also seeks declarations that claims of those patents are invalid under 35 U.S.C. 102 and 103, at least under the defendants' theory of infringement, and names prior art for each, such as Japanese Publication 2011-003645 (Fujisawa) and U.S. Patent 8,736,067 (Hirano) for the '914 patent.

Relief requested

The prayer asks for declarations that SK hynix has not infringed and is not infringing any valid claim of the eight patents and that claims of seven of them are invalid; a permanent injunction barring the defendants "and all those acting through or for them, directly and indirectly, from asserting the Patents-in-Suit against any third party based on any alleged use of SK hynix's accused products"; judgment for SK hynix on each of its claims; a finding that the case is exceptional under 35 U.S.C. 285; and costs, expenses, and attorneys' fees. SK hynix demands a jury trial. The suit is brought under the Declaratory Judgment Act, 28 U.S.C. 2201 and 2202.

What to watch next

The same day, Mago Barca IP LLC sued SK hynix Inc. in the Eastern District of Texas, Mago Barca IP LLC v. SK hynix Inc., No. 2:26-cv-00916. That complaint asserts five of the eight patents in this case, the '914, '690, '971, '877, and '170 patents, against SK hynix HBM3 and DDR4 products, and seeks damages and an ongoing royalty rather than an injunction; see the separate page on that case. Watch for the defendants' response here, including any motion to dismiss, stay, or transfer, and for filings in either court that address the other case. The case can end at any time by settlement or dismissal.