Samsung Electronics Co Ltd v. Acorn Semi LLC

1. Case Identification

• Case #: IPR2020-01183
• Patent #: 9,209,261
• Filed: June 24, 2020
• Petitioner(s): Samsung Electronics Co., Ltd.
• Patent Owner(s): Acorn Semi, LLC
• Challenged Claims: 1-3, 17-18, and 21-24

2. Patent Overview

• Title: Method for Depinning the Fermi Level of a Semiconductor at an Electrical Junction and Devices Incorporating Such Junctions
• Brief Description: The ’261 patent describes metal-semiconductor electrical junctions that include a thin metal oxide interface layer between the contact metal and the semiconductor. This interface layer is configured to reduce the height of the Schottky barrier that would otherwise exist, thereby improving the electrical properties of the junction, particularly for contacts on transistor source/drain regions.

3. Grounds for Unpatentability

Petitioner’s challenges rely on a central assertion that the ’261 patent is not entitled to its purported 2002 priority date due to a lack of written description in its parent applications for key limitations. Petitioner argued the correct priority date is no earlier than June 18, 2015, which makes certain references, particularly Grupp, available as prior art.

Ground 1: Anticipation over Grupp - Claims 1-3, 17-18, and 21-24 are anticipated by Grupp

• Prior Art Relied Upon: Grupp (Patent 7,176,483).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that under the ’261 patent’s correct 2015 priority date, Grupp (issued 2007) qualifies as prior art under 35 U.S.C. §102. Grupp, which is a continuation-in-part from the same family as the ’261 patent, allegedly disclosed every limitation of the challenged claims. For independent claim 1, Grupp described an electrical junction with a titanium dioxide (a metal oxide) interface layer between a metal and a group IV semiconductor (e.g., C, Ge, Si). Grupp further taught this junction could be used for contacts to source/drain regions of a transistor, that the layer reduces the Schottky barrier height, and that the layer can have a thickness between 0.1 nm and 5 nm. For dependent claims, Grupp disclosed using n-type semiconductors (claim 2), a stack of metals deposited on the interface layer (claim 3), and contact metals that do not form a silicide or react with the semiconductor (claims 17-18).

Ground 2: Obviousness over Jammy - Claims 1-3 and 17-18 are obvious over Jammy

• Prior Art Relied Upon: Jammy (Patent 6,724,088).
• Core Argument for this Ground:
  • Prior Art Mapping: Jammy disclosed a MOSFET structure with a metal oxide interface layer (an aluminum oxide "quantum conductive barrier") disposed between a contact metal (conductive studs of tungsten, titanium, or titanium nitride) and a group IV semiconductor (n-type doped silicon source/drain regions). Jammy also disclosed an interface layer thickness of 0.5 nm to 5 nm, which falls within the claimed range. Petitioner argued the only limitation not explicitly disclosed was that the layer is "configured to reduce" the Schottky barrier height.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would have understood that Jammy’s fabrication process (using an HF clean followed by deposition) would create a thin silicon oxide monolayer at the interface. This passivation layer would satisfy dangling bonds on the silicon surface, depinning the Fermi level and reducing the barrier height compared to an intimate contact. A POSITA would be motivated to reduce this barrier height to lower contact resistance, which improves transistor performance characteristics like switching frequency and power consumption.
  • Expectation of Success: A POSITA would have had a high expectation of success. The barrier-lowering effect of thin interfacial oxide layers was well-known and quantifiable using established principles, such as the Rhoderick barrier height equation, which demonstrates that passivating the surface reduces the barrier height from the pinned "Bardeen case" toward the lower "Schottky case."

Ground 3: Anticipation over Jammy - Claims 21-24 are anticipated by Jammy

• Prior Art Relied Upon: Jammy (Patent 6,724,088).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued Jammy anticipated claims 21-24, which are directed to a device structure rather than the functional "configured to reduce" limitation of claim 1. For independent claim 21, Jammy disclosed a junction comprising a conductor (conductive studs), a semiconductor selected from the claimed list (silicon is explicitly listed), and an interface layer disposed between them. Jammy also disclosed the interface layer comprises a metal oxide (aluminum oxide) and has a thickness within the claimed 0.1 nm to 5 nm range. For dependent claims, Jammy disclosed the semiconductor is an n-type doped source/drain of a transistor (claim 22), the contact metal is deposited on the interface layer (claim 23), and the semiconductor is an n-type doped group IV semiconductor (claim 24).

4. Key Technical Contentions (Beyond Claim Construction)

• Invalid Priority Claim: Petitioner’s primary technical contention was that the ’261 patent is not entitled to its claimed August 12, 2002 priority date because its parent applications fail the written description requirement of §112. This argument was foundational to the anticipation ground over Grupp.
  • The parent applications allegedly lacked support for the full genus of "metal oxide" interface layers, disclosing only TiO2 as a specific example, which is insufficient to describe the entire class.
  • The parents also allegedly failed to describe the full genus of "group IV semiconductor," as they did not disclose carbon or germanium-carbon alloys and described bandgaps inconsistent with carbon.
  • Finally, the parent applications allegedly described only a single metal or alloy layer, not a "stack of metals" as recited in claims 3 and 23.

5. Arguments Regarding Discretionary Denial

• §325(d) - Same or Substantially Same Art/Arguments: Petitioner argued that discretionary denial under §325(d) was improper because the USPTO had not previously considered the art in a substantive manner. Although Grupp and Jammy were cited in Information Disclosure Statements during prosecution, no Examiner ever applied them against any claim or, crucially, considered the dispositive priority date arguments presented in the petition.
• §314(a) - Fintiv Factors: Petitioner argued the Fintiv factors favored institution. The petition was filed promptly after receiving infringement contentions that identified the nine asserted claims. Petitioner stated it would move to stay the co-pending district court litigation if IPR was instituted and noted the court's willingness in past cases to grant such stays. Petitioner also committed to ceasing its assertion of Grupp and Jammy in the district court case to avoid overlap and preserve resources, arguing this minimized the risk of duplicative efforts or inconsistent results.

6. Relief Requested

• Petitioner requested institution of an inter partes review and cancellation of claims 1-3, 17-18, and 21-24 of the ’261 patent as unpatentable.