Samsung Electronics Co Ltd v. Acorn Semi LLC

1. Case Identification

• Patent #: 9,461,167
• Filed: June 29, 2020
• Petitioner(s): Samsung Electronics Co., Ltd.
• Patent Owner(s): Acorn Semi, LLC
• Challenged Claims: 1-6 and 8-16

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 ’167 patent describes electrical junctions, particularly for transistors, that use a composite interface layer between a contact metal and a semiconductor. This interface layer, comprising a metal oxide and an oxide of the semiconductor, is configured to reduce specific contact resistance at the junction.

3. Grounds for Unpatentability

Ground 1: Anticipation over Grupp - Claims 1-6 and 8-16 are anticipated by Grupp under 35 U.S.C. §102.

• Prior Art Relied Upon: Grupp (Patent 7,176,483).
• Core Argument for this Ground:
  • Petitioner’s argument hinges on challenging the priority date of the ’167 patent. Petitioner asserted that the challenged claims are not entitled to their purported August 12, 2002 priority date because the parent applications fail to provide adequate written description and enabling support for at least three key limitations introduced in the ’167 patent’s application. These limitations are: (1) an interface layer providing a specific contact resistivity of “less than 1 Ω-µm²,” (2) the interface layer comprising a generic “metal oxide,” and (3) the contact metal being a “stack of metals.”
  • Petitioner argued that this failure to support the claims throughout the priority chain invalidates the priority claim, making the effective filing date of the challenged claims February 19, 2016. Grupp, issued in 2007, therefore qualifies as prior art under §102.
  • Prior Art Mapping: Petitioner contended that Grupp anticipates every limitation of the challenged claims. Independent claim 1 is met because Grupp discloses an electrical junction with an interface layer between a metal and a semiconductor (a transistor source/drain). This interface layer is configured to achieve a specific contact resistance of “less than or equal to approximately 1 Ω-µm²,” which falls within the challenged claim’s range. Furthermore, Grupp’s interface layer comprises both an oxide of the semiconductor (a passivating layer of silicon oxide) and a metal oxide (a separation layer of titanium dioxide, TiO₂).
  • Petitioner further mapped Grupp to the dependent claims, arguing Grupp discloses a semiconductor oxide thickness of 0.1 nm to 5 nm (claim 2), the use of an n-type doped semiconductor (claim 3), a "stack of metals" as the contact metal (claim 4), the inclusion of titanium in the metal stack (claim 5), and the use of titanium oxide as the metal oxide (claim 6).

4. Key Claim Construction Positions

• Petitioner argued that the claim term "specific contact resistivity" should be construed to mean "specific contact resistance." This construction was based on the assertion that persons of ordinary skill in the art (POSAs) used the terms interchangeably. Critically, the ’167 patent specification never uses the phrase "specific contact resistivity" but repeatedly discusses achieving a minimum "specific contact resistance," indicating the terms were intended to be synonymous.

5. Key Technical Contentions (Beyond Claim Construction)

• Lack of Enablement for Resistivity Range: Petitioner’s primary technical contention was that the ’167 patent’s priority applications do not enable the full scope of the limitation “specific contact resistivity… of less than 1 Ω-µm².” Petitioner argued this is an open-ended range with no lower bound, extending down to approximately zero. However, the specification’s own disclosure (annotated Fig. 8) illustrates that achieving specific contact resistance below a certain minimum (the nadir of a "total current" curve) is physically impossible with the described technology. Because the parent applications fail to teach a POSA how to make and use the invention across this full, overbroad range, they do not provide enabling support, thereby breaking the priority chain.
• Lack of Written Description Support: Petitioner contended that the parent applications lack written description for key claim terms. It was argued that applications prior to 2011 only disclosed a single species of metal oxide (TiO₂) for the interface layer, which is insufficient to support a claim to the entire genus of "metal oxide." Additionally, Petitioner asserted that the parent applications fail to describe a "stack of metals" deposited on the interface layer, instead only describing a single metal or alloy. This lack of descriptive support for limitations in each challenged claim was presented as another basis for denying the benefit of the earlier priority date.

6. Arguments Regarding Discretionary Denial

• Arguments Against §325(d) Denial: Petitioner argued that discretionary denial would be inappropriate because the examiner during the original prosecution never substantively considered Grupp. While Grupp was listed in an Information Disclosure Statement (IDS), it was never cited against any claim. More importantly, the examiner never analyzed the critical priority date issue, which is the foundation of Petitioner's invalidity argument. Therefore, the Board was being presented with a novel argument that the USPTO had not previously considered.
• Arguments Against §314(a) Fintiv Denial: Petitioner argued that the Fintiv factors weighed in favor of institution. Petitioner stated its intent to file a motion to stay the parallel district court litigation (Acorn Semi, LLC v. Samsung Electronics Co. Ltd.). It was noted that the presiding court has a history of granting such stays post-institution, even in advanced cases. Petitioner also asserted it acted with diligence, filing the IPR petition promptly after the patent owner served infringement contentions identifying the full 108 asserted claims across six patents. The significant overlap in issues would be mitigated by a stay, and the strong merits of the previously unaddressed priority challenge favored institution.

7. Relief Requested

• Petitioner requested the institution of an inter partes review and the cancellation of claims 1-6 and 8-16 of the ’167 patent as unpatentable.