Samsung Electronics Co Ltd v. Acorn Semi LLC

1. Case Identification

• Case #: IPR2020-01279
• Patent #: 9,905,691
• Filed: July 10, 2020
• Petitioner(s): Samsung Electronics Co., Ltd.
• Patent Owner(s): Acorn Semi, LLC
• Challenged Claims: 1-4, 6, 8, 10-13, 15-20, 22, and 25-30

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 ’691 patent describes metal-semiconductor junctions and structures that incorporate a specific interface layer between the metal and the semiconductor. This interface layer includes both a metal oxide and a semiconductor oxide, and is designed to depin the Fermi level to control the junction's electrical properties, such as contact resistivity.

3. Grounds for Unpatentability

Ground 1: Anticipation by Goodnick - Claims 1-3 and 13 are anticipated by Goodnick under 35 U.S.C. §102.

• Prior Art Relied Upon: Goodnick (S.M. Goodnick et al., a 1981 journal article).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Goodnick, which investigated the influence of thin silicon dioxide (SiO₂) layers on metal-silicon contacts, disclosed every limitation of claims 1-3 and 13. Goodnick described an experiment where aluminum (metal) was deposited on a thin SiO₂ layer grown on a silicon substrate (semiconductor). Petitioner asserted this process resulted in a structure with an aluminum metal contact, a silicon semiconductor region, and an interface layer containing both aluminum oxide (Al₂O₃) and the remaining SiO₂. This structure was alleged to meet claim 1’s requirements for a metal contact, a semiconductor region, a metal oxide layer, and a passivating dielectric tunnel barrier layer comprising a semiconductor oxide.
  • Key Aspects: The core of this ground was that the chemical reaction between aluminum and SiO₂ described in Goodnick inherently created the claimed layered structure.

Ground 2: Obviousness over Goodnick and Taubenblatt - Claims 1, 3, 6, 10-12, 13, 15, 16, 19, 20, and 22 are obvious over Goodnick in view of Taubenblatt 1982.

• Prior Art Relied Upon: Goodnick (a 1981 journal article) and Taubenblatt 1982 (M.A. Taubenblatt and C.R. Helms, a 1982 journal article).
• Core Argument for this Ground:
  • Prior Art Mapping: While Goodnick taught an interface with aluminum oxide, several challenged claims required an oxide of titanium. Petitioner argued that Taubenblatt 1982 remedied this by describing the formation of an interface layer containing titanium oxide (TiOx) and SiO₂ when titanium is deposited on a SiO₂ layer and annealed. Petitioner contended it would have been obvious to apply the method taught in Taubenblatt 1982 (using titanium) to the general structure in Goodnick (a thin oxide on silicon). This combination allegedly disclosed a titanium metal contact, a silicon substrate, and an interface with both a TiOx (metal oxide) layer and an SiO₂ (semiconductor oxide) layer, meeting the limitations of the challenged claims.
  • Motivation to Combine: A POSITA would combine these references to create a low-resistance interface layer that also passivates the silicon surface. Taubenblatt 1982 showed that the resulting TiOx-SiO₂ layer combined the passivating benefits of SiO₂ with the lower resistance of TiOx, delivering the "best of both worlds" for reducing specific contact resistivity.
  • Expectation of Success: Success was expected because the combination required only conventional semiconductor processing steps, such as growing a thermal oxide, depositing titanium, and annealing, all of which were well-known techniques.

Ground 3: Obviousness over Goodnick, Jammy, Taubenblatt, and Chang - Claims 18 and 25-30 are obvious over Goodnick in view of Jammy, Taubenblatt 1982, and Chang.

• Prior Art Relied Upon: Goodnick (a 1981 journal article), Jammy (Patent 6,724,088), Taubenblatt 1982 (a 1982 journal article), and Chang (C.Y. Chang et al., a 1971 journal article).

• Core Argument for this Ground:

  • Prior Art Mapping: This ground built upon the previous combinations to meet the additional limitations in claims 18 and 25-30, specifically that the semiconductor region is a source or drain of a transistor and that the junction has a "specific contact resistivity" of less than 1 Ω-μm². Petitioner argued Jammy supplied the teaching of a transistor having n-type doped source/drain regions. It would have been obvious to apply the TiOx-SiO₂ interface from the Goodnick/Taubenblatt combination to the transistor source/drain regions of Jammy to improve device performance. To achieve the claimed low resistivity, Petitioner asserted a POSITA would have looked to Chang, which taught that specific contact resistance is a strong function of doping and decreases as doping increases, disclosing levels as high as 10²¹ dopant atoms/cm³.
  • Motivation to Combine: A POSITA would be motivated to increase the doping of Jammy's source/drain regions as taught by Chang to further reduce contact resistivity. Lowering resistivity in a transistor was known to be highly desirable for improving switching speed and reducing power consumption.
  • Expectation of Success: A POSITA would have reasonably expected to achieve a contact resistivity below 1 Ω-μm² by combining the resistivity-lowering TiOx-SiO₂ interface layer with the high doping levels taught by Chang. Petitioner noted that prior art had already demonstrated similar results.

• Additional Grounds: Petitioner asserted additional obviousness challenges, including combining Goodnick with Jammy (Ground 2) to supply a transistor context, and combining Goodnick, Jammy, and Taubenblatt (Ground 4) for claims requiring both a titanium oxide and a transistor context.

4. Key Claim Construction Positions

• Petitioner argued that the claim term "specific contact resistivity" (appearing in claims 18 and 25-30) was commonly used interchangeably with "specific contact resistance" by a person of ordinary skill in the art at the time of the invention. This construction was important because the patent specification discussed "specific contact resistance," and Petitioner's arguments relied on prior art teachings related to lowering this value.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under §325(d) was unwarranted because the primary references (Goodnick, Taubenblatt 1982, Chang) were never considered by the examiner during prosecution of the ’691 patent or its parent applications.
• Petitioner further argued that discretionary denial under Fintiv would be inappropriate. It contended that a stay of the parallel district court litigation was likely upon institution, the litigation was not advanced, and Petitioner acted promptly to file its IPR petition after infringement contentions identified the full scope of asserted claims. Finally, Petitioner asserted the strong merits of its petition weighed heavily in favor of institution.

6. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-4, 6, 8, 10-13, 15-20, 22, and 25-30 of the ’691 patent as unpatentable.