PTAB

IPR2014-00700

Bear Archery Inc v. ams LLC

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Highly Insulating Monocrystalline Gallium Nitride Thin Films and Devices
  • Brief Description: The ’319 patent relates to semiconductor devices fabricated on highly insulating, single-crystal Gallium Nitride (GaN) thin films. The technology focuses on achieving high resistivity in the GaN layer, purportedly by controlling carbon concentration, to improve performance in high-power and high-frequency applications like field-effect transistors (FETs).

3. Grounds for Unpatentability

Ground 1: Anticipation by Akasaki - Claims 1-2, 4-10, 12-13, 15-21, 23-24 are anticipated under 35 U.S.C. §102 by Akasaki.

  • Prior Art Relied Upon: Akasaki (Patent 5,686,736).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Akasaki, which discloses GaN-based light-emitting semiconductor devices, teaches every element of the challenged claims. Akasaki discloses a device structure with a sapphire substrate, an Aluminum Nitride (AlN) buffer layer, and an overlying "undoped" GaN layer, which directly corresponds to the structure in independent claim 1. The central dispute concerned the "highly insulating" limitation. Petitioner contended that a person of ordinary skill in the art (POSITA) would have understood that Akasaki's process for growing the "undoped" GaN layer—Metal-Organic Chemical Vapor Deposition (MOCVD) using trimethylgallium (TMG)—inherently resulted in unintentional carbon incorporation. This known side effect of the MOCVD process would produce a GaN layer with a resistivity well in excess of the 10^5 Ω-cm threshold required by the ’319 patent, thereby rendering it "highly insulating." Akasaki’s disclosure of various device types and materials was argued to meet the limitations of the dependent claims.

Ground 2: Obviousness over Akasaki and Khan - Claims 1-2, 4-10, 12-13, 15-21, 23-24 are obvious over Akasaki in view of Khan.

  • Prior Art Relied Upon: Akasaki (Patent 5,686,736) and Khan (Patent 5,192,987).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that even if Akasaki’s "undoped" GaN layer was not considered inherently insulating, it would have been obvious to modify Akasaki's device to include one. Akasaki provided the foundational device structure with a GaN layer on a substrate with a buffer layer. Khan explicitly taught the advantages of using a highly resistive, insulating GaN layer within a semiconductor device to reduce leakage currents and improve device isolation. Khan described this layer as "insulating GaN" and explained its role in preventing parasitic current paths.
    • Motivation to Combine: A POSITA would combine the teachings to improve the electrical performance of Akasaki's GaN devices. Reducing substrate leakage current was a well-known objective in semiconductor design. A POSITA would have recognized the problem of potential current leakage in the Akasaki device and would have been motivated to apply Khan’s solution—incorporating an insulating GaN layer—to achieve better device performance and electrical confinement.
    • Expectation of Success: The combination involved applying a known solution (Khan's insulating layer) to a known problem in a conventional device structure (Akasaki's). Both references utilized standard MOCVD fabrication techniques, ensuring that a POSITA would have a high expectation of successfully integrating Khan's insulating layer into Akasaki's device without undue experimentation.

Ground 3: Obviousness over Khan and Zhang - Claims 1-2, 4-10, 12-13, 15-21, 23-24 are obvious over Khan in view of Zhang.

  • Prior Art Relied Upon: Khan (Patent 5,192,987) and Zhang ("Properties of Si-Doped AlGaN and GaN/AlGaN Heterostructures Grown on Sapphire by MOCVD," 1997).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground asserted that Khan provided the general concept of using an insulating GaN layer, while Zhang provided a specific, enabling example of creating the exact structure claimed. Khan taught the benefits of an insulating GaN layer on a substrate for electrical isolation. Zhang, a contemporary research paper, detailed the fabrication of a GaN/AlGaN structure on a sapphire substrate using an AlN buffer layer. Crucially, Zhang explicitly described its initial 2-3 μm thick GaN layer as "unintentionally doped" and "highly resistive," noting its function was to "electrically isolate the active layers from the substrate." This disclosure directly mapped all key structural and functional limitations of claim 1.
    • Motivation to Combine: A POSITA seeking to implement the device concept taught in Khan would naturally consult contemporary scientific literature, such as Zhang, for practical guidance and proven methods. Zhang provided a clear and successful experimental example of how to grow the highly resistive GaN layer on a buffered substrate that Khan proposed for improving device performance. The combination was thus a straightforward application of a specific, published technique to achieve a known goal.
    • Expectation of Success: Because Zhang documented the successful fabrication and characterization of the claimed structure, a POSITA would have had a very high expectation of success in reproducing the results to implement Khan’s teachings.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including combinations of Khan and Akasaki (in reverse), and Lin (Patent 6,177,688) in view of Akasaki, which relied on similar rationales for improving device isolation using known insulating layers.

4. Key Claim Construction Positions

  • "highly insulating": Petitioner argued this term was explicitly defined by the patentee during prosecution to overcome prior art. Based on these statements, the term should be construed to mean "having a resistivity of at least 10^5 Ω-cm." This construction was critical to Petitioner's arguments, as it set a quantifiable target that Petitioner argued was inherently met or made obvious by the prior art's disclosure of "undoped" or "unintentionally doped" GaN layers.

5. Key Technical Contentions

  • Petitioner's arguments across multiple grounds relied on a core technical assertion: that a POSITA in the mid-to-late 1990s would have known that growing "undoped" GaN using the prevalent MOCVD process inherently introduced carbon impurities from the metal-organic precursors (e.g., TMG). This unintentional carbon doping was understood to significantly increase the resistivity of the GaN film, making it "highly insulating" as defined in the ’319 patent. This principle was foundational to the anticipation argument that Akasaki's disclosure of an "undoped" layer was sufficient to teach the "highly insulating" limitation.

6. Relief Requested

  • Petitioner requests institution of an inter partes review of claims 1-2, 4-10, 12-13, 15-21, 23-24 of the ’319 patent and cancellation of those claims as unpatentable.