PTAB

IPR2023-01381

Innoscience Zhuhai Technology Co Ltd v. Efficient Power Conversion Corp

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: III-Nitride Transistors with Compensated or Semi-Insulating Layers
  • Brief Description: The ’294 patent relates to III-nitride transistors, purporting to improve performance and reduce leakage current by incorporating a "compensated GaN layer" or a "semi-insulating III-N layer" positioned between the gate contact and the barrier layer.

3. Grounds for Unpatentability

Ground 1: Obviousness over Smith, alone or combined with Kigami or Uemoto - Claims 1-12

  • Prior Art Relied Upon: Smith (Application # US 2007/0164315), Kigami (Japanese Patent Publication No. JP2006-253224), and Uemoto (Application # US 2008/0087915).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Smith discloses all elements of the claimed transistor structure, including a substrate, transition layers, a buffer layer (termed a "channel layer" in Smith), a barrier layer, and a doped GaN "cap layer" above the barrier. Petitioner contended this doped GaN cap layer meets the "compensated GaN layer" limitation of claim 1 and the "semi-insulating III-N layer" of claim 4. For the "compensated" limitation, Petitioner asserted that it was well-known that as-grown doped GaN films are naturally hydrogen passivated, meaning Smith's disclosed cap layer inherently had passivated impurities. For the "semi-insulating" limitation, Smith expressly teaches that its cap layer can be a semi-insulating layer formed by co-doping with deep-level acceptor dopants (C, Fe, etc.), as recited in dependent claims 5 and 6.
    • Motivation to Combine (for §103 grounds): To the extent Smith alone is deemed insufficient, Petitioner argued a POSITA would combine it with Kigami or Uemoto. Both Kigami and Uemoto explicitly teach methods of intentionally introducing hydrogen to passivate impurities in GaN layers to improve transistor performance by reducing leakage, stabilizing threshold voltage, and increasing resistivity. As Smith was also concerned with improving these same characteristics, a POSITA would be motivated to apply the known hydrogenation techniques of Kigami or Uemoto to Smith's transistor to achieve these predictable benefits.
    • Expectation of Success (for §103 grounds): The mechanisms and effects of hydrogen passivation in GaN materials were well-understood and widely documented by the priority date, providing a POSITA with a high expectation of success in applying these techniques to Smith's device.

Ground 2: Obviousness over Uemoto in view of Smith - Claims 1-12

  • Prior Art Relied Upon: Uemoto (Application # US 2008/0087915) and Smith (Application # US 2007/0164315).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Uemoto discloses a III-nitride transistor with nearly all claimed features. Specifically, Uemoto teaches a Mg-doped GaN layer (layer 15) that is processed with a hydrogen diffusion film to create a highly resistive region where impurities are inactivated. Petitioner argued this structure is a "compensated GaN layer" under either party's proposed claim construction. Uemoto further discloses the conventional substrate, buffer, and barrier layers beneath this compensated layer.
    • Motivation to Combine (for §103 grounds): Petitioner argued that while Uemoto provides the core invention, it does not explicitly disclose a "semi-insulating layer" with deep level dopants or a "spacer layer," as recited in dependent claims. Smith teaches forming stable, semi-insulating layers by co-doping with deep-level dopants to reduce leakage currents and improve stability. Smith also teaches using multi-layer barrier/spacer structures to improve performance. A POSITA would combine Smith's teachings with Uemoto's base device to incorporate these known, beneficial features and improve Uemoto's overall performance and robustness.
    • Expectation of Success (for §103 grounds): Incorporating Smith's semi-insulating and spacer layers into Uemoto's similar transistor structure involved applying conventional techniques in an ordinary and expected manner, leading to a reasonable expectation of success.

4. Key Claim Construction Positions

  • Petitioner argued that the key term "compensated GaN layer" should be construed as a product-by-process limitation: "Doped GaN layer formed with a step to passivate its impurities."
  • Petitioner contended this construction is supported by the patent's specification, which describes the "critical step" of passivation using hydrogen. Under this construction, the prior art only needs to show the resulting structure (a GaN layer with passivated impurities), not the specific process of forming it. This interpretation is central to the argument that Smith's inherently passivated "as-grown" layer meets the limitation. Petitioner also argued that the Patent Owner's proposed construction ("A semiconductor GaN gate material in which one type of dopant...partially cancels the electrical effects of the other...") is vague and overly broad.

5. Arguments Regarding Discretionary Denial

  • Fintiv Denial: Petitioner argued discretionary denial under Fintiv is improper. Per PTAB interim guidance, Fintiv factors are not applied to petitions when there is a parallel International Trade Commission (ITC) proceeding. Further, the parallel district court case has been stayed and has minimal investment from the court or parties.
  • §325(d) Denial: Petitioner argued denial under 35 U.S.C. §325(d) is improper because the primary prior art references (Smith, Uemoto, Kigami) were not before the examiner during prosecution. Petitioner asserted the references are not cumulative because they teach "forming a 'compensated GaN layer,'" the very feature that applicants argued was missing from the examined art and which the examiner relied upon for allowance.

6. Relief Requested

  • Petitioner requests institution of inter partes review and cancellation of claims 1-12 of the ’294 patent as unpatentable.