PTAB

IPR2019-01072

LONGi Green Energy Technology Co Ltd v. Hanwha Q Cells & Advanced Materials Corp

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: METHOD FOR MANUFACTURING A SOLAR CELL WITH A SURFACE-PASSIVATING DIELECTRIC DOUBLE LAYER, AND CORRESPONDING SOLAR CELL
  • Brief Description: The ’215 patent describes a solar cell featuring a dielectric double layer on a silicon substrate to improve efficiency. The structure comprises a first, thin aluminum oxide layer for surface passivation, and a second, thicker layer of silicon nitride, silicon oxide, or silicon carbide containing embedded hydrogen.

3. Grounds for Unpatentability

Ground 1: Claims 12-14 are obvious over Bhattacharyya

  • Prior Art Relied Upon: Bhattacharyya (Application # 2006/0102972).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Bhattacharyya disclosed all elements of the challenged claims. It taught a solar cell with a "very thin" aluminum oxide layer (the first dielectric layer) in direct physical contact with a silicon substrate, and a second layer of silicon-enriched silicon nitride (the second dielectric layer) directly on top. Petitioner contended that the claimed thickness of less than 50 nm for the first layer was inherently disclosed, as Bhattacharyya’s description of the layer as "very thin" and its reliance on quantum tunneling for device operation would have required a thickness well under 10 nm.
    • Motivation to Combine (for §103 grounds): While asserted as a single-reference ground, Petitioner argued it was obvious to embed hydrogen into Bhattacharyya’s second dielectric layer. Bhattacharyya disclosed using Plasma Enhanced Chemical Vapor Deposition (PECVD) to form the silicon nitride layer, and Petitioner asserted that using hydrogen-containing precursors (like silane and ammonia) in PECVD was the industry standard at the time, which would necessarily embed hydrogen.
    • Expectation of Success: A person of ordinary skill in the art (POSITA) would have had a high expectation of success, as forming hydrogenated silicon nitride via PECVD was a routine, well-understood process for improving passivation in solar cells.

Ground 2: Claims 12-14 are obvious over Hagino

  • Prior Art Relied Upon: Hagino (Application # 2004/0112426).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted Hagino taught a solar cell structure that rendered the claims obvious. Hagino disclosed a "passivation film" (first dielectric layer) of aluminum oxide on a silicon substrate, with an "antireflection film" (second dielectric layer) of silicon nitride deposited directly on top. Crucially, Hagino explicitly disclosed a thickness range of "approximately 3 nm – 30 nm" for the passivation film, directly teaching the limitations of claims 12 (<50 nm) and 14 (<30 nm). Further, Hagino’s disclosure of forming the silicon nitride layer via Chemical Vapor Deposition (CVD) using silane and ammonia would have necessarily embedded hydrogen into that layer.
    • Motivation to Combine (for §103 grounds): This ground was presented as rendering the claims obvious without combination. Petitioner argued Hagino disclosed all claimed features, and any minor variations were obvious modifications of Hagino’s own teachings.
    • Expectation of Success: A POSITA would have expected success in implementing Hagino’s teachings, as it described a complete solar cell structure using conventional materials and processes to achieve passivation and antireflection, the same goals as the ’215 patent.

Ground 3: Claims 12-14 are obvious over Bhattacharyya or Hagino in view of Duerinckx and/or Hoex 2006

  • Prior Art Relied Upon: Bhattacharyya, Hagino, Duerinckx (a 2002 journal article on defect passivation), and Hoex 2006 (a 2006 journal article on ultralow surface recombination).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground served as an alternative argument, contending that if Bhattacharyya or Hagino were deemed insufficient alone, the combination with Duerinckx and/or Hoex 2006 rendered the claims obvious. Duerinckx was cited to establish that hydrogen-containing silicon nitride layers were the state-of-the-art for surface and bulk passivation in 2002, reinforcing the obviousness of including hydrogen. Hoex 2006 was cited for its teaching that ultrathin aluminum oxide films (7-30 nm) provide excellent surface passivation, confirming the obviousness of the claimed thickness ranges.
    • Motivation to Combine: A POSITA would combine these references to improve the known solar cell designs of Bhattacharyya or Hagino. Duerinckx provided the industry-standard method for passivation (hydrogenation), and Hoex 2006 provided the optimal, known thickness for an effective aluminum oxide passivation layer. The motivation was to combine these known, optimized elements to achieve the predictable result of improved solar cell efficiency and reduced manufacturing costs.
    • Expectation of Success: A POSITA would have reasonably expected success because the combination involved applying well-understood principles (hydrogen passivation, optimal layer thickness) to a known device architecture (the double-layer stack) to enhance a predictable property (surface passivation).

4. Key Claim Construction Positions

  • "interposed between": Petitioner argued this term, central to the patent’s allowance, requires the first dielectric layer to be in direct physical contact with both the silicon substrate below it and the second dielectric layer above it. This construction was based on the specification’s description of a "double layer" and statements made during prosecution to distinguish prior art that allegedly had a three-layer stack.

5. Key Technical Contentions (Beyond Claim Construction)

  • Quantum Tunneling Implies Thickness: Petitioner’s argument against Bhattacharyya relied on a key technical contention that the device’s geometry required quantum tunneling for electrons to pass through the first dielectric layer. For tunneling to be effective, this layer must be extremely thin (less than 10 nm), thus inherently satisfying the claim limitations of <50 nm and <30 nm, even without an explicit disclosure of a numerical range in the reference.

6. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 12-14 of the ’215 patent as unpatentable.