PTAB

IPR2013-00459

OSRAM GmbH v. SCHUbert E Fred

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1. Case Identification

2. Patent Overview

  • Title: Crystallographic Wet Chemical Etching of III-Nitride Material
  • Brief Description: The ’475 patent discloses methods for the crystallographic wet chemical etching of III-Nitride materials, such as Gallium Nitride (GaN), grown on a substrate. The invention’s stated goal was to produce atomically smooth, non-c-plane surfaces to improve reflectivity and performance in semiconductor devices like laser diodes and transistors.

3. Grounds for Unpatentability

Ground 1: Anticipation by Akasaki - Claims 1, 2, 4, 11-14, and 16 are anticipated by Akasaki under 35 U.S.C. §102(a).

  • Prior Art Relied Upon: Akasaki (Japanese Patent Application Publication No. H10-41585).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Akasaki taught every element of the challenged claims. Akasaki described a two-step process for improving the "mirror surfacing" of end faces on a III-nitride semiconductor laser. The process involved a first dry etch step (reactive ion beam etching) that exposed non-c-plane sidewalls of the GaN epitaxial layer system. A second wet etch step followed, which immersed the device in a heated potassium hydroxide (KOH) solution to remove the damaged layer from the exposed faces. Petitioner asserted this second step was a crystallographic etch that produced smooth, parallel end faces, thus disclosing the claimed method of exposing non-c-plane surfaces and then crystallographically etching them to obtain crystallographic plane surfaces.

Ground 2: Anticipation by Sonobe - Claims 1, 2, 4, 11-14, and 16 are anticipated by Sonobe under 35 U.S.C. §102(b).

  • Prior Art Relied Upon: Sonobe (Japanese Patent Application Publication No. H8-255952).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that Sonobe also disclosed a two-step etching process that anticipated the claims. Sonobe’s method was designed to clean and smooth a GaN-based semiconductor on a sapphire substrate. The first step used a dry reactive ion etch to expose non-c-plane surfaces by etching vertically through the top c-plane. The second step was a wet etching process that immersed the GaN system in a heated solution of nitric acid and phosphoric acid. Petitioner argued this wet etch removed the damaged layer created by the dry etch and produced smooth, crystallographic non-c-plane surfaces, thereby teaching all limitations of the challenged independent and dependent claims.

Ground 3: Obviousness over Weyher and Kelly - Claims 1, 2, 4, 11-14, and 16 are obvious over Weyher in view of Kelly under 35 U.S.C. §103(a).

  • Prior Art Relied Upon: Weyher (a 1997 journal article on chemical polishing of GaN) and Kelly (German Application # DE19640594A).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner asserted Weyher taught that one of the two c-plane sides of a GaN crystal—specifically, the side typically attached to the sapphire growth substrate—could be crystallographically etched with KOH to create a micro-rough surface. Roughening semiconductor surfaces was well-known to improve light extraction efficiency in LEDs. Kelly taught a laser lift-off (LLO) technique to separate a GaN epitaxial layer from its sapphire substrate, thereby exposing the very surface that Weyher identified as etchable.
    • Motivation to Combine: A person of ordinary skill in the art (POSITA) aiming to improve light emission from a GaN-based LED would combine these references. A POSITA would use the LLO process from Kelly to access the GaN surface previously attached to the substrate and then apply Weyher's crystallographic wet etching process to roughen that newly exposed surface, a known technique for improving light emission.
    • Expectation of Success: The combination involved the predictable application of known techniques (LLO and chemical etching) for their established functions to solve a known problem (internal reflection in LEDs). Therefore, a POSITA would have a reasonable expectation of success.

  • Additional Grounds: Petitioner asserted additional anticipation challenges based on Kozawa and Youtsey ’98. Petitioner also presented further obviousness challenges, including combinations of Weyher/Cheung and Donnelly/Youtsey ’98, which relied on similar motivations to combine substrate removal or dry etching techniques with known wet crystallographic etching processes.

4. Key Claim Construction Positions

  • "Crystallographic Etching": Petitioner proposed this term be construed as "preferentially etching a crystal plane." This construction was based on the patent’s specification, which described the goal of obtaining crystallographic plane surfaces and using etchants that act on specific crystal planes.
  • "Non-c-plane": Petitioner argued that, based on the specification and prosecution history, a "non-c-plane" should be construed as a plane not designated with a "c" (such as a- or m-planes) that lies at an angle to the c-plane. Petitioner noted that in co-pending litigation, the Patent Owner had proposed a broader construction where "non-c-plane" includes the negative c-plane. Petitioner asserted that its invalidity grounds were sound even under the Patent Owner's broader construction.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1, 2, 4, 11-14, and 16 of the ’475 patent as unpatentable.