PTAB

IPR2019-01158

LG Innotek Co. Ltd. v. Seoul Semiconductor Co., Ltd.

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1. Case Identification

2. Patent Overview

  • Title: Light Emitting Diode Chip Having Wavelength Converting Layer and Method of Fabricating the Same, and Package Having the Light Emitting Diode Chip and Method of Fabricating the Same
  • Brief Description: The ’448 patent discloses a light-emitting diode (LED) chip structure designed for improved light efficiency. The structure includes a semiconductor stack on a substrate, a wavelength converting layer (e.g., phosphor), and one or more distributed Bragg reflectors (DBRs) to reflect light and increase output.

3. Grounds for Unpatentability

Ground 1: Obviousness over Chang and Reeh - Claims 1-5, 7-14, 18, and 19 are obvious over Chang in view of Reeh.

  • Prior Art Relied Upon: Chang (a 2008 IEEE journal article on nitride-based LEDs) and Reeh (Patent 6,812,500).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Chang taught all elements of the independent claims except for the specific configuration of the wavelength converting layer. Chang described a lateral topology LED with a semiconductor stack on a sapphire substrate and a hybrid backside reflector combining a DBR (alternating TiO2/SiO2 layers) and an aluminum mirror to enhance light output. Reeh was cited to supply the teaching of a wavelength converting layer (e.g., a phosphor in an epoxy resin) that covers the free side surfaces of the LED semiconductor body and substrate. Reeh explicitly taught this configuration to convert blue light into yellow light to generate white light.
    • Motivation to Combine: A person of ordinary skill in the art (POSITA) would combine the teachings to improve the performance of Chang's LED. A POSITA would modify Chang’s blue LED by incorporating Reeh’s well-known technique for creating a white-light-emitting device. The asserted motivations included achieving better mixing of blue and converted yellow light, reducing reabsorption for higher luminous efficiency, and improving thermal and photochemical stability by using inorganic phosphors as taught by Reeh.
    • Expectation of Success: Petitioner asserted that combining these known elements—an efficient LED structure from Chang and a conventional phosphor encapsulation from Reeh—would have been a predictable modification with a high expectation of success.

Ground 2: Obviousness over Chang, Reeh, and Komoto - Claims 3-5, 7, 15-16, and 19 are obvious over Chang in view of Reeh and Komoto.

  • Prior Art Relied Upon: Chang (a 2008 IEEE journal article), Reeh (Patent 6,812,500), and Komoto (Patent 6,340,824).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground built upon the Chang-Reeh combination by adding Komoto to teach the insulating layers recited in the dependent claims. To the extent the Chang-Reeh combination did not explicitly teach a first insulating layer disposed on the semiconductor structure and a second insulating layer on the first, Komoto supplied this teaching. Komoto disclosed a gallium nitride LED where the surface is covered by two protective films of silicon oxide to enhance device performance, stability, and reliability.
    • Motivation to Combine: A POSITA would be motivated to add Komoto's protective insulating layers to the Chang-Reeh LED to gain the known benefits of protecting the device from environmental damage and reducing surface leakage currents. Petitioner argued this was a common and predictable design choice for improving LED reliability.
    • Expectation of Success: Applying protective insulating layers as taught by Komoto to the LED of Chang-Reeh was presented as a routine and predictable modification.

Ground 3: Obviousness over Yoo and Chang - Claims 1-5, 7-12, 14-16, 18, and 19 are obvious over Yoo in view of Chang.

  • Prior Art Relied Upon: Yoo (Application # 2005/0093004) and Chang (a 2008 IEEE journal article).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that Yoo, as the primary reference, disclosed a lateral topology blue LED chip with a semiconductor stack, electrodes, and a wavelength converting layer (phosphor) formed over the chip to cover its surfaces. However, Yoo only disclosed a reflector in the context of a different, vertical topology LED. Chang was introduced to supply the teaching of a hybrid backside reflector (DBR plus a metal mirror) suitable for the lateral topology LED taught by Yoo.
    • Motivation to Combine: A POSITA would be motivated to improve the light output intensity of Yoo's LED. Recognizing that photons emitted downward toward the substrate would be lost, a POSITA would look to known solutions and find Chang’s hybrid backside reflector. Applying Chang's reflector to Yoo’s LED would effectively reflect these downward-emitted photons, significantly enhancing overall light output.
    • Expectation of Success: Petitioner contended that modifying Yoo's LED with Chang's reflector was a predictable combination of known elements to achieve the expected result of increased brightness.

  • Additional Grounds: Petitioner asserted additional obviousness challenges under Ground 2B, arguing claims 4-5, 7, and 13 are obvious over Yoo-Chang in view of Komoto. This ground relied on adding Komoto's teaching of protective insulating films to the Yoo-Chang combination for reasons analogous to those in Ground 2.

4. Key Technical Contentions (Beyond Claim Construction)

  • Lateral vs. Vertical LED Topology: A central technical argument, particularly for the grounds involving Yoo, was the distinction between lateral and vertical LED structures. Petitioner argued that during prosecution of the ’448 patent, the applicant overcame a rejection over Yoo by arguing that adding insulating layers to Yoo's vertical reflector design would render it inoperable. Petitioner contended its proposed Yoo-Chang combination results in a lateral topology LED where the backside reflector is not between electrically connected layers, thereby avoiding the deficiencies argued by the applicant during prosecution and rendering the claims obvious.

5. Arguments Regarding Discretionary Denial

  • Non-Duplicative Petitions: Petitioner argued that this petition was not duplicative of another concurrently filed petition against the ’448 patent. The petitions were asserted to challenge different, though overlapping, sets of claims. More significantly, they relied on different primary references (this petition used Chang and Yoo; the other used Komoto and Sano) that taught key features from different perspectives (e.g., backside vs. electrode-side DBRs), leading to materially different unpatentability arguments.

6. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-5, 7-16, 18, and 19 of the ’448 patent as unpatentable.