PTAB

IPR2020-00557

Cree Inc v. Document Security Systems Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Chip Shaping For Flip-Chip Light Emitting Diode
  • Brief Description: The ’460 patent describes a flip-chip light-emitting diode (LED) with a shaped substrate, such as a pyramidal shape, designed to improve light extraction efficiency. This shaping reduces total internal reflection (TIR), a problem in prior art LEDs that used cuboidal substrates which trapped a significant portion of the generated light.

3. Grounds for Unpatentability

Ground 1: Claims 1-7 are obvious over Slater.

  • Prior Art Relied Upon: Slater (6,791,119).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Slater discloses a flip-chip LED containing all the basic structural elements of the challenged claims. Slater teaches a transparent substrate (110') overlying light-emitting layers and explicitly describes modifying substrate geometries to include "pyramidal" and "truncated pyramidal" shapes to improve light extraction. Petitioner asserted that Slater's depiction of a beveled sidewall (110c) to reduce TIR, combined with its explicit teachings, renders a fully pyramidal substrate obvious. Furthermore, Slater’s cross-sectional drawings show the substrate's lateral extent is bound by the underlying doped layer, and its ohmic contacts are placed on the bottom of the device, thereby not occluding the light-emitting substrate, which satisfies the "most" light limitation.
    • Motivation to Combine (within a single reference): A person of ordinary skill in the art (POSITA) would have been motivated to apply Slater's explicit teaching of pyramidal substrate geometries to its LED embodiment shown in FIG. 5. The stated purpose of this modification in Slater is to increase light extraction efficiency—the same problem the ’460 patent purports to solve.
    • Expectation of Success: The modification would have been a simple application of a specifically disclosed shape to a compatible device, both taught within Slater, to achieve the predictable result of improved light output.

Ground 2: Claims 1-8 are obvious over AAPA in view of Camras.

  • Prior Art Relied Upon: Applicant's Admitted Prior Art ("AAPA") from the ’460 patent specification, and Camras (6,784,463).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that the AAPA discloses the foundational flip-chip LED structure, including a transparent but cuboidal substrate, doped layers, and non-occluding bottom-side ohmic contacts. Camras remedies the deficiency of the AAPA’s cuboidal substrate by disclosing a flip-chip LED with a transparent substrate (117) shaped into a centered, truncated pyramid. Camras teaches that this shape approximates a dome or hemisphere to reduce TIR and improve light extraction compared to conventional rectangular prism substrates. Camras also discloses that the upper portion of the first doped layer (114) can have a pyramidal shape.
    • Motivation to Combine: A POSITA would combine Camras's shaped substrate with the basic AAPA LED structure because both references address the identical problem of light trapping in cuboidal substrates. Camras explicitly presents its shaped substrate as a solution for the very problem inherent in the AAPA device.
    • Expectation of Success: The combination involved substituting a known element (the cuboidal substrate of AAPA) with an improved, known alternative (the pyramidal substrate of Camras) to achieve the predictable and intended result of decreased light trapping and increased efficiency.

Ground 3: Claims 1-7 are obvious over AAPA in view of Haitz and Steigerwald.

  • Prior Art Relied Upon: AAPA, Haitz (5,087,949), and Steigerwald (6,573,537).
  • Core Argument for this Ground:
    • Prior Art Mapping: As in the previous ground, the AAPA provides the basic LED structure. Haitz was cited for its teaching of shaping the uppermost layer of an LED into a centered, truncated pyramid to approximate a hemisphere and thereby improve light extraction. Steigerwald was introduced to further support the "most" light limitation, as it teaches that in flip-chip LEDs with features like index-matched substrates and highly reflective contacts, "virtually all light generated from the active region is coupled into the superstrate," ensuring most light exits through the substrate.
    • Motivation to Combine: A POSITA would have been motivated to modify the known AAPA device with Haitz's pyramidal shaping to solve the known TIR problem. The teachings of Steigerwald would be incorporated to further enhance extraction efficiency, an interest shared by both Haitz and Steigerwald. The combination represents a straightforward application of known light-extraction techniques to a conventional LED.
    • Expectation of Success: Combining these known elements to solve a well-understood problem would have been expected to predictably improve the light extraction efficiency of the AAPA device.
  • Additional Grounds: Petitioner asserted additional obviousness challenges based on combinations of Slater with Steigerwald, and Slater with Haitz and Steigerwald, relying on similar theories that the secondary references explicitly teach elements (like pyramidal shaping or features ensuring "most" light emission) to improve upon the primary Slater reference.

4. Key Claim Construction Positions

  • Term: "ohmic contacts ... so that at least most of the light is emitted from the junction layer into the surrounding environment is emitted through said substrate" (claims 1, 6, and 8).
    • Petitioner argued this phrase is a non-limiting statement of intended result. It merely describes the functional outcome of the structurally claimed elements (e.g., the placement of ohmic contacts) and therefore carries no patentable weight.
    • In the alternative, if the phrase were deemed limiting, Petitioner contended that the prosecution history (specifically, arguments to overcome the Krames reference) defines its meaning. Under this alternative construction, the phrase only requires that the ohmic contacts be arranged to occlude the substrate less than other device surfaces, a condition met by placing the contacts on the bottom of the flip-chip device.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-8 of Patent 6,784,460 as unpatentable.