PTAB

IPR2016-00863

Synaptics Inc v. Amkor Technology Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Methods of Forming Solder Bumps on Exposed Metal Pads
  • Brief Description: The ’174 patent discloses methods for forming solder bump interconnections on metal pads of integrated circuits. The technology centers on creating an underbump metallurgy (UBM) structure that includes a conductive barrier layer, where the structure is formed on only a portion of the metal pad to leave an exposed area, purportedly to prevent electrical shorting between adjacent bumps.

3. Grounds for Unpatentability

Ground 1: Claims 1-3, 6, 8-15, and 17-31 are obvious over Fay in view of IBM.

  • Prior Art Relied Upon: Fay (Patent 6,780,751) and IBM (Patent 5,937,320).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Fay, a reference for forming electroplated lead-free solder bumps, teaches the core limitations of the challenged claims. Fay describes a process where a seed metallization layer (the claimed "underbump metallurgy layer") is deposited over metal pads and a surrounding insulating layer. A photoresist is then used to define openings where a UBM layer (the claimed "conductive barrier layer") is electroplated onto the seed layer. Subsequently, the photoresist is stripped and the exposed portions of the seed layer are etched away. Petitioner asserted this process inherently results in a final structure where the barrier layer is on a first portion of the metal pad, leaving a second exposed portion of the pad free of both the barrier and insulating layers, as required by independent claim 1. Furthermore, Petitioner argued the resulting layers in Fay are "conformal" (as required by claim 17) because they do not extend beyond the edges of the metal pad.
    • Motivation to Combine: The combination with IBM was argued primarily as an alternative, asserting that if Fay's UBM were not considered a "layer," a person of ordinary skill in the art (POSITA) would have been motivated to substitute it with the well-defined nickel barrier layer taught by IBM. The motivation arises from the significant overlap between the references; both Fay and IBM teach methods for forming tin-rich solder bumps using similar process flows (e.g., depositing a seed layer, using photoresist for patterning, and etching). A POSITA would combine these known elements to achieve the predictable result of a reliable barrier layer within Fay's established process.
    • Expectation of Success: Petitioner contended that success would be predictable because the key inventive aspects of Fay (such as micro-etching steps to improve solder wetting) are performed independently of the barrier layer's specific form (e.g., post vs. layer). Therefore, substituting IBM's known barrier layer into Fay's process would have been a straightforward modification with a high expectation of success.

Ground 2: Claim 4 is obvious over Fay and IBM in view of Delco.

  • Prior Art Relied Upon: Fay (Patent 6,780,751), IBM (Patent 5,937,320), and Delco (Patent 6,180,265).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground specifically addressed the limitation in claim 4 requiring that "the exposed second portion of the metal pad surrounds the conductive barrier layer." Petitioner argued that while Fay's cross-sectional figures show an exposed portion of the metal pad, Delco explicitly teaches a configuration where the solder bump and its underlying metallurgy are formed on a central portion of a larger bond pad, leaving an exposed annular ring. Delco discloses this surrounding exposed area as a solution to the known problem of preventing shorts between adjacent solder bumps.
    • Motivation to Combine: A POSITA practicing the method of Fay/IBM would combine it with Delco's teaching to address the well-understood issue of electrical shorting. Delco provided a simple, known design choice for bump placement to mitigate this risk. Petitioner argued that applying Delco's layout—creating a surrounding exposed pad area—to the process of Fay/IBM was an obvious design modification to achieve the known benefit of improved electrical isolation.
    • Expectation of Success: Success was predictable because the layout of the exposed pad is a simple geometric consideration. A POSITA would understand that there are only two finite possibilities: the exposed pad either surrounds the UBM structure or it does not. Delco taught the advantages of the surrounding configuration, making its implementation in Fay's process a predictable and successful design choice.

4. Key Claim Construction Positions

  • Petitioner proposed that the claim term "an entirety of the underbump metallurgy layer and the conductive barrier layer is... conformal with respect to the surface of the metal pad" (recited in claim 17) should be construed to mean "neither the underbump metallurgy layer nor the conductive layer extends beyond an edge of the metal pad or onto the passivation layer." This construction was argued to be consistent with the patent's specification and the prosecution history, where the Patent Owner distinguished prior art on the basis that its barrier layers extended onto the passivation layer.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-4, 6, 8-15, and 17-31 of Patent 7,358,174 as unpatentable.