PTAB

IPR2016-00865

Synaptics Inc v. Amkor Technology Inc

Log In
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 structures on integrated circuits. The methods involve creating an underbump metallurgy (UBM) structure on a metal pad, where a conductive barrier layer is formed on only a portion of the pad, leaving another portion of the metal pad exposed to prevent electrical shorts between adjacent bumps.

3. Grounds for Unpatentability

Ground 1: Obviousness over ASE and Delco - Claims 1, 4, 6, 8, 13-15, and 19 are obvious over ASE in view of Delco.

  • Prior Art Relied Upon: ASE (Application # 2003/0124833) and Delco (Patent 6,180,265).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that ASE, which describes a "lift-off" bumping process, teaches all limitations of claim 1. Specifically, ASE’s process results in a conductive layer (comprising adhesion, barrier, and wetting sub-layers) formed on a central portion of a metal pad after a photoresist is removed. This leaves a "second exposed portion" of the metal pad between the edge of the conductive layer and the surrounding insulating passivation layer, as required by the claim. Delco was cited to supplement the teaching that forming a bump on only a limited portion of an exposed bond pad was a known technique to prevent shorting. Delco explicitly discloses a structure where an exposed portion of a nickel-plated aluminum pad surrounds a multilayer metal structure, reinforcing the obviousness of the claimed configuration.
    • Motivation to Combine: Petitioner contended that a person of ordinary skill in the art (POSITA) would combine ASE and Delco because both are analogous art teaching bump formation and address the problem of preventing shorts. A POSITA reviewing ASE’s process would have looked to Delco for its explicit teachings on how to size and place bump structures on a limited portion of a pad to improve reliability. The similar cross-sectional views and problem-solution context in both references would have prompted a POSITA to apply Delco's teachings to the ASE process.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success in applying Delco's known technique for preventing shorts to the similar process in ASE, as it amounted to a simple substitution of like elements with predictable results.

Ground 2: Obviousness over ASE and IBM - Claims 17, 18, 20, and 21 are obvious over ASE in view of IBM.

  • Prior Art Relied Upon: ASE (Application # 2003/0124833) and IBM (Patent 5,937,320).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed claims 17 and 18, which add limitations related to an "underbump metallurgy layer" and its relationship to the conductive barrier layer. Petitioner argued that it would have been obvious to modify ASE’s process in light of IBM by adding an additional conductive barrier layer (e.g., nickel) on top of ASE’s existing UBM stack. ASE discloses a three-layer UBM stack (adhesion/barrier/wetting) with a copper wetting layer as the top layer interfacing with the solder. IBM explicitly teaches that with the market trend toward tin-rich solders, a nickel barrier layer should be placed between the copper wetting layer and the tin-rich solder bump to prevent an aggressive and unreliable reaction between the tin and copper.
    • Motivation to Combine: The primary motivation was to improve the reliability of ASE’s bumping process to accommodate the known market trend toward lead-free, tin-rich solders. A POSITA, recognizing that ASE’s copper wetting layer would react aggressively with tin-rich solder, would have been motivated to look for a solution. IBM directly addresses this exact problem and teaches the solution: interposing a nickel barrier layer. This provided a strong reason to modify ASE’s UBM structure by adding the barrier layer taught by IBM.
    • Expectation of Success: A POSITA would have reasonably expected success because modifying ASE’s process involved adding a known material (a nickel barrier layer) for its well-understood purpose (slowing tin-copper reactions) to achieve a predictable improvement in reliability.

4. Key Claim Construction Positions

  • "conformal with respect to the surface of the metal pad" (Claim 17): Petitioner proposed this term 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 specification and arguments made during prosecution to distinguish over prior art (IBM) where a barrier layer extended onto the passivation layer.
  • "underbump metallurgy layer" (Claims 17-18): Petitioner proposed this term be construed as "metal layer under a bump, used to connect the bump to a bond pad." This construction was based on the ordinary meaning in the art, where UBM could refer to either the entire stack of metal layers under a bump or a subset of those layers.
  • "on": Petitioner argued the term "on" as used in the claims should be construed to include both direct and indirect contact, consistent with the patent's specification.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1, 4, 6, 8, 13-15, and 17-21 of the ’174 patent as unpatentable.