PTAB

IPR2014-01153

ATopTech Inc v. Synopsys Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Subgrid Detailed Router
  • Brief Description: The ’941 patent relates to a method for routing wires in the physical design of an integrated circuit. It discloses a subgrid detailed router that performs wire path searches at a coarse grid level while using codes that contain availability data for a finer subgrid, aiming to achieve higher routing resolution without the increased runtime of conventional routers.

3. Grounds for Unpatentability

Ground 1: Obviousness over Nakajima and JP `446` - Claims 1-12, 16-20, 26-35, and 39-45 are obvious over Nakajima in view of JP `446`.

  • Prior Art Relied Upon: Nakajima (Patent 4,855,929) and [JP `446](https://ai-lab.exparte.com/case/ptab/IPR2014-01153/doc/1006) (Japanese Patent Application JP 3-278446).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that this combination teaches all limitations of the challenged claims, which cover methods for extending wire representations between adjacent grids or regions. Nakajima was asserted to teach a detailed routing method using "grid points," each with binary data indicating availability (vacant, occupied, x-track prohibited, y-track prohibited). Petitioner contended these "grid points" are logically equivalent to the claimed "subgrids" because each can only accommodate a single wire. Nakajima further disclosed comparing the availability data of adjacent grid points to determine if a route could be extended. JP 446 was argued to provide the necessary hierarchical context, disclosing a two-stage routing process with "general wiring grids" (coarse) and "detailed grids" (fine) to reduce data volume. By placing Nakajima's detailed, single-level routing method into the hierarchical framework of JP 446, Petitioner argued the combination teaches extending a wire representation from one region to another by comparing availability data at a finer subgrid level.
    • Motivation to Combine: Petitioner contended that a person of ordinary skill in the art (POSITA) would have been motivated to combine the references because both patents address automated wire routing for integrated circuits. At the time of the invention, hierarchical routing was a well-known strategy for managing the complexity of large designs. A POSITA would have recognized the benefit of applying Nakajima's efficient detailed routing and data structure at the finest level within the established hierarchical routing scheme taught by JP 446. This combination would predictably improve routing performance without requiring undue experimentation.
    • Expectation of Success: Petitioner argued a POSITA would have had a high expectation of success because combining different levels of routing abstraction (global and detailed) was a standard and well-understood practice in the field of electronic design automation.

Ground 2: Obviousness over Nakajima, JP `446`, and Schiele - Claims 13, 14, 36, and 37 are obvious over Nakajima in view of JP `446` and Schiele.

  • Prior Art Relied Upon: Nakajima (Patent 4,855,929), JP `446 (Japanese Patent Application JP 3-278446), and Schiele (a 1990 ACM/IEEE conference paper).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground supplemented the primary combination to address claims requiring the modification of subgrid availability based on "bloated" obstacles. Petitioner argued that while Nakajima and JP 446 provide the core routing framework, Schiele explicitly teaches the concept of "bloating." Schiele described creating "obstruction zones" by "oversizing the obstacles" to account for design rules. Specifically, Schiele taught that the amount of oversizing is determined by "the minimum distance rule and half of the width of the intended element," which Petitioner argued directly maps to the limitation in claim 14. The petition asserted that a POSITA would implement this by changing the availability indicia of any subgrids falling within Schiele's calculated obstruction zone to "non-available," as required by claim 13.
    • Motivation to Combine: A POSITA would combine Schiele with the other references because accounting for physical design rules is a fundamental requirement of any practical routing tool. Schiele provided a known and explicit method for translating design rules (e.g., wire spacing) into geometric constraints ("obstruction zones") that could be used directly by a grid-based router like the one described by combining Nakajima and JP 446. Incorporating Schiele's teachings was argued to be a necessary and obvious step to make the base router functional and effective.
    • Expectation of Success: Success was expected as bloating obstacles was a standard, published technique for enforcing design rules in automated layout systems, and its application to a grid-based system was straightforward.

4. Key Claim Construction Positions

  • "Subgrids": Petitioner proposed that "subgrids" should be construed as the "lowest level of a hierarchy within a hierarchical detailed router, in which each subgrid can have only a single wire/net passing there-through." This construction was argued to be critical because it allows Nakajima's "grid points," which also permit only a single wire, to be mapped directly to the claimed "subgrids," thereby overcoming the Examiner's stated reason for allowance during prosecution.

5. Relief Requested

  • Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 1-14, 16-20, 26-37, and 39-45 as unpatentable.