PTAB

IPR2026-00220

Taiwan Semiconductor Mfg Co Ltd v. Chun Hsien Lin

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: Semiconductor Device with Trench of Various Widths
  • Brief Description: The ’735 patent describes a semiconductor device and fabrication method intended to achieve a "void-free" metal fill in a gate trench. The invention purports to solve this known problem by shaping the trench to include a "neck" located between the top and bottom, where the neck is narrower than the top and narrower than or equal to the bottom.

3. Grounds for Unpatentability

Ground 1A: Anticipation of Claims 1, 3-6 by Chuang

  • Prior Art Relied Upon: Chuang (Application # 2010/0044783).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Chuang discloses every limitation of claims 1 and 3-6. Chuang teaches a semiconductor device with a gate structure formed in a trench that has a profile modified to be wider at its top opening than at its bottom. This structure includes a substrate, a dielectric layer, and a multi-layer gate structure (high-k dielectric, work function metal, and fill metal) sequentially disposed in the trench. Petitioner asserted that Chuang’s trench, with vertical lower sidewalls and oblique upper sidewalls, inherently forms a “top,” a “bottom,” and a “neck” where the vertical and oblique sections meet. The width of this neck is equal to the bottom width and narrower than the top width, directly corresponding to the geometry recited in claim 1. Dependent claims 3-6 are also allegedly met, as Chuang discloses the required >90° sidewall angle (claim 3), an interfacial insulation layer (claim 4), doped source/drain regions (claim 5), and spacers on the gate structure sidewalls (claim 6).

Ground 1B: Obviousness of Claim 2 over Chuang in view of Brask

  • Prior Art Relied Upon: Chuang (Application # 2010/0044783) and Brask (Patent 7,176,090).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that claim 2 is obvious over the combination of Chuang and Brask. Chuang discloses all features of claim 1, including a trench with an upper section (top to neck) and a lower section (neck to bottom), but does not explicitly disclose the "substantially 2:1" height ratio between these sections as required by claim 2. Brask, which also addresses trench geometry for improved metal fill, remedies this by teaching preferred height ranges for its upper and lower trench segments. Brask discloses an upper trench segment height of 400-800 angstroms and a lower segment height of 100-500 angstroms.
    • Motivation to Combine: A POSITA, seeking to implement Chuang’s device, would combine its teachings with Brask’s to determine optimal and workable dimensions for the trench segments. Since both references address the same problem of void-free trench filling, a POSITA would have looked to Brask for specific, proven height ranges to apply to Chuang’s more generally described structure.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because combining the references involved applying known, preferred dimensional ranges to a known structure to optimize a predictable property (metal fill quality). Petitioner argued that achieving a 2:1 ratio (e.g., 600 angstroms to 300 angstroms) falls squarely within Brask’s disclosed ranges and would be an obvious design choice resulting from routine optimization.

Ground 2A: Anticipation of Claims 1, 3-6 by Lin

  • Prior Art Relied Upon: Lin (Application # 2008/0265322).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that Lin, like Chuang, independently anticipates claims 1 and 3-6. Lin describes a method for manufacturing a transistor with a "Y structure metal gate," which is formed in a recess (trench). This device includes a substrate, an inter-level dielectric layer, and a gate structure comprising a high-k material layer, a barrier layer with work function properties, and a conductive metal layer. Petitioner mapped Lin’s Y-shaped recess to the claimed trench, where the beveled upper edges form the wide "top" and the vertical lower sidewalls form the "neck" and "bottom." The width of the neck is narrower than the top and equal to the bottom, meeting the limitations of claim 1. Petitioner further asserted that Lin discloses the features of dependent claims 3-6, including the non-vertical beveled edge creating an angle >90° (claim 3), an interfacial layer (claim 4), doped source/drain regions (claim 5), and spacers (claim 6).

  • Additional Grounds: Petitioner asserted additional challenges, including that claim 2 is obvious over Lin in view of Brask, and that claims 1-2 are anticipated by or obvious over Brask alone. These grounds relied on similar arguments regarding the disclosure of the claimed trench geometry and height ratios.

4. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-6 of the ’735 patent as unpatentable.