PTAB

IPR2016-01313

Qualcomm Inc v. DSS Technology Management Inc

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Petition
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1. Case Identification

2. Patent Overview

  • Title: Semiconductor Structure and Local Interconnect
  • Brief Description: The ’924 patent discloses a semiconductor transistor structure featuring a specific local interconnect. The purported invention is the use of a single electrically conducting plug to form a direct connection between a transistor's gate and a diffusion region (source or drain) formed in the substrate.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 1-3, 14, and 16 by Sakamoto

  • Prior Art Relied Upon: Sakamoto (Patent 5,475,240).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Sakamoto discloses each and every limitation of the challenged claims. For independent claim 1, Sakamoto was alleged to teach a semiconductor structure comprising a silicon substrate, a diffusion region formed in the substrate, a gate formed on the substrate juxtaposed to but not contacting the diffusion region, a sidewall spacer adjacent to the gate, an insulator layer covering the gate and diffusion region, and a single conducting plug in a via that provides direct electrical communication between the gate and the diffusion region. Petitioner further mapped Sakamoto’s disclosure to the dependent claims, arguing it teaches an N+ diffusion region (claim 2), an insulator layer of silicon oxide (claim 3), exposure of the polysilicon gate and diffusion region in the via absent the plug (claim 14), and a gate comprising polysilicon (claim 16).

Ground 2: Obviousness of Claims 4-6 and 13 over Sakamoto in view of Cederbaum

  • Prior Art Relied Upon: Sakamoto (Patent 5,475,240) and Cederbaum (Patent 5,100,817).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addresses dependent claims specifying the material of the conducting plug. Petitioner asserted that while Sakamoto discloses a plug made of polycrystalline silicon, Cederbaum discloses a conducting plug made of tungsten, which is a refractory metal. This teaching from Cederbaum allegedly supplies the limitations of claims 4 ("metal plug"), 5 ("refractory metal plug"), and 6 (listing materials including tungsten). For claim 13, Petitioner argued Cederbaum teaches a conducting plug comprising an outer "glue layer" of titanium nitride (TiN) and an inner plug material of tungsten, satisfying the claim's limitations.
    • Motivation to Combine: Petitioner contended a person of ordinary skill in the art (POSITA) would combine the teachings of Sakamoto and Cederbaum for several reasons. First, both references address the same problem of improving stacked transistor structures in SRAM memory cells and disclose nearly identical device structures. Second, substituting Sakamoto’s polysilicon plug with Cederbaum’s refractory metal plug was a simple design choice, as using refractory metals for plugs was well-known. Third, Cederbaum explicitly teaches that refractory metals like tungsten have superior conductivity and lower resistivity than polysilicon, providing a clear technical incentive for the modification.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success in making this combination. Substituting one known conductive plug material for another in an otherwise identical and well-understood semiconductor structure was a predictable and routine design modification intended to achieve the known benefits of the superior material.

4. Key Claim Construction Positions

  • Term: "diffusion region formed in said substrate"
    • Proposed Construction: Petitioner proposed this term be construed to mean "a conductive terminal region, such as a source or drain, that contains dopants implanted in the silicon substrate."
    • Relevance: This construction was central to Petitioner's argument, as it grounded the claim language in the specific, well-understood process of ion implantation used to create source/drain regions at the time of the invention. By defining the "diffusion region" as being formed by implanted dopants, Petitioner could more directly map the structures disclosed in the prior art, which described forming such regions via ion implantation, to the claim limitations. The petition noted that the patent owner in related litigation agreed the term requires a "conductive terminal region...formed in the substrate," with the only dispute being whether it must contain implanted dopants.

5. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-6, 13, 14, and 16 of Patent 5,965,924 as unpatentable.