Taiwan Semiconductor Mfg Co Ltd v. Marlin Semiconductor Ltd

1. Case Identification

• Case #: IPR2025-01527
• Patent #: 9,117,909
• Filed: September 9, 2025
• Petitioner(s): Taiwan Semiconductor Manufacturing Company Ltd.
• Patent Owner(s): Marlin Semiconductor Limited
• Challenged Claims: 1-6

2. Patent Overview

• Title: Non-Planar Transistor
• Brief Description: The ’909 patent discloses a method of forming a non-planar transistor, specifically a FinFET structure. The claimed invention involves a substrate with active and isolation regions, shallow and deep trenches, and protruding fin structures with a specific profile: a substantially vertical upper sidewall and a tilted lower sidewall.

3. Grounds for Unpatentability

Ground 1: Claims 1-4 and 6 are obvious over Lin in view of Liaw.

• Prior Art Relied Upon: Lin (Patent 7,994,020) and Liaw (Patent 8,629,512).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Lin, a FinFET reference, discloses a device with most claimed features, including a substrate with active/isolation regions, shallow trenches, and a deep trench with a shoulder portion. However, Lin's protrusions have vertical sidewalls. Liaw was argued to supply the missing limitations: a protruding structure with a tapered lower portion and an explicit method for forming the conductive gate electrode and gate dielectric, which Lin assumes but does not detail.
  • Motivation to Combine: A POSITA would combine Liaw's tapered protrusion design with Lin's structure to improve device stability and reduce the likelihood of failure, as taught by Liaw. This modification also helps minimize defects when filling gaps between protrusions. A POSITA would also look to Liaw for specific guidance on forming the gate structure to complete the device described in Lin.
  • Expectation of Success: Petitioner asserted success was expected because both references are in the field of FinFET fabrication and address controlling device dimensions for reliable performance. Combining a known technique (Liaw’s tapered protrusions) to improve a similar device (Lin’s FinFET) would yield predictable results.

Ground 2: Claim 5 is obvious over the combination of Lin and Liaw, further in view of Chang.

• Prior Art Relied Upon: Lin (Patent 7,994,020), Liaw (Patent 8,629,512), and Chang (Patent 8,546,891).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground specifically targets the claim 5 limitation requiring the deep trench's "shoulder portion" to include a "round corner." While Lin taught a shoulder portion, it was depicted with sharp corners. Petitioner asserted Chang expressly teaches forming deep trenches with a non-constant slope, resulting in a curved profile or "round corner" at the shoulder.
  • Motivation to Combine: A POSITA would be motivated to incorporate Chang’s rounded shoulder design into the Lin/Liaw device to minimize deformation and defects that can occur when depositing dielectric material in the trenches. This known technique from Chang would predictably improve the performance and stability of the base Lin/Liaw device.
  • Expectation of Success: Petitioner argued that applying Chang's known plasma dry etch process to form rounded corners on Lin's trench structure was a simple substitution of one known process for another to obtain predictable benefits.

Ground 3: Claims 1-3, 5, and 6 are obvious over Chang.

• Prior Art Relied Upon: Chang (Patent 8,546,891).

• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued that Chang, standing alone, discloses all limitations of the challenged claims. Chang allegedly teaches a FinFET device with an active region containing protrusions and shallow trenches, surrounded by an isolation region with a deeper trench. Critically, Chang's protrusions are formed with an upper portion having a substantially vertical sidewall and a flared, tilted lower portion. Chang also explicitly discloses the curved profile of the deep trench sidewalls, meeting the "shoulder portion" and "round corner" limitations of claims 1 and 5.

• Additional Grounds: Petitioner asserted an additional obviousness challenge against claim 4 over Chang in view of Liu (Application # 2013/0056826), arguing Liu taught adjusting the insulation layer height to be higher than the lower portion of the protrusion for improved gate control.

4. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under 35 U.S.C. §325(d) is inappropriate because the prior art and arguments presented in the petition were not previously before the USPTO during prosecution of the ’909 patent. Petitioner noted it would rebut any other discretionary denial arguments raised by the Patent Owner under the procedures outlined in the Stewart Memorandum.

5. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-6 of Patent 9,117,909 as unpatentable.