Ricoh Americas Corp v. Round Rock Research

1. Case Identification

• Case #: IPR2016-00635
• Patent #: 6,147,405
• Filed: February 18, 2016
• Petitioner(s): Ricoh Americas Corp.
• Patent Owner(s): Round Rock Research, LLC
• Challenged Claims: 1-3

2. Patent Overview

• Title: Semiconductor Device with Mixed Metal Silicide/Nitride Contact
• Brief Description: The ’405 patent relates to a conductive contact for a semiconductor device, such as a MOSFET. The invention is directed to a contact structure comprising metal silicide that is interspersed with metal nitride throughout the entire silicide layer, including at the interface with the underlying substrate.

3. Grounds for Unpatentability

Ground 1: Claims 1-3 are obvious over Byun 1996

• Prior Art Relied Upon: Byun 1996 (Jeong Soo Byun et al., Epitaxial C49-TiSi2 Formation on (100)Si Substrate Using TiNx and Its Electrical Characteristics as a Shallow Contact Metallization, Journal of the Electrochemical Society, June 1996).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Byun 1996, a journal article on titanium silicide formation, discloses every limitation of the challenged claims. Specifically, Byun 1996 describes annealing a titanium nitride (TiNx) film on a silicon substrate at 800°C. Petitioner asserted this process inherently creates a titanium silicide (TiSi2) layer with titanium nitride (TiN) interspersed throughout. Petitioner pointed to Byun 1996’s analytical data, including Auger Electron Spectroscopy (AES) depth profiles and cross-sectional transmission electron microscopy (XTEM) images, as direct evidence that TiN is present throughout the silicide and, critically, at the substrate-silicide interface. Petitioner contended that during prosecution, the Examiner overlooked these specific figures and analyses which demonstrate the key claim limitation.
  • Key Aspects: The core of this ground was that the dispositive evidence for unpatentability was present in a reference already considered during prosecution but that its most relevant teachings were not addressed by the Examiner or Applicant.

Ground 2: Claims 1-3 are obvious over Iwata

• Prior Art Relied Upon: Iwata (Patent 5,849,634).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended that Iwata, which teaches a method of forming a silicide film, discloses a semiconductor device with a contact layer comprising TiSi2 crystal grains with TiN interspersed between the grains. Petitioner argued that this structure meets the claim 1 limitation of "metal silicide interspersed with metal nitride." Iwata’s method involves processing steps that replace silicon dioxide between the silicide grains with TiN. Petitioner asserted this process results in TiN being present throughout the silicide film, including at the substrate boundary. The dependent claims were also allegedly disclosed, as the contact is made of titanium (claim 2) and the nitrogen content (claim 3) would have been an obvious matter of design choice based on Iwata's process parameters.

Ground 3: Claims 1-3 are obvious over Byun 1996 in view of Iwata and Ogawa

• Prior Art Relied Upon: Byun 1996, Iwata (Patent 5,849,634), and Ogawa (Japanese Patent Application JP 2-96374).

• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued this combination of references teaches all limitations of the challenged claims. Byun 1996 and Iwata were presented as establishing the foundational process of forming TiSi2 contacts containing TiN. Ogawa was added to provide explicit teachings on the technical benefits of incorporating nitrogen impurities into titanium silicide films. Ogawa explains that introducing nitrogen at the grain boundaries of the silicide film improves its properties by inhibiting secondary grain growth, which in turn prevents surface degradation, increases heat resistance, and enhances electrical conductivity.
  • Motivation to Combine: Petitioner argued a person of ordinary skill in the art (POSITA) would combine these references because they all address the same technical field and solve the known problem of improving the stability and performance of silicide contacts. A POSITA would look to Ogawa for its clear explanation of why adding nitrogen—as done in the processes of Byun 1996 and Iwata—is beneficial. The combination was presented as a predictable application of known principles to achieve improved results.
  • Expectation of Success: A POSITA would have a high expectation of success in applying Ogawa’s teachings to the processes of Byun 1996 or Iwata, as it involved incorporating a known impurity (nitrogen) into a known material (titanium silicide) to achieve well-documented and predictable improvements in film stability and electrical properties.

• Additional Grounds: Petitioner asserted an additional obviousness challenge based on the combination of Byun 1996 and Iwata, relying on a similar motivation that the references represent known alternatives for forming silicide films with improved heat-resistance and electrical properties.

4. Key Claim Construction Positions

• "substrate": Petitioner argued, based on the patent’s own lexicography, that this term should be construed as "one or more semiconductor layers or structures which include active or operable portions of semiconductor devices."
• "the contact comprising metal silicide interspersed with metal nitride throughout the metal silicide": Petitioner asserted that the use of the open-ended term "comprising" means that the contact is not limited to only the recited materials and may include other materials, such as pure metal silicide or other compounds.
• "substrate-silicide interface": Citing the prosecution history, Petitioner proposed this term be construed as "the boundary between the silicon substrate and the silicide."

5. Relief Requested

• Petitioner requested institution of an inter partes review (IPR) and cancellation of claims 1, 2, and 3 of Patent 6,147,405 as unpatentable.