PTAB

IPR2021-00254

STMicroelectronics Inc v. Monterey Research LLC

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Methods of Switching a Resistive Memory Device
  • Brief Description: The ’951 patent describes methods for operating a resistive memory device by switching an active layer, positioned between two electrodes, between a higher-resistance "erased" state and a lower-resistance "programmed" state to store data. The state changes are accomplished by applying an electrical potential across the electrodes, which can be in the same direction for both switching operations.

3. Grounds for Unpatentability

Ground 1: Obviousness over Baek Paper - Claims 1-16 are obvious over Baek Paper.

  • Prior Art Relied Upon: Baek Paper (I.G. Baek et al., Highly Scalable Non-volatile Resistive Memory using Simple Binary Oxide Driven by Asymmetric Unipolar Voltage Pulses, IEEE, Dec. 2004).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Baek Paper, which was not considered during prosecution, discloses all elements of independent claims 1, 8, 11, and 14. Baek described a resistive memory with a metal oxide active layer between two electrodes that switches between a higher-resistance "reset" state (erased) and a lower-resistance "set" state (programmed). Petitioner asserted Baek’s teaching that switching occurs "independent of bias polarity" shows that applying an electrical potential in the same direction for both state changes was known. Furthermore, Baek taught "Set Current Compliance," explicitly disclosing the limitation of selecting and limiting current for the set operation (claims 5-6, 9-10, 12-13, 15-16).
    • Motivation to Combine (N/A for anticipation, but for obviousness): While Baek explicitly taught limiting the "set" current, Petitioner argued it would have been obvious to a person of ordinary skill in the art (POSITA) to also limit the "reset" current. This would have been motivated by the well-known need to prevent damage from excessive currents and to ensure reliable switching, problems that apply equally to both reset and set operations.
    • Expectation of Success: A POSITA would have had a high expectation of success in applying a current limit to the reset operation, as it was a known technique to solve a known problem (potential device damage) using predictable electrical principles.

Ground 2: Obviousness over Baek Paper and Sim - Claims 5-6, 9-10, 12-13, and 15-16 are obvious over Baek Paper in view of Sim.

  • Prior Art Relied Upon: Baek Paper and Sim (Hyunjun Sim, et al., Resistance-Switching Characteristics of Polycrystalline Nb2O5 for Nonvolatile Memory Application, IEEE, May 2005).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground supplements the teachings of Baek Paper with Sim to explicitly address current limiting for both state changes. While Baek disclosed current limiting for the "set" state, Sim explicitly taught using "current compliance" (i.e., limiting current) for both the set and reset operations in a similar resistive memory device.
    • Motivation to Combine: A POSITA would combine Sim’s teaching of limiting the reset current with the device in Baek Paper to gain the known benefits of increased reliability and prevention of circuit damage. Petitioner noted that the references address overlapping technology, were published within months of each other, and share several authors from the same company (Samsung), making combination particularly logical and straightforward.
    • Expectation of Success: The combination involved applying a known technique (Sim's reset current limiting) to a similar device (Baek's) to achieve a predictable improvement in device performance and longevity.

Ground 3: Anticipation and Obviousness over Scheuerlein - Claims 17-19 are anticipated by or obvious over Scheuerlein.

  • Prior Art Relied Upon: Scheuerlein (Application # US 2007/0008785).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground targets method claims 17-19, which require "first" and "second" current limiting structures. Scheuerlein, also not before the examiner, disclosed a switchable resistor memory element that changes between an "erased" (higher-resistance) and a "programmed" (lower-resistance) state. Crucially, Scheuerlein taught using two separate and distinct current mirrors: a "first current limiting structure" to limit the set current and a "second current limiting structure" (a reset driver) to limit the reset current. This directly maps to the limitations of independent claim 17. For dependent claims 18 and 19, Scheuerlein disclosed that the set current is "substantially less than" the reset current, thereby teaching that the currents determined by the two structures are different and that one is lower than the other.
    • Motivation to Combine (for obviousness portion): Petitioner argued that even if not explicitly anticipating, it would have been obvious to use a current mirror for the reset operation based on Scheuerlein's teachings. Scheuerlein taught that the reset current should be "equal to" a desired level and separately taught that a current mirror is a known circuit for providing a constant current, making its use for the reset operation a predictable design choice.
    • Expectation of Success: A POSITA would have expected success in using separate current mirrors as taught by Scheuerlein to implement the claimed method, as it involved the application of standard circuit components for their intended and well-understood purpose.

  • Additional Grounds: Petitioner asserted additional anticipation and obviousness challenges (Grounds 3 and 4) based on the Baek Patent Application (Application # US 2006/0054950), both alone and in combination with Sim, which presented teachings and arguments highly similar to those based on the Baek Paper.

4. Key Claim Construction Positions

  • Petitioner contended that if the Board applies means-plus-function treatment under 35 U.S.C. §112 ¶6 to the term "current limiting structure[s]" in claims 17-19, the corresponding structure disclosed in the ’951 patent specification is a "current mirror." This construction is central to the argument that Scheuerlein, which explicitly discloses using current mirrors to limit set and reset currents, anticipates these claims.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under Fintiv would be inappropriate. The Board's final written decision would likely issue in June 2022, several months before the earliest possible trial date of October 2022 in the parallel district court litigation. Petitioner also argued that the IPR presents unique issues, as it challenges all 19 claims while the district court case involves only claims 1-2 and 5-16. Finally, Petitioner asserted the merits of the challenge are particularly strong, as the petition relies on prior art not considered by the examiner that directly teaches the features the examiner previously found patentable.

6. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-19 of Patent 7,495,951 as unpatentable under 35 U.S.C. §§ 102 and 103.