Western Digital Technologies Inc v. Godo Kaisha IP Bridge 1

1. Case Identification

• Case #: IPR2024-01494
• Patent #: 11,968,909
• Filed: September 27, 2024
• Petitioner(s): Western Digital Technologies, Inc.
• Patent Owner(s): Godo Kaisha IP Bridge 1
• Challenged Claims: 1-20

2. Patent Overview

• Title: Magnetoresistive Device
• Brief Description: The ’909 patent discloses a magnetoresistive device for use in technologies like MRAM (magnetoresistive random-access memory). The device features a magnetic tunnel junction (MTJ) structure comprising first and second ferromagnetic layers separated by a crystalline magnesium oxide (MgOx) tunnel barrier layer with specific properties, such as oxygen vacancy defects and a low barrier height, intended to improve the tunnel magnetoresistance (TMR) ratio.

3. Grounds for Unpatentability

Ground 1: Claims 1-20 are obvious over Bowen in view of Soukup, Sunai, and/or Parkin.

• Prior Art Relied Upon: Bowen (a 2001 journal article), Soukup (a 1970 journal article), Sunai (Japanese Application # JP2002204004A), and Parkin (Patent 7,270,896).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Bowen disclosed the core MTJ structure: a single-crystal MgO(001) tunnel barrier between two ferromagnetic layers (Fe and FeCo). The central limitations of crystalline MgOx (001) with oxygen vacancy defects (0<x<1) and a low barrier height (0.1 to 0.85 eV) were either inherently disclosed or rendered obvious. Bowen observed a lower-than-expected barrier height (0.9 eV) and attributed it to "stoichiometric and/or thickness inhomogeneities," which Petitioner contended a person of ordinary skill in the art (POSITA) would understand as oxygen vacancy defects. Soukup was introduced to explicitly teach that nonstoichiometry (i.e., oxygen vacancies) in MgO thin films lowers the barrier height, experimentally observing a barrier height of 0.33 eV, which falls squarely within the challenged claims' ranges. For claim 7, which requires Boron, Petitioner asserted a POSITA would have replaced Bowen's electrodes with Boron-containing CoFeB electrodes as taught by Sunai or Parkin to further improve TMR.
  • Motivation to Combine: A POSITA would combine Soukup's teachings with Bowen's MTJ to improve MRAM performance, a key goal in the art. The art recognized that lowering the barrier height could increase the TMR, and Soukup provided a known method—adjusting oxygen stoichiometry—to achieve this. Similarly, a POSITA would incorporate the CoFeB electrodes taught by Sunai and Parkin into Bowen’s structure because CoFeB was known to increase TMR compared to the Fe and FeCo electrodes used by Bowen.
  • Expectation of Success: A POSITA would have had a high expectation of success. Soukup had already fabricated an MgO barrier achieving a 0.33 eV height, demonstrating the feasibility of creating low-barrier-height films. The improvement in TMR from using CoFeB electrodes was also well-documented and predictable.

Ground 2: Claims 1-20 are obvious over Nagahama in view of Soukup, Sunai, and/or Parkin.

• Prior Art Relied Upon: Nagahama (European Application # EP1391942A1), Soukup (a 1970 journal article), Sunai (Japanese Application # JP2002204004A), and Parkin (Patent 7,270,896).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Nagahama, a publication co-authored by the ’909 patent’s named inventor, disclosed nearly all elements of the claimed invention. Nagahama taught an MTJ with a "(001)-highly-oriented MgO barrier layer" between two ferromagnetic layers. Petitioner argued that such a structure inherently includes oxygen vacancy defects (MgOx where 0<x<1), as such defects are ubiquitous in MgO films. As in Ground 1, Soukup was cited to make explicit the link between these inherent defects and the claimed low barrier height range (e.g., Soukup's 0.33 eV). The combination of Nagahama and Soukup thus rendered claims 1-6 and 8-20 obvious. For claim 7, Petitioner again relied on Sunai or Parkin to teach the obvious substitution of Nagahama's ferromagnetic layers with Boron-containing CoFeB layers.
  • Motivation to Combine: The motivation was strong, as both Nagahama and Soukup were directed at improving tunneling devices. Nagahama’s primary goal was to increase TMR in MTJs. A POSITA seeking to further this goal would combine Soukup's teachings on lowering barrier height via oxygen vacancy control with Nagahama’s advanced MTJ design. The motivation to incorporate Sunai's or Parkin's CoFeB electrodes was to achieve a straightforward and predictable improvement in TMR, consistent with Nagahama’s stated objective.
  • Expectation of Success: Success was reasonably expected because the combination involved applying known principles (lowering barrier height to improve TMR) to a known device structure. Soukup’s work demonstrated that adjusting stoichiometry could predictably alter barrier height, and the benefits of CoFeB electrodes were well-established.

4. Key Technical Contentions (Beyond Claim Construction)

• Inherency of Defects and Barrier Height: Petitioner's central technical argument was that the claimed "oxygen vacancy defects" and resulting low "barrier height" were not inventive but were inherent properties of prior art MgO films. The petition contended that any process for creating crystalline MgO barriers, like those in Bowen and Nagahama, would necessarily result in some level of non-stoichiometry (MgOx where 0<x<1). This, in turn, would inherently lower the barrier height into or near the claimed range, a phenomenon explicitly studied by Soukup.

5. Arguments Regarding Discretionary Denial

• §314(a) / Fintiv Factors: Petitioner argued that discretionary denial under Fintiv was unwarranted. The parallel district court litigation was in its infancy, having been recently transferred with no trial date set. The median time to trial in that district would place any trial long after the Final Written Decision in this IPR.
• §325(d) Factors: Petitioner asserted that denial under §325(d) would be improper because the Examiner made a material error during prosecution and never considered the key prior art combinations presented in the petition. Specifically, the Examiner was never presented with Soukup’s explicit teaching of a 0.33 eV barrier height in MgO films. The allowance was based on the erroneous belief that the claimed barrier height range was novel, an error the petition's new combination of references aimed to correct.

6. Relief Requested

• Petitioner requests institution of inter partes review and cancellation of claims 1-20 of Patent 11,968,909 as unpatentable.