PTAB

IPR2025-01281

SanDisk Technologies Inc v. Longitude Flash Memory Solutions Ltd

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Non-Volatile Memory Devices and Methods of Fabrication
  • Brief Description: The ’365 patent relates to non-volatile memory (NVM), specifically silicon-oxide-nitride-oxide-silicon (SONOS) flash memory devices. The patent purports to improve data retention capabilities by using a vertically-oriented, multi-layer charge-trapping region, such as an oxide-nitride-nitride-oxide (ONNO) or oxide-nitride-oxide-nitride-oxide (ONONO) stack.

3. Grounds for Unpatentability

Ground 1: Obviousness over Lee ’255 and Lee ’961 - Claims 1-3, 5, 9-12, 14-23, 28-33, 35-37, and 42-45 are obvious over Lee ’255 in view of Lee ’961.

  • Prior Art Relied Upon: Lee ’255 (Application # 2012/0068255) and Lee ’961 (Korean Patent Publication No. 2011-0118961).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Lee ’255 teaches a three-dimensional (3D) semiconductor memory device with a vertical, annular channel and a standard oxide-nitride-oxide (ONO) charge trap structure. While Lee ’255 discloses most limitations of the independent claims, its charge trapping region is a single nitride layer. Lee ’961 was argued to remedy this deficiency by teaching a similar 3D memory device architecture but explicitly addressing the problem of poor data retention in single-layer nitride traps. Lee ’961’s solution is a multi-layer charge trap layer (e.g., nitride-oxide-nitride) to improve data retention.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine the references to improve the known data retention problem of the SONOS device in Lee ’255. Petitioner asserted that Lee ’961 provides the express motivation by teaching that its multi-layer charge trap layer solves charge leakage issues common in devices like those in Lee ’255. The combination would involve replacing the single nitride layer of Lee ’255 with the multi-layer structure from Lee ’961 for its predictable benefit.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because both references describe very similar 3D charge trap memory devices, use compatible materials and fabrication processes, and address the same technical challenges. Lee ’255 was also argued to expressly contemplate that its structure is compatible with additional oxide or oxynitride layers.

Ground 2: Obviousness over Lee ’255, Lee ’961, and Fujiwara - Claims 6-8, 25-27, 34, and 38-41 are obvious over Lee ’255, Lee ’961, and Fujiwara.

  • Prior Art Relied Upon: Lee ’255 (Application # 2012/0068255), Lee ’961 (’961 publication), and Fujiwara (Application # 2006/0065919A1).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground builds upon the combination in Ground 1 to address claims reciting "oxygen-lean" and "oxygen-rich" nitride layers. Petitioner argued that Fujiwara teaches a charge-trapping memory transistor with a multi-layer nitride structure designed to enhance charge retention. Specifically, Fujiwara discloses a silicon nitride charge storage layer composed of a lower, oxygen-rich silicon oxynitride (SiON) "transition" layer and an upper, oxygen-lean silicon nitride (SiNx) "bulk" layer.
    • Motivation to Combine: A POSITA, having combined Lee ’255 and Lee ’961 to create a device with a multi-layer charge trap, would be motivated to further optimize its performance. Petitioner contended that Fujiwara provides the explicit teaching to do so by optimizing the oxygen concentrations within the multi-layer trap for the intended purpose of improving charge retention. This was presented as a known technique to enhance a known device (the Lee '255/Lee '961 combination) to achieve predictable results.
    • Expectation of Success: A POSITA would expect success in applying Fujiwara’s teachings because the underlying materials, equipment, and processes are mainstream and fully compatible with the architecture of the primary combination. Implementing Fujiwara's optimized oxygen concentrations would involve routine process-tuning to achieve the known data-retention benefits.

4. Key Claim Construction Positions

  • “oxygen-rich nitride” and “oxygen-lean nitride”: Petitioner argued that based on an explicit example in the ’365 patent, a POSITA would understand "oxygen-lean" to mean a nitride layer with about 5% or less oxygen and "oxygen-rich" to mean a nitride layer with about 15% or more oxygen.
  • “high work function gate electrode”: Petitioner proposed this term be given its plain and ordinary meaning, which encompasses materials known to a POSITA to have high work functions, such as polysilicon doped with p-type impurities.
  • “formed on the inside sidewall of”: Petitioner contended that "formed on" does not require direct physical contact. This construction is based on the patent's own claim dependency, where claim 27 requires an "anti-tunneling layer between" two nitride layers, while parent claim 26 requires one of those nitride layers to be "formed on" the other. This interpretation allows for intervening layers.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-3, 5-12, 14-23, and 25-45 of the ’365 patent as unpatentable.