PTAB

IPR2025-00229

Micron Technology Inc v. Yangtze Memory Technologies Co Ltd

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Staircase Structure for Memory Device
  • Brief Description: The ’838 patent discloses 3D NAND memory devices featuring a staircase structure to facilitate electrical interconnections. The invention centers on a specific landing pad configuration where the pad's first side surface is in contact with an adjacent insulating layer, and its second side surface is laterally displaced from a side surface of the underlying conductive layer it is disposed upon.

3. Grounds for Unpatentability

Ground 1: Obviousness over Kim - Claims 1, 4-7, 12-17, and 19-20 are obvious over Kim.

  • Prior Art Relied Upon: Kim (Patent 10,229,929).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Kim, a single reference, discloses every limitation of the challenged claims. Kim teaches a 3D memory device with a staircase contact structure comprising alternating insulating layers (the "first material layer") and conductive gate electrodes (the "second material layer"). At the end of each gate electrode, Kim discloses a "pad unit" that includes a "protrusion pad" (the claimed "landing pad"). Petitioner asserted that Kim’s protrusion pad is formed within an opening in an auxiliary insulating layer, placing its first side surface in "contact" with that layer. Further, Kim teaches that the protrusion pad is formed "inside and spaced apart from the edges" of the underlying gate electrode portion, meaning its second side surface is "laterally displaced" from the side surface of the second material layer, as claimed.
    • Motivation to Combine (for §103 grounds): This ground relied on a single reference, arguing it rendered the claims obvious without combination.

Ground 2: Obviousness over Kim and Yang - Claims 3 and 18 are obvious over Kim in view of Yang.

  • Prior Art Relied Upon: Kim (Patent 10,229,929), Yang (Patent 9,941,153).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed dependent claims 3 and 18, which require the lateral displacement of the landing pad to be between 10 nm and 300 nm. Petitioner contended that while Kim taught the laterally displaced structure, it did not provide specific dimensions. Yang, which teaches a structurally analogous 3D memory device with inset landing pads, was asserted to supply this missing element. Yang provides example dimensions for its structure, including pad setbacks ranging from approximately 20 nm to 190 nm, to prevent electrical failures during etching. Petitioner argued that applying these conventional dimensions to Kim’s device would result in a lateral displacement squarely within the claimed range.
    • Motivation to Combine (for §103 grounds): A POSITA, when implementing the device in Kim, would need to determine appropriate dimensions not specified in the reference. Petitioner argued a POSITA would combine Kim with Yang because both references describe similar staircase structures with inset pads and share the common goal of avoiding electrical failures caused by over-etching. This shared purpose and structural similarity would have motivated a POSITA to apply Yang’s known, successful dimensions to Kim's device.
    • Expectation of Success (for §103 grounds): The high degree of structural and functional similarity between the devices in Kim and Yang would have provided a POSITA with a reasonable expectation of success in applying Yang’s dimensions.

Ground 3: Obviousness over Lee - Claims 1, 4-7, 12, 16-17, and 19-20 are obvious over Lee.

  • Prior Art Relied Upon: Lee (Application # 2014/0191389).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that Lee also discloses all elements of the independent claims. Lee describes a 3D memory device with a staircase structure and "pad portions" (the "landing pad") formed in openings within insulating layers, establishing "contact" with the first material layer. Critically, Lee expressly teaches an optional modification to its manufacturing process: forming "barrier layers" on the sidewalls of precursor material layers before forming the conductive layers. Petitioner contended that this taught modification would shorten the resulting conductive layer, causing the landing pad to overhang and be "laterally displaced" from the side surface of the underlying conductive layer, thus meeting the final key limitation.
    • Motivation to Combine (for §103 grounds): This ground relied on a single reference, arguing the express teaching of an optional but advantageous modification within Lee rendered the resulting structure obvious.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including that claims 3 and 18 are obvious over Lee in view of Haller (Patent 9,520,402) for teaching a specific ~30 nm etch stop spacer dimension, and that claims 13-15 are obvious over Lee in view of Park (Patent 10,297,543) for teaching the use of "rounded" or curved pad surfaces to prevent short circuits.

4. Arguments Regarding Discretionary Denial

  • Petitioner argued against discretionary denial under Fintiv, stating that the district court trial date of June 15, 2026, is distant enough for the IPR to conclude first and that minimal investment has occurred in the parallel litigation for the asserted patent. Petitioner also stipulated that it would not advance any of the grounds raised in the IPR petition in the district court, thereby eliminating issue overlap.
  • Petitioner further contended that denial under §325(d) would be inappropriate because the primary prior art reference, Kim, was not cited or considered during prosecution. While Lee was listed on the face of the ’838 patent, it was not substantively analyzed by the examiner, who only rejected the original claims for double patenting.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1, 3-7, and 12-20 of the ’838 patent as unpatentable.