Yangtze Memory Technologies Co Ltd v. Micron Technology Inc

1. Case Identification

• Case #: IPR2025-00498
• Patent #: 8,803,214
• Filed: February 14, 2025
• Petitioner(s): Yangtze Memory Technologies Company, Ltd.
• Patent Owner(s): Micron Technology, Inc.
• Challenged Claims: 1-7, 9-12, and 14-20

2. Patent Overview

• Title: Non-Volatile Memory Devices and Methods of Forming the Same
• Brief Description: The ’214 patent relates to three-dimensional (3D) nonvolatile memory devices, such as 3D NAND flash memory. The technology involves stacking multiple layers of memory cells vertically over a substrate to increase memory density and proposes specific device structures and fabrication methods to address challenges in manufacturing these complex architectures.

3. Grounds for Unpatentability

Ground 1: Anticipation/Obviousness over Kang - Claims 1-7, 9-12, and 14-20 are unpatentable over Kang

• Prior Art Relied Upon: Kang (Application # 2010/0140685).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Kang, which discloses 3D vertical NAND flash memory devices, anticipates or renders obvious all challenged claims. For independent claim 1, Petitioner asserted that Kang’s FIG. 1E embodiment discloses a memory device with a substrate (402), a plurality of first and second memory cells located in different device levels over the substrate, and corresponding first and second control gates (430b, 430c) to control access to those cells. Petitioner further mapped Kang’s ring-shaped charge storage layer (411) to the claimed "memory element" located within a "cavity" of the control gates. Finally, Petitioner argued Kang discloses data lines (bit line 494) selectively coupled to a common source (408) through conductive material (active pillar 406). Petitioner similarly mapped Kang’s disclosure to the limitations of independent claims 9 and 15 and all challenged dependent claims, including those requiring double-gate (claim 6) and surrounded-gate (claim 7) transistors.
  • Motivation to Combine (for §103 grounds): As a single-reference ground, Petitioner argued that all elements were expressly or inherently disclosed. In the alternative for obviousness, Petitioner contended a person of ordinary skill in the art (POSITA) would have readily understood from Kang’s disclosure how to arrive at the claimed configurations.

Ground 2: Anticipation/Obviousness over Fukuzumi - Claims 1-7, 9-12, and 14-20 are unpatentable over Fukuzumi

• Prior Art Relied Upon: Fukuzumi (Application # 2009/0146190).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner presented Fukuzumi as an independent basis for invalidity, arguing it also discloses all limitations of the challenged claims. For independent claim 1, Petitioner mapped Fukuzumi’s disclosure of a 3D memory device comprising a substrate (Ba), vertically stacked first and second memory cells (MTr1mn, MTr2mn) in different device levels, and first and second control gates (word lines WL1, WL2). Petitioner identified Fukuzumi’s charge storage layer (391b) as the claimed "memory element" residing in a "cavity" (memory hole 37). The argument concluded by mapping Fukuzumi’s data lines (BL) as being selectively coupled to a common source (p-well region Ba1) through a columnar semiconductor (CLmn), which constitutes the claimed "conductive material." Petitioner applied similar logic to argue that Fukuzumi anticipates or renders obvious the remaining independent and dependent claims.

Ground 3: Obviousness over Kang and Ahn - Claim 16 is obvious over Kang in view of Ahn

• Prior Art Relied Upon: Kang (Application # 2010/0140685) and Ahn (Korean Application # 10-2010-0034612).

• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued that claim 16, which depends from claim 15, is obvious. Kang was asserted to teach all limitations of claim 15 but discloses a memory element made of silicon nitride. Claim 16 adds the limitation that the memory elements comprise polysilicon. Ahn, which also relates to 3D flash memory, was cited for its explicit teaching that a charge trap layer (memory element) can be formed from "a silicon nitride film or a polysilicon film."
  • Motivation to Combine: A POSITA would combine Ahn’s teaching of a polysilicon memory element with Kang's device structure. Petitioner asserted the motivation arises from the known benefits of polysilicon, including better reliability and long-term data retention compared to silicon nitride. Because Ahn presents the two materials as interchangeable options for the same function, a POSITA would have seen it as a simple and advantageous substitution.
  • Expectation of Success: A POSITA would have a reasonable expectation of success because substituting one known charge-trapping material for another was a predictable design choice in the art. Ahn's disclosure of the materials as direct alternatives confirmed the feasibility of the combination.

• Additional Grounds: Petitioner asserted additional obviousness grounds, including that claim 6 is obvious over Fukuzumi in view of Kang (substituting Kang’s double-gate transistor into Fukuzumi’s structure) and that claim 16 is obvious over Fukuzumi in view of Ahn (substituting Ahn’s polysilicon memory element into Fukuzumi’s device). These grounds relied on similar modification theories and motivations as those detailed above.

4. Key Claim Construction Positions

• Petitioner contended that the term “cavity” recited in claims 1 and 15 should be construed as "a hole with a larger diameter than holes in the layers immediately above and below the control gate." This construction is central to Petitioner’s argument that the prior art’s vertically penetrating holes, which widen at the control gate layers relative to adjacent insulating layers, meet the claim limitation. Petitioner noted this construction was proposed in related district court litigation.

5. Arguments Regarding Discretionary Denial

• §325(d) Denial: Petitioner argued denial under 35 U.S.C. §325(d) is unwarranted because the primary prior art references (Kang, Fukuzumi, and Ahn) were never presented to, or considered by, the Examiner during the original prosecution of the ’214 patent.
• §314(a) Denial (Fintiv): Petitioner argued that discretionary denial under Fintiv would be improper. At the time of filing, the ’214 patent was not asserted in any pending litigation. While acknowledging the Patent Owner’s pending motion to add the patent to a parallel district court case, Petitioner asserted that exceptional circumstances—including the compelling merits of the petition and the minimal investment in the district court case regarding this patent prior to its earlier dismissal—warrant institution.

6. Relief Requested

• Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 1-7, 9-12, and 14-20 of the ’214 patent as unpatentable.