Micron Technology Inc v. Yangtze Memory Technologies Co Ltd

1. Case Identification

• Case #: IPR2025-00244
• Patent #: 10,886,291
• Filed: December 13, 2024
• Petitioner(s): Micron Technology, Inc.
• Patent Owner(s): Yangtze Memory Technologies Company, Ltd.
• Challenged Claims: 1-5, 8-9, 11-12, and 14-19

2. Patent Overview

• Title: Joint Opening Structures of Three-Dimensional Memory Devices and Methods for Forming the Same
• Brief Description: The ’291 patent relates to fabricating joint opening structures in three-dimensional (3D) NAND memory devices. The technology involves a two-deck process to form a continuous vertical memory channel, focusing on an inter-tier "third channel structure" that connects the memory structures of the lower and upper decks.

3. Grounds for Unpatentability

Ground 1: Claims 1-5, 8-9, 11-12, and 14-19 are obvious over Costa.

• Prior Art Relied Upon: Costa (Application # 2018/0182771).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Costa, a reference not considered during prosecution, discloses every limitation of the challenged claims. Costa teaches a multi-tier 3D memory fabrication process that addresses the same high-aspect-ratio etching challenges as the ’291 patent. Petitioner asserted a direct mapping for independent claims 1 (method) and 11 (apparatus), contending that Costa’s process of forming stacked layers, through holes, and channel structures in two successive tiers is the same as that claimed. Specifically, Costa’s “joint-level doped semiconductor portion (173)” was argued to be the claimed “third channel structure,” and its “drain region (63)” was mapped to the “fifth channel structure.” These two structures were the basis for allowance of the ’291 patent. Petitioner contended Costa discloses these features, including a third channel structure that covers the first through hole and is in contact with the second channel structure, and a fifth channel structure formed in contact with the fourth channel structure. The arguments for apparatus claim 11 mirrored those for method claim 1, as the claimed structural elements correspond directly to the results of the method steps.
  • Motivation to Combine: As a single-reference ground, the argument focused on obvious modifications. Petitioner asserted that even if Costa’s third channel structure (173) is shown as the same size as the underlying hole, a person of ordinary skill in the art (POSITA) would be motivated to make it wider. This modification would provide a larger landing pad to account for known misalignment issues in non-self-aligned processes and better protect the underlying channel during subsequent fabrication steps. Such a design choice was a well-known technique to improve alignment margin and increase manufacturing yield. For dependent claim 5, which requires recessing certain layers, Petitioner argued a POSITA would be motivated to do so to reduce overall device height and improve contact resistance, both recognized goals in the art.
  • Expectation of Success: Petitioner asserted a POSITA would have a high expectation of success in making any necessary modifications. For example, recessing the channel and filling structures as required by claim 5 would involve standard anisotropic etching techniques that Costa already discloses and were well understood in the field. Similarly, widening the third channel structure involves routine adjustments to lithographic masks.

4. Key Claim Construction Positions

• Petitioner argued that the claims should be given their plain and ordinary meaning but addressed a specific interpretation of "first functional layer" from claim 4 advanced by the Patent Owner in co-pending litigation.
• The Patent Owner allegedly interprets the claim to cover a reversed sequence of sub-layer formation (e.g., forming a storage layer before a tunneling layer, even though the claim recites forming the storage layer "on the surface of the first tunneling layer").
• For the purposes of the petition, Petitioner adopted this interpretation for claim 4 and argued that Costa’s disclosure meets the limitations even under this reversed-order construction, as Costa teaches the formation of all the required sub-layers (tunneling, storage, barrier, and passivation) for its functional memory film.

5. Arguments Regarding Discretionary Denial

• Petitioner presented extensive arguments that discretionary denial under both 35 U.S.C. §314(a) (based on Fintiv factors) and §325(d) would be inappropriate.
• Fintiv Factors: Petitioner argued the factors weigh strongly in favor of institution. The scheduled trial date in the parallel district court litigation (June 15, 2026) is distant, ensuring that a Final Written Decision in the IPR would issue long before trial. Further, investment in the parallel litigation was described as minimal, as the ’291 patent was part of a recently added "Wave 3" of patents for which discovery was in its infancy. To eliminate any issue overlap, Petitioner stipulated that it would not pursue in the district court any invalidity ground raised or that could have been reasonably raised in the IPR.
• §325(d) Factors: Petitioner argued denial would be improper because its challenge is based on Costa, a prior art reference that was not before the Examiner during the original prosecution of the ’291 patent. Petitioner contended that Costa squarely discloses the very features—the "third channel structure" and "fifth channel structure"—that were identified as the basis for patentability, presenting a compelling case of unpatentability.

6. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-5, 8-9, 11-12, and 14-19 of the ’291 patent as unpatentable.