PTAB

IPR2025-00500

Yangtze Memory Technologies Co Ltd v. Micron Technology Inc

Key Events

Petition

petition

Title: Integrated Circuitry with Dummy Structures
Brief Description: The ’737 patent discloses integrated circuitry for three-dimensional (3D) NAND memory devices. The technology addresses a manufacturing problem where stacked, horizontally extending features may sag, bend, or break after sacrificial material is removed; the patent purports to solve this by forming vertical "dummy structures" in the end portions of the stack to provide physical support.

Prior Art Relied Upon: Chae (Application # 2010/0133598)
Core Argument for this Ground:
- Prior Art Mapping: Petitioner argued that Chae discloses all limitations of the challenged claims. Chae teaches a 3D nonvolatile memory device with a stack of conductive gate electrodes divided into a memory cell region (“primary portion”) and a contact region (“end portion”) with a stair-step shape. To solve the same problem of stack collapse during etching, Chae explicitly discloses forming "supporters" that extend vertically through the gate lines in the contact region. Petitioner contended these supporters are structurally and functionally identical to the claimed "dummy structures," and that Chae’s "active pillars" in the memory region correspond to the claimed "operative structures."

Prior Art Relied Upon: Chae (Application # 2010/0133598) and Kiyotoshi (Application # 2011/0156132)
Core Argument for this Ground:
- Prior Art Mapping: This ground addressed claims requiring specific structural forms, such as the operative and dummy structures comprising hollow cylinders filled with a dielectric. While Chae teaches solid pillars, Kiyotoshi discloses forming semiconductor channels as hollow, "macaroni-shaped" cylinders filled with a dielectric material.
- Motivation to Combine: A POSITA would combine Kiyotoshi’s teaching with Chae’s device to gain known performance benefits. Kiyotoshi explains that a macaroni shape improves transistor characteristic uniformity and reduces interference between memory cells. A POSITA would have been motivated to apply this known technique to improve Chae’s similar 3D NAND device.
- Expectation of Success: Petitioner asserted success would be expected, as the proposed modification involves applying known fabrication techniques (e.g., LPCVD, ALD), as detailed in Kiyotoshi, to a conventional 3D NAND architecture like Chae’s.

Prior Art Relied Upon: Jeong (Application # 2017/0352674)
Core Argument for this Ground:
- Prior Art Mapping: This ground focused on independent claim 18, which requires "the contacts and dummy structures having different horizontal cross-sections relative one another." Petitioner argued that Jeong, which also discloses a 3D memory device with operative vertical patterns and supportive dummy pillars, directly teaches this limitation. Jeong expressly states that the plan-view size or diameter of its dummy pillars is smaller than that of its contact plugs, thereby disclosing different horizontal cross-sections. This disclosure was argued to anticipate or, at a minimum, render obvious claim 18 and dependent claim 20.
Additional Grounds: Petitioner asserted an additional obviousness challenge against claims 18 and 20 over Chae in view of Hwang (Application # 2011/0151667). This argument relied on modifying Chae’s circular contacts to have a rectangular cross-section, as taught by Hwang, to reduce electrical resistance, which would result in contacts and dummy structures having different cross-sectional shapes.

"dummy structure": Petitioner argued this term should be construed as an "electrically inoperable structure that mimics a physical property of an operative structure." This construction was based on the patent’s specification and an agreement between the parties in related district court litigation.

Priority Date of Claims 18 and 20: A central contention was that claims 18 and 20 are not entitled to the priority date of any parent applications. Petitioner argued that the limitation "the contacts and dummy structures having different horizontal cross-sections" lacks written description support in the parent specifications. The parent patents allegedly fail to describe the cross-section of contacts at all, rendering any depiction in their figures merely diagrammatic and insufficient to demonstrate possession of the invention. This position, if accepted, subjects claims 18 and 20 to prior art like Jeong, which was published after the claimed priority date but before the ’737 patent’s filing date.

Petitioner argued that discretionary denial under §325(d) would be improper because the primary references relied upon (Chae, Jeong, Hwang) were never presented to or considered by the USPTO during the original examination. While Kiyotoshi was cited in an IDS, Petitioner contended it was not used in the combination or for the specific teachings relied upon in the petition, and that the Examiner erred in overlooking its relevance.
Petitioner also argued against discretionary denial under §314(a) and the Fintiv factors, stating that the ’737 patent is not currently asserted in any parallel litigation. Petitioner noted that while the Patent Owner has filed a motion to add the patent to a district court case, the petition was filed before a decision on that motion, representing exceptional circumstances that weigh against denial.

Petitioner requested the institution of an inter partes review and the cancellation of claims 1-12, 14, 15, 18, and 20-22 of the ’737 patent as unpatentable.