DCT

1:23-cv-00326

Greenthread LLC v. Western Digital Corp

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:23-cv-00326, D. Del., 03/24/2023
  • Venue Allegations: Venue is alleged to be proper in the District of Delaware because Defendants are incorporated in Delaware and have purportedly committed acts of infringement within the district.
  • Core Dispute: Plaintiff alleges that Defendant’s semiconductor memory products, such as NAND flash memory, infringe six patents related to semiconductor devices employing graded dopant regions to improve performance.
  • Technical Context: The technology at issue concerns methods of manufacturing semiconductor devices with non-uniform dopant concentrations to create electric fields that aid or control the movement of charge carriers, a technique with market significance for improving the speed and efficiency of memory chips and processors.
  • Key Procedural History: The complaint alleges that Western Digital had notice of the patents-in-suit as early as August 2015. It also references prior litigation involving the same patent family against other technology companies (e.g., Samsung, Intel), noting that courts in the Eastern District of Texas, Western District of Texas, and District of Oregon have previously adopted the Plaintiff’s proposed claim constructions for key terms.

Case Timeline

Date Event
2004-09-03 Priority Date for all six Patents-in-Suit
2013-04-16 U.S. Patent No. 8,421,195 Issued
2015-04-27 Inventor Dr. Rao assigns patents to Plaintiff Greenthread
2015-08-14 Alleged first notice of patents to Western Digital via email
2015-11-17 U.S. Patent No. 9,190,502 Issued
2019-12-17 U.S. Patent No. 10,510,842 Issued
2020-08-04 U.S. Patent No. 10,734,481 Issued
2021-09-14 U.S. Patent No. 11,121,222 Issued
2022-04-26 U.S. Patent No. 11,316,014 Issued
2022-04-29 Alleged date after which Western Digital was again informed of infringement via litigation against Dell/Intel
2023-01-23 Alleged date of filing of amended complaint in other litigation providing further notice to Western Digital
2023-03-24 Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 8,421,195 - "Semiconductor Devices with Graded Dopant Regions"

  • Patent Identification: U.S. Patent No. 8,421,195, "Semiconductor Devices with Graded Dopant Regions," issued April 16, 2013.

The Invention Explained

  • Problem Addressed: The patent family addresses performance limitations in conventional semiconductor devices that arise from using uniformly doped regions. These limitations include reduced switching speeds in transistors and, in CMOS devices like DRAM and image sensors, undesirable effects from spurious minority charge carriers, such as degraded data retention (refresh time) and reduced image quality (’842 Patent, col. 1:41-53, col. 3:45-54).
  • The Patented Solution: The invention proposes using a non-uniform, or "graded," dopant concentration within the semiconductor substrate. This gradient creates a built-in "drift field" that actively directs the flow of charge carriers. This field can be used to accelerate desired carriers to improve speed or, as illustrated in the patent figures, to sweep unwanted minority carriers away from sensitive surface circuitry deep into the substrate, thereby preventing them from corrupting data or sensor readings (’842 Patent, Abstract; ’842 Patent, Fig. 5B).
  • Technical Importance: This approach provided a method for improving the operational speed, efficiency, and reliability of semiconductor devices, which is critical for scaling down feature sizes in products like processors and flash memory (’842 Patent, Abstract).

Key Claims at a Glance

  • The complaint alleges infringement of at least one claim without specifying which one (Compl. ¶45). Independent claim 1 is representative.
  • Essential elements of independent claim 1 include:
    • A CMOS Semiconductor device comprising a surface layer and a substrate.
    • An active region with a source and drain on the surface layer.
    • A "single drift layer" between the surface layer and substrate, which has a "graded concentration of dopants" creating a "first static unidirectional electric drift field" to move minority carriers from the surface layer to the substrate.
    • At least one "well region" within the drift layer, which also has a "graded concentration of dopants" creating a "second static unidirectional electric drift field" to move minority carriers from the surface layer to the substrate.

U.S. Patent No. 9,190,502 - "Semiconductor Devices with Graded Dopant Regions"

  • Patent Identification: U.S. Patent No. 9,190,502, "Semiconductor Devices with Graded Dopant Regions," issued November 17, 2015.

The Invention Explained

  • Problem Addressed: As a continuation of the '195 Patent, this patent addresses the same technical problems related to the performance limitations of semiconductor devices built with uniformly doped regions (’502 Patent, col. 1:40-67).
  • The Patented Solution: The solution is materially the same as that described for the ’195 Patent: the use of graded dopant concentrations to create static drift fields that control charge carrier movement for improved device performance (’502 Patent, Abstract; col. 4:1-17).
  • Technical Importance: The technical importance is identical to that of the '195 Patent, focusing on enabling faster, more efficient, and more reliable semiconductor devices (’502 Patent, Abstract).

Key Claims at a Glance

  • The complaint alleges infringement of at least one claim without specifying which one (Compl. ¶53). Independent claims 1 and 7 are representative.
  • Essential elements of independent claim 1 include:
    • A semiconductor device with a surface layer, substrate, and active region.
    • A "single drift layer" with a "graded concentration of dopants" creating a "first static unidirectional electric drift field" to aid carrier movement from the substrate to the surface layer.
    • At least one "well region" with a "graded concentration of dopants" creating a "second static unidirectional electric drift field" to aid carrier movement from the substrate to the surface layer.

Multi-Patent Capsules

  • U.S. Patent No. 10,510,842: "Semiconductor Devices with Graded Dopant Regions," issued December 17, 2019. This patent continues the same technology family, describing a semiconductor device with a substrate and multiple active regions where at least one portion has a graded dopant concentration to aid carrier movement from the device surface toward the substrate (’842 Patent, col. 4:44-60). The complaint asserts at least one claim (Compl. ¶61) against Western Digital’s semiconductor products, such as its NAND flash memory (Compl. ¶37).
  • U.S. Patent No. 10,734,481: "Semiconductor Devices with Graded Dopant Regions," issued August 4, 2020. This patent also belongs to the same family and describes a device with a well region containing a graded dopant region to aid carrier movement from the surface to the substrate (’481 Patent, Claim 1). The complaint asserts at least one claim (Compl. ¶69) against Western Digital’s semiconductor products, alleging they contain these infringing graded dopant regions (Compl. ¶37).
  • U.S. Patent No. 11,121,222: "Semiconductor Devices with Graded Dopant Regions," issued September 14, 2021. This patent continues the same technology, describing a VLSI semiconductor device with active regions and well regions, where graded dopant concentrations are used to aid carrier movement towards areas of the substrate where there are no active regions (’222 Patent, Claim 1). The complaint asserts at least one claim (Compl. ¶77) against Western Digital’s semiconductor products (Compl. ¶37).
  • U.S. Patent No. 11,316,014: "Semiconductor Devices with Graded Dopant Regions," issued April 26, 2022. This patent also continues the technology, describing an electronic system containing a semiconductor device with graded dopant regions in wells to aid carrier movement and form digital logic (’014 Patent, Claim 1). The complaint asserts at least one claim (Compl. ¶85) against Western Digital’s products (Compl. ¶37).

III. The Accused Instrumentality

  • Product Identification: The accused instrumentalities are "Western Digital Accused Products," defined as semiconductor devices and electronic products containing them, such as flash-based solid-state drives (“SSDs”), removable flash-based cards, and universal serial bus (“USB”) thumb drives (Compl. ¶2, ¶7). The complaint identifies the "SanDisk 15nm 16 GB NAND flash memory" as an exemplary accused product (Compl. ¶11).
  • Functionality and Market Context: The accused products are data storage devices sold under brands including Western Digital and SanDisk for computer, consumer electronics, and mobile telecommunications markets (Compl. ¶8). The relevant technical functionality is the physical architecture of the NAND flash memory chips within these devices (Compl. ¶37). The complaint provides a visual of a Texas Instruments 1-megabit DRAM display from the Smithsonian to establish the inventor's historical stature in the field of memory device development (Compl. p. 8). This photo shows a silicon wafer and packaged chip, underscoring the inventor's work on the fundamental components at issue in this case (Compl. p. 8).

IV. Analysis of Infringement Allegations

The complaint alleges that Western Digital’s accused products, particularly its NAND flash memory devices, are manufactured using processes that create "regions with graded dopant concentrations" (Compl. ¶37). It asserts that these structures meet every limitation of at least one claim of each of the Greenthread Patents (Compl. ¶36). The complaint states that its "Exhibit 8" provides a detailed analysis of how the exemplary SanDisk product infringes, but this exhibit was not attached to the publicly filed complaint (Compl. ¶11). Therefore, the specific, element-by-element infringement theory is not detailed in the provided document.

  • Identified Points of Contention:
    • Technical Questions: A central evidentiary dispute will likely concern the physical characteristics of the accused devices. The key question is whether reverse engineering and expert analysis will confirm that the accused NAND flash products possess a "graded" dopant concentration, as opposed to uniform or abruptly stepped concentrations. Further, it raises the question of whether any identified gradient produces the "static unidirectional electric drift field" required by the claims to aid carrier movement in the specified manner.
    • Scope Questions: The infringement analysis will turn on whether the physical structures within the accused devices can be mapped to the claimed elements. This raises questions such as: Does a distinct "single drift layer," as claimed in the '195 Patent, exist in the accused products, or is the region between the surface and substrate functionally and structurally different? Can the various doped regions in a complex 3D NAND architecture be fairly characterized as the "active regions" and "well regions" described in the patents?

V. Key Claim Terms for Construction

  • The Term: "graded dopant concentration"

    • Context and Importance: This term is the technological core of all asserted patents. Its construction will be dispositive for infringement, as it defines the essential feature that distinguishes the invention from prior art devices with uniform doping. Practitioners may focus on this term because its breadth will determine whether various non-uniform doping profiles found in modern semiconductors are covered.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The specification suggests the gradient can be "linear, quasi linear, exponential or complimentary error function," which may support a construction covering any intentional, non-uniform profile that produces a net drift field (’842 Patent, col. 3:1-3).
      • Evidence for a Narrower Interpretation: The specification consistently contrasts the invention with "uniformly doped" regions, which could support an argument that the term requires a smooth, continuous change in concentration and does not read on abrupt, stepped junctions between regions of different uniform concentrations (’842 Patent, col. 1:52-53).

  • The Term: "static unidirectional electric drift field"

    • Context and Importance: This term describes the function and character of the field created by the graded dopant concentration. The dispute will likely center on what "static" and "unidirectional" mean in the context of a complex, operating semiconductor device.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: A party could argue that "static" simply means the field is built-in due to the doping, as opposed to being externally applied, and "unidirectional" means there is a net, dominant direction of force on the charge carriers, even if minor field vectors exist in other directions.
      • Evidence for a Narrower Interpretation: The figures, such as Figure 5B of the '842 Patent, depict a simple, downward-only movement. A party could argue this supports a narrower construction requiring a field that is largely uniform in direction and present even in a quiescent state, potentially excluding more complex fields that may exist in the accused devices during operation.

VI. Other Allegations

  • Indirect Infringement: The complaint does not plead specific facts to support claims of induced or contributory infringement, focusing instead on Defendants' own alleged acts of making, using, and selling the accused products (Compl. ¶34).
  • Willful Infringement: The complaint explicitly alleges willful infringement (Compl. ¶46, ¶54, etc.). The allegations are based on Western Digital’s alleged pre-suit knowledge of the patents, citing a direct email communication to its attorney on August 14, 2015, as well as subsequent notice through Greenthread’s litigation against Dell and Intel, which involved the same Western Digital products (Compl. ¶38, ¶39).

VII. Analyst’s Conclusion: Key Questions for the Case

  • A primary issue will be one of evidentiary proof: Can Greenthread demonstrate, through reverse engineering and expert testimony, that the dopant profiles within Western Digital’s mass-produced NAND flash memory chips actually possess the specific "graded dopant concentration" required by the claims, and not merely stepped or otherwise non-uniform profiles?
  • The case will also turn on a question of claim scope: While prior courts have adopted Greenthread’s claim constructions, a central issue in this new case will be whether the term "graded dopant concentration" is broad enough to read on the manufacturing processes and resulting structures of the accused products. The outcome of this definitional dispute will likely determine infringement.
  • Finally, a key question for damages will be willfulness: Given the complaint’s specific allegations of pre-suit notice dating back to 2015, the court will need to determine if Western Digital acted recklessly by continuing its alleged infringement, which could expose it to the risk of enhanced damages.