DCT

1:23-cv-00579

Greenthread LLC v. Monolithic Power Systems Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:23-cv-00579, D. Del., 05/26/2023
  • Venue Allegations: Venue is alleged to be proper in the District of Delaware because the Defendant is a Delaware corporation and has allegedly committed acts of infringement in the district.
  • Core Dispute: Plaintiff alleges that Defendant’s semiconductor devices and electronic products containing them infringe six patents related to the use of graded dopant regions to improve semiconductor performance.
  • Technical Context: The technology concerns the fundamental design of semiconductor devices, proposing that a non-uniform (graded) concentration of dopants can create electric fields that improve device speed, efficiency, and reliability.
  • Key Procedural History: The complaint alleges that Defendant had pre-suit knowledge of the patent family because a publication corresponding to the '195 Patent was cited by the USPTO during the prosecution of one of Defendant's own patents. The patents-in-suit were invented by Dr. G.R. Mohan Rao and assigned to Greenthread in 2015.

Case Timeline

Date Event
2004-09-03 Priority date for all six asserted Greenthread Patents
2013-04-16 U.S. Patent No. 8,421,195 issues
2015-04-27 Dr. Rao assigns patents to Plaintiff Greenthread
2015-11-17 U.S. Patent No. 9,190,502 issues
2019-12-17 U.S. Patent No. 10,510,842 issues
2020-08-04 U.S. Patent No. 10,734,481 issues
2021-09-14 U.S. Patent No. 11,121,222 issues
2022-04-26 U.S. Patent No. 11,316,014 issues
2023-05-26 Complaint filed

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

U.S. Patent No. 8,421,195 - “Semiconductor Devices with Graded Dopant Regions,” issued April 16, 2013

The Invention Explained

  • Problem Addressed: The patent describes limitations in conventional semiconductor devices, which typically use uniformly doped regions. In Bipolar Junction Transistors (BJTs), this uniform doping limits the speed of charge carriers, thereby capping the maximum frequency of operation. In other devices like DRAMs, unwanted minority carriers can degrade performance by causing issues such as discharging stored data, while in image sensors they can reduce image quality ('195 Patent, col. 1:40-52, col. 2:59-67).
  • The Patented Solution: The invention proposes intentionally creating a non-uniform, or "graded," dopant concentration within specific regions of a semiconductor device. This gradient establishes a "static unidirectional electric drift field" that actively aids the movement of charge carriers. This field can be used to accelerate desired carriers to improve switching speed or to sweep unwanted minority carriers away from critical active areas and into the substrate where they can be harmlessly recombined ('195 Patent, col. 3:9-25; Fig. 5B).
  • Technical Importance: This technique provides a method to enhance device performance—including speed, power efficiency, and data integrity—at the structural level, offering an alternative or complement to performance gains from shrinking transistor feature sizes ('195 Patent, col. 1:53-58).

Key Claims at a Glance

  • The complaint asserts at least one claim of the '195 Patent without specifying which; Claim 1 is the first independent claim ('195 Patent, col. 4:13-41).
  • Essential Elements of Independent Claim 1:
    • A CMOS Semiconductor device comprising: a surface layer; a substrate; an active region including a source and a drain on the surface layer.
    • A single drift layer between the surface layer and the substrate.
    • The drift layer has a graded concentration of dopants extending between the surface layer and the substrate.
    • This graded concentration creates a first static unidirectional electric drift field to aid the movement of minority carriers from the surface layer to the substrate.
    • At least one well region in the single drift layer, which itself has a graded concentration of dopants.
    • This second graded concentration creates a second static unidirectional electric drift field to aid minority carrier movement from the surface layer to the substrate.
  • The complaint reserves the right to assert other claims, including dependent claims (Compl. ¶47).

U.S. Patent No. 9,190,502 - “Semiconductor Devices with Graded Dopant Regions,” issued November 17, 2015

The Invention Explained

  • Problem Addressed: As part of the same patent family, the '502 Patent addresses the same fundamental problems as the '195 Patent. It notes that in devices like DRAMs and image sensors, spurious minority carriers generated by normal operation can "discharge dynamically-held 'actively held high' nodes," degrading refresh times and pixel resolution ('502 Patent, col. 3:24-33).
  • The Patented Solution: The solution is again the implementation of graded dopant regions to create built-in electric fields. The patent describes this as a "novel technique" that creates a drift field to "sweep these unwanted minority carriers from the active circuitry at the surface into the substrate in a monolithic die as quickly as possible" ('502 Patent, col. 3:40-44). The specification explains this can be implemented via a "deeply-implanted layer" or an "epitaxial layer" ('502 Patent, col. 3:47-49).
  • Technical Importance: The invention aims to improve the reliability and performance of high-density integrated circuits where managing unwanted electrical noise and charge leakage is critical ('502 Patent, col. 3:24-33).

Key Claims at a Glance

  • The complaint asserts at least one unspecified claim of the '502 Patent; Claim 1 is an independent claim ('502 Patent, col. 4:19-48).
  • Essential Elements of Independent Claim 1:
    • A semiconductor device comprising: a surface layer; a substrate; an active region with a source and drain.
    • A single drift layer between the surface and substrate with a graded concentration of dopants, generating a first static unidirectional electric drift field to aid carrier movement from substrate to surface layer.
    • At least one well region within the drift layer, also having a graded concentration of dopants, generating a second static unidirectional electric drift field to aid carrier movement from substrate to surface layer.
  • The complaint reserves the right to assert other claims (Compl. ¶55).

Multi-Patent Capsule: U.S. Patent No. 10,510,842

  • Patent Identification: U.S. Patent No. 10,510,842, “Semiconductor Devices with Graded Dopant Regions,” issued December 17, 2019.
  • Technology Synopsis: This patent continues the theme of using graded dopant concentrations to create electric fields within a semiconductor device. These fields are designed to improve performance by controlling the movement of charge carriers, such as by accelerating their transit or by sweeping unwanted carriers away from active regions to improve signal integrity ('842 Patent, Abstract; col. 3:2-10).
  • Asserted Claims: At least one unspecified claim is asserted (Compl. ¶65); the patent contains independent claims 1 and 9.
  • Accused Features: The complaint alleges that Defendant’s semiconductor products, including those used in power management and other integrated circuits, contain structures with graded dopant regions that infringe (Compl. ¶¶ 38, 43-45).

Multi-Patent Capsule: U.S. Patent No. 10,734,481

  • Patent Identification: U.S. Patent No. 10,734,481, “Semiconductor Devices with Graded Dopant Regions,” issued August 4, 2020.
  • Technology Synopsis: This patent describes semiconductor devices, such as CMOS transistors, DRAM, and image sensors, that incorporate a graded dopant concentration in regions like the substrate or wells. This grading creates a built-in drift field intended to enhance performance by improving refresh times, reducing programming times, or increasing pixel resolution by managing minority carrier movement ('481 Patent, Abstract; col. 3:50-60).
  • Asserted Claims: At least one unspecified claim is asserted (Compl. ¶73); the patent contains independent claims 1 and 20.
  • Accused Features: The complaint alleges that a wide range of Defendant's semiconductor products contain infringing graded dopant structures (Compl. ¶¶ 38, 43-45).

Multi-Patent Capsule: U.S. Patent No. 11,121,222

  • Patent Identification: U.S. Patent No. 11,121,222, “Semiconductor Devices with Graded Dopant Regions,” issued September 14, 2021.
  • Technology Synopsis: This patent claims VLSI semiconductor devices and systems containing them, where performance is enhanced by using graded dopant concentrations. The resulting static electric fields are described as aiding carrier movement away from the active surface toward the substrate to prevent interference with digital logic operations, thereby improving device reliability ('222 Patent, Abstract; cl. 1).
  • Asserted Claims: At least one unspecified claim is asserted (Compl. ¶81); the patent contains independent claims 1, 21, 39, 41, 42, 43, and 44.
  • Accused Features: The complaint accuses Defendant’s semiconductor devices of incorporating the patented graded dopant technology (Compl. ¶¶ 38, 43-45).

Multi-Patent Capsule: U.S. Patent No. 11,316,014

  • Patent Identification: U.S. Patent No. 11,316,014, “Semiconductor Devices with Graded Dopant Regions,” issued April 26, 2022.
  • Technology Synopsis: This patent claims electronic systems that include a semiconductor device with graded dopant regions. The invention focuses on creating engineered drift fields to control carrier movement, which can improve the operational frequency of digital logic, enhance refresh times in memory, or improve visual quality in image sensors ('014 Patent, Abstract; col. 1:48-58).
  • Asserted Claims: At least one unspecified claim is asserted (Compl. ¶89); the patent contains independent claims 1 and 21.
  • Accused Features: The complaint’s infringement allegations cover Defendant's broad portfolio of semiconductor products that allegedly use graded dopant regions (Compl. ¶¶ 38, 43-45).

III. The Accused Instrumentality

  • Product Identification: The complaint broadly accuses "MPS Accused Products," defined as semiconductor devices and electronic products containing them (Compl. ¶5). This includes a wide range of product categories, such as "switching converters and controllers, multi-phase controllers, power management integrated circuits, USB switches, load switches, MOFSET drivers, digital isolators, isolated DC/DC converters," and many others containing transistors (Compl. ¶38). The complaint identifies the "MPS MP86905 monolithic half-bridge" as an exemplary accused product (Compl. ¶42). A screenshot in the complaint shows the product page for the "MPQ4425M-AEC1," an automotive-grade LED driver, which is also identified as an Accused Product (Compl. p. 4; ¶8, fn. 2).
  • Functionality and Market Context: The complaint alleges that the Accused Products are semiconductor devices that incorporate "infringing structures" (Compl. ¶5). The core accused functionality is the use of regions with "graded dopant concentrations" to improve device performance, such as switching speed (Compl. ¶¶ 43, 45). The complaint alleges Defendant sells these products through direct and indirect channels, including to customers for "product development" and "design wins" (Compl. ¶¶ 7, 9). The complaint includes a screenshot from Defendant's website for the EVKT-MP2651, an evaluation kit used to demonstrate the capabilities of a buck-boost charger IC and secure design wins with customers (Compl. p. 5; ¶10).

IV. Analysis of Infringement Allegations

The complaint alleges that an exemplary product, the MPS MP86905, "meets each and every element of at least one claim of the Greenthread Patents" and refers to a detailed analysis in an "Exhibit 8" (Compl. ¶¶ 42, 49). However, Exhibit 8 was not filed with the complaint. The infringement theory articulated in the body of the complaint is that Defendant designs and manufactures its devices using processes that "utilize substantially similar process steps, including process steps for creating regions with graded dopant concentrations" (Compl. ¶44-45).

'195 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A CMOS Semiconductor device, comprising: a surface layer; a substrate; an active region including a source and a drain, disposed on one surface of said surface layer; Defendant designs, manufactures, and sells semiconductor devices, including the exemplary MP86905 monolithic half-bridge, for use in integrated circuits. ¶5, ¶38, ¶42 col. 4:14-18
a single drift layer disposed between the other surface of said surface layer and said substrate, said drift layer having a graded concentration of dopants... The Accused Products allegedly include and utilize regions with graded dopant concentrations. ¶45, ¶49 col. 4:19-22
...generating a first static unidirectional electric drift field to aid the movement of minority carriers from said surface layer to said substrate; The complaint alleges the accused structures are used to improve performance, such as switching speed, consistent with the function of the claimed drift field. ¶43, ¶45 col. 4:23-26
and at least one well region disposed in said single drift layer, said well region having a graded concentration of dopants... The Accused Products are alleged to be substantially similar to the exemplary device shown in Exhibit 8, which allegedly has infringing structures with graded dopants. ¶45 col. 4:27-36

'502 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A semiconductor device comprising: a surface layer; a substrate; an active region including a source and a drain, disposed on one surface of said surface layer; Defendant’s Accused Products are semiconductor devices containing transistors and other structures for use in various electronic products. ¶5, ¶38 col. 4:20-25
a single drift layer disposed between the other surface of said surface layer and said substrate, said drift layer having a graded concentration of dopants... The complaint alleges that Defendant’s devices are made with processes that create regions with graded dopant concentrations. ¶44, ¶45, ¶57 col. 4:26-32
...generating a first static unidirectional electric drift field to aid the movement of minority carriers from said substrate to said surface layer; The complaint alleges these structures improve the performance of the Accused Products, which is the stated purpose of the claimed drift field. ¶43, ¶45 col. 4:33-36
and at least one well region disposed in said single drift layer, said well region having a graded concentration of dopants... The complaint alleges the Accused Products are illustrative of the technology and meet the claim limitations, as detailed in the unfiled Exhibit 8. ¶45, ¶57 col. 4:37-45
  • Identified Points of Contention:
    • Evidentiary Questions: The complaint's infringement allegations rely heavily on conclusory statements and reference to an unfiled exhibit. A primary point of contention will be whether Plaintiff can produce evidence from the accused products themselves—through reverse engineering or discovery—to show the presence of the claimed "graded dopant concentration" in a "drift layer" and "well region."
    • Technical Questions: A key technical question will be whether any dopant variations found in the accused products are sufficiently "graded" to create the "static unidirectional electric drift field" required by the claims, or if they are merely incidental process variations without the claimed function of "aiding carrier movement." The complaint's allegation that the purpose is to "improve switching speed" (Compl. ¶43) suggests this functional requirement is central to its theory.

V. Key Claim Terms for Construction

For U.S. Patent No. 8,421,195 and U.S. Patent No. 9,190,502

  • The Term: "graded dopant concentration"
  • Context and Importance: This term is the core of the asserted patents' novelty. The definition will be critical for determining infringement. Practitioners may focus on this term because its construction will decide whether any variation in doping concentration is sufficient, or if a specific, intentionally engineered profile with a demonstrable function is required.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The specification states the gradient can be "linear, quasi linear, exponential or complimentary error function" ('195 Patent, col. 3:1-3), suggesting that the precise profile is not limiting, as long as a gradient exists.
    • Evidence for a Narrower Interpretation: The specification repeatedly ties the graded dopant concentration to a specific function: creating an "aiding drift electric field" to "enhance the diffusing minority carrier's speed" or "sweep... unwanted minority carriers" ('195 Patent, col. 1:54-58, col. 3:41-44). A defendant may argue that this functional language requires the gradient to be significant enough to achieve a material performance improvement, such as the "2x-5x" improvement in cut-off frequency mentioned in the specification ('195 Patent, col. 3:9-10).

VI. Other Allegations

  • Indirect Infringement: The complaint alleges inducement of infringement, stating that Defendant designs and markets infringing products for use in the U.S. (Compl. ¶52, ¶60). It further alleges that Defendant assists customers in designing its products into their own systems and provides "Evaluation Kits," which may be argued as evidence of encouraging infringing acts by third parties (Compl. ¶¶ 10-11).
  • Willful Infringement: Willfulness is alleged based on both pre-suit and post-suit knowledge. The complaint asserts pre-suit knowledge by alleging that a Greenthread patent publication, which issued as the '195 Patent, was cited by the USPTO during the prosecution of Defendant's own U.S. Patent No. 8,598,637, putting Defendant on notice of the technology "since before 2013" (Compl. ¶39). Knowledge as of the filing of the suit is also alleged (Compl. ¶40).

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

This case appears to center on highly technical questions of semiconductor structure and the legal interpretation of the claims that define it. The resolution will likely depend on the following key questions:

  • A primary issue will be one of claim construction: how will the court define "graded dopant concentration"? The case will likely turn on whether this term requires a specific, intentionally engineered dopant profile that produces a material performance improvement, or if it can be construed more broadly to cover other types of non-uniform dopant distributions found in the accused products.
  • A central question will be evidentiary: beyond the conclusory allegations and reference to an unfiled exhibit in the complaint, what factual evidence will emerge during discovery to demonstrate that Defendant's products actually contain the specific multi-part "drift layer" and "well region" structures with the functionally-defined "graded" dopant profiles required by the claims?
  • A key question for damages will be willfulness: does the complaint's allegation that Defendant was aware of the technology via a citation in its own patent's prosecution history constitute pre-suit knowledge sufficient to support a finding of willful infringement, potentially leading to enhanced damages?