Greenthread LLC v. Texas Instruments Inc Pursuant To Court Order Docket In Lead Case 2 23cv212

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Greenthread, LLC (Texas)
  • Defendant: Texas Instruments Incorporated (Delaware)
  • Plaintiff’s Counsel: McKool Smith, P.C.
• Case Identification: 2:23-cv-00157, E.D. Tex., 04/06/2023
• Venue Allegations: Plaintiff alleges venue is proper because Defendant maintains regular and established places of business in the district, including manufacturing facilities, and has committed alleged acts of infringement within the district.
• Core Dispute: Plaintiff alleges that Defendant’s broad portfolio of semiconductor products infringes six patents related to the use of graded dopant regions to improve semiconductor device performance.
• Technical Context: The technology at issue involves creating non-uniform dopant concentrations within semiconductor devices to generate electric fields that enhance the speed, efficiency, and reliability of components like transistors and memory cells.
• Key Procedural History: The complaint notes that the sole inventor of the patents-in-suit, Dr. G.R. Mohan Rao, is a former Senior Vice President of Defendant Texas Instruments. It also alleges that Defendant had pre-suit knowledge of the patented technology due to a citation of a Greenthread application during the prosecution of a Texas Instruments patent. The complaint further notes that claim constructions for the Greenthread patents have been adopted in prior litigation against other defendants.

Case Timeline

Date	Event
2004-09-03	Priority Date for all six patents-in-suit
2009-08-06	TI files application for its '683 patent, during which Greenthread's application was cited as prior art
2013-04-16	U.S. Patent No. 8,421,195 issues
2015-04-27	Inventor Dr. Rao assigns patents to 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
2023-04-06	Complaint filed

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

U.S. Patent No. 10,510,842 - Semiconductor Devices with Graded Dopant Regions

The Invention Explained

• Problem Addressed: The patent describes limitations in conventional semiconductor devices that use "uniformly doped" regions ('842 Patent, col. 1:54-59). This uniformity can limit the operating frequency of transistors and, in devices like DRAMs or image sensors, allow "spurious minority carriers" to degrade performance by, for example, reducing data retention time or creating "dark current" noise ('842 Patent, col. 2:15-26, col. 4:46-54).
• The Patented Solution: The invention proposes creating regions with a "graded dopant concentration" to establish an aiding "drift electric field" ('842 Patent, col. 3:3-5). This engineered field can accelerate the movement of desired charge carriers to improve switching speeds or, conversely, create a "subterranean" field to sweep unwanted minority carriers away from sensitive surface circuitry and deep into the substrate, thereby improving performance and reliability ('842 Patent, Abstract; col. 4:54-64).
• Technical Importance: This technique offered a way to enhance core performance metrics across a wide range of semiconductor applications by manipulating the fundamental physics of charge carrier transport within the device structure ('842 Patent, Abstract).

Key Claims at a Glance

• The complaint asserts infringement of at least one claim without specification (Compl. ¶ 51). Independent Claim 1 is representative.
• Essential elements of Independent Claim 1 include:
  • A substrate of a first doping type.
  • First and second separate active regions on the substrate where transistors can be formed.
  • Transistors formed in at least one of the active regions.
  • At least a portion of an active region having "at least one graded dopant concentration to aid carrier movement from the first surface to the second surface of the substrate." ('842 Patent, col. 4:45-62).
• The complaint reserves the right to assert additional claims (Compl. ¶ 50).

U.S. Patent No. 10,734,481 - Semiconductor Devices with Graded Dopant Regions

The Invention Explained

• Problem Addressed: As a continuation of the same patent family, the '481 Patent addresses the same technical problems stemming from uniformly doped regions in semiconductors, including limited operating frequency and performance degradation due to stray charge carriers in logic, memory, and imaging devices ('481 Patent, col. 1:50-58, col. 2:24-32).
• The Patented Solution: The solution is again the use of a graded dopant concentration to create a drift field. The specification explains this can improve performance in applications like "VLSI logic, DRAM/image IC, [and] nonvolatile memory IC" by controlling carrier movement to either enhance speed or mitigate noise ('481 Patent, Abstract; col. 4:55-61).
• Technical Importance: The invention provides a foundational technique for improving the performance of a wide array of high-volume semiconductor products by engineering the dopant profile to overcome inherent physical limitations ('481 Patent, Abstract).

Key Claims at a Glance

• The complaint asserts infringement of at least one claim without specification (Compl. ¶ 57). Independent Claim 1 is representative.
• Essential elements of Independent Claim 1 are similar to Claim 1 of the ’842 Patent but add a key limitation:
  • A substrate, first and second active regions, and transistors.
  • A portion of an active region with a "graded dopant concentration."
  • An additional element of "at least one well region adjacent to the first or second active region containing at least one graded dopant region" to aid carrier movement from the surface to the substrate ('481 Patent, col. 4:54-col. 5:3).
• The complaint reserves the right to assert additional claims (Compl. ¶ 56).

U.S. Patent No. 8,421,195 ('195 Patent)

Technology Synopsis

The earliest-issued patent in the asserted family, the '195 Patent discloses using graded dopant regions to create electric drift fields that improve semiconductor performance. It describes applications in devices like IGBTs, DRAMs, and image sensors by accelerating carrier transport or sweeping unwanted carriers away from active regions ('195 Patent, Abstract; col. 2:10-23).

Asserted Claims

At least one unspecified claim (Compl. ¶ 41).

Accused Features

Broad categories of semiconductor products that allegedly contain regions with graded dopant concentrations (Compl. ¶¶ 11, 34).

U.S. Patent No. 9,190,502 ('502 Patent)

Technology Synopsis

This patent continues the family's focus on improving semiconductor device performance by using graded dopant concentrations. The technology creates drift fields to control charge carrier movement, enhancing speed and reducing noise in applications from logic circuits to image sensors ('502 Patent, Abstract; col. 2:2-10).

Asserted Claims

At least one unspecified claim (Compl. ¶ 45).

Accused Features

Semiconductor products, exemplified by the BQ25123, alleged to be fabricated with processes that create graded dopant regions (Compl. ¶¶ 33, 34).

U.S. Patent No. 11,121,222 ('222 Patent)

Technology Synopsis

Continuing the same specification, the '222 Patent describes using graded dopant regions to establish electric drift fields. This technique is presented as a solution to improve operating frequency, refresh times in DRAM, and visual quality in image sensors by managing carrier transport ('222 Patent, Abstract; col. 2:5-19).

Asserted Claims

At least one unspecified claim (Compl. ¶ 63).

Accused Features

Texas Instruments' semiconductor devices alleged to incorporate graded dopant regions to improve performance, such as switching time (Compl. ¶¶ 11, 34).

U.S. Patent No. 11,316,014 ('014 Patent)

Technology Synopsis

The most recently issued patent in the asserted family, the '014 Patent also claims inventions related to semiconductor devices with graded dopant regions. It describes creating drift fields to enhance performance in digital logic, memory, and sensors by accelerating or clearing charge carriers ('014 Patent, Abstract; col. 2:19-32).

Asserted Claims

At least one unspecified claim (Compl. ¶ 69).

Accused Features

A wide range of Texas Instruments semiconductor ICs alleged to utilize graded dopant concentrations (Compl. ¶ 11).

III. The Accused Instrumentality

Product Identification

The complaint accuses a wide range of "Texas Instruments Accused Products," including amplifiers, processors, analog-to-digital converters, microcontrollers, and various other ICs (Compl. ¶ 11). It identifies the BQ25123 as one "exemplary" accused product (Compl. ¶ 33).

Functionality and Market Context

The complaint alleges that the Accused Products are semiconductor devices fabricated using processes that create "regions with graded dopant concentrations" (Compl. ¶ 34). This functionality is alleged to improve performance, for instance by "improving switching time in transistors" (Compl. ¶ 34). Plaintiff asserts that Texas Instruments is a "global semiconductor company" with approximately 80,000 products and 100,000 customers (Compl. ¶ 5). The complaint includes a photograph of a museum display for a one-megabit CMOS dynamic memory device to highlight the inventor's prior work and leadership role at Texas Instruments (Compl. p. 9).

IV. Analysis of Infringement Allegations

The complaint alleges that Defendant’s products, exemplified by the BQ25123, meet every element of at least one claim of each of the Greenthread Patents (Compl. ¶¶ 33, 39, 45, 51, 57, 63, 69). The core of the infringement theory is that Defendant "fabricates and designs" its semiconductor products using processes that inherently or intentionally create "regions with graded dopant concentrations" as claimed in the patents (Compl. ¶ 34). The complaint incorporates by reference an "Exhibit 8," which it states demonstrates how an exemplary product infringes, but this exhibit was not filed with the complaint (Compl. ¶ 12). Therefore, a detailed element-by-element analysis is not possible based on the complaint alone.

• Identified Points of Contention:
  • Scope Questions: A primary dispute may concern the scope of the term "graded dopant concentration." The question will be whether the dopant profiles in Defendant's products, which Defendant may characterize as "uniform" or as having only incidental process variations, meet the patent's requirement for a "graded" concentration that "aid[s] carrier movement."
  • Technical Questions: The central evidentiary question will be whether Plaintiff can prove, through reverse engineering or discovery of Defendant's fabrication processes, that the accused products actually contain the claimed structures. The complaint's general allegations raise the question of what specific evidence exists to show that the accused products' dopant profiles create the functional "drift field" described in the patents, as opposed to being a non-infringing artifact of manufacturing.

V. Key Claim Terms for Construction

• The Term: "graded dopant concentration"
• Context and Importance: This term is the technological core of all asserted patents and appears in the independent claims. The outcome of the infringement analysis will likely depend on its construction. Practitioners may focus on this term because its interpretation will determine whether standard semiconductor manufacturing variations fall within the claim scope, or if the claims are limited to specific, intentionally engineered dopant profiles.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The claims require a graded concentration that functions "to aid carrier movement" ('842 Patent, col. 4:60-62). Plaintiff may argue that any dopant profile, regardless of how it was formed, that results in this functional outcome meets the claim limitation. The specification broadly contrasts the invention with "uniformly doped" prior art, suggesting any non-uniform, functional profile could be considered "graded" ('842 Patent, col. 1:54-55).
  • Evidence for a Narrower Interpretation: The specification describes the gradient as creating a "suitable aiding drift electric field" and provides examples such as "linear, quasi linear, exponential or complimentary error function" profiles ('842 Patent, col. 3:1-5). Defendant may argue that the term is limited to such intentionally-created, mathematically definable profiles designed to produce a specific field, and does not read on unintentional or minor variations from a "uniform" target.

VI. Other Allegations

• Indirect Infringement: The complaint does not set forth specific factual allegations to support claims for indirect infringement (inducement or contributory infringement), focusing its narrative on Defendant's direct infringement through making, using, and selling the accused products (Compl. ¶ 32).
• Willful Infringement: Willfulness is explicitly alleged (Compl. ¶ 35). The complaint bases this allegation on purported pre-suit knowledge, stating that Texas Instruments was aware of the technology "at least through the USPTO's citation of Greenthread's application as prior art during prosecution of Texas Instrument's U.S. Patent No. 8,278,683," which was filed in 2009 (Compl. ¶ 35). The allegations of continued infringement after the filing of the suit may serve as a basis for post-suit willfulness (Compl. ¶¶ 41, 47, 53, 59, 65, 71).

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

• A core issue will be one of definitional scope: Can the claim term "graded dopant concentration", which the patents describe as creating a functional drift field, be construed to read on the dopant profiles present in Defendant’s mass-produced commercial semiconductors? The case may turn on whether incidental, process-inherent non-uniformities satisfy this limitation, or if proof of an intentionally engineered, sloped profile is required.
• A key evidentiary question will be one of technical proof: As the complaint’s infringement allegations rely on an unprovided exhibit, a central focus of the litigation will be Plaintiff's ability to demonstrate through technical evidence, likely from extensive reverse engineering and analysis of fabrication data, that the accused products in fact possess the claimed structural and functional features.
• The case also presents a question of intent and history: Given the inventor's distinguished twenty-two-year career at Texas Instruments, combined with the specific allegation of knowledge via patent prosecution, a notable aspect of the case will be whether this unique factual background can support a finding of willful infringement.