Texas Instruments Inc v. Greenthread LLC

1. Case Identification

• Case #: IPR2024-00674
• Patent #: 11,121,222
• Filed: March 12, 2024
• Petitioner(s): Texas Instruments Incorporated
• Patent Owner(s): Greenthread LLC
• Challenged Claims: 44

2. Patent Overview

• Title: CMOS Device Having Graded Dopant Concentrations
• Brief Description: The ’222 patent discloses a Complementary Metal-Oxide Semiconductor (CMOS) device with graded dopant concentrations. The technology aims to improve device performance by using specific doping profiles to create electric fields that aid the movement of charge carriers away from the active surface layer and into the substrate.

3. Grounds for Unpatentability

Ground 1: Obviousness over Payne - Claim 44 is obvious over Payne.

• Prior Art Relied Upon: Payne (Patent 4,684,971).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Payne, which is directed to a high-density CMOS structure, discloses every element of challenged claim 44. Payne teaches a nested well structure where shallow surface regions (the claimed "well region") are formed within deeper tub regions (the claimed "single drift layer"). Payne explicitly discloses a "high-low implant profile" with a dopant concentration that decreases with depth, which constitutes the graded concentration required for both the drift layer and the well region. Petitioner asserted that this downward-sloping graded concentration profile inherently creates a first static, unidirectional electric drift field in the deep tub and a second such field in the shallow well, both of which aid the movement of minority carriers from the surface layer into the substrate where no active regions exist.
  • Key Aspects: This ground asserted that a single prior art reference renders the claim obvious, relying on the inherent properties of the disclosed graded doping profile, which the patent owner’s predecessor-in-interest had previously admitted during prosecution of a parent patent would create the claimed electric fields.

Ground 2: Obviousness over Sakai in view of Kawagoe - Claim 44 is obvious over Sakai in view of Kawagoe.

• Prior Art Relied Upon: Sakai (Patent 4,907,058) and Kawagoe (Patent 6,043,114).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended that Sakai discloses a nested "twin double well" CMOS structure analogous to Payne's, thereby teaching the claimed "single drift layer" (Sakai's deep wells) and the "well region" disposed therein (Sakai's shallow wells). Sakai also teaches a high-to-low dopant concentration between its shallow and deep wells. While Sakai teaches the core structure, Kawagoe explicitly teaches implementing a gradually decreasing dopant concentration in CMOS wells. The combination of Sakai’s structure with Kawagoe’s graded profile provides a structure with a graded concentration extending from the surface layer to the substrate, which creates the claimed first and second static electric drift fields.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine Sakai and Kawagoe to improve device reliability. Both are Hitachi patents directed at CMOS technology. Sakai teaches high-density structures for memory devices (SRAMs), and it was well known that increasing device density makes them more susceptible to soft errors caused by alpha particles. Kawagoe directly addresses this problem, teaching that its graded dopant profile reduces soft errors by creating an electric field that sweeps unwanted, alpha-particle-generated carriers away from the active regions and into the substrate. A POSITA would thus apply Kawagoe's known soft-error reduction technique to Sakai's high-density device.
  • Expectation of Success: A POSITA would have a high expectation of success because creating the required graded dopant profile in Sakai's structure would involve well-known and predictable fabrication techniques, such as ion implantation and thermal diffusion, which were widely taught in the art.

4. Arguments Regarding Discretionary Denial

• §314(a) (Fintiv Factors): Petitioner argued against discretionary denial under Fintiv, asserting that the merits of the petition are exceptionally strong, particularly the single-reference obviousness ground over Payne. Furthermore, the scheduled trial date in the parallel district court litigation (March 3, 2025) is after the anticipated Final Written Decision (FWD) for a related IPR proceeding (IPR2023-01244) that this petition seeks to join, minimizing concerns about inefficiency and duplicative efforts.
• §325(d): Petitioner argued that the Board should not deny institution under §325(d) because the Examiner made a material error during prosecution and the current grounds are not cumulative to the art considered. The Examiner’s allowance was based on a reference (Hong) that is not prior art to the ’222 patent. The key prior art references asserted in the petition—Payne, Sakai, and Kawagoe—were either not discussed by the Examiner (Payne, Sakai) or not cited at all (Kawagoe). Therefore, the Examiner never considered the specific teachings and combinations presented in the petition.

5. Relief Requested

• Petitioner requests institution of an inter partes review (IPR) and cancellation of claim 44 of the ’222 patent as unpatentable.