PTAB

IPR2019-00006

Samsung Electronics Co., Ltd. v. Invensas Bonding Technologies, Inc.

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1. Case Identification

2. Patent Overview

  • Title: Method for Bonding Using Etching and Chemical Bonding
  • Brief Description: The ’898 patent discloses a method for bonding semiconductor wafers at low or room temperature. The method involves slightly etching a bonding layer to activate the surface, terminating the surface with a desired chemical species, and then bringing the surfaces together to form a high-strength chemical bond.

3. Grounds for Unpatentability

Ground 1: Obviousness over Li and Reiche - Claims 1-4, 9, 13-16, 21, 26, 32, and 37 are obvious over Li in view of Reiche.

  • Prior Art Relied Upon: Li (a 1998 article in Jpn. J. Appl. Phys.) and Reiche (a 1997 Electrochemical Society Proceedings article).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Li disclosed all steps of the claimed bonding method. Li taught a systematic process for low-temperature direct bonding of silicon and SiO₂ surfaces, beginning with a surface activation step using ammonia or oxygen plasma in a reactive ion etcher (RIE). This activation, which constitutes the claimed "etching," was followed by bringing wafers into contact at room temperature and annealing at 200°C to achieve a strong bond (>1000 mJ/m²). Petitioner asserted that Li's plasma step inherently "terminates" the surface with species (e.g., Si-(NxHy) or Si-OH groups) that subsequently form the claimed chemical bond.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine Li and Reiche because they address the same problem of improving low-temperature wafer bonding. Li disclosed a general plasma activation process and acknowledged the need for "smooth, flat samples." Reiche investigated the specific effects of RIE plasma treatments on wafer bonding, providing detailed analysis on how to control the process to maintain surface smoothness while achieving strong bonds. Reiche’s detailed teachings on optimizing the plasma process would have been a natural and obvious improvement to apply to Li's method.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because Reiche provided explicit instructions for modifying plasma treatments (e.g., adjusting gas concentrations) to achieve minimal changes in surface roughness, directly addressing a known requirement for the process described in Li.

Ground 2: Obviousness over Kräuter and Reiche - Claims 1-4, 13-16, 26, 32, and 37 are obvious over Kräuter in view of Reiche.

  • Prior Art Relied Upon: Kräuter (a 1998 article in Sensors and Actuators A) and Reiche (a 1997 Electrochemical Society Proceedings article).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that Kräuter, like Li, disclosed the core elements of the challenged claims. Kräuter investigated low-temperature bonding of silicon wafers using oxygen plasma activation in a plasma etching apparatus to enhance bond strength. This process created a highly hydrophilic surface terminated by silanol (Si-OH) groups. The wafers were then bonded at room temperature and annealed at 200°C, achieving bonding energies over 1000 mJ/m². This process mapped directly to the claimed steps of etching, terminating, bringing surfaces together, and forming a strong chemical bond.
    • Motivation to Combine: The motivation to combine Kräuter with Reiche was similar to that for Ground 1. Kräuter disclosed an oxygen plasma process for bonding and noted the need for "sufficiently smooth" surfaces. Reiche provided a detailed investigation into the effects of such oxygen RIE processes on surface roughness. A POSITA would combine the references to apply Reiche's specific optimization techniques to Kräuter's process to ensure surface integrity while maximizing bond strength.
    • Expectation of Success: Success would be expected because both references taught using oxygen plasma activation on the same types of silicon/oxide surfaces to achieve the same goal of strong, low-temperature bonds. Applying Reiche's specific process controls to Kräuter's general method was a predictable optimization.

Ground 3: Obviousness over Kräuter, Reiche, and Tong - Claims 9 and 21 are obvious over Kräuter, Reiche, and Tong (1994).

  • Prior Art Relied Upon: Kräuter (a 1998 article), Reiche (a 1997 proceeding), and Tong (a 1994 article in Materials Chemistry and Physics).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground specifically addressed claims 9 and 21, which required the terminating species to comprise nitrogen. The combination of Kräuter and Reiche, as argued in Ground 2, taught a process that terminated surfaces with OH groups. Petitioner argued that Tong explicitly taught the superiority of using an ammonium hydroxide (NH₄OH) treatment—a nitrogen-comprising species—to achieve higher bond strengths compared to treatments that result in OH-terminated surfaces.
    • Motivation to Combine: A POSITA, starting with the process of Kräuter and Reiche aimed at achieving high bond strength, would be motivated to further improve the process. Tong provided a known technique for achieving even stronger bonds by replacing the standard OH-termination with a nitrogen-based NH₄OH treatment. Therefore, a POSITA would find it obvious to modify the Kräuter/Reiche process by substituting the OH termination with the superior nitrogen-based termination taught by Tong.
    • Expectation of Success: This modification was presented as an obvious-to-try scenario with a high expectation of success, as it involved substituting one known surface termination agent (leading to OH groups) with another known agent (Tong's NH₄OH) that was documented to produce better results for the same purpose.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including that claims were obvious over Kissinger and Reiche, and over Kissinger, Reiche, and Tong (1994). These grounds relied on similar logic, substituting Kissinger as the primary reference which also taught plasma activation for low-temperature wafer bonding.

4. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-4, 9, 13-16, 21, 26, 32, and 37 of the ’898 patent as unpatentable under 35 U.S.C. §103.