PTAB

IPR2019-00004

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

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1. Case Identification

2. Patent Overview

  • Title: Method for Low-Temperature Wafer Bonding
  • Brief Description: The ’549 patent discloses a method for bonding wafers at low or room temperature. The process is based on slightly etching a surface to activate it, terminating the activated surface with a desired chemical species, and then bringing it into contact with another surface to form a strong chemical bond without requiring high-temperature annealing.

3. Grounds for Unpatentability

Ground 1: Claims 53, 60-63, 67-70, 74-77, 83-86, and 89 are obvious over Li in view of Reiche.

  • Prior Art Relied Upon: Li (a 1998 journal article on low-temperature silicon bonding) and Reiche (a 1997 proceeding on plasma pretreatment for Si/Si bonding).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Li teaches a systematic process for low-temperature direct bonding of silicon and/or SiO2 surfaces. Li’s process involves a surface activation step using ammonia or oxygen plasma in a reactive ion etcher (RIE), followed by room-temperature bonding and a 200°C anneal to achieve a strong bond (>1000 mJ/m²). Petitioner contended this method teaches the core limitations of independent claim 53: exposing a surface to a plasma to enhance activation, terminating the surface with a species (e.g., NHx or OH groups from the plasma), and bringing it together with a second surface to obtain a strong chemical bond.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine Li with Reiche because Li identifies the need for smooth surfaces for successful bonding and uses plasma activation, while Reiche provides a detailed analysis of how RIE plasma treatments affect surface roughness. Reiche specifically teaches how to control plasma parameters to achieve hydrophilic surfaces and strong bonds while minimizing surface roughening. A POSITA would look to Reiche's detailed teachings to optimize the plasma activation step generally described in Li.
    • Expectation of Success: Petitioner asserted success would be expected because both references operate in the same field of wafer bonding, use similar plasma activation techniques, and pursue the same goal of strong, low-temperature bonds. Applying Reiche's specific optimization parameters to Li's process would predictably result in the desired outcome of a strong bond on a smooth surface.

Ground 2: Claims 53, 61, 67-68, 74-75, 83-84, and 86 are obvious over Kissinger in view of Reiche.

  • Prior Art Relied Upon: Kissinger (a 1993 journal article on low-temperature wafer-bond strengthening) and Reiche (a 1997 proceeding on plasma pretreatment).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Kissinger discloses the key elements of the claimed method. Kissinger describes using an oxygen plasma to activate wafer surfaces, followed by an RCA clean to make the surfaces hydrophilic (terminated with OH-groups), spontaneous bonding at room temperature, and subsequent annealing at 200°C. This process achieved very high bond strengths of almost 2000 mJ/m², mapping to the core steps of the challenged claims.
    • Motivation to Combine: The motivation to combine is analogous to Ground 1. A POSITA would be motivated to combine Kissinger's plasma activation method with Reiche's detailed analysis of RIE plasma treatments to better control and optimize the process. Reiche’s teachings on minimizing surface roughness during plasma etching would have been seen as a way to improve the quality and reliability of the bond strengthening described by Kissinger.
    • Expectation of Success: Petitioner claimed a POSITA would have had a high expectation of success, as Reiche provides a detailed recipe for achieving the very results (strong bonds, smooth surfaces) that Kissinger seeks to obtain through a similar plasma activation process.

Ground 3: Claims 63, 69, 76, and 89 are obvious over Kissinger and Reiche in view of Tong (1994).

  • Prior Art Relied Upon: Kissinger (a 1993 journal article), Reiche (a 1997 proceeding), and Tong (1994) (a 1994 review article on wafer bonding).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground builds on the Kissinger/Reiche combination to specifically address dependent claims requiring a nitrogen-comprising termination species. Petitioner argued that Kissinger's use of an RCA clean inherently teaches a nitrogen species, as the standard RCA1 solution contains ammonium hydroxide (NH4OH).
    • Motivation to Combine: Alternatively, if Kissinger's process was not viewed as inherently teaching nitrogen termination, a POSITA would be motivated to modify it by incorporating the teachings of Tong (1994). Tong explicitly teaches that treating wafers with NH4OH results in significantly higher bond strengths compared to treatments that yield OH-terminated surfaces (as in Kissinger's baseline process). A POSITA seeking to maximize bond strength—a primary goal of Kissinger—would be motivated to substitute the superior NH4OH treatment from Tong.
    • Expectation of Success: This was presented as a simple substitution of one known cleaning/termination agent for another to achieve a predictable improvement (stronger bonds), a routine optimization in the art.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including combining Li, Reiche, and Tong (Mar. 1994) to teach storing wafers in ambient post-bonding (Claim 92), and a similar combination based on Kissinger to teach the same.

4. Relief Requested

  • Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 53, 60-63, 67-70, 74-77, 83-86, 89, and 92 as unpatentable.