PTAB

IPR2019-00001

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

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1. Case Identification

2. Patent Overview

  • Title: Method for Bonding at Low or Room Temperature
  • Brief Description: The ’744 patent discloses a method for achieving high-strength bonds between wafers at low or room temperature. The process involves smoothing a bonding layer, performing a slight etch to activate the surface, terminating the surface with a desired chemical species, and bonding it to another prepared surface.

3. Grounds for Unpatentability

Ground 1: Obviousness over Li and Reiche - Claims 41, 44, and 45 are obvious over Li in view of Reiche.

  • Prior Art Relied Upon: Li (Y. Li et al., Systematic Low Temperature Silicon Bonding Using Pressure and Temperature, 1998) and Reiche (M. Reiche et al., The Effect of a Plasma Pretreatment on the Si/Si Bonding Behaviour, 1997).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Li taught the core elements of the claimed method, including a low-temperature process for bonding silicon and/or SiO₂ surfaces. Li's process involved activating the surfaces with an ammonia or oxygen plasma using a reactive ion etcher (RIE), followed by annealing at 200°C to achieve a high bond strength of over 1000 mJ/m². This mapped to the primary limitations of independent claim 41. For dependent claim 44, which requires maintaining surface roughness during etching, Petitioner asserted Reiche taught that RIE plasma treatments could be configured to only minimally alter surface roughness (a change of just 0.029 nm). For dependent claim 45, Petitioner argued Li’s disclosure of using an ammonia plasma taught the use of a "nitrogen-based" species for termination.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine Li and Reiche as both references seek to improve bond strength in low-temperature wafer bonding. Petitioner argued that since Li teaches a general plasma activation process and surface roughness is a known critical parameter, a POSITA would look to a reference like Reiche, which provides specific details on controlling roughness during the exact type of RIE process Li employed.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because Reiche provided explicit data and parameters for minimizing surface roughness during oxygen plasma RIE. Applying these known control techniques to Li's similar RIE process was argued to be a predictable modification.

Ground 2: Obviousness over Kräuter and Reiche - Claims 41 and 44 are obvious over Kräuter in view of Reiche.

  • Prior Art Relied Upon: Kräuter (G. Kräuter et al., Low Temperature Silicon Direct Bonding for Application in Micromechanics, 1998) and Reiche (M. Reiche et al., The Effect of a Plasma Pretreatment on the Si/Si Bonding Behaviour, 1997).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Kräuter, like Li, disclosed the fundamental steps of claim 41. Kräuter described a low-temperature bonding method using oxygen plasma activation followed by a chemical treatment to terminate surfaces with OH-groups. This process achieved high bond strengths (>1000 mJ/m²) after annealing at 200°C. The argument relied on the same logic as Ground 1 for claim 44, where Reiche was cited to teach the specific limitation of performing the plasma etch while keeping the surface roughness "substantially the same."
    • Motivation to Combine: The motivation was similar to Ground 1. Both Kräuter and Reiche address enhancing bond strength at moderate temperatures using plasma activation. Petitioner contended a POSITA implementing Kräuter's plasma process would be motivated to consult Reiche for its detailed analysis on how to control the known, critical variable of surface roughness.
    • Expectation of Success: Success would be expected because both references use oxygen plasma etching on silicon wafers. Applying Reiche's teachings on roughness control to Kräuter's process was argued to be a straightforward and predictable implementation of a known technique to optimize a known process.

Ground 3: Obviousness over Kräuter, Reiche, and Tong - Claim 45 is obvious over Kräuter and Reiche in view of Tong (1994).

  • Prior Art Relied Upon: Kräuter (G. Kräuter et al., 1998), Reiche (M. Reiche et al., 1997), and Tong (Q. Tong et al., Semiconductor Wafer Bonding: Recent Developments, 1994).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground built upon the combination in Ground 2 to address the "nitrogen-based" species limitation of claim 45. While Kräuter taught terminating surfaces with OH-groups, Petitioner argued Tong taught the superiority of using a nitrogen-based species. Tong disclosed that soaking silicon wafers in ammonium hydroxide (NH₄OH) prior to bonding results in a higher bond strength compared to treatments that terminate with OH-groups.
    • Motivation to Combine: A POSITA, having established the base process from Kräuter and Reiche, would be motivated to improve it. Since Kräuter's goal was to achieve high bond strengths, and Tong provided a direct comparison showing that nitrogen-based termination via NH₄OH was superior to the OH-group termination used by Kräuter, a POSITA would be motivated to substitute Kräuter's termination step with Tong's to achieve a better result.
    • Expectation of Success: Petitioner argued this was a simple and predictable substitution of one known surface termination agent for another known and superior agent to achieve an expected improvement. This represented an obvious design choice for a POSITA seeking to optimize the bonding process.

  • Additional Grounds: Petitioner asserted additional obviousness challenges against claims 41 and 44 over Kissinger in view of Reiche, and against claim 45 over Kissinger, Reiche, and Tong. These grounds relied on analogous arguments, with Kissinger serving as the primary reference teaching a low-temperature bonding process using plasma activation.

4. Relief Requested

  • Petitioner requests institution of inter partes review (IPR) and cancellation of claims 41, 44, and 45 of Patent 7,553,744 as unpatentable.