Low-temperature bonding of a LiNbO3 waveguide chip to a Si substrate in ambient air for hybrid-integrated optical devices

Ryo Takigawa*, Eiji Higurashi, Tadatomo Suga, Satoshi Shinada, Tetsuya Kawanishi

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)


We report the low-temperature bonding of a lithium niobate (LiNbO 3) chip with gold (Au) thin film to a silicon (Si) substrate with patterned Au film for hybrid-integrated optical devices. The bonding was achieved by introducing the surface activation by plasma irradiation into the flip-chip bonding process. After the Au thin film (thickness: 500 nm) on the LiNbO3 chip (6 mm by 6 mm) and the patterned Au film (thickness: 2 μm) on the Si substrate (12 mm by 12 mm) were cleaned by using argon (Ar) radio-frequency (RF) plasma, Au-Au bonding was carried out in ambient air with applied static pressure (̃50 kgf). The LiNbO3 chips were successfully bonded to the Si substrates at relatively low temperature (< 100 °C). However, when the bonding temperature was increased to be greater than 150 °C, the LiNbO3 chips cracked during bonding. The tensile strength (calculated by dividing the total cross-sectional area of the initial, undeformed micropatterns) of the interface was estimated to be about 70 MPa (bonding temperature: 100 °C). It was sufficient for use in optical applications. These results show the potential for producing highly functional optical devices and for low-cost packaging of LiNbO3 devices.

Original languageEnglish
Title of host publicationOptomechatronic Micro/Nano Devices and Components II
Publication statusPublished - 2006 Dec 1
Externally publishedYes
EventOptomechatronic Micro/Nano Devices and Components II - Boston, MA, United States
Duration: 2006 Oct 32006 Oct 4

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherOptomechatronic Micro/Nano Devices and Components II
Country/TerritoryUnited States
CityBoston, MA


  • Au-Au bonding
  • Hybrid integration
  • LiNbO/Si hybrid structure
  • Surface-activated bonding

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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