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

doi:10.1117/12.690741

18 October 2006 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

Author Affiliations +

Proceedings Volume 6376, Optomechatronic Micro/Nano Devices and Components II; 637603 (2006) https://doi.org/10.1117/12.690741
Event: Optics East 2006, 2006, Boston, Massachusetts, United States

Abstract

We report the low-temperature bonding of a lithium niobate (LiNbO₃) 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.

Citation Download Citation

Ryo Takigawa, Eiji Higurashi, Tadatomo Suga, Satoshi Shinada, and Tetsuya Kawanishi "Low-temperature bonding of a LiNbO₃ waveguide chip to a Si substrate in ambient air for hybrid-integrated optical devices", Proc. SPIE 6376, Optomechatronic Micro/Nano Devices and Components II, 637603 (18 October 2006); https://doi.org/10.1117/12.690741

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