Ryo Takigawa

The feasibility of room-temperature (RT) bonding of vertical-cavity surface-emitting laser (VCSEL) chips on silicon (Si) substrates with Au microbumps was demonstrated by Au–Au surface-activated bonding. The diameter at the top, the height, and the pitch of Au microbumps measured approximately 5, 2, and 10 µm, respectively. Following activation of the Au surfaces with argon radio-frequency plasma, Au–Au bonding was carried out using contact at RT in ambient air. The measured results of light–cur

This paper demonstrates the application of ultra-precision cutting to the fabrication of ridged LiNbO₃ waveguides for use in low-loss photonic integrated circuits. Ridged waveguides with sidewall verticality of 88° and ultra-smooth sidewalls were obtained in LiNbO₃ crystals using this technique. In addition, the possibility of fabricating bent ridged waveguides via this mechanical micromachining method was examined. The root mean square surface roughness of the machined sidewall was 4.5 nm over

In this study, passive alignment and mounting of lithium niobate (LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) chips, with a large mismatch in the coefficient of thermal expansion with most semiconductors, are demonstrated for hybrid-integrated optical devices. LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> chips were aligned passively using the visual index alignment m

The air-gap structure between integrated LiNbO(3) optical modulators and micromachined Si substrates is reported for high-speed optoelectronic systems. The calculated and experimental results show that the high permittivity of the Si substrate decreases the resonant modulation frequency to 10 GHz LiNbO(3) resonant-type optical modulator chips on the Si substrate. To prevent this substrate effect, an air-gap was formed between the LiNbO(3) modulator and the Si substrate. The ability to fabricate

Lithium niobate-on-insulator (LNOI) waveguides fabricated on a silicon wafer using a room-temperature bonding method have potential application as Si-based high-density photonic integrated circuits. A surface-activated bonding method using a Si nanoadhesive layer was found to produce a strong bond between LN and SiO₂/Si at room temperature, which is sufficient to withstand both the wafer-thinning (LN thickness <5 μm) and surface micromachining processes used to form the strongly confi

In this paper, we report room-temperature bonding of LiNbO3 (LN) and SiO2/Si for the realization of a LN on insulator (LNOI)/Si hybrid wafer. We investigate the applicability of a modified surface activated bonding (SAB) method for the direct bonding of LN and a thermally grown SiO2 layer. The modified SAB method using ion beam bombardment demonstrates the room-temperature wafer bonding of LN and SiO2. The bonded wafer was successfully cut into 0.5 × 0.5 mm2 dies without interfacial debonding ow

This paper focuses on the residual stress in a lithium niobate (LN) film layer of a LN-on-insulator (LNOI)/Si hybrid wafer. This stress originates from a large mismatch between the thermal expansion coefficients of the layers. A modified surface-activated bonding method achieved fabrication of a thin-film LNOI/Si hybrid wafer. This low-temperature bonding method at 100 °C showed a strong bond between the LN and SiO₂ layers, which is sufficient to withstand the wafer thinning to a LN thickness of

A lithium niobate (LiNbO3)/silicon (Si) hybrid structure has been developed by the surface-activated bonding of LiNbO3 chips with gold (Au) thin film to Si substrates with patterned Au film. After organic contaminants on the Au surfaces were removed using argon radiofrequency plasma, Au-to-Au bonding was carried out in ambient air. Strong bonding at significantly low temperatures below 100◦C without generating cracks has been demonstrated. key words: low-temperature bonding, Au-to-Au bonding, su

We newly introduce a compliant rim to realize hermetic sealing of electronic components at low temperature. The compliant rim easily deforms under pressing load owing to its cone-shaped cross section and, therefore, intermetallic bonding can be performed at low temperature. We demonstrate the room-temperature vacuum sealing using the compliant rim made of Au with the aid of ultrasonic vibration of submicron amplitude. A test vehicle fabricated using silicon and glass showed that the air leak rat

This paper focuses on the bonding interface of LiNbO3 and Si wafers bonded by laser irradiation. The nanostructure and composite distribution across the bonding interface were investigated. The experimental interface analysis showed that no cracks or voids were formed at the nanolevel. It was also found that the bonding interface had a disordered amorphous layer containing Nb, O, and Si. This indicates that a strong bond was achieved because fusion bonding proceeded at the interface between LiNb

Abstract The heterogeneous integration of an LNOI waveguide device on a mature Si platform is interesting for the creation of a future high density and multi-functional platform. This paper reports the fabrication of a bent LNOI waveguide on Si substrate using surface activated bonding with a Si nanoadhesive layer and post-bond ultra-precision cutting at room temperature. This bonding method demonstrates the sufficient bond strength between an LN wafer and thermally grown SiO 2 to withstand duct

An InP substrate was directly bonded on a diamond heat spreader for efficient heat dissipation. The InP surface activated by oxygen plasma and the diamond surface cleaned with an NH₃/H₂O₂ mixture were contacted under atmospheric conditions. Subsequently, the InP/diamond specimen was annealed at 250 °C to form direct bonding. The InP and diamond substrates formed atomic bonds with a shear strength of 9.3 MPa through an amorphous intermediate layer with a thickness