Residual Stress in Lithium Niobate Film Layer of LNOI/Si Hybrid Wafer Fabricated Using Low-Temperature Bonding Method

Abstract

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 approximately 5 μm using conventional mechanical polishing. Using micro-Raman spectroscopy, the residual stress in the bonded LN film in this trilayered (LN/SiO2/Si) structure was investigated. The measured residual tensile stress in the LN film layer was approximately 155 MPa, which was similar to the value calculated by stress analysis. This study will be useful for the development of various hetero-integrated LN micro-devices, including silicon-based, LNOI-integrated photonic devices.

Monolithic integrated cavity optomechanical accelerometer based on push-pull photonic crystal zipper cavity

“…The proof mass is suspended in the center of the acceleration-sensitive unit by highly stressed nanotethers. A high mechanical quality factor is achieved due to the inplane stress 21 of the lithium niobate single crystal thin film. The electrostatic force driving unit consists of four groups of parallel electrodes.…”

“…The 4.6-μm silicon dioxide layer is designed to improve the grating coupling efficiency. After calculation, 21 the inplane tensile stress in an lithium niobate (LN) layer is about 510 MPa. The mechanical vibration mode of the accelerometer is analyzed by finite element simulation with COMSOL multiphysics, as shown in Fig.…”

Progress in wafer bonding technology towards MEMS, high-power electronics, optoelectronics, and optofluidics

“…One of the feasible methods is using the heterogeneous integrated LiNbO 3 thin film to conduct the modulation to achieve the target of large capacity, large bandwidth, and high-speed data transmission. [88][89][90][91] Therefore, heterogeneous integration of LiNbO 3 is the first problem that needs to be overcome.…”

Planarization of Lithium Niobate Surface Using a Thin Film Catalyst in Pure Water

“…Recently, Matsuyama proposed an X-ray mirror element for X-ray microscopy using piezoelectric material as a mirror substrate [4]. Thanks to the non-linear optical, electro-optical, piezo-electrical, and pyro-electrical characteristics, single crystal Lithium Niobate (LiNbO3: LN) is the material of choice for the required mirrors [5]. This novel deformable mirror could correct the low spatial frequency mirror shape with nanometer precision with high stability.…”