Residual stress in lithium niobate film layer of LNOI/Si hybridwafer fabricated using low-temperature bonding method

Ryo Takigawa, Toru Tomimatsu, Eiji Higurashi, Tanemasa Asano

Research output: Contribution to journalArticle

2 Citations (Scopus)

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 SiO 2 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/SiO 2 /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.

Original languageEnglish
Article number136
JournalMicromachines
Volume10
Issue number2
DOIs
Publication statusPublished - 2019 Feb 18

Keywords

  • Large mismatch of thermal expansion coefficient
  • Lithium niobate-on-insulator/Si hybrid wafer
  • Low-temperature wafer bonding
  • Residual stress in LN film layer
  • Surface-activated bonding

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Mechanical Engineering
  • Electrical and Electronic Engineering

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