Sealing technique for wafer-level integrated cavity using In-Ag multilayers

L. Karpenkopf, N. Frage, A. Ripp, N. Froumin, M. P. Dariel

Research output: Contribution to journalConference articlepeer-review

2 Scopus citations


The performance of MOEMS (Micro-Optical-Electronic-Micro-Systems) may be significantly improved and their service life-time extended by packaging under vacuum. For numerous applications the bonding process temperature has to be below 200°C and sealed joints must withstand a reflow temperature (about 250-280°C) without debonding and unsealing. The Ag-In system has been selected for developing such a bonding process. In this study, the kinetics and sequence of intermetallic phase growth in a Ti/Ag/In/Ag multilayer structure with various ratios of thicknesses, deposited on a silicon substrate, was investigated by DSC (Differential Scaning Callorimetry), SEM and XRD analysis. The joints were examined by DSC to determine the re-melting temperatures and the quality of a cavity sealing was evaluated using a helium leak detection system. It was established that annealing a Ag/In multilayer with a total Ag to In layer thickness ratio equal to 3 and an overall thickness of about 10μm under vacuum of 10-7torr at 190°C for 40 min allows achieving a void-free joint consisting of two intermetallic phases Ag2In (γ) and AgIn2 (φ). A further appropriate thermal treatment at a relatively low temperature in air leads to the formation of the joint with a re-melting temperature higher than 300°C. The helium leak rate of the integrated cavity was experimentally estimated in the 5-10×10-9 mbar 1 s-1 range.

Original languageEnglish
Article number08
Pages (from-to)63-69
Number of pages7
JournalProgress in Biomedical Optics and Imaging - Proceedings of SPIE
StatePublished - 21 Jul 2005
EventReliability, Packaging, Testing and Characterization of MEMS/MOEMS IV - San Jose, CA, United States
Duration: 24 Jan 200525 Jan 2005


  • Ag-In thin layers
  • Intermetallic phases
  • Joining
  • Reactive diffusion

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Biomaterials
  • Radiology Nuclear Medicine and imaging


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