Bonding-based wafer-level vacuum packaging using atomic hydrogen pre-treated Cu bonding frames

Koki Tanaka, Hideki Hirano, Masafumi Kumano, Joerg Froemel, Shuji Tanaka

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


A novel surface activation technology for Cu-Cu bonding-based wafer-level vacuum packaging using hot-wire-generated atomic hydrogen treatment was developed. Vacuum sealing temperature at 300 °C was achieved by atomic hydrogen pre-treatment for Cu native oxide reduction, while 350 °C was needed by the conventional wet chemical oxide reduction procedure. A remote-type hot-wire tool was employed to minimize substrate overheating by thermal emission from the hot-wire. The maximum substrate temperature during the pre-treatment is lower than the temperature of Cu nano-grain re-crystallization, which enhances Cu atomic diffusion during the bonding process. Even after 24 h wafer storage in atmospheric conditions after atomic hydrogen irradiation, low-temperature vacuum sealing was achieved because surface hydrogen species grown by the atomic hydrogen treatment suppressed re-oxidation. Vacuum sealing yield, pressure in the sealed cavity and bonding shear strength by atomic hydrogen pre-treated Cu-Cu bonding are 90%, 5 kPa and 100 MPa, respectively, which are equivalent to conventional Cu-Cu bonding at higher temperature. Leak rate of the bonded device is less than 10-14 Pa m3 s-1 order, which is applicable for practical use. The developed technology can contribute to low-temperature hermetic packaging.

Original languageEnglish
Article number181
Issue number4
Publication statusPublished - 2018 Apr 13


  • Atomic hydrogen
  • Cu thermos-compression bonding
  • Hot wire
  • Nano-grain
  • Wafer bonding
  • Wafer-level vacuum packaging


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