MEMS atomic vapor cells sealed by Cu-Cu thermocompression bonding

MEMS atomic vapor cells have a large variety of applications in atomic devices such as chip-scale atomic clocks (CSACs), atomic magnetometers and atomic gyroscopes. We report here on the successful wafer-level hermetic sealing of such cells by Cu-Cu thermocompression bonding. This innovative method is used as an alternative to anodic bonding and allows to overcome some of its limitations. In particular, it enables a lower oxygen contamination inside the sealed volume and makes possible the use of alternative materials as substrates. These results pave the way to an improvement of the CSACs performances regarding long term frequency drift and lifetime.