Sealing of MEMS Atomic Vapor Cells Using Cu-Cu Thermocompression Bonding

Abstract

MEMS atomic vapor cells have a large variety of applications in chip-scale atomic devices such as clocks, gyroscopes or magnetometers. These cells are usually hermetically sealed by anodic bonding of borosilicate to silicon, a proven and reliable method, yet showing specific limitations such as inherent oxygen contamination of the cavity or limitation to a few combinations of materials. As an alternative, we report on the successful wafer-level fabrication of cells sealed by Cu-Cu thermocompression bonding. This alternative technique allows to overcome the constraints of anodic bonding while allowing a new variety of other materials. Characterization of the bonding quality is presented as well as a spectroscopic characterization in view of use for chip-scale atomic clocks (CSACs).