250°C wafer-level vacuum sealing using electroplated copper bonding frame planarized by fly-cutting

This article reports a wafer-level heterogeneous integration and vacuum packaging technology by thermocompression bonding using electroplated Cu sealing frame planarized by single-point diamond fly-cutting. A high grain boundary density on the Cu surface induced by mechanical stress application during fly-cutting process enables vacuum sealing with bonding temperature as low as 250°C. At such low bonding temperature, a less amount of gases is desorbed, resulting in a sealed cavity pressure lower than 100 Pa. Furthermore, the shear strength higher than 150 MPa using 50 μm width sealing frames is also achieved. The availability of the proposed technology as an integration platform for wafers with several μm structure is also demonstrated.