Wafer-Level Hermetic Seal Bonding at Low-Temperature with Sub-Micron Gold Particle Using Stencil Printing

Wafer-level low-temperature hermetic seal bonding has been successfully demonstrated using sub-micron-size gold particles (0.3 mu m mean diameter) with adopting a narrow-width rim structure to reduce the required total bonding force down to the range available on commercial wafer bonders. Conventional stencil printing combined with a newly developed suspended metal mask was employed as a cost-effective fabrication method to form sealing lines over the rim structure. Au-Au thermo-compression bonding using 10 ae m-wide rim structure was performed at 200 degrees C for 30 minutes with the bonding pressure of 200 MPa. An excellent hermeticity was achieved and the encapsulated pressure inside the sealed cavity was estimated to be around 100 Pa.