MEMS Wafer-Level Packaging Technology Using LTCC Wafer

This paper describes a versatile and reliable wafer-level hermetic packaging technology using an anodically bondable low-temperature co-fired ceramic (LTCC) wafer, in which multilayer electrical feedthroughs can be embedded. The LTCC wafer allows many kinds of microelectromechanical systems (MEMS) to be more flexibly designed and more easily packaged. The hermeticity of vacuum-sealed cavities was confirmed after 3000 cycles of thermal shock (-40 °C× 30 min/+125 °C× 30 min) by the diaphragm method. To practically apply the LTCC wafer to a variety of MEMS, the electrical connection between the MEMS on a Si wafer and feedthroughs in the LTCC should be established by a simple and reliable method. We have developed a new electrical connection method: the electrical connection is established by porous Au bumps, which are part of the Au vias exposed in wet-etched cavities on the LTCC wafer. A 100% yield of both electrical connection and hermetic sealing was demonstrated. A thermal shock test up to 3000 cycles confirmed the reliability of this packaging technology.