MEMS Wafer-Level Packaging Technology Using LTCC Wafer

摘要

This paper describes a versatile and reliable waferlevel 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 micro-electromechanical 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 ℃ × 30 min/+125 ℃ × 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.