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We report a new wafer-level packaging technology for miniature MEMS in a hermetic micro-environment. The unique and new feature of this technology is that it only uses low cost wafer-level processes such as eutectic bonding, Bosch etching and mechanical lapping and thinning steps as compared to more expensive process steps that will be required in other alternative wafer-level technologies involving thru-silicon vias or membrane lids. We have demonstrated this technology by packaging silicon-based AlN microsensors in packages of size 1.3 x 1.3 mm 2 and 200 micrometer thick. Our initial cost analysis has shown that when mass produced with high yields, this device will cost $0.10 to $0.90.The technology involves first preparing the lid and MEMS wafers separately with the sealring metal stack of Ti/Pt/Au on the MEMS wafers and Ti/Pt/Au/Ge/Au on the lid wafers. On the MEMS wafers, the Signal/Power/Ground interconnections to the wire-bond pads are isolated from the sealring metallization by an insulating AlN layer. Prior to bonding, the lid wafers were Bosch-etched in the wirebond pad area by 120 m and in the center hermetic device cavity area by 20 m. The MEMS and the lid wafers were then aligned and bonded in vacuum or in a nitrogen environment at or above the Au-Ge Eutectic temperature, 363 o C. The bonded wafers were then thinned and polished first on the MEMS side and then on the lid side. The MEMS side was thinned to 100 ms with a nearly scratch-free and crack-free surface. The lid side was similarly thinned to 100 ms exposing the wire-bond pads. After thinning, a 100 m thick lid remained over the MEMS features providing a 20 m high hermetic microenvironment. Thinned MEMS/Lid wafer-level assemblies were then sawed into individual devices. These devices can be integrated into the next-level assembly either by wire-bonding or by surface mounting.The wafer-level packaging approach developed in this project demonstrated RF Feedthroughs with <0.3 dB insertion loss and adequate RF performance through 2 GHz. Pressure monitoring Pirani structures built inside the hermetic lids have demonstrated the ability to detect leaks in the package. In our preliminary development experiments, we have demonstrated >50% hermetic yields. *Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company for the United States Department of Energy under contract DE-AC04-94AL85000. I. IntroductionRF MEMS resonators and switches allow miniaturization of RF systems by offering unique and compelling performance improvements in miniature volumes.The high-Q and miniature size of RF MEMS resonators provides the opportunity for substantial miniaturization of RF filters and frequency references. The low loss and low capacitance of RF MEMS switches offer improved adaptability and switching functions. However, to take advantage of these technologies over incumbent components, the technology's performance benefits must be maintained in a miniature volume. How these components are packaged and integrated play a cru...

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