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The authors have successfully demonstrated an alternative method for high yield packaging process, offering a morphological insensitive and wafer level process. It enables not only the encapsulation to be hermetic but also the vias to be electrically-interconnected simultaneously. The mushroom structure of cap wafer makes the seal-line of solder void-free and the assembly process easier in wafer-alignment, giving room for the mismatched-volume between solder and trench. The mushroom structure is formed by SF6-based isotropic Si etch and the solder of Sn is electroplated by thick photoresist lithography. The vias are successfully sealed with solders shaped like a dome at the top corner and electrically interconnected. A gross leak detection of pressurized dye-penetration shows that this scheme is morphologically insensitive compared with the "face-to-face" bonding method.
Date of Conference: 5-9 June 2005