Structure Design And Process Integration Of Wafer Level Vacuum Packaging For MEMS

Hermeticity packaging is a critical technology in the MEMS fabrication technology. Wafer level packaging is considered to be the most potential method to achieving small size and low-cost of MEMS, expected to replace traditional metal packaging and ceramic packaging as the new generation large-scale packaging style for MEMS.Based on the packaging requirements of a specific MEMS, designed a bond solution to achieve bond between two wafers with electroplating solder layer ring on the wafer. This work researched the wafer-level vacuum packaging MEMS device structure design and process integration of the whole process.Because of the decreasing of cavity volume, wafer level packaging requires lower leakage than traditional metal packaging or ceramic packaging. Reasonable structure design, reliable bonding process and efficient getter technology are the precondition for the wafer level packaging. The author researched the design of bond ring width and metal layer structure, metallization and electroplating process, obtained the reasonable sealing structure. Though the method of acoustic scanning test, the author obtained the suitable process parameter of soldering bond, such as reflow time, the thickness of electroplating solder layer and bond pressure. Getter is a material to absorb gas in the cavity and maintain the vacuum persistently. The method of determining gettering properties are presented, and some pilot study on the Ti film getter are performed.Finally, the solder bonding and getter technology are integrated into two wafer level packaging styles respectively, the Chip-to-Wafer (C2W) and Wafer-to-Wafer (W2W), to implement wafer level vacuum packaging of the MEMS, and the wafer-level vacuum packaging sample were tested, the shear strength and hermeticity of the two kinds of sample are both meet the requirement of MIL STD 883.