Vacuum package using anodic bonding assisted by the reflow of low-melting temperature metal
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In this paper, we present a highly effective vacuum seal method, which is based on anodic bonding assisted by the reflow of lowmelting temperature metal. To form sacrificial gap for evacuating the packaged cavity before hermetically sealing, the reflow process of Au/Sn/Cr posts due to low-melting temperature Sn metal was introduced. Using this technique to form the evacuation gap, the micro-precise alignment between packaging wafers was obtained. The package method enabled to eliminate contaminant caused by package process. The diaphragm structure sensing pressure was used to investigate the proposed package method. The vacuum level in the packaged cavity was obtained lower than 5 Pa. In comparison to the conventional package method without using the reflow process to form the evacuation gap, the vacuum level has been improved by a factor of 8. The yield and uniformity of the package method were also confirmed to be higher than the conventional package method without using the reflow process to form the evacuation gap. This vacuum package method can be implemented to remove air damping for optimal performance of mechanical oscillators such as accelerometers, gyroscopes, energy harvesters, and micro-mirrors.
KeywordsVacuum package Anodic bonding Low-melting temperature metal reflow
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- 1.Esashi, M., “Wafer Level Packaging of MEMS,” Journal of Micromechanics and Microengineering, Vol. 18, No. 7, Paper No. 073001, 2008.Google Scholar
- 2.Tachibana, H., Kawano, K., Ueda, H., and Noge, H., “Vacuum Wafer Level Packaged Two-Dimensional Optical Scanner by Anodic Bonding,” Proc. of 22nd International Conference on Micro Electro Mechanical Systems, pp. 959–962, 2009.Google Scholar
- 6.Tanaka, S., Honjoya, Y., and Esashi, M., “AUSN Solder Vacuum Packaging using Melted Solder Floodgates and Laser-Activated Non-Evaporable Getters for SIC Diaphragm Anticorrosive Vacuum Sensors,” Proc. of IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), pp. 492–495, 2010.Google Scholar
- 7.Chu, H. M., Sasaki, T., and Hane, K., “Design, Fabrication, and Vacuum Package Process for High Performance of 2D Scanning MEMS Micromirror,” Proc. of 16th International Conference on Solid-State Sensors, Actuators and Microsystems, pp. 558–561, 2011.Google Scholar
- 11.Elfrink, R., Renaud, M., Kamel, T., De Nooijer, C., Jambunathan, M., and et al., “Vacuum-Packaged Piezoelectric Vibration Energy Harvesters: Damping Contributions and Autonomy for a Wireless Sensor System,” Journal of Micromechanics and Microengineering, Vol. 20, No. 10, pp. 104001, 2010.CrossRefGoogle Scholar
- 13.Bang, Y. S., Kim, J. M., Kim, Y., Kim, J. M., and Kim, Y. K., “Fabrication and Characterization of RF MEMS Package Based on LTCC Lid Substrate and Gold-Tin Eutectic Bonding,” Proc. of Actuators and Microsystems Conference on Solid-State Sensors, pp. 2115–2118, 2007.Google Scholar
- 14.Lin, Y. C., Baum, M., Haubold, M., Fromel, J., Wiemer, M., and et al., “Development and Evaluation of AuSi Eutectic Wafer Bonding,” Proc. of Actuators and Microsystems Conference on Solid-State Sensors, pp. 244–247, 2009.Google Scholar
- 15.Welch, W. C. and Najafi, K., “Gold-Indium Transient Liquid Phase (TLP) Wafer Bonding for MEMS Vacuum Packaging,” Proc. of IEEE 21st International Conference on Micro Electro Mechanical Systems, pp. 806–809, 2008.Google Scholar
- 17.Sasaki, M., Sasaki, T., Hane, K., and Miura, H., “An Optically Flat Micromirror using a Stretched Membrane with Crystallization-Induced Stress,” Journal of Optics A: Pure and Applied Optics, Vol. 10, No. 4, Paper No. 044004, 2008.Google Scholar