Poly-SiGe-Based MEMS Thin-Film Encapsulation

• Published in: Journal of microelectromechanical systems Vol. 21; no. 1; pp. 110 - 120
• Main Authors: Bin Guo, Bo Wang, Lianggong Wen, Helin, P., Claes, G., De Coster, J., Du Bois, Bert, Verbist, A., Van Hoof, R., Vereecke, G., Haspeslagh, L., Tilmans, H. A. C., Decoutere, S., Osman, H., Puers, R., De Wolf, I., Tanaka, S., Severi, S., Witvrouw, A.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.2012; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acceleration; Accelerometers; Atmospheric pressure; Cavity resonators; Cleaning; Deposition; Devices; Electrodes; Exact sciences and technology; Hermeticity; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical instruments, equipment and techniques; Microelectromechanical systems; Micromechanical devices; Micromechanical devices and systems; Packaging; Physics; poly-SiGe; Resonators; Sealing; Silicon germanides; Silicon germanium; Thin films; thin-film packaging; vacuum sealing; Accelerometers; Acceleration sensor; Encapsulation; Sealing materials; Atmospheric pressure; Ge-Si alloys; Sealing; Hermeticity; Thin films; Wafer bonding; Cavities; Thermal testing; Vacuum techniques; thin-film packaging; Complementary MOS technology; Piezoelectric transducers; Seals; vacuum sealing; poly-SiGe; Porosity; Piezoelectric devices; Microelectromechanical device
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2011.2170823

This paper presents an attractive poly-SiGe thin-film packaging and MEM (microelectromechanical) platform technology for the generic integration of various packaged MEM devices above standard CMOS. Hermetic packages with sizes up to 1 mm 2 and different sealed-in pressures ( ~ 100 kPa and ~ 2 kPa) are demonstrated. The use of a porous cover on top of the release holes avoids deposition inside the cavity during sealing, but leads to a sealed-in pressure of approximately 100 kPa, i.e. atmospheric pressure. Vacuum ( ~ 2 kPa) sealing has been achieved by direct deposition of a sealing material on the SiGe capping layer. Packaged functional accelerometers sealed at around 100 kPa have an equivalent performance in measuring accelerations of about 1 g compared to a piezoelectric commercial reference device. Vacuum-sealed beam resonators survive a 1000 h 85°C/85%RH highly accelerated storage test and 1000 thermal cycles between -40°C and 150°C.