A Unified Epi-Seal Process for Fabrication of High-Stability Microelectromechanical Devices

• Published in: Journal of microelectromechanical systems Vol. 25; no. 3; pp. 489 - 497
• Main Authors: Yushi Yang, Ng, Eldwin J., Yunhan Chen, Flader, Ian B., Kenny, Thomas W.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Contacts; Damping; Deposition; Devices; Doping; Electrodes; Encapsulation; hermetic encapsulation; high quality factor; high stability resonator; Holes; low pressure; Microelectromechanical systems; Micromechanical devices; Resists; Silicon; Thin films; Wafer-level encapsulation; hermetic encapsulation; Wafer-level encapsulation; low pressure; high stability resonator; high quality factor
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2016.2537829

This paper presents a thin-film wafer-level encapsulation process based on an epitaxial deposition seal that incorporates both narrow and wide lateral transduction gaps (0.7-50 μm), both in-plane and out-of-plane electrodes, and does not require release etch-holes in the device layer. Resonant structures fabricated in this process demonstrate high-quality factors ( f × Q products of up to 2.27e + 13 Hz) and exceptional stability (±18 ppb over one month) with no obvious aging trends. Studies on cavity pressure indicate that vacuum levels better than 0.1 Pa can be achieved after final encapsulation, thus reducing gas damping for high surface-to-volume devices. The vast diversity of functioning devices built in this process demonstrates the potential for combinations of high-performance MEMS devices in a single process and/or single chip.