Advanced MEMS Process for Wafer Level Hermetic Encapsulation of MEMS Devices Using SOI Cap Wafers With Vertical Feedthroughs

Torunbalci, Mustafa Mert
Alper, Said Emre
Akın, Tayfun
This paper reports a novel and inherently simple fabrication process, so-called advanced MEMS (aMEMS) process, that is developed for high-yield and reliable manufacturing of wafer-level hermetic encapsulated MEMS devices. The process enables lead transfer using vertical feedthroughs formed on an Silicon-On-Insulator (SOI) wafer without requiring any complex via-refill or trench-refill processes. It requires only seven masks to fabricate the hermetically capped sensors with an experimentally verified process yield of above 80%. Hermetic encapsulation is achieved by Au-Si eutectic bonding at 400 degrees C, and the pressure inside the encapsulated cavity has been characterized to be as low as 1 mTorr with successfully activated thin-film getters. The pressure inside the encapsulated cavity can also be adjusted in the range of 1 mTorr-5 Torr by various combinations of outgassing and gettering options in order to satisfy the requirements of different applications. The package pressure is being monitored for the selected chips and is observed to be stable below 10 mTorr since their fabrication about 10 months ago. The shear strengths of several packages are measured to be as high as 30 MPa with average shear strength of 22 MPa, indicating a mechanically strong bonding. The robustness of the packages is tested by thermal cycling between 100 degrees C and 25 degrees C, and absolutely no degradation is observed in the hermeticity and the package pressure. The package pressure is also verified to remain unchanged after storing the packages at a high storage temperature of 150 degrees C for 24 h. Furthermore, the packaged chips are observed to withstand a high temperature shock test performed at 300 degrees C for 5 min, at the end of which the characteristics of the encapsulated sensor indicates that the package still remains hermetic (no detectable leaks) and also the package pressure remains constant at similar to 20 mTorr.


Torunbalci, M. M.; Alper, S. E.; Akın, Tayfun (2015-06-25)
This paper presents a novel, inherently simple and low-cost fabrication and hermetic packaging method developed for SOI-MEMS devices, where an SOI wafer is used for the fabrication of MEMS structures as well as vertical feedthroughs, while a glass cap wafer is used for hermetic encapsulation and routing metallization. Glass-to-silicon anodically bonded seals yield a very stable cavity pressure of 150 mTorr after 15 days. The shear strength of the fabricated packages is above 7 MPa. Temperature cycling and u...
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Torunbalci, Mustafa Mert; Gavcar, Hasan Dogan; Yesil, Ferhat; Alper, Said Emre; Akın, Tayfun (2021-01-01)
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Demirhan Aydın, Gülşah; Akın, Tayfun; Kalay, Yunus Eren; Department of Micro and Nanotechnology (2022-8-11)
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Wafer level hermetic sealing of MEMS devices with vertical feedthroughs using anodic bonding
Torunbalci, Mustafa Mert; Alper, Said Emre; Akın, Tayfun (2015-04-01)
This paper presents a new method for wafer-level hermetic packaging of MEMS devices using a relatively low temperature anodic bonding technique applied to the recently developed advanced MEMS (aMEMS) process. The aMEMS process uses vertical feedthroughs formed on an SOI cap wafer, eliminating the need for any complex via-refill or trench-refill steps while forming the vertical feedthroughs. The hermetic sealing process is achieved at 350 degrees C by using an anodic bonding potential of 600 V. The bonding p...
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This paper presents a novel wafer-level packaging method for shunt, capacitive RF MEMS switches using BCB as the adhesive interlayer. Fabrication and electrical characteristics of the proposed package were initially evaluated for 50 Omega CPW lines. Microwave measurements of these packaged test structures were fitted to a circuit model, which was later employed to optimize the package for RF MEMS switches. The proposed packaging method was next successfully integrated with an in-house RF MEMS fabrication pr...
Citation Formats
M. M. Torunbalci, S. E. Alper, and T. Akın, “Advanced MEMS Process for Wafer Level Hermetic Encapsulation of MEMS Devices Using SOI Cap Wafers With Vertical Feedthroughs,” JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, pp. 556–564, 2015, Accessed: 00, 2020. [Online]. Available: