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- Bleiker, Simon J., et al.
(författare)
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Cost-Efficient Wafer-Level Capping for MEMS and Imaging Sensors by Adhesive Wafer Bonding
- 2016
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Ingår i: Micromachines. - Basel, Switzerland : Multidisciplinary Digital Publishing Institute (MDPI). - 2072-666X. ; 7:10, s. 192-
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Tidskriftsartikel (refereegranskat)abstract
- Device encapsulation and packaging often constitutes a substantial part of the fabrication cost of micro electro-mechanical systems (MEMS) transducers and imaging sensor devices. In this paper, we propose a simple and cost-effective wafer-level capping method that utilizes a limited number of highly standardized process steps as well as low-cost materials. The proposed capping process is based on low-temperature adhesive wafer bonding, which ensures full complementary metal-oxide-semiconductor (CMOS) compatibility. All necessary fabrication steps for the wafer bonding, such as cavity formation and deposition of the adhesive, are performed on the capping substrate. The polymer adhesive is deposited by spray-coating on the capping wafer containing the cavities. Thus, no lithographic patterning of the polymer adhesive is needed, and material waste is minimized. Furthermore, this process does not require any additional fabrication steps on the device wafer, which lowers the process complexity and fabrication costs. We demonstrate the proposed capping method by packaging two different MEMS devices. The two MEMS devices include a vibration sensor and an acceleration switch, which employ two different electrical interconnection schemes. The experimental results show wafer-level capping with excellent bond quality due to the re-flow behavior of the polymer adhesive. No impediment to the functionality of the MEMS devices was observed, which indicates that the encapsulation does not introduce significant tensile nor compressive stresses. Thus, we present a highly versatile, robust, and cost-efficient capping method for components such as MEMS and imaging sensors.
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| 2. |
- Lietaer, Nicolas, et al.
(författare)
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Wafer-level packaged MEMS switch with TSV
- 2011
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Konferensbidrag (refereegranskat)abstract
- A miniaturized wafer-level packaged MEMS acceleration switch with through silicon vias (TSVs) was fabricated, based on technologies suitable for harsh environment applications. The high aspect ratio TSVs were fabricated through the silicon-on-insulator (SOI) substrate prior to the fabrication of the MEMS structures. Doped polysilicon was used as the conductor for the TSVs, which has the advantage of a thermal coefficient of expansion that matches that of the silicon substrate material. The fragile MEMS structures were protected from the environment by wafer-level bonding of a glass cap using benzocyclobutene (BCB). The BCB layer which was spray-coated onto the patterned glass wafer provides a good bond strength and temperature stability. As opposed to having lateral interconnects at the interface between the cap wafer and the device wafer, the use of TSVs significantly reduces the footprint and allows flip-chip bonding of the devices onto a substrate. The bare MEMS chips were mounted directly onto a printed circuit board (PCB) thereby avoiding an entire packaging level and reducing the system complexity and cost. This was done using an isotropic conductive adhesive (ICA) based on metalized polymer spheres, which is believed to be an interconnect technology more suitable for harsh environments than metal-based BGA and CSP technology. The initial characterization of completed chips mounted on a PCB shows promising results.
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