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Out of Plane High Aspect Ratio Micro Wires as Suspension Elements in Inertial Sensors

Greiner, Felix and Schlaak, Helmut F. :
Out of Plane High Aspect Ratio Micro Wires as Suspension Elements in Inertial Sensors.
Abstract Book 4th ANKA/KNMF Users' Meeting Karlsruhe
[Conference or Workshop Item], (2012)

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Item Type: Conference or Workshop Item
Title: Out of Plane High Aspect Ratio Micro Wires as Suspension Elements in Inertial Sensors
Language: English
Abstract:

Micro- and nanowires with high aspect ratios, arranged as slim and tall standing metal pillars offer promising features for microsystems [1–7]. The goals are:

- 1st fabrication of high aspect ratio out of plane metal wires next to low aspect ratio blocks,

- 2nd multilayer material link of these metal structures (one wire + two metal blocks),

- 3rd realization and characterization of an acceleration sensor applying these structures. The KNMF services refer to the fabrication of templates made by aligned X-ray lithography. The high aspect ratio templates provide vertical cylindrical holes with aspect ratios from 16 to 33 next to template openings with low aspect ratios (Fig. 1 d). The remaining process steps are to be processed at Technische Universität Darmstadt (TUD). Results from KNMF 2010-004-000365 proposal are shown in Tab. 1.

Two main issues still remain before the MEMS can prove to work as an inertial sensor:

a) The structures (columns) on the X-ray exposure mask are approximately 1 µm smaller than designed. Therefore, the vertical wire is less robust and buckles (Tab. 1 b, c). Hence, the mass load has to be reduced and the process steps in Fig. 1 g have to be designed for a better wire protection. The mass load reduction can be achieved by a reduced electroforming height in Fig. 1 f. The process steps can more efficiently protect the wire, if the seed layer is designed differently. The connection from the bottom circuit path to the top of the sacrificial SU-8 3005 layer currently runs at the outer edges of the mass block (Fig. 2 a). There, it has to be wet etched for an efficient removal of the sacrificial layer. This step can be omitted, if the connection from the circuit path to the seed layer runs at the inner edges of the mass block (Fig. 2 a). The inner connection offers enough flexibility for the movement of the metal blocks when measuring acceleration.

b) The electrodeposition shows to be inhomogeneous due to the design of the circuit path layer. The circuit path layer shows substantial resistances and it delivers the electrodeposition current. A layer redesign including local thickening can solve this problem (Fig. 2 b).

Both improvements shown in Fig. 2 have been successfully implemented in a similar UV lithography approach at TUD [2–4], [7] and are scheduled in the KNMF proposal 2012-008- 000970.

Acknowledgements

The aligned X-ray exposures in the KNMF proposal 2010-004-000365 done by F J Pantenburg and P Meyer are greatly acknowledged.

References

[1] P. F. Greiner, J. Eberhardt, and H. F. Schlaak, “Metallic Micro Nails MAde by direct LiG process - MiNiMAL,” in Proceedings of the 2nd KNMF User Meeting, Karlsruhe, 2010, p. 69.

[2] P. F. Greiner and H. F. Schlaak, “High Aspect Ratio Metal Nano and Micro Pillars as Suspension Elements in MEMS,” in 9th International Workshop on High Aspect Ratio Micro Structure Technology, HsinChu, Taiwan, 2011, pp. 53–54.

[3] F. Greiner, J. Eberhardt, and H. F. Schlaak, “Senkrechte metallische Nano- und Mikrodrähte mit hohem Aspektverhältnis als neuartige Federelemente in Mikrosystemen - Vertical High Aspect Ratio Nano and Micro Wires as Novel Suspension Elements in MEMS,” in Proceedings of the Mikrosystemtechnik Kongress 2011, Berlin, Offenbach, 2011, pp. 328–331.

[4] F. Greiner and H. Schlaak, “High aspect ratio metal micro and nano pillars for minimal footprint MEMS suspension,” Microsystem Technologies, pp. 1–7, 2012.

[5] J. J. Schneider, H. F. Schlaak, D. Pavlidis, F. Küppers, and W. Ensinger, “Elektromechanische Sensoren mit eindimensionalen Nanoobjekten - ELEMENT, FKZ 16SV5475,” Berlin, 18-Jun-2012.

[6] F. Dassinger, M. Hottes, F. Greiner, H. F. Schlaak, and W. Ensinger, “Mikro-Nano-Integration für die Inertialsensorik,” Sensor Magazin, vol. 27, no. 3, p. 24, Sep-2012.

[7] F. Greiner, S. Quednau, F. Dassinger, R. Sarwar, H. F. Schlaak, M. Guttmann, and P. Meyer, “Fabrication techniques of multiscale 3D-MEMS with vertical metal micro- and nanowire integration,” J. Micromech. Microeng., submitted, 2012.

Title of Book: Abstract Book 4th ANKA/KNMF Users' Meeting
Place of Publication: Karlsruhe
Classification DDC: 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften
Divisions: 18 Department of Electrical Engineering and Information Technology
18 Department of Electrical Engineering and Information Technology > Institute for Electromechanical Design
18 Department of Electrical Engineering and Information Technology > Institute for Electromechanical Design > Microtechnology and Electromechanical Systems
Date Deposited: 06 Feb 2013 09:27
Last Modified: 06 Feb 2013 09:27
URN: urn:nbn:de:tuda-tuprints-31320
URI: http://tuprints.ulb.tu-darmstadt.de/id/eprint/3132
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