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Z .Sensors and Actuators 87 2000 4651 www.elsevier.nlrlocatersna

Summary: Z .Sensors and Actuators 87 2000 46­51
High aspect-ratio polysilicon micromachining technology
Farrokh Ayazi)
, Khalil Najafi
Center For Integrated MicroSystems, Department of Electrical Engineering and Computer Science, UniĠersity of Michigan,
1301 Beal AĠenue, Ann Arbor, MI 48109-2122 USA
Received 30 December 1999; received in revised form 20 March 2000; accepted 25 March 2000
This paper presents a single wafer, all-silicon, high aspect-ratio multi-layer polysilicon micromachining technology that combines deep
dry etching of silicon with conventional surface micromachining to realize tens to hundreds of microns thick, high aspect-ratio,
electrically isolated polysilicon structures with sub-micron air-gaps. Vertical polysilicon sense electrodes as tall as the main body
polysilicon structure can be realized in this technology. A 70-mm-tall, 2.5-mm-wide polysilicon vibrating ring gyroscope with 1.2 mm
capacitive air-gaps and electrodes as tall as the ring structure has been fabricated using this technology. Vertical polysilicon beams that
are 220 mm tall with a 100:1 aspect-ratio have been also fabricated. The all-silicon feature of such a technology improves long term
stability and temperature sensitivity, while fabrication of large area, vertical pick-off electrodes with sub-micron gap spacing will increase
the sensitivity of MEMS devices by orders of magnitude. This technology is also capable of simultaneously producing electrically isolated
Z . Z .2-D planar and 3-D vertical polysilicon structures on the same silicon substrate. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Silicon micromachining; High aspect-ratio; Polysilicon micromachining; Deep trench etching; Thick polysilicon
1. Introduction


Source: Ayazi, Farrokh - School of Electrical and Computer Engineering, Georgia Institute of Technology
Georgia Institute of Technology, School of Electrical and Computer Engineering, Center for MEMS and Microsystems Technologies


Collections: Engineering