22 January 2005 Bonding and deep RIE: a powerful combination for high-aspect-ratio sensors and actuators
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Abstract
In this paper we present the very promising results for two methods of the so-called Bonding and Deep RIE (BDRIE) technology, characterised by bonding of two wafers with pre-patterned vertical gaps and subsequent RIE trench etching of the active layer. In case of the anodically bonded silicon-glass compound detection electrodes for vertical movement are integrated. The silicon layer contains the movable structure as well as drive and detection electrodes for lateral movement. It is advantageous that finally the mechanical active elements consist of single crystalline silicon without any additional layers. The BDRIE approach allows a great variation of parameters. The active layer thickness can be defined due to application issues. Our examples show active layers thickness ranging from 30 up to 200 μm, patterned by dry etching steps with maximum aspect ratio between 20:1 and 30:1. Structures with trench width variations of more than 50 (widest/smallest trench) have been fabricated successfully. Methods and results of preventing notching and backside etching of the active layer are presented as well. The size of the vertical gap can be as small as 1.5 μm for a very sensitive detection or several tens or hundreds of microns in order to reduce damping and parasitic capacitance. Holes for release in the movable structure are not necessary and will therefore not restrict the design. However, restrictions are given by the minimum size of bond area and the relation between layer thickness, free standing area above the groove and bond pressure, which are discussed within the paper. Applications of BDRIE are inertial sensors like gyroscopes, step-by-step switchgears as well as micro mirrors.
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Karla Hiller, Karla Hiller, Matthias Kuechler, Matthias Kuechler, Detlef Billep, Detlef Billep, Bernd Schroeter, Bernd Schroeter, Marco Dienel, Marco Dienel, Dirk Scheibner, Dirk Scheibner, Thomas Gessner, Thomas Gessner, } "Bonding and deep RIE: a powerful combination for high-aspect-ratio sensors and actuators", Proc. SPIE 5715, Micromachining and Microfabrication Process Technology X, (22 January 2005); doi: 10.1117/12.591509; https://doi.org/10.1117/12.591509
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