Etching of silicon in alkaline solutions: a critical look at the {111} minimum


Nijdam, A.J. and Suchtelen, J. van and Berenschot, J.W. and Gardeniers, J.G.E. and Elwenspoek, M.C. (1999) Etching of silicon in alkaline solutions: a critical look at the {111} minimum. Journal of Crystal Growth, 198-19 (Part 1). pp. 430-434. ISSN 0022-0248

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Abstract:Anisotropic wet-chemical etching of silicon in alkaline solutions is a key technology in the fabrication of sensors and actuators. In this technology, etching through masks is used for fast and reproducible shaping of micromechanical structures. The etch rates Image depend mainly on composition and temperature of the etchant. In a plot of etch rate versus orientation, there is always a deep, cusped minimum for the {1 1 1} orientations. We have investigated the height of the {1 1 1} etch-rate minimum, as well as the etching mechanisms that determine it. We found that in situations where masks are involved, the height of the {1 1 1} minimum can be influenced by nucleation at a silicon/mask-junction. A junction which influences etch or growth rates in this way can be recognized as a velocity source, a mathematical concept developed by us that is also applicable to dislocations and grain boundaries. The activity of a velocity source depends on the angle between the relevant {1 1 1} plane and the mask, and can thus have different values at opposite {1 1 1} sides of a thin wall etched in a micromechanical structure. This observation explains the little understood spread in published data on etch rate of {1 1 1} and the anisotropy factor (often defined as Image
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Copyright:© 1999 Elsevier Science B.V
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Electrical Engineering, Mathematics and Computer Science (EEMCS)
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