Physical chemistry of wet chemical anisotropic etching of silicon


Elwenspoek, M. (1996) Physical chemistry of wet chemical anisotropic etching of silicon. In: Proceedings of the ASME Dynamic Systems and Control Division. American Society of Mechanical Engineers, pp. 901-907. ISBN 9780791817469

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Abstract:In this paper we explain a view to understand the anisotropy of the etching of silicon in certain wet chemical agents (such as KOH). The starting point is the assumption that the <111> face of silicon is a flat face, the etch rate of which is then governed by a nucleation barrier. We review the atomic surface structure of the <001>, <110> and <111> face, with the result that the <111> face is the only flat face. We discuss the consequence of the assumption of steps on the orientation dependence of the etch rate, and we show that the observed experimental facts perfectly fit to this idea. We also review recent in situ STM images of slightly misaligned <111> n-silicon that show moving steps, and an increasing number of etchpits as a function of the voltage difference between silicon and an NaOH solution, reaching a maximum close to the passivation voltage. This observation is discussed in terms of the driving force for etching and the step free energy. Finally, the order of magnitude of the step free energy is discussed
Item Type:Book Section
Copyright:© 1996 American Society of Mechanical Engineers
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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Metis ID: 112466