Abstract

Anisotropic etching of silicon is one of the fundamental techniques for the fabrication of micromachined structures such as microsensors and microactuators. Although the technique is used extensively in industry, the fundamentals of the atomic etching mechanism are still not well understood. This work addresses the modelling aspect of anisotropic etching of silicon and begins with an idealized model in which the etch behaviour depends only on the crystal features presented to the etchant. New experiments on Sin and Sid at 25wt.% and 19wt.% TMAH using wagon-wheel etching masks, specially designed for the scope of this thesis, enable the extension of the idealized model by addressing certain anomalies observed in the variation of the resulting structures as a function of etch time (1) As anomalies, it is found that same crystal planes in the same etchant often exhibit different etch rates. Moreover, for certain specific mask-edge positions, these etch rates are found to vary substantially with time, modifying under-etch profiles and surface roughness. (2) As to explain these anomalies, models of interactions at the boundaries between adjacent facets are developed.