T.-C. Shen

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It is known that chemical reaction rates can be different on different crystal planes. KOH is a common etchant for Si and the reaction rate on {100} planes is much faster than the {111} planes. Therefore a square etch window on a (100) Si surface can become an inverse pyramid at some point after KOH etch. However, it is not clear how a 3-­‐dimensional cubic crystal will evolve by KOH etching. In this study we use a dicing saw to create arrays of rectangular crystal pillars of different dimensions in two different orientations followed by 6M KOH etch at 50º C. We use scanning electron microscopy to record the evolution of the pillar morphology with and without an oxide cap layer. We find that the complex geometry is a result of the competition between different crystal planes.

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