Atomistic modelling of anisotropic etching of crystalline silicon
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Doctoral thesis (article-based)
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Dissertations / Laboratory of Physics, Helsinki University of Technology, 123
AbstractAn atomistic model for the simulation of anisotropic wet chemical etching of crystalline silicon is developed. Special attention is paid to the relation between the atomistic processes, the mesoscopic features of the surface morphology and the macroscopic anisotropy of the process, bridging the different length scales. The development of the atomistic model is made by direct comparison of atomistic kinetic Monte Carlo and Cellular Automaton simulations with experimental results, guided by first-principles calculations. The model explains the anisotropy of the etching process and the orientation-dependent surface morphology as two different manifestations of the same atomistic mechanisms, namely, the weakening of backbonds following OH termination of surface atoms and the existence of significant interaction between the terminating species (H / OH). The versatility of the atomistic model is demonstrated by the concentration and time dependence of the simulated under-etched structures and surface morphology. A substantial effort has been made to develop an efficient program in order to simulate the etching process in arbitrarily oriented, large, micrometer-scale systems in the presence (or absence) of masking patterns and considering the effects of temperature and etchant concentration. The program has a great potential for use in the optimization of the processing parameters in industrial applications.
anisotropic wet chemical etching, surface morphology, Monte Carlo, cellular automaton, mask, convex corner, crystalline silicon, activation energy, surface processing
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