Mechanism of wet anisotropic etching of silicon for nano-scale applications

The fabrication processes of recent MEMS devices require the use of anisotropic etching and variety of concave structures.; Analysis of these structures uncovered phenomenon in the etch rates of surfaces exposed by anisotropic etchant. This phenomenon could not be explained without consideration of the composition of these surfaces on atomic level.; My study raised the step-based modeling of these planes, their relative interactions, and dependence on the etching environment. Control of this environment and better understanding of the different factors that influence the etch rates of these surfaces is the main theme of my work.; To help with the analysis of the studied surfaces a set of the experiments was done using a wagon-wheel pattern that provided the necessary assortment of concave structures for the purpose of this research. A mathematical model was built to help understand the processes that are responsible for anomalies in the etch rates and profiles of surfaces exposed on sidewalls of spokes in the wagon-wheel experiment.; Detailed examination of the profiles of the surfaces and their relative location within the same concave structure suggested the possibility of application of these surfaces in creation of different patterns for nano-applications. The major concern is the control of etch rates of these planes in order to achieve the necessary precision for the application on such scale. Light illumination of the etched surfaces is analyzed as a possible component in providing the necessary level of control.; Influence of the light intensity and different wavelengths is studied with the thought of application of the respective parameters in order to achieve a satisfactory control over the etch rates of illuminated surfaces.