Deep etching of silicon with xenon difluoride
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Fabrication of microelectromechanical systems (MEMS) requires systems for depositing and selectively removing of parts of a substrate material. The most commonly used material in micromachining of different MEMS devices is silicon. Therefore, depositing and etching of silicon is of great importance in micromachining. One of the candidates for selective etching of silicon is xenon difluoride. XeF2 etches silicon isotropically in its gaseous form without a need for plasma generation. XeF2 is extremely selective to silicon compared to other common materials in micromachining; such as SiO2, Si3N4, aluminum, and copper. In this thesis, design and fabrication of a XeF2 etching system is described. The system can both be controlled manually or by a computer. Different etching methodologies were examined and the results are presented. These experimental results are compared with the theoretical calculations. The second part of the thesis deals with simulation of the etching process. The simulation which is described in this report could predict the odd shape of the etching profiles after deep etching of samples with XeF2. The simulation algorithms are based on a theory which was developed for explaining the shape of etched profiles.