| Over the past decade, MEMS researchers have started investigating new fabrication techniques for realizing 3D curved micro and nano-structures. Hydrogen annealing has been explored as one such technique because it can produce atomically smooth (surface roughness &sim0.1nm RMS), 3D curved surfaces in a batch-fabrication compatible manner. However, it has not found much application outside of surface smoothing due to limited understanding of the phenomenon, and lack of modeling tools. This thesis addresses both issues, and explores two applications of the phenomenon. Fundamental investigations were carried out to show that hydrogen is not essential for the phenomenon, resulting in the use of "silicon migration" when referring to the phenomenon. Additionally, it was demonstrated that the silicon migration is limited to regions of exposed silicon, enabling control of where migration does and does not occur. A 3D simulator was developed for predicting and visualizing the shape transformation caused by silicon migration. Simulation results were compared against fabrication results to verify correctness. Finally, two unique applications of silicon migration were explored. First, migration was used to reshape a silicon template for 3D nano-pores integrated with micro-channels. Devices were successfully fabricated, and tested for cleared nano-pores. Second, migration was used to homogenize the features of single crystal silicon photonic crystals. The annealed samples showed an expected increase in reflectivity and decrease in polarization dependence. The results of this work demonstrate that silicon migration can be a viable process for creating novel micro and nano-structures. |
