INVESTIGATION OF THERMAL EFFECT OF MICROSTRUCTURES FABRICATED VIA FOCUSED ION BEAM RASTER SCANNING

Microstructures fabricated by use of focused ion beam (FIB) direct scanning is useful for microsystems. However, a new phenomenon was found recently by our experimental results. After the FIB bombardment in the defined area, the microstructures were formed under the competence between the ion sputtering induced surface roughening and surface diffusion induced surface smoothing. The process was called self-organized formation. The generated microstructures were characterized by atomic force microscope (AFM). The measured results show that the dimensions of the microstructures were changed with time. In other word, the measured results were different between the samples just processed and that one finished over one week, and the former with smaller dimensions than the latter. The reason maybe due to the thermal effect induced by the FIB bombardment. We called it a natural annealing. The fabricated microstructures were not in stable state due to the internal stress caused by ion sputtering and thermal diffusion. At initial state, it is in dynamic balance. After the natural annealing with several days, the dynamic balance is changed by the thermal diffusion which caused the dimensions of the microstructures varied continuously. In addition, the surface oxidation is also another factor.