Fabrication of micro- and nano-structures by focused ion beam

The micro- and nano-structures of material are some of the most important microscopic characteristics that govern macroscopic behaviour in terms of physical properties. To best use and fully benefit from these structures, it is important to properly develop deterministic fabrication techniques that can achieve these structures with high accuracy. Recent developments in the technology of focused ion beam (FIB) has led to beam sizes ranging from 400nm to 3.5nm, which makes FIB machining an idea tool for both micro and nano fabrication. We aim at developing a deterministic fabrication approach to accurately obtain predicable micro- and nano-structures and develop proper solutions to overcome the challenges in FIB machining, including dimensional, geometrical material and machining efficiency challenge.
The deterministic approach is implemented through the development of a surface topography model which predicts the surface generated during FIB machining process and a divergence compensation approach which is used to obtain fabrication parameters to compensate for the predicted machining error. Ion beam machining process is characterized by an ion-solid sputtering model. The sputter yield and sputtered atoms’ distribution are evaluated using a Monte Carlo simulation with the simulation of the dynamic surface generation realised by the level set method.
The developed fabrication approaches have been fully demonstrated through a number of case studies which show that the surface topography of the machined material can be precisely predicted; the divergence compensation method can reduce the machining error and the machined surface form accuracy can be dramatically improved. Subsequent measurement of the actual fabricated micro- and nano-structures using the settings provided by the model helps to overcome the existing dimensional, geometrical, machining efficiency and machinability challenges in FIB machining.