A Boltzmann Transport Equation Model for Substrate Damage During Focused Helium Ion Beam Fabrication of Nanostructures

In this work, a Boltzmann transport equation model is proposed for the substrate damage simulation during focused helium ion beam processing. The model links the helium ion moderation, cascade collisions and lattice displacement. The travels of helium and displaced atoms are described by the transport equations for helium ions and displaced atoms, respectively, which are the core of the model. The main outputs of the equation model solved by a deterministic method include the spatial and temporal distribution of the helium ions, the energy transfer information and the spatial and temporal distribution of deposited point defects which directly reflects the substrate damage. The model has the advantage of being fully informative, accurate and efficient compared to existing methods. The comparisons between simulation results and experiments conducted on silicon and silicon carbide prove that the proposed model can effectively and accurately simulate substrate damage during focused helium ion beam processing.