Modeling of focused ion beam induced surface chemistry

A new macroscopic model for focused ion beam induced surface chemistry is presented. The model consists of two parts. The first part is based on previous work by several authors and assumes a uniform current distribution for the ion beam. In this case an analytical solution for the reaction yield can be obtained. Compared to previous work, the new model shows an improved agreement with experimental data and delivers physically meaningful parameter values. In an extended model a Gaussian beam shape has been used to account for the spatial and temporal variations in the current distribution, which are present in a real focused ion beam system. In this case the analytical solution for the yield dependence has to be solved using a spatially depended ion flux and integrated over the whole area of the pixel, which was done numerically. This model shows very good agreement with experimental data and delivers a consistent set of parameters values. In addition, experimental changes in parameter values such as beam size (defocusing) and pixel step size are accurately reflected in the simulation. (C) 2000 American Vacuum Society. [S0734-211X(00)15106-6].