TEM sample preparation is an important application of focused ion beams (FIB). When TEM samples of inhomogeneous materials are prepared, an artifact called curtaining may occur. A curtain is an elongated elevated area downstream a localized material region, in the direction of the ion beam. The purpose of this project is to study the influence of process parameter variations on the curtaining effect by FIB¿sample interaction simulations, and thereby to help unravel the fundamentals of curtaining during TEM lamella preparation. Accurate sputtering yield data are a prerequisite for accurate FIB topography simulations. Reliable experimental data at the very small glancing angles employed during TEM sample preparation do not exist. Therefore, as a first task sputtering yields will be measured and used to calibrate Monte Carlo simulations. Monte Carlo simulations will then be used to generate sputtering yields as a function of incidence angle (¿sputtering yield tables¿) for the ion energies/target materials of interest. Using the sputtering yield tables, topography simulations will be performed for reference process conditions in order to verify the simulation model against experimental data. Features to be evaluated will be the angle of the milled surface with respect to the wafer surface and the height and shape of the curtain. The final and ultimate task is to study the dependence of the curtaining effect on process parameter variations. Parameters include the beam angle, diameter, shape, and energy. Each of the parameters will be varied with the other parameters fixed to the reference conditions. In all cases experimental results will be provided by FEI, while TU Vienna will do all modeling and simulation work.