Microscopically, a rough surface (or any other feature) can be considered as a set of perturbations from the idealized surface. In reality, the microstructure of such a roughness may include spatial components some being smaller (subresolution) and some larger spatial frequency than the spot size of the SEM, and this should affect SE yields from such a target with respect to an ideal smooth surface. Yet to explore such influences by simulation, Monte Carlo SEM simulations are necessary but quite resource hungry, and thus somewhat limited in ability to include much fine detail, and with SEM simulation codes still being developed to include such effects easily, until now we typically simulate perfect smooth idealized structures. Other examples of such simulation resource-limited simplification of features could be etch halos at base of an etched feature, pits, bumps, craters, scratches or defects on or below the surface, CMP dishing, top corner rounding or footing at the base of a resist line or contact hole, or many other possibilities. We know these will add signatures to the simulated image, but it is important to understand how important are they to achieving realistic results.
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