Two-Dimensional Simulation and Modeling in Scanning Electron Microscope Imaging and Metrology Research
Michael T. Postek, Andras Vladar, J R. Lowney, William J. Keery
Traditional Monte Carlo modeling of the electron beam specimen interactions in a scanning electron microscope (SEM) produces information about electron beam penetration and output signal generation at either a single beam landing location, or multiple landing positions. If the multiple landings lie on a line, the results can be graphed in a line scan-like format, Monte Carlo results formatted as a line scan have proven useful in providing one-dimensional information about the sample (e.g. linewidth). When used this way, this process is called forward line scan modeling. In the present work, the concept of image simulation (or the first step in the inverse modeling of images) is introduced where the forward-modeled line scan data is carried one step further to construct theoretical 2 dimensional micrographs (i.e., theoretical SEM images) for comparison with similar experimentally obtained micrographs. This provides, for the first time, an ability to mimic and closely match theory and experiment using SEM images. Calculated and or measured libraries of simulated images can be developed with this technique. The library concept will prove to be very useful in the determination of dimensional and other properties of simple structures like integrated circuitpars where the shape of the features is preferably measured from a single top-down image or a line scan. This paper presents one approach to the generation of 2-dimensional simulated images and presents some suggestions as to their application to critical dimension metrology.
critical dimension, linewidth, metrology, modeling, Monte Carlo, scanning electron microscope