Two‐dimensional simulation and modeling in scanning electron microscope imaging and metrology research

Abstract

Summary: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 line scans 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 are carried one step further to construct theoretical two-dimensional (2-D) micrographs (i.e., theoretical SEM images) for comparison with similar experimentally obtained micrographs. This provides 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, such as integrated circuit parts, 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-D simulated images and presents some suggestions as to their application to critical dimension metrology.

Does your SEM really tell the truth? How would you know? part 3: vibration and drift

“…In addition, using the Monte Carlo modeling approach, workers at NIST developed procedures for manufacturing 2-D artifi cial images to test the instrument and the measurement algorithms (7). Additionally, more recent work, geared to speeding up the modeling process, dealt with a much faster approach to image modeling which could generate credible images for and city water (right) (HFW = 75 nm).…”

Application of Monte Carlo simulation to SEM image contrast of complex structures

“…Another application of this program was concerned with the simulation of twodimensional (2D) SE and BSE images of a simple notch. 11 Recently, the MONSEL program has been extended by Seeger et al to simulate SE and BSE images of a complex structure consisting of many triangles to create a complex specimen surface. 12 Certain programming techniques enabled faster calculations.…”

Modeling for accurate dimensional scanning electron microscope metrology: then and now

“…Figure 7 demonstrates how similar a MC‐modeled image of dense photoresist lines can resemble an actual SEM image. The modeled image, as described in Postek et al (2002), was created by generating a high‐resolution single “X” linescan in the NIST MONSEL program. Then many of these “X” linescans were replicated as described above to make a high pixel‐resolution artificial SEM image.…”

“…The MC‐generated artificial images can be used to test the applicability of these algorithms to the measurement task. Table I shows the results of the application of several common algorithms to the measurement of a simulated palladium on silicon line image prepared like as those described above (Postek et al , 2002). Note how different the measurement results are between the different algorithms that have been applied (variation in pitch measurements can be attributed to pixel size and induced line edge roughness).…”