Monte Carlo study for correcting the broadened line‐scan profile in scanning electron microscopy

• Published in: Journal of microscopy (Oxford) 2020-01, Vol.277 (1), p.23-31
• Main Author: ZHANG, P.
• Format: Article
• Language: English
• Subjects: Algorithms; Computer simulation; Effective electron beam shape; Electron beams; Electron microscopes; Entropy; Focusing; Monte Carlo simulation; Parameters; Scanning electron microscopy; SEM; size measurement
• ISSN: 0022-2720; 1365-2818
• DOI: 10.1111/jmi.12860

Summary Line‐scan profile is always broadened due to the probe shape of the primary electron (PE) beam in scanning electron microscopy (SEM), which leads to an inaccurate dimension metrology. Currently, the effective electron beam shape (EEBS) is suggested as the broadening function to overcome this issue for theoretical analysis, rather than the widely used Gaussian profile. However, EEBS is almost impossible to be acquired due to it strongly depends on both the sample topography and the electron beam focusing condition, which makes it is impossible to be applied in practical analysis. Taking the case of gate linewidth measurement, an approach is proposed to find a best‐fit traditional Gaussian profile, which can optimally replace the EEBS in the case of the same sample structure and experimental condition for construction of a database of the parameter in traditional Gaussian profile. This approach is based on the use of the ideal and broadened line‐scan profiles which are both obtained from Monte Carlo (MC) simulation, but respectively by an ideal and a focusing incident electron beam model. The expected value of parameter can be obtained through deconvoluting (here using a maximum‐entropy algorithm) the broadened line‐scan profile then fitting it to the ideal profile. Experimenters can benefit from this database to obtain true line‐scan profiles for accurate gate linewidth measurement. This work should prove useful for samples of other structures and be an extension of the database in the future.