Study on EEBS for linewidth imaging by a Monte Carlo method

Abstract

A systematic analysis about the influences of electron beam focusing on scanning electron microscope (SEM) imaging for silicon (Si) trapezoidal lines was performed based on a sophisticated Monte Carlo (MC) simulation program. It was found that the focus position and the aperture angle highly affect the final quality of SEM imaging. The effective electron beam shape (EEBS) is hence suggested as the broadening function to overcome this issue for theoretical analysis, rather than the widely-used Gaussian profile. However, EEBS is hardly acquired due to it strongly depends on both the sample topography and the electron beam focusing condition, which make it is impossible to be applied in practical analysis. 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 establishing a database of the parameter in traditional Gaussian profile. Experimenters will benefit from this database to obtain true line-scan profiles for accurate gate linewidth measurement. This investigated result could greatly improve the accuracy of linewidth measurement.