Experiment-based estimation of point spread function in electron-beam lithography: Forward-scattering part

The point spread function (PSF) plays an important role in electron beam (e-beam) lithography, e.g., estimation of resist profile, proximity effect correction, etc. One of the essential tasks is how to estimate the PSF with accuracy and efficiency. Conventional approaches include estimation of PSF's based on certain functions or through a Monte Carlo simulation. A new approach to estimating PSF's based on experimental data is proposed to provide an alternative to the conventional approaches. It utilizes the relationship between a PSF and a line spread function (LSF), and that between a LSF and the remaining resist profile. Since effects of all phenomena and processes involved in the exposure step are reflected in experimental results, the proposed approach has a good potential to generate realistic PSF's for any substrates and e-beam tools as long as experiments can be carried out. In this paper, the implementation of the new approach for estimation of the forward scattering part of PSF is described along with the simulation and experiment results.