Impacts of point spread function accuracy on patterning prediction and proximity effect correction in low-voltage electron-beam-direct-write lithography

摘要

Electron-beam-direct-write lithography at lower accelerating voltages has been considered as a candidate for next-generation lithography. Although long-range proximity effects are substantially reduced with the voltage, proximity effect correction (PEC) is still necessary since short-range proximity effects are relatively prominent. The effectiveness of model-based PEC can be limited severely if an inaccurate point spread function (PSF) characterizing electron scattering within resist is adopted. Recently, a new PSF form using a promising calibration method has been developed to more accurately characterize the electron scattering and thus significantly improve patterning fidelity at 5 keV. However, influences of adopting the conventional and new PSF forms for the usage of patterning practical circuit layouts have not been intensively studied. This work extensively investigates impacts of PSF accuracy on patterning prediction and PEC under different resist thickness conditions suitable for various lithographic half-pitch nodes, where the critical features of practical circuit layouts are used to quantitatively evaluate their performance. In addition, patterning fidelity limitation suffered from proximity effects is examined to determine whether PEC should be applied. Simulation results indicate that the new PSF form can significantly improve the fitting accuracy, patterning prediction, and PEC results over the conventional PSF forms, especially for circuit layouts with smaller feature sizes.