Extreme Ultraviolet Lithography Simulation by Tracing Photoelectron Trajectories in Resist

Abstract

In order to evaluate the roughness of a resist pattern after development, photoelectron trajectories excited by extreme-ultraviolet (EUV) light are traced, and the resist pattern quality is discussed on the basis of a time-dependent resist development simulation. Binding energies of all subshells of atoms in poly(methyl methacrylate) (PMMA) and Si, and the photoionization cross section (dipole oscillator strength) are obtained by solving the Schrödinger equation with the Hartree–Fock–Slater potentials. The angular distribution of photoelectron emission is also taken into account. The photoelectron range from the generated position is around 30 nm in PMMA. If EUV light exposure has the square-wave intensity distribution, the critical dimension (CD) error and line edge roughness (LER) are almost negligible. If the aerial image is laterally sinusoidal, however, even if the contrast is unity, the pattern is seriously distorted. If the contrast is 0.5, the pattern is hardly formed for the doses less than 5.0 mJ/cm2.