Theoretical analysis of energy degradation of electrons in the resists

In the electron-beam lithography and extreme-ultraviolet lithography electrons above ionization energy collide with resist materials and bring out their ionizations and electronic excitations. The degradation mechanism of the electrons in resists plays the important role to determine the resist properties. The energy distribution of the electrons ejected in collisions with the resist molecules and the yields of ions and excited states of resist molecule, and the contributions of molecular orbitals to the yields were calculated by using the binary-collision theory and the continuous-slowing-down approximation. Phenol was used as a model of phenol resists. The results show that the electron impacts produce mainly secondary electrons with the lower energy. The selectivity in the ionization and excitation processes was found to increase with decreasing the incident energy. The outermost molecular orbital ionizes more dominantly with decreasing the incident energy. The lower incident energy preferentially generates the electrically-excited triplets than the singlets of resist molecules.