Particle-in-cell simulations of EUV-induced hydrogen plasma in the vicinity of a reflective mirror

Particle-In-Cell (PIC) simulations were performed in this work to study the dynamics of the EUV induced hydrogen plasma. Monte-Carlo Collision (MCC) model was employed to deal with the collisions between charged particles and background gas molecules. The dynamic evolution of the plasma sheath, as well as the flux and energy distribution of ions impact on the mirror surface, was discussed. It was found that the emission of secondary electrons under the EUV irradiation on the ruthenium coating of mirrors creates a positively charged wall and then prevents the ion from impacting onto the mirror and therefore changes the flux and energy distribution of ions reach the mirror. Furthermore, gas pressure has notable effect on the plasma sheath and the characteristics of the ions impinging on the mirrors. With greater gas pressure, the sheath potential decreases more rapidly. The flux of ions received by the mirror grows approximately linearly and the energy corresponding to the peak flux decreases slightly in the meantime. Meanwhile, EUV source intensity barely changes the sheath potential and its influence on the ion impact is mainly limited to the approximate linear increase of ion flux.