Research on efficient and stable control of EUV-induced hydrogen plasma

Abstract

We use the numerical model to study the control method for the ion sputter flux and energy at the surface of multilayer mirrors in hydrogen plasmas induced by extreme ultraviolet (EUV) radiation. This plasma is generated via photoionization by EUV photons with wavelengths at 13.5 nm and collision ionization by high-energy electrons. An electric field is formed by applying different bias voltages to the cylindrically symmetrical cavity and sample holder, which guides the transfer of charged particles and increases their energy. The evolution of pulsed EUV-induced plasma under the field is described by a two-dimension particle-in-cell model and the Monte Carlo simulation to represent collisions between charged particles and background molecules. The results show that the distribution of the electric field varies during the pulse and point out that the secondary electrons, which gain energy from the varying field and generate more plasma by collisions with hydrogen molecules, are crucial plasma sources in this scheme. We then propose a stable and efficient control method for EUV-induced hydrogen plasma by optimizing the cavity structure as an ellipsoid and treating the surface of the cavity in contact with the plasma.