Transient population dynamics of nanoparticles during pulsed EUV exposures

The transient population dynamics of charged (positive or negative) and neutral nanoparticles have been investigated in a pulsed extreme ultra-violet (EUV) exposure environment with 3D particle-in-cell (3DPIC) simulations. At the initial stage of the simulation, all the particles are kept neutral. As the number of EUV pulses increases over time, the population of neutral particle decreases faster at the expense of negatively charged particle generation outside the beam location. However, a small population (<1%) of neutral particles becomes positively charged due to EUV photon interaction within the beam area and remains in steady state over time. The critical pulse numbers have been estimated for different nanometer size particles above which most of the particles outside the beam locations become negatively charged: smaller the particle size, larger the critical pulse number.