Particle charging during pulsed EUV exposures with afterglow effect

Abstract Nanoparticle charging processes along with background spatial–temporal plasma profile have been investigated using 3D particle-in-cell simulations in a pulsed extreme ultraviolet (EUV) exposure environment. The particle charge polarity (positive or negative) strongly depends on its size, location, and background transient plasma conditions. The particle (100 nm diameter in size and conducting material) charge reaches a steady state in a single pulse (20 µ s) within the EUV beams compared to particles outside the beam requiring multiple pulses. The larger the particle size, the lower the number of pulses required to reach a steady state. The charge of a particle decreases with pressure at a faster rate outside the beam compared to inside. These results are crucial for particle contamination (defectivity) control strategies for EUV lithography machines.