Particle charging during pulsed EUV exposures with afterglow effect

The nanoparticle charging processes along with background spatial-temporal plasma profile have been investigated with 3DPIC simulation in a pulsed EUV exposure environment. It is found that the particle charge polarity (positive or negative) strongly depends on its size, location and background transient plasma conditions. The particle (100 nm diameter) charge reaches steady state in a single pulse (20 us) within the EUV beam in contrast to particles outside the beam that requires multiple pulses. The larger the particle size, the less number of pulses are required to reach steady state. It is found that the charge of a particle decreases with pressure in a faster rate outside the beam compared to inside. The results are of importance for particle contamination (defectivity) control strategy for EUV lithography machines.