Particle charging in afterglow of EUV-induced plasma

Micro- and nanoparticle control is essential for high yield in lithography machines. Particles in modern EUV machines are exposed to a plasma, created by the interaction of the high-energetic EUV photons and the background hydrogen gas. In this paper, we explore the particle charging in this pulsed EUV-induced plasma based on 3D-particle-in-cell simulations. It is found that the particle charging dynamics strongly depends on the size of the particle. Micrometer-sized particles typically reach steady state charge in a single pulse period (20 μs), while sub-micrometer particles require multiple pulses. The charge and plasma affect the forces on a particle. Understanding this force balance is essential for controlling particle motion inside EUV scanners and preventing the yield loss that they can cause.