Particle mobilization by EUV-induced plasma and fast electrons

With state-of-the-art EUV lithography moving to the 3 and 2 nm nodes, yield control and connected to that particle contamination control are crucial aspect of High-Volume Manufacturing (HVM). While much progress has been made in recent years, the continuously tightening node requirements translate into ever more stringent requirements on particle contamination control. Besides for lithographic scanners, operating in a low background pressure hydrogen gas environment, particle contamination control is also important for space exploration (which also operates in low pressure environments), where particles may lead to malfunctioning moving parts, loss of solar power generation, and human health hazards. A key factor in release of particles in these low-pressure environments is the ionization of the low-pressure background gas by energetic photons (for instance EUV in lithographic scanners, and broadband energetic radiation in space), and resulting plasma with fast electrons of 25 eV and above. Experiments show that these electrons can mobilize and remove particles on most materials, and that the governing effects strongly depend on the substrate material, coating and surface finishing. This paper will discuss work on understanding and modeling these effects and describe possible solution paths to improve particle contamination control, both for lithographic scanners and for space exploration.