First time-resolved measurements of ions from extreme ultraviolet-induced plasmas
First time-resolved measurements of ions from extreme ultraviolet-induced plasmas lead image
Extreme ultraviolet (EUV) radiation has industrial applications in semiconductor technologies, for instance in lithography scanners. EUV-induced plasmas, a type of plasma induced when energetic photons ionize a low pressure gas, affect the operation of EUV optical components. With this in mind, fully understanding EUV-induced plasma conditions can lead to enhanced operation of lithography tools.
Beckers et al. measured the energy of ions from an EUV-induced plasma. Previous measurements on ions from these plasmas have been time-averaged, but for the first time scientists have provided time-resolved measurements. To gather these measurements Beckers et al. used an Electrostatic Quadrupole Plasma (EQP) analyzer.
“Normally, this type of EQP already is able to measure in a temporally resolved fashion but is way too slow to apply to the current experiment. We adapted the electronics to make this diagnostic suitable and enable these experiments,” author Job Becker said.
The authors presented time-resolved measurements of fluence and energy distribution functions for H+, H2+ and H3+ ions.
“Momentary fluxes of ions appear three orders of magnitude higher than earlier reported average ion fluxes and the mean ion energy was unexpectedly found to remain elevated much longer than expected,” Beckers said.
Their research demonstrated two unexpected results in terms of plasma dynamics. As the shapes of the fluence and energy distribution functions developed, they remained roughly unaltered over the course of the plasma decay. As well, H2+ was surprisingly detected up to 50 μs in the afterglow phase.
The authors expect this research to be built upon by further investigation of fundamental EUV-induced plasma processes at increased source repetition rates, and by applying gas mixtures instead of using pristine gases.
Source: “Time-resolved energy distribution functions for ions in the afterglow of a pulsed EUV-induced plasma in hydrogen,” by J. Beckers, T. H. M. van de Ven, and V. Y. Banine, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5125739 .
