Researchers from ETH-Zurich in Switzerland have discovered a previously untapped source of EUV light as part of investigations into modelling the light source. The scientists developed a theoretical model of an EUV emission that explains how the emission depends on the three-dimensional shape of the plasma.
The new light source could be useful for various applications including semiconductor lithography, the process used to make integrated circuits.
In the experiments, Andrea Giovannini and Reza Abhari from ETH-Zurich blasted a 30µm diameter droplet of tin with a high-powered laser 6,000 times a second. They measured the spatial distribution of the resulting EUV emission and found that 30 per cent of it came from behind the region of the droplet that was struck by the laser. According to their model, this unexpected distribution was due to the fact that the plasma partially surrounding the droplet was elongated in the direction of the laser pulse.
Devices that produce narrow beams of EUV for purposes like in semiconductor lithography use mirrors to focus the emission. But, until now, no one knew to collect the EUV light radiating from behind the droplet.
Thanks to this work, Giovannini said, future devices can exploit this previously unknown source of EUV emission. The new experiments can also inform the development of EUV devices by showing where mirrors should be placed around a droplet in order to collect and focus as much EUV light as possible.
The researchers describe their experiments in the Journal of Applied Physics, which is produced by AIP Publishing.