Plasma-based EUV light source

Patent Granted Neutral atoms or condensed matter cannot emit EUV radiation. For matter to emit it, ionization must take place first. EUV light can only be emitted by electrons which are bound to multicharged positive ions; for example, to remove an electron from a +3 charged carbon ion (three electrons already removed) requires about 65 eV.[2] Such electrons are more tightly bound than typical valence electrons. The thermal production of multicharged positive ions is only possible in a hot dense plasma, which itself strongly absorbs EUV.