RF plasma based mitigation has been studied as an improved debris mitigation scheme for extreme ultraviolet (EUV) sources. The RF plasma ionizes sputtered neutral debris and, when used in conjunction with a collimator (also known as a foil trap), inhibits that debris from reaching the collector optics. An ionization fraction of 61±3% has been measured. In addition, increased scattering of the ion component of the debris has led to a decrease in erosive flux reaching the diagnostics. Results from in-situ high-precision quartz crystal oscillators, ex-situ surface characterization (Auger, XPS), and secondary plasma characterization is presented for a series of mitigation schemes, including a foil trap in conjunction with the RF plasma.
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