Ionic Debris Assessment of Various EUVL Systems

摘要

Debris generation in EUV sources is a real threat to the lifetime of collector optics. Debris measurements in thesesources are of immense importance to enable source suppliers to estimate collector lifetime. Ion debris measurementsperformed so far are not consistent and in part incomplete. To verify lifetime claims from different EUV sourcesuppliers, SEMATECH, which is leading this investigation, has collaborated with and provided funding to the Center forPlasma Material Interactions (CPMI) at the University of Illinois to build a fully calibrated and standardized sphericalsector electrostatic energy analyzer (ICE). This device is capable of measuring ion debris flux in absolute units. Inaddition to ion flux, the detector is also capable of identifying different ion species present in the plasma, which can bediscriminated based on energy-to-charge ratio. The lifetime of collector optics is calculated using the measured ion flux.This device was fabricated for SEMATECH with the sole aim of traveling to different EUV source suppliers' sitesaround the world and collecting ion debris data. SEMATECH has measured ion debris from different EUV sourcesaround the world, using a 1 to 14keV ion energy range under different source operational conditions (chamber pressure,pinch frequency, pinch power, angle). These measurements identify the need for debris mitigation in all the EUVsources investigated under this project. They also give source suppliers an opportunity to improve and optimize theperformance of their respective sources. The information on absolute ion fluxes is an advantage to source suppliers,allowing them to design and develop effective debris mitigation schemes, which can again be tested for theireffectiveness using the ion diagnostic tool. As the debris consists of ions and neutrals, the next logical step is to developa standardized neutral detector to measure the flux and energy distribution of neutrals present in EUV plasma sources.Taking into account both ions and neutral fluxes, more definitive conclusions on the performance of a EUV source canbe made and better collector lifetime estimation models can be derived. The Illinois Calibrated ESA (ICE) tool is nowpart of the SEMATECH "Flying Circus" equipment set.