Study of EUVL mask defect repair using FIB-GAE method

摘要

We evaluated a new FIB-GAE (Focused Ion Beam-Gas Assisted Etching) repairing process for the absorber defects onEUVL mask. XeF2 gas and H20 gas were used as etching assist agent and etching stop agent respectively. The H20 gaswas used to oxidize Ta-nitride side-wall and to inactivate the remaining XeF2 gas after the completion of defect repair.At the Photomask Japan 2008 we had reported that side-etching of Ta-nitride caused CD degradation in EUVL. In thepresent paper we report on the performance of defect repair by FIB, and of printability using SFET (Small FieldExposure Tool). The samples evaluated, were in form of bridge defects in hp225nm L/S pattern. The cross sectionalSEM images certified that the newly developed H20 gas process prevented side-etching damage to TaBN layer andmade the side-wall close to vertical. The printability also showed excellent results. There were no significant CDchanges in the defocus characterization of the defect repaired region. In its defect repair process, the FIB method showedno signs of scan damage on Cr buffered EUV mask. The repair accuracy and the application to narrow pitched patternare also discussed.