Advanced laser repair of EUV photomasks

In the last year, initial feasibility study results were published which showed that simulated fall-on particles and TEOS deposited pindot features could be removed with low-fluence femtosecond-pulsed laser repair processes with no detectable multi-layer damage as seen in AFM scans. At the time, actinic EUV inspection metrology was not available. In this work, this metrology is used with both process testing and removal of a more diverse range of different defect types both isolated (on multilayer and on absorber) and in patterns of various types and densities. In addition, follow-up work is shown to complete full factorial design of experiments tests for TEOS pindots in OMOG line and space patterns. These results are then parametrically analyzed and compared to simulation results and theoretical first-principles to better understand the mechanisms for defect removal from the EUV mask surface.