| AVS 54th International Symposium | |
| Nanometer-scale Science and Technology | Friday Sessions |
| Session NS-FrM |
| Session: | Nanolithography and Nanoprocess Technology |
| Presenter: | E. Loginova, Rutgers University |
| Authors: | E. Loginova, Rutgers University B. Yakshinskiy, Rutgers University S. Yulin, Fraunhofer Institut (IOF), Germany T. Feigel, Fraunhofer Institut (IOF), Germany J. Keister, Brookhaven National Laboratory T. Lucatorto, National Institute of Standards and Technology C. Tarrio, National Institute of Standards and Technology S. Hill, National Institute of Standards and Technology O. Dulub, Tulane University U. Diebold, Tulane University M. Chandok, Intel Corporation M. Fang, Intel Corporation T.E. Madey, Rutgers University |
| Correspondent: | Click to Email |
The magnitude of secondary electron yield (SEY) at EUV wavelengths is a major factor in determining contamination rates of multilayer mirrors (MLMs) in EUV projection optics, and we have found striking resonance effects in measurements of SEY from MLMs. Low energy secondary electrons (0 to ~ 20 eV) can cause dissociation of adsorbed hydrocarbons from the background gas, and lead to carbon film growth on MLM surfaces. SEY data (electrons/photon) were measured using synchrotron radiation over the range 40 eV to 180 eV for TiO2 and Ru single crystals (clean, O-covered, C-covered, air exposed) and compared with measurements for Mo/Si multilayer films capped by Ru, TiO2, and RuO2. For photon beams incident at 45 degrees, the shapes of the curves for Ru multilayers, especially the maxima at ~ 65 eV due to the Ru 4p excitation, are very similar to the data for pure Ru; such similarities are found also for a TiO2 crystal and TiO2-capped MLMs. Thus, the cap layer properties dominate the SEY characteristics: this agrees with theory, which predicts that a film several nm thick contributes ~90% to the SEY characteristics of the mirrors. For incidence angles close to the surface normal, and for photon energies near 92 eV (13.5 nm), dramatic energy- and angle-dependent resonances in SEY are observed for the capped MLMs, with SEYs 2 to 3 times higher than off-resonance. Calculations show excellent correlations between the photon electric field strength in the cap layers and the angular-dependent SEYs.