The task of EUV-reflectometry for HVM of EUV-masks: first steps

High volume manufacturing (HVM) of EUV-masks requires increase in accuracy, precision and practicability. HVM requirements for reflectometry of EUV-masks are expected to be < 0.05 % in peak reflectance, and < 0.002 nm in centroid wavelength (3 sigma). Absolute accuracies should be of the same value at 1 sigma. This should be accomplished along with the reduced measuring spot size of down to < 0.01 mm2 as well as monitored alignment and positioning using fiducial mark. With the existing EUV-reflectometer developed for mask blank characterization, 0.1 % in peak reflectivity precision and 0.005 nm for centroid wavelength (1 sigma) are routinely achieved on both reflective multilayer coated and absorber coated blanks. It has been demonstrated that our EUV-lamp enables EUV-MBR operation without wear or components change for > 300 million pulses, which is > 100.000 full spectra measured at different sites or > 10.000 samples measured at 9 spots each. In this work we are presenting our present status as well as the first steps to achieve the demanded target for HVM of EUV masks. We will analyze the factors and parameters which are critical to achieve this level quality.