EUV Source Metrology

In this chapter, a survey of selected metrology tools for EUV photon sources is presented. Section 13.2 discusses absolutely calibrated measurement of the in-band energy with a photodiode that is combined with a multilayer mirror acting as the band limiting element. Another narrowband metrology approach based on anomalous transmission is presented as a compact alternative. In Section 13.3, literature on spectroscopy for the EUV sources is surveyed, and a transmission grating spectrometer based on a set of high-line-density freestanding gratings is introduced for broadband spectroscopy. The spectral characteristics of HHG, DPP, and LPP sources, including industrial EUV sources, characterized by the transmission grating spectrometer, are discussed.