Tetsuo Harada

EUV lithography has been used for high-volume manufacturing of semiconductor devices since 2019. An EUV lithography photomask is a reflection type with Mo/Si multilayer coatings. Since the EUV reflection phase is critical for printability, actinic (at-wavelength) inspection tools and microscopes were developed. In this report, we introduce an EUV specific issue of photomasks and EUV inspection tools for high-volume manufacturing. An EUV microscope is also important for EUV mask development. We made coherent EUV scatterometry microscopes to observe EUV phase images, which captured EUV diffraction from mask patterns without imaging optics. EUV phase images will be helpful for the development of high-contrast EUV masks.

When DNA/Si-MOSFET was irradiated with soft X-ray, the drain current was reduced due to DNA damage. Based on radiation analysis of DNA thin films by X-ray absorption spectroscopy (XAS), several damage patterns were suggested.

We have previously confirmed that when a transistor using DNA is irradiated with soft X-rays, the drain current value decreased, which is thought to be due to DNA damage. In this study, for the purpose of investigating the radiation damage mechanism of DNA, we attempted to analyze the structural changes of single-stranded DNA using total electron yield soft X-ray absorption spectroscopy (TEY-XAS). The obtained spectra suggested the possibility of forming a pyrimidine dimer at the DNA base and elimination of the methyl group from thymine.

We aim to develop a novel technique to produce a high energy γ-ray beam of several GeV by adopting inverse Compton scattering of soft X-rays at an electron storage ring. Now an experimental project to demonstrate such a beam is being advanced at NewSUBARU by using X-rays from a short undulator and reflecting it backwardly with a Mo/Si multi-layer mirror. It will open up a way to construct new γ-ray sources at the next generation rings and to carry out new photoproduction experiments for the studies of heavy hadrons.