Development of a Compact X-ray Source and Super-sensitization of Photo Resists for Soft X-ray Imaging

Abstract

A compact soft X-ray source via inverse Compton scattering has been developed at Waseda University. The energies of the generated X-rays are within "water window" region (250 -500 eV) and development of a soft X-ray microscope is expected which can get the elemental mapping of carbon and/or nitrogen without dehydration. We have studied to develop a high resolution soft X-ray imaging system with photo resists for nanoscale observation. However, the yield of generated X-rays had been too small for the practical use of the soft X-ray microscopy. To enhance the X-ray yield, we have upgraded the generation system and succeeded in increasing the detected photons 10-fold. Total generated photons were estimated to be over 1.5E+5 photons/s. Also, super-sensitization of photo resists has been attempted to reduce the required X-ray amount. By irradiating quasi-monochromatic X-rays in the water window region from synchrotron radiation at BL12 of the SAGA-LS, the sensitivity of a deep-UV photo resist, TDUR-P722 (Tokyo Ohka Kogyo Co., Ltd) was evaluated. After UV light (including 254 nm) exposure up to the sensitivity threshold and baking as PEB process, it was found that the resist becomes more sensitive. This UV "pre-exposure" method reduced the required 400 eV X-ray amount by over 65 %.

Feasibility study of broadband efficient “water window” source

“…Although our proposal is based on a simple microscope construction, the key component is the UTA emitted at 3.2 nm from a hot dense Bi plasma point source, combined with Sc/Cr MLMs and sensitive EUV resists based on photochemical reaction [24,25].…”