天野 壮

We have completed a system that can achieve both deep x-ray lithography and submicron x-ray lithography with a single beamline by introducing the combination of x-ray plane and cylindrical mirrors. This x-ray lithography system can provide a large-scale microfabrication processing with 210 × 300 mm2 (A4 size). To exploit multiscale lithography, the beamline has a beam transport vacuum duct with a two-stage stacked structure and a 5-axis stage. This two-stage stacked structure allows us to fabricate both micron scale structures with high aspect ratios and submicron scale structures using the same beamline. In addition, x-ray imaging and computer tomography (CT) system are connected to the x-ray lithography system for nondestructive inspection and evaluation of the fabricated microstructures. The x-ray imaging system constructed this study has a relatively low energy range of x-ray energy in the beamline, which is in the range of 2–15 keV or less. Therefore, relatively good absorption contrast can be obtained for plastic materials, biomaterials, and the like. Since nondestructive imaging of the processed shape by x-ray lithography is possible, it is a very useful system in processing and evaluation can be performed simultaneously. This system also enables us to obtain the live images with keeping the creature alive in liquid using an indirect x-ray imaging system which converts x-ray images to visible light images through the fluorescent plate.

<p>To generate continuously repetitive soft X-ray pulses in the water window from laser-produced plasmas, a one-dimensionally translating substrate system with a closed He gas cryostat that can continuously supply various cryogenic targets has been developed. The system was successfully operated at a lowest temperature of 15 K and at a maximum up-down speed of 12 mm/sec. Solid Ar and N₂ layers were formed, and the water window spectra from them were studied. The emission intensity from Ar was found to be about 8 times stronger than that from N₂. Developed laser plasma source demonstrated high average power of 140 mW in the water window soft X-ray, when a commercial Nd:YAG Q-switched laser was used to irradiate a solid Ar target with energy of 1 J at a repetition rate of 1 Hz. It can be used for various applications, including soft X-ray microscopy, in place of synchrotron facilities.</p>

Low-temperature crystallization of Si, Ge and Si_XGe_1−X films by SR-soft x-ray irradiation using short undulator light is examined. By setting the photon energy to that of the core electron orbital, the crystallization is examined experimentally and discussed theoretically from a view point of Ge diffusion. The temperature during the crystallization of Si, Ge or Si_0.5Ge_0.5 by soft x-ray was 80 to 140 degree C lower than that by the conventional rapid thermal annealing. The elementary process of the soft x-ray irradiation is thought to be the atom-diffusion following the localized excitation of the core-electrons and the generation of Coulomb repulsion. For the low-temperature crystallization, the quasi-nuclei are formed via the elementary process.<br>

Tunable and high-power terahertz radiation sources using relativistic electron beams from a compact linear accelerator LEENA are under development. The synchrotron radiation and Smith-Purcell radiation in THz regime were successfully measured. The coherent radiation power from an electron bunch shorter than 1ps is estimated theoretically to be about 10⁷ larger than the incoherent one. Recent experimental results on the generation of the THz radiation and the numerical results on the high-power coherent radiation from a short electron bunch are reported.

Microprocessing of poly(tetrafluoroethylene) (Teflon) and poly(methyl methacrylate) (PMMA) samples was carried out using soft X-ray from a laser produced Xe plasma source we developed. In the Teflon sample, a contact angle of a modified surface with a water drop increased from 90° to 110° to by an irradiation without a mirror and a mask, while the angle decreased to 50° by an irradiation with them. Scanning electron microscopy showed numerous microprotuberances and a masked pattern having micro-concavities on the each sample surface. These suggested that the changes of the contact angle were ascribable to the microstructures of the Teflon surface. We succeeded in controlling the wettability of the Teflon surface from hydrophobic to hydrophilic by microprocessing using the laser plasma X-ray. In the PMMA sample, its etching rate was investigated using an irradiation with a large number of pulses (192000 pulses) and a low power density of 8×10⁴ W/cm². The etching rate was calculated to be 5 pm/pulse and this was concluded to be a result by only photo-etching without thermal effect. We demonstrated pure photo-etching depth of ∼1 µm.

Tunable and high-power terahertz radiation sources using relativistic electron beams from a compact linear accelerator LEENA are under development. The synchrotron radiation and Smith-Purcell radiation in THz regime were successfully measured. The coherent radiation power from an electron bunch shorter than 1ps is estimated theoretically to be about 10⁷ larger than the incoherent one. Recent experimental results on the generation of the THz radiation and the numerical results on the high-power coherent radiation from a short electron bunch are reported.