Fabrication of ultrathin and highly uniform silicon on insulator by numerically controlled plasma chemical vaporization machining

Metal-oxide semiconductor field-effect transistors fabricated on a silicon-on-insulator (SOI) wafer operate faster and at a lower power than those fabricated on a bulk silicon wafer. Scaling down, which improves their performances, demands thinner SOI wafers. In this article, improvement on the thinning of SOI wafers by numerically controlled plasma chemical vaporization machining (PCVM) is described. PCVM is a gas-phase chemical etching method in which reactive species generated in atmospheric-pressure plasma are used. Some factors affecting uniformity are investigated and methods for improvements are presented. As a result of thinning a commercial 8 in. SOI wafer, the initial SOI layer thickness of 97.5±4.7 nm was successfully thinned and made uniform at 7.5±1.5 nm. © 2007 American Institute of Physics.Yasuhisa Sano, Kazuya Yamamura, Hidekazu Mimura, Kazuto Yamauchi, and Yuzo Mori, "Fabrication of ultrathin and highly uniform silicon on insulator by numerically controlled plasma chemical vaporization machining", Review of Scientific Instruments 78(8), 086102 (2007) https://doi.org/10.1063/1.2766836

Feasibility study of high-resolution coherent diffraction microscopy using synchrotron x rays focused by Kirkpatrick-Baez mirrors

High-flux coherent x rays are necessary for the improvement of the spatial resolution in coherent x-ray diffraction microscopy (CXDM). In this study, high-resolution CXDM using Kirkpatrick-Baez (KB) mirrors is proposed, and the mirrors are designed for experiments of the transmission scheme at SPring-8. Both the photon density and spatial coherence of synchrotron x rays focused by the KB mirrors are investigated by wave optical simulation. The KB mirrors can produce nearly diffraction-limited two-dimensional focusing x rays of ∼1 μm in size at 8 keV. When the sample size is less than ∼1 μm, the sample can be illuminated with full coherent x rays by adjusting the cross-slit size set between the source and the mirrors. From the estimated photon density at the sample position, the feasibility of CXDM with a sub- 1-nm spatial resolution is suggested. The present ultraprecise figuring process enables us to fabricate mirrors for carrying out high-resolution CXDM experiments.Yukio Takahashi, Yoshinori Nishino, Hidekazu Mimura, Ryosuke Tsutsumi, Hideto Kubo, Tetsuya Ishikawa, and Kazuto Yamauchi, "Feasibility study of high-resolution coherent diffraction microscopy using synchrotron x rays focused by Kirkpatrick–Baez mirrors", Journal of Applied Physics 105, 083106 (2009) https://doi.org/10.1063/1.3108997

Microstitching interferometer and relative angle determinable stitching interferometer for half-meter-long X-ray mirror

Haruhiko Ohashi, Takashi Tsumura, Hiromi Okada, Hidekazu Mimura, Tatsuhiko Masunaga, Yasunori Senba, Shunji Goto, Kazuto Yamauchi, and Tetsuya Ishikawa "Microstitching interferometer and relative angle determinable stitching interferometer for half-meter-long x-ray mirror", Proc. SPIE 6704, Advances in Metrology for X-Ray and EUV Optics II, 670405 (1 October 2007); https://doi.org/10.1117/12.733476

Single-Shot Spectrometry for X-Ray Free-Electron Lasers

An experimental scheme to realize single-shot spectrometry for the diagnostics of x-ray free-electron lasers (XFELs) is presented. The combination of an ultraprecisely figured mirror and a perfect crystal form a simple, high-precision spectrometer that can cover an energy range from a few eV to a hundred eV with high resolution. The application of the spectrometer to determine XFEL pulse widths was investigated theoretically and experimentally. It has been shown that the present system can determine pulse widths from sub-fs to ps in a single shot even for spontaneous radiation. The system can be easily extended to even shorter pulses.Makina Yabashi, Jerome B. Hastings, Max S. Zolotorev, Hidekazu Mimura, Hirokatsu Yumoto, Satoshi Matsuyama, Kazuto Yamauchi, and Tetsuya Ishikawa. Phys. Rev. Lett. 97(8), 084802 (2006)

Atomic-scale flattening of SiC surfaces by electroless chemical etching in HF solution with Pt catalyst

The authors present a method for flattening SiC surfaces with Pt as a catalyst in HF solution. The mechanism for flattening SiC surfaces is discussed. The flattened 4H-SiC (0001) surface is composed of alternating wide and narrow terraces with single-bilayer-height steps, which are induced by the rate difference of the catalytic reactions between adjacent terraces. Scanning tunneling microscopy images reveal a 1×1 phase on the terraces. The 1×1 phase is composed of coexisting of F- and OH-terminated Si atoms, which originate from the polarization of the underlying Si-C bonds. © 2007 American Institute of Physics.Kenta Arima, Hideyuki Hara, et al. "Atomic-scale flattening of SiC surfaces by electroless chemical etching in HF solution with Pt catalyst", Appl. Phys. Lett. 90(20), 202106 (2007) https://doi.org/10.1063/1.2739084

At-wavelength figure metrology of hard x-ray focusing mirrors

We have developed an at-wavelength wave-front metrology of a grazing-incidence focusing optical systems in the hard x-ray region. The metrology is based on numerical retrieval from the intensity profile around the focal point. We demonstrated the at-wavelength metrology and estimated the surface figure error on a test mirror. An experiment for measuring the focusing intensity profile was performed at the 1-km-long beamline (BL29XUL) of SPring-8. The obtained results were compared with the profile measured using an optical interferometer and were confirmed to be in good agreement with it. This technique is a potential method of characterizing wave-front aberrations on elliptical mirrors for sub-10-nm focusing. © 2006 American Institute of Physics.Yumoto H., Mimura H., Matsuyama S., et al. At-wavelength figure metrology of hard x-ray focusing mirrors. Review of Scientific Instruments, 77, 6, 063712 (2006) https://doi.org/10.1063/1.221687

Direct determination of the wave field of an x-ray nanobeam

We present a remarkably accurate method for determining the wave field of an x-ray nanobeam. The intensity profile of a beam was directly measured over a range of three orders of magnitude while its phase distribution was successfully recovered using an iterative algorithm. The evolution of the wave field along the beam propagation direction was precisely simulated, and there was good agreement with the experimental results.Hidekazu Mimura, Hirokatsu Yumoto, Satoshi Matsuyama, Soichiro Handa, Takashi Kimura, Yasuhisa Sano, Makina Yabashi, Yoshinori Nishino, Kenji Tamasaku, Tetsuya Ishikawa, and Kazuto Yamauchi Phys. Rev. A 77, 015812 (2008)

Efficient focusing of hard x rays to 25 nm by a total reflection mirror

Nanofocused x rays are indispensable because they can provide high spatial resolution and high sensitivity for x-ray nanoscopy/spectroscopy. A focusing system using total reflection mirrors is one of the most promising methods for producing nanofocused x rays due to its high efficiency and energy-tunable focusing. The authors have developed a fabrication system for hard x-ray mirrors by developing elastic emission machining, microstitching interferometry, and relative angle determinable stitching interferometry. By using an ultraprecisely figured mirror, they realized hard x-ray line focusing with a beam width of 25 nm at 15 keV. The focusing test was performed at the 1-km -long beamline of SPring-8. © 2007 American Institute of Physics.Hidekazu Mimura, Hirokatsu Yumoto, et al. "Efficient focusing of hard x rays to 25nm by a total reflection mirror", Appl. Phys. Lett. 90(5), 051903 (2007) https://doi.org/10.1063/1.2436469

Results of x-ray mirror round-robin metrology measurements at the APS, ESRF, and SPring-8 optical metrology laboratories

This paper presents the first series of round-robin metrology measurements of x-ray mirrors organized at the Advanced Photon Source (APS) in the USA, the European Synchrotron Radiation Facility in France, and the Super Photon Ring (SPring-8) (in a collaboration with Osaka University,) in Japan. This work is part of the three institutions' three-way agreement to promote a direct exchange of research information and experience amongst their specialists. The purpose of the metrology round robin is to compare the performance and limitations of the instrumentation used at the optical metrology laboratories of these facilities and to set the basis for establishing guidelines and procedures to accurately perform the measurements. The optics used in the measurements were selected to reflect typical, as well as state of the art, in mirror fabrication. The first series of the round robin measurements focuses on flat and cylindrical mirrors with varying sizes and quality. Three mirrors (two flats and one cylinder) were successively measured using long trace profilers. Although the three facilities' LTPs are of different design, the measurements were found to be in excellent agreement. The maximum discrepancy of the rms slope error values is 0.1 μrad, that of the rms shape error was 3 nm, and they all relate to the measurement of the cylindrical mirror. The next round-robin measurements will deal with elliptical and spherical optics.Lahsen Assoufid, Amparo Rommeveaux, Haruhiko Ohashi, Kazuto Yamauchi, Hidekazu Mimura, Jun Qian, Olivier Hignette, Tetsuya Ishikawa, Christian Morawe, Albert Macrander, Ali Khounsary, and Shunji Goto "Results of x-ray mirror round-robin metrology measurements at the APS, ESRF, and SPring-8 optical metrology laboratories", Proc. SPIE 5921, Advances in Metrology for X-Ray and EUV Optics, 59210J (16 September 2005); https://doi.org/10.1117/12.623209.Optics and Photonics 2005, 2005, San Diego, California, United State

At-wavelength figure metrology of total reflection mirrors in hard x-ray region

Hirokatsu Yumoto, Hidekazu Mimura, Satoshi Matsuyama, Soichiro Handa, Akihiko Shibatani, Keiko Katagishi, Yasuhisa Sano, Makina Yabashi, Yoshinori Nishino, Kenji Tamasaku, Tetsuya Ishikawa, and Kazuto Yamauchi "At-wavelength figure metrology of total reflection mirrors in hard x-ray region", Proc. SPIE 6317, Advances in X-Ray/EUV Optics, Components, and Applications, 631709 (29 August 2006); https://doi.org/10.1117/12.681587