SPring-8, the large synchrotron radiation facility

Scientists of a research group led by Masaharu Oshima (Professor of the School of Engineering, The University of Tokyo) installed a scanning photoelectron microscope system enabling three-dimensional nanoscale electron spectroscopy for chemical analysis (3D nano-ESCA) at the University of Tokyo Synchrotron Radiation Outstation Beamline at SPring-8 and demonstrated the possibility of angle-resolved observation with a spatial resolution of 70 nm for the first time in the world. The research group includes Koji Horiba (Assistant Professor) as the leading researcher, Satoshi Toyoda (Specially Appointed Assistant Professor), and Naoka Nagamura (Postdoctoral Fellow) of the above group; Hiroshi Kumigashira (Professor) and Kenta Amemiya (Associate Professor) of the High Energy Accelerator Research Organization (KEK); and their colleagues. At the University of Tokyo Synchrotron Radiation Outstation Beamline, eight undulators are connected in series, producing soft X-rays with the world's highest brilliance. The 3D nano-ESCA system is equipped with a newly developed zone plate (a circular diffraction grating) and an electron analyzer with a wide acceptance angle of 60^o that can collectively detect multiple photoelectrons. By irradiating a soft X-ray beam focused to a diameter of 70 nm onto a predetermined position on a sample, the angle-resolved high-resolution energy analysis of photoelectrons is realized. The 3D nano-ESCA system is a type of scanning photoelectron microscope; unlike conventional photoelectron microscopes, it is capable of yielding accurate depth profiles by the maximum entropy method from the intensity of photoelectrons obtained by angle-resolved observation.

The scientists from the research group of The University of Tokyo demonstrated the possibility of depth profiling for arbitrary positions on samples by applying the above analytical system to the LSI gate electrode patterns, and they reported their achievement in a scientific paper. In addition, they realized pinpoint photoelectron spectroscopy for resistive nonvolatile memories with a width of several hundred nanometers and graphene field-effect transistors (FETs), and their system is expected to be applied to the pinpoint failure analysis of various nanodevices.

The results of this research were published in Review of Scientific Instruments, in which many instruments related to synchrotron radiation have been reported.