Nobuo Handa

Chemical state information of bulk specimens obtained by SEM-based soft-X-ray emission spectrometry.

Electron-beam-induced soft-X-ray emission spectroscopy (SXES) that uses a grating spectrometer has been introduced to a conventional scanning electron microscope (SEM) for characterizing desired specimen areas of bulk materials. The spectrometer was designed as a grazing incidence flat-field optics by using aberration corrected (varied line spacing) gratings and a multichannel plate detector combined with a charge-coupled device camera, which has already been applied to a transmission electron microscope. The best resolution was confirmed as 0.13 eV at Mg L-emission (50 eV), which is comparable with that of recent dedicated electron energy-loss spectroscopy instruments. This SXES-SEM instrument presents density of states of simple metals of bulk Mg and Li. Apparent band-structure effects have been observed in Si L-emission of Si wafer, P L-emission of GaP wafer, and Al L-emissions of intermetallic compounds of AlCo, AlPd, Al2Pt, and Al2Au.

Laminar and blazed type holographic gratings for a versatile soft x-ray spectrograph attached to an electron microscope and their evaluation in the 50–200 eV range

Laminar and blazed type holographic varied-line-spacing spherical gratings for use in a versatile soft x-ray flat-field spectrograph attached to an electron microscope are designed, fabricated, and evaluated. The absolute diffraction efficiencies of laminar (or blazed) master and replica gratings at 86.00° incidence evaluated by synchrotron radiation show over 5% (or 8%) in the 50-200 eV range with the maxima of 22% (or 26%-27%). Also the resolving power evaluated by a laser produced plasma source is in excess of 700 at the energy near the K emission spectrum of lithium (~55 eV) for all gratings. Moreover, the K emission spectrum of metallic Li with high spectral resolution is successfully observed with the spectrograph attached to a transmission electron microscope.

Progress in Electron Beam Mastering of 100 Gbit/inch2 Density Disc

We developed an electron beam recorder (EBR) capable of recording master discs under atmospheric conditions using a novel differential pumping head. Using the EBR and optimized fabrication process for Si-etched discs with reactive ion etching (RIE), a bottom signal jitter of 9.6% was obtained from a 36 Gbit/inch2 density disc, readout using a near-field optical pickup with an effective numerical aperture (NA) of 1.85 and a wavelength of 405 nm. We also obtained the eye patterns from a 70 Gbit/inch2 density disc readout using an optical pickup with a 2.05 NA and the same wavelength, and showed almost the same modulation ratio as the simulation value. Moreover, the capability of producing pit patterns corresponding to a 104 Gbit/inch2 density is demonstrated.

Exciting Possibilities of Soft X-ray Emission Spectroscopy as Chemical State Analysis in EPMA and FESEM

A novel wavelength dispersive soft X-ray emission spectrometer (WD-SXES) has been developed. It covers nominally the X-ray energy range between 50 and 210 eV [1, 2]. One of the characteristic features of the WD-SXES is parallel detection of the signal so that it can be used like a conventional energy dispersive spectrometer. One other feature is a high energy resolution, which is about 0.2 eV. This resolution is comparable to the one acquired with X-ray photoelectron spectroscopy or electron energy loss spectroscopy. This feature enables us to obtain various information about chemical bonding in bulk samples from observed spectra with a high energy resolution.

A new grating X-ray spectrometer for 2-4 keV enabling a separate observation of In-Lβ and Sn-Lα emissions of indium tin oxide

A new multilayer-coated varied line-spaced grating, JS4000, was fabricated and tested for extending the upper limit of a grating X-ray spectrometer for electron microscopy. This grating was designed for 2-3.8 keV at a grazing incidence angle of 1.35°. It was revealed that this new multilayer structure enables us to take soft-X-ray emission spectra continuously from 1.5 to 4.3 keV at the same optical setting. The full-width at half maximum of Te-L(α1,2) (3.8 keV) emission peak was 27 eV. This spectrometer was applied to indium tin oxide particles and clearly resolved Sn-L(α) (3444 eV) and In-L(β1) (3487 eV) peaks, which could not be resolved by a widely used energy-dispersive X-ray spectrometer.

Development of an objective flat-field spectrograph for electron microscopic soft x-ray emission spectrometry in 50-4000 eV

We have developed an objective soft x-ray flat-field spectrograph installed in electron microscopes (EMs). The spectrograph has two attractive features. One is that it is designed to cover a wide energy range of 50-4000 eV by using four varied-line-spacing holographic gratings (VLSHGs) optimized for 50–200 eV, 155–350 eV, 300–2200 eV, and 2000–4000 eV. The gratings dedicated for the respective energy ranges can be accommodated in the single spectrograph. This advantage comes from that the positions of the source points and image planes are assumed as the common parameters in the design of all gratings. Therefore, it allows to easily change the energy range by only choosing an appropriate grating and its position. The other is the application of a newly invented W/B4C multilayer coating. It has been adopted to the grating for the 2000–4000 eV range to overcome the considerable decrease of the diffraction efficiency in the energy range above ~2 keV. The novel coating makes it possible to enhance uniformly the diffraction efficiency at a constant incidence angle in the whole energy range.

A multilayer grating with a novel layer structure for a flat-field spectrograph attached to transmission electron microscopes in energy region of 2-4 keV

A multilayer mirror with a novel layer structure to uniformly enhance the reflectivity in a few keV energy range at a fixed angle of incidence is invented and applied to a multilayer grating for use in a flat-field spectrograph attached to a conventional electron microscope. The diffraction efficiency of the fabricated multilayer grating having the new layer structure is evaluated at the angle of incidence of 88.65° in the energy region of 2.1-4.0 keV. It is shown that the multilayer grating is effective to uniformly enhance the diffraction efficiency and able to be practically used in this energy region.

Development of a soft x-ray diffractometer for a wideband multilayer grating with a novel layer structure in the 2-4 keV range

We have been developing a wavelength-dispersive soft x-ray spectrograph covering an energy region of 50-4000 eV to attach to a conventional electron microscope. Observation of soft x-ray emission in the 2-4 keV range needs a multilayer coated grating. In order to evaluate the performance of the optical component in the energy region, a goniometric apparatus has been newly developed and the preliminary performance has been tested using synchrotron radiation.

Optical properties of immersion objective lenses and collimation of secondary electrons in low-voltage SEM

Optical properties of two kinds of immersion lenses, i.e. the radial gap magnetic lens and the combined electric and magnetic field lens have been compared. When the specimen allows the application of a leakage electric field about 600 V and the accelerating voltage on the specimen is lower than 2 kV, the combined field lens is better than the radial gap lens, because the spherical and chromatic aberration coefficients are small and the collimation efficiency of secondary electrons is perfect. However, if the leakage electric field is not allowed, the radial gap lens is superior to the combined field lens. In the case of the radial gap lens, a weak electric field has to be applied to the specimen for collimating electrons emitted with large angle from the specimen. When the specimen is set lower than the magnetic field maximum position, a solenoid coil placed inside the yoke of the lens is useful to bring up the off axial electrons.

Immersion lenses for low-voltage SEM and LEEM

Spherical and chromatic aberration coefficients Cs and Cc of various immersion lenses for low voltage SEM and LEEM are calculated. The minimum values of magnetic immersion lens are Cs equals Cc equals 1 mm. For the combined electrostatic and magnetic lenses, those values are at most Cs equals 1 mm and Cc equals 0.7 mm, when the specimen is free from the electrostatic field. When the specimen is immersed in the electrostatic field, those values reduce to Cs equals 0.2 mm and Cc equals 0.1 mm at 1 kV.