Toshihide Tsuru

Compact ellipsometer employing a static polarimeter module with arrayed polarizer and wave-plate elements

A portable ellipsometer with a compact static polarimeter using an arrayed polarizer, an arrayed wave plate, and a CCD image sensor is developed. A high level of repeatability at a measurement speed of 0.3 s is demonstrated by measurement of SiO(2) films ranging from 2 to 300 nm in thickness deposited on an Si wafer. There is the potential to realize an ultracompact ellipsometer module by integrating the optical source and receiver, suitable for deployment in a variety of manufacturing equipment and measurement instruments.

High throughput and wide field of view EUV microscope for blur-free one-shot imaging of living organisms

We present and demonstrate the use of an extreme ultraviolet (EUV) microscope that was developed in-house. Images are acquired using Bragg reflection multilayer optics and a laser-produced plasma light source. The upper-limit spatial resolution of the EUV microscope is 130 nm with a 10 ns exposure time and 250 x 250 microm(2) field of view. Resolution is superior to that of visible microscopes with the same size of field of view, and the exposure time is short enough to observe fine structures in-vivo. Observation of the cerebral cortex of a mouse is demonstrated.

Nanopipes in undoped AlGaN epilayers

The surface morphologies of nanopipes were imaged using a scanning electron microscope and an atomic force microscope in undoped AlGaN epilayers grown by metal organic vapor phase epitaxy on GaN-based layers, The nanopipes usually appear as dodecagonal and hexagonal pyramidal indentations for larger and smaller sizes, respectively, with a pinhole at each of their centers. The results indicate that {1 1 (2) over bar 1} facets may play an important role as well as {1 0 (1) over bar 1} facets during the nanopipe formation in undoped AlGaN epilayers, Energy dispersive X-ray spectroscopy shows that Al atoms have precipitated more distinctly on the facets of the nanopipes. The image of yellow cathodoluminescence is characterized by a bright ring around the outer region of pyramidal indentations. This is suggested to be a result of competition between the higher concentration of the defects responsible for the yellow luminescence and the thinner epilayer in the facet site

Development of a period-by-period EUV multilayer milling system for the final nm figure error correction by 0.1 nm per period

A period-by-period ion milling system has been developed for final reflection wavefront error correction of an imaging EUV multilayer mirror by a stepwise 0.1 nm-per-period correction of the residual nm figure errors. For effective, gentle and uniform milling of the surface areas selected by a template, the system is designed with a rotating substrate holder exposed to a 150 mm-wide ion beam with a dose homogenizer mask plate. For demonstration of the wavefront correction principle, local milling of a dielectric multilayer mirror for visible light was carried out by the system. The wavefront as measured by a phase shifting interferometer showed that the reflection phase was advanced by the milling, which formed a geometrical depression at the multilayer mirror surface. This confirmed the physical optics principle of our method and proved the procedure of the method being promising and practical for the accurate reflection phase correction of an EUV multilayer mirror.

Multi-bits coding by multi-directional valley pits permitting stamper mass-production and remote direction readout by polarization reflection

A new concept of high-density memories by arrays of multidirectional V-shape pits and remote polarization readout is proposed. The polarization readout principles are examined by two model experiments. The first experiment with an array of 1 mum deep V-pits fabricated by FIB on a Si wafer, carried out under polarization microscope observation, confirmed the concept by the expected contrast variation among the pits images. Accuracy of the remote readout was examined by the second experiment configuring total reflection V-pits by a rectangular prism glued underneath a glass plate. Polarization detection sensitivity of the V-pit direction was found to be +/-0.14 degrees , which should easily accommodate 1.4 degrees =180 degrees /128 separation for 7 bits recording at every single V-pit.

Normal Incidence Reflectometry of Concave Multilayer Mirrors Using Synchrotron Radiation to Evaluate the Period Thickness Distribution

For the purpose of fabricating curved multilayer mirrors, we developed an ion beam sputtering deposition system with a programmable shutter for thickness distribution control. In this report we fabricated a Mo/Si multilayer concave mirror of a 100 mm diameter and a 300 mm radius of curvature to be used at 13.5 nm at an angle of incidence of 5°. At first a test multilayer was deposited without thickness distribution control and the lateral distribution of deposition rate was evaluated. We used the normal incidence EUV reflectometry to determine the multilayer period thickness while we usually use the small angle X‐ray diffractometry when the substrate is plane. The measurements were performed at BL‐12A of the Photon Factory, KEK. In an analysis of a spectral reflectance, the side band structure as well as the main peak was taken into account. The natural thickness at the outermost part was found to be 13% thinner than that at the center. Next a Mo/Si multilayer of uniform thickness over the substrate was d...

Defects in flux and Czochralski grown β-BaB2O4 crystals observed by light scattering tomography

Abstract It is a very interesting fact that the β-BaB 2 O 4 (BBO) crystals are grown both by the flux method and the Czochralski (CZ) method from a stoichiometric melt. Defects in the BBO crystals grown by these two methods were examined in detail by light scattering tomography (LST). Many narrow and extremely thin platelets were optically observed on the rhombohedral ( R ) planes of the CZ and also of the flux-grown BBO crystals. This phenomenon of very similar defects being observed in both crystals is unique, because defects in crystals usually depend on how they were grown.

Three‐Dimensionally Controlled Ion Milling for Reflection Phase Manipulation of EUV Multilayer Mirrors

For accurate nm‐figure error correction of EUV multilayer mirror optics, a three‐dimensionally controlled ion milling method was developed. To demonstrate the reflection phase manipulation of an EUV multilayer, 10 periods of a 40‐period Mo/Si multilayer were partially removed. A partially milled Mo/Si multilayer with a contact double slit was successfully fabricated for interference fringe observations, which were carried out using a Young’s EUV interferometer with a reflection configuration. The fringe pattern revealed a small reflection phase change after multilayer surface milling. EUV interferometry results demonstrated the effectiveness of the proposed method for sub‐nanometer digital wavefront error correction in the case of multilayer mirror optics used in diffraction‐limited imaging.

Area‐selected Ion Milling for Reflection Wavefront Error Correction of Soft X‐ray Multilayer Mirrors

For accurate reflection wavefront error correction of imaging soft X‐ray multilayer mirrors, a period‐by‐period ion milling system was developed. A stable and homogenized radial distribution of ion beam was realized for an ion milling over a whole area of 100 mm‐wide multilayer. To demonstrate the wavefront error correction principle, a dielectric multilayer mirror for visible light was locally milled by our system. Wavefront as measured by a phase shifting interferometer showed the reflection phase of local milling multilayer advanced. Area‐selected ion millings with mask templates made of Mo and Si, and by photoresist contact masks were carried out. Although striped patterns generated by the difference of spectroscopic reflectance between Mo and Si were observed at peripherals of milling area when templates were used, a clear and sharp edge pattern was obtained with contact mask. Soft X‐ray reflectance of a Mo/Si multilayer milled with photoresist contact mask showed good feasibility of precise wavefront error correction of multilayers. These results proved our phase correction method is promising and practical for the 0.1 nm‐period correction of soft X‐ray multilayer mirror.

Multilayer polarization elements and their applications to polarimetric studies in vacuum ultraviolet and soft X-ray regions

Multilayer polarization elements and their applications to polarimetric studies in 20 similar to 400 eV region are mainly reviewed. General principle of selecting material combinations to get high linear polarizance multilayers of reflection type is given with practical examples, with periodic or non-periodic layer structures depending on the usage. Transmission type is introduced as linear polarizer and phase shifter. Their applications include polarization diagnosis of laboratory optical systems and synchrotron radiation bean-dines of linear and circular polarization, magnetic rotation experiments such as Faraday rotation and magnetic Kerr rotation on magnetic films and multilayers, and ellipsometry to measure optical constants of thin films precisely. Polarization analysis of soft X-ray fluorescence using multilayer-coated grating is also mentioned. Finally this review is summarized with outlook of further developments.