Tetsuo Sakamoto

DEVELOPMENT OF AN ION AND ELECTRON DUAL FOCUSED BEAM APPARATUS FOR THREE-DIMENSIONAL MICROANALYSIS

We are developing a novel three-dimensional (3D) microanalysis method by means of successive cross-sectional Auger mapping. In this method, a 3D elemental map will be obtained by repetition of the cross-sectioning of a sample using a gallium focused ion beam (Ga FIB) and Auger mapping of the cross section using an electron beam (EB). On the basis of this concept, an ion and electron dual focused beam apparatus was developed by combining a Ga FIB and a mass spectrometer with a scanning Auger microprobe. In this paper, we describe the concept and instrumentation of the dual focused beam apparatus. Two types of preliminary experiments; i) successive cross-sectioning of a microparticle (6.8 µm) and ii) successive cross-sectional sample current imaging of a bonding wire of an IC, demonstrated the capability to create flat analytical surfaces favorable for the 3D analysis with arbitrary shape and heterogeneity.

Analysis of surface composition and internal structure of fly ash particles using an ion and electron multibeam microanalyzer

Abstract An ion and electron multibeam microanalyzer was developed and applied to analysis of coal fly ash particles. Employing ordinary TOF-SIMS function, it was found that the surface of the fly ash particles mainly consisted of Ca, C, Si, and Na. A special analysis technique with a combination of “shave-off” cross-sectioning and TOF-SIMS mapping of the cross section was adopted to a single fly ash particle in order to reveal the internal structure. It was found that the particle had a cenosphere structure. TOF-SIMS mapping of the cross-sectioned particle clarified that the particle had the following layers, outermost layer (Na, Si, Ca-rich), shell (Na-rich), inner shell (Na, Si, Al-rich).

Development of ion and electron dual focused beam apparatus for high spatial resolution three-dimensional microanalysis of solid materials

We constructed an ion and electron dual focused beam apparatus to develop a novel three-dimensional (3D) microanalysis technique. In this method, a Ga focused ion beam (Ga FIB) is used as a tool for successive cross sectioning of the sample in the “shave-off” mode, while an electron beam (EB) is used as a primary probe for Auger mapping of the cross sections. Application of postionization with EB to Ga-FIB secondary ion mass and two-dimensional (2D) elemental mapping with Ga-FIB-induced Auger electrons are also in the scope of the apparatus. The 3D microanalysis was applied to a bonding wire on an integrated circuit (IC). A series of EB-induced sample current images of the successive cross sections were obtained as a function of the cross-sectioning position. This result showed the capability to realize the 3D Auger microanalysis. Two-dimensional elemental mapping with Ga-FIB-induced Auger electrons was realized for the first time on the IC surface. Its applicability to surface analysis was evaluated.

Chemical state of boron in coal fly ash investigated by focused-ion-beam time-of-flight secondary ion mass spectrometry (FIB-TOF-SIMS) and satellite-transition magic angle spinning nuclear magnetic resonance (STMAS NMR).

The chemical states of boron in coal fly ash, which may control its leaching into the environment, were investigated by focused-ion-beam time-of-flight secondary ion mass spectrometry (FIB-TOF-SIMS) and satellite-transition magic angle spinning nuclear magnetic resonance (STMAS NMR) spectroscopy. The distribution of boron on the surface and in the interior of micron-sized fly ash particles was directly observed by FIB-TOF-SIMS. Coordination numbers of boron and its bonding with different atoms from particles of bulk samples were investigated by STMAS NMR. Boron in coal fly ash with relatively poor leaching characteristics appears as trigonal BO(3) and coexists with Ca and Fe at the outer layer of every particle and inside CaO-MgO particles. In contrast, boron in coal fly ash with better leaching characteristics appears as CaO- or MgO-trigonal BO(3) and tetragonal BO(4), and it is distributed only on the outer surface of each ash particle without showing any correlation with a particular element.

An ion and electron multibeam system for three‐dimensional microanalysis

The failure analysis of electronic devices and deduction of the emission origins of dust particles in clean processes or in urban air require a precise three-dimensional microanalysis method. In order to investigate the new three-dimensional microanalysis for these samples with arbitrary shape and heterogeneity, we are developing a novel three-dimensional microanalyser consisting of a focused electron beam for Auger mapping and a gallium focused ion beam for cross-sectioning and for time-of-flight SIMS mapping. Our multibeam system is based on these three purposes. An ion and electron dual focused-beam apparatus was constructed to realize our concept. In this paper, the concept and the application of our analysis to a wire-pad contact region is described. The results of the elemental map in the contact interface show the superiority of our method.

Asian dust exposure triggers acute myocardial infarction

Aims To elucidate whether Asian dust is associated with the incidence of acute myocardial infarction (AMI) and to clarify whether patients who are highly sensitive to Asian dust will develop AMI. Methods and results Twenty-one participating institutions located throughout Kumamoto Prefecture and capable of performing coronary intervention were included in the study. Data for ground-level observations of Asian dust events were measured at the Kumamoto Local Meteorological Observatory. Data collected between 1 April 2010 and 31 March 2015 were analysed, and 3713 consecutive AMI patients were included. A time-stratified case-crossover design was applied to examine the association between Asian dust exposure and AMI. The occurrence of Asian dust events at 1 day before the onset of AMI was associated with the incidence of AMI [odds ratio (OR), 1.46; 95% confidence interval (CI), 1.09-1.95] and especially, non-ST-segment elevation myocardial infarction was significant (OR 2.03; 95% CI, 1.30-3.15). A significant association between AMI and Asian dust was observed in patients with age ≥75 years, male sex, hypertension, diabetes mellitus, never-smoking status, and chronic kidney disease (CKD). However, Asian dust events had a great impact on AMI onset in patients with CKD (P < 0.01). A scoring system accounting for several AMI risk factors was developed. The occurrence of Asian dust events was found to be significantly associated with AMI incidence among patients with a risk score of 5-6 (OR 2.45; 95% CI: 1.14-5.27). Conclusion Asian dust events may lead to AMI and have a great impact on its onset in patients with CKD.

Behavior of Gallium Secondary Ion Intensity in Gallium Focused Ion Beam Secondary Ion Mass Spectrometry

We studied the behavior of Ga+ secondary ion intensity in relation to oxygen matrix effect in gallium focused ion beam secondary ion mass spectrometry (Ga FIB SIMS). In two types of experiments, namely, ambient oxygen gas introduction and removal of native oxide film, the Ga+ intensity was found to behave in relation to the oxygen matrix effect in the same way as the matrix ion intensity. From the results, we proposed a way to cancel the oxygen matrix effect by using implanted Ga as an internal standard. Furthermore, the accumulation manner of Ga in a sample was examined by changing the Ga+ dose rate and the incident angle of the FIB in order to clarify the experimental conditions under which the use of Ga+ standard is applicable.

Three‐dimensional microanalysis of the wire–pad contact region of integrated circuits

We have developed a three-dimensional microanalyser by combination of a gallium focused ion beam (Ga-FIB), a secondary electron detector and a time-of-flight (ToF) mass spectrometer. The Ga-FIB can create successive flat cross-sections parallel to the interface. We performed ToF-SIMS mapping by switching the d.c. mode of the Ga-FIB in the cross-sectioning to pulse mode after turning the cross-section through 90°. Combination of these ToF maps on each cross-section yields detailed three-dimensional information from the interface region. The Au wire bonding interface after heat treatment was analysed. Analysis of the three-dimensional elemental distribution in the contact region of the Au wire and Al pad was realized. An Au-Al alloy was found in the deep section of the contact interface, Al was distributed in the outer part as a ring and the center part was enclosed by Au. The deduced structure of the contact region of the Au wire and Al pad was discussed.

Quantitative Determination of Composition of Particle Type by Morphology of Nanoparticles in Diesel Exhaust and Roadside Atmosphere

Particles were collected in diluted diesel exhaust under high-idle and high-torque operating conditions and from the air above roadsides. We analyzed particle morphology of particles that were 30, 50, 70, and 100 nm in electrical mobility diameter (Dm) by transmission electron microscope. We classified ten types of particles based on particle morphology and found that diesel exhaust particles (DEPs) of Dm=70 and 100 nm composed at least 14% and 58%, respectively, of atmospheric particles at each particle size. From the two-dimensional transmission electron microscope images, we derived three-dimensional morphological properties of the agglomerates and found that the numbers and diameters of the primary particles in the agglomerates were similar to those of DEPs at a given Dm. However, the active surface areas of the roadside atmospheric particles were systematically smaller than those of DEPs.

Fabrication of Stacked Organic Electroluminescence Devices with a Combination of Spin Coating and Electrospray Deposition

A combination of spin coating and electrospray deposition (ESD) was applied for the fabrication of an organic light-emitting diode (OLED) with a stacked structure. Two kinds of polymer materials were used to fabricate a multilayered structure. One was poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV; Sigma-Aldrich) and the other was poly[2,5-di(hexyloxy)cyanoterephthalylidene] (CN-PPV; Sigma-Aldrich). With the addition of acetone to polymer material (MEH-PPV and CN-PPV) solution, smaller droplets were produced at the emitter resulting in thin-film fabrication under a dry condition. This condition was adopted for CN-PPV film deposition on MEH-PPV surface made by the spin coating method. The double-layered OLED obtained successfully emitted light at a bias voltage of 15 V. Layer-by-layer stacking of CN-PPV and MEH-PPV was confirmed by the UV-induced fluorescence spectrum. In case of the layer-by-layer structure, the obtained spectrum showed a linear combination of spectrum from MEH-PPV and CN-PPV.