The blocking barrier effect on aluminum electromigration due totitanium layers in multilayered interconnects of LSI's

Experimental evidence of an increase in the resistance of a cathode-side metal line without any void generation is presented for a multilayered metal structure terminated by via-holes during electromigration tests. This resistance increase is reversed to the initial value by high temperature storage after electromigration testing. The increase in the resistance of multilayered metal structures is attributed to the vacancy accumulation in the cathode side due to the blocking barrier effect of the refractory metal layer in the via-hole     

Contrast enhancement in the phase plate transmission electron microscopy using an objective lens with a long focal length

A new optical condition using an objective lens (OL) of a long focal length (objective mini lens: OM) was tested to enhance image contrast in phase plate transmission electron microscopy (P-TEM). A phase plate was set on the selected area aperture plane where diffraction patterns were formed under the optical condition using the OM. A phase shift by the phase plate was added to the electron waves to visualize phase objects. The application of the OM to the P-TEM should provide higher phase contrast than that obtained by the OL for the phase objects. One of the reasons for the contrast enhancement is that high-angle scattering electron waves which would give the background intensity were not used for image formation due to the large spherical aberration. Another reason is that the cut-on frequency above which the phase shift was added by the phase plate could be smaller using the OL with a long focal length. Experimental results and model calculations showed the contrast enhancement of the biological specimens using the OM.     

Mechanical and AC loss properties in mono-and multi-filamentary Bi-223 Ag-sheathed tapes

The evaluation of the bending strain tolerance and AC loss properties for monoand multi-filamentary Bi-2223 Ag-sheathed tape were carried out at liquid nitrogen temperature. For tapes with a filament number of over 19, the critical current (I_c) was maintained at the same values up to the bending strain of 0.3%, although the I_c of the mono-filamentary tape at the condition of 0.2% strain degraded to 90% of the value for the no-strain condition. The AC loss of the monofilamentary tape was the hysteresis type. On the contrary, the AC loss of the multi-filamentary tape was substantially dominated by the eddy current loss in the Ag matrix.     

Study on the device characteristics of a quasi-SOI power MOSFETfabricated by reversed silicon wafer direct bonding

The device characteristics of a quasi-SOI power MOSFET were investigated to obtain its optimum device structure. The oxide at the original bottom surface of the bulk power MOSFET of the quasi-SOI power MOSFET formed by reversed silicon wafer direct bonding acts as the buried oxide of the conventional SOI power MOSFET. The short channel effect of the quasi-SOI power MOSFET was larger than that in the conventional SOI power MOSFET. It was suppressed by increasing the width of the oxide in the body region, and the parasitic bipolar effect was suppressed by decreasing it. We also propose a new device structure which can suppress the short channel effect and parasitic bipolar effect of a quasi-SOI power MOSFET based on the results of these experiments     

A 3-V, 2%-mW multibit current-mode ΣΔ DAC with 100 dBdynamic range

The area ratio of analog to digital for mixed-mode chip has been inversely proportional to the process design rule for a given dynamic range objective, in contradiction to the LSI trend. This paper presents a design approach to realize a high degree of size reduction with process design rules for analog circuitry and a signal processing architecture for digital circuitry. A five-level current-mode ΣΔ digital-to-analog converter (DAC) system reveals full scale total harmonic: distortion plus noise (THD+N) of -90 dB and dynamic-range of 100 dB at 3 V (low power of 22 mW). Analog-area down-scaling can be accomplished by this architecture to be 1.09 mm², using 0.6-μm double-poly double-metal (DPDM) CMOS. For the digital filter, a pipeline instruction sequence with multiplierless architecture also gives small area of 1.98 mm²     

Novel method for simultaneous formation of wires and vias of a printed circuit board using nanoporous body

A new type of a flexible printed circuit board with landless vias is developed using a novel method called interconnection via nanoporous structure (INPS). This method can make wires and vias of the printed circuit board simultaneously by a single photo-exposure process. A new photo-induced selective plating method was used to impregnate a nanoporous substrate with copper, and a new photomask was designed, which constitutes of a completely vacant large hole for via and aggregation patterns of very fine holes for wire. Because of the simple process, the INPS board is characterized by landless vias and very fine circuit. Owing to the structure, it is also characterized by flexibility and detachable wires.     

Evaluation of immunochromatographic test kits for food allergens using processed food models

It has been mandatory to label five allergenic substances (AS; egg, milk, wheat, buckwheat and peanut) in all processed foods, since April 2002 in Japan. Two kinds of ELISA kits have been provided as screening test kits for the Japanese official method. The kits have many advantages but some disadvantages, i.e., the kits are not necessarily suitable for daily monitoring in food manufacturing plants, because they require various analytical equipments and the use of complicated procedures. To overcome these drawbacks, we have developed other diagnostic kits based on immunochromatography that should enable more rapid and simple screening for food allergens. Then we examined the performance of these immunochromatographic test kits (IC kits) in terms of sensitivity, repeatability and cross-reactivity to AS proteins in 11 kinds of food models with various heating conditions and physical properties. We also examined processed food models including AS protein of constant concentration, using the IC kits and ELISA kits, and compared the results. The IC kits detected AS proteins at 5 microg/g in the extracts from processed food models, and provided highly reproducible results. Cross-reactivity among the AS proteins was not observed. The results obtained using the IC kits showed performance equivalent to that of the ELISA kits we examined in unheating processed food models including AS proteins of constant concentration. The IC kits should be more suitable for daily monitoring in food manufacturing plants.     

Oxidation resistant ceramic foam from a silicone preceramic polymer/polyurethane blend

Silicon oxycarbide (SiOC) ceramic foams, produced by the pyrolysis of a foamed blend of a methylsilicone preceramic polymer and polyurethane (PU) in a 1/1 wt.% ratio, exhibit excellent physical and mechanical properties. The proposed process allows to easily modify the density and morphology of the foams, making them suitable for several engineering applications. However, it has been shown that, due to residual carbon present in the oxycarbide phase after pyrolysis, the foams are subjected to an oxidation process that reduces their strength after high temperature exposure to air (12 h 1200°C). A modified process, employing the same silicone resin preceramic polymer but a much lower PU content (silicone resin/PU=5.25/1 wt.% ratio), has been developed and is reported in this paper. Microstructural investigations showed that carbon rich regions deriving from the decomposition of the polyurethane template are still present in the SiOC foam, but have a much smaller dimension than those found in foams with a higher PU content. Thermal gravimetric studies performed in air or oxygen showed that the low-PU containing ceramic foams display an excellent oxidation resistance, because the carbon-rich areas are embedded inside the struts or cell walls and are thus protected by the dense silicon oxycarbide matrix surrounding them. SiOC foams obtained with the novel process are capable to maintain their mechanical strength after oxidation treatments at 800 and 1200°C (12 h), while SiOC foams obtained with a higher amount of PU show about a 30% strength decrease after oxidation at 1200°C (12 h).     

A New Process to Make a Porous PTFE Structure from Aqueous PTFE Dispersion with the Help of Hydrogel

A novel method to make a porous material having relatively large cell diameter (200–300 m), which consisted of mainly poly(tetrafluoroethylene) (PTFE), was developed from aqueous PTFE dispersion by using the characteristics of hydrogel with the addition of carbon nanofiber (CNF). The porous material was produced as follows: firstly, an aqueous agar gel containing PTFE and CNF was prepared; secondly, the gel was freeze-dried; thirdly, the dried gel was heat-treated at 400°C where the agar was almost decomposed and PTFE became molten. The porous material showed electric conductivity (about 50 ), high porosity (about 96 vol%), and relatively uniform cell structures without shrinkage during freeze drying and heat treatment. While the method without CNF resulted in large shrinkage during heat treatment, meaning that CNF prevented the shrinkage. It was explained by the idea that the existence of rigid CNF, which was dispersed in the cell wall, prohibited the shrinkage of PTFE during heat treatment. It was unexpectedly found by SEM analysis that the porous materials had another macro-porous structure inside the cell wall, suggesting that the developed materials had a double porous structure.     

Detection of light-absorbing iron oxide particles using a modified single-particle soot photometer

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