CO2 laser-induced weakening in chemically strengthened glass: Improvement in processability and its visualization by Raman mapping

Chemically strengthened glass has become essential in our daily lives and the demand is rapidly increasing in a variety of fields. However, the conventional cutting process is not applicable because of its tough layer with the compressive stress. To achieve higher-throughput production of the glass, we report spatially selective weakening of the compression layer by CO₂ laser scanning and provide its visualization by Raman mapping. We demonstrate cutting the scanned glass without shattering using a typical scribing wheel. Finally, we discuss the improvement in processability from the viewpoint of microscopic structures by means of thermal analysis and Raman spectroscopy.     

Fabrication process of intrinsic Josephson junction stacks in Bi2Sr2CaCu2O8+x crystals by double-sided patterning process using dilute hydrochloric acid

We have developed a new double-sided patterning (DSP) process that employs dilute acid (pH = 1.65) to fabricate Bi₂Sr₂CaCu₂O_8+x (Bi-2212) stacks of intrinsic Josephson junctions. These stacks, which were fabricated from a single crystal of Bi-2212, were surrounded by an acid-treated product. The critical aspect of this process is that the Bi-2212 surrounding the photoresist pattern was converted into a transparent material, BiOCl, which was connected with the Bi-2212 crystal. Consequently, this process provides a simple way to achieve DSP of the surfaces of Bi-2212 crystals. This new DSP process realizes a remarkably improved reproducibility in fabricating Bi-2212 stacks that exhibit good current–voltage characteristics with a large hysteresis and multiple branches at T = 77 K.     

The combinational or selective usage of the laser SQUID microscope,the non-bias laser terahertz emission microscope,and fault simulations in non-electrical-contact fault localization

Recently, in the field of fault localization of LSI chips, several non-electrical contact techniques have been proposed. The techniques include the laser SQUID microscope (L-SQ) and the non-bias laser terahertz emission microscope (NB-LTEM). Both techniques have pros and cons. The L-SQ, for examples, can localize open defects in some cases, but it requires closed circuit. The NB-LTEM can localize open defects and short defects, and not requires closed circuit. The NB-LTEM, however, cannot localize open defects in some cases. The fault simulation specially designed for the L-SQ or the NB-LTEM makes it precise or efficient to localize defects. The combinational or selective usage of the L-SQ, the NB-LTEM and the related simulations makes it possible to localize defects in many cases. In this paper, we would like to review our results and organize them from the viewpoint of failure mode and defect sites.     

Laser THz emission microscope as a novel tool for LSI failure analysis

We have proposed and developed a novel technique for a non-contact inspection of defective interconnections in an LSI chip using a laser terahertz emission microscope (LTEM). The LTEM measures the THz emission images of an LSI chip by scanning it with fs laser pulses. When a fs laser pulse irradiates a p–n junction in an LSI chip, transient photocurrent flows into interconnections resulting in the emission of the THz pulse into free space. We investigated the characteristics of the THz emissions from simple test element group samples which consist of p–n junctions connected to metal lines. It was found that the metallic lines connected to photo-excited p–n junctions worked as THz emission antennae which enhance the emission efficiency of THz pulses near their resonant frequencies corresponding to the line lengths. This result indicates that THz emission signals from p–n junctions in circuits strongly depend on the structure of the interconnections. We show the successful results on the inspection of defective interconnections in MOSFET devices and C7552 ISCAS’85 benchmark circuits using LTEM. By comparing the THz emission images between a normal circuit and a defective one, it is possible to identify the p–n junctions connected to the defective interconnections without electrical contacts.     

Structure and Viscoelastic Properties of Starches Separated from Different Legumes

A comparison between the morphological, structural, thermal and viscoelastic properties of starches separated from pigeon pea, chickpea, field pea, kidney bean and blackgram was made. The shape of the starch granules in the different legumes varied from oval to elliptical or spherical. X-ray diffraction of the legume starches indicated a typical C-pattern (mixture of A- and B-type). Granules of blackgram and pigeon pea starch had a higher degree of crystallinity than those of field pea and kidney bean starches. Apparent amylose content of field pea, kidney bean, chickpea, blackgram and pigeon pea starch was 37.9%, 36.0%, 34.4-35.5%, 32.9-35.6% and 31.8%, respectively. Distribution of isoamylase-branched materials among the starches revealed that the proportions of long and short side chains of amylopectin ranged between 13.6-18.5% and 41.7-46.5%, respectively. Field pea and kidney bean starch had the highest apparent amylose content and the lowest amount of long side chains of amylopectin, respectively. Blackgram and pigeon pea starch possessed higher proportions of both long and short side chains of amylopectin than field pea and chickpea starches. The onset, peak and conclusion temperatures of gelatinization (T_o T_p and T_c, respectively) were determined by differential scanning calorimetry. T_o and T_c ranged from 59.3 to 77.3°C, 66.8 to 79.6°C, 55.4 to 67.6°C and 68.3 to 69.3°C, respectively, for chickpea, blackgram, field pea and kidney bean starch. The enthalpy of gelatinization (ΔH_gel) of field pea, kidney bean, chickpea, blackgram and pigeon pea starches was 3.6, 3.0, 2.6-4.2, 1.6-1.7 and 2.6 J/g, respectively. Pastes of blackgram and pigeon pea starches showed lower storage and loss shear moduli G′ than field pea, kidney bean and chickpea starches. The changes in moduli during 10 h at 10°C revealed retrogradation in the order of: field pea> kidney bean> chickpea> blackgram> pigeon pea starch. In blackgram and pigeon pea starches, the lower proportion of amylose plus intermediate fraction and higher proportion of short and long side chains of amylopectin are considered responsible for the higher crystallinity, gelatinization temperature and enthalpy of gelatinization.