Mechanical stress control in a VLSI-fabrication process: a method for obtaining the relation between stress levels and stress-induced failures

An ideal fabrication process is designed to minimize mechanical stress in semiconductor devices and to improve device reliability. Mechanical stress levels were predicted by in-house simulations supported by a thin-film database. These stress levels were correlated with stress-induced defects by TEM analysis supported by fail bit addressing on matured megabit SRAMs. Amorphous-doped silicon film with various annealing temperatures were used for the gate electrode to change the mechanical stress in devices and to get the direct relationship between predicted stress levels and stress related defects. The authors describe brief guidelines for suppressing dislocations in the small geometry shallow-trench isolation process utilizing this system. Polysilicon thickness in the W-polycide gate electrode is designed to minimize mechanical stress in the gate oxide and to suppress the gate oxide failure in probe and class tests. Moreover, critical stress generates dislocations during post source/drain ion implantation anneal obtained by a ball indentation method. This indicated that lower temperature anneal is effective in suppressing the dislocations. A two-step anneal was introduced to suppress dislocations and to enable higher ion activation.     

Molecular motions of non-crystalline poly(aryl ether-ether-ketone) PEEK and influence of elecron beam irradiation

The dynamic mechanical relaxation of non-crystalline poly(aryl ether-ether-ketone) PEEK and the one irradiated with electron beam were studied. The three distinct γ, β, α′ relaxation maxima were observed in unirradiated PEEK from low to high temperature. It was revealed from the study on the irradiation effects that three different molecular processes are overlapped in γ relaxation peak, i.e., molecular motion of water bound to main chain (peak temperature; at ?100°C), local motion of main chain (at ?80°C), and local mode of the aligned and/or oriented moiety (at ?40°C). The β relaxation connected with the glass transition occurred at 150°C and it shifted to higher temperature by irradiation. The α′ relaxation which can be attributed to rearrangement of molecular chain due to crystallization was observed in unirradiated PEEK ～ 180°C and its magnitude decreased with the increase in irradiation dose. This effect indicates the formation of structures inhibiting crystallization such as crosslinking and/or short branching during irradiation. A new relaxation, β′, appeared in the temperature range of 40° to 100°C by irradiation and its magnitude increased with dose. This relaxation was attributed to rearrangement of molecular chain from loosened packing around chain ends, which were introduced into the non-crystalline region by chain scission under irradiation, to more rigid molecular packing, From these observations, we proposed that deterioration in mechanical properties of non-crystalline PEEK by high energy electron beam was brought about not only by chain scission but structural changes such as crosslinking and/or branching in the main chain.     

Degradation of organophosphorus pesticides in aqueous extracts of young green barley leaves (Hordeum vulgare L)

The degradation of the organophosphorus pesticides malathion, chlorpyrifos, guthion, diazinon, methidathion and parathion in an aqueous extract of young green barley leaves (Hordeum vulgare L) was monitored by gas chromatography. Aqueous solutions of various amounts of freeze‐dried young barley leaves containing 5.75 mg l⁻¹ of malathion were incubated at 37 °C and pH 7.4 over prolonged time periods. Over 95% of the malathion degraded in 4 h in a 3% (30 g l⁻¹) solution of young green barley leaves. When the barley solution was autoclaved at 120 °C for 25 min prior to the addition of malathion, no degradation of malathion was observed. When 10 mg l⁻¹ each of the above six pesticides was incubated in a 15% (150 g l⁻¹) solution of young green barley leaves for 3 h at 37 °C and pH 7.4, malathion and chlorpyrifos degraded 100%, whereas parathion (75%), diazinon (54%), guthion (41%) and methidathion (23%) showed lesser degrees of degradation. © 1999 Society of Chemical Industry     

A CCD video delay line with charge-integrating amplifier

The authors describe a charge coupled device (CCD) sense amplifier in a video delay line which overcomes the major limitations of conventional floating diffusion amplifier (FDA) technology, such as limited output voltage and operating temperature range. These advances are implemented with a switched-capacitor integrator (SCI) using an op amp with a newly developed output stage in a CMOS-CCD process. This circuit is effected within the constraints of 5-V operation by using negative pulses to reach the low channel potential of the CCD in the pinning region in the final gate of the CCD. The chip operates with 14.3-MHz clock and 5-V power supply, and can process a 1.0-V_p-p signal voltage under 1% distortion, and under 4% gain variation from -20 to 70°C     

Improved Jsc in CIGS thin film solar cells using a transparent conducting ZnO:B window layer

A comparative study of the cell performance of CIGS thin-film solar cells fabricated using ZnO:Al and ZnO:B window layers has been carried out. ZnO:B films were deposited by RF magnetron sputtering using an undoped ZnO target in a B₂H₆–Ar gas mixture. The short-circuit current (J_sc) was found to improve upon the replacement of the ZnO:Al layer with ZnO:B layers. This improvement in J_sc is attributed to an increase in quantum efficiency due to the higher optical transmission of the ZnO:B layer in the near-infrared region. The best cell fabricated with a MgF₂/ZnO:B/i-ZnO/CdS/CIGS/Mo structure yielded an active area efficiency of 18.0% with V_oc=0.645 V, J_sc=36.8 mA/cm², FF=0.76, and an active area of 0.2 cm² under AM 1.5 illumination.     

<Superscript>59</Superscript>Co NMR at Pulsed High Magnetic Fields

We report the ⁵⁹Co-NMR observation by spin-echo method at pulsed high magnetic fields up to 48 T. The 22 mm bore-resistive coil magnet with an inductance of 7.59 mH has a total time duration of 50 ms. After discharging the capacitor bank, NMR signals were observed near the maximum field. By repeatedly pulsing the RF sequence around the maximum field, spin echoes at different fields were recorded to give the NMR spectrum.     

Investigation of controllable self-organized honeycomb micro-structure

Patterned micro- and nanostructure are of great significance in industrial applications such as electronics, optics and sensors. Microporous honeycomb film of polyhpenylene oxide (PPO) was fabricated as the template via evaporation of solution in carbon bisulfide under humid ambience. The effect of fabrication conditions on patterned microstructure was investigated by self-organization experiments to build quantitative relationship between ambient conditions such as humidity, concentration and honeycomb microstructure (diameter and height), through which the honeycomb film formation can be controlled to self-organize desirable PPO patterned microstructure. Especially, the height of honeycomb was derived from the diameter of honeycomb, and its validity was clarified by morphological comparison between PPO template and PDMS molded structure. Moreover, soft mold experiments were conducted to demonstrate its high efficiency and excellence as an alternative to construct regular micro-pattern.     

High oleic acid oil suppresses lung tumorigenesis in mice through the modulation of extracellular signal-regulated kinase cascade

This study was undertaken to estimate the effect of dietary high oleic acid oil (OA) on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in mice. Diet containing 10% oil was fed to mice through experimental periods. On day 30 after NNK injection (100 mg/kg body weight, i.p.), the treatment increased the level of prostaglandin E₂ (PGE₂) as well as proliferating cell nuclear antigen, a marker of cell proliferation in a high linoleic acid oil (LA)-fed group but not in an OA-fed group. The NNK treatment also induced the activation of an extracellular signal-regulated kinase (Erk) cascade (Erk, Mek and Raf-1) in an LA-fed group. On the other hand, OA feeding abolished the NNK-induced activation of the Erk cascade. In conjugation with these events, OA feeding reduced lung tumor incidence and tumor multiplicity (percentage of mice with tumors) in mice compared with LA feeding at the 20th experimental week. These results suggest that OA suppresses lung tumorigenesis and that this suppression is correlated with the inhibition of PGE₂ production and inactivation of the Erk cascade.     

Effects of CuO Addition on Electrical Properties of 0.6BiFeO3–0.4(Bi0.5K0.5)TiO3 Lead‐Free Piezoelectric Ceramics

0.6BiFeO₃–0.4(Bi_0.5K_0.5)TiO₃ (0.6BF–0.4BKT) ceramic samples with 0.0–4.0 mol% CuO were prepared by the solid‐state reaction. The CuO addition aided the densification of the samples and slightly increased the lattice constant. The relaxor‐like defuse dielectric peak of 0.6BF–0.4BKT became sharper with increasing the CuO content. Polarization–electric field curve of the undoped 0.6BF–0.4BKT was a pinched loop in the as‐sintered state, while that was a square hysteresis with a large remanent polarization of 48 μC/cm² after the thermal quenching, demonstrating a strong domain wall pinning due to defect dipoles. We found that the CuO addition up to 2.0 mol% facilitates the polarization switching in the as‐sintered samples to increase the remanent polarization and the piezoelectric d₃₃ coefficient. The results of the structural and electrical investigations suggested that the copper ion acts as a donor in 0.6BF–0.4BKT by compensating the potassium vacancy created by the evaporation of K₂O during the calcination and sintering processes.