Superconductor integrated circuit fabrication technology

Today's superconductor integrated circuit processes are capable of fabricating large digital logic chips with more than 10 K gates/cm/sup 2/. Recent advances in process technology have come from a variety of industrial foundries and university research efforts. These advances in processing have reduced critical current spreads and increased circuit speed, density, and yield. On-chip clock speeds of 60 GHz for complex digital logic and 750 GHz for a static divider (toggle flip-flop) have been demonstrated. Large digital logic circuits, with Josephson junction counts greater than 60 k, have also been fabricated using advanced foundry processes. Circuit yield is limited by defect density, not by parameter spreads. The present level of integration is limited largely by wiring and interconnect density and not by junction density. The addition of more wiring layers is key to the future development of this technology. We describe the process technologies and fabrication methodologies for digital superconductor integrated circuits and discuss the key developments required for the next generation of 100-GHz logic circuits.     

Environmental assessment in early process development

A short‐cut method for environmental assessment during process development is presented. The method can deal with data uncertainties in early phases, includes all relevant environmental impacts, and is simple and easy to apply. Therefore, it can be used in early phases of process development. The environmental relevance of each substance is represented by the Environmental Factors. These factors are derived from 14 impact categories, where each compound is classified using an ABC methodology. The impact categories are then grouped into six impact groups: Resources, Grey Input, Component Risk, Organisms, Air and Water/Soil. From these, input and output environmental factors are deduced. This factor is combined with mass balance data to yield a number of indices that can be used to optimize the environmental performance of a process in an integrated manner. The method is applied to three case studies: a comparison of chemical and biotechnological production of 6‐aminopenicillanic acid, a comparison of two process alternatives in the enzymatic production of α‐cyclodextrin and the development of a new process for the fermentative production of pyruvate. Copyright © 2004 Society of Chemical Industry     

Influence of Stress-Induced Leakage Current on Reliability of HfSiOx

HfSiO_x with TiN gate is investigated under substrate injection with respect to stress-induced leakage current (SILC). Most damage caused by electrical stress was found in the high- layer and not in the interface to silicon. Dependent on the application, SILC can exhibit several levels of severity. In pure logic circuits, a large area approximation is sufficient. However, for memory applications, the current increase in small area is important as well. Both contributions are investigated, revealing no lifetime-limiting current increase. With an improved deposition process, SILC can even be suppressed.     

Comparison of computer simulation and experimental results for a 16 µm HBr/CO2laser

An improved version of a computer model simulates 16μm laser output from an optically pumped HBr/CO2/Ar laser cavity. A rate equation approach is used to examine the time history of vibrational and rotational excitation and subsequent lasing from the HBr/ CO2gas mixture. Rotational nonequilibdum phenomena in HBr and CO2are included. The effect of bleaching a particular vibrational-rotational transition with optical saturation is modeled in detail. The results of the computer simulation are compared to the laboratory observations from two separate experiments. The model predicts accurately the effect of changing partial pressures of the constituent gases on 16μm power and energy. The model reveals the important kinetic mechanisms yielding these trends. Finally, the model is modified to simulate optical pumping by an HF laser of an HF/CO2/Ar gas mixture. A case by case comparison with the results of the HBr model prediction show significantly lower 9.4 μm powers and energies for any given HF pressure and no evidence of 16μm laser output from the HF/CO2gas mixture.     

X-ray microbeam and recrystallization studies of plastic deformation around fatigue cracks

X-ray microbeam technique and recrystallization method were used to measure plastic zones around 20 kHz fatigue cracks in mild steel. Both methods render approximately the same extension of a plastic zone. In order to obtain the amount of deformation within a plastic zone measurements of integral line breadth and recrystallization temperature were calibrated by specimens deformed with known per cent static tension. But since static and cyclic loading cause different dislocation structures (especially the dislocation density is much more inhomogeneous in fatigued specimens) quantitative comparison is difficult. Furthermore the two methods display different values of the actual amount of deformation. X-ray line broadening indicates an average dislocation density, whereas recrystallization displays a maximum amount of deformation, which corresponds to the local dislocation concentrations.     

Attitudes towards specific uses of the computer Quantitative, decisionmaking and record-keeping applications

A survey of 203 undergraduates indicated that there are three clusters of computer applications about which respondents hold similar attitudes: quantitative applications (e.g. processing bills), decisionmaking applications (e.g. diagnosing medical problems) and record-keeping applications (e.g. storing information about criminals). Respondents were favourable towards quantitative and record-keeping applications but rejected decisionmaking applications, especially those involving decisions traditionally made by psychologists. Experience with computers and perceptions of the computer as efficient, humanizing and enjoyable were correlated significantly with attitudes towards specific applications. Locus of control and interpersonal trust were not related to attitudes. Interpretations of potentially dehumanizing effects of computers were discussed, along with implications of attitudes towards specific applications for decisions about how computers ought to be used.