Advanced IX projection photolithography

Pattern techniques in the semiconductor industry are driven by the need to improve cost/performance per bit. The key to reducing cost per bit and improving performance is increased density. Tighter photolithography ground rules (smaller images with reduced line width and registration tolerances) are primary sources of increased density. Enhanced ground rules coupled with larger wafers are certain to form the basis for the next generation of VLSI chips. The trend toward tighter ground rules and larger wafers is causing many semiconductor manufacturers to migrate away from IX projection tools, the workhorses of present-day production lines, to step and repeat exposure tools. The higher numerical aperture of step and repeat tools, coupled with chip-by-chip focus, guarantees improved resolution compared to today’s IX projection tools. The price paid for increased numerical aperture is reduced field size and, subsequently, reduced throughput and higher exposure cost per wafer. Ideally, it would be preferable to improve the resolution of the IX projection tool/process to make it competitive with the step and repeat tool, while maintaining the high throughput of IX systems. Effective use of shorter exposure (< 350 nm) wavelengths in IX systems is the key to extending resolution capability.     

Engineering a heavy atom derivative for the X-ray structure analysis of cyclodextrin glycosyltransferase

Based on a preliminary structural model of cyclodextrin glycosyltransferasefrom Bacillus circulans (EC 2.4.1.19 [EC] ), Ser428 and Ser475 ofthe enzyme were mutated to cysteines in order to produce suitableheavy atom derivatives. Mutant Ser475 - Cys could not be expressedas protein. Mutant Ser428 - Cys was expressed in Escherichiacoli and purified. It crystallized isomorphously and gave riseto a mercury derivative that improved the electron density map.The structural results show that the new mercury-binding siteis in a pocket at the protein surface.     

In Situ Tensile Measurements of Single Fibers by Scanning Electron Microscopy

A newly developed tensile module allows tensile experiments of single fibers to be carried out under visual observation in the scanning electron microscope. This allows correlation of measured data with observed changes in the microstructure, such as surface irregularities and crack formation. With point heating, the thermal behavior of the fibers may be studied up to 2500°C. The results are presented with tensile elongation recordings and micrograph sequences of the structural changes. Carbon fibers with and without an aluminum coating were selected as testing specimens.     

Lyso platelet activating factor (LysoPAF) and its enantiomer. Total synthesis and carbon-13 NMR spectroscopy

Described is a reaction sequence for the total synthesis of lyso platelet activating factor (lysoPAF; 1-O-alkyl-sn-glycero-3-phosphocholine) and its enantiomer. The procedure is versatile and yields optically pure isomers of defined chain length. The synthesis is equally suited for the preparation of lysoPAF analogues and its enantiomers with unsaturation in the long aliphatic chain. First,rac-1(3)-O-alkylglycerol is prepared by alkylation ofrac-isopropylideneglycerol with alkyl methanesulfonate followed by acid-catalyzed removal of the ketal group. The primary hydroxy group of alkylglycerol is then protected by tritylation, the secondary hydroxy group is acylated, and the protective trityl group is removed under mild acidic conditions with boric acid on silicic acid, essentially without acyl migration. Condensation of the diradylglycerol with bromoethyl dichlorophosphate in diethyl ether, hydrolysis of the resulting chloride, and nucleophilic displacement of the bromine with trimethylamine givesrac-1-O-alkyl-2-acylglycero-3-phosphocholine in good overall yield. The racemic alkylacylglycerophosphocholine is finally treated with snake venom phospholipase A₂ (Ophiophagus hannah) which affords 1-O-alkyl-sn-glycero-3-phosphocholine (lysoPAF) of natural configuration in optically pure form. The “unnatural” 3-O-alkyl-2-O-acyl-sn-glycerol-1-phosphocholine enantiomer, which is not susceptible to phospholipase A₂ cleavage, gives 3-O-alkyl-sn-glycero-1-phosphocholine upon deacylation with methanolic sodium hydroxide. Homogeneity and structure of the intermediates and final products were ascertained by carbon-13 nuclear magnetic resonance spectroscopy on monomeric solutions.     

Zeitstandfestigkeit bei 700 bis 1000 °C von hitzebeständigen Chrom-Nickel-Stahlgußsorten und -Schmiedestählen für Industrieöfen und für Reformerrohre in der Erdölchemie

In Zeitstandversuchen bei 700 bis 1000 °C ermittelte Werte der Zeitstandfestigkeit für 1000 und 10 000 h Beanspruchungsdauer von sieben hitzebeständigen Stahlgußsorten mit rd. 0,10 bis 0.45% C, 0,8 bis 1,5% Si, 20 bis 28% Cr, 20 bis 48% Ni und gegebenenfalls mit Gehalten an Kobalt, Niob und Wolfram sowie einiger Schmiedestähle mit vergleichbarer chemischer Zusammensetzung. Graphischnumerische Extrapolation auf 100 000 h Beanspruchungsdauer. Einflußgrößen auf die Vorhersagegenauigkeit des Extrapolationsverfahrens. Zuverlässigkeit der extrapolierten Werte der 100000–h-Zeitstandfestigkeit bei Temperaturen oberhalb 950 °C. Vergleich der Zeitstandfestigkeit von Stahlguß und Schmiedestählen.     

Außergewöhnliches Warmumformungsverhalten von Eisen-Silicium-Legierungen

Untersuchung der Warmumformbarkeit von sehr reinen Eisen-Silicium-Legierungen auf einer Warmtorsionsmaschine. Außergewöhnlich gutes Umformverhalten und Umformungsabfall um vier Zehnerpotenzen in einem kleinen Temperaturbereich bei hohen Temperaturen. Erklärung der Hochtemperaturversprödung in Analogie zur Blausprödigkeit. Berücksichtigung der Umformungsgeschwindigkeit und des Siliciumgehalts. Abschätzen der Geschwindigkeitsempfindlichkeit aus den Versuchsergebnissen.