The pyrolysis of agglomerating coal was analyzed by thermogravimetric analysis (TGA) coupled to microgas chromatography (μGC) to determine the effects of reactor confinement on solid product yield, tar evolution, and gas composition. The primary volatile products generated from pyrolysis are studied using two TGA crucibles with height to width aspect ratios of 0.11:1.0 and 2.0:1.0 for heating rates of 1, 3, and 10 K min −1 . Mass balances were determined from measurements of the solid residual, gaseous flow rates, and tar products captured via glass impingers. The measurements resulted in mass balance closures greater than 99%. The higher aspect ratio confinement provided a zone where the residence time of volatile species was extended to 0.35 s from 0.04 s for the low aspect ratio confinement. The extended residence time was found to increase the solid yield by 0.6−5.7% for the low and mid ranged volatile material coals by secondary tar reactions which form coke. There was a trend of increasing solid yield with a decreasing heating rate because of the shorter residence time of the released volatile material at the higher heating rates. A decrease in tar production by 2.1−2.5% was observed in the higher aspect ratio confinement. The differences in product evolution between the two confinements were determined to be due to reactions occurring in the range of 783−848 K, which produce hydrogen, methane, and coke. In the confinement of higher aspect ratio, hydrogen production increased by 10% and 30% for low and mid VM coals, respectively, along with a 40% increase in methane production for both coals. The higher productions of methane, hydrogen, and solid residual between 820 and 1100 K for increased residence time of 0.27−0.35 s are due to demethylation and recombination reactions during the formation of char from recondensed tar products.

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Copper wafers are polished with an experimental slurry prepared to contain strong oxidizing components for revealing grain structures. Two types of surface morphologies, twinned and equiaxed grains, are observed on two groups of wafers, following chemical mechanical planarization (CMP). An atomic force microscope surface analysis indicates that the equiaxed grain structure provides better overall surface quality than the twinned structure. A polishing model is proposed to explain the surface relief among the twinned subgrains. The results suggest that Cu electroplating and the subsequent annealing processes should be optimized to promote uniform equiaxed grains for better integration with CMP and other chip manufacturing processes.

Highly selective 2 nd step copper slurries developed by Rodel have efficient barrier (TaN) polishing rates at extremely low down force (1000 Å/min at one psi, and 2000 Å/min at 3 psi). Removal rates of dielectrics (TEOS or low k CDO) can be independently adjusted from zero to nearly any designed value and copper removal rates can be independently controlled from 20 to 500 Å /min, while maintaining the high barrier removal rates. In addition, zero loss of low-k dielectric capping layers has been demonstrated, and zero loss of high metal density (90%) domain of pattern wafers with 30 seconds overpolishing has been demonstrated. Experiments also show that the high selectivity is a true CMP effect and not due to static etching. IntroductionCopper (Cu) chemical mechanical polishing (CMP) employs a two-step polishing process. A first step Cu slurry is used to remove both the bulk copper film layer and any remaining Cu residue on a wafer. The second step CMP process employs slurry that is used for removal of the barrier film, such as tantalum (Ta) or tantalum nitride (TaN). Both slurries are designed to minimize dishing and erosion.