Metal residues

FIGURE 17.42 Super-shallow scratches. Some of these scratches can be below the defect detection limit. The left picture shows multiple shallow scratches using experimental slurry. It is believed that a solid form of by-product generated during the CMP process is responsible for this very high density of very shallow scratches. The right picture shows an example of an isolated scratch observed on a patterned wafer using commercial copper slurry. 

FIGURE 17.43 A scratch after copper barrier CMP on a wafer with fragile low-1 material. The left picture shows that the low-1 dielectric is about as weak as the copper line and deforms under the stress of the scratch. Source Fisher P. CAMP 2006. The right picture shows a soft scratch in the field area where the porous low-1 is locally completely removed. The underlayer of TEOS is not damaged. 

FIGURE 17.44 The picture on the left shows copper residues that are due to WIWNU. The residues are symmetrical in the middle radius. The right image shows copper residues that are pattern dependent. This wafer has been plated using a first-generation bottom-up fill copper electroplating technique without levelers. 

FIGURE 17.46 A cartoon of possible defects after copper CMP in the case of underlayer topography. 

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Slags are also removed from the liquation ketde periodically. When chloride slags are formed these are cast into chunks and transferred to a wet plant for leaching to remove chlorides and treatment of the metallic residue. If borax slags are employed, metal values in the slag are recovered by further pyrometaHurgical treatment. 

Selenium and precious metals can be removed selectively from the chlorination Hquor by reduction with sulfur dioxide. However, conditions of acidity, temperature, and a rate of reduction must be carefliUy controlled to avoid the formation of selenium monochloride, which reacts with elemental selenium already generated to form a tar-like substance. This tar gradually hardens to form an intractable mass which must be chipped from the reactor. Under proper conditions of precipitation, a selenium/precious metals product substantially free of other impurities can be obtained. Selenium can be recovered in a pure state by vacuum distillation, leaving behind a precious metals residue. 

Arsenic exists as grey, yellow and black forms of differing physical properties and susceptibilities towards atmospheric oxygen. The general chemistry is similar to that of phosphorus but whereas phosphorus is non-metallic, the common form of arsenic is metallic. Traces of arsenides may be present in metallic residues and drosses these may yield highly toxic arsine, ASH3, with water. 

Elimination of contaminants, including metallic residues, from process streams and equipment... 

Metall-oxyd, n. metallic oxide, -oxydhydrat, n. metal (lie) hydroxide, -papier, n. metal (lie) paper, -poliermittel, n. metal polish, -probe, /, test for metal, assay, -putzmittel, n. metal polish, -rohr, n., -rbhre, /. metal tube oi-pipe, -rohrehett, n. (small) metal tube or pipe, -riickstand, m. metallic residue, -sa-fran, m. crocus of antimony, -salz, n. metallic salt. 

After a study of the three alternatives we concluded that pyroredox offered the most promise for anode residue recovery. Pyroredox is a molten-salt process in which plutonium metal is oxidized chemically into the salt phase and then reduced chemically into the metal phase. Most of the impurities are not oxidized and remain in the metal residue. Thus, for a Pu-Ga anode residual, the reactions would be ... 

Temperature control Adequately sized pressure relief Elimination of contaminants, including metallic residues, from process streams and equipment Selection of materials of construction compatible with the chemicaKs) in use, properly cleaned and passivated Elimination of ingress of reactive chemicals, e.g. water, air Date labelling and inventory control in storage Cleaning and inspection of reusable containers, tankers etc. before refilling ... 

In polyester synthesis via ring-opening polymerizations, metal catalysts are often used. For medical applications of polyesters, however, there has been concern about harmful effects of the metallic residues. Enzymatic synthesis of a metal-free polyester was demonstrated by the polymerization of l,4-dioxan-2-one using Candida antarctica lipase (lipase CA). Under appropriate reaction conditions, the high molecular weight polymer (molecular weight = 4.1 x 10" ) was obtained. 

The slime is recovered and heated in a brick-lined tank to melt the sulfur. The molten sulfur is filtered in a heated stainless-steel pressure filter to separate remaining nickel sulfide pieces and insoluble precious metals, and cast into moulds. The residue is remelted and cast into anodes, the resulting anode slime is now a relatively concentrated precious metal residue and is treated for the extraction of individual metals. 

Carbon monoxide poses no significant residual risk to feedstock (e.g., hay or grain). If metal carbonyls have been released, the topmost layer of unprotected feedstock should be destroyed. The remaining material should be quarantined until tested for metal residue. It is unlikely that sufficient residue would remain on leaves of forage vegetation to pose a significant threat. 

Finerty MW, Madden JD, Feagley SE, Grodner RM (1990) Effect of environs and seasonality on metal residues in tissues of wild and pond-raised crayfish in southern Louisiana. Arch Environ Contam Toxicol 19 94—100... 

Clark, D.R. Jr., A.S. Wenner, and J.F. Moore. 1986. Metal residues in bat colonies, Jackson County, Florida, 1981-1983. Florida Field Natural. 14 38-45. 

Kairu, J.K. 1996. Heavy metal residues in birds of Lake Nakuru, Kenya. African Jour. Ecol. 34 397-400. 

White, D.H., K.A. King, and R.M. Prouty. 1980. Significance of organochlorine and heavy metal residues in wintering shorebirds at Corpus Christi, Texas, 1976-77. Pestic. Monit. Jour. 14 58-63. 

Haseltine, S.D., B.M. Mulhern, and C. Stafford. 1980. Organochlorine and heavy metal residues in black duck eggs from the Atlantic flyway, 1978. Pestic. Monitor. Jour. 14 53-57. 

Kuehl, D.W., R. Haebler, and C. Potter. 1994. Coplanar PCB and metal residues in dolphins from the U.S. Atlantic coast including Atlantic bottlenose obtained during the 1987/88 mass mortality. Chemosphere 28 1245-1253. 

Metcalfe-Smith, J.L. 1994. Influence of species and sex on metal residues in freshwater mussels (Family Unionidae) from the St. Lawrence River, with implications for biomonitoring programs. Environ. Toxicol. Chem. 13 1433-1443. 

Fleming, WJ. 1981. Environmental metal residues in tissues of canvasbacks. Jour. Wildl. Manage. 45 508-511. Flint, P.L., M.R. Petersen, and J.B. Grand. 1997. Exposure of spectacled eiders and other diving ducks to lead in western Alaska. Canad. Jour. Zool. 75 439-443. 

Custer, T.W. and B.L. Mulhcrn. 1983. Heavy metal residues in prefledgling black-crowned night-herons from three Atlantic coast colonies. Bull. Environ. Contam. Toxicol. 30 178-185. 

Haseltine, S.D., G.H. Heinz, W.L. Reichel, and J.F. Moore. 1981. Organochlorine and metal residues in eggs of waterfowl nesting on islands in Lake Michigan off Door County, Wisconsin, 1977-78. Pestle. Monitor. Jour. 15 90-97. 

Hernandez, L.M., M.J. Gonzalez, M.C. Rico, M.A. Fernandez, and A. Aranda. 1988. Organochlorine and heavy metal residues in falconiforme and ciconiforme eggs (Spain). Bull. Environ. Contam. Toxicol. 40 86-93. 

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