After-coppering

The cobalt complex is usually formed in a hot acetate-acetic acid medium. After the formation of the cobalt colour, hydrochloric acid or nitric acid is added to decompose the complexes of most of the other heavy metals present. Iron, copper, cerium(IV), chromium(III and VI), nickel, vanadyl vanadium, and copper interfere when present in appreciable quantities. Excess of the reagent minimises the interference of iron(II) iron(III) can be removed by diethyl ether extraction from a hydrochloric acid solution. Most of the interferences can be eliminated by treatment with potassium bromate, followed by the addition of an alkali fluoride. Cobalt may also be isolated by dithizone extraction from a basic medium after copper has been removed (if necessary) from acidic solution. An alumina column may also be used to adsorb the cobalt nitroso-R-chelate anion in the presence of perchloric acid, the other elements are eluted with warm 1M nitric acid, and finally the cobalt complex with 1M sulphuric acid, and the absorbance measured at 500 nm. 

Roncero, V., E. Duran, F. Soler, J. Masot, and L. Gomez. 1992. Morphometric, structural, and ultrastructural studies of tench (Tinea tinea L.) hepatocytes after copper sulfate administration. Environ. Res. 57 45-58. 

Yoshimura, N., K. Kida, S. Usutani, and M. Nishimura. 1995. Histochemical localization of copper in various organs of brindled mice after copper therapy. Pathol. Inter. 45 10-18. 

Many deaths of weanlings in about 37 days, and of adults in 53 days. Survivors were anorexic, diarrheic, anemic, and had front-leg abnormalities successful recovery after copper therapy (12)... 

It has recently been noted that if copper-induced MEE does occur, it is a very rare event. Despite extensive use of copper in many industries, only a handful of MEE cases are reported in the literature. Further limitations of these reports include possible contamination of the fume by other substances more likely to have caused MFF, atypical symptoms and complaints, and lack of consistency among types of work associated with symptoms. One reason that MFF may have rarely been described after copper exposure is that aerosolized copper particulates formed during welding, thermal cutting, and other hot work are mostly greater than respirable or submicron size. Studies of air in a brass foundry found that only 5% of the total copper exposure was respirable (aerosol less than or equal to 1 )im), whereas 40% of the zinc oxide exposures were to an aerosolized particulate of respirable size. ... 

An increased SOD capacity after copper supply was also found in other organisms (Shatzman and Kosman, 1978, in the fungus Dactylium dendroides Naiki, 1980, Sac-charomyces Ljutakova et al., 1984, rat liver Lee and Hassan, 1985, Saccharomyces). The increased biosynthesis of SOD in copper-treated yeast was suggested to be the result of an enhanced intracellular 02 flux (Lee and Hassan, 1985). 

FIGURE 1.18 Cross section SEM image of copper wafer after copper clearing step. The barrier is still present at this stage. The features shown are 50% in density and 2 pm in width (from Ref. 46). 

Copper does form compounds with BTA in solutions. The pH of the solution influences the stability of these compounds and thereby the effectiveness of their corrosion inhibition. For the same reason, for this chemical, pH also influences the removal of BTA from a copper film after copper CMP. The reaction between BTA and copper favors the release of BTA at low pH. In order to minimize organic contamination, the interaction between the organic chemical and the film to be polished has to be... 

FIGURE 17.22 Schematic illustration of possible defects after copper CMP in the case of underpolishing. 

FIGURE 17.28 Scratch-induced voids after copper CMP (pitting). 

FIGURE 17.31 Edge of the line trenching after copper CMP. The left image shows that the copper line edge is an accentuated form of copper pitting. 

FIGURE 17.38 Ta erosion after copper CMP. The Ta in the field area at the edge of high metal density copper structures is completely removed. There is no color variation in the array of copper lines because the Ta is completely removed. This is called Ta pullback. 

FIGURE 17.39 Ta erosion after copper CMP. The Ta in the field area is not completely eroded. Inside the area of fine copper line, the Ta is locally completely eroded. The arrays of very fine lines have an uneven coloration with stained appearance. This type of Ta erosion can be confused with copper residues. It is possible to have both Ta erosion and copper residues simultaneously as shown in the bottom picture. In arrays of very fine copper lines, SEM and AFM are needed to remove the doubt. 

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. 

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