Copper pitting

FIGURE 17.27 Copper pitting on the copper structure after Ta CMP. 

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

FIGURE 17.29 Stress-induced pitting. The copper grain growth makes copper to reduce its volume slightly and leave some voids. It is visible in the middle of a long copper line. 

FIGURE 17.30 Copper-filled failure-induced pitting after Ta CMP. 

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There is an increasing tendency to treat drinking waters to remove organic material. This is to minimise the formation of haloforms, produced when the water is chlorinated, which have heeilth implications . Organics are known to affect certain corrosion processes, e.g. type I copper pitting and the formation of protective corrosion product layers. However, the outcome of this development is difficult to predict as not all the organic material present is removed. 

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. 

Levy D. B., Custis K. H., Casey W. H., and Rock P. A. (1997) The aqueous geochemistry of the abandoned Spenceville copper pit, Nevada County, California. J. Environ. Qual. 26, 233-243. 

Fig. 1.10 Copper pitting corrosion in drinking water system (a) stereomicrography of perforated membrane and (b) scanning electron micrograph of perforated pit [28].

D.A. Lyde, M.N. Nadagouda, A comprehensive investigation of copper pitting corrosion in a drinking water distribution system, Corros. Sci. 52 (2010) 1927—1938. 

Pitting usually occurs on metals that are covered by a passive film, which protects them from corrosion under normal conditions. Pitting is known to occur on magnesium, aluminum, titanium, carbon steel, stainless steel, and copper. Pits develop at weak spots on the surface film and at sites where the film has been damaged. 

The specifications categorize the longest permissible dimensions of any copper pits and dents and define a point value-based rating system (as shown in Table 12.2). 

In addition to copper pits and dents, the specifications contain procedures on how to inspect for scratches, wrinkles, and inclusions. 

Figure 6.12 Type I copper pitting corrosion. (Courtesy of Russ Green, TMi)...

Woolf, J. (1996, May 28). A Whole lotta hole Brace yourself Utah, Chile may have a bigger copper pit. Salt Lake Tribune. 

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