Plasma sputtering, aluminum alloys

As the sample volatilization is due to cathodic sputtering only, matrix interferences as a result of the thermochemical properties of the elements do not occur. This has been shown impressively in early comparative studies of glow discharge atomic spectrometry and spark emission spectrometry with aluminum samples (Fig. 107) [480]. It must be stated, however, that with advanced sparks, where through the use of fiber optics only those parts of the spark plasma are observed that are not involved in sample ablation, matrix interferences in the case of spark emission spectrometry are also lower. The analysis of similar alloys with different metallographic structures by glow discharge atomic spectrometry can often be carried out with one calibration. 

Aluminum is often used as an alloy with a few atomic % Si and/or Cu to reduce electromigration (Fig. 1). This alloy is difficult to etch because copper does not form readily volatile compounds [73]. Fleating of the wafer to some 200 °C and intense ion bombardment to sputter off involatile products are then necessary to effect etching. Residual chlorine remaining on the wafer after aluminum etching can be deleterious because it can promote corrosion, especially in Al-Cu alloys. Hence wafer rinsing with DI water is common. Dry passivation by exposure to a fluorocarbon plasma has... 

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