Auger Electron Spectroscopy for Quantitative Analysis
Elemental analysis tools, like Auger electron spectroscopy, can often be exceptionally helpful for providing qualitative data about the composition of a material. An unknown material can be quickly analyzed to look for the presence of harmful corrosive elements or organic contaminants that may be relevant to a failure. In some cases, however, knowing whether or not an element is present does not tell the whole story; manufacturers may have guidelines which set limits on the amount of a given substance that may be present on a device, or specifications for the material composition of certain parts of their product. In these cases, it is necessary to perform a more thorough, quantitative analysis.
Quantitative analysis with Auger electron spectroscopy is usually performed by collecting an energy spectrum from the device, then performing complex mathematical operations (almost exclusively done in software) to determine relative weight and atomic percentages of all the elements in the sample. One of the primary things that must be taken into account in these calculations are the Auger sensitivity factors of the various elements in the spectrum. The sensitivity factors are empirically derived “correction factors” that are used to compensate for relative differences in elemental behavior (relative probabilities of Auger electron emission, for example). Without taking these sensitivity factors into account while performing Auger electron spectroscopy, accurate quantitative analysis would be impossible.
Auger electron spectroscopy is useful not only for the qualitative analysis of contaminants during a failure analysis – though it excels at analyzing surface contamination to determine its constituent elements – but also for performing the precise characterization of materials. With the right approach, it is possible to use Auger spectroscopy to determine the exact composition of (for example) the insulative layers on an integrated circuit or the solder used on a printed circuit board. For these applications, the high sensitivity and low penetration of Auger electron spectroscopy is perfectly suited – allowing detection of elements at even one-hundredth of a percent!
Derek Snider is a failure analyst at Insight Analytical Labs, where he has worked since 2004. He is currently an undergraduate student at the University of Colorado, Colorado Springs, where he is pursuing a Bachelors of Science degree in Electrical Engineering.