Of all the emission techniques used to analyse failed chips, Auger electron spectroscopy is one of the most sensitive and useful. Like most such procedures, the aim is to detect flaws in the composition of underlying materials rather than finding cracks, delaminations, or errors in the electrical components themselves. Experienced failure analysts perform a thorough analysis of the chip before deciding to opt for a spectroscopy test to either confirm or disprove their hypothesis regarding the cause of the failure.

Auger spectroscopy depends on what we call the "Auger effect." This consequence of the way atoms react with impinging particles wasn't always regarded as being useful. In fact, it was originally classified as a "nuisance effect" when scientists were examining how electrons and photons are ejected from atoms.

Auger Spectroscopy Sensitivity Factors

When a photon collides with an electron in one of the inner shells of the atom, that electron is ejected leaving a vacancy which is quickly filled by an electron from one of the outer shells. Because this "filling" electron moves from a higher energy state to a lower one, the excess energy is flung out of the atom as a photon. But sometimes, this photon collides with yet another electron from inside the atom which gets ejected. This second electron is called the "auger electron."

By analyzing the properties of the Auger electron, we're able to obtain very detailed information about the composition of the materials

There are several factors which can increase or decrease the sensitivity of the experiment. For example, the Auger electrons are ejected at high speeds. There's always a danger that they'll collide with something else before they're picked up by the detector thus spoiling the experiment. For this reason, it's useful only for measuring surface compositions. Otherwise, the ejected electrons will never reach the surface. At the most, it can be ejected a few nanometers from below.

This is also why the experiment is conducted in vacuum. We can't risk the Auger electron hitting an air molecule on the way to the detection chamber. The vacuum also "boils away" the adsorbate layer of gasses on the chip which can otherwise mess up the measurements.

Auger electron spectroscopy is now a straight forward way to measure the composition of materials. It's so prevalent that it's now an indispensable tool in the hands of experienced failure analysis engineers and is a key contributor to the process of ensuring that the electronic chips we use everyday are reliable and robust.

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