When analysing an integrated circuit, it’s best to begin with non destructive techniques (NDTs) so as to preserve our options for later tests and also save on costs. In addition, a chip with an unusual defect should be preserved for as long as possible for future reference. One such technique is emission microscopy (EMMI) which actually covers a broad range of techniques where particles being emitted from the integrated circuit are analysed. In today’s article, we look at a specific type of electronic failure analysis using emission microscopy which deals with light being emitted from defective portions of the package.

Emission Microscopy in Failure Analysis

Depending on the type of emission which takes place, we can classify emission microscopy techniques into Light Emission Microscopy (LEM) as compared to electron emission microscopy where we detect electrons including techniques such as Auger spectroscopy.

Photo emission spectroscopy is a field under development. The two elements of operation in a semiconductor are electrons and “holes.” In solid state physics, a hole is a situation where an otherwise complete electron shell is missing an electron. The manner in which these “holes” are created and give rise to electrons as well as the means by which they’re neutralized by combining with an electron is called “carrier generation and recombination.”

This ongoing process generates light at a very low level which cannot be detected by the naked eye. For this reason, we need to enhance the emissions and see them using a specialized light emissions microscope.

By examining this emission, we can get an idea about what’s wrong with a chip by comparing it with the emissions of a “normal” chip. It’s important to realize that by merely examining these emissions we can’t get a full picture of what is wrong. The analysis of the photo emissions gives us a general idea of the type of defect that can take place. It doesn’t confirm the location of the failure since the complex interactions on a chip mean that a defect in one place can effect the emissions in another.

As a failure analysis technique, emission microscopy is always combined with other, more precise tests to get a confirmation of the problem. This isn’t the only detection technique which works this way. We’ve seen before how liquid crystal imaging also tries to highlight areas of the chip which are generating excess heat. The initial test is always followed up by a thorough analysis of the problem to get a handle on real location of the defect.