Scanning Electron Microscopy Failure Analysis - How it works
One of the basic requirements of electronic failure analysis is the ability to actually view a detailed close up of the Integrated Circuit (IC) at the point which needs to be tested. Though techniques such as acoustic microscopy are invaluable, they must be used in conjunction with a first class real life image. Such a combination of techniques is common in the failure analysis of ICs. Failure analysis using Scanning Electron Microscopy is the technique that is used for obtaining this detailed image.
In this article, we look at why and how electron microscopy services are able to generate such intense representations.
Regular microscopes focus visible light onto the sample and return the images to the human eye. There's a limit however to the amount of magnification that we can obtain no matter how good the equipment. This is because normal light has a wavelength that allows us to obtain a maximum magnification of only around 2000x. Moreover, the images lack the proper depth since the focal length has to be adjusted accordingly.
Using electron microscopy however, it's possible to generate images that are a thousand times more detailed than those delivered by an optical microscope. Though we think of electrons as particles, they can just as easily behave exactly like waves and as with all waves, they have a wavelength which is inversely proportional to their momentum which in turn is under our control depending on how much energy we pump into the electron beam. The images generated are monochromatic since no color information is passed. But a tremendous depth is generated which makes electron scanning microscopy uniquely suited for failure analysis.
A side effect of the electron microscopy service is that the beam of electrons can also end up generating x-rays by knocking out an electron in the ground state of some atoms. This leaves a "hole" which a higher shell electron hurries to fill up thus discharging the "characteristic x-rays" which provides useful information about the elemental structure of the sample. It overlaps with x-ray imaging techniques and is like killing two birds with one stone.
Semi conductors are particularly well suited to failure analysis using scanning electron microscopy due to the unique mechanism by which they conducts charge carriers. It eases the preparation of the sample which usually requires a coating of some conductor like gold or platinum. In fact, in no other field is electron microscopy used so widely as it is in failure analysis.