1.1 New technology enables wider use of electron microscopy

The capability that makes the system especially suitable for in-line inspection of sensitive materials is the build in low vacuum and environmental mode that can be used to inspect non-conductive materials such as polymers, glass and even wet biological samples. Traditionally SEM’s have been operated under high vacuum conditions (10-5 mbar) to ensure good resolution and high signal to noise levels. Under such conditions, any sample that is poorly conducting quickly accumulates charge and is therefore impossible to image in a SEM without the use of additional coatings such as gold or carbon. The use of such coatings made SEM inspection a destructive process and virtually eliminated its usefulness as an in-line inspection tool.

The need for high resolution nanometer level inspection of silicon-based microsystems and micro-electronics components has increased dramatically over the last decades as dimensions have shrunken to below one micrometer. At this level of magnification, conventional optical inspection, the inspection workhorse of silicon wafer processing, is impossible because of fundamental wavelength limitations. By combining a traditional high vacuum SEM mode seamlessly with a low vacuum and environmental mode, the FEI Quanta 600 FEG therefore fills a real need in inspection requirements in microfabrication. The low vacuum (pressure < 2 mbar) and environmental SEM mode (pressure < 40 mbar) are realised through injection of water vapour in the SEM inspection chamber. This virtually eliminates charging effects on non-conducting samples because of charge transport away from the sample by ionised water vapour and furthermore enables imaging of vacuum incompatible materials (e.g. wet biological samples).

1.2 User friendly instrument

The instrument is very user friendly in its operation. This is mainly a consequence of the fact that most of the functionality of the system is under computer control and accessible through a well organised and tested user interface.

In addition to electron microscopy, the system also has a capability to perform energy dispersive X-ray analysis. This allows on the fly elemental analysis of the sample surface, for areas as small as half a micron in diameter.