LOW ACCELERATING VOLTAGE SEM IMAGING AND METROLOGY USING BACKSCATTERED ELECTRONS

An approach to measure semiconductor structures for nondestructive submicrometer metrology in the scanning electron microscope (SEM) at low accelerating voltage is described utilizing the collection and measurement of only the backscattered electron signal rather than the more commonly used secondary electron signal. In this technique, the backscattered electron signal is collected using a high-efficiency microchannel-plate electron detector system with the front face of the detector biased negatively to reject the low-energy secondary electrons thus collecting only the backscattered electrons. The advantage of using the backscattered electron signal is discussed, as well as a comparison to measurements using the secondary electron signal. The potential of this technique for application to accurate SEM metrology and standards development is also discussed.