Application of the low-loss scanning electron microscope image to integrated circuit technology part 1 - Applications to accurate dimension measurements

Scanning electron microscopes (SEMs) are the most extensively used tools fo r dimensional metrology and defect inspection for integrated circuit techno logies with 180 nm and smaller features. Currently, almost all SEMs are des igned to collect as many secondary and backscattered electrons as possible. These signals are mainly secondary electrons (SE1, SE2, and SE3) detected with various detection schemes. To facilitate the electron collection, very strong electric and magnetic fields are applied not just in the path of th e primary electron beam but to the emerging electrons as well. These new sy stems provide strong signals, thus better signal-to-noise ratios and thus r esulting in higher throughput than older ones. On the other hand, the use o f secondary electrons means that measurement results are much more prone to the detrimental effects of electron beam interactions, sample charging, an d sample contamination than measurements with higher energy backscattered e lectrons. The use of backscattered electrons, especially low-loss electrons (LLE), can provide better surface sensitivity, edge accuracy, and repeatab ility, possibly at the expense of measurement speed. This two-part study in vestigates the benefits and drawbacks of low-loss electron imaging to edge characterization for dimensional metrology and enhancement of fine surface features done through filtration or separation of the generated LLE signal and the use of energy-dependent signals. Part 1 reviews and illustrates the potential for accurate dimensional measurements at low accelerating voltag e by LLE, and Part 2 will concentrate on the enhancement of surface feature s in chemical-mechanically planarized specimens with the use of a novel LLE detector.