CONTRAST EFFECTS USING A 2-DETECTOR SYSTEM IN LOW-VOLTAGE SCANNING ELECTRON-MICROSCOPY

A system of two opposite Everhart-Thornley detectors A and B has forme rly been applied in conventional SEM for electron energies between 5 a nd 20 keV to separate material, topographic and other types of contras t by sum and difference signals. This technique can also be used succe ssfully for low-voltage scanning electron microscopy. The decreasing i nformation depth with decreasing electron energy shows differences in the surface composition and contamination which cannot be observed bey ond 5 keV. Also below 5 keV material and topographic contrast can be s eparated and increased by the A + B and A - B signals, respectively.