Specimen biasing to enhance or suppress secondary electron emission from charging specimens at low accelerating voltages,

Abstract

Biasing of the specimen is shown to produce improved images in the scanning electron microscope at low beam energies (0.8–2.5 keV) when charging effects (induced by the primary electron beam), topographic effects, or detector shadowing effects would otherwise be present. Examples of such improvement are given for gallium arsenide field‐effect transistors (positive charging), patterned photoresist layers on silicon wafers (negative charging and shadowing in contact holes), fractured polymethylmethacrylate (negative charging), polyethylene wrapper material (positive charging), and polished diamond tools (positive charging). It is concluded that specimen biasing may be a simpler and more convenient way to achieve some of the advantages of the converted backscattered secondary electron (CBSE) technique for imaging, but without some of the fundamental disadvantages of that technique. Characterization of this backscattered electron‐derived image bears further investigation for possible metrological applications.

Reduction of charging effects using vector scanning in the scanning electron microscope

“…The effects of positive charging are important for low-voltage SEM operation since positive specimen charging would typically result in a loss in SE signal as low-energy SEs are prevented from leaving the sample by local electric fields (Postek et al 1989). Figure 10(a) shows the image of a positively charged resist pattern obtained with a beam voltage 900 V using raster scanning.…”

Analysis of electron range versus energy relationship of insulators in low‐voltage scanning electron microscopy

“…If (J > 1, the surface is positively charged, while if (J< 1 it is negatively charged. According to the report that the negative charge-up induces the unstable disturbance in observation (Postek et al 1989), we may precume that the threshold condition as to observability is the state where 0 = I .…”

Charging compensation of alumina samples by using an oxygen microinjector in the environmental scanning electron microscope

“…The nonconductive materials observed in the conventional scanning electron microscope (SEM) may raise the electron accumulate and the local potential on the analyzed surface, which results in the electrical charging up (Cazaux 1986, Postek et al 1989. The charging effects cause beam deflection and increase imaging aberration and error of the x-ray analysis (Goldstein et al 1992, Le Gressus et al 1991.…”