Qualitative voltage contrast is produced without difficulty in any SEM. Complete separation of the voltage contrast from other sources of contrast is not a straightforward matter because of the nonlinear relations between the phenomena causing contrast and the video signal.
Quantitative measurements depend on the availability of electron energy analysers which can detect accurately the shift in secondary electron energies due to potentials appearing on integrated circuit tracks, without being affected by transverse fields due to potentials on other conductors or insulators. The principles underlying existing detectors are explained, their effectiveness assessed, and a new form of electron detector is suggested.
Dinnis, A. R.
"Detectors for Quantitative Electron Beam Voltage Measurements,"
Scanning Microscopy: Vol. 2
, Article 17.
Available at: https://digitalcommons.usu.edu/microscopy/vol2/iss3/17