Thermal field emission for low voltage scanning electron microscopy

SUMMARY Low voltage scanning electron microscopy is a technique of great importance to the semiconductor industry, where inspection and testing of non‐conductive devices must be done at ∼ 1 keV beam energy. In order to perform scanning electron microscopy for inspection at high speed, improved cathodes are required in order to achieve good resolution at low energy with high beam current, the chromatic spread in the electron beam is shown to be the limiting factor in the SEM and a comparison of thermionic, field emission and Schottky cathodes is made to determine which can provide the best performance. It is concluded that a thermal field emission or Schottky, cathode is superior to either conventional field emission or thermionic cathodes.