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Effect of Specimen Bias on the Contrast of High Resolution Low Voltage SEM Images in a Semi-In-Lens JSM-6320f Fe-SEM

Nanometer-resolution surface imaging by secondary electrons (SE) is now routinely obtainable in field-emission SEM or STEM microscopes. The resolution in SE images obtained in a modern field-emission (FE) SEM is still limited by the electron probe size although the localization of the SE generation processes sets the ultimate resolution limit that will be achievable in SE images. The combination of a FE gun with improved probe forming lenses and detection systems makes it possible to image nanometer-scale surface features at low voltages. Because of the reduced electron beam range and the new SE detection system, image contrast formation in low voltage FE-SEMs is quite different to that in conventional SEMs. In a FE-SEM, SEs are detected through the combination of a strong magnetic field of the lens and a weak electrostatic extraction field of the detector. The detection efficiency varies with the energy of the emitted SEs.