Scanning Electron Microscopy


Electron beam testing using voltage contrast in the scanning electron microscope has been established as a useful tool for nondestructive and nonloading functional testing and failure analysis of integrated circuits (IC). The accuracy of quantitative voltage measurements within the IC with the electron beam probe is determined by the performance of the secondary electron (SE) spectrometer used.

For simulating the performance of SE-spectrometers a program-package has been developed by aid of which the voltage-and field-distributions within the spectrometers can be evaluated using a finite element method. Thus it is possible to trace electron trajectories throughout the spectrometer. By considering a great number of SE-trajectories, the detected integral SE-signal for different voltages at the IC can be determined as a function of the retarding field voltage within the spectrometer. In this way the performance of an existing spectrometer is simulated.

The experimentally measured SE-signals are compared with the simulation data. This comparison showed that the program-package realistically simulates the spectrometer properties. Therefore this program-package enables an improvement of existing SE-spectrometers and in principle also the development of new spectrometer-assemblies. Here the suitability for optimizing a SE-spectrometer is shown.

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