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Dispersion and detection of signal electrons in environmental SEM
Romanovský, V. ; Neděla, Vilém ; Hutař, O.
The environmental scanning microscope is based on convenient adaptation of classical SEM employing the focused primary electron beam. For the proper function of the electron gun the pressure in this part of the microscopemust be less than 10.sup.-3./sup. Pa. The working pressure in the specimen chamber in environmental microscope reaches the order of hundreds of Pa.Therefore, the effective vacuum separation of these two parts is necessary. This can be obtained by the use of two or more apertures limiting the gas flow. It is also necessary to evacuate the space between the apertures by a vacuum pump of a high pumping speed. The increasing of pressure in the specimen chamber brings some difficulties, especially the dispersion of signal electrons by the influence of interaction with the gaseous environment.
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Imaging of semiconductor structures in environmental SEM
Romanovský, Vladimír ; Hutař, Otakar
The charging effects are encountered very often when the semiconductor specimens are observed. There are several possibilities how to eliminate these undesirable phenomena. One of the newest methods how to suppress charging of specimens is environmental scanning electron microscopy (ESEM). Ionisation of gas molecules caused by impacts of primary beam electrons and signal electrons in the close vicinity of the specimen surface removes the surface charge. The ionisation detectors used in ESEM enable one to obtain similar information as in classical SEM.
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Dimension measurement in a cathode lens equipped low-energy SEM
Hutař, Otakar ; Oral, Martin ; Müllerová, Ilona ; Frank, Luděk
The paper deals with calibration of magnification in a cathode lens equipped SEM, which provides a high resolution in the energy range below 2000 eV, where both the charging-up and edge effect phenomena, complicating the measurement of dimensions, are suppressed. An analytical expression for the image magnification, in the dependence on the electron impact energy and the working distance, is derived and verified with respect to the measured values. Finally, a procedure suitable for the routine calibration is proposed.
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