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Secondary electron contrast of dopped regions in semiconductor - a matter of surface treatment?
Frank, Luděk ; Müllerová, Ilona ; El-Gomati, M.
Direct observation of doped patterns in semiconductor, usually on cleavedsections through multilayers but recently also in plan views of patterneddoping of a technological layer, is acquiring high interest because of its straightforward application in the semiconductor technology. Plenty of experimental data has been collected [1-4] from conventional SEM observation and recently first results showed improved contrasts attainable with specimen immersed into electric field. Main features are the sign of contrast- the p-type regions are always brighter than the n-type ones, and the contrast grows toward lower energies.
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Ultrahigh vacuum scanning low energy electron microscope (UHV SLEEM) for surface studies
Müllerová, Ilona ; Frank, Luděk
The aim of project is to study clean and well-defined surfaces via interaction of electrons at energies from 0 to 25 keV with a high spatial resolution. During the period 1995-2001 we have built an Ultrahigh Vacuum Scanning Low Energy Electron Microscope for surface studies. The image resolution below 50 nm can be achieved at 10 eV. The residual pressure in the specimen vicinity is 10.sup.-10./sup. mbar. The paper briefly describes main parameters of the instrument.
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Examination of semiconductor structures with slow electrons
Frank, Luděk ; Müllerová, Ilona
Possibilities for visualization of the doped areas and variances in the local density of electron states are briefly reviewed. First examples are presented of utilizing very slow electrons in a cathode lens equipped SEM for this purpose. These include acquisition of the doping contrast via secondary electrons and observation of the local energy band structure by means of elastically backscattered electrons.
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Scanning low and very low energy electron microscopy
Müllerová, Ilona ; Frank, Luděk
The main aspects of the SEM performed in the low energy (below 5 keV) and very low energy (below 50 to 100 eV) ranges are briefly summarised. They include the necessity to vary the beam energy along the column, in order to suppress the energy dependence of the resolution, and to tune the compromise between the resolution and the field on the specimen surface. Applications under "normal" vacuum conditions are mentioned.
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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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