R. A. Sennov

Depth range of primary electrons, electron beam broadening, and spatial resolution in electron-beam studies

A comparative analysis of the electron range in solids as a function of the initial electron energy (in the range 1–50 keV) and parameters of matter is performed. A relationship between the full length range of electrons and the depth of their penetration into the target material is established using simple empirical relations. The broadening of an electron beam upon its penetration into a material is considered and the spatial resolution of electron-beam instruments (in particular, in the backscattering mode) is determined.

Methodological aspects of the electron-beam investigation of dielectric target charging

The basic characteristics of dielectric target charging with (2–30)-keV electron beams were investigated using the example of a typical insulator, Al2O3. A new hypothetical scenario of dielectric charging, based on the reduction of secondary-electron current due to the formation of polarized excitons in the positive layer of a charged target, is proposed on the basis of modeling calculations and the experimental data.

Increasing spatial resolution in the backscattered electron mode of scanning electron microscopy

A new method for increasing spatial resolution in the detection of backscattered electrons and induced current in scanning electron microscopy (SEM) is proposed in terms of regularized Fourier transform. The real size of an electron probe and its blurring in a solid target sample are considered in forming the algorithm. The experiments reveal an almost 100% improvement in resolution in the processed images.

A method and devices of electron microtomography in scanning electron microscopy

A method of microtomography of layered microstructures during detection of backscattered electrons in a scanning electron microscope is described. This method is based on the formation of layer-by-layer images hidden under the surfaces of microstructures using reflected electrons filtered within a narrow energy window. An improved deflector-type spectrometer with toroidal electrostatic sector electrodes is applied for microtomography and spectroscopy. To improve the sharpness and accuracy of separation of individual buried heteroboundaries, the modulation principle of video-signal detection is implemented.

Characterization of semiconductor detectors of (1–30)-keV monoenergetic and backscattered electrons

Semiconductor detectors of backscattered electrons are basic elements of all modern scanning electron microscopes. Their quality is determined by the properties of planar p-n junctions and the parameters of the protective layer on the detector surface. The main characteristics of semiconductor detectors are considered, their response functions are calculated, and the threshold signal cutoff energies are found both for a monoenergetic electron beam and for detection of the total energy spectrum of backscattered electrons. The experimental results are in good agreement with the computational model data.

Determination of the mean energy of backscattered electrons in dependence on the exit angle

A semiconductor detector was used to measure the mean energy of backscattered electrons as a function of the exit angle. New regularities of electron backscattering were found. A nonmonotonic dependence of the mean energy of backscattered electrons on the exit angle and the primary electron energy for materials with different atomic numbers was revealed.

Heteroepitaxial III–V films on fianite substrates and buffer layers

GaAs, GaSb, AlGaAs, and InGaAs epitaxial films and multilayer AlGaAs/InGaAs/GaAs heterostructures for PHEMT field-effect transistors have been obtained on fianite substrates by metal-organic vapour phase epitaxy. Films of different III–V compounds, including GaN, were grown on Si and GaAs substrates with a simple single buffer layer (fianite) and double buffer layer (fianite on porous Si and GaAs). It is established that the use of a two-layer buffer improves the structural quality and homogeneity of III–V films. A possibility of controlling the phase composition of GaN films using a corresponding buffer layer is shown. It is found that the use of a two-layer buffer increases the electrical homogeneity and decreases the electrical activity of defects in GaN films.

Some kinetic aspects of the charging of dielectric targets by a (1–50)-keV electron beam

The electron-emission characteristics of dielectrics irradiated with electron beams with a current density of about 10−5 A cm−2 have been experimentally investigated. An ambiguous relationship between the secondary electron-emission properties, the charged-surface potential, and the positive and negative charges accumulated in the surface region of dielectric targets is demonstrated. The character and values of various experimentally observed time charging constants, inconsistent with a number of theoretical models and estimates, are qualitatively explained.

Energy Spectra of Electrons Backscattered from Bulk Solid Targets

Energy distribution spectra of backscattered electrons in the range 5–25 keV are obtained experimentally. An inverse problem of the reconstruction of the true electron spectrum is solved taking into account the instrument response function of the spectrometer; on the basis of the obtained solution, we specify functions of the real energy distribution of the electrons backscattered from homogeneous and layered samples.

Nondestructive contactless electron-beam diagnostics of microelectronic device structures

An electron-beam diagnostic complex based on a scanning electron microscope is described. The complex allows the nondestructive contactless studies of microelectronic device structures and architectures and the simultaneous determination of the distribution of electrically active elements; i.e., the complex makes it possible to examine defects. The parallel diagnostic tests are based on the method of contactless detection of local electron-beam-induced potentials and on reflection electron microtomography in a scanning electron microscope.