Biology Commons^™

A Reflection Upon The Applicability Of Electron Beam Induced Current (Ebic) As A Sensitive Microanalytical Technique (Ppb Range) For Silicon Materials Research, Martin Kittler, Winfried Seifert

Scanning Microscopy

This paper discusses the application of electron-beam-induced current (EBIC) technique as a tool which is able to provide at least qualitative microanalytical information not available from other techniques. Three examples are given which demonstrate a sensitivity in the parts per billion (ppb) range: temperature dependence of dislocation contrast as a fingerprint of level of metal (Cu) contamination, iron determination down to 1013 atoms per cm3, and visualization of phosphorous striations in silicon grown by float-zone (FZ) method (FZ-grown Si).

Microanalytical information by EBIC is rather indirect and, usually, identification of the impurity species is not possible. Conclusions about impurity content …

Imaging Of Cherenkov And Transition Radiation From Thin Films And Particles, N. Yamamoto, A. Toda

Scanning Microscopy

Cherenkov radiation and transition radiation, which are generated by high energy electrons with constant velocity, can be detected in a transmission electron microscope using a cathodoluminescence (CL) detection system. The characteristic peaks due to interference were observed in the emission spectra from thin films of mica, silicon and silver, and their dependence on sample thickness and accelerating voltage was studied. Particles of BaTiO3 and MgO also showed characteristic feature in the spectra which changed with their size. A recently developed imaging system revealed the two-dimensional intensity distribution of these radiations; for example, oscillating contrast, such as equal thickness contour appears …

Surface Recombination Velocity And Bulk Carrier Lifetime Measurement Of Silicon Crystals By Using Photoluminescence Time Decay, Karsten Thölmann, Masakazu Yamaguchi, Akihiro Yahata

Scanning Microscopy

The time decay for photoluminescence (PL) emitted from silicon crystals has been used to obtain both bulk carrier lifetime (Tb) and surface recombination velocity (S). Experimental results were interpreted with the assumptions that the sample was under a low-excitation condition and that the ratio of radiative to non-radiative recombination rates was constant throughout the carrier decay process. Analysis was applied to several wafers covered with different kinds of silicon dioxide (SiO₂). The results indicate that PL time decay measurement is effective to obtain the values of Tb and S.

Can Cathodoluminescence And Scanning Electron Acoustic Microscopy Be Considered Complementary Techniques?, J. F. Bresse

Scanning Microscopy

Cathodoluminescence (CL) and Scanning Electron Acoustic Microscopy (SEAM) give complementary information on direct bandgap semiconductors when dopant impurities are introduced. CL deals with the electrical properties of the semiconductor and SEAM deals with the thermal and elastic properties and eventually with the piezoelectric properties in low doped III-V compounds. As function of the introduction of impurities for the doping of the semiconductor, the Near-Band-Edge (NBE) CL emission increases up to a maximum. and decreases when the impurities are no longer introduced in electrically active sites, but create complexes giving rise to the appearance of a Deep Level (DL) emission. The …

Metastable Reconstructions On Si(111), Y. -N. Yang, E. D. Williams

Scanning Microscopy

We report unambiguous atomic scale evidence demonstrating that the atom density in the high temperature "1x1" phase of Si(111) is ~6% higher than the 7x7. Such evidence is provided by scanning tunneling microscopy (STM) observation of excess adatom density, and related island formation, on surfaces with very large terraces. The unusually large terraces were produced by heating the sample with DC current in the step-down direction at 1200°C. By trapping adatoms on the terraces through a quench, we have also created areas of metastable reconstructions, i.e., 9x9, 2x2, c2x4 and √3x√3, much larger than previously reported. For …

Boron Reconstructed Si(111) Surfaces Produced By B2o3 Decomposition, J. Nogami, S. Yoshikawa, J. C. Glueckstein, P. Pianetta

Scanning Microscopy

Scanning tunneling microscopy has been used to study the growth of boron on the Si(111) surface. Boron was deposited in the form of B₂O₃ which was decomposed by heating the substrate. With this technique, it is possible to control the B coverage, and also to produce the well known √3 x √3 reconstruction at annealing temperatures as low as 600°C. The optimal conditions for the formation of the √3 x √3 surface by B₂O₃ decomposition are given. In addition, the nature of the √3 x √3 surface over …

X-Ray Absorption Studies Of Strain In Epitaxial (Si-Ge) Atomic Layer Superlattice And Alloy Films, T. Tyliszczak, A. P. Hitchcock, Z. H. Lu, J. -M. Baribeau, T. E. Jackman

Scanning Microscopy

The Si 1s (K-shell) X-ray absorption spectra of a series of strained Si_xGe_100-x alloy thin films and several {(Si)_m(Ge)_n}_p atomic layer superlattices (ALS) grown epitaxially on Si(100) and Ge(100) substrates have been investigated using plane polarized synchrotron radiation. Polarization dependent components of the signal are attributed to anisotropic states associated with strain-induced tetragonal distortions. The sense of the polarization is shown to be identical for all compositions (x = 25 to 92) of SiGe alloys grown on Si(100) substrates. The opposite polarization dependence is found to occur for all Si_xGe …

Znse Heteroepitaxial Growth On Si (100) And Gaas (100), D. K. Biegelsen, R. D. Bringans, J. E. Northrup, L. -E. Swartz

Scanning Microscopy

The early stages of ZnSe heteroepitaxy on Si(100), Si(100):As and GaAs(100) are compared and contrasted, based on results of scanning tunneling microscopy and photoemission spectroscopy. High Se reactivity with the substrate constituents leads to bulk phase formation which is detrimental to heteroepitaxy. As-termination of Si(100) not only passivates the surface, but also provides an ideal buffer for ZnSe overgrowth. Lacking a similar buffer layer, stoichiometric control of the GaAs(100) surface is investigated to find a means for controlled heteroepitaxy.

Balancing Surface Energy Terms For Stable Growth Of Planar Surfaces, M. Albrecht, P. O. Hansson, S. Christiansen, W. Dorsch, H. P. Strunk, E. Bauser

Scanning Microscopy

We investigate the driving forces that determine the growth mode of heteroepitaxial Ge layers grown from solution on Si substrates with orientations (001), (011) and (111) by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Using liquid phase epitaxy, we can study the influences of strain and surface energy terms independently on effects due to limited surface diffusion. In (001) and (011) orientated layers, {111} faceted islands form (Stranski-Krastanov growth). In contrast, (111) orientated layers grow in a two-dimensional step flow growth mode (Frank-van der Merwe growth).

We model these investigations in terms of energy minimisation considering surface energy …

Caesium On Si(100) Studied By Biassed Secondary Electron Microscopy, M. Azim, C. J. Harland, T. J. Martin, R. H. Milne, J. A. Venables

Scanning Microscopy

An ultra-high vacuum scanning electron microscope (UHV-SEM) has been used to study sub-monolayers of Cs on Si(100) surface. Cs adsorption on the surface causes a considerable change in the work function. Coverages below 1/2 monolayer (ML) have been estimated by correlating the work function changes with the secondary electron (SE) signal. It has been found that this signal is sensitive down to ~ 0.005 ML when the sample is biassed to a few hundred volts.

Electron trajectories from a biassed sample have been simulated for electrons originating from different areas with different work functions across the sample. This indicates that …

Surface Morphology And Strain Relief In Surfactant Mediated Growth Of Germanium On Silicon (111), M. Horn-Von Hoegen, M. Pook, A. Al Falou, B. H. Müller, M. Henzler

Scanning Microscopy

The growth of Ge on Si is strongly modified by adsorbates called surfactants. The relevance of the stress on surface morphology and the growth mode of Ge on Si(111) is presented in a detailed in situ study by high resolution low energy electron diffraction (LEED) during the deposition. The change from islanding to layer-by-layer growth mode is seen in the oscillatory intensity behaviour of the 00-spot. As a strain relief mechanism, the Ge-film forms a microscopic rough surface of small triangular and defect-free pyramids in the pseudomorphic growth regime up to 8 monolayers. As soon as the pyramids are …

Quantitative Scanning Electron Acoustic Microscopy Of Silicon, M. Domnik, L. J. Balk

Scanning Microscopy

So far results of scanning electron acoustic microscopy (SEAM) have retained a widely qualitative meaning only due to the enormous uncertainty in understanding sound generation and contrast mechanisms in SEAM micrographs. In this work, a detailed treatment of these mechanisms has been undertaken for silicon resulting in precise knowledge of the signal generation processes and a well understood interpretation of the contrast mechanisms involved in imaging thermo-mechanical and electronic features.

Influence Of Annealing On The Interface Structure And Strain Relief In Si/Ge Heterostructures On (100) Si, D. J. Lockwood, J. -M. Baribeau, T. E. Jackman, P. Aebi, T. Tyliszczak, A. P. Hitchcock, R. L. Headrick

Scanning Microscopy

Research work on the general problem of the nature and thermal stability of the Si/Ge semiconductor interface is reviewed. We report on our recent studies of the interface structure in [(Si)_m(Ge)_n]_p superlattices and (Ge)_n layers buried in Si as revealed by Raman scattering, extended X-ray absorption fine structure, and X-ray techniques. Strain relaxation and interdiffusion in the superlattices caused by annealing have been investigated, and it is found that considerable strain-enhanced intermixing together with partial relaxation of Ge-Ge bonds occurs even for very short anneal times at 700°C. Further annealing leads to diffusion at …

Strain Distribution During Growth Of Ge/Si(001) And The Effect Of Surfactant Layers, J. E. Macdonald, J. M. C. Thornton, A. A. Williams, P. Ashu, C. C. Matthai, H. A. Van Der Vegt, E. Vlieg

Scanning Microscopy

Grazing incidence X-ray diffraction has been employed to determine directly the distribution of strain in the plane of the interface during deposition of Ge onto Si(001). The corresponding strain distribution has also been deduced for a relaxed island whose atomic structure has been determined by molecular dynamics. The results illustrate the central role of elastic deformation of islands in the initial stage of strain relief. The results are also compared with those for growth with a Sb surfactant layer which suppresses island formation. An investigation of surfactant-like behaviour is also presented for homoepitaxial growth of Ag on Ag(111), where sub-monolayer …

Strained And Relaxed Semiconducting Silicide Layers Heteroepitaxially Grown On Silicon, J. Chevrier, Le Thanh Vinh, J. Derrien

Scanning Microscopy

The semiconducting silicide ß-FeSi₂, which can be grown epitaxially on silicon, is potentially an interesting material for integrated optoelectronic devices. Its semiconducting state stabilised by a solid state Jahn Teller effect is very unusual. Indeed the epitaxial growth of FeSi₂ on silicon (111) in a Molecular Beam Epitaxy (MBE) chamber has revealed the existence of a metallic strained FeSi₂ phase which is the result of a simultaneous electronic and structural transition. The stability and the relaxation of this strained phase which is specifically due to the epitaxy of FeSi₂ on the silicon (111) face …

On The Origin Of Electron-Beam-Induced-Current Contrast Of Extended Defects In Silicon, M. Kittler, W. Seifert

Scanning Microscopy

The paper reviews the origin of bright and dark Electron-Beam-Induced Current (EBIC) contrast due to extended defects in silicon, inclusively a brief discussion of contrast modelling. Particular emphasis is put on the role of impurities demonstrated to determine contrast in many cases (extrinsic contrast origin). The understanding of the prevalent contrast type -dark contrast due to enhanced recombination at defects -is well supported by existing phenomenological contrast models which can, therefore, be used as a basis for contrast interpretation. In the context of extrinsic vs. intrinsic contrast origin, the influence of defect dimensionality on contrast is addressed, indicating that grain …

Diffraction And Imaging Theory Of Inelastically Scattered Electrons - A New Approach, Z. L. Wang, J. Bentley

Scanning Microscopy

A new dynamical theory is developed for describing inelastic electron scattering in thin crystals. Compared to existing theories, the first advantage of this new theory is that the incoherent summation of the diffracted intensities contributed by electrons after exciting vast numbers of degenerate excited states has been evaluated before any numerical calculation. The second advantage is that only the modulus squared of the transition matrix elements are needed in the final computation. This greatly reduces the effort in searching for "phase shifts" in inelastic scattering matrix calculations. By iterative operation of this single-inelastic scattering theory, multiple-inelastic electron scattering of phonons, …

Energy Loss Of Electrons Below 10 Kev, Hans Bichsel

Scanning Microscopy

Monte Carlo calculations are used to obtain the energy loss and spatial distribution of electrons penetrating matter. For this purpose, reliable cross section for the inelastic collisions must be known. As an approximation valid for large energy losses, the Coulomb cross section can be used. It can be modified in a simple way to account for the binding of electrons and for the exchange effect. In the Gryzinski model, collisions with moving electrons are assumed. In the quantum mechanical Bethe approximation, σ is closely related to the dipole oscillator strength (DOS), and its extension to finite momentum transfers, the generalized …

Electron Beam Nano-Etching In Oxides, Fluorides, Metals And Semiconductors, C. J. Humphreys, T. J. Bullough, R. W. Devenish, D. M. Maher, P. S. Turner

Scanning Microscopy

Etching, lithography, hole formation, surface restructuring and external machining can all be performed on a nanometre scale using an intense electron beam. Results are presented for a range of different materials which demonstrate the variety of mechanisms by which electron beam nano-etching can occur. For example, in crystalline 13-alumina hole formation occurs by surface indentations growing inwards to join up and form a nanometre diameter hole. In amorphous alumina, on the other hand, hole formation is from the inside-out: oxygen gas bubbles form under the electron beam, coalesce, and burst to leave a well defined nanometre diameter hole. In MgO …

Contribution Of Densely Distributed Electron Beam Induced Current Contrasts In Annealed Cz Silicon To Bulk Recombination, M. Kittler, W. Seifert

Scanning Microscopy

The paper presents a detailed analysis of Electron Beam Induced Current (EBIC) diffusion-length and contrast data for samples containing defect accumulations. The formulae given allow one to estimate to which extent the average diffusion length is determined by recombination-active defects showing EBIC contrast.

This analysis may be used to identify essential sources of bulk recombination in annealed silicon. In the light of our results stacking faults are an essential source of bulk recombination in intrinsically gettered p-type Cz silicon.

Application Of Photovoltage Imaging To Semiconductor Wafer Characterization, Kanji Kinameri, Chusuke Munakata, Noriaki Honma, Hiromichi Shimizu

Scanning Microscopy

A technique for imaging the distribution of ac surface photovoltages induced in a semiconductor wafer by the irradiation with a blue or near-infrared chopped photon beam is applied to non-destructive inspection of faults in Si or GaAs wafers. Faults detected include crystal defects, radiation damage, surface charge-up, striation and junction inhomogeneity. The principles of inspecting for the above mentioned wafer faults are quantitatively presented by numerical analyses of dependence of ac surface photovoltage on wafer electronic characteristics. The minimum detectable changes in minority carrier lifetime, interface trap density, fixed oxide charge density and resistivity for a depleted p-type Si wafer …

Current Filament Formation In Gold Compensated Silicon Pin Diodes, H. Baumann, T. Pioch, H. Dahmen, D. Jäger

Scanning Electron Microscopy

In semiconducting materials with current controlled negative differential conductivity an inhomogeneous current density distribution can arise leading to a well-defined spatial pattern in the form of current filaments. Detailed experiments are performed on silicon pin diodes showing a pronounced multistability in the current voltage characteristics. By using the voltage contrast and the electron beam induced voltage (EBIV) methods in a SEM, it is confirmed that each jump in the current is accompanied with the formation or disappearance of a well defined transverse electrical structure between the two contacts as a result of a current filament. This non-uniform state of the …

Delineation Of Emitter-Collector Shorts In Bipolar Test Structures By Voltage Contrast Scanning Electron Microscopy, A. H. Carim, R. Sinclair, W. T. Stacy

Scanning Electron Microscopy

In examining emitter-collector shorts and their relationship to structural defects, we desire a nondestructive method for locating the short-circuited devices in large test arrays. Voltage contrast scanning electron microscopy (VC-SEM) and an established electrochemical anodization technique have been used to identify electrically faulty bipolar transistors. Direct comparison of these approaches was achieved by examining the same emitters with each method. The results indicate that VC-SEM may serve as a useful technique for delineating E-C shorts because of its nondestructive and purely electrical nature. In our qualitative investigation, the sensitivity and voltage resolution available by VC-SEM were not sufficient to differentiate …