Name: comprehensive characterization of extended defects in semiconductor materials by a scanning electron microscope
Uploaded: 2016-05-28T14:00:00
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Description: Watch this Scientific Journal Video about Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope at JoVE.com

Support of this work by the German Research Foundation (DFG) within the framework of the Research Training Group 1621 is gratefully acknowledged by Paul Chekhonin. All authors are grateful to Dietmar Temmler (Fraunhofer FEP Dresden) for providing the electron beam processed Si samples showing liquid phase re-crystallisation. Special thanks go to Stefan Saager and Jakob Holfeld for the preparation of the figures for the SEM equipment and the EBSD set-up. We thank Michael Stavola for detailed discussions and help with this work.

<ol>
	<li>Alexander, H., Schr&#246;ter, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+6,+Dislocations.">Chapter 6, Dislocations.</a> Electronic Structure and Properties of Semiconductors. , 249-319 (1991).</li><li>Mahajan, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defects+in+semiconductors+and+their+effects+on+devices.">Defects in semiconductors and their effects on devices.</a> Acta Mater. 48, 137-149 (2000).</li><li>Holt, D. B., Yacobi, B. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Extended Defects in Semiconductors- Electronic Properties, Device Effects and Structures. , (2007).</li><li>Hornstra, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+of+grain+boundaries+in+the+diamond+lattice.">Models of grain boundaries in the diamond lattice.</a> Physica. 25 (1-6), 409-422 (1959).</li><li>Randle, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystallographic+characterization+of+planes+in+the+scanning+electron+microscope.">Crystallographic characterization of planes in the scanning electron microscope.</a> Mater. Charact. 34 (1), 29-34 (1995).</li><li>Wilkinson, A. J., Meaden, G., Dingley, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+elastic+strain+measurement+from+electron+backscatter+diffraction+patterns:+New+levels+of+sensitivity.">High-resolution elastic strain measurement from electron backscatter diffraction patterns: New levels of sensitivity.</a> Ultramicroscopy. 106 (4-5), 307-313 (2006).</li><li>Wilkinson, A. J., Meaden, G., Dingley, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+resolution+mapping+of+strains+and+rotations+using+electron+backscatter+diffraction:+New+levels+of+sensitivity.">High resolution mapping of strains and rotations using electron backscatter diffraction: New levels of sensitivity.</a> Ultramicroscopy. 106 (4-5), 307-313 (2006).</li><li>Drozdov, N. A., Patrin, A. A., Tkachev, V. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recombination+radiation+on+dislocations+in+silicon.">Recombination radiation on dislocations in silicon.</a> JETP Lett. 23 (11), 597-599 (1976).</li><li>Dean, P. J., Williams, G. M., Blackmore, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+type+of+optical+transition+observed+in+MBE+grown+CdTe.">Novel type of optical transition observed in MBE grown CdTe.</a> J Phys. D: Appl. Phys. 17 (11), 2291-2300 (1984).</li><li>Nacke, M., Allardt, M., Chekhonin, P., Hieckmann, E., Skrotzki, W., Weber, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigations+on+residual+strains+and+the+cathodoluminescence+and+electron+beam+induced+current+signal+of+grain+boundaries+in+silicon.">Investigations on residual strains and the cathodoluminescence and electron beam induced current signal of grain boundaries in silicon.</a> J. Appl. Phys. 115 (16), 163511-1-163511-8 (2014).</li><li>Ikeda, K., Sekiguchi, T., Ito, S., Suezawa, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EBIC+and+Cathodoluminescence+Study+of+the+Bonded+Silicon+Wafers.">EBIC and Cathodoluminescence Study of the Bonded Silicon Wafers.</a> Solid State Phenom. 63-64, 481-488 (1998).</li><li>Sekiguchi, T., Ito, S., Kanai, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cathodoluminescence+study+on+the+tilt+and+twist+boundaries+in+bonded+silicon+wafers.">Cathodoluminescence study on the tilt and twist boundaries in bonded silicon wafers.</a> Mater. Sci. Eng. B. 91-92 (4), 244-247 (2002).</li><li>Lee, W., Chen, J., Chen, B., Chang, J., Sekiguchi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cathodoluminescence+study+of+dislocation-related+luminescence+from+small-angle+grain+boundaries+in+multicrystalline+silicon.">Cathodoluminescence study of dislocation-related luminescence from small-angle grain boundaries in multicrystalline silicon.</a> Appl. Phys. Lett. 94, 112103 (2009).</li><li>Donolato, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theory+of+beam+induced+current+characterization+of+grain+boundaries+in+polycrystalline+solar+cells.">Theory of beam induced current characterization of grain boundaries in polycrystalline solar cells.</a> J. Appl. Phys. 54 (3), 1314-1322 (1983).</li><li>Kittler, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regular+Dislocation+Networks+in+Silicon+as+a+Tool+for+Nanostructure+Devices+used+in+Optics,+Biology,+and+Electronics.">Regular Dislocation Networks in Silicon as a Tool for Nanostructure Devices used in Optics, Biology, and Electronics.</a> Small. 3 (6), 964-973 (2007).</li><li>Kveder, V., Kittler, M., Schr&#246;ter, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recombination+activity+of+contaminated+dislocations+in+silicon:+A+model+describing+electron-beam-induced+current+contrast+behavior.">Recombination activity of contaminated dislocations in silicon: A model describing electron-beam-induced current contrast behavior.</a> Phys. Rev. B. 63, 115208 (2001).</li><li>Higgs, V., Lighthowlers, E. C., Norman, C. E., Kightley, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterisation+of+dislocations+in+the+presence+of+transition+metal+contamination.">Characterisation of dislocations in the presence of transition metal contamination.</a> Mater. Sci. Forum. 83-87, 1309-1314 (1992).</li><li>Donolato, C., Bell, R. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+grain+boundaries+in+polycrystalline+solar+cells+using+a+computerized+electron+beam+induced+current+system.">Characterization of grain boundaries in polycrystalline solar cells using a computerized electron beam induced current system.</a> Rev. Sci. Instrum. 54 (8), 1005-1008 (1983).</li><li>Wilkinson, A. J., Meaden, G., Dingley, D. J., Schwartz, A. J., Kumar, M., Adams, B. L., Field, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=chap.+17,+Mapping+Strains+Using+Electron+Backscatter+Diffraction.">chap. 17, Mapping Strains Using Electron Backscatter Diffraction.</a> Electron Backscatter Diffraction in Material Science. , 231-249 (2009).</li><li>Childs, G. B., Ericks, L. Y., Powell, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Thermal Conductivity of Solids at Room Temperature and Below: A Review and Compilation of the Literature. , (1973).</li><li>Yacobi, B. G., Holt, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Cathodoluminescence Microscopy of Inorganic Solids. , (1990).</li><li>Everhart, T. E., Hoff, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+Kilovolt+Electron+Energy+Dissipation+vs+Penetration+Distance+in+Solid+Materials.">Determination of Kilovolt Electron Energy Dissipation vs Penetration Distance in Solid Materials.</a> J. Appl. Phys. 42 (13), 5837-5846 (1971).</li><li>Zaefferer, S., Elhami, N. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theory+and+application+of+electron+channelling+contrast+imaging+under+controlled+diffraction+conditions.">Theory and application of electron channelling contrast imaging under controlled diffraction conditions.</a> Acta Mater. 75, 20-50 (2014).</li><li>Schulze, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Metallphysik. , (1967).</li><li>Jiang, J., Britton, T. B., Wilkinson, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+intragranular+stresses+and+dislocation+densities+during+cyclic+deformation+of+polycrystalline+copper.">Evolution of intragranular stresses and dislocation densities during cyclic deformation of polycrystalline copper.</a> Acta Mater. 94, 193-204 (2015).</li><li>Inoue, M., Sugimoto, H., Tajima, M., Oshita, Y., Ogura, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microscopic+and+spectroscopic+mapping+of+dislocation-related+photoluminescence+in+multicrystalline+silicon+wafers.">Microscopic and spectroscopic mapping of dislocation-related photoluminescence in multicrystalline silicon wafers.</a> J. Mater. Sci.: Mater. Electron. 19, 132-134 (2008).</li><li>Kato, G., Tajima, M., Toyota, H., Ogura, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polarized+photoluminescence+imaging+analysis+around+small-angle+grain+boundaries+in+multicrystalline+silicon+wafers+for+solar+cells.">Polarized photoluminescence imaging analysis around small-angle grain boundaries in multicrystalline silicon wafers for solar cells.</a> Jpn. J. Appl. Phys. 53, 080303 (2014).</li><li>Tajima, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectroscopy+and+Topography+of+Deep-Level+Luminescence+in+Photovoltaic+Silicon.">Spectroscopy and Topography of Deep-Level Luminescence in Photovoltaic Silicon.</a> IEEE J. Photov. 4 (6), 1452-1458 (2014).</li><li>Yablon, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+and+mechanical+effects+of+frozen-in+stresses+and+strains+in+optical+fibres.">Optical and mechanical effects of frozen-in stresses and strains in optical fibres.</a> IEEE J. Sel. Top. Quant. 10 (2), 300-311 (2004).</li><li>Herring, R., Norouzpour, M., Saitoh, K., Tanaka, N., Tanji, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+three-dimensional+strain+state+in+crystals+using+self-interfered+split+HOLZ+lines.">Determination of three-dimensional strain state in crystals using self-interfered split HOLZ lines.</a> Ultramicroscopy. 156, 37-40 (2015).</li></ol>

The authors have nothing to disclose.

The SEM offers the possibility to locate extended defects in the semiconductor material as well as to characterize their structural, optical and electrical properties by the application of ccEBSD, CL and EBIC investigations. In general, it is not possible to perform all three methods simultaneously on the same sample. However, a combination of results obtained by the different complementary investigation methods, when performed in a reasonable sequence, leads to a deeper understanding of the physical nature of the effects caused by extended defects.
For the CL measurements giving information on the optical properties of extended defects, a critical step in the protocol is the sample positioning procedure (step 1.6) due to undesired annealing of defects in the sample during the heating of the indium foil (which ensures a good thermal and electrical contact of the sample with the sample holder). An alternative to the procedure proposed is to mount the sample onto the sample holder by conductive silver paste at RT. However, from experience it is known that the organic solvent in the paste can cause carbon contamination on the sample surface during the scan in the SEM. The contamination degrades the quality of the CL images as well as of the EBSD diffraction patterns. Additionally, the step 4.21 requires special attention, where an abrupt rise of the luminescence intensity of silicon can occur during the cooling-down of the sample. This can harm the performance of the photomultiplier. On the contrary, for the case of unexpected low luminescence intensity for the actual sample, one should try to improve the adjustment of the light-collecting mirror (protocol No. 4.23) because the preliminary mirror alignment was performed on a test sample at RT in a slightly different range of wavelength.
Concerning instrumental limitations of the method, one has to take into account that at very low temperatures the stage with the sample can be moved only by &#177; 5 mm in the x- and y-directions which restricts the area of the samples under investigation. This limitation is due to the danger of brittle fracture of the He transfer tube. The sample dimensions for cryo-experiments given in 1.1 and 1.2 are also limited by experimental conditions. So the surface area of the samples should be adjusted to the size of the sample holder to ensure an optimal thermal contact on the heat sink. The low recommended thickness of the silicon samples limits the temperature gradient in the sample for the cryo-experiments. For a sample thickness of 200 &#181;m, the temperature in the center of the interaction volume for the primary electrons in the surface region was found to be increased by less than 5 K in comparison to the temperature measured at the surface of the sample holder. The high scan speed and the low magnification proposed only for the cool-down procedure in steps 4.5 and 4.17, ensure that the region of interest is kept clean. This is because of the heat transfer by the scanning electron beam which maintains a temperature always slightly above the temperature of the rest of the sample regions which act as condensation trap for residual gas in the SEM chamber. Generally, all the parameters listed in step 4.24 for CL spectroscopy are optimized for the measurement of the so called D line luminescence in bulk silicon by the experimental set up according to the equipment list. The parameters have to be adapted if investigations of the luminescence are to be carried out on other semiconductor materials.
Independent of the energy range of the luminescence observed, a further limitation of the CL measurements results from the light-collecting mirror because light coming from radiative recombination processes in the whole recombination volume is collected by the mirror and thus determines the grey value of the corresponding CL image pixel which is assigned to the position of the electron beam on the sample surface. Because the diameter of the recombination volume (which is comparable to the excitation volume) is larger than the pixel size even at low magnification, this effect causes a spatial smearing of the luminescence signal, and, therefore, limits the spatial resolution. Nevertheless, the CL investigation enables an imaging of the local distribution of mono- or panchromatic luminescence with a medium spectral resolution and could be combined with photoluminescence investigations to give a higher spectral resolution. Recently, as an alternative experimental method to CL measurements, a microscopic and spectroscopic mapping of dislocation related photoluminescence was proposed by the group of Tajima and co-workers26. The spatial resolution of the photoluminescence mapping is clearly lower than in CL images, but the photoluminescence investigations additionally allows the polarization of the deep level emission band correlated to dislocations to be determined in LAGBs with twist and tilt structures27,28.
In the case of EBIC investigations, which give insight into the electrical properties of extended defects, there are no alternative methods for the imaging of the locally varying charge-collection efficiency in semiconductor materials with a comparably spatial resolution. However, also for EBIC measurements, critical steps are included in the protocol. So in step 5.13, the variation of the EBIC image with decreasing temperature is expected to arise from the temperature dependent properties of the extended defects. However, the quality of the contacts can change at temperatures below RT and hence influence the EBIC image. Temperature affects the Schottky contact, made with an appropriate layer of Al in the case of p-type and with Au in the case of n-type silicon, because of the different coefficients of thermal expansion separating the contact layer from the silicon substrate. Furthermore, the ohmic contact made by a gallium-indium eutectic is not stable at temperatures below 160 K. Normally, the reduction of the contact quality leads to a strongly decreased EBIC signal for large areas. In this case, the contacts have to be renewed. For EBIC investigations at RT, it is also conceivable that the contacts for the EBSD measurements can be made by bonding the sample to an appropriate carrier board. Another instrumental limitation of EBIC measurements is caused by the protruding of the contact tip holders above the sample surface. To prevent a collision between the contact tip holder and the pole piece of the SEM the WD should be at least 15 mm.
In the experimental procedure for ccEBSD investigations which can be used to estimate the long-range strain field of extended defects, the following steps are critical. The most challenging part of the experiment is the sample preparation, especially the last polishing procedure (protocol No. 3.1) which has to be performed carefully to avoid the generation of additional surface defects. If no Kikuchi pattern can be obtained, often the quality of the sample surface is not sufficient. However, from silicon single crystals with slip lines on the surface after plastic deformation, a good diffraction pattern could be obtained which was well suited for the ccEBSD evaluation procedure. The surface roughness of these samples was analyzed by atomic force microscopy yielding a height variation in the range of up to 500 nm. Therefore, extremely high internal strains or amorphous surface layers seem to be responsible for blurred diffraction patterns rather than the imperfect smoothness of the sample surface. A further issue could be a low signal from the coherently scattered electrons in comparison to the background. Then an increase of the probe current at constant acceleration voltage and/or a more accurate determination of the background signal (protocol step No. 6.12) are helpful. To minimize sample movement during a long-lasting ccEBSD measurement it is recommended to fix the sample mechanically (protocol No. 3.2).
Instrumental limitations for the ccEBSD investigations can arise if the tilt of the sample surface relative to the incident electron beam is realized by the tilt of the stage. There are then strong restrictions for the movement of the sample due to a collision risk with the pole piece and the chamber walls. Furthermore, it is strongly recommended to use only line scans that are parallel to the tilt axis (and thus appear horizontally on the SEM screen), because, first, vertical scans have a large sum error for the internal strains due to the error of sample tilt. Second, during EBSD, the lateral resolution is higher (factor of about 3 for 70&#176; tilt) along the tilt axis than perpendicular to it. The lower limit for the value of the strain tensor components calculated for Si from ccEBSD investigations is about 2 x 10-4 which is the random error. Additionally it must be emphasized that the ccEBSD technique cannot be applied in the presence of large lattice rotations (&#62;4&#176;) referring to the reference point or very close to grain boundaries, where EBSD patterns from different grains overlap. The physical limitation of the ccEBSD investigations concerning the spatial resolution of the strain determination is due to the range of the electron diffraction which was found to be approximately 50 nm along the sample tilt axis. In comparison with X-ray diffraction experiments for the determination of internal strains, this is a clear advantage because of the significantly larger interaction volume of X-rays even in the case of X-ray &#181;-diffraction. For semiconductor materials, the investigation of perturbations of the isotropic refractive index by a polarscope can also be applied for the determination of internal stresses, but the spatial resolution of this method is lower than some hundred nm29. An alternative method for the determination of the spatially resolved three-dimensional strain state in crystals is based on the splitting of higher order Laue zones (HOLZ) lines. This method has to be performed in a transmission electron microscope (TEM) using an electron biprism for electron interferometry30. However, in contrast to the ccEBSD investigations in the SEM, the TEM investigation requires the preparation of a foil from the sample that changes the internal strains due to relaxation effects.
In future studies, ccEBSD measurements will also be performed at low temperatures. This will allow the investigation the structural, optical and electrical properties, not only on the same extended defect, but also at the same temperature.

It has been known for decades that extended defects exert an influence on the electronic structure of semiconductor materials1-3. The effect of extended defects on the performance of electronic devices and other applications such as sensors and solar-cell materials is under extensive experimental and theoretical investigation. Nevertheless, there is no generally accepted theory for the calculation of the electronic states of semiconductors in the presence of extended defects. This is due to the complexity of electronic structure calculations in the case of deviations from the ideal crystal lattice and also to the large diversity regarding the types and configuration of extended defects, as well as the possible combinations among them and with 0-dim intrinsic and extrinsic defects.
The main types of extended defects are dislocations (1-dimensional defects) and grain boundaries (2-dimensional defects). In the following, we concentrate on both of these types of extended defects in terms of the experiments that can be performed in the scanning electron microscope (SEM). The experimental methods presented here give information about structural, optical and electrical properties of extended defects and, therefore, indirect knowledge of the electronic states in semiconductor materials containing extended defects. The control of the defect-related electronic states is a central issue for the application of semiconductors and the operation of semiconductor devices.
For the structural investigation of extended defects, the electron backscatter diffraction (EBSD) technique can be applied. Usually, an EBSD measurement is performed by point mapping with a stationary electron beam at each point. EBSD then yields information about the crystallographic orientation of the crystal lattice of the sample in the case of single-crystalline material and of the grains in polycrystalline materials. For that purpose the experimentally determined diffraction patterns formed by the Kikuchi bands have to be analyzed by comparison with simulated patterns determined from the crystal space group of the material. If the software for the evaluation of the orientation data is able to calculate the misorientation angle between the crystallographic coordinate systems of neighboring mapping points, the type of grain boundary between them can be determined. If the misorientation angle is smaller than 15&#176;, a low angle grain boundary (LAGB) is present; otherwise it is a high angle grain boundary (HAGB). The type of HAGB is characterized by its&#160;&#931; value where &#931;-1 is the fraction of lattice points lying on a coincidence lattice. So, &#931; = 3 stands for the highly symmetric twin boundary4. If the EBSD mapping on two planes of the sample surface can be measured with an accurate knowledge of the positions of the mappings, the type of the grain boundary plane with Miller indices hkl can also be evaluated by a method proposed by Randle5.
Recently, a new procedure for the evaluation of the electron diffraction pattern was derived by Wilkinson et al.6 which allows the calculation of all components of the complete local strain tensor, i.e., absolute values of the three normal strain and the three shear strain components. This calculation is performed for each measuring point in a mapping from the corresponding diffraction pattern with respect to a reference pattern taken on an unstrained crystal region with the same crystallographic orientation. This evaluation procedure is based on the determination of small shifts of characteristic features of the EBSD pattern using the cross-correlation technique which gives the name ccEBSD. Relative to a chosen reference point, the strain components and lattice rotations can be measured with precisions of 10-4 and 0.006&#176;, respectively7. Applying ccEBSD measurements in line scans across grain boundaries, or along arrangements of dislocations, one can determine locally the amount as well as the range of the strain fields of these extended defects.
The optical properties of dislocations and grain boundaries can be investigated by spectral and imaging cathodoluminescence (CL) techniques. The luminescence signal is caused by the radiative recombination of electron-hole pairs which are generated in the semiconductor material by the primary electron beam of the SEM. The intensity of the luminescence is proportional to the radiative recombination efficiency which is the ratio of the total minority carrier life time to the radiative recombination time. When this ratio is influenced locally by defects, a contrast in the luminescence distribution can be observed in the CL images. Normally, extended defects act as non-radiative recombination centers and, therefore, the luminescence from band-band-recombination is decreased in the vicinity of extended defects in comparison to the undisturbed semiconductor. However, in the case of Si, Ge and some compound semiconductor materials, at dislocations as well as on grain boundaries, characteristic luminescence bands are observed showing photon energies lower than that of the (direct or non-direct) band-to-band recombination in the bulk material8-10. As an example, extensive CL investigations of bonded silicon wafers and of multi-crystalline silicon by Sekiguchi and co-workers11-13 revealed that dislocations and LAGBs are responsible for the occurrence of shallow and deep levels in the band gap. The corresponding radiative transitions are denoted as D lines in the CL spectra. Nevertheless, the role of the strain field accompanying arrangements of dislocations and of dislocation contamination by oxygen precipitation and transition metal impurities is still controversial for the interpretation of the D line luminescence. But, if an assignment of the energy position of the luminescence line to a distinct extended defect can be successfully made, then the occurrence of this specific line in the luminescence spectrum can be taken as a signal for the presence of this defect. To increase the luminescence intensity, i.e., the radiative recombination in relation to the non-radiative one, CL investigations have to be performed at low temperatures (cryo-CL) for semiconductor materials with indirect band structures.
The electrical properties of the extended defects considered here are characterized by imaging the electron beam induced current (EBIC) in the SEM. This current can be observed when electron-hole pairs generated by the primary electron beam are separated by a built-in electric field. This field can be generated by the electric potential of the extended defects themselves or by Schottky contacts on the sample surface. The EBIC image contrast results from local variations of the charge-collection efficiency due to a varying recombination behavior at electrically active defects. The extended defects usually show an increased carrier recombination so that they appear darker in an EBIC image than defect free regions. In the framework of physically based models of defects14, a quantitative evaluation of the spatial dependence of the EBIC signal, which is called contrast profile, enables the determination of the minority carrier diffusion length and lifetime as well as the surface recombination velocity. Because these parameters are dependent on temperature, EBIC investigations should also be performed at low temperature (cryo-EBIC) to obtain an enhanced signal to noise ratio. Alternatively, temperature dependent EBIC measurements enable the determination of the concentration of deep level impurities at dislocations according to a model which was proposed by Kittler and co-workers15,16.
It should be noted that the optical and electrical properties of extended defects in semiconductors can be influenced significantly by contamination and by 0-dim intrinsic defects17 which cannot be resolved by scanning electron microscopy. However, the combination of the experimental methods, ccEBSD, CL and EBIC, offers the chance to visualize the extended defects and to quantify their fundamental properties in the SEM. For future applications, where not only failure analysis, but also defect control and defect engineering are intended, this powerful tool will play an important role in the improvement of the performance of semiconductor devices.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>cryogenic liquids:&#160;&#160;&#160;</td>
			<td>Linde http://www.linde-gas.de, Air Liquide http://www.airliquide.de/</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>liquid helium ( LHe )</td>
			<td></td>
			<td></td>
			<td>for cooling of the cryostat</td>
		</tr>
		<tr>
			<td>liquid nitrogen ( LN2 )</td>
			<td></td>
			<td></td>
			<td>for cooling of the PMT R5509-73</td>
		</tr>
		<tr>
			<td>indium wire</td>
			<td>chemPUR http://chempur.de/&#160;</td>
			<td>900898</td>
			<td>CL sample preparation: for good electrical and thermal coupling between cryostat and sample</td>
		</tr>
		<tr>
			<td>mica</td>
			<td>plano GmbH http://www.plano-em.de/&#160;</td>
			<td>V3</td>
			<td>isolation of EBIC sample holder and good thermal coupling to the cryostat</td>
		</tr>
		<tr>
			<td>aluminium wire, gold wire</td>
			<td>chemPUR http://chempur.de/&#160;</td>
			<td>009013, 900891</td>
			<td>purity 99.99 %, material for formation of Schottky contact for EBIC measurements</td>
		</tr>
		<tr>
			<td>Indium-Gallium eutectic solution</td>
			<td>Alfa Aesar&#160;</td>
			<td>12478</td>
			<td>to form ohmic contact on the backside of the sample for EBIC measurements</td>
		</tr>
		<tr>
			<td>liquid chemicalsVLSI Selectipur 
			&#160;(de-ionized water, acetone, ethanol)</td>
			<td>VWR</td>
			<td>52182674, 
			51152090</td>
			<td>for sample preparation: cleaning and surface treatment</td>
		</tr>
		<tr>
			<td>hydrofluoric acid</td>
			<td>VWR</td>
			<td>1,003,382,500</td>
			<td>necessary to remove surface oxide layer on Silicon samples immediately before investigation; follow safety precautions!&#160;</td>
		</tr>
		<tr>
			<td>MicroCloth</td>
			<td>Buehler http://www.buehler.com/&#160;</td>
			<td>40-7222</td>
			<td>polishing cloth</td>
		</tr>
		<tr>
			<td>MasterMet 1 (0.02&#181;m)</td>
			<td>Buehler http://www.buehler.com/&#160;</td>
			<td>40-6380-006</td>
			<td>SiO2 polishing suspension</td>
		</tr>
		<tr>
			<td>scanning electron microscope (SEM)</td>
			<td>Carl Zeiss AG http://www.zeiss.de/microscopy/&#160;</td>
			<td>Ultra 55</td>
			<td>field emission gun</td>
		</tr>
		<tr>
			<td>SEM-CL system</td>
			<td>EMSystems</td>
			<td></td>
			<td>Customized, following equipment belongs to CL system:</td>
		</tr>
		<tr>
			<td>&#160;SEM stage for cryostat</td>
			<td>Kammrath &#38; Weiss http://www.kammrath-weiss.com&#160;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>KONTI cryostat</td>
			<td>Cryovac http://www.cryovac.de/</td>
			<td>3-06-4609C-7674</td>
			<td>cooling of sample</td>
		</tr>
		<tr>
			<td>liquid He transfer line for KONTI cryostat</td>
			<td>Cryovac http://www.cryovac.de/</td>
			<td>3-01-3506C-SO</td>
			<td></td>
		</tr>
		<tr>
			<td>cryogenic Temperature Controller</td>
			<td>Cryovac http://www.cryovac.de/</td>
			<td>TIC-304 MA</td>
			<td>controlling the flow rate of cryogenic</td>
		</tr>
		<tr>
			<td>Photomultiplier Tube (PMT)&#160;</td>
			<td>Hamamatsu http://www.hamamatsu.com</td>
			<td>R5509-73</td>
			<td>for NIR spectral range&#160;</td>
		</tr>
		<tr>
			<td>PMT housing and cooler</td>
			<td>Hamamatsu http://www.hamamatsu.com</td>
			<td>C9940-2</td>
			<td></td>
		</tr>
		<tr>
			<td>HV power supply&#160;</td>
			<td>Heinzinger electronic GmbH http://www.heinzinger.de/</td>
			<td>LNC 3000-10 neg</td>
			<td>for operating of the PMT</td>
		</tr>
		<tr>
			<td>Monochromator&#160;</td>
			<td>Sol Instruments Ltd. http://www.solinstruments.com</td>
			<td>MS2004i</td>
			<td></td>
		</tr>
		<tr>
			<td>PMT&#160;</td>
			<td>Hamamatsu http://www.hamamatsu.com</td>
			<td>R3896</td>
			<td>for visible spectral range</td>
		</tr>
		<tr>
			<td>CCD digital camera&#160;</td>
			<td>Proscan GmbH, Proscan Special Instruments Ltd. http://www.proscan.de</td>
			<td>HS 101 H</td>
			<td>for visible spectral range</td>
		</tr>
		<tr>
			<td>control program</td>
			<td>Proscan GmbH, Proscan Special Instruments Ltd. http://www.proscan.de</td>
			<td>PSI line</td>
			<td>for controlling spectral CL measurements with CCD or PMT detectors</td>
		</tr>
		<tr>
			<td>laptop</td>
			<td>Dell</td>
			<td>Latitude 110L</td>
			<td>hardware for running the control program</td>
		</tr>
		<tr>
			<td>&#160;LHe dewar</td>
			<td>cryotherm http://www.cryotherm.de/</td>
			<td>Stratos 100 SL</td>
			<td>container for cryogenic</td>
		</tr>
		<tr>
			<td>LN2 dewar</td>
			<td></td>
			<td></td>
			<td>container for cryogenic</td>
		</tr>
		<tr>
			<td>protective glasses</td>
			<td>pulsafe</td>
			<td></td>
			<td>protective equipment</td>
		</tr>
		<tr>
			<td>protective gloves</td>
			<td>tempex</td>
			<td>Protect line&#160; Mod. 4081052</td>
			<td>protective equipment</td>
		</tr>
		<tr>
			<td>heating tape</td>
			<td>Thermocax Isopad GmbH http://www.isopad-solutions.com</td>
			<td>IT-TeMS 6</td>
			<td>to prevent or reduce icing of the flexible hoses during cooling</td>
		</tr>
		<tr>
			<td>diaphragm pump&#160;</td>
			<td>Vacuubrand GmbH &#38; Co KG http://www.vacuubrand.com</td>
			<td>ME4</td>
			<td>to provide the flow rate of the cryogenic</td>
		</tr>
		<tr>
			<td>vacuum accessoires: flexible hoses, seals, locking rings</td>
			<td></td>
			<td></td>
			<td>connectors for cryogenic CL or EBIC set-up</td>
		</tr>
		<tr>
			<td>specimen current EBIC amplifier</td>
			<td>KE developments / Deben http://deben.co.uk/</td>
			<td>Type 31</td>
			<td>Measuring the EBIC current</td>
		</tr>
		<tr>
			<td>high vacuum chamber with metal evaporation</td>
			<td>customized</td>
			<td></td>
			<td>formation of Schottky contact for EBIC measurements</td>
		</tr>
		<tr>
			<td>heating plate</td>
			<td>Retsch GmbH http://www.retsch.de</td>
			<td>SG1</td>
			<td>CL sample preparation</td>
		</tr>
		<tr>
			<td>EBSD detector Nordlys</td>
			<td>HKL</td>
			<td></td>
			<td>no more available; can be replaced by the Oxford EBSD detectors NordlysMax3 or NordlysNano</td>
		</tr>
		<tr>
			<td>EBSD acquisition and evaluation software Channel 5</td>
			<td>HKL</td>
			<td></td>
			<td>no more available; can be replaced by the Oxford EBSD Software AZtecHKL</td>
		</tr>
		<tr>
			<td>ccEBSD program ccEBSD_v1.07.exe</td>
			<td>in house written program</td>
			<td></td>
			<td>for use please contact authors</td>
		</tr>
		<tr>
			<td>EBSD interface with remote control system</td>
			<td>Carl Zeiss AG http://www.zeiss.de/microscopy/&#160;</td>
			<td></td>
			<td>necessary for the electron beam control and parameter transfer between EBSD system and SEM&#160;&#160;</td>
		</tr>
		<tr>
			<td>Vibromet2</td>
			<td>Buehler, http://www.buehler.com/&#160;</td>
			<td>671635160</td>
			<td>vibratory polisher</td>
		</tr>
	</tbody>
</table>

comprehensive characterization of extended defects in semiconductor materials by a scanning electron microscope

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

Watch this Scientific Journal Video about Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope at JoVE.com

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

The optical, electrical, and structural properties of dislocations and of grain boundaries in semiconductor materials can be determined by experiments performed in a scanning electron microscope. Electron microscopy has been used to investigate cathodoluminescence, electron beam induced current, and diffraction of backscattered electrons.

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications ...

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