Modern methods of sample preparation have made it possible to analyze complete, packaged integrated circuits by transmission electron microscopy. TEM has two unique capabilities that cannot be matched by other characterization methods: 1) it is a direct crystallographic probe and 2) it has excellent spatial resolution, 0.2 nm. Small personal computers can be used to translate the micrographic data into statistical information that can be analyzed by non-TEM trained engineers. The data can also be stored in a MICROSTRUCTURAL DATABANK. The experimental data is automatically compared by the computer with previously established criteria. This methodology generates additional information that is used for quality and reliability assurance testing of integrated circuits. The method is applicable to devices that are removed from electronic systems after field operation, as well as to devices that have been lifetime tested. Two examples are described and discussed: aluminum grain size distribution analysis and silicide layer thickness measurement.

Planar defects have been detected by transmission electron microscopy in silicon epitaxial layers that have been grown from Ga solutions below 500 °C. According to fringe contrast analysis, this defect can be modelled by a plane of Ga atoms within the Si lattice. This plane forms during crystal growth due to local preferential incorporation of Ga atoms at crystallographically defined sites, that occur repetitively in the trains of monomolecular growth steps at the liquid/solid growth interface.

Oxidation of silicon wafers containing lattice damage at the surface normally results in the formation of extrinsic stacking faults. Optical microscope investigation following decorative etching shows that on certain samples the faults have a straight line appearance while on others the ends of the defect are much enlarged giving a “dog-bone” shape. TEM investigation confirmed that the dog-bone shaped faults were decorated with colonies of precipitates near their edges. These colonies resided on the (111) fault planes and extended over several thousand angstroms. Precipitate spots were not found in the diffraction pattern due to the small volume fraction, but translational Moire fringes were observed for certain matrix g-vectors, thus aiding in the crystallographic analysis. EDX analysis was also performed and revealed that precipitates were due to Cu and Ni contamination. The electrical impact of the defects on P-N junction was measured, showing a strong influence on both reverse and forward bias current/ voltage characteristics.

Reacted films on compound semiconductor substrates present challenging materials characterization problems which often require the application of transmission electron microscopy (TEM) techniques. In this paper, both the problem - solving potential of the TEM techniques and the limits imposed by preparation of thin film/compound semiconductor TEM specimens are discussed. Studies of the Ni/GaAs, CuCl(aq)/CdS and Pd/GaAs reactions exemplify the role of TEM in identifying and determining the spatial distribution of interface - stabilized polymorphs and new ternary phases (e.g. tetragonal Cu2S, Ni3GaAs and PdxGaAs). These examples also serve to clarify the relationship between TEM and complementary analysis techniques such as Rutherford backscattering spectrometry, Auger electron spectroscopy and glancing-angle x-ray diffraction. In particular, it is argued that a combination of (1) high-spatial-resolution information obtained by TEM and (2) an indication of the “average” behavior provided by data from a complementary characterization technique provide the minimum quality and quantity of data necessary to understand most reactions on compound semiconductor substrates.

The structural aspects of dislocations in GaAs which had been plastically deformed at high stress were studied by TEM. The glide of well-defined dislocations in their slip-plane was observed during the recombination-enchanced relaxation of the dislocations from their high-stress configuration. The strong asymmetry of dislocation velocity previously observed by other techniques is confirmed. High-resolution, electron micrographs of dissociated end-on screw dislocations were compared to computer simulated micrographs of model structures of the dislocation core. No definite conclusion regarding the exact core structure could be made due to the movement of the defects during the observation.

A transmission electron microscope was used to study the origin of grown-in dislocations observed in quaternary InGaAsP layers grown by vapor phase epitaxy on (001) InP substrates. Many of the grown-in dislocations were found to exist as dislocation dipoles and were connected to particles formed at the lnGaAsP/lnP interface. X-ray micro-analysis has indicated that the particles are quaternary alloys having chemical compositions slightly richer in both Ga and P than that of the lattice-matched InGaAsP layer. In some cases, this compositional deviation led to a significant lattice mismatch. As the particle grows larger, a strain relaxation occurs by generating misfit dislocations around the particle in the form of a dislocation half loop. If these dislocation half loops do not develop into a complete loop by totally surrounding the particle, they leave two unclosed dislocation segments (a dislocation dipole), which are replicated by the quaternary overlayer along the substrate normal direction, i.e., [001]. These dislocations eventually become a source for grown-in dislocations.

GaP and GaP/GaAsP epitaxial layers have been grown on Si substrates by metal-organic chemical vapor deposition (MOCVD). These layers were characterized by SEM and TEM plan-view and cross-sectional examination. At growth temperatures ranging from 600° C to 800° C, the initial stages of growth were dominated by three-dimensional nucleation. TEM studies showed that at high temperatures the nuclei were generally misoriented with respect to each other yielding, upon coalescence, polycrystalline layers. The growth of single-crystal layers was achieved by nucleating a 30–50 nm layer of GaP at 500° C, followed by annealing and continued growth at 750 ° C. The defect density in these structures was investigated as a function of various growth parameters and substrate conditions. A high density of structural defects was generated at the Si/GaP interface. The use of 2° off (100) Si substrates resulted in GaP layers free of antiphase domains. These results and their implications are discussed.

The application of HRTEM to the study of equilibrium segregation in linear and planar silicon defects is evaluated with image calculations. For this purpose, models for interstitial segregation in the Σ=9 grain boundary and donor segregation in the 30° partial dislocation are proposed. These models possess columns of impurity atoms.

Systematic image simulations were first examined for an impurity column in an otherwise perfect <110> silicon crystal. Optimum contrast and exposure times require samples of thickness equal to the transmitted beam extinction distance. Arsenic and boron are detectable with a column concentration of about 5%. With diffuse phase contrast imaging, this limit is roughly halved.

The above imaging conditions may be used to distinguish different defect core models.

Observation of segregated impurities requires somewhat higher concentrations in addition to image comparisons with a clean defect. Quantitative analysis necessitates careful image simulation comparisons and improvements in knowledge of microscope parameters.

The effect of partial coherency on electron diffraction patterns of Cd1−xMnxTe – Cd1−yMny Te superlattices has been investigated. Observed diffraction patterns are compared with intensity calculations performed using dynamical diffraction theory with a model of an extended incoherent monochromatic source. From this study, a new method of electron diffraction for characterization of multilayer structures can be developed. Under the condition that the lateral coherent distance of the incident beam covers two adjacent layers, diffraction beams arising from the two layers give rise to an interference fringe in a diffraction spot. With this type of diffraction pattern, one can determine the refractive index of a crystal in the multilayer structure.

Surface modification using ion beam techniques is recognized as an important method for improving surface controlled properties of metallic, ceramic, and semiconductor materials. Determination of the microstructure and composition in regions located within a few hundred nanometers of the surface is essential to gaining an understanding of the mechanisms responsible for the improved properties. Analytical electron microscopy (AEM), high resolution microscopy, and microdiffraction are ideally suited for this purpose. These techniques are powerful tools for characterizing microstructure in terms of solute concentration profiles, second phase formation, lattice damage, crystallinity of the implanted layer and annealing behavior. Such analyses allow correlations with theoretical models, property measurements and results of complementary techniques. The proximity of the regions of interest to the surface also places stringent requirements on specimen preparation techniques. The power of AEM in examining the effects of ion implantation will be illustrated by reviewing the results of several investigations. A brief discussion of some important aspects of specimen preparation will also be included.

The nature of disorder produced by low energy Ar+ and I+ ions (and atoms) in the III–V compound semiconductors InP and InSb, and in the II–VI semiconductors CdTe, ZnS and ZnSe has been studied in detail by conventional and high resolution transmission electron microscopy. It is demonstrated that for Ar+ ion bombardment the disorder in the III–V compounds comprises segregated indium islands which accumulate on the machined surfaces, while for the II–VI compounds the disorder consists of dense arrays (∼1011 cm−2) of small dislocation loops near to each bombarded surface. When Ar+ ions or Ar atoms are used for thin specimen preparation by milling prior to electron microscopy, the disorder produced gives contrast which seriously obscures images and so complicates their interpretation. This problem concerning the presence of artifactual defects can be greatly reduced or even eliminated by the use of reactive I+ ion milling for the final thinning of specimens.

Transmission electron microscopy (TEM) of ferromagnetic materials requires special and often time-consuming procedures to obtain good images. Tilting and high resolution experiments are particularly difficult. A survey of several investigations of microstructures in ferromagnetic materials ranging from pure iron to commercial magnet materials is presented. The topics of these investigations include determination of Burgers vectors and interstitial/vacancy character for dislocation loops, cavity shape analyses, magnetic domain/microstructure correlations, and characterization of structures resulting from isotropic spinodal decomposition. Problems encountered during these studies as they relate to magnetic materials and the modifications to standard microscope operating procedures required to overcome these problems are presented. This discussion includes specimen requirements, specimen loading and insertion, and alignment corrections required during specimen tilting.

Tsuei and Johnson previously reported significantly enhanced superconducting transition temperatures for rapidly solidified Al-Si alloys. Here we report a microstructural study of melt spun Al80 Si20 ribbons to determine the mechanism responsible for this enhancement.

Results of this investigation revealed three distinct microstructures from the top surface to the more rapidly cooled bottom surface (which was in contact with the melt-spinning wheel). Near the top, the microstructure is of hypoeutectic morphology even though this is a hypereutectic alloy. The predominant microstructure is cellular. A 1 to 3 Wm thick layer at the bottom of the ribbon was found to be responsible for the largest enhancement. This layer is composed of fine-grained supersaturated fcc Al containing densely distributed dc Si precipitates. Microdiffraction analysis revealed a cube/cube orientation relationship between the precipitates and the matrix. These results provide insight into the possible mechanism for the enhancement.

There has been a resurgence of the TEM/STEM being applied to the inspection and microanalysis of solid state electronic structures and devices. As the IC industry scaled down to submicron lines and spaces the IC designer, manufacturing processor and failure analyst required better “eyes” than the SEM could give. In addition to the image improvement, the TEM/STEM provided the microanalysis capability of microelectron diffraction (<30 angstroms) and sub-micron EDXA of ultra-thinned samples.

Of great importance in many fields of endeavor is the analysis of solutes segreoated to grain boundaries in solids. Such segregation is usually (but not always) limited to the boundary plane, and can, therefore, be thought of as being “two-dimensional”.

The dependence of the characteristic and bremsstrahlung X-ray counts, the peak to background (P/B) ratio and the spatial resolution on the incident beam energy between 100 keV and 400 keV were measured using a high voltage electron microscope (HVEM). The bremsstrahlung count decreases much faster than that of the characteristic count with the increase of the incident beam energy. The decrease rate depends on Z number. It is ascertained that the P/B ratio and the spatial resolution at 400 keV were 2 or 3 and 2.5 times better than those at 100 keV, respectively.

Transition metal carbides and nitrides are important in a wide range of materials problems which include precipitates in high strength alloys and ceramic wear coatings. Electron energy loss spectroscopy (EELS) is a high spatial resolution (probe sizes < 100nm) analytical technique which is sensitive to variations in carbon or nitrogen stoichiometry. This sensitivity to light elements depends on the ability to relate the measured EELS spectrum to a material's electronic structure. The unique capabilities of EELS for the characterization of carbonitrides with high spatial resolution are discussed along with some of the experimental and analytical methods used to relate measured spectra to electronic structure. Data are presented for several members of the systems Ti-N-C and Cr-Fe-C.

Electron energy-loss spectroscopy in the transmission electron microscopy (TEELS) is a powerful technique to investigate the “electron and atom interaction in specimen microareas”.

This paper reports some experimental data of TEELS concerning specimen thickness effect and advantages of 400 kV TEM, and introduces newly developed digital processing of EELS spectra, which is a powerful technique to get the information from the specimen materials.

Convergent-beam diffraction in the transmission electron microscope is a powerful technique for the characterization of crystalline materials. Examples are presented to show the way in which convergent-beam zone-axis patterns can be used to determine: the unit cell; the symmetry; the strain of a crystal. The patterns are also recognizable and so can be used, like fingerprints, to identify phases.

Recent applications of the “Atom Location by Channelling Enhanced Microanalysis” (ALCHEMI) are summarised. This is a quantitative method for determining the sites of impurity atoms in crystals using an electron microscope and X-ray analysis system. Since the fractional site occupancies are given in terms of measured X-ray counts alone, it involves no adjustable parameters. New experiments have been performed on the temperature dependence of characteristic X-ray production under channelling conditions for InP and GaAs. We conclude that low temperatures will give more accurate results for “ALCHEMI” in some materials due to the reduction in diffuse inelastic phonon scattering, and that the study of this temperature dependence may provide new information from small areas or particles on the correlations amongst atom motions due to thermal vibration.