Materials characterization, using surface analysis and depth profiling techniques, plays a vital role in all aspects of semiconductor technology from basic research to manufacturing. The techniques are: SEM/EDX/WDX - Scanning Electron Microscopy/Energy Dispersive X-ray/Wavelength Dispersive X-ray AES - Auger Electron Spectroscopy ESCA - Electron Spectroscopy for Chemical Analysis SIMS - Secondary Ion Mass Spectrometry RBS - Rutherford Backscattering Spectrometry LIMS - Laser Ionization Mass Spectrometry Chemical and elemental analysis of the first several atomic layers of a surface are performed. Detection limits range from less than a part per million to several atomic per cent, and areas of analysis can be as small as 5000 Angstroms in diameter. SEM capabilities provide topographical information at magnifications up to 200,000x. An overview of these surface analysis techniques will be presented with an emphasis on the wide range of applications in the semiconductor industry. Recent advances in one technique in particular, ESCA, will be discussed.

X-ray diffraction experiments directly and nondestructively probe atomic scale structural correlations. When the samples are crystalline, x-ray scattering patterns may be obtained quickly and show extremely high sensitivity to variations in structural order. X-ray topography methods are specially arranged so as to cover large sample areas efficiently. All of these features are particularly useful in the semiconductor industry where careful control of crystalline perfection in nearly perfect materials is essential for device fabrication. This report highlights a few basic methods of semiconductor characterization using x-ray diffraction and serves as an introduction to the literature with an emphasis on topics of interest to a semiconductor process development engineer. The topics include double crystal x-ray diffraction, asymmetric crystal topography and Lang topography. In additon, since the use of synchrotron radiation sources is of growing importance for materials research programs in the semiconductor industry, its use in white beam topography is discussed. All of these experiments have been usefully pursued at Hewlett-Packard Laboratories. The references chosen show typical applications, but are far from exhaustive. Except for the synchrotron radiation techniques, the experiments can all be performed with commercially available equipment.

Synchrotron radiation photoemission spectroscopy (SRPS) in the 1-4 KeV photon energy range is a useful tool for interface characterization. We present results of a series of studies of the near-interface region of Si/Si02 which confirm that a bond strain gradient exists in the oxide as a result of lattice mismatch. These experiments include measurement of photoemission lineshape changes as a function of photon energy, corresponding changes in the electron escape depth near the interface, and surface extended x-ray absorption fine structure (SEXAFS) measurements directly indicating the shortening of the Si-Si second nearest neighbor distance in the near-interface region of the oxide.

A detailed discussion is presented concerning the use of the ion beam spectroscopic techniques of RBS, PIXE, and channeling. Emphasis is placed on extracting relevant atom site information of impurities and alloy elements in the III - V compound semiconductor series. This is accomplished through integration of the three types of spectroscopy mentioned with data being presented on specific site location of substitutional impurities through plannar contstrained assymetric angular scans across axial channeling directions.

This paper presents an overview of the application of deep level transient spectroscopy (DLTS) for the characterization and identification of electronic defects in semiconductors. The range of defect problems that has been studied by DLTS is illustrated with results from crystalline semiconductors, semiconductor - insulator interfaces, and amorphous semiconductors,

High resolution infrared absorption measurements of the localized vibrational mode (LVM) of light substitutional impurities in compound semiconductors have provided direct spectroscopic evidence for the impurity site location in the lattice without the need for supplementary measurements. Additional structure arises whenever the impurity is surrounded by differing isotopes of the nearest neighbor (nn) host atoms as opposed to the single LVM line that occurs when the nn are composed of a single isotope. For the examples of carbon and silicon in GaAs, the advantages of sensitivity and nondestructive nature are explored as well as the problems in obtaining an accurate calibration to the actual impurity concentration. Various influences on the LVM measurement considered are the effect of sample temperature, instrument resolution, and mathematical manipulations to the data. Finally, other materials are considered in light of the possible potential for application of this new feature of the LVM technique.

An infrared wavelength modulated absorption spectrometer capable of measuring changes in the absorption coefficient of levels of 10-5 cm-1 in the spectral range 0.2-20 microns was employed to study bulk and surface absorption in semiconductors. The results of the study of deep levels in semi-insulating GaAs, surface layers on Si, GaAs, and HgCdTe, oxygen complexes in floating-zone silicon, and determination of strain in ion implanted layers are presented.

Oxygen is present in most silicon used for device fabrication and has important impact on fabrication yields and materials properties. This paper presents two aspects of the use of infrared absorption for the characterization of oxygen in silicon. The first part of the paper presents a summary of the efforts of various researchers to develop quantitative, non-destructive measurement of oxygen levels in silicon by means of the measurement of the 9 μm absorption band's absorption coefficient. The second part of the presentation presents evidence for the existence of two distinct species of oxygen in silicon based on spectroscopic evidence. This evidence suggests the existence of a substitutional species, with an absorption band at 19.5 μm, in addition to the familiar interstitial species with an absorption at 9 μm. Some of the consequences of this observation are discussed.

Deep level studies of undoped semi-insulating CdTe were made using Schottky barrier diodes prepared with aluminum as the barrier metal. Four deep levels located at 208, 246, 455 and 585 meV above the valence band were seen in deep level capacitance transient spectroscopy (DLTS) data. Deep level densities were found to be 6.5x1012, 2.4x10", 6.3x1012 and 1.2x1013cm-8, respectively. DLTS data were supplemented by thermally stimulated capacitance (TSCAP) and admittance spectroscopy. The possibility of a deep level due to interface states is discussed.

The dynamics of the reflection high energy electron diffraction (RHEED) intensities during molecular beam epitaxial (MBE) growth potentially contains significant information regarding the dynamics of growth and the morphology of the growth front. Results of computer simulations based upon an atomistic model of the MBE growth kinetics are presented, along with measurements of the specular beam intensity behaviour during growth of GaAs/AlxGai-xAs(100) system. The measurements are shown to be a practical, real-time monitor for optimizing growth conditions for realization of high quality normal and inverted interfaces in heterojunctions, multiple quantum wells and superlattices. When combined with the computer simulations, they provide an understanding of the role of atomistic and collective surface kinetic processes of critical importance to MBE growth.

The optical modulation technique of photoreflectance (PR) has been applied to the characterization of GaAs/AlGaAs thin films, multiple quantum wells (MQW) and modulation-doped heterojunctions exhibiting a two dimensional electron gas (2DEG). It is shown that PR can yield much' of the same information as electroreflectance but because of its contactless nature PR is easier to implement and thus ideal for the characterization of microstructures.

Knowledge of the dynamical properties of impurities and defects in crystals is indispensable for understanding the properties of semiconductors 1,2. Picosecond and nonlinear spectroscopy, which has been shown to be very sensitive to defect states, has only rarely been used to study these important energy levels. In this communication most of the important picosecond and nonlinear effects in CdSe are proved to be controlled by native defects and a simple Klasens-like model shown sufficient for explaining the dynamics of this material.

The Faraday rotation is a sensitive method for determining the effective mass ot the charge carriers in a two-dimensional (20) electron gas. One of the most important techniques in studying surfaces and interfaces of silicon is the metal-oxide-semiconductor (MOS) technique. The electric field applied between the metal layer and the silicon results in a quantization of the charge distribution. The resonance effective mass, the scattering parameters, and the populations of the subbands may be determined at light frequencies close or equal to the cyclotron frequency. The technique could also be applied to study other semiconductors. In III-V compound semiconductors and narrow-gap semiconductors the effective mass is much smaller than in silicon. Since the tree carrier Faraday rotation is inversely proportional to the effective mass squared, the 21) Faraday rotation should be easily observable in these semiconductors.

We measured picosecond photoinduced absorption in hydrogenated amorphous silicon using independently tunable pump and probe wavelengths. We demonstrated a time modulation technique for obtaining picosecond photoinduced absorption decays that eliminates the bulk thermal background present with amplitude modulation techniques. The same apparatus is used to obtain photoinduced absorption decays over the microsecond time range. The picosecond photoinduced absorption decays are sensitive to changes in the pump and probe wavelengths.

The EELS and XPS measurements are used to analyze the amorphous silicon-carbon-hydrogen alloy films deposited by r.f. reactive sputtering method (RS a-SixCl_x:H). Based on the results of EELS and XPS, considering other optical and electrical measurements, that the structural change occured at 1-x (carbon content)=0.4 in the alloy film was further verified.

We report measurements of the first-order Raman spectra of the longitudinal optic phonon from the <100-> and <111> surface of GaAs and InP which have been polished by various procedures. Non-destructive depth profiling was accomplished by using different lines of an Ar+ laser. The observed lineshape changes have been quantitatively accounted for by a model based on the convolution of the penetration depth of the light and the skin depth of the polish-induced surface strain. For the <100`- surface we find the polish-induced surface strain to be compressive, fairly homogeneous and about 2-3% in both materials, relatively independent of particle size. The inhomogeneity of the surface strain in the polishing plane is less than 0.3%. The strain skin depth is substantially less than the particle size although it does increase with increasing size and polish time. For the <111> surface, although the surface strain is also compressive, the average surface strain is only about 0.6% for GaAs and 1.2% for InP. The inhomogeneous strain is about 1.4% in both materials. Also for this surface the damage skin depth is of order the particle size. For both surfaces we find that disorder is a minor effect for the grit sizes used and the dominant damage is plastic deformation.

We have used various techniques to characterize the structure, electrical and optical properties of amorphous and polycrystalline Si and Ge films. From Raman scattering measurements, the changes in structural order for various types of a-Si systems have been characterized. From the measured Raman linewidth of the transverse optical phonons for annealed Si and Ge films, the mean deviation of the tetrahedral angle has been obtained, which leads to an activation energy for the relaxation in the amorphous phase. A systematic analysis of the structure and physical properties of polycrystalline films prepared by molecular beam deposition(MBD) under ultra-high-vacuum, has been carried out. The crystal-lization temperature, texture, and grain-size were examined as a function of deposition conditions including the effects of residual gas species. A definite correlation has been established between the electrical and optical properties and the measured structural parameters.

Laser Raman scattering by phonons and two-magnons in antiferromagnetic and paramagnetic phases of manganese telluride has been measured and compared to theoretical prediction. Spectra were obtained experimentally on polished single crystals of. MnTe, using an argon ion laser, a spex double-grating spectromemter, and a photon counting detection system. We report the observation of one E2 phonon, predicted by a group theoretical analysis of the D46h crystal space group, at frequency of 178±1 cm -1, and abroad second order peak at frequency of 360±10 cm-1 which is attributed to a two-magnon scattering. A theoretical calcu-lation of the magnetic spin-wave dispersion was performed, starting from a Heisenberg spin Hamiltonian. A closed form solution of energy versus momentum in three-dimensions was obtained containing three unknown superexchange constants J1, J2, and J3. A Monte Carlo com-puter simulation of two-magnon joint density of states in the full Brillouin zone was used to fit experimental data. The best fit to experiment was obtained for superexchange constants: J1 = -1.440 meV, J2 = +0.220 meV, J3 = -0.024 meV. The spin wave dispersion curves in different symmetry directions were plotted using the obtained superexchange values.

We have used Raman scattering as a non-destructive, contactless method for determining the width of the space charge layer as well as the bulk free carrier concentration, N, from 4100). n-GaAs. In the general case, for optical penetration depths larger than the depletion widths, the Raman spectra will show the peak of the coupled plasmon-LO phonon modes from the bulk (14, L_) as well as the uncoupled LO phonon mode from the depletion layer. The intensity of this latter feature is dependent on the relation between the width of the layer, Ls, and the penetration depth of the incident light. We have investigated the room temperature Raman spectra in the backscattering configuration from a number of <100> n-GaAs (Si-doped) samples with 4 x 101/ cm-1(N<1 x 101 cm using as an excitation several different wavelengths of an At laser. From the position of the L.f., L- modes, we have determined the bulk carrier concentration, N. By comparing the intensity at different wavelengths of the uncoupled LO mode originating in the space charge layer with the signal from a piece of undoped4C100), material, it is possible to experimentally evaluate Ls. We find that there is very good agreement between the experimental values and those obtained from a generalized theory for both degenerate and non-degenerate materials. Thus, these experimental results demonstrate that for <100),III-V semiconductors, not only can Raman scattering be used as a contactless method for evaluating N, but also to determine the width of the space charge region for carrier concentrations up to 1 x 10 19 cm -3

Polycrystalline Niobium/Lead junctions using barriers of partially oxidized amorphous silicon (a-Si) were investigated. The method of elastic supercRnducting tunneling spectroscopy is used for this purpose. A thin layer of Ak (10 A) is used to passivate the Nb surface against the formation of conductive Nb sub-oxides. A detailed study of the behavior of oxidized a-Si layers as the tunneling barrier is reported. The insulator is shaped as a double height barrier to account for the partially oxidized nature of the a-Si deposited layer. The average barrier heights are 15 ± 5 meV and 1.2 ± 0.2 eV for the a-Si and SiOx layers respectively. The extremely low value obtained for the effective barrier height of a-Si is associated with the high density of localized states in the mobility gap of the a-Si. The conduction is explained to be electron tunneling between localized states within the "gap". A systematic degradation of the Nb/Pb BCS tunneling characteristics with increasing a-Si thickness has been observed which correlates with deviations from the metal-insulator-metal microscopic tunneling theory. These anomalies are associated with the intrinsic properties of the unoxidized fraction of the a-Si layer.

Electron Paramagnetic Resonance is a valuable tool for the characterization of defects in semiconductors. After a short introduction into the method, various examples are discussed in detail. These include intrinsic and impurity-related point defects in silicon, transition metals in semiconductors, and antisite defects in III-V compounds.