ABSTRACT:: High temperature (950°C) annealing is used to stimulate relaxation in UHV/CVD SiGe thin films. It is found that the films are stable to thicknesses which exceed the stability criterion of Matthews and Blakeslee [1] by a small amount. In unstable films, the misfit dislocation density increases with annealing time, reaching a maximum value. For films which exceed the empirical stability criterion by a relatively small amount, the misfit dislocations relax the film to a strain given by the film thickness and the empirical stability criterion. However, large remnant strains are observed when the relaxation process introduces relatively high dislocation densities (≳5 misfits/micron). Associated with large remnant strains are a marked propensity for dislocation banding and looping deep into the substrate with extended annealing. These results are discussed with respect to the magnitude of the misfit dislocation nucleation barrier and the energy associated with interactions among misfit dislocations.

The strain profiles of individual layers of a selected group of stable bcc(110)/fcc(111) metallic superlattices which have been determined by x-ray diffraction methods are compared, and discussed in terms of a number of mechanisms proposed for explaining their anomalous properties. The superlattices in this group are distinguished in terms of a highly anisotropic lattice spacing mismatch of their adjoining bcc and fcc layers (∼20% vs. 3%). The most prominent structural feature of the bcc layers consists of a highly anisotropic in-plane contraction accompanied with a small out-of-plane strain. The fee layers are found to show large out-of-plane expansions which based on their small in-plane expansions cannot be explained within framework of standard elasticity theory.

We describe the results of an investigation into the formation and properties of dislocations in electronic devices. We have made electron transparent specimens from metastable GeSi/Si p-n junction diodes and introduced dislocations into the devices by heating in situ in the electron microscope. A modification made on the specimen holder for our microscope enables us to measure the characteristics of these devices while they remain under observation in the microscope. We can therefore observe the changes in the electrical properties of the devices as dislocations form. We confirm that the introduction of dislocations has a deleterious effect on parameters such as the reverse leakage current through a diode. However the magnitude of the effect we observe can not be explained by a generation-recombination process and instead we suggest a model based on the creation of point defects or the diffusion of metals during the formation of dislocations. We also consider the kinetics of dislocation formation, and in particular how the extent of dislocation formation in a device depends on the subsequent processing steps which it undergoes.

We show that GaInP2 exhibits a directional anisotropy of the electrical conductivity when grown under the appropriate growth conditions. We relate this anisotropy to the characteristic surface microstructure of the material.

The first magneto—transport data taken on thin pseudomorphic FeSi films with the CsCl structure are presented. FeSi appears to be a Kondo system with a Kondo temperature of TK ∼ 15 K. On air-exposed films which have not been protected by a Si-cap an ultrathin magnetic oxide is formed leading to large anomalies in the Hall effect and the magnetoresistance as the film thickness approaches 20 Å.

The growth and properties of thin films of InN on a variety of substrates nucleated by a 400Å layer of AIN have been shown to be dependent on the lattice mismatch (LMM) with the substrate. Examples are drawn from growth of InN thin films by reactive magnetron sputtering on high symmetry faces of a variety of crystalline substrates [(00.1) sapphire, (111) silicon and (111) yttria-stabilized zirconia, and (001) mica] and amorphous fused quartz. Striking is a comparison of the electrical transport properties for nucleated and unnucleated InN films. For example, the ratio of the Hall mobilities for nucleated and unnucleated InN films deposited on (00.1) sapphire (LMM for AIN and InN of 13.0% and 29.0%, respectively) is ∼102, while this ratio for nucleated and unnucleated InN films on (111) zirconia (LMM for AIN and InN of −14.8% and −7.8%, respectively) is ∼10−2. While all the factors underlying these results are not necessarily obvious, it is rather apparent that this trend in Hall mobility stems from a contrasting trend in film resistivity at a more nearly constant value for the carrier concentration.

A comparison between the morphology and magnetic properties has been made with thin films of Fe grown on GaAs(lOO) and of Ni grown on natural mica in the 10Å to 1000Å thickness range, in ultra high vacuum. The films are characterized in-situ by Auger spectroscopy and by an in-situ UHV M/H hysteresis loop tracer. If the films are thermally annealed, above 550°C for less than a few seconds, the film morphology changes. The Fe films form surface assembled clusters which are epitaxial with the GaAs substrate with diameters of order of the original average film thickness, while the Ni films grow large grains. The Auger signals show that the Fe clustering exposes the GaAs substrate while the Ni films are continuous and cover the mica substrate. In-situ adsorption studies of CO on the Ni films were consistent with the continuous nature of the Ni films. Hysteresis M/H curves are taken as a function of thickness and plots of coercivity versus film thickness or average cluster size shows a maximum near 100Å for both the Ni and the Fe films. The maximum is believed to be due to a trade-off between super-paramagnetism and magnetostatic forces, but with the grains in the Ni film playing the role of the clusters in the Fe film.

Two related studies of the effects of elevated temperature annealing on reactive rf magnetron sputtered InN films have been conducted. In the first study, thin films of InN were deposited and annealed in 5 mTorr of nitrogen gas using a conventional high-vacuum (HV) magnetron sputtering system. Films were grown at 100°C and following annealing at an elevated temperature (Ta) for 4 hours were removed from the system for physical characterization. The physical properties of the annealed films improved with thermal treatment and were strikingly coincident with the properties of a second set of films grown at Ta. In the second study, films were deposited at 400°C in 5 mTorr of nitrogen gas using an ultrahigh-vacuum (UHV) sputtering system. Samples were annealed (at 550°C) and electrically characterized under UHV conditions using a custom designed annealing furnace with an integral Van der Pauw probe. Contrary to expectations, the carrier concentration of these films showed a steady decrease with extended annealing and the carrier mobility nearly doubled after 15 hours of treatment.

The experimental conditions which render the exact stoichiometry of PZT(52/48) thin films deposited on Pt thin film on Si(100) by reactive cosputtering have been investigated. As-deposited PZT is amorphous containing α-PbO2 microcrystallites. As annealing temperature increases, the amorphous PZT films crystallize into pyrochlore and perovskite with pseudo-cubic structure in sequence. The perovskite PZT annealed above 750 °C evolves into a phase of morphotropic phase boundary. In the perovskite PZT thin films, the leakage current increases with annealing time. Also, the dielectric constant increases with film thickness and annealing temperature, which is discussed in conjunction with PZT/Pt interfacial morphology.

Transparent, electrically conducting, indium tin oxide films were prepared by r.f. reactive sputtering and electron beam evaporation. The refractive indices, n, and extinction coefficients, k, of the films together with their thicknesses were determined from spectroscopic (250nm–750nm) ellipsometry measurements. Elucidation of these parameters allowed an evaluation of the influence of the deposition conditions on the morphology, stoichionietry and microstructure of the films.

Using effective medium theory the effect of the oxygen concentration on the void content of the sputtered films could be modelled. At concentrations greater than 15–20%, a saturation in the optical properties was observed as the films approached ideal stoichionietry. The refractive indices of both annealed and untreated evaporated films exhibited a decrease with increasing substrate temperature (up to 300°C) which is consistent with an increase in the microcrystallite size. Measurements on the annealed samples revealed a blue-shift in both n and k spectra as the oxygen pressure during evaporation was reduced to the background value of about 106 mbar. This, we attribute to the Burstein-Moss shift associated with the increased number of oxygen vacancies.

Supplementary investigations using profilometry, atomic force microscopy and optical transmission spectroscopy confirm the reliability of the results obtained by this technique.

We investigated the electrical and optical properties, the chemical composition, the surface morphology and the crystallinity of sputtered Sn-doped In2O3 films deposited on different substrate positions. Both the electric conductivity and the optical transparency are related to the free carrier density and moreover the preferred crystal orientation. The former relation is attributed to the Burstein-Moss effect and the latter suggests the Sn doping mechanism.

The internal stresses and anelastic properties of an electrodeposited Ni/Cu multilayered membrane as measured dynamically using a vibrating membrane method are reported. Our results indicate that the as-deposited membrane has a high internal stress approaching the yield strength. Due to the accuracy of the experimental method, the damping of the multilayered membrane can be measured in the presence of the high internal stresses. It is shown that the relatively large damping capacity exhibited by the multilayered film is different from classical damping associated with the modulus defect, and may be related to an interfacial relaxation effect such as sliding.

Cobalt silicide formed by diffusion of Co through a Ti compound has been reported for both bilayer and multilayer Co/Ti-Si structurest[2-4]. To compare the bilayer and multilayer systems in terms of the Co silicide interfacial morphology, both bilayers and six layers of 20nm Co and lOnm Ti were sputter deposited on (100)Si in a system where background. oxygen and carbon were gettered by each Ti layer. The samples were annealed from 550°C to 800°C for 60 sec by lamp RTA in N2 ambient. XTEM micrographs revealed that significant differences in interfacial morphology existed between bilayer and multilayer samples. The interfacial amorphous Ti(O.C) diffusion barrier layer was found to be more effective in the multilayer system producing uniform CoSix layers as thin as ∼5nm after 550°C RTA, whereas the silicide formed in the bilaver samples under the same condition was rough. RBS analysis showed that the transformation temperature from CoSi to CoSi2 was 800°C in bilayers and even higher for multilayers. The higher transformation temperature is attributed to the additional Co available in the multilayer system and its effect on Co monosilicide phase stability as previously reported[10].

Silicon oxidation kinetics in the thin regime are studied by a unique method in which thermally grown as well as densified CVD-deposited oxides are incrementally reoxidized and measured. Strikingly higher oxidation rates are obtained through deposited oxides, as compared to thermal oxides, suggesting that oxidations are suppressed after an initial layer is grown rather than enhanced during initial layer formation. We show that these findings tend to support initial oxidation models based on stress.

Si containing stainless steels form complex oxide scales during high temperature oxidation at 900°C. These scales consist of an outer iron chromium manganese spinel layer, an intermediate Cr2O3 (chromia) layer and an inner SiO2 (silica) layer. During isothermal oxidation, alloys exhibit minimum weight gain when the inner silica layer is continuous, due to its effectiveness as a diffusion barrier. This continuous silica scale can be formed in a short time only by a combination of fine alloy grain size and high silicon content. However, formation of a continuous silica layer may lead to scale spallation on cooling, thus having a deleterious effect on the oxidation resistance of the alloy.

SiGe alloys have recently been of interest for fabrication of heterojunction bipolar transistors using pre-existing or modified silicon-processing technology. These devices are faster than devices using pure silicon. Because of the interest in developing SiGe device structures, various elements of processing relevant to fabrication of the devices are being investigated. One such element has been the use of thermal oxidation for isolation of SiGe devices. Utilization of the technique requires an understanding of oxidation behavior of SiGe layers under a variety of oxidation conditions. Past studies in the literature have investigated the oxidation of SiGe at atmospheric pressure or at very high pressures (∼650–1300 atmospheres). The present study investigates the wet-oxidation of SiGe structures at intermediate pressures (∼25 atmospheres) and temperatures (∼750°C). Unlike atmospheric oxidation, most of the Ge (from SiGe) remains in the oxidized silicon (SiO2) in the form of GeO2. Occasional segregation of Ge to the oxidizing interface is noted. The microstructural behavior of partially and entirely oxidized structures is presented.

High-pressure oxidation of silicon (HIPOX) is one of various techniques used for electrical-isolation of semiconductor-devices on silicon substrates. The effect of HIPOX-related stresses on isolation structures is of interest because structural-defects, if formed, could electrically degrade devices. The present investigation was performed to study the origin and behavior of defects in recessed HIPOX structures. The structures were exposed to a boron implant. The experimental observations indicate that glide dislocations arise when the following features are present: (i) HIPOX, (ii) recessed edge, (iii) boron implant. The origin and behavior of the defects are modelled and explained in terms of implant-induced dislocation-sources creating glide-dislocations in the structures. The microstructure of the structures described above, and defect-modelling is presented.

In the oxidation of iron-rich olivine (Mg,Fe)2SiO4 at elevated temperatures interfaces between olivine and the magnetite spinel (Fe3O4) are formed. The orientation relation between these structures is such that the planar spacing for the principal low index planes are very closely matched in the two materials. Regions of different contrast are observed in the olivine up to 5–10 nm from the interface. It is proposed that this contrast is due to enhanced iron concentration in this region caused by the strain field around the magnetite precipitates.

A highly brilliant x-ray beam from a synchrotron radiation source is a powerful tool to perform non-destructive x-ray diffraction analysis of an under-film corroded region of zinc-coated steel sheets. Investigations to identify corrosion products under the outdoor salt-spray test condition and to reveal their one-dimensional distribution were carried out Simonkolleite (ZnCl2•4Zn(OH)2 ) was identified for the first time at the tip of the under-film corroded region. By the one-dimensional analysis, it was shown that the x-ray diffraction intensity of simonkolleite increased, where that of metal zinc decreased. It was suggested that simonkolleite was formed as the first corrosion product under the outdoor salt-spray test condition.

The distribution, number density, and nature of extended defects in crystalline silicon which is exposed to plasma-generated atomic hydrogen at a temperature of 250°C are characterized by transmission electron microscopy. Cross-sectional and plan-view modes are used for these characterizations. Extended defects are typically detected in the near surface region of a < 001 > crystal and their number density may exceed 109 defects-cm2, depending on die plasma exposure time, wafer temperature, gas pressure, and power. These defects exhibit contrast features which are characteristic of small dislocation loops (> 50nm in dia) and the nature of their associated strain field is assessed by diffraction-contrast techniques. The relationship between loop-like contrast features and die so-called hydrogen-induced platelet is established by both diffraction-contrast and phase-contrast imaging techniques. The results show that loop-like and platelet-like images exhibit contrast features which are consistent with a compressive strain field and therefore it is concluded that the extended defects in this study are interstitial in nature.