Advantages of SOI materials for CMOS technology arc discussed. The lending SOI materials for CMOS applications appear to be SIMOX and BSOl presently. Progress made in two types of SIMOX, namely, standard and thin BOX. is presented. Recent results from 200mm SIMOX are included. Finally, various defects in annealed SIMOX are discussed. An effort has been made to present data which is typical of commercial SIMOX.

Heteroepitaxial CoxNi1-xSi2 layers with good crystalline quality have been formed by ion beam synthesis. Rutherford Backscattering (RBS) - Channeling, Auger Electron Spectroscopy (AES), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD) have been used to study the buried layers. For a sample with x=0.66, we found that this ternary suicide layer contains 11% type B and 89 % type A orientation. The TEM investigation reveals that the type B component is mainly located at the interfaces with a thickness of a few monolayers. XRD studies show that the strain of the type B component is smaller than that of the type A component, and this is probably the reason for such a unique distribution of the type B component in the epilayer.

A buried epitaxial IrSi3 layer has been produced in (111) oriented Si by high dose Ir+-implantation (1 MeV, 1.7×1017 Ir+/cm2, 550°C) and subsequent annealing (5 h at 1100°C). Transmission electron microscopy and ion channeling show that the hexagonal IrSi3 prefers to form with its (2110) plane oriented parallel to Si(111), while its [0001] direction is parallel to either [112], [121], or [211]. Thus, the IrSi3 film is made up of three differently oriented crystals, each occupying about 1/3 of the suicide volume.

A dose of 3.5×1016 Ir+/cm2 leads to the formation of a band of large, isolated precipitates. They have the same epitaxial relationship to Si, but the Si(111) plane is no longer the only one to which the (2110) of IrSi3 is parallel. Instead precipitates are also observed oriented parallel to (111), (111), and (111) in Si in roughly equal numbers. Consequently, there are now 12 possible orientations of IrSi3 crystals. We assume that strain relief and interface area minimization are the main factors suppressing the additional orientations in the continuous IrSi3 films formed by the coalescence of precipitates at higher doses.

By subsequent implantation of iron and cobalt into silicon buried layers of semiconducting ß-(Fe1-xCo1-x)Si2 are formed. The band gap energy as well as the spreading resistance decrease with increasing cobalt content. The microstructure of the suicide layers is characterized by XTEM images.

Single crystal (100) silicon substrates were implanted at 300 keV with substoichiometric oxygen doses ranging from 1 × 1016 to 1 × 1017 cm-2. Samples were annealed for 2 hours over the temperature range from 1100°C to 1250°C and were subsequently analysed by both cross sectional transmission electron microscopy (XTEM) and scanning electron microscopy (SEM). The nucleation and growth of oxide precipitates within the implanted layer was followed during annealing. The emphasis was placed upon studying the process of Ostwald ripening which is known to play an important role in the formation of the incipient buried layer. Besides, a clear trend of the SiO2 precipitates to arrange in well defined regions was revealed and this was attributed, as distinct from the earlier claims, to an inherent process of self organisation.

A novel methodology for altering the amount and/or nature of post-anneal disorder in SIMOX substrates has been investigated. A pre-anneal, secondary Si-ion implant (with an ion range less than that of the primary O-ion implant) is shown to effectively getter Si interstitials to the near-surface region during annealing. As a consequence, post-anneal disorder at the front. Si/SiO2 interface is significantly reduced. Alternatively, a Si-ion implant with an ion range greater than that of the O-ion implant can alter the post-anneal disorder at the back Si/SiO2 interface.

The maskless ion implantation with the focused ion beam as a new method for ion beam synthesis of cobalt suicide wires is presented. In order to perform the implantation a special achromatic mass separator was implemented into the ion column, liquid alloy ion sources for cobalt ions were developed and a substrate heating was built. Ion implantation was performed with 30 keV Co+ and 60 keV Co++ ions. The dose dependence for room temperature implantation and the influence of the substrate temperature were investigated.

The formation of a Si/IrSi3/Si heterostructure by 1-MeV Ir ion implantation and subsequent annealing has been studied for different doses (0.1-2.25 × 1017 Ir/cm2), substrate temperatures (450°-600°C) and annealing temperatures (1000°-1200°C) using Rutherford backscattering spectrometry, ion channeling and cross-sectional transmission electron microscopy. The heterostructure formation is observed to depend strongly on the processing conditions. The best structure, nearly continuous and precipitate-free, is obtained by implanting 1.8-2.0 × 1017 Ir/cm2 at a substrate temperature of 550°C and annealing at 1100°C for 5 h. A stoichiometric IrSi3 layer can also be produced by furnace annealing at 1150°C for 1 h or by rapid-thermal-annealing at 1200°C for 3 min. Other substrate temperatures generally lead to a structure with a discontinuous IrSi3 layer frequently interrupted by large surface precipitates or islands. The origin of these islands, as well as the dependence of the heterostructure on processing parameters, is discussed.

Defect microstructure and the near-surface strain of high-dose oxygen implanted silicon-on-insulator material (SIMOX) were investigated as a function of dose, implant temperature, and annealing temperature by transmission electron microscopy and high resolution x-ray diffraction. Dislocation half loops (DHLs) begin to form by stress assisted climb at a critical stress level due to implantation-induced damage. DHLs evolve into through-thickness defect (TTD) pairs by expansion during annealing. Both DHL and TTD-pair density increase with higher implant dose and lower implant temperature. Possible methods for defect density reduction are suggested based on the results of this study.

High dose Ge implantation into p-type <100> Si wafers at 150 keV has been performed at doses of 3.6×1016, 6.7×1016 and 9.0×1016 cm-2. The Ge distribution and the crystal quality of the implanted layer before and after annealing at various temperatures have been studied by RBS and channelling experiments. It is found that for the medium and high dose samples before annealing, more than 90% of the Ge atoms are in interstitial sites and after annealing at 1000°C, more than 50% of the Ge atoms have become substitutional. The situation is better for the low dose sample where less than 70% of the Ge atoms are in interstitial sites before annealing and about 80% of them become substitutional after annealing at 1000°C. The ESR spectra of these samples are of lorentzian shape with a g-value of about 2.007 and a spin density of about 6×1016 cm-3. The ESR signals of these samples have been inferred to be mainly due to Si-dangling bonds in the GeSi alloy layer and can be eliminated by annealing at 1000°C for 10 minutes. Electrical characterization of the GeSi layer by spreading resistance profiling technique shows that the implantation damage has been extended deep into the substrate before annealing. After annealing at 1000°C, these defects are removed but the spreading resistance of the surface GeSi layer is found to remain higher than that of the substrate.

We have investigated the synthesis of carbon-silicon-nitride compounds by ion implantation. In these experiments, 100 keV nitrogen ions were implanted into polycrystalline β-SiC (cubic phase) at various substrate temperatures and ion doses. These thin films were characterized in detail by x-ray diffraction with a position-sensitive detector, transmission electron microscopy with chemical analysis, and Rutherford backscattering spectroscopy. The as-implanted samples show a buried amorphous layer at a depth of 170 nm. The peak concentration of nitrogen saturates at approximately 45 at. % with doses above ~9.0×1017 N/cm2 at 860°C. These results suggest formation of a new phase by nitrogen implantation into β-SiC.

Fabrication of Si1-xGex and Si-1-x-yGexCy layers on Si(100) by high-dose ion implantation of 72Ge ions without and with 12C ions and subsequent high-energy and low-energy ion-beam-induced epitaxial crystallization (IBIEC) has been investigated. Structural properties of the surface layers were observed by RBS-channeling technique. Si(100) wafers were implanted with 150keV and 80keV Ge ions at room temperature so as to produce a peak concentration of Ge amounting to approximately 2 and 14 at.%, respectively. C ions were additionally implanted to a fluence of 10% of Ge concentration for the SiGeC samples. IBΓEC experiments performed with 400keV 18Ar ion bombardments have induced crystallization of the amorphous layers of SiGe and SiGeC on Si up to the surface at 400°C for both samples with low Ge concentration (2%) and high Ge concentration (14%). IBIEC using 72Ge ions with energies whose projected ranges are within the amorphous layer was alternatively performed for SiGe layer on Si. Bombardments of 140keV and 40keV Ge ions at 400°C have induced crystallization up to the surface with a slight disorder in the grown layer. Present experimental results suggest a novel ion beam synthesis method of fabrication of SiGe (SiGeC) on Si at low temperatures.

The chemical change in the surface of H13 steel or aluminum is produced by implanting a reactive elements, such as Ti, Mo and W. The X-ray diffraction pattern shows that implanted Ti at 400 C has reacted with carbon(0.35 in wt.%) forming a second phase TiC. Auger analysis shows that the carbon atoms have been condensed in the Ti implanted region. Carbon peak concentration of 30 At.% is greater than Ti atom peak concentration of 12 At.%.

Several second phases are formed during pulsed Mo ion implantation 2 into aluminum with high ion flux of 50˜80µA/cm2 which raises the target temperature from 400°C to 600°C.

More second phases are formed by dual Mo+C implantation with high dose of 3˜5×10 17/cm2 and high flux of 50˜75µA/cm2 . And the target temperature is raised from 400 to 600°C. The FeMo Fe3Mo2, Fe2MoC, Mo2C, MoC, MoCx, phases and iron carbides are identified by X-ray diffraction technique.

Surface modification by ion implantation of 18O ions was investigated as a technique for altering the high-temperature oxidation of aluminide intermetallic compounds and related alloys. Specimens of NbAl3 and TiAl were implanted to a dose of 1×1018 ions/cm2 at 168 keV. Doses and accelerating energies were calculated to obtain near-stoichiometric concentrations of oxygen. Use of 18O allowed the implanted oxygen profiles to be measured using secondary ion mass spectroscopy (SIMS). The near surface oxides formed were studied using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy. Specimens were also examined using x-ray diffraction and SEM. This paper presents results for specimens examined in the as-implanted state. The oxide formed due to implantation is a layer containing a mixture of Nb or Ti and amorphous Al oxides.

ȥ111Ɂ -Si was implanted with 250 keV Co ions at a target temperature of 350°C. The ion dose was varied between 1×1014 cm-2 and 2×1017 cm-2 . The evolution of the defect and impurity profile was investigated by Rutherford Backscattering Spectrometry (RBS), channeling and transmission electron microscopy (TEM).

Up to a dose of 1 × 1015 Co cm-2 no defects can be detected. At higher Co doses, we find correlated defects in the center of the Co distribution and point defects in the region below. Moreover, damage accumulation at the surface is observed. The concentration of defects increases with increasing ion dose and reaches its level of saturation at a dose of 2 × 1016 cm-2.

The Co profiles of samples implanted at 350°C differ considerably from the Gaussian shape. The near surface and the back flank are parts of Gaussian distributions. However, the standard deviation of the near surface flank is always smaller than that of the back flank. Moreover, the distributions show tails into the substrate at depths > 320 nm. This proves that radiation damage acts as an effective center for the nucleation of CoSi2.

During annealing we find a redistribution of Co towards the defective regions for Co doses between 1 × 1016 cm-2 and 5× 1016 cm-2.

Metal Vapour Vacuum Arc (MEWA) Ion Source was employed, for the first time, to synthesize metal suicides. Refractory metal suicides NbSi2, TaSi2, WSi2 and MoSi2 were successfully formed by implanting respective metal ions into Si(111) wafers. It was found that the high current density metal ion implantation not only provided the metal components but also caused a simultaneous annealing for various metal-suicide phases to grow. When the impLantation was conducted at 40 kV, the Nb ion current density was up to 76 µA/cm2 at a dose of 4x1017/cm 2, and the Ta, W and Mo ion current densities were up to 65 µA/cm2 at a dose of 5×1017 ions/cm2 , hexagonal NbSi2, TaSi2, MoSi2 and WSi2 were formed. Post annealing transformed the WSi2 and MoSi2 phases from hexagonal to tetragonal structure, featuring lower resistance than that of the as-implanted ones.

The formation of intermetallic layers between copper wires and lead-tin solders is indicative of the strong metallurgical bond required for a durable solder joint Previous studies have shown that these interracial compounds grow at significant rates (up to 1 µm/day at 100°C), and differences in thermal expansion and hardness between the metals and the intermetallics can lead to the mechanical failure of the solder joint during service. Most previous measurements of the compound formation rate have used elevated temperatures to facilitate the direct observation of the intermetallic thickness by optical microscopy, SEM, or TEM. In this study, Rutherford backscattering spectrometry (RBS) has been used to study the intermetallic growth rate using sputter-deposited thin films of Cu and PbSn. The extraordinary depth sensitivity of RBS (~10 nm) allows these measurements to be made in relatively short times, without the need for heat treatment to accelerate the reaction. Measurements have indicated that at least 23 nm of Cu6Sn5 and 30 nm of Cu3Sn form between Cu and PbSn solder in less than one hour. Faster deposition methods are being investigated to further characterize this rapid reaction. Iron has been proposed as a diffusion barrier material to inhibit intermetallic growth in solder joints. Preliminary measurements of the solder/Fe reaction indicates a much slower rate of growth, with less than 50 nm of total intermetallic forming over 8 hours.

Bombardment of silicon surfaces by low-energy nitrogen ions has been investigated as a possible process for growing films of silicon nitride at relatively low temperature(<500°C). Broad ion beams of energy 300–1200eV have been used to grow ultrathin silicon nitride films. Film thickness and chemical states are analyzed using ellipsometery, X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy(AES). As a result, thicknesses dependence on ion energy, substrate temperature and implantation time have been investigated. The thicknesses of films obtained appear to increase with ion energy in the range from 300 to 1200eV, and with time of bombardment. The thicknesses are also observed to vary slightly with substrate temperature. The growth mechanism has also been investigated and discussed. The average activation energy of nitridation rates is about 3.5meV which indicates nonthermal process kinetics, compared to an activation energy of 0.2–0.6eV for thermal nitridation. AES results show that the atomic ratio [N]/[Si] is about 1.5, larger than that of pure Si3N4. All the analyses show that silicon nitride films of about 60Å thickness have been grown on silicon by low-energy ion beam nitridation.

In this paper, the technique of microscope-spectrophotometry, used to nondestructively characterize the microstructure of ion beam synthesized iron-disilicide layers, is described. The results obtained agree extremely well, in terms of layer thickness and interfacial roughness, with those from Rutherford backscattering. The results also show that it is possible to interpret the measured spectral reflectance data in terms of: 1) defect annealing; 2) iron redistribution; and 3) phase transformations from the β to the α phase.

Results of a computer simulation of Ostwald ripening during ion beam synthesis of a SIMOX layer are presented. Based on investigations of the as-implanted state the simulation starts with equal-sized SiO2 precipitates, homogeneously distributed in a layer. The simulation shows clearly that Ostwald ripening forms structures in such a system by means of self-organisation.

This structure forming process explains in a simple and consistent manner structures of in the concentration profile like ”humps”, ”spikes” and ”banding”, which have been observed experimentally.