The kinetics of intrinsic and dopant-enhanced solid phase epitaxy (SPE) have been measured in buried amorphous Si (a-Si) layers produced by ion implantation. Buried a-Si layers formed by self-ion implantation provide a suitable environment for studies of the intrinsic growth kinetics of amorphous Si, free from the rate-retarding effects of H. For the first time, dopant-enhanced SPE rates have been measured under these H-free conditions. Buried a-Si layers containing uniform As concentration profiles ranging from 1–16.1 × 1019 As.cm−3 were produced by multiple-energy ion implantation and time resolved reflectivity was used to measure SPE rates over the temperature range 480–660°C. In contrast to earlier studies, the dopant-enhanced SPE rate is found to depend linearly on the As concentration over the entire concentration range measured. The SPE rate can be expressed in the form, v/vi(T) = 1 + N/[No exp(-ΔE/kT)], where vi(T) is the intrinsic SPE rate, N is the dopant concentration and No = 1.2 × 1021 cm−3, ΔE = 0.21 eV.

The annealing properties of defects in BF2+ implanted silicon were investigated using positron annihilation, TEM and SIMS techniques. For the as-implanted specimens, the major species of defects was identified to be divacancies. After thermal annealing, vacancy-fluorine complexes were formed. The size of open volume in the vacancy-fluorine complexes became larger with increasing annealing temperature. Even after 1100 °C, the vacancy-fluorine complexes were still stable with the size of open volume close to V5. The depth profile of vacancy-fluorine complexes was not largely changed after re-crystallization. In this way, the fluorine atoms played an important role in forming the defects with a large size of open volume. After 1100°C annealing, the fluorine atoms piled up at two regions; the projected range of fluorine and the original amorphous/crystalline interface, where bubbles were observed by TEM. The vacancy-fluorine complexes detected by positron annihilation might be precursors of the bubbles observed by TEM.

The gettering behavior of Cu and Fe was investigated in CZ silicon containing both internal-gettering sites in the bulk due to SiO2 precipitation and a device-side layer of cavities formed by He ion implantation and annealing. The objective was to quantify the effectiveness of impurity gettering at cavities relative to the widely used internal-gettering process. Both rapid thermal anneals and furnace anneals were used during the gettering sequences to reveal transient effects as well as the final, thermodynamically-equilibrated condition. For temperatures of 700, 800 and 850°C, the cavity gettering was observed to dominate the internal gettering as indicated both by the number of gettered atoms in the cavities and the residual solution concentration in the device region. The results are interpreted in detail by numerically solving the diffusion equation with sink-related source terms based on earlier, fundamental studies of the underlying mechanisms of internal and cavity gettering.

Secondary defect and impurity distributions in MeV self-implanted Czochralski (Cz) and float-zone (FZ) silicon have been investigated by transmission electron microscopy, optical microscopy with preferential chemical etching, and secondary ion mass spectroscopy. We found that the ion fluence and the oxygen content of the implanted wafers affect the number and depth distribution of extended defects remaining after annealing. Intrinsic oxygen also redistributes during annealing of Cz wafers, producing two regions of relatively high oxygen concentration: one at extended defects near the ion projected range, and another, shallower region, which correlates with the distribution of vacancy-type defects. Both of these regions are also able to getter metallic impurities, depending on the implantation and annealing conditions. These defect issues may adversely affect the quality of the near surface device region, and must be controlled for successful gettering by ion implantation.

New implementations in MBE growth techniques allow high accuracy in δ-doping profiles in Silicon crystals. In this work we present a self-consistent numerical calculations of the electronic structure of δ-FETs, field effect transistors where electric transport channel is a quasi-two-dimensional plan of Antimonide doping in a Silicon crystal. We made the calculations to the heavy and light electrons at 77 and 300K varying the gate voltage in devices with one to three coupled deltas. We obtain the effective potential, the sub-bands and respective electronic densities, basic calculations to point at optimization of the device. We made considerations on theirs DC - capacitances and free electron density spreadings to achieve the gate-voltage best performance.

Ion beam synthesis of SiC/Si heterostructures was performed by MIEVVA (metal vapor vacuum arc) implantation under various implantation and annealing conditions. The implanted SiC/Si heterostructures were characterized by various techniques. Carbon redistribution in overstoichiometrically implanted samples during annealing to form a stoichiometric SiC layer has been observed for the first time. The FTIR spectra were found to be composed of two components, one attributed to amorphous SiC and the other to ß-SiC. It was also found that there are critical dose and critical energy at which the crystalline fraction increases abruptly. Other results on electrical and optical characterization are also presented and discussed.

The formation of SiC precipitates during the high-dose implantation of carbon ions into Si(100) is studied by means of TEM for implantation conditions, which are suitable for the ion beam synthesis of buried SiC layers in silicon. It is observed that in crystalline silicon nm-sized epitaxially oriented 3C-SiC precipitates are formed which are almost identical in size, nearly independent of the depth and dose (4 – 9 ×1017 C+/cm2). With increasing dose, it is mainly the density of precipitates which increases. Amorphization of the silicon host lattice leads to depth intervals with a strongly decreased density of oriented crystalline SiC precipitates. The irradiation induced formation of larger randomly oriented SiC crystallites is observed to occur in amorphized regions after prolonged implantation. Both the irradiation induced destruction and formation of SiC precipitates contribute to the generation of a nearly box-shaped precipitate density distribution at doses near the stoichiometry dose.

We studied high dose implantation of tungsten into 6H-silicon carbide in order to synthesize an electrically conductive layer. Implantation was performed at 200 keV with a dose of 1.2×1017 W+cm−2 at temperatures between 200°C and 400°C. The influence of implantation temperature on the distribution of W in SiC was investigated and compared to results obtained earlier from room temperature (RT) and 500°C implants. Rutherford backscattering spectrometry (RBS) was employed to study the structure and composition of the implanted layers. Implantation at temperatures between RT and 300°C did not influence the depth distribution of C, Si and W. The W depth profile shows a conventional Gaussian shape. Implanting at higher temperatures led to a more confined W rich layer in the SiC. This confinement is explained by Ostwald ripening which is enabled during implantation at temperatures above 300°C. The depth of the implantation induced damage decreases slightly with increasing implantation temperature, except for 400°C implantation. The amount of damage, however, is significantly reduced only for implantation at 500°C.

In this contribution, we present a study aimed at investigating the basic properties of radiation induced defects in ZnS and ZnO and the influence of the atmosphere on the annealing characteristics of the defects. Positron annihilation experiments (both lifetime and Dopplerbroadening measurements) were performed on both single- and polycrystalline samples, irradiated with 3 MeV protons or 1 MeV electrons. For ZnS it was found that both electron and proton irradiation caused significant changes in the positron annihilation characteristics. The annealing of proton irradiated ZnS in air leads to significant oxidation and eventual transformation into ZnO.

The formation of amnorphous layers in GaAs during ion bombardment at elevated temperatures, where dynamic annealing of radiation-induced defects is substantial, is shown to be extremely sensitive to the ion flux. fluence. and implantation temperature. For example. with increasing fluence. damage can first build up extremely slowly. then suddenly collapse to the amorphous phase. Alternatively. for a constant ion fluence, a change in flux by one order of magnitude can change the critical temperature for amorphisation by 27°C. and at constant flux and fluence. a change of only 6°C can alter the residual damage from small clusters barely visible by conventional transmission electron microscopy and Rutherlord backscattering to a thick amorphous layer. The temperature at which this occurs is strongly dependent upon the ion flux and fluence.

Bulk ion implantations of AlxGa1-xAs (x = 0.6 or 0.85) were performed at 77 K with 1.5 MeV Kr+, 1 MeV Ar+ or 1.5 MeV++ ions, and the resulting damage state examined by using Rutherford backscattering spectrometry-channeling at 77 K and 293 K and transmission electron microscopy at 300 K. Amorphization of a portion of the AlxGa1-x As layer occurred at 77 K only for the 1.5 MeV Kr+ implantation, although the dose required to cause amorphization was higher for the higher Al content alloy. TRIM calculations[10–11 ] show that with this implantation the density of high energy density cascades varies as a function of depth through the layer and that these are superimposed on a high, uniform density of defects. Comparison of the ion channeling spectra at 77 K and 293 K shows that recovery occurs over a portion of the layer in the Al0.6Ga0.4As but is not detected in the Al0.85Ga0.15As layer. In both alloys, the room temperature microstructure consists of an amorphous and a crystalline region. The amorphous region extends from the deeper AlxGa1-xAs/GaAs interface into the layer, and is separated from the crystalline material by a crystalline region containing planar defects. The difference between the alloys is in the extent of this latter region, which decreases in width with increasing Al content. These results will be used to examine current models for amorphization in the AlxGa1-xAs system.

Highly carbon doped GaAs layers grown by metal organic vapor phase epitaxy (MOVPE) Has been investigated by transmission electron microscopy (TEM). Electron irradiation has been applied to generate point defects interacting with native defects, e.g., substitutional carbon. This irradiation induces periodically arranged striations perpendicular to the growth direction, which were observed in situ by TEM. Furthermore, precipitates (Ø= 10–15nm) were formed containing non-crystalline material, which most likely is gallium. To explain these phenomena a precipitation mechanism is proposed. It involvs small fluctuations of the incorporated C as well as the interaction of irradiation induced point defects, mainly As and C interstitials and As vacancies.

Transmission electron microscopy of He-implanted Si-Ge and InGaAs shows an attractive interaction between cavities and dislocations. Calculation indicates that cavities are attracted to dislocations through surrounding strain fields, and strong binding (100s of eV) occurs when a cavity intersects the core. In a strained SiGe/Si heterostructure, He implantation enhances relaxation rates, and cavities bound to misfit dislocations show evidence of increasing relaxation at equilibrium by lowering dislocation energies. The interaction is expected for all crystalline solids, and gives insight into voids in GaN/sapphire and bubbles in He-implanted metals.

A unique germanium redistribution phenomenon occurs in the synthesis of SiGe by 74Ge+, ion implantation. A number of silicon samples were implanted with 74Ge+ ion using a range of substrate temperatures (R.T. to 600°C) with different germanium fluences (1.5 × 1016 cm-2 to 4 × 1016 cm-2) and implantation energies (100keV - 180KeV). Samples were germanium profiled using Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS).The experimental results show that the peak range of the germanium implant increases progressively above 150°C and a shift of 40nm in the peak germanium range was measured for a sample implanted at 600°C. The ‘hot’ implants have an extended tail profile contrary to the Debye model for root-mean-square deviations of the lattice atoms from their equilibrium sites which should ideally contribute to dechanneling. The data suggest strongly that dynamic annealing related diffusion (DARD) processes exist, whereby mobile non-equilibrium point defects influence diffusion to take place at the elevated implantation temperature. The SIMS spectra of samples implanted with high Ge fluences at elevated temperature show “uphill” diffusion.

Clusters of independently tailored areal density and size distribution were grown on semiconductor surfaces in ultra-high vacuum and used as masks for selective ion beam modification. First studies were undertaken to characterize the vertical interface between areas exposed to low energy ion beams and areas covered by clusters (crystalline silicon). Selective etching was employed to create a patterned surface as a substrate for heteroepitaxial growth of thick Ge layers to test defect density reduction due to finite size growth areas. The quality of the overlayers is discussed.

Focused ion beam (FIB) irradiation of a thin Ni2Si layer deposited on a Si substrate was carried out and studied using an in-situ transmission electron microscope (in-situ TEM). Square areas on sides of 4 by 4 and 9 by 9 μm were patterned at room temperature with a 25keV Ga+-FIB attached to the TEM. The structural changes of the films indicate a uniform milling; sputtering of the Ni2Si layer and the damage introducing to the Si substrate. Annealing at 673 K results in the change of the Ni2Si layer into an epitaxial NiSi2 layer outside the FIB irradiated area, but several precipitates appear around the treated area. Precipitates was analyzed by energy dispersive X-ray spectroscopy (EDS). Larger amount of Ni than the surrounding matrix was found in precipitates. Selected area diffraction (SAD) patterns of the precipitates and the corresponding dark field images imply the formation of a Ni rich silicide. The relation between the FIB tail and the precipitation is indicated.

A combined ion beam and molecular beam epitaxy (CIBMBE) method was applied for the deposition of a Ge1−x, Cx, alloy on Si(100) using a low-energy ( 50 – 100 eV ) C+ ion beam and a Ge molecular beam. Metastable Ge1−xCx solid solutions were formed up to x= 0.047, and the CIBMBE method was shown to have a very high potential to grow metastable Ge1−xCx alloys. It was also revealed that the sticking coefficient of C+ ions into Ge was ˜28% for Ei = 100 eV and ˜18% for Ei. = 50 eV. Structural characterization suggests that the deposited films are single crystals grown epitaxially on the substrate with twins on {111} planes. Characterization of lattice dynamics using Raman spectroscopy suggested that the deposited layers have a small amount of ion irradiation damage.

Ion beam synthesis of CoSi2 layers in Si by NIEVVA (Metal Vapor Vacuum Arc) implantation has been performed under various conditions. The formation and characteristics of these CoSi2 layers have been studied by XTEM, RBS, AFM, X-ray diffraction, ellipsometry, electrical and Hall effect measurements. It was found that a higher substrate temperature during implantation results in an as-implanted Co distribution closer to the surface and hence the formation of a shallower CoSi2 layer after annealing. Buried CoSi2 layers of good crystal quality and low resistivity CoSi2 can be formed by MEVVA implantation and annealing under appropriate conditions. A strong temperature dependence of the Hall coefficient showing a large peak at around 100K was observed for the CoSi2 layers formed in p-type Si substrates but not in n-type substrates. The properties and their dependence on the processing conditions, in particular, the substrate temperature during implantation, are presented and discussed.

Copper films on Si(100) were prepared by partially ionized beam at 0 kV and 3 kV acceleration voltages in order to investigate effects of ion energy on electrical property with thickness. X-ray diffraction(XRD) pattern analysis was used to investigate crystallinity of the copper films, microstructure by Scanning electron microscope(SEM) and surface roughness by atomic force microscopy(AFM). The crystallinity of the copper films grown at the 3 kV was more (111) textured than that at the 0 kV. The copper films grown at the both conditions had nearly same grain size below a thickness of 1000 Å. The 1800 Å Cu film grown at the 3 kV was 3 times rough than that at the 0 kV. The resistivity of copper films increased due to surface and grain boundary scattering, and the change of resistivity was discussed in terms of surface roughness, grain size and film density assisted by average depositing energy.

The interaction of nitrogen trifluoride (NF3) with silicon (Si) surfaces has been investigated by x-ray photoelectron spectroscopy (XPS). Si (100) surfaces were subjected to NF3 ion bombardment as a means of approximating plasma processing under controlled conditions. Samples were also exposed to actual NF3 DC plasmas and the results compared to ion beam and plasma processing using nitrogen (N2). The results indicate that nitridation of silicon is possible using NF3 although it seems to be limited by simultaneous etching. Additionally, results suggest bonding between both Si-F and Si-N species and perhaps F-N-Si moieties. NF3 plasma processing has lead to curious results for F 1s spectra which are not fully understood at present.