Microwave remote plasma oxidation were used to study the oxidation of Si and SiGe samples at a lower temperature. C–V measurements were performed to investigate the trap density, and the corresponding bonding structures of thin oxide were revealed by FTIR analysis. SIMS depth profiles were used to reveal the extent of the Ge segregation in SiGe samples. The system can grow ultra thin SiO2 with lower effective trap density. And Ge segregation can be largely suppressed by atomic oxygen oxidation at a lower temperature.

Ni films 250 to 1500 Å thick are prepared on polished amorphous quartz substrates in ultrahigh vacuum by ion beam sputter deposition. The growing film is bombarded simultaneously with Xe+ ions at an oblique angle of incidence. The structural and magnetic modifications are studied for different film thicknesses as a function of Xe+ ion energies (50–200 eV) and relative flux of arriving Ni atoms/Xe ions at the substrate. Lattice spacings and degree of texturing are determined by x-ray diffraction. Magnetic in-plane anisotropy is determined by longitudinal magneto-optic Kerr effect measurements. Our results show that an uniaxial in-plane magnetic anisotropy is induced with the hard magnetization direction parallel to the plane of incidence of the secondary Xe+ ions, and a (111) texture with an increased plane spacing of 0.5% is measured. The microstructure of the film and the magnitude of the anisotropy is sensitive to film thickness and flux ratio. For films prepared without secondary ion bombardment, the plane spacings correspond to those for bulk Ni, and isotropic magnetic behavior is observed.

Thin films of approximately equiatomic NiTi have been produced by ion beam sputtering, and by ion beam assisted deposition (IBAD), using 0.1 and 0.5 keV argon ions at fluences giving ion/atom arrival ratios (R-ratios) ranging between 0.26 and 2.21. Ion beam sputtering produced amorphous films which showed several percent titanium loss relative to the alloy target composition. Concurrent irradiation of the growing films with argon ions accentuated the titanium depletion, and R-ratios greater than approximately 1.4 at an assist-beam energy of 0.5keV produced resputtering rates that exceeded the deposition rate. Analysis of experiments with assist-beam energies of 0.5 keV produced a value of 1.75 for εTi/εNi, the ratio of sputteryields for titanium and nickel, in an amorphous alloy film at approximately 325K. Though data for 0.1 keV assist-beam irradiation could be interpreted to yield a similar value for εTi/εNi, resputtering at these energies displayed unexpected dependencies on R-ratio, and is apparently sensitive to the assist-beam incidence angle as well as the R-ratio. No evidence of crystallization of the films was found for the R-ratios examined. However, concurrent ion irradiation produced phenomenological evidence of short range ordering. Nanophase precipitates observed in TEM foils from films produced by ion beam assisted deposition, discovered in previous work and there identified as Ni3Ti, have been found in fact to be titanium nitride.

Thin Ti films have been bombarded at room temperature with 350–500 eV deuterium ions at current densities up to 0.5 mA/cm2. Analysis using scanning electron microscopy, x-ray diffraction, transmission electron microscopy, and secondary ion mass spectroscopy were carried out before and after bombardment. It was determined that deuterium diffuses rapidly throughout the Ti film, that the films were in a state of high compressive stress, and that the TiD2 phase was formed. No evidence of deuterium gas bubbles was found.

WN films were deposited on clean Si substrates by Reactive Ion Beam Sputtering in a UHV system. The growth mode of the films as a function of the nitrogen ion energy was investigated by in situ Auger Electron Spectrometry. The energy of the incident ions was varied from 250 eV to 3 keV. We observed a significant nitridation of the silicon at the very beginning of the deposition. This nitridation is more pronounced for the lower energy and is more reduced for 2 keV-ions. It seems to follow the trend of the film composition: 250 eV-ions and 2 keV-ions result in N-rich films (N/W≈1) and W-rich films (N/W≈0.5), respectively. All these results are discussed in terms of sputtering yield, backscattering and sticking coefficient and are explained by taking into account: first, the interaction between the incident ions and the target, and second, the interaction between the species emitted by the target and the growing film.

In IBAD BN and RIBSD Si3N4 layers deposited at room temperature, the internal stress can always be reduced below -1 GPa by a post-deposition annealing. When the deposition temperature is increased up to 600°C, the stress in Si3N4 layers is not significantly reduced and, in IBAD BN films, it is even greater than expected from the development of the thermal stress, which indicates that no relaxation of the stress occurs during deposition. This implies that the spatial extent of the ion peening effect may largely exceed the penetration depth of ions and of recoil atoms in the solid. In order to confirm this hypothesis, sequences of deposition/in situ annealing/deposition have been performed. In RIBSD films, the relaxation of the annealed sublayer can be observed. In IBAD films, the deposition of the upper layer results in an increase of the stress in the superficial zone of the annealed sublayer.

Titanium nitride films were prepared by reactive ion beam assisted deposition (RIBAD) with Ar+/Ti ratios ranging from 1.0 to 2.3. The compositions, phases and textures of these films were studied by AES and XRD as a function of Ar+/Ti ratio and nitrogen partial pressure. The results indicate that the IBAD titanium nitride films deposited at high Ar+/Ti ratio and low nitrogen partial pressure may have reduced nitrogen concentration, (200) preferred orientation, and possibly contain the Ti2N phase.

Electron holography, and high spatial resolution (17Å) computer controlled Parallel Electron Energy Loss Spectrometry (PEELS) were used to probe the structure of and chemical profile across a thin silicon Oxide-Nitride-Oxide (ONO) layered structure of nominal width 10Å-50Å-10Å. We found that the layer widths are on the average 13Å-28Å-18Å, the first oxide layer was discontinuous, and the second oxide layer contained nitrogen. The nitride layer had a silicon to nitrogen concentration ratio of 1.0 ± 0.1. These results show, for the first time, the power of holography in characterizing thin, light element, amorphous layers and the importance of computer controlled parallel energy loss line scans for obtaining analytical information at the highest spatial resolution with minimum dose.

Films of Al and Al2O3 were formed by physical vapor deposition (PVD) and ion beam assisted deposition (IBAD) onto (100) Si, glass and graphite substrates. Ion to atom arrival rate (R) ratios for IBAD varied from 0.004 to 0.1 and film thicknesses varied from 150 to 1000 nm. The O/Al ratio of oxide films and the oxygen content of Al films decreased with increasing R ratio. Al incorporation into both types of films increased with R ratio up to a value of ∼4 at% at R=0.1. Al films were crystalline with a strong (111) fiber texture becoming more pronounced with increasing R ratio. Film morphology is characterized by large columnar grains at R=0, with a breakup of the columnar structure by R=0.04. Al2O3 films are amorphous under all deposition conditions. Average film stress for PVD Al2O3 films is tensile with a value of 0.68 GPa, becoming compressive at ∼1.3 eV/atom and saturating at a value of ∼-0.65 GPa at R=0.04. Indentation experiments of Al2O3/(100)Si with a 300 g Vickers indenter showed that the changes in crack length are consistent with a model in which the residual film stress is controlling.

Molecular dynamics simulations were used to follow low-energy ion/surface interactions in Si MBE including kinetic energy redistribution in the lattice as a function of time, projectile and lattice atom trajectories, and the nature, number, and depth of residual defects. The simulations were carried out using the Tersoff many-body potential for Si. Irradiation events were initiated with 10 and 50 eV Si atoms incident normal to the Si(001)2xl surface at an array of points in the primitive surface unit cell. Epitaxy, exchange reactions, and defect (vacancy and interstitial) formations were observed. Quasidynamic simulations suggested that the interstitials preferentially diffuse toward the surface and are annealed out over times corresponding to monolayer deposition at typical Si MBE growth temperatures.

Low temperature Si and Si1−xGex epitaxy is one of the major thrusts in the trend towards low temperature Si processing for future generation ULSI circuits and novel Si-based devices. A remote plasma-enhanced chemical vapor deposition (RPCVD) technique has been developed to achieve Si homoepitaxy and Si1−xGex heteroepitaxy at low temperatures (≤450'C). P-type films have been grown by introducing 90 ppm or 5000 ppm B2H6/He into the system during the growth process to achieve in situ electrically active boron doping. A mesa diode structure with minimal thermal budget in the fabrication process has been employed to evaluate the properties of the boron-doped Si and Si1−xGex films grown at 450°C by RPCVD. Leakage current densities are reduced for diodes grown at 14–18 W (40–50 Å/min. growth rates) compared to similar devices grown at 6.6 W (5 Å/min.). N-type films have been grown by the introduction of 50 ppm PH3/He. Secondary ion mass spectroscopy (SIMS) has been employed to analyze the boron and phosphorus incorporation efficiencies and doping profiles under different conditions. Boron and phosphorus doping profile transitions as sharp as 50–100 Å/decade have been achieved. Transmission electron microscopy (TEM) has been used to investigate the microstructure of the B-doped films.

We report the successful growth of ZnTe and ZnSe epitaxial layers on GaAs by pulsed laser deposition. A frequency doubled Nd:YAG laser was used to ablate/evaporate II-VI bulk targets and pressed powder targets in an ultra high vacuum enclosure. For typical growth temperatures in the range 200°-400°C x-ray analysis of the layers revealed sharp <100> peaks with no evidence of growth in other orientations. Polarization dependent Raman spectroscopy was also used to further characterize the epitaxial layers, by verifying the selection rules for backscattering from <100> oriented films. The low temperature photoluminescence spectra show distinct near-band-edge features indicating high crystalline quality. The photoluminescence of the films grown from bulk targets was superior to that of films grown from pressed powder targets, indicating that the use of high purity bulk targets is critical. Our results indicate that pulsed laser deposition is a promising new growth technique for the fabrication of II-VI epitaxial layers with unique advantages.

The successful methods for laser ablation and deposition of epitaxial thin films of metal oxides, especially the high-temperature superconductors (HTSC), have been adapted to pulsed laser deposition (PLD) of the narrow-band compound semiconductor HgCdTe, and the wide-band semiconductor β-SiC. Useful film quality is readily obtained in both cases: the HgCdTe films on CdTe wafers function in IR photodetection and the 3-SiC is epitaxial on both Si (100) and (111) wafers.

CaF2 films have been deposited by evaporation onto H-passivated (111) Si in the presence of an rf discharge. The discharge is seen to promote epitaxy. Emission spectroscopy reveals strong CaF2 bands and a weak Ca line, indicating that deposition is largely molecular but that some breakup of the CaF2 molecules occurs in the discharge. Electrical and optical properties of these films were substantially better than those of sputter-deposited films.

We report the epitaxial growth of CuO thin films prepared by lowenergy and high-density O+ ion beams mass-separated from an oxygen plasma. We have successfully produced O+ beams of 50 μA/cm2 while maintaining an ambient pressure of 3×10−9 Torr during the growth. CuO grows on MgO(100) with epitaxial relationship of (111)CuO // (100)MgO and [110]CuO // [110]MgO at room temperature and even under conditions where the flux density of O+ beams is at least one order of magnitude lower than the minimum flux density of O2 required to form CuO.

MgO thin films were deposited on silicon and sapphire substrates using ion-beam reactive sputtering. Films have been analyzed using x-ray diffraction, transmission electron microscopy, and atomic force microscopy. Highly oriented (100) MgO films have been obtained on Si (100) substrates. The in-plane orientation is predominantly [100]MgO//[100]Si, although a twist of up to ±10° between grains is observed. Epitaxial films of MgO were deposited on four different orientations of sapphire. The MgO film orientation was (111) on c-cut (0001) Al2O3 and exhibited double positioning boundaries in TEM analysis. On r-cut (1102) Al2O3, the MgO appeared to be oriented (730) with tilt and twist of ±2° between the grains. Epitaxial MgO films oriented (110) and (111) were obtained on m-cut (1010) and a-cut (1120) sapphire orientations, respectively. In-plane directions were extracted from TEM analysis on all the samples. Atomic force microscopy revealed fairly smooth MgO films on sapphire, varying from 0.35 nm average roughness for the MgO film on the m-cut substrate to 0.80 nm on the r-cut substrate.

R&D projects of ion beam systems and ion beam process technology have been conducted under the National Research and Development Program known as the “Large-Scale project”. The project includes development of five large-scale ion beam systems and their application for surface modifications. Under another program called the National Research Facility Development Project, the Ion Engineering Center Corporation has been established in order to promote industrial applications of ion beam processes. This paper reviews those projects and recent progress on development of large-scale ion beam systems and related materials processing technology. Major research projects which have been funded by the Ministry of Education for ion beam related researches are also reviewed.

Using MeV ions for the modification of electronic materials offers a number of advantages: minimizing surface damage; implantation into completed devices – for example, through contacts or photoresist layers; producing controlled radiation damage for flux pinning where the ions pass completely through the sample and thus do not modify its chemical nature; and enhancing the electronic excitation of the target material versus collisional damage, as in adhesion enhancement processes. In all cases, however, one requires a detailed understanding of the new damage mechanisms that occur and how they can be modified in a controlled way by annealing. In this report I shall present examples from a number of our experiments: resistivity and index of refraction modification in semiconductors; adhesion enhancement; mixing of multilayer structures; and modification of the electronic properties of insulators and superconductors.

Ionising radiations have been observed to produce significant improvements in thin film adhesion by several experimental groups. We present the results of an exhaustive and conclusive series of experiments on the effect of clean processing and heavy ion irradiation on the adhesion of metal films to substrates of silicon and tantalum. The experiments were performed in a unique research-scale Ultra High Vacuum Cluster tool, to gain control of the all important surface and interface compositions.

Our results show that adhesion is greatest for films deposited on atomically clean surfaces. Such films adhere better than conventionally deposited films subjected to a post deposition irradiation treatment. Clean processed samples show no benefit from subsequent radiation processing. Our results are consistent with the radiation enhanced adhesion phenomenon being due to the radiolysis of interfacial contaminant layers, producing an interface with lower interfacial energy and hence better bonding. Where adhesion enhancement is observed, the process is consistent with a semi-empirical model of the process using an activation energy of some 5 eV per atom.

In this study, the critical dose for ion-beam mixing of Co and Si with Ge-ions which results in homogenous CoSi2 formation after rapid thermal annealing was found. For this purpose, Co was deposited by sputtering on chemically cleaned, <100>-oriented Si and subsequently mixed with Ge ions at doses in the range of 2. 1014 to 1. 1015 cm−2. Silicidation was performed in a rapid thermal annealing (RTA) system at temperatures between 700° and 100°C. Rutherford backscattering measurements showed that annealing at 700°C results in an incomplete reaction when ion-beam mixing at a dose of 2.1014 cm−2 or no ion-beam mixing was performed. After annealing at 1000°C, TEM samples revealed an inhomogeneous CoSi2 film consisting of large grains embedded in the Si. Mixing at doses at or above 5.1014 cm−2 and subsequent RTA at 700°C resulted in uniform CoSi2 layers. Higher annealing temperatures cause larger grains and resistivity values as low as 18 μΩcm. Therefore, we demonstrated that the critical dose leading to complete formation of smooth CoSi2 films with abrupt interface is 5.1014 cm−2 which is nearly the same value as the amorphization dose of Ge in Si.