Solid solutions of SiC and III-V compound semiconductors are recognized as promising materials for novel semiconductor applications. This paper reports on experiments which explore the possibility of synthesizing thin buried layers of (SiC)l-x(AIN)x having composition of about x = 0.2 by co-implanting N+ and Al+ ions into 6H-SiC wafers maintained at temperatures in the range 200 - 800°C. Structural and compositional evaluation of as-implanted samples was carried out using a combination of Rutherford backscattering/channelling spectrometry and infrared reflectance spectroscopy. It is shown that the structures are highly sensitive to the substrate temperature. The use of sufficiently high temperatures (400 - 800°C) enables the crystallinity of the host material as well as relatively low damage levels to be maintained during implantation. The formation of AI-N bonds within the implanted layers is also confirmed over the temperature range studied.

Ion beam synthesis of SiC/Si heterostructures was performed by MEVVA (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 β-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

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 1.2x 1017 WIcm 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.

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 x 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 formatLion 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.

Submicrometer cobalt disilicide wires in Si(100) were fabricated by ion beam synthesis. We implanted cobalt ions through the openings of an implant mask made by direct electron beam writing. The formation of the wires was achieved by rapid thermal annealing at temperatures up to 1100°C for 10s. The produced wires have thicknesses of about 85 nm and widths depending on the widths of the implant mask which were varied between 1 μm and 100 nm. These wires were characterized by means of cross-section transmission electron microscopy and magnetoresistance measurements at low temperatures. The results can be well explained by weak localization with strong spirn-orbit scattering and superconducting fluctuation (Maki-Thompson) corrections.

The stability of cobalt silicide formed on narrow polysilicon line degraded rapidly with shrinkage of linewidth as shown by the increase of sheet resistance after annealing. Stability was improved by adding a titanium interlayer under cobalt with or without a Ti or TiN cap layer. The stability was affected by silicide thickness and substrate doping. In best cases an increase of sheet resistance after annealing was still observed. Adding an Ar ion bombardment step improved the thermal stability drastically. This structure did not show any sheet resistance change after a 30 min annealing at 850°C, either with or without interlayer or cap layer.

Ion beam synthesis of CoSi2 layers in Si by MEVVA (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.

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.

Development of ion doping and hydrogenation equipment using plasma ion implantation (PII) is being studied. It is shown that low energy, high throughput operation could eliminate problems associated with etching, charging, cooling, and contamination. The applications of a new plasma source and neural network implementation optimization are also reported.

As the dimensions of integrated circuits shrink towards the deep sub-micromeLer regime, silicon-on-insulator is regarded to be more favorable than silicon substrates. The biggest drawback of SOI is cost which will become more critical for next generation 300-nm silicon wafers. Plasma immersion ion implantation (PIII) provides a viable alternative for the fabrication of SOI wafers as the processing time is very short and independent of wafer size. Pill is being employed to synthesize two types of SOI materials, SPIMOX (Separation by Plasma IMplantation of OXygen) and bonded SOL. In SPIMOX fabrication, both oxygen and water plasmas have been attempted and the results indicate that a discrete buried oxide layer can indeed be formed. In the case of wafer bonding, PIII is utilized for smart-cutting, a process in which implanted hydrogen or helium causes the bonded wafer to crack along the plane thereby making one side of the wafer recyclable. This article reviews the work done and current status of SOI fabrication by PIII.

New doping processes which can alternate the ion implantation to achieve the ultra shallow junction are reviewed. Mainly two ways have been proposed. One uses plasma and the other uses vapor phase reaction. 0.17μm Surface Channel (SC) - PMOSFET's have been successfully fabricated by especially plasma doping method.

PH3 SDS (safe delivery system) gas was used for the first time in P11 doping experiments to fabricate n+p junctions and NMOS devices. Two gas recipes (PH3 diluted in H2 and He) were investigated. Under lower pressure, a minimum etching effect was observed. A 4x1015/cm2 phosphorus dose and a 22 Ω/□ sheet resistance were achieved in 4 seconds. Very low contamination level was involved. An anomalous tail of P profile in Si substrate was observed using SIMS measurements.

A plasma immersion ion implantation (PIII) hydrogenation process using an inductively-coupled plasma (ICP) source is implemented for defect passivation in polycrystalline silicon (poly-Si) thin film transistors (TFT's). Device parameter improvement saturates in 4 minutes, which is considerably shorter than for other reported hydrogenation methods. Stress test indicates that the devices hydrogenated by this novel technique have much better long-term reliability. The hydrogenation effects on two types of trap states are analyzed the current-voltage characteristics of the devices. The densities of deep states and tail states are significantly reduced after short time hydrogenation.

Cluster ion implantation is an attractive alternative to conventional ion implantation, particularly for shallow junction formation. It is easy to obtain high-current ion beams with low equivalent energy using cluster ion beams. The implanted boron distribution in 5keV B10H14 implanted Si is markedly shallower than that in 5keV BF2 ion implanted Si. The implanted depth is less than 0.04 μm, indicating that cluster ion implantation is capable of forming shallow junctions. The sheet resistance of 3keV B10H14 implanted samples falls below 500 Ω/sq after annealing at 1000°C for 10s. Shallow implantation can be realized by a high energy cluster beam without space-charge problems in the incident beam. Defect formation, resulting from local energy deposition and multiple collisions, is unique for cluster ions. The thickness of the damaged layer formed by cluster ion bombardment increases with the size of the cluster, if implant energy and ion dose remain constant. This is one of the nonlinear “cluster effects,” which may allow some control over the implant damage distributions that accompany implanted ions, and which have been shown to have a great effect on dopant redistribution during annealing

Polycrystalline Si (Poly-Si) films were successfully grown at temperature less than 500 °C by using a direct Si ion beam deposition technique. In this process, the ion beam energy of Si- is directly coupled to the formation of the films. High substrate temperature (>600 °C), normally required for conventional CVD techniques, has been a major barrier for the Poly-Si Thin Film Transistor Liquid Crystal Display (TFT LCD) which uses a glass substrate. Thus, the ability to produce Poly-Si film below the glass transition temperature and to control the grain size will make this direct Si- ion beam deposition process a potential alternative technique for future TFT LCD. The grain size dependence on the ion beam energy and substrate temperature was investigated using a Transmission Electron Microscope (TEM). The grain size could be controlled from 0.1 μm to 1 μm at ion beam energies from 10 to 50 eV with a substrate temperature less than 500 °C. The resistivity of the as-deposited film was of the order of 100 Ωcm due to in-situ doping effect.

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 kW. The copper films grown at the both condiitions 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.

Cu thin films with a thickness around 850 Å were prepared on Ti45N55/Ti/Si(100) substrates at room temperature by partially ionized beam deposition (PIBD) with an ion energy of 3 keV at pressure of 8×10−7-1 x 10−6 Torr. The Cu/Ti45N55/Ti/Si samples were annealed at 8×10−6-1 × 10−5 Torr with annealing temperature of 500 to 700 °C for 30 min.. Thermal stability of the PIB-Cu films was investigated with Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), Scanning electron microscopy (SEM), and X-ray diffraction (XRD). The as deposited Cu films had a (111) texture and there was no change of phase in annealed Cu films regardless of annealing temperature. Grain size of the annealed Cu films increased with annealing temperature. SEM studies show no hillock and no voiding on the Cu film surface up to annealing temperature of 700 °C. For PIB-Cu/Ti45N55/Ti/Si samples, all the layers were intact and there was no indication of interdiffusion by conventional depth profiling techniques (RBS, AES) up to 700 °C in vacuum for 30 minutes.

A combined ion beam and molecular beam epitaxy (CIBMBE) method was applied for the deposition of a Ge1-xCx 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-x,Cx 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 deposition offers a number of interesting possibilities for creating nonlinear materials for photonic devices such as waveguides. Ion beams have been used by a number of groups to create metal and semiconductor nanocrystallites in silica and other glassy substrates in a geometry suitable for shallow channel waveguides. In this paper, we describe the use of He ion beams to initiate nucleation of Ag nanocrystallites in ion-exchanged soda-lime glass. The nanocrystallites are remarkably uniform in size, and exhibit substantial third-order optical nonlinearity. The combination of ion exchange and ion implantation has an advantage over conventional implantation techniques because it produces guiding layers deep enough (several microns) to form practical channel waveguides. In addition, we have shown that it is possible, by means of subsequent laser irradiation, to further alter the properties of the nonlinear composite material. In this particular case, irradiation by visible or infrared laser beams following ion implantation induces oxidation of the silver nanocrystallites, as documented by Auger analysis of the composite material. Furthermore, the third-order nonlinearity of the composite material changes sign, changing a self-focusing nonlinearity into one which is self-defocusing. These experiments suggest a number of possibilities for combining ion- and laser-beam irradiation to create laterally structured waveguide materials as well as nonlinear channel waveguides.

The formation and optical properties of nanometer dimension metal colloid composites formed by the sequential implantation of Cd then Ag and by single element implantations of Cd and Ag in silica were characterized by transmission electron microscopy (TEM) and optical spectroscopy. A nominal dose of 6×1016 ions/cm2 as determined by current integration was used for both ion species. The doses used for the sequential implantations were a 1 to 1 ratio of Cd to Ag. Sequential implantations of Cd and Ag led to the formation of both multi-component metal nanoclusters and elemental nanoclusters. The electron diffraction measurements indicated that the polycrystalline particles of Ag5Cd8 and elemental Ag were formed. The optical response was consistent with results expected from effective medium theory.