High-energy Implantation Research Articles

Implant damage and redistribution of indium in indium-implanted thin silicon-on-insulator

The indium implant damage and diffusion behavior in thin silicon-on-insulator (SOI) with a 200 nm top silicon layer were studied for different implantation energies and doses. Rutherford backscattering spectrometry in the channeling mode (RBS/C) was used to characterize the implant damage before and after annealing. Secondary ion mass spectrometry (SIMS) was used to study the indium transient enhanced diffusion (TED) behavior in the top Si layer of the SOI structure. An anomalous redistribution of indium after relatively high energy (200 keV) and dose (1 × 10 14 cm −2) implantation was observed in both bulk Si and SOI substrates. However, there exist differences in these two substrates that are attributable to the more predominant out-diffusion of indium as well as the influence of the buried oxide layer in the SOI structure.

Effects of buried oxide layer on indium diffusion in separation by implantation of oxygen

The diffusion of indium in both the top silicon and the buried oxide (BOX) layers in separation by implantation of oxygen (SIMOX) is investigated. For all indium-implanted samples, there is a significant redistribution of indium atoms from the top Si-BOX interface toward the bottom BOX-Si interface, thereby affecting the indium concentrations in the two silicon-BOX interfaces. In the case of relatively high-dose and high-energy indium implantation (1×1014cm−2 at 200keV), an anomalous segregation of indium is observed in both the bulk Si and the SIMOX substrates. However, there is a notable transportation of indium atoms from the top Si layer toward the bottom BOX-Si interface in the SIMOX, thereby affecting not only the indium concentrations in the two silicon-BOX interfaces but also the indium distribution in the top silicon layer. The unique indium-diffusion behavior in the SIMOX is believed to be a composite effect of indium trapping by the two Si-BOX interfaces, indium atoms being drawn away from the top silicon layer by the buried oxide, as well as implant damages in the top silicon. The asymmetrical structure of the BOX layer with Si islands accumulating at the bottom BOX-Si interface and the abundance of oxygen-related defects in the BOX layer are also believed to be responsible for the indium-diffusion behavior in the BOX layer.

In situ X-ray diffraction investigations during high-energy oxygen ion implantation in transition metals

An in situ X-ray diffraction study was performed to characterize aspects of the kinetics of structural phase formations in transition metals during oxygen implantation. A specially designed high-temperature vacuum chamber for X-ray measurements was installed at the high-energy implantation beamline of the 3MV-Tandetron accelerator. Titanium and molybdenum sheets were implanted with oxygen ions with an energy of 1.5MeV up to a fluence of 1.6×1018O+-ions/cm2 without sample cooling. During implantation, the phase formation was continually investigated by in situ and real-time X-ray diffraction (XRD) with a position-sensitive proportional counter system. The phase formation was studied during annealing process by in situ XRD. The obtained results were compared with ex situ XRD measurements performed by different techniques at a standard diffractometer. The analysis of XRD patterns indicates the formation of a buried MoO2 layer in molybdenum. In the Ti samples no buried oxide is formed due to significant oxygen diffusion.

Damage effects produced in the near-surface region of x-cut LiNbO3 by low dose, high energy implantation of nitrogen, oxygen, and fluorine ions

The damage effects produced in the near-surface region of x-cut LiNbO3 by low dose, high energy implantation of carbon, nitrogen, oxygen, and fluorine ions are investigated as a function of the dose and substrate temperature during the implant process. The damage profiles were obtained by the Rutherford backscattering RBS-channeling technique, whereas the compositional profiles were performed by secondary ion mass spectrometry. The experimental results showed that the mechanisms governing the damage formation at the surface are strongly connected to the interaction of defects produced when the electronic energy loss exceeds a given threshold close to 220 eV/Å. In particular, we observed a damage pileup compatible with a growth of three-dimensional defect clusters.

Investigations of Defects Introduced in 4H-SiC n-Type Epitaxial Layers by Hydrogen DC Plasma

Hydrogen is known to passivate donor and acceptor levels in SiC bulk, and also at the surface by forming bonds with Si atoms. Introduction of H atoms can then improve the electrical performance of Schottky diodes by reducing the metal-SiC interface state density. However it is necessary to verify if H-related complexes are formed or not, creating trap centers and corresponding deep levels. In this work, the electrical characteristics of defects introduced near the surface of n-type 4H-SiC epitaxial layers by DC hydrogen plasma were investigated. C-V technique revealed a donor-nature defect located deeper than the projected range of W ions, emitting electrons at temperatures > 300 K. Two deep levels were detected by DLTS measurements after high implantation energies, while the defect concentration decreases and only one defect is detected after lower implantation energies. The activation energies are similar to the double defect RD1/2, associated to the vacancy pair V-C-V-Si. Cathodoluminescence spectra showed the existence of a peculiar luminescence peak related to H introduction, which intensity increases with plasma energy.

High-energy ion beam implantation of hydroxyapatite thin films grown on TiN and ZrO2 inter-layers by pulsed laser deposition

Current drawbacks in the hydroxyapatite (HA) thin film production for applications in bone surgery are their poor mechanical strength and limited adherence. This paper presents the ion beam implantation technique as an efficient method to improve the mechanical characteristics of HA films. Crystalline films of HA were grown by pulsed laser deposition, using a KrF* excimer laser (λ=248 nm, τ⩾20 ns). The depositions were performed from pure HA targets on Ti–5Al–2.5Fe alloys coated with TiN or ZrO2 buffer layers. Samples were then implanted with Ar+ ions of high-energy (1.5 MeV) at a dose of 1016 cm−2. The as-deposited and implanted films were characterized by light microscopy and energy dispersive X-ray spectrometry. The mechanical properties of films were studied by nanoindentation and nano-scratch techniques using a Berkovich indenter tip. Films become harder and exhibit a higher Young modulus after implantation. The best values (5 GPa hardness and 130 GPa Young modulus, respectively) were obtained for the implanted films grown on TiN. An influence of the buffer layer nature on the mechanical behavior of films was observed. Films grown on ZrO2 are brittle and crack at moderate load (∼12 mN) during scratch while these ones deposited on TiN successfully withstand loading. Residual stresses occur into the HA/ZrO2 structure during processing and ion bombardment.

Fabrication of trench-gate power MOSFETs by using a dual doped body region

Fabrication of trench-gate power MOSFETs by using a dual doped body region has been proposed to further improve the device performance. For the usual scheme that employs a uniform doped body region, a device with a blocking voltage larger than 30 V and a specific on-state resistance of about 1.0 Ω cm can be obtained via the proper choice of trench depth, epitaxial thickness, and body doping concentration. On the other hand, a dual doped body region is produced by dual high-energy and low-energy implantation of boron dopant. By this scheme, a device with a blocking voltage larger than 30 V and a specific on-state resistance of about 0.8 Ω cm can be further achieved. Hence, with reducing the cell pitch size to be below 2 μm, this device fabrication scheme should be promising and practical for achieving a specific on-resistance smaller than 0.1 mΩ cm 2 and a blocking voltage higher than 30 V.

High-energy ion projection for deep ion implantation as a low cost high throughput alternative for subsequent epitaxy processes

Three-dimensional (3D) doping into depths up to 40 μm is of great interest for numerous device types. In particular, the production of high-power devices requires low cost vertically structured doping. State of the art epitaxial growth combined with diffusion and/or low-energy ion implantation is time consuming and cost intensive. We suggest 3D structured high-energy ion projection implantation as a simple cost effective and reliable alternative. This method allows controlled fast doping with high homogeneity and reproducibility. This article outlines some details of a feasibility study of the technique and discusses advantages and problems.

Reaction kinetics of annealing of high energy implantation by XRD

The annealing of structural defects caused by high energy implantation is studied using X-ray diffraction. The implanted sample (dose: 1 × 10 14 ions/cm 2) was isochronally annealed in flowing nitrogen in steps of 50 K upto 823 K for 10 min each, using a RTA system developed in Mumbai University. XRD patterns were recorded after each annealing and analyzed for strain and curvature. Also, the screw dislocation density was estimated at each stage of annealing using the FWHM of w scans in high resolution mode. The XRD profiles were simulated using the dynamical theory of X-ray diffraction for layer damage i.e. thickness, mismatch with respect to substrate, Debye Waller factor and sample curvature. The activation energy and characteristic temperature of annealing were estimated through reaction kinetics, utilizing the experimental XRD for progressive changes with temperature, of strain and dislocation density.

Retarding transient enhanced diffusion of boron in silicon with high energy silicon co-implants

A significant retardation of transient enhanced diffusion of 5 keV boron implanted in silicon has been achieved when it was co-implanted with 1 MeV silicon. Almost complete retardation was observed when this was done in SOI substrates which isolate the layers containing most of the point defects due to the high energy silicon implant from the near surface regions. Measurements of the defect profile from the silicon implant using accurate Rutherford backscattering channelling analysis, coupled with high resolution SIMS analysis of the boron profile provide a comprehensive picture of the dopant/defects relationship. Other data from positron annihilation spectroscopy complete the picture for the vacancy-type defects, while data from spreading resistance measurements indicate the activation efficiency of the boron under these conditions. Other high energy implants were tested and a variety of SOI material was used to investigate the role of the depth of the barrier layer in retarding the TED.

Temperature dependence of photoluminescence from localized states of silicon nanocrystals in silicon‐implanted quartz

Silicon nanocrystals were produced in fused quartz by using very high Si-ion implantation energy (2 MeV); hence the penetration depth of 2 μm is 20 times larger than those of other works. We have measured carefully the photoluminescence (PL) intensity in the temperature range between 4 and 300 K. By using a model taking account of a process of radiative recombination from the triplet and singlet states and two non-radiative decay processes, a tunnelling process and a thermal activation process, we obtained a good agreement between the theoretical curve and the experimental data. This calculation is the first attempt to explain quantitatively the temperature dependence of the PL intensity of the silicon nanocrystals.

High dose low temperature Ti and Al implantation in metals

This article presents the results of investigation of Ti and Al ion implantation into copper and uranium. Titanium and aluminium are selected as implanted ions because these materials are the main candidates to the production of corrosion resistant protective coatings. Special features of near-surface transient layers formation at high dose low energy implantation are investigated. The temperature dependencies of Al concentration in near-surface layers of Cu are plotted. The time and energy dependence of Al and Ti concentration curves on the irradiation energy in the range 1.0–4.0 keV is studied. The calculations of the impurity radiation-stimulated diffusion at the high dose implantation are carried out.

Predictive Monte Carlo ion implantation simulator from sub-keV to above 10 MeV

In this paper is reported a general and accurate binary-collision-approximation- (BCA-)based Monte Carlo ion implantation model for implants into crystalline silicon. The combination of an improved semiempirical electronic stopping power model and Ziegler-Biersack-Littmark universal potential enables us to simulate a wide variety of implant species with only two different electronic stopping parameters for different implant species. With the model parameters fixed for a given implant species, excellent agreement is found with experimental secondary ion mass spectroscopy data for the energy range from sub-keV to above 10 MeV, and for different implant directions including random equivalent orientation, 〈100〉, 〈111〉, and 〈110〉 channeling directions. When compared with other BCA-based Monte Carlo simulators, it is demonstrated that more accurate results can be obtained for ultralow energy and very high energy implants. Furthermore, it is shown that, while the existing ion implantation simulators with the electronic stopping power based on the effective charge theory fail to predict the long tails of the deeply channeled implant species (such as Al), our model can predict these long tails successfully. Finally, an efficient damage model is also presented, which requires only one additional free parameter to accurately account for the damage accumulation and dechanneling effect. For high dose implants, substantial speed improvement over MARLOWE-based Monte Carlo simulators is observed.

ESR characterization of activation of implanted phosphorus ions in silicon carbide

Phosphorus ion implantations of 6H-SiC in the mean phosphorus concentration of the implanted layer of ∼1 × 10 18 cm −3 were performed both at multi-fold energy between 9 and 21 MeV and at 340 keV. In the high-energy implantations at room temperature, 400, 800 and 1200 °C and in the 340 keV implantations at 800 °C, electron spin resonance spectra arising from isolated shallow phosphorus donors have been observed after post-implantation annealing at 1650 °C, but were not observed in as-implanted state.

Influence of Hydrogen Plasma Treatment on He Implantation-Induced Nanocavities in Silicon

ABSTRACTHe implantation followed by thermal anneal is a well-established technique for creating layers or bands of cavities in silicon. This process is a consequence of the interaction between He and ion-implant-induced vacancies. Applications of such cavity layers include gettering and localized minority carrier lifetime control, and compliant substrates for lattice-mismatched heteroepitaxy. Studies have shown that the presence of interstitial-type defects can lead to the shrinkage of He-cavities due to the interstitial capture by the cavities. However, few of them deal with the interaction of cavities with vacancies. Here we present results on the formation of He-cavities in Si in the presence of atomic hydrogen and vacancies produced by effusion of hydrogen. Following a helium implant, samples were hydrogenated with an electron cyclotron resonance (ECR) hydrogen plasma. Control samples without any hydrogenation were also used. We studied the influence of hydrogen on void morphology. While hydrogen enhances void size at higher energy implants, the enhancement effect is absent in lower energy implants. The results underscore the role of vacancies in void formation and growth.

Linear optical properties of a Ti-SiO2 nanoparticle composite

We report the linear optical properties of a titanium nanoparticle composite formed by implantation of low energy Ti+ into single crystalline SiO2. A surface plasmon resonance (SPR) induced absorption band is found in the 650–850 nm wavelength range, i.e., in the visible (red) and near infrared regions, indicating the formation of Ti nanoparticles in the subsurface layer of the SiO2 matrix. The average size of the particles is ∼2.6 nm and the volume fraction is as low as 0.016. At the implantation energy of 9 keV and total dose of 3×1016 ions/cm2, the SPR absorption band becomes distinguishable only at temperatures greater than 600 °C and reaches its maximum at ∼800 °C (1/2Tm). Enhanced nucleation with nearly constant particle size with increasing temperature contributes to the increased SPR absorption intensity at temperatures ⩽800 °C. The SPR absorption intensity decreases significantly near 1000 °C (2/3Tm). A blueshift of the SPR absorption maximum with substrate temperature is also observed. The shape of the SPR absorption band and the difference between low and high energy implantations is discussed.

Cw and pulsed EPR study of lithium irradiated n-type 21R SiC

The impact of light and medium mass ions in crystals in the MeV range is of particular interest in high energy implantations. In the present work, extensive continuous wave (cw) and pulsed electron paramagnetic resonance (EPR) studies of a 21R SiC Lely platelet, after irradiation with 8 MeV 7Li2+ ions in the random direction, up to a maximum dose of approximately 1 × 1016 particles/cm2 are presented. The existence of new types of defects induced in the end-of-range region of impinging ions is discussed and analyzed. Due to the complexity of the induced structure, the technique of progressive annealing was utilized, revealing interesting features in the experimental spectra. The results are compared to known literature and an attempt is made to explain the occurring similarities. Furthermore, a new paramagnetic defect was isolated and analyzed, persisting up to 1100 °C during the annealing procedure.

Micromachining of three-dimensional GaAs membrane structures using high-energy nitrogen implantation

In this paper we present an alternative technology for micromachining gallium arsenide (GaAs) using deep ion implantation. Energetic nitrogen ions at 630 keV and 4 MeV have been used to implant deeply into an n-type GaAs substrate with doses of 2 × 1014 and 1 × 1015 cm−2. After annealing at 600 °C, the nitrogen implanted n-GaAs top layer was converted to semi-insulating GaAs with a thickness of 1 μm for 630 keV and 2.5 μm for 4 MeV nitrogen ions. A pulsed electrochemical etching process has been developed to selectively remove n-GaAs and to leave the top patterned semi-insulating GaAs layer as a mechanical membrane structure. Various GaAs microstructures, such as cross-bridge, coiled and corrugated membranes, have been successfully fabricated using this micromachining technology.

Athermal annealing at room temperature and enhanced activation of low- energy boron implants with high-energy Si coimplantation

Interactions between shallow implanted boron and high-energy silicon implants have been investigated. Athermal annealing of implantation damage induced by low energy boron implants at room temperature was observed after coimplantation and such annealing effects were more obvious when the dosage of preimplanted Si was increased. Electrical measurements after rapid thermal annealing showed that the activation of B was greatly increased with the dosages of high-energy Si coimplantation. An enhancement of substitutional ratio of B was observed by aligned nuclear reaction analysis.

Interface Characteristics of SiO2 / Si Structure with High Energy Boron Implantation

Boron profiles and interface characteristics of structure when boron was implanted by high energy implantation were studied. A very narrow (∼0.3 μm) channel-stop layer can be formed under a 1.5 μm thick layer by high energy implantation. An ion dose of is adequate to form a channel-stop layer. The surface state density was after implantation and decreased to a value of following 1 h of heat-treatment at 1000°C. The surface state density was decreased by heat-treatment and recovered to a value equal to that of nonimplanted samples. © 2002 The Electrochemical Society. All rights reserved.