High Energy Ion Implantation Research Articles

Plasma based ion implantation technology for high-temperature oxidation-resistant surface coatings

Ir–Re alloy surface coatings were performed by means of plasma based ion implantation (PBII) technology, using a coaxial type arc-vacuum metal-plasma source, in order to prevent surface oxidation of the engineering tools (WC alloys) at high temperature. The energy controllability of the PBII process allows implantation of high-energy ions, to improve adhesion properties, and subsequent deposition at low temperature for producing very pure metal and alloys. The properties of the Ir–Re alloy produced with the PBII technology (PBII-film) were studied in comparison with films prepared by a conventional sputtering method (SP-films), which needs a Cr interlayer for assuring good adhesion. Both types of coatings were heat treated at 570 °C for approximately 170 h, in nitrogen atmosphere, and analyzed by Scanning Electron Microscopy, Auger Electron Microscopy and cross sectional Transmission Electron Microscopy. The results showed that the heat treatment did not alter the surface of the PBII-films. On the contrary, the SP-film surface became very rough after heat treatment. Because the Cr diffused from interlayer to the surface and oxidized. Therefore, PBII-films were also more resistant to scratch tests.

High concentration erbium doping of silicon-rich SiO 2 thin films on silicon

In this work, high concentration erbium doping in silicon-rich SiO 2 thin films is demonstrated. Si plus Er dual-implanted thermal SiO 2 thin films on Si substrates have been fabricated by using a new method, the metal vapor vacuum arc ion source implantation with relatively low ion energy, strong flux and very high dose. X-Ray photoelectron spectroscopy measurement shows that very high Er concentrations on the surfaces of the samples, corresponding to ∼10 at.% or the doping level of ∼10 21 atoms cm −3, are achieved. This value is much higher than that obtained by using other fabrication methods such as the high-energy ion implantation and molecular beam epitaxy. Reflective high-energy electron diffraction, atomic force microscopy and cross-section high-resolution transmission electron microscopy observations show that the excess Si atoms in SiO 2 matrix accumulate to form Si clusters and then crystallize gradually into Si nanoparticles embedded in SiO 2 films during dual-ion implantation followed by rapid thermal annealing. Er segregation and precipitates are not formed. Photoluminescence at the wavelength of 1.54 μm exhibits very weak temperature dependence due to the introduction of Si nanocrystals into the SiO 2 matrix. The 1.54-μm light emission signals from annealed samples decrease by less than a factor of 2 when the measuring temperature increases from 77 K to room temperature.

Low- and high-energy plasma immersion ion implantation for modification of material surfaces

Low- and high-energy plasma immersion ion implantation (PIII) of nitrogen has been performed on austenitic stainless steel and high-carbon low-alloy steel to modify their surface properties. In the case of austenitic stainless steel, an expanded austenite layer with surface microhardness of 650 HV was formed with a thickness of 7–8 μm for an elevated treatment temperature of 400 °C, irrespective of the treatment energy. X-Ray photoelectron spectroscopy (XPS) investigations revealed that, at high energy, nitrogen is in a bound state and chromium nitride is formed in the subsurface region, followed by expanded austenite. In the case of high-carbon low alloy steel, the diffusion coefficient of nitrogen obtained by PIII is higher than that obtained by glow-discharge plasma nitriding. The results indicate that if implantation is followed by diffusion, low-energy PIII gives similar or better results than high-energy PIII as far as the treated layer thickness, phase formation and microhardness are considered. Low-energy PIII has a lower hardware cost and reduced sheath dimensions, and thus uniformity in surface modification is achieved.

Masking Process for High-Energy and High-Temperature Ion Implantation

Masking Process for High-Energy and High-Temperature Ion Implantation

Ion implantation of sulphur, boron and nitrogen in diamond: a charge-based deep level transient spectroscopic investigation

Charge-based deep level transient spectroscopy (Q-DLTS) has been used for the first time to investigate the defect states that arise following high-energy ion implantation of B, N and S into polycrystalline diamond. Despite the use of a two-step high-temperature annealing process following the implantations, all samples showed defects within the energy range of 0.16–0.18 eV that can be attributed to damage. In the case of N and B, no evidence for single substitutional species was found. However, for sulphur, levels detected in the range of 0.28–0.42 eV seem most likely to be attributable to the presence of sulphur and not simply damage. The results are discussed in terms of the correlation of these observations to those made by others using differing techniques.

SIMS INVESTIGATIONS OF GETTERING CENTERS IN ION-IMPLANTED AND ANNEALED SILICON

ABSTRACT High-energy ion implantation in silicon leads to the formation of defects around the mean projected ion range R p. These defects are capable of collecting unwanted impurities like metal atoms. A similar effect has been observed in the depth range around half of the projected ion range, R p/2. This gettering ability around R p/2 is supposed to rely on excess vacancies, generated by the implantation process itself. SIMS is a preferential tool in the detection of gettering centres: If copper is applied at the backside of the sample and trapped in the gettering layers during annealing, enrichments of copper in certain areas can be seen in SIMS depth profiles [1]. If the R p/2-effect was caused by excess vacancies, then one attempt to remove these additional gettering centres would be to implant additional Si atoms which could recombine with the vacancies: In order to test this assumption, three Si+ implanted samples were implanted with additional Si+ ions having a projected range that corresponds to ...

Implantation Induced Defects in the Retrograde Well with a Buried Layer

This work investigates the implantation induced extended defects in the retrograde p- and n-well with/without a buried layer after postimplantation thermal annealing at 950°C in ambient. A preferential etchant of mixed solution was used to delineate the defects induced by high-energy ion implantation. It is found that the extended defects elongated to the top surface of the retrograde well with a buried layer, which was implanted with high-energy boron ion at 1500 keV to a dose of resulting in the etching pits of extended defects at a density of about © 2002 The Electrochemical Society. All rights reserved.

Development of a continuously variable energy radio frequency quadrupole accelerator for SiC power semiconductor device fabrication

High energy ion implantation is an important process for controlling deep junction conductivity of SiC semiconductor devices. An radio frequency quadraupole (RFQ) accelerator can accelerate high current ions, but the conventional RFQ accelerator is unable to accelerate various ions with different energies. In order to form the box profile with a low number of defects, a high current MeV ion implanter was constructed using a newly designed continuously variable energy RFQ accelerator and high temperature ion implantation chamber. Results of the experiment showed that the resonance frequency varied from 11.7 to 29.3 MHz, so the output beam energy could be changed over a range of about 6.3 times. The results also showed a higher Q-value of over 5000 compared with that of a conventional machine of 1500. Beam acceleration tests were performed using Al ions, and beams were accelerated from 20 to 750 keV using an radio frequency power of 15 kW. The ions were implanted into 4H-SiC, and the projected ranged was 0.76 μm measured by secondary ion mass spectroscopy.

Binding energy of vacancies to clusters formed in Si by high-energy ion implantation

Measurements of the binding energy (Eb) of vacancies to vacancy clusters formed in silicon following high-energy ion implantation are reported. Vacancy clusters were created by 2 MeV, 2×1015 cm−2 dose Si implant and annealing. To prevent recombination of the excess vacancies (Vex) with interstitials from the implant damage near the projected range (Rp), a Si-on-insulator substrate was used such that the Rp damage was separated from the Vex by the buried oxide (BOX). Two Vex regions were observed: one in the middle of the top Si layer (V1ex) and the other at the front Si/BOX interface (V2ex). The rates of vacancy evaporation were directly measured by Au labeling following thermal treatments at temperatures between 800 and 900 °C for times ranging from 600 to 1800 s. The rate of vacancy evaporation from V2ex was observed to be greater than from V1ex. The binding energy of vacancies to clusters in the middle of the silicon top layer was 3.2±0.2 eV as determined from the kinetics for vacancy evaporation.

Binding energy of vacancy clusters generated by high-energy ion implantation and annealing of silicon

We have measured the evolution of the excess-vacancy region created by a 2 MeV, 1016/cm2 Si implant in the silicon surface layer of silicon-on-insulator substrates. Free vacancy supersaturations were measured with Sb dopant diffusion markers during postimplant annealing at 700, 800, and 900 °C, while vacancy clusters were detected by Au labeling. We demonstrate that a large free vacancy supersaturation exists for short times, during the very early stages of annealing between the surface and the buried oxide (1 μm below). Afterwards, the free vacancy concentration returns to equilibrium in the presence of vacancy clusters. These vacancy clusters form at low temperatures and are stable to high temperatures, i.e., they have a low formation energy and high binding energy.

Comparison of oxide leakage currents induced by ion implantation and high field electric stress

We compare in this work the electrical properties of gate leakage currents induced through the thin SiO2 oxide layer of metal-oxide-semiconductor structures by high-energy ion implantation (Boron B2+) and high field electrical stresses where electrons are injected from the gate in the Fowler–Nordheim regime. Even if the high-frequency capacitance–voltage characteristics are very different after both treatments, comparable increases and similar shapes are found at low field in static gate current–voltage curves, typical of equivalent oxide damage. Moreover, these stress or implantation induced leakage currents are both removed in a similar way by a thermal anneal under forming gas at 430°C. We conclude that similar defects could be induced through the oxide by both processes and generate those excess currents by a defect assisted tunneling mechanism.

Trans-projected-range effect in proximity gettering of impurities in silicon

Deep gettering layers have been formed in n-type Si wafers by high-energy ion implantation of Si +, P +, Ge + and As + and subsequent annealing. The samples have then been contaminated with Cu by implanting the impurity into the back face and performing an additional thermal treatment. The resulting copper depth profiles measured by secondary ion mass spectrometry show strong gettering of Cu well beyond the projected ion range R P and formation of a separate gettering band therein. We call this phenomenon the “trans- R P effect”. It has been observed for both the P and As implants, but not for the Si and Ge implants. This effect indicates the presence of a significant amount of defects much deeper than R P . The size of these defects is below the resolution limit of our transmission electron microscopy analysis and we suggest that they are small interstitial clusters. Their gettering ability is higher than that of the extended defects at R P as the amount of Cu atoms gettered beyond R P is much greater than that in the implanted gettering layer. A mechanism for the defect formation and clustering in the trans- R P region is proposed, and an explanation for the differences in the results for the P and As implants is given.

Diamond Pressure and Temperature Sensors for High-Pressure High-Temperature Applications

A high-pressure high-temperature diamond based sensor has been developed for the use in diamond anvil cells. The electronic structure of the sensor is that of p-i-p unipolar diode with boron doped p-type regions separated by an i-region containing compensated boron acceptors. The sensor has been fabricated by high-temperature high-energy boron ion implantation followed by high-energy carbon ion irradiation on the working surface of an anvil made of type IIa natural diamond. The performance of the sensor has been tested at pressures up to 70 kbar and temperatures up to 800 C. The sensor has a resolution of 5 bar for pressure and of 0.01 °C for temperature.

Quantitative evolution of vacancy-type defects in high-energy ion-implanted Si: Au labeling and the vacancy implanter

In ion implantation related research in Si, the role of interstitial clusters in dopant diffusion is fairly well understood. But there is relatively poor understanding of vacancy clusters, mainly due to the inadequacy of present techniques to profile and especially to count vacancy defects. Recently, two important steps have been taken in the direction of understanding the vacancy-type defects. The first is the demonstration that high-energy ion implantation (HEI) can be used as a vacancy implanter to introduce vacancies (V) in Si that are separated from the interstitials (I) by relying on spatial separation of the Frenkel pairs due to the average forward momentum of the recoils. The second is the development of two techniques, Au labeling and cross-section X-ray microbeam diffuse scattering, which permit quantitative measurements of the vacancy-type defect clusters and their depth distribution. In this work we highlight the Au labeling technique and use the vacancy implanter in conjunction with Au labeling to study the evolution of excess vacancy defects (V ex) created by HEI of Si + in Si(1 0 0) as a function of fluence and temperature. We show that a precise injection of V ex is possible by controlling implanted fluence . We also show that the V ex clusters formed by the HEI are extremely stable and their annihilation is governed by interstitial injection rather than vacancy emission in the temperature range of 800–900°C.

Formation of a conducting layer by high energy metal ion implantation into diamond

A conducting layer of Al or Cu was formed under the surface of synthetic Ib diamond (100) by high-energy metal ion implantation of 1×10 15–2.8×10 17 ions cm −2 with ion energies of 3 MeV (Al) and 8 MeV (Cu). The distribution peaks of heavily implanted Al and Cu, investigated by secondary ion mass spectroscopy (SIMS), were approximately 1.3 and 2.2-μm deep from the diamond surfaces, respectively. The results agreed with simulation results of TRIM. The Raman line of implanted diamond surfaces was observed at approximately 1333 cm −1, though they were broad and slightly shifted from the diamond Raman peak. The diamond structure was clearly observed at the implanted surfaces by reflection high energy electron diffraction (RHEED) measurements. From these results, it was concluded that the surfaces of the implanted diamond were not totally damaged. The sheet resistance of the metal implanted layers measured by a four-probe method decreased with increasing the ion dose and reached a minimum value of approximately 170 Ω/□. By comparing this resistance value with that of a similarly implanted layer in a SiO 2 glass substrate, it was concluded that electrons were transported mainly through the implanted metal layer for high dose specimens, while electron transport via defects was dominant for low dose specimens.

Growing of bulk crystals and structuring waveguides of fluoride materials for laser applications

We report on recent progress in the synthesis, the crystal growth and the epitaxial growth of fluoride and other laser materials. Results on the fabrication of single crystalline waveguides for dielectric down - and upconversion lasers pumped by semiconductor diode lasers are summarized. Epitaxial growth (molecular beam epitaxy (MBE), liquid phase epitaxy (LPE), pulsed laser deposition (PLD)) and surface modifying techniques (high energy ion implantation, ion diffusion) have been applied in several laboratories. Progress in techniques fabricating optical waveguides from glassy media is addressed as well. Particular emphasis is given on the structuring (wet etching, chemical polishing, ion beam etching) of fluoride crystals for the purpose of obtaining 2-D and 1-D optical waveguides. Results on the structuring of LiYF 4 by wet and ion beam etching are reported. With respect to laser action, the generation of short wavelength light by upconversion (UC) processes, stimulated Raman scattering (SRS) and second harmonic generation (SHG) is discussed. Reports on the first crystalline waveguide lasers of fluoride crystals LiYF 4 and LaF 3, both doped with neodymium, are presented.

Polycrystalline Silicon Thin Film Transistors Fabricated by Employing Selective Self Ion-Implantation and Excimer Laser Annealing

Polycrystalline silicon thin film transistors (poly-Si TFT’s) fabricated by excimer laser annealing (ELA) are promising devices for active-matrix liquid-crystal display (AMLCD) due to their high field-effect mobilities and low thermal budgets [1,2]. It is well known that the electrical characteristics of poly-Si TFTs depend on the grain size and the defect density of the poly-Si film. In the fabrication of low temperature poly-Si TFT’s, excimer laser annealing is considered as most a promising tool for preparing poly-Si films with low defect densities. However, grain size is very sensitive to the laser energy density, and nucleation takes place randomly [3,4]. Selective self ion-implantation (Si+) has also been reported as a tool for artificial nucleation prior to thermal annealing. If high-energy ion-implantation is employed, high-density defects and high-density nucleation can be provided artificially in amorphous silicon films [5]. In this paper, we propose a novel method to prepare good quality poly-Si films by employing selective self ionimplantation and ELA. We fabricated poly-Si TFT’s by employing the proposed method and confirmed the improved electrical characteristics of poly-Si films in both the onand the off-state through measurements of the TFT characteristics.

β-SiC-on insulator waveguide structures for modulators and sensor systems

In this work waveguide structures using the cubic polytype of SiC are analyzed. The β-SiC-on-insulator wageguides were fabricated by two different methods. In the first case, a technological process similar to that used for SIMOX material was used, a buried SiO 2 layer being formed by high-energy (∼2 MeV) ion implantation of oxygen in SiC/Si wafers. For the second case, the heteroepitaxy of SiC on SOI (SIMOX) wafers was used. The losses of the waveguides have been measured at 0.633, 1.3 and 1.55 μm in both TE and TM polarization and a detailed analysis and interpretation of the different loss mechanisms is presented. Using these two types of waveguides we have designed waveguide modulators using the Pockels effect. A 2D semiconductor device simulator was used to determine the electric field configuration in a double-Schottky diode structure and the local modulation of the refractive index was used to determine the effective index modulation of the guided mode. Optical simulations were performed using the spectral index and the effective index methods. Different 2D geometries are analyzed and the material parameters needed for fabricating such a device are determined. Such devices have potential for high-speed Si-based photonic devices compatible with silicon technology.

Quantification of excess vacancy defects from high-energy ion implantation in Si by Au labeling

It has been shown recently that Au labeling [V. C. Venezia, D. J. Eaglesham, T. E. Haynes, A. Agarwal, D. C. Jacobson, H.-J. Gossmann, and F. H. Baumann, Appl. Phys. Lett. 73, 2980 (1998)] can be used to profile vacancy-type defects located near half the projected range (12 Rp) in MeV-implanted Si. In this letter, we have determined the ratio of vacancies annihilated to Au atoms trapped (calibration factor “k”) for the Au-labeling technique. The calibration experiment consisted of three steps: (1) a 2 MeV Si+ implant into Si(100) followed by annealing at 815 °C to form stable excess vacancy defects; (2) controlled injection of interstitials in the 12 Rp region of the above implant via 600 keV Si+ ions followed by annealing to dissolve the {311} defects; and (3) Au labeling. The reduction in Au concentration in the near-surface region (0.1–1.6 μm) with increasing interstitial injection provides the most direct evidence so far that Au labeling detects the vacancy-type defects. By correlating this reduction in Au with the known number of interstitials injected, it was determined that k=1.2±0.2 vacancies per trapped Au atom.

Synthesis of silicide structures by high energy ion projection

A new approach in ion beam synthesis of silicides is investigated. Using a heavy ion projector buried silicide structures were produced by high energy ion implantation in silicon. The ion projection allows to perform structured implantation with submicron lateral dimensions. Structured silicides as CoSi 2, Rh 3Si 4, CrSi 2 and MnSi 1.73 have been fabricated by hot implantation and subsequent annealing either by a furnace or rapid thermal annealing (RTA). RBS and spreading resistance measurements were performed to characterize the samples.