Energy Ion Implantation Research Articles

Robust p-type doping of copper oxide using nitrogen implantation

We demonstrate robust p-type doping of Cu2O using low/medium energy ion implantation. Samples are made by controlled oxidation of annealed Cu metal foils, which results in Cu2O with levels of doping close to intrinsic. Samples are then implanted with nitrogen ions using a kinetic energy in the few keV range. Using this method, we are able to produce very high levels of doping, as evidenced by a 350 meV shift in the Fermi level towards the VB maximum.The robustness of the nitrogen implanted samples are tested by exposing them to atmospheric contaminants, and elevated temperatures. The samples are found to survive an increase in temperature of many hundreds of degrees. The robustness of the samples, combined with the fact that the materials used are safe, abundant and non-toxic and that the methods used for the growth of Cu2O and N+ implantation are simple and cheap to implement industrially, underlines the potential of Cu2O:N for affordable intermediate band photovoltaics.

Defect engineering for shallow n‐type junctions in germanium: Facts and fiction

An overview is given on the status of n‐type dopant activation and diffusion in Ge, based on a standard ion implantation and annealing scheme. Emphasis is on defect engineering approaches to optimize either or both parameters. A detailed discussion is given on the use of co‐implantation by neutral or other n‐type dopants. As a case study, the impact of the C ion implantation energy and dose on n‐type junctions in p‐Ge by P + C co‐implantation will be given. It is demonstrated that for fixed P implant conditions, there exist an optimum energy and dose for achieving a minimum junction depth by the formation of C–PV complexes. An alternative approach is the use of self‐interstitial management at the end‐of‐range of the P implantation. Finally, an overview is given of alternatives for obtaining shallow, highly activated n‐type junctions in Ge. They rely on: non‐standard implantation schemes, ultra‐short annealing methods or relying on in situ doped epitaxial deposition.

Synthesis of Fe16N2 compound Free-Standing Foils with 20 MGOe Magnetic Energy Product by Nitrogen Ion-Implantation.

Rare-earth-free magnets are highly demanded by clean and renewable energy industries because of the supply constraints and environmental issues. A promising permanent magnet should possess high remanent magnetic flux density (Br), large coercivity (Hc) and hence large maximum magnetic energy product ((BH)max). Fe16N2 has been emerging as one of promising candidates because of the redundancy of Fe and N on the earth, its large magnetocrystalline anisotropy (Ku > 1.0 × 107 erg/cc), and large saturation magnetization (4πMs > 2.4 T). However, there is no report on the formation of Fe16N2 magnet with high Br and large Hc in bulk format before. In this paper, we successfully synthesize free-standing Fe16N2 foils with a coercivity of up to 1910 Oe and a magnetic energy product of up to 20 MGOe at room temperature. Nitrogen ion implantation is used as an alternative nitriding approach with the benefit of tunable implantation energy and fluence. An integrated synthesis technique is developed, including a direct foil-substrate bonding step, an ion implantation step and a two-step post-annealing process. With the tunable capability of the ion implantation fluence and energy, a microstructure with grain size 25–30 nm is constructed on the FeN foil sample with the implantation fluence of 5 × 1017/cm2.

Design and application of ion-implanted polySi passivating contacts for interdigitated back contact c-Si solar cells

Ion-implanted passivating contacts based on poly-crystalline silicon (polySi) are enabled by tunneling oxide, optimized, and used to fabricate interdigitated back contact (IBC) solar cells. Both n-type (phosphorous doped) and p-type (boron doped) passivating contacts are fabricated by ion-implantation of intrinsic polySi layers deposited via low-pressure chemical vapor deposition and subsequently annealed. The impact of doping profile on the passivation quality of the polySi doped contacts is studied for both polarities. It was found that an excellent surface passivation could be obtained by confining as much as possible the implanted-and-activated dopants within the polySi layers. The doping profile in the polySi was controlled by modifying the polySi thickness, the energy and dose of ion-implantation, and the temperature and time of annealing. An implied open-circuit voltage of 721 mV for n-type and 692 mV for p-type passivating contacts was achieved. Besides the high passivating quality, the developed passivating contacts exhibit reasonable high conductivity (Rsh n-type = 95 Ω/□ and Rsh p-type = 120 Ω/□). An efficiency of 19.2% (Voc = 673 mV, Jsc = 38.0 mA/cm2, FF = 75.2%, and pseudo-FF = 83.2%) was achieved on a front-textured IBC solar cell with polySi passivating contacts as both back surface field and emitter. By improving the front-side passivation, a VOC of 696 mV was also measured.

Impact of carbon co-implantation on boron distribution and activation in silicon studied by atom probe tomography and spreading resistance measurements

The impact of carbon (C) co-implantation on boron (B) activation in crystalline silicon was investigated. The detailed distribution of B and C atoms and B activation ratios dependent on the C ion-implantation energies were examined based on three-dimensional spatial mappings of B and C obtained by atom probe tomography and from depth profiles of their concentrations from secondary ion mass spectrometry and depth profiles of carrier concentrations with spreading resistance measurements. At all C implantation energies (8, 15, and 30 keV), B out-diffusion during activation annealing was reduced, so that more B atoms were observed in the C co-implanted samples. The carrier concentration was decreased throughout the entire implanted region for C implantation energies of 15 and 30 keV, although it was only increased at greater depths for C co-implantation at 8 keV. Two different effects of C co-implantation, (I) reduction of B out-diffusion and (II) influence of B activation, were confirmed.

Influence of dispersion of ion irradiation D + on distribution of deuterium in titanium

In single crystals of titanium was studied deuterium segregation induced by ion irradiation. Segregation created at room temperature deuterium ion implantation energy of 700 keV and analyzed by the nuclear reaction D (d, p) T. During the experiment changed the duration of continuous exposure and the duration of stops. It was found that with increasing radiation dose continuous average concentration of the implant in the irradiated volume gradually increases. It has been found that a long interruption of ion bombardment leads to an abrupt increase of the concentration. Analysis of the depth distribution of deuterium showed that during stopping the accumulation of radiation near the surface of the implant due to the redistribution of the target volume. The obtained results are discussed in terms of the evolution of the defect structure of the target in the course of continuous exposure and stop time of implantation.

Attainment of dual-band edge work function by using a single metal gate and single high-k dielectric via ion implantation for HP CMOS device

Attainment of dual band-edge effective work functions by using a single metal gate and single high k gate dielectric via P/BF2 implantation into a TiN metal gate for HP HKMG CMOS device applications are investigated under a gate-last process flow for the first time. The flat band voltage (VFB) modulations of about −750mV/570mV for N-/P-type MOS device with P/BF2 implanted TiN/HfO2/ILSiO2 gate stack are obtained respectively in the experiment range. Suitable low threshold voltages of CMOSFETs are gotten while simultaneously shrinking the EOT. The effects of P/BF2 ion implantation energy, dose and TiN gate thickness on the properties of implanted TiN/HfO2/ILSiO2 gate stack are studied, the possible mechanisms are discussed. This technique has been successfully integrated into the fabrications of aggressively scaled HP HKMG CMOSFETs and 32 CMOS frequency dividers under a gate-last process flow.

Modeling of Inner Surface Modification of a Cylindrical Tube by Plasma-Based Low-Energy Ion Implantation**supported by National Natural Science Foundation of China (Nos. 50725519, 51271048, 51321004)

The inner surface modification process by plasma-based low-energy ion implantation (PBLEII) with an electron cyclotron resonance (ECR) microwave plasma source located at the central axis of a cylindrical tube is modeled to optimize the low-energy ion implantation parameters for industrial applications. In this paper, a magnetized plasma diffusion fluid model has been established to describe the plasma nonuniformity caused by plasma diffusion under an axial magnetic field during the pulse-off time of low pulsed negative bias. Using this plasma density distribution as the initial condition, a sheath collisional fluid model is built up to describe the sheath evolution and ion implantation during the pulse-on time. The plasma nonuniformity at the end of the pulse-off time is more apparent along the radial direction compared with that in the axial direction due to the geometry of the linear plasma source in the center and the difference between perpendicular and parallel plasma diffusion coefficients with respect to the magnetic field. The normalized nitrogen plasma densities on the inner and outer surfaces of the tube are observed to be about 0.39 and 0.24, respectively, of which the value is 1 at the central plasma source. After a 5 μs pulse-on time, in the area less than 2 cm from the end of the tube, the nitrogen ion implantation energy decreases from 1.5 keV to 1.3 keV and the ion implantation angle increases from several degrees to more than 40°; both variations reduce the nitrogen ion implantation depth. However, the nitrogen ion implantation dose peaks of about 2×1010 – 7×1010 ions/cm2 in this area are 2 – 4 times higher than that of 1.18×1010 ions/cm2 and 1.63×1010 ions/cm2 on the inner and outer surfaces of the tube. The sufficient ion implantation dose ensures an acceptable modification effect near the end of the tube under the low energy and large angle conditions for nitrogen ion implantation, because the modification effect is mainly determined by the ion implantation dose, just as the mass transfer process in PBLEII is dominated by low-energy ion implantation and thermal diffusion. Therefore, a comparatively uniform surface modification by the low-energy nitrogen ion implantation is achieved along the cylindrical tube on both the inner and outer surfaces.

Modeling of Ion Implantation and Rapid Thermal Treatments during the Formation of Active Regions of Submicron and Nanometer Silicon IС

The physical models and numerical algorithms allowing one to accurately simulate advanced technological processes, such as low−energy ion implantation and rapid thermal processing (RTA) are presented. A software system on the basis of these models has been designed and integrated into the microelectronics device and process modeling system Silvaco ATHENA. It enables the use of models and calculation methods alternative to those implemented in the well−known software products, mainly for solving the problems with shallow depths of doped regions

Heated ion implantation for high-performance and highly reliable silicon-on-insulator complementary metal–oxide–silicon fin field-effect transistors

We have investigated the impact of heated ion implantation (I/I) on the performance and reliability of silicon-on-insulator (SOI) complementary metal–oxide–silicon (CMOS) fin field-effect transistors (FinFETs). An implantation temperature equal to and higher than 400 °C is needed to maintain the crystallinity of the Si substrate during I/I within the experimental conditions of ion species, implantation energy, and ion dose in this study. By heated I/I at 500 °C, the 11-nm-thick SOI layer perfectly maintains the crystallinity even after I/I, and a defect-free crystal is obtained by activation annealing. It was clarified that the cap layer is essential for the suppression of the out-diffusion during heated I/I. Heated I/I on the source and drain improves the on-current–off-current (Ion–Ioff), threshold voltage (Vth) variability, and bias temperature instability (BTI) characteristics of nMOS and pMOS FinFETs as compared with those after room-temperature I/I.

Metallic Nano Particles Embedded in Sapphire

ABSTRACTSapphire is best known for its hardness that makes it ideal for many mechanical and optical applications, but its resistance to radiation damage and its optical properties, combined with metallic nano-particles, make it promising for future opto-electronic and plasmonic devices. In this paper, we present an overview of our work on the fabrication of metallic nano-particles embedded in synthetic sapphire by means of ion implantation, thermal annealing and high energy ion irradiation. We show that we can have control over the amount and size of the nano particles formed inside the matrix by carefully choosing the parameters during the preparation process. Furthermore, we show that anisotropic nano particles can be obtained by an adequate high energy ion irradiation of the originally spherical nano particles. We also have studied the linear and non-linear optical properties of these nano-composites and have confirmed that they are large enough for future applications.

Swelling of ion-irradiated 3C–SiC characterized by synchrotron radiation based XRD and TEM

An experimental technique was established to characterize irradiation-induced volume swelling through a combined utilization of synchrotron radiation-based X-ray diffraction (XRD) and transmission electron microscopy (TEM). 3C–SiC specimens were irradiated by Si2+ ions (5MeV) with fluences up to 5×1017ion/cm2 at 1000°C. In order to avoid the accumulation of implanted Si ions in the SiC layer, specific thicknesses of the epitaxy layer and implanted ion energy were chosen. Unresolvable black spot defects were studied by TEM, and the average size and density were calculated. XRD radial scan results of surface (002), (111), (022), (113), and (200) including peak shift and asymmetry peak broadening were observed. Different interplanar spacing information of single crystal SiC can be obtained from this XRD measurement method, making it possible to investigate the lattice expansion and volume swelling more precisely. While TEM provided a direct visualization of the microstructures and the interplanar spacing was measured from HRTEM images. It is suggested that irradiation induced point defects and compressive stress from the Si substrate were the cause of anisotropic (a=b<c) volume swelling of irradiated 3C–SiC in this study.

Observation of point defect injection from electrical deactivation of arsenic ultra‐shallow distributions formed by ultra‐low energy ion implantation and laser sub‐melt annealing

AbstractThe stability and the evolution of electrical properties of high concentration arsenic ultra‐shallow junctions in silicon have been studied with regard to their effect on the evolution of point defects. The activation of 2 keV 1 × 1015 cm‐2 As implants was performed using millisecond sub‐melt laser annealing at two different temperatures, 1100 and 1300 °C. The electrical deactivation upon subsequent thermal treatment at 700 °C was indirectly monitored through the diffusion of five 10 nm‐wide boron layers aimed to detect the injection of self‐interstitials coming from dopant clustering. Thermal treatments were repeated on samples implanted with Ge at condition similar to the As ones. The comparison helped to discriminate between interstitials coming from lattice damage evolution and dopant clustering. The results show the relevance of the laser annealing temperature in order to ensure junction stability in terms of active carrier concentration and junction depth. (© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Influence of titanium ion implantation on nucleation of diamond films on tungsten carbide

Diamond film has been deposited on substrate of cobalt cemented tungsten carbide (WC–Co). An exploration is carried out to reveal effect of Ti ion implantation and ion implantation energy on the diamond nucleation and growth on tungsten carbide. Diamond nucleation density is enhanced with Ti ion implantation and a dense nucleation belongs to a sample at 35 kV. A diamond film growing subsequently consists of oriented diamond crystals with columnar structure and such crystals uniformly distribute and grow well on tungsten carbide.

X-Ray Induced Depth Profiling of Ion Implantations into Various Semiconductor Materials

The continuing shrinking of the component dimensions in ULSI technology requires junction depths in the 20-nm regime and below to avoid leakage currents. These ultra shallow dopant distributions can be formed by ultra-low energy (ULE) ion implantation. However, accurate measurement techniques for ultra-shallow dopant profiles are required in order to characterize ULE implantation and the necessary rapid thermal annealing (RTA) processes.

A mathematical model for void evolution in silicon by helium implantation and subsequent annealing process

We propose a physically based model that describes the diameter and the density of voids in silicon introduced via high dose helium ion implantation and subsequent annealing. The model takes into account interactions between vacancies, interstitials, small vacancy clusters, and voids. Void evolution in silicon occurs mainly by a migration and coalescence process. Various factors such as implantation energy and dose, anneal temperature, atmospheric pressure, and impurity level in silicon can influence the migration and coalescence mechanism and thus play a role in the void evolution process. Values for model parameters are consistent with known values for point defect parameters and assumed diffusion limited reaction rates. A single “fitting parameter” represents the rate of cavity migration and coalescence and is, therefore, related to surface diffusion of adatoms. Results obtained from simulations based upon the model were compared to our experimental results and to previously reported experimental results obtained over a wide range of conditions. Data from the literature included experiments with helium ion implantation energies in the range 30–300 keV, doses of 1 × 1016−1 × 1017 cm−2, subsequent annealing temperatures in the range 700–1200 °C, and annealing duration in the range 15 min–2 h. Excellent agreement is found between the simulated results and those from reported experiments. The extracted migration and coalescence rate parameter show an activation energy consistent with surface diffusivity of silicon. It shows a linear dependence on helium dose, and increases with decreased implantation energy, decreased ambient pressure, decreased substrate impurities, increased temperature ramp rate, or increased Ge fraction in cavity layer, all consistent with the proposed physical mechanism.

Structure and phase transformations caused by oxygen ion implantation into titanium

Secondary-ion mass spectrometry and transmission electron microscopy are used to investigate structural changes and phase transformations during 16O and 18O ion implantation into titanium at 100 and 300 K. For all implanted ion energies, there are the doses (saturation doses) after which the interstitial oxygen profile takes a final steady-state shape. The steady-state profile corresponds to a definite stable set of oxide phases, including TiO, rutile TiO2, and TiO1.5 layers. Under steady-state conditions, the film is composed of several oxide phases, whose structures depend on the target temperatures used in the irradiation process. At 100 K, the steady-state oxide system contains an amorphous phase layer with gas-filled bubbles instead of crystalline rutile.

Variation in the electrical properties of 100 V/100 a rated mesh and stripe TDMOSFETs (Trench Double-Diffused MOSFETs) for motor drive applications

The vertical power metal-oxide semiconductor field-effect transistors (MOSFETs) with deep trench structures are the most promising candidates to overcome the trade-off relationship between the ON-resistance (RON) and the blocking voltage (BVDS). Especially, 100 V/100 A rated trench power MOSFETs are used in components of many power systems, such as motors and LED lighting drive ICs, DC-DC converters in electric vehicles, and so on. In this work, we studied variations of the electrical characteristics, such as threshold voltage (VTH), BVDS, and drain current drivability, with p-well doping concentration via the SILVACO simulator. From simulation results, we found the BVDS and the drain current (ID) as functions of the p-well doping concentration at an ion implantation energy of 80 keV. With increasing of p-well doping concentration in the guard ring region, both VTH and BVDS slowly increased, but ID decreased, because the boron lateral diffusion during the fabrication process below gate trench region affected the doping concentration of the p-body at the active region. Additionally, 100 V/100 A rated trench double-diffused MOSFETs (TDMOSFETs) with meshes and stripes were successfully developed by using a silicon deep etching process. The variations in the electrical properties, such as VTH, BVDS, and drain current drivability, of the two different kinds of fabricated devices, with cell design and density in TDMOSFETs were also studied. The BVDS and the VTH in the stripe-type TDMOSFET were 110 and 3 V, respectively. However, the VTH of mesh-type device was smaller 0.5 V than that of stripe-type because of corner effect. The BVDS improved about 20 V compared to stripe-type TDMOSFET due to edge termination, and the maximum drain current (ID.MAX) was improved by about 10% due to an increase in the gate width at the same chip size. These effects were reflected in devices with different cell densities. When the cell density was increased, however, the increase in the drain current density changed due to mobility degradation cause by increase in the temperature of the device during high-power operation.

Production of Nitrogen-Doped Graphene by Low-Energy Nitrogen Implantation

Nitrogen doping of graphene is a suitable route to tune the electronic structure of graphene, leading to n-type conductive materials. Herein, we report a simple way to insert nitrogen atoms into graphene by low-energy nitrogen bombardment, forming nitrogen-doped graphene. The formation of nitrogen-doped graphene is investigated with high resolution X-ray photoelectron spectroscopy, allowing to determine the doping level and to identify two different carbon–nitrogen species. By application of different ion implantation energies and times, we demonstrate that a doping level of up to 0.05 monolayers is achievable and that the branching ratio of the two nitrogen species can be varied.

Corrosion properties of stainless steel 316 L after energetic nitrogen insertion

Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz regime, a more efficient nitriding process is possible than with either pulsed plasma immersion ion implantation (PIII) or continuous low energy ion implantation (LEII). Using such an experimental setup, it is shown that the pulse length modulation (PLM) itself produces a slight beneficial effect on the corrosion behaviour of austenitic stainless steel 316L at 400°C. However, differences in the diffusion and phase formation exist. For 5% PLM, a lower nitrogen flux resulted in the formation of expanded austenite with a very low lattice expansion, while the highest PLM (40%) led to a reduced layer thickness caused by higher sputtering induced by the increased ion bombardment itself. Nitriding at 400°C increases the corrosion resistance of 316L stainless steel for all PLM. The effect is more pronounced for 15 and 30% PLM