Light Ion Implantation Research Articles

Controlling Magneto‐Ionics by Defect Engineering Through Light Ion Implantation

Controlling Magneto‐Ionics by Defect Engineering Through Light Ion Implantation

Large enhancement of magnetic moment in nitridated CeFe12

Due to success of desired doping, ion implantation has been widely used for semiconductor processing. In this work, we used nitrogen ion implantation to enhance magnetism in CeFe12 epitaxial thin films. To optimize nitrogen contents in CeFe12 and minimize the damage caused by the high-energy ion beam, we varied the thickness of the capping Mo layer. The saturation magnetization increased nearly 25% by nitrogen ion implantation into CeFe12 thin film. This phenomenon is explained by density functional theory calculations and confirmed by the magnetic resonance technique. The ion implantation and design strategy can be used for light-ion implantation into lattices to modulate magnetic, optical, and electrical properties.

Effects of light-ion low-fluence implantation on the pressure response of double-walled carbon nanotubes

Low-fluence light-ion $(^{11}\mathrm{B}^{+})$ medium-energy (150 keV/ion) implantation preprocessing of double-walled carbon nanotubes (DWCNTs) has been effected to ``decorate'' them with defects. These are intended to serve as nucleation sites for potential $s{p}^{3}$ interlinking between tube walls in close proximity, following on strong deformation of the tube cross sections under cold compression to 20--25 GPa in diamond anvil cells. The pressure response of such implanted DWCNTs has been monitored in situ using Raman spectroscopy, and compared with those of unimplanted reference DWCNTs. Pressure dependences of the ${G}^{+}$ mode frequency and D to ${G}^{+}$ band intensity ratio, and radial breathing modes, have been monitored. These Raman signatures show that some degree of mechanical softening occurs in the implanted tube bundles, without major disruption to tube integrity in both samples. Consequently, the collapse pressure to racetrack or peanut shaped cross-sectional profiles is lowered substantially, from ${P}_{\mathrm{c}}\ensuremath{\sim}18\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ in the reference tube bundles to ${P}_{\mathrm{c}}\ensuremath{\sim}11\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ in the implanted case. Defect structures also proliferate more readily in the implanted sample under pressure. Therefore, the light-ion low-fluence implantation lowers the threshold pressure for deformation of tube cross sections to high-curvature profiles decorated with defects. Considerations of whether irreversible $s{p}^{3}$ interlinking at low volume fractions is discerned in the Raman data from implanted tube bundles under compression, and the stability of such bonding is discussed.

Simulation of Ion Paths in the Target Material for the Injection Complex of the BELA Facility

To realize the simulation experiments with the use of two ion beams at the injection complex of the BELA accelerator (Based on ECR ion source Linear Accelerator), it is necessary to determine the energy and irradiation angle of the beam of light ions which will be implanted into the region of radiation damage induced by heavy-ion beam. The depth of light-ion implantation is determined by the energy and kind of particles initiating the damage, as well as by their incidence angle. It is supposed that the incidence direction of heavy ions will coincide with the normal to the specimen surface. In our work, the necessary implantation zone for the iron ion beam with an energy of 3.2 MeV is located at depths of 300–800 nm. The simulation of the hydrogen and helium ion paths in the material of the iron target in the energy range from 150 to 600 keV at the angle to the normal from 0° to 65° is performed. The range of energies and irradiation angles for the hydrogen and helium ions are determined for the implantation into the radiation-induced defect-formation zone.

Modification mechanisms of silicon thin films in low-temperature hydrogen plasmas

To achieve quasi-atomic precision etching of thin film materials in advanced transistors, a method based on light ion implantation and consisting of two sequential steps—(1) surface modification in hydrogen ICP or CCP plasmas, and (2) selective removal of modified layers in wet solutions or remote plasmas—was recently proposed. In this paper, to better understand this process (called Smart Etch thereafter), molecular dynamics simulations are performed to study the modification of crystalline Si (1 0 0) substrates under low-energy (x = 1–3) ion implantation and mixed ion/H radical bombardment. In agreement with the experiments, simulations of (x = 1–3) ion bombardment of Si show a self-limited implantation with a surface evolution composed of two stages: a rapid volume modification (with no etching) followed by a slow saturation and the formation of a stable [a:Si–H] layer at a steady state. The mechanisms of ion-induced damage (Si–Si bond breaking, formation of H2 molecules, creation of SiHx groups) are investigated and allow us to bring new insights to both the well-known Smart Cut™ and more recent Smart Etch technologies. Si exposure to both ions and H radicals (H2 plasma) also shows a self-limited transformation but the modified layers are simultaneously etched during the implantation. Both the modified layer thickness and the ion dose required to reach the steady state increase with the ion energy. The ion composition and the radical-to-ion flux ratio (Γ) must be considered as well. In particular, the etch rate strongly increases with Γ, compromising even the possibility to achieve a Smart Etch of silicon.

Helium plasma modification of Si and Si3N4 thin films for advanced etch processes

To achieve the etching of silicon nitride spacers with a perfect anisotropy and an almost infinite selectivity, an alternative method consisting of two sequential steps—surface modification in hydrogen or helium plasma followed by the selective removal of modified layers in wet solutions or by exposure to gaseous reactants—was recently proposed. In this paper, molecular dynamics (MD) simulations of low-energy (5–250 eV) He+ bombardment on c-Si and amorphous Si3N4 surfaces are performed to understand all mechanisms driving the light ion implantation in this process. The modification of the Si and Si3N4 substrates with the ion dose is investigated, as well as their structure and composition at steady state. Simulations show a self-limited ion implantation with a surface evolution composed of two stages: a rapid volume transformation (with almost no sputtering) followed by a slow saturation and the formation of a stable He-implanted layer at steady state. The mechanisms of ion-induced damage (Si-Si or Si-N bond breaking, He trapping) induce the creation of a less dense modified layer, full of He-filled cavities and containing weaker bonds, which can facilitate its subsequent removal in a second step. The impact of the ion energy on the modified thickness and sputtering is studied. Finally, a comparison between MD and experiments performed on Si3N4 substrates is reported, showing a both qualitative and quantitative agreement.

Investigation of Surface Morphology of 6H-SiC Irradiated with He+ and H2+ Ions

Light ion implantation is one of the important procedures of smart cut for SiC-based semiconductor fabrication. This work investigated the surface morphologies and microstructures of single crystal 6H-SiC irradiated by one or both of H2+ and He+ ions at room temperature and then annealed at specific temperatures. Blisters evolved from the coalescence of H nanocracks were formed in the H2+ and He++H2+ irradiated sample surface, while circular ripples originated from the pressure release of helium bubbles after high temperature annealing were formed in the He+ irradiated sample surface. The lateral radius a of the blisters in the irradiated sample with low H2+ fluence was larger than that in the irradiated sample with high H2+ fluence and with He++H2+ ions. About 8–58% of implanted H atoms contributed to the formation of the blisters. Compared with other irradiated samples, the ratio of w0/a and the density of the blisters in the He++H2+ irradiated samples were largest. The stress field of the blisters was simulated using finite element method and the inner pressure in the blisters was also calculated. The corresponding mechanism was analyzed and discussed.

Applications of Nuclear and Particle Physics Technology: Particles & Detection — A Brief Overview

A brief overview of the technology applications with significant societal benefit that have their origins in nuclear and particle physics research is presented. It is shown through representative examples that applications of nuclear physics can be classified into two basic areas: 1) applying the results of experimental nuclear physics and 2) applying the tools of experimental nuclear physics. Examples of the application of the tools of experimental nuclear and particle physics research are provided in the fields of accelerator and detector based technologies namely synchrotron light sources, nuclear medicine, ion implantation and radiation therapy.

Deep level defects in 4H-SiC introduced by ion implantation: the role of single ion regime

We characterized intrinsic deep level defects created in ion collision cascades which were produced by patterned implantation of single accelerated 2.0 MeV He and 600 keV H ions into n-type 4H-SiC epitaxial layers using a fast-scanning reduced-rate ion microbeam. The initial deep level transient spectroscopy measurement performed on as-grown material in the temperature range 150–700 K revealed the presence of only two electron traps, Z1/2 (0.64 eV) and EH6/7 (1.84 eV) assigned to the two different charge state transitions of the isolated carbon vacancy, VC (=/0) and (0/+). C–V measurements of as-implanted samples revealed the increasing free carrier removal with larger ion fluence values, in particular at depth corresponding to a vicinity of the end of an ion range. The first DLTS measurement of as-implanted samples revealed formation of additional deep level defects labelled as ET1 (0.35 eV), ET2 (0.65 eV) and EH3 (1.06 eV) which were clearly distinguished from the presence of isolated carbon vacancies (Z1/2 and EH6/7 defects) in increased concentrations after implantations either by He or H ions. Repeated C–V measurements showed that a partial net free-carrier recovery occurred in as-implanted samples upon the low-temperature annealing following the first DLTS measurement. The second DLTS measurement revealed the almost complete removal of ET2 defect and the partial removal of EH3 defect, while the concentrations of Z1/2 and EH6/7 defects increased, due to the low temperature annealing up to 700 K accomplished during the first temperature scan. We concluded that the ET2 and EH3 defects: (i) act as majority carrier removal traps, (ii) exhibit a low thermal stability and (iii) can be related to the simple point-like defects introduced by light ion implantation, namely interstitials and/or complex of interstitials and vacancies in both carbon and silicon sub-lattices.

Silicon Nitride Spacer Etching with Nearly Atomic Precision for 2D and 3D Devices

With transistors size scaling down, device processing requirements become more and more stringent. For technology node beyond 14 nm, one of the most critical step is the spacer etching. It requires a perfect anisotropy (no CD loss) without damaging nor consumption of the exposed material like silicon, silicon germanium and oxide [1,2]. In planar transistor, the silicon or silicon germanium consumption is limited by the short over-etch process (30-50%). However for 3D devices, the silicon fin is directly exposed during the removal of the silicon nitride on the active area sidewalls. This is the major issue since in this case, important over etch is required (>200%) to fully remove the residues at the bottom of the fin. Therefore, the spacer etch is considered today as one of the most challenging etch process for 2D but more especially 3D devices. In this paper we propose to compare conventional etch process to new approaches to reach the stringent etch requirements for 2D and 3D devices. The first part of this study focuses on the characterization of CH2F2/O2/He/CH4 plasma performed in an Inductively-Coupled Plasma (ICP) etch tool. It was shown that playing on different parameters (bias, reagent, bias pulsing…) the maximum selectivity to silicon reached 13.5. In our experimental conditions, the lower Si consumption is estimated to 0.6 nm and 3 nm for 2D and 3D device applications. Whatever the operating plasma conditions, XPS analyses shown that selectivity to silicon has been explained by an oxide formation at the top of the silicon layer. A second part of the study will focus on an original approach for planar transistor application [3]. This approach consists in light ion implantation of hydrogen in the silicon nitride layer (in an inductively or capacitively-coupled plasma reactor), and then in a second step, in a highly selective removal process based on gaseous hydrofluoric acid (HF). Film modification and reaction with removal process have been understood thanks to XPS and infrared spectroscopy. In this part, the implanted material has been characterized and the chemical reactions with gaseous HF have been investigated. It has been pointed out that implantation proceeds by increasing the H bonding with N and Si atoms which allowed the selective reaction of gaseous HF with the damaged thickness by forming an hexafluorosilicate salt. This salt was then easily removable in an aqueous solution showing a clean surface after treatment. It has also been demonstrated that playing on the gaseous HF concentration inside the chamber improved the selectivity to non-implanted SiN and silicon dioxide up to 31 and 39 respectively. This method has been turned out to be an accurate method to etch silicon nitride with a nearly atomistic precision. A third part discusses about the spacer etching for 3D devices like FinFET or stacked nanowires. In this part, due to the complex architecture of patterns, the implantation has been performed thanks to ion implantation and a tilted angle has been used to target specific silicon nitride areas to remove. It will be shown that argon ion is the most suitable implant element for a fast etch of implanted SiN on blanket wafers and test are ongoing on pattern samples to validate the technique. [1] B. E. E. Kastenmeier, P. J. Matsuo, and G. S. Oehrlein, J. Vac. Sci. Technol. A 17 (6), 3179 (1999). [2] K. Eriguchi, Y. Nakakubo, A. Matsuda, Y. Katao, K. Ono, IEEE Electr. Device L. 30 (7), 712 (2009). [3] N. Posseme, O. Pollet, and S. Barnola, J. Appl. Phys. 105, 051605 (2014).

Understanding of a new approach for silicon nitride spacer etching using gaseous hydrofluoric acid after hydrogen ion implantation

Silicon nitride spacer etching is one of the most critical step for the fabrication of CMOS transistors in microelectronics. It is usually done by plasma etching using a fluorocarbon based chemistry. However, from the 14 nm technology node and beyond, this etching process no longer allows the etch specifications to be reached (nonformation of a foot, poor critical dimension control below 1 nm). To overcome this issue, a new process was developed. It consists of two steps: in a first step, the silicon nitride film is modified by light ion implantation (hydrogen), and then followed by a removal step of this modified film by hydrofluoric acid (HF). In this paper, the authors propose to remove the implanted/modified silicon nitride using gaseous HF and understand the associated etching mechanisms using infrared spectroscopy and x-ray photoelectron spectroscopy at different stages of the process sequence (after implantation/modification, gaseous HF process, and post-treatment).

Thin Layer Etching of Silicon Nitride: Comparison of Downstream Plasma, Liquid HF and Gaseous HF Processes for Selective Removal after Light Ion Implantation

For technology nodes beyond 14nm silicon nitride spacer etching has become a major challenge. Conventional plasma etching techniques based on CHF3/O2 cannot achieve thorough nitride removal on horizontal surfaces without inducing either CD loss or Si/SiGe source/drain recess. This leads to either gate leakage increase or poor raised source/drain epitaxy. To overcome atomic scale control issues faced with continuous plasma processes, several techniques aiming at achieving atomic layer etching or thin layer etching were recently described [1]. An original etching approach has been reported which consists in modifying the silicon nitride through H2 ion implantation by plasma (ICP or CCP) and then selectively removing the modified fraction of the layer thanks to chemical etching [2]. Layer modification depth is controlled thanks to plasma parameters (bias voltage and process time). This unconventional technique was demonstrated on 14nm FDSOI logic device and showed less than 1nm spacer CD loss, less than 0.6nm SiGe recess which enabled defect-free source/drain epitaxy [2]. Mechanisms for silicon nitride modifications and selective removal are discussed in this article by comparing downstream plasma, liquid-phase HF and gas-phase HF as removal techniques.

Surface modification of Nafion membranes by ion implantation to reduce methanol crossover in direct methanol fuel cells

The surface of Nafion membranes was modified by light ion implantation to reduce methanol crossover without affecting bulk membrane properties.

Analysis technique for ultra shallow junction using medium energy ion scattering time‐of‐flight elastic recoil detection analysis

An analysis technique for an ultra shallow junction in shrunk semiconductor devices was developed using medium energy ion scattering (MEIS) time‐of‐flight (TOF) elastic recoil detection analysis (ERDA). The energy of the recoiled and forward‐scattered ions was analyzed using a toroidal electrostatic analyzer with an energy resolution of less than 0.4 keV in MEIS‐ERDA. TOF was used for a mass separation in MEIS‐ERDA with high energy resolution, because an energy resolution of conventional ERDA with an absorber foil was degraded by the energy loss straggling on the foil. The probe beam of 100‐keV N+ was chopped by a function generator for the TOF measurement. Three standard samples of 2‐keV B+ implanted Si with doses of 0.5, 1.0, and 1.5 × 1016/cm2 were measured using MEIS‐TOF‐ERDA. The measured depth profile of the B+ implanted Si sample with a dose of 0.5 × 1016/cm2 was in good agreement with the simulated profile. The projected range and its straggling of 2‐keV B+ implantation into a Si substrate measured using MEIS‐TOF‐ERDA were 6.3 and 6.1 nm, respectively. The results indicated that an ultra shallow junction fabricated by low energy and light ion implantation can be analyzed using developed MEIS‐TOF‐ERDA. Copyright © 2014 John Wiley & Sons, Ltd.

Proposed mechanism to represent the suppression of dark current density by four orders with low energy light ion (H−) implantation in quaternary alloy-capped InAs/GaAs quantum dot infrared photodetectors

Here we propose a carrier transport mechanism for low energy H− ions implanted InAs/GaAs quantum dot infrared photodetectors supportive of the experimental results obtained. Dark current density suppression of up to four orders was observed in the implanted quantum dot infrared photodetectors, which further demonstrates that they are effectively operational. We concentrated on determining how defect-related material and structural changes attributed to implantation helped in dark current density reduction for InAs/GaAs quantum dot infrared photodetectors. This is the first study to report the electrical carrier transport mechanism of H− ion-implanted InAs/GaAs quantum dot infrared photodetectors.

More than one order enhancement in peak detectivity (D*) for quantum dot infrared photodetectors implanted with low energy light ions (H−)

In(Ga)As/GaAs-based quantum dot infrared photodetectors (QDIPs) have emerged as one of the most suitable devices for infrared detection. However, quantum dot devices suffer from lower efficiencies due to a low fill-factor (∼20%–25%) of dots. Here, we report a post-growth technique for improving the QDIP performance using low energy light ion (H−) implantation. At high bias, there is evidence of suppression in the field-assisted tunneling component of the dark current. Enhancement in peak detectivity (D*), a measure of the signal-to-noise ratio, by more than one order, from ∼109 to 2.44 × 1010 cm Hz1/2/W was obtained from the implanted devices.

Heterogeneous Integration of Compound Semiconductors

The ability to tailor compound semiconductors and to integrate them onto foreign substrates can lead to superior or novel functionalities with a potential impact on various areas in electronics, optoelectronics, spintronics, biosensing, and photovoltaics. This review provides a brief description of different approaches to achieve this heterogeneous integration, with an emphasis on the ion-cut process, also known commercially as the Smart-Cut™ process. This process combines semiconductor wafer bonding and undercutting using defect engineering by light ion implantation. Bulk-quality heterostructures frequently unattainable by direct epitaxial growth can be produced, provided that a list of technical criteria is fulfilled, thus offering an additional degree of freedom in the design and fabrication of heterogeneous and flexible devices. Ion cutting is a generic process that can be employed to split and transfer fine monocrystalline layers from various crystals. Materials and engineering issues as well as our current understanding of the underlying physics involved in its application to cleaving thin layers from freestanding GaN, InP, and GaAs wafers are presented.

Optical waveguides obtained by swift-ion irradiation on silica ( a-SiO 2)

The preparation of optical waveguides for visible light in silica ( a-SiO 2) by means of swift heavy-ion irradiation (F at 5 MeV, Cl at 20 MeV) is reported. They originate from the refractive index enhancement (compaction) brought about by the electronic excitation. Their main features are discussed in relation to those prepared by light ion irradiation (H, He) and implantation. In particular, irradiation fluences to achieve waveguiding may be considerably reduced. On the other hand, the measured refractive index profiles have been used to discuss the mechanisms of electronic damage. Moreover, the measurement of the index profiles provides a novel optical method, alternative to IR spectroscopy, to estimate the radius of the irradiation-induced tracks.

High resolution fluorescence imaging of damage regions in H+ ion implanted Nd:MgO:LiNbO3 channel waveguides

We report on the fluorescence imaging of channel waveguides fabricated by light ion (H+) implantation in neodymium (Nd) doped MgO:LiNbO3 crystals. The spectroscopic properties of Nd ions have been found to be modified only at the nuclear damage region while remaining unaltered at the electronic one. The fluorescence image of the light ion implanted waveguide has been found to be completely different from that obtained by medium-mass ion implantation, revealing the different waveguide formation mechanisms taking place in each case.

Extended Defects Created by Light Ion Implantation in Ge

The effect of the implantation temperature in the range room temperature - 300oC has been studied in hydrogen and helium implanted germanium at high fluence and in the energy range of few tens of keV with either conventional implantation or plasma based ion implantation. The microstructure of the as-implanted Ge samples has been studied by Grazing Incidence Small-Angle X-ray Scattering and/or Transmission Electron Microscopy. For H-implanted Ge, small (001) and {111} platelets and {113} defects are nucleated at RT. With increasing the implantation temperature, microcracks, cavities and plate-like cavity clusters are created as well. The formation of these types of defects is ascribed to the interplay between dynamic and kinetic effects occurring during the implantation. As for He implanted Ge, a continuous cavity layer is formed whatever the implantation temperature in the range studied.