Ion Energy Flux Research Articles

Observations of Significant Ion Energy Outflows Associated With Cusp Ion Outflows and the Role of Poynting Flux as an Energy Source

AbstractThe cusp ion outflow on Earth has been extensively studied for decades. However, the energy flux associated with the ion outflow, which is of equivalent importance to the number flux or mass flux, has been rarely studied. Here, we present the first systematic study on the cusp ion energy flux and the energy budget along the cusp magnetic flux tube using quasi‐conjunction observations from the Polar and Fast satellites. Significant ion energy fluxes (several 10s mW/ mapped to 100 km altitude) away from the Earth are frequently observed in the mid‐altitude cusp (3–6 Re). Observations at low altitudes (2 Re) show that the upward ion energy flux is associated with ion outflows originating from the ionosphere. In addition, we show that the ion outflows experience intense energization well above the ionosphere. The only possible energy source for this energization is the earthward Poynting flux in mid‐altitude. The electrons are accelerated downward and are another energy sink (not source). The altitude profile of the energy fluxes suggests a transition region between 2 and 4 Re where both ion heating and electron acceleration primarily occur and where significant Poynting flux is dissipated. Analysis of the E/B ratio shows that the Poynting flux is carried by both the Alfven waves and quasi‐static structures. The above results place important constraints on possible local ion energization mechanisms.

Nonlinear gyrokinetic modelling of high confinement negative triangularity plasmas

Nonlinear gyrokinetic simulations correctly predict particle as well as ion and electron energy fluxes of high confinement plasmas with a negative triangularity cross sectional shape, showing that core transport in these plasmas is well described by standard gyrokinetic models. Experimentally inferred power balance fluxes are mostly reproduced within one standard deviation across a wide portion of the minor radius. Experimental conditions are reproduced by ion scale simulations, without the need to include density and temperature profile curvature effects. The experimental case is used as baseline to predict that the non-dimensional confinement scaling in negative triangularity plasmas increases strongly with plasma current while slightly degrading at increasing normalized pressure and decreasing collisionality. Recent experiments showed that low toroidal rotation negatively impacts confinement; consistent with the experiment, simulations predict that low rotational shear significantly affects confinement unless the plasma effective charge is maintained above a minimum level. Core confinement is predicted to significantly degrade in low aspect ratio devices.

PLASMA PARAMETRS AND SILICON ETCHING KINETICS IN CF4 + C4F8 + O2 MIXTURE: EFFECT OF CF4/C4F8 MIXING RATIO

In this work, we investigated the influence of fluorocarbon component ratio in the CF4 + C4F8 + O2 gas mixture on electro-physical plasma parameters, steady-state densities of active species and silicon etching kinetics under typical reactive-ion process conditions. The combination of plasma diagnostics (double Langmuir probes, optical emission spectroscopy) and plasma modeling confirmed known peculiarities of plasma chemistry of individual fluorocarbons in the presence of oxygen as well as provided an extended analysis of both fluorine and oxygen atom kinetics in the three-component gas mixture. It was shown that the substitution of CF4 by C4F8 at the constant fraction of O2 a) causes the weak disturbance in electrons- and ions-related plasma parameters (electron temperature, electron density, ion energy flux); b) provides drastically increasing density of polymerizing CFx (x = 1, 2) radicals; and c) results in monotonically decreasing F atoms density. The latter is due to simultaneous changes in both F atom formation rate and their loss frequency, especially in C4F8-rich plasmas. From experiments, it was found that Si etching rate is by more than 85% controlled by its chemical component (in a form of ion-stimulated heterogeneous reaction Si + xF → SiFx) and decreases with increasing C4F8 fraction in a feed gas. The change in effective reaction probability contradicts with the growth of polymer deposition rate and film thickness (as it follows from changes in gas-phase plasma characteristics) but may reflect the weakening of surface passivation by oxygen atoms. For citation: Efremov A.M., Bobylev A.V., Kwon K.-H. Plasma parametrs and silicon etching kinetics in CF4 + C4F8 + O2 mixture: effect of CF4/C4F8 mixing ratio. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 6. P. 29-37. DOI: 10.6060/ivkkt.20246706.6982.

The Phenomenon of a Cathode Spot in an Electrical Arc: The Current Understanding of the Mechanism of Cathode Heating and Plasma Generation

A vacuum arc is an electrical discharge, in which the current is supported by localized cathode heating and plasma generation in minute regions at the cathode surface called cathode spots. Cathode spots produce a metallic plasma jet used in many applications (microelectronics, space thrusters, film deposition, etc.). Nevertheless, the cathode spot is a problematic and unique subject. For a long time, the mechanisms of spot initiation, time development, instability, high mobility, and behavior in magnetic fields have been described by approaches that caused some controversy. These spot characteristics were discussed in numerous publications over many years. The obscurity and confusion of different studies created the impression that the cathode spot is a mysterious phenomenon. In the present work, a number of typical representative publications are reviewed with the intention of clarifying problems and contradictions. Two main theories of cathodic arcs are presented along with an analysis of the experimental data. One of the approaches illustrates the cathode heating by Joule energy dissipation (volume heat source, a sharp rise in current density, etc.), nearly constant cathode potential drop, and other certain initial conditions. On the other hand, a study using a mathematically closed approach shows that the spot initiation and development are determined not by electron emission current rise but by a rise in arc power density, affecting heat sources including the energy of ion flux to the cathode (surface heat source).

Effects of magnetic field gradient on capacitively coupled plasma driven by tailored voltage waveforms

This study utilized one-dimensional implicit particle-in-cell/Monte Carlo collision simulations to investigate the impact of different harmonic numbers and magnetic field strengths on capacitive-coupled argon plasma. Under the conditions of a pressure of 50 mTorr and a voltage of 100 V, simulations were conducted for magnetic field strengths of 0 and 100 G, magnetic field gradients of 10–40, 10–60, 10–80, 10–100, and 100–10 G, as well as discharge scenarios with harmonic numbers ranging from 1 to 5. Through in-depth analysis of the results, it was observed that the combined effect of positive magnetic field gradients and harmonic numbers can significantly enhance plasma density and self-bias properties to a greater extent. As the magnetic field gradient increases, the combined effect also increases, while an increase in harmonic numbers weakens the combined effect. Furthermore, this combined effect expands the range of control over ion bombardment energy. This provides a new research direction for improving control over ion energy and ion flux in capacitive-coupled plasmas.

The Effect of Fast Solar Wind on Ion Distribution Downstream of Earth’s Bow Shock

The solar wind gets thermalized and compressed when crossing a planetary bow shock, forming the magnetosheath. The angle between the upstream magnetic field and the shock normal vector separates the quasi-parallel from the quasi-perpendicular magnetosheath, significantly influencing the physical conditions in these regions. A reliable classification between both magnetosheath regions is of utmost importance since different phenomena and physical processes take place on each. The complexity of this classification is increased due to the origin and variability of the solar wind. Using measurements from the Time History of Events and Macroscale Interactions during Substorms mission and OMNI data between 2008 and 2023, we demonstrate the importance of magnetosheath classification across various solar wind plasma origins. We focus on investigating the ion energy fluxes in the high-energy range for each solar wind type, which typically serves as an indicator for foreshock activity and thus separating the quasi-parallel from quasi-perpendicular magnetosheath. Dividing the data set into different regimes reveals that fast solar wind plasma originating from coronal holes causes exceptionally high-energy ion fluxes even in the quasi-perpendicular environment. This stands in stark contrast to all other solar wind types, highlighting that magnetosheath classification is inherently biased if not all types of solar wind are considered in the classification. Combining knowledge of solar wind origins and structures with shock and magnetosheath research thus contributes to an improved magnetosheath characterization. This is particularly valuable in big-data machine-learning applications within heliophysics, which requires clean and verified data sets for optimal performance.

Deposition processes of superhard diamond-like carbon films co-adjusted by ion energy and ion flux in arc discharges

As a kind of protective material, Diamond-Like Carbon (DLC) film can effectively improve the mechanical and tribological properties of the substrate surface. In DLC family, tetrahedral amorphous carbon (ta-C) with ultra-high hardness and excellent protective properties has been widely concerned in the field of hard protective materials. It is well known that the structure and properties of ta-C are strongly dependent on carbon plasma characteristics in the plasma environment. Therefore, it is extremely crucial to obtain the optimal process window of ta-C described by plasma micro-parameters with general significance. This paper proposed the Langmuir probe was used to diagnose the carbon plasma of the afterglow generated by arc evaporation, aiming to investigate the characteristics of carbon plasma and sheath. The effect of ion energy and ion flux adjusted by the pulse bias voltage and arc current on the sp3 hybrid bonds and hardness of DLC films was studied, aiming to find out which conditions satisfied the formation of ta-C. The results showed the microstructure and properties of DLC films were co-adjusted by ion energy and ion flux. When the carbon ions met the appropriate ion energy range (50–300 eV) and low ion flux (<8.99 × 1010 cm−2 s−1), the films tended to form ta-C structures with high sp3 bonds. However, under the condition of high ion energy and high ion flux, the structure of the films changed from sp3 bonds to sp2 bonds, resulting in the graphitization and formation of DLC films with high sp2 bonds. This work will provide new solutions to guide the design and acquisition of high-performance DLC films.

Hybrid simulation of radio frequency biased inductively coupled Ar/O&lt;sub&gt;2&lt;/sub&gt;/Cl&lt;sub&gt;2&lt;/sub&gt; plasmas

In the etching process, a bias source is usually applied to the substrate of the inductively coupled plasma (ICP) to realize independent modulation of the ion energy and ion flux. In this work, a hybrid model, i.e. a global model combined bi-directionally with a fluid sheath model, is employed to investigate the plasma properties and ion energy distribution function (IEDF) in biased inductively coupled Ar/O&lt;sub&gt;2&lt;/sub&gt;/Cl&lt;sub&gt;2&lt;/sub&gt; plasmas. The results indicate that at a bias frequency of 2.26 MHz, the Cl&lt;sup&gt;–&lt;/sup&gt; ion density and ClO&lt;sup&gt;+&lt;/sup&gt; ion density first increase with bias voltage rising, and then they decrease, and finally they rise again, which is different from the densities of other charged species, such as O and Cl atoms. At the bias frequency of 13.56 MHz and 27.12 MHz, except Cl&lt;sup&gt;–&lt;/sup&gt; and &lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}$ {\text{Cl}}_2^ + $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231369_M3.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231369_M3.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; ions, the evolutions of other species densities with bias voltage are similar to the results at lower bias frequency. The evolution of the species densities with bias frequency depends on the bias voltage. For instance, in the low bias voltage range (&lt; 200 V), the densities of charges species, O and Cl atoms increase with bias frequency increasing due to a significant increase in the heating of the plasma by the bias source. However, when the bias voltage is high, say, higher than 300 V, except &lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}$ {\text{Cl}}_2^ + $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231369_M4.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231369_M4.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; and Cl&lt;sup&gt;–&lt;/sup&gt; ions, the densities of other charged species, O and Cl atoms first decrease with bias frequency increasing and then they increase due to a decrease and then an increase in the heating of the plasma by the bias source. In addition, as the bias frequency increases, the peak separation of IEDF becomes narrow, the high energy peak and low energy peak approach each other and they almost merge into one peak at high bias frequency. The results obtained in this work are of significant importance in improving the etching process.

Energy transport analysis of NSTX plasmas with the TGLF turbulent and NEO neoclassical transport models

This work presents a study of plasma transport at low aspect ratio on the National Spherical Torus Experiment tokamak, where the turbulent and neoclassical energy fluxes calculated by the quasilinear Trapped Gyro Landau Fluid (TGLF) model and the multi species drift-kinetic Neoclassical solver (NEO) are validated against experimental data. The turbulent energy transport of two plasma discharges, one in the L-mode confinement regime and another in the H-mode regime, is dominated by electrostatic drift-wave instabilities, while the ion heat transport has a significant neoclassical contribution. The data analysis workflow is described in detail to understand how the variations of mapping and fitting of experimental data affect the power balance solution and subsequent flux-matching plasma profile predictions with the TGYRO solver. On average, the predicted plasma profiles are consistent with experimental data. However, the solutions are sensitive to various input parameters, including boundary conditions, and the electron-ion coupling. Linear gyrokinetic stability analysis demonstrates close agreement of the real frequencies of unstable modes between TGLF and CGYRO gyrokinetic simulations, but higher growth rates are predicted by TGLF, especially for the H-mode case. Estimates of the low-k modes’ contributions to the total flux are consistent with linear stability analysis and the E × B suppression of turbulence in TGLF simulations with the SAT1 saturation model, while the SAT2 saturation model over-predicts the low-k modes’ contribution in the H-mode case. Moreover, the results with SAT1 model are consistent with power balance analysis, which indicates only neoclassical ion energy fluxes inside ρ < 0.4 in the L-mode case and ρ⩽0.7 in the H-mode case. The presence of multi-scale turbulence and ion-scale driven zonal flow mixing effects are also observed in TGLF scans of the electron turbulent heat flux over a range of temperature gradients and the electron-ion temperature ratio, which could explain the strong model sensitivity to variations of input parameters.

Characterization of transversely confined electron beam-generated plasma using two-dimensional particle-in-cell simulations

Electron beam-generated plasmas (EBPs) have been used to modify the surface properties. In certain applications, EBPs are transversely confined and their properties are of value to the treatment. In this paper, the characteristics of an electron beam-generated argon plasma, confined within a narrow gap, are investigated using a two-dimensional particle-in-cell simulation. The employed particle-in-cell/Monte Carlo collision model accounts for the electron and ion kinetics, as well as collisions between electrons and the background gas, including the elastic scattering, excitation, and impact ionization. Our simulations reveal a strong correlation between the plasma density and the beam density within the plasma bulk. The excitation of obliquely growing waves is observed, which is found to have a significant impact on the transport of beam electrons, thereby leading to the non-uniformities of plasma density and electron temperature. Specifically, the obliquely growing waves increase the local plasma density while reducing the electron temperature. These contrasting effects compensate for each other, and therefore, to some extent, smooth out the distributions of ion flux and energy flux. We further examine the variations of plasma parameters with respect to the beam current density, beam energy, and gas pressure. Increasing the beam current density or decreasing the beam energy results in higher plasma density and electron temperature, while increasing pressure leads to a higher plasma density but electron temperature scarcely changes. Based on the simulation results, we propose an approach to achieve independent control of the ion flux and energy flux by adjusting beam current density, beam energy, and pressure.

Correspondence of Pi2 Pulsations, Aurora Luminosity, and Plasma Flux Fluctuation Near a Substorm Brightening Aurora: Arase Observations

AbstractAlthough many substorm‐related observations have been made, we still have limited insight into propagation of the plasma and field perturbations in Pi2 frequencies (∼7–25 mHz) in association with substorm aurora, particularly from the auroral source region in the inner magnetosphere to the ground. In this study, we present conjugate observations of a substorm brightening aurora using an all‐sky camera and an inner‐magnetospheric satellite Arase at L ∼ 5. A camera at Gakona (62.39°N, 214.78°E), Alaska, observed a substorm auroral brightening on 28 December 2018, and the footprint of the satellite was located just equatorward of the aurora. Around the timing of the auroral brightening, the satellite observed a series of quasi‐periodic variations in the electric and magnetic fields and in the energy flux of electrons and ions. We demonstrate that the diamagnetic variations of thermal pressure and medium‐energy ion energy flux in the inner magnetosphere show approximately one‐to‐one correspondence with the oscillations in luminosity of the substorm brightening aurora and high‐latitudinal Pi2 pulsations on the ground. We also found their anti‐correlation with low‐energy electrons. Cavity‐type Pi2 pulsations were observed at mid‐ and low‐latitudinal stations. Based on these observations, we suggest that a wave phenomenon in the substorm auroral source region, like ballooning type instability, play an important role in the development of substorm and related auroral brightening and high‐latitude Pi2, and that the variation of the auroral luminosity was directly driven by keV electrons which were modulated by Alfven waves in the inner magnetosphere.

Discharge characteristics of a low-pressure geometrically asymmetric cylindrical capacitively coupled plasma with an axisymmetric magnetic field

We investigate the discharge characteristics of a low-pressure geometrically asymmetric cylindrical capacitively coupled plasma discharge with an axisymmetric magnetic field generating an E × B drift in the azimuthal direction. Vital discharge parameters, including electron density, electron temperature, DC self-bias, and electron energy probability function (EEPF), are studied experimentally for different magnetic field strength (B) values. A transition in the plasma parameters is observed for a specific range of magnetic fields where the discharge is highly efficient with lower electron temperature. Outside this range of magnetic field, the plasma density drops, followed by an increase in the electron temperature. The observed behavior is attributed to the transition from geometrical asymmetry to magnetic field-associated symmetry due to reduced radial losses and plasma confinement in the peripheral region. The DC self-bias increases almost linearly from a large negative value to nearly zero, i.e., it turns into a symmetric discharge. The EEPF undergoes a transition from bi-Maxwellian for unmagnetized to Maxwellian at intermediate B and finally becomes a weakly bi-Maxwellian at higher values of B. The above transitions present a novel way to independently control the ion energy and ion flux in a cylindrical capacitively coupled plasma system using an axisymmetric magnetic field with an enhanced plasma density and lower electron temperature that is beneficial for plasma processing applications.

Gyrokinetic simulations of ion temperature gradient instability in deuterium–tritium plasma in the CFETR hybrid scenario

The linear instabilities and nonlinear transport driven by the ion temperature gradient (ITG) instability are numerically investigated in deuterium–tritium plasma in the CFETR hybrid scenario by using the NLT code. In both linear and nonlinear simulations, effects of the tritium fraction ɛT and the temperature ratio of deuterium and tritium τDT = TD/TT are studied, with TD and TT being the temperature of deuterium and tritium, respectively. Results from linear simulations illustrate that the ITG instability can be well stabilized as ɛT increases. When ɛT = 0.5, the maximum growth rate occurs at around τDT = 1.5. During the nonlinear simulations, the anomalous particle and energy flux in deuterium–tritium plasma are analyzed. For τDT = 1.0, it is found that the tritium (deuterium) particle flux is inward (outward) and the largest inward tritium particle flux appears at ɛT = 0.5. The total ion energy flux is found to be insensitive to ɛT. In the case with ɛT = 0.5, as τDT decreases from 3.0 to 0.5, the particle flux for tritium (deuterium) changes from the outward (inward) direction to the inward (outward) direction. The quasilinear analysis clarifies that the particle flux driven by the temperature gradient is the key part in determining the direction of the particle flux. Besides, the largest and the smallest energy flux appear at around τDT = 1.5 and 0.5, respectively. It is indicated that better energy confinement and better particle confinement for tritium could be realized by choosing smaller τDT (or higher TT).

Sputtering of amorphous Si by low-energy Ar+, Kr+, and Xe+ ions

Atomic layer plasma technologies require localizing ions' impact within nanometers up to an atomic layer. The possible way to achieve this is the decrease in the ion energy up to surface binding energy. At such low ion kinetic energies, the impact of different plasma effects, causing the surface modification, can be of the same order as kinetic ones. In this work, we studied the sputtering of amorphous silicon films by Ar+, Kr+, and Xe+ ions at energies of 20–200 eV under the low-pressure inductively coupled plasma discharge in pure argon, krypton, and xenon, respectively, at a plasma density of 1–1.5 × 1010 cm−3. Under the plasma conditions, a high asymmetry of discharge allowed to form ion flux energy distribution functions with narrow energy peak (5 ± 2 eV full width at half maximum). Real time in situ control over the ion composition and flux as well as the sputtering rate (the ratio of the film thickness change to the sputtering time) provided accurate determination of the sputtering yields Y(Ei). It is shown that at ion energy above ∼70 eV, the “classical” kinetic sputtering mechanism prevails. In this case, Y(Ei) grows rather rapidly with ion energy, increasing with the decrease in the ion mass: the closer the ion mass to the target atom mass, the higher the Y(Ei). Below 70 eV, the growth of Y(Ei) strongly slows down, with Y(20eV) being still high (&amp;gt;10−3), indicating the impact of plasma. The obtained trends of Y(Ei) are discussed in light of surface modification studied by atomic force microscopy and angular x-ray photoelectronic spectroscopy.

On the multi-scale dynamics and energy flow near reconnection regions in the magnetopause and magnetotail using the MMS, Cluster and THEMIS observations during the geomagnetic storm of 31 December 2015

Magnetic reconnection is a very important energy conversion process that plays a vital role in solar wind-magnetosphere coupling. This study presents a unique analysis of the coordinated observations from MMS, Cluster and THEMIS spacecraft during a geomagnetic storm on 31 December 2015. The analyses are aimed to understand the intricacies of the short-scale processes during 4 different short (20 min) encounters and a long duration (8 h) traversal of all the satellites covering the main and the recovery phase of the storm. The main results show that at the reconnection sites in the magnetotail, the FAC density is majorly contributed by the electrons moving anti-parallel to the magnetic field. Significantly, the FACs estimated from the Curlometer method and plasma (or local) method agree well and authenticate the interpretations. The majority of the electron population is found to shift towards the mid (0.2–2 keV) and high-energy (2–30 keV) range during the reconnection, wherein higher (∼one order more) ion and electron energy flux is observed under the effect of the intense storm compared to non-storm cases. The Hall electric field is found to be the major contributor to the total electric field during magnetic reconnection whereas, we observe the growing significance of the pressure divergence term during later phases of the storm. Longer duration (8-hour) continuous observations from the unique alignment of the four spacecrafts show a dominance of magnetic (plasma) properties over plasma (magnetic) properties in the magnetotail (magnetopause). The magnetotail (magnetopause) is found to be highly dynamic with higher (lower) levels of the electric and magnetic field, ion and electron temperature, and simultaneous lower (higher) levels of plasma density, energy flux, and FACs. The drastic enhancements of the plasma and field parameters happen in the sun-earth plane and during different crossings at the magnetopause and magnetotail. The simultaneous observations from magnetopause and magnetotail during a moderate geomagnetic storm indicate further needful coordinated investigations on the nature of reconnections on the day and night side and variations during the intense category of storms.

Investigation of the dual-frequency bias effect on inductively coupled Cl2 plasmas by hybrid simulation

In the etching process, a bias source is usually applied to the bottom electrode in inductively coupled plasmas (ICPs) to achieve independent control of the ion flux and ion energy. In this work, a hybrid model, which consists of a global model combined bi-directionally with a fluid sheath model, is employed to investigate the dual-frequency (DF) bias effect on the inductively coupled Cl2 plasmas under different pressures. The results indicate that the DC self-bias voltage developed on the biased electrode is approximately a linear function of the phase shift between the fundamental frequency and its second harmonic, and the value only varies slightly with pressure. Therefore, the ion energy on the bottom electrode can be modulated efficiently by the bias voltage waveform, i.e. the fluctuation of the ion energy with phase shift is about 40% for all pressures investigated. Besides, the ion energy and angular distribution functions (IEADFs) in DF biased inductive discharges is complicated, i.e. the IEADFs exhibits a four-peak structure under certain phase shift values. Although the species densities and ion fluxes also evolve with phase shift, the fluctuations are less obvious, especially for Cl2 + ions at low pressure. In conclusion, the independent control of the ion energy and ion flux are realized in DF biased ICPs, and the results obtained in this work are of significant importance for improving the etching process.

Numerical framework for multi-scale modeling planar DC magnetron sputtering

In this study, we propose a numerical framework for multi-scale modeling planar Direct Current (DC) magnetron sputtering for a single alloy target. In the model, we account for electromagnetics, fluid dynamics, discharge chemistry and thermal transport across multiple length scales. Specifically, we employ Lattice Boltzmann Method (LBM) for transport phenomena, Finite Elements Method (FEM) for magnetron discharge transport, and binary collision approximation Monte-Carlo method for sputtering and atomic deposition. Our modeling framework could predict the composition, uniformity, and deposition flux of deposited thin film alloys. Furthermore, the simulation also provides the information of plasma in the chamber such as electron, ion densities, argon ion energy and argon ion flux bombarding on the target. Through parametric analyses, we found that substrate film composition is scaled with both chamber pressure and inverse chamber temperature, although the effect of chamber temperature is considerably marginal under low pressure conditions. We also found that magnetic fields do not influence the film composition, but it significantly affects the substrate deposition flux and film uniformity. Our work provides useful insights to operational heuristics involved in magnetron sputtering and other physical chemical processes.

Ion kinetic energy- and ion flux-dependent mechanical properties and thermal stability of (Ti,Al)N thin films

Ion-irradiation-induced changes in structure, elastic properties, and thermal stability of metastable c-(Ti,Al)N thin films synthesized by high-power pulsed magnetron sputtering (HPPMS) and cathodic arc deposition (CAD) are systematically investigated by experiments and density functional theory (DFT) simulations. While films deposited by HPPMS show a random orientation at ion kinetic energies (Ek)>105 eV, an evolution towards (111) orientation is observed in CAD films for Ek>144 eV. The measured ion energy flux at the growing film surface is 3.3 times larger for CAD compared to HPPMS. Hence, it is inferred that formation of the strong (111) texture in CAD films is caused by the ion flux- and ion energy-induced strain energy minimization in defective c-(Ti,Al)N. The ion energy-dependent elastic modulus can be rationalized by considering the ion energy- and orientation-dependent formation of point defects from DFT predictions: The balancing effects of bombardment-induced Frenkel defects formation and the concurrent evolution of compressive intrinsic stress result in the apparent independence of the elastic modulus from Ek for HPPMS films without preferential orientation. However, an ion energy-dependent elastic modulus reduction of ∼18% for the CAD films can be understood by considering the 34% higher Frenkel pair concentration formed at Ek=182 eV upon irradiation of the experimentally observed (111)-oriented (Ti,Al)N in comparison to the (200)-configuration at similar Ek. Moreover, the effect of Frenkel pair concentration on the thermal stability of metastable c-(Ti,Al)N is investigated by differential scanning calorimetry: Ion-irradiation-induced increase in Frenkel pairs concentration retards the wurtzite formation temperature by up to 206 °C.

Control of the ion flux and energy distribution of dual-frequency capacitive RF plasmas by the variation of the driving voltages

Due to its advantages of spatial uniformity and ion energy control, a dual-frequency (DF) capacitive-coupled plasma is widely used in semiconductor etching and deposition processes. In low-pressure discharges, the mean free path of ions is longer than the sheath width, and the ion energy distribution function is sensitive to the driving voltage waveform. In this respect, it is necessary to use a particle-in-cell (PIC) simulation to observe ion movement according to the time-varying electric field in the sheath. This study uses a two-dimensional PIC simulation parallelized with a graphics processing unit to monitor the ion energy distribution and flux according to the DF voltage waveform. We suggested a method to control the ion energy through a phase-resolved ion energy distribution in the region, where the ion transit time is longer than the high-frequency period and shorter than the low-frequency period.

Wafer Type Ion Energy Monitoring Sensor for Plasma Diagnosis

We propose a wafer-type ion energy monitoring sensor (IEMS) that can measure the spatially resolved distribution of ion energy over the 150 mm plasma chamber for the in situ monitoring of the semiconductor fabrication process. The IEMS can directly be applied to the semiconductor chip production equipment without further modification of the automated wafer handling system. Thus, it can be adopted as an in situ data acquisition platform for plasma characterization inside the process chamber. To achieve ion energy measurement on the wafer-type sensor, the injected ion flux energy from the plasma sheath was converted into the induced currents on each electrode over the wafer-type sensor, and the generated currents from the ion injection were compared along the position of electrodes. The IEMS operates without problems in the plasma environment and has the same trends as the result predicted through the equation.