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Hydrocarbon contamination is associated with light transmission losses in modern lithography machines, which contain extreme-ultraviolet-induced plasma. A volume-averaged global and deposition/etch surface model of a reference hydrogen/methane inductive discharge is developed to investigate the plasma–surface interactions. The simulation results are validated against a wide variety of experiments and verified with respect to multiple sets of computational data. The deposition rate is calculated for a variation in methane impurity (10–10 000 ppm), power, pressure, and net mass flow. The simulations conclude that the hydrocarbon plasma deposition can be minimized by reducing methane impurity and excluding solid organic structures. [ABSTRACT FROM AUTHOR]

Hydrogen is often envisioned as a green fuel and energy carrier. However, a greenhouse gas‐free production method is still needed for this purpose. A promising method is the pyrolysis of methane. In this study, we present the three‐dimensional simulation of methane pyrolysis in a microwave plasma torch operated in an argon–methane mixture. Due to the high gas temperatures, the chemistry is dominated by reactions between neutral particles. Therefore, the plasma is treated only as a heat source using space‐resolved gas temperature measurements as input. The end‐of‐pipe results of the simulation are compared to measured values, showing good agreement for methane conversion. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) etching of materials by plasmas is an ultimate challenge in microstructuring applications. A method is proposed to reach a controllable 3D structure by using masks in front of the surface in a plasma etch reactor in combination with local magnetic fields to steer the incident ions in the plasma sheath region toward the surface to reach 3D directionality during etching and deposition. This effect has the potential to be controlled by modifying the magnetic field and/or plasma properties to adjust the relationship between sheath thickness and mask feature size. However, because the guiding length scale is the plasma sheath thickness, which for typical plasma densities is at least tens of micrometers or larger, controlled directional etching and deposition target the field of microstructuring, e.g., of solids for sensors, optics, or microfluidics. In this proof-of-concept study, it is shown that E → × B → drifts tailor the local sheath expansion, thereby controlling the plasma density distribution and the transport when the plasma penetrates the mask during an RF cycle. This modified local plasma creates a 3D etch profile. This is shown experimentally as well as using 2d3v particle-in-cell/Monte Carlo collisions simulation. [ABSTRACT FROM AUTHOR]

This feature article presents recent results on the analysis of plasma/polymer interactions and the nucleation of ultra‐thin plasma films on polymeric substrates. Because of their high importance for the understanding of such processes, in situ analytical approaches of the plasma volume as well as the plasma/substrate interfaces are introduced before the findings on plasma surface chemistry. The plasma activation of polymeric substrates is divided into the understanding of fundamental processes on model substrates and the relevance of polymer surface complexity. Concerning thin film nucleation and growth, both plasma‐enhanced chemical vapor deposition and plasma‐enhanced atomic layer deposition processes as well as the combination of both processes are considered both for model substrates and technical polymers. Based on the comprehensive presentation of recent results, selective perspectives of this research field are discussed. [ABSTRACT FROM AUTHOR]

Zirconia layers are often used as thermal barriers. In recent years, depositions by chemical vapor deposition methods using a metalorganic precursor (MOCVD) have been primarily investigated. Here, we combine MOCVD with plasma activation ‐ plasma‐enhanced chemical vapor deposition (PECVD]) ‐ of the gas phase and/or the growth surface to lower the growth temperature and to allow for a flexible coating design. PECVD causes the precursor to be transformed into a chemically active species, yielding thin films with a five times higher sticking coefficient compared to MOCVD. This leads to the onset of crystallization at lower surface temperatures. Carbon is incorporated at oxygen sites, so that the crystalline structure of zirconia is preserved, but the electrical conductivity is affected. The thermal conductivity is like that of pure zirconia. [ABSTRACT FROM AUTHOR]

Large language models (LLMs) like ChatGPT have the potential to revolutionize research by aiding in literature searches, data analysis, and programming tasks. LLMs can efficiently gather and filter relevant information from the internet, making them useful for interdisciplinary fields like plasma research. They can also accelerate data analysis and generate readable scientific texts. However, LLMs have limitations, such as the potential to amplify wrong statements and produce incorrect or oversimplified explanations. In plasma research, where knowledge is limited and interdisciplinary, it is crucial for scientists to use multiple sources and critically assess information. LLMs also pose challenges for scientific journals, as they can lead to the reproduction of known information and an increase in published papers. The integration of LLMs into the scientific community's workflow will require the input and guidance of critical scientists. [Extracted from the article]

Correlatively employing density functional theory and experiments congregated around high power pulsed magnetron sputtering, a plasma-surface model for metastable Cr0.8Al0.2N (space group Fm3...m) is developed. This plasma-surface model relates plasma energetics with film composition, crystal structure, mass density, stress state, and elastic properties. It is predicted that N Frenkel pairs form during Cr0.8Al0.2N growth due to high-energy ion irradiation, yielding a mass density of 5.69 g cm-3 at room temperature and Young’s modulus of 358–130 GPa in the temperature range of 50–700K for the stress-free state and about 150 GPa larger values for the compressive stress of 4 GPa. Our measurements are consistent with the quantum mechanical predictions within 5% for the mass density and 3% for Young’s modulus. The hypothesis of a stress-induced Young’s modulus change may at least in part explain the spread in the reported elasticity data ranging from 250 to 420 GPa. [ABSTRACT FROM AUTHOR]

In-vacuum characterization of magnetron targets after High Power Impulse Magnetron Sputtering (HiPIMS) has been performed by X-ray photoelectron spectroscopy (XPS). Al-Cr composite targets (circular, 50mm diameter) mounted in two different geometries were investigated: an Al target with a small Cr disk embedded at the racetrack position and a Cr target with a small Al disk embedded at the racetrack position. The HiPIMS discharge and the target surface composition were characterized in parallel for low, intermediate, and high power conditions, thus covering both the Ar-dominated and the metal-dominated HiPIMS regimes. The HiPIMS plasma was investigated using optical emission spectroscopy and fast imaging using a CCD camera; the spatially resolved XPS surface characterization was performed after in-vacuum transfer of the magnetron target to the XPS chamber. This parallel evaluation showed that (i) target redeposition of sputtered species was markedly more effective for Cr atoms than for Al atoms; (ii) oxidation at the target racetrack was observed even though the discharge ran in pure Ar gas without O2 admixture, the oxidation depended on the discharge power and target composition; and (iii) a bright emission spot fixed on top of the inserted Cr disk appeared for high power conditions. [ABSTRACT FROM AUTHOR]

Spokes are patterns of increased light emission, observed to rotate in front of the targets of magnetron sputtering discharges. They move through the plasma at velocities of several km sâˆ'1 in or against the E â†' Ă— B â†' direction of the discharge. The high velocity and their initial creation at arbitrary positions render measurements of spokes challenging. For more demanding plasma diagnostic techniques that require data acquisition over multiple discharge pulses, synchronisation to the spoke movement is necessary. In this publication, we present optical emission spectroscopy of spokes in both high power impulse magnetron sputtering (HiPIMS) as well as direct current magnetron sputtering (DCMS) discharges, performed by triggering a camera on the spoke movement. Optical filters between plasma and camera allow us to isolate emission lines of metal and working gas neutrals and ions. Based on these optical measurements and previous probe studies, the dynamics of electrons drifting through spokes in both DCMS and HiPIMS is discussed. In HiPIMS, the much shorter mean free path for inelastic electron collisions enables strong ionisation inside the spoke, causing a sudden variation in electron density which leads to the distinct spoke shape. In contrast, the spoke shape for DCMS discharges seems to rather be indicative of electron energy variations. [ABSTRACT FROM AUTHOR]

The elementary surface processes occurring on chromium targets exposed to reactive plasmas have been mimicked in beam experiments by using quantified fluxes of Ar ions (400–800 eV) and oxygen atoms and molecules. For this, quartz crystal microbalances were previously coated with Cr thin films by means of high-power pulsed magnetron sputtering. The measured growth and etching rates were fitted by flux balance equations, which provided sputter yields of around 0.05 for the compound phase and a sticking coefficient of O2 of 0.38 on the bare Cr surface. Further fitted parameters were the oxygen implantation efficiency and the density of oxidation sites at the surface. The increase in site density with a factor 4 at early phases of reactive sputtering is identified as a relevant mechanism of Cr oxidation. This ion-enhanced oxygen uptake can be attributed to Cr surface roughening and knock-on implantation of oxygen atoms deeper into the target. This work, besides providing fundamental data to control oxidation state of Cr targets, shows that the extended Berg's model constitutes a robust set of rate equations suitable to describe reactive magnetron sputtering of metals. [ABSTRACT FROM AUTHOR]

Al2O3 thin films have been deposited at substrate temperatures between 500 °C and 600 °C by reactive magnetron sputtering using an additional arbitrary substrate bias to tailor the energy distribution of the incident ions. The films were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The film structure being amorphous, nanocrystalline, or crystalline was correlated with characteristic ion energy distributions. The evolving crystalline structure is connected with different levels of displacements per atom (dpa) in the growing film as being derived from TRIM simulations. The boundary between the formation of crystalline films and amorphous or nanocrystalline films was at 0.8 dpa for a substrate temperature of 500 °C. This threshold shifts to 0.6 dpa for films grown at 550 °C. [ABSTRACT FROM AUTHOR]

Particle beam experiments were conducted in an ultra-high-vacuum vessel to mimic target poisoning during reactive magnetron sputtering of aluminum. Aluminum targets were exposed to quantified beams of argon ions, oxygen atoms and molecules, and aluminum vapour. The growth and etch rates were measured in situ by means of an Al-coated quartz crystal microbalance. The chemical state of the target surface was monitored in-situ by real-time Fourier transform infrared spectroscopy. The surface processes were modelled through a set of balance equations providing sputter yields and sticking coefficients. The results indicate that the oxygen uptake of the aluminum surface is enhanced by a factor 1 to 2 by knock-on implantation and that the deposition of aluminum is not affected by the oxidation state of the surface. [ABSTRACT FROM AUTHOR]

Plasma deposition of aluminum oxide by reactive magnetron sputtering (RMS) using an aluminum target and argon and oxygen as working gases is an important technological process. The undesired oxidation of the target itself, however, causes the so-called target poisoning, which leads to strong hysteresis effects during RMS operation. The oxidation occurs by chemisorption of oxygen atoms and molecules with a simultaneous ion bombardment being present. This heterogenous surface reaction is studied in a quantified particle beam experiment employing beams of oxygen molecules and argon ions impinging onto an aluminum-coated quartz microbalance. The oxidation and/or sputtering rates are measured with this microbalance and the resulting oxide layers are analyzed by x-ray photoelectron spectroscopy. The sticking coefficient of oxygen molecules is determined to 0.015 in the zero coverage limit. The sputtering yields of pure aluminum by argon ions are determined to 0.4, 0.62, and 0.8 at 200, 300, and 400 eV. The variation in the effective sticking coefficient and sputtering yield during the combined impact of argon ions and oxygen molecules is modeled with a set of rate equations. A good agreement is achieved if one postulates an ion-induced surface activation process, which facilitates oxygen chemisorption. This process may be identified with knock-on implantation of surface-bonded oxygen, with an electric-field-driven in-diffusion of oxygen or with an ion-enhanced surface activation process. Based on these fundamental processes, a robust set of balance equations is proposed to describe target poisoning effects in RMS. [ABSTRACT FROM AUTHOR]

The roughness evolution during plasma deposition of amorphous hydrogenated carbon (a-C:H) films is investigated. Films were deposited from an inductively coupled methane plasma using a wide range of process parameters. Plasma deposition is uniquely described by the dissipated energy per source gas molecule Emean. Depending on Emean, a specific set of radicals contributes to film growth causing a characteristic roughness development. The film roughness is measured using atomic force microscopy and spectroscopic ellipsometry and is expressed using the static and dynamic scaling coefficients α and β, respectively. For low Emean<20 eV, α∼0.65 and β∼0.19 indicating film deposition via a growth precursor with a large surface diffusion length. For Emean>20 eV, α∼0.9 and β∼0.25 indicating film deposition via a growth precursor with a small surface diffusion length. [ABSTRACT FROM AUTHOR]

The temperature dependence of the interaction of methyl radicals with the surface of a hard, amorphous hydrogenated carbon film is investigated using in situ real-time ellipsometry and infrared spectroscopy. This interaction is considered as an important process during plasma deposition of polymer-like hydrocarbon films or formation of polycrystalline diamond in methane-containing discharges. At room temperature CH[sub 3] adsorbs at sp²-coordinated CC bonds at the physical surface of the hard C:H film and forms a completely sp³-hybridized C:H adsorbate with a thickness of ∼0.17 nm. In the following, steady-state film growth is observed with a sticking coefficient of s(CH3)= 10[sup -4]. At a substrate temperature of T= 570 K, incident CH[sub 3] causes net erosion with an etching yield of Y(CH[sub 3])= 10[sup -4]. At temperatures above 650 K the sticking coefficient of CH[sub 3] becomes positive again, leading to a graphite-like C:H adsorbate. CH[sub 3] adsorption is described by a reaction scheme based on the creation of dangling bonds at the film surface via abstraction of surface-bonded hydrogen by incoming CH[sub 3] radicals. These dangling bonds act as CH3 adsorption sites at room temperature or as a precursor for chemical erosion at elevated temperature. [ABSTRACT FROM AUTHOR]