Inductively Coupled Plasma Reactor Research Articles

Effect of coil and chamber structure on plasma radial uniformity in radio frequency inductively coupled plasma

Enhancing plasma uniformity can be achieved by modifying coil and chamber structures in radio frequency inductively coupled plasma (ICP) to meet the demand for large-area and uniformly distributed plasma in industrial manufacturing. This study utilized a two-dimensional self-consistent fluid model to investigate how different coil configurations and chamber aspect ratios affect the radial uniformity of plasma in radio frequency ICP. The findings indicate that optimizing the radial spacing of the coil enhances plasma uniformity but with a reduction in electron density. Furthermore, optimizing the coil within the ICP reactor, using the interior point method in the Interior Point Optimizer significantly enhances plasma uniformity, elevating it from 56% to 96% within the range of the model sizes. Additionally, when the chamber aspect ratio k changes from 2.8 to 4.7, the plasma distribution changes from a center-high to a saddle-shaped distribution. Moreover, the plasma uniformity becomes worse. Finally, adjusting process parameters, such as increasing source power and gas pressure, can enhance plasma uniformity. These findings contribute to optimizing the etching process by improving plasma radial uniformity.

Numerical simulation of inductively coupled Ar/O<sub>2</sub> plasma

In the inductively coupled plasma (ICP) discharge, surface processes, such as reflection, de-excitation, and recombination, can occur when active species arrive at material surfaces, which accordingly influences the plasma properties. In this work, a fluid model is used to study the Ar/O<sub>2</sub> plasma generated by ICP reactors made of different materials. In simulation, sticking coefficient is employed to estimate the surface reactions on different materials. As the reactor material changes from stainless steel to anodized aluminum to Cu, the sticking coefficient of surface reaction O→1/2O<sub>2</sub> decreases accordingly. It is found that the reactor material has a great effect on species density. In the stainless steel reactor, the density of O atoms at grounded state and excited state are much lower because more O<sub>2</sub> molecules are generated from the surface reaction, yielding a much higher density of <inline-formula><tex-math id="M5">\begin{document}$ {\text{O}}_2^ + $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M5.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M5.png"/></alternatives></inline-formula> molecular ions which are mainly created from the ionization process of O<sub>2</sub> molecules. Similarly, the high density of O<sub>2</sub> molecules also enhances the production of <inline-formula><tex-math id="M6">\begin{document}${{{\mathrm{O}}} _2}\left( {{{\mathrm{a}}^1}{\Delta _{\mathrm{g}}}} \right)$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M6.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M6.png"/></alternatives></inline-formula> molecules through the excitation process and O<sup>–</sup> ions through the dissociation attachment reaction. On the contrary, more electrons are consumed via the collisions between electrons and O<sub>2</sub> molecules or <inline-formula><tex-math id="M7">\begin{document}$ {\text{O}}_2^ + $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M7.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M7.png"/></alternatives></inline-formula> molecular ions. Therefore, the electron density obtained in the Cu reactor is highest. The density of Ar<sup>+</sup> ions and Ar<sub>m</sub> atoms also increase with sticking coefficient decreasing. The density of O<sup>+</sup> ions and <inline-formula><tex-math id="M8">\begin{document}$ {\text{O}}_2^ + $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M8.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M8.png"/></alternatives></inline-formula> molecular ions peak below the coil in the stainless steel reactor, whereas the radial uniformities are improved in the Cu reactor. In the three reactors, the electrons distribute evenly at the reactor center region. The O density and <inline-formula><tex-math id="M9">\begin{document}${{{\mathrm{O}}} _2}\left( {{{\mathrm{a}}^1}{\Delta _{\mathrm{g}}}} \right)$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M9.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240436_M9.png"/></alternatives></inline-formula> density significantly peak at the reactor center, while the maximum value of Ar<sup>+</sup> density and Ar<sub>m</sub> density are below the coil. As for O(<sup>1</sup>D), the maximum density below the coil region moves toward the reactor center as the reactor material changes from stainless steel to Cu. Finally, the effect of sticking coefficient of O→1/2O<sub>2</sub> is studied. The results show that the O atom density decreases with the sticking coefficient increasing, but the opposite trend is observed in O<sub>2</sub> molecular density. It is noticed that the sticking coefficient has little effect on species density when it is higher than 0.5.

Numerical modeling of a hydrogenated silicon inductively coupled plasma discharge (SiH4/H2/Ar)

In favor of the global manufacturing industry, recent developments in plasma processing technology are of great importance, especially in semiconductor manufacturing processes. Mainly when plasma discharge studies are required. In our work, we have studied the properties of 2D numerical modeling of the deposition of thin films based on silicon diluted with argon and hydrogen SiH4/H2/Ar in an inductively coupled plasma (ICP) reactor operating at low pressure within a range of 0.5 to 1 Torr and a low temperature of about 500 K; in addition to, a qualitative study of the highest influencing parameters on the deposit. The plasma discharge in this reactor is fed by a radio frequency source; whose working frequency is of the order of 13.56 MHz, is modeled by a fluid approach that describes the plasma in terms of macroscopic quantity; assuming a specific form of the distribution function and taking the velocity moments of the Boltzmann equation coupled with the maxwell equations. This results in a set of coupled partial differential equations that can be solved using the finite element method until a steady state is obtained. The results obtained show the evolution of the fundamental characteristics of the plasma discharge in an ICP reactor, giving a compromise between a high electron density and a low temperature at the surface which improves the deposition of thin-film silicon, to achieve a more efficient and less financially demanding deposition while preserving the surface from deterioration.

Etching of iron and iron–chromium alloys using ICP-RIE chlorine plasma

The dry etching process of Fe, Cr and Fe–Cr alloys under a chlorine-based plasma is studied. The objective is to create new surface functionalities. The approach combines an experimental study of an ICP (Inductively Coupled Plasma) reactor with the development of a multi-scale etching model including kinetic, sheath and surface models. The results from plasma etching of substrates made of Fe, Cr and Fe–Cr alloys are presented. Optical emission spectroscopy and interferometry measurements show strong modifications of the plasma when Fe or Cr samples are present in the reactor. It is shown that Fe is easier to etch than Cr. The study highlights the role of chemical etching by the formation of volatile products such as FeCl3. The Cr content in Fe–Cr alloys has a strong impact on both the lateral and vertical etch rates, as well as on the roughness along the profile. For Fe-Cr alloys, the experimental and calculated values of etch rate are very similar. The concept of hard zones is introduced to get a better agreement between simulation results and experimental ones. This good agreement demonstrates the capability of the developed simulator to implement new phenomena.

Comprehensive Data Collection Device for Plasma Equipment Intelligence Studies

In this study, various diagnostic tools were constructed and plasma factors measured to evaluate the intelligence of plasma process equipment. We used an ICP (Inductively Coupled Plasma) reactor with a radio frequency (RF) power of 13.56 MHz, a power of 400 to 800 W, and a pressure of 10 to 30 mTorr. Plasma parameters such as electron density (ne), electron temperature (Te), plasma potential (Vp), and floating potential (Vf) were measured using several instruments (VI probe and mass/energy analyzer, etc.) and subsequently analyzed. Regression analysis was performed to correlate the measured data with the plasma parameters. As a result, the plasma density (ne) and temperature (Te) were observed to be in good agreement with the non-invasive measurement results. In particular, the VI probes were highly correlated with almost all the measured plasma parameters. Therefore, the results of this study provide a basis for the estimation of plasma parameters using non-invasive measurement techniques.

Surface composition and micromasking effect during the etching of amorphous Ge-Sb-Se thin films in SF6 and SF6/Ar plasmas

A functional waveguide for photonic applications must fulfil some specific requirements in terms of dimension, shape, etch rate and roughness. In this study, Ge-Sb-Se thin films were etched using an Inductively Coupled Plasma reactor via fluorine-based chemistry. In a SF6 plasma, etch rate and roughness highlight a micro masking effect which originates from the formation of SbF3, (Se)-Sb-Fx and (Sb)-Se-F environments. The latter have been identified with in situ XPS. Systematically, a SF6 plasma is associated with a quasi-isotropic profile and a rough surface. In a SF6/Ar plasma, the impact of pressure and the argon content has been investigated. The addition of argon affects directly the fluorine atom flux and the argon atom flux which were calculated using a global model. It was found that there is a strong coherence between the fluorine atom flux, the proportion of fluorine at the surface and the RMS roughness. A synergistic effect, between ion bombardment and reactive neutral species, is observed when varying both parameters. Surface is free of fluorinated products for a high percentage of argon (95%) and low-pressures (<4mTorr). A smooth surface and a quasi-vertical profile were achieved in a SF6/Ar plasma with a gas mixture ratio 5/95 and at a pressure of 1.5 mTorr.

Control of ion-flux and ion-energy in direct inductively coupled plasma reactor for interfacial-mixing plasma-enhanced atomic layer deposition

The effects of low-energy (&amp;lt;15 eV) high-flux O2+ ion bombardment on the properties of Al2O3 films deposited on 3D nanostructures by plasma-enhanced atomic layer deposition (PE-ALD) were investigated. High-dose O2+ ion bombardment (&amp;gt;1017 cm−2 cycle−1) during the oxidation steps caused interfacial mixing, and AlSiOx films with abrupt interfaces were formed on Si surfaces. Interfacially mixed AlSiOx films were selectively formed on single-crystal Si, amorphous Si, and degraded SiO2 surfaces, whereas normal ALD Al2O3 films were formed on thermally grown SiO2 surfaces. At the same time, the interfacially mixed AlSiOx films were selectively formed on the horizontal top and bottom faces of the 3D nanostructures, whereas normal ALD Al2O3 films were formed on the vertical sidewalls. The morphology and thickness of the film deposited on the amorphous Si surface were the same as those on the single-crystal Si surface. The interfacially mixed AlSiOx film possessed rough surface morphology and a layered structure of Al-/Si-/Al-rich AlSiOx layers. The low-energy high-flux O2+ ion bombardment condition required for the interfacial-mixing ALD was realized in a direct inductively coupled plasma (ICP) reactor with a self-resonant planar coil, in which high-density plasma was excited near the substrate. The O2+ ion flux was found to be controllable over a wide range through variation in the O2 pressure. The ratio of O2+ ion flux at 0.01 Torr to that at 1 Torr was 289. The steep decrease of the ion flux with increasing pressure was attributed to the decrease of electron density in the upstream plasma for intensifying electron energy loss and the decrease of the ambipolar diffusion coefficient in the downstream plasma. A comparison of electron densities near the substrate and those at the presheath edge calculated from measured positive ion fluxes using the Bohm criterion revealed that negative ions, which significantly affect the positive ion flux, scarcely exist near the substrate. The interfacial-mixing PE-ALD has the potential to realize area-selective and topographically selective depositions, which are key technologies for fabricating next-generation electronic devices with 3D nanostructures. The direct ICP reactor is suitable for realizing selective deposition using the interfacial-mixing ALD.

Role of sulfur in catalyzing fluorine atom fast etching of silicon with smooth surface morphology

Chemical reaction probabilities, defined as the number of silicon atoms removed per incident fluorine atom, have been investigated in mixtures of NF3 and SF6 plasmas in an inductively-coupled plasma reactor. Fluorine atom densities were measured by optical emission actinometry, and isotropic etching rates were measured by the degree of undercutting of SiO2-masked silicon by cross-sectional scanning electron microscopy. In addition, atomic force microscopy was used to examine surface morphology of etched Si surfaces. The F atom reaction probabilities derived from isotropic etching rates indicate an ∼30-fold higher reaction probability in SF6 plasmas compared with values in NF3 plasmas. Surfaces etched in SF6 plasmas were much smoother than those etched in NF3 plasmas. The addition of only 10% SF6 to an NF3 plasma produced a much higher reaction probability (∼5-fold) than in a pure NF3 plasma. This surprising enhancement of reaction probabilities for F with Si in SF6 plasmas is further investigated, based on the mechanism of adsorbed sulfur acting as a catalyst to greatly enhance the etching rate of Si. Dilute sulfur solutions in isopropyl alcohol were allowed to evaporate on the masked Si samples, depositing sulfur in relatively high concentrations near mask edges in ∼2 μm diameter periodic “strings of beads.” The sulfur-dosed sample etched several times faster at the center of each bead than a sample not exposed to sulfur that was placed side by side. The catalytic effect of sulfur is ascribed to an enhanced F sticking coefficient and/or decreased desorption rate on a surface covered with sulfur.

Design and optimization of an ICP reactor with planar antenna as a driver in ISTAPHM and validation of AMPICP model

The present work is related to the method for designing a driver for low pressure plasma sources using the AMPICP model. Particularly, it is related to equipment for producing plasma, which can be used for driver of the simulator project (ISTAPHM) of the interactions between ICRF antenna and plasma on Tokamak Nuclear Fusion Reactors. Here, two important aspects of this modeling are discussed: firstly, optimization of geometrical parameters for driver of source plasma in ISTAPHM and secondly, Simulation and computation of the EM fields adjusted for a planar antenna (PA) of driver. The work is focused on the characterization of low pressure Inductively Coupled Plasma (ICP) source and the features of a helicon chamber. Numerical simulations of ICP with PA were presented to optimize the plasma characteristics. The results of the AMPICP model for designing of ICP reactor as the driver in ISTAPHM were also evaluated using the power balance model. This paper also presents a two dimensional simulation for the EM field inside the ICP reactor for homogeneous plasma and compares the optimized and laboratory results with each other. From the measurements of the magnetic field inside the reactor using a magnetic probe, the electron number density and effective collision frequency can be estimated. The form of magnetic field lines inside the vessel was investigated and theoretical field lines were presented in the paper. The results of analyses as a function of operating parameters were presented to be measured with fixed and movable Langmuir probes. Optical Emission Spectra were recorded for different gas flow rates and filling pressures at constant power level by spectrometer. The variation in the intensity ratio of the selected emission lines, electron temperature and density was studied as a function of gas flow rate and filling pressure.

Finite-element analysis of the effect of sheath-gas composition in an inductively-coupled plasma

The sheath gas plays an important role in inductively-coupled plasmas (ICPs) in preventing thermal damage to the side wall of the torch. The sheath gas (hydrogen in our case) is more difficult to ionise than argon (the main plasma gas) due to its lower electrical conductivity at the working temperature, preventing plasma formation and concomitant high temperatures in the immediate vicinity of the torch inside wall. The sheath gas also has a higher flow rate, reducing the time for heat transfer from the plasma to the inside wall. Numerous models to simulate an ICP reactor have been published in the open literature, none of which take into account the effect of characteristics of the sheath gas on the performance of an ICP on the heat transfer from the plasma to the sidewall of the reactor. The H2:Ar gas ratio can have severely detrimental effects on the efficiency of the plasma because of the higher ionisation potential of H2. Excess hydrogen in the sheath gas may also constitute material wastefulness. Both of these factors have an implication on the economics of the plasma process. This research aims at finding the optimum sheath-gas flow for the Necsa torch, used for spheroidisation. The work was done on the commercial finite-element programme COMSOL Multiphysics.

Influence of a centered dielectric tube on inductively coupled plasma source: Chamber structures and plasma characteristics**Project supported by the National Natural Science Foundation of China (Grant Nos. 11305028, 11305032, and 11320101005).

A high-density RF ion source is an essential part of a neutral beam injector. In this study, the authors attempt to retrofit an original regular RF ion source reactor by inserting a thin dielectric tube through the symmetric axis of the discharge chamber. With the aid of this inner tube, the reactor is capable of generating a radial magnetic field instead of the original transverse magnetic field, which solves the E × B drift problem in the current RF ion source structure. To study the disturbance of the dielectric tube, a fluid model is introduced to study the plasma parameters with or without the internal dielectric tube, based on the inductively coupled plasma (ICP) reactor. The simulation results show that while introducing the internal dielectric tube into the ICP reactor, both the plasma density and plasma potential have minor influence during the discharge process, and there is good uniformity at the extraction region. The influence of the control parameters reveals that the plasma densities at the extraction region decrease first and subsequently slow down while enhancing the diffusion region.

Protein retention on plasma-treated hierarchical nanoscale gold-silver platform.

Dense arrays of gold-supported silver nanowires of about 100 nm in diameter grown directly in the channels of nanoporous aluminium oxide membrane were fabricated and tested as a novel platform for the immobilization and retention of BSA proteins in the microbial-protective environments. Additional treatment of the silver nanowires using low-temperature plasmas in the inductively-coupled plasma reactor and an atmospheric-pressure plasma jet have demonstrated that the morphology of the nanowire array can be controlled and the amount of the retained protein may be increased due to the plasma effect. A combination of the neutral gold sublayer with the antimicrobial properties of silver nanowires could significantly enhance the efficiency of the platforms used in various biotechnological processes.

Cryogenic etching of silicon with SF6 inductively coupled plasmas: a combined modelling and experimental study

A hybrid Monte Carlo—fluid model is applied to simulate the wafer-temperature-dependent etching of silicon with SF6 inductively coupled plasmas (ICP). The bulk plasma within the ICP reactor volume as well as the surface reactions occurring at the wafer are self-consistently described. The calculated etch rates are validated by experiments. The calculations and experiments are performed at two different wafer temperatures, i.e. 300 and 173 K, resembling conventional etching and cryoetching, respectively. In the case of cryoetching, a physisorbed SFx layer (x = 0–6) is formed on the wafer, which is negligible at room temperature, because of fast thermal desorption, However, even in the case of cryoetching, this layer can easily be disintegrated by low-energy ions, so it does not affect the etch rates. In the investigated pressure range of 1–9 Pa, the etch rate is always slightly higher at cryogenic conditions, both in the experiments and in the model, and this could be explained in the model due to a local cooling of the gas above the wafer, making the gas denser and increasing the flux of reactive neutrals, like F and F2, towards the wafer.

Low Temperature Nitriding of 304 Austenitic Stainless Steel Using RF-ICP Method: the Role of Ion Beam Flux Density

The significant role of ion beam flux during nitriding 304 austenitic stainless steel has been investigated by using a radio frequency inductively-coupled plasma reactor into which a sample with negative bias voltage was inserted. A milliammeter is used to detect the current of ions which collide with the sample and optical emission spectroscopy is used to discern the reactive species included in the nitrogen plasma. The nitriding efficiency is indicated by X-ray diffraction and the microhardness test. The reported data reveal that the ion beam flux density as well as the deposition pressure, bias voltage and time can strongly affect the nitriding of stainless steel via the expanded multiphase microstructure inside the nitrided layer. The increase in the density of ion flux results in an ascent in the intensity of the expanded peak and a simultaneous decline in the intensity of the γ austenite peak. The evolution trend of ion beam flux density is described as a function of the operating pressure and the bias voltage. The maximum ion flux density has been achieved at 10 Pa pressure and −500 V bias voltage. A reasonable nitriding region has been, consequently, suggested after comparing this work with previously reported results.

(Henry B. Linford Award for Distinguished Teaching Address) Low Temperature Plasma Etching of Copper, Silver, and Gold Films

Copper, silver and gold films have garnered considerable interest due to the numerous applications possible as a result of their unique electrical and optical properties. Specifically, low resistivity and good electromigration resistance make these films attractive as interconnect layers in integrated circuits and microelectronic devices, while nano structures of these metals can be used to form plasmonic devices. Fabrication of structures, devices and circuits with these metals generally requires etching or patterning methods. However, the Group 11 metals are inherently difficult to reactively plasma etch at reasonable (<100 oC) temperatures because of the limited volatility of compounds that can be formed with these metals. As a result, additive processes (e.g., lift-off or electroplating followed by polishing) have been the preferred approach to generating patterns/structures. In contrast, pattern formation by subtractive etching offers simplicity, consistency with the patterning processes used for other films in device manufacture, and in some cases may alleviate limitations (size effect in Cu) in the fabrication of future generation devices. In this presentation, etching of Cu, Ag, and Au in hydrogen-based plasmas at temperatures at or below room temperature is described. Group 11 metal hydrides form readily in an H2 plasma, suggesting that these compounds are the likely etch products, despite their limited thermodynamic stability. Due to the low ion flux and momentum of hydrogen ions under the conditions used in the inductively-coupled plasma reactor system, sputtering alone cannot account for the etch rates observed (13, 33, and 26 nm/min respectively for Cu, Ag, and Au at 20 mTorr and 10 oC in H2). In these cases, desorption of metal hydrides is promoted by ion, and likely photon, bombardment. Exposure of Cu, Ag, and Au to Ar and He plasmas demonstrates that Ag and Au etch rates increase with increasing atomic mass, while Cu etch rates decrease with ion mass, suggesting that chemical reactions may be more important than physical processes for Cu etching.A limitation to the use of H2 plasmas for patterning of Cu, Ag, and Au is that photoresist layers are etched rapidly under the conditions used, thereby requiring hard masks such as SiO2. Furthermore, the feature slope generated with pure H2 plasmas is ~80o. Plasma etching with methane (CH4) plasmas under the same plasma conditions as those for H2 plasmas allows the use of a photoresist mask due to the deposition of a carbon layer during the etch process. An added benefit for Cu etching is that the etch rate increases to 17 nm/min relative to that of H2 (13 nm/min) with no change in wall slope. These enhancements relative to H2 plasma etching appear to be due to the formation of etch products that have improved thermodynamic stability compared to copper hydrides (e.g., CH3Cu and CH3CuH-). Preliminary etch studies of Ag and Au films using CH4 plasmas demonstrate that chemical aspects of the etch process are important, since etch rates are not reduced even with hydrocarbon deposition during the etch process.

Large Scale Homogeneous Growth Mechanics of Microcrystalline Silicon Films on Rough Surface

Large scale homogenous growth of microcrystalline silicon (μc-Si:H) on cheap substrates by inductively coupled plasma (ICP) of Ar diluted SiH4 has been studied. From XRD and Raman spectrum, we find that substrates can greatly affect the crystalline orientation, and the μc-Si:H films are comprised of small particles. Thickness detection by surface profilometry shows that the thin μc-Si:H films are homogenous in large scale. Distributions of both ion density and electron temperature are found to be uniform in the vicinity of substrate by means of diagnosis of Langmuir probe. Based on these experimental results, it can be proposed that rough surfaces play important roles in the crystalline network formation and Ar can affect the reaction process and improve the characteristics of μc-Si:H films. Also, ICP reactor can deposit the thin film in large scale.

Designing Ultra Low-k Dielectric Materials for Ease of Patterning

AbstractOrganosilicate materials with dielectric constants (k) ranging from 3.0 to 2.2 are in production or under development for use as interlayer dielectric materials in advanced interconnect logic technology. The dielectric constant of these materials is lowered through the addition of porosity which lowers the film density, making the patterning of these materials difficult. The etching kinetics and surface roughening of a series of low-k dielectric materials with varying porosity and composition were investigated as a function of ion beam angle in a 7% C4F8/Ar chemistry in an inductively-coupled plasma reactor. A similar set of low-k samples were patterned in a single damascene scheme. With a basic understanding of the etching process, we will show that it is possible to proactively design a low-k material that is optimized for a given patterning. A case study will be used to illustrate this point.

Ni-P, Ni-B and SiO2 as Materials for Hard Mask in Deep Silicon Etching for MEMS Fabrication using ICP reactor

Ni-P, Ni-B and SiO2 films were used as hard mask materials in Si etching using a high-density inductively coupled plasma (ICP) reactor for MEMS fabrication. The Ni-P and Ni-B films were deposited using an electroless method, and the SiO2 film was thermally grown in a conventional furnace. Two etching processes were used to characterize the masks. The first uses SF6/Ar gas mixture varying bias power and process time, and the second is a Bosch like process, using C4F8 as a passivation gas. The Ni-P mask showed the highest resistance to etching, being applicable in Si deep etching (>100m); while the SiO2 mask was found to be less resistive, especially under strong ion bombardment (high bias power). The Ni-B mask was found to be highly porous, resulting in formation of micropillars during ecthing, which may be interesting for some apllications such as sensors.

High-rate, low-temperature synthesis of composition controlled hydrogenated amorphous silicon carbide films in low-frequency inductively coupled plasmas

It is commonly believed that in order to synthesize high-quality hydrogenated amorphous silicon carbide (a-Si1−xCx : H) films at competitive deposition rates it is necessary to operate plasma discharges at high power regimes and with heavy hydrogen dilution. Here we report on the fabrication of hydrogenated amorphous silicon carbide films with different carbon contents x (ranging from 0.09 to 0.71) at high deposition rates using inductively coupled plasma (ICP) chemical vapour deposition with no hydrogen dilution and at relatively low power densities (∼0.025 W cm−3) as compared with existing reports. The film growth rate Rd peaks at x = 0.09 and x = 0.71, and equals 18 nm min−1 and 17 nm min−1, respectively, which is higher than other existing reports on the fabrication of a-Si1−xCx : H films. The extra carbon atoms for carbon-rich a-Si1−xCx : H samples are incorporated via diamond-like sp3 C–C bonding as deduced by Fourier transform infrared absorption and Raman spectroscopy analyses. The specimens feature a large optical band gap, with the maximum of 3.74 eV obtained at x = 0.71. All the a-Si1−xCx : H samples exhibit low-temperature (77 K) photoluminescence (PL), whereas only the carbon-rich a-Si1−xCx : H samples (x ≥ 0.55) exhibit room-temperature (300 K) PL. Such behaviour is explained by the static disorder model. High film quality in our work can be attributed to the high efficiency of the custom-designed ICP reactor to create reactive radical species required for the film growth. This technique can be used for a broader range of material systems where precise compositional control is required.

Chemical modeling of a high-density inductively-coupled plasma reactor containing silane

We carried out the modeling of chemical reactions in a silane-containing remote Inductively Coupled Plasma Enhanced Chemical Vapor Deposition (ICPECVD) system, intended for deposition of silicon, silicon oxide, and silicon nitride layers. The required electron densities and Electron Energy Distribution Functions (EEDF) were taken from our earlier Langmuir-probe measurements. The EEDF exhibited a fraction (0.5%) of fast electrons in the energy range between 20 and 40 eV, strongly deviating from Maxwell–Boltzmann (MB) distribution. We considered 16 electron impact dissociation/ionization reactions and 26 secondary reactions for homogeneous propagation of plasma species. We noticed a significant difference (orders of magnitude) between the concentrations of the species obtained using experimental EEDFs and MB energy distributions, pointing to the importance of the fast electron tail. For silicon oxide films, a qualitative agreement between the radical densities in plasma at different total pressures and the deposition rate was observed.