To obtain high-quality SiNxfilms applicable to an extensive range of processes, such as gate spacers in fin field-effect transistors (FinFETs), the self-aligned quadruple patterning process, etc, a study of plasma with higher plasma density and lower plasma damage is crucial in addition to study on novel precursors for SiNxplasma-enhanced atomic layer deposition (PEALD) processes. In this study, a novel magnetized PEALD process was developed for depositing high-quality SiNxfilms using di(isopropylamino)silane (DIPAS) and magnetized N2plasma at a low substrate temperature of 200 °C. The properties of the deposited SiNxfilms were analyzed and compared with those obtained by the PEALD process using a non-magnetized N2plasma source under the same conditions. The PEALD SiNxfilm, produced using an external magnetic field (ranging from 0 to 100 G) during the plasma exposure step, exhibited a higher growth rate (∼1 Å/cycle) due to the increased plasma density. Additionally, it showed lower surface roughness, higher film density, and enhanced wet etch resistance compared to films deposited using the PEALD process with non-magnetized plasmas. This improvement can be attributed to the higher ion flux and lower ion energy of the magnetized plasma. The electrical characteristics, such as interface trap density and breakdown voltage, were also enhanced when the magnetized plasma was used for the PEALD process. Furthermore, when SiNxfilms were deposited on high-aspect-ratio (30:1) trench patterns using the magnetized PEALD process, an improved step coverage of over 98% was achieved, in contrast to the conformality of SiNxdeposited using non-magnetized plasma. This enhancement is possibly a result of deeper radical penetration enabled by the magnetized plasma.

Plasma enhanced atomic layer deposition (PEALD) of silicon nitride (SiNx) using very high frequency (VHF, 162 MHz) plasma source was investigated at the process temperatures of 100, 200, and 300 °C. Two aminosilane precursors having different numbers of amino ligands, bis(tert-butylamino)silane (BTBAS) and di(sec-butylamino)silane (DSBAS), were used as Si precursors. A comparative study was also conducted to verify the effect of the number of amino ligands on the properties of SiNx film. At all process temperatures, DSBAS, having one amino ligand, performed better than BTBAS in various aspects. SiNx films deposited using DSBAS had lower surface roughness, higher film density, lower wet etch rate, improved electrical characteristics, and higher growth rate than those deposited using BTBAS. With the combination of a VHF plasma source and DSBAS with one amino ligand, the SiNx films grown at 300 °C exhibited low wet etch rates (≤2 nm/min) in a dilute HF solution (100:1 of deionized water:HF) as well as low C content below the XPS detection limit. Also, excellent step coverage close to 100% on high aspect ratio (30:1) trench structures was obtained by using VHF plasma, which could provide sufficient flux of plasma species inside the trenches in conjunction with DSBAS having fewer amino ligands than BTBAS.

Low-hydrogen-containing amorphous silicon (a-Si) was deposited at a low temperature of 80 °C using a very high frequency (VHF at 162 MHz) plasma system with multi-split electrodes. Using the 162 MHz VHF plasma system, a high deposition rate of a-Si with a relatively high deposition uniformity of 6.7% could be obtained due to the formation of high-ion-density (>1011 cm−3) plasma with SiH4 and a lack of standing waves by using small multi-split electrodes. The increase in the radio frequency (RF) power decreased the hydrogen content in the deposited silicon film and, at a high RF power of 2000 W, a-Si with a low hydrogen content of 3.78% could be deposited without the need for a dehydrogenation process. The crystallization of the a-Si by ultraviolet (UV) irradiation showed that the a-Si can be crystallized with a crystallinity of 0.8 and a UV energy of 80 J without dehydrogenation. High-resolution transmission electron microscopy showed that the a-Si deposited by the VHF plasma was a very small nanocrystalline-like a-Si and the crystalline size significantly grew with the UV irradiation. We believe that the VHF (162 MHz) multi-split plasma system can be used for a low-cost low-temperature polysilicon (LTPS) process.

Important issues for silicon nitride (SiNx) plasma enhanced atomic layer deposition (PEALD) are lowering the process temperature and minimization of plasma damage. In this study, the characteristics of PEALD SiNx films deposited at a low processing temperature of 100 degrees C with di-isopropylamino silane (DIPAS) and N-2 plasma excited by using a very high frequency (VHF, 162 MHz) floating multi-tile electrode capacitively coupled plasma (CCP) source and a conventional VHF CCP source are reported in addition to the characteristics of both plasma sources. The PEALD SiNx film deposited with the floating multi-tile electrode exhibited higher growth rate (similar to 0.6 angstrom/cycle), higher N/Si ratio film (N/Si similar to 0.98, even though it is lower than the stoichiometric similar to 1.33 of N/Si for Si3N4) with no trace of carbon, lower surface roughness, and higher conformality in a trench compared to those deposited by the conventional CCP. In addition, improved electrical properties of the SiNx films such as lower leakage current, lower interface trap density, and higher breakdown voltage of PEALD SiNx film were obtained with the floating multi-tile electrode. These enhanced properties of SiNx films deposited by the floating multi-tile electrode are believed to be related to the higher plasma density, higher radical density, and lower ion energy bombarding the substrate observed for the multi-tile electrode through the enhanced power efficiency of the differentially-coupled multi-tile plasma source.

The design of a Very-High-Frequency (VHF) 162 MHz driven atmospheric-pressure Capacitively-Coupled-Plasma (CCP), with top and bottom electrodes operated in push-pull configuration, powered via a Power-SplittingTransmission-Line-Driver (PSTLD), is presented. Application to the reprocessing of carbon dioxide into carbon-monoxide in this "high" VHF atmospheric plasma is presented, demonstrating some behaviour of the plasma source. rf power in the system is characterized using measured current (- 1 ' s Amps peak) and voltage (10 ' s Volts peak) waveforms at the electrode; Both are sinusoidal confirming a glow-discharge operational condition. Analysis of Optical Emission Spectra results find a highly non-equilibrium plasma, with high vibrational temperatures (from N2) in the range -4000 K, while gas temperature, monitored by a thermocouple at the gas outlet, remains low -300 K, and confirmed by analysis of the N2 rotational bands. The relative density of CO produced, as a by-product of CO2 dissociation, is measured optically using N2 as an actinometer. The CO density increases with rf power and longer gas residence times in the plasma volume. The high VHF atmospheric plasma is found to operate in pure CO2 flows (no helium) with minimal gas heating for the full range of power densities (specific energy input of 0.4-2 eV per molecule) investigated.

An experimental investigation of electrode voltage/discharge current, plasma density, including negative ions and ion flux, and ion energy distributions (IEDs) is performed in a low-pressure oxygen discharge excited by a multi-tile electrode, very high frequency (162 MHz) capacitively coupled plasma system. The results show a mode transition vs RF power. An inflection point is observed in the measured electrode voltage and current near to the mode transition. The negative ion density inferred from the measured electron density and ion flux using resonance hairpin probe and planar probe, respectively, shows an initial increase and then decrease after mode transition. The IED shows a symmetric narrow distribution and the mean energy first increases up to the transition point and then decreases with further increase in RF power. A change in the current coupling mechanism and variation in the discharge impedance due to the presence of negative ions are responsible for the observed mode transition.

Silicon nitrides, deposited by capacitively coupled plasma (CCP)-type plasma enhanced atomic layer deposition (PEALD), are generally applied to today's nanoscale semiconductor devices, and are currently being investigated in terms of their potential applications in the context of flexible displays, etc. During the PEALD process, 13.56 MHz rf power is generally employed for the generation of reactive gas plasma. In this study, the effects of a higher plasma generation frequency of 162 MHz on both plasma and silicon nitride film characteristics are investigated for the purpose of silicon nitride PEALD, using bis(diethylamino)silane (BDEAS) as the silicon precursor, and N2 plasma as the reactant gas. The PEALD silicon nitride film deposited using the 162 MHz CCP exhibited improved film characteristics, such as reduced surface roughness, a lower carbon percentage, a higher N/Si ratio, a lower wet etch rate in a diluted HF solution, lower leakage current, and higher electric breakdown field, and more uniform step coverage of the silicon nitride film deposited in a high aspect ratio trench, as compared to silicon nitride PEALD using 13.56 MHz CCP. These improved PEALD silicon nitride film characteristics are believed to be related to the higher ion density, higher reactive gas dissociation, and lower ion bombardment energy to the substrate observed in N2 plasma with a 162 MHz CCP.

This paper presents an experimental study of electron and negative ion dynamics in a pulsed 100 MHz capacitive discharge. The plasma is produced in an O-2 and Ar/O-2/C4F8 gas mixture at 2 Pa gas pressure. Laser photo-detachment combined with a microwave resonance probe is used to diagnose the absolute densities of multiple negative ion species, F- and O-. In pure oxygen discharge, both the quasi-steady state electron and negative ion densities increase during the active glow with an increase in RF power level. In the afterglow plasma, the electron density decay rate is similar to 10-15 mu s, whereas the O- decays more slowly with a decay time constant in the range of 30-35 mu s. At a low RF power, a peak in the O- density is observed in the early afterglow plasma. In the Ar/O-2/C4F8 gas mixture, the quasi-steady state electron density in the active glow plasma increases with RF power, whereas the O- density decreases and F- density increases. In comparison to pure O-2 discharge, in the Ar/O-2/C4F8 gas mixture the electron density decay is faster. In the afterglow the F- density is ten times higher than the O- density. These results suggest a change in the dominant negative ion production mechanism within the discharge pulse from dissociative electron attachment of CxFy in the active on-phase to electron attachment to fluorine atoms in the afterglow plasma.

The plasma density (n(e)) profile, rotational (T-rot) and vibrational (T-vib) temperatures, and their dependence on the RF power (500-1500 W) and gas pressure (50-500 mTorr) is investigated in a high to very high frequency (VHF) (162 MHz) capacitively coupled nitrogen plasma excited by a multi-tile electrode (tiles) system. The density profile is measured in the mid-plane of the discharge using a resonance hairpin probe, and the rotational and vibrational temperatures are measured at both tile centre and tile-tile boundary using optical emission spectroscopy. It is observed that the plasma density increases monotonically with a rise in RF power and decreases with an increase in the operating gas pressure. At a low gas pressure (50 mTorr), plasma density profile shows a maximum at the tile centre and a minimum at the tile-tile boundary, whereas, at high gas pressure tile-edge effects are observed. Measured rotational temperature (similar to 350-450 K) is slightly above room temperature for both positions and independent of RF power and operating gas pressure. Vibrational temperature is in the range of similar to 6500-9400 K, and increases with RF power, analogue to the plasma density. It is noticed that the plasma uniformity can be substantially improved, to better than 90%, by changing the power-pressure matrix. A large difference between measured vibrational and rotational gas temperature suggests that the plasma produced by VHF multi-tile electrode is under highly non-equilibrium condition and thus highly efficient to produce unique gas phase chemistry.

For the low power and high-performance semiconductor devices, a silicon oxynitride (SiOxNy) layer is required as the gate sidewall spacer material by replacing oxygen of the silicon oxide (SiO2) sidewall layer with nitrogen through a plasma nitriding process. In this study, as a plasma nitriding process, instead of conventional radio frequency plasma nitriding utilizing high frequency (HF; 13.56 MHz, etc.) plasmas, a very high frequency (VHF) plasma operated at 162 MHz with a multi-tile push-pull plasma source has been used in nitriding the SiO2 layer at room temperature and the effects of the VHF (162 MHz) plasma on SiOxNy formation from a SiO2 layer and electrical characteristics of the SiOxNy formed by the plasma nitridation were investigated. The use of the VHF (162 MHz) multi-tile push-pull plasma formed similar to 10 nm thick SiOxNy with a very high nitrogen percentage of similar to 24% on the SiO2 layer surface. Also, when the surface roughness of the SiOxNy and electrical characteristic of MOS capacitors fabricated with the SiOxNy formed by the VHF (162 MHz) plasma were compared with those formed by a capacitively coupled plasma at 60 MHz, a lower surface roughness and much lower leakage current of MOS capacitor could be obtained.

Self-consistent particle-in-cell simulations are carried out to investigate the effect of discharge voltage, driving frequency, and the extent of the electrode gap on the formation of electric field transients. The shape of the electron energy distribution function into the bulk plasma and the nature of the mode transition in plasma density are presented for the driving frequency range of 27.12 MHz to 80 MHz. The present results, taken in conjunction with our previous study [Sharma et al., Phys. Plasmas 23, 110701 (2016)] that only looked at the driving frequency dependence in collisionless capacitive Ar discharges, provide a comprehensive and detailed account of the dynamics of such discharges over a multiparameter operational space.

We propose a new technique for diagnosing negative ion properties using Langmuir probe assisted pulsed laser photo-detachment. While the classical technique uses a laser pulse to convert negative ions into electron-atom pairs and a positively biased Langmuir probe tracking the change of electron saturation current, the proposed method uses a negatively biased Langmuir probe to track the temporal evolution of positive ion current. The negative bias aims to avoid the parasitic electron current inherent to probe tip surface ablation. In this work, we show through analytical and numerical approaches that, by knowing electron temperature and performing photo-detachment at two different laser wavelengths, it is possible to deduce plasma electronegativity (ratio of negative ion to electron densities) α, and anisothermicity (ratio of electron to negative ion temperatures) γ−. We present an analytical model that links the change in the collected positive ion current to plasma electronegativity and anisothermicity. Particle-In-Cell simulation is used as a numerical experiment covering a wide range of α and γ− to test the new analysis technique. The new technique is sensitive to α in the range 0.5 < α < 10 and yields γ− for large α, where negative ion flux affects the probe sheath behavior, typically α > 1.

One-dimensional particle-in-cell simulation is used to simulate the capacitively coupled argon plasma for a range of driving frequency from 13.56 MHz to 100 MHz. The argon chemistry set can, selectively, include two metastable levels enabling multi-step ionization and metastable pooling. The results show that the plasma density decreases when metastable atoms are included with higher discrepancy at higher excitation frequency. The contribution of multistep ionization to overall density increases with excitation frequency. The electron temperature increases with the inclusion of metastable atoms and decreases with excitation frequency. At lower excitation frequency, the density of Ar** (3p5 4p, 13.1 eV) is higher than Ar* (3p5 4s, 11.6 eV), whereas, at higher excitation frequencies the Ar* (3p5 4s, 11.6 eV) is the dominant metastable atom. The metastable and electron temperature profile evolve from a parabolic profile at lower excitation frequency to a saddle type profile at higher excitation frequency. With metastable, the electron energy distribution function (EEDF) changes its shape from Druyvesteyn type, at low excitation frequency, to bi-Maxwellian, at high frequency plasma excitation, however a three-temperature EEDF is observed without metastable atoms.

The dynamical characteristics of a single frequency low pressure capacitively coupled plasma (CCP) device under varying applied RF voltages and driving frequencies are studied using particle-in-cell/Monte Carlo collision simulations. An operational regime is identified where for a given voltage the plasma density is found to remain constant over a range of driving frequencies and to then increase rapidly as a function of the driving frequency. The threshold frequency for this mode transition as well as the value of the constant density is found to increase with an increase in the applied voltage. Over the constant density range, for a given voltage, the sheath width is seen to increase as a function of the increasing driving frequency, thereby changing the ion energy without affecting the ion density. Our parametric study thus indicates that the twin knobs of the applied voltage and driving frequency offer a means of independently controlling the density and the ion energy in a low pressure CCP device that may be usefully exploited for plasma processing applications.

Abstract The behaviour of absolute electron density and density of F − , O − and C F 3 − is studied in asymmetric capacitively coupled plasma discharge produced in an Ar/O 2 /C 4 F 8 (80:10:10) gas mixture excited at 60 and 100 MHz. The measurements are performed using a hairpin probe and laser photo-detachment at 532 nm and 355 nm laser wavelengths. For both 60 and 100 MHz driving frequencies, the results show that the electrons and F − density increases almost linearly with the increase in rf power. On the other hand, the O − density increases in 60 MHz and decreases in 100 MHz with a rise in rf power. For a fixed rf power in the 60 MHz discharge, the O − density increases and electron density decreases with gas pressure. The corresponding F − density first increases, reaching a maximum value, and then decreases with a further increase in gas pressure. A similar trend in electron, F − and O − density versus gas pressure is observed in 100 MHz suggesting that the initial increase in densities is dominated by the ionization and dissociative attachment, whereas, at a higher gas pressure, electron–ion recombination, ion-neutral recombination and ion–ion neutralization play a significant role in the losses of charged particles. The ratio of F − density to O − density is ~80:20 and ~95:5 in 60 MHz and 100 MHz respectively. The density of both electrons and F − is higher in 100 MHz when compared to 60 MHz discharge. The observed trend is explained on the basis of productions and loss mechanisms for electrons and negative ions. It is concluded that the higher F − density in 100 MHz in comparison to 60 MHz is mainly due to higher electron density and dissociation degree.

The behaviour of absolute electron density and density of F-, O- and CF3- is studied in asymmetric capacitively coupled plasma discharge produced in an Ar/O-2/C4F8 ( 80: 10: 10) gas mixture excited at 60 and 100 MHz. The measurements are performed using a hairpin probe and laser photo-detachment at 532 nm and 355 nm laser wavelengths. For both 60 and 100 MHz driving frequencies, the results show that the electrons and F- density increases almost linearly with the increase in rf power. On the other hand, the O- density increases in 60 MHz and decreases in 100 MHz with a rise in rf power. For a fixed rf power in the 60 MHz discharge, the O- density increases and electron density decreases with gas pressure. The corresponding F- density first increases, reaching a maximum value, and then decreases with a further increase in gas pressure. A similar trend in electron, F- and O- density versus gas pressure is observed in 100 MHz suggesting that the initial increase in densities is dominated by the ionization and dissociative attachment, whereas, at a higher gas pressure, electron-ion recombination, ion-neutral recombination and ion-ion neutralization play a significant role in the losses of charged particles. The ratio of F- density to O- density is similar to 80:20 and similar to 95:5 in 60 MHz and 100 MHz respectively. The density of both electrons and F- is higher in 100 MHz when compared to 60 MHz discharge. The observed trend is explained on the basis of productions and loss mechanisms for electrons and negative ions. It is concluded that the higher F- density in 100 MHz in comparison to 60 MHz is mainly due to higher electron density and dissociation degree.

Depositing a barrier film for moisture protection without damage at a low temperature is one of the most important steps for organic-based electronic devices. In this study, the authors investigated depositing thin, high-quality SiN x film on organic-based electronic devices, specifically, very high-frequency (162 MHz) plasma-enhanced chemical vapor deposition (VHF-PECVD) using a multi-tile push-pull plasma source with a gas mixture of NH 3 /SiH 4 at a low temperature of 80 °C. The thin deposited SiN x film exhibited excellent properties in the stoichiometry, chemical bonding, stress, and step coverage. Thin film quality and plasma damage were investigated by the water vapor transmission rate (WVTR) and by electrical characteristics of organic light-emitting diode (OLED) devices deposited with SiN x , respectively. The thin deposited SiN x film exhibited a low WVTR of 4.39 × 10 −4 g (m 2 · day) −1 for a single thin (430 nm thick) film SiN x and the electrical characteristics of OLED devices before and after the thin SiN x film deposition on the devices did not change, which indicated no electrical damage during the deposition of SiN x on the OLED device.

To prevent moisture and oxygen permeation into flexible organic electronic devices formed on substrates, the deposition of an inorganic diffusion barrier material such as SiNx is important for thin film encapsulation. In this study, by a very high frequency (162 MHz) plasma-enhanced chemical vapor deposition (VHF-PECVD) using a multi-tile push-pull plasma source, SiNx layers were deposited with a gas mixture of NH3/SiH4 with/without N-2 and the characteristics of the plasma and the deposited SiNx film as the thin film barrier were investigated. Compared to a lower frequency (60 MHz) plasma, the VHF (162 MHz) multi-tile push-pull plasma showed a lower electron temperature, a higher vibrational temperature, and higher N-2 dissociation for an N-2 plasma. When a SiNx layer was deposited with a mixture of NH3/SiH4 with N-2 at a low temperature of 100 C-omicron, a stoichiometric amorphous Si3N4 layer with very low Si-H bonding could be deposited. The 300 nm thick SiNx film exhibited a low water vapor transmission rate of 1.18 x 10(-4) g (m(2) . d)(-1), in addition to an optical transmittance of higher than 90%.