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We report on the formation of anodic aluminum oxide (AAO) film using phytic acid (C6H18O24P6), a naturally obtainable and non-toxic organic acid electrolyte. When the temperature of the phytic acid electrolytes changes from 0 °C to 20 °C, the pore size increases, and the AAO film becomes less dense because the growth rate of the AAO film increases. In particular, when the temperature of the phytic acid electrolyte is above 15 °C, the AAO film changes dramatically. According to XRD analysis, the alpha-alumina intensity was relatively higher in the AAO film grown at low-temperatures (0, 5, 10 °C) than high-temperatures (15, 20 °C). It was possible to obtain a result that the properties were better. The microstructural change of the AAO film according to the temperature of the phytic acid electrolytes affected the breakdown voltage and the number of contamination particles that are generated, which are important properties for plasma corrosion protection coating materials. The AAO film grown in the low-temperature has the most suitable properties for use as a plasma corrosion protection coating material. Notably, the breakdown voltage of the AAO film is 0.45 kV at 14.9 μm thickness, with no observable crack on its surface after the plasma corrosion test. These findings provide significant evidence to support the application of phytic acid as an electrolyte to grow AAOfilms, and the AAOfilm grown in a phytic acid bath can be applied as a plasma corrosion protection coating material.

We developed a hybrid probe comprised of an electrical probe and optical probe to investigate the properties of the far scrape-off layer (SOL) plasma and the blob in Korea Superconducting Tokamak Advanced Research (KSTAR). The hybrid probe is attached to a horizontal manipulator, and the radial profiles of plasma parameters such as electron temperature, ion flux, and the Dα signals are measured with time resolution (100 μs) by varying the radial position (0.15–0.4 m away from the last closed flux surface (LCFS)). In ELMy H-mode discharge, the blob radial velocity is obtained from the time delay between the start of the peak Dα signal and the peak electrical probe current and the corresponding radial position. The obtained blob radial velocity is in good agreement with the radial velocity of the filament obtained using the two radially separated electric probes at the far-SOL in the KSTAR. The profiles of the blob radial velocity for five discharges are obtained depending on the radial position in similar experimental parameters. The blob radial velocity is estimated as 44.1–250 m/s and 25.4–135 m/s at the radial position of 0.15 m (near the LCFS) and 0.4 m (near the outer wall), respectively. It is observed that the blobs are propagated to the outer wall with various radial velocities, and the radial velocity slows down as they get closer to the outer wall. The hybrid probe measurement found that the blob properties are about 2 to 10 times larger than the background plasma, and these show the same trend with the blob radial velocity. The hybrid probe is expected to contribute to the analysis and understanding of far-SOL plasma research in fusion reactors.

Spatial distributions of the effective electron temperature (Teff) and plasma potential were studied from the measurement of an electron energy probability function in a side type ferrite-core inductively coupled plasma with an argon–helium mixture. As the helium gas was diluted at the fixed total gas pressure of 5 mTorr in an argon discharge, the distribution of the plasma density and plasma potential changed from a concave to a flat profile, and finally became a convex profile, while all spatial profiles of Teff were hollow shapes with helium dilution in the argon discharge. This evolution of the plasma potential with helium gas could be explained by the increased energy relaxation length (λe), indicating the transition of electron kinetics from local to non-local kinetics.

Low temperature reactive plasmas have been widely used in various nanofabrication processes. We have developed a large area wafer-type colorimetric plasma diagnostic system based on a polymerizable supramolecular sensor (PSS). The supramolecular diacetylene based PSS allows efficient mapping of the ion density distribution. The colour change of the thin PSS film was found to be very sensitive to plasma and afforded a real time colorimetric and fluorometric monitoring of spatial ion density distribution. This PSS method, which does not require electrical circuits and batteries, will find great utility in the field of plasma diagnostics.

A method for measuring a transferred power to plasma is proposed in an inductively coupled plasma. Antenna currents are monitored when the plasma is turned on at a certain input power. The transferred power can be obtained by subtraction of the power at the same current when the plasma is turned off without inert gas, to the input power. This method is compared to the conventional method against various input powers and it is in good agreement. The circuit analysis of an impedance matching network is also discussed in this work.

To enable the industrial application of large-area capacitive coupled plasma (CCP), we studied non-uniformity of CCP with a 450 mm electrode. The field difference is one factor that reduces plasma uniformity. This effect is increased when the electrode's area is enlarged; therefore, we designed a multi-electrode CCP to overcome this problem. We found the optimal power conditions for each electrode to provide the best uniformity. Then, we powered on only one electrode to determine the property of each electrode. Our experiments showed some diffusion issues, and these results matched the results of the previous uniformity experiments.

Real time feedback control of plasma density was developed and carried out in an inductively coupled plasma. This control method uses a floating probe as a sensor because it can measure plasma density in real time without modification of the plasma reactors and it does not perturb the plasma. The results show that through feedback control, plasma density can be maintained constant within a steady state error of less than 0.3% even if there is a sudden pressure disturbance. This feedback control method is expected to improve the repeatability and reliability of plasma reactors.

Different electrical characteristics depending on the impedance matching conditions were observed in inductively coupled plasma during the E–H mode and H–E mode transition and their hysteresis. At the auto matching condition, there was no hysteresis loop on the E–H and H–E transition, while the hysteresis loop was clearly observed at the fixed matching condition. This result shows that the impedance matching condition is the primary cause for the hysteresis loop.

A study of the E–H mode transition was performed in Ar, O 2 , N 2 , and mixture gas inductively coupled plasma (ICP) from the measurement of the electron energy distribution function (EEDF). Changes of the EEDF and characteristics of the discharge on the E–H mode transition were discussed. At each E-mode, the measured EEDFs had different shapes depending on the gas type and pressure, while the EEDFs evolved into Maxwellian distribution with the E–H transition due to electron–electron collisions. This study was also focused on the transition ICP power when the discharge transits from E-mode to H-mode. As the ICP power increased in Ar discharge, the transition ICP power had minimum value at a particular pressure, while the transition ICP power was gradually increased with gas pressures in molecule gas discharge. The transition ICP power with gas mixing ratios was also studied in Ar/O 2 /N 2 mixture gas discharge.

Changes in the plasma non-uniformity and the electron energy distribution function (EEDF) by increasing RF bias power were observed in inductively coupled plasma using spatially resolved radial EEDF measurements. As the bias power was increased at a fixed ICP power at a low gas pressure, The EEDF was evolved from a bi-Maxwellian to a Maxwellian distribution. The plasma density was decreased in all radial positions and thus plasma non-uniformity was slightly changed. However, strongly improved plasma spatial non-uniformity was observed at a high gas pressure with a decrease in the center-plasma density and an increase in the radial edge-plasma density. This result could be understood by combined effects of the ion acceleration loss and the non-uniform power deposition due to the RF bias power.

The impedance transition and electron series resonance at an RF bias substrate were observed in 13.56 MHz inductively coupled plasma (ICP). As ICP coil power increased, the impedance of the RF bias transitioned from a capacitive to an inductive load. When bias voltages and discharge impedances reached minimums, bias voltages and currents were in-phase during the transition. The transition can be understood as a series LC resonance between the sheaths (capacitor) and plasma bulks (inductance due to electron inertia). This corresponds to the electron series resonance (ESR) observed in very high-frequency capacitive discharges, and a new ESR frequency which considers sheath resistances is presented.

We have investigated the characteristics of Ar/O"2 plasmas in terms of the photoresist (PR) and low-k material etching using a ferrite-core inductively coupled plasma (ICP) etcher. We found that the O"2/(O"2+Ar) gas flow ratio significantly affected the PR etching rate and the PR to low-k material etch selectivity. Fourier transform infrared spectroscopy (FTIR) and HF dipping test indicated that the etching damage to the low-k material decreased with decreasing O"2/(O"2+Ar) gas flow ratio.

The characteristics of photoresist (PR) ashing using N 2 plasmas in a ferrite core inductively coupled plasma etcher have been studied and the effect of bias power and gas flow rate on PR ash rate and low- k material etch rate has been investigated. Fourier transform infrared spectroscopy revealed that the ashing process with N 2 gas produced less damage to the low- k material compared to the process with O 2 gas. The HF etch test was used to evaluate the ash damage to the low- k material.

The inductively coupled plasma (ICP) device is one of the high-density plasma sources being used for the present integrated circuit etching process on an ultra-large scale. Here, we develop a Fokker–Planck code for the ICP source, and evaluate an electron energy diffusion coefficient based on the solution of the wave equations for an ICP reactor. The electron energy distribution function (EEDF) dependence on various external parameters, such as wave frequency, gas pressure and magnetic field, is investigated using the Fokker–Planck code. The effects of changing external parameters on ICP heating characteristics are also discussed. It is shown that the heating of low-energy electrons is enhanced with increasing system collisionality, which is defined as the ratio of collision frequency to effective wave frequency.

The electron heating mechanism in ICP is briefly reviewed in the collisionless regime. We suggest a parallel resonance antenna (PRA) that by varying capacitance in a capacitor ( C v ) as an external parameter can control not only the antenna current distribution, but also plasma uniformity. Radial plasma uniformity can be controlled and optimized by controlling coil currents between the coil segments, operating pressure, and chamber geometry in a recently developed antenna system. These results are consistent with the previous modeling paper [Appl. Phys. Lett. 77 (2000) 492].

When a small ac voltage with two frequencies was biased to a probe in low pressure inductively coupled plasma, sideband current signals were observed. It was found that two frequencies of the small bias voltage are mutually modulated in the plasma, and this modulation results in the sideband current signals. Experiments for measurement of the sidebands were carried out at various pressures, correlations between the sidebands and the plasma state were investigated. The sidebands were not observed when the plasma was not generated; therefore these signals were produced by the nonlinearity of the sheath. The electron temperature could be obtained from the sideband signals, and it was in good agreement with that from a single Langmuir Probe.

Electron heating is fundamental and essential to sustain plasma in an inductively coupled plasma as well as other plasmas. Ohmic heating randomized by collisions, especially electron–neutral collisions, is dominant at high pressure (ν en ≫ω). Stochastic heating (collisionless heating) is caused by collisions with inhomogeneous fields in inductive mode or moving sheath in the capacitive mode of inductively coupled plasma (ICP). These electron-heating mechanisms in ICP are classified in this paper and recent experimental and theoretical results focusing on the electron energy distribution function (EEDF) and rf fields in the collisionless regime are presented. We suggest that further issues need to be resolved to better understand the main heating process in low-pressure ICP operation.

We have studied the characteristics of photoresist (PR) ashing using N 2 /O 2 plasmas in ferrite-core inductively coupled plasma etcher. By varying the O 2 /(O 2 + N 2 ) gas flow ratio, we have changed the PR ash rate and the low-k material etch rate, obtaining the PR ash rate and the PR to low-k materials etch selectivity, respectively, of 15,000 A/min and 180. Fourier transform infrared spectroscopy and HF etch test coincidentally indicated that the ash damage to the low-k material decreased with decreasing the O 2 /(O 2 + N 2 ) gas flow ratio.