Akinori Ebe

Development of internal-antenna-driven large-area RF plasma sources using multiple low-inductance antenna units

Abstract Large-area and high-density radio frequency (RF) plasmas at 13.56 MHz have been produced by inductive coupling of internal-type low-inductance antenna units. The present study has been carried out to develop the basic discharge techniques which can be applied to production of meter-scale large-area and/or large-volume plasma sources with high density for a variety of plasma processes. The plasma source could be operated stably to attain plasma density as high as 1×1012 cm−3 at argon pressures of approximately 1 Pa. It has been demonstrated that high plasma density can be obtained efficiently using the low-inductance internal antenna configuration with effectively suppressed electrostatic coupling. Discharge experiments in a meter-scale chamber demonstrated uniform plasma production with densities as high as 6×1011 cm−3 at an argon pressure of 1.3 Pa and a RF power of 4 kW.

Large-Area and High-Speed Deposition of Microcrystalline Silicon Film by Inductive Coupled Plasma using Internal Low-Inductance Antenna

A novel inductively-coupled RF plasma source with internal low-inductance antenna (LIA) units was developed to synthesize microcrystalline silicon (µc-Si) film on a large glass substrate. A film thickness profile on a 600×720 mm2 glass substrate was achieved with high plasma uniformity and a variation of less than ±5% without a standing-wave effect. Raman and transmission electron microscope (TEM) analysis revealed that highly crystallized µc-Si films, which were directly deposited on a glass substrate, were synthesized without an amorphous-phase incubation layer at the substrate interface. A bottom-gate thin-film transistor (BG-TFT) was fabricated employing an optimized µc-Si layer and exhibited a field-effect mobility of 3 cm2/(Vs), which is one order higher than that of a typical amorphous silicon TFT.

Characterization of Inductively-Coupled RF Plasma Sources with Multiple Low-Inductance Antenna Units

We have developed a cylindrical RF plasma source by the inductive coupling of multiple low-inductance antenna (LIA) units and analyzed the plasma density profile of this source using fluid simulation. Experiments using four LIA units showed a stable source operation even at 2000 W RF power, attaining plasma densities as high as 10^{11}–10^{12} cm^3 in an argon pressure range of 0.67 –2.6 Pa. The amplitude of antenna RF voltage was measured to be less than 600 V, which is considerably smaller than those obtained using conventional ICP antennas. The radial distribution of plasma density sustained using four LIA units showed excellent agreement with profiles numerically predicted using a fluid-simulation code.

Properties of carbon nitride thin films prepared by ion and vapor deposition

Abstract This paper reports on mechanica, and optical properties of carbon nitride films coatings formed by the ion and vapor deposition (IVD) method. The thin films were formed by nitrogen ion bombardment and simultaneous carbon vapor deposition on substrates of fused silica and silicon (100) wafers. The energy of nitrogen ion was varied from 0.2 to 10.0 keV and the composition ratio (C/N) was varied from 5.0 to 14.0. The X-ray diffraction study indicated that the films were amorphous. The FT-IR spectra showed a small peak between 2100 and 2200 cm−1 indicating the presence of a triple bonded C-N stretching mode and the XPS ones showed a broad peak of i-carbon with a peak-shoulder at a bonding energy for diamondlike covalent bond. All formed films have a high hardness.

Effects of Antenna Size and Configurations in Large-Area RF Plasma Production with Internal Low-Inductance Antenna Units

Recent trends of liquid crystal display (LCD) fabrication toward a significant enlargement of glass substrates require large-area plasma sources with a scale length exceeding 1 m. To meet this requirement, large-area plasma sources with internal low-inductance antenna (LIA) units have been developed for uniform processes, in which design principles for selecting antenna size and configurations in the multiple installation of the LIA units are established. In this study, the effects of antenna size were examined in terms of plasma production characteristics indicating small increase in plasma density with a decrease in antenna size (or antenna impedance). Furthermore, plasma density distributions with the LIA units were investigated to understand the nature of plasma diffusion, which can be utilized for designing plasma profiles with multiple LIA units. First, it was shown that the plasma density distributions followed exponential decay as a function of distance from the antenna. Secondly, the measured plasma density profiles with multiple LIA units were shown to agree well with those obtained by superposing those described by exponential functions, which can be utilized for prediction.

Characterization of Ion Energy Distribution in Inductively Coupled Argon Plasmas Sustained with Multiple Internal-Antenna Units

We have characterized the ion energy distribution in argon plasmas sustained by multiple internal antenna units as a function of Ar pressure. The distribution has been measured using an ion energy analyzer with a mass separator. The peak of ion energy distribution depended more strongly on pressure and corresponded to the magnitude of plasma potential. The full width at half maximum of the distributions decreased with decreasing antenna RF voltage caused by a decrease in Ar pressure.

Development of Large Area Plasma Reactor Using Multiple Low-Inductance Antenna Modules for Flat Panel Display Processing

This article reports characteristics of plasmas sustained with LIA modules and profile control capabilities. Experiments with a meter-scale reactor demonstrated uniform plasma production to attain densities as high as 5x1011 cm-3 at an argon pressure of 1.3 Pa and an RF power of 4 kW. Design issues for large-area plasma sources with a scale-size of 3 m were also presented to exhibit the feasibility of novel large-area plasma sources to meet the requirements of the next-generation meters-scale processing.

Internal stress in thin films prepared by ion beam and vapor deposition

Abstract The effect of ion beam irradiation on the internal stress in thin films prepared by ion beam and vapor deposition (IVD) was studied. The thin films were prepared by the evaporation of nickel or silicon metals and simultaneous irradiation on Si(100) substrates by argon ion beams. The energies of the argon ions were changed in the range 0.5–10.0 keV, while the transport ratio of vapor atoms to ions was changed from 5 to 15. The internal stresses in the thin films were measured by the displacements of the substrates after deposition, and the results show that the internal stress changed from compressive to tensile with increasing ion beam energy. In addition, the control of the internal stresses in multilayer films prepared by IVD was investigated. It was found that it is possible to control the internal stress in a multilayer film by a suitable combination of the layers.

Effect of sputtering-cleaning on adhesion of the metallic films to polymer substrates

Abstract The effect of sputtering-cleaning on adhesion and chemical bonding at the metal/polymer interface was studied. Titanium (Ti) films were deposited on polymer substrates, polyethylene and polytetrafluoroethylene (PTFE) after sputtering-cleaning treatment. The sputteringcleaning treatment consisted of argon ion irradiation at 0.3 keV. Adhesion was measured by a pull test, and the chemical bonding at the interface was investigated by X-ray photoelectron spectroscopy. Adhesion of both polymer substrates was improved by sputtering-cleaning. In the case of PE, the ratio of C-Ti bonding at the interface increased after sputtering-cleaning and resulted in adhesion improvement. C-Ti and F-Ti bonding appeared at the interface between the Ti film and the PTFE substrate, but improvement in adhesion of Ti/PTFE was attributed to the change of the interfacial morphology on the basis of the scanning electron spectroscopy observation and adhesion of Au to PTFE.

The synthesis and properties of BN films prepared by ion irradiation and vapor deposition

Abstract Boron nitride films were deposited on tungsten carbide substrates by evaporation of boron and simultaneous nitrogen ion irradiation with energies in the range of 0.2 to 20.0 keV. The effect of preparation conditions on the mechanical properties such as hardness and adhesion was studied, and the deposition process for obtaining a hard film with good adhesion was investigated. For stoichiometric films, decreasing the ion energy increased the hardness, but decreased the film adhesion. On the other hand, boron-rich films showed a better adhesion, but a decrease in hardness. From these results, multilayer films were prepared using high and low energy ions; stoichiometric films prepared by low energy ions were deposited on boron-rich films prepared by high energy ions. The multilayer films combined the advantages of both preparation conditions, high hardness and enhanced adhesion.