Hiroshi Fujiyama

Quantitative modeling of reactive sputtering process for MgO thin film deposition

Reactive sputtering process of magnesium target in d.c. planar magnetron discharge using argon and oxygen gases as buffer and reactive gases, respectively, has been investigated. A drastic mode transition between metallic and oxide modes has been observed due to a large difference in the secondary electron emission coefficients of magnesium and magnesium oxide. To describe the experimental results quantitatively, a new reactive sputtering model has been developed. The model is fundamentally based on a simple reactive gas balance model proposed by Berg et al. in 1988, but includes the change in the secondary electron emission coefficient of target. The modified model can deal with the change of plasma properties through the change of ion to electron current ratio at the target, and can quantitatively describe experimental results such as oxygen flow rate dependence of deposition rate and discharge voltage, which were obtained at a constant discharge current.

Inner coating of long-narrow tube by plasma sputtering

Long-narrow tubes are widely used in industry as water pipes, gas pipes and cooling pipes, etc. It is necessary to protect the inside of a metallic or dielectric tube against inner wall corrosion due to the inner surface being damaged by high temperature fluid or chemically reactive liquid. For thin film sputter coating on the inner wall of long-narrow tubes, the authors have developed the coating reactors using a coaxial magnetron pulsed plasma (CMPP) and a coaxial electron cyclotron resonance plasma (CECRP).

Dynamics of Silicon Particles in DC Silane Plasmas Transported by a Modulated Magnetic Field

By using a Mie scattering method, dynamics of silicon particles in DC and AC silane plasmas in the presence of a modulated magnetic field, B, perpendicular to the discharge electric field, E, were observed. In AC plasmas, Mie scattering signals were not observed. In DC plasmas, silicon particles were transported in the opposite direction of the E ×B drift, and particle density was decreased with increasing applied magnetic flux density. The experimental results support the assumption that spatially inhomogeneous discharge current by E ×B drift causes the balance among electrostatic force, ion drag force and force of gravity exerted on the particles to be lost and generates the particle transport.

Substrate temperature effects on amorphous carbon film growth, investigated by infrared spectroscopy in multiple internal reflection geometry

The substrate temperature effects on the amorphous carbon film growth were investigated, by using the deposition rates and in situ and “real-time” infrared spectroscopy in multiple internal reflection geometry. The deposition rates were decreased, in contrast with the increases of substrate temperature. The growth mode was also changed with substrate temperatures: the film growth depends on the gas phase reaction at low substrate temperature; on the other hand, at high temperature the film grows with the decomposition of the CH3 species.

MgO deposition using reactive ionized sputtering

Abstract We have developed a reactive ionized sputtering system, which composed of a conventional planar magnetron (PM) discharge and inductively coupled plasma (ICP), produced with an internal coil antenna. From the investigation on its discharge properties, we have confirmed that: (1) high density ICP of 10 11 –10 12 cm −3 was successfully produced, (2) the target input power used for sputtering and ICP RF power were independently controllable, (3) the simultaneous operation of PM and ICP were effective for enhancing the ionization, and further excitation of sputtered magnesium atoms. In addition, from the hysteresis observation of reactive sputtering mode, we have confirmed that, the metallic mode sputtering was maintained even for large oxygen flow rate. Preliminary deposition results indicated for the first time that, high crystalline MgO films were deposited at almost the same deposition rate as that of Mg films, under the reactive ionized sputtering condition.

Ceramics inner coating of narrow tubes by a coaxial magnetron pulsed plasma

Abstract We have developed a double-ended anode coaxial magnetron pulsed plasma (DCMPP) for the purpose of coating fine ceramics with, for example, titanium nitride (TiN) on the inner surface of a narrow insulated tube by reactive sputtering. In the magnetron pulsed plasma, the magnetron effect and J × B plasma transport by a pulsed discharge occurred simultaneously. Discharge characteristics and optimum conditions for uniform and high-rate sputter-coating were investigated. By using DCMPP, goldcolored TiN films could be deposited on the inner surfaces of narrow glass tubes of 8 mm in inner diameter and 400 mm in length. The deposition rate was about 20 nm min −1 for a deposition time of 600 s. By using a light absorption method, it was found that axial uniformity of the prepared films was within 25% over 400 mm.

Particle formation and a-Si:H film deposition in narrow-gap RF plasma CVD

The effects of electrode distance are discussed in a diode type plasma enhanced chemical vapor deposition (PECVD) system as an important external control parameter for the preparation of hydrogenated amorphous silicon (a-Si:H) using an RF silane (SiH4) plasma. The electron temperature is increased by shortening the electrode distance due to a plasma self-organization mechanisms, leading to an increase in the growth rate of a-Si:H films. Furthermore, shortening the distance between the heated electrodes (anode and/or cathode) gives rise to decrease in SiH4 density in the discharge space near the electrodes resulting in suppression of the particle formation. Through the control of particle formation by changing the electrode distance, the defect properties in the resulting films are successfully controlled.

Structural and bonding properties of carbon nitride films prepared by dc magnetron sputtering

Abstract Amorphous carbon nitride (CN x ) films have been deposited onto Si(100) substrates by reactive sputtering of a graphite target in a pure N 2 ambient. A modified cylindrical DC magnetron plasma was used as a sputter deposition source and the effects of substrate DC self-bias voltage caused by RF bias on film properties were investigated. X-ray photoelectron spectroscopy (XPS) spectra of N 1s and C 1s electron confirmed the existence of multiple bonding states for carbon and nitrogen (sp 2 and sp 3 ) in the film. Fourier transform infrared (FTIR) spectroscopy studies showed a systematic variation in spectra by a DC self-bias voltage. Raman spectra revealed two peaks corresponding to G band (1580 cm −1 ) and D band (1370 cm −1 ). The ratio of integrated intensities of D and G band ( I D / I G ) increased with DC self-bias voltage, suggesting increased disorder by the ion bombardment on growing film. Variation in the morphology of CN x films deposited at different bias voltage was examined by scanning electron microscopy (SEM).

Transport of negatively charged particles by E × B drift in silane plasmas

Abstract The motion of dust particles in glow discharge plasmas is influenced by the applied magnetic field, B , perpendicular to the discharge electric field, E . The negatively charged particles in a weakly magnetized plasma can be transported by the ambipolar electric field due to the E × B drift of the magnetized electrons. In this paper we propose a transport model to indicate the behavior of dust particles and evaluate “the ambipolar E × B drift” in weakly magnetized plasmas, in which only electrons can be magnetized, in terms of the drift velocities of charged particles (electrons, ions and negatively charged massive particles) calculated from the equations of motion. The calculation results in the present model agree qualitatively with the experimental results.

Application of the Child-Langmuir law to magnetron discharge plasmas

In order to investigate the influence of magnetic field on magnetron plasmas, the dependence of discharge-current density (J/sub d/) on magnetic flux densities (B) perpendicular to the electric field over the whole discharge space in a magnetron apparatus with flat multi-targets has been studied. The dependencies on working gas pressures (P) and voltages (V) have been also studied in the configuration. From the experimental results, it was found that J/sub d/ was approximately proportional to B/sup 2/, P/sup 2/ and V/sup 3/2/. The sheath structure in the apparatus has been investigated as a function of B by both a probe method and a spectroscopic one. The cathode-fall thickness was roughly proportional to B/sup -1/. From a numerical analysis on kinetics of /spl gamma/ electrons emitted from the cathode surface, it was found that the dependence of J/sub d/ on B could be explained by the Child-Langmuir law, in which the sheath thickness was replaced by the equivalent electron Larmor radius. >