Yushi Kato

Plasma potential profile in a 2.45 GHz electron cyclotron resonance multicharged ion source

Plasma potentials are measured in a 2.45 GHz electron cyclotron resonance (ECR) multicharged ion source. Both axial and radial potential profiles are determined for an argon plasma by using a Langmuir probe at various pressures. Multicharged ions up to Ar12+ are observed in the extracted beam. The plasma potentials are positive with respect to the plasma chamber wall and are on the order of several tens of volts. The values in profile measurements of the plasma potential are consistent with the spatial averaged values obtained by ion beam measurement. Along the mirror axis the plasma potential, the electron temperature, and density increase as the ECR zone is approached, and are roughly flat or hollow near the ECR zone. The radial profiles are loosely peaked or flat at the position off the ECR zone, and asymmetrical or hollow near the ECR zone. Due to some serious problems for the probe measurement, the plasma potential is deduced by several methods and the density is estimated from ion saturation currents.Plasma potentials are measured in a 2.45 GHz electron cyclotron resonance (ECR) multicharged ion source. Both axial and radial potential profiles are determined for an argon plasma by using a Langmuir probe at various pressures. Multicharged ions up to Ar12+ are observed in the extracted beam. The plasma potentials are positive with respect to the plasma chamber wall and are on the order of several tens of volts. The values in profile measurements of the plasma potential are consistent with the spatial averaged values obtained by ion beam measurement. Along the mirror axis the plasma potential, the electron temperature, and density increase as the ECR zone is approached, and are roughly flat or hollow near the ECR zone. The radial profiles are loosely peaked or flat at the position off the ECR zone, and asymmetrical or hollow near the ECR zone. Due to some serious problems for the probe measurement, the plasma potential is deduced by several methods and the density is estimated from ion saturation currents.

Modelling for Production of Multicharged Ions in ECR Source

Fundamentals of the ECR (electron cyclotron resonance) multiply charged ion source have been experimentally studied with a tandem-type mirror field configuration using low-frequency microwaves (2.45 GHz). By differential pumping, it is possible to sustain discharge in extremely low gas pressures, where multicharged ions can be efficiently produced. A model is proposed to enable investigation of charge-state distribution of argon ions in a plasma and extracted ion currents. The model includes processes of cumulative ionization, recombination, and charge exchange with neutral particles. Ion confinement times depending on the charge state are also included in the consideration of atomic collision and ion diffusion in the direction along the magnetic field ( z -axis). The calculations, which take account of charge exchange with neutral particles, are consistent with experimental results. Critical comparison between the data and these calculations suggests that high-temperature electrons are essentially import...

Production of multiply charged Si and Fe ions from solid materials by sputtering and evaporating methods in a 2.45 GHz ECR source

Multicharged Si and Fe ions are produced from solid materials in a 2.45 GHz electron cyclotron resonance (ECR) ion source. The ECR plasma is confined in a magnetic mirror field superimposed on an octupole magnetic field. Ar gas is normally chosen for working gas at pressures of 10−4 to 10−3 Pa. Si and Fe ions are produced by sputtering and evaporating solid materials, which are safe and easy to handle. The Fe (or Si) target is mounted at the tip of an insulated holder and inserted into the plasma. The negative dc bias voltages are applied to the target and multicharged Fe (or Si) ions are produced. Fe filament is evaporated in the ECR plasma by direct ohmic heating, and multicharged Fe ions are produced. Multicharged ions up to Fe6+ are produced by using both methods of sputtering and evaporating and Si4+ by using the sputtering method. The maximum ratio of the Fe and Si ion currents to total Ar ion current are about 15% and 13% obtained by the sputtering method, respectively. The maximum current densitie...

Enhanced production of multi-charged ions using pulse-modulated microwave in a 2.45 GHz electron cyclotron resonance source

Fundamental phenomena of an electron cyclotron resonance (ECR) multi-charged ion source (2.45 GHz) have been experimentally studied. The ECR plasma is confined in the mirror field superimposed by the octupole magnetic field. An ECR zone and potential well are formed near the bottom of the mirror trap. Multi-charged ions pass through the extractor at the mirror end, and the charge state distributions of extracted ions are investigated. Pulse-modulated microwave produces the ECR plasma with afterglow, relaxes the potential well, and then enhances the extracted multi-charged ion currents. Time-averaged Ar4+−9+ currents increase, even when the microwave power is nearly equal to or lower than the continuous microwave. The rectangular pulse width and the duty ratio are typically about 0.05 ms and 50%, respectively. The origin of enhanced production by pulse-modulated microwave is discussed by taking account of plasma parameters. Measurement of plasma parameters by a Langmuir probe and dependence of current incr...

Pulse height analysis using Si-pin diode of x-ray irradiated from a 2.45 GHz electron cyclotron resonance multicharged ion source

Production of multicharged ions is experimentally studied on an electron cyclotron resonance (ECR) source. The ECR zone for a microwave frequency of 2.45 GHz is formed at the bottom of a mirror trap. The x-ray spectra are measured by Si-pin diode detector in the various operating conditions. Available energy range of the x-ray measurement is several keV approximately several tens keV. Measurements are carried out at either line of sight including the ECR zone along the geometrical axis or at off-ECR zone from the side wall. The temperatures determined at both positions are about 2–3 keV from the observed spectrum with assuming nonrelativistic maxwellian plasma. The intensities of Ar Kα and bremsstrahlung radiation correlate to pressure and microwave power dependence of multicharged-ion production. But the dependence of the temperature is not clear. Therefore the multicharged-ion production largely depends on an abundance of high energy electrons rather than the change of the temperature of them in this en...

Sputtering‐assisted production of multicharged boron ions from solid material in a 2.45 GHz electron cyclotron resonance source

Multiply charged boron ions have been successfully produced and extracted from 2.45 GHz electron cyclotron resonance (ECR) ion source without gaseous feedstocks. A target material, solid‐state boride, is immersed in an ECR plasma and dc bias voltages are applied to it. Argon is chosen for operating gas. The extracted boron ion current increases as the target approaches the ECR zone. The increase of boron atomic flux into the ECR zone enhances production of the boron ions. The enhancement is deduced from the dependence of boron ion current on solid angle subtended by the target at the ECR zone. The total boron ion current is equal to about 10% of the total argon one. The B2+ current is equal to 10%–20% of B+ one. The B3+ current can be detected at low microwave powers (∼150 W). The isotopes of boron are closely separated in natural abundance ratio.

An ECR sheet plasma with a slot antenna and permanent magnets

A plasma source is developed to create broad thin films. Instead of generating large plasmas, substrates will be scrolled in uniform sheet plasmas to extend the process area. The plasmas are generated by electron cyclotron resonance; microwaves are radiated from a rectangular waveguide with a slot on its E-plane. This slot antenna is put between two permanent magnets. Their poles face each other so that a cusp field is formed in front of the slot. Plasmas are generated with gas; plasma parameters are measured by the Langmuir probe method and visible-range spectroscopy. The density uniformity is 9% within 20 cm length when a short plunger terminates the slot antenna. Spectra of bands and oxygen atomic lines are observed.

Production of multicharged iron ions by using pyrolytic boron nitride crucible and application to material processing

Multiply charged ions of iron are produced from solid material in a 2.45 GHz electron cyclotron resonance (ECR) ion source by using a crucible made from pyrolytic boron–nitride (pBN) with several shields suppressing radiation. The evaporator is set on the geometrical axis. The multicharged ions are extracted from the opposite side of mirror end against the evaporator. Extraction voltage is normally 10 kV. The optimum conditions for production of multicharged iron ions are investigated experimentally. The ion beams can be provided to a newly constructed beam line for the ion irradiation of the substrate installed on the beam line. Multicharged iron ion beams have been utilized to form iron silicides and to enhance light catalytic performance of titanium–dioxide (TiO2) thin films. Formation of iron disilicide (β-FeSi2) has been identified, as well as enhancement of photocatalytic performance of the TiO2 thin films in the visible light region without degradation in the UV light region.

Electron cyclotron resonance multicharged ion source with elemental boron

Fundamental experiments have been carried out by using a two‐stage electron cyclotron resonance (ECR) ion source (2.45 GHz) to produce multiply charged boron ions without gaseous feedstocks. A boron target, inserted into the ECR source, is heated and efficiently sputtered by dc bias. The B2+ ion current is successfully extracted under low microwave power (∼100 W). Dependence of extracted B+ ion current on dc bias voltage is similar to that of theoretical sputtering yield on incident ion energy.

Vacuum-ultraviolet spectroscopic measurement on an electron-cyclotron-resonance multicharged-ion source

The production mechanism of multichaged ions has been experimentally investigated in an electron-cyclotron-resonance (ECR) ion source with a mirror configuration upon which a multipole field using low-frequency microwaves (2.45 GHz) is superimposed. Spectral lines emitted from the ECR plasma are measured with a normal-incidence vacuum-ultraviolet (VUV) monochromator of wavelength range 40 - 170 nm. The normal operating gas is argon. The electron density and temperature are measured with a 35 GHz microwave interferometer and a probe, respectively. The dominant species in the extracted ion current are consistent with those of VUV emission from the ECR plasma. Spectroscopic characteristics of the plasma are presented under the various operating conditions. Measurements of the line intensity ratios, which are related to , indicate high under conditions suitable for the multicharged-ion production, namely such that the pressure and the electron density are extremely low and the microwave power is moderately high.