Yoshimi Hakamata

Voltage distribution characteristics of series connected SF/sub 6/ gas and vacuum interrupters immediately after a large AC current interruption

Transient voltage distribution characteristics of a hybrid interrupter module have been examined using an experimental model of a hybrid breaker. Tests were conducted to study the voltage distribution between the SF/sub 6/ gas and the vacuum interrupters immediately after a long current interruption. It is found that the voltage distribution is determined by the resistive impedances of respective interrupters during the post arc current flow and by the capacitive impedances of the interrupters contact gaps after the post arc current diminishes. >

Bucket type ion source using a microwave plasma cathode

Abstract For plasma processes one wants a large diameter and long life ion source. A filamentless ion source is desired when using reactive gases. We examined microwave plasma regarding its capability as an electron source and succeeded in extracting an electron current in the ampere range from the plasma. Then we developed a bucket type ion source using a microwave plasma cathode which replaces the conventional filament.

Primary electron orbit calculation in a bucket‐type ion source for ion milling

Primary electrons in a bucket‐type source for ion milling were investigated. Electron orbits were obtained using a computer program which solves the motion equation of electrons in a three‐dimensional magnetic field. Calculations and experiments showed that trapped primary electron density in the source agreed well with generated plasma density. The program was used to develop a large‐area ion milling machine with a 58‐cm‐diam bucket‐type source. The machine that was developed provided a uniform ion beam and milling rate.

Post arc current of vacuum interrupter after large current interruption

Postarc current characteristics of a vacuum interrupter have been examined under a condition of high-current interruption. A measurement technique was developed in which a shunt for measuring postarc current was set in a synthetic test circuit voltage source. Postarc current was measured after a 20-57 kA current interruption. The magnitude was greatly influenced by the rate of current decline. Residual resistance between electrodes was calculated from the measured values of recovery voltage and postarc current. The recovery of residual resistance was very rapid immediately after current zero and become slow later. >

Acceleration of high current heavy ions using a variable energy radio‐frequency quadrupole linac and measurement of the input beam emittance

A high current ion beam injection system and a variable energy radio‐frequency quadrupole (RFQ) accelerator with an external LC resonance circuit are tested. A four‐rod RFQ electrode of 2.3 m length is newly designed to obtain a milliampere class MeV ion beam. To increase accelerated beam current, injected beam emittance into the RFQ is measured and compared with the designed RFQ acceptance. Injected beam emittance tends to increase with the beam current increase. The beam acceleration tests are carried out with a cw rf power supply of 100 kW (10–30 MHz, continuously variable). Results show that the time‐averaged beam currents of N+ and Ar2+ are 1.1 mA (0.4 MeV) and 1.03 mA (1.0 MeV), respectively, and that the peak current of these beams is about 5 mA. As representative ion species for fabricating semiconductor devices, P+ and P2+ are accelerated, and the time‐averaged beam current of 0.48 mA (0.56 MeV) and 0.28 mA (0.81 MeV) are obtained, respectively. This high current MeV ion implanter has great poten...

Ion beam acceleration by an RFQ with an LC resonance circuit

Abstract For the development of a high current MeV implanter, ion beam acceleration using a variable energy RFQ system has been studied. The RFQ system consisted of an LC resonance circuit and conventional RFQ electrodes of 1.3 m in length. The output energy could be continuously varied by changing the resonance frequency of the circuit. The electrodes were designed to accelerate nitrogen ion beams (N + ) from 10 keV to 270 keV in order to investigate fundamental acceleration characteristics of the system. The designed intervane voltage was 26 kV. By improving the LC resonance circuit to generate a high voltage of radio frequency, a shunt impedance of over 70 kΩ was obtained, which was sufficient for MeV-range acceleration. Experimental results showed that N + beams were accelerated to 265 keV and Ar 2+ beams to 740 keV. Energy was varied by changing the frequency, in agreement with the calculated value. It was concluded that the RFQ system driven by the LC circuit should be very useful for MeV ion implantation in semiconductor device fabrication.

Ion beam injection system for a variable energy RFQ accelerator

Abstract A new injection system designed for a variable energy RFQ (radio frequency quadrupole) accelerator was developed from the viewpoint of introducing a high current ion beam into the RFQ. This injection system consists of a high current multiply charged ion source, a sector-type mass-separator, and a magnetic quadrupole triplet. The ion source is designed for effective production of a milliampere class lower-charge-state multiply charged ion beam. The mass-separator has a double-focusing action in order to mass-separate the high current beam. The quadrupole lens functions to focus the beam at the RFQ inlet position. In the experiments an Ar + injection beam current of 2.2 mA and an Ar 2+ current of 1.7 mA are obtained. The injection beam size is 10 mm O. A combination of this injection system with a variable energy RFQ accelerator should provide a milliampere class MeV ion implanter.

Discharge characteristics of bucket‐type ion source using a microwave plasma cathode

A large diameter and long‐life ion source is considered desirable for plasma processes. The advent of better filamentless ion sources is desired due to frequent utilization of reactive gases. We have proposed a bucket‐type ion source which uses a microwave plasma cathode in place of a conventional filament. This paper experimentally examined the V–I characteristics of arc discharge. An arc current of 2‐5 A was obtained at an arc voltage of 60‐150 V. The V–I characteristics were comparable to that of a conventional bucket‐type ion source using a filament. The V–I characteristics and the electron density distribution in the arc plasma are changed depending on the shape of the electron extraction electrode which was coaxially placed in the arc discharge chamber (200 mm diameter). The electrode diameter was optimized at 40 mm for this chamber. Two kinds of ion beams, argon and oxygen, were extracted from the ion source and both their beam current densities were over 1 mA/cm2. These values are sufficient for practical applications to ion beam milling.A large diameter and long‐life ion source is considered desirable for plasma processes. The advent of better filamentless ion sources is desired due to frequent utilization of reactive gases. We have proposed a bucket‐type ion source which uses a microwave plasma cathode in place of a conventional filament. This paper experimentally examined the V–I characteristics of arc discharge. An arc current of 2‐5 A was obtained at an arc voltage of 60‐150 V. The V–I characteristics were comparable to that of a conventional bucket‐type ion source using a filament. The V–I characteristics and the electron density distribution in the arc plasma are changed depending on the shape of the electron extraction electrode which was coaxially placed in the arc discharge chamber (200 mm diameter). The electrode diameter was optimized at 40 mm for this chamber. Two kinds of ion beams, argon and oxygen, were extracted from the ion source and both their beam current densities were over 1 mA/cm2. These values are sufficient for p...

Ion Milling Machine for Thin Film Magnetic Head Fabrication

a thin film head formed by dry processes appears in Fig. 1 [2]. The magnetic head consists of a substrate, lower magnetic core, conducting coil, upper core, and protective film. The flow chart of Fig. 2 summarizes the process for production of the head. Here, sputter formation of films and ion etching play vital roles. The ion etching is performed using an ion milling machine. Whereas mostly dry processes enable fabrication of high-quality thin film heads