K. Takayama

Plasma filament ion source

Abstract This paper reports the use of a plasma filament instead of a heated solid filament in the Freeman ion source to make a new ion source which has a very long lifetime and especially enables the steady supply of a high intensity oxygen ion beam. The plasma filament is a highly ionized and high density plasma ( n e >10 13 cm −3 ), and composed of ions, high temperature electrons ( T e =3–9 eV ) and metastable atoms. It has been recognized that the O + ion beams are obtained using an argon or a neon plasma filament. The lifetime of this ion source is longer than that of the Freeman ion source.

Ion source with plasma cathode for ion assisted deposition

Abstract An ion source with a plasma cathode has been developed to attain a long lifetime for oxygen ion production. In this ion source, a plasma of a nonreactive working gas serves as a cathode in place of a thermionic tungsten hot cathode used in the Kaufman ion source. This ion source consists of two compartments, i.e. a plasma generator provided with a metallic hot cathode and a plasma chamber interconnected by a narrow tapered duct. The pressure difference between the two parts made by differential pumping prevents the feed gas supplied to the plasma chamber from flowing into the plasma generator. Mass spectrometry results show that this ion source has the ability of generating a considerable amount of O+ ions. This ion source is also eminently suitable for oxygen ion production.

A high current sheet plasma ion source

Abstract A cylindrical solid beam has great disadvantages in high current, high energy ion implantation. These disadvantages are poor heat dissipation, nonuniformity of the beam itself and difficulty of irradiation on large area samples. A sheet ion source and an irradiation system have been developed, in which beltlike samples could be run perpendicular to a sheet ion beam. The design and operation principles are reported.

Plasma compression type hollow cathode ion source

Abstract In general, a hollow cathode ion source (HCIS) for implantation industries has the fatal demerit of low gas efficiency. This paper reports that this disadvantage of HCIS is solved by inserting insulated narrow slits between the anode and the cathode in order to compress the cross section of the discharge path. As a result, the large pressure differences between outer and inner regions of the ion source can be held and the gas efficiency is increased.

Simple hollow cathode ion source

Abstract A simple hollow cathode ion source has been developed and investigated for increasing ion source lifetime and beam current capability. The experimental results of a LaB6 cathode show that a plasma density of up to 1012/cm3 can be generated with a discharge current of 4.0 A and a pressure of 6.7 Pa, resulting in extracted ion beams that are extremely quiet and stable. The ions of non-volatile elements of cathode materials can be easily obtained by virtue of the sputtering effect of a SUS cathode. The lifetime of our ion sources can be shown to be more than 150 hours.

Characteristics of sheet plasma ion source

A sheet plasma ion source has been developed. The new technology will allow simultaneous irradiation of large area samples of 500 mm in width with a high‐current ion beam. As a first step of this development, a sheet ion beam of 90 mm width and currents of 38 mA had been successfully extracted from the stable sheet plasma. Both characteristics of the sheet plasma discharge and the sheet ion beam extraction are reported in this article.

A concept for isotope separation in a sheet plasma by using ion cyclotron resonance heating

Abstract The concept of a novel method for separation of isotopes, the sheet plasma method, is described. A unique feature of this method is to perform isotope separation in a special kind of magnetized plasma: a sheet plasma: ions of a desired isotopic species in this plasma are selectively energized by ion cyclotron resonance heating. Owing to the unique characteristics of sheet plasmas — (i) the guiding centers of all gyrating ions he in the vicinity of the midplane of a plasma and (ii) the plasma thickness is as thin as twice the mean ion Larmor radius — extremely efficient separation of isotopes is possible.

Hollow cathode ion source for application to an implanter

Abstract A hollow cathode ion source has been studied in order to improve the life-time of an ion source for an ion implanter. Both volatile and refractory elements are shown to be ionized using two types of discharge state of the hollow cathode namely hot and cold cathode discharge. The life-time of LaB 6 as the hot cathode is more than 150 h and the ion beam currents reach more than 10 mA cm −2 at the extraction voltage of 10 kV. For the cold cathode operation, stable currents of ∼40 to 70 μA are extracted of refractory metal ions such as W and Mo.

Detection of CH3 radicals in an RF CH4H2 plasma by photoionization mass spectrometry

Abstract To investigate processes occurring during thin-film deposition by plasma chemical vapor deposition, a study was made of the radical species in an RF CH 4 H 2 plasma using photoionization mass spectrometry. The method avoids fragmentation of particles as can occur in conventional mass spectrometry by using photons for their ionization. In the present experiment, a capacitive 13.56-MHz RF plasma reactor was used and the total gas pressure was 2.7 × 102Pa. Besides the CH3 radical on whose detection emphasis was laid, CH2, CH, C2H3 and C2H4 were detected in the excited CH 4 H 2 plasma using a quadrupole mass spectrometer with a Kr or Ar resonance lamp. The lamp was microwave-operated at 2.45 GHz to produce the ultraviolet resonance radiation with two components of energies 10.03 and 10.64 eV in Kr or 11.62 and 11.83 eV in Ar. Suppression of undesirable ionization of particles by impact of accelerated photoelectrons generated by lamp radiations was achieved by voltage control of the ion-lens electrodes. The detection sensitivity of the apparatus was estimated as having a CH3 number density of typically 2.0 × 1011cm−3. Data were obtained on the dependence of CH3 radical density upon the CH4 mole fraction of the CH 4 H 2 source gas.

Plasma filament ion source for high current implanter

Abstract A plasma filament ion source has been developed as a long lifetime ion source for use in ion implanters. In this ion source, a plasma filament replaces a conventional metallic filament used in a Freeman type ion source. This ion source consists of two compartments, i.e. a plasma generator and an ion source chamber interconnected by a tapered narrow duct. The pressure difference between the two parts made by differential pumping prevents the feed gas from flowing into the plasma generator. With any combination of a plasma filament of either argon or neon and a feed gas of either AsF 5 or PF 5 , the lifetime was found to be more than 90 h with an extraction voltage of 40 kV and a corresponding ion current density of 20 mA/cm 2 ; a considerable amount of As + and P + ions were observed in mass spectra. This ion source is eminently suitable for oxygen ion production and useful for realizing a full cryopumping ion implanter system.