ダブルホロー陰極イオン源の高融点金属イオン生成

抄録

There is a great demand for ions of various kinds of refractory materials, such as molybdenum (Mo), nickel (Ni) and tungsten (W) for new material production and plasma processing. We have developed a hollow cathode ion source with which ion beams of refractory materials of high current can be produced using sputter technique. We call this ion source the Double Hollow Cathode Metal ion source, which is a joined two hollow cathode tubes with different cathode diameter. This ion source is compact construction and easy operation in a state. In this ion source, most solid materials can be sputtred and ionized by the cold hollow cathode discharge mode. This ion source consists of three parts: a first cylindrical hollow cathode (40mm diameter), a second narrow hollow cathode (4mm diameter) as a sputter target, and an anode. The main discharge of this ion source is established the anode and cathode (first hollow cathode). The discharge path between these electrodes is made narrower by inserting a hollow cathode (second hollow cathode) and by applying a magnetic field along the narrowed discharge path. With increasing the sputter voltage of the second hollow cathode (up to 1kV), this ion source can be effectively produced metallic ions of refractory materials to be sputtered these hollow cathode. Our preliminary experimental results of this ion source has shown that refractory materials (Mo) of the second hollow cathode can be sputtered and ionized by a high temperature, high density plasma formed inside a narrow canal applying the negative voltage (sputter voltage) to this electrode and the axial magnetic field (600G). The current of metal ion beams increases with increasing the sputter voltage Vs of this second hollow cathode. The argon pressure in the first hollow cathode tube is approximately 0.25Torr and the discharge current Id is fixed at 0.8A. The metal ion percentage α (Mo⁺/(Ar⁺+Mo⁺)) reaches 25% at Vs=800V. The total ion beam current is obtain 1.6mA for a 10kV extraction voltage.