Numerical simulation and optimization of discharge chamber miniaturization for the double hollow cathode sputtering type metal ion source

Abstract The double hollow cathode metal ion source produces metal elements by hollow cathode sputtering and has a high material utilization rate. However, at present, a high magnetic mirror field is generated by an electromagnet, which is huge in volume and the edge field of a high magnetic mirror field seriously affects ion extraction. Miniaturization of the discharge chamber is a feasible method to solve this problem. In this paper, a two-dimensional fluid model of the double hollow cathode discharge structure under magnetic mirror field constraints is developed to study the double hollow cathode discharge and ion sputtering. The results show that the sputtering depth flux is formed above the sputtering voltage of 400 V. The evolution of the sputtering depth profile results from the combined effect of the wall ion flux, spatial radial electric field, and ion collisions. The location of the maximum ion sputtering depth depends mainly on the energetic ions entering the hollow cathode from the anode. The magnetic field and thermal electron emission strongly correlate with the sputtering depth. A small discharge chamber structure is proposed with a hollow cathode length of 36 mm, which is 24 mm smaller than the ion source established by Peking University in 2017, using a magnetic mirror field of 1400 Gs at the center point, which can be realized in the form of a permanent magnet. The electron density in the center of the discharge chamber is 2.88 × 10 21 m -3 and 99% of the electrons are confined within a radius of about 3.7 mm.