A Study on Beam Extraction Characteristics of RF and DC Filament Ion Source for High Current Ion Implanters

Abstract

In high current implantation, improving the ion extractability is a decisive factor contributing to the equipment efficiency and process cost reduction. A direct current filament ion source and inductively coupled plasma ion source were prepared to observe the degree of plasma extraction according to the ion source characteristics. The plasma parameters used to optimize beam extraction for the filament and RF discharges were 600 W, Ar 2 × 10 −5 Torr, and Ø200 × 250 mm discharge space. In the thermionic ion source, the ion density, electron temperature, and Bohm current density were 5 × 10 9 1/cm 3 , ≥ 6 eV, and ≈ 3.5 A/m 2 , respectively. In the RF ion source, the ion density, electron temperature, and Bohm current density were approximately 5 × 10 10 1/cm 3 , ≈ 3 ∼ 4 eV, and ≈ 25 A/m 2 , respectively. Optimization and analysis of ion extraction according to the plasma and accelerator parameters were calculated using IBSimu. The beam emittance, which is the most important parameter of the ion beam quality, was measured as the beam envelope onto the phase space by an ellipse. A change in the plasma meniscus shape was observed according to the plasma parameters in the ion source, and the emittance of the extracted ion beam was calculated according to the electrode gap distance and aperture structure.