Production of high density and large volume plasma by using a polyphase AC voltage source

Production of high density and large volume plasma for a plasma source ion implantation has been studied. Plasma is produced by a polyphase AC voltage source with maximum voltage and power of 2 kV and 12 kVA, respectively. Produced N2 plasma had a small ripple frequency of 720 Hz and a ripple ratio of 20% though frequency of the AC voltage source was 60 Hz. At output voltage of 600 V and N2 gas pressure of 5 Pa, plasma density in 6-phase operation and 12-phase operation were 8×108 cm−3 and 4×109 cm−3, respectively. The plasma density in 12-phase operation was about five times larger than that in 6-phase operation. Electron temperature of 0.9 eV was obtained in both operations. The uniform plasma was produced in the inner region of the ring basket electrode which had a radius of 20 cm and length 80 cm at 12-phase operation. The plasma density was increased in proportion to the N2 gas pressure and output voltage of the AC voltage source. When line-cusp magnets were attached to the process chamber wall, the plasma density increased about 2.5 times.