Helium (He) inductively coupled plasma (ICP) was generated by a right-helical-type RF antenna. At a fixed He pressure of 20 mTorr, the optical emission spectrum from the He plasma was measured with RF power. The E-H mode transition and the characteristic hysteresis of the mode transition were confirmed by a change in the spectral line intensity of the 33D−23P transition at 587.6 nm. By laser absorption spectroscopy using a laser light with a wavelength of 1083 nm resonant to the 23S→23P absorption transition, the line-integrated He 23S metastable density was measured and found to show consistent behavior with the spectral line intensity of the 33D−23P transition during the E-H mode transition. The line-integrated He 23S metastable atom density exhibited distinctly different longitudinal distributions in the E and H modes.
- 2SMetastable atom density
- E-H mode Transition
- He inductively coupled plasma