Negative ion densities in chlorine- and boron trichloride-containing inductively coupled plasmas
- Sandia National Laboratories, Albuquerque, New Mexico 87185-1423 (United States)
The chlorine negative ion density and the electron density in chlorine- and boron trichloride-containing inductively coupled plasmas were investigated experimentally. Measurements were performed in a GEC reference cell operated in the inductively coupled mode. The chlorine negative ion density was measured as an excess electron density produced by photodetachment of electrons from the negative ions by 266 nm radiation from a frequency-quadrupled Nd:YAG laser. Both the excess electron density and the steady-state electron density were measured using a microwave interferometer. Various gas mixtures were investigated including pure Cl{sub 2}, pure BCl{sub 3}, combinations of the two, and combinations of these gases with N{sub 2} and Ar. Cl{sup {minus}} densities up to 4{times}10{sup 11} cm{sup {minus}3} were measured depending on the gas mixture. The ratio of electron density to Cl{sup {minus}} density was as high as 3 in Cl{sub 2} mixtures, and up to 5 in BCl{sub 3} mixtures. The plasma was probed at lower photon energy (355 nm) to photodetach electrons from other potential negative ions present in the plasma: to within the sensitivity of the measurement (1.3{times}10{sup 8} cm{sup {minus}3}), no other negative ions such as BCl{sub x}{sup {minus}} or Cl{sub 2}{sup {minus}} ions were detected. Significant interactions between Cl{sub 2} and Ar were observed as determined by changes in the Cl{sup {minus}} density. The Cl{sup {minus}} density also changed when BCl{sub 3} was added to Cl{sub 2} discharges. Addition of Ar or N{sub 2} to Cl{sub 2} plasmas had little effect on Cl{sup {minus}} density, but nitrogen addition had very dramatic effects when added to BCl{sub 3}, causing a factor of 2 increase in the Cl{sup {minus}} density. {copyright} {ital 1997 American Vacuum Society.}
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 549299
- Journal Information:
- Journal of Vacuum Science and Technology, A, Vol. 15, Issue 4; Other Information: PBD: Jul 1997
- Country of Publication:
- United States
- Language:
- English
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