Negative ion density in inductively coupled chlorine plasmas
- Sandia National Laboratories, Albuquerque, New Mexico 87185-1423 (United States)
Laser photodetachment spectroscopy has been used to infer the density of chlorine negative ions in an inductively coupled chlorine plasma. Time dependent, excess electron density produced by photodetaching electrons from Cl{sup {minus}} was detected by a microwave interferometer operating at 80 GHz. By focusing the microwave probe beam through the center of the discharge, negative ion density measurements could be performed in a small, 1.5 cm{sup 3}, volume. As the rf power into the plasma increased from 155 to 340 W at 20 mTorr, the Cl{sup {minus}} density in the center of the bulk plasma increased from 3.4 to 5.2{times}10{sup 11} cm{sup {minus}3}. As the pressure was increased from 15 to 50 mTorr at 240 W, the Cl{sup {minus}} density increased from 3.5 to 5{times}10{sup 11} cm{sup 3}. Over this parameter space, the negative ion density equaled the electron density to within a factor of 2. The negative ion radial distribution was relatively constant, with a 20{percent} decrease in the center of the plasma for some operating conditions. When the surface of the bias electrode was changed from stainless steel to silicon, the electron density remained constant but the Cl{sup {minus}} density decreased by a factor of 2 to 3. {copyright} {ital 1996 American Vacuum Society}
- OSTI ID:
- 285899
- Journal Information:
- Journal of Vacuum Science and Technology, A, Vol. 14, Issue 4; Other Information: PBD: Jul 1996
- Country of Publication:
- United States
- Language:
- English
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