Atomic chlorine concentration and gas temperature measurements in a plasma etching reactor

The technique of diode laser absorption has been used to measure gas temperatures and atomic chlorine concentrations in a Cl2 glow discharge. The infrared transition used is between the 2P1/2←2P3/2 spin‐orbit levels and occurs at 882.36 cm−1. The measured atomic chlorine translational temperature was 770±100 K, and was relatively independent of plasma conditions over the range studied. This temperature was confirmed by an analysis of the rotational band shape of nitrogen second‐positive emission which yields a nitrogen rotational temperature. Measured atomic chlorine concentrations ranged from 1.8×1014 to 6.6×1014 cm−3, representing atomic chlorine fractions from 3% to 8%. Atomic chlorine concentration increased with both increasing discharge power and pressure.

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