Bochum 2015 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 9: Diagnostics I
P 9.2: Fachvortrag
Dienstag, 3. März 2015, 11:00–11:25, HZO 30
Quantum cascade laser absorption spectroscopy for the detection of transient species in plasmas — •Jean-Pierre van Helden1, Marko Hübner1, Andy Nave1, Norbert Lang1, Paul Davies2, and Jürgen Röpcke1 — 1Leibniz Institute for Plasma Science and Technology, F.-Hausdorff-Str. 2, 17489 Greifswald, Germany — 2Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
The detection and quantitative measurement of transient species is a major challenge in industrial plasma applications. We present examples applying laser-based diagnostics in the mid-infrared using lead salt diode lasers and quantum cascade lasers (QCLs). The first example is the measurement of chlorine atoms using the 2P1/2 ← 2P3/2 spin-orbit transition at 882 cm−1 in a pure Cl2 ICP plasma by tunable diode laser absorption spectroscopy. The gas temperature and the Cl atom density were monitored as a function of gas pressure and RF power. The second example is the detection of CF2 radicals around 1106.2 cm−1 in fluorocarbon plasmas employed to etch low-k dielectrics in industrial dielectric etching plasma processes. We found that the CF2 radical concentration during the etching plasma processes directly correlates to the layer structure of the etched wafer. Another example is the detection of SiH3 radicals around 2169 cm−1, which is considered to be the most relevant radical in silane based plasma processes. As far as we are aware these are the first measurement in a silane plasma using the external-cavity QCL absorption technique, providing a new and reliable method for measuring quantitatively the silyl radical.