Plasma Diagnostics V

Atomic fluorine is an important radical for etching and cleaning in semiconductor processing chambers. However, it is currently impractical to use two-photon laser induced fluorescence to measure atomic fluorine in situ due to the need for vacuum UV photons (170 nm). We present hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) measurements of atomic fluorine through the ²P_3/2 ²P_1/2 transition at 404 cm^-1. Measurements were conducted in an NF₃/Ar pin-to-plane nanosecond-pulsed plasma. Probe delay scans show the presence of coherence beats due to the hyperfine doublet structure of atomic F which confirms the identity of the Raman peak as atomic F. A supercontinuum pump/Stokes pulse was used to access the N-F stretch of NF₃ and enable time-resolved measurements of both NF₃ consumption and F production by the plasma.

Funding acknowledgement

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences under contract number DE-NA0003525. This research used resources of the Low Temperature Plasma Research Facility at Sandia National Laboratories, which is a collaborative research facility supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences. The views expressed in this paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government