Hybrid fs/ps CARS measurements of atomic fluorin

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.