AVS 45th International Symposium
    Plasma Science and Technology Division Tuesday Sessions
       Session PS1-TuM

Paper PS1-TuM6
Diagnostics of Pulsed Plasmas, and the Use of Pulsed Plasmas as a Diagnostic Tool

Tuesday, November 3, 1998, 10:00 am, Room 314/315

Session: Pulsed Plasmas
Presenter: M.V. Malyshev, Bell Laboratories, Lucent Technologies
Authors: M.V. Malyshev, Bell Laboratories, Lucent Technologies
V.M. Donnelly, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
Pulsed plasma (PP) experiments were carried out in a transformer coupled plasma (TCP) reactor in argon and chlorine plasmas. Time resolved electron temperatures (T@sub e@), electron energy distribution functions (EEDF), electron densities (n@sub e@), positive ion densities (n@sub i@ @super +@), and negative ion densities ~(n@sub i@ @super +@ - n@sub e@) were measured with combinations of trace rare gases optical emission spectroscopy (TRG-OES), Langmuir probe, and microwave interferometry (MWI). These plasma parameters were studied as a function of pressure and power and compared with CW plasma operation. Time resolved number densities of metastable states of rare gases (1s@sub 3@ and 1s@sub 5@) were determined from a model that computes TRG-OES intensities. As the RF power is switched on at the beginning of the 100 us pulse period in a 10 mTorr Cl@sub 2@ plasma, n@sub e@ is near zero and starts increasing slowly, while T@sub e@ rises rapidly to 8 eV and falls to 4 eV in 5 us and to 1.9 eV in 20 us. We also designed a series of PP experiments to circumvent an impediment (the lack and inconsistency of published cross sections for electron impact excitation out of metastable states) in our TRG-OES model. Time resolved OES signals and n@sub e@ (from MWI) were recorded and compared. The rise of optical emission excited from the ground state (e.g. Ar 750.4 nm) coincides with the rise of n@sub e@ during the plasma-ON period, while the emission that comes mainly from excitation out of metastables (e.g. Xe 881.9 nm) increases more rapidly. Assuming the ground state cross sections are correct, we used this comparison to scale cross sections for excitation out of the metastables. Recent theoretical calculations agree with our pulsed-plasma-corrected cross sections.