AVS 49th International Symposium
    Plasma Science Tuesday Sessions
       Session PS+MS-TuM

Paper PS+MS-TuM8
Gas Temperature Effects on CF@sub x@ Kinetics in a CF@sub 4@ Inductively Coupled Plasma

Tuesday, November 5, 2002, 10:40 am, Room C-105

Session: Plasma Diagnostics and Sensors
Presenter: J.P. Booth, Ecole Polytechnique, France
Authors: H. Abada, Ecole Polytechnique, France
J.P. Booth, Ecole Polytechnique, France
P. Chabert, Ecole Polytechnique, France
Correspondent: Click to Email
We have used Laser Induced Fluorescence to determine CF and CF@sub 2@ radical concentrations in steady state and pulse-modulated inductively-coupled plasmas in CF@sub 4@ at 5 and 33 mTorr. The rotationally-resolved LIF excitation spectra of the CF radical were used to determine the space and time resolved gas temperature. Strong temperature gradients were observed, with the temperature reaching 800 K in the reactor center at 33 mTorr, 250 W RF power. These measurements were used to correct the LIF measurements for the dependence of the partition function on the gas temperature, providing the first reliable measurements of CF and CF@sub 2@ kinetics in this system. The concentration profiles can be used to deduce the net flux of these species from or to the reactor walls, using Fick's law but also allowing for thermo-diffusion. The steady-state CF@sub 2@ profiles showed that this species is produced predominantly at the reactor walls by CF@sub x@@super +@ ion bombardment. Surprisingly, in the post-discharge the CF@sub 2@ density increases markedly for several milliseconds, before decaying slowly. We will explore the possible origins of this phenomenon, which include convection induced by gas cooling, vibrational relaxation and conversion of CF to CF@sub 2@ by chemical reaction. In contrast, the CF radical appears to be both produced and destroyed in the gas phase, and it's concentration decays monotonically and rapidly in the post-discharge.