AVS 47th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA1
Effect of Xenon Dilution on Fluorocarbon Plasma Chemistry and Electron Distribution Function

Tuesday, October 3, 2000, 2:00 pm, Room 311

Session: Plasma Diagnostics I
Presenter: H. Sugai, Nagoya University, Japan
Authors: H. Sugai, Nagoya University, Japan
T. Ishijima, Nagoya University, Japan
M. Ikeda, Nagoya University, Japan
Correspondent: Click to Email
Two types of unmagnetized high-density fluorocarbon plasmas, ICP (inductively coupled plasma, 13.56 MHz) and SWP (surface wave plasma, 2.45 GHz), are produced and compared in an identical vessel under the same gas conditions (10 % C@sub 4@F@sub 8@ + 90 % Ar, total pressure 20 mTorr). The ion and radical compositions are measured by a quadrupole mass spectrometer. The measurements at the same electron density of 2.5 x 10@super 11@ cm@super -3@ reveal that the ICP is more strongly dissociated than the SWP, with the smaller ratio of CF@sub x@ radical density to F radical density. Such different plasma chemistry between the two plasmas is attributed to the difference in the electron distribution functions (EDFs) observed in the experiment. Namely, the ICP has the EDF close to Maxwellian with higher electron temperature while the SWP has a bi-Maxwellian type of EDF composed of a cold electron group (lower temperature T@sub ec@) and a hot electron group (higher temperature T@sub eh@). The bi-Maxwellian EDF might be formed by stochastic heating at the plasma resonance layer in the SWP. Furthermore, replacement of the argon buffer gas with xenon gives rise to dramatic changes in plasma properties as follows. First, the xenon dilution makes it possible to obtain the same electron density by a factor of five less discharge power. Second, the radical density ratio of CF@sub x@ to F is increased by an order of magnitude in the Xe dilution, compared with the Ar dilution. Thirdly, the EDF measurement showed the value of T@sub ec@ lower by a factor of 2/3 in case of the Xe dilution. Finally, a global model of particle balance based on the measured EDFs supports these observations.