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

Paper PS2-TuA5
Determination of Electron Temperature, Fluorine Concentration, and Gas Temperature in Fluorocarbon/Argon Plasmas using Optical Emission Spectroscopy

Tuesday, October 3, 2000, 3:20 pm, Room 311

Session: Plasma Diagnostics I
Presenter: M. Schabel, Lucent Technologies, Bell Laboratories
Authors: M. Schabel, Lucent Technologies, Bell Laboratories
V.M. Donnelly, Lucent Technologies, Bell Laboratories
A. Kornblit, Lucent Technologies, Bell Laboratories
W. Tai, Lucent Technologies, Bell Laboratories
F. Klemens, Lucent Technologies, Bell Laboratories
Correspondent: Click to Email
Recent advances in the interpretation of optical emission spectra from plasmas has made it possible to measure parameters such as electron temperature (T@sub e@), relative electron density, and gas temperature (T@sub g@) with this nonintrusive technique. This allows for the characterization and real-time monitoring of plasmas under conditions where the use of Langmuir probes is difficult (i.e. deposition plasmas or in manufacturing). Here we discuss the application of several advanced optical emission techniques to characterize fluorocarbon/Ar plasmas in an Applied Materials IPS inductively-coupled reactor. We have employed trace rare gas optical emission spectroscopy (TRG-OES), optical actinometry, and N2 vibrational spectroscopy to determine T@sub e@, fluorine atom concentration, and T@sub g@ respectively. Two etching processes, containing mixtures of Ar, C@sub 2@F@sub 6@, and C@sub 4@F@sub 8@, were evaluated as a function of pressure (5-90 mTorr). In the case of TRG-OES and optical actinometry, a mixture containing equal parts of He, Ne, Ar, Kr, and Xe (~1% ea.) was added. Large partial pressures of Ar prevent its use in TRG-OES because of radiation trapping effects (only the Kr and Xe lines were used to determine T@sub e@). Above 40 mTorr, T@sub e@ is insensitive to variations in pressure, and is ~2.5 eV. Below 40 mTorr, T@sub e@ increases with a decrease in pressure to 7 eV at 5 mTorr. The relative fluorine concentration increases with pressure and with the fraction of fluorocarbon species in the gas. At 5 mTorr, T@sub g@ is ~1010 K. Finally, we evaluated the effect of replacing Ar in the process gas with He or Ne, thereby allowing for the emission of the added Ar to be included with the Kr and Xe lines for determining T@sub e@. The resulting change in the accuracy of T@sub e@ measured by TRG-OES will be discussed in addition to how the use of He or Ne affects T@sub e@ and the relative electron density.