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    Plasma Science Friday Sessions
       Session PS-FrM

Invited Paper PS-FrM1
Optical Diagnostics of Charged Particles in Processing Plasmas

Friday, November 2, 2001, 8:20 am, Room 104

Session: Diagnostics III
Presenter: A. Kono, Nagoya University, Japan
Correspondent: Click to Email
Behaviors of electrons and negative ions in low-pressure high-density inductively coupled plasmas have been studied using non-intrusive optical diagnostic techniques. An efficient multichannel laser Thomson scattering measurement system, which is highly resistant to Rayleigh scattering interference, was developed and used to study electron energy distribution functions (EEDFs). In measurements of C@sub 4@F@sub 8@/Ar plasma at a total pressure of 25 mTorr, non-Maxwellian EEDFs were observed, in contrast to Maxwellian EEDF observed for pure Ar plasma. A particle simulation suggests that the observed EEDFs result from local electron heating and subsequent cooling of electrons by inelastic collisions in the non-heating region. Laser photodetachment technique in combination with millimeter-wave Fabry-Perot resonance technique was used to study negative ion density. Measurements of CF@sub 4@/, C@sub 4@F@sub 8@/, SF@sub 6@/, and NF@sub 3@/Ar plasmas at 25 mTorr show that at an Ar dilution ratio as high as 95% and at electron densities around 10@super 11@ cm@super -3@, the negative ion density is higher than or nearly as high as the electron density. This indicates that in high-density C@sub 4@F@sub 8@, SF@sub 6@, and NF@sub 3@ plasmas electron attachment occurs as effectively as in low-density plasmas with low dissociation degrees of the feedstock gases; on the other hand, in high-density CF@sub 4@ plasma, electron attachment takes place much more effectively than in low-density plasma, suggesting that dissociation of CF@sub 4@ results in production of highly electron-attaching species.