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

Invited Paper PS+MS-TuM9
Electron Energy Distribution in C@sub 2@F@sub 4@/CF@sub 3@I Ultrahigh-Frequency and Inductively Coupled Plasmas

Tuesday, November 5, 2002, 11:00 am, Room C-105

Session: Plasma Diagnostics and Sensors
Presenter: T. Nakano, National Defense Academy, Japan
Authors: T. Nakano, National Defense Academy, Japan
S. Samukawa, Tohoku University, Japan
Correspondent: Click to Email
The electron energy distribution function (eedf) is an important factor in determining radical compositions in plasmas for nanometer-scale device fabrication. In this presentation, the electron energy distribution in plasma through a C@sub 2@F@sub 4@/CF@sub 3@I mixture, which is a novel chemistry proposed for low-damaged, fine structure etching of SiO@sub 2@, is studied by trace rare gas optical emission spectroscopy (TRG-OES) and probe measurements. The integrated eedf above 13.5 eV (S@sub eedf@) is evaluated from the Ar emission at 750.4 nm. The S@sub eedf@ exhibits a weaker dependence on the gas composition for the C@sub 2@F@sub 4@/CF@sub 3@I mixture than for the C@sub 4@F@sub 8@/Ar mixture which is conventional chemistry for SiO@sub 2@ etching. For practical etching conditions, the S@sub eedf@ for the C@sub 2@F@sub 4@/CF@sub 3@I mixture becomes smaller than 1/3 of that for the C@sub 4@F@sub 8@/Ar mixture in both ultrahigh-frequency (UHF) plasmas and inductively coupled plasmas (ICP). Thus, using the C@sub 2@F@sub 4@/CF@sub 3@I chemistry, low charging damage in SiO@sub 2@ etching is expected. The probe-measured electron temperature (T@sub e@), which indicates the degree of the exponential eedf decay in the low energy, is 2.5 eV in UHF plasma through the C@sub 2@F@sub 4@/CF@sub 3@I mixture and 4.1 eV in the ICP, while S@sub eedf@ is twice as large in the UHF plasma as in the ICP. This suggests an eedf enhancement in the middle energy region (5-10 eV) for the ICP, which prompts the dissociation of the feedstock gases. A quantitative estimation of the eedf using a bi-Maxwellian-like function, which is crucial to understanding the relationship between the eedf and feedstock gas dissociation, is in progress. The preliminary results also support the eedf enhancement in the middle energy region for the ICP.