AVS 46th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS-MoP

Paper PS-MoP21
Short Time Scale Instabilities of Ion Energies in an RF driven Fluorocarbon-Plasma

Monday, October 25, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: G.J. Peter, Balzers Instruments, Principality of Liechtenstein
Authors: G.J. Peter, Balzers Instruments, Principality of Liechtenstein
N. Müller, Balzers Instruments, Principality of Liechtenstein
H. Zogg, Balzers Instruments, Principality of Liechtenstein
H. Oehre, Balzers Instruments, Principality of Liechtenstein
Correspondent: Click to Email
Fluorocarbon gases are widely used for etching in the semiconductor manufacturing. Besides the desired etching, especially C@sub 4@F@sub 8@ tends to polymerisation and to a build-up of insulating coatings in the plasma chamber. The energy distributions of various ions from an RF-driven C@sub 4@F@sub 8@ -Plasma were investigated by a PPM (Plasma Process Monitor) to determine the influence of such coatings on the ion energy distribution. The PPM is a combination of a differentially pumped quadrupole mass filter and an energy analyser. An energy resolution of 0.3 eV and unit mass resolution over the whole mass range are achieved. The only part of the PPM exposed to the plasma is kept on floating potential so that coating here can not change the electrical potential. The maximum energy of the ions scattered out of the main discharge increased from initially 20 eV to 75 eV during the processing time of a single wafer (less than one minute). The energy rise was reproducible over several cycles. The initial energy was reached again after cleaning in a pure Argon plasma when a low content of C@sub 4@F@sub 8@ in Argon was used as sputter gas. So the effect can be attributed to the coating of the walls and electrodes. When pure C@sub 4@F@sub 8@ was used the coating was thus intense that it could not be removed by sputter cleaning any more. Electrical probes were tested to measure the shift of the plasma (sheet) potential, however they failed after a few minutes because they got coated. The results achieved show the usefulness of a mass spectrometer based plasma monitor whenever the ion energy is a critical process parameter. Applications are in basic plasma research as well as in pilot production plants.