AVS 45th International Symposium
    Plasma Science and Technology Division Thursday Sessions
       Session PS-ThP

Paper PS-ThP11
Analysis of Fast Neutrals in Plasma Monitoring

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Plasma Science and Technology Division Poster Session
Presenter: J. Wei, ABB Extrel
Authors: J. Wei, ABB Extrel
R.E. Pedder, ABB Extrel
Correspondent: Click to Email
Fast neutrals are generated in plasma and high energy ion sputtering processes. The kinetic energy of the fast moving molecules can be as high as a few hundred electron volts. The analysis of these fast neutrals with a regular residual gas analyzer has been shown to be very difficult in many cases. The first problem in the analysis is the decrease in the number of ions from the ionizer as the kinetic energy of the fast neutrals increases. The second problem is the loss of ion transmission through the quadrupole mass filter with the high energy ions from the fast neutrals. The combination of these problems often translates into distorted peak shapes in the mass spectrum and very low sensitivity for the fast neutrals. We will present the results on the analysis of fast moving neutrals with a quadrupole mass spectrometer. This quadrupole mass spectrometer is equipped with a biasable quadrupole mass filter assembly and an ion energy analyzer. With this setup, we can either slow down all the ions through a bias potential on the mass filter assembly or select only the ions at a given kinetic energy range and then slow them down to an optimum kinetic energy when they travel into the quadrupole mass filter. This bias potential on the quadrupole mass filter assembly minimizes the ion transmission loss through the quadrupole and restores the sensitivity for the detection of the fast neutrals. Furthermore, when the kinetic energy of the fast neutrals are a couple of electron volts or higher, we can use the energy analyzer to distinguish the fast neutrals from the same gas components or components with identical mass in the residual gas background.