AVS 50th International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS-WeP

Paper PS-WeP9
Molecular Beam Mass Spectrometry of the Microwave Discharge in Methane/Argon Gas Mixture

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: P. Pokorny, Institute of Physics ASCR, Czech Republic
Authors: M. Misina, Institute of Physics ASCR, Czech Republic
P. Pokorny, Institute of Physics ASCR, Czech Republic
Correspondent: Click to Email
Mass spectrometry (MS) of the neutrals in a processing plasma requires extraction of a gas sample through an orifice, ionization, mass separation and detection. Radicals are detected by the appearance potential MS (APMS).@footnote 1@ APMS relies on the difference in the electron energy threshold for ionization of a radical by a simple electron impact ionization and for production of an fragment ion from a molecule by dissociative ionization. However, the absolute measurement of the radical density is complicated by the interaction of the radicals with the walls during the transport from the extraction orifice to the ionization source. This is especially true for species with a high sticking coefficient. Therefore, the molecular beam MS (MBMS) was developed.@footnote 2@ MBMS includes more stages of differential pumping with several orifices by which a beam of neutrals from the plasma is extracted into the ionization chamber of a MS. In this paper the concentration of radicals and the composition of the neutral gas in the microwave electron-cyclotron-resonance methane/argon plasma for DLC film deposition was measured by APMS and MBMS for a range of process parameters such as microwave power, working gas composition and total pressure. The total pressure in the experiment ranged from 0.1 to 1 Pa. The microwave power up to 800 W was used. The most abundant radical was methyl with a concentration of in the range of the order of 10@super 12@ cm@super -3@. A high degree of dissociation and consumption of the methane in the ECR discharge was observed. In fact, the hydrogen dissociated from the methane was the dominant component of the working gas at higher microwave powers. @FootnoteText@@footnote 1@ P. Kae-Nune, J. Perrin, J. Guillon, J. Jolly, Plasma Sources Sci. Technol. 4 (1995) 250-259.@footnote 2@ H. Singh, J. W. Coburn, D. B. Graves, J. Vac. Sci. Technol. A 17(5) (1999) 2447-2455.