The present invention relates to a plasma source which is arranged in floating fashion on a vacuum chamber, wherein the plasma source comprises a source housing, and a filament is provided in the source housing and is arranged so as to be insulated therefrom, wherein means for measuring the potential drop between the source housing and the filament are provided. The measured potential drop can be used for regulating the voltage heating the filament. According to the invention, corresponding means are provided.
1. Plasma source on a vacuum chamber for generating a plasma in the vacuum chamber, wherein the plasma source comprises a source housing with an opening protruding into the vacuum chamber and wherein, in the source housing, a filament is provided to which a heater voltage (V heiz or U heiz ) can be applied to the filament through supply lines that pass through insulated via openings formed in the source housing, so that the filament can be heated by means of a current flow, characterized in that the source housing is placed on the vacuum chamber in a manner electrically insulated therefrom, and in that means are provided for measuring a potential drop (V float or U float ) between a supply line to the filament and the source housing that represents the state of the potential drop between the filament and a plasma ignited inside the source housing, and thus for the state of the emission of electrons from the filament, and means are provided for regulating the heater voltage (V heiz or U heiz ) that are configured to process the measured value of potential drop (V float or U float ) as control signal in order to adjust the state for the electron emission to be maintained.
2. Device with a plurality of plasma sources according to claim 1 , characterized in that the plasma sources are surrounded respectively by at least one source coil and the plasma sources are surrounded by an outer coil comprising several plasma sources extending above the processing height.
3. Device according to claim 1 , characterized in that the heater voltage is fed by means of at least one switched-mode power supply, wherein a discharge voltage (V disc or U disc ) required for the discharge is applied centrally and opposite the filament.
4. Method for generating a plasma in a vacuum chamber, the method comprising:
placing a plasma source with a source housing and a filament in the source housing on the vacuum chamber,
applying a heater voltage (V heiz or U heiz ) to the filament to heat the filament by means of a current flow,
maintaining the source housing opposite the vacuum chamber and on a floating potential,
measuring a potential drop (V float or U float ) between a supply line to the filament and the source housing inside which a plasma is burning and
using the measured potential drop for regulating a heater voltage (V heiz or U heiz ) applied to the filament,
wherein the heater voltage results in a current heating the filament and thus in an emission of electrons.
5. Method according to claim 4 , characterized in that the heater voltage is regulated in such a manner that the potential drop between the source housing and the filament is essentially maintained constant.
6. Method according to claim 4 , characterized in that the potential drop between the source housing and the filament is maintained at values between 0V and −10V.
7. Method according to claim 4 , characterized in that the floating potential comprises an electrically floating manner.