Plasma booster for plasma treatment installation
An arrangement for boosting or igniting a glow discharge plasma for coating workpieces has at least one hollow body of an electrically conductive material formed such that when an electric signal is applied to the hollow body at least in a certain pressure and voltage range, the geometric conditions for the ignition of a discharge in the interior of the hollow body are satisfied. The hollow body has at least one opening through which charge carriers can flow off into the environs of the arrangement in order to ignite and operate the plasma or to boost a plasma existing there. The arrangement has a mechanism which connects the hollow body electrically with the workpieces such that the hollow body is essentially at workpiece potential.
1. Arrangement for boosting and/or igniting a glow discharge plasma for the treatment, in particular for the coating, of workpieces, comprising:
at least one hollow body of an electrically conductive material, the hollow body comprising a hollow space and at least one opening at an entrance to the hollow space through which charge carriers can flow off into environs of the arrangement in order to make here possible ignition and operation of a plasma or to boost a plasma existing here, the hollow body comprising receptions for arranging workpieces at openings of the hollow body, wherein the hollow body is fastened on a carousel for the reception of workpiece carriers, wherein the hollow space of the hollow body is formed such that when an electric signal is applied to the hollow body, at least in a certain pressure and voltage range, geometric conditions for the ignition of a discharge in the interior of the hollow body are satisfied, and wherein the hollow space of the hollow body forms a hollow cathode space and with no workpiece arranged at said receptions, the geometric conditions for the ignition of a discharge at said at least one opening of the hollow body are satisfied, but with workpieces suitably arranged at said receptions, the geometric conditions for the ignition of a discharge are not satisfied at any opening of the hollow body, and wherein the arrangement comprises means which connect the hollow body electrically with the workpieces such that the hollow body is essentially at workpiece potential.
2. Arrangement as claimed in claim 1 , wherein the geometric conditions are satisfied for a pressure range between 1×10 −3 to 5×10 −2 mbar.
3. Arrangement as claimed in claim 1 , wherein the geometric conditions for an electric signal are satisfied with a voltage range between 200 to 2000 V.
4. Arrangement as claimed in claim 2 , wherein the electric signal is a DC voltage, an AC voltage, in particular a bipolar or unipolar pulsed AC voltage signal in the medium frequency range.
5. Arrangement as claimed in claim 1 , wherein the hollow body has a height h and a cross section with at least one geometrically characteristic parameter d, wherein the cross section has the form of a circle, an ellipse, a polygon or a form composed of different geometries, and the hollow body has at least one lateral face extending over the height h.
6. Arrangement as claimed in claim 5 , wherein the hollow body is covered at the top and/or bottom with a grid.
7. Arrangement as claimed in claim 5 , wherein the lateral face of the hollow body has several openings or slots over its height h.
8. Arrangement as claimed in claim 5 , wherein the at least one lateral face of the hollow body comprises grids or parallel wires or rods, or essentially consists of a grid or parallel wires or rods.
9. Arrangement as claimed in claim 5 , wherein the hollow body comprises several circular, elliptical, polygonal annuli or annuli of combined geometries, disposed one above the other, wherein the annuli are disposed at a distance a, which is sufficiently small to avoid the ignition of a hollow discharge between the annuli.
10. Arrangement as claimed in claim 9 , wherein the distance a is smaller than the cathode drop in a certain pressure and voltage range, in particular is between 1 to 60 mm.
11. Arrangement as claimed in claim 9 , wherein the annuli are formed as workpiece holders with receptions ( 7 ), wherein the receptions ( 7 ) or the workpieces ( 8 ) are disposed with respect to one another at a distance b, which is sufficiently small to avoid the ignition of a hollow discharge between the workpiece receptions ( 7 ) or the workpieces ( 8 ).
12. Arrangement as claimed in claim 11 , wherein distance a and/or b is smaller than the cathode drop in a certain pressure and voltage range, in particular is between 1 to 60 mm.
13. Arrangement as claimed in claim 5 , wherein distance d is less or equal to the twofold, however greater or equal to the simple cathode drop in a certain pressure and voltage range, in particular is between 20 to 200 mm.
14. Vacuum treatment installation for plasma treatment, in particular for the plasma coating of workpieces comprising an arrangement according to claim 1 .
15. Vacuum treatment installation as claimed in claim 13 , wherein the installation comprises an additional magnetic field generating device, which acts onto the hollow cathode discharge gap or boosts the plasma.
16. Vacuum treatment installation as claimed in claim 15 , wherein through the magnetic field generating device a magnetic field 13 is producible, that acts perpendicularly onto the hollow cathode discharge gap.
17. An arrangement as claimed in claim 1 , wherein a portion of an outside boundary of the hollow space is formed by a portion of at least one of the workpieces.
18. An arrangement as claimed in claim 1 , wherein said means which connect the hollow body electrically with the workpieces is configured so that the hollow body at least substantially as a whole is essentially at workpiece potential.
19. An arrangement as claimed in claim 1 , wherein said ignited and operated or boosted plasma is a plasma for treatment of the workpieces.
20. An arrangement as claimed in claim 1 , wherein said arrangement is for coating workpieces.