Multiple-cell source of uniform plasma

• US 6,250,250 B1
• Filed: 03/18/1999
• Issued: 06/26/2001
• Est. Priority Date: 03/18/1999
• Status: Expired due to Fees

• Current Assignee: Advanced Ion Beam Technology Incorporated
• Original Assignee: Advanced Ion Beam Technology Incorporated
• Inventors: Shkolnik, Alexander, Velikov, Leonid, Ritter, James, Maishev, Yuri
• Primary Examiner(s): Mills, Gregory
• Assistant Examiner(s): ALEJANDRO MULERO, LUZ L
• Application Number:
  US09/272,646
• Time in Patent Office: 831 Days
• Field of Search: 118/723.E, 118/723.ER, 118/723.MR, 118/723.MA, 156/345
• US Class Current: 118/723.0ER
• CPC Class Codes: H01J 37/32009 Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources plasma generation in general H05H1/24
• CPC Class Codes: H01J 37/32568 Relative arrangement or disposition of electrodes; moving means

Abstract

A multiple-cell plasma source consists of a pair of perforated plate-like cathodes and a perforated plate-like anode between the both cathode plates. Perforations in all three plates are coaxial and form a plurality of cells in which a Penning discharge plasma is generated due to the passage of axial components of the magnetic field through the individual cells. Since in all cells the plasma flow components are generated and work independently, there are no limitations for an increase in the surface area of the upper cathode plate, which has plasma emitting holes, so that the plasma source can treat objects of a large surface area. The plasma source of the invention has various means for controlling and adjusting the plasma pattern, distribution, parameters, and shape.

Claims

1. A multiple-cell plasma source for plasma treatment of surfaces of objects, comprising:

hollow housing means formed at least by a second cathode means, first cathode means with a plurality of through openings, said first cathode means being spaced from said second cathode means forming a space therebetween;

anode means located in said space between said first cathode means and said second cathode means, said anode means being electrically isolated from said hollow housing and having openings which are coaxial to said openings of said first cathode means;

said second cathode means, said openings of said first cathode means, and said openings of said anode means forming individual plasma generating cells of said plasma source;

magnetic field generating means for generating a magnetic field which is split into portions generating axial components of lines of forces of the magnetic field which pass through said cells;

working gas supply means for the supply of a working gas into said hollow housing means;

first electrical means for applying to said anode means a potential positive with respect to said first cathode means and to said second cathode means; and

a vacuum chamber which contains said object located opposite said openings of said first cathode means.

2. The plasma source of claim 1, further comprising:

means for isolating said first cathode means from said second cathode means;

openings in said second cathode means are coaxial to said openings in said first cathode means and in said anode means; and

tubular extensions made of a conductive material and extending from said openings of said second cathode means toward said openings of said anode means.

3. The plasma source of claim 2, further comprising second electric means for applying an adjustable voltage to said first cathode means.

4. The plasma source of claim 2, wherein said working gas supply means comprises a hollow collector chamber which is sealingly attached to said second cathode means, is open to said openings of said second cathode means, and has a gas supply tube for the supply of working gas into said collector chamber.

5. The plasma source of claim 4, wherein said openings in said anode means have inwardly tapered edges for limiting the surface of contact of plasma with said anode means.

6. The plasma source of claim 4, wherein said openings of said first cathode are tapered so that they diverge toward said object.

7. The plasma source of claim 4, further comprising second magnetic field generating means for controlling said plasma in said vacuum chamber.

8. The plasma source of claim 4 wherein said anode means, said first cathode means, and said second cathode means are plates.

9. The plasma source of claim 4, wherein said openings of the second cathode contain means for adjusting gasodynamic resistance of the working gas passing through said means to said first openings.

10. The plasma source of claim 9, wherein said means for adjusting comprises a threaded nozzle screwed into each said openings of the second cathode for adjusting a cross-section of said first openings of the second cathode for passage of said working gas.

11. The plasma source of claim 4, wherein said hollow housing, said first cathode means, said second cathode means, and said anode means have on a top view a shape selected from a round, oval, or rectangular shape.

12. The plasma source of claim 2, wherein said second cathode means is convex toward said anode means so that distances from said openings of said second cathode means toward said openings of said anode means are decreased from a periphery of said hollow housing toward the center of said hollow housing.

13. The plasma source of claim 2, wherein said second cathode means is concave toward said anode means so that distances from said openings of said second cathode means toward said openings of said anode means are increased from a periphery of said hollow housing toward the center of said hollow housing.

14. The plasma source of claim 2, wherein said means for isolating comprises a ring of an insulating material.

15. The plasma source of claim 2, wherein said means for isolating comprises a plate of an insulating material which covers the entire surface of said second cathode means, except said openings in said second cathode means and said tubular extensions.

16. The plasma source of claim 2, wherein said openings of said second cathode means have adjusting means for adjusting gasodynamic resistance of the working gas passing through said adjusting means to said first openings.

17. The plasma source of claim 16, wherein said adjusting means comprises a threaded nozzle screwed into each of said openings of said second cathode means for adjusting a cross-section of said openings of said second cathode means for passage of said working gas.

18. The plasma source of claim 1, wherein said openings in said anode means have inwardly tapered edges for limiting the surface of contact of plasma with said anode means.

19. The plasma source of claim 1, wherein said openings of said first cathode means are tapered so that they diverge toward said object.

20. The plasma source of claim 1, further comprising second magnetic field generating means for controlling said plasma in said vacuum chamber.

21. The plasma source of claim 1, wherein said anode means, said first cathode means, and said second cathode means are plates.

22. The plasma source of claim 1, wherein said hollow housing, said first cathode means, said second cathode means, and said anode means have on a top view a shape selected from a round, oval, or rectangular shape.

23. The plasma source of claim 1, wherein said hollow housing, said first cathode means, said second cathode means, and said anode means have on a top view a round shape and said first means for generating said magnetic field is a solenoid coil which surrounds said anode means and is electrically isolated therefrom.

24. The plasma source of claim 1, wherein said hollow housing, said first cathode means, said second cathode means, and said anode means have on a top view a rectangular shape and said first means for generating said magnetic field is a plurality of permanent magnets arranged around said anode means between said first cathode means and said second cathode means.

25. The plasma source of claim 1, wherein said cells have an arbitrary distribution.

26. The plasma source of claim 25, wherein said openings in said first cathode means have different diameters.

27. The plasma source of claim 1, wherein said openings in said anode means have different diameters.

28. A method for treating the surface of an object by plasma, comprising:

providing a multiple-cell plasma source having first cathode means, second cathode means and anode means therebetween with a plurality of cells, each said cell being formed by coaxial through openings at least in said first cathode means and said anode means;

placing said multiple-cell plasma source into vacuum;

generating a magnetic field between said first cathode means and said second cathode means;

splitting said magnetic field into portions which pass through said cells in the form of axial components;

passing a gaseous working medium through said cells, generating an electric field between said anode means and said first and second cathode means, igniting a Penning discharge in each said cell, and generating plasma in said cells in said multiple-cell plasma source;

extracting plasma from cells towards said object via said openings in said first cathode means in the form of distributed flows of plasma; and

treating the surface of said object with said distributed flows of plasma.

29. The method of claim 28, further comprising a step of controlling the pattern of distribution and characteristics of said plasma flows on the surface of said object.

30. The method of claim 29, wherein said second cathode means has through openings coaxial with said openings in said first cathode means and in said anode means, said step of controlling being performed by changing diameters of at least one of said through openings selected from the openings in said first cathode means and said anode means.

31. The method of claim 29, wherein said step of controlling being performed by changing a distribution pattern of said cells.

32. The method of claim 29, wherein said step of controlling being performed by changing a gasodynamic resistance to the flow of said gaseous working medium through openings which are used for the supply of said gaseous working medium into multiple-cell plasma source.

33. The method of claim 29, wherein said step of controlling being performed by changing distances between said first cathode means and said second cathode means in adjacent cells.