Rotating sputtering apparatus for selected erosion

• US 5,252,194 A
• Filed: 07/23/1992
• Issued: 10/12/1993
• Est. Priority Date: 01/26/1990
• Status: Expired due to Term

• Current Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Original Assignee: Varian Associates, Inc.
• Inventors: Demaray, Richard E., Anderson, Robert L., Helmer, John C., Cochran, Ronald R., Hoffman, Vance E. Jr., Park, Young H.
• Primary Examiner(s): NGUYEN, NAM X
• Application Number:
  US07/919,074
• Time in Patent Office: 446 Days
• Field of Search: 204/298.16, 204/298.17, 204/298.18, 204/298.19, 204/298.2, 204/298.21, 204/298.22, 204/298.31, 204/298.37, 204/192.12, 204/192.32, 156/345
• US Class Current: 204/298.2
• CPC Class Codes: C23C 14/3407 Cathode assembly for sputtering apparatus, e.g. Target
• CPC Class Codes: H01J 2237/3327 Coating high aspect ratio workpieces
• CPC Class Codes: H01J 37/3408 Planar magnetron sputtering
• CPC Class Codes: H01J 37/3447 Collimators, shutters, apertures
• CPC Class Codes: H01J 37/3455 Movable magnets
• CPC Class Codes: H01J 37/3494 Adaptation to extreme pressure conditions

Abstract

A magnetron sputter source providing a predetermined erosion distribution over the surface of a sputter target material is described. When the distribution is uniform, close coupling of the sputter target with the substrate to be coated is achieved, resulting in improved collection efficiency of the sputtered material by the wafer and improved film thickness uniformity. Elimination of erosion grooves provide for greater target consumption and longer target life. The cathode magnetron sputter source includes a rotating magnet assembly of a specific shape and a specific magnetic strength provides the desired erosion distribution. The target may be dished to improve uniformity near the periphery of the wafer.

The resulting magnetron cathode is used for the deposition of thin films. Further applications of uniform magnetron erosion or preselected erosion include uniform or preselected magnetron sputter etch or reactive ion etch and concurrent deposition and etch.

Claims

1. A magnetron apparatus comprising:

a vacuum chamber;

a first magnetron structure including an anode;

a cathode having a front surface in said vacuum chamber and a back surface;

closed loop magnetic means positioned behind said back surface for generating a magnetic field defining a closed loop magnetic tunnel on said front surface of said cathode in a region adjacent to said closed loop magnetic means;

means for rotating said magnetic means about an axis normal to and passing through said front surface, and

wherein said closed loop magnetic means comprises first and second portions, all points on said first portion being located a distance greater than or equal to a predetermined distance from said axis, and all points on said second portion being located a distance less than said predetermined distance from said axis, wherein said first portion of the magnetic means produces a substantially constant magnetic field strength along the adjacent region of said magnetic tunnel and wherein said second portion of the magnetic means produces a magnetic field of less intensity along the adjacent region of said magnetic tunnel.

2. A magnetron apparatus as in claim 1 wherein said front surface is flat so that rotation of said magnetic means sweeps out a circular erosion region on said front surface.

3. A magnetron apparatus as in claim 2 wherein said magnetic means is configured so that there are numbers R₁ and R₂ greater than zero such that the product of the average magnetic strength M(R) of said field at radius R and Σ

L(Arc(R))/R varies as the erosion profile E(R) with R for R₁ ≦

R≦

R₂.

4. A magnetron apparatus as in claim 1 wherein said magnetic means comprises a first closed loop pole piece and a second closed loop pole piece, said first pole piece having opposite magnetic polarity from said second pole piece, said axis of rotation passing between said first pole piece and said second pole piece.

5. A magnetron apparatus as in claim 1 wherein said magnetic means comprises pole pieces and said axis passes through one of said pole piece.

6. A magnetron apparatus as in claim 1 wherein said closed loop magnetic means has a v-shaped configuration in a neighborhood of said axis of rotation.

7. A magnetron apparatus as in claim 1 wherein said magnetic means includes an adjustable pole piece near said axis.

8. A magnetron apparatus as in claim 1 further including means for controlling the distance between said magnetic means and said front surface.

9. A magnetron apparatus as in claim 1 wherein said front surface is dish-shaped.

10. A magnetron apparatus as in claim 9 wherein a portion of said magnetic means comprises a pole piece configured conformally with a portion of said dish-shaped front surface.

11. A magnetron apparatus as in claim 1 wherein said front surface of said cathode is adapted to support a wafer so that said closed loop magnetic tunnel crosses the surface of said wafer for sputter etching said wafer.

12. A magnetron apparatus as in claim 1 further including a second magnetron structure disposed in opposition to said first magnetron structure.

13. A magnetron apparatus as in claim 1 wherein said magnetic means includes an array of magnetic elements, each positioned adjacent one another spaced evenly apart from said back surface and in substantial alignment with said closed loop magnetic tunnel.

14. A magnetron apparatus as in claim 13 wherein said means for rotating rotates said array about said axis.

15. A magnetron apparatus as in claim 1 wherein said magnetron apparatus comprises a sputter deposition apparatus.

16. A magnetron apparatus as in claim 1 wherein said magnetron apparatus comprises an etch apparatus.

17. A magnetron apparatus as in claim 1 wherein said second portion of said closed loop magnet means comprises two segments, said first segment producing a magnetic field of substantially uniform intensity along the adjacent region of said magnetic tunnel and said second segment producing a magnetic field of variable intensity along the adjacent region of said magnetic tunnel.

18. A magnetron apparatus comprising:

a vacuum chamber;

a magnetron structure including an anode;

a cathode having a front surface in said vacuum chamber and a back surface;

magnetic means positioned behind said back surface for generating a magnetic field defining arcuate magnetic field lines intersecting said front surface and enclosing a closed loop path adjacent to said front surface, said closed loop path defining a centerline whereat said magnetic field strength is greatest;

means for rotating said magnetic means about an axis passing through and normal to said surface;

said magnetic means comprising an array of individual magnets positioned between two continuous, generally parallel closed loop pole pieces defining a centerline therebetween, said centerline generally corresponding to said centerline of said magnetic field, wherein the strength and positioning of the magnets in said array is such that the magnetic field strength of said closed loop path is substantially a constant value at all locations on said magnetic field centerline greater than a predetermined distance from said axis and is less than said constant value at all locations less than said predetermined distance from said axis.

19. A magnetron apparatus as in claim 18 wherein said closed loop path comprises an erosion path.

20. A magnetron apparatus as in claim 18 further including means defining an electric field generally crossing said arcuate magnetic field lines.

21. A magnetron apparatus as in claim 20 wherein said magnetic field lines cooperate with said electric field to define only a single plasma ring.

22. A magnetron apparatus as in claim 18 wherein said magnetron apparatus comprises a sputter deposition apparatus.

23. A magnetron apparatus as in claim 18 wherein said magnetron apparatus comprises an etch apparatus.

24. A system for processing a wafer comprising:

a vacuum chamber including an anode;

a first magnetron apparatus within said vacuum chamber comprising;

a first magnetron structure;

a first cathode having a front surface in said vacuum chamber and a back surface;

first closed loop magnetic means positioned behind said back surface of said first cathode for generating a magnetic field defining a closed loop magnetic field on said front surface of said first cathode in a region adjacent to said closed loop magnetic means; and

means for rotating said first magnetic means about an axis which passes through and is normal to said first cathode front surface; and

a second magnetron apparatus within said vacuum chamber comprising;

a second magnetron structure;

a second cathode having a front surface in said vacuum chamber and a back surface;

second closed-loop magnetic means positioned behind said back surface of said second cathode for generating a magnetic field defining a closed loop magnetic field on said front surface of said second cathode in a region adjacent to said closed loop magnetic means; and

means for rotating said second magnetic means about an axis which passes through and is normal to said second cathode front surface;

wherein said first and second closed loop magnetic means each comprises first and second portions, all points on said first portion of each closed loop magnetic means being located a distance greater than or equal to a predetermined distance from the axis about which said magnetic means is rotated, and all points on said second portion of said closed loop magnetic means being located a distance less than said predetermined distance from the axis about which said magnetic means is rotated, wherein said first portion of each magnetic means produces a substantially constant magnetic field strength along the adjacent region of the adjacent cathode and wherein said second portion of the magnetic means produces a magnetic field of less intensity along the adjacent region of said cathode;

wherein said first and second cathodes face each other, and wherein said first magnetron apparatus is primarily used for sputtering and said second magnetron apparatus is primarily used for etching.

25. A rotating magnet for use in a magnetron apparatus, comprising:

first and second closed loop pole pieces defining a magnet centerline therebetween;

an array of individual magnets positioned between said pole pieces; and

means for rotating said magnet about an axis;

wherein said closed loop comprises first and second regions, the first region being defined as the portion of the magnet along the points on the centerline greater than a predetermined distance from the axis of rotation, and the second region being defined as that portion of the magnet along the points on the centerline less than said predetermined distance from the axis of rotation, all of the magnets positioned in said first region being substantially equal in strength and substantially evenly spaced apart so as to produce a magnetic field which has a substantially constant intensity adjacent to said magnet centerline, and wherein at least some of the magnets positioned in said second region have a substantially lower strength than the magnets of said first region, such that the magnetic field intensity adjacent to the magnet centerline in said second region is substantially less than in said first region.

26. The magnet of claim 25 wherein the magnetic field intensity in a portion of said second region is constant.

27. The magnet of claim 25 wherein the magnetic field intensity in a portion of said second region varies as a function of the distance from the axis of rotation.

28. The magnet of claim 25 wherein said pole pieces are substantially evenly spaced apart in said first region.