Cooling water jet pack for high power rotary cathodes
A sputtering target assembly, including a cylindrical backing tube, a magnet assembly disposed within the backing tube, and a conduit disposed within the backing tube and adapted for transporting coolant. The conduit includes at least one first opening positioned for providing the coolant in a substantially circumferential direction from the conduit toward an inner surface of the backing tube into a gap volume between a front side of the magnet assembly and the inner surface of the backing tube.
1. A sputtering target assembly, comprising:
a cylindrical backing tube;
a magnet assembly disposed within the backing tube, such that a gap volume is formed between the magnet assembly and an inner surface of the backing tube; and
a conduit disposed within the backing tube and configured to provide coolant directly into the gap volume, at an angle α of 45° or less, wherein:
the angle α is taken with respect to a first line along which coolant initially flows out of the conduit, and a second line tangential to the backing tube at a point where the first line intersects the inner surface of the backing tube; and
substantially all of the coolant in the gap volume flows in a single circumferential direction that is substantially perpendicular to a longitudinal axis of the cylindrical backing tube.
2. The sputtering target assembly of claim 1 , wherein:
the magnet assembly extends substantially parallel to the longitudinal axis of the cylindrical backing tube;
the magnet assembly comprises a first end, a second end, and a side portion extending between the first and second end;
the conduit comprises:
a coolant plenum; and
a coolant channel fluidly connected to the coolant plenum and located adjacent to the side portion of the magnet assembly;
the coolant plenum is disposed within the backing tube adjacent to a back portion of the magnet assembly;
the coolant plenum is adapted to stiffen the magnet assembly;
the coolant plenum contains an inlet located at a first end of the backing tube and connected to a water coolant source; and
an outlet located is at a second end of the backing tube opposite to the first end and adapted to allow the water coolant to exit from within the backing tube.
3. The sputtering target assembly of claim 2 , wherein the angle α is between 5 and 35°.
4. The sputtering target assembly of claim 2 , wherein the coolant plenum comprises at least one baffle or partition adapted to direct flow of coolant in the single circumferential direction.
5. The sputtering target assembly of claim 2 , wherein the coolant channel is embedded in a side portion of cover plate of the magnet assembly.
6. The sputtering target assembly of claim 1 , wherein at least one of a cover plate comprising the front side of the magnet assembly or the inner surface of the backing tube are roughened to induce turbulent flow of the coolant.
7. The sputtering target assembly of claim 1 , wherein the conduit comprises at least one nozzle directed at the inner surface of the backing tube.
8. The sputtering target assembly of claim 1 , wherein the conduit comprises a single slit that extends substantially parallel to the longitudinal axis of the cylindrical backing tube, the slit having a length that is substantially equal the length of the magnet assembly.
9. The sputtering target assembly of claim 2 , wherein the conduit comprises a plurality of the coolant channels, which are spaced apart along the length of the magnet assembly.
10. The sputtering target assembly of claim 9 , wherein at least some of the coolant channels are formed at different angles in an axial direction relative to the backing tube to provide cross flow streams of coolant.
11. The sputtering target assembly of claim 9 , wherein the coolant channels disposed adjacent to ends of the magnet assembly have a larger diameter than the coolant channels disposed adjacent to a middle portion of the magnet assembly.
12. The sputtering target assembly of claim 9 , wherein the coolant channels have substantially the same diameter and are distributed uniformly along the length of the magnet assembly.
13. The sputtering target assembly of claim 9 , wherein the coolant channels are non-uniformly distributed along the length of the magnet assembly, such that there are more coolant channels per unit length adjacent to ends of the magnet assembly than adjacent to a middle portion of the magnet assembly.
14. The sputtering target of claim 1 , further comprising a copper indium gallium sputtering material located on an outer surface of the backing tube.
15. The sputtering target assembly of claim 1 , further comprising at least one wiper fin disposed within the backing tube which contacts an inner surface of the backing tube while the backing tube rotates past the at least one wiper fin to agitate a coolant boundary layer located along the inner surface of the backing tube.
16. The sputtering target assembly of claim 1 , wherein the conduit comprises a coolant inlet located in an inlet section of the backing tube which is separated from an outlet by a separator such that only the gap volume provides a substantial fluidic connection between the coolant inlet and the outlet.
17. A method for cooling a sputtering target assembly, comprising:
providing a sputtering target assembly comprising:
a cylindrical backing tube;
a magnet assembly disposed within the backing tube, such that a gap volume is formed between the magnet assembly and an inner surface of the backing tube; and
a conduit disposed within the backing tube adjacent to the magnet assembly; and
flowing a coolant from the conduit directly into the gap volume, at an angle α of 45° or less, such that substantially all of the coolant in the gap volume flows in a single circumferential direction that is substantially perpendicular to a longitudinal axis of the cylindrical backing tube,
wherein the angle α is taken with respect to a first line along which the coolant initially flows out of the conduit, and a second line tangential to the backing tube at a point where the first line intersects the inner surface of the backing tube.
18. The method of claim 17 , wherein the flowing of the coolant comprises:
flowing the coolant through a coolant plenum disposed within the backing tube adjacent to a back portion of the magnet assembly from an inlet located at a first end of the backing tube;
flowing the coolant from the coolant plenum into a coolant channel located adjacent to a side portion of the magnet assembly; and
flowing the coolant from the coolant channel directly into the gap volume.
19. The method of claim 18 , further comprising:
flowing the coolant from the gap volume into an interior backing tube volume; and
flowing the coolant from the interior backing tube volume out through an outlet located at a second end of the backing tube opposite to the first end.
20. The method of claim 17 , wherein:
the coolant comprises water; and
the angle α is between 5° and 35°.
21. The method of claim 17 , wherein the coolant flows into the gap volume through a plurality of coolant channels that are spaced apart along substantially the entire length of the magnet assembly formed in the conduit, or through one slit extending substantially the entire length of the magnet assembly, such that the coolant is provided along a majority of the axis of the backing tube.
22. The method of claim 21 , wherein a velocity profile of coolant provided from the coolant channels along a front side of the magnet assembly is substantially constant.
23. The method of claim 21 , wherein a velocity profile of coolant from each of the coolant channels along a front side of the magnet assembly varies.
24. The method of claim 17 , wherein:
the coolant is provided into the gap volume in a turbulent flow, such that a Reynolds number of the coolant provided from the conduit into the gap volume is at least 3000;
the coolant comprises water; and
the water is provided at a flow rate of at least 5 gal/min.
25. The method of claim 17 , wherein the coolant provided from the conduit into the gap volume flows at a higher volume adjacent to ends of the magnet assembly than adjacent to a middle portion of the magnet assembly.
26. The method of claim 17 , wherein the coolant provided from the conduit into the gap volume flows at the same volume adjacent to ends of the magnet assembly as adjacent to a middle portion of the magnet assembly.
27. The method of claim 17 , wherein the coolant is provided from the conduit as a plurality of cross streams.
28. The method of claim 17 , further comprising:
rotating the backing tube while the magnet assembly remains static;
sputtering a copper indium gallium material from an outer surface of the backing tube; and
providing a selenium containing gas to form a copper indium gallium selenide layer on a substrate.
29. The method of claim 17 , further comprising agitating a coolant boundary layer located along the inner surface of the backing tube by contacting at least one wiper fin to the inner surface of the rotating backing tube, wherein the at least one wiper fin is static while the backing tube rotates.
30. The method of claim 17 , wherein the step of flowing the coolant from the conduit in a substantially circumferential direction toward the inner surface of the backing tube and into the gap volume comprises flowing the coolant from the conduit located in an inlet section of the backing tube which is separated from an outlet by a separator such that only the gap volume provides a substantial fluidic connection between the conduit and the outlet.