Method of making a CIG target by cold spraying

1. A method of making a sputtering target, comprising:

providing a backing structure; and

forming a copper indium gallium sputtering target material on the backing structure by cold spraying;

wherein:

the sputtering target material is formed by cold spraying the sputtering target material directly onto the backing structure comprising a cylindrical backing structure to form a cylindrical sputtering target;

the step of cold spraying comprises spraying a powder comprising copper, indium and gallium in a process gas stream and providing the process gas stream containing the powder from a nozzle onto the backing structure such that the powder is not melted and such that a microstructure of the powder does not substantially change; and

at least one of an average particle size of the powder is at least 35 μm, a velocity of the process gas stream is at least 150 m/s, or a process gas pressure is 20 bar or less; and

further comprising providing water into the process gas to form an oxide coating on the particles of the powder prior to the step of providing the process gas stream containing the powder from the nozzle onto the backing structure.

2. A method as claimed in claim 1 , wherein kinetic energy is used to deposit the sputtering target material by at least one of rapid heating or welding effects between the powder and the backing structure without using combustion.

3. A method as claimed in claim 1 , wherein the average particle size of the powder is at least 35 μm.

4. A method as claimed in claim 3 , wherein the average particle size of the powder is at least 60 μm and at least 80% of the powder particle sizes range from 35 μm to 150 μm.

5. A method as claimed in claim 1 , wherein the velocity of the process gas stream is greater than 150 m/s and less than 500 m/s.

6. A method as claimed in claim 5 , wherein the velocity of the process gas stream is 200 to 480 m/s.

7. A method as claimed in claim 1 , wherein a temperature of the process gas is 150° C. or below and the copper indium gallium sputtering target material comprises less than 33 wt % copper.

8. A method as claimed in claim 7 , wherein the temperature of the process gas is 40° C. to 120° C.

9. A method as claimed in claim 1 , wherein a temperature of the process gas is 325° C. or below and the copper indium gallium sputtering target material comprises at least 33 wt % copper.

10. A method as claimed in claim 9 , wherein the temperature of the process gas is 220° C. to 300° C.

11. A method as claimed in claim 1 , wherein the process gas at an exit of the nozzle has a mach number of 1 to 2.3.

12. A method as claimed in claim 1 , wherein the process gas at an exit of the nozzle has a mach number of 1.1 to 1.8.

13. A method as claimed in claim 1 , wherein the process gas has a loading measured by a powder to gas ratio of between 60 and 110 g/m 3 .

14. A method as claimed in claim 1 , wherein:

the average particle size of the powder is at least 60 μm;

particle sizes of the powder range from 35 μm to 150 μm;

the velocity of the process gas stream is 200 to 480 m/s;

the temperature of the process gas is 40 to 150° C. and the copper indium gallium sputtering target material comprises less than 33 wt % copper, or the temperature of the process gas is 220 to 300° C. and the copper indium gallium sputtering target material comprises at least 33 wt % copper; and

the process gas pressure is 1 to 3.8 bar.

15. A method as claimed in claim 1 , wherein the process gas is selected from at least one of nitrogen, air, argon, helium or mixtures thereof.

16. A method as claimed in claim 15 , wherein the process gas is selected from at least one of nitrogen, air or mixtures thereof.

17. A method as claimed in claim 1 , wherein the powder is selected from at least one of:

a pre-alloyed or mechanically alloyed copper indium gallium powder;

a mixed powder blend of elemental copper, elemental indium and elemental gallium;

a mixed powder blend of elemental, binary alloy or ternary alloy powders comprising copper, indium and gallium; or

separate elemental or alloy powders comprising copper, indium and gallium which are simultaneously fed from separate powder reservoirs into the process gas.

18. A method as claimed in claim 1 , wherein the powder is provided into the process gas stream at a rate of at least 60 g/min and a mass loading of 60 to 180 g/m 3 .

19. A method as claimed in claim 1 , wherein the backing structure rotates about its axis during the step of cold spraying.

20. A method as claimed in claim 1 , further comprising reusing the powder which is incident on the backing structure but which does not adhere to the backing structure.

21. A method as claimed in claim 1 , further comprising depositing a localized surface structure of the sputtering target material at an end of the cold spraying such that the sputtering target material has a greater thickness on least one end of the target than in a middle of the target or a greater thickness in the middle of the target than on at least one end of the target.

22. A method as claimed in claim 1 , wherein a cold spray apparatus used in the step of cold spraying comprises at least one of an injector nozzle comprising a non-stick material, a powder feed line comprising a non-stick material, or a feed unit comprising a non-stick material or a non-mechanical feed mechanism.

23. A method as claimed in claim 1 , wherein the step of cold spraying comprises spraying the powder comprising copper, indium and gallium in the process gas stream through a nozzle having a converging bore in an inlet portion and a straight or diverging bore in an outlet portion.

24. A method as claimed in claim 23 , further comprising heating the powder located in a powder feed line by the process gas prior to providing the powder into the nozzle.

25. A method as claimed in claim 23 , wherein the nozzle comprises the straight bore having a constant diameter in the outlet portion.

26. A method as claimed in claim 23 , further comprising feeding the powder to the nozzle through a powder feed line which extends into the outlet portion of the nozzle.

27. A method as claimed in claim 23 , wherein the powder is accelerated through the nozzle such that larger size particles reach at least a minimum speed and smaller particles reach a speed below a maximum speed allowable for deposition of the sputtering target material.

28. A method as claimed in claim 27 , wherein the nozzle comprises the converging bore in the inlet portion, the diverging bore in an outlet portion, and a throat portion located between the inlet and the outlet portions, the throat portion having a constant inner diameter bore and a predetermined length.

29. A method as claimed in claim 1 , wherein:

from 0% to 10% of primary phase regions in the sputtering target material are of a size greater than 10 μm in any random 1 cm by 1 cm area of the sputtering target;

an average primary phase region in the sputtering target material is of a size not greater than 5 μm; and

the sputtering target material has an overall uniform composition.

30. A method as claimed in claim 1 , wherein the sputtering target material has an overall uniform composition of about 29-41 wt % copper, about 36-62 wt % indium, and about 8-25 wt % gallium.

31. A method as claimed in claim 1 , wherein the sputtering target material has an overall uniform composition of about 8-15 wt % copper, about 55-80 wt % indium, and about 10-25 wt % gallium.

32. A method as claimed in claim 1 , wherein the process gas pressure is 20 bar or less.

33. A method as claimed in claim 1 , wherein the process gas pressure is 1 to 3.8 bar.

34. A method as claimed in claim 1 , wherein the powder comprising copper, indium and gallium comprises a CIG alloy powder which is prealloyed with Se and which contains 0.01 wt % to 10 wt % Se.

35. A method as claimed in claim 1 , wherein the powder comprising copper, indium and gallium comprises a CIG alloy powder which is prealloyed with Se and which contains 0.01 wt % to 0.5 wt % Se.

36. A method as claimed in claim 1 , wherein the powder comprising copper, indium and gallium comprises CIG alloy powder particles which are coated with a layer of material that is mechanically harder than the CIG alloy and wherein the material comprises Se.

37. A method as claimed in claim 1 , wherein the target material further comprises a metallic Na or a Na-containing compound and the target material contains 0.1 wt % to 1.0 wt % Na.

38. A method as claimed in claim 1 , further comprising rotating the backing structure at 200 to 800 rpm and translating the nozzle at 180 to 1200 mm/min while maintaining a spray distance of 80-150 mm.

39. A method of making a sputtering target, comprising:

providing a backing structure; and

forming a copper indium gallium sputtering target material on the backing structure by cold spraying;

wherein:

the step of cold spraying comprises spraying a powder comprising copper, indium and gallium in a process gas stream;

at least one of an average particle size of the powder is at least 35 μm, a velocity of the process gas stream is at least 150 m/s, or a process gas pressure is 20 bar or less;

the powder comprising copper, indium and gallium comprises CIG alloy powder particles which are coated with a layer of material that is mechanically harder than the CIG alloy; and

the material comprises Se.

40. A method as claimed in claim 39 , wherein the average particle size of the powder is at least 35 μm.

41. A method as claimed in claim 40 , wherein the average particle size of the powder is at least 60 μm and at least 80% of the powder particle sizes range from 35 μm to 150 μm.

42. A method as claimed in claim 39 , wherein the velocity of the process gas stream is greater than 150 m/s and less than 500 m/s.

43. A method as claimed in claim 42 , wherein the velocity of the process gas stream is 200 to 480 m/s.

44. A method as claimed in claim 39 , wherein the process gas pressure is 20 bar or less.

45. A method as claimed in claim 44 , wherein the process gas pressure is 1 to 3.8 bar.