Method for making tungsten-titanium sputtering targets and product

• US 4,838,935 A
• Filed: 05/31/1988
• Issued: 06/13/1989
• Est. Priority Date: 05/31/1988
• Status: Expired due to Term

• Current Assignee: Cominco Electronic Materials Incorporated
• Original Assignee: Cominco Ltd. (Sgl Carbon Se)
• Inventors: Dunlop, John A., Rensing, Hans
• Primary Examiner(s): Lechert, Jr., Stephen J.
• Application Number:
  US07/200,344
• Time in Patent Office: 378 Days
• Field of Search: 419/10, 419/48, 419/54, 419/60, 75/230, 204/292
• US Class Current: 75/230
• CPC Class Codes: C22C 1/045 Alloys based on refractory metals
• CPC Class Codes: C23C 14/3414 Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy

Abstract

Tungsten-titanium sputtering targets with improved characteristics are made from high-purity tungsten powder and a second powder consisting of high-purity titanium hydride powder or high-purity titanium hydride powder and high-purity titanium powder. The second powder contains at least 5%, preferably 25% to 100% by weight of titanium hydride powder. A powder mixture having a binodal particle size distribution with respect to the tungsten and second powders is placed under a containment pressure in a die. The die is heated in a vacuum hot-press chamber to a temperature sufficient to dehydride the titanium hydride, and to remove gases and alkali metals. The die is then heated to a second temperature in the range of 1350° to 1550° C. while maintaining the containment pressure and vacuum. A compaction force in the range of 2000 to 5000 psi is then applied to form a compact. The compaction force and vacuum are subsequently released and the compact is cooled. The compact is easily machined to give a sputtering target having a density of at least 95%, preferably, at least 100% of theoretical density, a total gas content of less than 850 ppm, a carbon content of less than 100 ppm and low particulates upon sputtering.

Claims

1. In a method for the manufacture of tungsten-titanium sputtering targets from tungsten powder and titanium powder, the improvement comprising replacing at least a portion of the titanium powder with titanium hydride powder.

2. The improvement as claimed in claim 1, wherein the portion of titanium powder replaced with titanium hydride powder is at least about 5% by weight.

3. The improvement as claimed in claim 1, wherein the portion of titanium powder replaced with titanium hydride powder is in the range of about 25 to 100% by weight.

4. A method for the manufacture of a sputtering target having improved characteristics and consisting essentially of tungsten and titanium comprising the sequential steps of:

(a) providing a heat-resistant pressing die having a cavity with a configuration and dimensions desirable for producing a sputtering target, said die having at least one movable pressing ram adapted for application of axial compaction forces to material in said cavity;

(b) mixing tungsten powder and a second powder consisting of at least one material chosen from the group consisting of titanium hydride and titanium hydride and titanium to form a homogeneous mixture, said second powder containing titanium hydride in an amount sufficient to improve characteristics of said target;

said mixture having a binodal particle size distribution with respect to said tungsten powder and said second powder, and said mixture containing tungsten powder and second powder in amounts sufficient to provide the desired composition of said sputtering target;

(c) adding mixture to said cavity in an amount sufficient to yield a compact having substantially the dimensions of said sputtering target;

(d) placing said die with added mixture in a vacuum hot-press chamber;

(e) applying a containment pressure to said mixture in said die by means of said at least one ram, said containment pressure being sufficient to contain said mixture in said die;

(f) evacuating said chamber and said die to a vacuum of at least about 10^-4 torr;

(g) heating said die and said mixture in said chamber to a first temperature sufficient to dehydride said titanium hydride and to volatilize alkali metals while maintaining said containment pressure and while continuing said evacuating;

(h) maintaining said first temperature for a time sufficient to remove gases and any alkali metals substantially from said mixture;

(i) heating said die and said mixture in said chamber to a second temperature in the range cf about 1350°

to 1550°

C. while maintaining said containment pressure and said vacuum;

(j) applying a compaction force to said mixture at a value in the range of about 2000 to 5000 psi by means of said at least one ram when said second temperature is attained to form a compact of said mixture, said value of said compaction force being dependent on the configuration and dimensions of said sputtering target;

(k) maintaining said compaction force under said vacuum and at said second temperature for a time sufficient to effect full compaction of said mixture;

(l) releasing said compaction force;

(m) releasing said vacuum;

(n) slowly cooling said die to a temperature of about 300°

C. or less to relieve stress in said compact;

(o) removing the cooled compact from said die;

(p) recovering a sputtering target having improved characteristics.

5. A method as claimed in claim 4, wherein said tungsten powder has particle sizes smaller than about 37 micron.

6. A method as claimed in claim 4, wherein said second powder has particle sizes smaller than about 150 micron.

7. A method as claimed in claim 4, wherein said second powder contains titanium hydride powder in an amount of at least about 5% by weight.

8. A method as claimed in claim 4, wherein said second powder contains titanium hydride powder in an amount in the range of about 25% to 100% by weight.

9. A method as claimed in claim 4, wherein said mixing is done under an inert gas.

10. A method as claimed in claim 4, wherein the containment pressure in step (e) is in the range of about 1000 to 1500 psi.

11. A method as claimed in claim 4, wherein, in step (g), the die is heated at a rate of up to about 20°

C./min to a first temperature of about 1100°

C. while maintaining said containment pressure and a vacuum in the range of about 10^-4 to 10^-6 torr.

12. A method as claimed in claim 4, wherein, in step (i), the die is heated at a rate of up to about 20°

C./min to a second temperature in the range of about 1375 to 1450°

C. while maintaining said containment pressure and a vacuum in the range of about 10^-4 to 10^-6 torr.

13. A method as claimed in claim 4, wherein said vacuum is released after releasing said compaction force, while simultaneously backfilling said chamber with a noble gas and maintaining a flow of noble gas through said chamber during said cooling, said flow being sufficient to cool said die at a rate in the range of about 20 to 40°

/min.

14. A method as claimed in claim 13, wherein said noble gas is helium.

15. A method as claimed in claim 4, wherein said sputtering target consists essentially of 90% tungsten and 10% titanium by weight.

16. A method as claimed in claim 4, wherein said improved characteristics of the recovered sputtering target comprise a density of at least about 95% of theoretical density, essentially no porosity, a total gas content of less than about 850 ppm, a carbon content of less than about 100 ppm and reduced particulates during sputtering.

17. A method as claimed in claim 16, wherein said density is at least equal to the theoretical density.

18. A method as claimed in claim 4, wherein said die has two opposing movable pressing rams.

19. A method as claimed in claim 4, wherein said cooled compact having substantially the dimensions of said sputtering target is machined to the desired dimensions.

23. A tungsten-titanium sputtering target made by the method of claim 4.

24. A tungsten-titanium sputtering target made by the method of claim 15.

25. A tungsten-titanium sputtering target made by the method of claim 16.

20. A method for the manufacture of a sputtering target having predetermined configuration and dimensions and having improved characteristics, and consisting essentially of tungsten and titanium comprising the sequential steps of:

(a) mixing an amount of high purity tungsten powder, having a particle size distribution of the C-10-type with a D50 of about ten micron and a D80 of bout eighteen micron, with an amount of a second powder having particle sizes smaller than about 150 micron to form a mixture, said second powder consisting of at least one material chosen from the group consisting of high purity titanium hydride powder, and high purity titanium hydride powder and high purity titanium powder, said second powder containing titanium hydride powder in an amount in the range of about 25 to 100% by weight, said amount of tungsten powder and said amount of second powder being sufficient to provide a sputtering target of the desired composition,

(b) adding an amount of said mixture to a cavity in a graphite die, said die having an upper movable, lockable, graphite ram and a lower movable, lockable, graphite ram adapted for application of axial compaction forces to said mixture in said cavity on opposite sides thereof and said die having the configuration and substantially the desired dimensions of the sputtering target, said amount of mixture being sufficient to provide a compact of substantially said desired composition and said desired dimensions upon compaction;

(c) placing said die with added mixture in a chamber adapted for evacuation and heating;

(d) applying a containment pressure at a value in the range of about 100 to 1500 psi to said mixture in said die by means of moving at least one of said rams;

(e) evacuating said chamber and said die to a vacuum in the range of about 10^-4 to 10^-6 torr;

(f) heating said die with added mixture in said chamber at a rate of up to about 20°

C./min to a first temperature of about 1100°

C. while maintaining said containment pressure and continuing said evacuating;

(g) maintaining said die with added mixture at said first temperature for a time sufficient to remove gases and any alkali metals substantially from said mixture while maintaining said containment pressure and continuing said evacuating;

(h) heating said die with added mixture at a rate of up to about 20°

C./min to a second temperature in the range of about 1375°

to 1450°

C. while maintaining said containment pressure and maintaining said vacuum in the range of about 10^-4 to 10^-6 torr;

(i) applying a compaction force to said mixture by applying increased axial forces by means of moving at least one of said rams, said compaction force having a value in the range of about 2000 to 5000 psi to form a compact of said mixture, said value of the compaction force being dependent on the configuration and dimensions of said sputtering target;

(j) maintaining said compaction force, said second temperature and said vacuum until no movement of the rams is observed and full compaction of said mixture is effected;

(k) locking said rams in position;

(l) releasing said compaction force;

(m) releasing said vacuum and simultaneously backfilling said chamber with helium;

(n) cooling said die and said compact to a temperature of about 50°

C. at a rate in the range of about 20°

to 40°

C./min by maintaining a flow of helium through said chamber;

(o) removing the cooled compact from the die;

(p) machining said compact having substantially the dimensions of said sputtering target to said desired dimensions; and

(q) recovering a sputtering target of said desired dimensions and having a density of at least about 95% of theoretical density, a combined gas content of oxygen, hydrogen and nitrogen of less than about 850 ppm, a carbon content of less than about 100 ppm, essentially no porosity and low particulates upon sputtering.

21. A method as claimed in claim 20, wherein said sputtering target consists essentially of 90% tungsten and 10% titanium by weight.

22. A method as claimed in claim 20, wherein said second powder consists essentially of 100% by weight of titanium hydride powder.

26. A tungsten-titanium sputtering target made by the method of claim 20.

27. A tungsten-titanium sputtering target made by the method of claim 21.

28. A tungsten-titanium sputtering target made by the method of claim 22.