Sputtering target

Abstract

A sputtering target containing molybdenum and at least one metal from the group tantalum and niobium. The average content of tantalum and/or niobium is from 5 to 15 at % and the molybdenum content is greater than or equal to 80 at %. The sputtering target has at least a matrix with an average molybdenum content of greater than or equal to 92 at % and particles which are composed of a solid solution containing at least one metal from the group of tantalum and niobium, and molybdenum, with an average molybdenum content of greater than or equal to 15 at % and are embedded in the matrix. There is also described a method of producing a sputtering target.

Claims

1. A sputtering target, comprising: molybdenum and at least one metal selected from the group consisting of tantalum and niobium; an average content of said at least one metal selected from the group consisting of tantalum and niobium lying between 5 and 15 at %, and a molybdenum content being greater than or equal to 80 at %; wherein a microstructure of the sputtering target is defined by: a matrix having particles selected from the group consisting of: a tantalum-rich phase, a niobium-rich phase, and a tantalum-and-niobium-rich phase, said matrix having an average molybdenum content of greater than or equal to 92 at % surrounding said particles and forming a contiguous structure; and interfaces between said matrix and said particles which are free of oxides; said particles embedded in said matrix being spatially separated from one another and having a crystal composition made up of: molybdenum with an average molybdenum content of greater than or equal to 15 at % and less than or equal to 50 at %, and at least one metal selected from the group consisting of tantalum and niobium; wherein said matrix at least partially comprises a recrystallized microstructure; and wherein said particles at least partially have a recrystallized microstructure.

2. The sputtering target according to claim 1, wherein the average molybdenum content of said particles is greater than or equal to 20 at % and less than or equal to 50 at %.

3. The sputtering target according to claim 2 wherein the average molybdenum content of said particles is greater than or equal to 25 at % and less than or equal to 50 at %.

4. The sputtering target according to claim 1, wherein the target has a forming texture in which at least one of said matrix or said particles has the following predominant orientations: in a forming direction (110); in a normal direction: at least one orientation selected from the group consisting of (100) and (111).

5. The sputtering target according to claim 1, wherein said particles have an average aspect ratio of greater than or equal to 2.

6. The sputtering target according to claim 5, wherein the average aspect ratio is greater than or equal to 5.

7. The sputtering target according to claim 1, wherein an average distance between said particles perpendicular to a forming direction is less than or equal to 250 μm.

8. The sputtering target according to claim 1, wherein an average distance between said particles perpendicular to a forming direction is less than or equal to 50 μm.

9. The sputtering target according to claim 1, wherein an average grain size of said matrix is less than or equal to 100 μm.

10. The sputtering target according to claim 9, wherein the average grain size of said matrix is less than or equal to 60 μm.

11. The sputtering target according to claim 1, consisting of from 5 to 15 at % of said at least one metal selected from the group consisting of tantalum and niobium, balance Mo, and typical impurities.

12. The sputtering target according to claim 1, wherein said metal is niobium.

13. A method of producing the sputtering target according to claim 1, the method comprising the following steps: producing a powder mixture with a molybdenum content of greater than or equal to 80 at % and powder of said at least one metal selected from the group consisting of tantalum and niobium with an average content of between 5 and 15 at %; consolidating the powder mixture by hot isostatic pressing; and performing at least one heat treatment step in a temperature range from 1300° C. to 1900° C. for a duration in a range from 1 to 10 hours such that said microstructure of the sputtering target is defined by: said matrix having said particles selected from the group consisting of: said tantalum-rich phase, said niobium-rich phase, and said tantalum-and-niobium-rich phase, said matrix having the average molybdenum content of greater than or equal to 92 at %; and said interfaces between said matrix and said particles which are free of oxides; said particles being embedded in said matrix, said particles being spatially separated from one another and having said crystal composition made up of molybdenum with the average molybdenum content of greater than or equal to 15 at % and less than or equal to 50 at %, and the at least one metal selected from the group consisting of tantalum and niobium; wherein said matrix at least partially comprises said recrystallized microstructure; wherein said particles at least partially have said recrystallized microstructure; and wherein the at least one heat treatment step causes oxides to be transported away from said interfaces between said matrix and said particles resulting in said interfaces between said matrix and said particles being free from oxides.

14. The method according to claim 13, further comprising performing at least one forming step either: between the consolidating step and the at least one heat treatment step; or after the at least one heat treatment step; or before and after the at least one heat treatment step.

15. The method according to claim 13, which comprises performing the at least one heat treatment step in a reducing atmosphere.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is illustrated by way of example below with the aid of two production examples:

(2) The FIGURE shows an etched (Murakami) longitudinal polished section of a sputtering target according to the invention. Forming direction and normal direction span the plane of the image and are marked by arrows.

DESCRIPTION OF THE INVENTION

Example 1

(3) To produce a sputtering target according to the invention, the following powders were used: Mo powder having a Fisher particle size of 4.7 μm, an oxygen content of 0.035% by weight and a carbon content of 0.0018% by weight Nb powder having a Fisher particle size of 7.8 μm, an oxygen content of 0.19% by weight and a carbon content of 0.05% by weight

(4) To produce four plates composed of a molybdenum alloy with 10 at % of niobium (corresponds to 9.71% by weight of niobium) and each having a weight of 450 kg, 185 kg of niobium powder and 1615 kg of molybdenum powder were mixed in a mechanical mixer for 20 minutes. The powder mixture was canned in steel cans and hot isostatically pressed (HIP). At an HIP temperature of 1200° C. for 5 hours at a pressure of 100 MPa, full densification of the powder was achieved.

(5) The HIPped plates were rolled at 1250° C. on a hot rolling apparatus at a total degree of deformation of 84% to a length of 2.5 m and a width of about 1 m. The rolled plates were then heat treated at 1550° C. for 3 hours in a hydrogen atmosphere in a furnace.

(6) Samples were taken from the sputtering targets produced in this way and were ground, polished and etched by means of conventional metallographic methods.

(7) For all of the following analytical methods, a longitudinal sample (forming direction and normal direction spanning the plane of the image) was taken from each sputtering target, a picture having a magnification of 100× and an image section of 1040 μm×780 μm was taken and the averages in each case were determined therefrom (The FIGURE shows such an image section by way of example).

(8) To determine the average molybdenum content in the particles or in the matrix, the sample was measured by means of EDX in a scanning electron microscope.

(9) Table 1 shows the average molybdenum contents of the particles and of the matrix (determined as average of five measurements in each case).

(10) TABLE-US-00001 TABLE 1 Mo content in particles Mo content in matrix Measurement point 1 32.1 at % 95.5 at % Measurement point 2 21.4 at % 93.7 at % Measurement point 3 16.3 at % 92.3 at % Measurement point 4 29.2 at % 92.9 at % Measurement point 5 24.4 at % 94.1 at % Average 24.7 at % 93.7 at %

(11) To determine the grain size of the matrix, the line section method using five lines of 780 μm each at equidistant spacings in the forming direction and the normal direction was employed. The grain size was calculated from the average of the two directions and from the average of the four images (one per sputtering target (plate)) and was 52 μm.

(12) As further parameter for the microstructure present, the average aspect ratio of the solid solution particles (in this example Nb-rich particles) was determined. For this purpose, all particles which have a length of greater than or equal to 10 μm in the forming direction were measured in the forming direction and the normal direction and the ratio of the two lengths was calculated. The particles had an average length in the forming direction of 144 μm and in the normal direction of 22 μm, giving an average aspect ratio of 6.4.

(13) The distance between the Nb-rich particles in the normal direction (perpendicular to the forming direction) was likewise determined by means of line section methods. For this purpose, five lines each having a length of 780 μm were laid with equidistant spacings over the image and the average distance between the particles (particle periphery to particle periphery in the normal direction) was determined and found to be 81 μm.

(14) The sputtering behaviour of the sputtering targets produced as described above was determined by means of sputtering experiments at Ar (argon) pressures in the range from 2.5×10.sup.3 to 1×10.sup.−2 mbar and a power of 400 or 800 watt. Soda-lime glass was used as substrate material. The sputtering targets could be sputtered without the occurrence of arc processes.

Example 2

(15) To produce a tubular MoNb sputtering target, the following powders were used: Mo powder having a Fisher particle size of 4.9 μm, an oxygen content of 0.039% by weight and a carbon content of 0.0022% by weight Nb powder having a Fisher particle size of 7.8 μm, an oxygen content of 0.19% by weight and a carbon content of 0.05% by weight

(16) To produce two tubes composed of a molybdenum alloy with 10 at % of niobium (corresponds to 9.71% by weight of niobium) and having a weight of 420 kg, 87 kg of niobium powder and 753 kg of molybdenum powder were mixed for 20 minutes in a mechanical mixer. The powder mixture was canned in tubular steel cans and hot isostatically pressed (HIP). At an HIP temperature of 1250° C. for 4 hours at a pressure of 105 MPa, full densification of the powder was achieved.

(17) The HIPped tubes were removed from the cans and forged at 1250° C. to a degree of deformation of 30% on a radial forging plant. The forged tubes were subsequently heat treated at 1500° C. for 5 hours and subsequently forged a second time at 1200° C. with a degree of deformation of 30% in a second forging step to give tubular sputtering targets having a length of 3 m.

(18) A longitudinal sample (forming direction/direction of advance and normal direction/radial direction span the plane of the image) was taken from each of the two tubular sputtering targets and ground, polished and etched by means of conventional metallographic methods.

(19) To determine the average molybdenum content in the particles and in the matrix, the sample was measured by means of EDX in a scanning electron microscope.

(20) Table 2 shows the average molybdenum contents of the particles and of the matrix (determined as average of five measurements in each case).

(21) TABLE-US-00002 TABLE 2 Mo content in particles Mo content in matrix Measurement point 1 22.1 at % 98.6 at % Measurement point 2 14.3 at % 97.3 at % Measurement point 3 17.8 at % 95.5 at % Measurement point 4 19.2 at % 98.2 at % Measurement point 5 21.0 at % 99.1 at % Average 18.9 at % 97.7 at %

(22) At a magnification of 100× and an image section of 1040 μm×780 μm, the particle size of the matrix was determined by means of line section methods. Here, five lines each having a length of 780 μm were in each case used at equidistant spacings in the forming direction and the normal direction. The grain size was calculated from the average of the two directions and the two samples and was 59 μm.

(23) As further parameter for the microstructure present, the average aspect ratio of the solid solution particles (in this example Nb-rich particles) was determined. For this purpose, all particles which have a length in the forming direction of greater than or equal to 10 μm were measured in the forming direction and the normal direction and the ratio of the two lengths was calculated. The particles had an average length in the forming direction of 101 μm and in the normal direction of 20 μm, giving an average aspect ratio of 5.

(24) The distance between the Nb-rich particles in the normal direction (perpendicular to the forming direction) was likewise determined by means of line section methods. For this purpose, five lines each having a length of 780 μm were laid at equidistant spacings over the image and the average distance between the particles (particle periphery to particle periphery) was determined and found to be 97 μm.