CYLINDRICAL TITANIUM OXIDE SPUTTERING TARGET AND PROCESS FOR MANUFACTURING THE SAME

Abstract

Known cylindrical sputtering targets comprise a substrate and a target material that forms a layer on the substrate, said layer has a thickness d, wherein the target material comprises TiOx as the main component, and x is within a range of 1<x<2. Starting therefrom and in order to provide large-sized cylindrical sputtering targets with a thick target layer comprising sub-stoichiometric TiO.sub.2 it is proposed that x is within a range of 1.45<x<1.7 that allows a target layer thickness d which is larger than 10 mm.

Claims

1. A cylindrical sputter target comprising a substrate and a target material that forms a layer on the substrate, said layer has a thickness d, wherein the target material comprises TiOx as the main component, and x is within a range of 1<x<2, and characterized in that d is larger than 10 mm and x is within a range of 1.45<x<1.7, wherein the target material is free from visible surface cracks, or if surface cracks exist, they have a maximum length of less than 1 cm.

2. The sputtering target according to claim 1, wherein d is at least 12 mm.

3. The sputtering target according to claim 1, wherein 1.50 <x <1.65.

4. The sputtering target according to claim 1, wherein the target material has a Vickers hardness HV, wherein HV<500 HV10.

5. The sputtering target according to claim 1, wherein the target material comprises a Ti.sub.4O.sub.7 phase in a concentration of at least 30 vol.-%, and a Ti.sub.3O.sub.5 phase in a concentration of at least 40 vol.-%.

6. The sputtering target according to claim 1, wherein the target material comprises a Ti.sub.4O.sub.7 phase and Ti.sub.3O.sub.5 phase in a total concentration of at least 75 vol. %.

7. The sputtering target according to claim 1, wherein the target material comprises a Ti.sub.3O.sub.5 phase in a first concentration (in vol.-%) and a Ti.sub.4O.sub.7 phase in a second concentration (in vol.-%), wherein the ratio of first concentration and second concentration Ti.sub.3O.sub.5/Ti.sub.4O.sub.7 is at least 1.2.

8. The sputtering target according to claim 1, wherein the target material comprises an Anatase phase of TiO.sub.2 in a total concentration of less than 1 vol.-%.

9. (canceled)

10. Sputtering target according to claim 1, wherein the target material comprises a homogeneous degree of sub-stoichiometry, in the sense that the degree of sub-stoichiometry of ten samples of 10 g each has a standard deviation in the of sub-stoichiometry degree of less than 5%.

11. A process for producing a sputtering target, which comprises (a) providing a substrate made of a metal or alloy, (b) providing a ceramic powder comprising a metal oxide powder of the chemical formula TiOy as the main component, whereby TiOy is deficient in oxygen as compared with the stoichiometric composition TiO.sub.2, (c) forming a ceramic layer on the substrate by plasma spraying, wherein said ceramic powder is made in a semi-molten state in a high temperature plasma gas in a reducing atmosphere, and it is transported and deposited onto the substrate by the plasma gas so as to obtain a target comprising a layer with a thickness d of a target material that comprises TiOx as the main component, whereby TiOx is deficient in oxygen as compared with the stoichiometric composition TiO.sub.2, wherein y in said metal oxide powder TiOy is within a range of 1.3<y<1.7, and wherein x in said target material TiOx is within a range of 1.45<x<1.7, and the layer thickness d is more than 10 mm.

12. The process according to claim 11, wherein the thickness d is at least 12 mm, and wherein 1.50<x<1.65.

13. The process according to claim 11, wherein a cylindrical substrate is used as the substrate.

14. The process according to claim 11, wherein providing the ceramic powder according to method step (b) comprises providing an oxygen deficient titania powder having a particle size in the range of from 25-125 m.

15. A cylindrical sputtering target provided by a process according to claim 10.

16. The sputtering target according to claim 1, wherein d is at least 14 mm.

17. The sputtering target according to claim 1, wherein 1.50<x<1.55.

18. The sputtering target according to claim 1, wherein the target material has a Vickers hardness HV, wherein HV<475 HV10.

19. The sputtering target according to claim 1, wherein the target material comprises a Ti.sub.4O.sub.7 phase and Ti.sub.3O.sub.5 phase in a total concentration of at least 99 vol.-%.

20. The sputtering target according to claim 1, wherein the target material comprises a Ti.sub.3O.sub.5 phase in a first concentration (in vol.-%) and a Ti.sub.4O.sub.7 phase in a second concentration (in vol.-%), wherein the ratio of first concentration and second concentration Ti.sub.3O.sub.5/Ti.sub.4O.sub.7 is at least >1.4.

21. The process according to claim 11, wherein the thickness d is at least 14 mm, and wherein 1.50<x<1.55.

22. The process according to claim 11, wherein providing the ceramic powder according to method step (b) comprises providing an oxygen deficient titania powder having a particle size in the range of from 40-90 m.

Description

PREFERRED EMBODIMENTS OF THE INVENTION

[0064] The invention will now be explained in more detail with reference to a patent drawing and an embodiment. In detail,

[0065] FIG. 1 shows an X-ray diffraction diagram of a target layer material according to the invention in combination with the typical deflection signals of Ti.sub.3O.sub.5 and Ti.sub.5O.sub.7 crystalline phases, and

[0066] FIG. 2 shows an X-ray diffraction diagram of a target layer material according to the invention in combination with the typical deflection signals of TiO.sub.2 in its rutile crystalline phase.

PREPARATION OF SPUTTERING TARGET

[0067] As feedstock material a non-stoichiometric oxygen deficient titania powder was provided having a particle size in the range of from 25-125 m. The degree of sub-stoichiometry is represented in the formula TiOy by y1.4.

[0068] A stainless steel tube was provided with an of outer diameter of 133 mm and an inner diameter of 125 mm. Suitable lengths of the substrate tube are in the range between 500 to 4.000 mm. The tube was coated with a rough Ni layer. The coated stainless steel tube was used as a substrate for depositing a target material by plasma spraying, whereby the rough Ni undercoating acts a bonding layer for the target material.

[0069] For plasma spraying the TiOy feedstock materials, a water-cooled plasma torch device was used. The plasma torch was operated with a mixture of hydrogen and argon with variable mixing ratio. The hydrogen/argon mixing ratio determines the reduction/oxidation state of the plasma; details about the mixing ratio used in the examples are provided further below. The process gas may also contain Helium. The sub-stoichiometric TiOy powder was injected via a carrier gas directly into the plasma flame. The powder feed rate is set at a value in the region between 50 g/min and 350 g/min.

[0070] The sub-stoichiometric titanium dioxide coated on the substrate is solidified under conditions which prevent it from regaining oxygen and reconverting to TiO.sub.2. Especially at high feed rates or at high power levels the substrate may be cooled (e.g. gas cooling on outside or water cooling on the inside to 35 C.) during the plasma spraying in order to quench the titanium dioxide in its deposited sub-stoichiometric form. A TiOx target material layer with a thickness of more than 10 mm is prepared, whereby in the formula TiOx the grade of sub-stoichiometry is represented by x1.54 and x1.81 (see table 1). The resulting sputtering target comprises the substrate and the target layer of TiOx.

EXAMPLE 1

[0071] A rotatable substrate tube with a tube length of 550 mm was provided comprising a backing tube of stainless steel of outer diameter 133 mm, inner diameter 125 mm, length 550 mm. The outer cylinder surface was coated with a Ni layer.

[0072] It was water cooled on the inside to 35 C. and thereby coated by plasma spraying with a powder of sub-stoichiometric titanium oxide (TiOy, whereby y=1,69) having a particle size of from 40 to 90 m using argon as the primary plasma gas and hydrogen as the secondary plasma gas (70 vol.-% argon, 30 vol.-% hydrogen). The power level was 60 kW (400 ).

[0073] The resulting target layer has a thickness of from 11 mm and it consists of sub-stoichiometric titanium dioxide (TiOx, where x is 1.71, see Table 1). The subsequently performed ethanol visualization test shows that it is crack free. The hammer impact test shows strong adhesion of the target material to the substrate tube and less susceptibility to cracking compared to comparative example 1.

[0074] The process for production of the sputter target was repeated several times but target layers of 12 mm and more were produced instead a target layer thickness of 11 mm. The ethanol visualization test showed a crack free layer which could be produced with high reproducibility for a maximum layer thickness of 11 mm.

EXAMPLE 2

[0075] Example 1 was repeated using a starting powder of sub-stoichiometric titanium oxide (TiOy, whereby y=1.40) having a particle size of from 5 to 45 m was used as the feedstock material. Argon was used as the primary plasma gas and hydrogen as the secondary plasma gas (70 vol.-% argon, 30 vol.-% hydrogen). The power level was the same as in Example 1.

[0076] The resulting target layer has a thickness of from 14 mm and it consists of sub-stoichiometric titanium oxide (TiOx, where x is 1.63). When spraying onto a target base under the conditions of Example 2 the TiO.sub.y was converted into a sub-stoichiometric rutile form of titanium dioxide. The subsequently performed ethanol visualization test shows that it is crack free. The hammer impact test shows strong adhesion of the target material to the substrate tube and less susceptibility to cracking compared to comparative example 1.

[0077] The process for production of the sputter target was repeated several times but target layers of 15 mm and more were produced instead a target layer thickness of 14 mm. The ethanol visualization test showed a crack free layer could be produced with high reproducibility for a maximum layer thickness of 14 mm.

EXAMPLE 3

[0078] Example 1 was repeated using a powder of sub-stoichiometric titanium oxide (TiOy, whereby y=1.32) having a particle size of from 40 to 90 m. Argon was used as the primary plasma gas and hydrogen as the secondary plasma gas (70 vol.-% argon, 30 vol.-% hydrogen). The power level was the same as in Example 1.

[0079] The resulting target layer has a thickness of from 18 mm and it consists of sub-stoichiometric titanium oxide (TiOx, where x is 1.54). On spraying onto a target base under the conditions of Example 2 the TiO.sub.2 was converted into a sub-stoichiometric rutile form of titanium dioxide.

EXAMPLE 4

[0080] Example 3 was repeated using a rotatable substrate tube with a tube length of 2000 mm. The resulting target layer has a thickness of from 16 mm and it consists of sub-stoichiometric titanium oxide (TiOx, where x is 1.53).

EXAMPLE 5

[0081] Example 3 was repeated using a rotatable substrate tube with a tube length of 3852mm. The resulting target layer has a thickness of from 15 mm and it consists of sub-stoichiometric titanium oxide (TiOx, where x is 1.54).

COMPARATIVE EXAMPLE 1

[0082] Example 1 was repeated using a powder of sub-stoichiometric titanium oxide (TiOy, whereby y=1.81) having a particle size of from 40 to 90 m. Argon was used as the primary plasma gas and hydrogen as the secondary plasma gas (70 vol.-% argon, 30 vol.-% hydrogen). The power level was the same as in Example 1.

[0083] The resulting target layer has a thickness of from 11 mm and it consists of sub-stoichiometric titanium oxide (TiOx, where x is 1.82). When spraying onto a target base under the conditions of Example 2 the TiOy feedstock particles were converted into a sub-stoichiometric TiOx. The mayor phase is Ti.sub.9O.sub.17 and it includes small amounts of the rutile form and the anatase form of titanium dioxide (see Table 1).

[0084] Cracks occur in the target material.

[0085] Therefore, the production of the sputter target according to Comparative Example 1 was repeated, but instead of a layer thickness of 11 mm, the target material deposition was stopped at a layer thickness of 10 mm and less. The ethanol visualization test showed a crack free layer which could be produced with high reproducibility only for a maximum layer thickness of 10 mm.

TABLE-US-00001 TABLE 1 Stoechio- Stoe- Maximal Short nomination TiO.sub.2 TiO.sub.2 chiometry chiometry crack free in Anatase Rutile Ti.sub.9O.sub.17 Ti.sub.4O.sub.7 Ti.sub.3O.sub.5 Hardnes Powder Target layer thickness Example the specification Vol.-% Vol.-% Vol.-% Vol.-% Vol.-% HV10 (y-value) (x-value) (mm) 1 TiO.sub.1,7 0 4.0 24 32 40 520 1.69 1.71 11 2 TiO.sub.1,6 0 2.0 0 42 56 480 1.40 1.63 14 3 TiO.sub.1,5 0 1.0 0 40 59 450 1.32 1.54 18 Comp. 1 TiO.sub.1,8 1.0 6.0 93 0 0 570 1.82 1.81 10

[0086] The results of the XRD measurement are shown in FIGS. 1 and 2 and summarized in Table 1.The major phases of the target material of Examples 1 to 3 are Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7. The total volume share of these phases is at least 75 vol.-%. In the qualitatively best sample (Example 3) the total share of these phases is even 99 vol.-%. The ratio of the volume shares of the phases Ti.sub.3O.sub.5/Ti.sub.4O.sub.7 calculated on the basis of the XRD graph is 0.59/0.40=1.48.

[0087] The TiO.sub.1.8 material (Comp. Example 1) shows cracks and delaminating when the layer thickness of the target material is higher than 10 mm. That maximal crack free target layer thickness made of TiO.sub.1.8 material is significantly lower than that which can be achieved with target materials TiO.sub.1.6 and TiO.sub.1.5 Due to the absence of the phases Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7 a volume ratio of those phases cannot be calculated.

[0088] In the XRD analysis diagram of FIG. 1 the measured defracted intensity I (in relative units; %) of sample 2 (TiO.sub.1.6) is plotted against diffraction angle 2theta. It shows that Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7 are the major phases of the microstructure. In addition to that the XRD analysis diagram of FIG. 2 shows that the microstructure of said TiO1.6 sample has no defraction signal line that can be clearly contributed to TiO.sub.2 in its rutile crystalline form.