Method for preparing high-performance tantalum target

Abstract

A method for preparing a high-performance tantalum target, a high-performance target prepared by the method, and a use of the high-performance target. The method for preparing the high-performance tantalum target comprises: firstly, preparing a tantalum ingot into a forging blank by a method of cold forging in conjunction with hot forging; then, rolling the forging blank by a hot rolling method; and finally, performing leveling, and performing discharging, milling and surface treatment according to a size of a finished product, so as to obtain the tantalum target. The tantalum target prepared by the method has uniform crystallization, with a grain size between 50 m and 120 m. A texture component where a texture (110) dominants in the thickness direction of the target is obtained. A total proportion of three textures (111), (110) and (100) is between 40% and 50%, ensuring a consistent sputtering rate of the tantalum target during use.

Claims

1. A method for preparing a high-performance tantalum target material, wherein it comprises: first preparing a tantalum ingot into a forged blank by a process of cold forging in combination with hot forging, wherein the hot forging comprises upsetting and stretching a target blank at a temperature of 800 C. to 1200 C., wherein an upsetting ratio is controlled within 55%-80%, and during the stretching, a forging feed L=0.6-0.8 h, and a reduction h=0.12-0.15 h, wherein h represents height of the target blank before the hot forging; then rolling by a hot rolling process; and finally leveling, and blanking, cutting and performing surface treatment, so as to obtain the tantalum target material.

2. The method for preparing the high-performance tantalum target material according to claim 1, wherein the process of cold forging in combination with hot forging comprises: first performing primary forging to the tantalum ingot by the cold forging, performing secondary forging by the hot forging after a first pickling and heating treatment, and then performing tertiary forging by the hot forging process after a second pickling and heating treatment.

3. The method for preparing the high-performance tantalum target material according to claim 2, wherein the cold forging process is swaging, with a forging ratio controlled within 25%-40%.

4. The method for preparing the high-performance tantalum target material according to claim 2, wherein a third pickling and heating treatment are performed after the tertiary forging, wherein a mixed acid liquor of HCl and HF at a volume ratio of 5:2 or a mixed acid liquor of HCl, HF, and H2SO4 at a volume ratio of 5:3:2 is used for the third pickling; and the third heating treatment is carried out at a temperature being 25%-45% of a melting point of tantalum material for 60-120 min.

5. The method for preparing the high-performance tantalum target material according to claim 1, wherein prior to the upsetting and stretching, the target blank is first preheated to 200 C. and then coated with 1-3 mm thick glass frit.

6. The method for preparing the high-performance tantalum target material according to claim 1, wherein the tantalum ingot is a cast ingot with Ta content99.99% and a diameter between 160 mm and 300 mm.

7. The method for preparing the high-performance tantalum target material according to claim 1, wherein the step of rolling by the hot rolling process comprises: first preheating the forged blank to 900-1200 C., then rolling, and pickling.

8. The method for preparing the high-performance tantalum target material according to claim 7, wherein a total rolling ratio is controlled within 65%-85%, a rolling temperature is controlled at 800-1200 C., the rolling adopts cross rolling with rolling direction turned clockwise by 45 for each time, a rolling ratio of first 8 passes is controlled within 50%-75%, and followed by subsequent rolling.

9. The method for preparing the high-performance tantalum target material according to claim 7, wherein reheating in furnace is performed at a temperature of 900-1200 C. after every 2-6 passes during the rolling.

10. The method for preparing the high-performance tantalum target material according to claim 7, wherein prior to the rolling, the forged blank is uniformly coated with 1-3 mm thick glass frit on surface thereof.

11. The method for preparing the high-performance tantalum target material according to claim 7, wherein the pickling is carried out in a mixed acid liquor of HCl, HF, H2SO4 at a volume ratio of 5:3:2, and a pickling time is controlled between 5 min and 10 min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The technical solutions and technical advantages of the present invention are illustrated below with reference to the drawings, in which

(2) FIG. 1 shows the metallographic test result after forging according to cold forging method of the prior art;

(3) FIG. 2 shows the metallographic test result after forging according to an embodiment of the present invention;

(4) FIG. 3 shows schematic diagram of the metallographic test method for analyzing uniformity of the grain sizes in the thickness direction of the target material.

(5) FIG. 4 shows the metallographic test result after rolling according to a method of the prior art.

(6) FIG. 5 shows the metallographic test result after rolling according to one embodiment of the present invention.

(7) FIG. 6 shows the texture test result after rolling according to cold rolling method of the prior art.

(8) FIG. 7 shows the texture test result after rolling according to one embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(9) A method for preparing a high-performance tantalum target material according to a preferred embodiment of the present invention will be described below in details. The overall processing solution of the method is as follows:

(10) tantalum ingotprimary forgingpicklingheating treatmentsecondary forgingpicklingheating treatmenttertiary forgingpicklingheating treatmentrollingpicklingheating treatmentlevelingblankingcuttingsurface treatmentchecking of the finished product.

(11) The specific solution is as follows:

(12) 1. Tantalum ingot: 160 mmdiameter300 mm; chemical composition: Ta99.99%.

(13) 2. Primary forging: cold forging, adopting swaging process, in which tantalum ingot with a large diameter is forged with a forging ratio controlled within 25%-40%.

(14) 3. Pickling: HCl:HF=5:2 (volume ratio), the pickling time is controlled to be 2-5 min, the treatment is mainly for removing surface impurities, and it is stopped till the luster of tantalum metal can be observed visually without mottles.

(15) 4. Heating treatment: the heating treatment is carried out at a temperature being 25%-45% of the melting point of tantalum material for 60 min.

(16) 5. Secondary forging: hot forging process is used. Specifically, it is first preheated to 200 C., then coated with 1-3 mm thick glass frit; subsequently, the target blank is heated to 800 C. to 1200 C., and subjected to primary upsetting and stretching, wherein the upsetting ratio is controlled within 55%-80%, and during stretching, the forging feed L=0.6-0.8 h (h represents height of the blank before forging), and the reduction h=0.12-0.15 h. To achieve a relatively uniform deformation, the feed position for the current compression should be staggered with the feed position for the previous compression during stretching. Standard gauge block is used as a cushion block to ensure uniformity and controllability in each reduction.

(17) 6. Pickling: HCl:HF:H.sub.2SO.sub.4=5:3:2 (volume ratio), the pickling time is controlled within 5 to 10 min to remove surface impurities, and it is stopped till the luster of tantalum metal can be observed visually without mottles.

(18) 7. Heating treatment: the heating treatment is carried out at a temperature being 25%-45% of the melting point of tantalum material for 60 min.

(19) 8. Tertiary forging: hot forging is used. Specifically, it is first preheated to 200 C., then coated with 1-3 mm thick glass frit; subsequently, the target blank is heated to 800 C. to 1200 C., and subjected to secondary upsetting and stretching, wherein the upsetting ratio is controlled within 55%-80%. During stretching, the forging feed L=0.6-0.8 h (h represents height of the blank before forging), and the reduction h=0.12-0.15 h. To achieve a relatively uniform deformation, the feed position for the current compression should be staggered with the feed position for the previous compression during stretching. Standard gauge block is used as a cushion block to ensure uniformity and controllability in each reduction. In upsetting, the height is adjusted according to size of the finished product.

(20) 9. Pickling: HCl:HF:H.sub.2SO.sub.4=5:3:2 (volume ratio), the pickling time is controlled within 5 to 10 min to remove surface impurities, and it is stopped till the luster of tantalum metal can be observed visually without mottles.

(21) 10. Heat treatment: the heating treatment is carried out at a temperature being 25%-45% of the melting point of tantalum material for 60 min.

(22) 11. The forged blank is preheated to 900 C. to 1200 C.

(23) 12. Rolling, the thickness is controlled to be the thickness of the finished product required by customers plus a machining allowance of 2-4 mm.

(24) 1) To reduce oxidation of materials during rolling, the blank is coated with glass frit on surface thereof before rolling, and coating of the glass frit shall be uniform with a thickness controlled within 1-3 mm.

(25) 2) Total rolling ratio is controlled within 65%-85%.

(26) 3) Reheating in furnace is required after it is rolled for every 2-6 passes. The heating temperature is the same as the temperature for preheating the blank, i.e. 900 C. to 1200 C.

(27) 4) The temperature of the material is monitored in real time with a remote sensing thermometer during rolling. The rolling temperature should not be less than 800 C., and be controlled between 800 C. and 1200 C.

(28) 5) Cross rolling is adopted, wherein rolling direction turns clockwise by 45 for each time. The rolling ratio of the first 8 passes is controlled within 50%-75%, and the subsequent rolling is mainly for compensating tolerance. The thickness tolerance of the same plate is controlled within 0.5 mm.

(29) 13. Pickling is carried out in a mixed acid liquor of HCl, HF and H.sub.2SO.sub.4 at a volume ratio of 5:3:2, and the pickling time is controlled between 5 min and 10 min to remove surface impurities, and it is stopped till the luster of tantalum metal can be observed visually without mottles.

(30) 14. Heating treatment: the heating treatment is carried out at a temperature being 25%-45% of the melting point of tantalum material for 60 min.

(31) 15. Leveling, the leveling temperature is 600 C. to 800 C.

(32) 16. Blanking, an allowance of 5-10 mm is provided according to size of the finished product during blanking.

(33) 17. Cutting, the cutting is carried out according to size of the finished product.

(34) 18. Surface treatment: surface defects are removed by combination of mechanical finishing and artificial finishing.

(35) 19. Checking of finished product: the target material is detected in grain size, outline dimension, surface roughness, and planeness (different customers have different requirements).

(36) FIG. 1 shows the metallographic test after forging of the tantalum ingot according to cold forging method of the prior art;

(37) FIG. 2 shows the metallographic test after forging of the tantalum ingot according to one embodiment of the present invention. In the embodiment according to the present invention, a tantalum ingot is forged by a process of cold forging in combination with hot forging, and the forged blank is subjected to the metallographic test, with results shown in FIG. 2.

(38) The results shown in FIG. 1 are compared with the results shown in FIG. 2. FIG. 1 shows after forging according to the method of the prior art, the grain size of the forged blank is nonuniform, and phenomenon of evident delamination occurs. In contrast, as shown in FIG. 2, the forged blank after forging according to the embodiment of the present invention has a uniform grain size and no evident delamination.

(39) After the forged blank is rolled by hot rolling according to an embodiment of the present invention, the resultant target material is subjected to the metallographic test according to the test method shown in FIG. 3, and uniformity of grain size in the thickness direction of the target material is analyzed.

(40) As shown in FIG. 3, the red region A is the region where metallograph is taken. Metallographs are taken continuously at a height of 1.5 mm for each time, and then the metallographs are spliced together in sequence.

(41) FIG. 4 shows the metallographic test result of target material after the blank is rolled according to cold rolling process in the prior art.

(42) FIG. 5 shows the metallographic test result of target material after the forged blank is hot rolled according to hot rolling process of the present invention.

(43) By comparison, in the target material obtained by the method in the prior art, as shown in FIG. 4, the grain size is nonuniform, phenomenon of delamination occurs, and the grain size in the central part is larger. However, in FIG. 5, the target material obtained by the method of the present invention has uniform grain size.

(44) In addition, the target material formed after hot rolling according to the method of the present invention is subjected to texture detection. Table 1 shows detection result data of the textures of the target material rolled according to the cold rolling process in the prior art. Table 2 shows detection result data of the textures of the target material rolled according to the method of the present invention. Average grain size and proportion of each of texture components (111), (110) and (100) that are detected at points (from the top down) taken at different parts of the target material with equal intervals are listed in the tables.

(45) TABLE-US-00001 TABLE 1 Detection result data of textures of the target material rolled according to the prior art Average grain Texture Texture Texture Part size (m) {100} {110} {111} From 1# 28.7 21.7 17.8 11.7 12.3 top to 2# 32.5 23.9 18.7 9.94 22.4 bottom 3# 31.6 24.sup. 11.2 5.6 39.2 4# 35.1 29.5 8.82 6.25 42.6 5# 30.5 23.5 17.5 7.74 19 6# 25.8 22.3 15.3 9.7 19.3 Whole 31.2 25.sup. 14.8 8.43 26

(46) TABLE-US-00002 TABLE 2 Detection result data of textures of the target material rolled according to the method of the present invention Average grain Texture Texture Texture Part size (m) {100} {110} {111} From 1# 29.9 19.8 9.56 19.1 12.9 top to 2# 27.5 16.5 11.5 21.1 10.2 bottom 3# 29.4 18.8 12.1 21.5 11.5 4# 32.9 20.5 12 21.4 10.1 5# 33.4 22.sup. 11.9 28.1 6.65 6# 31.2 20.8 9.91 27 10.2 7# .sup.31 18.8 11.3 26 8.74 8# 33.8 21.sup. 14.4 19.1 11.3 9# 38.2 24.9 13.3 23 9.99 Whole 31.6 20.6 11.7 22.9 10.3

(47) FIG. 6 shows diagram of texture result of the target material rolled according to a method in the prior art; and FIG. 7 shows diagram of texture result of the target material rolled according to an embodiment of the present invention.

(48) As can be seen from table 1 and FIG. 6, in the target material cold rolled according to the method in the prior art, distribution of texture components is not uniform, and texture (111) is dominant and gradually increases from the surface to the central part of the target material. The total proportion of three textures (111), (110) and (100) is between 42% and 57%.

(49) By analysis on the results shown in table 2 and FIG. 7, it can be seen that in the tantalum target material rolled according to the method of the present invention, texture components are distributed uniformly, and texture (110) is dominant. The total proportion of three textures (111), (110) and (100) is between 42% and 48%.

(50) Consequently, by treating the high-performance rolled blank via the hot rolling process according to the present invention, a uniform high-performance tantalum target material having texture components in which texture (110) dominates in the thickness direction of the target material and meeting requirements for use in high-end sputtering machine station. Compared with common tantalum target material, the high-performance tantalum target material not only achieves texture components where texture (110) dominates in the thickness direction of the target material, but also sets forth higher requirements for uniformity in the textures (the total proportion of three textures (111) (110) and (100) comprises between 40% and 50%), thereby ensuring a consistent sputtering rate during use.

(51) The above merely demonstrates preferred embodiments of the present invention. It should be noted that several improvements and modifications may be made by an ordinary person skilled in the art without deviation from the principle of the present invention, and such improvements and modifications shall be regarded as falling within the protection scope covered by the present invention.