High-purity bismuth target material and method for manufacturing the same

Abstract

The application provides a high-purity bismuth target material and a preparation method thereof, and the preparation method comprises the following steps: vacuum hot-press sintering is performed on high-purity bismuth powder to obtain a high-purity bismuth target blank; the holding temperature of the vacuum hot-press sintering is 180-200 DEG C, and the holding time of the vacuum hot-press sintering is 35-45 min; and the heating rate of the vacuum hot-press sintering is 5-8 DEG C / min. The preparation method can be used to prepare the bismuth target material with high purity, high relative density, good conductivity and a defect-free surface.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of target materials, and particularly relates to a high-purity bismuth target material and a preparation method thereof. BACKGROUND

[0002] Target material is a basic consumable material in the process of magnetron sputtering, and the quality of the target material plays a crucial role in the performance of the thin film. The target material is widely used in various fields, mainly including optical target material, display thin film target material, semiconductor field target material, recording medium target material, superconducting target material, etc. Among them, the semiconductor field target material, the display target material and the recording medium target material are the three most widely used target materials. In order to improve the thin film preparation rate and ensure the growth quality of the thin film, the sputtering target material needs to meet certain index requirements.

[0003] The bismuth target material has the characteristics of high purity and high density, and can be used for preparing various metal films and alloy films on an electron beam evaporation coating machine. In addition, the bismuth target material can also be used for preparing various optical thin films, such as antireflection film, reflective film and optical filter, etc.

[0004] For the bismuth target material, the preparation method and raw material will affect its performance, and how to prepare a bismuth target material with high purity, high relative density, good electrical conductivity and no surface defects has become an important research content. SUMMARY

[0005] In view of the above technical problems, the application provides a high-purity bismuth target material and a preparation method thereof.

[0006] To achieve the above object, the application provides the following technical scheme:

[0007] In a first aspect, a preparation method of a high-purity bismuth target material is provided, comprising:

[0008] vacuum hot-pressing sintering of high-purity bismuth powder to obtain a high-purity bismuth target blank; the temperature of the vacuum hot-pressing sintering is 180-200℃, the holding time of the vacuum hot-pressing sintering is 35-45min, and the heating rate of the vacuum hot-pressing sintering is 5-8℃ / min.

[0009] Further, the pressure of the vacuum hot-pressing sintering is 37-43Mpa.

[0010] Further, the vacuum degree of the vacuum hot-pressing sintering is ≤10Pa.

[0011] Further, the preparation method of the high-purity bismuth powder comprises:

[0012] dissolving bismuth nitrate in dilute nitric acid to obtain solution A;

[0013] A urea solution is added to the solution A until the pH value of the solution A reaches 8-10, and after stirring for a period of time, the solution is transferred to a reaction kettle for hydrothermal reaction to obtain a precursor slurry;

[0014] The precursor slurry is subjected to solid-liquid separation, washing and drying to obtain a precursor powder, and the precursor powder is calcined to obtain bismuth oxide;

[0015] The bismuth oxide is reduced to obtain high-purity bismuth powder.

[0016] Further, in the solution A, the molar ratio of bismuth nitrate to nitric acid is 3:1.0-1.45.

[0017] Further, the temperature of the hydrothermal reaction is 170-200℃, and the time of the hydrothermal reaction is 8-12h.

[0018] Further, the calcination temperature is 350-450℃, and the calcination time is 4-6h.

[0019] Further, the reduction is hydrogen reduction, and the temperature of the hydrogen reduction is 750-850℃.

[0020] Further, it further includes the post-processing step of cutting to remove excess material on the surface of the high-purity target blank and then milling the surface.

[0021] In a second aspect, a high-purity bismuth target material is provided, which is prepared by the above preparation method.

[0022] Further, the relative density of the high-purity bismuth target material is more than 99%, the electrical conductivity is more than 900S / m, the impurity content is less than 100ppm, and the surface of the high-purity bismuth target material is free of spots and color difference.

[0023] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0024] The preparation method provided in the present application can prepare a bismuth target material with high purity, high relative density, good electrical conductivity and a surface free of defects. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0026] Figure 1 Picture of high-purity bismuth planar target prepared in Example 1.

[0027] Figure 2 Picture of high-purity bismuth flat target prepared for Comparative Example 3. DETAILED DESCRIPTION

[0028] The present application provides a preparation method of high-purity bismuth target material, comprising:

[0029] The high-purity bismuth powder is subjected to vacuum hot-press sintering to obtain a high-purity bismuth target blank; the holding temperature of the vacuum hot-press sintering is 180-200℃, the holding time of the vacuum hot-press sintering is 35-45min (for example, 35min, 38min, 40min, 42min, 45min, etc.), and the heating rate of the vacuum hot-press sintering is 5-8℃ / min (for example, 5℃ / min, 6℃ / min, 7℃ / min, and 8℃ / min, etc.).

[0030] The above preparation method uses high-purity bismuth powder as raw material to perform vacuum hot-press sintering, and controls the process conditions of the vacuum hot-press sintering, so that the prepared target material has relatively high density and electrical conductivity, and the appearance of the target material is also relatively good.

[0031] In some preferred embodiments, the pressure of the vacuum hot-press sintering is 37-43MPa, for example, 37MPa, 38MPa, 39MPa, 40MPa, 41MPa, 42MPa, 43MPa, etc.

[0032] In some preferred embodiments, the vacuum degree of the vacuum hot-press sintering is ≤10Pa.

[0033] In some preferred embodiments, the preparation method of the high-purity bismuth powder comprises:

[0034] Bismuth nitrate is dissolved in dilute nitric acid to obtain solution A;

[0035] Urea solution is added to solution A until the pH value of solution A reaches 8-10 (for example, 8, 8.5, 9, 9.5, 10, etc.), and after stirring for a period of time, it is transferred to a reaction kettle for hydrothermal reaction to obtain a precursor slurry;

[0036] The precursor slurry is subjected to solid-liquid separation, washing, and drying to obtain a precursor powder; the precursor powder is calcined to obtain bismuth oxide;

[0037] The bismuth oxide is reduced to obtain high-purity bismuth powder.

[0038] Compared with the bismuth powder prepared by the grinding process, the high-purity bismuth powder prepared by the above preparation method has lower impurity content; compared with the ordinary precipitation, the hydrothermal precipitation reaction of the above preparation method is more thorough, has higher yield, and even the insoluble substances in the reactants can be dissolved and reacted; and compared with the bismuth compound prepared by using other pH adjusters (such as ammonia water and NaOH solution), the bismuth compound prepared by using the urea solution as the pH adjuster has a slower and more uniform reaction process, the obtained product is more uniform, and the particle size is relatively small, so that the high-purity bismuth powder is obtained by calcination-reduction of the former, and the target material is prepared by using the high-purity bismuth powder as the raw material, and the prepared target material has higher density and better conductivity.

[0039] In some preferred embodiments, the molar ratio of bismuth nitrate to nitric acid in the solution A is 3:1.0-1.45, such as 3:1, 3:1.1, 3:1.2, 3:1.3, 3:1.4, 3:1.45, etc. It has been found that the bismuth compound prepared by using the raw materials with the above ratio has higher density and conductivity of the bismuth target material prepared by calcination-reduction-vacuum hot-press sintering of the bismuth compound.

[0040] In some preferred embodiments, the temperature of the hydrothermal reaction is 170-200℃, such as 170℃, 180℃, 190℃, 200℃, etc.; and the time of the hydrothermal reaction is 8-12h, such as 8h, 9h, 10h, 11h, 12h, etc.

[0041] In some preferred embodiments, the calcination temperature is 350-450℃, such as 350℃, 380℃, 400℃, 420℃, 450℃, etc.; and the calcination time is 4-6h, such as 4h, 4.5h, 5h, 5.5h, 6h, etc.

[0042] In some preferred embodiments, the reduction is hydrogen reduction; and the temperature of the hydrogen reduction is 750-850℃, such as 750℃, 780℃, 800℃, 820℃, 850℃, etc. The reduction time can be determined according to the reduction requirement.

[0043] In some preferred embodiments, the method further comprises the post-processing step of cutting and removing the excess material on the surface of the high-purity target blank, and then milling the surface.

[0044] In some preferred embodiments, the relative density of the high-purity bismuth target material is more than 99%, the conductivity is more than 900S / m, the impurity content is less than 100ppm, and the surface of the high-purity bismuth target material is free of spots and color difference.

[0045] In order to facilitate the understanding of the present application, the present application will be described in more detail below in combination with the drawings of the specification and the preferred embodiments, but the protection scope of the present application is not limited to the following specific embodiments.

[0046] Example 1

[0047] (1) A dilute nitric acid solution was prepared by weighing nitric acid (mass concentration 76%): deionized water = 1:3 according to the volume ratio; a certain amount of 3.7 mol / L urea aqueous solution was weighed for standby; and a certain amount of bismuth nitrate pentahydrate powder was weighed for standby.

[0048] (2) The weighed bismuth nitrate pentahydrate was dissolved in dilute nitric acid, and the molar ratio of bismuth nitrate pentahydrate to dilute nitric acid was HNO3:Bi(NO3)3·5H2O = 3:1.25, and the magnetic stirrer was continuously stirred at 80°C. After the bismuth nitrate pentahydrate was completely dissolved, the stirring time was 10-15 min. Urea aqueous solution was continuously added to the stirred solution until the pH value of the solution reached 10. Stirring was continued for 30 min.

[0049] (3) The solution obtained in step (2) was added to a high-pressure reaction kettle, which was sealed and placed in a muffle furnace, and heated at 180°C for 10h. After the reaction kettle was cooled to room temperature, the product was centrifuged, washed with deionized water, and then dried in an oven for 10h to obtain a precursor powder. The yield of the precursor powder was measured to be 85.22%.

[0050] (4) The precursor powder obtained in step (3) was calcined at 400°C to obtain bismuth oxide powder. The powder Malvin was measured to be D90=0.447μm.

[0051] (5) The bismuth oxide powder obtained in step (4) was hydrogenated at 800°C to obtain high-purity bismuth powder.

[0052] (6) The bismuth powder obtained in step (5) was vacuum hot-pressed and sintered at a heating rate of 5°C / min to 180°C, the pressure was 40Mpa, the vacuum degree was ≤10pa, and then the temperature was kept for 40min to obtain a high-purity bismuth target blank. The high-purity bismuth target blank was cooled to room temperature in the furnace for 4h, and then the high-purity bismuth target material was taken out.

[0053] (7) The high-purity bismuth target blank after cooling was cut by diamond wire cutting to remove the excess material on the surface of the high-purity bismuth target blank, and a high-purity bismuth target blank with a specific shape was obtained.

[0054] (8) The high-purity bismuth target blank was fixed on a numerical control milling machine, and the surface was milled with a 150-mesh resin diamond grinding wheel at a speed of 600r / min. After the milling was completed, a high-purity bismuth planar target was obtained. The picture of the obtained high-purity bismuth planar target is shown in Figure 1 , it can be seen from Figure 1 that the obtained target material does not have color difference and spots. After detection, the target material density is 99.03%, the electrical conductivity is 984S / m, and the total impurity content is 28ppm.

[0055] Example 2

[0056] (1) A solution was prepared by weighing nitric acid and deionized water in a volume ratio of 1:3 to prepare a dilute nitric acid solution; a certain amount of 3.7 mol / L urea aqueous solution was weighed for standby, and a certain amount of bismuth nitrate pentahydrate powder was weighed for standby.

[0057] (2) The weighed bismuth nitrate pentahydrate metal salt was dissolved in dilute nitric acid, and the molar ratio of bismuth nitrate pentahydrate to dilute nitric acid was HNO3:Bi(NO3)3·5H2O=3:1.25, and the magnetic stirrer was continuously stirred at 80°C. After the bismuth nitrate pentahydrate was completely dissolved, the stirring time was 10-15 min; continuously add urea aqueous solution to the stirred solution until the pH value of the solution reaches 10. Continue to stir for 30 min.

[0058] (3) The solution obtained in step (2) was added to a high-pressure reaction kettle, which was sealed and placed in a muffle furnace, and heated at 180°C for 10h. After the reaction kettle was cooled to room temperature, the product was centrifuged, washed with deionized water, and then dried in an oven for 10h to obtain a precursor powder.

[0059] (4) The obtained precursor powder was calcined at 400°C to obtain bismuth oxide powder.

[0060] (5) The bismuth powder obtained in step (4) was hydrogenated at 800°C to obtain high-purity bismuth powder;

[0061] (6) The bismuth powder obtained in step (5) was vacuum hot-pressed and sintered at a heating rate of 5°C / min to 190°C, the pressure was 40Mpa, the vacuum degree was ≤10pa, then the temperature was kept for 40min, and the furnace was cooled to room temperature for 4h, and the high-purity bismuth target blank was taken out.

[0062] (7) The high-purity bismuth target blank after cooling was cut by diamond wire cutting to remove the excess material on the surface of the high-purity bismuth target blank to obtain a high-purity bismuth target blank with a specific shape. The high-purity bismuth target blank was fixed on a numerical control milling machine, and a 150-mesh resin diamond grinding wheel was used to mill the surface at a speed of 600r / min. After milling, a high-purity bismuth plane target was obtained. The target material does not have color difference and spots, and the density of the target material is 99.28%, the electrical conductivity is 998S / m, and the total impurity content is 30ppm.

[0063] Example 3

[0064] (1) A solution was prepared by weighing nitric acid and deionized water in a volume ratio of 1:3 to prepare a dilute nitric acid solution; a certain amount of 3.7 mol / L urea aqueous solution was weighed for standby, and a certain amount of bismuth nitrate pentahydrate powder was weighed for standby.

[0065] (2) Dissolve the weighed bismuth nitrate pentahydrate in dilute nitric acid, the molar ratio of dilute nitric acid to bismuth nitrate pentahydrate is HNO3:Bi(NO3)3·5H2O = 3:1.25, and continuously stir using a magnetic stirrer at 80°C until the bismuth nitrate pentahydrate is completely dissolved, the stirring time is 10-15 min; continuously add the aqueous urea solution to the stirred solution until the pH value of the solution reaches 10, and continue to stir for 30 min.

[0066] (3) Put the solution obtained in step (2) into a high-pressure reaction kettle, seal it, and place it in a muffle furnace, heat at 180°C for 10 h, then cool the reaction kettle to room temperature, centrifuge the product, wash with deionized water, dry in an oven for 10 h, and obtain the precursor powder.

[0067] (4) Calcine the obtained precursor powder at 400°C to obtain bismuth oxide powder.

[0068] (5) Hydrogenate the bismuth powder obtained in step (4) at 800°C to obtain high-purity bismuth powder.

[0069] (6) Vacuum hot-press sinter the bismuth powder obtained in step (5) at a heating rate of 5°C / min to 200°C, the pressure is 40Mpa, the vacuum degree is ≤10pa, then keep the temperature for 40 min, cool to room temperature for 4h, and take out the high-purity bismuth target blank.

[0070] (7) Cut off the excess material on the surface of the high-purity bismuth target blank using diamond wire cutting after cooling, and obtain a high-purity bismuth target blank with a specific shape. Fix the obtained high-purity bismuth target blank on a numerical control milling machine, and mill the surface using a 150-mesh resin diamond grinding wheel at a milling speed of 600r / min. After milling, a high-purity bismuth plane target is obtained.

[0071] The obtained target material has no color difference and spots, and the detection of the target material density is 99.65%, the conductivity is 1038S / m, and the total impurity content is 27ppm.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 3 is only that in step (1), 3.7mol / L dilute ammonia water is prepared, and in step (2), dilute ammonia water is used instead of aqueous urea solution as a pH adjuster.

[0074] The Malvern of the obtained bismuth powder is D90=1.134μm; the obtained target material has no color difference and spots, and the detection of the target material density is 96.13%, the conductivity is 320S / m, and the total impurity content is 28ppm.

[0075] Comparative Example 3 and Comparative Example 1 can be seen that, after using dilute ammonia water instead of urea aqueous solution as the pH regulator, the particle size of the powder prepared by hydrothermal reaction is significantly increased, and the density and conductivity of the target material prepared finally are significantly reduced. It is analyzed that this is because, compared with ammonia solution, the precipitation reaction of urea aqueous solution with cations is slower, the precipitate prepared is more likely to be a single oxide with uniform composition, and the particle size of the product obtained is smaller, and thus the target material prepared from the product has higher density and higher conductivity.

[0076] Example 4

[0077] The difference between this example and Example 3 is only that the heating rate in step (6) is different, and the heating rate in this example is 8 ℃ / min.

[0078] The target material obtained has no color difference and spots, and the detected density of the target material is 99.53%, the conductivity is 1031 S / m, and the total impurity content is 28 ppm.

[0079] Example 5

[0080] The difference between this example and Example 3 is only that the holding time in step (6) is different, and the holding time in this example is 35 min.

[0081] The target material obtained has no color difference and spots, and the detected density of the target material is 99.60%, the conductivity is 1034 S / m, and the total impurity content is 27 ppm.

[0082] Example 6

[0083] The difference between this example and Example 3 is only that the holding time in step (6) is different, and the holding time in this example is 45 min.

[0084] The target material obtained has no color difference and spots, and the detected density of the target material is 99.58%, the conductivity is 1035 S / m, and the total impurity content is 28 ppm.

[0085] Example 7

[0086] The difference between this example and Example 3 is only that the molar ratio of dilute nitric acid to bismuth nitrate pentahydrate HNO3:Bi(NO3)3·5H2O in step (2) is different, and the molar ratio in this example is 3:1.45.

[0087] The target material obtained has no color difference and spots, and the detected density of the target material is 99.46%, the conductivity is 1016 S / m, and the total impurity content is 29 ppm.

[0088] Example 8

[0089] The difference between this embodiment and embodiment 3 is only that the molar ratio of bismuth nitrate pentahydrate to dilute nitric acid in step (2) is different, and the molar ratio in this embodiment is 3:1.70.

[0090] The obtained target material has no color difference and spots, and the detected density of the target material is 97.42%, the conductivity is 650 S / m, and the total impurity content is 28 ppm.

[0091] It is found that the molar ratio of bismuth nitrate pentahydrate to dilute nitric acid in the raw material also affects the density and conductivity of the target material by comparing the bismuth target materials obtained in comparative example 1, embodiment 7 and embodiment 8.

[0092] Comparative Example 2

[0093] The difference between this comparative example and embodiment 1 is only that the heating rate in step (6) is different, and the heating rate in this comparative example is 10 ℃ / min.

[0094] The obtained target material has no color difference and spots, and the measured density of the target material is 98.12%, the conductivity is 810 S / m, and the total impurity content is 32 ppm.

[0095] Comparative Example 3

[0096] The difference between this comparative example and embodiment 1 is only that the heat pressing holding temperature in step (6) is different, and the heat pressing holding temperature in this comparative example is 170 ℃.

[0097] The obtained target material has no color difference and spots, and the measured density of the target material is 98.56%, the conductivity is 685 S / m, and the total impurity content is 30 ppm.

[0098] Comparative Example 4

[0099] The difference between this comparative example and embodiment 1 is only that the heat pressing holding temperature in step (6) is different, and the heat pressing holding temperature in this comparative example is 210 ℃.

[0100] The picture of the obtained target material is shown in Figure 2 From Figure 2 it can be seen that the surface of the obtained target material has spots and color difference. The detected density of the target material is 99.76%, the conductivity is 1125 S / m, and the total impurity content is 30 ppm.

[0101] Comparative Example 5

[0102] The difference between this comparative example and embodiment 3 is only that the temperature is increased to 200 ℃ at a heating rate of 5 ℃ / min, and then holding for 60 min.

[0103] The obtained target material has no color difference and spots, and the measured density of the target material is 98.12%, the conductivity is 680 S / m, and the total impurity content is 29 ppm.

[0104] Comparative Example 6

[0105] The only difference between this comparative example and Example 3 is that the temperature is raised to 200°C at a rate of 5°C / min, and then held for 20 min.

[0106] The target material obtained has no color difference and spots, and the measured density of the target material is 98.72%, the conductivity is 496 S / m, and the total impurity content is 29 ppm.

[0107] Comparing the target materials obtained in the above examples and comparative examples, it is found that by strictly controlling the hot pressing temperature range, the temperature rising rate range and the holding time range, a bismuth target material with high relative density, high conductivity and no color difference and spots on the surface can be prepared. If the hot pressing temperature, holding time and temperature rising rate are not properly controlled, the target material prepared has either a low relative density and low conductivity, or has defects such as color difference and spots on the surface.

[0108] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as falling within the scope of protection of the present application.

Claims

1. A method for producing a high-purity bismuth target material, characterized by, The application relates to a high-purity bismuth target material and a preparation method thereof. The high-purity bismuth target blank is prepared by vacuum hot-press sintering of high-purity bismuth powder; the holding temperature of the vacuum hot-press sintering is 180-200 DEG C, the holding time of the vacuum hot-press sintering is 35-45 min, and the heating rate of the vacuum hot-press sintering is 5-8 DEG C / min; The preparation method of the high-purity bismuth powder comprises the following steps: Bismuth nitrate is dissolved in dilute nitric acid to obtain solution A; in the solution A, the molar ratio of bismuth nitrate to nitric acid is 3:1.0-1.45; Urea solution is added into the solution A until the pH value of the solution A reaches 8-10; after stirring for a period of time, the solution A is transferred into a reaction kettle to perform hydrothermal reaction, and a precursor slurry is obtained; The precursor slurry is subjected to solid-liquid separation, washing and drying to obtain a precursor powder; the precursor powder is calcined to obtain bismuth oxide; The bismuth oxide is reduced to obtain high-purity bismuth powder.

2. The method of producing a high-purity bismuth target material according to claim 1, wherein The pressure of the vacuum hot-press sintering is 37-43 Mpa, and the vacuum degree of the vacuum hot-press sintering is less than or equal to 10 Pa.

3. The method of producing a high-purity bismuth target material according to claim 1, wherein The temperature of the hydrothermal reaction is 170-200 DEG C, and the time of the hydrothermal reaction is 8-12 h.

4. The method of producing a high-purity bismuth target material according to claim 1, wherein The calcination temperature is 350-450 DEG C, and the calcination time is 4-6 h.

5. The method of producing a high-purity bismuth target material according to claim 1, wherein The reduction is hydrogen reduction, and the temperature of the hydrogen reduction is 750-850 DEG C.

6. The method of producing a high-purity bismuth target material according to claim 1, wherein The surface of the high-purity target blank is cut to remove excess materials, and then a milling surface post-processing step is performed.

7. A high purity bismuth target material, characterized by, The high-purity bismuth target material prepared by the preparation method in any one of claims 1-6 has a relative density of more than 99%, an electrical conductivity of more than 900 S / m, an impurity content of less than 100 ppm, and no spots and color difference on the surface of the high-purity bismuth target material.

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