A method for manufacturing a tungsten-silicon alloy target

Abstract

The application relates to a preparation method of a tungsten-silicon alloy target material, which comprises the following steps: mixing tungsten powder and silicon powder, then performing compression, and then performing hot-pressing sintering to obtain a tungsten-silicon alloy target material; wherein the compression comprises sequentially performed first compression and gradient ultrasonic compression; and the pressure and ultrasonic power are synchronously increased in the gradient ultrasonic compression. The preparation method provided by the application significantly improves the use performance of the obtained tungsten-silicon alloy target material by means of a specific compression process; the compactness of the obtained tungsten-silicon target material has a relative density of more than 99%, and the problem of powder falling caused by insufficient alloying of the tungsten-silicon alloy target material during use is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of target material preparation, in particular to a preparation method of tungsten-silicon alloy target material. BACKGROUND

[0002] At present, since the tungsten-silicon alloy thin film has good conductivity, high-temperature resistance, corrosion resistance and the like, it is widely used in semiconductor integrated circuits, and its main preparation processes include physical vapor deposition and chemical vapor deposition, such as sputtering plating technology for film layer preparation. The role of the target material is particularly important during sputtering plating, and its performance will significantly affect the performance of the obtained thin film, and the preparation process of the tungsten-silicon alloy target material will significantly affect the performance of the obtained target material.

[0003] At present, the preparation of tungsten-silicon alloy target material is mainly realized by hot-pressing sintering. For example, CN103695852A discloses a manufacturing method of tungsten-silicon target material. The manufacturing method of the tungsten-silicon target material comprises: providing high-purity tungsten powder and high-purity silicon powder; mixing the tungsten powder and the silicon powder by using a wet mixing process to form a mixed powder; using a cold pressing process to make the mixed powder into a tungsten-silicon target material blank; and using a vacuum hot-pressing process to make the tungsten-silicon target material blank into a tungsten-silicon target material.

[0004] For another example, CN105671483A discloses a manufacturing method of tungsten-silicon target material, which comprises: providing tungsten powder and silicon powder; uniformly mixing the tungsten powder and the silicon powder by using a powder mixing process to form a mixed powder; densifying the mixed powder by using a cold pressing process to form a tungsten-silicon target material blank; placing the tungsten-silicon target material blank in a package, and densifying the tungsten-silicon target material blank in the package by using a hot isostatic pressing process; and removing the package to obtain a tungsten-silicon target material.

[0005] However, the tungsten-silicon alloy target material obtained by the current process has the problems of loose particle drop and powder drop during use, which causes the problem of wafer contamination during use of the target material. SUMMARY

[0006] In view of the problems in the prior art, the purpose of the present application is to provide a preparation method of tungsten-silicon alloy target material to solve the problems of loose particle drop and powder drop of the tungsten-silicon alloy target material obtained by the current process during use, which causes the problem of wafer contamination during use of the target material.

[0007] To achieve this purpose, the present application adopts the following technical solutions:

[0008] The present application provides a preparation method of tungsten-silicon alloy target material, which comprises:

[0009] mixing tungsten powder and silicon powder, then pressing, and then hot-pressing sintering to obtain a tungsten-silicon alloy target material;

[0010] The pressing includes a first pressing and a gradient ultrasonic pressing in sequence; the pressure and ultrasonic power are increased synchronously in the gradient ultrasonic pressing.

[0011] The preparation method provided by the application significantly improves the performance of the obtained tungsten-silicon alloy target material, the compactness of the obtained tungsten-silicon target material has a relative density of more than 99%, and the problem of powder falling due to insufficient alloying of the tungsten-silicon alloy target material during use is avoided.

[0012] As a preferred technical solution of the application, the particle size of the tungsten powder is ≤10 μm.

[0013] Preferably, the particle size of the silicon powder is ≤10 μm.

[0014] As a preferred technical solution of the application, the mass ratio of the tungsten powder and the silicon powder is (2-2.5):1.

[0015] As a preferred technical solution of the application, the pressure of the first pressing is 100-120 N.

[0016] Preferably, the time of the first pressing is 1-1.5 min.

[0017] As a preferred technical solution of the application, the frequency of the ultrasonic in the gradient ultrasonic pressing is 20-30 MHz.

[0018] As a preferred technical solution of the application, the increasing rate of the pressure in the gradient ultrasonic pressing is 100-120 N / min.

[0019] Preferably, the increasing rate of the ultrasonic power in the gradient ultrasonic pressing is 500-520 W / min.

[0020] As a preferred technical solution of the application, the terminal pressure of the gradient ultrasonic pressing is 500-600 N.

[0021] Preferably, the terminal ultrasonic power of the gradient ultrasonic pressing is 2800-3000 W.

[0022] Preferably, the gradient ultrasonic pressing is maintained for 1-2 min after the terminal pressure and the terminal ultrasonic power are reached.

[0023] As a preferred technical solution of the application, the absolute value of the difference between the thickness of the obtained pressing block and the set thickness is ≤0.1 mm.

[0024] As a preferred technical solution of the application, the pressure control in the hot-pressing sintering is 1500-1700 kN.

[0025] Preferably, the temperature control in the hot-pressing sintering is 1400-1500℃.

[0026] As a preferred technical solution of the present application, the holding pressure and temperature time of the hot-pressing sintering is 4-5h.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] The preparation method provided by the present application realizes the improvement of the use performance of the obtained tungsten-silicon alloy target material by means of the combination of specific gradient pressure and gradient ultrasonic power, so that the alloying degree of the prepared alloy target material is significantly improved, and the problem of wafer contamination caused by the falling of elemental powder and insufficiently alloyed powder is avoided. DETAILED DESCRIPTION

[0029] In order to better illustrate the present application and facilitate the understanding of the technical solutions of the present application, the typical but non-limiting embodiments of the present application are as follows:

[0030] The present embodiment provides a preparation method of a tungsten-silicon alloy target material, which comprises:

[0031] The tungsten powder and the silicon powder are mixed and then pressed, and then hot-pressing sintering is performed to obtain a tungsten-silicon alloy target material.

[0032] The pressing comprises first pressing and gradient ultrasonic pressing performed in sequence; and the pressure and the ultrasonic power are increased synchronously in the gradient ultrasonic pressing.

[0033] In the present application, the initial pressure of the gradient ultrasonic pressing is the same as the holding pressure of the first pressing; and the initial ultrasonic power is 800-1000W.

[0034] Specifically, the particle size of the tungsten powder is ≤10μm.

[0035] Specifically, the particle size of the silicon powder is ≤10μm.

[0036] In the present application, the particle size of the tungsten powder and the silicon powder refers to any particle aggregate within the specified range, which meets the requirements, for example, the particle size of the tungsten powder is ≤10μm, for example, a uniform aggregate of particles with a particle size of 5μm, or a uniform aggregate of particles with a particle size of 1μm, or a uniform aggregate of particles with a particle size of 3μm, or a uniform aggregate of particles with a particle size of 7μm, or a uniform aggregate of particles with a particle size of 10μm, or an aggregate of all particles within a certain range, such as an aggregate of all particles within 5-10μm, or an aggregate of all particles within 1-5μm, or an aggregate of all particles within 3-10μm, or an aggregate of all particles within 1-10μm, and other ranges can be deduced accordingly.

[0037] Based on the foregoing description, the particle size of the tungsten powder in the present application is ≤10 μm, for example, it can be 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.5 μm, 0.1 μm, 0.05 μm or 0.01 μm, etc., but not limited to the listed values, other values not listed in this range are also required.

[0038] The particle size of the silicon powder in the present application is ≤10 μm, for example, it can be 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.5 μm, 0.1 μm, 0.05 μm or 0.01 μm, etc., but not limited to the listed values, other values not listed in this range are also required.

[0039] Specifically, the mass ratio of the tungsten powder and the silicon powder is (2-2.5):1, for example, it can be 2:1, 2.05:1, 2.1:1, 2.15:1, 2.2:1, 2.25:1, 2.3:1, 2.35:1, 2.4:1, 2.45:1 or 2.5:1, etc., but not limited to the listed values, other values not listed in this range are also required.

[0040] Specifically, the pressure of the first pressing is 100-120 N, for example, it can be 100 N, 102 N, 104 N, 106 N, 108 N, 110 N, 112 N, 114 N, 116 N, 118 N or 120 N, etc., but not limited to the listed values, other values not listed in this range are also required.

[0041] Specifically, the time of the first pressing is 1-1.5 min, for example, it can be 1 min, 1.05 min, 1.1 min, 1.15 min, 1.2 min, 1.25 min, 1.3 min, 1.35 min, 1.4 min, 1.45 min or 1.5 min, etc., but not limited to the listed values, other values not listed in this range are also required.

[0042] Specifically, the frequency of the ultrasound in the gradient ultrasonic pressing is 20-30 MHz, for example, it can be 20 MHz, 21 MHz, 22 MHz, 23 MHz, 24 MHz, 25 MHz, 26 MHz, 27 MHz, 28 MHz, 29 MHz or 30 MHz, etc., but not limited to the listed values, other values not listed in this range are also required.

[0043] Specifically, the increasing rate of the pressure in the gradient ultrasonic pressing is 100-120 N / min, for example, it can be 100 N / min, 102 N / min, 104 N / min, 106 N / min, 108 N / min, 110 N / min, 112 N / min, 114 N / min, 116 N / min, 118 N / min or 120 N / min, etc., but not limited to the listed values, other unlisted values in the range are also required.

[0044] Specifically, the increasing rate of the ultrasonic power in the gradient ultrasonic pressing is 500-520 W / min, for example, it can be 500 W / min, 502 W / min, 504 W / min, 506 W / min, 508 W / min, 510 W / min, 512 W / min, 514 W / min, 516 W / min, 518 W / min or 520 W / min, etc., but not limited to the listed values, other unlisted values in the range are also required.

[0045] In the present application, the increasing rate of the pressure and the increasing rate of the ultrasonic power in the gradient ultrasonic pressing can be converted to N / s, W / s units to more accurately adjust the increasing rate, such as when approaching the end pressure and end power, due to the use of increasing in minutes, the increasing step is too large, at this time, the pressure and power can be increased to the corresponding end pressure and end power in the form of N / s, W / s, the increasing process is continuous increasing, rather than increasing and then waiting for a period of time, so as to ensure that the pressure end and the ultrasonic power end are reached at the same time.

[0046] Specifically, the end pressure of the gradient ultrasonic pressing is 500-600 N, for example, it can be 500 N, 510 N, 520 N, 530 N, 540 N, 550 N, 560 N, 570 N, 580 N, 590 N or 600 N, etc., but not limited to the listed values, other unlisted values in the range are also required.

[0047] Specifically, the end ultrasonic power of the gradient ultrasonic pressing is 2800-3000 W, for example, it can be 2800 W, 2820 W, 2840 W, 2860 W, 2880 W, 2900 W, 2920 W, 2940 W, 2960 W, 2980 W or 3000 W, etc., but not limited to the listed values, other unlisted values in the range are also required.

[0048] Specifically, the gradient ultrasonic pressing is maintained for 1-2 min after reaching the end-point pressure and end-point ultrasonic power, for example, it can be 1 min, 1.1 min, 1.2 min, 1.3 min, 1.4 min, 1.5 min, 1.6 min, 1.7 min, 1.8 min, 1.9 min or 2 min, etc., but not limited to the listed values, other values not listed in the range are also required.

[0049] Specifically, the absolute value of the difference between the thickness of the green compact obtained by the gradient ultrasonic pressing and the set thickness is ≤0.1 mm, for example, it can be 0.1 mm, 0.09 mm, 0.08 mm, 0.07 mm, 0.06 mm, 0.05 mm, 0.04 mm, 0.03 mm, 0.02 mm, 0.01 mm or 0.001 mm, etc., but not limited to the listed values, other values not listed in the range are also required.

[0050] Specifically, the pressure in the hot-pressing sintering is controlled to be 1500-1700 kN, for example, it can be 1500 kN, 1520 kN, 1540 kN, 1560 kN, 1580 kN, 1600 kN, 1620 kN, 1640 kN, 1660 kN, 1680 kN or 1700 kN, etc., but not limited to the listed values, other values not listed in the range are also required.

[0051] Specifically, the temperature in the hot-pressing sintering is controlled to be 1400-1500℃, for example, it can be 1400℃, 1410℃, 1420℃, 1430℃, 1440℃, 1450℃, 1460℃, 1470℃, 1480℃, 1490℃ or 1500℃, etc., but not limited to the listed values, other values not listed in the range are also required.

[0052] Specifically, the holding time of the hot-pressing sintering is 4-5 h, for example, it can be 4 h, 4.1 h, 4.2 h, 4.3 h, 4.4 h, 4.5 h, 4.6 h, 4.7 h, 4.8 h, 4.9 h or 5 h, etc., but not limited to the listed values, other values not listed in the range are also required.

[0053] Further, in order to illustrate the excellent effects that the target material prepared by the tungsten-silicon alloy target material preparation method provided by the present application can achieve, actual examples are used for illustration, which are as follows:

[0054] Example 1

[0055] The present application provides a tungsten-silicon alloy target material preparation method, which comprises:

[0056] The tungsten powder and the silicon powder are mixed and then pressed, and then hot-pressed and sintered to obtain a tungsten-silicon alloy target material.

[0057] The particle size of the tungsten powder is ≤10 μm, and the particle size of the silicon powder is ≤10 μm; the mass ratio of the tungsten powder and the silicon powder is 2.4:1;

[0058] The pressing comprises a first pressing and a gradient ultrasonic pressing performed in sequence; the pressure and the ultrasonic power are synchronously increased in the gradient ultrasonic pressing;

[0059] The pressure of the first pressing is 115 N; and the time of the first pressing is 1.2 min;

[0060] The initial pressure in the gradient ultrasonic pressing is 115 N, the initial ultrasonic power is 900 W, the frequency of the ultrasonic in the gradient ultrasonic pressing is 24 MHz; the increasing rate of the pressure in the gradient ultrasonic pressing is 115 N / min; the increasing rate of the ultrasonic power in the gradient ultrasonic pressing is 510 W / min; the terminal pressure of the gradient ultrasonic pressing is 550 N; the terminal ultrasonic power of the gradient ultrasonic pressing is 2829 W; the gradient ultrasonic pressing is maintained for 1.5 min after reaching the terminal pressure and the terminal ultrasonic power; and the absolute value of the difference between the thickness of the obtained compact and the set thickness is 0.1 mm;

[0061] The pressure control in the hot-pressing sintering is 1600 kN; the temperature control in the hot-pressing sintering is 1440℃; and the holding time of the hot-pressing sintering is 4.5 h.

[0062] The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0063] Embodiment 2

[0064] The application provides a preparation method of a tungsten-silicon alloy target material, which comprises the following steps:

[0065] The tungsten powder and the silicon powder are mixed and then pressed, and then hot-pressed and sintered to obtain a tungsten-silicon alloy target material;

[0066] The particle size of the tungsten powder is ≤5 μm, and the particle size of the silicon powder is ≤5 μm; the mass ratio of the tungsten powder and the silicon powder is 2.2:1;

[0067] The pressing comprises a first pressing and a gradient ultrasonic pressing performed in sequence; the pressure and the ultrasonic power are synchronously increased in the gradient ultrasonic pressing;

[0068] The pressure of the first pressing is 110 N; and the time of the first pressing is 1.4 min;

[0069] The initial pressure in the gradient ultrasonic pressing is 110N, the initial ultrasonic power is 870W, the frequency of the ultrasonic waves in the gradient ultrasonic pressing is 27MHz; the increasing rate of the pressure in the gradient ultrasonic pressing is 110N / min; the increasing rate of the ultrasonic power in the gradient ultrasonic pressing is 505W / min; the terminal pressure of the gradient ultrasonic pressing is 570N; the terminal ultrasonic power of the gradient ultrasonic pressing is 2982W; the gradient ultrasonic pressing is kept for 1.5min after reaching the terminal pressure and the terminal ultrasonic power; the absolute value of the difference between the thickness of the compact obtained by the gradient ultrasonic pressing and the set thickness is 0.05mm;

[0070] The pressure control in the hot-pressing sintering is 1650kN; the temperature control in the hot-pressing sintering is 1450℃; the holding time of the hot-pressing sintering is 4.5h.

[0071] The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0072] Example 3

[0073] The application provides a preparation method of a tungsten-silicon alloy target material, which comprises the following steps:

[0074] The tungsten powder and the silicon powder are mixed and then pressed, and then hot-pressing sintering is performed to obtain a tungsten-silicon alloy target material;

[0075] The particle size of the tungsten powder is 3-8μm, the particle size of the silicon powder is ≤5μm, and the mass ratio of the tungsten powder to the silicon powder is 2:1.

[0076] The pressing comprises a first pressing and a gradient ultrasonic pressing which are sequentially performed; the pressure and the ultrasonic power are synchronously increased in the gradient ultrasonic pressing;

[0077] The pressure of the first pressing is 100N; and the time of the first pressing is 1min.

[0078] The initial pressure in the gradient ultrasonic pressing is 100N, the initial ultrasonic power is 800W, the frequency of the ultrasonic waves in the gradient ultrasonic pressing is 30MHz; the increasing rate of the pressure in the gradient ultrasonic pressing is 100N / min; the increasing rate of the ultrasonic power in the gradient ultrasonic pressing is 520W / min; the terminal pressure of the gradient ultrasonic pressing is 500N; the terminal ultrasonic power of the gradient ultrasonic pressing is 2880W; the gradient ultrasonic pressing is kept for 2min after reaching the terminal pressure and the terminal ultrasonic power; the absolute value of the difference between the thickness of the compact obtained by the gradient ultrasonic pressing and the set thickness is 0.1mm.

[0079] The pressure control in the hot-pressing sintering is 1500kN; the temperature control in the hot-pressing sintering is 1500℃; the holding time of the hot-pressing sintering is 4h.

[0080] The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0081] Example 4

[0082] The application provides a preparation method of a tungsten-silicon alloy target material, and the preparation method comprises the following steps:

[0083] The tungsten powder and the silicon powder are mixed and then hot-pressed and sintered to obtain the tungsten-silicon alloy target material;

[0084] The particle size of the tungsten powder is ≤2 μm, and the particle size of the silicon powder is 1-10 μm; and the mass ratio of the tungsten powder to the silicon powder is 2.5:1;

[0085] The pressing comprises first pressing and gradient ultrasonic pressing which are sequentially performed; and the pressure and the ultrasonic power are synchronously increased in the gradient ultrasonic pressing;

[0086] The pressure of the first pressing is 120 N; and the time of the first pressing is 1.5 min;

[0087] The initial pressure in the gradient ultrasonic pressing is 120 N, the initial ultrasonic power is 1000 W, the frequency of the ultrasonic in the gradient ultrasonic pressing is 20 MHz; the increasing rate of the pressure in the gradient ultrasonic pressing is 120 N / min; the increasing rate of the ultrasonic power in the gradient ultrasonic pressing is 500 W / min; the terminal pressure of the gradient ultrasonic pressing is 600 N; the terminal ultrasonic power of the gradient ultrasonic pressing is 3000 W; the gradient ultrasonic pressing is maintained for 1 min after reaching the terminal pressure and the terminal ultrasonic power; and the absolute value of the difference between the thickness of the pressing block obtained by the gradient ultrasonic pressing and the set thickness is 0.01 mm;

[0088] The pressure control in the hot-pressing sintering is 1700 kN; the temperature control in the hot-pressing sintering is 1400 ℃; and the holding time of the hot-pressing sintering is 5 h.

[0089] The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0090] Example 5

[0091] The difference from Example 1 is that the increasing rate of the pressure in the gradient ultrasonic pressing is 50 N / min. The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0092] Example 6

[0093] The difference from Example 1 is that the increasing rate of the pressure in the gradient ultrasonic pressing is 150 N / min. The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0094] Example 7

[0095] The difference from Example 1 is only that the increasing rate of ultrasonic power in gradient ultrasonic pressing is 300 W / min. The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0096] Example 8

[0097] The difference from Example 1 is only that the increasing rate of ultrasonic power in gradient ultrasonic pressing is 600 W / min. The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0098] Example 9

[0099] The difference from Example 1 is only that the particle size of the tungsten powder is ≤20 μm and the particle size of the silicon powder is ≤20 μm. The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0100] Comparative Example 1

[0101] The difference from Example 1 is only that the ultrasonic in gradient ultrasonic pressing is omitted, i.e. only gradient pressing is used. The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0102] Comparative Example 2

[0103] The difference from Example 1 is only that the ultrasonic in gradient ultrasonic pressing is changed to constant ultrasonic power ultrasonic, and the ultrasonic power is the average of the initial ultrasonic power and the terminal ultrasonic power, which is 2350 W. The performance of the obtained tungsten-silicon alloy target material is shown in Table 1.

[0104] Comparative Example 3

[0105] The difference from Example 1 is only that the first pressing is not performed.

[0106] Table 1

[0107]

[0108]

[0109] In the present application, the relative density refers to the ratio of the test density of the tungsten-silicon alloy target material to the theoretical density.

[0110] From the results of the above examples and comparative examples, it can be seen that the preparation method provided in the present application significantly improves the use performance of the obtained tungsten-silicon alloy target material by means of a specific pressing process. The tungsten-silicon target material has a relative density of ≥99%, and the problem of powder dropping due to insufficient alloying of the tungsten-silicon alloy target material in use is avoided.

[0111] It is to be understood that the application is not limited to the details of the above-described embodiments but covers any modifications within the scope and the spirit of the application.

[0112] The preferred embodiments of the application have been described in detail above, but the application is not limited to the specific details described above. Any modifications to the application, equivalent substitutions for the components used in the application, and the addition of auxiliary components, the selection of specific methods, etc. all fall within the scope of protection and disclosure of the application.

[0113] In addition, it should be noted that each of the specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the application will not further describe various possible combinations.

[0114] Furthermore, any combination of the various embodiments of the application can also be made, as long as it does not deviate from the idea of the application, it should also be considered as disclosed by the application.

Claims

1. A method of producing a tungsten-silicon alloy target material, characterized by, The preparation method comprises: The tungsten powder and the silicon powder are mixed and then are pressed and sintered by hot pressing to obtain a tungsten-silicon alloy target; The particle size of the silicon powder is ≤10 μm; the pressing comprises first pressing and gradient ultrasonic pressing performed in sequence; the pressure and the ultrasonic power are increased synchronously in the gradient ultrasonic pressing; the increasing rate of the pressure in the gradient ultrasonic pressing is 100-120 N / min; the increasing rate of the ultrasonic power in the gradient ultrasonic pressing is 500-520 W / min; the pressure of the first pressing is 100-120 N, and the time is 1-1.5 min; the frequency of the ultrasonic in the gradient ultrasonic pressing is 20-30 MHz; the terminal pressure of the gradient ultrasonic pressing is 500-600 N; the terminal ultrasonic power of the gradient ultrasonic pressing is 2800-3000 W; and the gradient ultrasonic pressing is maintained for 1-2 min after reaching the terminal pressure and the terminal ultrasonic power.

2. The preparation method according to claim 1, characterized in that, The particle size of the tungsten powder is ≤10 μm.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the tungsten powder to the silicon powder is (2-2.5):

1.

4. The preparation method according to claim 1, characterized in that, The absolute value of the difference between the thickness of the compact obtained by the gradient ultrasonic pressing and the set thickness is ≤0.1 mm.

5. The method of claim 1, wherein the step of forming the first and second layers is performed by a method selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The pressure control in the hot pressing sintering is 1500-1700 kN.

6. The method of claim 1, wherein the step of forming the first and second layers is performed by a method selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The temperature control in the hot pressing sintering is 1400-1500 ℃.

7. The preparation method according to claim 1, characterized in that, The holding time of the hot pressing sintering is 4-5 h.

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