A method for preparing a pre-nitrided soft magnetic high-entropy alloy target material, the target material and application

Abstract

The application belongs to the field of soft magnetic high-entropy alloy material and magnetron sputtering technology, and particularly relates to a pre-nitriding soft magnetic high-entropy alloy target material preparation method, a target material and application, which comprises the following steps: proportioning alloy materials according to the component content of the soft magnetic high-entropy alloy, completing smelting and processing into a target material, and adopting a gas nitriding process to perform nitriding treatment on the target material; polishing the surface of the target material after the nitriding treatment to obtain a pre-nitriding soft magnetic high-entropy alloy target material for magnetron sputtering; and based on the pre-nitriding soft magnetic high-entropy alloy target material, using a magnetron sputtering process to perform sputtering plating on the surface of a substrate to form a soft magnetic high-entropy alloy nitride film; the application avoids the poisoning of the target caused by the traditional sputtering of nitrogen gas and the non-uniformity in the micro area of the sputtered film on the substrate caused by the different distribution of nitrogen gas, reduces the pollution of the internal cavity of the sputtering equipment, and improves the film forming quality of the film and the soft magnetic performance of the film.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of soft magnetic high-entropy alloy materials and magnetron sputtering technology, and particularly relates to a preparation method of a pre-nitrided soft magnetic high-entropy alloy target material, a target material and application. BACKGROUND

[0002] With the development of device miniaturization and lightness, magnetron sputtering thin film technology is widely used. Magnetron sputtering has the characteristics of high film forming efficiency, good film forming consistency and high density, and is widely used. The magnetic thin film prepared by magnetron sputtering is applied to various electric and magnetic devices. Soft magnetic high-entropy alloy thin film (HEATFs) shows better resistivity, thermal stability, corrosion resistance and strong mechanical properties than other soft magnetic thin films, and is a very promising material. However, its resistivity is still low, and large eddy current loss is easily generated in high-frequency application, resulting in failure of the thin film. Studies have shown that the introduction of N element in the sputtering process can effectively reduce the coercivity while improving the resistivity and maintaining the ideal magnetic properties.

[0003] The traditional method of introducing N element is to introduce nitrogen gas in the sputtering process to incorporate N element, and to form a N-doped thin film on the substrate. However, this magnetron sputtering technology has defects. First, the surface lattice defects of the target material have high chemical activity, and in a high nitrogen atmosphere, the metal elements in the soft magnetic target material may form metal nitrides with nitrogen molecules, causing poisoning of the target material, reducing the magnetron sputtering efficiency of the target material, and resulting in uneven quality of the thin film formed on the substrate in the time axis. Secondly, the element ratio in the micro area may fluctuate due to the disturbance and uneven distribution of nitrogen in the gas flow. In addition, long-term high nitrogen atmosphere sputtering may contaminate the target chamber, affecting the use of the equipment in subsequent sputtering of other materials. CN109402590B discloses a method for preparing a high-entropy alloy coating by magnetron sputtering, which first ball-mills Cr, Mn, Fe, Ni-B, Al-Si in a certain proportion to alloy, and then sintered into a high-entropy alloy target. Then, a high-entropy alloy coating is prepared on the surface of a steel substrate by magnetron sputtering, and finally, nitriding is performed in a nitriding furnace. CN103805996B discloses a composite treatment method for metal material surface by coating and nitriding, which first deposits a nitride thin film on the surface of a metal material substrate by magnetron sputtering or arc ion plating, and the thin film has a thickness of 0.1-50 microns. Then, ion nitriding technology is used to treat the coated surface. However, the above method is not applicable to the preparation of soft magnetic high-entropy alloy thin film. Therefore, how to more reasonably introduce N element is crucial to reduce the impact of traditional nitrogen introduction on the target material, thin film quality and equipment chamber. SUMMARY

[0004] The application aims to overcome the shortcomings of the prior art, and provides a method for preparing a pre-nitrided soft magnetic high-entropy alloy target, the target and application. The high-entropy alloy target prepared by pre-nitriding can maintain the excellent performance characteristics of the soft magnetic nitride film during sputtering of the film, and can reduce the influence of traditional nitrogen treatment on the quality of the alloy target and the film and the pollution of the equipment chamber.

[0005] The complete technical solution of the application comprises:

[0006] A method for preparing a pre-nitrided soft magnetic high-entropy alloy target comprises the following steps:

[0007] (1) Preparation of a soft magnetic high-entropy alloy target: alloy materials are proportioned according to the component content of the soft magnetic high-entropy alloy, and a soft magnetic high-entropy alloy target is obtained by smelting; the components of the soft magnetic high-entropy alloy include Fe, Co, Ni, and Zr and / or B elements;

[0008] (2) Nitriding treatment of the target: a gas nitriding process is used to perform nitriding treatment on the soft magnetic high-entropy alloy target;

[0009] (3) Surface treatment and processing of the target: surface treatment is performed on the surface of the target after the nitriding treatment, and a pre-nitrided soft magnetic high-entropy alloy target for magnetron sputtering is obtained.

[0010] The surface treatment is polishing.

[0011] Further, the target is subjected to homogenization heat treatment before the nitriding treatment.

[0012] Further, the smelting in step (1) is vacuum induction smelting, and the purity of the metal blocks used for smelting is not less than 99.99%.

[0013] Further, the component content of the soft magnetic high-entropy alloy in step (1) is determined by a high-throughput screening component design method.

[0014] Further, in step (2), the nitriding gas in the gas nitriding process is ammonia.

[0015] Further, in step (2), the nitriding treatment temperature is 450℃-550℃, and the nitriding time is 10h-15h.

[0016] Further, in step (2), the nitriding treatment adopts two-stage nitriding.

[0017] Further, the two-stage nitriding includes a strong nitriding stage and a diffusion stage; in the strong nitriding stage, the treatment time accounts for 15-25% of the total nitriding time, and the ammonia decomposition rate is 15%-30%; in the diffusion stage, the ammonia decomposition rate is 50%-70%.

[0018] Further, a pre-nitrided soft magnetic high-entropy alloy target prepared by the method.

[0019] Further, the application of the soft magnetic high-entropy alloy target material, based on the pre-nitriding soft magnetic high-entropy alloy target material, uses the magnetron sputtering process to sputter and coat the surface of the substrate, forming a soft magnetic high-entropy alloy nitride film.

[0020] Further, the soft magnetic high-entropy alloy nitride film obtained by the application.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] (1) The pre-nitriding treatment of the target material avoids the poisoning of the target and the non-uniformity of the micro-area of the sputtered film on the substrate caused by the different distribution of nitrogen gas in the traditional sputtering process. The nitrogen element is introduced during the heat treatment process, which is simple to operate and does not require additional processes.

[0023] (2) Nitrogen element incorporation controllability: During the nitriding process, the nitrogen potential can be controlled by controlling the ammonia gas, and the nitrogen atom concentration of the nitriding layer can be controlled. This method can realize the regulation of the film performance by adjusting the target material. At the same time, high-temperature nitriding can greatly promote the penetration of nitrogen elements.

[0024] (3) Reduce the internal stress of the target material and improve the uniformity of the target material: control the heat treatment conditions during the heat treatment process of the target material, increase the atomic movement in the target material, promote the uniformity of the target material, release the internal stress, and improve the film forming quality.

[0025] (4) Reduce the pollution of the internal chamber of the sputtering equipment, suitable for commercial production: In industrial production, the magnetron sputtering coating machine is a general machine, and most common coating machines often replace the target material. The conventional method of introducing a large amount of nitrogen gas into the magnetron sputtering coating machine may cause nitrogen pollution in the internal chamber of the coating machine, which may affect the quality of other coating and affect the commercial industrial production. DETAILED DESCRIPTION

[0026] The application will be described in detail below in conjunction with the embodiments, but it should be understood that the embodiments are only used to exemplarily describe the application, and cannot constitute any limitation on the protection scope of the application. All reasonable modifications and combinations within the scope of the inventive concept of the application fall within the protection scope of the application.

[0027] The application discloses a method for pre-nitriding a soft magnetic high-entropy alloy target to improve the soft magnetic performance of a thin film, and the method comprises the following steps: performing nitriding treatment on the soft magnetic high-entropy alloy target to form a nitriding layer with a certain thickness on the surface of the target; and when performing magnetron sputtering on the thin film, metal atoms and nitrogen atoms on the surface of the target are knocked out to form a uniform soft magnetic high-entropy alloy nitride film layer on the substrate of the thin film. The method is characterized in that the nitriding treatment and the heat treatment are performed on the target, which not only improves the uniformity of the distribution of the nitrogen element during sputtering, but also promotes the homogenization of the target, reduces the internal stress of the target, and improves the film forming quality of the thin film and the soft magnetic performance of the thin film.

[0028] The application adopts the following technical solutions:

[0029] (1) High-entropy alloy target preparation: according to the determined high-entropy alloy component content, the alloy materials are proportioned, smelted and processed into a target.

[0030] The high-entropy alloy components are determined by optimizing the high-throughput screening component design method, and the high-throughput screening method is further described to illustrate the alloy component optimization process of the application.

[0031] (1.1) Multi-component gradient thin film sputtering: by using a magnetron sputtering process, the components of the high-entropy alloy target are deposited on the surface of each substrate by controlling the chamber atmosphere conditions, thereby obtaining a plurality of thin film samples with different component contents.

[0032] Firstly, the content of each component element determined by the application is in the preset range of:

[0033] 1) Zr: 10.5~14.2 at%, Fe: 21.7~50.5 at%, Co: 16.4~53.4 at%, Ni: 12.3~22.1 at%; or

[0034] 2) B: 7.5~12.1 at%, Fe: 20.3~54.5 at%, Co: 13.5~58.5 at%, Ni: 11.2~22.5 at%; or

[0035] 3) B: 4.6~8.8 at%, Zr: 2.7~6.5 at%, Fe: 20.3~54.5 at%, Co: 13.5~58.5 at%, Ni: 11.2~22.5 at%.

[0036] In the process, in order to make the composition content of the thin film sample in the preset range, and the content of each component in each sample is as uniform as possible, which is beneficial to subsequent high-throughput screening. Due to the different atomic binding forces of each target material in the sputtering process, the atomic detachment speed of each target material is different, the present application analyzes the space distribution rule of the atomic detachment of each target material (the concentration of target element atoms in space gradually decreases with the increase of the distance from the target material), analyzes the main influencing factors (the total number of samples, the horizontal and vertical spacing of each sample), and selects the following experimental method:

[0037] High-purity Fe, high-purity Co, high-purity Ni, and high-purity M target materials are used, and are uniformly placed in four positions of the chamber, wherein the M target material is a Zr target material, or a B target material, or a mixed target material of Zr and B. The angles of the four target positions are adjusted to be 45° with the horizontal angle, the sample holder is placed in the middle of the four target materials, and a plurality of high-resistivity non-magnetic material substrates are placed on the sample holder.

[0038] First, a fixed sputtering time t0 and the same sample at a fixed distance d0 from the target material are selected, and the deposition thickness of each target element on the sample surface under different powers is measured to represent the detachment speed under different powers. Subsequently, taking Fe component as a reference, the reference sputtering power (250W) of Fe target material and the detachment speed of Fe under the power are determined, and then the corresponding power is selected for other components, so that the detachment speed under the corresponding sputtering power meets:

[0039]

[0040] In the formula: is the component the detachment speed under the selected corresponding power, is the detachment speed of Fe component under the reference sputtering power, is the component the minimum atomic percentage content in the preset range, is the component the maximum atomic percentage content in the preset range, is the minimum atomic percentage content of Fe in the preset range, is the maximum atomic percentage content of Fe in the preset range.

[0041] When M is a Zr target material or a B target material, the maximum and minimum atomic percentage content of the M component are the maximum and minimum atomic percentage content of Zr and B elements respectively. When M is a Zr / B mixed target material, the maximum atomic percentage content of the M component is the sum of the maximum atomic percentage content of Zr and B elements, and the minimum atomic percentage content of the M component is the sum of the minimum atomic percentage content of Zr and B elements.

[0042] Subsequently, the placement parameters (horizontal spacing, vertical spacing and number) of the samples are determined. The Fe target and the M target are selected, and the deposition rate (deposition thickness on the substrate surface per deposition time) of the sample closest to the Fe target and the deposition rate of the sample farthest from the Fe target are measured under different sample spacing (horizontal spacing, vertical spacing) and sample number conditions, and the degree of attenuation is counted. The relationship between the degree of attenuation and the sample horizontal spacing, vertical spacing and sample number is obtained by multiple linear regression, wherein when M is a Zr target and a B target, the deposition rates of Zr and B elements are counted and analyzed correspondingly, and when M is a Zr / B mixed target, the total deposition rate of the two elements is counted and analyzed.

[0043] According to the obtained relationship, the corresponding sample spacing and number are selected to satisfy:

[0044]

[0045]

[0046] wherein, is the maximum value of the atomic percentage content ratio of the Fe component to the M component in the preset range, is the maximum value of the atomic percentage content ratio of the M component to the Fe component in the preset range in the high-flux test. Similarly, when M is a Zr target and a B target, the maximum and minimum atomic percentage contents of the M component are the maximum and minimum atomic percentage contents of Zr and B elements, and when M is a Zr / B mixed target, the maximum atomic percentage content of the M component is the sum of the maximum atomic percentage contents of Zr and B elements, and the minimum atomic percentage content of the M component is the sum of the minimum atomic percentage contents of Zr and B elements. is the deposition rate of Fe atoms on the sample closest to the Fe target, is the deposition rate of Fe atoms on the sample farthest from the Fe target; is the deposition rate of M atoms on the sample closest to the M target, is the deposition rate of M atoms on the sample farthest from the M target.

[0047] The finally selected parameters are: horizontal spacing 2.5 cm, vertical spacing 1.3 cm, and number 60.

[0048] (1.2) Sample testing and target component design: The obtained multiple thin film samples are tested, and the high-entropy alloy component content is screened according to the performance requirements of saturation magnetization, coercive force and resistivity, and the specific content of each component element of the high-entropy alloy target is determined accordingly.

[0049] (2) Nitriding treatment of high-entropy alloy target: The target is subjected to nitriding treatment by using a gas nitriding process.

[0050] (3) High-entropy target alloy surface treatment and processing: polishing the surface of the nitrided target and preparing the target for magnetron sputtering.

[0051] (4) High-entropy nitrided target sputtering film: using a magnetron sputtering process to sputter a film on the surface of the substrate to form a soft magnetic high-entropy alloy nitride film.

[0052] Further, the target preparation method in step (1) is vacuum induction melting, and preferably, the purity of all metal blocks used for melting is not less than 99.99%.

[0053] Further, in step (2), the target obtained in step (1) is placed in a nitriding furnace for nitriding treatment. In the gas nitriding process, the nitriding gas is ammonia, and by controlling the nitrogen potential in the strong nitriding stage and the diffusion stage, a thicker nitriding layer is obtained.

[0054] In the strong nitriding stage, a low ammonia decomposition rate is used to obtain a high concentration of the nitriding layer, and in the diffusion stage, a high ammonia decomposition rate is used to allow the nitrogen atoms to diffuse deeper.

[0055] Preferably, the nitriding treatment temperature is 450°C to 550°C, and the nitriding time is 10h to 15h.

[0056] Preferably, in the strong nitriding stage, the treatment time accounts for 15 to 25% of the total nitriding time, and the ammonia decomposition rate is 15% to 30%; in the diffusion stage, the ammonia decomposition rate is 50% to 70%.

[0057] Optionally, after the target preparation is completed, the target is first cut and processed and subjected to homogenization heat treatment before nitriding treatment. In terms of target cutting processing size and heat treatment process, a response surface model is constructed for experimental design, and the optimized parameter combination is obtained according to the experimental results. The controllable variables selected include: target cutting thickness X1, with a value range of 10 to 20mm; target cutting diameter X2, with a value range of 100 to 150mm; heat treatment times X3, with a value range of 1 to 3 times; heat treatment temperature X4, with a value range of 700 to 1000°C; heat treatment time X5, with a value range of 1 to 15 hours.

[0058] The component content deviation degree Y is selected as a response variable. Factor level coding is performed, actual experimental parameters are constructed according to the coding values of each experiment in the design, designs not meeting the actual requirements are removed, central composite experimental design is performed, multiple experiments are performed, and the component content deviation degree Y of each experiment is measured and calculated. A second-order polynomial regression model based on the component content deviation degree and the controllable variables is established, the least square method is used to fit the coefficient estimates of the regression model, the predicted component content deviation degree Y obtained by the regression model is taken as the objective function, and the target is to minimize Y. Set the initial solution and perform iterative optimization, and when the set maximum number of iterations is reached, the current solution at this time is the optimized parameter combination. Specifically, the target material cutting diameter is 142 mm, the cutting thickness is 16 mm, a two-stage heat treatment process is adopted, wherein the first-stage heat treatment temperature is 820 DEG C, and the heat treatment holding time is 10 h; the second-stage heat treatment temperature is 980 DEG C, and the heat treatment holding time is 1.5 h.

[0059] The inert gas plus two-stage homogenization heat treatment method is adopted, the first-stage heat treatment temperature is lower than the second-stage heat treatment temperature, and the heat treatment time is longer, which can ensure good homogenization effect while avoiding local overburning and abnormal grain growth caused by high temperature and long holding time.

[0060] Preferably, in the step (3), the thickness of the nitriding layer of the polished target material is greater than 40 microns, so as to ensure that the target material can complete a complete sputtering;

[0061] Preferably, in the step (4), the sputtering temperature is room temperature, the working gas is Ar gas, the working gas is 99.99% argon, the vacuum degree is 3.0~4.0×10-4Pa, the sputtering time is 30~45 min, and the high-entropy alloy target material adopts direct current sputtering, and the sputtering power is 300 W.

[0062] Other embodiments of the present disclosure will be readily apparent to those skilled in the art upon considering the disclosure presented herein, together with the annexed drawings and descriptions. The present application is intended to cover any variations, uses, or adaptations of the present disclosure that follow, in general, the principles of the present disclosure and include those commonly known or customary within the art to which the present disclosure pertains. The specification and drawings are, accordingly, to be regarded as illustrative only, and the true scope and spirit of the present disclosure are indicated by the claims.

Claims

1. A method for preparing a pre-nitrided soft magnetic high-entropy alloy target material, characterized in that, It comprises the following steps: (1) The alloy material is proportioned according to the component content of the soft magnetic high-entropy alloy, and the soft magnetic high-entropy alloy target material is obtained by smelting; the components of the soft magnetic high-entropy alloy include Fe, Co, Ni, and Zr and / or B elements; the content of each component element is in the preset range of: 1) Zr: 10.5-14.2 at%, Fe: 21.7-50.5 at%, Co: 16.4-53.4 at%, Ni: 12.3-22.1 at%; or 2) B: 7.5-12.1 at%, Fe: 20.3-54.5 at%, Co: 13.5-58.5 at%, Ni: 11.2-22.5 at%; or 3) B: 4.6-8.8 at%, Zr: 2.7-6.5 at%, Fe: 20.3-54.5 at%, Co: 13.5-58.5 at%, Ni: 11.2-22.5 at%; (2) The soft magnetic high-entropy alloy target material is treated by gas nitriding process; (3) The surface of the soft magnetic high-entropy alloy target material is treated to obtain a soft magnetic high-entropy alloy target material for magnetron sputtering with pre-nitriding.

2. The method of claim 1, wherein the pre-nitrided soft magnetic high-entropy alloy target is prepared by a process comprising: The smelting method in step (1) is vacuum induction smelting, and the purity of the metal block used for smelting is not less than 99.99%. ​ 3. The method for preparing a pre-nitrided soft magnetic high-entropy alloy target according to claim 2, characterized in that, The component content of the soft magnetic high-entropy alloy in step (1) is determined by a high-throughput screening component design method.

4. The method of claim 3, wherein the pre-nitrided soft magnetic high-entropy alloy target is prepared by a process comprising: providing a soft magnetic high-entropy alloy target; and exposing the soft magnetic high-entropy alloy target to a nitrogen-containing plasma. In step (2), the nitriding gas in the gas nitriding process is ammonia.

5. The method of claim 4, wherein the pre-nitrided soft magnetic high-entropy alloy target is prepared by a process comprising: In step (2), the nitriding treatment temperature is 450-550°C, and the nitriding time is 10-15h. ​ 6. The method of claim 5, wherein the pre-nitrided soft magnetic high-entropy alloy target is prepared by a process comprising: In step (2), the nitriding treatment adopts two-stage nitriding. ​ 7. The method of claim 6, wherein the pre-nitrided soft magnetic high-entropy alloy target is prepared by a process comprising: providing a soft magnetic high-entropy alloy target; and exposing the soft magnetic high-entropy alloy target to a nitrogen-containing plasma. The two-stage nitriding includes a strong nitriding stage and a diffusion stage; in the strong nitriding stage, the treatment time accounts for 15-25% of the total nitriding time, and the ammonia decomposition rate is 15-30%; in the diffusion stage, the ammonia decomposition rate is 50-70%.

8. A soft magnetic high-entropy alloy target material with pre-nitriding prepared by the method of claim 7.

9. Use of the soft magnetic high-entropy alloy target according to claim 8, characterized in that Based on the soft magnetic high-entropy alloy target material with pre-nitriding, a soft magnetic high-entropy alloy nitride film is formed on the surface of the substrate by using a magnetron sputtering process.

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