A low-temperature preparation method for oriented growth of a nickel-zinc ferrite film (222)

Abstract

The application provides a (222) orientation growth nickel-zinc ferrite film low-temperature preparation method, and belongs to the technical field of film preparation.The application is based on the principle of oxidation-reduction reaction, uses a rotary spraying device to uniformly attach an oxidizing solution and a reducing solution on a glass substrate in a certain proportion through an ultrasonic atomization system, forms a continuous and dense ferrite film after a series of chemical reactions, changes the concentration of ferrous chloride in the reducing solution, controls the deposition rate of different crystal surfaces, and then controls the growth orientation of the NiZn ferrite film.The NiZn ferrite film prepared through the above process low-temperature deposition can realize compatibility with a semiconductor process, the orientation gradually grows along the (222) preferred orientation from the (311) orientation of the NiZn ferrite, the microstructure gradually forms obvious triangular grains, so that the film growth is more uniform, and the film quality is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of thin film preparation technology, specifically relating to a (222) orientation-grown nickel-zinc ferrite thin film low-temperature preparation method. Background Technology

[0002] In today's rapidly developing integrated circuit industry, high frequency, miniaturization, and integration have become the main development trends of electronic devices. In particular, the integration and functional requirements of basic product devices for System-on-Chip (SoC), Microsystem-on-Chips (MS), and System-in-Package (SIP) are increasing. This necessitates continuous innovation and breakthroughs in design and manufacturing technologies to achieve higher integration and richer functionality. Inductors, as one of the three major passive linear components in electronic circuits, have important applications in consumer electronics, industrial equipment, radio frequency communication, and power transmission. They urgently need to be highly integrated through microelectronic manufacturing processes, integrating with other electronic components and functional modules into the same chip or package to achieve higher integration, simplified circuit layout, and reduced system size and complexity. While metallic magnetic thin films are compatible with semiconductor processes, their low resistivity limits the high-frequency integration of integrated devices. NiZn ferrite thin films, belonging to the spinel class, have advantages due to their high resistivity and low eddy current loss and skin effect at high frequencies, making them promising for applications in SoCs, MS, and SIPs. Therefore, the preparation of high-quality NiZn ferrite thin films is particularly important.

[0003] However, traditional methods for preparing NiZn ferrite thin films include physical and chemical methods. Common physical methods include sputtering and pulsed laser deposition, while common chemical methods include chemical vapor deposition and sol-gel methods. However, all of these methods require high-temperature (>600℃) annealing, making them difficult to integrate with semiconductor processes. M. Abe et al. (Abe, Masanori, and Yutaka Tamaura. "Ferrite-plating in aqueous solution: A new method for preparing magnetic thin film." Japanese journal of applied physics 22.8A (1983): L511.) first proposed a low-temperature deposition technique to prepare Fe2O3 and CoFe2O4 thin films on copper, PET, and stainless steel substrates. This method is applicable to substrates of various material types, but none of them involve oriented growth. N. Matsushita et al. (N. Matsushita, Chee Ping Chong, T. Mizutani and M. Abe, "High-rate low-temperature (90℃) deposition of Ni-Zn ferrite films highly permeable in gigahertz range," in IEEE Transactions on Magnetics, vol. 38, no. 5, pp. 3156-3158, Sept. 2002) achieved low-temperature fabrication of NiZn ferrite films on glass substrates using spin-spraying. They investigated the effect of pH values ​​in the range of 6.8–9.2 on preferred orientation, finding that the film sample exhibited the highest saturation magnetization M at pH 8.4. s 482emu / cm 3 and minimum coercivity H c- / / 17Oe exhibits a distinct preferred orientation at pH 6.8 and 8.7 (111), but this preferred orientation disappears at pH 9.2, although no (222) oriented growth is observed. O.Obi et al. (Obi O, Liu M, Lou J, et al. Spin-spray deposited NiZn-Ferrite films exhibiting μ r >50at GHz range[J].Journal of Applied Physics,2011,109(7).) A 0.7μm thick Ni was prepared on a 0.1mm thick glass substrate by spin spraying under an external magnetic field of 360Oe.0.27 Zn 0.1 Fe 2.63 O4 thin film, saturation magnetization M s 358 emu / cm 3 In-plane coercivity H c- / / The permeability is 11Oe, which is more than three times higher than that of films grown without magnetic field induction, but there is no obvious orientation growth. Wang X et al. (Wang X, Zhou Z, Behugn S, et al. Growth behavior and RF / microwave properties of low temperature spin-sprayed NiZn ferrite[J]. Journal of Materials Science: Materials in Electronics, 2015, 26: 1890-1894.) prepared 0.7 μm NiZn ferrite on a 0.2 mm thick glass substrate by spin coating. 0.27 Zn 0.1 Fe 2.63 O4 thin films were used to control the grain size of NiZn thin films by adjusting the pH values ​​of the oxidizing and reducing solutions, thereby regulating their magnetic properties. The study found that the film had the smallest grain size of 70 nm and the largest magnetic permeability when the pH value of the oxidizing solution was 9.6 and the pH value of the reducing solution was 4.6. Its initial magnetic permeability was greater than 200 at 0.5 GHz, but the XRD pattern showed no preferred orientation.

[0004] Currently, research on the preparation of NiZn ferrite thin films using spin-spraying mainly focuses on the static magnetic properties (coercivity H) of the materials. c Saturation magnetization M s While the ferrous chloride concentration in the solution is adjusted to control the grain morphology, the (222) orientation growth of NiZn ferrite films is significantly improved, resulting in a marked improvement in film growth quality. This invention provides a method for controlling the (222) orientation growth of NiZn ferrite films by regulating the (ferrous chloride) concentration in the solution, thereby significantly improving the film growth quality. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the background technology by proposing a low-temperature preparation method for (222) oriented growth of nickel-zinc ferrite thin films. This invention regulates the (222) orientation of the NiZn ferrite thin film by controlling the molar concentration of ferrous chloride in the reducing solution. The resulting film exhibits significant (222) oriented growth, a triangular morphology, and high magnetic properties including high saturation magnetization (4πMs > 3000 Gs), low coercivity (Hc < 11Oe), and high cutoff frequency (f). r >300MHz.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for low-temperature preparation of (222) oriented nickel-zinc ferrite thin films includes the following steps:

[0008] Step 1: Cleaning the reaction table:

[0009] After polishing the reaction platform with 2000-grit sandpaper until the surface is smooth, clean it with anhydrous ethanol / acetone solution and let it air dry naturally.

[0010] Step 2, Prepare the solution:

[0011] 2.1 Using soluble nitrite as an oxidant and acetate as a reaction buffer, deionized water was added and mixed thoroughly to obtain an oxidant solution, wherein the molar concentration of acetate was 20-30 mmol / L and the molar concentration of nitrite was 2-4 mmol / L.

[0012] 2.2 Using ferrous chloride, zinc chloride, and nickel chloride as reducing agents, deionized water was added and mixed evenly to obtain a reducing agent solution, wherein the molar concentration of ferrous chloride was 9–12 mmol / L, the molar concentration of zinc chloride was 0.5–2 mmol / L, and the molar concentration of nickel chloride was 1–2 mmol / L.

[0013] Step 3, Thin Film Preparation:

[0014] The glass substrate is placed in the center of the reaction stage after cleaning in step 1. Under the conditions of substrate temperature of 85-95℃, oxidant solution supply rate of 15-20mL / min, reducing agent solution supply rate of 15-20mL / min, atomization power of 0.1-0.5W, working gas pressure of 0.02-0.05MPa, and reaction stage rotation speed of 120-140r / min, a thin film is deposited by spin spraying. The deposition time is 20-40min. After deposition, a NiZn ferrite film with a thickness of 1-2μm can be formed on the glass substrate.

[0015] Furthermore, in step 3, after heating the cleaned reaction platform to 50-60°C, the glass substrate is placed in the center of the reaction platform, and the principle of thermal expansion and contraction is used to make the substrate adhere more closely.

[0016] This invention provides a low-temperature preparation method for (222) oriented growth of nickel-zinc ferrite thin films. The core idea is based on the principle of redox reaction. Using a rotary spraying device, an oxidizing solution and a reducing solution are uniformly attached to a glass substrate in a certain proportion via an ultrasonic atomization system. After a series of chemical reactions, a continuous and dense ferrite thin film is formed. By changing the concentration of ferrous chloride in the reducing solution, the deposition rate of different crystal planes is controlled, thereby regulating the growth orientation of the NiZn ferrite thin film. The NiZn ferrite thin film prepared by the above low-temperature deposition process is compatible with semiconductor processes. Simultaneously, the orientation gradually changes from the (311) orientation of the NiZn ferrite to the (222) preferred orientation, and the microstructure gradually forms obvious triangular grains, resulting in more uniform film growth and significantly improved film quality.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. The rotary spraying method provided by the present invention can prepare NiZn ferrite thin films in an air environment. The process is simple, the operation is controllable, and it can be applied to a variety of substrates.

[0019] 2. The present invention provides a low-temperature preparation method for (222) oriented growth of nickel-zinc ferrite thin films. By changing the Fe content in the main formula, the microstructure is optimized and the film quality is improved, resulting in triangular grains with (222) crystal orientation.

[0020] 3. The present invention provides a (222) orientation-grown nickel-zinc ferrite thin film low-temperature preparation method, the reaction can be carried out at a temperature of <100℃ and no high-temperature annealing treatment is required, which can achieve compatibility with modern semiconductor processes. Attached Figure Description

[0021] Figure 1 The XRD patterns of the NiZn ferrite films obtained in comparative examples and Examples 1-4 are shown.

[0022] Figure 2 Scanning electron microscope (SEM) images of the NiZn ferrite films obtained in comparative examples and Examples 1-4;

[0023] Figure 3 Hysteresis loop diagrams of the NiZn ferrite thin films obtained in comparative examples and Examples 1-4;

[0024] Figure 4 The magnetic spectrum curves of the NiZn ferrite films obtained in the comparative example and Example 4 are shown. Detailed Implementation

[0025] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0026] Example 1

[0027] A method for low-temperature preparation of (222) oriented nickel-zinc ferrite thin films, specifically including the following steps:

[0028] Step 1: Cleaning the reaction table:

[0029] After polishing the reaction platform with 2000-grit sandpaper until the surface is smooth, clean it with anhydrous ethanol / acetone solution and let it air dry naturally.

[0030] Step 2, Prepare the solution:

[0031] 2.1 Using sodium nitrite as an oxidant and sodium acetate as a reaction buffer, deionized water was added and mixed thoroughly to obtain an oxidant solution, wherein the molar concentration of sodium acetate was 26 mmol / L and the molar concentration of sodium nitrite was 2 mmol / L.

[0032] 2.2 Using ferrous chloride, zinc chloride, and nickel chloride as reducing agents, deionized water was added and mixed thoroughly to obtain a reducing agent solution, wherein the molar concentration of ferrous chloride was 9 mmol / L, the molar concentration of zinc chloride was 0.9 mmol / L, and the molar concentration of nickel chloride was 1.7 mmol / L.

[0033] Step 3, Preheating the substrate:

[0034] Place the glass substrate in the center of the reaction platform after cleaning in step 1, set the parameters of the spin coating equipment, the vacuum pump pressure is 0.03MPa, and the substrate is adsorbed; set the reaction platform temperature to 95℃, the rotation speed to 130r / min, start connecting deionized water to nozzles 1 and 2 and set the flow rate to 17mL / min, the ultrasonic atomization power to 0.3W, and the preheating time to 20min.

[0035] Step 4, Thin film preparation:

[0036] The experimental solution of the spin coating equipment was changed. The nozzle 1 was connected to the oxidant solution prepared in step 2.1, the flow rate was set to 17 mL / min, the ultrasonic atomization power was 0.3 W, the nozzle 2 was connected to the reducing agent solution prepared in step 2.2, the flow rate was set to 17 mL / min, the ultrasonic atomization power was 0.3 W, and the reaction time was 20 min. After the reaction was completed, it was allowed to cool to room temperature. After the substrate was removed, a NiZn ferrite film grown along the (222) orientation was obtained.

[0037] The NiZn ferrite thin film obtained in step 4 was characterized by the following tests: the orientation of the film along the (222) crystal direction was characterized by X-ray diffraction (XRD); the magnetic properties of the sample were tested by vibrating sample magnetometer (VSM); the microstructure of the sample was characterized by scanning electron microscopy (SEM); and the magnetic spectrum of the sample was tested by vector network analyzer (VNA).

[0038] Example 2

[0039] The difference between this embodiment and Example 1 is that in step 2.2, the molar concentration of ferrous chloride is adjusted to 10 mmol / L; the remaining steps are exactly the same as in Example 1.

[0040] Example 3

[0041] The difference between this embodiment and Example 1 is that in step 2.2, the molar concentration of ferrous chloride is adjusted to 11 mmol / L; the remaining steps are exactly the same as in Example 1.

[0042] Example 4

[0043] The difference between this embodiment and Example 1 is that in step 2.2, the molar concentration of ferrous chloride is adjusted to 12 mmol / L; the remaining steps are exactly the same as in Example 1.

[0044] Comparative Example

[0045] Compared with Example 1, the comparative example differs in that the molar concentration of ferrous chloride in step 2.2 is adjusted to 8 mmol / L; the remaining steps are exactly the same as in Example 1.

[0046] The test results for comparative examples and Examples 1-4 are shown in the table below:

[0047]

[0048] Figure 1 The XRD patterns of the NiZn ferrite films obtained in the comparative examples and Examples 1-4 are shown in the figure. As can be seen from the figure, the (222) orientation of Examples 1-4 is more obvious than that of the comparative examples. That is, the (222) orientation of the NiZn ferrite film can be enhanced by increasing the molar concentration of ferrous chloride in the reducing solution. Figure 2 The images show scanning electron microscope (SEM) images of the NiZn ferrite films obtained in the comparative examples and Examples 1-4. As can be seen from the images, the grain boundaries of the ferrite samples in Examples 1-4 are clearer than those in the comparative examples. In particular, Example 4 shows clear triangular grains, which directly demonstrates that the orientation of the NiZn ferrite film (222) can be effectively controlled by changing the molar concentration of ferrous chloride in the reducing solution. Figure 3 The figures show the hysteresis loops of the NiZn ferrite films obtained in the comparative examples and Examples 1-4. As can be seen from the figures, the saturation magnetization of Examples 1-4 is higher than that of the comparative examples. Figure 4 The magnetic spectrum curves of the NiZn ferrite films obtained in the comparative example and Example 4 are shown in the figure. As can be seen from the figure, although the magnetic permeability decreased, the cutoff frequency increased.

Claims

1. A method for low-temperature preparation of (222) oriented nickel-zinc ferrite thin films, characterized in that, Includes the following steps: Step 1: Cleaning the reaction table: After sanding the reaction platform until the surface is smooth, clean it with anhydrous ethanol and acetone, and let it air dry naturally. Step 2, Prepare the solution: 2.1 Add the buffer acetate and the oxidant soluble nitrite to deionized water, mix well to obtain the oxidant solution, wherein the molar concentration of acetate is 20~30 mmol / L and the molar concentration of nitrite is 2~4 mmol / L; 2.2 Ferrous chloride, zinc chloride, and nickel chloride were added to deionized water and mixed thoroughly to obtain a reducing agent solution, wherein the molar concentration of ferrous chloride was 9-12 mmol / L, the molar concentration of zinc chloride was 0.5-2 mmol / L, and the molar concentration of nickel chloride was 1-2 mmol / L. Step 3, Thin Film Preparation: The glass substrate is placed in the center of the reaction stage after cleaning in step 1. Under the conditions of substrate temperature of 85~95℃, oxidant solution supply rate of 15~20mL / min, reducing agent solution supply rate of 15~20mL / min, atomization power of 0.1~0.5W, working gas pressure of 0.02~0.05MPa, and reaction stage rotation speed of 120~140r / min, a thin film is deposited by spin spraying. The deposition time is 20~40min. After deposition, the NiZn ferrite thin film is obtained. By changing the concentration of ferrous chloride in the reducing solution, the deposition rate of different crystal planes can be controlled, thereby regulating the growth orientation of NiZn ferrite films.

2. The method for low-temperature preparation of (222) oriented growth nickel-zinc ferrite thin films according to claim 1, characterized in that, In step 3, after heating the cleaned reaction platform to 50~60℃, the glass substrate is placed in the center of the reaction platform.

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