High-resonance frequency high-permeability soft magnetic thin film and method of manufacturing

Abstract

High-resonance frequency high magnetic permeability soft magnetic thin film and preparation method, relate to the technical field of thin film preparation.The thin film of the present application comprises a substrate and a soft magnetic pattern layer arranged on the surface of the substrate, characterized in that the soft magnetic pattern layer comprises a first rhombic cell array and a second rhombic cell array, the first rhombic cell array and the second rhombic cell array are arranged in columns to form interlaced complement, the first rhombic cell array and the second rhombic cell array are both composed of a predetermined number of rhombic cells arranged orthogonally, in the same column of rhombic cells, the long diagonal lines of any two adjacent rhombic cells are connected; all the rhombic cells are of the same shape and size.The present application has the advantages of high application frequency and high magnetic permeability.

Description

Technical Field

[0001] This invention relates to the field of thin film preparation technology, and more specifically to a method for preparing thin films that combine high resonant frequency and high magnetic permeability, particularly for application in GHz-level inductors. Background Technology

[0002] With the widespread adoption of 5G technology and the Internet of Things (IoT), electronic products are increasingly feature-rich and performantly. System-on-a-Chip (SoC) has become a hot topic in the industry, characterized by integrating more and more functions into increasingly smaller sizes. Secondly, passive devices, such as inductors, are widely used in many systems (e.g., filters, amplifiers, electromagnetic interference systems, impedance matching, and switching power supplies). Therefore, reducing the size and cost of magnetic devices and integrating inductors into integrated circuit systems or reducing the size of inductors themselves has become a focus in the industry, thus placing new demands on high-frequency soft magnetic thin film materials. Metallic soft magnetic thin films, due to their mature fabrication processes and high initial permeability (μ), offer advantages in this area. r Its compatibility with semiconductor processes has made it a hot research topic.

[0003] Considering the practical needs and performance requirements of high-frequency magnetic devices, magnetic thin films need to meet three basic conditions: high permeability within the operating frequency range, relatively stable permeability with frequency, and compatibility with semiconductor fabrication processes. Essentially, the application frequency of magnetic devices is mainly related to the material's saturation magnetization, permeability, and resonant frequency. Constrained by the Snoek limit, magnetic thin films prepared using traditional techniques and methods are unlikely to reach gigahertz frequencies, thus limiting the development of high-frequency integrated devices in this frequency range. Increasing the in-plane uniaxial anisotropic effective field (H...) k ) and saturation magnetization (M s ) is to improve f r Effective methods include: (1) applying a static magnetic field during thin film deposition to induce magnetic anisotropy in the thin film; (2) using a tilting deposition process to control the magnetic anisotropy of the thin film; and (3) utilizing a substrate with wrinkles on its surface to control the magnetic anisotropy of the thin film due to its surface magnetic charge mechanism.

[0004] Chinese Patent Publication No. CN 114334347A discloses a "High-Frequency Low-Loss Amorphous Soft Magnetic Composite Film Material and Its Preparation Method." This method involves coating amorphous soft magnetic powder with insulation, mixing it with resin, casting and drying to form an amorphous composite film, and then stacking multiple composite films into a multilayer film. This achieves stable permeability in the MHz band and a loss angle below 0.08. However, due to its relatively low operating frequency and permeability (around 20), it is not suitable for use in the GHz band.

[0005] Chinese Patent Publication No. CN 110607503A, entitled "A Soft Magnetic Composite Film for High-Frequency Magnetic Cores and Its Preparation Method Thereof", describes a method for preparing a soft magnetic film and an insulating layer by alternating stacking of the two layers. The composite film has the following composition: [(Ni 100-x Fe x ) 100-y (SiO2) y / SiO2] n The soft magnetic thin film obtained by this method achieves a higher resonant frequency while maintaining a certain permeability, resulting in a cutoff frequency above 1 GHz and a permeability greater than 100 at 100 MHz. Although the material prepared by this method achieves a cutoff frequency above 1 GHz, its permeability is still relatively low, and a larger volume is required to achieve the same inductance value in the inductor.

[0006] Chinese Patent Publication No. CN100407342C discloses a multilayer thin film composed of TL (where T is Fe or FeCo, and L is C, B, or N). This film, prepared by alternating alloy layers and high-resistivity layers, achieves a saturation magnetization of over 1.3T and a real part of complex permeability exceeding 400 at 1 GHz, resulting in a high resonant frequency while maintaining high saturation magnetization. However, the fabrication process involves the composite of multiple films, making preparation difficult and resulting in low film quality, which poses challenges for subsequent device processing.

[0007] Based on the aforementioned published patent documents and research, it is difficult to simultaneously increase the resonant frequency of thin films and maintain high permeability, thus limiting the application of thin films at high frequencies. Furthermore, while multilayer film structures can improve the resonant frequency of thin films, their fabrication processes are somewhat complex, posing challenges to subsequent device manufacturing. Summary of the Invention

[0008] The purpose of this invention is to provide a soft magnetic thin film with high resonant frequency and high permeability, and a method for its preparation, which takes into account both high application frequency and high permeability.

[0009] The technical solution adopted by the present invention to solve the aforementioned technical problem is a high resonant frequency and high permeability soft magnetic thin film, comprising a substrate and a soft magnetic patterned layer disposed on the surface of the substrate. The soft magnetic patterned layer comprises a first rhombic unit array and a second rhombic unit array, the first and second rhombic unit arrays being arranged in an alternating and complementary manner in columns. Both the first and second rhombic unit arrays are composed of a predetermined number of rhombic units arranged orthogonally. In the same column of rhombic units, the long diagonal of any two adjacent rhombic units is connected; all rhombic units have the same shape and size.

[0010] Furthermore, the characteristic row spacing of the first rhombic cell array is 60 micrometers, and the characteristic row spacing of the second rhombic cell array is 60 micrometers. The characteristic row spacing refers to the minimum distance between two adjacent columns of rhombic cells within the same rhombic cell array.

[0011] The long diagonal of the rhombic unit is 140–150 micrometers, and the short diagonal is 90–100 micrometers. The thickness of the soft magnetic film is 75–125 nm. The material of the soft magnetic patterned layer is NiFe, FeCoN, or FeCoB.

[0012] The present invention also provides a method for preparing a soft magnetic thin film with high resonant frequency and high permeability, characterized by comprising the following steps:

[0013] (1) Clean the Si(100) substrate;

[0014] (2) Photoresist is spin-coated on the substrate and ultraviolet light is irradiated under the mask to denature the photoresist and form a pattern of soft magnetic pattern layer.

[0015] (3) Deposit soft magnetic thin film material to form a soft magnetic patterned layer.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The present invention provides a method for preparing a thin film to improve the application frequency of the thin film. The resulting soft magnetic thin film has an application frequency greater than 3 GHz and a permeability exceeding 300, thus achieving a thin film that balances high application frequency and high permeability. Attached Figure Description

[0018] Figure 1 This is a mask diagram of the rhombus pattern in this invention;

[0019] Figure 2 This is a partially enlarged schematic diagram of the present invention;

[0020] Figure 3 The following are the hysteresis loops of Example 1 and Comparative Examples 1 and 2; wherein, (a) is the hysteresis loop of the NiFe thin film obtained in Example 1; (b) is the hysteresis loop of the NiFe thin film obtained in Comparative Example 1; and (c) is the hysteresis loop of the NiFe thin film obtained in Comparative Example 2.

[0021] Figure 4 The magnetic spectrum curves are those of Example 1 and Comparative Examples 1 and 2; where (a) is the magnetic spectrum curve of the NiFe thin film obtained in Example 1; (b) is the magnetic spectrum curve of the NiFe thin film obtained in the comparative example; and (c) is the magnetic spectrum curve of the NiFe thin film obtained in Comparative Example 2.

[0022] Figure 5 This is a schematic diagram of the structural parameters of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0024] The purpose of this invention is to provide a method for preparing thin films with high resonant frequencies (2-3 GHz) while also achieving relatively high permeability (300-450 Ω), thus providing a material basis for high-frequency applications of devices. This invention is based on a high-vacuum electron beam evaporation system, utilizing photolithography to introduce shape anisotropy and inter-pattern interactions into the thin film, thereby improving the anisotropy of the film and controlling its resonant frequency. This results in a soft magnetic thin film that balances high application frequencies and high permeability.

[0025] The core idea of ​​this invention is: 1. By photolithographically etching a non-rhomboid pattern array on the substrate surface, the influence of edge pinning on the distribution of magnetic moments, the displacement of magnetic domain walls, and shape anisotropy can be controlled by changing the included angle and diagonal length of the rhomboid patterns. In the rhomboid pattern array, the magnetic moments pinned in the film edge are arranged along the rhomboid edge, and a certain angle is formed between adjacent magnetic moments distributed along the edge. The two included angles in the rhomboid pattern are of different sizes, so that the magnetic moment distribution density is different under the influence of the edge pinning effect, resulting in different area densities within the Nell wall of the rhomboid pattern. Furthermore, there are two kinds of dipole interactions between the large-angle included angle and the small-angle included angle of two adjacent rhomboid patterns (large-angle included angle with small-angle included angle and small-angle included angle with large-angle included angle), thereby introducing an additional anisotropic field in addition to shape anisotropy. Secondly, in high-frequency applications, alloy soft magnetic films often result in high ohmic losses due to their low resistivity. The rhombic pattern in this invention reduces the area of ​​the alloy soft magnetic film on the substrate, thereby reducing the eddy current loss of the film. The rhombic pattern also increases the effective area of ​​the magnetic film, thus increasing the magnetic flux through the film.

[0026] The high resonant frequency, high permeability soft magnetic thin film of the present invention includes a substrate and a soft magnetic patterned layer disposed on the surface of the substrate. The soft magnetic patterned layer comprises a first rhombic unit array and a second rhombic unit array, wherein the first and second rhombic unit arrays are arranged in an alternating and complementary manner, specifically, the columns of the first and second rhombic unit arrays are staggered and fill the gaps between the columns. See also... Figure 1 , Figure 2 and Figure 5 The first and second rhombus unit arrays are both composed of a predetermined number of rhombus units arranged orthogonally. In the same column of rhombus units, the long diagonals of any two adjacent rhombus units are connected. All rhombus units have the same shape and size. Figure 2 Two rhombus cell arrays are shown with different shades. The characteristic row spacing of the same rhombus cell array is equal; the characteristic row spacing is the minimum distance between two adjacent columns of rhombus cells within the same rhombus cell array, such as... Figure 5The marker a. Figure 5 In the diagram, b is the long diagonal and c is the short diagonal.

[0027] The long diagonal of the rhombic unit is 140–150 micrometers, and the short diagonal is 90–100 micrometers. The thickness of the soft magnetic film is 75–125 nm.

[0028] The thin film preparation method provided by this invention includes the following steps:

[0029] Step 1: Clean the substrate and let it air dry for later use;

[0030] Step 2: Spin-coat photoresist onto the substrate at a speed of 1000 rpm for 10 seconds and then at a speed of 3000 rpm for 20 seconds. After masking, irradiate with ultraviolet light for 3-5 seconds to denature the photoresist. Finally, clean the substrate in the developer until the photolithographic diamond pattern is developed.

[0031] Step 3: After photolithography is completed, clean the substrate and let it dry. Then fix the substrate on the sample holder and put the target into the vacuum chamber.

[0032] Step 4: Using an electron beam evaporation system, under a background vacuum of 1.3 × 10⁻⁶ -3 Pa~3×10 -3 The material was pre-melted for 4-5 minutes under the conditions of electron gun current of 30mA-40mA and voltage of 10kV; after the pre-melting was completed, the evaporation rate was set to 0.2nm / s-0.3nm / s to deposit a soft magnetic film on the substrate.

[0033] Step 5: After the soft magnetic film deposition is completed, the remaining photoresist is washed away with acetone solution;

[0034] Furthermore, the soft magnetic film is a NiFe film, an FeCoN film, or an FeCoB film, etc.

[0035] Furthermore, the substrate is Si, Si / SiO2, etc.

[0036] Furthermore, the diagonal length of the rhombus pattern can be adjusted according to the actual situation: the two diagonal lengths of the rhombus pattern are in the range of 140μm, 150μm and 90μm, 100μm; the spacing between adjacent rhombus patterns is 30μm; the spacing between the rhombuses is 1 / 2 of the feature row spacing.

[0037] In step 3, the evaporation rate is preferably set to 0.1 nm / s to 0.2 nm / s.

[0038] Furthermore, in step 3, the thickness of the obtained soft magnetic film is 75–125 nm.

[0039] The preparation method of the present invention uses ultraviolet lithography to photolithographically print rhomboid patterns with different diagonal lengths on a substrate, thereby introducing the interaction between patterns or the anisotropic field of the pattern shape into the thin film, so that the deposited soft magnetic thin film generates different anisotropic fields, thereby increasing the resonant frequency of the thin film.

[0040] Example 1

[0041] A method for preparing thin films to increase their application frequency specifically includes the following steps:

[0042] Step 1: Turn on the main power and individual switches of the electron beam evaporation system, and turn on the water chiller, mechanical pump, molecular pump, film thickness gauge and electron gun in sequence to preheat the equipment;

[0043] Step 2: Clean the 5mm×5mm Si(100) substrate by ultrasonic cleaning in acetone, ethanol and deionized water for 15 minutes in sequence, and then air dry it for later use.

[0044] Step 3: Spin-coat photoresist onto the substrate at a speed of 1000 rpm for 10 seconds and then at a speed of 3000 rpm for 20 seconds. After masking, irradiate with ultraviolet light for 3-5 seconds to denature the photoresist. Finally, clean the substrate in the developer until a pattern with diagonal lengths of 140 μm and 100 μm and a diamond spacing of 30 μm is developed on the substrate.

[0045] Step 4: After cleaning the photolithographic substrate as described in Step 2, air dry it for later use;

[0046] Step 5: Place the NiFe target material into the water-cooled crucible in the vacuum chamber, place the substrate on the sample holder, and fix one end of the substrate on the sample holder.

[0047] Step 6: Deposit NiFe thin films using a high-vacuum electron beam evaporation system with a base vacuum of 2.0 × 10⁻⁶. -4 Pa, the electron gun current is set to 40mA and the voltage is set to 10kV during pre-melting, and the pre-melting time is controlled at 4 minutes; after the pre-melting is completed, the evaporation rate is set to 0.2nm / s, and a NiFe film with a thickness of 100nm is deposited on the Si substrate.

[0048] Step 7: After thin film deposition is complete, sequentially close the high-pressure valve, molecular pump, fore-stage valve, and mechanical pump. Open the vacuum chamber, remove the sample, and clean the inside of the chamber with a lint-free cloth. After cleaning, close the vacuum chamber door, turn off the power to each component and the main system power, and the thin film preparation is complete.

[0049] Step 8, Testing: The NiFe thin film obtained in Step 5 was tested. The hysteresis loop was measured using a vibrating sample magnetometer (VSM, LakeShore 8604). The magnetic spectrum curve of the thin film sample was obtained using a vector network analyzer (Agilent N5227APNA).

[0050] Example 2

[0051] The difference between this embodiment and embodiment 1 is that in step 3, the length of the rhomboid diagonal of the substrate after photolithography and development is 140μm and 90μm; the remaining steps are the same as in embodiment 1.

[0052] Example 3

[0053] The difference between this embodiment and embodiment 1 is that in step 3, the length of the rhomboid diagonal of the substrate after photolithography and development is 140μm and 100μm; the remaining steps are the same as in embodiment 1.

[0054] Example 4

[0055] The difference between this embodiment and embodiment 1 is that in step 3, the length of the rhomboid diagonal of the substrate after photolithography and development is 140μm and 90μm; the remaining steps are the same as in embodiment 1.

[0056] Example 5

[0057] The difference between this embodiment and embodiment 1 is that in step 3, the length of the rhomboid diagonal of the substrate after photolithography and development is 150μm and 100μm; the remaining steps are the same as in embodiment 1.

[0058] Example 6

[0059] The difference between this embodiment and embodiment 1 is that in step 3, the length of the rhomboid diagonal of the substrate after photolithography and development is 150μm and 90μm; the remaining steps are the same as in embodiment 1.

[0060] Example 7

[0061] The difference between this embodiment and embodiment 1 is that in step 3, the length of the rhomboid diagonal of the substrate after photolithography and development is 150μm and 100μm; the remaining steps are the same as in embodiment 1.

[0062] Example 8

[0063] The difference between this embodiment and embodiment 1 is that in step 3, the length of the rhomboid diagonal of the substrate after photolithography and development is 150μm and 90μm; the remaining steps are the same as in embodiment 1.

[0064] Comparative Example 1

[0065] Compared with Example 1, the comparative example differs in that the substrate is not photolithographically processed, and steps 3 and 4 are omitted. The remaining steps are the same as in Example 1.

[0066] Comparative Example 2

[0067] Compared with Example 1, the comparative example differs in that the substrate undergoes long strip pattern photolithography with a strip width of 20 μm and a strip spacing of 30 μm. The remaining steps are the same as in Example 1.

[0068] Figure 3 The figures show the in-plane hysteresis loops along the easy and difficult axes of the NiFe thin films obtained in Examples 1, 2, 3, and Comparative Examples 1, 2; wherein, (a) is the in-plane hysteresis loop of the NiFe thin film obtained in Example 1; and (b) is the in-plane hysteresis loop of the NiFe thin film obtained in the comparative examples. Figure 3 It can be seen that the NiFe thin film prepared in Example 1 has obvious magnetic anisotropy.

[0069] Figure 4 The magnetic spectrum curves are those of Example 1 and the comparative example; wherein, (a) is the magnetic spectrum curve of the NiFe thin film obtained in Example 1; and (b) is the magnetic spectrum curve of the NiFe thin film obtained in the comparative example. Figure 4 It can be seen that the NiFe thin film obtained in Example 1 has an application frequency greater than 3GHz and a real part of permeability greater than 300 at 100MHz.

Claims

1. A high-resonance-frequency, high-permeability soft magnetic thin film, comprising a substrate and a soft magnetic patterned layer disposed on the surface of the substrate, characterized in that, The soft magnetic pattern layer includes a first rhombus unit array and a second rhombus unit array. The first and second rhombus unit arrays are arranged in an alternating and complementary manner in columns. Both the first and second rhombus unit arrays are composed of a predetermined number of rhombus units arranged orthogonally. In the same column of rhombus units, the long diagonal of any two adjacent rhombus units is connected. All rhombus units have the same shape and size.

2. The high resonant frequency, high permeability soft magnetic thin film as described in claim 1, characterized in that, The first rhombic cell array has a feature row spacing of 60 micrometers, and the second rhombic cell array has a feature row spacing of 60 micrometers.

3. The high resonant frequency, high permeability soft magnetic thin film as described in claim 1, characterized in that, The long diagonal of the rhomboid unit is 140–150 micrometers, and the short diagonal is 90–100 micrometers.

4. The high resonant frequency, high permeability soft magnetic thin film as described in claim 1, characterized in that, The thickness of the soft magnetic film is 75–125 nm.

5. The high resonant frequency, high permeability soft magnetic thin film as described in claim 1, characterized in that, The material of the soft magnetic patterned layer is NiFe, FeCoN, or FeCoB.

6. The method for preparing a high-resonance-frequency, high-permeability soft magnetic thin film as described in claim 1, characterized in that, Includes the following steps: (1) Clean the Si(100) substrate; (2) Photoresist is spin-coated on the substrate and ultraviolet light is irradiated under the mask to denature the photoresist and form a pattern of soft magnetic pattern layer. (3) Deposit soft magnetic thin film material to form a soft magnetic patterned layer.

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