High voltage multilayer thin film capacitor and method of making same

Abstract

The application relates to a high-voltage multilayer thin film capacitor and a preparation method thereof, and belongs to the technical field of multilayer thin film capacitors. The high-voltage multilayer thin film capacitor comprises a conductive substrate, an intermediate body and an outer electrode layer; the intermediate body is arranged on the conductive substrate and comprises L thin film dielectric layers and L-1 inner electrode layers, the L thin film dielectric layers and the L-1 inner electrode layers are alternately and superimposedly arranged; the top layer and the bottom layer of the intermediate body are thin film dielectric layers; the outer electrode layer is electrically connected with each inner electrode layer and the conductive substrate; and the thin film dielectric layer is made of a ferroelectric-antiferroelectric composite solid solution. The application can improve the capacitance volume efficiency, the breakdown electric field and the energy storage performance of the thin film capacitor.

Description

Technical Field

[0001] The present invention relates to a high-voltage multilayer film capacitor and a preparation method thereof, belonging to the technical field of multilayer film capacitors. Background Art

[0002] As an indispensable component of electronic devices and equipment, capacitors play a vital role in electronic products' tuning, bypassing, coupling, filtering, and other circuits. With the advancement of technology, the demand for capacitors in 3C products, automotive electronics, and other applications is increasing, driving the development of the capacitor industry.

[0003] In terms of improving the performance of capacitors, researchers at home and abroad have done a lot of work and have achieved some results. For example, the Chinese invention patent with the authorization announcement number CN110660583B discloses a single-layer thin film capacitor, which includes a dielectric film and an electrode layer, wherein the dielectric film includes a flexible metal substrate and a strontium titanate film formed on the flexible metal substrate, and the electrode layer is formed on the strontium titanate layer. The dielectric film of the thin film capacitor is a ceramic film, which has the characteristics of high dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density, and has good flexibility. It can replace polymer films, which promotes the development trend of thin film capacitors towards miniaturization, lightness, high integration and multifunctionality.

[0004] However, the above-mentioned single-layer thin film capacitor still has the problem of low capacitance, and ferroelectrics have the characteristics of high remnant polarization, which leads to low energy efficiency. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a high-voltage multilayer film capacitor and a preparation method thereof, which can improve the breakdown electric field and energy storage performance of the film capacitor.

[0006] A first aspect of the present invention relates to a high voltage multilayer film capacitor comprising: a conductive substrate, an intermediate body and an outer electrode layer;

[0007] The intermediate body is provided on a conductive substrate and includes L thin-film dielectric layers and L-1 inner electrode layers, wherein the L thin-film dielectric layers and the L-1 inner electrode layers are alternately stacked; the top and bottom layers of the intermediate body are both thin-film dielectric layers; the outer electrode layer is electrically connected to each inner electrode layer and the conductive substrate;

[0008] Any of the thin film dielectric layers is composed of (Pb x La 1-x )(Zr y Ti 1-y )O3-mBiFeO3-nBaTiO3、(Pb x La 1-x )(Zr yTi 1-y )O3-m(Bi 0.5 Na 0.5 )TiO3-nBaTiO3、(Pb x La 1-x )(Zr y Ti 1-y )O3-z(Bi 0.5 Na 0.5 )TiO3 composite solid solution; wherein x = 0.90 ~ 0.97, y ≥ 0.90, m + n ≤ 0.5 and m, n ﹥ 0, 0 ﹤ z ≤ 0.5. It is worth noting that (Pb x La 1-x )(Zr y Ti 1-y )O3 is an antiferroelectric material Pb(Zr y Ti 1-y )O3 is modified by introducing La element, among which Zr and Ti are both tetravalent, which can achieve continuous solid solution, and the introduction of heterovalent element La at the Pb position is equivalent to donor doping. Therefore, there are some free electrons in the material to form positive defects, and the Pb vacancies formed in the sintering process introduce holes to form negative defects, which can not only maintain the balance of charge, but also form defect association through positive and negative defects, which is beneficial to maintain or even improve the insulation performance of the material.

[0009] For some specific embodiments, x can be 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, etc.

[0010] For some specific embodiments, y can be 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, etc.

[0011] For some specific embodiments, m+n can be 0.1, 0.2, 0.3, 0.4, 0.5, etc.

[0012] For some specific embodiments, the combination of m and n can be m=0.05, n=0.05, m=0.1, n=0.2, m=0.1, n=0.2, m=0.3, n=0.05, m=0.4, n=0.1, etc.

[0013] For some specific embodiments, z can be 0.1, 0.2, 0.3, 0.4, 0.5, etc.

[0014] For some specific implementation schemes, L=10-20.

[0015] In some specific embodiments, the conductive substrate is a platinum / titanium / silicon dioxide / silicon substrate, and the intermediate is disposed on the surface of the platinum.

[0016] A second aspect of the present invention relates to a method for preparing a high-voltage multilayer film capacitor, comprising the following steps:

[0017] Step S1, preparation of a precursor: dissolving the raw materials of a dielectric precursor into a solvent according to the chemical composition of the thin film dielectric layer, and mixing until fully dissolved to obtain a dielectric precursor solution;

[0018] Step S2, preparing a thin-film dielectric layer: aging the dielectric precursor solution prepared in step S1, and then spin-coating it on a conductive substrate or an inner electrode layer. The wet film after spin coating is dried, and then pyrolyzed to evaporate the residual organic matter. Then, the film is kept at 500-800°C for 25-35 minutes, and crystallized by a rapid thermal annealing process to obtain a thin-film dielectric layer.

[0019] Step S3, preparing an inner electrode layer: depositing an inner electrode material onto the surface of the thin film dielectric layer prepared in step S2 to obtain an inner electrode layer;

[0020] Step S4, preparation of MLCC: repeat steps S2 and S3 in sequence to obtain an intermediate body composed of L thin-film dielectric layers and L-1 inner electrode layers alternately stacked, wherein the outermost side of the intermediate body away from the conductive substrate is the thin-film dielectric layer; then, annealing treatment is performed at 500-620°C for 25-35 minutes, and then external electrodes are set at preset port positions to obtain MLCC.

[0021] For some specific implementation schemes, the raw materials of the dielectric precursor in step S1 are composed of ferroelectric raw materials, antiferroelectric raw materials and a titanium source, the titanium source is tetrabutyl titanate, the ferroelectric raw materials are selected from bismuth acetate, sodium acetate, ferric nitrate, and barium nitrate, and the antiferroelectric raw materials include lead acetate, lanthanum acetate and zirconium n-propoxide.

[0022] In some specific embodiments, the solvent in step S1 is one or more of 2-methoxyethanol, propionic acid, ethylene glycol, and acetic acid.

[0023] For some specific implementation schemes, the concentration of the dielectric precursor solution is 0.1-0.4 M. Preferably, the mass ratio of the raw material to the solvent in step S1 is 1:(3-5).

[0024] For example, the concentration of the dielectric precursor solution may be 0.1M, 0.2M, 0.3M, 0.4M, etc.

[0025] For example, the mass ratio of the raw material to the solvent can be 1:3, 1:3.5, 1:4, 1:4.2, 1:5, etc.

[0026] In some specific embodiments, the mixing treatment in step S1 is: stirring at 60-150° C. for 0.5-3 hours to obtain a mixture; and then, continuously stirring the obtained mixture at room temperature for 1-3 hours.

[0027] For some specific implementation schemes, the aging treatment in step S2 is: standing at room temperature for 3 to 10 days.

[0028] For some specific implementation schemes, the drying treatment in step S2 is: baking at 190-210° C. for 1-3 minutes.

[0029] For some specific embodiments, the pyrolysis treatment in step S2 is: heating at 390-410° C. for 9-11 minutes.

[0030] Compared with the prior art, the present invention has the following technical effects:

[0031] 1) A ferroelectric-antiferroelectric composite solid solution was constructed based on an antiferroelectric solid solution modified with an appropriate amount of lanthanum as a thin-film dielectric layer. This thin-film dielectric layer exhibits relaxivity, and the resulting MLCC has higher energy storage density and efficiency, overcoming the poor performance of pure ferroelectrics.

[0032] 2) Through the rational selection of the raw material composition formula of the precursor and the preparation process parameters, the finished product exhibits high breakdown field strength and energy storage performance; and through the design of the electrode structure, the compressive strength of the MLCC is greatly improved, from 0.5-1MV / cm to 2-4MV / cm;

[0033] 3) The secondary annealing process is used to improve the crystallinity, ferroelectricity and antiferroelectricity of the material, and improve the breakdown electric field and energy storage performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the X-ray diffraction pattern of Example 1;

[0035] Figure 2 1 is a cross-sectional SEM image of Example 1; wherein 100 is a substrate, 200 is a thin film dielectric layer, and 300 is an inner electrode layer;

[0036] Figure 3 The hysteresis loop diagrams of Examples 1 to 3 and Comparative Example 1;

[0037] Figure 4 The graphs are showing the energy storage performance of Examples 1 to 3 as a function of the electric field. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below in conjunction with specific embodiments. Experimental methods without specific conditions specified in the examples were carried out according to conventional methods and conditions.

[0039] Example 1

[0040] This embodiment relates to a high-voltage multilayer film capacitor, the preparation method of which includes the following steps:

[0041] Step S1, preparation of precursor: according to the chemical composition of the thin film dielectric layer (Pb 0.97 La 0.03 )(Zr 0.95 Ti 0.05 )O3-0.5(Bi 0.5 Na 0.5 ) TiO3, dissolving the raw materials of the dielectric precursor in a solvent, stirring at 60° C. for 0.5 hour to obtain a mixture; then, continuously stirring the obtained mixture at room temperature for 1 hour until it is fully dissolved to obtain a clear and transparent dielectric precursor solution;

[0042] Step S2, Preparation of a Thin Film Dielectric Layer: The dielectric precursor solution prepared in step S1 is aged for 3 days and then spin-coated onto a conductive substrate or an inner electrode layer. The spin-coated wet film is baked at 190°C for 1 minute to obtain a dry film, and then pyrolyzed at 390°C for 9-11 minutes to evaporate any residual organic matter. This is followed by annealing at 500°C for 25 minutes to crystallize and obtain a thin film dielectric layer. The conductive substrate is a platinum / titanium / silicon dioxide / silicon substrate.

[0043] Step S3, preparing an inner electrode layer: depositing a gold inner electrode onto the surface of the thin film dielectric layer prepared in step S2 through a stainless steel shadow mask to obtain an inner electrode layer;

[0044] Step S4, preparation of MLCC: Repeat steps S2 and S3 in sequence to obtain an intermediate body consisting of 10 thin-film dielectric layers and 9 internal electrode layers alternately stacked on a conductive substrate; then anneal at 500°C for 1 minute, and then set silver external electrodes at preset port positions to obtain a high-voltage MLCC.

[0045] The raw materials of the precursor in step S1 are lanthanum nitrate, lead acetate, zirconium n-propoxide, tetrabutyl titanate, sodium acetate, and bismuth acetate mixed in a molar ratio of 0.03:0.97:0.95:0.55:0.25:0.25; the solvent in step S1 is 2-methoxyethanol; the mass ratio of the raw materials of the precursor to the solvent in step S1 is 1:3; the concentration of the dielectric precursor solution in step S1 is 0.1M.

[0046] Example 2

[0047] This embodiment relates to a high-voltage multilayer film capacitor, the preparation method of which includes the following steps:

[0048] Step S1, preparation of precursor: according to the chemical composition of the thin film dielectric layer (Pb 0.97 La 0.03 )ZrO3-0.1BiFeO3-0.2BaTiO3, dissolving the raw materials of the dielectric precursor in a solvent and stirring at 90° C. for 1.5 hours to obtain a mixture; then, continuously stirring the obtained mixture at room temperature for 1.5 hours until it is fully dissolved to obtain a clear and transparent dielectric precursor solution;

[0049] Step S2, Preparation of a Thin Film Dielectric Layer: The dielectric precursor solution prepared in step S1 is aged for 5 days and then spin-coated onto a conductive substrate or an inner electrode layer. The spin-coated wet film is baked at 195°C for 1.5 minutes to obtain a dry film, and then pyrolyzed at 395°C for 9.5 minutes to evaporate any residual organic matter. This is followed by annealing at 600°C for 28 minutes to crystallize and obtain a thin film dielectric layer. The conductive substrate is a platinum / titanium / silicon / silicon substrate.

[0050] Step S3, preparing an inner electrode layer: depositing a gold inner electrode onto the surface of the thin film dielectric layer prepared in step S2 through a stainless steel shadow mask to obtain an inner electrode layer;

[0051] Step S4, preparation of MLCC: Repeat steps S2 and S3 in sequence to obtain an intermediate body consisting of 13 thin-film dielectric layers and 12 internal electrode layers alternately stacked on a conductive substrate; then anneal at 550°C for 2 minutes, and then set silver external electrodes at preset port positions to obtain a high-voltage MLCC.

[0052] The raw materials of the precursor in step S1 are lanthanum nitrate, lead acetate, zirconium n-propoxide, tetrabutyl titanate, barium nitrate, bismuth acetate, and ferric nitrate mixed in a molar ratio of 0.03:0.97:1:0.2:0.2:0.1:0.1; the solvent in step S1 is propionic acid; the mass ratio of the raw materials of the precursor to the solvent in step S1 is 1:3.5; the concentration of the dielectric precursor solution in step S1 is 0.2M.

[0053] Example 3

[0054] This embodiment relates to a high-voltage multilayer film capacitor, the preparation method of which includes the following steps:

[0055] Step S1, preparation of precursor: according to the chemical composition of the thin film dielectric layer (Pb 0.9 La 0.1 )(Zr 0.95 Ti 0.05 )O3-0.06(Bi 0.5Na 0.5 )TiO3-0.35BaTiO3, dissolving the raw materials of the dielectric precursor in a solvent and stirring at 150° C. for 3 hours to obtain a mixture; then, continuously stirring the obtained mixture at room temperature for 3 hours until it is fully dissolved to obtain a clear and transparent dielectric precursor solution;

[0056] Step S2, preparation of a thin-film dielectric layer: The dielectric precursor solution prepared in step S1 is aged for 10 days and then spin-coated onto a conductive substrate or an inner electrode layer. The spin-coated wet film is baked at 210°C for 3 minutes to obtain a dry film, and then pyrolyzed at 410°C for 11 minutes to evaporate residual organic matter. This is followed by annealing at 800°C for 35 minutes to crystallize and obtain a thin-film dielectric layer. The conductive substrate is a platinum / titanium / silicon dioxide / silicon substrate.

[0057] Step S3, preparing an inner electrode layer: depositing a gold inner electrode onto the surface of the thin film dielectric layer prepared in step S2 through a stainless steel shadow mask to obtain an inner electrode layer;

[0058] Step S4, preparation of MLCC: Repeat steps S2 and S3 in sequence to obtain an intermediate body consisting of 17 thin-film dielectric layers and 16 internal electrode layers alternately stacked on a conductive substrate; then anneal at 620°C for 5 minutes, and then set silver external electrodes at preset port positions to obtain a high-voltage MLCC.

[0059] The raw materials of the precursor in step S1 are lanthanum nitrate, lead acetate, zirconium n-propoxide, tetrabutyl titanate, sodium acetate, barium nitrate, and bismuth acetate mixed in a molar ratio of 0.1:0.9:0.95:0.46:0.03:0.35:0.03; the solvent in step S1 is ethylene glycol; the mass ratio of the raw materials of the precursor to the solvent in step S1 is 1:5; the concentration of the dielectric precursor solution in step S1 is 0.4M.

[0060] Comparative Example 1

[0061] This comparative example relates to a high-voltage multilayer thin-film capacitor. Unlike Example 1, the thin-film dielectric layer is made of BaTiO3. The preparation method for this comparative example differs from that for Example 1 in that the dielectric precursor in step S1 is made of a mixture of tetrabutyl titanate and barium nitrate in a 1:1 molar ratio.

[0062] In order to further illustrate the beneficial technical effects of the high-voltage multilayer film capacitors involved in each embodiment of the present invention, the electrical performance of the high-voltage multilayer film capacitors prepared in Examples 1 to 3 and Comparative Example 1 was tested. Specifically, the electric field strength was gradually increased to reach the breakdown electric field under 5kHz alternating current, and the following results were obtained: Figure 3The hysteresis loop diagram shown in FIG. 1 is shown in FIG. 2 ; the result obtained by integrating the hysteresis loop of the discharge section with respect to the polarization axis is the energy storage density, and the result obtained by dividing the energy density by the value of integrating the hysteresis loop of the charge section with respect to the polarization axis is the energy storage efficiency; the electrical performance test results are shown in Tables 1 and Figure 4 .

[0063] Table 1 Performance test table

[0064] Test items <![CDATA[Energy storage density (J / cm 3 ).]]> Energy storage efficiency (%) Breakdown strength (MV / cm) Example 1 78.5 87.4 3.72 Example 2 65.3 79.5 2.84 Example 3 49.5 77.6 3.04 Comparative Example 1 15.6 51.5 0.86

[0065] It can be seen from the data in Table 1 that the high-voltage multilayer film capacitors involved in the embodiments of the present invention have higher energy storage density, energy storage efficiency and breakdown strength than the comparative example products.

[0066] On this basis, taking Example 1 as an example, Figure 1 and Figure 2 , analyze the characteristics of the materials in the embodiments of the present invention:

[0067] Figure 1 The X-ray diffraction pattern comparison diagram of the single-layer thin film dielectric layer 200 and the substrate 100 in Example 1, wherein the substrate is a single crystal and a large number of orientation peaks cannot be As shown in the test geometry, the diffraction peak at 23° represents the titanium layer, and the diffraction peak at 48° represents the platinum layer. Due to the limited X-ray detection depth, the deeper titanium dioxide layer and silicon layer have no effective signal and no diffraction peak is shown. As a reference, the substrate 100 shows that the thin film dielectric layer 200 has no second phase and is a single phase of perovskite structure with a weak texture (100) and partial (110) and (111) orientations. Figure 2 The SEM photograph shows that there is a good interface between the thin film dielectric layer 200 and the inner electrode layer 300, and there is no obvious electrode diffusion. Therefore, it can also reflect to a certain extent that the product prepared by the embodiment of the present invention has good electrical properties.

[0068] It should be emphasized that the above are only preferred embodiments of the present invention and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A high voltage multilayer film capacitor, characterized in that: include: conductive substrate, intermediate body and outer electrode layers; The intermediate body is provided on a conductive substrate and includes L thin-film dielectric layers and L-1 inner electrode layers, wherein the L thin-film dielectric layers and the L-1 inner electrode layers are alternately stacked; the top and bottom layers of the intermediate body are both thin-film dielectric layers; the outer electrode layer is electrically connected to each inner electrode layer and the conductive substrate; Any of the thin film dielectric layers is composed of (Pb x La 1-x )(Zr y Ti 1-y )O3-mBiFeO3-nBaTiO3、(Pb x La 1-x )(Zr y Ti 1-y )O3-m(Bi 0.5 Na 0.5 )TiO3-nBaTiO3、(Pb x La 1-x )(Zr y Ti 1-y )O3-z(Bi 0.5 Na 0.5 )TiO3 composite solid solution; wherein, x = 0.90 ~ 0.97, y ≥ 0.90, m + n ≤ 0.5 and m, n ﹥ 0, 0 ﹤ z ≤ 0.

5.

2. The high-voltage multilayer film capacitor according to claim 1, characterized in that: L=10～20。 3. A method for preparing a high-voltage multilayer film capacitor according to claim 1 or 2, characterized in that: The following steps are involved: Step S1, preparation of a precursor: dissolving the raw materials of a dielectric precursor into a solvent according to the chemical composition of the thin film dielectric layer, and mixing until fully dissolved to obtain a dielectric precursor solution; Step S2, preparing a thin-film dielectric layer: aging the dielectric precursor solution prepared in step S1, and then spin-coating it on a conductive substrate or an inner electrode layer. The wet film after spin coating is dried, and then pyrolyzed to evaporate residual organic matter. Then, the film is kept at 500-800°C for 25-35 minutes to crystallize to obtain a thin-film dielectric layer. Step S3, preparing an inner electrode layer: depositing an inner electrode material onto the surface of the thin film dielectric layer prepared in step S2 to obtain an inner electrode layer; Step S4, preparation of MLCC: repeating steps S2 and S3 in sequence to obtain an intermediate body formed by alternating stacking of L thin-film dielectric layers and L-1 inner electrode layers, wherein the outermost side of the intermediate body away from the conductive substrate is the thin-film dielectric layer; Then, the temperature is kept at 500-620°C for 1-5 minutes, and then external electrodes are set at the preset port positions to obtain MLCC.

4. The preparation method according to claim 3, characterized in that The raw materials of the dielectric precursor in step S1 are composed of ferroelectric raw materials, antiferroelectric raw materials and a titanium source, wherein the titanium source is tetrabutyl titanate, the ferroelectric raw materials are selected from bismuth acetate, sodium acetate, ferric nitrate and barium nitrate, and the antiferroelectric raw materials include lead acetate, lanthanum acetate and zirconium n-propoxide.

5. The preparation method according to claim 3, characterized in that The concentration of the dielectric precursor solution is 0.1-0.4M.

6. The preparation method according to claim 5, characterized in that The mass ratio of the raw materials to the solvent in step S1 is 1:(3-5).

7. The preparation method according to claim 3, characterized in that The mixing treatment in step S1 is as follows: stirring at 60-150° C. for 0.5-3 hours to obtain a mixture; and then continuously stirring the obtained mixture at room temperature for 1-3 hours.

8. The preparation method according to claim 3, characterized in that The aging treatment in step S2 is: standing at room temperature for 3 to 10 days.

9. The preparation method according to claim 3, characterized in that The drying process in step S2 is: baking at 190-210° C. for 1-3 minutes.

10. The preparation method according to claim 3, characterized in that The pyrolysis treatment in step S2 is: keeping the temperature at 390-410° C. for 9-11 minutes.

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