A high dielectric constant ceramic substrate and its preparation method

Abstract

The invention discloses a high-dielectric-constant ceramic substrate and a preparation method thereof, relating to the technical field of ceramic substrate preparation, comprising a semiconducting SrTiO3 ceramic substrate and an insulating film. The insulating films are arranged on two opposite planes of the SrTiO3 ceramic substrate. Pure aluminum is sputtered onto two surfaces of the SrTiO3 ceramic substrate by magnetron vacuum sputtering to form an aluminum film, which is then subjected to heat treatment. An Al2O3 layer is formed on the surface of the aluminum film, and a doped interface layer is formed at the interface between the aluminum film and the SrTiO3 ceramic substrate. The Al2O3 layer and the doped interface layer constitute the insulating film. The thickness of the Al2O3 layer of the insulating film increases with the time of heat treatment, thereby increasing the insulation withstand voltage performance and reducing the dielectric loss of the high-dielectric-constant ceramic substrate. A higher capacitance-to-volume ratio is achieved on a single-layer ceramic capacitor, thereby resolving the technical problems of low capacitance-to-volume ratio and high dielectric loss in existing single-layer ceramic capacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic substrate preparation, and in particular to a high dielectric constant ceramic substrate and a preparation method thereof. Background Art

[0002] Ceramic capacitors are widely used electronic components in modern electronics, particularly in high-speed signal processing, high-frequency circuits, and overvoltage protection. Single-layer ceramic capacitors, a type of ceramic capacitor, are widely used in many applications due to their simple structure and high-voltage resistance.

[0003] Advantages of single-layer ceramic capacitors:

[0004] High voltage resistance: Single-layer ceramic capacitors have higher voltage resistance than multilayer ceramic capacitors.

[0005] Good stability: Due to its simple structure and mature manufacturing process, single-layer ceramic capacitors have good stability.

[0006] Small size, suitable for high-frequency applications: Single-layer ceramic capacitors are relatively small in size and are suitable for high-frequency circuits. They can effectively filter signal noise and ensure stable operation of the circuit.

[0007] High reliability: Due to its simple structure, single-layer ceramic capacitors are less likely to have problems such as internal short circuits. Therefore, their failure rate is low and their reliability is high, making them suitable for use in electronic products that require high stability.

[0008] However, as electronic devices become increasingly multifunctional, performance requirements for capacitors continue to increase. Single-layer ceramic capacitors face a series of technical challenges in their development. The main problems currently faced by single-layer ceramic capacitors are:

[0009] 1. Small capacitance: The capacitance of single-layer ceramic capacitors is usually small, which limits their use in some applications with high capacitance requirements, such as high-power power filtering or energy storage.

[0010] 2. Larger size: Compared with multilayer ceramic capacitors, single-layer ceramic capacitors have a larger volume at the same capacitance. With the increasing demand for miniaturization of electronic equipment, single-layer ceramic capacitors are not as advantageous as multilayer ceramic capacitors in designs with limited space.

[0011] 3. High dielectric loss: Although single-layer ceramic capacitors have good high-frequency characteristics, their dielectric loss is still high under certain high-frequency operating conditions, which may affect their performance. Especially in high-frequency pulse signals, the high dielectric loss problem may cause the capacitor to heat up and affect the stability of the circuit.

[0012] 4. Material dependence: Single-layer ceramic capacitors usually rely on specific ceramic materials (such as barium titanate, etc.). These materials may degrade in performance under high temperature or other extreme working conditions, affecting the long-term stability and reliability of the capacitor.

[0013] As an important type of ceramic capacitor, single-layer ceramic capacitors occupy a key position in modern electronics due to their advantages such as high voltage resistance, strong stability, and high reliability. However, with technological advancements and changing application requirements, single-layer ceramic capacitors still face challenges in terms of capacitance, volume, and dielectric loss.

[0014] In summary, it is found that the existing technology has at least the following technical problems:

[0015] Existing single-layer ceramic capacitors have technical problems of low capacitance to volume ratio and high dielectric loss. Summary of the Invention

[0016] The object of the present invention is to provide a high dielectric constant ceramic substrate and a preparation method thereof, so as to solve the technical problems of low capacitance to volume ratio and high dielectric loss in existing single-layer ceramic capacitors.

[0017] The various technical effects that can be produced by the preferred technical solutions among the various technical solutions provided by the present invention are described in detail below.

[0018] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0019] The present invention provides a high dielectric constant ceramic substrate, comprising a semiconducting SrTiO3 ceramic substrate and an insulating film, wherein the insulating film is provided on two opposite planes of the SrTiO3 ceramic substrate; wherein pure aluminum is sputtered onto two surfaces of the SrTiO3 ceramic substrate to form aluminum films on the two surfaces of the SrTiO3 ceramic substrate; the thickness of the aluminum film increases with the sputtering time, and the thickness of the aluminum film is 0.1 to 3.0 μm; the SrTiO3 ceramic substrate sputtered with the aluminum film is placed in a muffle furnace, heated to a heat treatment temperature within 30 minutes, and then subjected to a heat preservation operation to achieve heat treatment; after the heat treatment is completed, the SrTiO3 ceramic substrate is placed in a muffle furnace, heated to a heat treatment temperature within 30 minutes, and then subjected to a heat preservation operation to achieve heat treatment; after the heat treatment is completed, the SrTiO3 ceramic substrate is placed in a muffle furnace, heated to a heat treatment temperature within 30 minutes, and then subjected to a heat preservation operation to achieve heat treatment; The SrTiO3 ceramic substrate is naturally cooled to room temperature; thereby, an Al2O3 layer is formed on the surface of the aluminum film, and a doped interface layer is formed at the interface between the aluminum film and the SrTiO3 ceramic substrate; the Al2O3 layer and the doped interface layer constitute the insulating film; the SrTiO3 ceramic substrate and the two layers of the insulating films arranged opposite to each other constitute a high dielectric constant performance ceramic substrate; the thickness of the insulating film on the SrTiO3 ceramic substrate is 0.1 to 3.0 μm; the thickness of the Al2O3 layer of the insulating film increases with the heat treatment time, so that the insulating withstand voltage performance of the high dielectric constant performance ceramic substrate is higher and the dielectric loss is lower.

[0020] In one embodiment, the thickness of the SrTiO 3 ceramic substrate is 0.1 to 0.3 mm.

[0021] In one embodiment, the pure aluminum is 90.0% to 99.9% aluminum.

[0022] In one embodiment, the sputtering time of the SrTiO 3 ceramic substrate is controlled to be 1 min to 30 min.

[0023] In one embodiment, the heat treatment temperature is 450°C to 650°C.

[0024] In one embodiment, the heat preservation operation time is 0.5 hours to 4 hours.

[0025] A preparation method is also provided, comprising the following steps: S1, using SrTiO3 powder, adding a binder and a solvent, and preparing a semiconducting SrTiO3 ceramic substrate by ball milling, tape casting, lamination, cutting, debinding, and reduction sintering;

[0026] S2, ultrasonically cleaning the semiconducting SrTiO3 ceramic substrate in S1 with pure water and ethanol in sequence;

[0027] S3, drying the SrTiO3 ceramic substrate cleaned in S2 for later use;

[0028] S4: sputter coating onto SrTiO3 ceramic substrate;

[0029] S4.1. Place the SrTiO3 ceramic substrate obtained in S3 on a magnetron vacuum sputtering machine carrier and into the receiving chamber of the magnetron vacuum sputtering machine. Evacuate the receiving chamber to a pressure of less than 6.0E-4Pa.

[0030] S4.2. Fill the chamber in S4.1 with argon gas until the pressure reaches 1.0E-2Pa.

[0031] S4.3. Use pure aluminum and perform target sputtering using a magnetron vacuum sputtering machine. The sputtering time is controlled within 1 minute to 30 minutes to deposit a layer of aluminum film on the surface of the SrTiO3 ceramic substrate. The thickness of the aluminum film is controlled to be 0.1 to 3.0 μm.

[0032] S4, taking out the SrTiO3 ceramic substrate sputtered in S3 from the magnetron vacuum sputtering machine carrier;

[0033] S5. Place the sputtered SrTiO3 ceramic substrate in a muffle furnace, raise the temperature to the heat treatment temperature within 30 minutes under air environment, and then keep the temperature for 0.5 hours to 4 hours;

[0034] The heat treatment temperature of the SrTiO3 ceramic substrate in the muffle furnace is 450°C to 650°C;

[0035] S6, naturally cooling the SrTiO3 ceramic substrate after the heat treatment in S5 to room temperature;

[0036] Through the heat treatment step S5, an Al2O3 layer is formed on the surface of the aluminum film of the SrTiO3 ceramic substrate, and a doped interface layer is formed at the interface between the aluminum film and the SrTiO3 ceramic substrate.

[0037] The beneficial effects of the present invention are as follows:

[0038] 1. By sputtering an aluminum film on the surface of a semiconducting SrTiO3 ceramic substrate, a ceramic / aluminum film acceptor doping interface is formed through heat treatment, an Al2O3 layer is formed on the surface of the aluminum film, and a doped interface layer is formed on the interface between the aluminum film surface and the SrTiO3 ceramic substrate. The doped interface layer and the Al2O3 layer form an insulating film.

[0039] The thickness of the insulating film is mainly affected by the heat treatment temperature and time. The higher the heat treatment temperature and the longer the time, the thicker the Al2O3 layer will be. The insulating withstand voltage performance of the high dielectric constant ceramic substrate will be higher, and its dielectric loss will be lower.

[0040] The high dielectric constant ceramic substrate of the present invention can be used to produce single-layer ceramic capacitors with larger capacity or smaller size of the same capacity of the same size, thereby achieving a higher capacitance-to-volume ratio of the single-layer ceramic capacitor and miniaturization in volume. At the same time, the single-layer ceramic capacitor can maintain a higher insulation withstand voltage performance, thereby solving the technical problems of the existing single-layer ceramic capacitors with a low capacitance-to-volume ratio and high dielectric loss.

[0041] 2. Existing Technology: (1) A mixture of various oxides, primarily copper oxide, is coated on a semiconducting SrTiO3 ceramic substrate, which is then sintered at approximately 1000°C to form a grain boundary layer structure. This process generally produces a dielectric constant of 12,000 to 45,000. This dielectric constant is sensitive to the oxidation sintering process parameters and the setter atmosphere, resulting in poor quality stability across production batches.

[0042] (2) Silver paste is applied on the semiconducting BaTiO3 ceramic substrate and sintered. Ag is doped on the surface of the semiconducting ceramic substrate to form an interface insulating layer. This type of ceramic has low insulation resistance and poor withstand voltage, and is only suitable for use in very low operating voltage situations, such as 3.3V.

[0043] Compared with the prior art, the high dielectric constant ceramic substrate of the present invention has a simple manufacturing process, a low heat treatment temperature, and a formed insulating film of good quality. The product batch quality of the high dielectric constant ceramic substrate is highly stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are only some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 It is a schematic structural diagram of the high dielectric constant performance ceramic substrate of the present invention.

[0046] The accompanying drawings are numerals as follows:

[0047] 00. High dielectric constant performance ceramic substrate;

[0048] 1. SrTiO3 ceramic substrate;

[0049] 2. Insulating film; 21. Al2O3 layer; 22. Doped interface layer. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0051] In a specific embodiment, a high dielectric constant ceramic substrate and a preparation method thereof are provided, wherein a semiconducting SrTiO3 ceramic substrate and an insulating film are used to form the high dielectric constant ceramic substrate; the insulating film is arranged on two opposite planes of the SrTiO3 ceramic substrate; wherein pure aluminum is sputtered onto two surfaces of the SrTiO3 ceramic substrate by magnetron vacuum sputtering to form an aluminum film, which is then heat treated; an Al2O3 layer is formed on the surface of the aluminum film, and a doped interface layer is formed at the interface between the aluminum film and the SrTiO3 ceramic substrate; the Al2O3 layer and the doped interface layer constitute the insulating film; the thickness of the Al2O3 layer of the insulating film increases with the heat treatment time, so that the insulating withstand voltage performance of the high dielectric constant ceramic substrate is higher and the dielectric loss is lower; a higher capacitance-to-volume ratio is achieved on a single-layer ceramic capacitor; and the technical problems of low capacitance-to-volume ratio and high dielectric loss in existing single-layer ceramic capacitors are effectively solved.

[0052] In addition, all the contents of the configurations shown in the following embodiments are not necessarily essential as the solution to the invention described in the claims.

[0053] An embodiment of a high dielectric constant ceramic substrate is Figure 1 As shown, it includes a semiconducting SrTiO3 ceramic substrate 1 and an insulating film 2, wherein the insulating film 2 is provided on two opposite planes of the SrTiO3 ceramic substrate 1; wherein pure aluminum is sputtered onto both surfaces of the SrTiO3 ceramic substrate 1 to form aluminum films on both surfaces of the SrTiO3 ceramic substrate 1; the SrTiO3 ceramic substrate 1 with the aluminum films sputtered thereon is placed in a muffle furnace, heated to a heat treatment temperature within 30 minutes, and then kept warm to achieve heat treatment; after the heat treatment, the SrTiO3 ceramic substrate 1 is naturally cooled to room temperature; thereby, an Al2O3 layer 21 is formed on the surface of the aluminum film, and a doped interface layer 22 is formed at the interface between the aluminum film and the SrTiO3 ceramic substrate; the Al2O3 layer 21 and the doped interface layer 22 constitute the insulating film 2; the SrTiO3 ceramic substrate 1 and the two oppositely disposed insulating films 2 constitute a ceramic substrate with high dielectric constant performance, i.e., a high dielectric constant performance ceramic substrate 00.

[0054] Regarding the aluminum content of the above-mentioned pure metallic aluminum, the pure metallic aluminum is 90.0% to 99.9% aluminum.

[0055] The parameter requirements for the SrTiO3 ceramic substrate 1 are as follows: the thickness of the SrTiO3 ceramic substrate 1 is 0.1-0.3 mm, the shape is square, and the length and width are 38 mm x 38 mm.

[0056] The parameter requirements for the aluminum film are: the sputtering time of the SrTiO3 ceramic substrate 1 is 1 minute to 30 minutes; the thickness of the aluminum film increases with the sputtering time, and the thickness of the aluminum film is 0.1 to 3.0 μm.

[0057] Regarding the above-mentioned heat treatment temperature and heat preservation operation time, the heat treatment temperature is 450° C. to 650° C., and the heat preservation operation time is 0.5 hour to 4 hours.

[0058] The Al2O3 layer 21 formed during the heat treatment, the thickness of the insulating film 2 on the SrTiO3 ceramic substrate 1 is 0.1~3.0um; the thickness of the Al2O3 layer 21 of the insulating film 2 becomes thicker as the heat treatment time increases, so that the higher the insulation withstand voltage performance of the high dielectric constant performance ceramic substrate 00, the greater the dielectric loss.

[0059] Based on the structure of the above embodiment of the high dielectric constant ceramic substrate, a preparation method is provided, comprising the following steps: S1, using SrTiO3 powder, adding a binder and a solvent, and preparing a semiconducting SrTiO3 ceramic substrate by ball milling, casting, laminating, cutting, debinding, and reduction sintering;

[0060] S2, ultrasonically cleaning the semiconducting SrTiO3 ceramic substrate in S1 with pure water and ethanol in sequence;

[0061] S3, drying the SrTiO3 ceramic substrate cleaned in S2 for later use;

[0062] S4: sputter coating onto SrTiO3 ceramic substrate;

[0063] S4.1. Place the SrTiO3 ceramic substrate obtained in S3 on a magnetron vacuum sputtering machine carrier and into the receiving chamber of the magnetron vacuum sputtering machine. Evacuate the receiving chamber to a pressure of less than 6.0E-4Pa.

[0064] S4.2. Fill the chamber in S4.1 with argon gas until the pressure reaches 1.0E-2Pa.

[0065] S4.3. Use pure aluminum metal and a magnetron vacuum sputtering machine to perform target sputtering. The sputtering time is controlled within 1 minute to 30 minutes to deposit a layer of aluminum film on the surface of the SrTiO3 ceramic substrate. The thickness of the aluminum film is controlled to be 0.1 to 3.0 μm.

[0066] S4, taking out the SrTiO3 ceramic substrate coated in S3 from the magnetron vacuum sputtering machine carrier;

[0067] S5. Place the coated SrTiO3 ceramic substrate in a muffle furnace, raise the temperature to the heat treatment temperature within 30 minutes under air environment, and then keep the temperature for 0.5 hours to 4 hours;

[0068] The heat treatment temperature of the SrTiO3 ceramic substrate in the muffle furnace is 450°C to 650°C;

[0069] S6, naturally cooling the SrTiO3 ceramic substrate after the heat treatment in S5 to room temperature;

[0070] Through the heat treatment step S5, an Al2O3 insulating layer is formed on the surface of the aluminum film of the SrTiO3 ceramic substrate, and a doped interface layer is formed at the interface between the aluminum film and the SrTiO3 ceramic substrate.

[0071] Experiment 1 was conducted using the high dielectric constant ceramic substrate of the above embodiment and the method for preparing the high dielectric constant ceramic substrate of the embodiment:

[0072] (1) Trim the semiconducting SrTiO3 ceramic substrate into a square substrate with a length x width of 38 mm x 38 mm and a thickness of T1 = 0.3 mm. Ultrasonic cleaning is performed using pure water and ethanol in sequence to remove surface oil and particles. After cleaning, the substrate is dried in an oven for later use.

[0073] (2) The SrTiO3 ceramic substrate processed in (1) is placed on a magnetron vacuum sputtering machine carrier and sent into the containing chamber of the magnetron vacuum sputtering machine. The vacuum is evacuated until the pressure in the containing chamber is less than 6.0E-4Pa, and argon is filled until the pressure in the containing chamber reaches 1.0E-2Pa. Pure aluminum is sputtered through the target for 1 minute to deposit an aluminum film with a thickness of about 0.1um on the surface of the SrTiO3 ceramic substrate.

[0074] (3) Take out the SrTiO3 ceramic substrate that has been sputtered in (2), put the SrTiO3 ceramic substrate into a muffle furnace, and raise the temperature in the furnace to 450°C within 30 minutes under air environment, and then keep it warm for 0.5 hours. After the heat treatment, cool the SrTiO3 ceramic substrate naturally to room temperature, thereby making a high dielectric constant ceramic substrate.

[0075] (4) A Ti / Au conductive layer was fabricated on the high dielectric constant ceramic substrate processed in (3) using a magnetron vacuum sputtering process, and then cut into a first test piece having a length x width of 0.8 mm x 0.8 mm.

[0076] (5) Conduct electrical performance test on the first test piece.

[0077] The electrical performance test results of the first test piece are shown in the following table:

[0078] Performance Project Electrostatic capacitance Cp Loss DF Insulation IR Withstand voltage BDV Test conditions 1.0V, 1KHz 1.0V, 1KHz 25V, 60s 10V / s, boost Test value 3835pF 120×10-4 1.8GΩ 96V

[0079] The calculated dielectric constant is K1=Cp*T1*113.3 / S1=3835*0.30*113.3 / (38*38)=203674.

[0080] Wherein, T1 is the thickness of the SrTiO3 ceramic substrate in Experiment 1, S1 is the area of ​​the first test piece, and Cp is the electrostatic capacitance.

[0081] Experiment 2 was conducted using the high dielectric constant ceramic substrate of the above embodiment and the method for preparing the high dielectric constant ceramic substrate of the embodiment:

[0082] (1) The semiconducting SrTiO3 ceramic substrate was trimmed into a square substrate with a length x width of 38 mm x 38 mm and a thickness of T2 = 0.20 mm. Ultrasonic cleaning was performed using pure water and ethanol in sequence to remove surface oil and particles. After cleaning, the substrate was dried in an oven for later use.

[0083] (2) The SrTiO3 ceramic substrate processed in (1) is placed on a magnetron vacuum sputtering machine carrier and sent into the containing chamber of the magnetron vacuum sputtering machine. The vacuum is evacuated until the pressure in the containing chamber is less than 6.0E-4Pa, and argon is filled until the pressure in the containing chamber reaches 1.0E-2Pa. Pure aluminum is sputtered through the target for 15 minutes to deposit an aluminum film with a thickness of about 1.5um on the surface of the SrTiO3 ceramic substrate.

[0084] (3) Take out the SrTiO3 ceramic substrate that has been sputtered in (2), put the SrTiO3 ceramic substrate into a muffle furnace, and raise the temperature in the furnace to 500°C within 30 minutes under air environment, and then keep it warm for 2 hours. After the heat treatment is completed, the SrTiO3 ceramic substrate is naturally cooled to room temperature to prepare a high dielectric constant ceramic substrate.

[0085] (4) A Ti / Au conductive layer was fabricated on the high dielectric constant ceramic substrate processed in (3) using a magnetron vacuum sputtering process, and then cut into a second test piece having a length x width of 0.8 mm x 0.8 mm.

[0086] (5) Conduct electrical performance test on the second test piece.

[0087] The electrical performance test results of the second test piece are shown in the following table:

[0088] Performance Project Electrostatic capacitance Cp Loss DF Insulation IR Withstand voltage BDV Test conditions 1.0V, 1KHz 1.0V, 1KHz 25V, 60s 10V / s boost Test value 4750pF 85×10-4 6.9GΩ 158V

[0089] The calculated dielectric constant is K2=Cp*T2*113.3 / S2=4750*0.2*113.3 / (38*38)=168179.

[0090] Wherein, T2 is the thickness of the SrTiO3 ceramic substrate in Experiment 2, S2 is the area of ​​the second test piece, and Cp is the electrostatic capacitance.

[0091] Experiment 3 was conducted using the high dielectric constant ceramic substrate of the above embodiment and the method for preparing the high dielectric constant ceramic substrate of the embodiment:

[0092] (1) Trim the semiconducting SrTiO3 ceramic substrate into a square substrate with a length x width of 38 mm x 38 mm and a thickness of T3 = 0.12 mm. Ultrasonic cleaning is performed using pure water and ethanol in sequence to remove surface oil and particles. After cleaning, the substrate is dried in an oven for later use.

[0093] (2) The SrTiO3 ceramic substrate processed in (1) is placed on a magnetron vacuum sputtering machine carrier and sent into the containing chamber of the magnetron vacuum sputtering machine. The vacuum is evacuated until the pressure in the containing chamber is less than 6.0E-4Pa, and argon is filled until the pressure in the containing chamber reaches 1.0E-2Pa. Pure aluminum is sputtered through the target for 30 minutes to deposit an aluminum film with a thickness of about 3um on the surface of the SrTiO3 ceramic substrate.

[0094] (3) Take out the SrTiO3 ceramic substrate that has been sputtered in (2), put the SrTiO3 ceramic substrate into a muffle furnace, and raise the temperature in the furnace to 650°C within 30 minutes under air environment, and then keep it warm for 4 hours. After the heat treatment, cool the SrTiO3 ceramic substrate naturally to room temperature to prepare a high dielectric constant ceramic substrate.

[0095] (4) A Ti / Au conductive layer was fabricated on the high dielectric constant ceramic substrate processed in (3) using a magnetron vacuum sputtering process, and then cut into a third test piece having a length x width of 0.8 mm x 0.8 mm.

[0096] (5) Conduct electrical performance test on the third test piece.

[0097] The electrical performance test results of the third test piece are shown in the following table:

[0098] Performance Project Electrostatic capacitance Cp Loss DF Insulation IR Withstand voltage BDV Test conditions 1.0V, 1KHz 1.0V, 1KHz 25V, 60s 10V / s, boost Test value 4924pF 78×10-4 8.9GΩ 267V

[0099] The calculated dielectric constant is K3=Cp*T3*113.3 / S3=4924*0.12*113.3 / (38*38)=113321.

[0100] Wherein, T3 is the thickness of the SrTiO3 ceramic substrate in Experiment 3, S3 is the area of ​​the third test piece, and Cp is the electrostatic capacitance.

[0101] Existing high-k dielectric ceramic substrates typically use a mixture of various oxides, primarily copper oxide, coated on a semiconducting SrTiO3 ceramic substrate. The substrate is then sintered at around 1000°C to form a grain boundary layer structure. This process typically produces a dielectric constant of 12,000 to 45,000. This dielectric constant is sensitive to the oxidation sintering process parameters and the setter atmosphere, resulting in poor batch stability.

[0102] There is also a method of coating silver paste on a semiconducting BaTiO3 ceramic substrate and sintering it. Ag is doped on the surface of the semiconducting ceramic substrate to form an interface insulating layer. This type of ceramic has low insulation resistance and poor withstand voltage, and is only suitable for use in very low operating voltage situations, such as 3.3V.

[0103] From the above three experiments, it can be seen that by sputtering the aluminum film on the surface of the semiconducting SrTiO3 ceramic substrate, a ceramic / aluminum film acceptor doping interface will be formed through heat treatment, an Al2O3 layer will be formed on the surface of the aluminum film, and a doped interface layer will be formed on the interface between the aluminum film surface and the SrTiO3 ceramic substrate. The doped interface layer and the Al2O3 layer form an insulating film.

[0104] The thickness of the insulating film is mainly affected by the heat treatment temperature and time. The higher the heat treatment temperature and the longer the time, the thicker the Al2O3 layer will be, the higher the insulation withstand voltage performance of the ceramic substrate will be, and its dielectric loss will be reduced.

[0105] The high dielectric constant ceramic substrate of the present invention can realize the production of single-layer ceramic capacitors with larger capacity or smaller size with the same size, so that the single-layer ceramic capacitors maintain higher insulation withstand voltage performance.

[0106] Moreover, compared with the prior art, the high dielectric constant ceramic substrate of the present invention has a simple manufacturing process, a low heat treatment temperature, and a formed insulating film of good quality, so that the product batch quality of the high dielectric constant ceramic substrate is highly stable.

[0107] The technical features of the above embodiments may be combined arbitrarily. To simplify the description, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. A high dielectric constant ceramic substrate, characterized in that: It includes a semiconducting SrTiO3 ceramic substrate and an insulating film, wherein the insulating film is provided on two opposite planes of the SrTiO3 ceramic substrate; wherein pure aluminum is sputtered onto both surfaces of the SrTiO3 ceramic substrate by magnetron vacuum sputtering to form aluminum thin films on both surfaces of the SrTiO3 ceramic substrate; The thickness of the aluminum film increases with the sputtering time, and the thickness of the aluminum film is 0.1 to 3.0 μm; The SrTiO3 ceramic substrate sputtered with the aluminum film is placed in a muffle furnace, heated to a heat treatment temperature within 30 minutes, and then kept warm to achieve heat treatment; after the heat treatment, the SrTiO3 ceramic substrate is naturally cooled to room temperature; thereby forming an Al2O3 layer on the surface of the aluminum film and a doped interface layer at the interface between the aluminum film and the SrTiO3 ceramic substrate; The Al2O3 layer and the doped interface layer constitute the insulating film; the SrTiO3 ceramic substrate and the two oppositely arranged insulating films constitute a high dielectric constant performance ceramic substrate; The thickness of the insulating film on the SrTiO3 ceramic substrate is 0.1 to 3.0 μm; the thickness of the Al2O3 layer of the insulating film increases with the heat treatment time, so that the insulating withstand voltage performance of the high dielectric constant ceramic substrate is higher and the dielectric loss is lower.

2. The high dielectric constant ceramic substrate according to claim 1, characterized in that: The thickness of the SrTiO3 ceramic substrate is 0.1-0.3 mm.

3. The high dielectric constant ceramic substrate according to claim 1, wherein: The pure aluminum is 90.0% to 99.9% aluminum.

4. The high dielectric constant ceramic substrate according to claim 1, characterized in that: The sputtering time of the SrTiO3 ceramic substrate is controlled within 1 minute to 30 minutes.

5. The high dielectric constant ceramic substrate according to claim 1, wherein: The heat treatment temperature is 450°C to 650°C.

6. The high dielectric constant ceramic substrate according to claim 5, characterized in that: The heat preservation operation time is 0.5 hours to 4 hours.

7. A method for preparing a high dielectric constant ceramic substrate according to claim 1, characterized in that: The following steps are involved: S1. Using SrTiO3 powder, adding binder and solvent, and preparing semiconducting SrTiO3 ceramic substrate by ball milling, tape casting, lamination, cutting, debinding, and reduction sintering; S2, ultrasonically cleaning the semiconducting SrTiO3 ceramic substrate in S1 with pure water and ethanol in sequence; S3, drying the SrTiO3 ceramic substrate cleaned in S2 for later use; S4: sputter coating onto SrTiO3 ceramic substrate; S4.

1. Place the SrTiO3 ceramic substrate obtained in S3 on a magnetron vacuum sputtering machine carrier and into the receiving chamber of the magnetron vacuum sputtering machine. Evacuate the receiving chamber to a pressure of less than 6.0E-4Pa. S4.

2. Fill the chamber in S4.1 with argon gas until the pressure reaches 1.0E-2Pa. S4.

3. Using pure aluminum, perform target sputtering using a magnetron vacuum sputtering machine with a sputtering time controlled between 1 and 30 minutes to deposit an aluminum film on the surface of the SrTiO3 ceramic substrate. The thickness of the aluminum film is controlled between 0.1 and 3.0 μm. S4, taking out the SrTiO3 ceramic substrate sputtered in S3 from the magnetron vacuum sputtering machine carrier; S5. Place the sputtered SrTiO3 ceramic substrate in a muffle furnace, raise the temperature to the heat treatment temperature within 30 minutes under air environment, and then keep the temperature for 0.5 hours to 4 hours; The heat treatment temperature of the SrTiO3 ceramic substrate in the muffle furnace is 450°C to 650°C; S6, naturally cooling the SrTiO3 ceramic substrate after the heat treatment in S5 to room temperature; Through the heat treatment step S5, an Al2O3 layer is formed on the surface of the aluminum film of the SrTiO3 ceramic substrate, and a doped interface layer is formed at the interface between the aluminum film and the SrTiO3 ceramic substrate.

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