Preparation method and application of composite substrate

Abstract

The invention belongs to the field of ceramic and metal compounding, and particularly discloses a preparation method and application of a composite substrate, and the preparation method comprises the following steps: pre-oxidizing a copper base material to form a copper oxide layer on the surface of the copper base material; forming an aluminum oxide layer on at least one surface of the ceramic substrate by adopting a magnetron sputtering method; the copper oxide layer and the aluminum oxide layer are attached and then subjected to heat treatment, and the composite substrate is obtained. According to the preparation method, the aluminum oxide layer is prepared on the surface of the ceramic substrate through the magnetron sputtering method, the bonding strength of the copper layer and the ceramic substrate can be remarkably improved under the condition that the heat conductivity of the composite substrate is not affected, and the bonding strength of the copper layer and the ceramic substrate reaches 10-15 MPa.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ceramic and metal composites, and particularly relates to a preparation method of a composite substrate and application thereof. BACKGROUND

[0002] With the development of electronic technology, the chip integration is continuously improved, the circuit wiring width is fine, the power dissipation per unit area is larger and larger, which causes the heat generation to increase and easily causes the failure of devices. Direct Bond Copper (DBC) ceramic substrate becomes an important electronic packaging material due to its good heat conduction performance.

[0003] The DBC ceramic substrate realizes the direct copper bonding of the ceramic substrate by the liquid phase wetting of copper-oxygen eutectic to the surface layer of alumina and the reaction and combination thereof. The DBC ceramic substrate of the prior art has the problems of small contact area between the copper layer and the ceramic layer, low bonding strength and inability to meet the actual application. SUMMARY

[0004] In order to overcome at least one technical problem existing in the prior art, one of the purposes of the present application is to provide a preparation method of a composite substrate.

[0005] The second purpose of the present application is to provide the application of the preparation method of the composite substrate in the preparation of electronic products.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] The first aspect of the present application provides a preparation method of a composite substrate, comprising the following steps:

[0008] Pre-oxidizing the copper base material to form a copper oxide layer on the surface of the copper base material;

[0009] Forming an alumina layer on at least one surface of the ceramic substrate by a magnetron sputtering method;

[0010] After the copper oxide layer and the alumina layer are attached, heat treatment is performed to obtain the composite substrate.

[0011] The application makes copper substrate containing copper oxide layer and ceramic substrate containing aluminum oxide layer into an integrated structure by heat treatment. According to Cu-O binary phase diagram, the system is in liquid state when oxygen mass fraction is 0.39% and temperature is above 1065℃. Therefore, when copper oxide layer and aluminum oxide layer are heat treated and bonded, Cu-O system and aluminum oxide form eutectic phase CuAlO2, and play a role of infiltrating ceramic substrate surface and realizing combination of copper substrate and ceramic substrate. The application uses magnetron sputtering method to prepare aluminum oxide layer, can more accurately control component content, thickness and particle size of aluminum oxide layer, can reduce surface roughness of aluminum oxide layer, ensure copper oxide eutectic liquid phase fully infiltrates, promote combination, and further improve combination strength.

[0012] In some embodiments of the application, the copper substrate is copper foil.

[0013] In some embodiments of the application, the pre-oxidation temperature is 500-700℃; in some specific embodiments of the application, the pre-oxidation temperature is any one of 500℃, 520℃, 550℃, 570℃, 600℃, 620℃, 650℃, 670℃, 700℃ or a range value formed by any two of them; in some preferred embodiments of the application, the pre-oxidation temperature is 580-700℃; in some preferred embodiments of the application, the pre-oxidation temperature is 580-620℃.

[0014] In some embodiments of the application, the pre-oxidation temperature is 500-700℃; in some specific embodiments of the application, the pre-oxidation temperature is any one of 500℃, 520℃, 550℃, 570℃, 600℃, 620℃, 650℃, 670℃, 700℃ or a range value formed by any two of them; in some preferred embodiments of the application, the pre-oxidation temperature is 580-700℃; in some preferred embodiments of the application, the pre-oxidation temperature is 580-620℃.

[0015] In some embodiments of the application, the pre-oxidation temperature is 500-700℃; in some specific embodiments of the application, the pre-oxidation temperature is any one of 500℃, 520℃, 550℃, 570℃, 600℃, 620℃, 650℃, 670℃, 700℃ or a range value formed by any two of them; in some preferred embodiments of the application, the pre-oxidation temperature is 580-700℃; in some preferred embodiments of the application, the pre-oxidation temperature is 580-620℃.

[0016] In some embodiments of the present application, the pre-oxidation is performed under an oxygen-containing gas, the oxygen-containing gas containing oxygen, the molar ratio of the oxygen and the oxygen-containing gas being (2x10 -4 ~ 6x10 -4 ): 1; in some specific embodiments of the present application, the molar ratio of the oxygen and the oxygen-containing gas is any one of 2x10 -4 : 1, 3x10 -4 : 1, 4x10 -4 : 1, 5x10 -4 : 1, 6x10 -4 : 1 or a range formed by any two of them; in some preferred embodiments of the present application, the molar ratio of the oxygen and the oxygen-containing gas is (4x10 -4 ~ 5x10 -4 ): 1.

[0017] In some embodiments of the present application, the oxygen-containing gas further comprises an inert gas; the inert gas is selected from at least one of nitrogen, helium, neon, argon.

[0018] In some embodiments of the present application, the sputtering target of the magnetron sputtering is metallic aluminum.

[0019] In some embodiments of the present application, the time of the magnetron sputtering is 0.2~2h; in some specific embodiments of the present application, the time of the magnetron sputtering is any one of 0.2h, 0.5h, 0.7h, 1h, 1.2h, 1.4h, 1.5h, 1.6h, 1.8h, 2h or a range formed by any two of them; in some preferred embodiments of the present application, the time of the magnetron sputtering is 0.5~1h; in some preferred embodiments of the present application, the time of the magnetron sputtering is 0.5~0.7h.

[0020] In some embodiments of the present application, the temperature of the ceramic substrate during the magnetron sputtering is 150~350℃; in some specific embodiments of the present application, the temperature of the ceramic substrate during the magnetron sputtering is any one of 150℃, 170℃, 200℃, 220℃, 240℃, 250℃, 260℃, 280℃, 300℃, 320℃, 340℃, 350℃ or a range formed by any two of them; in some preferred embodiments of the present application, the temperature of the ceramic substrate during the magnetron sputtering is 180~220℃.

[0021] In some embodiments of the present application, the sputtering atmosphere of the magnetron sputtering is a mixture of an inert gas and an oxidizing gas, the molar ratio of the oxidizing gas and the mixture being (5x10 -7 ~ 5x10 -31, 1x10 -7 1, 1x10 -6 1, 5x10 -6 1, 1x10 -5 1, 5x10 -5 1, 1x10 -4 1, 5x10 -4 1, 1x10 -3 1, 5x10 -3 1, 1x10 -6 1, 1x10 -3 1, 1x10 -5 1, 1x10 -3 1, 1x10

[0022] In some embodiments of the present application, the inert gas in the magnetron sputtering is selected from at least one of nitrogen, helium, neon, and argon.

[0023] In some embodiments of the present application, the oxidizing gas comprises at least one of water vapor and oxygen.

[0024] In the present application, the parameter selection of the magnetron sputtering has an important influence on the aluminum oxide layer. The type and volume ratio of the oxidizing gas have a certain influence on the crystal form and crystallinity of the aluminum oxide. When the oxidizing property is too low, elemental aluminum is co-deposited, and when the oxidizing property is too high, the proportion of amorphous aluminum oxide is high. The temperature has a certain influence on the crystal form and particle size of the aluminum oxide. When the temperature is too high, the proportion of α-Al2O3 is high, and when the temperature is too low, the crystallinity is low, and the proportion of amorphous aluminum oxide is high, which is not conducive to the infiltration of the copper-oxygen eutectic liquid phase. The magnetron sputtering time mainly affects the thickness of the aluminum oxide film, and the thickness of the aluminum oxide film will affect the bonding strength and thermal conductivity of the composite substrate.

[0025] In some embodiments of the present application, the temperature of the heat treatment is 1065-1080℃; in some specific embodiments of the present application, the temperature of the heat treatment is any one of 1065℃, 1067℃, 1070℃, 1072℃, 1075℃, 1077℃, 1080℃ or a range value formed by any two of them; in some preferred embodiments of the present application, the temperature of the heat treatment is 1067-1075℃; in some preferred embodiments of the present application, the temperature of the heat treatment is 1067-1072℃.

[0026] In some embodiments of the present application, the heat treatment time is 20-80 min; in some specific embodiments of the present application, the heat treatment time is any one of 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or a range formed by any two of them; in some preferred embodiments of the present application, the heat treatment time is 30-50 min.

[0027] In some embodiments of the present application, the alumina layer contains γ-Al2O3 and θ-Al2O3, and the mass of γ-Al2O3 and θ-Al2O3 is 30-60% of the total mass of the alumina layer.

[0028] In some specific embodiments of the present application, the mass percentage of γ-Al2O3 and θ-Al2O3 in the alumina layer can be selected from any one of 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60% or a range formed by any two of them. In some preferred embodiments of the present application, the mass percentage of γ-Al2O3 and θ-Al2O3 is 34-56%; in some preferred embodiments of the present application, the mass percentage of γ-Al2O3 and θ-Al2O3 is 43-56%; in some preferred embodiments of the present application, the mass percentage of γ-Al2O3 and θ-Al2O3 is 46-56%. When the mass percentage of γ-Al2O3 and θ-Al2O3 is within the range defined in the present application, sufficient wetting can be promoted, γ-Al2O3 and θ-Al2O3 are metastable crystal phases, and the surface energy of the copper-oxygen eutectic liquid phase in contact with them is higher than that of α-Al2O3, so the contact angle of the copper-oxygen eutectic liquid phase on γ-Al2O3 and θ-Al2O3 is small, and the wetting is more sufficient, which is beneficial to improve the bonding strength.

[0029] In some embodiments of the present application, the thickness of the alumina layer is 0.9-2.1 μm; in some specific embodiments of the present application, the thickness of the alumina layer can be selected from any one of 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm or a range formed by any two of them. In some preferred embodiments of the present application, the thickness of the alumina layer is 1.2-1.9 μm; in some preferred embodiments of the present application, the thickness of the alumina layer is 1.2-1.5 μm.

[0030] In some embodiments of the present application, the alumina layer also contains α-Al2O3.

[0031] In some embodiments of the present application, the particle size of a-Al2O3 in the alumina layer is 50-230 nm; in some specific embodiments of the present application, the particle size of a-Al2O3 in the alumina layer can be selected from any one value or a range value formed by any two values selected from 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm. In some preferred embodiments of the present application, the particle size of a-Al2O3 in the alumina layer is 60-90 nm; in some preferred embodiments of the present application, the particle size of a-Al2O3 in the alumina layer is 74-86 nm.

[0032] In some embodiments of the present application, the particle size of a-Al2O3 in the alumina layer is 50-230 nm; in some specific embodiments of the present application, the particle size of a-Al2O3 in the alumina layer can be selected from any one value or a range value formed by any two values selected from 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm. In some preferred embodiments of the present application, the particle size of a-Al2O3 in the alumina layer is 60-90 nm; in some preferred embodiments of the present application, the particle size of a-Al2O3 in the alumina layer is 74-86 nm.

[0033] In some embodiments of the present application, the particle size of a-Al2O3 in the alumina layer is 50-230 nm; in some specific embodiments of the present application, the particle size of a-Al2O3 in the alumina layer can be selected from any one value or a range value formed by any two values selected from 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm. In some preferred embodiments of the present application, the particle size of a-Al2O3 in the alumina layer is 60-90 nm; in some preferred embodiments of the present application, the particle size of a-Al2O3 in the alumina layer is 74-86 nm.

[0034] In some embodiments of the present application, the ceramic substrate is selected from an alumina ceramic substrate or an aluminum nitride ceramic substrate.

[0035] The second aspect of the present application provides an application of the preparation method of the composite substrate of the first aspect of the present application in the preparation of electronic products.

[0036] In some embodiments of the present application, the electronic product is selected from a sensor, an LED module, a laser diode, a photovoltaic device, a microwave radio frequency device, or a 5G optical communication device.

[0037] The present application has the beneficial effect that the preparation method in the present application can significantly improve the bonding strength of the copper layer and the ceramic substrate without affecting the thermal conductivity of the composite substrate by preparing an aluminum oxide layer on the surface of the ceramic substrate through a magnetron sputtering method, so that the bonding strength of the copper layer and the ceramic substrate reaches 10-15 MPa.

[0038] In addition, the preparation method in the present application can further improve the bonding strength of the copper base material and the ceramic substrate by adjusting the specific parameters of the magnetron sputtering method and further adjusting the thickness and crystal structure of the aluminum oxide layer, which is beneficial to ensure the stable performance of the product, so as to obtain a composite substrate with high reliability and good heat conduction performance. DETAILED DESCRIPTION

[0039] The specific embodiments of the present application are further described in detail below with reference to examples, but the implementation and protection of the present application are not limited thereto. It should be noted that if the following processes are not specifically described in detail, they can be implemented or understood by referring to the prior art. If the reagents or instruments used are not marked with the manufacturer, they are conventional products that can be purchased on the market.

[0040] In the following examples, the mole fraction of oxygen refers to the ratio between the number of moles of oxygen and the total number of moles of oxygen-containing gas (i.e., the mixture of oxygen and nitrogen) used during pre-oxidation, i.e., the mole fraction of oxygen = the number of moles of oxygen ÷ the total number of moles of oxygen-containing gas; for example, the mole fraction of oxygen in Example 1 is 4x10 -4 , which means the number of moles of oxygen ÷ the number of moles of oxygen-containing gas = 4x10 -4 .

[0041] In the following examples, magnetron sputtering is carried out in a mixture of inert gas (such as helium) and oxidizing gas (such as water vapor or oxygen), and the mole fraction of the oxidizing gas = the number of moles of the oxidizing gas ÷ the number of moles of the mixture; for example, the mole fraction of water vapor in Example 1 is 1x10 -5 , which means the number of moles of water vapor ÷ the number of moles of the mixture = 1x10 -5 .

[0042] Example 1

[0043] This example provides a preparation method of a composite substrate, comprising the following steps:

[0044] S1, pre-oxidation treatment: take the thickness of 0.2mm oxygen-free copper foil ultrasonic cleaning for 3 minutes, remove the surface of the oxygen-free copper foil oil, then heated to 600℃ in a tube furnace with a heating rate of 10℃ / min for 1h pre-oxidation step is carried out in the presence of oxygen gas, oxygen gas is oxygen and nitrogen mixed gas, oxygen molar fraction is 4x10 -4 , so that the copper foil surface forms a copper oxide layer, and the pre-oxidized copper foil is obtained.

[0045] S2, magnetron sputtering treatment: the formation of aluminum oxide layer on the aluminum nitride ceramic substrate by magnetron sputtering, the vacuum degree of magnetron sputtering is set to 100Pa, direct current discharge 220V, 0.5A; magnetron sputtering is carried out in the presence of oxygen atmosphere, the composition of the oxidation atmosphere is: is composed of helium and water vapor, the mixed gas of helium and water vapor is introduced with a gas flow of 100sccm, and the molar fraction of water vapor is controlled to be 1x10 -5 , the magnetron sputtering time is controlled to be 0.5h, and the substrate temperature (i.e. the temperature of the aluminum nitride ceramic substrate) is set to 200℃.

[0046] S3, heat treatment: the pre-oxidized copper foil prepared in step S1 is heat treated with the aluminum nitride ceramic substrate with an aluminum oxide layer in the nitrogen atmosphere, so that the copper oxide layer in the pre-oxidized copper foil contacts and reacts with the aluminum oxide layer. The pre-oxidized copper foil is bonded to the aluminum nitride ceramic substrate with an aluminum oxide layer, the heat treatment temperature is 1070℃, the heat treatment time is 30min, and the composite substrate in this example is prepared.

[0047] The specific parameter data in steps S1, S2 and S3 of this example are shown in Table 1.

[0048] Examples 2-6

[0049] The difference between the preparation method of the composite substrate in examples 2-6 and example 1 is only that the composition of the oxidation atmosphere during magnetron sputtering in step S2 is different, as shown in Table 1, wherein example 2 and example 5 use oxygen instead of water vapor in example 1 and change the molar fraction of oxygen.

[0050] Examples 7-10

[0051] The difference between the preparation method of the composite substrate in examples 7-10 and example 1 is only that the sputtering time during magnetron sputtering in step S2 is different, as shown in Table 1.

[0052] Examples 11-14

[0053] The preparation method of the composite substrate in Examples 11-14 is different from that of Example 1 only in that the substrate temperature during magnetron sputtering in step S2 is different, and the specific parameters are shown in Table 1 below.

[0054] Examples 15-20

[0055] The preparation method of the composite substrate in Examples 15-20 is different from that of Example 1 only in that the specific parameters of step S1, step S2 and step S3 are different, and the specific parameters are shown in Table 1 below.

[0056] Table 1 Preparation parameters of the composite substrate in Examples 1-20

[0057]

[0058]

[0059] Comparative Example 1

[0060] The present example provides a preparation method of a composite substrate, comprising the following steps:

[0061] S1, pre-oxidation treatment: take an oxygen-free copper foil with a thickness of 0.2 mm, ultrasonic clean for 3 minutes to remove oil stains on the surface of the oxygen-free copper foil, then heat up to 600℃ at a rate of 10℃ / min in a tube furnace for pre-oxidation for 1h, the molar fraction of oxygen in the oxidation atmosphere is 4×10 -4 to form an oxide film on the surface of the copper foil, and obtain a pre-oxidized copper foil.

[0062] S2, pre-oxidation treatment: pre-oxidation treatment is performed on the aluminum nitride ceramic substrate, the pre-oxidation temperature is set to 1000℃, the oxidation time is 2h, the oxidation atmosphere is a mixture of nitrogen and oxygen, the molar fraction of oxygen in the oxidation atmosphere is 0.25%, and the molar fraction of nitrogen is 99.75%. After pre-oxidation treatment, an aluminum oxide layer is formed on the aluminum nitride ceramic substrate, and the thickness of the aluminum oxide layer is 1.2μm.

[0063] S3, thermal treatment bonding: the pre-oxidized copper foil prepared in step S1 is bonded to the aluminum nitride ceramic substrate with the aluminum oxide layer formed in step S2 under a nitrogen atmosphere, so that the oxide film in the pre-oxidized copper foil contacts and reacts with the aluminum oxide layer. The pre-oxidized copper foil is bonded to the aluminum nitride ceramic substrate with the aluminum oxide layer, the thermal treatment temperature is 1070℃, and the thermal treatment time is 30min, thereby obtaining the composite substrate in the present example.

[0064] Comparative Example 2

[0065] The present example provides a preparation method of a composite substrate, comprising the following steps:

[0066] S1: Put the aluminum nitride ceramic substrate into an aqueous solution for hydrolysis, the pH value of the aqueous solution is 13, the hydrolysis temperature is 200°C, and the hydrolysis time is 8 hours.

[0067] S2: The hydrolyzed aluminum nitride ceramic substrate is heat treated at a temperature of 1200°C for 2 hours to obtain an aluminum nitride ceramic substrate covered with a θ-Al2O3 ceramic layer on the surface.

[0068] S3: The aluminum nitride ceramic substrate covered with the Al2O3 ceramic layer is attached to the surface of the pre-oxidized Cu, and sintered at 1050°C in a N2 protective atmosphere for 30 minutes to obtain the composite substrate in this example.

[0069] Performance test

[0070] The performance of the aluminum oxide layer and the composite substrate in Examples 1-20 and Comparative Examples 1-2 is tested according to the following test methods, and the specific test methods are as follows:

[0071] Mass percentage of γ-Al2O3 and θ-Al2O3 in the aluminum oxide layer: pure γ-Al2O3 and pure θ-Al2O3 phase aluminum oxide are purchased, then mixed with α-Al2O3 according to a mass ratio of 1:1, respectively, and the intensity ratio K1 and K2 of the characteristic peaks of each are tested by XRD; then the aluminum oxide layer is tested by XRD, and K1 and K2 are used to fit the mass content of the γ-Al2O3 and θ-Al2O3 phases;

[0072] Thickness of the aluminum oxide layer: take the substrate sample after step S2 in the above examples and comparative examples to take a cross-sectional SEM image, which can obtain the thickness information of the aluminum oxide layer;

[0073] Aluminum oxide particle size: take the substrate sample after step S2 in the above examples and comparative examples to take a cross-sectional SEM image, which can obtain the size information of the aluminum oxide particles in the aluminum oxide layer on the aluminum nitride ceramic substrate;

[0074] Bonding strength: use a peeling strength tester to tear off the copper foil in the composite substrate from the aluminum nitride ceramic substrate, and record the data by the machine to obtain the bonding strength of the copper foil and the ceramic substrate;

[0075] Thermal conductivity: use a thermal conductivity tester to test the thermal conductivity of the composite substrate;

[0076] The performance data of the ceramic substrate in Examples 1-20 and Comparative Examples 1-2 measured according to the above test methods are shown in Table 2 below.

[0077] Table 2 Performance data of the ceramic substrate

[0078]

[0079]

[0080] As shown in Table 2, in the composite substrates prepared in Examples 1-20 of the present application, the total mass percentage of γ-Al2O3 and θ-Al2O3 in the alumina layer is 34-56%, the thickness of the alumina layer is 0.98-2.06 μm, the average size of the alumina particles is 51-226 nm, the bonding strength of the copper foil to the ceramic substrate is 10.5-13.7 MPa, and the thermal conductivity is 25-36 W / (m·K). Compared with Comparative Examples 1-2, by adjusting the content of γ-Al2O3 and θ-Al2O3 in the alumina layer, the thickness of the alumina layer, and the particle size of the alumina, the present application can significantly improve the bonding strength of the copper foil to the ceramic substrate without affecting the thermal conductivity of the composite substrate, and the specific analysis is as follows:

[0081] Comparative Example 1 uses the pre-oxidation method commonly used in the prior art to treat the ceramic substrate, which has a long treatment time, and the bonding strength of the copper foil to the ceramic substrate of the prepared composite substrate is not as good as that of the examples of the present application.

[0082] Comparative Example 2 uses another hydrolysis treatment method of the prior art to treat the ceramic substrate, which has a long treatment time, and the alumina layer formed has a large thickness and a large particle size, and contains too much θ-Al2O3. It should be noted that θ-Al2O3 is not the more the better, and its thermal conductivity is not as good as that of α-Al2O3. In excess, it will have a negative effect on the thermal conductivity of the composite substrate, and a thicker alumina layer will further result in a composite substrate with poor thermal conductivity. In addition, a larger alumina particle size will result in poor bonding of the copper foil to the ceramic substrate, thereby significantly reducing the bonding strength.

[0083] As shown in Comparative Examples 1-6, the oxidizing property of the atmosphere during magnetron sputtering has a certain effect on the bonding strength of the composite substrate. Too strong or too weak oxidizing property is not conducive to improving the bonding strength of the composite substrate.

[0084] As shown in Comparative Example 1 and Examples 7-10, the magnetron sputtering time mainly affects the thickness of the alumina layer, and the thickness of the alumina layer in turn affects the bonding strength and thermal conductivity of the composite substrate. Too thin is not conducive to improving the bonding strength, and too thick has an adverse effect on the thermal conductivity.

[0085] As shown in Comparative Example 1 and Examples 11-14, the magnetron sputtering temperature affects the phase ratio of γ-Al2O3 and θ-Al2O3 and the particle size of the alumina, and in turn affects the bonding strength and thermal conductivity. Therefore, the magnetron sputtering temperature should be controlled within an appropriate range to ensure the performance of the composite substrate.

[0086] The above has described the embodiments of the present application in detail, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method of preparing a composite substrate, characterized by: The method comprises the following steps: pre-oxidizing a copper substrate to form a copper oxide layer on the surface of the copper substrate; forming an aluminum oxide layer on at least one surface of a ceramic substrate by a magnetron sputtering method; bonding the copper oxide layer and the aluminum oxide layer and then performing heat treatment to obtain the composite substrate.

2. The method for producing a composite substrate according to claim 1, characterized by: The pre-oxidation has at least one of the following characteristics: (a1) the temperature of the pre-oxidation is 500-700℃; (a2) the temperature rising rate of the pre-oxidation is 5-15℃ / min; (a3) the time of the pre-oxidation is 0.5-2h; (a4) the pre-oxidation is carried out under an oxygen-containing gas, the oxygen- containing gas containing oxygen, the molar ratio of the oxygen to the oxygen-containing gas being (2 x 10 -4 ~ 6 x 10 -4 ) :

1.

3. The method of producing a composite substrate according to claim 1, characterized by: The magnetron sputtering method has at least one of the following characteristics: (b1) the time of the magnetron sputtering is 0.2-2h; (b2) the temperature of the ceramic substrate during the magnetron sputtering is 150-350℃; (b3) the sputtering atmosphere of the magnetron sputtering is a mixed gas of an inert gas and an oxidizing gas, and the molar ratio of the oxidizing gas to the mixed gas is (5 x 10 -7 ~ 5 x 10 -3 ) :

1. (b3) the sputtering atmosphere of the magnetron sputtering is a mixed gas of an inert gas and an oxidizing gas, and the molar ratio of the oxidizing gas to the mixed gas is (5 x 10 -7 ~ 5 x 10 -3 ) :

1.

4. The method for producing a composite substrate according to claim 3, characterized by: The oxidation gas comprises at least one of water vapor and oxygen.

5. The method of producing a composite substrate according to claim 1, wherein: The heat treatment has at least one of the following characteristics: (c1) the temperature of the heat treatment is 1065-1080℃; (c2) the time of the heat treatment is 20-80min.

6. The method of producing a composite substrate according to claim 1, characterized by: The aluminum oxide layer contains γ-Al2O3 and θ-Al2O3, and the mass of γ-Al2O3 and θ-Al2O3 is 30-60% of the total mass of the aluminum oxide layer.

7. The method of producing a composite substrate according to claim 6, wherein: The aluminum oxide layer also contains α-Al2O3.

8. The method of producing a composite substrate according to claim 6 or 7, characterized by: In the aluminum oxide layer, the particle size of α-Al2O3, γ-Al2O3 and θ-Al2O3 is 50-230nm.

9. The method of producing a composite substrate according to claim 1, wherein: The thickness of the aluminum oxide layer is 0.9-2.1μm.

10. Application of the preparation method of the composite substrate according to any one of claims 1-9 in the preparation of electronic products.

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