Insulating substrate based on diamond ceramic layer and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductors, and particularly relates to an insulating substrate based on a diamond ceramic layer and a preparation method of the insulating substrate. The insulating substrate of the diamond ceramic layer is sequentially provided with an upper copper layer, the diamond ceramic layer and a lower copper layer from top to bottom along the thickness direction, the thickness of the diamond ceramic layer is 300-630 microns, and the thicknesses of the upper copper layer and the lower copper layer are both 250-300 microns. The insulating substrate is formed based on the diamond ceramic material, so that the thermal resistance from the power device to the packaging insulating substrate is reduced, the heat dissipation efficiency of the packaging insulating substrate is improved, and the heat dissipation efficiency of the silicon carbide power module is improved; the diamond ceramic layer provides electrical insulation and heat conduction, and the upper and lower copper layers provide heat dissipation and electrical conduction, so that the heat dissipation capability and the current bearing capability of the power module can be effectively improved, the working temperature of the module is reduced, the working power density of the silicon carbide chip is improved, and the reliability of the silicon carbide module is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to an insulating substrate based on a diamond ceramic layer and a preparation method thereof. Background Art

[0002] Power module packaging is a vital component of modern electronic devices and is widely used in power electronics, automobiles, renewable energy and other fields. In these applications, power modules are subjected to large currents and powers, so their heat dissipation performance has an important impact on the reliability and stability of the system. The thermal management of power module packaging usually relies on good heat dissipation design to ensure that the module can operate stably for a long time in a high temperature environment.

[0003] Traditional power module packaging usually uses aluminum oxide or aluminum nitride ceramic insulating substrates. These materials have high thermal conductivity and can effectively conduct heat, thereby improving the heat dissipation efficiency of the module. However, as power density continues to increase, the inherent difference in thermal expansion coefficient between aluminum oxide or aluminum nitride ceramic plates and copper will lead to poor heat dissipation efficiency at high temperatures, which can easily cause the ceramic plate to crack or the copper layer to peel off, and can no longer meet the increasingly stringent heat dissipation requirements. Summary of the invention

[0004] In order to solve the above problems, the present invention provides an insulating substrate based on a diamond ceramic layer and a preparation method thereof. The present invention is based on an insulating substrate formed of a diamond ceramic material to reduce the thermal resistance from the power device to the package insulating substrate, improve the heat dissipation efficiency of the package insulating substrate, thereby improving the heat dissipation efficiency of the silicon carbide power module and the operating temperature of the silicon carbide power module; at the same time, the thermal conductivity of the diamond ceramic layer is better than that of the traditional insulating layer, which will not cause the temperature of the upper copper layer or the lower copper layer directly bonded to the diamond ceramic layer to be too high, and the heat consumption energy is dissipated in time. The diamond ceramic layer provides electrical insulation and heat conduction, and the upper and lower copper layers provide heat dissipation and electrical conductivity, which can effectively improve the heat dissipation capacity and current carrying capacity of the power module, reduce the operating temperature of the module, increase the power density of the silicon carbide chip, prevent the silicon carbide chip from being damaged by excessive thermal stress, and improve the reliability of the silicon carbide rate module.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] On the one hand, the present invention provides an insulating substrate based on a diamond ceramic layer, wherein the insulating substrate of the diamond ceramic layer is provided with an upper copper layer, a diamond ceramic layer and a lower copper layer in sequence from top to bottom along the thickness direction, the thickness of the diamond ceramic layer is 300μm to 630μm, and the thickness of the upper copper layer and the lower copper layer are both 250μm to 300μm.

[0007] The insulating substrate of the diamond ceramic layer provided by the present invention uses diamond ceramic material as the diamond ceramic layer. Diamond, as an insulating material, has excellent thermal conductivity, and the thermal conductivity can reach above 2000W / m·K, which is far higher than that of traditional aluminum substrates and aluminum nitride materials. Diamond not only has extremely high thermal conductivity, but also has excellent mechanical strength, corrosion resistance and electrical insulation. Based on this, the power module packaging technology based on diamond as the ceramic layer substrate of the present invention can effectively improve the heat dissipation performance, reduce the operating temperature of the module, and thus improve the efficiency and service life of the module. In addition, the high thermal conductivity of the diamond material can also better protect other components in the power module and reduce performance degradation and failures caused by overheating. The present invention controls the matching of the thermal expansion coefficients of the diamond ceramic layer and the metal layer by adjusting the thickness of the diamond ceramic layer and the upper copper layer and the lower copper layer. The diamond ceramic layer provides electrical insulation and heat conduction, and the upper copper layer and the lower copper layer provide heat dissipation and electrical conductivity. This can effectively improve the heat dissipation capacity and current carrying capacity of the power module, reduce the operating temperature of the module, increase the power density of the silicon carbide chip, reduce the thermal stress and junction temperature of the silicon carbide chip, and achieve the purpose of quickly reducing the junction temperature of the power device, thereby improving the heat dissipation efficiency of the silicon carbide module, increasing the operating temperature of the silicon carbide power module, and ensuring the mechanical stability and long-term reliability of the insulating substrate.

[0008] It should be noted that the thickness of the diamond ceramic layer and the upper and lower copper layers needs to be balanced during design. When the diamond ceramic layer is too thick, the heat conduction path becomes longer, which will lead to a decrease in the efficiency of heat conduction, thereby affecting the heat dissipation effect, and will also increase the thermal resistance of the overall insulating substrate, resulting in local overheating or heat accumulation. It will also affect the matching of thermal expansion between the copper layer and the diamond ceramic layer, resulting in greater thermal stress, which may cause the bonding strength between the diamond ceramic layer and the copper layer to decrease, and easily cause interface delamination between the diamond ceramic layer and the copper layer, thereby affecting the mechanical stability and long-term reliability of the substrate. In addition, when the diamond ceramic layer is too thick, it will make the electrical isolation stronger, but it may also cause higher electrical losses, especially in high-frequency applications; when the thickness of the upper and lower copper layers is too thick, it will help improve the thermal conductivity and mechanical strength of the substrate, but it will increase the weight of the substrate, increase the mechanical stress during the production process, affect the overall rigidity and stability of the diamond ceramic layer, and cause a large difference in thermal expansion, thereby causing excessive thermal stress, so that more heat is concentrated in the copper layer, and the thermal conductivity of the diamond ceramic layer is limited, resulting in heat that cannot be effectively dissipated, affecting the reliability of the structure, especially in an environment with large temperature changes.

[0009] In some embodiments, a first bonding layer is provided between the diamond ceramic layer and the upper copper layer, a second bonding layer is provided between the diamond ceramic layer and the lower copper layer, the thickness of the first bonding layer and the second bonding layer are both 50nm to 100nm, and the first bonding layer and the second bonding layer are both titanium metal layers. It should be noted that copper particles can be directly plated after sputtering the titanium metal layer, that is, direct copper plating method, which can save process costs.

[0010] In some embodiments, the upper copper layer is provided with etching sites. The present invention forms a conductive circuit by etching sites, and the size of the etching sites is etched according to the actual use requirements.

[0011] In some embodiments, the method for preparing the diamond ceramic layer comprises the following steps: A substrate is provided, a mixed gas of a carbon source gas, a hydrogen source gas and an inert gas is used as a reaction gas, and diamond crystals are deposited on the substrate by chemical vapor deposition until the thickness is 300 μm to 630 μm to obtain a precursor, and the precursor is annealed at 1000° C. to 1200° C. to obtain a diamond ceramic layer.

[0012] It should be noted that the substrate is selected based on the performance of diamond crystals, the thermal conductivity of the substrate and its compatibility with diamond. In the present invention, the substrate is a molybdenum substrate, which is used as a substrate material for growing diamond crystals. Before growing diamond crystals, the substrate needs to be thoroughly cleaned to remove oil, oxides or other impurities; commonly used cleaning methods include ultrasonic cleaning, acid cleaning, etc., to ensure that the surface of the substrate is very smooth so that diamond crystals can grow evenly on the substrate surface.

[0013] During the chemical vapor deposition process, the substrate is placed in the chemical vapor deposition reaction chamber and connected to the gas supply system to ensure that the reaction chamber can maintain a stable temperature and pressure and has good gas flow and plasma control capabilities. The required reaction gas is configured and the reaction gas is excited with an inert gas. After the gas is controlled, the substrate needs to be heated to 700℃~1000℃. The purpose of heating is to increase the deposition rate of diamond and help the growth of diamond crystals. After the growth is completed, the diamond ceramic layer needs to be cooled slowly to avoid cracks or stress due to excessive temperature difference; after cooling, the substrate is removed from the reaction chamber. The grown diamond ceramic layer may have certain stresses. In order to reduce these stresses and improve the quality of the film, annealing treatment is required. The annealing temperature is controlled between 1000℃~1200℃, which can help the diamond crystals grow further and reduce stress.

[0014] In some embodiments, the temperature of chemical vapor deposition is 1000°C to 1200°C, the gas pressure is 50 Torr to 200 Torr, and the deposition rate is 1 μm / h to 5 μm / h. The gas pressure is controlled at 50 Torr to 200 Torr. Too high a pressure may lead to uneven deposition, while too low a pressure may affect the growth rate. In order to control the growth thickness of the diamond ceramic layer, the growth rate is controlled between 1 μm / h and 5 μm / h.

[0015] In some embodiments, the carbon source gas in the reaction gas is 1% to 2% of the volume of the hydrogen source gas, the inert gas is 0.1% to 0.5% of the volume of the hydrogen source gas, the carbon source gas is methane, the hydrogen source gas is hydrogen, and the inert gas is argon. The reaction gas is excited by a heat source to generate plasma, which decomposes methane and releases active carbon atoms, which are then deposited on the substrate to form diamond crystals. In a stable gas environment and at an appropriate temperature, diamond crystals begin to deposit on the surface of the substrate; the deposition of diamond crystals is a gradual accumulation process. Over time, diamond crystals gradually grow to form a diamond film. In order to avoid uneven film thickness or warping of the diamond film, the reaction gas distribution, temperature field and plasma distribution in the reaction chamber need to be precisely controlled, and the thickness of the diamond film needs to be continuously monitored to ensure uniform deposition. By controlling parameters such as gas flow, temperature, and pressure, the deposition rate can be adjusted to ensure uniform thickness of the diamond ceramic layer.

[0016] On the other hand, the present invention provides a method for preparing the above-mentioned insulating substrate based on the diamond ceramic layer, comprising the following steps: A first metal copper is sputtered and deposited on the upper and lower surfaces of the diamond ceramic layer by magnetron sputtering, and then a second metal copper is deposited by electroplating until the total thickness of the copper layer is 250 μm to 300 μm, thereby obtaining an upper copper layer and a lower copper layer, respectively, and thus obtaining an insulating substrate based on the diamond ceramic layer.

[0017] It should be noted that the deposition of metallic copper uses direct copper plating to metallize the surface of the diamond ceramic layer. First, a titanium metal layer is sputtered under vacuum conditions, followed by copper particles, and finally electroplating to thicken the layer. Finally, the thickness of the copper layer is increased by electroplating deposition. Before depositing metallic copper, the surface of the diamond ceramic layer is cleaned, impurities are removed using organic solvents, and microscopic particles are cleaned using ultrasound to ensure that there are no pollutants on the surface. The surface of the diamond ceramic layer is roughened using a sandblasting process to increase the contact area. After the surface has been treated as above, metallic copper is sputtered and deposited.

[0018] In some embodiments, the thickness of the first metal copper deposited by sputtering is 20 μm to 30 μm. It should be noted that after the sputtering is completed, the surface and adhesion of the copper layer are checked, and electroplating is performed on the sputtered copper layer until the total thickness of the copper layer is 250 μm to 300 μm. During the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid the occurrence of uneven thickness of the copper layer.

[0019] In some embodiments, after the electroplating deposition is completed, annealing is performed at 150°C to 300°C for 8h to 12h under nitrogen or inert gas. After the electroplating is completed, annealing treatment is required in a nitrogen or inert gas environment at 150°C to 300°C for 8h to 12h to enhance the bonding strength between the materials. After the annealing is completed, the surface is polished to eliminate surface unevenness and defects.

[0020] In some embodiments, the insulating substrate of the prepared diamond ceramic layer is etched with an upper copper layer to form an etching site to obtain a complete insulating substrate. Before etching the circuit on the surface of the upper copper layer, the surface is first cleaned with acetone or isopropyl ketone to remove organic matter on the surface, and then the surface is cleaned with ultrasound to remove microparticles. Finally, it is dried in a nitrogen or inert gas environment. After drying, a layer of photoresist is evenly applied on the surface of the copper layer. The thickness of the coating is usually 1μm to 5μm. After coating, the photoresist is pre-dried to remove the solvent in the photoresist and improve its adhesion. Use an ultraviolet light source to expose the photoresist through a mask, and place the exposed insulating substrate in a developer to dissolve the unexposed photoresist, leaving a patterned photoresist layer. Etching can be done by wet etching or dry etching. Wet etching is to use a chemical etching solution that can dissolve copper materials, such as sulfuric acid solution, for wet etching. This step requires controlling the etching time to ensure that only the upper copper layer not covered by the photoresist is removed; dry etching is to use plasma for dry etching, and selectively remove the upper copper layer through reactive gases such as chlorine. After wet etching is completed, acetone is used to remove the photoresist, leaving the etched upper copper layer. Finally, ultrasonic cleaning is performed to obtain an insulating substrate with a complete diamond ceramic layer.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The insulating substrate of the diamond ceramic layer provided by the present invention uses diamond ceramic material as the diamond ceramic layer. Diamond, as an insulating material, has excellent thermal conductivity, and its thermal conductivity can reach more than 2000W / m·K, which is far higher than the traditional aluminum substrate and aluminum nitride material. Diamond not only has extremely high thermal conductivity, but also has excellent mechanical strength, corrosion resistance and electrical insulation. Based on this, the power module packaging technology based on the diamond ceramic layer as the insulating substrate of the present invention can effectively improve the heat dissipation performance, increase the power density of the power module, and thus improve the efficiency and service life of the power module. The present invention controls the matching of the thermal expansion coefficients of the diamond ceramic layer and the metal layer by adjusting the thickness of the diamond ceramic layer and the upper copper layer and the lower copper layer. The diamond ceramic layer provides electrical insulation and heat conduction, and the upper copper layer and the lower copper layer provide heat dissipation and electrical conductivity. This can effectively improve the heat dissipation capacity and current carrying capacity of the power module, reduce the operating temperature of the module, reduce the thermal stress and junction temperature of the silicon carbide chip, and achieve the purpose of quickly reducing the junction temperature of the power device, thereby improving the heat dissipation efficiency of the silicon carbide module, increasing the operating temperature of the silicon carbide power module, and ensuring the mechanical stability and long-term reliability of the insulating substrate.

[0022] (2) The present invention adopts chemical vapor deposition to prepare the diamond ceramic layer. By controlling the gas flow, temperature, pressure and other parameters, the deposition rate can be adjusted so that the diamond crystals can grow evenly. The grown diamond ceramic layer may have certain stresses. In order to reduce these stresses and improve the quality of the film, annealing treatment can help the diamond crystals grow further and reduce the stress.

[0023] (3) The present invention provides a method for preparing an insulating substrate with a diamond ceramic layer, in which metallic copper is deposited on the diamond ceramic layer by magnetron sputtering and electroplating deposition to obtain an insulating substrate based on a diamond ceramic layer. The surface metal is uniform and fine, the thickness is controllable, and the adhesion performance is good, thereby improving the reliability of the insulating substrate with a diamond ceramic layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of an insulating substrate based on a diamond ceramic layer of the present invention.

[0025] Figure 2 It is a schematic structural diagram of the alumina insulating substrate of the present invention.

[0026] Figure 3 It is a schematic structural diagram of the aluminum nitride insulating substrate of the present invention.

[0027] Figure 4 It is a schematic structural diagram of the silicon nitride insulating substrate of the present invention.

[0028] Figure 5The schematic diagram of the structure of the silicon carbide power module prepared based on the insulating substrate of the diamond ceramic layer of the present invention.

[0029] Figure 6 This is a diagram showing the temperature distribution results of the insulating substrate when heated according to Example 1 of the present invention.

[0030] Figure 7 This is a diagram showing the temperature distribution results of the insulating substrate in comparative example 1 of the present invention.

[0031] Figure 8 This is a diagram showing the temperature distribution results of the insulating substrate in comparative example 2 of the present invention.

[0032] Fig. 9 This is a diagram showing the temperature distribution results of the insulating substrate in comparative example 3 of the present invention.

[0033] Illustration Description: 1. Upper copper layer, 2. Diamond ceramic layer, 3. Lower copper layer, 4. Solder layer, 5. Chip.

[0034] 21. Aluminum oxide layer, 22. Aluminum nitride layer, 23. Silicon nitride layer. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The invention is further described below through specific examples.

[0037] Example 1 An insulating substrate based on a diamond ceramic layer, such as Figure 1 As shown, the insulating substrate of the diamond ceramic layer is provided with an upper copper layer 1, a diamond ceramic layer 2 and a lower copper layer 3 in order from top to bottom in the thickness direction, the thickness of the diamond ceramic layer 2 is 630 μm, and the thickness of the upper copper layer 1 and the lower copper layer 3 are both 250 μm. The upper copper layer 1 is provided with an etching position.

[0038] A titanium metal bonding layer with a thickness of 100 nm is provided between the diamond ceramic layer 2 and the upper copper layer 1 and between the diamond ceramic layer 2 and the lower copper layer 3 .

[0039] The method for preparing the diamond ceramic layer 2 comprises the following steps: Step 1: provide a molybdenum substrate, and use ultrasonic cleaning and pickling to remove oil, oxides and other impurities from the molybdenum substrate.

[0040] Step 2, place the molybdenum substrate into a chemical vapor deposition reaction chamber, connect the gas supply system, and introduce a mixed gas formed by methane, hydrogen and argon, wherein methane accounts for 1.5% of the volume of hydrogen and argon accounts for 0.5% of the volume of hydrogen; heat the molybdenum substrate to 1000°C, and then perform chemical vapor deposition at 1000°C. The gas pressure during the deposition process is 100Torr, and the deposition rate is 3μm / h. Diamond is deposited on the molybdenum substrate to a thickness of 630μm. After the chemical vapor deposition is completed, it is cooled to room temperature. After cooling to room temperature, the molybdenum substrate is taken out of the reaction chamber and annealed at 1000°C to obtain a diamond ceramic layer 2.

[0041] The method for preparing the insulating substrate based on the diamond ceramic layer comprises the following steps: S1. Clean the upper surface of the diamond ceramic layer 2, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the upper surface of the diamond ceramic layer 2 to increase the contact area, and after the upper surface has been treated as above, use magnetron sputtering to deposit titanium metal under vacuum conditions, the thickness of the titanium metal layer is 100μm, as a bonding layer, and magnetron sputter copper metal on the bonding layer with a sputtering thickness of 30μm. After sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer with a thickness of 250μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, annealing treatment is required in a nitrogen environment at 300℃ for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain an upper copper layer 1.

[0042] S2. Clean the lower surface of the diamond ceramic layer 2, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the lower surface of the diamond ceramic layer 2 to increase the contact area, and after the above treatment, use magnetron sputtering to deposit titanium metal under vacuum conditions. The thickness of the titanium metal layer is 100μm as a bonding layer, and magnetron sputtering copper metal is performed on the bonding layer with a sputtering thickness of 30μm. After sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer with a thickness of 250μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, annealing treatment is required in a nitrogen environment, usually at 300℃ for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain a lower copper layer 3.

[0043] S3, cleaning the surface of the upper copper layer 1, cleaning it with acetone to remove the surface organic matter, then ultrasonically cleaning the surface to remove microparticles, and drying it in a nitrogen environment; after drying, evenly coating a layer of photoresist on the surface of the upper copper layer 1, the thickness of the coating is 2μm, pre-drying the photoresist after coating to remove the solvent in the photoresist, using an ultraviolet light source to expose the photoresist through a mask, placing the exposed substrate in a developer to dissolve the unexposed photoresist, leaving a patterned photoresist layer, and wet etching, that is, using a chemical etching solution that can dissolve copper materials, such as a sulfuric acid solution, for wet etching. This step requires controlling the etching time to ensure that only the upper copper layer 1 not covered by the photoresist is removed; after the wet etching is completed, using acetone to remove the photoresist, leaving the etched upper copper layer 1, to obtain an insulating substrate based on a diamond ceramic layer.

[0044] Example 2 An insulating substrate based on a diamond ceramic layer, such as Figure 1 As shown, the insulating substrate of the diamond ceramic layer is provided with an upper copper layer 1, a diamond ceramic layer 2 and a lower copper layer 3 in order from top to bottom in the thickness direction, the thickness of the diamond ceramic layer 2 is 300 μm, and the thickness of the upper copper layer 1 and the lower copper layer 3 are both 250 μm. The upper copper layer 1 is provided with an etching position.

[0045] A titanium metal bonding layer with a thickness of 50 nm is provided between the diamond ceramic layer 2 and the upper copper layer 1 and between the diamond ceramic layer 2 and the lower copper layer 3 .

[0046] The method for preparing the diamond ceramic layer 2 comprises the following steps: Step 1: provide a molybdenum substrate, and use ultrasonic cleaning and pickling to remove oil, oxides and other impurities from the molybdenum substrate.

[0047] Step 2, place the molybdenum substrate into a chemical vapor deposition reaction chamber, connect the gas supply system, and introduce a mixed gas formed by methane, hydrogen and argon, wherein methane accounts for 1.5% of the volume of hydrogen and argon accounts for 0.5% of the volume of hydrogen; heat the molybdenum substrate to 1000°C, and then perform chemical vapor deposition at 1000°C. The gas pressure during the deposition process is 100Torr, and the deposition rate is 3μm / h. Diamond is deposited on the molybdenum substrate to a thickness of 300μm. After the chemical vapor deposition is completed, it is cooled to room temperature. After cooling to room temperature, the molybdenum substrate is taken out of the reaction chamber and annealed at 1000°C to obtain a diamond ceramic layer 2.

[0048] The method for preparing the insulating substrate based on the diamond ceramic layer comprises the following steps: S1. Clean the upper surface of the diamond ceramic layer 2, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the upper surface of the diamond ceramic layer 2 to increase the contact area, and after the upper surface has been treated as above, use magnetron sputtering to deposit titanium metal under vacuum conditions, the thickness of the titanium metal layer is 50μm, as a bonding layer, and magnetron sputter copper metal on the bonding layer, the sputtering thickness is 30μm, after the sputtering is completed, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer to a thickness of 250μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid the occurrence of uneven coating thickness; after the electroplating is completed, annealing treatment is required in a nitrogen environment, annealing at 300℃ for 8h; after the annealing is completed, the copper surface is polished to eliminate surface unevenness and defects to obtain the upper copper layer 1.

[0049] S2. Clean the lower surface of the diamond ceramic layer 2, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the lower surface of the diamond ceramic layer 2 to increase the contact area, and after the above treatment, use magnetron sputtering to deposit titanium metal under vacuum conditions, the thickness of the titanium metal layer is 50μm, as a bonding layer, and magnetron sputter copper metal on the bonding layer with a sputtering thickness of 30μm. After sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer with a thickness of 250μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, annealing treatment is required in a nitrogen environment, usually at 300°C for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain a lower copper layer 3.

[0050] S3, cleaning the surface of the upper copper layer 1, cleaning it with acetone to remove the surface organic matter, then ultrasonically cleaning the surface to remove microparticles, and drying it in a nitrogen environment; after drying, evenly coating a layer of photoresist on the surface of the upper copper layer 1, the thickness of the coating is 2μm, pre-drying the photoresist after coating to remove the solvent in the photoresist, using an ultraviolet light source to expose the photoresist through a mask, placing the exposed substrate in a developer to dissolve the unexposed photoresist, leaving a patterned photoresist layer, and wet etching, that is, using a chemical etching solution that can dissolve copper materials, such as a sulfuric acid solution, for wet etching. This step requires controlling the etching time to ensure that only the upper copper layer 1 not covered by the photoresist is removed; after the wet etching is completed, using acetone to remove the photoresist, leaving the etched upper copper layer 1, to obtain an insulating substrate based on a diamond ceramic layer.

[0051] Example 3 An insulating substrate based on a diamond ceramic layer, such as Figure 1As shown, the insulating substrate of the diamond ceramic layer is provided with an upper copper layer 1, a diamond ceramic layer 2 and a lower copper layer 3 in order from top to bottom in the thickness direction, the thickness of the diamond ceramic layer 2 is 450 μm, and the thickness of the upper copper layer 1 and the lower copper layer 3 are both 280 μm. The upper copper layer 1 is provided with an etching position.

[0052] A titanium metal bonding layer with a thickness of 80 nm is provided between the diamond ceramic layer 2 and the upper copper layer 1 and between the diamond ceramic layer 2 and the lower copper layer 3 .

[0053] The method for preparing the diamond ceramic layer 2 comprises the following steps: Step 1: provide a molybdenum substrate, and use ultrasonic cleaning and pickling to remove oil, oxides or other impurities from the molybdenum substrate.

[0054] Step 2, place the molybdenum substrate into a chemical vapor deposition reaction chamber, connect the gas supply system, and introduce a mixed gas formed by methane, hydrogen and argon, wherein methane accounts for 1.5% of the volume of hydrogen and argon accounts for 0.5% of the volume of hydrogen; heat the molybdenum substrate to 1000°C, and then perform chemical vapor deposition at 1000°C. The gas pressure during the deposition process is 100Torr, and the deposition rate is 3μm / h. Diamond is deposited on the molybdenum substrate to a thickness of 450μm. After the chemical vapor deposition is completed, it is cooled to room temperature. After cooling to room temperature, the molybdenum substrate is taken out of the reaction chamber and annealed at 1000°C to obtain a diamond ceramic layer 2.

[0055] The method for preparing the insulating substrate based on the diamond ceramic layer comprises the following steps: S1. Clean the upper surface of the diamond ceramic layer 2, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the upper surface of the diamond ceramic layer 2 to increase the contact area, and after the upper surface has been treated as above, use magnetron sputtering to deposit titanium metal under vacuum conditions, the thickness of the titanium metal layer is 80μm, as a bonding layer, and magnetron sputter copper metal on the bonding layer, the sputtering thickness is 20μm, after sputtering, check the copper layer surface and adhesion, electroplate on the sputtered copper layer, the thickness is up to 280μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, it is necessary to anneal in a nitrogen environment at 300℃ for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain an upper copper layer 1.

[0056] S2. Clean the lower surface of the diamond ceramic layer 2, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the lower surface of the diamond ceramic layer 2 to increase the contact area, and after the above treatment, use magnetron sputtering to deposit titanium metal under vacuum conditions, the thickness of the titanium metal layer is 80μm, as a bonding layer, and magnetron sputter copper metal on the bonding layer with a sputtering thickness of 20μm. After sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer to a thickness of 280μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, annealing treatment is required in a nitrogen environment, usually at 300°C for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain a lower copper layer 3.

[0057] S3, cleaning the surface of the upper copper layer 1, cleaning it with acetone to remove the surface organic matter, then ultrasonically cleaning the surface to remove microparticles, and drying it in a nitrogen environment; after drying, evenly coating a layer of photoresist on the surface of the upper copper layer 1, the thickness of the coating is 2μm, pre-drying the photoresist after coating to remove the solvent in the photoresist, using an ultraviolet light source to expose the photoresist through a mask, placing the exposed substrate in a developer to dissolve the unexposed photoresist, leaving a patterned photoresist layer, and wet etching, that is, using a chemical etching solution that can dissolve copper materials, such as a sulfuric acid solution, for wet etching. This step requires controlling the etching time to ensure that only the upper copper layer 1 not covered by the photoresist is removed; after the wet etching is completed, using acetone to remove the photoresist, leaving the etched upper copper layer 1, to obtain an insulating substrate based on a diamond ceramic layer.

[0058] Comparative Example 1 An alumina insulating substrate, such as Figure 2 As shown, it includes: the alumina insulating substrate is provided with an upper copper layer 1, an aluminum oxide layer 21 and a lower copper layer 3 in order from top to bottom along the thickness direction, the thickness of the aluminum oxide layer 21 is 630 μm, and the thickness of the upper copper layer 1 and the lower copper layer 3 are both 250 μm. The upper copper layer 1 is provided with an etching position.

[0059] A titanium metal bonding layer with a thickness of 50 nm is provided between the aluminum oxide layer 21 and the upper copper layer 1 and between the aluminum oxide layer 21 and the lower copper layer 3 .

[0060] The method for preparing the above-mentioned alumina insulating substrate comprises the following steps: S1. Clean the upper surface of the aluminum oxide layer 21, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the upper surface of the aluminum oxide layer 21 to increase the contact area, and after the upper surface has been treated as above, use magnetron sputtering to deposit titanium metal under vacuum conditions, the thickness of the titanium metal layer is 50μm, as a bonding layer, and magnetron sputter copper metal on the bonding layer, the sputtering thickness is 30μm, after sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer to a thickness of 250μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, it is necessary to anneal in a nitrogen environment at 300°C for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain an upper copper layer 1.

[0061] S2. Clean the lower surface of the aluminum oxide layer 21, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the lower surface of the aluminum oxide layer 21 to increase the contact area, and after the above treatment, use magnetron sputtering to deposit titanium metal under vacuum conditions, the thickness of the titanium metal layer is 50μm, as a bonding layer, and magnetron sputter copper metal on the bonding layer with a sputtering thickness of 30μm. After sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer with a thickness of 250μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, annealing treatment is required in a nitrogen environment, usually at 300°C for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain a lower copper layer 3.

[0062] S3, cleaning the surface of the upper copper layer 1, cleaning it with acetone to remove the surface organic matter, then ultrasonically cleaning the surface to remove microparticles, and drying it in a nitrogen environment; after drying, evenly coating a layer of photoresist on the surface of the upper copper layer 1, the thickness of the coating is 2μm, pre-drying the photoresist after coating to remove the solvent in the photoresist, using an ultraviolet light source to expose the photoresist through a mask, placing the exposed substrate in a developer to dissolve the unexposed photoresist, leaving a patterned photoresist layer, and wet etching using a chemical etching solution that can dissolve copper materials, that is, wet etching with a sulfuric acid solution, this step needs to control the etching time to ensure that only the upper copper layer 1 not covered by the photoresist is removed; after the wet etching is completed, using acetone to remove the photoresist, leaving the etched upper copper layer 1, and an alumina insulating substrate can be obtained.

[0063] Comparative Example 2 An aluminum nitride insulating substrate, such as Figure 3As shown, the aluminum nitride insulating substrate is provided with an upper copper layer 1, an aluminum nitride layer 22 and a lower copper layer 3 in order from top to bottom along the thickness direction, the thickness of the aluminum nitride layer 22 is 630 μm, and the thickness of the upper copper layer 1 and the lower copper layer 3 are both 250 μm. The upper copper layer 1 is provided with an etching position.

[0064] A titanium metal bonding layer with a thickness of 50 nm is provided between the aluminum nitride layer 22 and the upper copper layer 1 and between the aluminum nitride layer 22 and the lower copper layer 3 .

[0065] The method for preparing the aluminum nitride insulating substrate comprises the following steps: S1. Clean the upper surface of the aluminum nitride layer 22, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the upper surface of the aluminum nitride layer 22 to increase the contact area, and after the upper surface has been treated as above, use magnetron sputtering to deposit titanium metal under vacuum conditions, the thickness of the titanium metal layer is 50μm, as a bonding layer, and magnetron sputter copper metal is sputtered on the bonding layer with a sputtering thickness of 30μm. After sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer with a thickness of 250μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, annealing treatment is required in a nitrogen environment at 300°C for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain an upper copper layer 1.

[0066] S2. Clean the lower surface of the aluminum nitride layer 22, use an organic solvent to remove impurities, use ultrasonic cleaning of microscopic particles to ensure that there are no pollutants on the surface, use sandblasting technology to roughen the lower surface of the aluminum nitride layer 22 to increase the contact area, and after the above treatment, use magnetron sputtering to deposit titanium metal under vacuum conditions, the thickness of the titanium metal layer is 50μm, as a bonding layer, and magnetron sputter copper metal on the bonding layer with a sputtering thickness of 30μm. After sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer with a thickness of 250μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, annealing treatment is required in a nitrogen environment, usually at 300°C for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain a lower copper layer 3.

[0067] S3, cleaning the surface of the upper copper layer 1, cleaning it with acetone to remove the surface organic matter, then ultrasonically cleaning the surface to remove microparticles, and drying it in a nitrogen environment; after drying, evenly coating a layer of photoresist on the surface of the upper copper layer 1, the thickness of the coating is 2μm, pre-drying the photoresist after coating to remove the solvent in the photoresist, using an ultraviolet light source to expose the photoresist through a mask, placing the exposed substrate in a developer to dissolve the unexposed photoresist, leaving a patterned photoresist layer, and wet etching using a chemical etching solution that can dissolve copper materials, that is, wet etching with a sulfuric acid solution, this step needs to control the etching time to ensure that only the upper copper layer 1 not covered by the photoresist is removed; after the wet etching is completed, using acetone to remove the photoresist, leaving the etched upper copper layer 1, and an aluminum nitride insulating substrate can be obtained.

[0068] Comparative Example 3 A silicon nitride insulating substrate, such as Figure 4 As shown, the silicon nitride insulating substrate is provided with an upper copper layer 1, a silicon nitride layer 23 and a lower copper layer 3 in order from top to bottom along the thickness direction, the thickness of the silicon nitride layer 23 is 630 μm, and the thickness of the upper copper layer 1 and the lower copper layer 3 are both 250 μm. The upper copper layer 1 is provided with an etching position.

[0069] A titanium metal bonding layer with a thickness of 50 nm is provided between the silicon nitride layer 23 and the upper copper layer 1 and between the silicon nitride layer 23 and the lower copper layer 3 .

[0070] The method for preparing the silicon nitride insulating substrate comprises the following steps: S1. Clean the upper surface of the silicon nitride layer 23, use an organic solvent to remove impurities, use ultrasonic waves to clean microscopic particles, ensure that there are no pollutants on the surface, use sandblasting technology to roughen the upper surface of the silicon nitride layer 23 to increase the contact area, and after the upper surface has been treated as above, use magnetron sputtering to deposit titanium metal under vacuum conditions, and the thickness of the titanium metal layer is 50μm, as a bonding layer, and magnetron sputter copper metal is sputtered on the bonding layer with a sputtering thickness of 30μm. After sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer with a thickness of 250μm; during the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness; after electroplating, annealing treatment is required in a nitrogen environment at 300°C for 8h; after annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain an upper copper layer 1.

[0071] S2. Clean the lower surface of the silicon nitride layer 23, use an organic solvent to remove impurities, use ultrasonic waves to clean microscopic particles, ensure that there are no pollutants on the surface, and use a sandblasting process to roughen the lower surface of the silicon nitride layer 23 to increase the contact area. After the above treatment, titanium metal is deposited by magnetron sputtering under vacuum conditions. The thickness of the titanium metal layer is 50μm as a bonding layer. Copper metal is magnetron sputtered on the bonding layer with a sputtering thickness of 30μm. After sputtering, check the surface and adhesion of the copper layer, and electroplate on the sputtered copper layer with a thickness of 250μm. During the electroplating process, it is necessary to ensure that the current distribution is uniform to avoid uneven coating thickness. After electroplating, annealing treatment is required in a nitrogen environment, usually at 300°C for 8h. After annealing, the copper surface is polished to eliminate surface unevenness and defects to obtain a lower copper layer 3.

[0072] S3, cleaning the surface of the upper copper layer 1, cleaning it with acetone to remove the surface organic matter, then ultrasonically cleaning the surface to remove microparticles, and drying it in a nitrogen environment; after drying, evenly coating a layer of photoresist on the surface of the upper copper layer 1, the thickness of the coating is 2μm, pre-drying the photoresist after coating to remove the solvent in the photoresist, using an ultraviolet light source to expose the photoresist through a mask, placing the exposed substrate in a developer to dissolve the unexposed photoresist, leaving a patterned photoresist layer, and wet etching using a chemical etching solution that can dissolve copper materials, that is, wet etching with a sulfuric acid solution, this step needs to control the etching time to ensure that only the upper copper layer 1 not covered by the photoresist is removed; after the wet etching is completed, using acetone to remove the photoresist, leaving the etched upper copper layer 1, and a silicon nitride insulating substrate can be obtained.

[0073] The heat dissipation performance of the insulating substrates of Example 1 and Comparative Examples 1 to 3 was studied, and the results are shown in Table 1.

[0074] Table 1 Thermal conductivity of insulating substrates of Example 1 and Comparative Examples 1 to 3

[0075] As shown in Table 1, according to heat transfer theory, the material with greater thermal conductivity has better heat transfer under the same conditions. The diamond ceramic material used in the present invention as an insulating layer has a thermal conductivity greater than the above three materials. Therefore, from a theoretical analysis, the use of diamond ceramic material as a diamond ceramic layer can reduce the junction temperature of the silicon carbide chip and help the module dissipate heat.

[0076] The silicon carbide power module is prepared by using the diamond ceramic layer of Example 1 of the present invention and the insulating substrates of Comparative Examples 1 to Comparative Examples 3. Taking the preparation of the silicon carbide power module based on the insulating substrate of the diamond ceramic layer of Example 1 as an example, the structure of the silicon carbide power module is as follows: Figure 5As shown, a solder layer 4 is arranged on the upper copper layer 1, a chip 5 is arranged on the solder layer 4, the material of the chip 5 is silicon carbide, the thickness of the solder layer 4 is 80 μm, and the specific specifications of the silicon carbide power module prepared based on the insulating substrate of the diamond ceramic layer in Example 1 and the insulating substrates of Comparative Examples 1 to Comparative Examples 3 are shown in Table 2.

[0077] It should be noted that the solder layer is generally tin paste or solder sheet, which is selected according to needs. The purpose of the solder is to weld the chip and the upper copper layer together. The solder layer and chip of the present invention are selected as an example, and the purpose is the same solder layer and chip. Compared with the substrate based on aluminum oxide, aluminum nitride, and silicon nitride as the insulating layer, the solder layer and chip are not included. A vacuum reflow soldering process is used to reduce the oxidation of components that may occur during the welding process. Reflow soldering heats the paste-shaped soft solder pre-applied on the pad to melt and solidify it. The vacuum value atmospheric pressure can be reduced to below 5mbar and maintained for a certain period of time, thereby establishing a mechanical and electrical connection between the surface mounted components and the pad. A soft soldering method. Reflow soldering is generally divided into four working zones: heating zone, insulation zone, reflow zone, and cooling zone. In addition, in order to reduce the void rate of the welding layer, high-quality welding is performed between the chip and the substrate in a vacuum environment. Silicon carbide chips are used, and the material of the solder layer is Sn5Pb 92.5 Ag 2.5 After the solder paste is printed on the steel screen, it is sent to the reflow oven for reflow. The highest reflow temperature is set to 310℃ and maintained for 120s to complete the reflow.

[0078] Table 2 Specifications of silicon carbide power modules prepared in Example 1 and Comparative Examples 1 to 3

[0079] The reflow soldering simulation of the silicon carbide power module of Example 1 and Comparative Examples 1 to 3 is compared to compare the maximum temperature under the same working conditions. In the simulation, the same working conditions are set, assuming that the power consumption of the silicon carbide chip is 20W, forced air cooling is used, the room temperature is 25°C, and the air flow rate is 100m / s. Based on the above simulation conditions, Figure 6 to Figure 9 The temperature distribution results of Example 1 and Comparative Examples 1 to 3 were simulated based on ANSYS Q3D software, where: Figure 6 This is a diagram showing the temperature distribution of the insulating substrate in Example 1 of the present invention. Figure 7 This is a diagram showing the temperature distribution of the insulating substrate in Comparative Example 1 of the present invention. Figure 8 This is a diagram showing the temperature distribution of the insulating substrate in Comparative Example 2 of the present invention. Fig. 9 This is a diagram showing the temperature distribution of the insulating substrate in comparative example 3 of the present invention. Figure 6 to Figure 9As shown in the figure, the maximum temperature of an insulating substrate based on a diamond ceramic layer is 104°C, the temperature of an insulating substrate with an aluminum oxide ceramic layer is 145.5°C, the temperature of an insulating substrate with an aluminum nitride ceramic layer is 135.7°C, and the temperature of an insulating substrate with a silicon nitride ceramic layer is 147.2°C. Based on the above simulation results, it is concluded that replacing the ceramic layer with diamond can improve the heat dissipation capacity by 28.5% compared with the aluminum oxide ceramic layer, 23.4% compared with the aluminum nitride ceramic layer, and 29.3% compared with the silicon nitride ceramic layer. It can be seen from the simulation results that the diamond-based ceramic layer insulating substrate not only has a low maximum temperature, but also has a lower temperature around the heat source than the other three ceramic substrates. This proves that the insulating substrate can dissipate heat better by using diamond as the ceramic layer.

[0080] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0081] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An insulating substrate based on a diamond ceramic layer, characterized in that: The insulating substrate of the diamond ceramic layer is provided with an upper copper layer (1), a diamond ceramic layer (2) and a lower copper layer (3) in order from top to bottom along the thickness direction; the thickness of the diamond ceramic layer (2) is 300 μm to 630 μm, and the thickness of the upper copper layer (1) and the lower copper layer (3) are both 250 μm to 300 μm.

2. The insulating substrate based on the diamond ceramic layer according to claim 1, characterized in that: A first bonding layer is provided between the diamond ceramic layer (2) and the upper copper layer (1), and a second bonding layer is provided between the diamond ceramic layer (2) and the lower copper layer (3).

3. The insulating substrate based on the diamond ceramic layer according to claim 2, characterized in that: The thickness of the first bonding layer and the second bonding layer are both 50nm-100nm, and both the first bonding layer and the second bonding layer are titanium metal layers.

4. The insulating substrate based on the diamond ceramic layer according to claim 1, characterized in that: The upper copper layer (1) is provided with an etching position.

5. The insulating substrate based on the diamond ceramic layer according to claim 1, characterized in that: The method for preparing the diamond ceramic layer (2) comprises the following steps: A substrate is provided, a mixed gas of a carbon source gas, a hydrogen source gas and an inert gas is used as a reaction gas, and diamond crystals are deposited on the substrate by chemical vapor deposition until the thickness is 300 μm to 630 μm to obtain a precursor, and the precursor is annealed at 1000° C. to 1200° C. to obtain a diamond ceramic layer (2).

6. The insulating substrate based on the diamond ceramic layer according to claim 5, characterized in that: The temperature of chemical vapor deposition is 1000° C. to 1200° C., the gas pressure is 50 Torr to 200 Torr, and the deposition rate is 1 μm / h to 5 μm / h.

7. The insulating substrate based on the diamond ceramic layer according to claim 5, characterized in that: The carbon source gas in the reaction gas accounts for 1% to 2% of the volume of the hydrogen source gas, and the inert gas accounts for 0.1% to 0.5% of the volume of the hydrogen source gas.

8. A method for preparing an insulating substrate based on a diamond ceramic layer according to any one of claims 1 to 7, characterized in that: The following steps are involved: A first metal copper is sputtered and deposited on the upper surface and the lower surface of the diamond ceramic layer (2) by magnetron sputtering, and then a second metal copper is deposited by electroplating until the total thickness of the copper layer is 250 μm to 300 μm, thereby obtaining an upper copper layer (1) and a lower copper layer (3), respectively, and thus obtaining an insulating substrate based on a diamond ceramic layer.

9. The method for preparing an insulating substrate based on a diamond ceramic layer according to claim 8, characterized in that: The thickness of the first metal copper deposited by sputtering is 20 μm to 30 μm.

10. The method for preparing an insulating substrate based on a diamond ceramic layer according to claim 8, characterized in that: After the electroplating deposition is completed, annealing is performed at 150°C to 300°C for 8h to 12h under nitrogen or inert gas.

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