A high thermal conductivity silicon carbide composite heat sink structure, its preparation method and application

Abstract

The present invention relates to the technical field of semiconductor laser material preparation, and specifically discloses a high-thermal-conductivity silicon carbide composite heat sink structure, a preparation method thereof, and an application. The present invention designs a stepped heat transfer heat sink structure with silicon carbide as the substrate. In the present invention, a thermal conductivity buffer film layer and a thermal conductivity film layer are sequentially deposited and grown on the silicon carbide substrate. The low-thermal-conductivity silicon carbide substrate is connected to the high-thermal-conductivity diamond thermal conductivity film layer by using the thermal conductivity buffer film layer, introducing a new heat dissipation channel and significantly improving the heat dissipation efficiency of the device. Moreover, the present invention also designs a new metal solder, avoiding the occurrence of cracks or chipping in the diamond film layer during the welding process. The present invention effectively solves the problems in the prior art that the materials of the heat sink structure of semiconductor lasers are expensive, the thermal conductivity is low and cannot meet the device requirements, and cracks or even chipping will occur in the diamond film layer when welding the chip, greatly improving the yield of semiconductor laser devices.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor laser material preparation, and specifically discloses a high-thermal-conductivity silicon carbide composite heat sink structure, a preparation method thereof, and an application thereof. Background Art

[0002] Semiconductor lasers have advantages such as high electro-optical conversion efficiency, small size, long life, adjustable wavelength and a wide range, etc., making them widely used in the fields of communication industry, laser pumping, medical laser surgery, industrial cutting manufacturing, military defense, etc. However, with the rapid development of the theory, materials, and preparation processes of semiconductor lasers, the performance parameters such as the output power, beam quality, and working life of semiconductor lasers have also been continuously improved, and thus the requirements for semiconductor laser packaging technology have become increasingly higher.

[0003] Although semiconductor lasers have relatively high electro-optical conversion efficiency, a large amount of waste heat will still be generated during long-term operation. If this waste heat cannot be dissipated in time, it will seriously affect the performance of semiconductor lasers. Especially for high-density packaged lasers such as horizontal or vertical stacks, the device is prone to heat accumulation inside due to the temperature gradient caused by repeated pulsed power supplies. When the accumulation is severe, it will cause the chip to generate thermal stress and deform, seriously reducing the beam quality and pumping efficiency of high-power semiconductor lasers. Therefore, the heat dissipation problem of semiconductor lasers has become a hot topic in the research field of semiconductor lasers.

[0004] In the prior art, for the solution to this problem, many solutions have been proposed by scientific researchers. Currently, high-power semiconductor lasers all adopt the conduction cooling method with hard solder packaging. That is, first, the laser chip is packaged onto the transition heat sink with hard solder to form a COS structure, and then the COS is packaged onto a copper heat sink with a higher thermal conductivity to complete the secondary packaging. Among them, the transition heat sink is located between the chip and the copper heat sink, undertaking the dual functions of heat dissipation transition and stress transition. The ideal transition heat sink material should have a high thermal conductivity and be able to match the expansion of the laser chip. The heat sink material with the highest reported thermal conductivity is diamond, whose thermal conductivity can reach 1200 W / (m·K) - 2200 W / (m·K). However, the cost of diamond heat sink material is too high and the operation requirements are too demanding to be mass-produced. The thermal conductivity of common silicon carbide is relatively poor, only reaching about 390 W / (m·K), which cannot meet the requirements of the device. There is also a method of combining the two, depositing diamond on a silicon carbide substrate or depositing silicon carbide on a diamond substrate to make a composite heat sink material. However, the thermal resistance is relatively large in both cases, and the problem of mismatch between the thermal expansion coefficient of the heat sink material and the semiconductor laser inevitably occurs, resulting in poor device performance. In addition, the existing metal solders are mostly gold-tin solders, which are expensive and have large stress, and will have a stress effect on the diamond film layer, resulting in cracks or even cracking of the diamond film layer during the welding process.

[0005] Based on this, the research and development of a heat sink material with high thermal conductivity, stable performance and capable of improving the performance of semiconductor lasers has great significance for the development of semiconductor lasers. Summary of the Invention

[0006] Aiming at the problems in the prior art that the materials of the heat sink structure of semiconductor lasers are expensive, the thermal conductivity is low and cannot meet the device requirements, and cracks or even cracking will occur in the diamond film layer during the welding of the chip, the present invention provides a high-thermal-conductivity silicon carbide composite heat sink structure, its preparation method and application. The present invention designs a stepped heat transfer heat sink structure with silicon carbide as the substrate. Among them, a thermal conduction buffer film layer and a thermal conduction film layer are sequentially deposited and grown on the silicon carbide substrate. The low-thermal-conductivity silicon carbide substrate and the high-thermal-conductivity diamond thermal conduction film layer are connected by the thermal conduction buffer film layer, introducing a new heat dissipation channel and significantly improving the heat dissipation efficiency of the device. Moreover, the present invention also designs a new metal solder to avoid cracks or cracking of the diamond film layer during the welding process.

[0007] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0008] In the first aspect of the present invention, a high-thermal-conductivity silicon carbide composite heat sink structure is provided, which sequentially includes a silicon carbide substrate, a thermal conduction buffer film layer, a thermal conduction film layer and a metal welding layer from bottom to top;

[0009] The material of the thermal conductive buffer film layer is a mixture of aniline-modified graphene and boron nitride-modified graphene;

[0010] The thermal conductive film layer is a diamond film layer;

[0011] The solder of the metal welding layer is Ge-Ag-Sn solder.

[0012] Compared with the prior art, in the present invention, a thermal conductive buffer film layer and a thermal conductive film layer are sequentially deposited and grown on a silicon carbide substrate. The thermal conductive buffer film layer uses aniline-modified graphene and boron nitride-modified graphene as raw materials, and the thermal conductive film layer uses diamond as raw material. Since the thermal conductivity of diamond is as high as 2200 W / (m·K), while the highest thermal conductivity of silicon carbide is only 390 W / (m·K), the difference in thermal conductivity between the two is very large. If the diamond film is directly grown on the silicon carbide substrate, although the cost can be saved to a certain extent, it is easy to have the problem that the thermal expansion coefficients of the heat sink material and the semiconductor chip do not match, resulting in an unsatisfactory heat dissipation effect. Therefore, the inventor adds a thermal conductive buffer film layer between the silicon carbide substrate and the diamond thermal conductive film layer. The thermal conductive buffer film layer is made of aniline-modified graphene and boron nitride-modified graphene. Graphene itself has good thermal conductivity, but a relatively large thermal resistance may occur at the interface where the single graphene material contacts the silicon carbide substrate, restricting the efficiency of heat conduction. Therefore, the present invention modifies it. The N atom in aniline forms a delocalized p-π conjugate with graphene, further improving the electron heat transfer ability of the graphene material; while boron nitride-modified graphene can serve as a bridge between graphene sheets to assist in forming a complete thermal conductive network and enhancing the thermal conductivity of graphene; the two work together to greatly improve the thermal conduction efficiency of the graphene material. The introduction of the thermal conductive buffer film layer adds a new heat dissipation channel, thereby further enhancing the heat dissipation efficiency of the heat sink structure.

[0013] In addition, due to the excessive stress of the commonly used Au-Sn solder, cracks or fractures are likely to occur in the diamond thermal conductive film layer during chip welding. The present invention uses Ge-Ag-Sn solder. Compared with the Au-Sn solder, the Ge-Ag-Sn solder has a lower cost and can provide sufficient wetting performance for the composite heat sink structure and the semiconductor chip to form a metallurgical bond. More importantly, the Ge-Ag-Sn solder can reduce the thermal stress caused by the mismatch of the thermal expansion coefficients between the chip and the heat sink, effectively avoiding the fracture of the diamond thermal conductive film layer caused by excessive stress, and greatly improving the yield of semiconductor laser devices.

[0014] Preferably, the mass ratio of the aniline-modified graphene to the boron nitride-modified graphene is 1:2 - 1:3.

[0015] Preferably, the thickness of the thermal conductive buffer film is 5 μm - 10 μm.

[0016] Preferably, the thickness of the heat-conducting film layer is 20 μm - 30 μm.

[0017] Preferably, the thickness of the metal welding layer is 3 μm - 5 μm.

[0018] Preferably, the preparation method of the aniline-modified graphene comprises the following steps: dispersing graphene in an alcohol solvent, adding aniline and a promoter, and carrying out a reflux reaction for 18 h - 24 h under an inert atmosphere to obtain aniline-modified graphene.

[0019] Aniline-modified graphene utilizes the lone pair of electrons on the N atom in the amino group of aniline in the unequal SP 2 orbital, which can conjugate with the large π bond on graphene to form a delocalized p-π conjugate system, becoming a kind of weak charge transfer complex, which helps the progress of electron heat transfer. Moreover, due to the two movable lone pairs of electrons on the N atom, the heat transfer performance is more excellent.

[0020] Further preferably, the mass ratio of graphene to aniline is 0.1:1 - 0.3:3.5.

[0021] Further preferably, the mass-volume ratio of aniline to the promoter is 1 g:3 mL - 1.5 g:5 mL.

[0022] Further preferably, the mass-volume ratio of graphene to the alcohol solution is 0.1 g:130 mL - 0.1 g:200 mL.

[0023] Further preferably, the promoter is isoamyl nitrite.

[0024] Preferably, the preparation method of the boron nitride-modified graphene comprises the following steps:

[0025] S1. Dispersing boron nitride in an organic alcohol, ultrasonicating, and centrifuging to obtain a pretreated boron nitride mixed solution;

[0026] S2. Mixing graphene and a crosslinking agent solution evenly, centrifuging at high speed, and discarding the supernatant to obtain pretreated graphene;

[0027] S3. At 60°C - 80°C, adding the organic alcohol and the pretreated boron nitride mixed solution to the pretreated graphene, mixing evenly, centrifuging, filtering, and freeze-drying to obtain boron nitride-modified graphene.

[0028] The present invention utilizes the boron nitride nanosheets on the surface of boron nitride-modified graphene to act as a bridge between graphene sheets, assisting in forming a complete heat-conducting network, thereby improving the heat conduction efficiency of graphene materials.

[0029] Further preferably, the organic alcohol is isopropyl alcohol.

[0030] More preferably, the mass-volume ratio of the boron nitride to the organic alcohol is 1 g: 80 mL - 2 g: 250 mL.

[0031] More preferably, in S1, the rotation speed of the centrifugation treatment is 2000 rpm - 3500 rpm, and the centrifugation time is 20 min - 30 min.

[0032] More preferably, in S2, the crosslinking agent solution is an aqueous solution of polydiallyldimethylammonium chloride with a mass concentration of 1% - 2.5%.

[0033] More preferably, in S2, the mass-volume ratio of the graphene to the crosslinking agent solution is 0.1 g: 100 mL - 0.5 g: 500 mL.

[0034] More preferably, in S2, the rotation speed of the high-speed centrifugation is 8000 rpm - 12000 rpm, and the high-speed centrifugation time is 10 min - 15 min.

[0035] More preferably, in S3, the mass-volume ratio of the pretreated graphene to the organic alcohol is 0.5 g: 30 mL - 50 mL.

[0036] More preferably, in S3, the rotation speed of the centrifugation is 1500 rpm - 2500 rpm, and the centrifugation time is 20 min - 30 min.

[0037] Preferably, the mass percentage contents of the components in the Ge-Ag-Sn solder are as follows: 10% - 15% of Ge, 5% - 10% of Ag, and the balance of Sn.

[0038] The second aspect of the present invention provides a method for preparing the high thermal conductivity silicon carbide composite heat sink structure, including the following steps:

[0039] Step 1: Deposit a thermal conductivity buffer film layer on the surface of a clean and dry silicon carbide substrate by using plasma enhanced chemical vapor deposition technology; obtain a first treated heat sink;

[0040] Step 2: Place the first treated heat sink in a microwave plasma chemical vapor deposition chamber to grow a thermal conductivity film layer; obtain a second treated heat sink;

[0041] Step 3: Prepare a metal welding layer on the surface of the second treated heat sink by using electron beam evaporation method to obtain the high thermal conductivity silicon carbide composite heat sink structure.

[0042] Preferably, in Step 1, the substrate temperature for depositing the thermal conductivity buffer film layer is 430°C - 480°C, the substrate bias voltage is 90 V - 110 V, and the radio frequency power is 100 - 110 W.

[0043] Preferably, in step two, the microwave power for growing the thermal conductive film layer is 2 kW - 4 kW, the deposition temperature is 850°C - 920°C; the hydrogen flow rate is 350 sccm - 450 sccm, and the methane flow rate is 22 sccm - 25 sccm.

[0044] Preferably, in step three, the process parameters of the electron beam evaporation method are: the vacuum degree is 1.0×10 -3 Pa - 5.0×10 -3 Pa, the evaporation distance is 40 cm - 60 cm, the electron gun voltage is 8 kV - 12 kV, the shape of the electron beam spot is circular, and the evaporation rate is 0.2 nm / s - 0.8 nm / s.

[0045] The third aspect of the present invention provides an application of the high - thermal - conductivity silicon carbide composite heat sink structure in a semiconductor laser.

[0046] In summary, the present invention designs a stepped heat transfer heat sink structure with silicon carbide as the substrate. The present invention sequentially deposits and grows a thermal conductive buffer film layer and a thermal conductive film layer on the silicon carbide substrate, thereby improving the thermal conductivity of the heat sink structure. The high - thermal - conductivity silicon carbide composite heat sink structure provided by the present invention effectively solves the problems in the prior art that the materials of the heat sink structure of semiconductor lasers are expensive, the thermal conductivity is low and cannot meet the device requirements, and cracks or even breakage will occur in the diamond film layer during chip welding, providing new materials for the preparation of semiconductor lasers.

[0047] The present invention designs a stepped heat transfer heat sink structure with silicon carbide as the substrate. Among them, a thermal conductive buffer film layer and a thermal conductive film layer are sequentially deposited and grown on the silicon carbide substrate. The low - thermal - conductivity silicon carbide substrate is connected to the high - thermal - conductivity diamond thermal conductive film layer by the thermal conductive buffer film layer. By utilizing the different intrinsic thermal conductivities of each layer of material, the purpose of stepped heat dissipation is achieved, which is more conducive to device heat dissipation. Moreover, the present invention also designs a new metal solder, which can not only provide sufficient wetting performance between the heat sink structure and the chip, but also reduce the thermal stress caused by the mismatch of the thermal expansion coefficients between the chip and the heat sink, avoiding cracks or breakage in the diamond film layer during the welding process. Using the technical solution of the present invention effectively solves the problems in the prior art that the materials of the heat sink structure of semiconductor lasers are expensive, the thermal conductivity is low and cannot meet the device requirements, and cracks or even breakage will occur in the diamond film layer during chip welding, greatly improving the yield of semiconductor laser devices and providing new preparation materials and theoretical basis for the efficient heat dissipation of semiconductor lasers. Detailed Embodiments

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] The preparation methods of aniline-modified graphene and boron nitride-modified graphene used in the following examples and comparative examples are as follows:

[0050] Preparation method of aniline-modified graphene:

[0051] Disperse 0.1 g of graphene in 150 mL of absolute ethanol, add 1.5 g of aniline and 5 mL of isoamyl nitrite, and under an inert atmosphere, reflux for 22 h, cool to room temperature, filter, wash the solid filtrate 3 times with absolute ethanol, and purify it with a 0.5-μm dialysis membrane to obtain aniline-modified graphene.

[0052] Preparation method of boron nitride-modified graphene

[0053] S1. Disperse 1.5 g of boron nitride in 150 mL of isopropanol, ultrasonicate, and centrifuge at a speed of 2500 rpm for 25 min to obtain a pretreated boron nitride mixture;

[0054] S2. Mix 0.3 g of graphene and 150 mL of 1% polydiallyldimethylammonium chloride solution evenly, stir for 8 h, then centrifuge at a high speed of 10000 rpm for 10 min, discard the supernatant to obtain pretreated graphene;

[0055] S3. At 70 °C, add 20 mL of isopropanol and the pretreated boron nitride mixture to the pretreated graphene, mix evenly, centrifuge at a speed of 2000 rpm for 20 min, filter, and freeze-dry to obtain boron nitride-modified graphene.

[0056] Example 1

[0057] This example provides a high-thermal-conductivity silicon carbide composite heat sink structure, which specifically includes the following:

[0058] Step 1. Deposit a 8-μm-thick thermal-conductivity buffer film layer on the surface of a clean and dry silicon carbide substrate by plasma-enhanced chemical vapor deposition technology to obtain a first-treated heat sink; wherein, the substrate temperature for depositing the thermal-conductivity buffer film layer is 450 °C, the substrate bias voltage is 100 V, and the radio frequency power is 100 W;

[0059] Step 2: Place the first processed heat sink in a microwave plasma chemical vapor deposition chamber and grow a diamond film layer with a thickness of 25 μm to obtain a second processed heat sink. Among them, the microwave power for growing the heat conduction film layer is 3 kW, the deposition temperature is 900 °C, the hydrogen flow rate is 400 sccm, and the methane flow rate is 24 sccm.

[0060] Step 3: Use electron beam evaporation to prepare a metal welding layer with a thickness of 4 μm on the surface of the second processed heat sink to obtain the high thermal conductivity silicon carbide composite heat sink structure. Among them, the vacuum degree is 3.0×10 -3 Pa, the evaporation distance is 55 cm, the electron gun voltage is 10 kV, the shape of the electron beam spot is circular, and the evaporation rate is 0.6 nm / s.

[0061] Among them, the material of the heat conduction buffer film layer is aniline modified graphene and boron nitride modified graphene with a mass ratio of 1:2.

[0062] The solder of the metal welding layer is Ge-Ag-Sn solder, and the mass percentage content of each component is as follows: 12% Ge, 5% Ag, and 83% Sn.

[0063] Example 2

[0064] This example provides a high thermal conductivity silicon carbide composite heat sink structure, which specifically includes the following:

[0065] Step 1: Use plasma enhanced chemical vapor deposition technology to deposit a heat conduction buffer film layer with a thickness of 10 μm on the surface of a clean and dry silicon carbide substrate to obtain a first processed heat sink. Among them, the substrate temperature for depositing the heat conduction buffer film layer is 435 °C, the substrate bias voltage is 105 V, and the radio frequency power is 100 W.

[0066] Step 2: Place the first processed heat sink in a microwave plasma chemical vapor deposition chamber and grow a diamond film layer with a thickness of 30 μm to obtain a second processed heat sink. Among them, the microwave power for growing the heat conduction film layer is 3 kW, the deposition temperature is 870 °C, the hydrogen flow rate is 420 sccm, and the methane flow rate is 25 sccm.

[0067] Step 3: Use electron beam evaporation to prepare a metal welding layer with a thickness of 3 μm on the surface of the second processed heat sink to obtain the high thermal conductivity silicon carbide composite heat sink structure. Among them, the vacuum degree is 1.0×10 -3 Pa, the evaporation distance is 50 cm, the electron gun voltage is 12 kV, the shape of the electron beam spot is circular, and the evaporation rate is 0.5 nm / s.

[0068] Among them, the material of the heat conduction buffer film layer is aniline modified graphene and boron nitride modified graphene with a mass ratio of 1:3.

[0069] The solder of the metal welding layer is a Ge-Ag-Sn solder, and the mass percentage contents of each component are as follows: 11% Ge, 8% Ag, and 81% Sn.

[0070] Example 3

[0071] This example provides a high thermal conductivity silicon carbide composite heat sink structure, which specifically includes the following:

[0072] Step 1: Deposit a 5-μm-thick thermal conductivity buffer film layer on the surface of a clean and dry silicon carbide substrate by using plasma enhanced chemical vapor deposition technology; obtain the first processed heat sink. Among them, the substrate temperature for depositing the thermal conductivity buffer film layer is 450 °C, the substrate bias voltage is 100 V, and the radio frequency power is 100 W.

[0073] Step 2: Place the first processed heat sink in a microwave plasma chemical vapor deposition chamber and grow a 20-μm-thick diamond film layer; obtain the second processed heat sink. Among them, the microwave power for growing the thermal conductivity film layer is 3 kW, the deposition temperature is 850 °C; the hydrogen flow rate is 450 sccm, and the methane flow rate is 23 sccm.

[0074] Step 3: Prepare a 4-μm-thick metal welding layer on the surface of the second processed heat sink by using electron beam evaporation method to obtain the high thermal conductivity silicon carbide composite heat sink structure. Among them, the vacuum degree is 4.0×10 -3 Pa, the evaporation distance is 60 cm, the electron gun voltage is 12 kV, the shape of the electron beam spot is circular, and the evaporation rate is 0.8 nm / s.

[0075] Among them, the material of the thermal conductivity buffer film layer is aniline-modified graphene and boron nitride-modified graphene with a mass ratio of 1:2.5.

[0076] The solder of the metal welding layer is a Ge-Ag-Sn solder, and the mass percentage contents of each component are as follows: 15% Ge, 5% Ag, and 80% Sn.

[0077] Comparative Example 1

[0078] This comparative example provides a high thermal conductivity silicon carbide composite heat sink structure, which is different from Example 1 in that: there is no thermal conductivity buffer film layer, and it specifically includes the following:

[0079] Step 1: Place a clean and dry silicon carbide substrate in a microwave plasma chemical vapor deposition chamber and grow a 25-μm-thick diamond film layer; obtain the second processed heat sink. Among them, the microwave power for growing the thermal conductivity film layer is 3 kW, the deposition temperature is 900 °C; the hydrogen flow rate is 400 sccm, and the methane flow rate is 24 sccm.

[0080] Step 2: Prepare a metal welding layer with a thickness of 4 μm on the surface of the second processed heat sink by electron beam evaporation to obtain the high - thermal - conductivity silicon carbide composite heat sink structure; where the vacuum degree is 3.0×10 -3 Pa, the evaporation distance is 55 cm, the electron gun voltage is 10 kV, the shape of the electron beam spot is circular, and the evaporation rate is 0.6 nm / s.

[0081] The solder of the metal welding layer is Ge - Ag - Sn solder, and the mass percentage content of each component is as follows: 12% Ge, 5% Ag, and 83% Sn.

[0082] Comparative Example 2

[0083] This comparative example provides a high - thermal - conductivity silicon carbide composite heat sink structure, which is different from Example 1 in that: the material of the thermal - conductivity buffer film layer is aniline - modified graphene layer, and the specific content is as follows:

[0084] Step 1: Deposit a layer of aniline - modified graphene layer with a thickness of 8 μm on the surface of a clean and dry silicon carbide substrate by plasma - enhanced chemical vapor deposition technology to obtain the first processed heat sink; where the substrate temperature for depositing the thermal - conductivity buffer film layer is 450 °C, the substrate bias voltage is 100 V, and the radio - frequency power is 100 W;

[0085] Step 2: Place the first processed heat sink in a microwave plasma chemical vapor deposition chamber and grow a layer of diamond film layer with a thickness of 25 μm to obtain the second processed heat sink; where the microwave power for growing the thermal - conductivity film layer is 3 kW, the deposition temperature is 900 °C; the hydrogen flow rate is 400 sccm, and the methane flow rate is 24 sccm;

[0086] Step 2: Prepare a metal welding layer with a thickness of 4 μm on the surface of the second processed heat sink by electron beam evaporation to obtain the high - thermal - conductivity silicon carbide composite heat sink structure; where the vacuum degree is 3.0×10 -3 Pa, the evaporation distance is 55 cm, the electron gun voltage is 10 kV, the shape of the electron beam spot is circular, and the evaporation rate is 0.6 nm / s.

[0087] The solder of the metal welding layer is Ge - Ag - Sn solder, and the mass percentage content of each component is as follows: 12% Ge, 5% Ag, and 83% Sn.

[0088] Comparative Example 3

[0089] This comparative example provides a high - thermal - conductivity silicon carbide composite heat sink structure, which is different from Example 1 in that: the material of the thermal - conductivity buffer film layer is boron nitride - modified graphene layer, and the specific content is as follows:

[0090] Step 1. Deposit a boron nitride modified graphene layer with a thickness of 8 μm on the surface of a clean and dry silicon carbide substrate by plasma enhanced chemical vapor deposition technology to obtain a first processed heat sink. The substrate temperature for depositing the thermal conductive buffer layer is 450 °C, the substrate bias voltage is 100 V, and the radio frequency power is 100 W.

[0091] Step 2. Place the first processed heat sink in a microwave plasma chemical vapor deposition chamber and grow a diamond film layer with a thickness of 25 μm to obtain a second processed heat sink. The microwave power for growing the thermal conductive film layer is 3 kW, the deposition temperature is 900 °C, the hydrogen flow rate is 400 sccm, and the methane flow rate is 24 sccm.

[0092] Step 3. Prepare a metal welding layer with a thickness of 4 μm on the surface of the second processed heat sink by electron beam evaporation to obtain the high thermal conductivity silicon carbide composite heat sink structure. The vacuum degree is 3.0×10 -3 Pa, the evaporation distance is 55 cm, the electron gun voltage is 10 kV, the shape of the electron beam spot is circular, and the evaporation rate is 0.6 nm / s.

[0093] The solder of the metal welding layer is Ge-Ag-Sn solder, and the mass percentage content of each component is as follows: 12% Ge, 5% Ag, and 83% Sn.

[0094] Comparative Example 4

[0095] This comparative example provides a high thermal conductivity silicon carbide composite heat sink structure, which is different from that of Example 1 in that the raw material of the metal welding layer is AuSn solder, and the specific content is as follows:

[0096] Step 1. Deposit a thermal conductive buffer layer with a thickness of 8 μm on the surface of a clean and dry silicon carbide substrate by plasma enhanced chemical vapor deposition technology to obtain a first processed heat sink. The substrate temperature for depositing the thermal conductive buffer layer is 450 °C, the substrate bias voltage is 100 V, and the radio frequency power is 100 W.

[0097] Step 2. Place the first processed heat sink in a microwave plasma chemical vapor deposition chamber and grow a diamond film layer with a thickness of 25 μm to obtain a second processed heat sink. The microwave power for growing the thermal conductive film layer is 3 kW, the deposition temperature is 900 °C, the hydrogen flow rate is 400 sccm, and the methane flow rate is 24 sccm.

[0098] Step 3. Prepare a metal welding layer with a thickness of 4 μm on the surface of the second processed heat sink by electron beam evaporation to obtain the high thermal conductivity silicon carbide composite heat sink structure. The vacuum degree is 3.0×10 -3Pa, the evaporation distance is 55 cm, the electron gun voltage is 10 kV, the shape of the electron beam spot is circular, and the evaporation rate is 0.6 nm / s.

[0099] Among them, the material of the thermal conductive buffer film layer is aniline-modified graphene and boron nitride-modified graphene with a mass ratio of 1:2.

[0100] Among them, the solder of the metal welding layer is AuSn solder, and the mass percentage content of each component is as follows: 80% Au and 20% Sn.

[0101] To further demonstrate the technical effects of the present invention, the thermal conductivity of the high-thermal-conductivity silicon carbide composite heat sink structures obtained in Examples 1-3 and Comparative Examples 1-4 was measured using a thermal conductivity meter from C-Therm in Germany; the present invention also counted the device yield of using the high-thermal-conductivity silicon carbide composite heat sink structures obtained in Examples 1-3 and Comparative Examples 1-4 to prepare semiconductor lasers, and the results are shown in Table 1.

[0102] Table 1 Test results of thermal conductivity and yield

[0103] Project Thermal conductivity W / (m·K) Device yield rate (%) Example 1 987 99.7 Example 2 976 99.4 Example 3 943 99.6 Comparative Example 1 634 98.4 Comparative Example 2 792 98.9 Comparative Example 3 801 99.1 Comparative Example 4 923 70.3

[0104] As can be seen from Table 1, the thermal conductivity of the high-thermal-conductivity silicon carbide composite heat sink structure provided by the present invention can be as high as 987 W / (m·K), far higher than the thermal conductivity of the silicon carbide substrate alone, and the composite heat sink structure provided by the present invention does not require the high cost of depositing a diamond film layer entirely. Moreover, the present application uses a metal solder with low stress, avoiding a too high scrap rate of the device and providing a new material for high-thermal-conductivity semiconductor lasers.

[0105] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high thermal conductivity silicon carbide composite heat sink structure, characterized in that: From bottom to top, it includes a silicon carbide substrate, a thermal conductive buffer film layer, a thermal conductive film layer and a metal welding layer; The material of the thermal conductive buffer film layer is a mixture of aniline-modified graphene and boron nitride-modified graphene; The heat-conducting film layer is a diamond film layer; The solder of the metal welding layer is Ge-Ag-Sn solder; The mass ratio of the aniline-modified graphene to the boron nitride-modified graphene is 1:2-1:3; The thickness of the thermally conductive buffer film is 5 μm-10 μm; The thickness of the thermal conductive film layer is 20 μm-30 μm; The thickness of the metal welding layer is 3 μm-5 μm.

2. The high thermal conductivity silicon carbide composite heat sink structure according to claim 1, characterized in that: The preparation method of aniline-modified graphene comprises the following steps: dispersing graphene in an alcohol solvent, adding aniline and a promoter, and performing a reflux reaction for 18 hours to 24 hours under an inert atmosphere to obtain aniline-modified graphene.

3. The high thermal conductivity silicon carbide composite heat sink structure according to claim 2, characterized in that: The mass ratio of graphene to aniline is 0.1:1-0.3:3.5; and / or The mass volume ratio of aniline to accelerator is 1g:3mL-1.5g:5mL; and / or The mass volume ratio of the graphene to the alcohol solution is 0.1 g:130 mL-0.1 g:200 mL; and / or The accelerator is isoamyl nitrite.

4. The high thermal conductivity silicon carbide composite heat sink structure according to claim 1, characterized in that: The preparation method of the boron nitride modified graphene comprises the following steps: S1. Dispersing boron nitride in organic alcohol, ultrasonicating, and centrifuging to obtain a pretreated boron nitride mixed solution; S2, mixing the graphene and the cross-linking agent solution evenly, centrifuging at high speed, and discarding the supernatant to obtain pretreated graphene; S3. Adding organic alcohol and the pretreated boron nitride mixed solution to the pretreated graphene at 60° C.-80° C., mixing evenly, centrifuging, filtering, and freeze-drying to obtain boron nitride modified graphene.

5. The high thermal conductivity silicon carbide composite heat sink structure according to claim 4, characterized in that: The organic alcohol is isopropanol; and / or The mass volume ratio of the boron nitride to the organic alcohol is 1g:80mL-2g:250mL; and / or In S1, the rotation speed of the centrifugal treatment is 2000 rpm-3500 rpm, and the time of the centrifugal treatment is 20 min-30 min; and / or In S2, the cross-linking agent solution is a polydiallyl dimethyl ammonium chloride aqueous solution with a mass concentration of 1%-2.5%; and / or In S2, the mass volume ratio of the graphene and the cross-linking agent solution is 0.1 g: 100 mL-0.5 g: 500 mL; and / or In S2, the rotation speed of the high-speed centrifugation is 8000 rpm-12000 rpm, and the time of the high-speed centrifugation is 10 min-15 min; and / or In S3, the mass volume ratio of the pretreated graphene and the organic alcohol is 0.1 g:10 mL-0.5 g:50 mL; and / or In S3, the centrifugal speed is 1500rpm-2500rpm, and the centrifugal time is 20min-30min.

6. The high thermal conductivity silicon carbide composite heat sink structure according to claim 1, characterized in that: The mass percentage of each component in the Ge-Ag-Sn solder is as follows: 10%-15% Ge, 5%-10% Ag and the balance Sn.

7. A method for preparing a high thermal conductivity silicon carbide composite heat sink structure according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: using plasma enhanced chemical vapor deposition technology to deposit a thermally conductive buffer film layer on the surface of a clean and dry silicon carbide substrate to obtain a first processed heat sink; Step 2: placing the first treated heat sink in a microwave plasma chemical vapor deposition chamber to grow a thermally conductive film layer to obtain a second treated heat sink; Step three: prepare a metal welding layer on the surface of the second treated heat sink by electron beam evaporation to obtain the high thermal conductivity silicon carbide composite heat sink structure.

8. The method for preparing a high thermal conductivity silicon carbide composite heat sink structure according to claim 7, characterized in that: In step 1, the substrate temperature for depositing the thermal conductive buffer film layer is 430° C.-480° C., the substrate bias voltage is 90V-110V, and the RF power is 100-110W; and / or In step 2, the microwave power for growing the thermal conductive film layer is 2kW-4kW, the pressure is 25kPa-30kPa, the deposition temperature is 850°C-920°C; the hydrogen flow rate is 350sccm-450sccm, and the methane flow rate is 22sccm-25sccm; and / or In step 3, the process parameters of the electron beam evaporation method are: vacuum degree is 1.0×10 −3 Pa-5.0×10 −3 Pa, evaporation distance is 40cm-60cm, electron gun voltage is 8kV-12kV, electron beam spot shape is circular, and evaporation rate is 0.2nm / s-0.8nm / s.

9. Application of the high thermal conductivity silicon carbide composite heat sink structure according to any one of claims 1 to 6 in a semiconductor laser.