Preparation method of heat-conducting and wave-absorbing SiC crystal and heat-conducting and wave-absorbing SiC crystal

Abstract

The invention relates to a preparation method of a heat-conducting and wave-absorbing SiC crystal and the heat-conducting and wave-absorbing SiC crystal, in particular to the field of semiconductors, and the preparation method comprises the steps that oxidation treatment and volatilization treatment are sequentially conducted on a silicon carbide crystal containing a microtube under the protective atmosphere, and the heat-conducting and wave-absorbing SiC crystal is obtained. According to the preparation method provided by the invention, the micro-tube wall in the silicon carbide crystal is oxidized to form amorphous SiOx, then volatilization treatment is carried out, the SiOx is volatilized, and closed nanopores are left, so that more electromagnetic wave scattering and absorption sites are provided for the silicon carbide crystal, and meanwhile, the silicon carbide crystal also has good heat-conducting property.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and specifically to a method for preparing a thermally conductive and microwave-absorbing SiC crystal, and the thermally conductive and microwave-absorbing SiC crystal itself. Background Technology

[0002] Currently, with the dual demands of 5G / 6G communication, high-power chips, and stealth technology for materials that can "heat up quickly and absorb microwaves widely," traditional single-function solutions of "thermal conductivity OR microwave absorption" are no longer sustainable. SiC, with its unique advantages of intrinsic high thermal conductivity, tunable dielectric, high-temperature stability, and compatibility with semiconductor processes, is leaping from a "power device substrate" to a core carrier for "integrated thermal conductivity and microwave absorption." Through innovative methods such as defect / doping design, lamellar core-shell structures, and gradient co-doping, its thermal conductivity can still maintain >120 W·m. -1 ·K -1 Simultaneously, it achieves broadband absorption of <-20dB within the 2-18GHz range and has already been implemented in 5G base stations, high-power chip heat sinks, and stealth structural components. Looking towards a future with higher frequencies and greater power, SiC-based thermally conductive and microwave absorbing materials will continue to break down the "thermal-electromagnetic" barrier, providing a new path for lightweight, highly reliable, and mass-producible electronic information and defense equipment.

[0003] Currently, PVT (Silicon Carbide Transmission) is the mainstream technology for fabricating SiC power device substrates. However, for SiC crystals specifically used for thermal conductivity and microwave absorption applications, PVT has some significant drawbacks. The core reason is that the requirements for SiC materials in power devices and thermal conductivity / microwave absorption are completely different:

[0004] Power devices: The focus is on electrical performance (such as breakdown field strength and carrier mobility) and crystal quality (low defects to ensure device yield and reliability).

[0005] Thermal conductivity and wave absorption: The focus is on achieving both rapid heating and wide absorption, while electrical performance is secondary.

[0006] However, there is still no efficient preparation method for thermally conductive and microwave-absorbing SiC crystals. Therefore, this invention provides a method for preparing thermally conductive and microwave-absorbing SiC crystals to achieve efficient preparation of such crystals. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing thermally conductive and microwave-absorbing SiC crystals and thermally conductive and microwave-absorbing SiC crystals, so as to achieve efficient preparation of thermally conductive and microwave-absorbing SiC crystals, and the obtained thermally conductive and microwave-absorbing SiC crystals have excellent thermal conductivity and microwave absorption properties.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a thermally conductive and microwave-absorbing SiC crystal, the method comprising:

[0010] Silicon carbide crystals containing microtubes are subjected to oxidation and volatilization treatments in a protective atmosphere to obtain thermally conductive and microwave-absorbing SiC crystals.

[0011] The preparation method provided by this invention involves oxidizing the microtube walls within a silicon carbide crystal to form amorphous SiO₂. x Then, it undergoes a volatilization treatment to remove SiO2. x The vaporization process leaves closed nanopores, thereby providing more electromagnetic wave scattering and absorption sites for silicon carbide crystals, while also exhibiting good thermal conductivity.

[0012] As a preferred embodiment of the present invention, the gas used in the oxidation process includes oxygen with a flow rate of 10-25 sccm.

[0013] As a preferred embodiment of the present invention, the oxidation treatment temperature is 2300-2500℃.

[0014] Preferably, the oxidation treatment pressure is 1-1.5 mbar.

[0015] Preferably, the oxidation treatment time is 10-15 hours.

[0016] As a preferred technical solution of the present invention, the gas used in the volatilization treatment includes a protective gas with a flow rate of 200-300 slm.

[0017] As a preferred embodiment of the present invention, the temperature of the evaporation treatment is 2300-2500℃.

[0018] Preferably, the pressure of the evaporation treatment is 1-1.5 mbar.

[0019] Preferably, the volatilization treatment time is 5-8 hours.

[0020] As a preferred technical solution of the present invention, the preparation process of the silicon carbide crystal containing microtubes is as follows: physical vapor transport growth is carried out using seed crystals and crystal growth raw materials to obtain silicon carbide crystals containing microtubes.

[0021] As a preferred embodiment of the present invention, the seed crystal comprises: ≥10 microtubes / cm 2 Silicon carbide seed crystals.

[0022] Preferably, the thickness of the seed crystal is ≥500μm.

[0023] Preferably, the crystal growth raw materials include silicon carbide particles and silicon powder.

[0024] Preferably, the mass of the silicon powder is 0.04-0.25% of the mass of the silicon carbide particles.

[0025] Preferably, the particle size of the silicon carbide particles is <0.178 μm.

[0026] Preferably, the particle size of the silicon powder is <6μm.

[0027] As a preferred technical solution of the present invention, the vertical distance from the surface of the growth material to the seed crystal at the start of the physical vapor transport growth is <10mm.

[0028] Preferably, the gas used for physical vapor transport growth includes: a protective gas or a protective gas and a dopant gas with a flow ratio of (40-60):1.

[0029] Preferably, the doping gas includes nitrogen and / or ammonia.

[0030] Preferably, the flow rate of the gas used for physical vapor transport growth is 85-130 sccm.

[0031] As a preferred technical solution of the present invention, the moving speed of the induction coil in the physical vapor transport growth is 0.1-0.2 mm / h.

[0032] Preferably, the growth pressure of the physical vapor transport growth is 1-1.5 mbar.

[0033] Preferably, the growth temperature of the physical vapor transport growth is 2300-2500℃.

[0034] Preferably, the growth time of the physical vapor transport growth is 140-160 hours.

[0035] In a second aspect, the present invention provides a thermally conductive and microwave-absorbing SiC crystal, which is prepared by the preparation method described in the first aspect.

[0036] The thermal conductivity of the thermally conductive and microwave-absorbing SiC crystal is ≥130 W·m. -1 ·K -1 The reflection loss is <-20dB.

[0037] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0038] (1) The preparation method provided by the present invention forms amorphous SiO by oxidizing the microtube wall inside the silicon carbide crystal. x Then, it undergoes a volatilization treatment to remove SiO2. xThe vaporization process leaves behind closed nanopores, transforming microtube defects into closed nanopores. This provides silicon carbide crystals with more electromagnetic wave scattering and absorption sites, resulting in excellent wave absorption and thermal conductivity.

[0039] (2) The preparation method provided by the present invention improves the micro density during the crystal growth process by designing specific particle size silicon carbide powder and silicon powder in the preparation process of silicon carbide crystal containing microtubes; furthermore, the density of microtubes is further improved by optimizing the growth pressure.

[0040] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0041] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0042] Currently, SiC, with its unique advantages of intrinsic high thermal conductivity, tunable dielectric, high-temperature stability, and compatibility with semiconductor processes, is leaping from a "power device substrate" to a core carrier for "integrated thermal conductivity and microwave absorption." However, the requirements for SiC materials in power devices and thermal conductivity / microwave absorption are completely different, making the current physical vapor transport method for preparing silicon carbide unable to achieve efficient preparation of thermally conductive and microwave-absorbing SiC crystals. Based on this, this invention optimizes the preparation process by oxidizing and volatilizing the microtubes of silicon carbide, enabling silicon carbide crystals to possess excellent thermal conductivity and microwave absorption properties, as detailed below:

[0043] I. This embodiment provides a method for preparing a thermally conductive and microwave-absorbing SiC crystal, the method comprising:

[0044] Silicon carbide crystals containing microtubes are subjected to oxidation and volatilization treatments in a protective atmosphere to obtain thermally conductive and microwave-absorbing SiC crystals.

[0045] In this invention, the silicon carbide crystal containing microtubes can be obtained by commercially available products, existing preparation methods, or the preparation method provided by this invention.

[0046] In this invention, the oxidation and volatilization treatments can be performed in a physical vapor transport growth apparatus after crystal growth, or other related equipment can be used.

[0047] The preparation process of the silicon carbide crystal containing microtubes is as follows: physical vapor transport growth is carried out using seed crystals and growth raw materials to obtain silicon carbide crystals containing microtubes.

[0048] In this invention, the protective atmosphere or protective gas refers to a gas that does not participate in the processing, such as protective gases like helium and neon.

[0049] The seed crystal includes: ≥10 microtubes / cm 2 Silicon carbide seed crystals, for example, can be 10 per cm. 2 11 pieces / cm 2 12 pieces / cm 2 13 pieces / cm 2 14 pieces / cm 2 15 pieces / cm 2 16 pieces / cm 2 17 pieces / cm 2 18 pieces / cm 2 19 pieces / cm 2 Or 20 pieces / cm 2 The values ​​may include, but are not limited to, the listed values; other unlisted values ​​within this range also meet the requirements.

[0050] The thickness of the seed crystal is ≥500μm, for example, it can be 500μm, 510μm, 520μm, 530μm, 540μm, 550μm, 560μm, 570μm, 580μm, 590μm or 600μm, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0051] The raw materials for crystal growth include silicon carbide particles and silicon powder.

[0052] The mass of the silicon powder is 0.04-0.25% of the mass of the silicon carbide particles, for example, it can be 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.15%, 0.17%, 0.19%, 0.21%, 0.23%, or 0.25%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0053] The silicon carbide particles have a particle size of <0.178 μm.

[0054] The particle size of the silicon powder is <6μm.

[0055] In this invention, the limitation on particle size refers to limiting it to an aggregate of particles of any single particle size, or an aggregate of all particles of any size within any subset of the particle size range.

[0056] Wherein, the vertical distance from the surface of the growth material to the seed crystal at the start of the physical vapor transport growth is <10mm, for example, it can be 1mm, 1.9mm, 2.8mm, 3.7mm, 4.6mm, 5.5mm, 6.4mm, 7.3mm, 8.2mm, 9.1mm or 10mm, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0057] The gases used in the physical vapor transport growth include: a protective gas or a protective gas and a dopant gas with a flow ratio of (40-60):1, such as 40:1, 42:1, 44:1, 46:1, 48:1, 50:1, 52:1, 54:1, 56:1, 58:1 or 60:1, etc., but are not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0058] In this invention, when a doping gas is introduced during physical vapor transport growth, the specific design is based on actual requirements to form a doped silicon carbide crystal. The doping source commonly used in the art is selected according to the requirements of the required silicon carbide crystal. It should be noted that doping does not affect the realization of other process performance of this invention. For example, the doping gas includes nitrogen and / or ammonia.

[0059] The flow rate of the gas used for physical vapor transport growth is 85-130 sccm, for example, it can be 85 sccm, 89.5 sccm, 94 sccm, 98.5 sccm, 103 sccm, 107.5 sccm, 112 sccm, 116.5 sccm, 121 sccm, 125.5 sccm or 130 sccm, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0060] The moving speed of the induction coil in the physical vapor transport growth process is 0.1-0.2 mm / h, for example, it can be 0.1 mm / h, 0.11 mm / h, 0.12 mm / h, 0.13 mm / h, 0.14 mm / h, 0.15 mm / h, 0.16 mm / h, 0.17 mm / h, 0.18 mm / h, 0.19 mm / h or 0.2 mm / h, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0061] The growth pressure for the physical vapor transport growth is 1-1.5 mbar, for example, it can be 1 mbar, 1.05 mbar, 1.1 mbar, 1.15 mbar, 1.2 mbar, 1.25 mbar, 1.3 mbar, 1.35 mbar, 1.4 mbar, 1.45 mbar or 1.5 mbar, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0062] The growth temperature for the physical vapor transport growth is 2300-2500℃, for example, it can be 2300℃, 2320℃, 2340℃, 2360℃, 2380℃, 2400℃, 2420℃, 2440℃, 2460℃, 2480℃ or 2500℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0063] The growth time for the physical vapor transport growth is 140-160 hours, for example, it can be 140 hours, 142 hours, 144 hours, 146 hours, 148 hours, 150 hours, 152 hours, 154 hours, 156 hours, 158 hours or 160 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0064] The gas used in the oxidation process includes oxygen with a flow rate of 10-25 sccm, such as 10 sccm, 11.5 sccm, 13 sccm, 14.5 sccm, 16 sccm, 17.5 sccm, 19 sccm, 20.5 sccm, 22 sccm, 23.5 sccm, or 25 sccm, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0065] The oxidation treatment temperature is 2300-2500℃, for example, it can be 2300℃, 2320℃, 2340℃, 2360℃, 2380℃, 2400℃, 2420℃, 2440℃, 2460℃, 2480℃ or 2500℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0066] The oxidation treatment pressure is 1-1.5 mbar, for example, it can be 1 mbar, 1.05 mbar, 1.1 mbar, 1.15 mbar, 1.2 mbar, 1.25 mbar, 1.3 mbar, 1.35 mbar, 1.4 mbar, 1.45 mbar or 1.5 mbar, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0067] The oxidation treatment time is 10-15 hours, for example, it can be 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours or 15 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0068] The gas used in the evaporation treatment includes a protective gas with a flow rate of 200-300 slm, such as 200 slm, 210 slm, 220 slm, 230 slm, 240 slm, 250 slm, 260 slm, 270 slm, 280 slm, 290 slm, or 300 slm, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0069] The temperature of the evaporation treatment is 2300-2500℃, for example, it can be 2300℃, 2320℃, 2340℃, 2360℃, 2380℃, 2400℃, 2420℃, 2440℃, 2460℃, 2480℃ or 2500℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0070] The pressure of the evaporation treatment is 1-1.5 mbar, for example, it can be 1 mbar, 1.05 mbar, 1.1 mbar, 1.15 mbar, 1.2 mbar, 1.25 mbar, 1.3 mbar, 1.35 mbar, 1.4 mbar, 1.45 mbar or 1.5 mbar, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0071] The volatilization treatment time is 5-8 hours, for example, it can be 5 hours, 5.3 hours, 5.6 hours, 5.9 hours, 6.2 hours, 6.5 hours, 6.8 hours, 7.1 hours, 7.4 hours, 7.7 hours or 8 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0072] II. This embodiment provides a thermally conductive and microwave-absorbing SiC crystal, which is prepared using a method for preparing thermally conductive and microwave-absorbing SiC crystals; the thermal conductivity of the thermally conductive and microwave-absorbing SiC crystal is ≥130 W·m. -1 ·K -1 The reflection loss is <-20dB, and under the preferred scheme, the reflection loss is <-30dB.

[0073] III. To illustrate the performance achievable by the thermally conductive and microwave-absorbing SiC crystal prepared by the method of this invention, the following practical example is used for explanation:

[0074] Example 1

[0075] This embodiment provides a method for preparing a thermally conductive and microwave-absorbing SiC crystal. The preparation process is as follows:

[0076] Silicon carbide crystals containing microtubes are subjected to oxidation and volatilization treatments in a protective atmosphere (argon) to obtain thermally conductive and microwave-absorbing SiC crystals.

[0077] The preparation process of the silicon carbide crystal containing microtubes is as follows: Physical vapor transport growth is performed using a seed crystal and a growth material to obtain the silicon carbide crystal containing microtubes; the seed crystal comprises: 15 microtubes / cm². 2 The silicon carbide seed crystal has a thickness of 500 μm. The raw materials for crystal growth include silicon carbide particles and silicon powder. The mass of silicon powder is 0.1% of the mass of silicon carbide particles. The particle size of silicon carbide particles is <0.178 μm, and the particle size of silicon powder is <6 μm.

[0078] At the start of the physical vapor transport growth, the vertical distance from the surface of the growth material to the seed crystal is 5 mm. The gases used include: a protective gas (argon) with a flow rate of 125 sccm; the induction coil moving speed is 0.15 mm / h; the growth pressure is 1.2 mbar; the growth temperature is 2400℃; and the growth time is 150 h.

[0079] The gases used in the oxidation process include: oxygen at a flow rate of 15 sccm, a temperature of 2400℃, a pressure of 1.2 mbar, and a time of 13 h;

[0080] The gases used in the volatilization process include: a protective gas (argon) with a flow rate of 250 slm, a temperature of 2400℃, a pressure of 1.2 mbar, and a time of 7 h.

[0081] Example 2

[0082] This embodiment provides a method for preparing a thermally conductive and microwave-absorbing SiC crystal. The preparation process is as follows:

[0083] Silicon carbide crystals containing microtubes are subjected to oxidation and volatilization treatments in a protective atmosphere (argon) to obtain thermally conductive and microwave-absorbing SiC crystals.

[0084] The preparation process of the silicon carbide crystal containing microtubes is as follows: Physical vapor transport growth is performed using a seed crystal and a growth material to obtain the silicon carbide crystal containing microtubes; the seed crystal comprises: 10 microtubes / cm. 2 The silicon carbide seed crystal has a thickness of 500 μm. The raw materials for crystal growth include silicon carbide particles and silicon powder. The mass of silicon powder is 0.2% of the mass of silicon carbide particles. The particle size of silicon carbide particles is <0.178 μm and the particle size of silicon powder is <6 μm.

[0085] At the start of the physical vapor transport growth, the vertical distance from the surface of the growth material to the seed crystal is 5 mm. The gases used include: a protective gas (argon) with a flow rate of 125 sccm; the induction coil moving speed is 0.18 mm / h; the growth pressure is 1.4 mbar; the growth temperature is 2450℃; and the growth time is 155 h.

[0086] The gases used in the oxidation process include: oxygen at a flow rate of 20 sccm, a temperature of 2450℃, a pressure of 1.4 mbar, and a time of 12 h;

[0087] The gases used in the volatilization process include: a protective gas (argon) with a flow rate of 280 slm, a temperature of 2450°C, a pressure of 1.3 mbar, and a time of 6 h.

[0088] Example 3

[0089] This embodiment provides a method for preparing a thermally conductive and microwave-absorbing SiC crystal. The preparation process is as follows:

[0090] Silicon carbide crystals containing microtubes are subjected to oxidation and volatilization treatments in a protective atmosphere (argon) to obtain thermally conductive and microwave-absorbing SiC crystals.

[0091] The preparation process of the silicon carbide crystal containing microtubes is as follows: Physical vapor transport growth is performed using a seed crystal and a crystal growth material to obtain the silicon carbide crystal containing microtubes; the seed crystal comprises: 20 microtubes / cm². 2 The silicon carbide seed crystal has a thickness of 800 μm. The raw materials for crystal growth include silicon carbide particles and silicon powder. The mass of silicon powder is 0.25% of the mass of silicon carbide particles. The particle size of silicon carbide particles is <0.178 μm and the particle size of silicon powder is <6 μm.

[0092] At the start of the physical vapor transport growth, the vertical distance from the surface of the growth material to the seed crystal is 8 mm. The gases used include a protective gas (argon) with a flow ratio of 60:1 and a dopant gas, the dopant gas being ammonia, with a flow rate of 85 sccm. The induction coil moving speed is 0.2 mm / h, the growth pressure is 1.5 mbar, the growth temperature is 2500℃, and the growth time is 140 h.

[0093] The gases used in the oxidation process include: oxygen at a flow rate of 25 sccm, a temperature of 2500℃, a pressure of 1.5 mbar, and a time of 10 h;

[0094] The gases used in the volatilization process include: a protective gas (argon) with a flow rate of 300 slm, a temperature of 2500℃, a pressure of 1.5 mbar, and a time of 8 hours.

[0095] Example 4

[0096] This embodiment provides a method for preparing a thermally conductive and microwave-absorbing SiC crystal. The preparation process is as follows:

[0097] Silicon carbide crystals containing microtubes are subjected to oxidation and volatilization treatments in a protective atmosphere (argon) to obtain thermally conductive and microwave-absorbing SiC crystals.

[0098] The preparation process of the silicon carbide crystal containing microtubes is as follows: Physical vapor transport growth is performed using a seed crystal and a crystal growth material to obtain the silicon carbide crystal containing microtubes; the seed crystal comprises: 25 microtubes / cm². 2 The silicon carbide seed crystal has a thickness of 600 μm. The raw materials for crystal growth include silicon carbide particles and silicon powder. The mass of silicon powder is 0.04% of the mass of silicon carbide particles. The particle size of silicon carbide particles is <0.178 μm and the particle size of silicon powder is <6 μm.

[0099] At the start of the physical vapor transport growth, the vertical distance from the surface of the growth material to the seed crystal is 3 mm. The gases used include: a protective gas (argon) with a flow ratio of 40:1 and a doping gas, the doping gas being nitrogen, with a flow rate of 130 sccm. The induction coil moves at a speed of 0.1 mm / h, the growth pressure is 1 mbar, the growth temperature is 2300℃, and the growth time is 160 h.

[0100] The gases used in the oxidation process include: oxygen at a flow rate of 10 sccm, a temperature of 2300℃, a pressure of 1 mbar, and a time of 15 h;

[0101] The gases used in the volatilization process include: a protective gas (argon) with a flow rate of 200 slm, a temperature of 2300℃, a pressure of 1 mbar, and a time of 5 h.

[0102] Example 5

[0103] The only difference from Example 1 is that the oxygen flow rate in the oxidation process is 5 sccm.

[0104] Example 6

[0105] The only difference from Example 1 is that the oxygen flow rate in the oxidation process is 30 sccm.

[0106] Example 7

[0107] The only difference from Example 1 is that the oxidation treatment time is 8 hours.

[0108] Example 8

[0109] The only difference from Example 1 is that the oxidation treatment time is 18 hours.

[0110] Example 9

[0111] The only difference from Example 1 is that the evaporation treatment time is 8 hours.

[0112] Example 10

[0113] The only difference from Example 1 is that the evaporation treatment time is 15 hours.

[0114] Example 11

[0115] The only difference from Example 3 is that the raw materials for crystal growth do not contain silicon powder.

[0116] Example 12

[0117] The only difference from Example 3 is that the mass of silicon powder in the crystal growth raw material is 0.5% of the mass of silicon carbide particles.

[0118] Example 13

[0119] The only difference from Example 3 is that the particle size of the silicon carbide particles is ≤0.5μm.

[0120] Example 14

[0121] The only difference from Example 3 is that the particle size of the silicon powder is ≤10μm.

[0122] Example 15

[0123] The only difference from Example 3 is that the growth pressure for silicon carbide crystal growth is 3 mbar.

[0124] Comparative Example 1

[0125] The only difference from Example 1 is that the silicon carbide crystal used does not contain microtubes.

[0126] Comparative Example 2

[0127] The only difference from Example 1 is that no evaporation treatment is performed.

[0128] The thermal conductivity and microwave absorption performance of the thermally conductive and microwave-absorbing SiC crystals obtained in the above embodiments and comparative examples were tested, and the results are shown in Table 1 below. The thermal conductivity was tested according to ISO 22007-2 standard using a Hot Disk transient thermal conductivity meter. The microwave absorption performance testing process was as follows: An isolation verification fixture (a hood-shaped heat dissipation structure was placed on the PCB board, forming a cavity with the PCB; a dummy chip was placed inside the cavity; and a thermally conductive and microwave-absorbing SiC crystal was placed on the inner surface of the heat dissipation structure facing the dummy chip) was used to test the isolation of the thermally conductive and microwave-absorbing SiC crystal from electromagnetic waves (in dB). A reflection loss of -10 dB means that 90% of the electromagnetic waves are absorbed by the incident wave; a reflection loss of -20 dB means 99% absorption efficiency; and a reflection loss of -30 dB means 99.9% absorption efficiency.

[0129] Table 1

[0130]

[0131] As shown in Table 1, in the solution provided by the present invention, amorphous SiO is formed by oxidizing the microtube walls inside the silicon carbide crystal. x Then, it undergoes a volatilization treatment to remove SiO2. x The vaporization process leaves closed nanopores, thereby providing more electromagnetic wave scattering and absorption sites for silicon carbide crystals, while also exhibiting good thermal conductivity.

[0132] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0133] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0134] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a thermally conductive and microwave-absorbing SiC crystal, characterized in that, The preparation method includes: Silicon carbide crystals containing microtubes are subjected to oxidation and volatilization treatments in a protective atmosphere to obtain thermally conductive and microwave-absorbing SiC crystals.

2. The preparation method according to claim 1, characterized in that, The gas used in the oxidation process includes oxygen at a flow rate of 10-25 sccm.

3. The preparation method according to claim 1, characterized in that, The oxidation treatment temperature is 2300-2500℃; Preferably, the oxidation treatment pressure is 1-1.5 mbar; Preferably, the oxidation treatment time is 10-15 hours.

4. The preparation method according to claim 1, characterized in that, The gas used in the evaporation process includes a protective gas with a flow rate of 200-300 slm.

5. The preparation method according to claim 1, characterized in that, The temperature for the evaporation treatment is 2300-2500℃; Preferably, the pressure of the evaporation treatment is 1-1.5 mbar; Preferably, the volatilization treatment time is 5-8 hours.

6. The preparation method according to claim 1, characterized in that, The preparation process of the silicon carbide crystal containing microtubes is as follows: physical vapor transport growth is carried out using seed crystals and growth raw materials to obtain silicon carbide crystals containing microtubes.

7. The preparation method according to claim 6, characterized in that, The seed crystal comprises: ≥10 microtubes / cm 2 Silicon carbide seed crystals; Preferably, the thickness of the seed crystal is ≥500μm; Preferably, the crystal growth raw material includes: silicon carbide particles and silicon powder; Preferably, the mass of the silicon powder is 0.04-0.25% of the mass of the silicon carbide particles; Preferably, the particle size of the silicon carbide particles is <0.178 μm; Preferably, the particle size of the silicon powder is <6μm.

8. The preparation method according to claim 6, characterized in that, At the start of the physical vapor transport growth, the vertical distance from the surface of the growing material to the seed crystal is <10mm; Preferably, the gas used for physical vapor transport growth includes: a protective gas or a protective gas and a doping gas with a flow ratio of (40-60):1; Preferably, the doping gas includes nitrogen and / or ammonia; Preferably, the flow rate of the gas used for physical vapor transport growth is 85-130 sccm.

9. The preparation method according to claim 6, characterized in that, The moving speed of the induction coil in the physical vapor transport growth process is 0.1-0.2 mm / h; Preferably, the growth pressure of the physical vapor transport growth is 1-1.5 mbar; Preferably, the growth temperature of the physical vapor transport growth is 2300-2500℃; Preferably, the growth time of the physical vapor transport growth is 140-160 hours.

10. A thermally conductive and microwave-absorbing SiC crystal, characterized in that, The thermally conductive and microwave-absorbing SiC crystal is prepared using the preparation method described in any one of claims 1-9; The thermal conductivity of the thermally conductive and microwave-absorbing SiC crystal is ≥130 W·m. -1 ·K -1 The reflection loss is <-20dB.

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