Silicon-infiltrated silicon carbide porous material block as well as preparation method and application thereof

Abstract

The invention discloses a siliconized silicon carbide porous material block and a preparation method and application thereof, the siliconized silicon carbide porous material block comprises an intermediate and a silicon carbide layer coating the surface of the intermediate, the intermediate comprises a porous silicon carbide block and silicon crystals located in the pores, and the mass ratio of the silicon carbide block to the silicon crystals is (70-95): (5-30). According to the method, a siliconized silicon carbide porous material block and conventional silicon carbide powder are mixed in proportion, then the mixture is used for crystal growth, a silicon carbide layer outside the siliconized silicon carbide block begins to decompose preferentially along with decomposition of the initial mixture, and silicon inside the porous material begins to decompose along with decomposition of silicon carbide after the middle and later growth periods, so that the silicon carbide is formed. The carbon-silicon ratio in the middle-later period atmosphere is kept stable, and the quality of the silicon carbide crystal with relatively high thickness is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and in particular to a silicon-infiltrated silicon carbide porous material block, a preparation method thereof, and an application thereof. Background Art

[0002] Silicon carbide crystal materials have the advantages of high hardness, wear resistance, thermal conductivity, and wide bandgap properties, and are widely used in the fields of electronics and power, high-temperature structural parts, and wear-resistant materials. Methods for preparing silicon carbide crystal materials include physical vapor transport (PVT), chemical vapor deposition (CVD), and liquid phase epitaxy (LPE). The preparation of silicon carbide crystal materials is a complex and technically demanding process. During the growth of silicon carbide crystals, factors such as raw material purity, inaccurate temperature control, gas environment, and improper growth rate can cause an imbalance in the carbon-silicon ratio, thereby affecting the quality of the silicon carbide crystals.

[0003] In order to solve the above-mentioned problem of imbalance in the carbon-silicon ratio, a silicon carbide crystal growth device based on the PVT method has been studied. In the middle and late stages of crystal growth, the silicon component in the vapor phase crystal growth component will be insufficient, resulting in an imbalance in the ratio of silicon component and carbon component, affecting the growth quality of the crystal. Therefore, in order to ensure the growth of the crystal in the middle and late stages, the silicon carbide crystal growth device is usually provided with a silicon supplement structure. For example, Chinese patent CN115595657A provides a growth device that can supplement silicon material in a carbon-rich state, and through the control of heating sublimation and opening and closing mechanisms, the silicon material is supplemented into the crystal growth chamber, the carbon-rich growth environment is adjusted, defects are avoided, and the crystal quality is improved. However, this method supplements the silicon source by optimizing the equipment structure, which increases the complexity of the equipment and the difficulty of maintenance. Chinese patent CN118880450A provides a silicon carbide crystal growth device with automatic silicon replenishment. A graphite tube and a silicon replenishment tube slidably connected to the bottom wall of a graphite crucible are provided. During the middle and late stages of crystal growth, the first and second air holes are controlled to communicate, allowing the silicon vapor in the silicon replenishment tube to enter the graphite crucible through the second and first air holes in sequence for silicon replenishment. This allows for controllable silicon replenishment, thereby ensuring the growth quality of the silicon carbide crystal. Although this invention allows for silicon replenishment in the late stages of growth, it introduces changes to the crucible structure, increasing its complexity and the difficulty of furnace loading.

[0004] Therefore, there is an urgent need for a method for replenishing silicon in the middle and late stages of silicon carbide crystal growth, and this method is simple to operate and does not involve the use of complex devices and equipment. Summary of the Invention

[0005] The purpose of the present invention is to provide a silicon-infiltrated silicon carbide porous block and its preparation method and application, so as to solve the above-mentioned problem of complex equipment and high operation difficulty in the method of silicon filling in the later stage of silicon carbide growth by improving the growth equipment and crucible.

[0006] To achieve the above objectives, the present invention provides a silicon-infiltrated porous silicon carbide block in a first aspect, comprising an intermediate and a silicon carbide layer covering the surface of the intermediate, wherein the intermediate comprises a porous silicon carbide block and silicon crystals located in the pores.

[0007] Preferably, the shape of the silicon carbide block is at least one of spherical, cylindrical, and square.

[0008] Preferably, the size of the silicon carbide block is 0.5 to 1 cm, and the pore size distribution in the silicon carbide block is 10 to 200 μm.

[0009] The divided silicon carbide blocks of the present invention are filtered through a sieve to obtain irregular particles. The maximum diameter of the irregular particles is 0.5 to 1 cm. The irregular particles include the above-mentioned spherical, cylindrical and square particles.

[0010] Preferably, the mass ratio of silicon carbide chunks to silicon crystals is 70-95:30-5.

[0011] A second aspect of the present invention provides a method for preparing a silicon-infiltrated porous silicon carbide block, comprising the following steps:

[0012] S1: dividing the whole block of silicon carbide raw material into silicon carbide blocks;

[0013] S2: placing the silicon carbide block in a heating furnace chamber filled with silicon vapor. The temperature gradient of the silicon carbide block decreases from the outside to the inside. Under the action of the temperature gradient, the silicon vapor diffuses into the pores of the silicon carbide block and cools and crystallizes inside the silicon carbide block to obtain a silicon-infiltrated silicon carbide block.

[0014] S3: After the siliconizing process is completed, a silicon carbide layer is deposited on the surface of the siliconized silicon carbide block by a CVD method to obtain a siliconized silicon carbide porous block.

[0015] In step S2 of the present invention, under vacuum conditions, the silicon source material (such as polycrystalline silicon) sublimates into a gas at a pressure of 1 to 10 Pa and a temperature of 1100 to 1400°C. The temperature of the vacuum chamber is controlled at 1100 to 1400°C, which is determined by controlling the initial mass ratio of the silicon carbide block and the high-purity polycrystalline silicon put into the vacuum chamber. For example, 90g of silicon carbide block and 10g of high-purity polycrystalline silicon powder are initially placed in the chamber.

[0016] Analysis of factors affecting the surface and internal temperature gradient of silicon carbide blocks in a high temperature environment in a vacuum chamber: the higher the porosity, the lower the effective thermal conductivity and the greater the temperature gradient; thermal conductivity: the thermal conductivity of porous SiC is usually 1-30W / (m·K), dense SiC is about 120W / (m·K), and the vacuum degree is <10 -3 When the temperature is greater than 0.05 Pa, only radiation and solid conduction are effective, and the temperature gradient is larger.

[0017] When using a silicon carbide block with a porosity of 70% to 80%, the temperature gradient is 20 to 60°C / mm. Taking a 0.5 cm silicon carbide block as an example, when the surface temperature is 1400°C, the internal center temperature is approximately 1300 to 1350°C.

[0018] Preferably, in step S2, the surface temperature of the silicon carbide block is 1300-1400° C., and the minimum temperature inside the silicon carbide block is 1100-1350° C. The silicon carbide block absorbs the silicon vapor through its porous structure, and then cools down to form silicon crystals in the pores of the silicon carbide block.

[0019] Preferably, in step S3, the temperature of depositing the silicon carbide layer by CVD method is 1200-1500° C. and the time is 5-50 hours.

[0020] The present invention adopts the CVD method to deposit the silicon carbide layer, and the reaction and deposition of the silicon carbide layer can occur at 1200-1300°C. After forming a thin layer of 2-10um at the initial temperature of 1200-1300°C (the packaging effect has been achieved at this time), the reaction temperature can be further increased to accelerate the reaction rate and deposition rate, shorten the process time, until the required silicon carbide layer is generated.

[0021] A third aspect of the present invention provides an application of a silicon-infiltrated porous silicon carbide block, and an application of the silicon-infiltrated porous silicon carbide block in the preparation of silicon carbide crystal materials.

[0022] In the existing technology, the PVT method is generally used to grow 4H-SiC single crystals. Its main process is: under low pressure and high temperature conditions, SiC powder with a large particle size (>200μm) decomposes and sublimates into various gaseous substances. Driven by the temperature gradient, it is transported to the seed crystal with a lower temperature and deposited, and then recrystallized into 4H-SiC single crystals. Among them, the main chemical reactions involved in the sublimation of the powder are:

[0023] SiC(s)→Si(g)+C(s) (1)

[0024] 2SiC(s)→Si(g)+SiC2(g) (2)

[0025] 2SiC(s)→C(s)+Si2C(g) (3);

[0026] From the above reaction formula, it can be seen that the content of Si in the gaseous substances produced by powder sublimation is relatively high, that is, the gas obtained by decomposition and sublimation is a gas with excessive silicon content. This is also the reason why the remaining powder is graphitized after long-term single crystal growth.

[0027] The S and Si2C in the sublimated gas phase react with the C in the graphite crucible to generate additional gas phase species:

[0028] Si2C(g)+C(s)→2SiC(s) (4)

[0029] 2C(s)+Si(g)→SiC2(g) (5)

[0030] C(s)+2Si(g)→Si2C(g) (6);

[0031] After the above reaction, the generated gaseous substances are transported to the seed crystal, react, and deposit to obtain 4H-SiC single crystal:

[0032] Si2C(g)+SiC2(g)→3SiC(s) (7)

[0033] Si(g)+SiC2(g)→2SiC(s) (8);

[0034] In the above reaction equation, in the early stages of growth, the Si content in the vapor phase is much greater than the supersaturated vapor pressure of other atmospheres. Therefore, during the temperature increase from 1700 to 2200°C, the vapor Si content remains high. In the later stages of growth, as the powder graphitizes, the vapor Si content provided by the powder decreases, resulting in an imbalance in the carbon-silicon ratio in the later stages of growth. By appropriately supplementing silicon and maintaining the carbon-silicon ratio in the later stages, the probability of late polymorphism in the silicon carbide crystal can be reduced.

[0035] Preferably, the silicon-infiltrated silicon carbide porous block and silicon carbide powder are mixed to obtain a mixture, and the mixture is subjected to crystal growth to obtain a silicon carbide crystalline material.

[0036] Preferably, the mass ratio of the silicon-infiltrated porous silicon carbide block to the silicon carbide powder is 10-30:70-90.

[0037] Preferably, the crystal growth parameters are: growing silicon carbide crystals by PVT method, growth temperature 2100-2300°C; axial temperature gradient 10-50°C / m, growth pressure 10-100 Torr, growth rate 0.05-0.8 mm / h, growth time 50-200 h.

[0038] Therefore, the present invention adopts the above-mentioned silicon-infiltrated porous silicon carbide block and its preparation method and application, which has the following beneficial effects:

[0039] (1) The present invention places silicon crystals in the pores of the silicon carbide block according to the decomposition of silicon carbide, and supplements silicon sources from the interior of the silicon carbide block in the later stage of silicon carbide crystal growth, thereby improving the growth quality of the silicon carbide crystal.

[0040] (2) The present invention mixes silicon-infiltrated silicon carbide porous blocks and conventional silicon carbide powder in proportion, and then uses the mixture for crystal growth. As the initial mixture decomposes, the silicon carbide layer on the outside of the silicon-infiltrated silicon carbide block begins to decompose preferentially. In the middle and late stages of growth, the silicon inside the porous block also begins to decompose as the silicon carbide decomposes, thereby maintaining a stable carbon-silicon ratio in the atmosphere in the middle and late stages and improving the quality of silicon carbide crystals with thicker thicknesses.

[0041] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a preparation flow chart of the present invention;

[0043] Figure 2 is the SEM image of silicon carbide block;

[0044] Figure 3 This is an appearance diagram of a silicon carbide crystal material of a comparative example;

[0045] Figure 4 This is an appearance diagram of the silicon carbide crystal material of Example 1. DETAILED DESCRIPTION

[0046] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the present invention is not limited to this embodiment.

[0047] Example 1

[0048] like Figure 1 As shown, a method for preparing silicon carbide crystalline material from a silicon-infiltrated silicon carbide porous block comprises the following steps:

[0049] S1: The whole block of silicon carbide raw material is divided into silicon carbide blocks. The shape of the cut silicon carbide blocks is irregular particles consisting of spheres, columns and squares. The size of the irregular particles obtained by the sieve is 0.5 cm, and the pore size distribution is 10-200 μm. The porous structure of the silicon carbide block is shown in Figure 2 .

[0050] S2: 10g of high-purity polycrystalline silicon powder is added to the heating furnace chamber and heated at 5Pa and 1200℃ to form silicon vapor. Then, 90g of silicon carbide block is placed in the heating furnace chamber filled with silicon vapor. The temperature of the heating furnace chamber is 1350℃. Since the silicon carbide block is porous, a temperature gradient is formed on the surface and inside. The temperature gradient of the silicon carbide block decreases from the outside to the inside. Under the action of the temperature gradient, the silicon vapor diffuses into the porous silicon carbide block. In the subsequent cooling process, it cools and crystallizes inside the silicon carbide block to form silicon crystals, obtaining a silicon-infiltrated silicon carbide block. Among them, the mass ratio of silicon carbide block to polycrystalline silicon powder is 90:10.

[0051] S3: After the siliconization process is completed, a silicon carbide layer is deposited on the surface of the siliconized silicon carbide block by using a CVD method. Specifically, a thin layer of 10 μm is formed by reaction deposition at 1200°C for 10 hours, and then deposited at 1500°C for another 5 hours to obtain a siliconized silicon carbide porous block.

[0052] S4: The siliconized silicon carbide porous block and silicon carbide powder are mixed in a mass ratio of 10:90, wherein the particle size of the silicon carbide powder is 500 μm and the purity is less than 5 ppm, to obtain a mixture, and the mixture is subjected to crystal growth. The crystal growth parameters are: PVT method is used to grow silicon carbide crystals, the growth temperature is 2200°C; the axial temperature gradient is 20°C / m, the growth pressure is 25 Torr, the growth rate is 0.5 mm / h, and the growth time is 70 hours to obtain a silicon carbide crystal material. The thickness of the silicon carbide crystal material is 35 mm. The appearance of the silicon carbide crystal material is shown in FIG. Figure 4 ,from Figure 4 It can be seen that the polymorphic ratio in silicon carbide crystals is low.

[0053] Examples 2 to 4

[0054] The difference between this embodiment and embodiment 1 is that the size of the silicon carbide block and the mass ratio of the silicon-infiltrated porous silicon carbide block to the silicon carbide powder are different. See Table 1 for details.

[0055] Table 1

[0056]

[0057]

[0058] Note: The middle and late stages of crystal growth refer to the last 20% of the entire crystal growth cycle.

[0059] Comparative Example 1

[0060] like Figure 3 As shown, Figure 3 This is the result of growing silicon carbide crystals without doping with silicon powder under conventional processes. Conventional silicon carbide crystal growth methods include the following steps:

[0061] 1. Loading stage:

[0062] (1) Assemble a graphite crucible, a seed crystal, and SiC powder (wherein the silicon carbide powder is silicon carbide particles of different particle sizes). The seed crystal is a 4H crystal type silicon carbide seed crystal with a small deflection angle between 0 and 4.

[0063] 2. Crystal growth stage

[0064] 1) Pump the pressure in the growth chamber to 10 -6 mbar below, and raise the temperature to a first temperature of 1200°C for 5 hours;

[0065] 2) introducing an inert gas into the growth chamber and raising the pressure to a growth pressure of 100 mbar for 2 hours. The purity of the inert gas is greater than 99.9999%.

[0066] 3) Heating stage: while maintaining the growth pressure in the chamber constant, the first temperature was raised to a second temperature of 2200° C. to grow silicon carbide crystals. The crystal growth parameters were the same as those in Example 1, and the growth time was 70 h.

[0067] 3. After growth is complete and cooling, remove the silicon carbide crystal from the growth device.

[0068] The crystal growth of Comparative Example 1 is shown in Table 2. As can be seen from Table 2, Comparative Example 1 is a conventional crystal growth process without silicon supplementation, and the polymorphic ratio is actually higher than that of the optimized crystal growth process of the embodiment of the present invention.

[0069] Table 2

[0070]

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A silicon-infiltrated porous silicon carbide block, characterized in that: The invention comprises an intermediate body and a silicon carbide layer covering the surface of the intermediate body. The intermediate body comprises a silicon carbide block with multiple pores and silicon crystals located in the multiple pores.

2. The silicon-infiltrated porous silicon carbide block according to claim 1, characterized in that: The shape of the silicon carbide block is at least one of spherical, cylindrical and square.

3. The silicon-infiltrated porous silicon carbide block according to claim 1, characterized in that: The size of silicon carbide is 0.5~1cm, and the pore size distribution in the silicon carbide block is 10~200μm.

4. The silicon-infiltrated porous silicon carbide block according to claim 1, characterized in that: The mass ratio of silicon carbide block to silicon crystal is 70~95:5~30.

5. The method for preparing a siliconized silicon carbide porous block according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: dividing the whole block of silicon carbide porous raw material into silicon carbide blocks; S2: placing the silicon carbide block in a heating furnace chamber filled with silicon vapor. The temperature gradient of the silicon carbide block decreases from the outside to the inside. Under the action of the temperature gradient, the silicon vapor diffuses into the pores of the silicon carbide block and cools and crystallizes inside the silicon carbide block to obtain a silicon-infiltrated silicon carbide block. S3: After the siliconizing process is completed, a silicon carbide layer is deposited on the surface of the siliconized silicon carbide block by a CVD method to obtain a siliconized silicon carbide porous block.

6. The method for preparing a silicon-infiltrated porous silicon carbide block according to claim 5, characterized in that: In step S2, the surface temperature of the silicon carbide block is 1300-1400°C, and the lowest internal temperature of the silicon carbide block is 1100-1350°C.

7. The method for preparing a silicon-infiltrated porous silicon carbide block according to claim 5, characterized in that: In step S3, the silicon carbide layer is deposited by CVD at a temperature of 1200-1500° C. for 5-50 hours.

8. Use of a silicon-infiltrated porous silicon carbide block according to any one of claims 1 to 4, characterized in that: Application of silicon-infiltrated silicon carbide porous blocks in the preparation of silicon carbide crystal materials.

9. The use of a silicon-infiltrated silicon carbide porous block according to claim 8, characterized in that: The silicon-infiltrated silicon carbide porous block and silicon carbide powder are mixed to obtain a mixture, and the mixture is subjected to crystal growth to obtain a silicon carbide crystal material.

10. The use of a silicon-infiltrated porous silicon carbide block according to claim 9, characterized in that: The mass ratio of the silicon-infiltrated silicon carbide porous block to the silicon carbide powder is 10-30:70-90.

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