Silicon-infiltrated silicon carbide porous compact, method for preparing the same, and use thereof

Abstract

The application discloses a silicon-infiltrated silicon carbide porous block and a preparation method and application thereof. The silicon-infiltrated silicon carbide porous block comprises an intermediate and a silicon carbide layer coated on the surface of the intermediate. The intermediate comprises a porous silicon carbide block and silicon crystals in the pores. The mass ratio of the silicon carbide block to the silicon crystals is 70-95:5-30. The silicon-infiltrated silicon carbide porous block and conventional silicon carbide powder are mixed according to a proportion, and then the mixture is used for crystal growth. With the decomposition of the initial mixture, the silicon carbide layer outside the silicon-infiltrated silicon carbide block starts to decompose preferentially. In the middle and later growth stages, the silicon in the pores also starts to decompose with the decomposition of the silicon carbide. The carbon-silicon ratio in the middle and later growth stages is kept stable, and the quality of the silicon carbide crystal with high thickness is improved.

Description

TECHNICAL FIELD

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

[0002] Silicon carbide crystal material has the advantages of high hardness, wear resistance, thermal conductivity, wide band gap characteristics, etc., and is widely used in the fields of electronic power, high-temperature structural parts, wear-resistant materials, etc. The preparation methods of silicon carbide crystal material include physical vapor transport method (PVT method), chemical vapor deposition method (CVD method), liquid phase epitaxy method (LPE method), etc. The preparation of silicon carbide crystal material is a complex and high-technology process. In the growth process of silicon carbide crystal, factors such as improper raw material purity, inaccurate temperature control, gas environment, and improper growth rate may cause imbalance of carbon-silicon ratio, thereby affecting the quality of silicon carbide crystal.

[0003] In order to solve the problem of imbalance of carbon-silicon ratio, a silicon carbide crystal growth device based on PVT method is studied. In the middle and later stages of crystal growth, the silicon component in the vapor phase crystal growth component may be insufficient, leading to imbalance of the ratio of silicon component and carbon component, and affecting the growth quality of the crystal. Therefore, in order to ensure the growth of the crystal in the middle and later stages, the silicon carbide crystal growth device usually has a silicon supplement structure. For example, a growth equipment is provided in Chinese patent CN115595657A, which can supplement silicon material in a carbon-rich state. By controlling the heating sublimation and opening and closing mechanism, the silicon material is supplemented into the crystal growth cavity, 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 and maintenance difficulty of the equipment. Chinese patent CN118880450A provides a silicon carbide crystal growth device capable of automatic silicon supplement. A graphite cylinder is arranged on the bottom wall of the graphite crucible, and a silicon supplement cylinder is slidably connected in the graphite cylinder. In the middle and later stages of crystal growth, the first gas hole and the second gas hole are controlled to be communicated, so that the silicon gas phase in the silicon supplement cylinder enters the graphite crucible through the second gas hole and the first gas hole in sequence to supplement silicon. In this way, the silicon supplement can be controlled, thereby ensuring the growth quality of the silicon carbide crystal. Although the invention can supplement silicon in the later growth stage, the structure of the crucible is changed, which increases the complexity of the crucible structure and the operation difficulty of the furnace loading.

[0004] Therefore, there is an urgent need for a method for supplementing silicon in the middle and later stages of silicon carbide crystal growth, which is simple to operate and does not involve the use of complex devices and equipment. SUMMARY

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

[0006] To achieve the above object, the present application provides a silicon-infiltrated porous silicon carbide block in the first aspect, which comprises an intermediate and a silicon carbide layer coated on the surface of the intermediate, and the intermediate comprises a porous silicon carbide block and silicon crystals in the pores.

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

[0008] Preferably, the size of the silicon carbide block is 0.5-1 cm, and the size of the pores in the silicon carbide block is distributed in the range of 10-200 μm.

[0009] The silicon carbide block obtained by the present application is irregular in shape, with a maximum diameter of 0.5-1 cm, and includes the above-mentioned spherical, cylindrical, and square shapes.

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

[0011] The present application provides a method for preparing a silicon-infiltrated porous silicon carbide block in the second aspect, which comprises the following steps:

[0012] S1: dividing a whole silicon carbide raw material into silicon carbide blocks;

[0013] S2: placing the silicon carbide blocks in a heating furnace chamber filled with silicon vapor, and reducing the temperature gradient of the silicon carbide blocks from the outside to the inside, so that the silicon vapor diffuses into the pores of the silicon carbide blocks under the action of the temperature gradient, and crystallizes in the interior of the silicon carbide blocks to obtain silicon-infiltrated silicon carbide blocks;

[0014] S3: after the silicon infiltration process is completed, a silicon carbide layer is deposited on the surface of the silicon-infiltrated silicon carbide blocks by CVD to obtain a silicon-infiltrated porous silicon carbide block.

[0015] In step S2 of the present application, the silicon source material (such as polycrystalline silicon) sublimates into a gaseous state under the conditions of a pressure of 1-10 Pa and a temperature of 1100-1400 ℃ in a vacuum condition, and the temperature of the vacuum chamber can be controlled at 1100-1400 ℃. The initial mass ratio of the silicon carbide blocks and high-purity polycrystalline silicon put into the vacuum chamber is determined, for example, 90 g of silicon carbide blocks and 10 g of high-purity polycrystalline silicon powder are initially put into the chamber.

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

[0017] When the temperature gradient is 20-60℃ / mm, and the silicon carbide block has a porosity of 70-80%, and the silicon carbide block has a thickness of 0.5 cm, the surface temperature is 1400℃, and the internal center temperature is about 1300-1350℃.

[0018] Preferably, in step S2, the temperature of the surface of the silicon carbide block is 1300-1400℃, and the lowest temperature of the internal part of the silicon carbide block is 1100-1350℃. After the silicon carbide block adsorbs the silicon vapor by using the porous structure thereof, the silicon vapor can form silicon crystals in the pores of the silicon carbide block by cooling.

[0019] Preferably, in step S3, the temperature for depositing the silicon carbide layer by the CVD method is 1200-1500℃, and the time is 5-50 h.

[0020] The present application can deposit the silicon carbide layer by the CVD method at 1200-1300℃, and a thin layer of 2-10 um is formed at the initial 1200-1300℃ (at this time, the packaging effect is achieved), and then the reaction temperature can be further increased to accelerate the reaction rate and the deposition rate, shorten the process time, and generate the required silicon carbide layer.

[0021] The third aspect of the present application provides an application of the silicon-infiltrated silicon carbide porous block, and an application of the silicon-infiltrated silicon carbide porous block in preparing a silicon carbide crystal material.

[0022] In the prior art, the PVT method is generally used to grow 4H-SiC single crystals, and the main process is as follows: under the conditions of low pressure and high temperature, SiC powder with a large particle size (>200 um) is decomposed and sublimated into various gas phase substances, which are transported to the seed crystal at a lower temperature under the driving of the temperature gradient and deposited to recrystallize into 4H-SiC single crystals. The main chemical reactions involved in the sublimation of the powder are as follows:

[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] As can be seen from the above reaction formula, the content of Si in the gas phase substances produced by the sublimation of the powder is relatively high, that is, the gas obtained by the decomposition and sublimation has a high content of silicon, which is also the reason for the graphitization of the remaining powder after a long time of single crystal growth.

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

[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] Through the above reactions, the generated gas phase material is transported to the seed crystal, reacts and deposits 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 formula, in the initial growth stage, the Si content in the gas phase vapor is much higher than the supersaturation vapor pressure of other atmospheres, so the vapor Si content is always high during the temperature rising process of 1700-2200℃. In the later growth stage, with the graphitization of the powder, the vapor Si content provided by the powder is reduced, which leads to the imbalance of the carbon-silicon ratio in the later growth stage. By appropriately supplementing Si, the carbon-silicon ratio in the later stage can be maintained, which can reduce the probability of polymorphism in the later stage of the silicon carbide crystal.

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

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

[0037] Preferably, the crystal growth parameters are as follows: the PVT method is used to grow the silicon carbide crystal, the growth temperature is 2100-2300℃, the axial temperature gradient is 10-50℃ / m, the growth pressure is 10-100Torr, the growth rate is 0.05-0.8mm / h, and the growth time is 50-200h.

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

[0039] (1) According to the decomposition of silicon carbide, the silicon crystal is arranged in the pores of the silicon carbide block, and the silicon source is supplemented from the inside of the silicon carbide block in the later growth stage of the silicon carbide crystal, thereby improving the growth quality of the silicon carbide crystal.

[0040] (2) The present application mixes silicon-infiltrated silicon carbide porous blocks and conventional silicon carbide powder according to a proportion, and then uses the mixture for crystal growth. With the decomposition of the initial mixture, the silicon carbide layer outside the silicon-infiltrated silicon carbide block starts to decompose preferentially, and in the later growth, the silicon in the porous interior also starts to decompose with the decomposition of silicon carbide, keeping the carbon-silicon ratio stable in the middle and late atmosphere, and improving the quality of silicon carbide crystals with higher thickness.

[0041] The technical solutions of the present application will be further described below with the aid of drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The preparation flow chart of the present application is shown in the figure.

[0043] Figure 2 The SEM image of the silicon carbide block is shown in the figure.

[0044] Figure 3 The appearance of the silicon carbide crystal material of the comparative example is shown in the figure.

[0045] Figure 4 The appearance of the silicon carbide crystal material of Example 1 is shown in the figure. DETAILED DESCRIPTION

[0046] The present application will be further described below, and it should be noted that the present embodiment is based on the technical solutions, and gives detailed implementation and specific operation process, but the present application is not limited to the present embodiment.

[0047] Example 1

[0048] As shown in Figure 1 , a method for preparing a silicon-infiltrated silicon carbide porous block to prepare a silicon carbide crystal material, comprising the following steps:

[0049] S1: The whole silicon carbide raw material is divided into silicon carbide blocks, and the shape of the cut silicon carbide block is irregular particles composed of spherical, cylindrical and square shapes, and the size of the irregular particles obtained by the screen 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 a 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 at a temperature of 1350℃. Due to the porous nature of the silicon carbide block, a temperature gradient is formed between its surface and interior. This temperature gradient decreases from the outside to the inside of the silicon carbide block. Under the influence of this temperature gradient, silicon vapor diffuses into the pores of the silicon carbide block and, during the subsequent cooling process, crystallizes inside the silicon carbide block to form silicon crystals, thus obtaining a silicon-diffused silicon carbide block. The mass ratio of silicon carbide block to polycrystalline silicon powder is 90:10.

[0051] S3: After the silicon infiltration process is completed, a silicon carbide layer is deposited on the surface of the silicon-infiltrated silicon carbide block using CVD. Specifically, a 10μm thin layer is first deposited at 1200℃ for 10h, and then deposited again at 1500℃ for 5h to obtain a silicon-infiltrated porous silicon carbide block.

[0052] S4: Silicon-infiltrated porous silicon carbide blocks and silicon carbide powder were mixed at a mass ratio of 10:90. The silicon carbide powder had a particle size of 500 μm and a purity of <5 ppm. The resulting mixture was then subjected to crystal growth. The crystal growth parameters were as follows: silicon carbide crystals were grown using the PVT method at a growth temperature of 2200℃; an axial temperature gradient of 20℃ / m; a growth pressure of 25 Torr; a growth rate of 0.5 mm / h; and a growth time of 70 h. The resulting silicon carbide crystal material had a thickness of 35 mm. The appearance of the silicon carbide crystal material is shown in [image description missing]. Figure 4 ,from Figure 4 As can be seen, the polymorphism ratio in silicon carbide crystals is relatively low.

[0053] Examples 2-4

[0054] The difference between this embodiment and Embodiment 1 is that the size of the silicon carbide block, the mass ratio of the silicon-infiltrated porous silicon carbide block, and 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 shows the crystal growth result without silicon powder doping under conventional processes. The conventional silicon carbide crystal growth method includes the following steps:

[0061] 1. Charging stage:

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

[0063] 2. Crystal growth stage

[0064] 1) The pressure in the growth chamber is reduced to 10 mbar or less, and the temperature is increased to a first temperature of 1200°C for 5 hours. -6

[0065] 2) Inert gas is introduced into the growth chamber, and the pressure is increased to a growth pressure of 100 mbar for 2 hours, and the purity of the inert gas is greater than 99.9999%.

[0066] 3) Temperature increasing stage: the first temperature is increased to a second temperature of 2200°C while maintaining the growth pressure in the chamber, and silicon carbide crystal growth is performed, and the crystal growth parameters are the same as in Example 1, and the growth time is 70 hours.

[0067] 3. After the growth is completed, the silicon carbide crystal is removed from the growth device after cooling.

[0068] The crystal growth of Comparative Example 1 is shown in Table 2. As can be seen from Table 2, the proportion of polymorphism in Comparative Example 1, which is a conventional crystal growth process without silicon supplementation, is actually higher than the results of the optimized crystal growth process of the embodiments of the present application.

[0069] Table 2

[0070]

[0071] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit them, and although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.​

Claims

1. A silicon-infiltrated porous silicon carbide block, characterized in that: It includes an intermediate and a silicon carbide layer covering the surface of the intermediate. The intermediate includes a porous silicon carbide block and silicon crystals located in the pores.

2. The silicon carbide porous block according to claim 1, characterized in that: The silicon carbide block is shaped as at least one of spheres, cylinders, and squares.

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

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

5. A method for preparing a silicon-diffused porous silicon carbide block according to any one of claims 1 to 4, characterized in that: Includes the following steps: S1: Divide the whole piece of porous silicon carbide raw material into silicon carbide blocks; S2: Place the silicon carbide block in a heating furnace cavity 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 silicon-diffused silicon carbide block. S3: After the silicon infiltration process is completed, a silicon carbide layer is deposited on the surface of the silicon-infiltrated silicon carbide block using the CVD method to obtain a silicon-infiltrated porous silicon carbide block.

6. The method for preparing a silicon-diffused 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℃, and the lowest internal temperature of the silicon carbide block is 1100~1350℃.

7. The method for preparing a silicon-diffused porous silicon carbide block according to claim 5, characterized in that: In step S3, the temperature for depositing the silicon carbide layer by CVD is 1200~1500℃, and the time is 5~50h.

8. The application of a silicon-diffused porous silicon carbide block according to any one of claims 1 to 4, characterized in that: Application of silicon-diffused porous silicon carbide blocks in the preparation of silicon carbide crystalline materials.

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

10. The application of the silicon-diffused porous silicon carbide block according to claim 9, characterized in that: The mass ratio of silicon carbide porous blocks to silicon carbide powder is 10~30:70~90.

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