Porous tantalum carbide as well as preparation method and application thereof

Abstract

The invention provides porous tantalum carbide as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) preparing slurry which comprises tantalum powder and a solvent; (2) infiltrating an organic foam template by adopting the slurry, and then drying and sintering to obtain porous tantalum; and (3) firing the porous tantalum in a methane atmosphere to obtain the porous tantalum carbide. Porous tantalum carbide is prepared by introducing an organic foam template, inclusions in the silicon carbide crystal growth process can be effectively reduced, the crystal form can be stabilized, the crystal growth yield is increased, and the crystal growth yield of silicon carbide is increased by 20% or above after the porous tantalum carbide provided by the invention is used.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology and relates to a porous tantalum carbide and its preparation method and application. Background Art

[0002] As a third-generation semiconductor material, silicon carbide (SiC) has excellent properties such as high breakdown field strength, high saturated electron drift rate, high thermal conductivity, and strong chemical stability, and has great application value in fields such as electric vehicles, rail transit, high-voltage power transmission and transformation, photovoltaic, and 5G communication.

[0003] During the process of growing silicon carbide single crystals by the PVT method, as the temperature rises, the silicon carbide powder sublimates, migrates upward under the action of the thermal driving force, and converges on the seed crystal. In this process, the sublimated powder will carry carbon particles into the silicon carbide single crystal. The common solution is to use a porous graphite plate placed above the raw material. The porous graphite plate can filter out most of the carbon particles carried by the sublimated powder, but there are still some carbon particles that penetrate through the porous graphite plate. Moreover, as the temperature rises, the porous graphite plate will gradually powderize in the later stage of crystal growth, releasing carbon particles into the crystal, forming carbon inclusions, which seriously affect the crystal quality.

[0004] Therefore, it is necessary to find a material to replace the porous graphite plate to solve the problem of carbon inclusions. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a porous tantalum carbide and its preparation method and application. The present invention prepares porous tantalum carbide by introducing an organic foam template, which can effectively reduce the inclusions in the process of growing silicon carbide crystals, and can stabilize the crystal form and improve the crystal growth yield. After using the porous tantalum carbide provided by the present invention, the crystal growth yield of silicon carbide is increased by more than 20%.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a preparation method of porous tantalum carbide, and the preparation method includes:

[0008] (1) Prepare a slurry, and the slurry includes tantalum powder and a solvent.

[0009] (2) Infiltrate the organic foam template with the slurry, and then perform drying and sintering to obtain porous tantalum.

[0010] (3) Fire the porous tantalum in a methane atmosphere to obtain the porous tantalum carbide.

[0011] The present invention prepares porous tantalum carbide by introducing an organic foam template, which can filter out most of the carbon particles carried by the sublimation of silicon carbide raw materials, and the porous tantalum carbide can maintain a stable structure during the crystal growth process, enabling the porous tantalum carbide to effectively reduce the inclusions during the silicon carbide crystal growth process, and can stabilize the crystal form and improve the crystal growth yield. After using the porous tantalum carbide provided by the present invention, the crystal growth yield of silicon carbide is increased by more than 20%.

[0012] In the present invention, the porous tantalum is fired in a methane atmosphere, which can more fully convert tantalum into tantalum carbide. If a solid substance such as carbon powder is used, it is impossible to convert the inside of the tantalum skeleton either. Although it is a porous structure, these fine pores prevent the carbon powder from entering the inside.

[0013] In the present invention, if tantalum carbide is directly used to prepare the slurry, its mechanical strength is insufficient after sintering because the melting point of tantalum carbide is very high. The advantage of first preparing the skeleton with tantalum and then carbonizing is that the melting point of tantalum is relatively low, and sufficient mechanical strength can be achieved under sintering at more than 2000 °C. Subsequently, carbonization can further promote the combination between tantalum and enhance the mechanical strength.

[0014] Preferably, the particle size D50 of the tantalum powder in step (1) is 20 μm - 50 μm. For example, it can be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0015] Preferably, the purity of the tantalum powder ≥ 99.99%. For example, it can be 99.99%, 99.995% or 99.999%, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0016] The present invention preferably uses high-purity tantalum powder to prepare the slurry, which is beneficial to minimizing the introduction of impurities to ensure the high purity of tantalum carbide, making it have better performance and quality stability; it is beneficial to increasing the active sites of the reaction and making the reaction between carbon and tantalum easier to proceed.

[0017] Preferably, the solvent includes water and alcohol, and the alcohol includes ethanol and / or isopropanol.

[0018] In the present invention, ethanol and / or isopropanol can reduce the agglomeration of tantalum powder particles in the slurry, improve the stability of the slurry, prevent the particles from precipitating or agglomerating during the later impregnation process, and avoid blocking the pores.

[0019] Preferably, the volume ratio of the water to the alcohol is 1:(0.6 - 1.4), for example, it can be 1:0.6, 1:0.8, 1:1, 1:1.2, or 1:1.4, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0020] Preferably, the slurry further includes a dispersant.

[0021] Preferably, the dispersant includes polyethylene glycol and / or sodium dodecyl sulfate.

[0022] Preferably, based on the total mass of the slurry, the mass fraction of the tantalum powder is 20% - 35%, for example, it can be 20%, 25%, 30%, or 35%, etc., and the mass fraction of the dispersant is 0.2% - 0.5%, for example, it can be 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] Preferably, the viscosity of the slurry is 100 mPa·s - 300 mPa·s, for example, it can be 100 mPa·s, 150 mPa·s, 200 mPa·s, 250 mPa·s, or 300 mPa·s, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0024] Preferably, the organic foam template in step (2) includes a modified polyurethane foam template.

[0025] Preferably, the porosity of the modified polyurethane foam template is 40% - 60%, for example, it can be 40%, 45%, 50%, 55%, or 60%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable

[0026] Preferably, the preparation method of the modified polyurethane foam template includes: soaking the polyurethane foam template in a crosslinking modification solution and performing a crosslinking modification reaction to obtain the modified polyurethane foam template.

[0027] In the present invention, the performance and thermal stability of the polyurethane foam template after crosslinking treatment are improved. At the same time, the crosslinking treatment can improve the porosity density of the foam template, and by controlling the porosity of the organic foam template, the porosity of the porous tantalum carbide is further controlled, thereby improving the filtering effect of impurities in the process of preparing single-crystal silicon carbide.

[0028] Preferably, the crosslinking modification solution includes a crosslinking agent to be crosslinked and a crosslinking agent.

[0029] Preferably, the crosslinking agent to be used includes any one or a combination of at least two of polyvinyl alcohol, polyethylene glycol, or polyvinylpyrrolidone, and is preferably polyvinyl alcohol.

[0030] In the present invention, polyvinyl alcohol is preferably used as the crosslinking agent to be used because it has a low decomposition temperature and no residue. If epoxy resin is used, some carbon elements will remain, affecting subsequent carbonization. Secondly, polyvinyl alcohol has a low viscosity and is more likely to carry the slurry into the mold, while epoxy resin has a higher viscosity. Finally, polyvinyl alcohol is inexpensive and has a low cost.

[0031] Preferably, the crosslinking agent includes a silane coupling agent.

[0032] Preferably, the silane coupling agent includes any one or a combination of at least two of methyltrimethoxysilane, vinyltrimethoxysilane, or dimethyldimethoxysilane.

[0033] Preferably, based on the total mass of the crosslinking modification liquid, the mass fraction of the crosslinking agent to be used is 1% - 4%, for example, it can be 1%, 2%, 3%, or 4%, etc., and the mass fraction of the crosslinking agent is 1% - 5%, for example, it can be 1%, 2%, 3%, 4%, or 5%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0034] Preferably, the crosslinking modification liquid further includes an acidic catalyst, and the acidic catalyst includes formic acid and / or acetic acid.

[0035] In the present invention, the acidic catalyst helps to improve the crosslinking effect.

[0036] Preferably, based on the mass of the crosslinking agent, the mass fraction of the acidic catalyst is 0.1% - 1%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0037] Preferably, the time of the crosslinking modification reaction is 10 min - 60 min, for example, it can be 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, etc., and the temperature is 100°C - 200°C, for example, it can be 100°C, 120°C, 140°C, 160°C, 180°C, or 200°C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0038] Preferably, after the crosslinking modification reaction, a pre-carbonization treatment is carried out to obtain the modified polyurethane foam template.

[0039] In the present invention, the pre-carbonization treatment can partially convert the organic components in the polyurethane foam into carbon, which is beneficial to improving its thermal stability and avoiding the collapse of the pore structure caused by rapid decomposition during the subsequent high-temperature carbonization process.

[0040] Preferably, the atmosphere for the pre-carbonization treatment is an inert atmosphere. Exemplarily, for example, it can be nitrogen or argon, etc.

[0041] Preferably, the temperature of the pre-carbonization treatment is 200°C - 400°C, for example, it can be 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C or 400°C, etc.; the time is 0.5 h - 4 h, for example, it can be 0.5 h, 1 h, 2 h, 3 h or 4 h, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0042] Preferably, between the crosslinking modification reaction and the pre-carbonization treatment, a step of alcohol washing is carried out.

[0043] Preferably, during the process of infiltrating the organic foam template with the slurry, a repeated rolling operation is carried out.

[0044] In the present invention, by adopting the repeated rolling operation, sufficient soaking can be ensured.

[0045] Preferably, the drying in step (2) is vacuum drying.

[0046] Preferably, the temperature of the vacuum drying is 60°C - 80°C, for example, it can be 60°C, 65°C, 70°C, 75°C or 80°C, etc.; the time is 10 - 20 h, for example, it can be 10 h, 12 h, 14 h, 16 h, 18 h or 20 h, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0047] In the present invention, vacuum drying is carried out at a relatively low temperature of 60°C - 80°C, which can enable the solvent to volatilize slowly without affecting the porosity.

[0048] Preferably, the sintering in step (2) includes a first sintering and a second sintering carried out in sequence.

[0049] The steps of the first sintering include: heating to 600°C - 800°C (for example, it can be 600°C, 650°C, 700°C, 750°C or 800°C, etc.) under vacuum conditions, then holding the temperature in an argon atmosphere, and then cooling to room temperature.

[0050] The steps of the second sintering include: under an argon atmosphere, heating to 2000°C - 2400°C (for example, it can be 2000°C, 2050°C, 2100°C, 2150°C, 2200°C, 2250°C, 2300°C, 2350°C or 2400°C, etc.), then holding the temperature, and then cooling to room temperature.

[0051] In the present invention, the second sintering is carried out at a temperature of 2000°C - 2400°C, which can promote the growth of tantalum particles, effectively enhance the strength of the skeleton, and then cooling to room temperature can eliminate stress.

[0052] Preferably, during the first sintering, the heating rate is 1°C / min - 5°C / min, for example, it can be 1°C / min, 2°C / min, 3°C / min, 4°C / min or 5°C / min, etc.; the holding time is 4h - 8h, for example, it can be 4h, 5h, 6h, 7h or 8h, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0053] In the present invention, controlling the heating rate of the temperature during the first sintering can effectively alleviate the decomposition rate of the polyurethane foam template and avoid the collapse of the foam structure caused by a sudden temperature rise.

[0054] Preferably, during the second sintering, the heating rate is 2°C / min - 7°C / min, for example, it can be 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min or 7°C / min, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0055] Preferably, during the second sintering, the holding time is 4h - 8h, for example, it can be 4h, 5h, 6h, 7h or 8h, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0056] Preferably, the temperature of the firing in step (3) is 2000°C - 2400°C, for example, it can be 2000°C, 2050°C, 2100°C, 2150°C, 2200°C, 2250°C, 2300°C, 2350°C or 2400°C, etc.; the time is 6h - 8h, for example, it can be 6h, 6.5h, 7h, 7.5h or 8h, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0057] In a second aspect, the present invention provides a porous tantalum carbide, which is prepared by the preparation method described in the first aspect.

[0058] In a third aspect, the present invention provides an application of the porous tantalum carbide as described in the second aspect, and the porous tantalum carbide is applied to the semiconductor field.

[0059] Specifically, in the process of growing silicon carbide single crystals by the PVT method, a porous tantalum carbide plate is used and placed above the raw materials for growth.

[0060] The numerical ranges described in the present invention not only include the above-listed point values, but also any point values between the above numerical ranges not listed. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0061] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0062] (1) The present invention prepares porous tantalum carbide by introducing an organic foam template. It can filter out most of the carbon particles carried by the sublimation of silicon carbide raw materials, and the porous tantalum carbide can maintain a stable structure during the crystal growth process, so that the porous tantalum carbide can effectively reduce the inclusions in the silicon carbide crystal growth process, and can stabilize the crystal form and improve the crystal growth yield. After using the porous tantalum carbide provided by the present invention, the crystal growth yield of silicon carbide is increased by more than 20%.

[0063] (2) The present invention selects to sinter the porous tantalum in a methane atmosphere, which can more fully convert tantalum into tantalum carbide. If a solid substance such as carbon powder is used, it is impossible to convert the inside of the tantalum skeleton either. Although it is a porous structure, these fine pores prevent the carbon powder from entering the inside. Specific Embodiments

[0064] The technical solutions of the present invention will be further described below through specific embodiments. For the convenience of understanding the present invention, the following examples are listed. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0065] It should be noted that the following room temperature refers to 25 °C.

[0066] Example 1

[0067] This example provides a preparation method of porous tantalum carbide, and the preparation method includes:

[0068] (1) Prepare a slurry with a viscosity of 200 mPa·s, and the slurry includes tantalum powder, a dispersant and a solvent; wherein, the particle size D50 of the tantalum powder is 40 μm, and the purity is 99.999%; the dispersant is sodium dodecyl sulfate; the solvent is pure water and ethanol with a volume ratio of 1:1; based on the total mass of the slurry, the mass fraction of the tantalum powder is 23%, and the mass fraction of the dispersant is 0.3%.

[0069] (2) Immerse the polyurethane foam template in the crosslinking modification solution, conduct a crosslinking modification reaction for 35 min at a temperature of 150 °C. After the reaction, conduct alcohol washing to rinse it clean, and then conduct a pre-carbonization treatment at 300 °C for 0.5 h under an argon atmosphere to obtain a modified polyurethane foam template with a porosity of 50%; wherein, the crosslinking modification solution includes a crosslinking agent to be crosslinked, a crosslinking agent, and an acidic catalyst. The crosslinking agent to be crosslinked is polyvinyl alcohol, the crosslinking agent is methyltrimethoxysilane, the acidic catalyst is formic acid, and the solvent used for alcohol washing is ethanol; based on the total mass of the crosslinking modification solution, the mass fraction of the crosslinking agent to be crosslinked is 2.5%, and the mass fraction of the crosslinking agent is 3%; based on the mass of the crosslinking agent, the mass fraction of the acidic catalyst is 0.5%.

[0070] (3) Infiltrate the modified polyurethane foam template with the slurry, and at the same time, repeatedly roll-press the modified polyurethane foam template, and then place it in a vacuum drying oven at 70 °C for 12 h of vacuum drying. After completion, place the dried modified polyurethane foam template in a tube furnace for the first sintering. The process of the first sintering is: under vacuum conditions, heat it up to 700 °C at a heating rate of 3 °C / min, then keep it warm for 6 h in a nitrogen atmosphere, and then cool it down to room temperature; subsequently, place the skeleton after the first sintering in a sintering furnace for the second sintering to obtain porous tantalum. The process of the second sintering is: heat it up to 2200 °C at a heating rate of 4 °C / min in an argon atmosphere, then keep it warm for 6 h, and then cool it down to room temperature.

[0071] (4) Place the porous tantalum in a sintering furnace, heat it up to 2200 °C, then introduce methane, keep it at a constant temperature for 7 h, and then cool it down to room temperature to obtain the porous tantalum carbide.

[0072] Example 2

[0073] This example provides a method for preparing porous tantalum carbide, and the preparation method includes:

[0074] (1) Prepare a slurry with a viscosity of 100 mPa·s. The slurry includes tantalum powder, a dispersant, and a solvent; wherein, the particle size D50 of the tantalum powder is 20 μm, and the purity is 99.999%; the dispersant is polyethylene glycol; the solvent is pure water and ethanol with a volume ratio of 1:1; based on the total mass of the slurry, the mass fraction of the tantalum powder is 25%, and the mass fraction of the dispersant is 0.35%.

[0075] (2) Immerse the polyurethane foam template in the crosslinking modification solution and conduct a crosslinking modification reaction for 10 min at a temperature of 200 °C. After the reaction, conduct alcohol washing to rinse it clean, and then conduct a pre-carbonization treatment at 200 °C for 2.5 h under an argon atmosphere to obtain a modified polyurethane foam template with a porosity of 40%; wherein, the crosslinking modification solution includes a crosslinking agent to be crosslinked, a crosslinking agent, and an acidic catalyst. The crosslinking agent to be crosslinked is polyvinyl alcohol, the crosslinking agent is methyltrimethoxysilane, the acidic catalyst is acetic acid, and the solvent used for alcohol washing is ethanol; based on the total mass of the crosslinking modification solution, the mass fraction of the crosslinking agent to be crosslinked is 1%, and the mass fraction of the crosslinking agent is 1%; based on the mass of the crosslinking agent, the mass fraction of the acidic catalyst is 0.1%.

[0076] (3) Infiltrate the modified polyurethane foam template with the slurry, and at the same time, repeatedly roll-press the modified polyurethane foam template, and then place it in a vacuum drying oven at 60 °C for 20 h of vacuum drying. After completion, place the dried modified polyurethane foam template in a tubular furnace for the first sintering. The process of the first sintering is as follows: Under vacuum conditions, heat it up to 600 °C at a heating rate of 1 °C / min, then keep it warm for 8 h in a nitrogen atmosphere, and then cool it down to room temperature; Subsequently, place the skeleton after the first sintering in a sintering furnace for the second sintering to obtain porous tantalum. The process of the second sintering is as follows: Heat it up to 2000 °C at a heating rate of 5 °C / min in an argon atmosphere, then keep it warm for 8 h, and then cool it down to room temperature.

[0077] (4) Place the porous tantalum in a sintering furnace, heat it up to 2000 °C, then introduce methane, keep it at a constant temperature for 8 h, and then cool it down to room temperature to obtain the porous tantalum carbide.

[0078] Example 3

[0079] This example provides a method for preparing porous tantalum carbide, and the preparation method includes:

[0080] (1) Prepare a slurry with a viscosity of 300 mPa·s, and the slurry includes tantalum powder, a dispersant, and a solvent; wherein, the particle size D50 of the tantalum powder is 50 μm, and the purity is 99.999%; the dispersant is sodium dodecyl sulfate; the solvent is pure water and isopropyl alcohol with a volume ratio of 1:1; based on the total mass of the slurry, the mass fraction of the tantalum powder is 27%, and the mass fraction of the dispersant is 0.4%.

[0081] (2) Immerse the polyurethane foam template in the crosslinking modification solution and carry out a crosslinking modification reaction for 60 min at a temperature of 100 °C. After the reaction, conduct alcohol washing to rinse it clean, and then conduct a pre-carbonization treatment at 400 °C for 2 h under an argon atmosphere to obtain a modified polyurethane foam template with a porosity of 60%; wherein, the crosslinking modification solution includes a crosslinking agent to be crosslinked, a crosslinking agent, and an acidic catalyst. The crosslinking agent to be crosslinked is polyvinyl alcohol, the crosslinking agent is vinyltrimethoxysilane, the acidic catalyst is acetic acid, and the solvent used for alcohol washing is ethanol; based on the total mass of the crosslinking modification solution, the mass fraction of the crosslinking agent to be crosslinked is 4%, and the mass fraction of the crosslinking agent is 5%; based on the mass of the crosslinking agent, the mass fraction of the acidic catalyst is 1%.

[0082] (3) Infiltrate the modified polyurethane foam template with the slurry, and at the same time, repeatedly roll-press the modified polyurethane foam template, and then place it in a vacuum drying oven at 80 °C for 10 h of vacuum drying. After completion, place the dried modified polyurethane foam template in a tubular furnace for the first sintering. The process of the first sintering is as follows: under a vacuum condition, heat it at a heating rate of 5 °C / min to 800 °C, then keep it at a constant temperature in a nitrogen atmosphere for 4 h, and then cool it down to room temperature; subsequently, place the skeleton after the first sintering in a sintering furnace for the second sintering to obtain porous tantalum. The process of the second sintering is as follows: heat it at a heating rate of 5 °C / min to 2400 °C in an argon atmosphere, then keep it at a constant temperature for 4 h, and then cool it down to room temperature.

[0083] (4) Place the porous tantalum in a sintering furnace, heat it to 2400 °C, then introduce methane, keep it at a constant temperature for firing for 6 h, and then cool it down to room temperature to obtain the porous tantalum carbide.

[0084] Example 4

[0085] The difference between this example and Example 1 is that in step (2), no crosslinking modification reaction is carried out.

[0086] The remaining preparation methods and parameters are the same as those in Example 1.

[0087] Example 5

[0088] The difference between this example and Example 1 is that in step (2), the crosslinking agent to be crosslinked is adjusted to polyethylene glycol.

[0089] The remaining preparation methods and parameters are the same as those in Example 1.

[0090] Example 6

[0091] The difference between this example and Example 1 is that in step (2), the crosslinking modification solution does not contain an acidic catalyst.

[0092] The remaining preparation methods and parameters are the same as those in Example 1.

[0093] Example 7

[0094] The difference between this example and Example 1 is that no pre-carbonization treatment is carried out in step (2).

[0095] The remaining preparation methods and parameters are the same as those in Example 1.

[0096] Example 8

[0097] The difference between this example and Example 1 is that the temperature of the vacuum drying in step (3) is 100 °C.

[0098] The remaining preparation methods and parameters are the same as those in Example 1.

[0099] Example 9

[0100] The difference between this example and Example 1 is that during the first sintering in step (3), the heating rate is 8 °C / min.

[0101] The remaining preparation methods and parameters are the same as those in Example 1.

[0102] Example 10

[0103] The difference between this example and Example 1 is that the temperature of the second sintering in step (3) is 1800 °C.

[0104] The remaining preparation methods and parameters are the same as those in Example 1.

[0105] Example 11

[0106] The difference between this example and Example 1 is that the temperature of the second sintering in step (3) is 2500 °C.

[0107] The remaining preparation methods and parameters are the same as those in Example 1.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 1 is that during the firing in step (3), methane is not introduced, but carbon powder is added.

[0110] The remaining preparation methods and parameters are the same as those in Example 1.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 1 is that step (2) is not carried out, and the modified polyurethane foam template in step (3) is replaced with a porous graphite plate.

[0113] The remaining preparation methods and parameters are the same as those in Example 1.

[0114] Performance Test

[0115] I. Use a porosity detector to test the porosity of the porous tantalum carbide provided in the above-mentioned examples and comparative examples.

[0116] II. Grow single-crystalline silicon carbide based on the porous tantalum carbide provided in the above-mentioned examples and comparative examples. The specific method is the PVT method.

[0117] Take out the single-crystalline silicon carbide grown above from the crystal growth furnace, calculate the proportion of qualified crystals without defects such as deformation in the total number of crystal growths, and record it as the crystal growth yield.

[0118] The above test results are shown in Table 1.

[0119] Table 1

[0120]

[0121] Analysis:

[0122] As can be seen from the above table, the present invention controls the porosity of the porous tantalum carbide by controlling the porosity of the polyurethane foam template, so that the porous tantalum carbide can effectively reduce the inclusions in the process of growing silicon carbide single crystals, stabilize the crystal form, and improve the crystal growth yield. After using the porous tantalum carbide provided by the present invention, the crystal growth yield of silicon carbide is increased by more than 20%.

[0123] Comparing Example 1 and Example 4, it can be seen that if the crosslinking modification reaction is not carried out in step (2), the strength of the porous tantalum carbide plate is insufficient and it is easy to break during the high-temperature process, resulting in a reduction in the filtering effect on the silicon carbide component and a decrease in the crystal growth yield.

[0124] Comparing Example 1 and Example 5, it can be seen that if the crosslinking agent is adjusted to polyethylene glycol, the viscosity of polyethylene glycol is insufficient during the preparation of the porous tantalum carbide, resulting in uneven mass distribution of tantalum carbide, and silicon carbide will crystallize on the porous tantalum carbide, resulting in a decrease in the crystal growth yield.

[0125] Comparing Example 1 and Example 6, it can be seen that if the crosslinking modification liquid in step (2) does not contain an acidic catalyst, the crosslinking effect becomes poor, and both the porosity and the crystal growth yield of the porous tantalum carbide decrease.

[0126] Comparing Example 1 and Example 7, it can be seen that if the pre-carbonization treatment is not carried out in step (2), the thermal stability of the polyurethane foam is poor, resulting in rapid decomposition during the subsequent high-temperature carbonization process, causing the pore structure to collapse, and thus both the porosity and the crystal growth yield of the porous tantalum carbide decrease.

[0127] It can be seen from the comparison between Example 1 and Example 8 that if the temperature of the vacuum drying in step (3) is too high, the tantalum paste covering the polyurethane skeleton will crack, resulting in the cracking of the subsequent porous tantalum carbide plate and reducing the crystal growth yield.

[0128] It can be seen from the comparison between Example 1 and Example 9 that if the heating rate is too large during the first sintering in step (3), the tantalum skeleton will crack due to the large temperature difference between the inside and the outside, reducing the crystal growth yield.

[0129] It can be seen from the comparison between Example 1 and Examples 10 - 11 that if the temperature of the second sintering in step (3) is too low, the porosity of the tantalum skeleton will decrease, affecting the filtering effect on the silicon carbide component, thereby reducing the crystal growth yield; if the temperature of the second sintering in step (3) is too high, the density of the tantalum skeleton will increase, also reducing the porosity and ultimately reducing the crystal growth yield.

[0130] It can be seen from the comparison between Example 1 and Comparative Example 1 that if carbon powder is added instead of methane during the firing in step (3), the inside of the tantalum skeleton cannot be converted. Although it is a porous structure, these fine pores prevent the carbon powder from entering the inside, resulting in the inability to convert the internal tantalum into tantalum carbide, and delamination cracking will occur due to the different thermal expansion rates of the two materials during the subsequent high - temperature process, causing a decrease in the crystal yield.

[0131] It can be seen from the comparison between Example 1 and Comparative Example 2 that if a porous graphite plate is used to prepare tantalum carbide, the inside of the graphite plate cannot react completely, and only the surface of the graphite plate is converted into tantalum carbide. Such a porous plate will directly crack due to the different thermal expansion coefficients of the two materials during high - temperature sintering and cannot be used for a long time during the crystal growth process, affecting the crystal quality.

[0132] The above are only the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing porous tantalum carbide, characterized in that, The preparation method includes: (1) Prepare a slurry, which includes tantalum powder and a solvent; (2) Infiltrate the organic foam template with the slurry, and then perform drying and sintering to obtain porous tantalum; (3) Fire the porous tantalum in a methane atmosphere to obtain the porous tantalum carbide.

2. The preparation method according to claim 1, characterized in that, In step (1), the particle size D50 of the tantalum powder is 20μm - 50μm; and / or, the solvent includes water and alcohol, and the alcohol includes ethanol and / or isopropanol; and / or, a dispersant is further included in the slurry; and / or, the viscosity of the slurry is 100mPa·s - 300mPa·s.

3. The preparation method according to claim 1, wherein In step (2), the organic foam template includes a modified polyurethane foam template; and / or, the porosity of the modified polyurethane foam template is 40% - 60%; and / or, the preparation method of the modified polyurethane foam template includes: soaking the polyurethane foam template in a crosslinking modification liquid and performing a crosslinking modification reaction to obtain the modified polyurethane foam template.

4. The preparation method according to claim 3, characterized in that, The crosslinking modification liquid includes a crosslinking agent to be crosslinked and a crosslinking agent; and / or, the crosslinking agent to be crosslinked includes any one or a combination of at least two of polyvinyl alcohol, polyethylene glycol, or polyvinylpyrrolidone; and / or, the crosslinking agent includes a silane coupling agent; and / or, the silane coupling agent includes any one or a combination of at least two of methyltrimethoxysilane, vinyltrimethoxysilane, or dimethyldimethoxysilane; and / or, based on the total mass of the crosslinking modification liquid, the mass fraction of the crosslinking agent to be crosslinked is 1% - 4%, and the mass fraction of the crosslinking agent is 1% - 5%; and / or, an acidic catalyst is further included in the crosslinking modification liquid, and the acidic catalyst includes formic acid and / or acetic acid; and / or, based on the mass of the crosslinking agent, the mass fraction of the acidic catalyst is 0.1% - 1%.

5. The preparation method according to claim 3 or 4, characterized in that, The time of the crosslinking modification reaction is 10min - 60min, and the temperature is 100℃ - 200℃; and / or, after the crosslinking modification reaction, a pre-carbonization treatment is performed to obtain the modified polyurethane foam template; and / or, the atmosphere of the pre-carbonization treatment is an inert atmosphere; and / or, the temperature of the pre-carbonization treatment is 200℃ - 400℃, and the time is 0.5h - 4h.

6. The preparation method according to claim 1, characterized in that, During the process of infiltrating the organic foam template with the slurry, an operation of repeated rolling is performed.

7. The preparation method according to claim 1, characterized in that, The drying in step (2) is vacuum drying; and / or, the temperature of the vacuum drying is 60℃ - 80℃, and the time is 10h - 20h; and / or, the sintering in step (2) includes a first sintering and a second sintering performed in sequence; The steps of the first sintering include: heating to 600℃ - 800℃ under vacuum conditions, then holding in an argon atmosphere, and then cooling to room temperature; The steps of the second sintering include: heating to 2000℃ - 2400℃ in an argon atmosphere, then holding, and then cooling to room temperature; and / or, during the first sintering, the heating rate is 2℃ / min - 7℃ / min, and the holding time is 4h - 8h; and / or, during the second sintering, the holding time is 4h - 8h.

8. The preparation method according to claim 1, wherein, The firing temperature described in step (3) is 2000°C - 2400°C, and the time is 6h - 8h.

9. A porous tantalum carbide, characterized in that, The porous tantalum carbide is prepared by the preparation method described in any one of claims 1 - 8.

10. Use of a porous tantalum carbide as described in claim 9, characterized in that, The porous tantalum carbide is applied to the semiconductor field.

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