Tantalum carbide / graphite composite material and method for preparing the same

Abstract

The present invention relates to the technical field of composite materials, and provides a TaC / graphite composite material and a preparation method thereof. The method comprises: depositing a TaC coating on the surface of a graphite substrate to obtain a preform; electrically connecting an electric pulse device to two surfaces of the preform opposite to each other in the thickness direction via a non-metallic electrode assembly, and performing an electric pulse treatment to obtain the composite material; the surface flatness of the TaC coating is less than 0.3 mm, and the conditions of the electric pulse treatment include: an equivalent current density (unit: A·mm ‑2 , k is 0.4~20A·mm ‑5 The number of electric pulse treatments is more than 2. The present invention reduces the residual stress between the substrate and the coating by performing electric pulse treatment after depositing the TaC coating on the substrate surface.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, and in particular to a preparation method of a TaC / graphite composite material and the TaC / graphite composite material prepared by the preparation method. BACKGROUND

[0002] In the field of semiconductor manufacturing, photovoltaic and third-generation semiconductor material processing, the TaC-coated graphite susceptor as a key process consumable is widely used in high-temperature epitaxial growth (such as MOCVD, CVD) and crystal growth equipment, and its core role is to provide high-temperature stability and chemical inert support for wafers or substrates. According to statistics, at present, the failure modes of TaC-coated graphite susceptor in the application process are mainly the cracking and peeling of the coating. However, due to the significant difference in the coefficient of thermal expansion (CTE) between the graphite matrix and the TaC coating (the CTE of graphite is about 4-5 × 10 -6 / K, and the CTE of TaC is 6-7 × 10 -6 / K, which fluctuates with the crystal direction and process conditions), during the cooling process after coating deposition, the interface will cause significant residual stress (usually up to hundreds of megapascals) due to the incoordination of thermal contraction. This residual stress not only causes defects such as coating micro-cracks and interface peeling, but also further aggravates the cycle thermal load in the subsequent high-temperature service process, which seriously reduces the service life and process reliability of the susceptor.

[0003] At present, the industry mainly relies on the following technical paths to relieve the residual stress between the TaC coating and the graphite susceptor: (1) gradient structure design: by introducing a transition layer to reduce the interface mutation, but it is limited by the process complexity and cost; (2) high-temperature heat treatment: using high-temperature heat relaxation to promote atomic diffusion, but the high-temperature oxidation risk of the graphite matrix limits its applicability, and the processing time is long and the energy consumption is high; (3) deposition parameter optimization: reducing the residual stress by reducing the deposition rate or adjusting the coating thickness, but it cannot eliminate the thermal stress. In addition, the above methods cannot realize the directional regulation of lattice distortion, and the process consistency is poor in complex geometric susceptors (such as porous or irregular structures). Therefore, how to more efficiently reduce the thermal stress between the graphite susceptor and the TaC coating is a problem to be solved. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned problems existing in the prior art, and to provide a TaC / graphite composite material and a preparation method thereof. The present application reduces the residual stress between the graphite substrate and the TaC coating by performing electric pulse treatment on the TaC coating deposited on the surface of the graphite substrate.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a preparation method of a TaC / graphite composite material, which comprises the following steps:

[0006] (1) depositing a TaC coating layer on the surface of a graphite substrate to obtain a preform;

[0007] (2) electrically connecting the preform through a non-metal electrode assembly to two surfaces of the preform in the thickness direction, and performing electric pulse treatment to obtain a TaC / graphite composite material;

[0008] The surface flatness of the TaC coating layer is 0.3 mm or less, and the electric pulse treatment conditions include: equivalent current density , unit: A·mm -2 , wherein D is the duty cycle, S is the contact area between the electrode on one side of the preform surface and the preform, unit: mm 2 , T is the coating thickness, unit: μm; k is 0.4-20 A·mm -5 , the number of electric pulse treatment is 2 or more times.

[0009] The second aspect of the present application provides a TaC / graphite composite material prepared by the preparation method as described above.

[0010] The present application has the following beneficial effects by adopting the above technical solutions:

[0011] (1) Because the resistance of the micro-damage of graphite and TaC materials is large, the current passing through the micro-damage will cause greater heating. The electric pulse treatment of the present application can repair the micro-damage of the graphite base produced in the machining process, such as dislocation entanglement and micro-cracks, and further release the residual stress between the graphite and the TaC coating layer caused by the difference in thermal expansion coefficient, effectively reducing the residual stress between the graphite substrate and the TaC coating layer at room temperature, preventing the coating from cracking due to excessive stress at room temperature, further improving the service life of the material, and avoiding the risk of oxidation of the graphite matrix in the traditional heat treatment process.

[0012] (2) The electric pulse treatment of the present application can also reduce the lattice distortion at the interface between the graphite matrix and the TaC coating layer, improve the stability of the interface, enhance the high-temperature mechanical stability and chemical stability of the material, and further improve the service life of the material.

[0013] (3) The electric pulse treatment technology of the present application has the advantages of low energy consumption, short processing time and low cost, which significantly shortens the production cycle.

[0014] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The endpoints of the ranges of values and the values thereof can be combined with other endpoints to form new ranges and values not expressly disclosed herein. In this document, the terms "approximately" and "about" are used to describe values that can be approximate, nearby, around, or close to a specific value, and are not to be construed as being limited to a precise value. Unless otherwise stated, data ranges include endpoints. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A schematic diagram of the electric pulse treatment is shown.

[0016] Figure 2 A schematic diagram of the electric pulse treatment is shown.

[0017] Figure 3 Transmission electron microscope photographs of the TaC grain boundary before and after the electric pulse treatment in Example 1 are shown, wherein (a) is before the treatment, and (b) is after the treatment.

[0018] BRIEF DESCRIPTION OF DRAWINGS

[0019] 1, electric pulse generating device; 2, insulating support; 3, conductive graphite clamp; 4, preform. DETAILED DESCRIPTION

[0020] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the present application.

[0021] Unless otherwise defined, all scientific and technical terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0022] The first aspect of the present application provides a preparation method of a TaC / graphite composite material, which comprises the following steps:

[0023] (1) depositing a TaC coating layer on the surface of a graphite substrate to obtain a preform;

[0024] (2) electrically connecting the electric pulse device through a non-metal electrode assembly to two opposite surfaces of the preform along the thickness direction, and performing electric pulse treatment to obtain a TaC / graphite composite material;

[0025] The surface flatness of the TaC coating layer is 0.3 mm or less (such as 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm), and the electric pulse treatment conditions include: an equivalent current density , unit: A·mm-2 wherein D is a duty cycle, S is the contact area of the electrode with the preform on one side of the preform surface, in mm 2 , T is the coating thickness, in μm, and k is 0.4-20 A / mm 5 (for example, 0.4 A / mm 5 , 1 A / mm 5 , 2 A / mm 5 , 4 A / mm 5 , 6 A / mm 5 , 8 A / mm 5 , 10 A / mm 5 , 12 A / mm 5 , 14 A / mm 5 , 16 A / mm 5 , 18 A / mm 5 , 20 A / mm 5 ), and the number of times of the electric pulse treatment is 2 or more (for example, 2, 4, 6, 8, 10, 12 times).

[0026] The graphite substrate can have a thermal expansion coefficient of 4x10 -6 / K-7.5x10 -6 / K, a density of 1.7-2.2 g / cm 3 , a porosity of 5-25%, and a grain size of less than 20 μm.

[0027] In some embodiments, the method further comprises pretreating the graphite substrate before deposition, for example, by grinding, polishing, sandblasting, etc. to make the surface of the graphite substrate have a certain roughness and flatness, and by cleaning, etc. to remove impurities on the surface of the graphite substrate. The grinding, polishing, sandblasting, etc. processes can be performed according to conventional operation methods in the art, as long as the surface of the graphite substrate has a certain roughness and flatness. For example, the graphite blank can be machined using a numerical control machine tool.

[0028] The cleaning process can be washing with water or pickling with acid, and can be rinsing and / or soaking, and can be performed by conventional means in the art, as long as the impurities on the surface of the graphite substrate can be removed. When washing with water, deionized water can be used, and the deionized water can have a resistivity of greater than 18 MΩ·cm.

[0029] After cleaning, the graphite substrate can be dried and then used in the subsequent deposition process. The drying method can be a conventional drying method, for example, the graphite substrate can be dried using a vacuum drying machine or air blowing (which can be dried at 70-200 °C for 10-60 min).

[0030] In some embodiments, the roughness of the surface of the graphite substrate is 0.2 μm or less (e.g., 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm), and the surface flatness is controlled to be within 0.1 mm (e.g., 0.02 mm, 0.05 mm, 0.08 mm, 0.1 mm). In this case, it is more advantageous to control the roughness and the surface flatness of the surface of the preform after the TaC coating is deposited to be in a lower range, thereby facilitating an increase in the degree of contact of the preform with the electrode.

[0031] In some embodiments, the TaC coating is deposited by CVD, and a CVD vapor deposition furnace can be used. The substrate can be placed horizontally in a deposition reaction chamber, the furnace door can be closed, and the reaction chamber can be pumped to a vacuum of 200 Pa or less. The temperature can then be raised to the deposition temperature at a rate of 2-10 ℃ / min.

[0032] In some embodiments, the deposition conditions include a temperature of 1100-1600 ℃ (e.g., 1100 ℃, 1200 ℃, 1400 ℃, 1600 ℃), a pressure of 5-20 kPa (e.g., 5 kPa, 10 kPa, 15 kPa, 20 kPa), and a time of 5-60 h (e.g., 5 h, 10 h, 20 h, 40 h, 60 h).

[0033] In some embodiments, the deposition conditions include a temperature of 1200-1500 ℃, a pressure of 8-15 kPa, and a time of 10-30 h.

[0034] In some embodiments, the gas system for CVD deposition includes a tantalum source, a carbon source, a reducing gas, and a dilution gas.

[0035] In some embodiments, the tantalum source includes at least one of TaF5, TaCl5, and TaBr5.

[0036] In some embodiments, the carbon source includes at least one of CH4, C2H4, C2H6, C3H6, and C3H8.

[0037] In some embodiments, the reducing gas is hydrogen.

[0038] The dilution gas can be an inert gas, i.e., a gas that does not react with other components, such as argon (Ar) or helium (He).

[0039] In some embodiments, the molar ratio of tantalum in the tantalum source, carbon in the carbon source, the reducing gas, and the dilution gas is 1:1-3 (e.g., 1, 1.5, 2, 2.5, 3):4-8 (e.g., 4, 5, 6, 7, 8):2-4 (e.g., 2, 2.5, 3, 3.5, 4).

[0040] In some embodiments, the thickness T of the TaC coating layer is 50-300 μm (e.g., 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm). When the thickness of the TaC coating layer is within this range, the flatness of the TaC coating layer is better, which can facilitate the uniform loading and action of the electric pulse.

[0041] After the final product is obtained, a vacuum cooling operation can be performed, and the specific operation method can be a conventional operation method in the art. For example, after the last deposition is completed, the furnace can be pumped to below 200 Pa, the temperature can be gradually reduced to room temperature at a cooling rate of 2 ℃ / min-10 ℃ / min, then Ar or N2 at a flow rate of 20 L / min-200 L / min can be introduced to adjust the pressure to normal pressure, and then the furnace can be opened to take out the product.

[0042] The obtained preform can be placed on an insulator and subjected to electric pulse treatment by an electric pulse device. The electric pulse device can be a conventional electric pulse device used in the art as long as it can output an electric pulse. The shape of the electrode assembly of the non-metal (e.g., graphite) is not particularly limited and can be cylindrical, prismatic, cuboid, array (e.g., dot array, line array, or surface array of different shapes on the interface with the surface of the preform), etc. Generally, the contact area of the electrode assembly of the non-metal with the surface of the preform is substantially the same.

[0043] The number of times of electric pulse treatment is not particularly limited as long as the surface of the preform can be substantially subjected to electric pulse treatment. The number of times of electric pulse treatment can be adjusted according to the shape and size of the electrode assembly. For example, when the contact area S of the electrode on one side of the preform with the preform accounts for more than half of the area of the one side of the preform, the electric pulse treatment can be performed once. If the contact area S of the electrode on one side of the preform with the preform accounts for a small proportion of the area of the one side of the preform, such as 1%, the contact position of the electrode with the preform can be adjusted in a certain order and the electric pulse treatment can be performed multiple times.

[0044] In some embodiments, the duty cycle D is 0.05-0.5 (e.g., 0.05, 0.1, 0.2, 0.3, 0.4, 0.5).

[0045] In the present application, the duty cycle D refers to the proportion of the energization time to the total time within one pulse cycle, which is dimensionless.

[0046] In some embodiments, the contact area S of the electrode on one side of the preform with the preform is 100-600 mm 2 (e.g., 100 mm 2 , 200 mm 2 , 300 mm2 400 mm 2 500 mm 2 600 mm 2 ).

[0047] In the present application, S is defined as the effective contact area between the electrode and the preform, wherein the electrode is arranged on a single side surface of the preform, and the contact area is defined by the geometrically coinciding area between the electrode and the surface of the preform.

[0048] In some embodiments, the equivalent current density is 10-50 A·mm -2 (e.g. 10 A·mm -2 , 20 A·mm -2 , 30 A·mm -2 , 40 A·mm -2 , 50 A·mm -2 ).

[0049] In some embodiments, the conditions of the electric pulse treatment further include: the frequency is 10-200 Hz (e.g. 10 Hz, 50 Hz, 100 Hz, 150 Hz, 200 Hz), and the time of a single electric pulse treatment is 0.1-3 s (e.g. 0.1 s, 0.5 s, 1 s, 2 s, 3 s).

[0050] In some embodiments, the conditions of the electric pulse treatment further include: the number of times of the electric pulse treatment is 2-10. When the time interval between two adjacent electric pulses is more than 10 s, such as 20 s, 30 s, 40 s, etc., it means that it is two electric pulse treatments, rather than one electric pulse treatment.

[0051] In some embodiments, the surface flatness of the electrode is 0.3 mm or less (such as 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm). The surface flatness of the TaC coating layer is 0.3 mm or less, which can further improve the effect of the electric pulse treatment and reduce the residual stress.

[0052] In some embodiments, the contact area S between the electrode and the preform on the single side surface of the preform accounts for 1-20% (e.g. 1%, 5%, 10%, 15%, 20%) of the area of the single side surface of the preform.

[0053] In some embodiments, the pulse waveform of the electric pulse treatment includes at least one of a rectangular wave, a square wave, a sine wave and a triangular wave, and is preferably a rectangular wave.

[0054] The second aspect of the present application provides a TaC / graphite composite material prepared by the preparation method as described above.

[0055] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0056] The materials and reagents used in the following examples can be obtained from commercial channels unless otherwise specified.

[0057] The present application will be described in detail below with reference to specific examples, which are used for understanding rather than limiting the present application.

[0058] Example 1 group

[0059] This example is used to illustrate the preparation method of the TaC / graphite composite material according to the present application.

[0060] The graphite substrate is polished to a roughness Ra of 0.2 μm or less, and the surface flatness is controlled within 0.1 mm; the graphite base is cleaned with deionized water and then dried at 120°C, ready for use.

[0061] The graphite substrate is placed in a chemical vapor deposition device for chemical vapor deposition. The deposition conditions include a temperature of 1300°C, a pressure of 12 kPa, and a time of 20 h. The deposition gas includes TaCl5, C2H6, H2 and Ar in a molar ratio of 1:1:6:3, forming a TaC coating with a thickness of about 100 μm to obtain a preform. After deposition, nitrogen is introduced to replace the remaining gas in the furnace, and the graphite base is removed from the deposition device after the furnace temperature decreases. The surface flatness of the TaC coating is 0.3 mm or less.

[0062] Reference Figure 1 The preform 4 is installed on a clean insulating platform 2, and the conductive graphite clamp 3 on the electric pulse generating device 1 is installed on the preform 4 at the position to be treated. The upper and lower conductive graphite clamps have the same size, and the contact area S of the electrode on one side of the preform surface with the preform is 314 mm 2 The contact area S of the electrode on one side of the preform surface with the preform accounts for 1% of the area of the one side of the preform surface, and the surface flatness of the electrode is 0.3 mm or less. The electric pulse generating device is used to sequentially perform electric pulse treatment on each position on the surface of the preform in the order shown in Table 1. Figure 2

[0063] Figure 3 ​The transmission electron microscope photos of TaC grain boundary before and after the electric pulse treatment in Example 1-1 are shown, wherein (a) is before the treatment, and (b) is after the treatment. It can be seen from the figures that the dislocation density at the TaC grain boundary is significantly reduced after the electric pulse treatment.

[0064] The residual stress of the composite material was tested by X-ray diffraction method, and the results are shown in Table 1.

[0065] Example 2 group

[0066] The method described in Example 1 was followed, except that the pulse waveform of the electric pulse treatment was different, and the residual stress results are shown in Table 1.

[0067] Example 2-1: The pulse waveform of the electric pulse treatment was a triangular wave.

[0068] Example 2-2: The pulse waveform of the electric pulse treatment was a sinusoidal wave.

[0069] Example 3 group

[0070] The method described in Example 1 was followed, except that the deposition time of the TaC coating was controlled so that the thickness of the TaC coating was different, and the residual stress results are shown in Table 1.

[0071] Example 3-1: The thickness of the TaC coating was 10 μm.

[0072] Example 3-2: The thickness of the TaC coating was 50 μm.

[0073] Example 3-3: The thickness of the TaC coating was 300 μm.

[0074] Example 3-4: The thickness of the TaC coating was 500 μm.

[0075] Comparative Example 1

[0076] The method described in Example 1 was followed, except that the preform was not subjected to electric pulse treatment, and the residual stress results are shown in Table 1.

[0077] Comparative Example 2

[0078] The method described in Example 1 was followed, except that the preform was subjected to heat treatment instead of electric pulse treatment, and the heat treatment conditions included a temperature of 1200℃, a pressure of 100 kPa, and a time of 100 min, and the residual stress results are shown in Table 1.

[0079] Comparative Example 3

[0080] The method described in Example 1 was followed, except that the number of times of electric pulse treatment was 1, and the residual stress results are shown in Table 1.

[0081] Comparative Example 4

[0082] The method described in Example 1 was followed, except that the deposition conditions of the TaC coating were controlled so that the surface flatness of the TaC coating was 0.4 mm, and the residual stress results are shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] Note: * indicates the same as Example 1.

[0087] From the above data, it can be seen that the deposition of the TaC coating on the surface of the graphite substrate can significantly reduce the residual stress between the graphite substrate and the TaC coating by electric pulse treatment, and the effect is comparable to or even better than heat treatment.

[0088] In the case of controlling the surface flatness of the TaC coating to be below 0.3 mm, the number of times of electric pulse treatment to be more than 2, and controlling the appropriate equivalent current density at the same time, the dislocation density at the grain boundary of the TaC coating can be significantly reduced, further reducing the residual stress and improving the stability of the phase boundary, which is beneficial to enhancing the high-temperature mechanical stability and chemical stability of the material, and further improving the service life of the material.

[0089] In the further control of the treatment time, duty cycle and other conditions within the preferred range, the residual stress can be further reduced.

[0090] From the data of Example 3 group, it can be seen that with the increase of the thickness of the TaC coating, the residual stress gradually increases under the same treatment conditions, therefore, the thickness of the TaC coating is preferably controlled within the preferred range. If the product requires a TaC coating with a larger thickness size, the residual stress can be further reduced by increasing the equivalent current density, the number of treatments and other methods.

[0091] It is to be understood that the terminology "including", "containing" or any other variation thereof does not exclude the presence of other elements or steps than those listed in the process, method, article, or apparatus. It is further understood that the steps and elements recited in any of the examples herein can be combined, removed or arranged in various ways without departing from the scope of the application. Further, the features described in relation to one example can be combined with features described in relation to other examples.

[0092] The above description is merely illustrative of the application, and is not to be taken in a limiting sense. Any modification, equivalent substitution, or improvement not described herein is to be included within the scope of the application.

Claims

1. A method for producing a TaC / graphite composite material, characterized by, The method comprises the following steps: (1) depositing a TaC coating layer on the surface of a graphite substrate to obtain a preform; (2) electrically connecting the preform to an electrode assembly through a non-metal electrode and performing electric pulse treatment to obtain a TaC / graphite composite material; The surface flatness of the TaC coating is 0.3 mm or less, and the conditions of the electric pulse treatment include: equivalent current density , A·mm -2 , wherein D is the duty cycle, S is the contact area between the electrode on the single-sided preform surface and the preform, mm 2 , T is the coating thickness, in the range of 50-300 μm; k is 0.4-20 A·mm -5 , and the number of times of the electric pulse treatment is 2 or more.

2. The production method according to claim 1, characterized by, the duty cycle D is 0.05-0.5; and / or The contact area S of the electrode with the preform on one side of the preform surface is 100-600 mm 2 .

3. The production method according to claim 1 or 2, characterized by, The equivalent current density is 10-50 A·mm -2 .

4. The production method according to claim 1 or 2, characterized by, the electric pulse treatment is performed under the following conditions: the frequency is 10-200 Hz, the time for a single electric pulse treatment is 0.1-3 s, and the number of electric pulse treatments is 2-10.

5. The production method according to claim 1 or 2, characterized by, The surface flatness of the electrode is less than or equal to 0.3 mm.

6. The production method according to claim 1 or 2, characterized by, The pulse waveform of the electric pulse treatment comprises at least one of a rectangular wave, a square wave, a sine wave, and a triangular wave.

7. The preparation method according to claim 6, characterized in that The pulse waveform of the electric pulse treatment is a rectangular wave.

8. The production method according to claim 1 or 2, characterized by, The deposition method of the TaC coating layer is CVD deposition.

9. The preparation method according to claim 8, characterized in that The deposition conditions of the CVD deposition comprise: the temperature is 1100-1600 ℃, the pressure is 5-20 kPa, and the time is 5-60 h.

10. The method of claim 9, wherein, The deposition conditions of the CVD deposition comprise: the temperature is 1200-1500 ℃, the pressure is 8-15 kPa, and the time is 10-30 h.

11. The method of claim 10, wherein, The gas system of the CVD deposition comprises a tantalum source, a carbon source, a reducing gas, and a dilution gas.

12. The method of claim 11, wherein, The molar ratio of tantalum in the tantalum source, carbon in the carbon source, the reducing gas, and the dilution gas is 1:1-3:4-8:2-4.

13. A TaC / graphite composite material prepared by the method of any one of claims 1-12.

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