TaC / graphite composite material and preparation method thereof

Abstract

The invention relates to the technical field of composite materials, and provides a TaC / graphite composite material and a preparation method thereof.The method comprises the steps that a TaC coating is deposited on the surface of a graphite base material, and a prefabricated body is obtained; an electric pulse device is electrically connected with the two opposite surfaces, in the thickness direction, of the prefabricated body through a non-metal electrode assembly, electric pulse treatment is carried out, and a composite material is obtained; the surface flatness of the TaC coating is less than 0.3 mm, and the conditions of the electric pulse treatment are as follows: the equivalent current density unit is A.mm <-2 >, k is 0.4-20 A.mm <-5 >, and the number of times of the electric pulse treatment is more than two. After the TaC coating is deposited on the surface of the base material, the electric pulse treatment is carried out, so that the residual stress between the base material and the coating is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a method for preparing a TaC / graphite composite material and the TaC / graphite composite material prepared by the preparation method. Background Art

[0002] In the fields of semiconductor manufacturing, photovoltaics, and third-generation semiconductor material processing, tantalum carbide (TaC)-coated graphite susceptors are widely used as key process consumables in high-temperature epitaxial growth (such as MOCVD, CVD) and crystal growth equipment. Their core function is to provide high-temperature stability and chemical inertness support for wafers or substrates. According to statistics, the main failure forms of TaC-coated graphite susceptors during application are cracking and shedding of the coating. However, due to the significant difference in the coefficient of thermal expansion (CTE) between the graphite substrate and the TaC coating (the CTE of graphite is approximately 4-5×10 -6 / K, while the CTE of TaC is 6-7×10 -6 / K, which fluctuates with crystal orientation and process conditions). During the cooling process after coating deposition, uncoordinated thermal contraction at the interface can induce significant residual stress (typically reaching hundreds of MPa). This residual stress not only causes defects such as coating microcracks and interface delamination, but can also be further exacerbated by cyclic thermal loads during subsequent high-temperature service, severely reducing the lifespan and process reliability of the susceptor.

[0003] Currently, the industry mainly relies on the following technical paths to alleviate the residual stress between TaC coating and graphite base: (1) Gradient structure design: reducing interface mutation by introducing a transition layer, but it is limited by process complexity and cost; (2) High-temperature heat treatment: using high-temperature thermal relaxation to promote atomic diffusion, but the risk of high-temperature oxidation of the graphite substrate limits its applicability, and the processing time is long and the energy consumption is high; (3) Deposition parameter optimization: reducing residual stress by reducing the deposition rate or adjusting the coating thickness, but it cannot eliminate thermal stress. In addition, none of the above methods can achieve directional control of lattice distortion, and the process consistency is poor in complex geometric bases (such as porous or special-shaped structures). Therefore, how to more efficiently reduce the thermal stress between the graphite base and TaC coating is an urgent problem to be solved. Summary of the Invention

[0004] The present invention aims to overcome the above-mentioned problems existing in the prior art and provides a TaC / graphite composite material and a preparation method thereof. The present invention reduces the residual stress between the graphite substrate and the TaC coating by depositing a TaC coating on the surface of the graphite substrate and subjecting the coating to an electric pulse treatment.

[0005] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a TaC / graphite composite material, the method comprising the following steps: (1) depositing a TaC coating on the surface of a graphite substrate to obtain a preform; (2) electrically connecting an electric pulse device to two surfaces of the preform opposite to each other in the thickness direction through a non-metallic electrode assembly, and performing an electric pulse treatment to obtain a TaC / graphite composite material; The surface flatness of the TaC coating is less than 0.3 mm, and the conditions of the electric pulse treatment include: equivalent current density , unit is A·mm -2 , where D is the duty cycle and S is the contact area between the electrode and the preform on one side of the preform surface, in mm 2 , T is the coating thickness in μm; k is 0.4~20A·mm -5 , the number of electric pulse treatments is more than 2 times.

[0006] The second aspect of the present invention provides a TaC / graphite composite material prepared by the preparation method described above.

[0007] The present invention adopts the above technical solution to achieve the following beneficial effects: (1) Since the resistance of the micro-damaged parts of graphite and TaC materials is relatively large, the current passing through the micro-damaged parts will cause a greater temperature rise. The present invention can repair the micro-damage generated by the graphite base during the machining process, such as dislocation entanglement and micro-cracks, through electric pulse treatment, and then release the residual stress caused by the inconsistency of thermal expansion coefficients between the graphite and TaC coating, effectively reducing the residual stress between the graphite substrate and the TaC coating 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 substrate during traditional heat treatment.

[0008] (2) The present invention can also reduce the lattice distortion at the interface between the graphite substrate and the TaC coating through electric pulse treatment, 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.

[0009] (3) The electric pulse processing technology of the present invention has the advantages of low energy consumption, short processing time and low cost, which significantly shortens the production cycle.

[0010] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Herein, unless otherwise specified, data ranges include endpoints. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Shown is a schematic diagram of electrical pulse treatment.

[0012] Figure 2 The figure shows a schematic diagram of the sequence of performing electric pulse treatment on the surface of the preform.

[0013] Figure 3 Shown are transmission electron microscope images of TaC grain boundaries before and after electric pulse treatment in Example 1, where (a) is before treatment and (b) is after treatment.

[0014] Description of Reference Numerals 1. Electric pulse generator; 2. Insulating carrier; 3. Conductive graphite fixture; 4. Preform. DETAILED DESCRIPTION

[0015] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0016] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention relates.

[0017] A first aspect of the present invention provides a method for preparing a TaC / graphite composite material, the method comprising the following steps: (1) depositing a TaC coating on the surface of a graphite substrate to obtain a preform; (2) electrically connecting an electric pulse device to two surfaces of the preform opposite to each other in the thickness direction through a non-metallic electrode assembly, and performing an electric pulse treatment to obtain a TaC / graphite composite material; The surface flatness of the TaC coating is less than 0.3 mm (for example, 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm). The conditions of the electric pulse treatment include: equivalent current density , unit is A·mm -2 , where D is the duty cycle, S The contact area between the electrode and the preform on one side of the preform surface, in mm 2 , T is the coating thickness in μm, and k is 0.4~20A / mm 5 (For example, 0.4A / mm 5 , 1A / mm 5 , 2A / mm 5 , 4A / mm 5 , 6A / mm 5, 8A / mm 5 , 10A / mm 5 , 12A / mm 5 , 14A / mm 5 , 16A / mm 5 , 18A / mm 5 , 20A / mm 5 ), the number of electric pulse treatments is 2 or more times (for example, 2 times, 4 times, 6 times, 8 times, 10 times, 12 times).

[0018] The thermal expansion coefficient of the graphite substrate can be 4×10 -6 / K~7.5×10 -6 / K, density can be 1.7-2.2g / cm 3 , the porosity can be 5-25% and the grain size can be less than 20 μm.

[0019] In some embodiments, the method further includes pre-treating the graphite substrate before deposition, such as by grinding, polishing, sandblasting, etc. to impart a certain degree of roughness and flatness to the graphite substrate surface, and removing impurities from the graphite substrate surface by cleaning, etc. Grinding, polishing, sandblasting, and other processes can be performed according to conventional procedures in the art, as long as the graphite substrate surface can impart a certain degree of roughness and flatness. For example, the graphite blank can be machined using a CNC machine tool.

[0020] The cleaning process can be performed with water, acid, rinsing, and / or immersion, and can be performed by conventional means in the art, as long as impurities on the surface of the graphite substrate can be removed. Deionized water can be used for washing, and the resistivity of the deionized water can be greater than 18 MΩ·cm.

[0021] After cleaning, the substrate can be dried and then used in the subsequent deposition process. The drying method can be a conventional drying method, such as using a vacuum dryer or air drying (drying at 70°C-200°C for 10-60 minutes).

[0022] In some embodiments, the surface roughness of the graphite substrate is less than 0.2 μm (e.g., 0.05 μm, 0.1 μm, 0.15 μm, or 0.2 μm), and the surface flatness is controlled within 0.1 mm (e.g., 0.02 mm, 0.05 mm, 0.08 mm, or 0.1 mm). In this case, it is more advantageous to control the surface roughness and surface flatness of the preform obtained after depositing the TaC coating to a lower range, thereby facilitating improved contact between the preform and the electrode.

[0023] In some embodiments, the TaC coating is deposited by CVD deposition, and the equipment used can be a CVD vapor deposition furnace. The substrate can be placed horizontally in the deposition reaction chamber, the furnace door is closed, the reaction chamber is evacuated to below 200 Pa, and then the temperature is increased to the deposition temperature at 2-10 ° C / min.

[0024] In some embodiments, the deposition conditions include: a temperature of 1100°C-1600°C (for example, 1100°C, 1200°C, 1400°C, 1600°C), a pressure of 5-20 kPa (for example, 5 kPa, 10 kPa, 15 kPa, 20 kPa), and a time of 5-60 h (for example, 5 h, 10 h, 20 h, 40 h, 60 h).

[0025] In some embodiments, the deposition conditions include: a temperature of 1200° C.-1500° C., a pressure of 8-15 kPa, and a time of 10-30 hours.

[0026] In some embodiments, the CVD deposition gas system includes a tantalum source, a carbon source, a reducing gas, and a diluent gas.

[0027] In some embodiments, the tantalum source comprises at least one of TaF5, TaCl5, and TaBr5.

[0028] In some embodiments, the carbon source comprises at least one of CH4, C2H4, C2H6, C3H6, and C3H8.

[0029] In some embodiments, the reducing gas is hydrogen.

[0030] The diluent gas may be an inert gas, that is, a gas that does not react with other components, such as argon Ar or helium He.

[0031] In some embodiments, the molar ratio of the tantalum element in the tantalum source, the carbon element in the carbon source, the reducing gas and the dilution gas is 1:1-3 (for example, 1, 1.5, 2, 2.5, 3):4-8 (for example, 4, 5, 6, 7, 8):2-4 (for example, 2, 2.5, 3, 3.5, 4).

[0032] In some embodiments, the thickness T of the TaC coating is 50-300 μm (e.g., 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, or 300 μm). When the thickness of the TaC coating is within this range, the TaC coating has better flatness, which facilitates uniform loading and application of the electrical pulse.

[0033] After obtaining the final product, a vacuum cooling operation can be performed. The specific operation method can be a conventional operation method in this field. For example, after the last deposition is completed, the furnace can be evacuated to below 200 Pa, and the temperature can be gradually lowered to room temperature at a cooling rate of 2°C / min-10°C / min. Then, 20 L / min-200 L / min of Ar or N2 is introduced to adjust the pressure to normal pressure, and then the furnace is opened to take out the product.

[0034] The resulting preform can be placed on an insulator and subjected to an electric pulse treatment using an electric pulse device. The electric pulse device can be any conventional device in the art, as long as it can output electric pulses. The shape of the non-metallic (e.g., graphite) electrode assembly is not particularly limited and can be cylindrical, prismatic, rectangular, or in an array (e.g., a point array, line array, or surface array of varying shapes at the interface with the preform surface). Generally speaking, the contact area between the non-metallic electrode assembly and the preform surface is substantially uniform.

[0035] There is no particular restriction on the number of times the electric pulse treatment is performed, as long as the surface of the preform can be basically treated with the electric pulse. Specifically, the number of electric pulses can be adjusted according to the shape and size of the electrode assembly. For example, when the contact area S between the electrode on the surface of a single preform and the preform accounts for more than half of the area of ​​the single preform surface, the treatment can be performed once; if the contact area S between the electrode on the surface of a single preform and the preform accounts for a small proportion of the area of ​​the single preform surface, such as 1%, the contact position between the electrode and the preform can be adjusted in a certain order and multiple electric pulse treatments can be performed.

[0036] In some embodiments, the duty cycle D is 0.05-0.5 (eg, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5).

[0037] In the present invention, the duty cycle D refers to the ratio of the power-on time to the total time in a pulse cycle, and is dimensionless.

[0038] In some embodiments, the contact area S between the electrode on one side of the preform and the preform is 100-600 mm 2 (For example, 100 mm 2 , 200 mm 2 , 300 mm 2 , 400 mm 2 , 500 mm 2 , 600 mm 2 ).

[0039] In the present invention, S is defined as the effective contact area between the electrode and the preform, wherein the electrode is oriented on a single surface of the preform, and the contact area is defined by the geometric overlap area between the electrode and the preform surface.

[0040] In some embodiments, the equivalent current density is 10~50A·mm -2 (For example, 10 A mm -2 , 20 A·mm -2 、30 A·mm -2 , 40 A·mm -2 , 50 A·mm -2 ).

[0041] In some embodiments, the conditions of the electric pulse treatment also include: a frequency of 10 Hz-200 Hz (for example, 10 Hz, 50 Hz, 100 Hz, 150 Hz, 200 Hz), and a single electric pulse treatment time of 0.1s-3s (for example, 0.1s, 0.5s, 1s, 2s, 3s).

[0042] In some embodiments, the electric pulse treatment condition further includes: the number of electric pulse treatments is 2 to 10. When the time interval between two adjacent electric pulses is greater than 10 seconds, such as 20 seconds, 30 seconds, or 40 seconds, it means that the electric pulse treatments are two times, not one time.

[0043] In some embodiments, the surface flatness of the electrode is less than 0.3 mm (e.g., 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm). A TaC coating with a surface flatness of less than 0.3 mm can further enhance the effectiveness of the electric pulse treatment and reduce residual stress.

[0044] In some embodiments, the contact area S between the electrode and the preform on a single-sided preform surface accounts for 1-20% (eg, 1%, 5%, 10%, 15%, 20%) of the area of ​​the single-sided preform surface.

[0045] In some embodiments, the pulse waveform of the electrical pulse treatment includes at least one of a rectangular wave, a square wave, a sine wave, and a triangle wave, preferably a rectangular wave.

[0046] The second aspect of the present invention provides a TaC / graphite composite material prepared by the preparation method described above.

[0047] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0049] The present invention will be described in detail below with reference to specific embodiments. These embodiments are intended to help you understand the present invention but are not intended to limit it.

[0050] Example 1 group This example is used to illustrate the preparation method of the TaC / graphite composite material of the present invention.

[0051] The graphite substrate was polished to a roughness Ra of less than 0.2 μm and a surface flatness of less than 0.1 mm. The graphite base was cleaned with deionized water and then dried at 120° C. for later use.

[0052] A graphite substrate was placed in a chemical vapor deposition apparatus and subjected to chemical vapor deposition. The deposition conditions included a temperature of 1300°C, a pressure of 12 kPa, and a time of 20 hours. The deposition gas included TaCl5, C2H6, H2, and Ar in a molar ratio of 1:1:6:3, forming a TaC coating with a thickness of approximately 100 μm to obtain a preform. After the deposition was completed, nitrogen was introduced to replace the remaining gas in the furnace, and the graphite base was removed from the deposition apparatus after the furnace temperature was lowered. The surface flatness of the TaC coating was less than 0.3 mm.

[0053] refer to Figure 1 , install the preform 4 on a clean insulating carrier 2, and install the conductive graphite fixture 3 on the electric pulse generator 1 on the position to be processed on the preform 4, where the upper and lower conductive graphite fixtures have the same area size, and the contact area S between the electrode on one side of the preform surface and the preform is 314mm 2 The contact area S between the electrode and the preform on one side of the preform surface accounts for 1% of the area of ​​the preform surface on one side, and the surface flatness of the electrode is less than 0.3 mm. Figure 2 The electric pulse treatment is performed on various locations on the surface of the preform in the order shown. The specific electric pulse parameters are shown in Table 1.

[0054] Figure 3Shown are transmission electron microscope photos of the TaC grain boundaries before and after the electric pulse treatment in Example 1-1, where (a) is before treatment and (b) is after treatment. It can be seen from the figure that the dislocation density at the TaC grain boundaries is significantly reduced after the electric pulse treatment.

[0055] The residual stress of the composite material was tested by X-ray diffraction method, and the results are shown in Table 1.

[0056] Example 2 group The operation was carried out according to the method described in Example 1, except that the pulse waveform of the electric pulse treatment was different. The residual stress results are shown in Table 1.

[0057] Example 2-1: The pulse waveform of the electric pulse treatment is a triangular wave.

[0058] Example 2-2: The pulse waveform of the electric pulse treatment is a sine wave.

[0059] Example 3 group The method described in Example 1 was followed, except that the deposition time of the TaC coating was controlled to achieve different thicknesses of the TaC coating. The residual stress results are shown in Table 1.

[0060] Example 3-1: The thickness of the TaC coating is 10 μm.

[0061] Example 3-2: The thickness of the TaC coating is 50 μm.

[0062] Example 3-3: The thickness of the TaC coating is 300 μm.

[0063] Example 3-4: The thickness of the TaC coating is 500 μm.

[0064] Comparative Example 1 The method described in Example 1 was followed, except that the preform was not subjected to electric pulse treatment. The residual stress results are shown in Table 1.

[0065] Comparative Example 2 The method described in Example 1 was followed, except that the preform was subjected to heat treatment instead of electric pulse treatment. The heat treatment conditions included a temperature of 1200° C., a pressure of 100 kPa, and a time of 100 min. The residual stress results are shown in Table 1.

[0066] Comparative Example 3 The operation was carried out according to the method described in Example 1, except that the number of electric pulse treatments was 1. The residual stress results are shown in Table 1.

[0067] Comparative Example 4 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. The residual stress results are shown in Table 1.

[0068] Table 1 Note: * indicates the same as Example 1.

[0069] From the above data, it can be seen that depositing TaC coating on the surface of graphite substrate through electric pulse treatment can significantly reduce the residual stress between graphite substrate and TaC coating, and the effect is equivalent to or even better than heat treatment.

[0070] By controlling the surface flatness of the TaC coating to below 0.3 mm, the number of electric pulse treatments to more than 2 times, and the appropriate equivalent current density, the dislocation density at the TaC grain boundary can be significantly reduced, further reducing the residual stress and improving the stability of the phase boundary. This is beneficial to enhancing the high-temperature mechanical stability and chemical stability of the material, and further improving the service life of the material.

[0071] By further controlling the processing time, duty cycle and other conditions within the preferred range, the residual stress can be further reduced.

[0072] The data from Example 3 show that residual stress increases with increasing TaC coating thickness under the same treatment conditions. Therefore, the thickness of the TaC coating is best controlled within a preferred range. If product requirements require a thicker TaC coating, residual stress can be further reduced by increasing the equivalent current density or the number of treatments.

[0073] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be noted that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a TaC / graphite composite material, characterized in that: The method comprises the following steps: (1) depositing a TaC coating on the surface of a graphite substrate to obtain a preform; (2) electrically connecting an electric pulse device to two surfaces of the preform opposite to each other in the thickness direction through a non-metallic electrode assembly, and performing an electric pulse treatment to obtain a TaC / graphite composite material; The surface flatness of the TaC coating is less than 0.3 mm, and the conditions of the electric pulse treatment include: equivalent current density , unit is A·mm -2 , where D is the duty cycle and S is the contact area between the electrode and the preform on one side of the preform surface, in mm 2 , T is the coating thickness in μm; k is 0.4~20A·mm -5 , the number of electric pulse treatments is more than 2 times.

2. The preparation method according to claim 1, characterized in that Duty cycle D is 0.05-0.5; and / or The contact area S between the electrode and the preform on one side of the preform surface is 100~600mm 2 and / or The thickness T of the TaC coating is 50-300 μm.

3. The preparation method according to claim 1 or 2, characterized in that The equivalent current density is 10~50A·mm -2 .

4. The preparation method according to any one of claims 1 to 3, characterized in that The conditions of the electric pulse treatment also include: a frequency of 10 Hz to 200 Hz, a time of a single electric pulse treatment of 0.1 s to 3 s, and a number of electric pulse treatments of 2 to 10 times.

5. The preparation method according to any one of claims 1 to 4, characterized in that The surface flatness of the electrode is 0.3 mm or less.

6. The preparation method according to any one of claims 1 to 5, characterized in that The pulse waveform of the electrical 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.

7. The preparation method according to any one of claims 1 to 6, characterized in that The TaC coating is deposited by CVD deposition; Preferably, the deposition conditions include: temperature of 1100° C.-1600° C., pressure of 5-20 kPa, and time of 5-60 h.

8. The preparation method according to claim 7, characterized in that The deposition conditions include: temperature of 1200° C.-1500° C., pressure of 8-15 kPa, and time of 10-30 hours.

9. The preparation method according to claim 8, characterized in that The gas system of the CVD deposition includes a tantalum source, a carbon source, a reducing gas and a diluent gas; Preferably, the molar ratio of the tantalum element in the tantalum source, the carbon element in the carbon source, the reducing gas and the diluent gas is 1:1-3:4-8:2-4.

10. The TaC / graphite composite material prepared by the preparation method according to any one of claims 1 to 9.

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