A hollow SiC needle and its preparation method

Abstract

The present invention relates to the field of semiconductor technology, and in particular to a method for preparing a hollow SiC needle and a hollow SiC needle prepared by the method. The method comprises the following steps: (1) depositing a SiC coating on a graphite substrate; (2) placing the product obtained in step (1) in a heating device; (3) evacuating the heating device to 10Pa-100Pa, heating the temperature to 600℃-900℃ at a heating rate of 3℃ / min-20℃ / min, and keeping the temperature for 10min-60min; (4) at the temperature of step (3), continuously introducing a first atmosphere into the heating device at a rate of 100mL / min-500mL / min, controlling the pressure to 5000Pa-20000Pa, and the time to 10min-90min, wherein the first atmosphere comprises at least one of air and oxygen; (5) repeating steps (3) and (4) 30-50 times. The method of the present invention has a simple flow and is easy to realize large-scale production. The hollow SiC needles prepared by the method of the invention have less graphite residue, long service life and high yield.

Description

Technical Field

[0001] The invention relates to the field of semiconductors, and in particular to a method for preparing a hollow SiC needle and the hollow SiC needle prepared by the method. Background Art

[0002] Epitaxy, referred to as EPI, is the process of using chemical vapor deposition to deposit a new single crystal layer that meets the requirements of conductivity type, resistivity, thickness and lattice structure integrity on a single crystal substrate along its original crystal axis. The new single crystal layer is called an epitaxial layer, and a silicon wafer with an epitaxial layer is called a silicon epitaxial wafer.

[0003] During the epitaxial PM (equipment maintenance and care) process, the top of the SiC needle with a hollow structure lifts up the epitaxial wafer to complete the PM. Therefore, the hollow SiC needle is one of the key consumables of integrated circuit silicon epitaxial equipment. However, due to the small size, complex structure and small inner hole of the hollow SiC needle, its production process is complicated, the production is difficult and the yield is low. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of complicated production process, great production difficulty and low yield of hollow SiC needles in the prior art, and to provide a method for preparing hollow SiC needles and hollow SiC needles prepared by the method. The method of the present invention has a simple process and is easy to achieve large-scale production. The hollow SiC needles prepared by the method of the present invention have less graphite residue, long service life and high yield.

[0005] A first aspect of the present invention provides a method for preparing a hollow SiC needle, the method comprising the following steps:

[0006] (1) Depositing SiC coating on graphite substrate;

[0007] (2) placing the product obtained in step (1) in a heating device;

[0008] (3) evacuating the heating device to 10Pa-100Pa, heating the temperature to 600°C-900°C at a heating rate of 3°C / min-20°C / min, and keeping the temperature for 10min-60min;

[0009] (4) at the temperature of step (3), continuously introducing a first atmosphere into the heating device at a rate of 100 mL / min-500 mL / min, controlling the pressure to be 5000 Pa-20000 Pa, for a time of 10 min-90 min, wherein the first atmosphere comprises at least one of air and oxygen;

[0010] (5) Repeat steps (3) and (4) 30 to 50 times.

[0011] The second aspect of the present invention provides a hollow SiC needle prepared by the method described in the first aspect of the present invention.

[0012] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0013] (1) The method of the present invention is simple and easy to implement and can be easily mass-produced;

[0014] (2) The hollow SiC needles prepared by the method of the present invention have less graphite residue, long service life and high yield.

[0015] The endpoints and any values ​​of the ranges disclosed in this article 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. DETAILED DESCRIPTION

[0016] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0017] As one of the commonly used basic materials in the manufacturing process of semiconductor devices, the purity of silicon wafers will directly affect the electrical performance, stability and service life of semiconductor devices. However, in the related art, there is usually the problem of impure graphite in silicon wafers, which requires additional processes to remove the impure graphite in silicon wafers. After a lot of research, it was found that the reason for the problem of impure graphite in silicon wafers may be that there is graphite residue in the hollow SiC needles used in the epitaxial PM process, which causes the residual graphite in the hollow SiC needles to diffuse onto the silicon wafer, thereby affecting the purity of the silicon wafer. Based on this, the present invention provides a method for preparing a hollow SiC needle, which can efficiently remove graphite in the hollow SiC needle and improve the service life and yield.

[0018] A first aspect of the present invention provides a method for preparing a hollow SiC needle, the method may include the following steps:

[0019] (1) Depositing SiC coating on graphite substrate;

[0020] (2) placing the product obtained in step (1) in a heating device;

[0021] (3) evacuating the heating device to 10Pa-100Pa (for example, 10Pa, 20Pa, 30Pa, 40Pa, 50Pa, 60Pa, 70Pa, 80Pa, 90Pa or 100Pa), heating the device to a temperature of 600°C-900°C (for example, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C) at a heating rate of 3°C / min-20°C / min (for example, 3°C / min, 5°C / min, 10°C / min, 15°C / min or 20°C / min), and keeping the temperature for 10min-60min (for example, 10min, 20min, 30min, 40min, 50min or 60min);

[0022] (4) at the temperature of step (3), continuously introducing a first atmosphere into the heating device at a rate of 100 mL / min-500 mL / min (e.g., 100 mL / min, 200 mL / min, 300 mL / min, 400 mL / min, or 500 mL / min), controlling the pressure to be 5000 Pa-20000 Pa (e.g., 5000 Pa, 10000 Pa, 15000 Pa, or 20000 Pa), for a time of 10 min-90 min (e.g., 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, or 90 min), wherein the first atmosphere comprises at least one of air and oxygen;

[0023] (5) Repeat steps (3) and (4) 30 to 50 times (e.g., 30 times, 35 times, 40 times, 45 times, or 50 times).

[0024] When the heating device is evacuated to 10Pa-50Pa in step (3), the removal efficiency of the graphite substrate can be further improved. In one embodiment, in step (3), the heating device is evacuated to 10Pa-50Pa.

[0025] The heating temperature in step (3) has a significant effect on the removal efficiency of the graphite matrix; when the heating temperature is low (for example, less than 600°C), it will affect the removal rate of the graphite matrix; when the heating temperature is high (for example, greater than 900°C), it will cause the graphite matrix to oxidize too quickly, and produce too much CO2 in a short time, causing blockage, thereby reducing the removal rate of the graphite matrix.

[0026] In one embodiment, in step (3), the temperature is raised to 750°C-850°C.

[0027] In the present invention, the heating device may be a heating device conventionally used in the art, such as a high-temperature vacuum resistance furnace.

[0028] In the present invention, in step (4), the speed of continuously introducing the first atmosphere into the heating device is v (in mL / min), the time is t (in min), and the number of times of repeating steps (3) and (4) in step (5) is n (in times); v, t and n satisfy: 50≤v×t / n≤1000, for example, v×t / n is equal to 50, 60, 70, 80, 90, 100, 200, 300, 400, 1500, 600, 700, 800, 900 or 1000.

[0029] In one example, v, t, and n satisfy: 75≤v×t / n≤800.

[0030] In one example, v, t, and n satisfy: 200≤v×t / n≤533.3.

[0031] Research has shown that when v, t and n satisfy a specific relationship, the removal efficiency of the graphite matrix can be further improved.

[0032] In one example, in step (4), the first atmosphere is continuously introduced into the heating device at a rate of 200 mL / min-400 mL / min.

[0033] In one embodiment, in step (4), the time is 30 min-60 min.

[0034] In one embodiment, in step (5), steps (3) and (4) are repeated 30 to 45 times.

[0035] In one example, the first atmosphere is at least one of air and oxygen.

[0036] In one example, the first atmosphere is air.

[0037] In the present invention, the graphite matrix may include at least one of isostatic graphite, compressed graphite and high-purity graphite.

[0038] In one example, the graphite matrix includes isostatic graphite.

[0039] In one example, the graphite substrate is isostatic graphite.

[0040] In the present invention, the thermal expansion coefficient of the graphite matrix can be 3.9×e -6 -5.4×e -6 (unit is 1 / K), for example, 3.9×e -6 , 4×e -6 , 4.1×e -6 , 4.2×e -6 , 4.3×e -6 , 4.4×e-6 , 4.5×e -6 , 4.6×e -6 , 4.7×e -6 , 4.8×e -6 , 4.9×e -6 , 5×e -6 , 5.1×e -6 , 5.2×e -6 , 5.3×e -6 or 5.4×e -6 , where e is a natural constant.

[0041] In one example, the thermal expansion coefficient of the graphite substrate is 4.2×e -6 -4.8×e -6 (Unit is 1 / K).

[0042] After research, it was found that when the thermal expansion coefficient of the graphite substrate is within a specific range, it affects the deposition of the SiC coating on the graphite substrate, thereby affecting the service life of the hollow SiC needle.

[0043] In the present invention, the porosity of the graphite matrix may be 10%-15%, for example, 10%, 11%, 12%, 13%, 14% or 15%.

[0044] In one example, the porosity of the graphite matrix is ​​10%-13.5%.

[0045] Research has shown that when the porosity of the graphite matrix is ​​within a specific range, the removal efficiency of the graphite matrix can be further improved.

[0046] In the present invention, a drawing can be designed according to the size of the hollow area of ​​the hollow SiC needle, and a graphite matrix can be prepared using a lathe according to the drawing.

[0047] In the present invention, the deposition can be performed in a deposition device commonly used in the art, such as a CVD deposition furnace.

[0048] In the present invention, the deposition conditions may include:

[0049] (A1) placing the graphite substrate in a deposition device, evacuating to 50Pa-300Pa (for example, 50Pa, 100Pa, 150Pa, 200Pa, 250Pa or 300Pa), heating to 850°C-1150°C (for example, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C or 1150°C) at a heating rate of 2°C / min-12°C / min (for example, 2°C / min, 5°C / min, 10°C / min or 12°C / min), and keeping the temperature for 10min-60min (for example, 10min, 20min, 30min, 40min, 50min or 60min);

[0050] (A2) continuously introducing argon at a rate of 40 L / min-70 L / min (e.g., 40 L / min, 50 L / min, 60 L / min, or 70 L / min) and continuously introducing hydrogen at a rate of 60 L / min-110 L / min (e.g., 60 L / min, 70 L / min, 80 L / min, 90 L / min, 100 L / min, or 110 L / min), heating at a heating rate of 3° C. / min-10° C. / min (e.g., 3° ​​C. / min, 5° C. / min, or 10° C. / min) to a temperature of 1150° C.-1500° C. (e.g., 1150° C., 1200° C., 1300° C., 1400° C., or 1500° C.), and maintaining the temperature for 40 min-90 min (e.g., 40 min, 50 min, 60 min, 70 min, 80 min, or 90 min);

[0051] (A3) at the temperature of step (A2), adjusting the pressure to 5000Pa-30000Pa (e.g., 5000Pa, 10000Pa, 15000Pa, 20000Pa, 25000Pa or 30000Pa), continuously introducing SiCl4 at a rate of 40L / min-90L / min (e.g., 40L / min, 50L / min, 60L / min, 70L / min, 80L / min or 90L / min) and continuously introducing CH4 at a rate of 40L / min-90L / min (e.g., 40L / min, 50L / min, 60L / min, 70L / min, 80L / min or 90L / min), and reacting for 4000min-6000min (e.g., 4000min, 4500min, 5000min, 5500min or 6500min). 0min or 6000min); introducing argon and hydrogen for 30min-70min (for example, 30min, 40min, 50min, 60min or 70min); evacuating the deposition equipment to 50Pa-300Pa (for example, 50Pa, 100Pa, 150Pa, 200Pa, 250Pa or 300Pa), and cooling the temperature to 15℃-30℃ (for example, 15℃, 20℃, 25℃ or 30℃) at a cooling rate of 5℃ / min-15℃ / min (for example, 5℃ / min, 10℃ / min or 15℃ / min); introducing argon to normal pressure at a speed of 40L / min-100L / min (for example, 40L / min, 50L / min, 60L / min, 70L / min, 80L / min, 90L / min or 100L / min).

[0052] In one embodiment, in step (A3), the pressure is adjusted to 5000Pa-25000Pa.

[0053] In one embodiment, in step (A2), the temperature is increased to 1200°C-1400°C.

[0054] In the present invention, the deposition conditions may further include, after placing the graphite substrate in a deposition device, closing the deposition device.

[0055] In the present invention, the pressure can be adjusted by introducing at least one of argon and hydrogen. The time for introducing argon and hydrogen can be 30 min-70 min (for example, 30 min, 40 min, 50 min, 60 min or 70 min).

[0056] In the present invention, the deposition conditions may further include, in step (A3), stopping the introduction of SiCl4 and CH4 after the reaction lasts for 4000 min to 6000 min.

[0057] In the present invention, the deposition conditions may further include, in step (A3), after introducing argon gas at a rate of 40 L / min-100 L / min to normal pressure, opening the deposition equipment and taking out the product.

[0058] In the present invention, the method may further include: in step (1), after depositing the SiC coating, grinding is performed. The grinding conditions may include a rotation speed of the guide wheel of 500 r / min-1500 r / min, and a grinding speed of the grinding wheel of 2500 r / min-3500 r / min.

[0059] In the present invention, the method may further include, before step (2), removing part of the graphite matrix by mechanical means, which can further improve the removal efficiency of the graphite matrix.

[0060] The method of the present invention adopts the pulsed gas introduction and vacuuming mode, which can significantly improve the removal efficiency of the graphite matrix and improve the yield rate of the hollow SiC needle.

[0061] The second aspect of the present invention provides a hollow SiC needle prepared by the method described in the first aspect of the present invention.

[0062] The present invention will be described in detail below by way of examples. The examples described in the present invention are only a part of the examples of the present invention, rather than all of the examples. Based on the examples in the present invention, all other examples obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0063] In the following examples, unless otherwise specified, all materials used were commercially available analytical grade.

[0064] The following examples are used to prepare hollow SiC needles.

[0065] Example 1

[0066] Proceed as follows:

[0067] (1) In the graphite matrix (isostatic graphite, thermal expansion coefficient is 4.5×e -6 1 / K, porosity 11%):

[0068] (A1) placing isostatically pressed graphite in a CVD deposition furnace, closing the furnace, evacuating to 200 Pa, heating to 1000° C. at a heating rate of 8° C. / min, and keeping the temperature for 40 min;

[0069] (A2) Argon gas was continuously introduced at a rate of 55 L / min and hydrogen gas was continuously introduced at a rate of 80 L / min, and the temperature was increased to 1300° C. at a heating rate of 7° C. / min, and the temperature was kept at this temperature for 70 min;

[0070] (A3) At 1300°C, adjust the pressure to 15000Pa, continuously introduce SiCl4 at a rate of 60L / min and CH4 at a rate of 60L / min, and react for 5000min; introduce argon and hydrogen for 50min; evacuate the CVD deposition furnace to 200Pa, and cool it to 20°C at a cooling rate of 10°C / min; introduce argon at a rate of 70L / min to normal pressure, open the CVD deposition furnace, and take out the product.

[0071] (2) The product obtained in step (1) is ground (the rotation speed of the guide wheel is 1000 r / min, and the grinding speed of the grinding wheel is 3000 r / min).

[0072] (3) placing the product obtained in step (2) in a vacuum resistance furnace.

[0073] (4) Evacuate the vacuum resistance furnace to 30 Pa, heat it to 800 °C at a heating rate of 12 °C / min, and keep it at that temperature for 30 min.

[0074] (5) At 800°C, air was continuously introduced into the vacuum resistance furnace at a rate of 300 mL / min (v), the pressure was controlled to be 15000 Pa, and the time was 45 min (t).

[0075] (6) Repeat steps (4) and (5) 40 times (n), where v×t / n is 337.5.

[0076] Example 2

[0077] Proceed as follows:

[0078] (1) In the graphite matrix (isostatic graphite, thermal expansion coefficient is 4.2×e -6 1 / K, porosity 10%):

[0079] (A1) placing isostatically pressed graphite in a CVD deposition furnace, closing the furnace, evacuating to 50 Pa, heating to 850° C. at a heating rate of 2° C. / min, and keeping the temperature for 10 min;

[0080] (A2) Argon gas was continuously introduced at a rate of 40 L / min and hydrogen gas was continuously introduced at a rate of 60 L / min, and the temperature was increased to 1250° C. at a heating rate of 3° C. / min, and the temperature was kept at this temperature for 40 min;

[0081] (A3) At 1250°C, adjust the pressure to 5000Pa, continuously introduce SiCl4 at a rate of 40L / min and CH4 at a rate of 40L / min, and react for 4000min; introduce argon and hydrogen for 30min; evacuate the CVD deposition furnace to 50Pa, and cool it to 15°C at a cooling rate of 5°C / min; introduce argon at a rate of 40L / min to normal pressure, open the CVD deposition furnace, and take out the product.

[0082] (2) The product obtained in step (1) is ground (the rotation speed of the guide wheel is 500 r / min, and the grinding speed of the grinding wheel is 2500 r / min).

[0083] (3) placing the product obtained in step (2) in a vacuum resistance furnace.

[0084] (4) Evacuate the vacuum resistance furnace to 10 Pa, heat it to 750°C at a heating rate of 3°C / min, and keep it at that temperature for 10 min.

[0085] (5) At 750°C, air was continuously introduced into the vacuum resistance furnace at a rate of 200 mL / min (v), the pressure was controlled to be 5000 Pa, and the time was 30 min (t).

[0086] (6) Repeat steps (4) and (5) 30 times (n), where v×t / n is 200.

[0087] Example 3

[0088] Proceed as follows:

[0089] (1) In the graphite matrix (isostatic graphite, thermal expansion coefficient is 4.8×e -6 1 / K, porosity 13.5%):

[0090] (A1) placing isostatically pressed graphite in a CVD deposition furnace, closing the furnace, evacuating to 300 Pa, heating to 1150° C. at a heating rate of 12° C. / min, and keeping the temperature for 60 min;

[0091] (A2) Argon gas was continuously introduced at a rate of 70 L / min and hydrogen gas was continuously introduced at a rate of 110 L / min, the temperature was increased to 1400° C. at a heating rate of 10° C. / min, and the temperature was kept at this temperature for 90 min;

[0092] (A3) At 1400°C, adjust the pressure to 25000Pa, continuously introduce SiCl4 at a rate of 90L / min and CH4 at a rate of 90L / min, and react for 6000min; introduce argon and hydrogen for 70min; evacuate the CVD deposition furnace to 300Pa, and cool it to 30°C at a cooling rate of 15°C / min; introduce argon at a rate of 100L / min to normal pressure, open the CVD deposition furnace, and take out the product.

[0093] (2) The product obtained in step (1) is ground (the rotation speed of the guide wheel is 1500 r / min, and the grinding speed of the grinding wheel is 3500 r / min).

[0094] (3) placing the product obtained in step (2) in a vacuum resistance furnace.

[0095] (4) Evacuate the vacuum resistance furnace to 50 Pa, heat it to 850°C at a heating rate of 20°C / min, and keep it at that temperature for 60 min.

[0096] (5) At 850°C, air was continuously introduced into the vacuum resistance furnace at a rate of 400 mL / min (v), the pressure was controlled to be 20,000 Pa, and the time was 60 min (t).

[0097] (6) Repeat steps (4) and (5) 45 times (n), where v×t / n is 533.3.

[0098] Example 4

[0099] This group of examples is used to verify the effects of changes in the graphite matrix.

[0100] This group of examples is carried out with reference to Example 1, except that the graphite substrate is changed, specifically:

[0101] Example 4a, isostatic graphite is replaced by compressed graphite (thermal expansion coefficient is 4.5×e -6 1 / K, porosity 11%);

[0102] Example 4b, the isostatic graphite is replaced by high purity graphite (thermal expansion coefficient is 4.5×e -6 1 / K, porosity is 11%).

[0103] Example 5

[0104] This group of examples is used to verify the impact of changes in the thermal expansion coefficient of the graphite substrate.

[0105] This group of examples is carried out with reference to Example 1, except that the thermal expansion coefficient of the graphite matrix is ​​changed, specifically:

[0106] Example 5a, replacing isostatic graphite with a thermal expansion coefficient of 3.9×e -6 1 / K isostatic graphite;

[0107] Example 5b, the isostatic graphite is replaced by a graphite having a thermal expansion coefficient of 5.4×e -6 1 / K isostatic graphite.

[0108] Example 6

[0109] This group of examples is used to verify the effect of changing the porosity of the graphite matrix.

[0110] This group of examples is carried out with reference to Example 1, except that the porosity of the graphite matrix is ​​changed, specifically:

[0111] Example 6a, replacing the isostatic graphite with isostatic graphite having a porosity of 14%;

[0112] In Example 6b, the isostatic graphite is replaced by isostatic graphite having a porosity of 15%.

[0113] Example 7

[0114] This group of examples is used to verify the effect of the change in pressure in step (4).

[0115] This group of examples is carried out with reference to Example 1, except that the pressure value in step (4) is changed, specifically:

[0116] Example 7a, evacuate the vacuum resistance furnace to 80 Pa;

[0117] Example 7b: evacuate the vacuum resistance furnace to 100 Pa.

[0118] Example 8

[0119] This group of examples is used to verify the effect of the change in temperature in step (4).

[0120] This group of examples is carried out with reference to Example 1, except that the temperature in step (4) is changed, specifically:

[0121] Example 8a, heating to 600°C;

[0122] Example 8b, the temperature is raised to 900°C.

[0123] Example 9

[0124] This group of examples is used to verify the effect of changing the air introduction rate in step (5).

[0125] This group of examples is carried out with reference to Example 1, except that the air introduction speed in step (5) is changed, specifically:

[0126] Example 9a, air is continuously introduced into the vacuum resistance furnace at a rate of 100 mL / min, wherein v×t / n is 112.5;

[0127] Example 9b, air is continuously introduced into the vacuum resistance furnace at a rate of 500 mL / min, wherein v×t / n is 562.5.

[0128] Example 10

[0129] This group of embodiments is used to verify the impact of the change in time in step (5).

[0130] This group of examples is carried out with reference to Example 1, except that the time in step (5) is changed, specifically:

[0131] Example 10a, time is 10 min, wherein v×t / n is 75;

[0132] Example 10b, the time is 90 min, wherein v×t / n is 675.

[0133] Embodiment 11

[0134] This group of embodiments is used to verify the impact of changes in the relationship between v, t and n.

[0135] This group of examples is carried out with reference to Example 1, except that v, t and n are changed, specifically:

[0136] Example 11a, v is 200 mL / min, t is 30 min, n is 45 times, wherein v×t / n is 133.3;

[0137] Example 11b, v is 400 mL / min, t is 60 min, n is 30 times, wherein v×t / n is 800.

[0138] Example 12

[0139] The method is carried out in accordance with Example 1, except that after the grinding process in step (2), part of the graphite matrix is ​​removed mechanically. Specifically:

[0140] (2) Grinding the product obtained in step (1) (the rotation speed of the guide wheel is 1000 r / min, and the grinding speed of the grinding wheel is 3000 r / min), and mechanically removing the graphite matrix until the graphite matrix at the bottom of the SiC hollow needle leaks out without affecting the appearance of the SiC hollow needle.

[0141] (4) Evacuate the vacuum resistance furnace to 30 Pa, heat it to 800 °C at a heating rate of 12 °C / min, and keep it at that temperature for 30 min.

[0142] (5) At 800°C, air was continuously introduced into the vacuum resistance furnace at a rate of 300 mL / min, the pressure was controlled at 15000 Pa, and the time was 45 min.

[0143] (6) Repeat steps (4) and (5) 40 times.

[0144] Comparative Example 1

[0145] The process is carried out in accordance with Example 1, except that after step (2), the product obtained by step (2) is placed in a heating container, the heating container is evacuated, the temperature is increased to 1200°C at a heating rate of 10°C / min, oxygen is introduced into the heating container, the temperature is maintained for 2 hours, and the temperature is naturally lowered after the end of the insulation.

[0146] Test Case

[0147] (1) Graphite residue

[0148] The hollow SiC needles prepared in the examples and comparative examples were subjected to a graphite residue test, and the specific test method is as follows:

[0149] The prepared sample was ground into powder, and its diffraction peak was tested by XRD. The test report was observed to see whether it contained the diffraction peak of graphite. The graphite residue was obtained by calculation and the results were recorded in Table 1.

[0150] (2) Thermal shock test

[0151] The hollow SiC needles prepared in the examples and comparative examples were subjected to thermal shock tests. The specific test method is as follows:

[0152] The sample was placed in a muffle furnace for a temperature test, heated to 800°C, kept warm for 15 minutes, then taken out and quickly placed in 20°C-25°C water for rapid cooling. The above operation was repeated, and the number of times cracks first appeared on the coating surface was recorded. The average value of three samples was taken for each data, and the results were recorded in Table 1.

[0153] (3) Yield test

[0154] The hollow SiC needles prepared in the embodiment and the comparative example were subjected to yield test, and the specific test method is as follows:

[0155] Use x-ray to perform nondestructive testing on the hollow SiC needle to check whether the hollow needle has cracks, gaps and impurities, and record the three types of test results. The results are recorded in Table 1.

[0156] Table 1

[0157]

[0158]

[0159] It can be seen from Table 1 that the hollow SiC needles prepared by the method for preparing hollow SiC needles of the present invention significantly reduce graphite residues and improve thermal shock resistance and yield compared with the comparative example.

[0160] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a hollow SiC needle, characterized in that: The method comprises the following steps: (1) Depositing SiC coating on graphite substrate; (2) placing the product obtained in step (1) in a heating device; (3) evacuating the heating device to 10Pa-100Pa, heating the temperature to 600°C-900°C at a heating rate of 3°C / min-20°C / min, and keeping the temperature for 10min-60min; (4) at the temperature of step (3), continuously introducing a first atmosphere into the heating device at a rate of 100 mL / min-500 mL / min, controlling the pressure to be 5000 Pa-20000 Pa, for a time of 10 min-90 min, wherein the first atmosphere comprises at least one of air and oxygen; (5) Repeat steps (3) and (4) 30 to 50 times; In step (4), the speed of continuously introducing the first atmosphere into the heating device is v, in units of mL / min, the time is t, in units of min, and the number of times steps (3) and (4) are repeated in step (5) is n, in units of times; v, t and n satisfy: 200≤v×t / n≤550.

2. The method according to claim 1, characterized in that In step (3), evacuate to 10Pa-50Pa; And / or, in step (3), the temperature is raised to 750°C-850°C.

3. The method according to claim 1 or 2, characterized in that: In step (4), the first atmosphere is continuously introduced into the heating device at a rate of 200 mL / min to 400 mL / min; And / or, in step (4), the time is 30 min-60 min; And / or, in step (5), steps (3) and (4) are repeated 30 to 45 times.

4. The method according to claim 1 or 2, characterized in that: The graphite matrix includes at least one of isostatic graphite, compressed graphite and high-purity graphite; And / or, the thermal expansion coefficient of the graphite matrix is ​​3.9×e -6 1 / K-5.4×e -6 1 / K; And / or, the porosity of the graphite matrix is ​​10%-15%.

5. The method according to claim 4, characterized in that The graphite matrix includes isostatic graphite; And / or, the thermal expansion coefficient of the graphite matrix is ​​4.2×e -6 1 / K-4.8×e -6 1 / K; And / or, the porosity of the graphite matrix is ​​10%-13.5%.

6. The method according to claim 1 or 2, characterized in that: The deposition conditions include: (A1) placing the graphite substrate in a deposition device, evacuating the temperature to 50 Pa-300 Pa, heating the temperature to 850° C.-1150° C. at a heating rate of 2° C. / min-12° C. / min, and keeping the temperature for 10 min-60 min; (A2) continuously introducing argon at a rate of 40 L / min-70 L / min and hydrogen at a rate of 60 L / min-110 L / min, heating at a heating rate of 3° C. / min-10° C. / min to a temperature of 1150° C.-1500° C., and maintaining the temperature for 40 min-90 min; (A3) At the temperature of step (A2), adjust the pressure to 5000Pa-30000Pa, continuously introduce SiCl4 at a rate of 40L / min-90L / min and continuously introduce CH4 at a rate of 40L / min-90L / min, and react for 4000min-6000min; introduce argon and hydrogen for 30min-70min; evacuate the deposition equipment to 50Pa-300Pa, and reduce the temperature to 15℃-30℃ at a cooling rate of 5℃ / min-15℃ / min; introduce argon at a rate of 40L / min-100L / min to normal pressure.

7. The method according to claim 1 or 2, characterized in that: The method further comprises: before step (2), removing part of the graphite matrix by mechanical means.

8. A hollow SiC needle prepared by the method according to any one of claims 1 to 7.

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