Graphite material with surface coated with silicon carbide coating and preparation method of graphite material

Abstract

The invention provides a graphite material coated with a silicon carbide coating on the surface and a preparation method of the graphite material. The graphite material coated with the silicon carbide coating on the surface is prepared through graphite surface laser treatment, high-temperature chemical purification and single-component chemical vapor reaction deposition methods. The drawing strength of the silicon carbide coating on the surface of the graphite material is 6 MPa or above, the impurity content is 2 ppm or below, and the thickness difference of the silicon carbide coating is within + / -5%. The preparation method is high in production efficiency, low in energy consumption, small in pollution and simple and rapid in preparation process, and the finally formed silicon carbide coating is uniform in thickness, high in strength, high in purity, resistant to oxidation, resistant to high-temperature scouring and the like.

Description

Technical Field

[0001] The invention relates to the technical field of graphite materials with silicon carbide coatings on their surfaces, and in particular to a graphite material with silicon carbide coatings on its surfaces and a preparation method thereof. Background Art

[0002] In the semiconductor crystal growth thermal field, especially in the process of silicon carbide epitaxial growth, high-purity graphite materials are required as trays and process chambers for heating and support at the same time, and the temperature can even reach 1300 ℃. In such a high-temperature environment for the epitaxial growth of silicon carbide, the graphite thermal field material needs to meet the following requirements: (1) The graphite thermal field material needs to have a high purity to prevent impurity elements from contaminating the crystal; (2) The exposed graphite material can easily react with silicon at high temperature to generate silicon carbide, so the graphite material needs to have a high resistance to silicon gas erosion and corrosion; (3) When the silicon carbide epitaxial wafer is taken out at 800 ℃, the graphite will oxidize when it contacts the outside air, so the graphite thermal field material needs to have a high anti-oxidation performance; (4) The graphite material is easy to shed powder, which will contaminate the semiconductor epitaxial product, so the graphite surface needs to be protected. In summary, it can be found that graphite thermal field materials need to achieve high purity (<5 ppm), erosion and corrosion resistance, high temperature resistance and oxidation resistance, and no powder falling on the surface to meet the harsh conditions of silicon carbide epitaxial growth.

[0003] At present, the above problems are mainly solved by coating silicon carbide on the surface. However, high-purity graphite materials for the semiconductor industry are mainly monopolized by German companies such as SGL, and the preparation of high-purity graphite and silicon carbide anti-oxidation coatings is mainly monopolized by foreign companies. It is urgent to break the foreign monopoly. The main problem now is that the preparation of silicon carbide coated products has problems such as immature process technology, uneven product thickness, low product purity, high price, and long preparation cycle. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing material preparation method and provide a method for preparing a graphite material with a surface coated with a silicon carbide coating, which has high production efficiency, low energy consumption, low pollution, and a simple and fast preparation process.

[0005] Another object of the present invention is to provide a graphite material with a silicon carbide coating on the surface, which is high in purity, resistant to erosion and corrosion, resistant to high temperature and oxidation, and does not fall off the surface.

[0006] Specific technical solutions: A graphite material with a silicon carbide coating on its surface, wherein the silicon carbide coating on the surface of the graphite material has a pulling strength of more than 6 MPa and an impurity content of less than 2 ppm.

[0007] The thickness difference of the silicon carbide coating on the surface of the graphite material is within ±5%.

[0008] A method for preparing a graphite material with a surface coated with a silicon carbide coating, the specific preparation process is: after the graphite material is subjected to laser surface treatment, it is then subjected to high-temperature chemical purification using polytetrafluoroethylene, and then the graphite material with a surface coated with a silicon carbide coating is prepared by chemical vapor deposition; wherein, during the chemical vapor deposition process, the silicon carbide coating material is uniformly deposited on the surface of the graphite material by using a horizontal lateral air intake method.

[0009] The horizontal side air intake method is specifically as follows: the deposition furnace used is a horizontal furnace, and evenly distributed air intakes are opened on the side. The deposition gas enters from one side and flows out from the other side. The flow direction of the deposition gas is parallel to the surface of the graphite material and is in a horizontal direction. During the deposition process, the graphite material circulates and rotates.

[0010] The graphite material is cyclically rotated using a rotating fixture.

[0011] The rotation speed of the rotating fixture is 1 rpm to 10 rpm.

[0012] In the high-temperature chemical purification process, polytetrafluoroethylene powder is used, which has a diameter of 5-20 microns and an amount of 10-30 times the mass of impurities in the graphite piece. The rate of conveying polytetrafluoroethylene powder is 10 g / min-30 g / min, and the chemical purification temperature is 2000-2500 °C.

[0013] In the chemical vapor deposition process, the silicon carbide precursor used is methyltrichlorosilane, the feed rate is 2-10 kg / h, the carrier gas and the reaction gas are high-purity hydrogen, the intake flow rate is 5-50 L / min, the dilution gas is high-purity argon, the intake flow rate is 3-30 L / min, and the chemical vapor deposition temperature is 1000-1400 °C.

[0014] During the laser surface treatment process, the laser scanning speed is 1-30 mm / s, the laser pulse width is 1-350 ns, the laser power is 50-500 W, the laser frequency is 1-2000 kHz, the distance between the laser head and the device surface is 10-30 cm, and the treatment speed is 100-500 cm 2 / min.

[0015] The invention also relates to a graphite material with a surface coated with a silicon carbide coating and prepared by the preparation method.

[0016] The present invention uses a combination of graphite surface laser treatment, high-temperature chemical purification and chemical vapor reaction deposition, which can not only make the surface treatment fast, pollution-free and high in bonding strength, but also have high purification efficiency and good purification effect, and can obtain high-purity graphite materials with a purity of less than 2 ppm. The special chemical deposition method can ultimately obtain a silicon carbide coating with uniform thickness and high purity, so that the pulling strength between the silicon carbide coating and the graphite substrate reaches more than 6 MPa.

[0017] There is no dust pollution in the whole process, and no pickling, grinding and sandblasting are required. No substances need to be added during the surface treatment process, and the whole preparation process is very environmentally friendly. The heat treatment temperature in the high-temperature chemical purification process is lower than that of the existing technology, which is more efficient and energy-saving.

[0018] The obtained graphite material with silicon carbide coating on the surface can be directly used in high-temperature furnaces protected by vacuum and inert gas, and can be used stably at temperatures of 1000-1600 °C, especially as an indispensable thermal field material in high-temperature thermal fields such as the thermal field of the third-generation semiconductor crystal growth furnace. The thickness of the final prepared coating is very uniform, with a thickness error within ±5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is an example of the preparation process of the graphite material coated with a silicon carbide coating on the surface of the present invention; Figure 2 This is an example of a graphite material with a surface coated with a silicon carbide coating prepared by the present invention; Figure 2 (a) is a front view of the silicon carbide coated graphite part prepared in Example 1, Figure 2 (b) is the reverse side view of the silicon carbide coated graphite component prepared in Example 2. Figure 2 (c) Figure 2 (d) is a microscopic morphology image of the silicon carbide coating prepared in Example 1 at different magnifications. It can be concluded that the surface of the graphite part is covered with a silicon carbide coating, and the coating is uniform.

[0020] Figure 1 Middle: 1 is the air inlet, 2 is the rotating fixture, 3 is the air outlet, and 4 is the graphite part. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below by way of examples, but the present invention is not limited to the following examples.

[0022] Example 1

[0023] The preparation method of the graphite thermal material with the surface coated with silicon carbide coating comprises the following steps: (1) Laser degreasing and roughening of graphite surface: The surface of the processed graphite parts was treated by laser degreasing. The laser scanning speed was 15 mm / s, the laser pulse width was 200 ns, the laser power was 100 W, the laser frequency was 1000 kHz, and the processing speed was 300 cm 2 / min, and the distance between the laser gun head and the sample surface was 20 cm.

[0024] (2) High-temperature chemical purification: The laser-treated graphite parts are purified in a high-temperature chemical purification furnace. The diameter of the PTFE powder is 10 μm, the amount used is 10 times the mass of the impurities in the graphite parts, the rate of conveying the PTFE powder is 10 g / min, and the chemical purification temperature is 2000 °C.

[0025] (3) Single-component chemical vapor deposition: In a chemical vapor deposition furnace, a high-purity graphite piece is punched and hung under a rotating fixture that can rotate freely. The surface of the graphite piece is parallel to the direction of the airflow, and the single-component chemical vapor deposition is carried out by the side-intake-rotating fixture method. The rotation speed of the rotating fixture is 3 rpm. The silicon carbide precursor used is methyltrichlorosilane with a purity of 99%. The feed rate is 3 kg / h, the carrier gas and the reaction gas are high-purity hydrogen with an intake flow rate of 10 L / min, the dilution gas is high-purity argon with an intake flow rate of 6 L / min, the chemical reaction deposition temperature is 1200 °C, and the deposition time is 10 h. Finally, a graphite material with a surface coated with silicon carbide is prepared.

[0026] Example 2

[0027] The method in Example 1 is followed, except that in step S2, the chemical purification temperature is 2200°C; in step S3, the feed rate is 6 kg / h, the intake flow rates of the carrier gas, the reaction gas and the dilution gas are all 12 L / min, and the chemical reaction deposition temperature is 1300°C.

[0028] Example 3

[0029] The method in Example 1 is followed, except that in step S2, the amount of polytetrafluoroethylene powder used is 30 times the mass of impurities in the graphite part, and the chemical purification temperature is 2400°C; in step S3, the feed rate is 9 kg / h, the intake flow rates of the carrier gas, the reaction gas and the dilution gas are all 18 L / min, and the chemical reaction deposition temperature is 1350°C.

[0030] Comparative Example 1

[0031] The method in Example 1 is followed, except that the graphite piece is not subjected to surface laser treatment.

[0032] Comparative Example 2

[0033] The method in Example 1 is followed, except that the graphite piece is not rotated in step S3.

[0034] Comparative Example 3

[0035] The method in Example 1 is followed, except that the air intake method in step S3 is different, and the air intake direction is perpendicular to the surface of the graphite sample.

[0036] Test Results

Claims

1. A graphite material with a silicon carbide coating on its surface, characterized in that: The pull-out strength of the silicon carbide coating on the surface of the graphite material is greater than 6 MPa, and the impurity content is less than 2 ppm.

2. The graphite material with a surface coated with a silicon carbide coating according to claim 1, characterized in that: The thickness difference of the silicon carbide coating on the surface of the graphite material is within ±5%.

3. The method for preparing a graphite material with a surface coated with a silicon carbide coating according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: subjecting a graphite material to laser surface treatment, and then using polytetrafluoroethylene for high-temperature chemical purification, and then preparing a graphite material with a surface coated with a silicon carbide coating by chemical vapor deposition; wherein, during the chemical vapor deposition process, a horizontal lateral air intake method is used to uniformly deposit the silicon carbide coating material on the surface of the graphite material.

4. The method for preparing a graphite material with a surface coated with a silicon carbide coating according to claim 3, characterized in that: The horizontal side air intake method is specifically as follows: the deposition furnace used is a horizontal furnace, and evenly distributed air intakes are opened on the side, and the deposition gas enters from one side and flows out from the other side, and the flow direction of the deposition gas is parallel to the surface of the graphite material and is in a horizontal direction; During the deposition process, the graphite material rotates in a cycle.

5. The method for preparing a graphite material with a surface coated with a silicon carbide coating according to claim 3 or 4, characterized in that: The graphite material is cyclically rotated using a rotating fixture.

6. The method for preparing a graphite material with a surface coated with a silicon carbide coating according to claim 5, characterized in that: The rotation speed of the rotating fixture is 1 rpm to 10 rpm.

7. The method for preparing a graphite material with a surface coated with a silicon carbide coating according to claim 3, characterized in that: In the high-temperature chemical purification process, polytetrafluoroethylene powder is used, which has a diameter of 5-20 microns and an amount of 10-30 times the mass of impurities in the graphite material. The rate of conveying polytetrafluoroethylene powder is 10 g / min-30 g / min, and the chemical purification temperature is 2000-2500 °C.

8. The method for preparing a graphite material with a surface coated with a silicon carbide coating according to claim 3, characterized in that: In the chemical vapor deposition process, the silicon carbide precursor used is methyltrichlorosilane, the feed rate is 2-10 kg / h, the carrier gas and the reaction gas are high-purity hydrogen, the intake flow rate is 5-50 L / min, the dilution gas is high-purity argon, the intake flow rate is 3-30 L / min, and the chemical vapor deposition temperature is 1000-1400 °C.

9. The method for preparing a graphite material with a surface coated with a silicon carbide coating according to claim 3, characterized in that: During the laser surface treatment process, the laser scanning speed is 1-30 mm / s, the laser pulse width is 1-350 ns, the laser power is 50-500 W, the laser frequency is 1-2000 kHz, the distance between the laser head and the device surface is 10-30 cm, and the treatment speed is 100-500 cm² / min.

10. A graphite material with a surface coated with a silicon carbide coating prepared by the preparation method according to any one of claims 3 to 9.

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