CVDSiC coated graphite product and preparation method thereof

Abstract

The invention provides a CVD SiC coating graphite product. The CVD SiC coating graphite product comprises a graphite substrate, a SiC transition layer and a SiC main coating, wherein the SiC transition layer and the SiC main coating are sequentially attached to the surface of the graphite substrate. A large number of submicron holes are formed in the surface of the SiC transition layer, and the thickness of the submicron holes is 10-30 microns; the SiC main coating is beta-SiC with a compact structure, and the thickness of the SiC main coating is 30-100 microns. Through the structural design and preparation that the SiC transition layer is rich in submicron holes, the difference of thermal expansion coefficients of the coating and the graphite matrix can be possibly reduced, the bonding strength of the coating and the graphite matrix is improved, meanwhile, instability expansion of cracks of the coating can be restrained, and therefore the cracking or falling risk of the SiC coating is greatly reduced, and the service life of the coating is prolonged. And the service life of the CVD SiC coating graphite product is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor coating, in particular to a CVD SiC coated graphite product and a preparation method thereof. BACKGROUND

[0002] The CVD SiC coated graphite product is a material produced by a chemical vapor deposition (CVD) process, which has an excellent unique combination of thermal, electrical and chemical properties, and is an indispensable consumable in the third-generation semiconductor, electronic-grade single crystal silicon, LED and IC integrated circuit high-end manufacturing field.

[0003] At present, with the continuous increase of wafer size, the size of the SiC coated graphite product is also increasing, and in addition, the local non-uniformity of the thermal field of the equipment itself during high temperature use may exist, the difference in the thermal expansion coefficient between the SiC coating and the graphite substrate is easy to cause the product to crack or peel locally, thereby reducing the service life of the product and increasing the user's use cost and production efficiency.

[0004] Chinese patent CN114525495A discloses a preparation method and application of a surface SiC coated graphite tray, which comprises the following steps: (1) taking a graphite tray as a substrate; (2) etching the graphite tray using a gas containing NH3; (3) blowing the surface of the etched graphite tray to remove the residual dust after etching; (4) depositing a SiC coating on the surface of the treated graphite tray by chemical vapor deposition. It utilizes ammonia gas to etch the surface of the graphite tray to obtain a rough and porous etched surface, which is beneficial to the mechanical engagement of the SiC coating to the tray substrate, and improves the bonding strength of the coating and the substrate. However, this method of changing the roughness of the graphite surface will affect the flatness of the coating, and the patent does not involve any specific effect data and corresponding characterization.

[0005] CN118684522A discloses a graphite base with embedded silicon carbide coating and its preparation method and application. The preparation method of the graphite base with embedded silicon carbide coating comprises the following steps: placing SiO powder and a graphite base in a reaction container, the graphite base being located on the volatilization path of the SiO powder; vacuumizing the reaction container and heating to 1100-1800℃, then introducing inert gas with a flow rate of 100-1000sccm into the reaction container and keeping warm, the SiO powder volatilizing to form SiO gas and reacting with the graphite base to form silicon carbide in the interior and surface of the graphite base; and controlling the temperature of the reaction container to be between 1100-1500℃, introducing dilution gas, silicon source and reducing gas into the reaction container to perform chemical vapor deposition reaction on the surface of the graphite base, thereby obtaining the graphite base with embedded silicon carbide coating. However, the purity of the SiC transition layer prepared by the method is difficult to guarantee, which cannot meet the requirement of high purity of products in the field of semiconductor applications, and the thermal cycling performance of the obtained product also has room for further improvement. SUMMARY

[0006] To improve the above-mentioned problems existing in the prior art, the present application provides a CVD SiC coated graphite product, which comprises a graphite base and a SiC transition layer and a SiC main coating layer attached to the surface of the graphite base in sequence. Before preparing the SiC main coating layer on the SiC transition layer, the surface of the SiC transition layer has sub-micron pores with a thickness of 5-30μm; and the SiC main coating layer is a dense β-SiC with a thickness of 30-120μm.

[0007] Preferably, the SiC transition layer coating has a certain composition gradient, taking the contact surface between the SiC transition layer and the surface of the graphite base as the starting point and the contact surface between the SiC transition layer and the SiC main coating layer as the end point, the content of Si gradually increases and the content of C gradually decreases from the starting point to the end point, which is beneficial to reducing the difference in thermal expansion coefficient between the coating and the base.

[0008] Meanwhile, the present application also provides a preparation method of the CVD SiC coated graphite product, which comprises the following steps:

[0009] Step one: preparation of SiC transition layer

[0010] The surface-cleaned and dried graphite base material is placed in a chemical vapor deposition furnace, and silicon source gas, carbon source gas and dilution gas are introduced. The deposition temperature is 1000-1550℃, the deposition pressure is 1-20KPa, and the deposition time is 0.3-3h.

[0011] Step two: etching treatment of SiC transition layer

[0012] The temperature of step one is kept, the input of silicon source gas, carbon source gas and dilution gas is stopped, and HCl+H2 gas is input instead, the flow rate is 50-100 L / min, the pressure is 10-50 KPa, and the processing time is 0.5-3 h.

[0013] Step three: preparation of SiC main coating

[0014] The input of HCl gas is stopped, and silicon source gas, carbon source gas and dilution gas are input instead. The deposition temperature is 1000-1550 ℃, the deposition pressure is 1-20 KPa, and the deposition time is 1-5 h.

[0015] The silicon source gas used in step one and step three of the application is one or more of SiCl4, CH3SiCl3, HSiCl3, H2SiCl2, H3SiCl and SiH4, the carbon source gas is one or more of CH4, C3H8 and C3H6, and the dilution gas is at least one selected from H2 and Ar.

[0016] The flow rate ratio of the various gases in step one is silicon source gas:carbon source gas:dilution gas=1:(0.1-20):(15-50), preferably 1:0.3-20:15-30. The flow rate ratio of the various gases in step three is silicon source gas:carbon source gas:dilution gas=1:(0.05-1.2):(15-50), preferably 1:0.3-1:5-30.

[0017] As a preferred embodiment, in step one of the application, the flow rate of the carbon source gas is gradually changed, and the carbon source gas / silicon source gas flow rate ratio is reduced from 20 to 0.3-1.5, while other process parameters and conditions remain unchanged.

[0018] In order to achieve a certain composition gradient of the SiC transition layer coating, as a preferred embodiment, in step one, the amount of carbon source gas is reduced within the selected range when chemical vapor deposition is started, so that the content of Si gradually increases and the content of C gradually decreases from the starting point to the end point. The advantage of this operation is that, taking the contact surface between the SiC transition layer and the surface of the graphite substrate as the starting point, and taking the contact surface between the SiC transition layer and the SiC main coating as the end point, the content of Si gradually increases and the content of C gradually decreases from the starting point to the end point, which is beneficial to reducing the difference in thermal expansion coefficient between the coating and the substrate.

[0019] For example, in step one, the flow rate ratio of the various gases is silicon source gas:carbon source gas:dilution gas=1:A1:(15-50) when deposition is started. The value of A1 is 1-20; as deposition proceeds, the flow rate of the silicon source gas / carbon source gas is linearly increased or nonlinearly increased. As a further preferred embodiment, the flow rate of the dilution gas remains constant during deposition.

[0020] As a further preferred, in step one, when starting chemical vapor deposition, the flow ratio of carbon source gas / silicon source gas is B, then every 5 minutes, the flow ratio of carbon source gas / silicon source gas is lowered by 1 (such as after the first 5 minutes, the flow ratio of carbon source gas / silicon source gas is B-1), and so on, until the flow ratio of carbon source gas / silicon source gas is 1.

[0021] As a further preferred, in step one, when starting chemical vapor deposition, the flow ratio of carbon source gas / silicon source gas is B, then every 15 minutes, the flow ratio of carbon source gas / silicon source gas is lowered by 3 (such as after the first 15 minutes, the flow ratio of carbon source gas / silicon source gas is B-3), and so on, until the flow ratio of carbon source gas / silicon source gas is 1~2.

[0022] As a preferred, in step one of the present application, the deposition temperature is relatively low, being 1000-1250℃, preferably 1180℃~1220℃, and the time is 1~2h, preferably 80~100min, in step three, the deposition temperature is relatively high, being 1250-1550℃, preferably 1420~1470℃, and the time is 50~75min, and the deposition temperature in step three - the deposition in step one ≥200℃. The relatively low deposition temperature in step one can reduce the grain size of the coating, and can reduce the internal stress of the transition layer, which is beneficial to improve the bonding strength of the transition layer; while the relatively high deposition temperature in step three can increase the grain size of the coating, which is beneficial to improve the erosion resistance of the coating.

[0023] The CVD SiC coated graphite product and the preparation method thereof have the following advantages:

[0024] (1) By etching the SiC transition layer, a structure rich in sub-micron pores is formed, which can eliminate part of the internal stress of the coating, and can also reduce the difference in thermal expansion coefficient between the SiC transition layer and the graphite substrate, thereby improving the bonding strength of the SiC transition layer and the graphite substrate.

[0025] (2) The structure rich in sub-micron pores in the SiC transition layer can ensure that the SiC main coating is firmly pinned to the SiC transition layer, thereby improving the bonding strength of the main coating and the transition layer, and this structure can also inhibit the unstable propagation of cracks in the SiC main coating, thereby greatly reducing the risk of cracking or peeling of the SiC coating.

[0026] (3) By gradually changing the flow ratio of carbon source gas / silicon source gas, the SiC transition layer coating prepared has a certain composition gradient, and the content of Si gradually increases from the inside to the outside, while the content of C gradually decreases, which can further reduce the difference in thermal expansion coefficient between the coating and the substrate.

[0027] (4) The preparation of the SiC transition layer, the etching treatment of the SiC transition layer and the preparation of the SiC main coating can be completed continuously in the same furnace without repeated additional treatments. This can improve production efficiency and reduce the risk of contamination of SiC coated graphite products, thus ensuring the purity of the products. Attached Figure Description

[0028] Appendix Figure 1 This is a surface SEM image of the SiC transition layer obtained in step one of Example 1;

[0029] Appendix Figure 2 This is a surface SEM image of the SiC transition layer after etching in step two of Example 1;

[0030] Appendix Figure 3 This is a surface SEM image of the SiC main coating in step three of Example 1;

[0031] Appendix Figure 4 This is a cross-sectional SEM image of the SiC coating obtained in Example 1. Detailed Implementation

[0032] Example 1

[0033] Step 1: Preparation of SiC transition layer

[0034] The surface-treated graphite substrate (i.e., a clean and dry graphite substrate) was placed in a chemical vapor deposition furnace, and silicon source gas, carbon source gas, and dilution gas were introduced. The flow rate ratio of each gas was SiCl4:CH4:H2 = 1:1:20 (the flow rate of SiCl4 was 20 L / min). The deposition temperature was 1200℃, the deposition pressure was 5 kPa, and the deposition time was 1 h.

[0035] Step 2: Etching of the SiC transition layer

[0036] Maintain the temperature of step one, stop the introduction of silicon source gas, carbon source gas and dilution gas, and instead introduce HCl+H2 gas at a flow rate of 100L / min and a pressure of 50KPa for 0.5h.

[0037] Step 3: Preparation of SiC Main Coating

[0038] The HCl+H2 gas flow was stopped, and the flow was replaced with silicon source gas, carbon source gas, and dilution gas, with a flow rate ratio of SiCl4:CH4:H2 = 1:1:30. The deposition temperature was 1450℃, the deposition pressure was 10 kPa, and the deposition time was 1.5 h.

[0039] Example 2

[0040] Example 2 The conditions are the same as Example 1 except that in the preparation of the SiC transition layer in Step 1, the flow rate of the carbon source gas is gradually changed, and the carbon source gas / silicon source gas flow rate ratio is reduced from 18 to 1: Initially, the flow rate ratio of the various gases is SiCl4:CH4:H2=1:18:30, and every 5 minutes, the carbon source gas / silicon source gas flow rate ratio is reduced by 1, i.e., the carbon source gas / silicon source gas flow rate ratio is sequentially reduced from 18 to 17, 16...2, 1, and the dilution gas flow rate remains unchanged. The prepared SiC transition layer coating has a certain composition gradient, and the content of Si gradually increases from the inside to the outside, while the content of C gradually decreases.

[0041] Example 3

[0042] Example 3 The conditions are the same as Example 1 except that in the preparation of the SiC transition layer in Step 1, the flow rate of the carbon source gas is gradually changed, and the carbon source gas / silicon source gas flow rate ratio is reduced from 18 to 1: Initially, the flow rate ratio of the various gases is SiCl4:CH4:H2=1:18:30, and every 15 minutes, the carbon source gas / silicon source gas flow rate ratio is reduced by 3 until it is 1 at the last 15 minutes, i.e., the carbon source gas / silicon source gas flow rate ratio is sequentially reduced from 18 to 15, 12...3, 1, and the dilution gas flow rate remains unchanged. The prepared SiC transition layer coating has a certain composition gradient, and the content of Si gradually increases from the inside to the outside, while the content of C gradually decreases.

[0043] Example 4

[0044] Example 2 The conditions are the same as Example 1 except that in the preparation of the SiC transition layer in Step 1, the flow rate of the carbon source gas is gradually changed, and the carbon source gas / silicon source gas flow rate ratio is reduced from 18 to 1: Initially, the flow rate ratio of the various gases is SiCl4:CH4:H2=1:18:30, and every 30 minutes, the carbon source gas / silicon source gas flow rate ratio is reduced by 6 until it is 1 at the last 30 minutes, i.e., the carbon source gas / silicon source gas flow rate ratio is sequentially reduced from 18 to 12, 6, 1, and the dilution gas flow rate remains unchanged. The prepared SiC transition layer coating has a certain composition gradient, and the content of Si gradually increases from the inside to the outside, while the content of C gradually decreases.

[0045] Example 5

[0046] Example 3 The conditions are the same as Example 1 except that in the preparation of the SiC transition layer in Step 1, the deposition temperature is 1450°C.

[0047] Example 6

[0048] Step 1: Preparation of SiC Transition Layer

[0049] The surface-treated graphite substrate (i.e. the surface-cleaned and dried graphite substrate) is placed in a chemical vapor deposition furnace, and a silicon source gas, a carbon source gas, and a dilution gas are introduced, with a flow ratio of SiH4:C3H6:H2=1:0.3:15. The deposition temperature is 1150°C, the deposition pressure is 3 KPa, and the deposition time is 3 h.

[0050] Step two: etching treatment of the SiC transition layer

[0051] The temperature of step one is maintained, the introduction of the silicon source gas, the carbon source gas, and the dilution gas is stopped, and HCl+H2 gas is introduced instead, with a flow rate of 50 L / min and a pressure of 10 KPa, for a treatment time of 3 h.

[0052] Step three: preparation of the SiC main coating layer

[0053] The introduction of the HCl gas is stopped, and the silicon source gas, the carbon source gas, and the dilution gas are introduced instead, with a flow ratio of SiH4:C3H6:H2=1:0.3:15, a deposition temperature of 1150°C, a deposition pressure of 3 KPa, and a deposition time of 4 h.

[0054] Example 7

[0055] Step one: preparation of the SiC transition layer

[0056] The surface-treated graphite substrate (i.e. the surface-cleaned and dried graphite substrate) is placed in a chemical vapor deposition furnace, and a silicon source gas and a dilution gas are introduced, with a flow ratio of CH3SiCl3:H2:Ar=1:10:5. The deposition temperature is 1000°C, the deposition pressure is 1 KPa, and the deposition time is 3 h.

[0057] Step two: etching treatment of the SiC transition layer

[0058] The temperature of step one is maintained, the introduction of the silicon source gas and the dilution gas is stopped, and HCl+H2 gas is introduced instead, with a flow rate of 80 L / min and a pressure of 50 KPa, for a treatment time of 2 h.

[0059] Step three: preparation of the SiC main coating layer

[0060] The introduction of the HCl gas is stopped, and the silicon source gas and the dilution gas are introduced instead, with a flow ratio of CH3SiCl3:H2:Ar=1:10:5, a deposition temperature of 1200°C, a deposition pressure of 20 KPa, and a deposition time of 3 h.

[0061] Comparative Example 1

[0062] The conditions are the same as in Example 1, except that the etching treatment of the SiC transition layer in step two is not performed. That is, step two is omitted, and step three is performed directly.

[0063] Comparative Example 2

[0064] The other conditions are consistent with Example 2, except that the etching treatment of the SiC transition layer in Step 2 is not performed. That is, Step 2 is omitted and directly proceed to Step 3.

[0065] Comparative Example 3

[0066] The other conditions are consistent with Example 5, except that the etching treatment of the SiC transition layer in Step 2 is not performed. That is, Step 2 is omitted and directly proceed to Step 3.

[0067] Comparative Example 4

[0068] The surface-treated graphite matrix material (i.e. the surface-cleaned and dried graphite matrix material) is placed in a chemical vapor deposition furnace, and a silicon source gas, a carbon source gas and a dilution gas are introduced, with a flow ratio of SiCl4:CH4:H2=1:1:20. The deposition temperature is 1200°C, the deposition pressure is 5 KPa, and the deposition time is 4 h.

[0069] Comparative Example 5

[0070] The surface-treated graphite matrix material (i.e. the surface-cleaned and dried graphite matrix material) is placed in a chemical vapor deposition furnace, and a silicon source gas, a carbon source gas and a dilution gas are introduced, with a flow ratio of SiCl4:CH4:H2=1:1:30. The deposition temperature is 1550°C, the deposition pressure is 10 KPa, and the deposition time is 1 h.

[0071] The SiC-coated graphite products prepared in the above examples and comparative examples are subjected to a thermal shock test to evaluate the quality of the coating by counting the number of times of cracks in the coating. The test results are recorded in Table 1, and the specific operation method is as follows: through thermal shock test, the sample is placed in a 400°C muffle furnace for 30 min, then quickly placed in cold water (25°C) for rapid cooling, repeated for many times until the silicon carbide coating cracks, and the test number when the crack appears is recorded.

[0072] .

Claims

1. A CVDSiC coated graphite product, characterized by: The CVDSiC coated graphite product comprises a graphite substrate and a SiC transition layer and a SiC main coating layer attached to the surface of the graphite substrate in sequence; the surface of the SiC transition layer has sub-micron pores before the SiC main coating layer is prepared on the SiC transition layer, and the thickness of the SiC transition layer is 5-30 μm; the SiC main coating layer is dense β-SiC with a thickness of 30-120 μm.

2. The CVDSiC coated graphite product of claim 1, wherein: The SiC transition layer coating has a certain composition gradient, with the contact surface between the SiC transition layer and the surface of the graphite substrate as the starting point and the contact surface between the SiC transition layer and the SiC main coating layer as the end point, the content of Si gradually increases and the content of C gradually decreases from the starting point to the end point.

3. A method for preparing the CVDSiC coated graphite product according to any one of claims 1-2, comprising the following steps: Step one: preparation of the SiC transition layer The surface-treated graphite substrate material is placed in a chemical vapor deposition furnace, and silicon source gas, carbon source gas and dilution gas are introduced, the deposition temperature is 1000-1550 ℃, the deposition pressure is 1-20 KPa, and the deposition time is 0.3-3 h; Step two: etching treatment of the SiC transition layer The temperature of step one is maintained, the introduction of silicon source gas, carbon source gas and dilution gas is stopped, and HCl+H2 gas is introduced instead, the flow rate is 50-100 L / min, the pressure is 10-50 KPa, and the treatment time is 0.5-3 h; Step three: preparation of the SiC main coating layer The introduction of HCl gas is stopped, and silicon source gas, carbon source gas and dilution gas are introduced instead. The deposition temperature is 1000-1550 ℃, the deposition pressure is 1-20 KPa, and the deposition time is 1-5 h.

4. A method of producing a CVD SiC coated graphite product according to claim 3, characterized in that: The silicon source gas used in step one and step three is one or more of SiCl4, CH3SiCl3, HSiCl3, H2SiCl2, H3SiCl and SiH4, the carbon source gas is one or more of CH4, C3H8 and C3H6, and the dilution gas is at least one selected from H2 and Ar.

5. A method of producing a CVD SiC coated graphite product according to claim 4, characterized in that: The flow rate ratio of the various gases in step one is silicon source gas: carbon source gas: dilution gas = 1: (0.1-20): (15-50), preferably 1: 0.3-20: 15-30; the flow rate ratio of the various gases in step three is silicon source gas: carbon source gas: dilution gas = 1: (0.05-1.2): (15-50), preferably 1: 0.3-1: 5-30.

6. A method of producing a CVD SiC coated graphite product according to claim 3, characterized in that: In step one, the flow rate of the carbon source gas is gradually changed, and the carbon source gas / silicon source gas flow rate ratio is reduced from 20 to 0.3-1.5, and the other process parameters and conditions remain unchanged.

7. A method of producing a CVD SiC coated graphite product according to claim 6, characterized in that: In step one, at the beginning of deposition, the flow rate ratio of the various gases is silicon source gas: carbon source gas: dilution gas = 1: A1: (15-50); the value of A1 is 1-20; as the deposition proceeds, the silicon source gas / carbon source gas increases linearly or non-linearly.

8. A method of producing a CVD SiC coated graphite product according to claim 7, characterized in that: In step one, at the beginning of chemical vapor deposition in step one, the carbon source gas / silicon source gas flow rate ratio is B, then every 5 min, the carbon source gas / silicon source gas flow rate ratio is lowered by 1, and so on, until the carbon source gas / silicon source gas flow rate ratio is 1; or In step one, the flow ratio of carbon source gas / silicon source gas is B when starting chemical vapor deposition, and then the flow ratio of carbon source gas / silicon source gas is lowered by 3 every 15 minutes, and so on until the flow ratio of carbon source gas / silicon source gas is 1-2.

9. A method of producing a CVD SiC coated graphite product according to claim 3, characterized by: In step one, the deposition temperature is 1000-1250℃, preferably 1180-1220℃, and the time is 1-2h, preferably 80-100min, in step three, the deposition temperature is 1250-1550℃, preferably 1420-1470℃, and the time is 50-75min, and the deposition temperature in step three minus the deposition in step one is ≥200℃.

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