3C type silicon carbide polycrystalline substrate and preparation method and application thereof

Abstract

The invention provides a 3C type silicon carbide polycrystalline substrate and a preparation method and application thereof, in any 3 * 3 mm < 2 > area in the 3C type silicon carbide polycrystalline substrate, the average size of three largest crystal grains is 10-200 [mu] m, the microcrack density in the 3C type silicon carbide polycrystalline substrate is 0 ea / cm < 2 >-5 ea / cm < 2 >, and the 3C type silicon carbide polycrystalline substrate contains nitrogen. According to the 3C type silicon carbide polycrystal disclosed by the invention, the microcrack density in the crystal grains is relatively low, even no microcrack exists, bonding holes are prevented from being formed when a substrate of a composite wafer is made while low resistivity is ensured, and an effective area for manufacturing a device is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor materials and relates to a 3C-type silicon carbide polycrystalline substrate and a preparation method and application thereof. Background Art

[0002] 3C-SiC polycrystalline material has the advantages of high temperature resistance, high pressure resistance, radiation resistance, chemical corrosion resistance, high hardness, and high thermal conductivity. Because of these advantages, 3C-SiC polycrystalline material can be used to make components such as heating plates and focusing rings in semiconductor processes. In addition, since 3C-SiC polycrystalline can achieve lower resistivity than commercially available 4H-SiC single crystals, 3C-SiC polycrystalline substrates can be used as a supporting layer and composited with 4H-SiC single crystal films to form polycrystalline silicon carbide composite wafers with lower resistivity than 4H-SiC single crystals. The polycrystalline silicon carbide composite wafer is made into devices such as MOSFET after undergoing steps such as epitaxy, etching, ion implantation, and packaging.

[0003] Compared with high-resistivity 3C-SiC polycrystals, low-resistivity 3C-SiC polycrystals are more likely to have long strip-shaped microcrack defects.

[0004] CN116657114A discloses a low-resistance silicon carbide substrate, a preparation method, and an application thereof, belonging to the field of semiconductor technology. The silicon carbide substrate comprises silicon carbide doped with nitrogen and free carbon, wherein the free carbon is randomly distributed inside the silicon carbide; the resistivity of the silicon carbide substrate is less than 10 mΩ·cm.

[0005] The low-resistance silicon carbide material prepared by the above scheme has a large number of microcracks distributed inside the grains, which will form bonding voids when used as the substrate of a composite wafer, greatly reducing the effective area for manufacturing devices. When used to manufacture focusing rings, heating plates and other components, due to ion bombardment, thermal stress, etc. during use, the microcracks can become the source of cracks in the material, and cracks will expand, leading to material failure. Summary of the Invention

[0006] The purpose of the present invention is to provide a 3C-type silicon carbide polycrystalline substrate, a preparation method and application thereof. The microcrack density in the 3C-type silicon carbide polycrystalline grains of the present invention is low or even free of microcracks. While ensuring low resistivity, it avoids the formation of bonding voids when serving as a substrate for a composite wafer, and the effective area used for manufacturing devices is greatly reduced.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a 3C type silicon carbide polycrystalline substrate, wherein any 3×3 mm 2The average size of the three largest grains in the area is 10 μm to 200 μm, for example, 10 μm, 20 μm, 50 μm, 100 μm or 200 μm, etc., and is not limited to the listed values. Other values not listed in this numerical range are also applicable. The microcrack density in the 3C-type silicon carbide polycrystalline substrate is 0 ea / cm 2 ~5ea / cm 2 , for example: 0ea / cm 2 、1ea / cm 2 、2ea / cm 2 、3ea / cm 2 、4ea / cm 2 or 5ea / cm 2 The present invention is not limited to the numerical values listed, and other numerical values not listed within the numerical range are also applicable.

[0009] The micro crack density of the present invention is per 1cm 2 The number of microcracks, i.e., gaps with an aspect ratio greater than 5. The microcrack density in the 3C-type silicon carbide polycrystalline substrate can be less than 1 ea / cm 2 For example, the microcrack density in the 3C-type silicon carbide polycrystalline substrate of the present invention is 0.1ea / cm 2 That is, the detection of 1cm 2 No cracks inside, 10cm 2 A crack was detected in the area.

[0010] In the 3C-type silicon carbide polycrystalline substrate described in the present invention, by controlling the size of the grains in the silicon carbide polycrystalline substrate, the density of microcracks in the material is reduced, thereby reducing the number of crack defect areas within the silicon carbide polycrystalline, avoiding the formation of bonding voids when making the base of the composite wafer, and significantly reducing the effective area used for manufacturing devices.

[0011] Preferably, the mass fraction of nitrogen in the 3C-type silicon carbide polycrystalline substrate is 1200 ppm to 4000 ppm, for example, 1200 ppm, 1500 ppm, 2000 ppm, 3000 ppm or 4000 ppm.

[0012] Preferably, the resistivity of the 3C-type silicon carbide polycrystalline substrate is 1 mΩ·cm to 10 mΩ·cm, for example, 1 mΩ·cm, 2 mΩ·cm, 5 mΩ·cm, 8 mΩ·cm or 10 mΩ·cm, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0013] In a second aspect, the present invention provides a method for preparing a 3C-type silicon carbide polycrystalline substrate as described in the first aspect, the preparation method comprising the following steps:

[0014] The substrate is placed in a reaction device, and a carbon silicon source, a carrier gas and a nitrogen source are introduced to perform a chemical vapor deposition reaction to obtain the 3C-type silicon carbide polycrystalline substrate.

[0015] Preferably, the material of the substrate includes graphite and / or silicon carbide, preferably graphite.

[0016] Preferably, the carbon-silicon source comprises a combination of a carbon source and a silicon source and / or a silicon-carbon compound, preferably a silicon-carbon compound.

[0017] Preferably, the molar ratio of carbon element to silicon element in the composition of the carbon source and the silicon source is 1:(0.8-1.2), for example: 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2, etc., and is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0018] Preferably, the carbon source includes any one of methane, ethylene or propane, or a combination of at least two of them. Typical but non-limiting combinations include a combination of methane and ethylene, a combination of ethylene and propane, or a combination of methane and propane.

[0019] Preferably, the silicon source includes any one of silicon tetrachloride, silicon trichloride or silicon dichloride, or a combination of at least two of them. Typical but non-limiting combinations include a combination of silicon tetrachloride and silicon trichloride, a combination of silicon trichloride and silicon dichloride, or a combination of silicon tetrachloride and silicon dichloride.

[0020] Preferably, the silicon-carbon compound includes trichloromethylsilane and / or methylsilane, preferably trichloromethylsilane.

[0021] Preferably, the carrier gas comprises hydrogen and / or argon, preferably hydrogen.

[0022] Preferably, the nitrogen source comprises nitrogen and / or ammonia, preferably nitrogen.

[0023] Preferably, the flow ratio of the carbon silicon source to the carrier gas is 1:(5-8), for example: 1:5, 1:5.5, 1:6, 1:7 or 1:8, etc., and is not limited to the listed values. Other unlisted values within this numerical range are also applicable.

[0024] The present invention can produce 3C-type silicon carbide polycrystals with suitable grains by controlling the flow ratio of the carbon silicon source to the carrier gas. The higher the flow ratio of the carbon silicon source to the carrier gas, the easier it is for 3C-SiC to nucleate in the gas phase. More nuclei mean more 3C-SiC grains, making the grain size smaller.

[0025] Preferably, the flow ratio of the carbon silicon source to the nitrogen source is 1:(6-10), for example: 1:6, 1:7, 1:8, 1:9 or 1:10, etc., and is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0026] Preferably, the flow rate of hydrogen is 5 L / min to 8 L / min, for example, 5 L / min, 5.5 L / min, 6 L / min, 7 L / min or 8 L / min, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0027] During the CVD reaction to form SiC, the introduction of a nitrogen source causes nitrogen doping into the 3C-SiC polycrystal, resulting in a decrease in the polycrystal's resistivity. At higher temperatures, more nitrogen is doped into the 3C-SiC polycrystal, resulting in a lower resistivity. However, at higher temperatures, grains grow more easily, leading to an increase in the number of microcracks. Therefore, it is generally observed that a lower resistivity in the 3C-SiC polycrystal corresponds to a higher number of microcracks.

[0028] Preferably, the temperature of the chemical vapor deposition reaction is 1360° C. to 1400° C., for example, 1360° C., 1380° C. or 1400° C., etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0029] Preferably, the pressure of the chemical vapor deposition reaction is 2000Pa to 4000Pa, for example, 2000Pa, 2500Pa, 3000Pa, 3500Pa or 4000Pa, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0030] Preferably, the substrate is removed after the chemical vapor deposition reaction.

[0031] Preferably, the method of removing the substrate includes cutting, mechanical grinding or chemical reaction.

[0032] In a third aspect, the present invention provides a silicon carbide composite substrate, comprising the 3C-type silicon carbide polycrystalline substrate as described in the first aspect and a single crystal silicon carbide wafer bonded to the surface of the 3C-type silicon carbide polycrystalline substrate.

[0033] In a fourth aspect, the present invention provides an application of the silicon carbide composite substrate as described in the third aspect, wherein the silicon carbide composite substrate is used for a focusing ring and / or a heating plate.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The microcrack density in the 3C-type silicon carbide polycrystalline grains of the present invention is low or even free of microcracks, which ensures low resistivity while avoiding the formation of bonding voids when used as a substrate for composite wafers, thereby significantly reducing the effective area for device fabrication.

[0036] (2) The 3C-type silicon carbide polycrystalline of the present invention can achieve a microcrack density of 2.47 ea / cm while ensuring a resistivity below 8.9 mΩ·cm. 2 Within. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] In the embodiments of the present invention and the comparative examples, a mixture of a carbon source and a silicon source can be selected as the carbon-silicon source, or a compound containing carbon and silicon can be selected as the carbon-silicon source. For ease of operation, the embodiments of the present invention and the comparative examples all use trichloromethylsilane, i.e., MTS, as the carbon-silicon source, and the molar ratio of carbon to silicon in the molecule is 1:1.

[0039] Example 1

[0040] This embodiment provides a 3C-type silicon carbide polycrystalline substrate, which is manufactured by the following method:

[0041] Isostatically pressed graphite was used as a substrate, processed into graphite sheets with a diameter of 190 mm and a thickness of 5 mm. 3C-SiC was grown using hot-wall chemical vapor deposition with horizontal inlet. Before growth began, the furnace chamber was heated to 1360°C and a pressure of 3000 Pa. At the start of deposition, MTS, hydrogen, and nitrogen were introduced with a flow ratio of 8:1 N2:MTS and 5:1 H2:MTS. After deposition, the gas flow was stopped, completing the growth process. The grown 3C-SiC polycrystal and graphite substrate were rolled to a diameter of 150 mm using a cylindrical grinder. The resulting 3C-SiC was then placed in a tube furnace, heated to 1000°C, and hot air was introduced to remove the graphite substrate. The grown 3C-SiC was ground and polished on both sides to produce a 6-inch 3C-type silicon carbide polycrystalline substrate.

[0042] Example 2

[0043] This embodiment provides a 3C-type silicon carbide polycrystalline substrate, which is manufactured by the following method:

[0044] Isostatically pressed graphite was used as a substrate, processed into graphite sheets with a diameter of 190 mm and a thickness of 5 mm. 3C-SiC was grown using hot-wall chemical vapor deposition with horizontal inlet. Before growth began, the furnace chamber was heated to 1400°C and a pressure of 3000 Pa. At the start of deposition, trichloromethylsilane (MTS), hydrogen, and nitrogen were introduced with a flow ratio of 8:1 for N2:MTS and 5:1 for H2:MTS. After deposition, the gas flow was stopped, completing the growth process. The grown 3C-SiC polycrystal and graphite substrate were rolled to a diameter of 150 mm using a cylindrical grinder. The resulting 3C-SiC was then placed in a tube furnace, heated to 1000°C, and hot air was introduced to remove the graphite substrate. The grown 3C-SiC was ground and polished on both sides to produce a 6-inch 3C-type silicon carbide polycrystalline substrate.

[0045] Example 3

[0046] This embodiment provides a 3C-type silicon carbide polycrystalline substrate, which is manufactured by the following method:

[0047] Isostatically pressed graphite was used as a substrate, processed into graphite sheets with a diameter of 190 mm and a thickness of 5 mm. 3C-SiC was grown using hot-wall chemical vapor deposition with horizontal inlet. Before growth began, the furnace chamber was heated to 1380°C and a pressure of 2000 Pa. At the start of deposition, trichloromethylsilane (MTS), hydrogen, and nitrogen were introduced with a flow ratio of 10:1 for N2:MTS and 5:1 for H2:MTS. After deposition, the gas flow was stopped, completing the growth process. The grown 3C-SiC polycrystal and graphite substrate were rolled to a diameter of 150 mm using a cylindrical grinder. The resulting 3C-SiC was then placed in a tube furnace, heated to 1000°C, and hot air was introduced to remove the graphite substrate. The grown 3C-SiC was ground and polished on both sides to produce a 6-inch 3C-type silicon carbide polycrystalline substrate.

[0048] Example 4

[0049] This embodiment provides a 3C-type silicon carbide polycrystalline substrate, which is manufactured by the following method:

[0050] Isostatically pressed graphite was used as a substrate, processed into graphite sheets with a diameter of 190 mm and a thickness of 5 mm. 3C-SiC was grown using hot-wall chemical vapor deposition with horizontal inlet. Before growth began, the furnace chamber was heated to 1360°C and a pressure of 4000 Pa. At the start of deposition, MTS, hydrogen, and nitrogen were introduced with a flow ratio of 6:1 N2:MTS and 5:1 H2:MTS. After deposition, the gas flow was stopped, completing the growth process. The grown 3C-SiC polycrystal and graphite substrate were rolled to a diameter of 150 mm using a cylindrical grinder, then placed in a tube furnace, heated to 1000°C, and hot air was introduced to remove the graphite substrate. The grown 3C-SiC was ground and polished on both sides to produce a 6-inch 3C-type silicon carbide polycrystalline substrate.

[0051] Example 5

[0052] This embodiment provides a 3C-type silicon carbide polycrystalline substrate, which is manufactured by the following method:

[0053] Isostatically pressed graphite was used as the substrate, processed into graphite sheets with a diameter of 190 mm and a thickness of 5 mm. 3C-SiC was grown using hot-wall chemical vapor deposition with horizontal inlet. Before growth began, the furnace chamber was heated to 1400°C and a pressure of 3000 Pa. At the start of deposition, MTS, hydrogen, and nitrogen were introduced with a flow ratio of 8:1 for N2:MTS and 8:1 for H2:MTS. After deposition, the gas flow was stopped, completing the growth process. The grown 3C-SiC polycrystal and graphite substrate were rolled to a diameter of 150 mm using a cylindrical grinder. The resulting 3C-SiC was then placed in a tube furnace, heated to 1000°C, and hot air was introduced to remove the graphite substrate. The grown 3C-SiC was ground and polished on both sides to produce a 6-inch 3C-type silicon carbide polycrystalline substrate.

[0054] Example 6

[0055] This embodiment provides a 3C-type silicon carbide polycrystalline substrate, which is manufactured by the following method:

[0056] Isostatically pressed graphite was used as the substrate, processed into graphite sheets with a diameter of 190 mm and a thickness of 5 mm. 3C-SiC was grown using hot-wall chemical vapor deposition with horizontal inlet. Before growth began, the furnace chamber was heated to 1380°C and a pressure of 3000 Pa. At the start of deposition, MTS, hydrogen, and nitrogen were introduced with a flow ratio of 8:1 for N2:MTS and 8:1 for H2:MTS. After deposition, the gas flow was stopped, completing the growth process. The grown 3C-SiC polycrystal and graphite substrate were rolled to a diameter of 150 mm using a cylindrical grinder. The resulting 3C-SiC was then placed in a tube furnace, heated to 1000°C, and hot air was introduced to remove the graphite substrate. The grown 3C-SiC was ground and polished on both sides to produce a 6-inch 3C-type silicon carbide polycrystalline substrate.

[0057] Comparative Example 1

[0058] The only difference between this comparative example and Example 1 is that the flow ratio of H2:MTS is 4:1, and the other conditions and parameters are exactly the same as those in Example 1.

[0059] Comparative Example 2

[0060] The only difference between this comparative example and Example 1 is that the flow ratio of H2:MTS is 10:1, and the other conditions and parameters are exactly the same as those in Example 1.

[0061] Comparative Example 3

[0062] The only difference between this comparative example and Example 1 is that the temperature of chemical vapor deposition is 1340° C., and other conditions and parameters are exactly the same as those in Example 1.

[0063] Comparative Example 4

[0064] The only difference between this comparative example and Example 1 is that the temperature of chemical vapor deposition is 1420° C., and other conditions and parameters are exactly the same as those in Example 1.

[0065] Comparative Example 5

[0066] The only difference between this comparative example and Example 1 is that the flow ratio of H2:MTS is 10:1, the temperature of chemical vapor deposition is 1420°C, and the other conditions and parameters are exactly the same as those in Example 1.

[0067] Performance testing:

[0068] The 3C silicon carbide polycrystalline substrates obtained in the examples and comparative examples were measured and recorded, and the test results are shown in Table 1:

[0069] Table 1

[0070]

[0071] As can be seen from Table 1, from Examples 1-6, the 3C-type silicon carbide polycrystalline of the present invention can achieve a microcrack density of 2.47 ea / cm while ensuring a resistivity below 8.9 mΩ·cm. 2 Within.

[0072] A comparison of Example 1 and Comparative Examples 1-2 shows that during the preparation of the 3C-type silicon carbide polycrystalline substrate of the present invention, the flow ratio of the carrier gas (hydrogen) to the carbon silicon source affects its structure. Controlling the flow ratio of the carbon silicon source to the carrier gas to 1:(5-8) results in a better structure and fewer microcracks in the 3C-type silicon carbide polycrystalline substrate. Excessive carrier gas flow rates lead to larger grain sizes and increased microcracks. Excessive carrier gas flow rates lead to smaller grain sizes but voids at the grain boundaries, failing to meet the requirements for low-defect polycrystalline materials.

[0073] A comparison of Example 1 and Comparative Examples 3-4 demonstrates that during the preparation of the 3C-type silicon carbide polycrystalline substrate described herein, the chemical vapor deposition (CVD) reaction temperature affects its structure and resistivity. Controlling the CVD reaction temperature between 1360°C and 1400°C yields a 3C-type silicon carbide polycrystalline substrate with a superior structure, fewer microcracks, and lower resistivity. Excessively high CVD reaction temperatures lead to larger grains and an increased number of microcracks. Excessively low CVD reaction temperatures result in resistivity exceeding 10 mΩ·cm, despite smaller grains and fewer microcracks.

[0074] By comparing Example 1 and Comparative Example 5, it can be seen that the present invention can obtain 3C silicon carbide polycrystals with appropriate internal grain size and low microcrack density or even no microcracks by controlling the flow ratio of the carrier gas to the carbon silicon source and the reaction temperature during the chemical vapor deposition process. While ensuring the low resistivity of the 3C silicon carbide polycrystals, the formation of bonding voids when making a base for a composite wafer is avoided, and the effective area used for device manufacturing is greatly reduced.

[0075] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A 3C type silicon carbide polycrystalline substrate, characterized in that: Any 3×3 mm 2 The average size of the three largest grains in the area is 10μm to 200μm, and the microcrack density in the 3C type silicon carbide polycrystalline substrate is 0ea / cm 2 ~5ea / cm 2 The 3C-type silicon carbide polycrystalline substrate contains nitrogen.

2. The 3C-type silicon carbide polycrystalline substrate according to claim 1, wherein: The mass fraction of nitrogen in the 3C-type silicon carbide polycrystalline substrate is 1200ppm to 4000ppm.

3. The 3C-type silicon carbide polycrystalline substrate according to claim 1 or 2, wherein: The resistivity of the 3C-type silicon carbide polycrystalline substrate is 1 mΩ·cm to 10 mΩ·cm.

4. A method for preparing a 3C-type silicon carbide polycrystalline substrate according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: The substrate is placed in a reaction device, and a carbon silicon source, a carrier gas and a nitrogen source are introduced to perform a chemical vapor deposition reaction to obtain the 3C-type silicon carbide polycrystalline substrate.

5. The preparation method according to claim 4, wherein The material of the substrate includes graphite and / or silicon carbide, preferably graphite; Preferably, the carbon-silicon source comprises a combination of a carbon source and a silicon source and / or a silicon-carbon compound, preferably a silicon-carbon compound; Preferably, the molar ratio of carbon element to silicon element in the composition of the carbon source and the silicon source is 1:(0.8-1.2); Preferably, the carbon source comprises any one of methane, ethylene or propane, or a combination of at least two thereof; Preferably, the silicon source comprises any one of silicon tetrachloride, silicon trichloride or silicon dichloride, or a combination of at least two thereof; Preferably, the silicon-carbon compound comprises trichloromethylsilane and / or methylsilane, preferably trichloromethylsilane; Preferably, the carrier gas comprises hydrogen and / or argon, preferably hydrogen; Preferably, the nitrogen source comprises nitrogen and / or ammonia, preferably nitrogen.

6. The preparation method according to claim 4 or 5, characterized in that The flow ratio of the carbon silicon source to the carrier gas is 1:(5-8); Preferably, the flow ratio of the carbon silicon source to the nitrogen source is 1:(6-10); Preferably, the flow rate of the hydrogen is 5 L / min to 8 L / min.

7. The preparation method according to any one of claims 4 to 6, characterized in that The temperature of the chemical vapor deposition reaction is 1360° C. to 1400° C.; Preferably, the pressure of the chemical vapor deposition reaction is 2000Pa to 4000Pa.

8. The preparation method according to any one of claims 4 to 7, characterized in that: removing the substrate after the chemical vapor deposition reaction; Preferably, the method of removing the substrate includes cutting, mechanical grinding or chemical reaction.

9. A silicon carbide composite substrate, characterized in that: The silicon carbide composite substrate comprises the 3C-type silicon carbide polycrystalline substrate according to any one of claims 1 to 3 and a single crystal silicon carbide wafer bonded to the surface of the 3C-type silicon carbide polycrystalline substrate.

10. An application of the 3C silicon carbide polycrystalline substrate according to any one of claims 1 to 3, characterized in that: The 3C-type silicon carbide polycrystalline substrate is used for a focusing ring and / or a heating plate.

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