Silicon carbide film and preparation method and preparation device thereof

Abstract

The invention provides a silicon carbide film as well as a preparation method and a preparation device thereof. The preparation device comprises a vertical reaction chamber, the top of the vertical reaction chamber is provided with an air inlet assembly, and the bottom of the vertical reaction chamber is provided with an air outlet; and the clamping tool is positioned in the vertical reaction chamber and is used for clamping a workpiece, so that the workpiece is parallel to the flowing direction of the introduced gas. The workpiece is kept parallel to the flowing direction of the introduced gas, so that the gas flows along the surface of the workpiece, a parallel flow boundary layer can be formed, and no obvious stagnation point exists, so that the retention time of the gas on the surface of the workpiece is longer, the sufficient reaction of reactants is facilitated, and a uniformly oriented organization structure is easier to form. Therefore, the preparation device can realize uniform deposition of the silicon carbide film, so that the prepared silicon carbide film has the advantages of high thickness uniformity, high conductivity, low defect density and the like, the performance of the device is remarkably improved, the service life of the device is remarkably prolonged, and the requirements of the semiconductor industry are met.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a silicon carbide film and a preparation method and a preparation device thereof. Background Art

[0002] Silicon carbide (SiC) has a series of excellent properties, such as high thermodynamic stability, excellent thermal conductivity, high electron mobility, low dielectric constant, large bandgap, oxidation resistance, and erosion resistance. Therefore, it has broad application prospects in the production of semiconductor devices, protective coatings for material surfaces, and space camera mirrors. It has been widely used in many fields such as semiconductors, electronics, nuclear energy, chemical industry, aerospace, etc.

[0003] Chemical vapor deposition (CVD) is one of the main methods for preparing SiC films, but the existing technology has the following problems: poor conductivity: Due to the high resistivity of SiC, it is difficult to meet the semiconductor industry's demand for its high conductivity; high defect density: Since SiC film is a polycrystalline, SiC film prepared by CVD generally has a multi-oriented structure. The different orientations of each grain during growth can easily lead to defects such as microcracks and holes in the SiC film, which will seriously affect the performance and service life of the device; poor thickness uniformity: SiC film prepared by CVD is prone to poor gas source concentration gradient in the flow field direction and poor thickness uniformity.

[0004] Therefore, how to make the prepared silicon carbide film have the advantages of high thickness uniformity, high conductivity and low defect density is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a silicon carbide film and its preparation method and preparation device. In the preparation device designed by the present invention, chemical vapor deposition is carried out by using a vertical reaction chamber with more consistent heat convection and gas diffusion directions, so that the vapor deposition is more uniform. In the vertical reaction chamber, the workpiece is kept parallel to the flow direction of the gas introduced, so that the gas flows along the surface of the workpiece, forming a parallel flow boundary layer without significant stagnation points, thereby allowing the gas to stay on the surface of the workpiece for a longer time, which is conducive to the full reaction of the reactants and more easily forms a uniformly oriented organizational structure. Therefore, the preparation device can achieve uniform silicon carbide film deposition, so that the prepared silicon carbide film has the advantages of high thickness uniformity, high conductivity and low defect density. The film thickness uniformity reaches within ±2%, and the orientation density of the (220) crystal plane can reach up to 100%, which significantly improves the performance and service life of the device and meets the needs of the semiconductor industry.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a device for preparing a silicon carbide thin film, the device comprising:

[0008] A vertical reaction chamber is provided with an air inlet assembly at the top and an air outlet at the bottom.

[0009] A clamping tool is located in the vertical reaction chamber and is used to clamp a workpiece so that the workpiece is parallel to the flow direction of the introduced gas.

[0010] In the preparation device designed by the present invention, chemical vapor deposition is performed in a vertical reaction chamber with more consistent heat convection and gas diffusion directions, making the vapor deposition more uniform. In the vertical reaction chamber, the workpiece is kept parallel to the flow direction of the gas introduced, so that the gas flows along the surface of the workpiece, forming a parallel flow boundary layer without significant stagnation points, thereby allowing the gas to stay on the workpiece surface for a longer time, which is conducive to the full reaction of the reactants and more likely to form a uniformly oriented microstructure. Therefore, the preparation device can achieve uniform silicon carbide film deposition, so that the prepared silicon carbide film has the advantages of high thickness uniformity, high conductivity and low defect density. The film thickness uniformity reaches within ±2%, and the orientation density of the (220) crystal plane can reach up to 100%, significantly improving the performance and service life of the device and meeting the needs of the semiconductor industry.

[0011] Preferably, the air inlet assembly comprises:

[0012] An air intake plate is provided with a plurality of air intake holes.

[0013] An air uniforming plate is located below the air inlet plate and above the workpiece, and a plurality of air uniforming holes are distributed on the air uniforming plate.

[0014] Preferably, the density of the air inlet holes on the air inlet plate is smaller than the density of the air uniforming holes on the air uniforming plate.

[0015] Preferably, the aperture of the air inlet holes on the air inlet plate is larger than the aperture of the air uniforming holes on the air uniforming plate.

[0016] Preferably, the air-distributing plate has at least one layer.

[0017] Preferably, the material of the air inlet plate and the air uniforming plate includes graphite.

[0018] Preferably, the clamping tool comprises:

[0019] A driving shaft, one end of which is vertically connected to the bottom of the vertical reaction chamber.

[0020] An auxiliary shaft is parallel to the horizontal plane and vertically connected to the driving shaft, and is used for clamping or limiting a workpiece.

[0021] The rotating shaft is parallel to the horizontal plane and vertically connected to the driving shaft by gear meshing, and is used to drive the workpiece to rotate in the vertical direction.

[0022] Preferably, the rotation speed of the rotating shaft is 10-30 rpm, for example, it can be 10 rpm, 15 rpm, 20 rpm, 25 rpm or 30 rpm.

[0023] Preferably, the preparation device further comprises three groups of independent heating components, which are respectively arranged corresponding to the top, middle and bottom of the vertical reaction chamber.

[0024] In a second aspect, the present invention provides a method for preparing a silicon carbide thin film, wherein the method adopts the preparation apparatus described in the first aspect, and the method comprises the following steps:

[0025] A workpiece is provided and clamped by a clamping fixture.

[0026] Reaction gas and carrier gas are introduced into the vertical reaction chamber through the gas inlet assembly, and the flow direction of the gas is kept parallel to the workpiece to perform chemical vapor deposition, so that a silicon carbide film is deposited on the workpiece.

[0027] Preferably, the reaction gas is silicon carbide vapor deposition raw material gas or silicon carbide synthesis gas source.

[0028] Preferably, the silicon carbide vapor deposition raw material gas includes trichloromethylsilane and / or methylsilane.

[0029] Preferably, the silicon carbide synthesis gas source includes a silicon source precursor and a carbon source precursor.

[0030] Preferably, the silicon source precursor includes any one of silicon tetrachloride, trichlorosilane or dichlorosilane, or a combination of at least two thereof, preferably silicon tetrachloride.

[0031] Preferably, the carbon source precursor includes any one of methane, ethylene or propane, or a combination of at least two thereof, preferably methane.

[0032] Preferably, the molar ratio of the silicon source precursor to the carbon source precursor is (1-5):1, for example, 1:1, 2:1, 3:1, 4:1 or 5:1.

[0033] Preferably, the carrier gas comprises hydrogen.

[0034] Preferably, the volume flow ratio of the carrier gas to the reaction gas is (1-5):1, for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1.

[0035] Preferably, during the process of introducing the silicon source precursor, the carbon source precursor and the carrier gas, a doping gas and / or a dilution gas is also introduced.

[0036] Preferably, the doping gas includes nitrogen or ammonia.

[0037] Preferably, the dilution gas includes hydrogen or argon.

[0038] Preferably, the volume flow ratio of the doping gas to the reaction gas is (0.5-7):1, for example, it can be 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1 or 7:1, etc.

[0039] Preferably, during the chemical vapor deposition process, the deposition temperature is 1400-1500° C., for example, 1400° C., 1450° C., or 1500° C.

[0040] Preferably, during the chemical vapor deposition process, the chamber pressure is 20-100 Torr, for example, 20 Torr, 30 Torr, 40 Torr, 50 Torr, 60 Torr, 70 Torr, 80 Torr, 90 Torr or 100 Torr, etc., preferably 40-60 Torr.

[0041] Preferably, during the chemical vapor deposition process, the rotation speed of the workpiece is 10-30 rpm, for example, 10 rpm, 15 rpm, 20 rpm, 25 rpm or 30 rpm.

[0042] Preferably, the preparation method comprises the following steps:

[0043] (1) A workpiece is provided and clamped by a clamping fixture in a vertical reaction chamber. The rotating shaft is then driven by a driving shaft to rotate, thereby driving the workpiece to rotate at a speed of 10-30 rpm.

[0044] (2) The vertical reaction chamber is heated to 1400-1500° C., and then a mixture of reaction gas, carrier gas, doping gas and dilution gas is introduced into the vertical reaction chamber through an air inlet plate and an air uniforming plate. The flow direction of the gas is kept parallel to the workpiece, and the chamber pressure is maintained at 20-100 Torr. Chemical vapor deposition is performed to deposit a silicon carbide film on the workpiece.

[0045] Wherein, the reaction gas includes a silicon source precursor and a carbon source precursor in a molar ratio of (1-5):1, the carrier gas includes hydrogen, and the volume flow ratio of the carrier gas to the reaction gas is (10-20):1; the volume flow ratio of the doping gas to the reaction gas is (0.5-7):1, and the volume flow ratio of the dilution gas to the reaction gas is (1-5):1 (for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1, etc.).

[0046] In a third aspect, the present invention provides a silicon carbide film, which is prepared by the preparation method described in the second aspect.

[0047] Preferably, the resistivity of the silicon carbide film is less than 550mΩ·cm, for example, it may be 500mΩ·cm, 200mΩ·cm or 100mΩ·cm, etc., preferably less than 100mΩ·cm, for example, it may be 90mΩ·cm, 80mΩ·cm, 70mΩ·cm, 60mΩ·cm, 50mΩ·cm, 40mΩ·cm, 30mΩ·cm, 20mΩ·cm or 10mΩ·cm, etc., and further preferably less than 5mΩ·cm.

[0048] Preferably, the defect density of the silicon carbide film is less than 30 / cm 2 , for example, it can be 25 / cm 2 , 20 pieces / cm 2 , 15 pieces / cm 2 or 10 / cm 2 etc., preferably <10 / cm 2 , for example, it can be 9 / cm 2 , 8 pieces / cm 2 , 7 pieces / cm 2 , 6 pieces / cm 2 , 5 pieces / cm 2 , 4 pieces / cm 2 , 3 pieces / cm 2 , 2 pieces / cm 2 or 1 / cm 2 wait.

[0049] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) In the preparation device designed by the present invention, chemical vapor deposition is performed using a vertical reaction chamber with more consistent heat convection and gas diffusion directions, so that the vapor deposition is more uniform. In the vertical reaction chamber, the workpiece is kept parallel to the flow direction of the gas introduced, so that the gas flows along the surface of the workpiece, forming a parallel flow boundary layer without significant stagnation points, thereby allowing the gas to stay on the surface of the workpiece for a longer time, which is conducive to the full reaction of the reactants and more likely to form a uniformly oriented organizational structure. Therefore, the preparation device can achieve uniform silicon carbide film deposition, so that the surface flatness of the prepared silicon carbide film is high, the height difference is small, and the film thickness uniformity reaches within ±2%. In addition, when the silicon carbide film is growing, the orientation density of the (220) crystal plane can reach up to 100%, which can effectively suppress the defects such as micro cracks and holes generated in the SiC film due to the different orientations of the grains of the silicon carbide film during growth, and the defect density is low.

[0052] (2) The silicon carbide film provided by the present invention has advantages such as high thickness uniformity, high conductivity, and low defect density, which can significantly improve the performance and service life of devices. The silicon carbide film is suitable for semiconductor tooling with high purity requirements, as well as high-temperature components with strict requirements on the thermal shock resistance and durability of the silicon carbide film. It can also be used in workpieces such as polycrystalline silicon carbide composite wafers and etching rings in semiconductor etching machines, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 Schematic diagram of a device provided in one embodiment of the present invention.

[0054] Figure 2 Schematic diagram of an air inlet assembly provided in one embodiment of the present invention.

[0055] Figure 3 This is the XRD pattern of the silicon carbide film provided in Example 3 of the present invention.

[0056] Figure 4 This is a surface SEM image of the silicon carbide film provided in Example 3 of the present invention.

[0057] Figure 5 This is a cross-sectional SEM image of the silicon carbide film provided in Example 3 of the present invention.

[0058] Figure 6 Schematic diagram of the structural defect density of the silicon carbide film provided in Example 3 of the present invention.

[0059] Figure 7 This is a schematic diagram of any structural defect in the silicon carbide film provided in Example 3 of the present invention.

[0060] Among them, 1-vertical reaction chamber; 2-air inlet assembly; 21-air inlet plate; 22-air inlet hole; 23-air uniform plate; 24-air uniform hole; 3-air outlet; 4-clamping tool; 41-drive shaft; 42-auxiliary shaft; 43-rotation axis; 5-workpiece. DETAILED DESCRIPTION

[0061] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0062] It should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0063] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0064] In a specific embodiment, the present invention provides a device for preparing a silicon carbide film, the schematic diagram of the device is as follows: Figure 1 Shown, including:

[0065] A vertical reaction chamber 1 is provided with an air inlet assembly 2 at the top of the vertical reaction chamber 1 and an air outlet 3 at the bottom of the vertical reaction chamber.

[0066] The clamping tool 4 is located in the vertical reaction chamber 1 and is used to clamp the workpiece 5 so that the workpiece 5 is parallel to the flow direction of the introduced gas.

[0067] A traditional horizontal reaction chamber may experience a decrease in deposition rate downstream of the airflow, seriously affecting the consistency of the film. In addition, in the traditional vapor deposition process, the flow direction of the airflow is perpendicular to the surface of the workpiece 5. At this time, the airflow directly impacts the substrate surface. The airflow direction may bring a higher impact effect, resulting in more efficient diffusion of the precursor gas on the substrate surface, but at the same time, a stagnation point area may be generated. There is a stagnation point in the center of the substrate (the flow rate approaches zero), which is prone to oversaturation and induces dendrite growth, resulting in local oversaturation, uneven deposition, and poor consistency of the organizational structure.

[0068] The present invention uses a vertical reaction chamber 1 for chemical vapor deposition. Since the existence of gravity may affect the sedimentation of particles, particle contamination is effectively prevented. In addition, the vertical reaction chamber 1 may be more suitable for uniform deposition because the heat convection and gas diffusion directions are more consistent. In addition, the vertical reaction chamber 1 keeps the workpiece 5 parallel to the flow direction of the gas introduced, so that the gas flows along the surface of the workpiece 5, forming a parallel flow boundary layer without significant stagnation points, thereby making the gas stay on the surface of the workpiece 5 for a longer time, which is conducive to the full reaction of the reactants and more likely to form a uniformly oriented organizational structure. Therefore, the preparation device can achieve uniform silicon carbide film deposition, so that the prepared silicon carbide film has the advantages of high thickness uniformity, high conductivity and low defect density. The film thickness uniformity reaches within ±2%, and the orientation density of the (220) crystal plane can reach up to 100%, which significantly improves the performance and service life of the device and meets the needs of the semiconductor industry.

[0069] Furthermore, the schematic diagram of the air inlet assembly 2 is as follows Figure 2 Shown, including:

[0070] An air intake plate 21 is provided with a plurality of air intake holes 22 .

[0071] The air uniforming plate 23 is located below the air inlet plate 21 and above the workpiece 5 , and a plurality of air uniforming holes 24 are distributed on the air uniforming plate 23 .

[0072] In the present invention, the combined design of the air inlet plate 21 and the air uniforming plate 23 is provided to ensure uniform distribution of the gas in the chamber.

[0073] It should be noted that “several” refers to at least one, for example, it can be 1, 5, 10, or 20, etc.

[0074] Furthermore, the density of the air inlet holes 22 on the air inlet plate 21 is smaller than the density of the air uniforming holes 24 on the air uniforming plate 23 .

[0075] In the present invention, the density of the air inlet holes 22 on the air inlet plate 21 is limited to be smaller than the density of the air uniforming holes 24 on the air uniforming plate 23, which helps to achieve uniform deposition distribution of gas on the surface of the workpiece 5 and provide uniform thickness of the silicon carbide film.

[0076] Furthermore, the diameter of the air inlet hole 22 on the air inlet plate 21 is larger than the diameter of the air uniforming hole 24 on the air uniforming plate 23 .

[0077] In the present invention, the diameter of the air inlet hole 22 on the air inlet plate 21 is limited to be larger than the diameter of the air uniform hole 24 on the air uniform plate 23, which helps to achieve uniform deposition distribution of gas on the surface of the workpiece 5 and provide uniform thickness of the silicon carbide film.

[0078] Furthermore, the air-distributing plate 23 has at least one layer, for example, 1 layer, 2 layers, or 3 layers.

[0079] Furthermore, the material of the air inlet plate 21 and the air uniforming plate 23 includes graphite.

[0080] Furthermore, the clamping tool 4 includes:

[0081] A driving shaft 41 , one end of which is vertically connected to the bottom of the vertical reaction chamber 1 . Exemplarily, the driving shaft includes a first end, which is fixedly connected to the bottom of the vertical reaction chamber 1 .

[0082] The auxiliary shaft 42 is parallel to the horizontal plane and vertically connected to the drive shaft 41, and is used to clamp or restrain the workpiece 5. Exemplarily, the drive shaft further includes a second end, wherein the first end and the second end are located at opposite ends of the drive shaft in the axial direction, and the first end and the second end are fixedly connected by a connecting rod. The auxiliary shaft is fixed to the second end, and the portion of the drive shaft connected to the auxiliary shaft does not rotate.

[0083] The rotating shaft 43 is parallel to the horizontal plane and vertically connected to the driving shaft 41 through gear meshing, and is used to drive the workpiece 5 to rotate in the vertical direction.

[0084] It should be noted that the present application does not limit the number of drive shafts 41. For example, the number of drive shafts 41 includes two, the two drive shafts 41 are arranged at intervals, and the gap between the auxiliary shafts 42 on the two drive shafts 41 is used to clamp or limit the workpiece; the number of drive shafts 41 can also include one or more than two. When the number of drive shafts 41 is one, the second end of the drive shaft 41 is connected to auxiliary shafts 42 on both sides along the radial direction, and the gap between the two auxiliary shafts 42 is used to clamp or limit the workpiece.

[0085] Exemplarily, the drive shaft further includes a rotating portion, which is sleeved on the connecting rod. The rotating portion is rotatable relative to the connecting rod, and the rotating shaft is meshedly connected with the rotating portion gear.

[0086] In other examples, the preparation apparatus further includes a drive member disposed outside the vertical reaction chamber, the drive member being in driving connection with a first end of a drive shaft, which is gear-engaged with a rotating shaft. The drive shaft further includes a hollow sleeve that securely connects a second end of the drive shaft to the vertical reaction chamber, with the first end disposed within the sleeve. Optionally, the sleeve has an opening that exposes at least a region of the first end that meshes with the rotating shaft.

[0087] It should be noted that the number of auxiliary shafts 42 is not limited, and for example, there can be two, etc. The number of rotating shafts 43 is not limited, and for example, there can be two, etc.

[0088] Furthermore, the rotation speed of the rotating shaft 43 is 10-30 rpm, for example, it can be 10 rpm, 15 rpm, 20 rpm, 25 rpm or 30 rpm.

[0089] The present invention uses a rotating shaft 43 with a suitable rotation speed to drive the workpiece 5 to rotate, which can effectively improve the uniformity of the deposition thickness of the silicon carbide film.

[0090] Furthermore, the preparation device also includes three groups of independent heating components, which are arranged corresponding to the top, middle and bottom of the vertical reaction chamber 1 respectively.

[0091] In the present invention, a plurality of independent heating components are provided for heating, and the temperature of several areas can be independently adjusted according to different deposition processes to ensure temperature uniformity.

[0092] In another specific embodiment, the present invention provides a method for preparing a silicon carbide thin film, wherein the method uses the preparation apparatus described above and comprises the following steps:

[0093] A workpiece is provided and clamped by a clamping fixture.

[0094] Reaction gas and carrier gas are introduced into the vertical reaction chamber through the gas inlet assembly, and the flow direction of the gas is kept parallel to the workpiece to perform chemical vapor deposition, so that a silicon carbide film is deposited on the workpiece.

[0095] The preparation method provided by the present invention can ensure that the growth direction of the silicon carbide film is only one as much as possible, inhibit the defects such as micro cracks and micro holes generated in the silicon carbide film due to the different orientations of the grains during growth, and improve the thickness uniformity and conductivity of the film deposition.

[0096] It should be noted that the present invention does not impose any specific limitation on the shape of the workpiece, and for example, the workpiece may be in various shapes such as square, circular, cylindrical, etc. Furthermore, the present invention does not impose any specific limitation on the size of the workpiece.

[0097] It should be noted that the present invention does not specifically limit the thickness of the silicon carbide film. For example, it can be in the range of 50 μm to 1 mm, such as 50 μm, 100 μm, or 1 mm. The deposition time of the silicon carbide film depends on the deposition thickness of the silicon carbide. For example, it can be in the range of 1-50 hours, such as 1 hour, 10 hours, or 50 hours.

[0098] Furthermore, the reaction gas is silicon carbide vapor deposition raw material gas or silicon carbide synthesis gas source.

[0099] Furthermore, the silicon carbide vapor deposition raw material gas includes trichloromethylsilane and / or methylsilane.

[0100] Furthermore, the silicon carbide synthesis gas source includes a silicon source precursor and a carbon source precursor.

[0101] Furthermore, the silicon source precursor includes any one of silicon tetrachloride, trichlorosilane or dichlorosilane, or a combination of at least two thereof, preferably silicon tetrachloride.

[0102] Furthermore, the carbon source precursor includes any one of methane, ethylene or propane, or a combination of at least two of them, preferably methane.

[0103] Furthermore, the molar ratio of the silicon source precursor to the carbon source precursor is (1-5):1, for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1.

[0104] Furthermore, the carrier gas includes hydrogen.

[0105] Furthermore, the volume flow ratio of the carrier gas to the reaction gas is (1-5):1, for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1.

[0106] Furthermore, during the process of introducing the silicon source precursor, the carbon source precursor and the carrier gas, doping gas and / or dilution gas are also introduced.

[0107] In the present invention, the introduction of dilution gas helps to ensure that the reaction gas is evenly distributed in the chamber, thereby reducing the thickness difference of the thin film deposition and improving the thickness uniformity.

[0108] Furthermore, the doping gas includes nitrogen or ammonia, preferably nitrogen.

[0109] Furthermore, the dilution gas includes hydrogen or argon, preferably hydrogen.

[0110] Furthermore, the volume flow ratio of the doping gas to the reaction gas is (0.5-7):1, for example, it can be 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1 or 7:1.

[0111] In the present invention, the introduction of doping gas such as nitrogen can effectively reduce the resistivity of the silicon carbide film and improve its conductivity.

[0112] Furthermore, during the chemical vapor deposition process, the deposition temperature is 1400-1500° C., for example, 1400° C., 1450° C., or 1500° C.

[0113] Furthermore, during the chemical vapor deposition process, the chamber pressure is 20-100 Torr, for example, 20 Torr, 30 Torr, 40 Torr, 50 Torr, 60 Torr, 70 Torr, 80 Torr, 90 Torr or 100 Torr, etc., preferably 40-60 Torr.

[0114] Furthermore, during the chemical vapor deposition process, the rotation speed of the workpiece is 10-30 rpm, for example, it can be 10 rpm, 15 rpm, 20 rpm, 25 rpm or 30 rpm.

[0115] Furthermore, the preparation method comprises the following steps:

[0116] (1) A workpiece is provided and clamped by a clamping fixture in a vertical reaction chamber. The rotating shaft is then driven by a driving shaft to rotate, thereby driving the workpiece to rotate at a speed of 10-30 rpm.

[0117] (2) The vertical reaction chamber is heated to 1400-1500° C., and then a mixture of reaction gas, carrier gas, doping gas and dilution gas is introduced into the vertical reaction chamber through an air inlet plate and an air uniforming plate. The flow direction of the gas is kept parallel to the workpiece, and the chamber pressure is maintained at 20-100 Torr. Chemical vapor deposition is performed to deposit a silicon carbide film on the workpiece.

[0118] Among them, the reaction gas includes a silicon source precursor and a carbon source precursor in a molar ratio of (1-5):1, the carrier gas includes hydrogen, and the volume flow ratio of the carrier gas to the reaction gas is (1-5):1; the volume flow ratio of the doping gas to the reaction gas is (0.5-7):1, and the volume flow ratio of the dilution gas to the reaction gas is (1-5):1 (for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1, etc.).

[0119] In another specific embodiment, the present invention provides a silicon carbide film, which is prepared using the preparation method described above.

[0120] Furthermore, the resistivity of the silicon carbide film is less than 550mΩ·cm, for example, it may be 500mΩ·cm, 200mΩ·cm or 100mΩ·cm, etc., preferably less than 100mΩ·cm, for example, it may be 90mΩ·cm, 80mΩ·cm, 70mΩ·cm, 60mΩ·cm, 50mΩ·cm, 40mΩ·cm, 30mΩ·cm, 20mΩ·cm or 10mΩ·cm, etc., and further preferably less than 5mΩ·cm.

[0121] Furthermore, the defect density of the silicon carbide film is less than 30 / cm 2 , for example, it can be 25 / cm 2 , 20 pieces / cm 2 , 15 pieces / cm 2 or 10 / cm 2 etc., preferably <10 / cm 2 , for example, it can be 9 / cm 2 , 8 pieces / cm 2 , 7 pieces / cm 2 , 6 pieces / cm 2 , 5 pieces / cm 2 , 4 pieces / cm 2 , 3 pieces / cm 2 , 2 pieces / cm 2 or 1 / cm 2 wait.

[0122] 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.

[0123] Example 1

[0124] This embodiment provides a method for preparing a silicon carbide thin film, the method comprising the following steps:

[0125] (1) A workpiece is provided and clamped by a clamping fixture in a vertical reaction chamber. Then, a driving shaft drives a rotating shaft to rotate, thereby driving the workpiece to rotate at a speed of 30 rpm.

[0126] Wherein, the workpiece is isostatically pressed graphite.

[0127] (2) The vertical reaction chamber is heated to 1400°C, and then a mixture of reaction gas, carrier gas, doping gas and dilution gas is introduced into the vertical reaction chamber through an air inlet plate and an air uniforming plate. The flow direction of the gas is kept parallel to the workpiece, and the chamber pressure is maintained at 50 Torr. Chemical vapor deposition is performed to deposit a silicon carbide film on the workpiece. After deposition for 10 hours, the introduction of the mixed gas is stopped, and the temperature is naturally lowered to obtain a silicon carbide film with a thickness of 300 μm.

[0128] Among them, the reaction gas includes silicon tetrachloride (flow rate of 10 slm) and methane (flow rate of 2.5 slm) with a molar ratio of 4:1, the carrier gas is hydrogen with a flow rate of 25 slm, and the volume flow ratio of the carrier gas to the reaction gas is 2:1; the doping gas is nitrogen with a flow rate of 10 slm, and the volume flow ratio of the doping gas to the reaction gas is 0.8:1; the dilution gas is hydrogen with a flow rate of 25 slm, and the volume flow ratio of the dilution gas to the reaction gas is 2:1.

[0129] Example 2

[0130] This embodiment provides a method for preparing a silicon carbide thin film, the method comprising the following steps:

[0131] (1) A workpiece is provided and clamped by a clamping fixture in a vertical reaction chamber. Then, a driving shaft drives a rotating shaft to rotate, thereby driving the workpiece to rotate at a speed of 30 rpm.

[0132] Wherein, the workpiece is isostatically pressed graphite.

[0133] (2) The vertical reaction chamber is heated to 1450°C, and then a mixture of reaction gas, carrier gas, doping gas and dilution gas is introduced into the vertical reaction chamber through an air inlet plate and an air uniforming plate. The flow direction of the gas is kept parallel to the workpiece, and the chamber pressure is maintained at 50 Torr. Chemical vapor deposition is performed to deposit a silicon carbide film on the workpiece. After 10 hours of deposition, the introduction of the mixed gas is stopped, and the temperature is naturally lowered to obtain a silicon carbide film with a thickness of 300 μm.

[0134] Among them, the reaction gas includes silicon tetrachloride (flow rate of 10 slm) and methane (flow rate of 2.5 slm) with a molar ratio of 4:1, the carrier gas is hydrogen with a flow rate of 25 slm, and the volume flow ratio of the carrier gas to the reaction gas is 2:1; the doping gas is nitrogen with a flow rate of 10 slm, and the volume flow ratio of the doping gas to the reaction gas is 0.8:1; the dilution gas is hydrogen with a flow rate of 25 slm, and the volume flow ratio of the dilution gas to the reaction gas is 2:1.

[0135] Example 3

[0136] This embodiment provides a method for preparing a silicon carbide thin film, the method comprising the following steps:

[0137] (1) A workpiece is provided and clamped by a clamping fixture in a vertical reaction chamber. Then, a driving shaft drives a rotating shaft to rotate, thereby driving the workpiece to rotate at a speed of 30 rpm.

[0138] Wherein, the workpiece is isostatically pressed graphite.

[0139] (2) The vertical reaction chamber is heated to 1500°C, and then a mixture of reaction gas, carrier gas, doping gas and dilution gas is introduced into the vertical reaction chamber through an air inlet plate and an air uniforming plate. The flow direction of the gas is kept parallel to the workpiece, and the chamber pressure is maintained at 50 Torr. Chemical vapor deposition is performed to deposit a silicon carbide film on the workpiece. After 10 hours of deposition, the introduction of the mixed gas is stopped, and the temperature is naturally lowered to obtain a silicon carbide film with a thickness of 300 μm.

[0140] Among them, the reaction gas includes silicon tetrachloride (flow rate of 10 slm) and methane (flow rate of 2.5 slm) with a molar ratio of 4:1, the carrier gas is hydrogen with a flow rate of 25 slm, and the volume flow ratio of the carrier gas to the reaction gas is 2:1; the doping gas is nitrogen with a flow rate of 10 slm, and the volume flow ratio of the doping gas to the reaction gas is 0.8:1; the dilution gas is hydrogen with a flow rate of 25 slm, and the volume flow ratio of the dilution gas to the reaction gas is 2:1.

[0141] Figure 3 The XRD pattern of the silicon carbide film prepared in this embodiment is shown. It can be seen from the figure that the prepared SiC film has a single (220) orientation and the orientation density of the (220) crystal plane reaches 100%.

[0142] Figure 4 The surface SEM image of the silicon carbide film prepared in this embodiment is shown. As can be seen from the image, the surface of the silicon carbide film has a hilly morphology.

[0143] Figure 5 The cross-sectional SEM image of the silicon carbide film prepared in this embodiment is shown. As can be seen from the image, the cross-sectional view of the silicon carbide film presents a microstructure growing in a single direction.

[0144] Figure 6 and Figure 7 A schematic diagram of the structural defect density of the silicon carbide film prepared in this embodiment and a schematic diagram of any structural defect in the silicon carbide film are shown respectively. It can be seen from the figure that the structural defect density of the silicon carbide film is low, and the defects are small closed holes.

[0145] Example 4

[0146] This embodiment provides a method for preparing a silicon carbide thin film, the method comprising the following steps:

[0147] (1) A workpiece is provided and clamped by a clamping fixture in a vertical reaction chamber. Then, a driving shaft drives a rotating shaft to rotate, thereby driving the workpiece to rotate at a speed of 30 rpm.

[0148] Wherein, the workpiece is isostatically pressed graphite.

[0149] (2) The vertical reaction chamber is heated to 1500°C, and then a mixture of reaction gas, carrier gas, doping gas and dilution gas is introduced into the vertical reaction chamber through an air inlet plate and an air uniforming plate. The flow direction of the gas is kept parallel to the workpiece, and the chamber pressure is maintained at 100 Torr. Chemical vapor deposition is performed to deposit a silicon carbide film on the workpiece. After deposition for 10 hours, the introduction of the mixed gas is stopped, and the temperature is naturally lowered to obtain a silicon carbide film with a thickness of 300 μm.

[0150] Among them, the reaction gas includes silicon tetrachloride (flow rate of 10 slm) and methane (flow rate of 2.5 slm) with a molar ratio of 4:1, the carrier gas is hydrogen with a flow rate of 25 slm, and the volume flow ratio of the carrier gas to the reaction gas is 2:1; the doping gas is nitrogen with a flow rate of 10 slm, and the volume flow ratio of the doping gas to the reaction gas is 0.8:1; the dilution gas is hydrogen with a flow rate of 25 slm, and the volume flow ratio of the dilution gas to the reaction gas is 2:1.

[0151] Example 5

[0152] The difference between this embodiment and embodiment 3 is that the chamber pressure is 10 Torr.

[0153] The rest of the preparation methods and parameters remained the same as in Example 3.

[0154] Example 6

[0155] The difference between this embodiment and embodiment 3 is that the doping gas is nitrogen with a flow rate of 101 slm, and the volume flow ratio of the doping gas to the reaction gas is 8:1.

[0156] The rest of the preparation methods and parameters remained the same as in Example 3.

[0157] Example 7

[0158] The difference between this embodiment and embodiment 3 is that the deposition temperature is 1300°C.

[0159] The rest of the preparation methods and parameters remained the same as in Example 3.

[0160] Example 8

[0161] The difference between this embodiment and embodiment 3 is that the mixed gas does not contain the doping gas.

[0162] The rest of the preparation methods and parameters remained the same as in Example 3.

[0163] Example 9

[0164] The difference between this embodiment and embodiment 3 is that the deposition temperature is 1600°C.

[0165] The rest of the preparation methods and parameters remained the same as in Example 3.

[0166] Comparative Example 1

[0167] The difference between this comparative example and Example 3 is that the vertical reaction chamber is replaced by a horizontal reaction chamber, so that the workpiece is perpendicular to the flow direction of the introduced mixed gas.

[0168] The rest of the preparation methods and parameters remained the same as in Example 3.

[0169] Performance Testing

[0170] The silicon carbide films prepared in the above examples and comparative examples were tested, including:

[0171] Resistivity test: carried out using LEI-1510EC eddy current square resistance meter; defect density test: carried out using E3500 surface defect detector; crystal plane orientation test: using XRD test method, by testing the diffraction peak integral intensity of different crystal planes, combined with the standard card data of the corresponding phase in the PDF card, calculate the orientation ratio of the (220) crystal plane.

[0172] The test results are shown in Table 1.

[0173] Table 1

[0174]

[0175] analyze:

[0176] Chemical vapor deposition is carried out in the preparation device designed by the present invention, which can achieve uniform silicon carbide film deposition, so that the surface flatness of the prepared silicon carbide film is high, the height difference is small, and the film thickness uniformity reaches within ±2%. In addition, when the silicon carbide film is growing, the orientation density of the (220) crystal plane can reach up to 100%, which can effectively suppress the generation of tiny cracks, holes and other defects in the SiC film due to the different orientations of the grains of the silicon carbide film during growth. The defect density is low and the conductive performance is excellent.

[0177] From the comparison between Example 3 and Example 5, it can be seen that if the chamber pressure is too low, the reaction gas residence time during the crystal growth process is too short, and the reaction gas is taken out of the reaction area before it has time to fully react, resulting in an increase in hole defects, which leads to a significant increase in the defect density of the silicon carbide film, and the orientation density of the (220) crystal plane drops to 65%.

[0178] From the comparison between Example 3 and Example 6, it can be seen that if the volume flow ratio of the doping gas to the reaction gas is too large, that is, the flow rate of the doping gas is too large, the concentration of the reaction gas required for the crystal growth process is insufficient, and it is more likely that unfilled areas will appear during the growth process, forming more void defects, thereby causing a sharp increase in the defect density of the silicon carbide film from 1.1 / cm 2 Increased to 173.5 / cm 2 , while the orientation density of the (220) crystal plane dropped to 47%.

[0179] By comparing Example 3 with Example 7 and Example 9, it can be seen that if the deposition temperature is too low, the NN bond is difficult to break and the N atom doping is small, which causes the resistivity of the silicon carbide film to increase sharply from 4.3mΩ·cm to 15000mΩ·cm, a significant change, and the defect density and the orientation density of the (220) crystal plane are significantly deteriorated; if the deposition temperature is too high, the crystal structure growth changes from a single orientation growth mode to a multi-orientation growth mode, which leads to a significant increase in the defect density.

[0180] From the comparison between Example 3 and Example 8, it can be seen that if the mixed gas does not contain doping gas, the silicon carbide film structure lacks carriers introduced by N atom doping, resulting in a significant increase in the resistivity of the silicon carbide film, which is not conducive to improving its conductive performance.

[0181] By comparing Example 3 with Comparative Example 1, it can be seen that if chemical vapor deposition of a silicon carbide film is carried out in a horizontal reaction chamber, the deposition rate may decrease downstream of the airflow, seriously affecting the consistency of the film. At the same time, a stagnation point area may be generated. There is a stagnation point in the center of the substrate (the flow rate approaches zero), which is prone to oversaturation and triggering dendrite growth, resulting in local oversaturation, uneven deposition, poor consistency of the organizational structure, and ultimately causing the conductivity of the silicon carbide film to decrease, defects to increase, and poor thickness uniformity.

[0182] It should be noted that while the present invention illustrates the process method through the above-described embodiments, the present invention is not limited to the above-described process steps, and does not necessarily rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent replacements for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A device for preparing a silicon carbide thin film, characterized in that: The preparation device comprises: A vertical reaction chamber, wherein the top of the vertical reaction chamber is provided with an air inlet assembly, and the bottom of the vertical reaction chamber is provided with an air outlet; A clamping tool is located in the vertical reaction chamber and is used to clamp a workpiece so that the workpiece is parallel to the flow direction of the introduced gas.

2. The preparation device according to claim 1, characterized in that The air inlet assembly comprises: An air intake plate, wherein a plurality of air intake holes are distributed on the air intake plate; An air-distributing plate, the air-distributing plate being located below the air inlet plate and above the workpiece, and having a plurality of air-distributing holes distributed on the air-distributing plate; Preferably, the density of the air inlet holes on the air inlet plate is smaller than the density of the air uniforming holes on the air uniforming plate; Preferably, the aperture of the air inlet hole on the air inlet plate is larger than the aperture of the air uniformity hole on the air uniformity plate; Preferably, the air-distributing plate has at least one layer; Preferably, the material of the air inlet plate and the air uniforming plate includes graphite.

3. The preparation device according to claim 1 or 2, characterized in that: The clamping tool comprises: a driving shaft, one end of which is vertically connected to the bottom of the vertical reaction chamber; an auxiliary shaft, the auxiliary shaft being parallel to the horizontal plane and vertically connected to the driving shaft, and being used for clamping or restraining a workpiece; A rotating shaft, parallel to the horizontal plane and vertically connected to the driving shaft by gear meshing, for driving the workpiece to rotate in a vertical direction; Preferably, the rotation speed of the rotating shaft is 10-30 rpm.

4. The preparation device according to any one of claims 1 to 3, characterized in that: The preparation device also includes three groups of independent heating components, which are arranged corresponding to the top, middle and bottom of the vertical reaction chamber respectively.

5. A method for preparing a silicon carbide film, characterized in that: The preparation method uses the preparation device according to any one of claims 1 to 4, and the preparation method comprises the following steps: Providing a workpiece, and clamping the workpiece by a clamping tool; Reaction gas and carrier gas are introduced into the vertical reaction chamber through the gas inlet assembly, and the flow direction of the gas is kept parallel to the workpiece to perform chemical vapor deposition, so that a silicon carbide film is deposited on the workpiece.

6. The preparation method according to claim 5, characterized in that The reaction gas is silicon carbide vapor deposition raw gas or silicon carbide synthesis gas source; Preferably, the silicon carbide vapor deposition raw material gas includes trichloromethylsilane and / or methylsilane; Preferably, the silicon carbide synthesis gas source includes a silicon source precursor and a carbon source precursor; Preferably, the silicon source precursor includes any one of silicon tetrachloride, trichlorosilane or dichlorosilane, or a combination of at least two thereof, preferably silicon tetrachloride; Preferably, the carbon source precursor includes any one of methane, ethylene or propane or a combination of at least two thereof, preferably methane; Preferably, the molar ratio of the silicon source precursor to the carbon source precursor is (1-5):1; Preferably, the carrier gas comprises hydrogen; Preferably, the volume flow ratio of the carrier gas to the reaction gas is (1-5):1; Preferably, during the process of introducing the silicon source precursor, the carbon source precursor and the carrier gas, a doping gas and / or a diluent gas is also introduced; Preferably, the doping gas includes nitrogen or ammonia; Preferably, the dilution gas comprises hydrogen or nitrogen; Preferably, the volume flow ratio of the doping gas to the reaction gas is (0.5-7):

1.

7. The preparation method according to claim 5 or 6, characterized in that: During the chemical vapor deposition process, the deposition temperature is 1400-1500° C.; Preferably, during the chemical vapor deposition process, the chamber pressure is 20-100 Torr, preferably 40-60 Torr; Preferably, during the chemical vapor deposition process, the rotation speed of the workpiece is 10-30 rpm.

8. The preparation method according to any one of claims 5 to 7, characterized in that The preparation method comprises the following steps: (1) providing a workpiece, clamping the workpiece by a clamping fixture in a vertical reaction chamber, and then driving a rotating shaft to rotate by a driving shaft, thereby driving the workpiece to rotate at a speed of 10-30 rpm; (2) heating the vertical reaction chamber to 1400-1500° C., then introducing a mixture of reaction gas, carrier gas, doping gas, and dilution gas into the vertical reaction chamber through an inlet plate and a uniform gas plate, with the gas flow direction parallel to the workpiece and the chamber pressure maintained at 20-100 Torr, to perform chemical vapor deposition, so that a silicon carbide film is deposited on the workpiece; Wherein, the reaction gas includes a silicon source precursor and a carbon source precursor in a molar ratio of (1-5):1, the carrier gas includes hydrogen, and the volume flow ratio of the carrier gas to the reaction gas is (1-5):1; the volume flow ratio of the doping gas to the reaction gas is (0.5-7):1, and the volume flow ratio of the dilution gas to the reaction gas is (1-5):

1.

9. A silicon carbide film, characterized in that: The silicon carbide film is prepared by the preparation method according to any one of claims 5 to 8.

10. The silicon carbide thin film according to claim 9, wherein The resistivity of the silicon carbide film is less than 550 mΩ·cm, preferably less than 100 mΩ·cm, and more preferably less than 5 mΩ·cm; Preferably, the defect density of the silicon carbide film is less than 30 / cm 2 , preferably <10 / cm 2 .

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