Silicon carbide epitaxial growth equipment and method

Abstract

The invention provides silicon carbide epitaxial growth equipment and a silicon carbide epitaxial growth method. According to the growth equipment, a gas supply system comprises a first flow control module and a second flow control module which are respectively connected with a control module; the epitaxial growth module comprises a shell, the top of the shell is provided with a spraying device, the spraying device comprises a first gas supply area and a second gas supply area surrounding the first gas supply area, the first gas supply area and the second gas supply area respectively comprise a plurality of ventilation holes, and the first gas supply area and the second gas supply area are respectively connected to a gas supply system through pipelines. Based on the first flow control module and the second flow control module, the gas amount / or the carbon-silicon ratio of the matched and corresponding first gas supply area / second gas supply area is controlled, and the bottom side in the shell is provided with a bearing disc which is used for placing a substrate and is arranged opposite to the spraying device. The spraying device is partitioned, and the amount of gas introduced into the air holes of each region can be controlled to improve the N doping concentration uniformity of the epitaxial layer of epitaxial growth of silicon carbide.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor deposition technology, and in particular to a silicon carbide epitaxial growth device and method. Background Art

[0002] Silicon carbide (SiC) material has great application prospects in new energy vehicles, high-voltage power transmission, aerospace and other fields due to its excellent material physical properties, such as wide bandgap, high electron mobility and strong radiation resistance.

[0003] Different from the traditional Si process route, SiC electronic power devices are all realized on the homoepitaxial layer, and the substrate only plays a supporting and conductive role. Therefore, SiC epitaxial equipment is an indispensable part of the entire industry chain. Chemical vapor deposition (CVD) is a common technology for preparing high-quality SiC homoepitaxial layers. According to the direction of the flow field inside the cavity, SiC-CVD equipment is divided into horizontal and vertical types. Compared with the former, vertical CVD equipment has greater advantages in surface defect control, reducing concentration drift between furnaces, extending maintenance cycles, and improving production efficiency.

[0004] N doping concentration uniformity is an important parameter for judging the performance of SiC epitaxial wafers. Good N doping concentration uniformity within the epitaxial wafer can not only reduce the discreteness of device performance, but also improve the reliability of the device. However, the current CVD equipment and epitaxial growth methods still have poor N doping concentration uniformity, which seriously affects the product yield. Summary of the invention

[0005] The purpose of the present invention is to provide a silicon carbide epitaxial growth device and (epitaxial growth) method to solve the problem of poor uniformity of N doping concentration in silicon carbide epitaxial growth in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a silicon carbide epitaxial growth device, comprising:

[0008] Control module, gas supply system and epitaxial growth module,

[0009] The gas supply system comprises a first flow control module and a second flow control module, which are electrically connected to the control module respectively;

[0010] The epitaxial growth module comprises: a housing,

[0011] The housing is provided with a graphite cylinder and a side wall heater surrounding the graphite cylinder and located outside the graphite cylinder and extending along the axis of the graphite cylinder.

[0012] A spray device is provided on the top of the shell, and the spray device includes a first air supply area and a second air supply area surrounding the first air supply area, and each of the spray device includes a plurality of air holes, and the air holes include a first air hole and a second air hole that are sleeved, and the first air supply area and the second air supply area are respectively connected to the gas supply system through pipelines, and the gas amount / or carbon-silicon ratio passing into the first air supply area is controlled based on a first flow control module, and the gas amount / or carbon-silicon ratio passing into the second air supply area is controlled based on a second flow control module.

[0013] A carrier plate for placing a substrate is provided at the bottom side of the shell, and the carrier plate is arranged opposite to the spray device and connected to a support portion, a bottom heater is provided in the support portion, and the support portion is connected to a driving device. The support portion is driven by the driving device to rotate and then the carrier plate is rotated, and the rotation of the carrier plate drives the substrate thereon to rotate. The structure of the spray device is improved by such a design, and the spray area is divided into zones, and the air holes in different zones correspond to different parts of the substrate surface. Then, by controlling the flow rate of hydrogen in the mixed gas and the ratio of the carbon source to the silicon source in the air holes in each zone, the uniformity of the N doping concentration of the epitaxial layer of the epitaxial growth of silicon carbide is improved.

[0014] Furthermore, the air holes include second air holes, which are arranged around the periphery of the first air holes, and the second air holes are used to introduce hydrogen into the reaction chamber; the first air holes are used to introduce a mixed gas of growth source gas and hydrogen into the vertical reaction chamber when the device is working, the growth source gas is a silicon source, a carbon source, hydrogen chloride and nitrogen, and the second air holes are used to introduce hydrogen into the vertical reaction chamber when the device is working, and the hydrogen introduced by the second air holes is a protective gas, and its flow rate is greater than that of the mixed gas introduced by the first air holes, because it can form a circle of protective layer around the mixed gas to prevent the growth source gas introduced by the first air hole from reacting with the residue on the side wall of the reaction chamber before flowing to the substrate surface.

[0015] Furthermore, the graphite cylinder is coaxially arranged with the shell, and a heat preservation component is also arranged in the shell, which is located outside the side wall heater. The spray device is equipped with an infrared temperature measuring component, which is used to detect the temperature of the reaction chamber in the shell.

[0016] The gas supply system includes a third flow control module, which is electrically connected to the control module.

[0017] The spray device has a third air supply area located outside the second air supply area, and has a plurality of air holes.

[0018] The gas amount and / or the carbon-silicon ratio introduced into the third gas supply area is controlled based on the third flow control module.

[0019] In a second aspect, the present invention further provides a method for epitaxial growth of silicon carbide, including an in-situ etching stage, including: introducing a mixed gas of hydrogen chloride and hydrogen into a reaction chamber based on a spray device, and in-situ etching a substrate placed in the reaction chamber by the mixed gas of hydrogen chloride and hydrogen;

[0020] Buffer layer growth stage, including:

[0021] A process gas having a first preset carbon-to-silicon ratio is introduced into the reaction chamber through a first air hole in the gas supply region of the spray device, and hydrogen is introduced into the reaction chamber through a second air hole to grow a buffer layer on the surface of the substrate;

[0022] The main layer growth stage includes:

[0023] Based on the first air permeable hole in the air supply area of ​​the spray device, a process gas including a second preset carbon-silicon ratio is introduced into the reaction chamber, and the second air permeable hole is introduced into the reaction chamber to introduce hydrogen gas, so as to grow a main layer of a preset thickness on the buffer layer to obtain a silicon carbide epitaxial wafer, wherein the second preset carbon-silicon ratio is greater than or equal to the first preset carbon-silicon ratio. In this way, different air supply areas are independently controlled, and the air permeable holes in different air supply areas correspond to different parts of the substrate surface, thereby improving the uniformity of the N doping concentration of the epitaxial layer of the silicon carbide epitaxial growth.

[0024] Preferably, during the growth stage of the main layer, the hydrogen flow rate of the second gas supply region entering the first gas permeable hole is greater than the hydrogen flow rate of the first gas supply region entering the first gas permeable hole, or the carbon-silicon ratio of the second gas supply region entering the first gas permeable hole is less than the carbon-silicon ratio of the first gas supply region entering the first gas permeable hole, or,

[0025] The spray device includes a first gas supply area, a second gas supply area and a third gas supply area, wherein the ratio of hydrogen introduced into the first gas holes in the first gas supply area, the second gas supply area and the third gas supply area is (11-15): (30-35): (32-36), or the carbon-silicon ratio introduced into the first gas holes in the first gas supply area, the second gas supply area and the third gas supply area is 0.9-1.1, 0.3-0.6 and 0.7-0.9. In this way, different gas supply areas are independently controlled, and the gas holes in different gas supply areas correspond to different parts of the substrate surface, thereby improving the uniformity of the N doping concentration of the epitaxial layer of the silicon carbide epitaxial growth.

[0026] Beneficial effects:

[0027] Through the silicon carbide epitaxial growth equipment proposed in this application, the structure of the spray device is improved, the spray area is divided into zones (multiple gas supply zones are set), air holes are set in each zone, and the structure of the air holes in different zones is optimized. The air holes in different zones correspond to different parts of the substrate surface, and then the hydrogen flow rate in the mixed gas passed through the air holes in each gas supply zone, and the carbon-silicon ratio of the carbon source and the silicon source are controlled to achieve the improvement of the uniformity of the N doping concentration of the epitaxial layer of the silicon carbide epitaxial growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A schematic cross-sectional view of an existing epitaxial growth module.

[0030] Figure 2 for Figure 1 Schematic diagram of the gas flow after gas is introduced into the gas flow.

[0031] Figure 3 It is a schematic structural diagram of an epitaxial growth module according to an embodiment of the present invention.

[0032] Figure 4 for Figure 3 Schematic diagram of the structure of the spray device.

[0033] Figure 5 It is a schematic structural diagram of a spray device according to another embodiment of the present invention.

[0034] Figure 5a for Figure 5 An enlarged schematic diagram of the air vents in FIG.

[0035] Figure 6 This is a schematic diagram of the functional modules of a spray device including three air supply areas in one embodiment of the present application.

[0036] Figure 7 FIG. 4 is a flow chart of a method for epitaxial growth of silicon carbide in one embodiment of the present invention.

[0037] Figure 8 This is a graph showing a trend of N doping concentration variation on the surface epitaxial layer of silicon carbide when the hydrogen flow rate is adjusted in another embodiment of the present invention.

[0038] Fig. 9 This is a graph showing a trend of N doping concentration changes in the epitaxial layer obtained by adjusting the C / Si ratio of the gas supply regions in another embodiment of the invention. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present invention are described below with reference to the drawings in the specification to prove that the present invention can be implemented. The embodiments of the invention can fully introduce the present invention to those skilled in the art, making its technical content clearer and easier to understand. The present invention can be embodied through many different forms of embodiments of the invention, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0040] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0041] In addition, the following descriptions of the various embodiments of the invention are made with reference to the attached diagrams to illustrate specific embodiments of the invention that the present invention can be implemented with. The directional terms mentioned in the present invention, such as "upper", "lower", "front", "back", "left", "right", "inner", "outer", "side", etc., are only with reference to the directions of the attached drawings. Therefore, the directional terms used are for better and clearer description and understanding of the present invention, rather than indicating or implying 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", "third", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0042] When some components are described as being "on" another component, the component may be directly placed on the other component; there may also be an intermediate component on which the component is placed, and the intermediate component is placed on the other component. When a component is described as being "mounted on" or "connected to" another component, the two may be understood to be directly "mounted on" or "connected", or one component may be indirectly "mounted on" or "connected to" another component via an intermediate component.

[0043] Overview

[0044] As described in the background technology, the N doping concentration uniformity of the silicon carbide epitaxial growth equipment is poor when performing silicon carbide epitaxial growth, which seriously affects the product yield. Figure 1As shown, a carrier plate 2 is arranged at the bottom of the reaction chamber 1 of the device, and the carrier plate 2 is connected to a rotating driving component (not shown), and the carrier plate 2 is driven to rotate based on the driving rotation of the driving component, and the rotation of the carrier plate 2 drives the substrate thereon to rotate, and a spray device 3 is arranged on the top side of the reaction chamber 1, and the air holes on the spray device 3 are connected to an external gas source through a pipeline (not shown). The substrate 7 (such as a silicon carbide substrate) is placed on the carrier plate 2, and epitaxial growth is performed using the growth source gas introduced through the air holes on the spray device 3. The current vertical airflow SiC epitaxial equipment still has problems such as difficulty in debugging and poor stability in terms of N doping concentration uniformity.

[0045] In view of the above problems, the inventors have improved the structure of the spray device. The preferred improvement of the structure of the spray device is to set the spray area in different zones, and the air holes in different zones correspond to different parts of the substrate surface. Then, the uniformity of the N doping concentration of the silicon carbide epitaxial layer is improved by controlling the hydrogen flow rate in the mixed gas and the carbon-silicon ratio of the carbon source and the silicon source in the air holes in each zone. The specifications of the substrate can be 4 inches, 6 inches or 8 inches.

[0046] Based on the above concept, the present application will be exemplarily described below in conjunction with the accompanying drawings.

[0047] Exemplary Structure

[0048] The present embodiment provides a silicon carbide epitaxial growth device. The silicon carbide epitaxial growth device includes a control module, a gas supply system and an epitaxial growth module. The gas supply system includes a first flow control module and a second flow control module (collectively referred to as flow control modules), which are electrically connected to the control module respectively.

[0049] The epitaxial growth module comprises: a shell, a graphite tube and a side wall heater surrounding the graphite tube and extending along the axis of the graphite tube on the outside thereof are arranged in the shell, and a reaction chamber (roughly a cavity surrounded by the graphite tube) is arranged in the shell. A spray device is arranged on the top of the shell, and the spray device comprises a first gas supply area and a second gas supply area surrounding the first gas supply area, and each of the spray devices comprises a plurality of air holes, each of which comprises a first air hole and a second air hole sleeved on the first air hole, and the first gas supply area and the second gas supply area are respectively connected to the gas supply system through pipelines (a flow meter can be arranged on the pipeline, which is electrically connected to a corresponding flow control module), the first flow control module controls the gas amount / or carbon-silicon ratio entering the first gas supply area, and the second flow control module controls the gas amount / or carbon-silicon ratio entering the second gas supply area, and a carrier plate for placing a substrate is arranged on the bottom side of the shell, and the carrier plate is arranged opposite to the spray device and connected to a support part, and a bottom heater is arranged in the support part, and the support part is connected to a driving device.

[0050] like Figure 3The structure of the epitaxial growth module is shown, which includes:

[0051] The shell 50 may be made of stainless steel and has a reaction chamber 10 in the shell 50.

[0052] A carrier plate 20 is provided at the bottom side of the reaction chamber 10. The carrier plate 20 is used to place a substrate 70 (the substrate 70 may be a silicon carbide substrate, and its specification may be 6 inches or 8 inches). The carrier plate 20 is connected to a support portion 21, and the support portion 21 is connected to a drive device 90, such as a drive motor. A bottom heater 22 is provided in the support portion. The support portion 21 is driven by the drive device 90 to rotate, and then the carrier plate 20 rotates. The rotation of the carrier plate 20 drives the substrate 70 thereon to rotate.

[0053] The housing 50 is provided with a graphite cylinder 40, which is coaxially arranged with the housing 50; the housing 50 is also provided with a side wall heater 60, which is sleeved on the graphite cylinder 40 (preferably, the side wall heater 60 and the graphite cylinder 40 are not in direct contact), and the housing 50 is also provided with a heat preservation component 80, which is located outside the side wall heater 60. The side wall heater and the bottom heater are collectively referred to as heaters.

[0054] The top of the housing 50 is provided with a spray device 30, which is connected to a gas supply system (also referred to as a supply system) through a pipeline. The gas supply system is controlled by a control module, and the gas supply system is connected to the gas supply area on the spray device 30 through a pipeline, and the control module independently controls the gas supply system to provide the amount of gas to the first air hole matching the corresponding gas supply area (such as by controlling the flow device (such as a flow meter) in the supply system). Preferably, the spray device 30 is equipped with an infrared temperature measuring component (not shown), which is used to detect the temperature in the reaction chamber (such as the temperature of the substrate or the temperature of the carrier plate).

[0055] like Figure 4 The spray device 30 shown in the figure includes three air supply areas, namely a first air supply area 30a, a second air supply area 30b and a third air supply area 30c, wherein the first air supply area 30a is an inner ring area (inner ring) in the middle of the circular area, the second air supply area 30b is an annular area (middle ring) around the first air supply area 30a, and the third air supply area 30c is an annular area (outer ring) around the second air supply area 30b. Each area is provided with a plurality of air holes 31, and the air holes 31 include a first air hole 31a and a second air hole 31b (see Figure 5a), the first air hole is used to introduce a mixed gas of growth source gas and hydrogen into the reaction chamber when the device is working, the growth source gas is silicon source gas (such as silane), carbon source gas (such as ethylene or propylene), hydrogen chloride gas (used to prevent the generation of silicon droplets and increase the epitaxial growth rate) and nitrogen, the second air hole is used to introduce hydrogen into the reaction chamber when the device is working, and the hydrogen introduced by the second air hole is used as a protective gas. The flow rate of the gas introduced by the second air hole is greater than the flow rate of the mixed gas introduced by the first air hole, because it can form a protective layer around the mixed gas to prevent the growth source gas introduced by the first air hole from reacting with residues on the surface of the graphite cylinder before flowing to the substrate surface. In this embodiment, three gas supply areas are set for the spray device, which are respectively connected to the gas supply system through pipelines and flow meters are set on the pipelines. During gas supply, these three gas supply areas are independently controlled (such as controlling the carbon-silicon ratio and / or hydrogen flow rate introduced into the first air hole of each gas supply area respectively). This ensures that the epitaxial layer grown on the surface of the substrate (such as 6 inches or 8 inches) has a better doping concentration (such as N doping) and thickness uniformity, thereby ensuring the product yield. In one embodiment, the hydrogen flow rate and C / Si ratio of the growth source gas and hydrogen mixed gas introduced into the first gas holes in the first gas supply area 30a, the second gas supply area 30b and the third gas supply area 30c are controlled. The first gas supply area 30a corresponds to the middle part of the surface of the substrate 70, the second gas supply area 30b corresponds to the periphery of the middle part of the surface of the substrate 70, and the third gas supply area 30c corresponds to the edge part of the surface of the substrate 70, so that the hydrogen flow rate and C / Si ratio introduced into the three areas can be different, so that the epitaxial layer grown on the surface of the substrate can have a higher doping concentration (such as N doping) and thickness uniformity.

[0056] As Figure 4 The variation of the implementation mode is as follows: Figure 5 and Figure 5a The spray device 30 will be described.

[0057] The spray device 30 has a first gas supply area 310 and a second gas supply area 320, wherein the second gas supply area 320 is located outside the first gas supply area 310. The first gas supply area 310 and the second gas supply area 320 are respectively provided with a plurality of air holes 31. The air holes 31 include a first air hole 31a and a second air hole 31b coaxially arranged, wherein the first air hole 31a is used to introduce process gas (such as carbon source gas, silicon source gas, nitrogen, hydrogen chloride gas and hydrogen (as carrier gas)) or protective gas (such as argon) into the reaction chamber, and the second air hole 31b is used to introduce hydrogen or protective gas (such as argon) into the reaction chamber. For example, protective gas is introduced through the air hole 31 during maintenance. During epitaxial growth, the first air hole 31a is used to introduce process gas into the reaction chamber and the second air hole 31b is used to introduce hydrogen into the reaction chamber, and the hydrogen introduced by the second air hole 31b can protect the process gas therein.

[0058] In one embodiment, see Figure 6 , the gas supply system includes a first flow control module, a second flow control module and a third flow control module, which are electrically connected to the control module respectively. The first flow control module is configured to control the hydrogen flow rate and / or carbon-silicon ratio C / Si ratio of the growth source gas and hydrogen mixed gas introduced into the first air hole in the first gas supply area a (corresponding to the middle part of the surface of the substrate 70) based on instructions. The second flow control module is configured to control the hydrogen flow rate and / or carbon-silicon ratio of the growth source gas and hydrogen mixed gas introduced into the first air hole in the second gas supply area b based on instructions. The third flow control module is configured to control the hydrogen flow rate and / or carbon-silicon ratio of the growth source gas and hydrogen mixed gas introduced into the first air hole in the third gas supply area c based on instructions. The first gas supply area to the third gas supply area are collectively referred to as the gas supply area. The first flow control module, the second flow control module and the third flow control module can be independently set or integrated together. The first flow control module, the second flow control module and the third flow control module are collectively referred to as flow control modules.

[0059] An embodiment of the present application also provides an epitaxial growth method (hereinafter referred to as the growth method) of the above-mentioned silicon carbide epitaxial device.

[0060] like Figure 7 As shown, the growth method comprises the following steps:

[0061] The in-situ etching stage includes:

[0062] A mixed gas of hydrogen chloride and hydrogen is introduced into the reaction chamber through a spray device, and the substrate in the reaction chamber is in-situ etched by the mixed gas of hydrogen chloride and hydrogen. In this step, the mixed gas of hydrogen chloride and hydrogen is introduced through the first air hole of each gas supply area of ​​the spray device, and hydrogen is introduced through the second air hole (preferably, the flow rate of hydrogen introduced through the second air hole is constant throughout the epitaxial growth stage).

[0063] Buffer layer growth stage, including:

[0064] Based on the gas supply area of ​​the spray device, process gases (a mixed gas of hydrogen chloride, silicon source, carbon source, nitrogen and hydrogen) are respectively introduced into the reaction chamber to grow a buffer layer on the surface of the substrate;

[0065] The main layer growth stage includes:

[0066] Based on the gas supply area of ​​the spray device, process gases (a mixture of hydrogen chloride, silicon source, carbon source, nitrogen and hydrogen) are introduced into the reaction chamber to grow a long main layer on the buffer layer to obtain a silicon carbide epitaxial wafer.

[0067] In one embodiment, after the main layer growth stage, all growth source gases are turned off and only hydrogen is introduced into the reaction chamber to cool the substrate to a preset temperature (such as a wafer removal temperature) and then removed and moved to a predetermined position by a robot.

[0068] In one embodiment, before the in-situ etching stage, the process further includes introducing hydrogen into the reaction chamber using a spray device and adjusting the pressure of the reaction chamber, and heating the reaction chamber using a heater.

[0069] In one embodiment, taking the spray device including three gas supply areas (inner ring / middle ring / outer ring) as an example, the growth method includes:

[0070] S1. Transferring the carrier plate with the substrate into the reaction chamber using a transmission device.

[0071] S2, introducing hydrogen into the reaction chamber, adjusting the pressure of the reaction chamber, and adjusting the temperature of the reaction chamber by heating with a heater. In step S2, the pressure of the reaction chamber is adjusted to 100-300 mbar, and the temperature of the reaction chamber is adjusted to 1580-1650°C.

[0072] S3, in-situ etching of the substrate. In this step, a mixed gas of hydrogen chloride and hydrogen is introduced into the reaction chamber, wherein the flow rate of hydrogen chloride is 600-3000 sccm, and the etching time is 5-10 min.

[0073] S4, using a control module to control the gas supply system, and respectively control the amount of gas supplied by the supply system to the first air hole in the gas supply area to grow a buffer layer on the surface of the substrate; the gas supply system is connected to the spray device (gas supply area) through a pipeline. The total amount of gas supplied to the first air hole in the gas supply area includes the flow of all process gases and / or carrier gas (hydrogen). This step includes introducing a mixed gas of growth source gas and hydrogen into the reaction chamber through the first air hole, and respectively controlling the hydrogen flow rate and C / Si ratio introduced into the first air hole in each area. The specific implementation method is as follows: silane is used as the silicon source, propane is used as the carbon source, the total C / Si ratio introduced into the buffer layer is set to 0.5-0.8, the total Cl / Si ratio is set to 7.5-10, the total C / Si ratio introduced into the epitaxial layer is set to 0.7-1.0, and the total Cl / Si ratio is set to 7.5-10. The hydrogen flow rate and C / Si ratio can be achieved by controlling the flow device (such as a flow meter) in the supply system. In this step, a flow control module is used to control the amount of gas in the first air hole in the corresponding air supply area.

[0074] S5. Use a flow control module to adjust the gas flow of each first air hole in the gas supply area to grow a main layer of a predetermined thickness on the buffer layer to obtain a silicon carbide (homogeneous) epitaxial wafer, wherein the carbon-silicon ratio of the main layer growth stage is greater than or equal to the carbon-silicon ratio of the buffer layer growth stage.

[0075] During the growth of the epitaxial layer, the hydrogen (H2) flow rate of the first air holes in the inner, middle and outer three gas supply areas can be adjusted respectively (the carbon-silicon ratio in each gas supply area does not need to be adjusted at this time), and the hydrogen (H2) flow rate of the first air holes in the inner, middle and outer three gas supply areas is gradually increased, so that the epitaxial layer has better N doping concentration uniformity. Increasing the H2 flow rate ratio of the first air holes in any partition of the gas supply area will increase the N doping concentration of the corresponding partition accordingly. For example: Based on the experimental data in Table 1 and combined with Figure 8 As shown, as the gas flow ratio of the first air holes H2 in the inner circle decreases, the corresponding doping concentration will also decrease. Preferably, the ratio of hydrogen gas introduced into the first air holes in the inner, middle and outer three air supply areas (the sum of hydrogen gas flowing through all the first air holes in each air supply area) is 13:33:34. The uniformity of the epitaxial layer concentration is optimal, reaching 1.84%. Figure 8 In the diagram, the X-axis is perpendicular to the flat edge / plane direction, and the Y-axis is parallel to the flat edge / plane direction.

[0076] serial number Inner ring H2 flow ratio Middle circle H2 flow ratio Outer ring H2 flow ratio Concentration uniformity A 14 33 33 7.89％ B 13↓ 33 34↑ 1.84％

[0077] Table 1

[0078] During the growth of the epitaxial layer, the concentration uniformity of the epitaxial layer can be adjusted by adjusting the C / Si ratio of the first air holes in the inner, middle and outer three circles (in the three gas supply areas). By increasing the C / Si ratio of the first air holes in any partition, the N doping concentration of the corresponding partition will be reduced accordingly; reducing the C / Si ratio of the first air holes will have the opposite effect. For example: Based on the experimental data in Table 2 and combined with Fig. 9 As shown,

[0079] As the C / Si ratio of the inner circle increases, the corresponding N doping concentration gradually decreases. When the C / Si ratios of the inner, middle and outer circles are 0.94, 0.48 and 0.75 respectively, the concentration uniformity reaches the best, which is 1.7%. Figure 8 In the diagram, the X-axis is perpendicular to the flat edge / plane direction, and the Y-axis is parallel to the flat edge / plane direction.

[0080] serial number Inner ring C / Si ratio C / Si ratio of center circle Outer ring C / Si ratio Concentration uniformity A 0.9 0.48 0.76 8％ B 0.94↑ 0.48 0.75↓ 1.7％

[0081] Table 2

[0082] The buffer layer grown on the substrate surface has a thickness of 1 um and an N-doping concentration of 1E18 cm-3. The epitaxial layer grown on the buffer layer has a thickness of 5-100 um and an N-doping concentration of 1E15-2E16 cm-3.

[0083] The silicon source is trichlorosilane (TCS) or silane (SiH4), and the carbon source is ethylene (C2H4) or propane (C3H8). After the epitaxial layer is completed, the product is cooled to 850-900°C in a hydrogen (H2) atmosphere, and then taken out by a robot and cooled to room temperature to obtain an epitaxial wafer (such as a silicon carbide homoepitaxial wafer).

[0084] In one embodiment, after the main body layer stage, a film taking stage is also included, including:

[0085] S6. Turn off all growth source gases and only introduce hydrogen into the reaction chamber for cooling, and use a robot to take it out and move it to a predetermined position.

[0086] In one embodiment, step S2 includes introducing hydrogen into the reaction chamber, including using the second air hole in the above-mentioned epitaxial equipment to introduce hydrogen into the reaction chamber, and slowly increasing the flow rate of hydrogen from 15L / min to 100-120L / min required by the process, and the hydrogen introduced into the second air hole can form a protective layer around the first air hole; the rotation speed of the base in the reaction chamber is adjusted to 500-1000 rpm.

[0087] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A silicon carbide epitaxial growth device, characterized in that: include: Control module, gas supply system and epitaxial growth module, The gas supply system comprises a first flow control module and a second flow control module, which are electrically connected to the control module respectively; The epitaxial growth module comprises: a housing, The housing is provided with a graphite cylinder and a side wall heater surrounding the graphite cylinder and located outside the graphite cylinder and extending along the axis of the graphite cylinder. A spray device is provided on the top of the shell, and the spray device includes a first air supply area and a second air supply area surrounding the first air supply area, and each of the spray devices includes a plurality of air holes, and the air holes include a first air hole and a second air hole that are sleeved, and the first air supply area and the second air supply area are connected to the gas supply system through pipelines, respectively. A carrier plate for placing a substrate is disposed at the bottom side of the housing, the carrier plate is disposed opposite to the spray device and connected to a support portion, a bottom heater is disposed in the support portion and the support portion is connected to a driving device, The amount of gas and / or the carbon-silicon ratio introduced into the first gas supply area is controlled based on the first flow control module, and the amount of gas and / or the carbon-silicon ratio introduced into the second gas supply area is controlled based on the second flow control module.

2. The silicon carbide epitaxial growth device according to claim 1, characterized in that: The graphite cylinder is coaxially arranged with the shell, and a heat-insulating component is also arranged in the shell and is located outside the side wall heater.

3. The silicon carbide epitaxial growth device according to claim 1, characterized in that: The spray device is provided with an infrared temperature measuring component, which is used to detect the temperature of the reaction chamber in the shell.

4. The silicon carbide epitaxial growth device according to claim 1, characterized in that: The gas supply system includes a third flow control module, which is electrically connected to the control module. The spray device has a third air supply area located outside the second air supply area, and has a plurality of air holes. The gas amount and / or the carbon-silicon ratio introduced into the third gas supply area is controlled based on the third flow control module.

5. The silicon carbide epitaxial growth device according to claim 1, characterized in that: The first air supply area and the second air supply area are designed as an integrated whole, and the first air hole is coaxially arranged with the second air hole matched therewith.

6. The silicon carbide epitaxial growth device according to any one of claims 1 to 5, characterized in that: The first air hole is used to introduce process gas or protective gas into the reaction chamber. The second air hole is used to introduce hydrogen into the reaction chamber, and the hydrogen surrounds the process gas introduced through the first air hole, or is used to introduce protective gas into the reaction chamber.

7. An epitaxial growth method, characterized in that: The growth method comprises the following steps: The in-situ etching stage includes: introducing a mixed gas of hydrogen chloride and hydrogen into the reaction chamber through a spray device, and in-situ etching the substrate placed in the reaction chamber through the mixed gas of hydrogen chloride and hydrogen; Buffer layer growth stage, including: A process gas having a first preset carbon-to-silicon ratio is introduced into the reaction chamber through a first air hole in the gas supply region of the spray device, and hydrogen is introduced into the reaction chamber through a second air hole to grow a buffer layer on the surface of the substrate; The main layer growth stage includes: Based on the first air hole in the gas supply area of ​​the spray device, a process gas including a second preset carbon-to-silicon ratio is introduced into the reaction chamber, and hydrogen is introduced into the reaction chamber through the second air hole, so as to grow a main layer of a preset thickness on the buffer layer to obtain a silicon carbide epitaxial wafer, wherein the second preset carbon-to-silicon ratio is greater than or equal to the first preset carbon-to-silicon ratio.

8. The epitaxial growth method according to claim 7, characterized in that: After the main layer growth stage, the method also includes closing all growth source gases and only introducing hydrogen into the reaction chamber, cooling the substrate to a preset temperature through the hydrogen, and taking it out and moving it to a predetermined position using a robot.

9. The epitaxial growth method according to claim 7, characterized in that: Before the in-situ etching stage, the method also includes introducing hydrogen into the reaction chamber based on a spray device and adjusting the pressure of the reaction chamber, and heating the reaction chamber based on a heater.

10. The epitaxial growth method according to claim 7, characterized in that: During the growth stage of the main layer, the hydrogen flow rate of the second gas supply region entering the first gas permeable hole is greater than the hydrogen flow rate of the first gas supply region entering the first gas permeable hole, or the carbon-silicon ratio of the second gas supply region entering the first gas permeable hole is less than the carbon-silicon ratio of the first gas supply region entering the first gas permeable hole, or, The spray device includes a first gas supply area, a second gas supply area and a third gas supply area, wherein the ratio of hydrogen introduced into the first gas holes in the first gas supply area, the second gas supply area and the third gas supply area is (11-15):(30-35):(32-36), or the carbon-silicon ratio introduced into the first gas supply area, the second gas supply area and the third gas supply area is 0.9-1.1, 0.3-0.6 and 0.7-0.9.

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