3C-SiC epitaxial wafer and preparation method thereof

Abstract

The invention relates to the technical field of silicon carbide materials, and discloses a 3C-SiC epitaxial wafer and a preparation method thereof. The method comprises the following steps: (1) carrying out first etching on a silicon substrate; (2) forming a first carbonization buffer layer on the surface of the etched silicon substrate; (3) carrying out heteroepitaxial growth on the first carbonized buffer layer in the presence of a first process gas; wherein the first process gas comprises a carbon source and a silicon source, and the carbon source comprises a chlorine-based carbon source. According to the method provided by the invention, the 3C-SiC epitaxial wafer with obviously lower fatal defect density can be prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide materials, and in particular to a 3C-SiC epitaxial wafer and a preparation method thereof. Background Art

[0002] Compared with traditional first- and second-generation semiconductor materials, silicon carbide, as a relatively mature third-generation wide bandgap semiconductor material, has many advantages, such as wider bandgap width, higher critical breakdown electric field, faster saturated electron migration speed, and higher thermal conductivity.

[0003] At present, most commercial silicon carbide epitaxial wafers are 4H crystals, obtained by homogeneous epitaxy on 4H-SiC substrates. Although the current process is relatively mature, there are still many stacking fault defects, and the cost of silicon carbide substrates is relatively high. Although the 4° step flow epitaxy method ensures the purity of the epitaxial crystal, it also causes further waste of the substrate. The balance between cost and performance is difficult to break, which restricts the commercialization and popularization of silicon carbide.

[0004] Traditional 4H-SiC wafers are mostly grown by homoepitaxial CVD. The quality of epitaxial films is controlled by optimizing parameters such as etching process and growth pressure. Currently, the fatal surface defects of traditional 4H-SiC silicon carbide epitaxial films are less than 0.3 / cm 2 . The performance of 4H-SiC power devices is significantly better than that of silicon devices, but the traditional 4H-SiC process route is costly and difficult to commercialize on a large scale. 3C-SiC can be grown heteroepitaxially on a silicon substrate, which greatly reduces the cost, but the 3C-SiC obtained by the traditional process route has many defects, and the performance and yield of the device are poor. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem that the 3C-SiC epitaxial wafer obtained by the existing process route has many defects and the performance and yield of the device are poor, and to provide a 3C-SiC epitaxial wafer and a preparation method thereof. The defects of the 3C-SiC epitaxial wafer prepared by the method described in the present invention are controllable, the cost is low, and it is more conducive to commercial application.

[0006] In order to achieve the above object, the present invention provides a method for preparing a 3C-SiC epitaxial wafer, the method comprising the following steps:

[0007] (1) performing a first etching on the silicon substrate;

[0008] (2) forming a first carbonized buffer layer on the surface of the etched silicon substrate;

[0009] (3) performing heteroepitaxial growth on the first carbonized buffer layer in the presence of a first process gas;

[0010] Wherein, the first process gas includes a carbon source and a silicon source, and the carbon source includes a chlorine-based carbon source.

[0011] Preferably, the chlorine-based carbon source is CH 3 Cl.

[0012] Preferably, in step (3), the first process gas further comprises HCl.

[0013] Preferably, in step (3), the chlorine-silicon ratio of the first process gas is 2-4:1.

[0014] Preferably, in step (3), the carbon-silicon ratio of the first process gas is 0.9-1.2:1.

[0015] Preferably, in step (3), the conditions for the heteroepitaxial growth include: temperature of 1250-1380° C., pressure of 50-80 mbar, and time of 1-3 h.

[0016] Preferably, in step (1), the first etching is hydrogen in-situ etching.

[0017] Preferably, in step (2), the process of forming the first carbonized buffer layer is carried out in the presence of a chlorine-based carbon source. More preferably, the chlorine-based carbon source is CH 3 Cl.

[0018] Preferably, in step (2), the operating conditions of the process of forming the first carbonized buffer layer include: temperature of 1250-1380° C., pressure of 60-80 mbar, and time of 5-20 min.

[0019] Preferably, the method further comprises the following steps: (4) removing the silicon substrate in the epitaxial growth substrate obtained in step (3).

[0020] Preferably, the silicon substrate is removed by wet chemical etching.

[0021] Preferably, the method further comprises the following steps:

[0022] (5) performing a second etching on the 3C-SiC wafer obtained in step (4);

[0023] (6) forming a second carbonized buffer layer on the surface of the etched 3C-SiC substrate;

[0024] (7) performing homoepitaxial growth on the second carbonized buffer layer in the presence of a second process gas;

[0025] Wherein, the second process gas includes a carbon source and a silicon source.

[0026] Preferably, in step (7), the carbon-silicon ratio of the second process gas is 0.9-1.1:1.

[0027] Preferably, in the second process gas of step (7), the carbon source is C 2 H 4 and / or CH 3 Cl, more preferably C 2 H 4 .

[0028] Preferably, in the second process gas of step (7), the silicon source is SiHCl 3 and / or SiH 4 , more preferably SiHCl 3 .

[0029] Preferably, in step (7), the conditions for the homoepitaxial growth include: a temperature of 1400-1500° C., a pressure of 60-100 mbar, and a time of 5-20 min.

[0030] Preferably, in step (5), the second etching is hydrogen in-situ etching.

[0031] Preferably, in step (6), the carbon source used in the process of forming the second carbonized buffer layer is C 2 H 4 and / or CH 3 Cl, more preferably C 2 H 4 .

[0032] Preferably, in step (6), the operating conditions of the process of forming the second carbonized buffer layer include: temperature of 1400-1500° C., pressure of 60-100 mbar, and time of 1-10 min.

[0033] The present invention also provides a 3C-SiC epitaxial wafer prepared by the method.

[0034] Through the above technical solution, a low fatal defect density (e.g. <0.3 / cm) can be obtained. 2 ) 3C-SiC epitaxial wafer, the performance of this 3C-SiC epitaxial wafer is superior, the cost is greatly reduced compared to the traditional 4H-SiC process, and the defects of 3C-SiC heteroepitaxially grown on traditional silicon substrates are controllable, which is more conducive to commercial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a crystal diffraction peak diagram of a 3C-SiC epitaxial wafer prepared according to the method of the present invention;

[0036] Figure 2This is a defect test diagram of the 3C-SiC epitaxial wafer prepared in Example 1. DETAILED DESCRIPTION

[0037] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0038] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0039] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating relative importance or implicitly indicating the number of the indicated technical features.

[0040] The method for preparing the 3C-SiC epitaxial wafer of the present invention comprises the following steps:

[0041] (1) performing a first etching on the silicon substrate;

[0042] (2) forming a first carbonized buffer layer on the surface of the etched silicon substrate;

[0043] (3) performing heteroepitaxial growth on the first carbonized buffer layer in the presence of a first process gas;

[0044] Wherein, the first process gas includes a carbon source and a silicon source, and the carbon source includes a chlorine-based carbon source.

[0045] In the preparation method of the 3C-SiC epitaxial wafer described in the present invention, the heteroepitaxial growth adopts ultra-high-speed epitaxial growth, and the growth rate is above 100μm / h. The traditional silicon source and carbon source gas will have silicon clusters when the growth rate exceeds 30μm / h, which affects the nucleation position and the amount of effective silicon source precursor in CVD, thereby increasing the defect density. Although commercial TCS gas can solve the silicon droplet problem, the TCS process temperature is generally around 1600°C, which greatly exceeds the melting point of the silicon-based substrate and is not suitable for 3C-SiC low-temperature growth. The present invention uses a chlorine-based carbon source to effectively solve this problem. The chlorine-based carbon source gas can be decomposed into in a relatively low temperature environment, which is suitable for low-temperature growth. The Si-Cl bond energy is greater than the Si-Si bond energy, which can effectively prevent the nucleation of silicon droplets. Therefore, the 3C-SiC epitaxial wafer prepared according to the method described in the present invention has a significantly lower fatal defect density.

[0046] In the present invention, "fatal defects" refer to the atomic steps that appear on the Si (001) surface during the etching stage before the growth of the carbide buffer layer. When SiC grows on this surface, the alignment between carbon atoms will shift due to the presence of atomic steps, resulting in stacking faults and antiphase domain (APD) extension defects; and during the epitaxial growth process, dropped objects drip onto the substrate surface, affecting the replication of atomic steps, thereby forming triangular defects and dropped object defects.

[0047] In the method of the present invention, the carbon source in the first process gas can be C 2 H 4 The chlorine-based carbon source may be used in combination with the chlorine-based carbon source or may be used alone. In a preferred embodiment, the carbon source in the first process gas is a chlorine-based carbon source.

[0048] In the method of the present invention, the chlorine-based carbon source is preferably CH 3 In this preferred case, the fatal defect density of the prepared 3C-SiC epitaxial wafer can be further reduced.

[0049] In the method of the present invention, the silicon source can be a silicon source gas commonly used in the art. In a preferred embodiment, the silicon source is SiHCl 3 and / or SiH 4 , more preferably SiH 4 .

[0050] In the method of the present invention, the first process gas may further include HCl. When the first process gas also includes a chlorine-based carbon source (especially CH 3 Cl) and HCl, HCl can make up for the consumption of Cl element in the chlorine-based carbon source, thereby more effectively preventing the nucleation of silicon droplets, so that the prepared 3C-SiC epitaxial wafer has a lower fatal defect density.

[0051] In the method of the present invention, preferably, the chlorine-silicon ratio of the first process gas is 2-4: 1, more preferably 2.5-3.8: 1, further preferably 3-3.5: 1, and most preferably 3.3: 1. When the chlorine-silicon ratio of the first process gas is within the above preferred range, the prepared 3C-SiC epitaxial wafer has a significantly lower fatal defect density.

[0052] In the method of the present invention, preferably, the carbon-silicon ratio of the first process gas is 0.9-1.2: 1, more preferably 1-1.1: 1, and most preferably 1.1: 1. When the carbon-silicon ratio of the first process gas is within the above preferred range, the prepared 3C-SiC epitaxial wafer has a significantly lower fatal defect density.

[0053] In the method described in the present invention, in step (3), the conditions for the heteroepitaxial growth may include: a temperature of 1250-1380°C, preferably 1300-1350°C, most preferably 1350°C; a pressure of 50-80mbar, preferably 60-70mbar, most preferably 60mbar; a time of 1-3h, preferably 1.5-2.5h, most preferably 2h.

[0054] In the method of the present invention, in step (3), the flow rate of the carbon source can be 150-300 sccm, preferably 180-250 sccm, and most preferably 210 sccm.

[0055] In the method described in the present invention, in step (3), the flow rate of the silicon source can be 135-270 sccm, preferably 150-250 sccm, more preferably 180-220 sccm, and most preferably 190 sccm.

[0056] In the method of the present invention, in step (3), the first process gas may further include a carrier gas. The carrier gas may be a conventional choice in the art. In a specific embodiment, the carrier gas is hydrogen. The flow rate of the carrier gas may be 100-120 slm, and most preferably 120 slm.

[0057] In the method of the present invention, preferably, in step (1), before etching the silicon substrate, the silicon substrate is first cleaned. The cleaning method may be a conventional method in the art, such as an RCA standard cleaning method.

[0058] In the method described in the present invention, in step (1), the first etching can be a conventional etching process in the art. In a specific embodiment, the first etching is hydrogen in-situ etching. In the present invention, by performing hydrogen in-situ etching on the silicon substrate, the damaged layer on the surface of the silicon substrate can be effectively removed, and other contaminants on the surface of the silicon substrate can be removed at the same time. The operating conditions of the hydrogen in-situ etching may include: an etching temperature of 1000-1200°C, most preferably 1200°C; a hydrogen flow rate of 100-120slm, most preferably 120slm; a pressure of 80-100mbar, most preferably 80mbar; an etching time of 5-10min, most preferably 5min.

[0059] In the method of the present invention, in step (2), the process of forming the first carbonized buffer layer is preferably carried out in the presence of a chlorine-based carbon source. In the process of forming the carbonized buffer layer, the chlorine-based carbon source is used as the carbon source, and the 3C-SiC crystal growth can be maintained at a normal process temperature, and the process of cooling the chamber before the traditional buffer layer growth can be removed, so that the coating can be prevented from falling off due to frequent temperature changes, and the number of fatal defects can be greatly reduced.

[0060] In the method of the present invention, the chlorine-based carbon source used in step (2) is preferably CH 3 In this preferred case, the fatal defect density of the prepared 3C-SiC epitaxial wafer can be further reduced.

[0061] In the method of the present invention, in step (2), the operating conditions of the process of forming the first carbonized buffer layer preferably include: temperature of 1250-1380°C, pressure of 60-80mbar, and time of 5-20min. Under the above preferred operating conditions, the carbonized buffer layer grows under low pressure, and the low pressure environment will reduce the equilibrium partial pressure of the silicon source and the carbon source, reduce the formation of Si-Si bonds and CC bonds, and thus can greatly reduce the stacking fault density. Most preferably, the operating conditions of the process of forming the first carbonized buffer layer preferably include: temperature of 1350°C, pressure of 70mbar, and time of 10min.

[0062] In the method of the present invention, in step (2), the flow rate of the carbon source can be 15-30 sccm, preferably 15-20 sccm, and most preferably 15 sccm.

[0063] In the method of the present invention, in step (2), the process of forming the first carbonized buffer layer needs to be carried out in the presence of a carrier gas. The carrier gas used can be a conventional choice in the art. In a specific embodiment, the carrier gas is hydrogen. The flow rate of the carrier gas can be 100-120 slm, and most preferably 120 slm.

[0064] According to the method of the present invention, through steps (1) to (3), the epitaxial growth substrate prepared comprises a silicon substrate and a 3C-SiC heteroepitaxial layer formed on the silicon substrate.

[0065] In some embodiments of the present invention, the method further comprises the following steps:

[0066] (4) Removing the silicon substrate from the epitaxial growth substrate obtained in step (3).

[0067] Through step (4), an independent 3C-SiC wafer with relatively high quality can be produced, which can be used for micro-electromechanical systems (MEMS).

[0068] In the method of the present invention, the method of removing the silicon substrate can be operated in a conventional manner in the art. In a specific embodiment, the silicon substrate is removed by a wet chemical etching method. The wet chemical etching method is a relatively mature technology in the art. For example, by using chemical solutions such as hydrofluoric acid and nitric acid in different proportions, the silicon substrate can be completely removed without damaging the 3C-SiC layer, thereby obtaining an independent 3C-SiC wafer.

[0069] In some embodiments of the present invention, the method further comprises the following steps:

[0070] (5) performing a second etching on the 3C-SiC wafer obtained in step (4);

[0071] (6) forming a second carbonized buffer layer on the surface of the etched 3C-SiC substrate;

[0072] (7) performing homoepitaxial growth on the second carbonized buffer layer in the presence of a second process gas;

[0073] Wherein, the second process gas includes a carbon source and a silicon source.

[0074] Through steps (5) to (7), a high-quality 3C-SiC epitaxial wafer with controllable extended defects can be obtained, which can be used for processing and manufacturing various devices.

[0075] In the method of the present invention, preferably, in step (5), before etching the 3C-SiC wafer, the 3C-SiC wafer is first cleaned. The cleaning method may be a conventional method in the art, such as an RCA standard cleaning method.

[0076] In the method described in the present invention, in step (5), the second etching can be a conventional etching process in the art. In a specific embodiment, the second etching is hydrogen in-situ etching. In the present invention, by performing hydrogen in-situ etching on the 3C-SiC wafer substrate, the sub-surface damage that may be caused by chemical corrosion of 3C-SiC can be removed. The operating conditions of the hydrogen in-situ etching may include: an etching temperature of 1200-1400°C, most preferably 1400°C; a hydrogen flow rate of 100-120slm, most preferably 100slm; a pressure of 80-100mbar, most preferably 100mbar; an etching time of 5-10min, most preferably 5min.

[0077] In the method of the present invention, in step (6), the carbon source used in the process of forming the second carbonized buffer layer can be C 2 H 4 and / or CH 3 Cl, more preferably C 2 H 4 When using C 2 H 4 When used as a carbon source, the pressure in the growth chamber can be reduced, which is more conducive to the growth of a high-quality carbonized buffer layer.

[0078] In the method of the present invention, in step (6), the operating conditions of the process of forming the second carbonized buffer layer preferably include: temperature of 1400-1500°C, pressure of 60-100 mbar, and time of 1-10 min. Under the above preferred operating conditions, the stacking fault density can be greatly reduced. Most preferably, the operating conditions of the process of forming the second carbonized buffer layer preferably include: temperature of 1450°C, pressure of 80 mbar, and time of 5 min.

[0079] In the method of the present invention, in step (6), the flow rate of the carbon source can be 15-30 sccm, preferably 30 sccm.

[0080] In the method of the present invention, in step (6), the process of forming the second carbonized buffer layer needs to be carried out in the presence of a carrier gas. The carrier gas used can be a conventional choice in the art. In a specific embodiment, the carrier gas is hydrogen. The flow rate of the carrier gas can be 100-120slm, and most preferably 100slm.

[0081] In the method of the present invention, in step (7), the carbon source in the second process gas can be C 2 H 4 In combination with a chlorine-based carbon source, C 2 H 4 In a preferred embodiment, the carbon source in the second process gas is C 2 H 4 .

[0082] In the method of the present invention, in step (7), the silicon source in the second process gas can be a silicon source gas commonly used in the art. In a preferred embodiment, the silicon source is SiHCl 3 and / or SiH 4 , more preferably SiHCl 3 .

[0083] In some embodiments, in step (7), the carbon source in the second process gas is C 2 H 4 , silicon source is SiHCl 3 The extension rate of this step is generally controlled at about 60 μm / h. The extension rate is fast. The use of chlorine-based silicon source can prevent the appearance of silicon clusters. 1 mol SiHCl 3 It has 3 mol of chlorine atoms and does not require additional HCl auxiliary gas; however, if the extension rate is increased to above 150 μm / h, additional HCl auxiliary gas is required.

[0084] In the method of the present invention, in step (7), the carbon-silicon ratio of the second process gas is preferably 0.9-1.1: 1, and most preferably 0.95: 1. When the carbon-silicon ratio of the second process gas is within the above preferred range, silicon droplets or carbonization will not occur during the preparation process, so the prepared 3C-SiC epitaxial wafer has a significantly lower fatal defect density.

[0085] In the method of the present invention, in step (7), the homoepitaxial growth conditions preferably include: temperature of 1400-1500°C, most preferably 1450°C; pressure of 60-100 mbar, most preferably 80 mbar; time of 5-20 min, most preferably 10 min. When the homoepitaxial growth conditions are within the above preferred ranges, no 4H-SiC impurities will appear, and the number of fatal defects is small, so the prepared 3C-SiC epitaxial wafer has a significantly lower fatal defect density.

[0086] In the method described in the present invention, in step (7), the flow rate of the carbon source can be 120-240 sccm, preferably 130 sccm.

[0087] In the method described in the present invention, in step (7), the flow rate of the silicon source can be 260-530 sccm, preferably 288 sccm.

[0088] In the method of the present invention, in step (7), the second process gas may further include a carrier gas. The carrier gas may be a conventional choice in the art. In a specific embodiment, the carrier gas is hydrogen. The flow rate of the carrier gas may be 100-120 slm, and most preferably 120 slm.

[0089] In the method of the present invention, in step (7), the second process gas may further include a doping gas, such as nitrogen. The flow rate of the doping gas may be determined according to actual needs.

[0090] The present invention also provides a 3C-SiC epitaxial wafer prepared by the above method. The 3C-SiC epitaxial wafer has a significantly lower fatal defect density. Specifically, the fatal defect density can be controlled at 0.5 / cm 2 Below, preferably 0.3 pieces / cm 2 the following.

[0091] The 3C-SiC epitaxial wafer and the preparation method thereof according to the present invention are further illustrated by examples. The examples are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0092] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0093] Example 1

[0094] The 3C-SiC epitaxial wafer A1 was prepared according to the following process:

[0095] (1) The silicon substrate was cleaned by the RCA standard cleaning method and then subjected to in-situ hydrogen etching at an etching temperature of 1200° C., a hydrogen flow rate of 120 slm, a chamber pressure of 80 mbar, and an etching time of 10 min.

[0096] (2) forming a first carbonized buffer layer on the surface of the etched silicon substrate, specifically, increasing the process temperature to a growth temperature of 1350°C, waiting for the chamber temperature to stabilize for 2 minutes, and introducing a carbon source CH 3 Cl with a flow rate of 15 sccm, hydrogen as carrier gas with a flow rate of 120 slm, chamber pressure of 70 mbar, and growth time of 10 min.

[0097] (3) performing heteroepitaxial growth on the first carbonized buffer layer. Specifically, introducing a carbon source CH 3 Cl, flow rate is 210sccm, silicon source SiH 4 , the flow rate is 190sccm, ensuring the carbon-silicon ratio is 1.1:1, HCl is introduced with a flow rate of 420sccm, ensuring the chlorine-silicon ratio is 3.3:1, hydrogen is used as a carrier gas with a flow rate of 120slm. The operating temperature is 1350℃, the chamber pressure is 60mbar, and the growth time is 120min.

[0098] (4) removing the silicon substrate in the epitaxial growth substrate obtained in step (3), specifically, removing the silicon substrate by wet chemical etching to obtain a 3C-SiC wafer.

[0099] (5) The 3C-SiC wafer prepared in step (4) was used as a substrate, the substrate was cleaned by the RCA standard cleaning method, and then hydrogen in-situ etching was performed, the etching temperature was 1400° C., the hydrogen flow rate was 100 slm, the chamber pressure was 100 mbar, and the etching time was 5 min.

[0100] (6) forming a second carbonized buffer layer on the surface of the etched 3C-SiC substrate. Specifically, the process temperature is increased to a growth temperature of 1450°C, and the chamber temperature is stabilized for 2 minutes. Then, a carbon source C is introduced. 2 H 4 , flow rate is 30sccm, hydrogen is used as carrier gas, flow rate is 100slm, chamber pressure is 80mbar, and growth time is 5min.

[0101] (7) performing homoepitaxial growth on the second carbonized buffer layer. Specifically, introducing a carbon source C 2 H 4 , flow rate is 130sccm; silicon source SiHCl is introduced 3 , flow rate is 288sccm, ensuring the carbon-silicon ratio is 0.95:1; hydrogen is used as the carrier gas, with a flow rate of 120slm; an appropriate amount of nitrogen doping is introduced; the process temperature is 1450℃; the chamber pressure is 80mbar; and the growth time is 10min.

[0102] Example 2

[0103] The 3C-SiC epitaxial wafer A2 was prepared according to the following process:

[0104] (1) The silicon substrate was cleaned by the RCA standard cleaning method and then subjected to hydrogen in-situ etching at an etching temperature of 1200° C., a hydrogen flow rate of 120 slm, a chamber pressure of 100 mbar, and an etching time of 10 min.

[0105] (2) forming a first carbonized buffer layer on the surface of the etched silicon substrate. Specifically, the process temperature is increased to a growth temperature of 1350° C., and the chamber temperature is stabilized for 2 minutes. Then, a carbon source CH 3 Cl with a flow rate of 30 sccm, hydrogen as carrier gas with a flow rate of 120 slm, chamber pressure of 80 mbar, and growth time of 10 min.

[0106] (3) performing heteroepitaxial growth on the first carbonized buffer layer. Specifically, introducing a carbon source CH 3 Cl, with a flow rate of 300 sccm, and silicon source SiH 4 , the flow rate is 270sccm, ensuring the carbon-silicon ratio is 1.1:1, HCl is introduced with a flow rate of 540sccm, ensuring the chlorine-silicon ratio is 4:1, hydrogen is used as a carrier gas with a flow rate of 120slm. The operating temperature is 1350℃, the chamber pressure is 80mbar, and the growth time is 120min.

[0107] (4) removing the silicon substrate in the epitaxial growth substrate obtained in step (3), specifically, removing the silicon substrate by wet chemical etching to obtain a 3C-SiC wafer.

[0108] (5) The 3C-SiC wafer prepared in step (4) was used as a substrate, the substrate was cleaned by the RCA standard cleaning method, and then hydrogen in-situ etching was performed, the etching temperature was 1400° C., the hydrogen flow rate was 100 slm, the chamber pressure was 100 mbar, and the etching time was 5 min.

[0109] (6) forming a second carbonized buffer layer on the surface of the etched 3C-SiC substrate. Specifically, the process temperature is increased to a growth temperature of 1450°C, and the chamber temperature is stabilized for 2 minutes. Then, a carbon source C is introduced. 2 H 4 , flow rate is 30sccm, hydrogen is used as carrier gas, flow rate is 100slm, chamber pressure is 80mbar, and growth time is 5min.

[0110] (7) performing homoepitaxial growth on the second carbonized buffer layer. Specifically, introducing a carbon source C 2 H 4 , flow rate is 240sccm; silicon source SiHCl is introduced 3 , the flow rate is 436sccm, ensuring the carbon-silicon ratio is 1.1:1; hydrogen is used as the carrier gas, with a flow rate of 120slm; an appropriate amount of nitrogen doping is introduced; the process temperature is 1500℃; the chamber pressure is 80mbar; and the growth time is 10min.

[0111] Example 3

[0112] The 3C-SiC epitaxial wafer A3 was prepared according to the following process:

[0113] (1) The silicon substrate was cleaned by the RCA standard cleaning method and then subjected to in-situ hydrogen etching at an etching temperature of 1000° C., a hydrogen flow rate of 100 slm, a chamber pressure of 80 mbar, and an etching time of 5 min.

[0114] (2) forming a first carbonized buffer layer on the surface of the etched silicon substrate. Specifically, the process temperature is increased to a growth temperature of 1250°C, and the chamber temperature is stabilized for 2 minutes. Then, a carbon source CH 3 Cl with a flow rate of 15 sccm, hydrogen as carrier gas with a flow rate of 120 slm, chamber pressure of 60 mbar, and growth time of 5 min.

[0115] (3) performing heteroepitaxial growth on the first carbonized buffer layer. Specifically, introducing a carbon source CH 3 Cl, with a flow rate of 150sccm, and silicon source SiH 4 , the flow rate is 166sccm, ensuring the carbon-silicon ratio is 0.9:1, HCl is introduced, the flow rate is 166sccm, ensuring the chlorine-silicon ratio is 2:1, hydrogen is used as a carrier gas, the flow rate is 100slm. The operating temperature is 1250℃, the chamber pressure is 60mbar, and the growth time is 120min.

[0116] (4) removing the silicon substrate in the epitaxial growth substrate obtained in step (3), specifically, removing the silicon substrate by wet chemical etching to obtain a 3C-SiC wafer.

[0117] (5) The 3C-SiC wafer prepared in step (4) was used as a substrate, the substrate was cleaned by the RCA standard cleaning method, and then hydrogen in-situ etching was performed, the etching temperature was 1200° C., the hydrogen flow rate was 100 slm, the chamber pressure was 80 mbar, and the etching time was 5 min.

[0118] (6) forming a second carbonized buffer layer on the surface of the etched 3C-SiC substrate. Specifically, the process temperature is increased to a growth temperature of 1400°C, and the chamber temperature is stabilized for 2 minutes. Then, a carbon source C is introduced. 2 H 4 , flow rate is 15sccm, hydrogen is used as carrier gas, flow rate is 100slm, chamber pressure is 60mbar, and growth time is 5min.

[0119] (7) performing homoepitaxial growth on the second carbonized buffer layer. Specifically, introducing a carbon source C 2 H 4 , flow rate is 130sccm; silicon source SiHCl is introduced 3 , flow rate is 288sccm, ensuring the carbon-silicon ratio is 0.9:1; hydrogen is used as carrier gas, with a flow rate of 100slm; an appropriate amount of nitrogen doping is introduced; the process temperature is 1400℃; the chamber pressure is 60mbar; and the growth time is 10min.

[0120] Example 4

[0121] The 3C-SiC epitaxial wafer A4 was prepared according to the following process:

[0122] (1) The silicon substrate was cleaned by the RCA standard cleaning method and then subjected to hydrogen in-situ etching at an etching temperature of 1200° C., a hydrogen flow rate of 120 slm, a chamber pressure of 80 mbar, and an etching time of 10 min.

[0123] (2) forming a first carbonized buffer layer on the surface of the etched silicon substrate. Specifically, the process temperature is increased to a growth temperature of 1350° C., and the chamber temperature is stabilized for 2 minutes. Then, a carbon source CH 3 Cl with a flow rate of 15 sccm, hydrogen as carrier gas with a flow rate of 120 slm, chamber pressure of 70 mbar, and growth time of 10 min.

[0124] (3) performing heteroepitaxial growth on the first carbonized buffer layer. Specifically, introducing a carbon source CH 3 Cl, flow rate is 210sccm, silicon source SiH 4, the flow rate is 190sccm, ensuring the carbon-silicon ratio is 1.1:1, HCl is introduced with a flow rate of 420sccm, ensuring the chlorine-silicon ratio is 3.3:1, hydrogen is used as a carrier gas with a flow rate of 120slm. The operating temperature is 1350℃, the chamber pressure is 60mbar, and the growth time is 120min.

[0125] Comparative Example 1

[0126] A 3C-SiC epitaxial wafer was prepared according to the method of Example 1, except that the carbon source introduced in step (3) was C 2 H 4 The silicon source introduced is SiHCl 3 , and a 3C-SiC epitaxial wafer D1 was obtained.

[0127] Example 5

[0128] A 3C-SiC epitaxial wafer was prepared according to the method of Example 1, except that in steps (2), (3), (6) and (7), the chamber pressure was 100 mbar, and a 3C-SiC epitaxial wafer A5 was obtained.

[0129] Example 6

[0130] A 3C-SiC epitaxial wafer was prepared according to the method of Example 1, except that in steps (3) and (7), the carbon-silicon ratio was controlled to 1.2:1, thereby obtaining a 3C-SiC epitaxial wafer A6.

[0131] Example 7

[0132] A 3C-SiC epitaxial wafer was prepared according to the method of Example 1, except that HCl was not introduced in step (3) to ensure that the chlorine-silicon ratio was 0.9:1, and a 3C-SiC epitaxial wafer A7 was obtained.

[0133] Example 8

[0134] A 3C-SiC epitaxial wafer was prepared according to the method of Example 4, except that in step (3), the carbon-silicon ratio was controlled to 1.2:1, and a 3C-SiC epitaxial wafer A8 was obtained.

[0135] Test Example 1

[0136] Crystal form test

[0137] The epitaxial wafers prepared in Example 1-8 were tested by Raman scattering method, and the crystal diffraction peak diagram obtained was as follows: Figure 1 shown.

[0138] pass Figure 1It can be judged from the peaks in that the crystal diffraction peaks of the epitaxial wafer prepared according to the method described in the present invention are all diffraction peaks of the 3c crystal form. It is further verified that the epitaxial wafer prepared according to the method described in the present invention is a 3C-SiC epitaxial wafer.

[0139] Test Example 2

[0140] (1) Thickness test

[0141] The thickness of the prepared 3C-SiC epitaxial wafer was tested using a Thermo Fisher iS50 FT-IR spectrometer using the TTIR method.

[0142] (2) Concentration test

[0143] The concentration of the prepared 3C-SiC epitaxial wafer was tested using Semilab's MCV spectrometer using the Schottky nodule method.

[0144] (3) Defect testing

[0145] The defects of the prepared 3C-SiC epitaxial wafers were tested using the Candela series defect detector 8520.

[0146] By using the principle of photoluminescence to scan the surface of the wafer, defect information of the entire surface can be fed back.

[0147] Killer defects: <0.3 / cm 2 ; Stacking fault defect (IGSF+Bpd) < 0.5 / cm 2 ;Pit<500.

[0148] The defect test diagram of the 3C-SiC epitaxial wafer prepared in Example 1 is as follows: Figure 2 shown.

[0149] (4) Roughness test

[0150] The surface roughness of the wafer was tested using an atomic force microscope.

[0151] Roughness is a basic parameter of epitaxial film. Roughness directly reflects whether the atomic steps in the epitaxial process are normally replicated and grown. Excessive roughness indicates that the step merging and bunching are increased, and the epitaxial parameter window is abnormal. Usually the roughness Ra is required to be less than 0.5.

[0152] The above test results are shown in Table 1.

[0153] Table 1

[0154]

[0155] It can be seen from the results in Table 1 that a defect-controllable 3C-SiC epitaxial wafer can be prepared according to the method described in the present invention, and the fatal defect density and stacking fault defect density of the prepared 3C-SiC epitaxial wafer are significantly lower.

[0156] By comparing Example 1 with Example 2, it can be seen that the low growth rate and relatively low growth pressure in the first stage are conducive to the growth of the film, and the roughness is relatively low, which means that the growth process is stable and conducive to the formation of high-quality films.

[0157] By comparing Example 1 with Example 3, it can be seen that by reducing the etching degree and process temperature, due to the lowering of temperature, the carbon-silicon ratio must also be reduced accordingly to meet the actual consumption balance of carbon source and silicon source in the reaction chamber; the Pit of Example 3 will be optimized to a certain extent, and the Pit comes from silicon-rich silicon droplets and pits formed after the surface particles are corroded, and the low-temperature process is used to prevent the increase of the Pit pit due to over-etching; correspondingly, the etching degree is reduced, and there are contaminated particles on the surface of the epitaxial wafer that have not been etched away, that is, the 3C-SiC epitaxial wafer of Example 3 has relatively more fatal defects.

[0158] By comparing Example 1 with Comparative Example 1, it can be seen that by replacing the carbon source and the silicon source, C 2 H 4 With SiHCl 3 Combination, only at a higher process temperature can it grow stably, but 3C silicon carbide has poor stability at high temperatures. In order to meet the formation of 3C silicon carbide, a lower process temperature is used, C 2 H 4 With SiHCl 3 The combined chemical reaction effect is poor, resulting in poor concentration uniformity and relatively more defects.

[0159] By comparing Example 1 with Example 5, it can be seen that a lower growth pressure assists the gas phase reaction of the silicon source and the carbon source, accelerates decomposition and adsorption and shedding, is beneficial to the balance of the chemical reaction, and can reduce interface defects such as stacking faults; and, suitable etching can further clean the surface cleanliness of the epitaxial wafer, thereby reducing the nucleation rate of fatal defects.

[0160] By comparing Example 1 with Example 6, it can be seen that the relatively low carbon-silicon ratio and the silicon-rich reaction chamber environment are beneficial to the reduction of Pit defects.

[0161] By comparing Example 1 with Example 7, it can be seen that adding an additional Cl element will accelerate the decomposition of the silicon source, increase the growth rate, and be beneficial to the control of the uniformity of the film thickness.

[0162] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a 3C-SiC epitaxial wafer, characterized in that: The method comprises the following steps: (1) performing a first etching on the silicon substrate; (2) forming a first carbonized buffer layer on the surface of the etched silicon substrate; (3) performing heteroepitaxial growth on the first carbonized buffer layer in the presence of a first process gas; Wherein, the first process gas comprises a carbon source and a silicon source, and the carbon source comprises a chlorine-based carbon source; Preferably, the chlorine-based carbon source is CH3Cl.

2. The method according to claim 1, characterized in that In step (3), the first process gas further comprises HCl.

3. The method according to claim 1 or 2, characterized in that: In step (3), the chlorine-silicon ratio of the first process gas is 2-4:

1.

4. The method according to any one of claims 1 to 3, characterized in that: In step (3), the carbon-silicon ratio of the first process gas is 0.9-1.2:

1.

5. The method according to claim 1 or 2, characterized in that: In step (3), the conditions for the heteroepitaxial growth include: temperature of 1250-1380° C., pressure of 50-80 mbar, and time of 1-3 h.

6. The method according to any one of claims 1 to 5, characterized in that: In step (1), the first etching is hydrogen in-situ etching.

7. The method according to any one of claims 1 to 5, characterized in that: In step (2), the process of forming the first carbonized buffer layer is carried out in the presence of a chlorine-based carbon source; Preferably, the chlorine-based carbon source is CH3Cl.

8. The method according to any one of claims 1 to 5, characterized in that: In step (2), the operating conditions of the process of forming the first carbonized buffer layer include: temperature of 1250-1380° C., pressure of 60-80 mbar, and time of 5-20 min.

9. The method according to any one of claims 1 to 8, characterized in that: The method further comprises the following steps: (4) removing the silicon substrate in the epitaxial growth substrate obtained in step (3); Preferably, the silicon substrate is removed by wet chemical etching.

10. The method according to claim 9, characterized in that The method further comprises the following steps: (5) performing a second etching on the 3C-SiC wafer obtained in step (4); (6) forming a second carbonized buffer layer on the surface of the etched 3C-SiC substrate; (7) performing homoepitaxial growth on the second carbonized buffer layer in the presence of a second process gas; Wherein, the second process gas includes a carbon source and a silicon source.

11. The method according to claim 10, characterized in that In step (7), the carbon-silicon ratio of the second process gas is 0.9-1.1:

1.

12. The method according to claim 10 or 11, characterized in that: In the second process gas of step (7), the carbon source is C2H4 and / or CH3Cl, preferably C2H4.

13. The method according to claim 10 or 11, characterized in that: In the second process gas of step (7), the silicon source is SiHCl3 and / or SiH4, preferably SiHCl3.

14. The method according to any one of claims 10 to 13, characterized in that: In step (7), the homoepitaxial growth conditions include: temperature of 1400-1500° C., pressure of 60-100 mbar, and time of 5-20 min.

15. The method according to any one of claims 10 to 14, characterized in that: In step (5), the second etching is hydrogen in-situ etching.

16. The method according to any one of claims 10 to 14, characterized in that: In step (6), the carbon source used in the process of forming the second carbonized buffer layer is C2H4 and / or CH3Cl, preferably C2H4.

17. The method according to any one of claims 10 to 14, characterized in that: In step (6), the operating conditions of the process of forming the second carbonized buffer layer include: temperature of 1400-1500° C., pressure of 60-100 mbar, and time of 1-10 min.

18. A 3C-SiC epitaxial wafer prepared by the method according to any one of claims 1 to 17.

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