Silicon carbide epitaxial substrate and method of manufacturing the same

Abstract

The technical problem to be solved by the present application is to improve the reliability of a silicon carbide epitaxial substrate. The technical solution of the present application is to use a silicon carbide epitaxial substrate (10) having a silicon carbide substrate (20) and an epitaxial layer (30) formed on the upper surface of the silicon carbide substrate (20). The upper surface (30a) of the epitaxial layer (30) has a plurality of surface defects. The length of the surface defects in plan view is L, the thickness of the epitaxial layer (30) is d, and the inclination angle of the silicon carbide substrate (20) is θ. The plurality of surface defects include small surface defects that satisfy L < d / tan θ. In this case, the density of the small surface defects is 100 / cm 2 The following.

Description

Technical Field Technical Field

[0001] This invention relates to silicon carbide epitaxial substrates and methods for manufacturing the same. Background Technology

[0002] Silicon carbide (SiC) possesses extremely high thermal and chemical stability, excellent mechanical strength, strong radiation resistance, and higher insulation breakdown voltage and thermal conductivity than silicon (Si). Semiconductor devices using silicon carbide can achieve performance that is difficult to achieve in semiconductor devices using existing semiconductor materials such as silicon. Therefore, silicon carbide is expected to be a next-generation semiconductor material in various fields.

[0003] Patent document 1 (Japanese Patent Application Publication No. 2022-151601) describes the manufacture of a silicon carbide epitaxial substrate by forming an epitaxial layer on the upper surface of a substrate formed of silicon carbide (hereinafter referred to as a silicon carbide substrate). It describes methods for reducing the density of linear surface defects generated on the upper surface of the epitaxial layer.

[0004] Non-Patent Document 1 describes the effect of dislocations present in a silicon carbide substrate on semiconductor devices using silicon carbide.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2022-151601 Non-patent literature Non-patent literature 1: Applied Physics, Vol. 82, No. 10, 846. Summary of the Invention

[0006] The technical problem that the invention aims to solve When an epitaxial layer is continuously formed on the upper surface of a silicon carbide substrate, the state of the growth chamber of the growth apparatus can change due to deposits caused by raw material gases. These changes in the state of the growth chamber affect the quality of the silicon carbide epitaxial substrate, and consequently, sometimes impact the reliability of semiconductor devices manufactured using silicon carbide epitaxial substrates.

[0007] In view of the above-mentioned actual situation, the purpose of the present invention is to improve the reliability of silicon carbide epitaxial substrates.

[0008] Technical solutions for solving technical problems One embodiment of the silicon carbide epitaxial substrate includes a silicon carbide substrate and an epitaxial layer formed on the upper surface of the silicon carbide substrate. The upper surface of the epitaxial layer has a plurality of surface defects. When the length of the surface defects in a top view is defined as L, the thickness of the epitaxial layer as d, and the deflection angle of the silicon carbide substrate as θ, the plurality of surface defects includes minute surface defects that satisfy L < d / tanθ. The density of the minute surface defects is 100 defects / cm². 2 the following.

[0009] One embodiment of a silicon carbide epitaxial substrate includes a silicon carbide substrate and an epitaxial layer formed on the upper surface of the silicon carbide substrate. A plurality of surface defects and a plurality of through-screw dislocations are formed on the upper surface of the epitaxial layer. Among the plurality of surface defects, when the length of the surface defect in top view is defined as L, the thickness of the epitaxial layer as d, and the deflection angle of the silicon carbide substrate as θ, a defect satisfying L < d / tanθ is called a micro-surface defect. In a graph where the horizontal axis represents the density of through-screw dislocations on the upper surface of the epitaxial layer and the vertical axis represents the density of micro-surface defects on the upper surface of the epitaxial layer, multiple data are used to make the intercept of the vertical axis zero. When performing linear fitting using the least squares method, the slope of the approximate curve obtained is less than 0.05. The multiple data are the measurement results of the density of through-screw dislocations and the density of micro-surface defects in each of the multiple regions when the upper surface of the epitaxial layer is divided into multiple regions, and these measurements are plotted in the graph.

[0010] One embodiment of a method for manufacturing a silicon carbide epitaxial substrate includes: (a) a step of preparing a silicon carbide substrate; and (b) a step of forming an epitaxial layer on the upper surface of the silicon carbide substrate in a growth chamber of a film deposition apparatus. In step (b), a silicon-based gas and a carrier gas are supplied to the growth chamber through a first pipe, and a carbon-based gas and a carrier gas are supplied to the growth chamber through a second pipe. In step (b), the epitaxial layer is continuously formed on the upper surface of 25 or more silicon carbide substrates at a film deposition rate greater than 40 μm / h. The upper surface of the epitaxial layer has multiple surface defects and multiple penetrating spiral dislocations. When the length of the surface defects in a top view is defined as L, the thickness of the epitaxial layer as d, and the deflection angle of the silicon carbide substrate as θ, the multiple surface defects include minute surface defects that satisfy L < d / tanθ. In step (b), the flow rates of the carrier gas in the first pipe and the carrier gas in the second pipe are adjusted such that the density of the minute surface defects is 100 per cm³. 2 the following.

[0011] Invention Effects One implementation method can improve the reliability of silicon carbide epitaxial substrates. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view of the silicon carbide epitaxial substrate of Embodiment 1.

[0013] Figure 2 This is a cross-sectional view of the silicon carbide substrate according to Embodiment 1.

[0014] Figure 3 This is a cross-sectional schematic diagram showing the two gas supply pipes in Embodiment 1.

[0015] Figure 4 This is a graph showing the distribution of carrier concentration on the upper surface of the epitaxial layer in Example 3.

[0016] Figure 5 This is a graph showing the distribution of carrier concentration on the upper surface of the epitaxial layer in Comparative Example 1.

[0017] Figure 6 This is a graph showing the distribution of carrier concentration on the upper surface of the epitaxial layer in Comparative Example 2.

[0018] Figure 7 This is a graph showing the distribution of carrier concentration on the upper surface of the epitaxial layer in Comparative Example 2.

[0019] Figure 8 This is a graph showing the deviation of carrier concentration in silicon carbide epitaxy during continuous film formation on multiple silicon carbide substrates in Example 3.

[0020] Figure 9 This is a graph showing the deviation of the carrier concentration of silicon carbide epitaxy when continuous films are formed on multiple silicon carbide substrates in Comparative Example 1.

[0021] Figure 10 This is a graph showing the deviation of the carrier concentration of silicon carbide epitaxy when continuous films are formed on multiple silicon carbide substrates in Comparative Example 2.

[0022] Figure 11 These are differential interference optical microscopic images obtained during the detection of minute surface defects.

[0023] Figure 12 These are analytical images obtained during the detection of penetrating spiral dislocations.

[0024] Figure 13 This is a top view showing the density distribution of penetrating spiral dislocations and the density distribution of minute surface defects on the entire upper surface of the silicon carbide epitaxial substrate of Example 3.

[0025] Figure 14This is a top view showing the density distribution of penetrating spiral dislocations and the density distribution of minute surface defects on the entire upper surface of the silicon carbide epitaxial substrate of Comparative Example 1.

[0026] Figure 15 This is a graph showing the relationship between the density of penetrating spiral dislocations and the density of minute surface defects.

[0027] Symbol Explanation 10: Silicon carbide epitaxial substrate; 20: Silicon carbide substrate; 20a: First surface; 20b: Second surface; 20n: Normal; 30: Epitaxial layer; 30a: Top surface; 41: Silane channel; 42: Propane channel. Detailed Implementation

[0028] In all the drawings used to illustrate the embodiments, the same components are generally labeled with the same symbols, and repeated descriptions are omitted. Furthermore, even top views sometimes include section lines to facilitate understanding of the drawings.

[0029] The radial direction referred to in this specification is along the diameter of the silicon carbide substrate.

[0030] Implementation Method 1 The following explains how improvements in the manufacturing conditions of the epitaxial layer formed on the upper surface of a silicon carbide substrate can enhance the reliability of silicon carbide epitaxial substrates and reduce their manufacturing costs.

[0031] Room for improvement For epitaxial layers formed on the upper surface of a silicon carbide substrate, the carrier concentration, epitaxial layer thickness, and in-plane density of various surface defects and dislocation system defects must be within desired ranges. Surface defects are irregularities or irregularities on the upper surface of the epitaxial layer. Figure 1 For epitaxial layers, thickness refers to Figure 1 The longitudinal dimension on the paper. Dislocation system defects refer to defects detected by methods such as photoluminescence, where the upper surface of the epitaxial layer lacks unevenness. The desired range is determined by the design concept of the power device. Conditions for a good silicon carbide epitaxial substrate include low carrier concentration, minimal deviation in epitaxial layer thickness, and low density of various defects.

[0032] As described in "The Technical Problem to be Solved by the Invention," during continuous film formation in epitaxial layer deposition, the state within the growth chamber of the film formation apparatus can change due to deposit precipitation caused by raw material gases. In other words, deposits adhere to the inner wall of the growth chamber. Due to the manner and location of deposit adhesion, the deviation in carrier concentration within the epitaxial layer can sometimes increase. When the deviation in carrier concentration within the epitaxial layer increases, the reliability and yield of the silicon carbide epitaxial substrate decrease.

[0033] From the perspective of improving the reliability of silicon carbide epitaxial substrates, it is desirable to have minimal deviation in carrier concentration within the epitaxial layer. To reduce carrier concentration deviation, it is advisable to shorten the maintenance cycle for removing deposits from the film deposition apparatus in order to maintain the state within the apparatus. Shortening the maintenance cycle means reducing the number of silicon carbide substrates that can be continuously deposited within the film deposition apparatus. Due to the lower operating rate of the film deposition apparatus, the manufacturing cost of silicon carbide epitaxial substrates increases.

[0034] Furthermore, silicon carbide substrates contain a large number of through dislocations, which are a type of dislocation system defect. Through dislocations can sometimes transform into surface defects with unevenness on the upper surface of the epitaxial layer during epitaxial deposition. Types of through dislocations include through edge dislocations and through screw dislocations. These defects can be a major cause of various failures in semiconductor devices using silicon carbide, especially silicon carbide power devices (Non-Patent Document 1). Through screw dislocations (TSDs) are defects generated within the epitaxial layer on the upper surface of the silicon carbide substrate. Through screw dislocations penetrate the epitaxial layer from the lower surface to the upper surface. Therefore, through screw dislocations can be identified by observing the upper surface of the epitaxial layer.

[0035] The surface defects include linear surface defects whose length L is represented by L = d / tanθ when the epitaxial layer thickness is set to d and the deflection angle of the silicon carbide substrate is set to θ. These linear surface defects are also known as carrot defects. A method for reducing these linear surface defects is disclosed in Patent Document 1.

[0036] For example, when the thickness of the epitaxial layer is 30 μm, the length L of the aforementioned linear surface defect is approximately 430 μm. The inventors of this invention discovered that, in addition to this relatively large linear surface defect, the upper surface of the epitaxial layer also produces linear surface defects with even smaller lengths L. That is, the linear surface defects include both linear surface defects represented by L = d / tanθ and smaller linear surface defects. In this specification, to distinguish these linear surface defects from each other, defects satisfying L < d / tanθ are referred to as micro-surface defects. In other words, the surface defects produced on the upper surface of the epitaxial layer include micro-surface defects that satisfy L < d / tanθ.

[0037] The presence of minute surface defects can also be a major cause of failure in various silicon carbide power devices. As these minute surface defects increase on the upper surface of the epitaxial layer, the reliability and yield of the silicon carbide epitaxial substrate decrease. Therefore, from the perspective of improving the reliability and yield of silicon carbide epitaxial substrates, it is desirable to reduce the density of minute surface defects on the upper surface of the epitaxial layer.

[0038] Furthermore, increasing the epitaxial layer deposition rate can reduce the manufacturing cost of silicon carbide epitaxial substrates. The epitaxial layer deposition rate, as referred to in this specification, is the speed at which the material constituting the epitaxial layer is deposited onto the upper surface of the silicon carbide substrate during the epitaxial layer deposition process. The epitaxial layer deposition rate is expressed as the thickness of the material deposited per unit time. The inventors of this invention have discovered that increasing the epitaxial layer deposition rate increases the size of minute surface defects.

[0039] Based on the above explanation, the technical problem regarding silicon carbide epitaxial substrates lies in suppressing state changes within the growth chamber of the film deposition apparatus caused by deposit precipitation due to raw material gases, when epitaxial layers are continuously formed on the upper surface of multiple silicon carbide substrates. In addition, there are technical problems such as suppressing deviations in carrier concentration within the epitaxial layers and suppressing the generation of minute surface defects on the upper surface of the epitaxial layers. Reducing the number of continuously formed epitaxial layers or decreasing the film deposition rate increases the manufacturing cost of the silicon carbide epitaxial substrate. Therefore, it is necessary to solve the following technical problems: maintaining a high film deposition rate without reducing the number of continuously formed epitaxial layers, while simultaneously suppressing deviations in carrier concentration within the epitaxial layers and suppressing the generation of minute surface defects on the upper surface of the epitaxial layers.

[0040] The inventors of this invention have discovered that the manner and position of deposits adhering to the growth chamber of the film-forming apparatus are related to the supply conditions of the feed gas, as described later. Therefore, the inventors of this invention have made improvements in changing the manner and position of deposits adhering to the inner wall, etc., of the growth chamber of the film-forming apparatus. Furthermore, the inventors of this invention have discovered that the aforementioned deviations in carrier concentration and the generation of minute surface defects are related to the supply conditions of the feed gas, as described later. Therefore, the inventors of this invention have made improvements in maintaining a small deviation in carrier concentration without reducing the number of films formed continuously, maintaining a high film-forming rate, and suppressing the generation of minute surface defects. These improvements will be described in detail below.

[0041] Structure of silicon carbide epitaxial substrate Figure 1 This is a cross-sectional view showing the silicon carbide epitaxial substrate 10 according to Embodiment 1. The silicon carbide epitaxial substrate 10 has a silicon carbide substrate 20 and an epitaxial layer 30.

[0042] The silicon carbide substrate 20 has a first surface 20a and a second surface 20b located on the opposite side of the first surface 20a, and the epitaxial layer 30 is located on the first surface 20a. The silicon carbide substrate 20 is composed of a single silicon carbide crystal. The polytype of the silicon carbide substrate 20 is preferably 4H. The size of the silicon carbide substrate 20 is not limited. From the viewpoint of mass production of semiconductor devices fabricated using the silicon carbide epitaxial substrate 10, the silicon carbide substrate 20 preferably has a diameter of 100 mm or more. The diameter of a 6-inch silicon carbide substrate is preferably 145 mm or more, more preferably 150 mm or more. The diameter of an 8-inch silicon carbide substrate is preferably 195 mm or more, more preferably 200 mm or more. The silicon carbide substrate 20 has a thickness determined according to the standard diameter. For example, in the case of a diameter of 100 mm or 150 mm, the thickness of the silicon carbide substrate 20 is 350 μm ± 25 μm or 500 μm ± 25 μm.

[0043] The silicon carbide epitaxial substrate 20 used in the silicon carbide epitaxial substrate 10 has a first surface 20a that is a Si surface. That is, silicon is exposed on the first surface 20a. The crystal orientation of the first surface 20a is (0001). On the other hand, the second surface 20b is a C surface. That is, carbon is exposed on the second surface 20b. The crystal orientation of the second surface 20b is (000-1).

[0044] Figure 2 This is a cross-sectional view of the silicon carbide substrate 20. The silicon carbide substrate 20 is preferably an angled substrate with an angle θ. Specifically, the first surface 20a, or the normal 20n of the first surface 20a, is preferably inclined by θ from the

[0001] direction to the

[1120] direction. The angle θ is preferably 0.5° or more and 8° or less, more preferably 0.5° or more and 5° or less.

[0045] The characteristics of the first surface 20a of the silicon carbide substrate 20 are described in detail. Preferably, the first surface 20a is polished using a chemical mechanical polishing (CMP) method. Specifically, it is preferable to polish using CMP until the surface roughness Ra of the first surface 20a reaches 1 nm or less. More preferably, the surface roughness Ra of the first surface 20a is 0.2 nm or less. The surface roughness Ra can be measured, for example, using a white light interference microscope. The surface roughness Ra is obtained, for example, by measuring three locations on the first surface 20a over a length of 100 μm and averaging the measured values ​​at those three locations. Ideally, the surface roughness Ra is 0 nm, but in reality, the surface roughness Ra is not 0 nm. Therefore, the lower limit of the preferred range for the surface roughness Ra is greater than 0.

[0046] Furthermore, the basal plane dislocation (BPD) density of the first surface 20a is preferably 3000 dislocations / cm². 2 The preferred density of BPDs is 2000 particles / cm³. 2 The following is a further preferred value: 1000 pieces / cm 2 The following describes how, regarding BPD density, for example, the first surface 20a can be etched using molten KOH (potassium hydroxide), and the number of BPDs appearing as etching marks can be determined using an optical microscope. Similar to surface roughness Ra, the lower limit of the preferred range for BPD density is greater than 0 particles / cm². 2 .

[0047] An epitaxial layer 30 is formed on the first surface 20a of a silicon carbide substrate 20 using an epitaxial growth method. The epitaxial layer 30 is composed of a single silicon carbide crystal. The thickness of the epitaxial layer 30 can be arbitrarily set according to the performance requirements of the semiconductor device fabricated using the silicon carbide epitaxial substrate 10. For example, the thickness of the epitaxial layer 30 can be more than 1 μm and less than 100 μm.

[0048] The upper surface 30a of the epitaxial layer 30 preferably has a plurality of linear surface defects. These linear surface defects comprise minute surface defects represented by L < d / tanθ. On the upper surface 30a of the epitaxial layer 30, the density of these minute surface defects is preferably less than 100 per cm². 2 The density of minute surface defects is 20 per cm³. 2 The following is a further preferred option: 5 per cm. 2 Furthermore, multiple penetrating spiral dislocations are formed within the epitaxial layer 30. On the upper surface 30a of the epitaxial layer 30, the density of penetrating spiral dislocations is preferably 400 dislocations / cm². 2 the following.

[0049] The micro-surface defects are uneven relative to the upper surface 30a. When viewed vertically from above, the micro-surface defects have a slender, linear shape. The length L of the micro-surface defects in the longitudinal direction when viewed from above depends on the thickness d of the epitaxial layer 30 and the deflection angle θ of the silicon carbide substrate 20, and there exists a relationship of L < d / tanθ. Here, "viewed from above" refers to, for example, as... Figure 13 That way, observe the upper surface of the epitaxial layer of the silicon carbide substrate.

[0050] The density of minute surface defects can be measured, for example, using a wafer inspection / observation apparatus capable of acquiring differential interference optical microscopy images. Such a wafer inspection / observation apparatus obtains the location and number of regions showing linear brightness variations in the acquired differential interference optical microscopy image, and calculates the density of minute surface defects.

[0051] Method for manufacturing silicon carbide epitaxial substrates The manufacturing method of the silicon carbide epitaxial substrate 10 according to Embodiment 1 will be described below. First, a silicon carbide substrate 20 is prepared. The silicon carbide substrate 20 has a first surface 20a with the crystal orientation and deflection angle described above. In addition, the surface roughness Ra of the first surface 20a is adjusted to 1 nm or less using the CMP method. The value of the surface roughness Ra is preferably small. For example, a commercially available silicon carbide substrate 20 can be obtained, and the first surface 20a can be polished using the CMP method.

[0052] Next, an epitaxial layer 30 is formed on the first surface 20a of the silicon carbide substrate 20 using an epitaxial growth method. Specifically, the epitaxial layer 30 is formed using chemical vapor deposition (CVD).

[0053] For example, a silicon carbide substrate 20 is introduced into the growth chamber of a film-forming apparatus, with its first surface 20a (0001) facing upwards and positioned on a holding member. The silicon carbide substrate 20 is heated to a temperature of 1500°C to 1800°C, and a carrier gas, a carbon source gas, a silicon source gas, and a dopant gas are introduced into the growth chamber to form an epitaxial layer 30. For example, hydrogen (H2) can be used as the carrier gas. The carbon source gas in the raw material gas can be a carbon-based gas such as propane (C3H8). The silicon source gas in the raw material gas can be a silicon-based gas such as silane (SiH4). The dopant gas can be nitrogen (N2). Alternatively, before forming the epitaxial layer 30, only the carrier gas can be introduced into the growth chamber to clean the first surface 20a of the silicon carbide substrate 20.

[0054] These gases are supplied to the growth chamber through two gas supply pipes. Figure 3 This is a schematic diagram showing the cross-section of the two gas supply pipes in Implementation Method 1.

[0055] like Figure 3 As shown, in epitaxial growth, multiple gas supply pipes supplying raw material gas and carrier gas to the growth chamber include a silane pipe 41 for supplying silane gas and a propane pipe 42 for supplying propane gas. Silane gas, serving as a raw material gas, and hydrogen gas, serving as a carrier gas, are supplied to the growth chamber through the silane pipe 41 (equivalent to the first pipe). Propane gas, serving as a raw material gas, nitrogen gas, and hydrogen gas, serving as a carrier gas, are supplied to the growth chamber through the propane pipe 42 (equivalent to the second pipe).

[0056] The carbon-to-silicon ratio (C / Si) of the gas used as a carbon source to the gas used as a silicon source is preferably 1 or more. Specifically, the C / Si ratio is preferably 1 or more and 1.6 or less.

[0057] The pressure in the growth chamber during the growth of the epitaxial layer 30 is preferably above 10 kPa and below 50 kPa.

[0058] As described in the following embodiments, in the method for manufacturing a silicon carbide epitaxial substrate 10 according to Embodiment 1, an epitaxial layer 30 is formed on the (0001) surface of a silicon carbide substrate 20. In Embodiment 1, the flow rate of the carrier gas is adjusted during the film formation process of the epitaxial layer 30. In this case, during the film formation process of the epitaxial layer 30, the state of the growth chamber of the film formation apparatus changes due to deposit precipitation caused by the raw material gas. That is, deposits adhere to the inner wall of the growth chamber of the film formation apparatus. However, by adjusting the flow rate of the carrier gas as described above, the manner and position of deposit adhesion change. As a result, the generation of small surface defects on the upper surface 30a of the epitaxial layer 30 can be suppressed. In addition, when the epitaxial layer 30 is continuously formed on multiple silicon carbide substrates 20 in the film formation apparatus, this adjustment can suppress the deviation of the carrier concentration in the epitaxial layer 30. That is, by adjusting the flow rate of the carrier gas, the influence on the reliability of the silicon carbide epitaxial substrate 10 due to deposit precipitation in the growth chamber can be suppressed.

[0059] Furthermore, from the viewpoint of improving the reliability of the silicon carbide epitaxial substrate 10, the temperature difference between the center and the end of the first surface 20a of the silicon carbide substrate 20 in the epitaxial layer 30 film formation process is preferably 50°C or less. More preferably, this temperature difference is 20°C or less, and even more preferably 10°C or less.

[0060] Example Sample preparation Hereinafter, a silicon carbide epitaxial substrate 10 is fabricated using the manufacturing method of the silicon carbide epitaxial substrate according to Embodiment 1, and the carrier concentration and density of micro-surface defects are measured, and the results are explained.

[0061] Examples 1-3, Comparative Examples 1 and 2 A silicon carbide substrate 20 with a diameter of 150 mm and a first surface 20a of (0001) with an offset angle θ of 4° was prepared. The first surface 20a was polished using CMP until the surface roughness Ra reached below 1 nm. Then, an epitaxial layer 30 was formed on the first surface 20a of the silicon carbide substrate 20. The growth temperature was set to 1600 °C, and the pressure in the growth chamber was set to 30 kPa. As shown in Table 1, the C / Si ratio in the raw material gas was set to 1.25. Hydrogen was used as the carrier gas, and propane and silane gases were used as the raw material gases. Nitrogen was used as the dopant source.

[0062] Table 1 shows the flow rate ratio of hydrogen in the silane gas pipeline between Examples 1-3 and Comparative Examples 1 and 2. When the flow rate ratio between Examples 1-3 and Comparative Example 1 was set to 100, the flow rate of hydrogen in the silane gas pipeline was set such that the flow rate ratio of Comparative Example 2 was 120.

[0063] Table 1 shows the flow rate ratio of hydrogen in the propane gas pipeline between Examples 1-3 and Comparative Examples 1 and 2. When the flow rate ratio of Comparative Examples 1 and 2 was set to 100, the flow rate of hydrogen in the propane gas pipeline was set such that the flow rate ratio of Example 1 was 65 and the flow rate ratio of Example 2 was 85.

[0064] In addition, in Example 3, when the hydrogen flow rate ratio in the propane gas pipeline of Comparative Examples 1 and 2 was set to 100, the hydrogen flow rate ratio in the propane gas pipeline was adjusted to between 65 and 85. In Example 3, the carrier concentration on the upper surface 30a of the epitaxial layer 30 after film deposition was measured, and the hydrogen flow rate in the propane gas pipeline in subsequent film deposition processes was adjusted based on the measurement results.

[0065] Table 1 shows the temperature difference between the center and the end of the first surface 20a of the silicon carbide substrate 20 in Examples 1-3 and Comparative Examples 1 and 2, respectively. In Examples 1-3, this temperature difference is set to be 50°C or less. Specifically, in Examples 1 and 2, the temperature difference is 20°C. In Example 3, the temperature difference is 10-40°C. It is preferable that the temperature difference is 10°C or less. In Comparative Examples 1 and 2, it is considered that the temperature difference is greater than 50°C, but it is not fixed, so the specific value of the temperature difference is not recorded in Table 1.

[0066] In Examples 1, 2, and Comparative Example 1, the epitaxial layer 30 was formed on only one silicon carbide substrate 20. In Example 3, the epitaxial layer 30 was continuously formed on 28 silicon carbide substrates 20. In Comparative Example 2, the epitaxial layer 30 was continuously formed on 15 silicon carbide substrates 20. The term "continuous formation of epitaxial layer" as used in this specification refers to a process in which the epitaxial layer 30 is formed on multiple silicon carbide substrates 20 without maintenance within the growth chamber of the film deposition apparatus. In other words, "continuous formation of epitaxial layer" refers to a process in which the epitaxial layer 30 is formed on multiple silicon carbide substrates 20 without releasing the vacuum state within the growth chamber of the film deposition apparatus.

[0067] In Examples 1-3, the film formation rate of the epitaxial layer 30 was set to 48 μm / h, and in Comparative Examples 1 and 2, the film formation rate of the epitaxial layer 30 was set to 45 μm / h and 43 μm / h, respectively. Thus, in Examples 1-3, the film formation rate of the epitaxial layer 30 was set to be greater than 40 μm / h.

[0068] [Table 1] Table 2 shows the analysis results for Examples 3-1, 3-2, 3-3, and Comparative Example 1-1. In Examples 3-1, 3-2, and 3-3, each randomly selected silicon carbide epitaxial substrate 10 was analyzed from silicon carbide epitaxial substrates 10 fabricated under the same conditions as in Example 3. In Comparative Example 1-1, each randomly selected silicon carbide epitaxial substrate 10 was analyzed from silicon carbide epitaxial substrates 10 fabricated under the same conditions as in Comparative Example 1.

[0069] In addition, through-through spiral dislocations in the silicon carbide epitaxial substrate 10 were detected for Examples 3-1, 3-2, 3-3 and Comparative Example 1-1. Based on the detection results, as shown in Table 2, the average value (average number) of through-through spiral dislocations in the upper surface 30a of the epitaxial layer 30 was calculated.

[0070] In addition, based on the detection results of minute surface defects on the upper surface 30a of the epitaxial layer 30, as shown in Table 2, the average value of minute surface defects on the upper surface 30a of the epitaxial layer 30 is calculated.

[0071] In addition, as shown in Table 2, for Examples 3-1, 3-2, 3-3 and Comparative Example 1-1, the slopes of the approximate curves representing the relationship between the density of penetrating spiral dislocations and the density of minute surface defects were calculated respectively.

[0072] [Table 2] Measurement The film deposition rates shown in Table 1 were calculated based on the thickness of the epitaxial layer after deposition and the deposition time. The thickness of the epitaxial layer was measured using a non-contact film thickness measuring device. The thickness of the epitaxial layer was measured using a UTS-2000 film thickness measuring device from Japan Spectrophotometer Co., Ltd.

[0073] Regarding the carrier concentrations shown in Table 1, the capacitance-voltage (CV) method was used to measure multiple locations in the X and Y directions within the upper surface 30a of the epitaxial layer 30. The carrier concentration measurements were performed using a CV measuring instrument, "CVmap92A," manufactured by FourDimensions. The X and Y directions are orthogonal to each other when viewed from above along the upper surface 30a of the epitaxial layer 30. The X direction is the direction of the orientation flat edge (along the

[1120] direction), and the Y direction is the direction orthogonal to the orientation flat edge direction. In the carrier concentration measurements at multiple locations on the upper surface 30a of a single silicon carbide epitaxial substrate 10, the maximum carrier concentration was designated as Max, the minimum carrier concentration as Min, and the average of all carrier concentration measurements at multiple locations was designated as Ave. The deviation of the carrier concentration within the upper surface 30a of the epitaxial layer 30 was expressed as 0.5 × (Max - Min) / Ave. In the determination of carrier concentration deviation shown in Table 1, a deviation of less than 20% is considered good (OK), and a deviation of more than 20% is considered bad (NG).

[0074] The detection of the minute surface defects shown in Table 1 was performed as follows: Surface observation of the epitaxial layer 30 was conducted using a confocal microscope with a differential interference lens. The obtained differential interference optical microscopy image was divided into 5mm × 5mm regions (single slices) for analysis. This surface observation was performed using the defect inspection device "SICA" (registered trademark) manufactured by Lasertec Corporation. Minor surface defects have unevenness relative to the surface, and therefore appear differently in brightness in the image compared to flat, normal crystalline regions. The average value of the minute surface defects shown in Table 1 was calculated by averaging the number of minute surface defects in each of the aforementioned regions as the number per unit area. In the determination of minute surface defects in Table 1, the average value of the minute surface defects is less than 100 defects / cm². 2 When the time is right, it is judged as good (OK), with 100 pieces / cm. 2 If the above conditions are met, the result is considered unacceptable (NG). The in-plane average value of the micro-surface defects shown in Table 2 is calculated by averaging the number of micro-surface defects in each of the above-mentioned regions as the number of defects per unit area.

[0075] The detection of through-spiral dislocations in the silicon carbide epitaxial substrate 10 shown in Table 1 was performed as follows: X-ray topology was used to measure the reflection image (0008 reflection image) of the

[0008] plane, and the obtained image was divided into 5mm × 5mm regions for analysis. The measurement of the 0008 reflection image was performed using the topology measurement system "XRTMicron" (registered trademark) manufactured by Rigaku Corporation. The in-plane average value of the through-spiral dislocation density shown in Table 2 was obtained by calculating the average value of the number of through-spiral dislocations in each of the above-mentioned regions as the number per unit area.

[0076] The slope of the approximate curve shown in Table 2 is obtained by graphically representing the density of penetrating spiral dislocations in the silicon carbide epitaxial substrate 10 on the horizontal axis and the density of minute surface defects in the upper surface 30a of the silicon carbide epitaxial substrate 10 on the vertical axis, making the intercept of the vertical axis 0, and calculating the slope of the approximate curve by performing linear fitting using the least squares method.

[0077] Results and Investigations Figure 4 , Figure 5 , Figure 6 and Figure 7 This indicates the distribution of carrier concentration within the upper surface 30a of the epitaxial layer 30. Figure 4 This is a graph showing the carrier concentration at various locations within the upper surface 30a of the epitaxial layer 30 formed under the same conditions as in Example 1. Figure 5 This is a graph showing the carrier concentration at various locations within the upper surface 30a of the epitaxial layer 30 formed under the same conditions as Comparative Example 1. Figure 6 This is a graph showing the carrier concentration at each position within the upper surface 30a of the epitaxial layer 30 constituting the first silicon carbide epitaxial substrate 10 in 15 silicon carbide epitaxial substrates 10 that were continuously deposited under the same conditions as Comparative Example 2. Figure 7 This is a graph showing the carrier concentration at various positions within the upper surface 30a of the epitaxial layer 30 constituting the fifth silicon carbide epitaxial substrate 10 among 15 silicon carbide epitaxial substrates 10 that were continuously deposited under the same conditions as Comparative Example 2.

[0078] exist Figure 4 , Figure 5 , Figure 6 and Figure 7 In the figure, the horizontal axis represents the radial position of the upper surface 30a of the silicon carbide epitaxial substrate 10, and the vertical axis represents the carrier concentration within the upper surface 30a of the epitaxial layer 30.

[0079] The silicon carbide epitaxial substrate 10 is a circular semiconductor substrate. The diameter of the silicon carbide substrate 20 is 150 mm. That is, the silicon carbide epitaxial substrate 10 has a diameter of 6 inches. Figure 4, Figure 5 , Figure 6 and Figure 7 The value of the horizontal axis represents the radial distance measured from the center of the upper surface 30a of the circular silicon carbide epitaxial substrate 10. Figure 4 , Figure 5 , Figure 6 and Figure 7 In the diagram, the rhombus shape represents the carrier concentration measured at multiple measurement points arranged radially in the X direction on the upper surface 30a of the silicon carbide epitaxial substrate 10. Figure 4 , Figure 5 , Figure 6 and Figure 7 In the diagram, the circular figures represent the carrier concentrations measured at multiple measurement points arranged radially in the Y direction on the upper surface 30a of the silicon carbide epitaxial substrate 10. Figure 4 , Figure 5 , Figure 6 and Figure 7 In the figure, the carrier concentration at the center of the upper surface 30a of the silicon carbide epitaxial substrate 10 is set to 100, and the relative carrier concentrations at other locations are recorded.

[0080] like Figure 4 As shown, the deviation of carrier concentration within the upper surface 30a of the epitaxial layer 30 formed under the same conditions as in Example 1 was calculated using the formula 0.5 × (Max - Min) / Ave. The result showed a carrier concentration deviation of 5.5%. In contrast, as... Figure 5 As shown, the deviation of carrier concentration in the upper surface 30a of the epitaxial layer 30 formed under the same conditions as Comparative Example 1 is 21.7%.

[0081] In addition, such as Figure 6 and Figure 7 As shown, the deviation in carrier concentration within the upper surface 30a of the epitaxial layer 30 formed continuously under the same conditions as Comparative Example 2 is 5.7% in the first silicon carbide epitaxial substrate 10 and 8.7% in the fifth silicon carbide epitaxial substrate 10. No patterns are shown for the sixth and subsequent silicon carbide epitaxial substrates 10, but... Figure 6 and Figure 7 As shown, as the number of continuously formed films increases, the deviation in carrier concentration also increases. As a result, although no graph is shown here, the deviation in carrier concentration within the upper surface 30a of the epitaxial layer 30 constituting the fifteenth silicon carbide epitaxial substrate 10 exceeds 20%.

[0082] Based on the above description, as shown in Table 1, Example 1 was deemed good (OK), and Examples 2 and 3 were also deemed good (OK). In contrast, Comparative Examples 1 and 2 were deemed bad (NG). Thus, in Examples 1 to 3, compared to Comparative Examples 1 and 2, the deviation in carrier concentration on the upper surface 30a of the epitaxial layer 30 can be suppressed. As in Example 3, when film deposition is continuously performed on 25 or more silicon carbide substrates 20, the deviation in carrier concentration can also be suppressed.

[0083] In this process, multiple silicon carbide substrates 20 are sometimes transported in groups of 25, placed in containers such as "boxes" or "carriers." As a result, processes such as the deposition of the epitaxial layer 30 are considered to be performed on batches of 25 silicon carbide substrates 20, with continuous film deposition occurring on these 25 substrates. In practice, film deposition is sometimes performed continuously on approximately 100 to 150 silicon carbide substrates 20. Since the silicon carbide substrates 20 are deposited in groups of 25, the manufacturing cost of the silicon carbide epitaxial substrate 10 increases when the number of substrates continuously deposited on the silicon carbide substrate 20 is less than 25. Therefore, performing continuous film deposition on 25 or more silicon carbide substrates 20 helps to improve the efficiency of the silicon carbide epitaxial substrate 10 manufacturing process. In other words, it can reduce the manufacturing cost of the silicon carbide epitaxial substrate 10.

[0084] In addition, silicon carbide substrates 20 are sometimes grouped into sets of 10 for film deposition and other processes. Therefore, performing film deposition continuously on 10 or more silicon carbide substrates 20 helps to improve the efficiency of the manufacturing process of silicon carbide epitaxial substrates 10.

[0085] Figure 8 , Figure 9 and Figure 10 This indicates the deviation of carrier concentration within the upper surface 30a of each epitaxial layer 30 when epitaxial layers 30 are continuously formed on the upper surfaces of multiple silicon carbide substrates 20. Figure 8 This is a graph showing the carrier concentration on the upper surface 30a of each epitaxial layer 30 when 28 epitaxial layers 30 are continuously formed under the same conditions as in Example 3. Figure 9 This is a graph showing the carrier concentration on the upper surface 30a of each epitaxial layer 30 when 25 epitaxial layers 30 are formed continuously under the same conditions as in Comparative Example 1. Figure 10 This is a graph showing the carrier concentration on the upper surface 30a of each epitaxial layer 30 when five epitaxial layers 30 are formed continuously under the same conditions as in Comparative Example 2.

[0086] Figure 8 , Figure 9 and Figure 10 The horizontal axis represents the number of silicon carbide substrates 20 that are continuously deposited on the upper surface of the silicon carbide substrate 20. Figure 8, Figure 9 and Figure 10 The vertical axis represents the deviation of carrier concentration. The value of the vertical axis is a numerical value representing the deviation calculated using the formula 0.5 × (Max - Min) / Ave.

[0087] like Figure 8 As shown, when film formation is performed under the same conditions as in Example 3, the deviation of carrier concentration is small, and even when film formation is performed continuously, the variation of carrier concentration deviation is small.

[0088] In contrast, such as Figure 9 As shown, when film deposition was performed under the same conditions as in Comparative Example 1, the deviation in carrier concentration increased with the increase in the number of silicon carbide substrates 20 deposited in a continuous manner. For example, in the fifteenth epitaxial layer 30, the deviation in carrier concentration exceeded 20%. Figure 9 The graph shows that when the number of films in continuous deposition exceeds approximately 30, the deviation in carrier concentration will exceed 20%.

[0089] In addition, such as Figure 10 As shown, when film deposition was performed under the same conditions as in Comparative Example 2, the deviation in carrier concentration increased with the increase in the number of silicon carbide substrates 20 in continuous film deposition. According to... Figure 10 The graph shows that when the number of films in continuous deposition exceeds approximately 20, the deviation in carrier concentration will exceed 20%.

[0090] Thus, in Example 3, compared to Comparative Examples 1 and 2, the deviation in carrier concentration on the upper surface 30a of the epitaxial layer 30 can be suppressed. As in Example 3, when film deposition is performed continuously on 25 or more silicon carbide substrates 20, the deviation in carrier concentration can also be suppressed. Therefore, the manufacturing cost of the silicon carbide epitaxial substrate 10 can be reduced, and the deviation in carrier concentration can be suppressed.

[0091] Figure 11 This represents a differential interference optical microscopic image obtained during the detection of minute surface defects. For example... Figure 11 As indicated by the middle arrow, minute surface defects appear as lines on the upper surface 30a of the epitaxial layer 30. Specifically, from... Figure 11 The upper side is illuminated. The linear depression on the upper surface 30a can be identified by the black line in the shadow. The linear protrusion on the upper surface 30a can be identified by the white line in the illuminated area.

[0092] Figure 12 This represents the analytical image (0008 reflection image) obtained using X-ray topography in the detection of penetrating spiral dislocations. For example... Figure 12 As indicated by the middle arrow, penetrating spiral dislocations appear as black spots on the upper surface 30a of the epitaxial layer 30. Figure 11 and Figure 12 These are images obtained by observing almost identical locations on the same silicon carbide epitaxial substrate 10. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 11 and Figure 12 By comparison, it was recognized that the locations where tiny surface defects occur correspond to the locations where penetrating spiral dislocations occur.

[0093] Figure 13 and Figure 14 This is a top view showing the density distribution of penetrating spiral dislocations and the density distribution of minute surface defects on the entire upper surface 30a of the silicon carbide epitaxial substrate 10. Figure 13 The left side shows the density distribution of through-spiral dislocations on the entire upper surface 30a of the silicon carbide epitaxial substrate 10 fabricated under the same conditions as in Example 3. Additionally, Figure 13 The right side shows the density distribution of minute surface defects on the entire upper surface 30a of the silicon carbide epitaxial substrate 10, fabricated under the same conditions as in Example 3. Additionally, Figure 14 The left side shows the density distribution of through-spiral dislocations on the entire upper surface 30a of the silicon carbide epitaxial substrate 10 fabricated under the same conditions as Comparative Example 1. Additionally, Figure 14 The right side shows the density distribution of minute surface defects on the entire upper surface 30a of the silicon carbide epitaxial substrate 10, which was fabricated under the same conditions as Comparative Example 1.

[0094] exist Figure 13 and Figure 14 In the image, the density of penetrating spiral dislocations and micro-surface defects on the upper surface 30a of the silicon carbide epitaxial substrate 10 is shown in various brightness levels within a 5mm × 5mm region. For example... Figure 13 and Figure 14 As shown, when using the manufacturing conditions of Comparative Example 1, a silicon carbide epitaxial substrate 10 with a low density of penetrating spiral dislocations was used compared to the manufacturing conditions of Example 3. Thus, when using the manufacturing conditions of Example 3, regardless of whether a silicon carbide epitaxial substrate 10 with a relatively high density of penetrating spiral dislocations is used, the density of minute surface defects on the entire upper surface 30a of the silicon carbide epitaxial substrate 10 can be reduced compared to the manufacturing conditions of Comparative Example 1.

[0095] like Figure 14As shown in Table 2, if only the density distribution of penetrating spiral dislocations is considered, the silicon carbide epitaxial substrate 10 fabricated under the same conditions as Comparative Example 1 also appears to have high quality. However, when the silicon carbide epitaxial substrate 10 is fabricated under the same conditions as Comparative Example 1, small surface defects are easily generated on the upper surface 30a of the epitaxial layer 30. From the viewpoint of improving the reliability and yield of the silicon carbide epitaxial substrate 10, it is important to suppress the density of small surface defects, as is the case with the silicon carbide epitaxial substrate 10 fabricated under the same conditions as Example 3.

[0096] like Figure 13 As shown on the right, the density of micro-surface defects in any region of the upper surface 30a of the silicon carbide epitaxial substrate 10 is 100 defects / cm². 2 Based on the measurement results, as shown in Table 1, the minor surface defects in Examples 1-3 and Comparative Example 2 were judged as good (OK). In contrast, the minor surface defects in Comparative Example 1 were judged as bad (NG).

[0097] Thus, in Examples 1-3, compared to Comparative Example 1, the generation of minute surface defects on the upper surface 30a of the epitaxial layer 30 can be suppressed. In Embodiment 1, by adjusting the hydrogen flow rate, a film deposition rate greater than 40 μm / h can be maintained, and the generation of minute surface defects can be suppressed. Therefore, the manufacturing cost of the silicon carbide epitaxial substrate 10 can be reduced, and deviations in carrier concentration can be suppressed.

[0098] Figure 15 This is a graph showing the relationship between the density of penetrating spiral dislocations and the density of minute surface defects. Figure 15 The horizontal axis represents the density of penetrating spiral dislocations within the silicon carbide epitaxial substrate 10. Figure 15 The vertical axis represents the density of minute surface defects on the upper surface 30a of the epitaxial layer 30. Figure 15 The multiple triangular diagrams shown represent the density of penetrating spiral dislocations and the density of micro-surface defects measured in each region when the upper surface 30a of the silicon carbide epitaxial substrate 10 of Comparative Example 1-1 is divided into multiple regions of 5mm × 5mm. Figure 15 The multiple circular diagrams shown represent the density of penetrating spiral dislocations and the density of micro-surface defects measured in each region when the upper surface 30a of the silicon carbide epitaxial substrate 10 of Example 3-1 is divided into multiple regions of 5mm × 5mm.

[0099] Figure 15 The solid line in the figure shows the approximate curve when using the least squares method to fit multiple data points obtained from multiple measurements as Comparative Example 1-1. That is, Figure 15 The graph shown was created using multiple datasets. The intercept of the y-axis for the approximate curve represented by the solid line is set to 0 (cm). 2).in addition, Figure 15 The dashed line shows the approximate curve obtained by linear fitting using the least squares method with multiple data points from multiple measurements taken in Example 3-1. The ordinate of the approximate curve shown by the dashed line is set to 0 (number / cm). 2 The data are plotted in the figure, which shows the measured density of penetrating spiral dislocations and the density of minute surface defects in multiple regions of the upper surface 30a of the silicon carbide epitaxial substrate 10.

[0100] A large slope in the approximate curve indicates a high probability that penetrating screw dislocations in the substrate will transform into minute surface defects. From the perspective of improving the reliability and yield of the silicon carbide epitaxial substrate 10, it is desirable that the slope of the approximate curve be less than 0.05. For example... Figure 15 As shown, the slope of the approximate curve for Comparative Example 1-1 is represented by y = 1.744x. Furthermore, the slope of the approximate curve for Example 3-1 is represented by y = 0.024x. That is, as shown in Table 2, the slope of the approximate curve for Comparative Example 1-1 is 1.744, and the slope of the approximate curve for Example 3-1 is 0.024. In the silicon carbide epitaxial substrate 10 of Example 3-1, the density of minute surface defects on the upper surface 30a of the epitaxial layer 30 can be suppressed to a very small degree.

[0101] Thus, in Example 3-1, compared to Comparative Example 1-1, the generation of minute surface defects on the upper surface 30a of the epitaxial layer 30 can be suppressed. In Embodiment 1, by adjusting the hydrogen flow rate, a relatively fast film deposition rate of 40 μm / h can be maintained, and the generation of minute surface defects can be suppressed. Therefore, the manufacturing cost of the silicon carbide epitaxial substrate 10 can be reduced, and deviations in carrier concentration can be suppressed.

[0102] In Embodiment 1, when the flow rate ratio of Comparative Examples 1 and 2 is set to 100, the flow rate ratio of hydrogen in the propane gas pipeline is adjusted to between 65 and 85. By adjusting the gas flow rate, a film deposition rate greater than 40 μm / h can be maintained, and the generation of minute surface defects and carrier concentration deviations on the upper surface 30a of the epitaxial layer 30 can be suppressed. Therefore, the manufacturing cost of the silicon carbide epitaxial substrate 10 can be reduced, and the reliability and yield of the silicon carbide epitaxial substrate 10 can be improved. Furthermore, when film deposition is performed continuously on 25 or more silicon carbide substrates 20, deviations in carrier concentration on the upper surface 30a of the epitaxial layer 30 can also be suppressed. In other words, the manufacturing cost of the silicon carbide epitaxial substrate 10 can be reduced, and carrier concentration deviations can be suppressed.

[0103] The invention described above is based on its embodiments. However, the invention is not limited to the above embodiments and can be modified without departing from its spirit.

[0104] For example, other epitaxial layers may be formed between the silicon carbide substrate and the epitaxial layer described above. In this case, the epitaxial layer described in this specification as an epitaxial layer formed on the upper surface of the silicon carbide substrate can be interpreted as an epitaxial layer formed on the silicon carbide substrate.

Claims

1. A silicon carbide epitaxial substrate, characterized in that, have: Silicon carbide substrate; and An epitaxial layer formed on the upper surface of the silicon carbide substrate. The upper surface of the epitaxial layer has multiple surface defects. When the length of the surface defect viewed from above is defined as L, the thickness of the epitaxial layer as d, and the deflection angle of the silicon carbide substrate as θ, the plurality of surface defects includes minute surface defects that satisfy L < d / tanθ. The density of the micro-surface defects is 100 per cm³. 2 the following.

2. The silicon carbide epitaxial substrate as described in claim 1, characterized in that: The density of the micro-surface defects is 20 per cm³. 2 the following.

3. The silicon carbide epitaxial substrate as described in claim 1, characterized in that: The density of the micro-surface defects is 5 per cm³. 2 the following.

4. The silicon carbide epitaxial substrate as described in claim 1, characterized in that: When the upper surface of the epitaxial layer is divided into multiple regions, and the maximum value of the carrier concentration in each region is set as Max, the minimum value of the carrier concentration in each region is set as Min, and the average value of the carrier concentration in each region is set as Ave., the deviation of the carrier concentration within the upper surface of the epitaxial layer is expressed by the formula 0.5 × (Max - Min) / Ave. The deviation of the carrier concentration is less than 20%.

5. The silicon carbide epitaxial substrate as described in claim 4, characterized in that: The deviation of the carrier concentration is less than 10%.

6. A silicon carbide epitaxial substrate, characterized in that, have: Silicon carbide substrate; and An epitaxial layer formed on the upper surface of the silicon carbide substrate. The upper surface of the epitaxial layer has multiple surface defects and multiple penetrating spiral dislocations. When the length of the surface defect viewed from above is defined as L, the thickness of the epitaxial layer as d, and the deflection angle of the silicon carbide substrate as θ, the plurality of surface defects includes minute surface defects that satisfy L < d / tanθ. In the graph, which uses multiple datasets, the horizontal axis represents the density of penetrating spiral dislocations and the vertical axis represents the density of minute surface defects. When the intercept of the vertical axis is set to 0, the slope of the approximate curve obtained by performing linear fitting using the least squares method is less than 0.

05. The multiple data are the data obtained by plotting the measurement results of the density of the penetrating spiral dislocations and the density of the micro-surface defects in each of the multiple regions when the upper surface of the epitaxial layer is divided into multiple regions.

7. A method for manufacturing a silicon carbide epitaxial substrate, characterized in that, include: (a) The process of preparing a silicon carbide substrate; and (b) The process of forming an epitaxial layer on the upper surface of the silicon carbide substrate within the growth chamber of the film-forming apparatus. In step (b), silicon-based gas and carrier gas are supplied to the growth chamber through a first pipe, and carbon-based gas and carrier gas are supplied to the growth chamber through a second pipe. In step (b), the epitaxial layer is continuously formed on the upper surface of more than 25 silicon carbide substrates at a film deposition rate greater than 40 μm / h. The upper surface of the epitaxial layer has multiple surface defects and multiple penetrating spiral dislocations. When the length of the surface defect viewed from above is defined as L, the thickness of the epitaxial layer as d, and the deflection angle of the silicon carbide substrate as θ, the plurality of surface defects includes minute surface defects that satisfy L < d / tanθ. In step (b), the flow rates of the carrier gas in the first pipe and the second pipe are adjusted so that the density of the minute surface defects is 100 per cm³. 2 the following.

8. The method for manufacturing a silicon carbide epitaxial substrate as described in claim 7, characterized in that: In step (b), the flow rates of the carrier gas in the first pipe and the second pipe are adjusted such that, in a graph where the horizontal axis represents the density of penetrating spiral dislocations and the vertical axis represents the density of minute surface defects, the intercept of the vertical axis is made 0, and the slope of the approximate curve obtained by linear fitting using the least squares method is less than 0.

05. The multiple data are the data obtained by plotting the measurement results of the density of the penetrating spiral dislocations and the density of the micro-surface defects in each of the multiple regions when the upper surface of the epitaxial layer is divided into multiple regions.

9. The method for manufacturing a silicon carbide epitaxial substrate as described in claim 7, characterized in that: The carrier gas is hydrogen.

10. The method for manufacturing a silicon carbide epitaxial substrate as described in claim 7, characterized in that: When the upper surface of the epitaxial layer is divided into multiple regions, and the maximum value of the carrier concentration in each region is set as Max, the minimum value of the carrier concentration in each region is set as Min, and the average value of the carrier concentration in each region is set as Ave., the deviation of the carrier concentration within the upper surface of the epitaxial layer is expressed by the formula 0.5 × (Max - Min) / Ave. In step (b), the flow rate of the carrier gas in the first pipe and the flow rate of the carrier gas in the second pipe are adjusted so that the deviation of the carrier concentration is less than 20%.

11. The method for manufacturing a silicon carbide epitaxial substrate as described in claim 10, characterized in that: In step (b), the epitaxial layer is continuously formed on the upper surface of 10 or more of the silicon carbide substrates. In step (b), the flow rate of the carrier gas in the first pipe and the flow rate of the carrier gas in the second pipe are adjusted so that the deviation of the carrier concentration is less than 10%.

12. The method for manufacturing a silicon carbide epitaxial substrate as described in claim 10, characterized in that: The carrier gas is hydrogen.

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