Sic epitaxial wafer

Abstract

To provide an SiC epitaxial wafer with large diameter, low triangular defect density, and high uniformity of carrier concentration.SOLUTION: An SiC epitaxial wafer according to the present embodiment has an SiC substrate and an SiC epitaxial layer. The SiC substrate has a diameter of 195 mm or more. The SiC epitaxial layer has a triangular defect density of 0.2 defects / cm2 or less and a carrier concentration variation of 20% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a SiC epitaxial wafer.

Background Art

[0002] Silicon carbide (SiC) has a breakdown electric field that is one order of magnitude larger and a bandgap that is three times larger than that of silicon (Si). In addition, silicon carbide (SiC) has characteristics such as a thermal conductivity that is about three times higher than that of silicon (Si). Therefore, silicon carbide (SiC) is expected to be applied to power devices, high-frequency devices, high-temperature operation devices, etc. For this reason, in recent years, SiC epitaxial wafers have been used for semiconductor devices as described above.

[0003] A SiC epitaxial wafer is obtained by laminating a SiC epitaxial layer on the surface of a SiC substrate. Hereinafter, the substrate before laminating the SiC epitaxial layer is referred to as a SiC substrate, and the substrate after laminating the SiC epitaxial layer is referred to as a SiC epitaxial wafer. The SiC substrate is manufactured by cutting from a SiC ingot. SiC devices such as power devices, high-frequency devices, and high-temperature operation devices are obtained by forming a device in the SiC epitaxial layer of a SiC epitaxial wafer and then dicing the SiC epitaxial wafer.

[0004] One of the indexes for evaluating a SiC epitaxial wafer is the carrier concentration. In order to improve the uniformity of chips obtained from one SiC epitaxial wafer, it is preferable that the carrier concentration in the plane of the SiC epitaxial wafer is uniform. For example, Patent Documents 1 and 2 disclose SiC epitaxial wafers having high in-plane uniformity of carrier concentration. Patent Document 3 also discloses a SiC epitaxial growth apparatus capable of increasing the temperature uniformity during manufacturing that affects the in-plane uniformity of the carrier concentration.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent No. 6969628 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2017-84989 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2019-96764 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In order to increase the number of SiC devices that can be obtained from a single SiC epitaxial wafer, an increase in the diameter of the SiC epitaxial wafer is required. However, increasing the diameter of the SiC epitaxial wafer is not easy.

[0007] When the SiC epitaxial wafer has a large diameter, the thermal stress applied to the manufacturing parts and the substrate increases. Large thermal stress greatly deforms the parts and causes dust generation. When particles accumulate on the SiC substrate, defects occur in the SiC epitaxial wafer. In order to suppress defects in the SiC epitaxial wafer, it is also conceivable to reduce the size of the SiC epitaxial growth apparatus and reduce the thermal stress applied to the parts. However, when the size of the SiC epitaxial growth apparatus is small, it becomes difficult to improve the in-plane uniformity of the SiC epitaxial wafer. That is, the larger the diameter of the SiC epitaxial wafer, the more difficult it is to achieve both a low defect density and a high in-plane uniformity.

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a SiC epitaxial wafer having a large diameter, a low triangular defect density, and a high uniformity of carrier concentration. [Means for Solving the Problems]

[0009] (1) The SiC epitaxial wafer according to the first aspect has a SiC substrate and a SiC epitaxial layer. The SiC substrate has a diameter of 195 mm or more. The SiC epitaxial layer has a triangular defect density of 0.2 pieces / cm 2 or less and a carrier concentration variation of 20% or less.

[0010] (2) In the SiC epitaxial wafer according to the above aspect, when the SiC epitaxial layer is viewed in plan from the stacking direction, it can be divided into a plurality of 5 mm square regions, and the ratio of the regions having no triangular defects among the plurality of regions may be 98% or more.

[0011] (3) In the SiC epitaxial wafer according to the above aspect, in a first region 60 mm or more and 95 mm or less away from the center when the SiC epitaxial layer is viewed in plan from the stacking direction, the carrier concentration variation may be 20% or less.

[0012] (4) In the SiC epitaxial wafer according to the above aspect, the film thickness variation of the SiC epitaxial layer may be 5% or less.

[0013] (5) In the SiC epitaxial wafer according to the above aspect, in a first region 60 mm or more and 95 mm or less away from the center when the SiC epitaxial layer is viewed in plan from the stacking direction, the film thickness variation may be 5% or less.

Advantages of the Invention

[0014] The SiC epitaxial wafer according to the above aspect has a large diameter, a low triangular defect density, and high carrier concentration uniformity.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0016] Hereinafter, the SiC epitaxial wafer and the like according to this embodiment will be described in detail with appropriate reference to the drawings. The drawings used in the following description may show an enlarged view of the characteristic portions for the sake of clarity of the features of this embodiment, and the dimensional ratios of the respective components may be different from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and can be appropriately changed and implemented without changing the gist thereof.

[0017] In this specification, the individual orientation is indicated by [], and the collective orientation is indicated by <>. Regarding negative indices, in crystallography, a "-" (bar) is attached above the number, but in this specification, a negative sign is attached before the number.

[0018] FIG. 1 is a cross-sectional view of the SiC epitaxial wafer 1 according to this embodiment. FIG. 2 is a plan view of the SiC epitaxial wafer 1 according to this embodiment.

[0019] The SiC epitaxial wafer 1 includes a SiC substrate 2 and a SiC epitaxial layer 3. The planar shape of the SiC epitaxial wafer 1 is substantially circular. The SiC epitaxial wafer 1 may have a notch 4 for grasping the direction of the crystal axis. Further, the SiC substrate 1 may have an orientation flat instead of the notch 4.

[0020] The SiC epitaxial wafer 1 is a wafer with a diameter of 8 inches (approx. 200 mm) or more. The diameter of the SiC epitaxial wafer 1 is 195 mm or more, preferably 199 mm or more. Also, the diameter of the SiC epitaxial wafer 1 is preferably 205 mm or less, more preferably 201 mm or less. The diameter of the SiC epitaxial wafer may be measured using a laser displacement meter.

[0021] The SiC substrate 2 is made of, for example, n-type SiC. The polytype of the SiC substrate 2 is not particularly limited and may be any of 2H, 3C, 4H, and 6H. The SiC substrate 2 is, for example, 4H-SiC. The diameter of the SiC substrate 2 is the same as the diameter of the SiC epitaxial wafer 1.

[0022] The SiC epitaxial layer 3 is laminated on one surface of the SiC substrate 2. The SiC epitaxial layer 3 is made of SiC.

[0023] The SiC epitaxial layer 3 according to the present embodiment has a triangular defect density of 0.2 pieces / cm 2 or less. The triangular defect density in the SiC epitaxial layer 3 is preferably 0.1 piece / cm 2 or less, more preferably 0.05 piece / cm 2 or less, still more preferably 0.03 piece / cm 2 or less, particularly preferably 0.01 piece / cm 2 or less. The lower limit of the triangular defect density in the SiC epitaxial layer 3 may be 0.003 piece / cm 2 The triangular defect density in the SiC epitaxial layer 3 may be 0 piece / cm 2 as well. The triangular defect density may be measured by measuring the density of triangular defects observed within the field of view using an optical microscope (manufactured by Lasertec: trade name SICA88).

[0024] A triangular defect is a defect that appears triangular when observing the surface of the SiC epitaxial layer 3 using an optical microscope. FIGS. 3 and 4 are diagrams for explaining the triangular defect. The triangular defect 5 spreads from the starting point 6 in the step-flow growth direction. The triangular defect 5 is formed in a direction such that the apex of the triangle and its opposite side (base) are arranged in order along the step-flow growth direction. The starting point 6 is, for example, a particle, damage such as a scratch on the SiC substrate 2, a two-dimensional nucleus formed on a terrace during step-flow growth, a crystal nucleus of a different polytype, a through screw dislocation (TSD), or the like.

[0025] The SiC epitaxial layer 3 can be divided into a plurality of regions A when viewed in plan from the stacking direction (<0001> direction). FIG. 5 is an example of an example in which the SiC epitaxial wafer according to the present embodiment is divided into a plurality of regions A. Each of the regions A is composed of a square with a side length a. The regions A are spread over the surface of the SiC epitaxial layer 3 without gaps. The center of one of the plurality of regions A coincides with the center C of the SiC epitaxial layer 3. Each of the regions A corresponds to each of the chips to be separated, and each becomes a SiC device.

[0026] For example, when the SiC epitaxial layer 3 is divided into a plurality of regions A with a side length a of 5 mm, the ratio of the regions having no triangular defect 5 is preferably 98% or more. In this case, the upper limit of the ratio of the regions having no triangular defect 5 may be 100% or 99%. Also, the upper limit of the ratio of the regions having no triangular defect 5 may be 99.97%. Also, for example, when the SiC epitaxial layer 3 is divided into a plurality of regions A with a side length a of 7 mm, the ratio of the regions having no triangular defect 5 is preferably 95% or more, and more preferably 98% or more. In this case, the upper limit of the ratio of the regions having no triangular defect 5 may be 100% or 99%. Also, the upper limit of the ratio of the regions having no triangular defect 5 may be 99.97%. For example, when the SiC epitaxial layer 3 is divided into a plurality of regions A with a side length a of 10 mm, the ratio of the region without triangular defects 5 is preferably 88% or more, more preferably 95% or more, and even more preferably 98% or more. In this case, the upper limit of the ratio of the region without triangular defects 5 may be 100% or 99%. Also, the upper limit of the ratio of the region without triangular defects 5 may be 99.97%. For example, when the SiC epitaxial layer 3 is divided into a plurality of regions A with a side length a of 15 mm, the ratio of the region without triangular defects 5 is preferably 75% or more, more preferably 88% or more, even more preferably 95% or more, and particularly preferably 98% or more. In this case, the upper limit of the ratio of the region without triangular defects 5 may be 100% or 99%. Also, the upper limit of the ratio of the region without triangular defects 5 may be 99.97%. For example, when the SiC epitaxial layer 3 is divided into a plurality of regions A with a side length a of 20 mm, the ratio of the region without triangular defects 5 is preferably 60% or more, more preferably 75% or more, even more preferably 88% or more, still more preferably 95% or more, and even more preferably 98% or more. In this case, the upper limit of the ratio of the region without triangular defects 5 may be 100% or 99%. Also, the upper limit of the ratio of the region without triangular defects 5 may be 99.97%. The ratio of the region without triangular defects 5 in the SiC epitaxial layer 3 is obtained by using an optical microscope (manufactured by Lasertec: product name SICA88), dividing it into a plurality of square regions A with a side length a of a specific value, where each does not overlap and is aligned without gaps, observing all the square regions A within the wafer surface, determining the number of square regions A with triangular defects, and calculating the area ratio of the region without triangular defects 5 from the general formula: ratio of the region without triangular defects 5 = {1 - (number of square regions A with triangular defects / number of all square regions A)} × 100.

[0027] The density of triangular defects 5 in the SiC epitaxial layer 3 is 0.2 pieces / cm 2If the following conditions are met, the ratio of the area without the above triangular defect 5 can be sufficiently achieved. Since the plurality of regions A correspond to the chips to be fabricated into devices, if the above ratio is satisfied, SiC devices can be obtained from the SiC epitaxial wafer 1 according to the present embodiment with a high yield. Also, the larger the length a of one piece is, the higher the current-carrying SiC device can be obtained.

[0028] In addition, the SiC epitaxial layer according to the present embodiment has a variation in carrier concentration of 20% or less, preferably 15% or less, more preferably 12% or less, still more preferably 10% or less, particularly preferably 5% or less, and even more particularly preferably 2% or less. The lower limit value of the variation in carrier concentration in the SiC epitaxial layer may be 0.5% or 1.5%. The variation in carrier concentration is obtained by dividing the difference between the maximum value and the minimum value of the carrier concentration of the SiC epitaxial layer 3 measured along a straight line extending in the <11-20> direction passing through the center C of the SiC epitaxial layer 3 by twice the average value. The measurement of the carrier concentration may be performed at equal intervals from the center C on the straight line, or the interval may vary. The measurement of the carrier concentration may be performed at intervals of 10 mm, 15 mm, 20 mm, 25 mm, or 30 mm.

[0029] For example, when the diameter of the SiC epitaxial wafer 1 is 200 mm (8 inches), the carrier concentration is measured at the center and at positions of ±20 mm, ±40 mm, ±60 mm, ±80 mm, and ±95 mm from the center along a straight line L extending in the <11-20> direction with the center C as a reference, and the carrier concentration uniformity is obtained from the respective carrier concentrations at these measurement points.

[0030] For example, when the diameter of the SiC epitaxial wafer 1 is 250 mm (10 inches), along a straight line L extending in the <11-20> direction with reference to the center C, the carrier concentration is measured at the center and at positions of ±25 mm, ±50 mm, ±75 mm, ±100 mm, and ±120 mm from the center, and the carrier concentration uniformity is determined from the respective carrier concentrations at these measurement points.

[0031] For example, when the diameter of the SiC epitaxial wafer 1 is 300 mm (12 inches), along a straight line L extending in the <11-20> direction with reference to the center C, the carrier concentration is measured at the center and at positions of ±30 mm, ±60 mm, ±90 mm, ±120 mm, and ±145 mm from the center, and the carrier concentration uniformity is determined from the respective carrier concentrations at these measurement points.

[0032] Here, the carrier concentration is the effective carrier concentration. The effective carrier concentration is the absolute value of the difference between the donor concentration and the acceptor concentration. The carrier concentration of the SiC epitaxial layer 3 can be measured, for example, by the mercury probe (Hg-CV) method or the secondary ion mass spectrometry (SIMS) method. The Hg-CV method measures the difference between the donor concentration and the acceptor concentration as the effective carrier concentration. The secondary ion mass spectrometry (SIMS) is a method of performing mass spectrometry on the secondary ions that pop out while shaving the layer in the thickness direction. The doping concentration can be measured from the mass spectrometry. The secondary ion mass spectrometry (SIMS) can measure the actual values of the donor concentration and the acceptor concentration respectively, and the effective carrier concentration can be determined by obtaining the difference between these.

[0033] The variation in the carrier concentration of the SiC epitaxial layer 3 is preferably 20% or less, more preferably 15% or less, still more preferably 12% or less, even more preferably 10% or less, particularly preferably 5% or less, and most particularly preferably 2% or less in a first region that is 60 mm or more and 95 mm or less away from the center when viewed in plan from the stacking direction. The lower limit value of the variation in the carrier concentration in the first region may be 0.5% or 1.5%. The first region is located on the outer peripheral side of the SiC epitaxial wafer 1 and is a portion where the carrier concentration is likely to vary. If the variation in this portion is within the above range, the element variation of the SiC device after device formation can be further reduced. The measurement of the carrier concentration in the first region is performed, for example, at points of ±60 mm, ±80 mm, ±95 mm from the center along a straight line extending in the <11-20> direction with the center C as a reference, and at points of ±60 mm, ±80 mm, +95 mm, -90 mm along a straight line extending in the <-1100> direction with the center C as a reference. -90 mm is arranged inside to avoid the notch 4. Note that the [11-20] direction or the [-1100] direction is denoted as "+".

[0034] Also, the SiC epitaxial layer 3 according to the present embodiment may have a film thickness variation of 5% or less. The film thickness variation of the SiC epitaxial layer 3 is preferably 4% or less, more preferably 3% or less, still more preferably 2% or less, and particularly preferably 1% or less. The lower limit value of the film thickness variation of the SiC epitaxial layer 3 may be 0.3% or 0.9%. The film thickness variation is obtained by dividing, by twice the average value, the difference between the maximum value and the minimum value of the film thickness of the SiC epitaxial layer 3 measured using infrared spectroscopy along a straight line passing through the center C of the SiC epitaxial layer 3 and extending in the <11-20> direction. The film thickness measurement points are the same as the carrier concentration measurement points.

[0035] The film thickness variation of the SiC epitaxial layer 3 is preferably 5% or less, more preferably 4% or less, still more preferably 3% or less, still more preferably 2% or less, and particularly preferably 1% or less in the first region that is 60 mm or more and 95 mm or less away from the center when viewed in plan from the stacking direction. In the first region, the lower limit value of the film thickness variation of the SiC epitaxial layer 3 may be 0.3% or 0.9%. The first region is located on the outer peripheral side of the SiC epitaxial wafer 1 and is a portion where the film thickness is likely to vary. If the variation in this portion is within the above range, the element variation of the SiC device after device formation can be further reduced.

[0036] Next, a method for manufacturing the SiC epitaxial wafer 1 according to the present embodiment will be described.

[0037] FIG. 6 is a cross-sectional schematic view of an example of a film formation apparatus for the SiC epitaxial wafer according to the present embodiment. The film formation apparatus 100 includes, for example, a chamber 10, a support 20, a lower heater 30, and an upper heater 40. The SiC substrate 2 is placed on a susceptor 50 and transported into the film formation apparatus.

[0038] The support 20 supports the susceptor 50. The support 20 is rotatable about its axis center, for example. The SiC substrate 2 is disposed on the support 20 in a state of being placed on the susceptor 50, for example. The lower heater 30 is, for example, inside the support 20 and heats the SiC substrate 2. The upper heater 40 heats the upper part of the chamber 10.

[0039] The chamber 10 includes, for example, a main body 11, a gas supply port 12, and a gas discharge port 13. The main body 11 surrounds the film formation space S. The gas supply port 12 is an inlet for supplying the gas G to the film formation space S. There are a plurality of gas supply ports 12 above the placement surface of the SiC substrate 2, for example. A film formation apparatus in which the gas supply port 12 is above the placement surface of the SiC substrate 2 is called a vertical furnace. The gas discharge port 13 is an outlet for discharging the gas G and the like remaining in the film formation space S. The gas discharge port 13 is, for example, below the placement surface of the SiC substrate 2.

[0040] The distance between the inner surface of the chamber 10 and the SiC substrate 2 is set to be 100 mm or more and 800 mm or less. By ensuring the distance between the inner surface of the chamber 10 and the SiC substrate 2, the generation of triangular defects 5 caused by particles from the chamber 10 can be suppressed. Also, by ensuring the distance between the inner surface of the chamber 10 and the SiC substrate 2, it becomes easier to flow gases other than the source gas, such as hydrogen or argon, outside the source gas supply section (near the inner surface of the chamber 10). When flowing a gas other than the source gas that is 5% or more of the total amount of gas introduced into the furnace near the inner surface of the chamber 10, the adhesion of the source gas to the inner wall of the chamber 10 can be suppressed. The source gas adhering to the inner wall can generate particulate by-products and may cause the occurrence of triangular defects 5. Also, by setting the distance between the inner surface of the chamber 10 and the SiC substrate 2 to be below a certain distance, the introduced source gas can be efficiently supplied to the SiC substrate 2, and the consumption of the source gas per unit film thickness can be suppressed. As a result, costs can be reduced.

[0041] The gas G is, for example, a source gas, a carrier gas, a dopant gas, or an etching gas. The source gas includes an Si-based source gas and a C-based source gas.

[0042] The Si-based source gas is a source gas containing Si in its molecule. The Si-based source gas is, for example, silane (SiH 4 ), dichlorosilane (SiH 2 Cl 2 ), trichlorosilane (SiHCl 3 ), tetrachlorosilane (SiCl 4 ), etc. The Si-based source gas preferably contains at least one selected from the group consisting of, for example, SiH 3 Cl, SiH 2 Cl 2 and SiHCl 3 .

[0043] The C-based source gas is a source gas containing C in its molecule. The C-based source gas is, for example, propane (C 3 H 8 ), ethylene (C 2 H4 ) etc. The C-based source gas preferably contains at least one selected from the group consisting of, for example, CH 4 , C 2 H 6 and C 3 H 8 .

[0044] The dopant gas is a gas containing an element serving as a carrier. The dopant gas preferably contains at least one of, for example, nitrogen (N 2 ) and ammonia (NH 3 ).

[0045] The carrier gas is a gas that transports the source gas to the SiC substrate 2 and is an inert gas with respect to SiC. The carrier gas preferably contains, for example, Ar.

[0046] The etching gas is a gas that reacts with SiC at a high temperature and has the effect of etching SiC. The etching gas is preferably, for example, hydrogen chloride (HCl).

[0047] In the film formation step, an SiC epitaxial layer 3 is formed on the SiC substrate 2. The SiC epitaxial layer is formed by supplying a mixed gas containing an Si-based source gas, a C-based source gas, an etching gas, a carrier gas, and a dopant gas to one surface of the SiC substrate 2. When supplying these mixed gases, some of the plurality of gas supply ports 12 locally emit the heavier gas in a non-uniform manner. Hereinafter, the gas supply port 12 from which the heavier gas is emitted is referred to as the first gas supply port.

[0048] The heavier gas is a gas having a molecular weight of 28 or more, for example, Ar. Locally emitting the heavier gas in a non-uniform manner is realized by gathering the first gas supply ports among the plurality of gas supply ports 12 within a certain range. The first gas supply ports among the plurality of gas supply ports 12 are arranged at the central part.

[0049] The area of the portion to which the first gas supply port belongs shall be 0.3% or more and 2.5% or less of the area of the top plate of the chamber 10. The area of the portion to which the first gas supply port belongs is the area of the region surrounded by the line connecting the outermost first gas supply ports. Also, the total area of the supply ports of the first gas supply port shall be 10% or more and 30% or less of the total area of the supply ports of the plurality of gas supply ports 12.

[0050] The flow rate of the heavier gas supplied from the first gas supply port shall be 1000 sccm or more and 4000 sccm or less.

[0051] When the heavier gas is unevenly distributed and supplied at a predetermined flow rate, the gas G convects within the film formation space S. Although the gas G generally passes through the surface of the SiC substrate 2 from the gas supply port 12 and forms a flow toward the gas discharge port 13, by deliberately causing the gas G to convect, the variation in the carrier concentration of the SiC epitaxial layer 3 can be suppressed. Also, by causing the gas G to convect, the variation in the film thickness of the SiC epitaxial layer 3 can be suppressed.

[0052] As described above, by controlling the flow of the gas G within the film formation space S and preventing the adhesion of particles to the SiC substrate 2, a large-diameter SiC epitaxial wafer 1 with a low triangular defect density and high carrier concentration uniformity can be obtained.

[0053] The SiC epitaxial wafer 1 according to this embodiment has few triangular defects and high in-plane carrier density uniformity despite its large diameter. Therefore, high-quality SiC devices can be obtained from the SiC epitaxial wafer 1 according to this embodiment at a high yield.

[0054] As described above, the preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Example

[0055] 「Example 1」 First, a 4H-SiC substrate with a diameter of 203 mm was prepared and placed inside a vertical furnace as shown in Fig. 6. The SiC substrate 2 was placed on the susceptor 50 and housed together with the susceptor 50 inside the chamber 10. The distance between the SiC substrate 2 and the inner wall of the chamber 10 was set to be 100 mm or more to suppress particle adhesion to the SiC substrate 2.

[0056] Next, a SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The carrier gas was Ar. Area ratio of the portion belonging to the supply port (first gas supply port) of the carrier gas to the top plate of the chamber: 2% Area ratio of the supply port (first gas supply port) of the carrier gas to all gas supply ports: 20% The flow rate of the carrier gas was set to be 1000 sccm or more and 4000 sccm or less.

[0057] The triangular defect density, the variation in carrier concentration, and the variation in film thickness of the SiC epitaxial wafer fabricated under the above conditions were measured.

[0058] The triangular defect density was measured using an optical microscope (manufactured by Lasertec: product name SICA88). The ratio of the area without triangular defects was calculated using an optical microscope (manufactured by Lasertec: product name SICA88). The SiC epitaxial wafer was divided into a plurality of square regions A with a side length a of 5 mm, which were arranged without overlapping and without gaps. All the square regions A in the plane of the SiC epitaxial wafer were observed, and the number of square regions A with triangular defects was determined. The ratio of the area without triangular defects = {1 - (the number of square regions A with triangular defects / the number of all square regions A)} × 100, calculated from the general formula.

[0059] The carrier concentration was measured using the Hg-CV method. The measurement points were set at the center and positions of ±20 mm, ±40 mm, ±60 mm, ±80 mm, and ±95 mm from the center along a straight line L extending in the <11-20> direction with the center C as the reference. The variation in carrier concentration was determined from the respective carrier concentrations at each measurement point. Also, the variation in carrier concentration in the first region was measured. The carrier concentration in the first region was measured at points of ±60 mm, ±80 mm, and ±95 mm from the center along a straight line extending in the <11-20> direction with the center C as the reference, and at points of ±60 mm, ±80 mm, +95 mm, and -90 mm from the center along a straight line extending in the <-1100> direction with the center C as the reference.

[0060] The film thickness variation was measured by infrared spectroscopy. The film thickness variation was also measured within the first region. The measurement points for the film thickness variation were the same as those for the carrier concentration.

[0061] The triangular defect density of the SiC epitaxial wafer of Example 1 was 0.03 pieces / cm 2 It was. Also, the variation in carrier concentration of the SiC epitaxial wafer of Example 1 was 13.4%. Also, the variation in carrier concentration in the first region of the SiC epitaxial wafer of Example 1 was 5.1%. Also, the variation in the film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 1 was 3.1%. Also, the variation in the film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Example 1 was 1.9%. Also, when the SiC epitaxial layer was divided into a plurality of regions with a side length of 5 mm, the ratio of the regions without triangular defects was 98% or more.

[0062] "Example 2" First, a 4H-SiC substrate with a diameter of 200 mm was prepared and housed inside a vertical furnace as shown in FIG. 6. The SiC substrate 2 was placed on the susceptor 50 and housed in the chamber 10 together with the susceptor 50. The distance between the SiC substrate 2 and the inner wall of the chamber 10 was set to be 100 mm or more to suppress the adhesion of particles to the SiC substrate 2.

[0063] Next, a SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The carrier gas was Ar. Area ratio of the portion belonging to the supply port of the carrier gas (first gas supply port) to the top plate of the chamber: 2% Area ratio of the supply port of the carrier gas (first gas supply port) to all gas supply ports: 15% The flow rate of the carrier gas was set to be 1000 sccm or more and 4000 sccm or less.

[0064] The triangular defect density, the variation in carrier concentration, the variation in carrier concentration in the first region, the variation in film thickness, and the variation in film thickness in the first region of the SiC epitaxial wafer fabricated under the above conditions were measured in the same manner as in Example 1. Also, the ratio of the region without triangular defects was calculated in the same manner as in Example 1.

[0065] The triangular defect density of the SiC epitaxial wafer of Example 2 was 0.20 pieces / cm 2 It was. Also, the variation in carrier concentration of the SiC epitaxial wafer of Example 2 was 11.8%. Also, the variation in carrier concentration in the first region of the SiC epitaxial wafer of Example 2 was 3.7%. Also, the variation in film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 2 was 6.5%. Also, the variation in film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Example 2 was 2.2%. Also, when the SiC epitaxial layer was divided into a plurality of regions with a side length of 5 mm, the ratio of the region without triangular defects was 98% or more.

[0066] "Example 3" First, a 4H-SiC substrate with a diameter of 200 mm was prepared and placed inside a vertical furnace as shown in FIG. 6. The SiC substrate 2 was placed on the susceptor 50 and accommodated in the chamber 10 together with the susceptor 50. The distance between the SiC substrate 2 and the inner wall of the chamber 10 was set to be 120 mm or more to suppress the adhesion of particles to the SiC substrate 2.

[0067] Next, a SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The carrier gas was Ar. Area ratio of the portion belonging to the supply port (first gas supply port) of the carrier gas to the top plate of the chamber: 2% Area ratio of the supply port (first gas supply port) of the carrier gas to all gas supply ports: 20% The flow rate of the carrier gas was set to be 1000 sccm or more and 4000 sccm or less.

[0068] The triangular defect density, the variation in carrier concentration, the variation in carrier concentration in the first region, the variation in film thickness, and the variation in film thickness in the first region of the SiC epitaxial wafer fabricated under the above conditions were measured in the same manner as in Example 1. Also, the ratio of the region without triangular defects was calculated in the same manner as in Example 1.

[0069] The triangular defect density of the SiC epitaxial wafer of Example 3 was 0.05 pieces / cm 2 It was. Also, the variation in carrier concentration of the SiC epitaxial wafer of Example 3 was 12.0%. Also, the variation in carrier concentration in the first region of the SiC epitaxial wafer of Example 3 was 11.9%. Also, the variation in film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 3 was 5.4%. Also, the variation in film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Example 3 was 4.3%. Also, when the SiC epitaxial layer was divided into a plurality of regions with a side length of 5 mm, the ratio of the region without triangular defects was 98% or more.

[0070] "Example 4" First, a 4H-SiC substrate with a diameter of 203 mm was prepared and housed inside a vertical furnace as shown in FIG. 6. The SiC substrate 2 was placed on the susceptor 50 and housed in the chamber 10 together with the susceptor 50. The distance between the SiC substrate 2 and the inner wall of the chamber 10 was set to be 120 mm or more to suppress the adhesion of particles to the SiC substrate 2.

[0071] Next, a SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The carrier gas was Ar. Area ratio of the portion belonging to the supply port (first gas supply port) of the carrier gas to the top plate of the chamber: 2% Area ratio of the supply port (first gas supply port) of the carrier gas to all gas supply ports: 15% The flow rate of the carrier gas was set to be 1000 sccm or more and 4000 sccm or less.

[0072] The triangular defect density, the variation in carrier concentration, the variation in carrier concentration in the first region, the variation in film thickness, and the variation in film thickness in the first region of the SiC epitaxial wafer fabricated under the above conditions were measured in the same manner as in Example 1. Also, the ratio of the region without triangular defects was calculated in the same manner as in Example 1.

[0073] The triangular defect density of the SiC epitaxial wafer of Example 4 was 0.02 pieces / cm 2 It was. Also, the variation in carrier concentration of the SiC epitaxial wafer of Example 4 was 9.9%. Also, the variation in carrier concentration in the first region of the SiC epitaxial wafer of Example 4 was 7.1%. Also, the variation in film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 4 was 4.5%. Also, the variation in film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Example 4 was 1.2%. Also, when the SiC epitaxial layer was divided into a plurality of regions with a side length of 5 mm, the ratio of the region without triangular defects was 98% or more.

[0074] "Comparative Example 1" In Comparative Example 1, the area ratio of the portion belonging to the supply port (first gas supply port) of the carrier gas to the top plate of the chamber was 42%, and the area ratio of the supply port (first gas supply port) of the carrier gas to all gas supply ports was 71%. Also, the flow rate of the carrier gas in Comparative Example 1 was made smaller than the flow rate in Example 1 and less than 1000 sccm.

[0075] With other conditions being the same as in Example 1, the triangular defect density, the variation in carrier concentration, and the film thickness variation of the SiC epitaxial wafer of Comparative Example 1 were measured. Also, the ratio of the region without triangular defects was calculated in the same manner as in Example 1.

[0076] The triangular defect density of the SiC epitaxial wafer of Comparative Example 1 was 0.26 pieces / cm 2 . Also, the variation in carrier concentration of the SiC epitaxial wafer of Comparative Example 1 was 29.35%. Also, the variation in carrier concentration in the first region of the SiC epitaxial wafer of Comparative Example 1 was 28.8%. Also, the film thickness variation of the SiC epitaxial layer of the SiC epitaxial wafer of Comparative Example 1 was 5.15%. Also, the film thickness variation of the epitaxial layer in the first region of the SiC epitaxial wafer of Comparative Example 1 was 5.1%. Also, when the SiC epitaxial layer was divided into a plurality of regions with a side length of 5 mm, the ratio of the region without triangular defects was less than 98%.

Explanation of Signs

[0077] 1 SiC epitaxial wafer 2 SiC substrate 3 SiC epitaxial layer 4 Notch 5 Triangular defect 6 Starting point 10 Chamber 11 Body 12 Gas supply port 13 Gas discharge port 20 Support 30 Lower heater 40 Upper heater 50 Susceptor A Region

Claims

1. A SiC substrate and a SiC epitaxial layer are provided. The SiC substrate has a diameter of 195 mm or more, The SiC epitaxial layer has a triangular defect density of 0.2 / cm ２ and a carrier concentration variation of 20% or less.

2. The SiC epitaxial layer can be divided into a plurality of 5 mm square regions when viewed in a plan view from the stacking direction, 2. The SiC epitaxial wafer according to claim 1, wherein a ratio of the regions having no triangular defects among the plurality of regions is 98% or more.

3. 2. The SiC epitaxial wafer according to claim 1, wherein the SiC epitaxial layer has a carrier concentration variation of 20% or less in a first region that is 60 mm or more and 95 mm or less away from a center when viewed in a planar view from the stacking direction.

4. The SiC epitaxial wafer according to claim 1 , wherein the SiC epitaxial layer has a thickness variation of 5% or less.

5. 5. The SiC epitaxial wafer according to claim 4, wherein the SiC epitaxial layer has a film thickness variation of 5% or less in a first region that is 60 mm or more and 95 mm or less away from a center when viewed in a plan view from the stacking direction.

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