Sic epitaxial wafer

Abstract

To provide an SiC epitaxial wafer with large diameter, thin thickness, and low triangular defects.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 and a thickness of 460 μm or less. The SiC epitaxial layer has a triangular defect density of 0.2 piece / cm2 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 one order of magnitude larger and a bandgap three times larger than that of silicon (Si). In addition, silicon carbide (SiC) has characteristics such as a thermal conductivity 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 the semiconductor devices as described above.

[0003] The 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 out 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 the SiC epitaxial wafer and then chip-forming the SiC epitaxial wafer.

[0004] In the SiC epitaxial wafer, triangular defects are one of the defects that need to be reduced. For example, Patent Document 1 discloses a SiC epitaxial wafer in which the areal density of triangular defects is 1.0 cm -2 or less.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

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 internal stress increases, and the shape may change significantly during the manufacturing process. By increasing the thickness of the SiC substrate, the shape change of the SiC epitaxial wafer can be suppressed, but it causes an increase in cost and an increase in the resistance of the device. On the other hand, simply reducing the thickness makes the SiC substrate more likely to move during evacuation when forming the SiC epitaxial layer or during the rotation of the SiC substrate. When the SiC substrate rubs against other parts, dust is generated, creating particles, which is one of the causes of triangular defects.

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a SiC epitaxial wafer that is large in diameter, has a thin thickness, and has few triangular defects.

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 and a thickness of 460 μm or less. The SiC epitaxial layer has a density of triangular defects of 0.2 pieces / cm 2 or less.

[0010] (2) In the SiC epitaxial wafer according to the above aspect, when viewed in plan from the stacking direction, the local thickness unevenness (LTV) in each of a plurality of unit exposure regions divided into 20 mm squares may be 4 μm or less.

[0011] (3) When viewed in plan from the stacking direction, the site flatness (SFQR) in each of a plurality of unit exposure regions divided into 20 mm squares of the SiC epitaxial wafer according to the above aspect may be 2 μm or less.

[0012] (4) The SiC epitaxial wafer according to the above aspect may have a Warp of 90 μm or less.

[0013] (5) When the reference plane is a plane connecting a support point located at a position overlapping with a circumference 7.5 mm inside from the outermost circumference and a portion overlapping when viewed from the thickness direction, the Bow of the SiC epitaxial wafer according to the above aspect may be 60 μm or less.

[0014] (6) The SiC epitaxial wafer according to the above aspect may have a SORI of 60 μm or less.

[0015] (7) In the SiC epitaxial wafer according to the above aspect, when viewed in plan from the stacking direction, the SiC epitaxial layer can be divided into a plurality of regions of 5 mm squares, and the ratio of the regions having no triangular defects among the plurality of regions may be 98% or more.

[0016] (8) In the SiC epitaxial wafer according to the above aspect, the variation in carrier concentration of the SiC epitaxial layer may be 20% or less.

[0017] (9) The SiC epitaxial wafer according to the above aspect may have a variation in film thickness of the SiC epitaxial layer of 5% or less.

Advantages of the Invention

[0018] The SiC epitaxial wafer according to the above aspect has a large diameter, a thin plate thickness, and few triangular defects.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0020] 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, for the sake of convenience, the characteristic parts enlarged to make the characteristics of this embodiment easier to understand, and the dimensional ratios of each component 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.

[0021] In this specification, individual orientations are indicated by [], and collective orientations are indicated by <>. Regarding negative exponents, in crystallography, a "-" (bar) is attached above the number, but in this specification, a negative sign is attached before the number.

[0022] FIG. 1 is a cross-sectional view of the SiC epitaxial wafer 1 according to the present embodiment. FIG. 2 is a plan view of the SiC epitaxial wafer 1 according to the present embodiment.

[0023] 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 epitaxial wafer 1 may have an orientation flat instead of the notch 4.

[0024] The SiC epitaxial wafer 1 is a wafer of 8 inches 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.

[0025] 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.

[0026] The thickness of the SiC substrate 2 is 460 μm or less, preferably 420 μm or less, more preferably 380 μm or less, more preferably 375 μm or less, more preferably 350 μm or less, more preferably 300 μm or less, more preferably 250 μm or less, more preferably 200 μm or less, more preferably 150 μm or less, more preferably 100 μm or less, and particularly preferably 50 μm or less. The thickness of the SiC substrate 2 may be 1 μm or more. When the thickness of the SiC substrate 2 is small, the yield of SiC devices that can be obtained from one SiC ingot increases. Also, when the thickness of the SiC substrate 2 is small, the increase in the resistance of the SiC device can be suppressed. The thickness of the SiC substrate may be measured using a laser displacement meter.

[0027] The SiC epitaxial layer 3 is laminated on one surface of the SiC substrate 2. The SiC epitaxial layer 3 is made of SiC.

[0028] The SiC epitaxial layer 3 according to this 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 lower limit of the triangular defect density in the SiC epitaxial layer 3 may also be 0 piece / cm 2 The triangular defect density may be measured by measuring the density of triangular defects observed in the field of view using an optical microscope (manufactured by Lasertec: product name SICA88).

[0029] Triangular defects are defects that appear triangular when the surface of the SiC epitaxial layer 3 is observed using an optical microscope. FIGS. 3 and 4 are diagrams for explaining triangular defects. 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.

[0030] ​The SiC epitaxial layer 3 can be divided into a plurality of regions when viewed in plan from the stacking direction (<0001> direction). Each of the regions is composed of a square with a side length of a. The regions are spread out on the surface of the SiC epitaxial layer 3 without gaps. The center of one of the plurality of regions coincides with the center of the SiC epitaxial layer 3. Each of the regions corresponds to each of the chips to be individualized, and each becomes a SiC device.

[0031] For example, when the SiC epitaxial layer 3 is divided into a plurality of regions with a side length of 5 mm, the ratio of the regions having no triangular defects 5 is preferably 98% or more. In this case, the upper limit of the ratio of the regions having no triangular defects 5 may be 100% or 99%. Also, the upper limit of the ratio of the regions having no triangular defects 5 may be 99.97%. Also for example, when the SiC epitaxial layer 3 is divided into a plurality of regions with a side length of 7 mm, the ratio of the regions having no triangular defects 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 defects 5 may be 100% or 99%. Also, the upper limit of the ratio of the regions having no triangular defects 5 may be 99.97%. Also for example, when the SiC epitaxial layer 3 is divided into a plurality of regions with a side length of 10 mm, the ratio of the regions having no 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 regions having no triangular defects 5 may be 100% or 99%. Also, the upper limit of the ratio of the regions having no triangular defects 5 may be 99.97%. Also for example, when the SiC epitaxial layer 3 is divided into a plurality of regions with a side length of 15 mm, the ratio of the regions having no 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 regions having no triangular defects 5 may be 100% or 99%. Also, the upper limit of the ratio of the regions having no triangular defects 5 may be 99.97%. For example, when the SiC epitaxial layer 3 is divided into a plurality of regions each with a side length of 20 mm, the ratio of the regions without triangular defects 5 is preferably 60% or more, more preferably 75% or more, still more preferably 88% or more, yet more preferably 95% or more, and even more preferably 98% or more. In this case, the upper limit of the ratio of the regions without triangular defects 5 may be 100% or 99%. Also, the upper limit of the ratio of the regions without triangular defects 5 may be 99.97%. The ratio of the regions without triangular defects 5 in the SiC epitaxial layer 3 is obtained by using an optical microscope (manufactured by Lasertec: product name SICA88) to divide it into a plurality of square regions A with a specific length a of one side, 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 regions without triangular defects 5 from the general formula: ratio of regions without triangular defects 5 = {1 - (number of square regions A with triangular defects / total number of square regions A)} × 100.

[0032] If the density of triangular defects 5 in the SiC epitaxial layer 3 is 0.2 per cm 2 If it is as follows, the above ratio of the regions without triangular defects 5 can be sufficiently realized. Since the plurality of regions correspond to the chips for the devices, if the above ratio is satisfied, SiC devices can be obtained from the SiC epitaxial wafer 1 according to this embodiment with a high yield. Also, the larger the length of one side, the more capable the obtained SiC device is of withstanding the application of a larger current.

[0033] In addition, the SiC epitaxial layer according to this embodiment has a variation in carrier concentration that is preferably 20% or less, more preferably 15% or less, still 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 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 passing through the center of the SiC epitaxial layer 3 and extending in the <11-20> direction by twice the average value. The measurement of the carrier concentration may be performed at equal intervals from the center on the straight line, or the intervals 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. The lower limit of the variation in carrier concentration in the SiC epitaxial layer may be 0.5% or 1.5%.

[0034] 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 extending in the <11-20> direction with the center as a reference, and the carrier concentration uniformity is determined from the respective carrier concentrations at these measurement points.

[0035] For another example, when the diameter of the SiC epitaxial wafer 1 is 250 mm (10 inches), 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 along a straight line extending in the <11-20> direction with the center as a reference, and the carrier concentration uniformity is determined from the respective carrier concentrations at these measurement points.

[0036] For example, when the diameter of the SiC epitaxial wafer 1 is 300 mm (12 inches), 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 along a straight line extending in the <11-20> direction with the center as a reference, and the carrier concentration uniformity is determined from the respective carrier concentrations at these measurement points.

[0037] 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.

[0038] 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 still 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 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, and ±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, and -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 "+". The lower limit of the variation in the carrier concentration in the first region may be 0.5% or 1.5%.

[0039] 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 film thickness variation is obtained by dividing 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 of the SiC epitaxial layer 3 and extending in the <11-20> direction by twice the average value. The film thickness measurement points are the same as the carrier concentration measurement points. The lower limit of the film thickness variation of the SiC epitaxial layer 3 may be 0.3% or 0.9%.

[0040] The 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 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 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. The measurement points of the film thickness are the same as those of the carrier concentration. In the first region, the lower limit of the thickness variation of the SiC epitaxial layer 3 may be 0.3% or 0.9%.

[0041] Also, the SiC epitaxial wafer 1 according to this embodiment preferably has a Warp of 90 μm or less, more preferably 75 μm or less, still more preferably 50 μm or less, and may be 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less. The SiC epitaxial wafer 1 with a Warp of 90 μm or less is advantageous in terms of transfer to the process equipment and alignment accuracy. The lower limit of Warp may be 0 μm or 1.0 μm.

[0042] FIG. 5 is a diagram schematically showing a method for evaluating the shape (deformation) of the SiC substrate due to Warp. Warp is the distance in the thickness direction between the highest point hp and the lowest point lp of the first surface 1a. The first surface 1a is the outer surface of the SiC epitaxial layer 3. The larger the Warp, the more deformed the SiC epitaxial wafer 1 is judged to be.

[0043] First, place the SiC epitaxial wafer 1 on three support points installed on the flat surface F. The support points are located, for example, at positions overlapping a circumference 7.5 mm inside the outer peripheral edge of the SiC epitaxial wafer 1. Determine a virtual plane Slp parallel to the flat surface F passing through the lowest point lp on the first surface 1a and a virtual plane Shp parallel to the flat surface F passing through the highest point hp on the first surface 1a. Warp is determined as the height-direction distance between the virtual plane Slp and the virtual plane Shp. The height direction is orthogonal to the flat surface F and is the direction away from the flat surface F.

[0044] For the SiC epitaxial wafer 1 according to this embodiment, the absolute value of Bow is preferably 60 μm or less, more preferably 45 μm or less, and may be 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less. The SiC epitaxial wafer 1 with the absolute value of Bow being 60 μm or less can appropriately adjust the focus to the processing surface even in a fine lithography process, and the SiC epitaxial wafer 1 can be processed with high accuracy. The lower limit value of Bow may be 0.5 μm as an absolute value.

[0045] FIG. 6 is a diagram schematically showing a method for evaluating the shape (deformation) of the SiC epitaxial wafer 1 due to Bow. Bow is the height-direction position of the center c of the SiC epitaxial wafer 1 with respect to the reference plane Sr. In other words, Bow is the signed distance of the center c of the SiC epitaxial wafer 1 from the reference plane Sr. The reference plane Sr is a plane connecting points sp that overlap each of the three support points when viewed from the thickness direction of the first surface 1a. The three support points are located, for example, at positions overlapping a circumference 7.5 mm inside the outer peripheral edge of the SiC epitaxial wafer 1. Each of the three support points is located at a position symmetric three times about the center of the SiC epitaxial wafer 1 supported by the support point as the central axis. The reference plane Sr is, for example, a three-point reference plane. The larger the absolute value of Bow, the more it is determined that the SiC epitaxial wafer 1 is deformed.

[0046] First, place the SiC epitaxial wafer 1 on three support points installed on the flat surface F. Connect three points sp on the first surface 1a located on the support points as viewed from the thickness direction to obtain a reference plane Sr. Then, with the reference plane Sr set to 0, the direction away from the flat surface F with respect to the reference plane Sr is defined as +, and the direction approaching the flat surface F with respect to the reference plane Sr is defined as -. Bow is obtained as the position in the height direction of the center c of the first surface 1a with respect to the reference plane Sr. In other words, Bow is obtained as the signed distance of the center c of the first surface 1a from the reference plane Sr.

[0047] The SiC epitaxial wafer 1 according to the present embodiment preferably has a SORI of 60 μm or less, more preferably 45 μm or less, and may be 30 μm or less, 25 μm or less, 20 μm or less, 10 μm or less, or 5 μm or less. The lower limit value of SORI may be 0 μm or 0.5 μm.

[0048] SORI is one of the parameters indicating the degree of warping of the substrate. When the back surface of the substrate is supported and measured without changing the original shape, it is represented by the sum of the normal distances from the least-squares plane calculated by the least-squares method using all the data on the substrate surface to the highest point and the lowest point on the substrate surface. As shown in FIG. 7, when the least-squares plane of the substrate surface is used as the reference height (least-squares plane height), it represents the sum value ((a)+(b)) of the distance (a) between the height at the highest point on the substrate surface and the reference height and the distance (b) between the height at the lowest point and the reference height. Here, all the data on the substrate surface refers to all the data related to the relative height of the wafer surface from the reference plane obtained using the interference fringe image of the laser light.

[0049] The SiC epitaxial wafer 1 according to this embodiment preferably has a local thickness non-uniformity (LTV) of 4 μm or less, more preferably 3 μm or less, and even more preferably 2.5 μm or less in each of a plurality of unit exposure regions divided into 20 mm squares. When this condition is satisfied, even in a fine lithography process, the focus can be appropriately adjusted to the processing surface, and the SiC epitaxial wafer 1 can be processed with high precision. The lower limit value of the local thickness non-uniformity (LTV) may be 0.1 μm.

[0050] FIG. 8 is a diagram showing a unit exposure region A. The unit exposure region A is each of a plurality of regions divided into squares with a side length of a when viewed in plan from the stacking direction (<0001> direction). The unit exposure regions A are spread over the surface of the SiC epitaxial wafer 1 without gaps. The center of one of the plurality of unit exposure regions A coincides with the center C of the SiC epitaxial wafer 1. For example, in the measurement of LTV, the side length a of the unit exposure region A is set to 20 mm. LTV is a value obtained by measuring the highest point and the lowest point within the site surrounded by the unit exposure region A when the SiC epitaxial wafer 1 is adsorbed to a vacuum chuck, and finding the difference in distance between the highest point and the lowest point.

[0051] The SiC epitaxial wafer 1 according to this embodiment preferably has a site flatness (SFQR) of 2 μm or less, more preferably 1.5 μm or less, and even more preferably 1 μm or less in each of a plurality of unit exposure regions divided into 20 mm squares. The lower limit value of the site flatness (SFQR) may be 0 μm or 0.05 μm.

[0052] SFQR is represented by the sum of the normal distances from the highest point to the lowest point on the substrate surface, calculated by the least-squares method using all the data of the sites surrounded by the unit exposure area A when the SiC epitaxial wafer 1 is adsorbed on the vacuum chuck. SFQR is different from SORI in that it is the measurement result of a predetermined site. For example, in the measurement of SFQR, the length a of one side of the unit exposure area A is set to 20 mm. Here, all the data of the sites surrounded by the unit exposure area A are all the data related to the relative height of the wafer surface from the reference plane.

[0053] Next, a method for manufacturing the SiC epitaxial wafer 1 according to the present embodiment will be described.

[0054] FIG. 9 is a cross-sectional schematic view of an example of a film forming apparatus for a SiC epitaxial wafer according to the present embodiment. The film forming apparatus 100 has, 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 forming apparatus 100.

[0055] The support 20 supports the susceptor 50. The support 20 is rotatable about the 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.

[0056] The chamber 10 has, for example, a main body 11, a gas supply port 12, and a gas discharge port 13. The main body 11 surrounds the film forming space S. The gas supply port 12 is an inlet for supplying the gas G to the film forming space S. There are a plurality of gas supply ports 12 above the placement surface of the SiC substrate 2, for example. A film forming 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 staying in the film forming space S. The gas discharge port 13 is, for example, below the placement surface of the SiC substrate 2.

[0057] 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.

[0058] The Si-based source gas is a source gas containing Si in the 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 .

[0059] The C-based source gas is a source gas containing C in the molecule. The C-based source gas is, for example, propane (C 3 H 8 ), ethylene (C 2 H 4 ), 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 .

[0060] 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 ).

[0061] The carrier gas is a gas that transports the source gas to the SiC substrate 2 and is a gas inert to SiC. The carrier gas preferably contains, for example, Ar.

[0062] The etching gas is a gas that reacts with SiC at high temperature to etch SiC. As the etching gas, for example, hydrogen chloride (HCl) is preferable.

[0063] The susceptor 50 supports the SiC substrate 2. FIG. 10 is a cross-sectional view of the state where the SiC substrate 2 is placed on the susceptor 50. The susceptor 50 has a main body 51 and a frame 52 protruding from the main body 51. The frame 52 prevents the rotating SiC substrate 2 from protruding outward during film formation.

[0064] The diameter R50 of the susceptor 50 is preferably 102.5% or more and 115% or less of the diameter R2 of the SiC substrate 2. By making the size of the susceptor 50 close to the size of the SiC substrate 2, the susceptor 50 bends along the curved SiC substrate 2 during epitaxial growth. When the SiC substrate 2 bends, by not greatly changing the distance between the SiC substrate 2 and the susceptor 50, the uniformity of the carrier concentration of the SiC epitaxial layer 3 formed on the SiC substrate 2 can be enhanced.

[0065] Also, the thickness T51 of the main body 51 of the susceptor 50 is preferably 1 mm or more and 4 mm or less. The main body 51 is the portion facing the SiC substrate 2. The thickness T51 of the main body 51 has a great influence on the ease of bending of the susceptor 50. Since the thickness T51 of the main body 51 is thin, when the SiC substrate 2 bends, the susceptor 50 can bend following the SiC substrate 2.

[0066] Also, the radial width W52 of the frame 52 of the susceptor 50 is, for example, 10 mm or less. By narrowing the width W52, the entire susceptor 50 becomes easier to bend.

[0067] In the film formation process, first, the SiC substrate 2 placed on the susceptor 50 is disposed in the chamber 10. 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 and argon, outside the source gas supply part (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 gas introduction amount into the chamber 10 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 generates particulate by-products and can be a cause of the generation 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 amount of the source gas per film thickness can be suppressed. As a result, the cost related to epitaxial growth can be suppressed.

[0068] Then, the inside of the chamber 10 is evacuated. The evacuation is performed at a low speed, and the evacuation rate is set to 5 kPa / second or less. By performing the evacuation at a low speed, the movement of the thin SiC substrate 2 during evacuation can be suppressed. If the SiC substrate 2 moves during evacuation, it rubs against the surrounding components and causes dust generation.

[0069] Then, an SiC epitaxial layer 3 is formed on the SiC substrate 2. The SiC epitaxial layer 3 is formed while rotating the SiC substrate 2. The rotation speed of the SiC substrate 2 is set to 200 rpm or less. If the rotation speed of the SiC substrate 2 is too fast, the SiC substrate 2 rubs against the surrounding components due to centrifugal force. By suppressing the rotation speed of the SiC substrate 2 during film formation, the generation of particles during film formation can be suppressed.

[0070] The SiC epitaxial layer 3 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, it is preferable to locally unevenly discharge the heavy molecular weight carrier gas from some of the plurality of gas supply ports 12. Hereinafter, the gas supply port 12 from which the heavy molecular weight carrier gas is discharged is referred to as the first gas supply port.

[0071] The heavy molecular weight carrier gas is a gas having a molecular weight of 28 or more, for example, Ar. Locally unevenly discharging the heavy gas 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.

[0072] The area of the portion to which the first gas supply port belongs is preferably 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 is preferably 10% or more and 30% or less of the total area of the supply ports of the plurality of gas supply ports 12.

[0073] The flow rate of the heavy gas supplied from the first gas supply port is preferably 1000 sccm or more and 4000 sccm or less.

[0074] When the heavy molecular weight carrier gas is unevenly distributed and supplied at a predetermined flow rate, the gas G convects in the film formation space S. Although the gas G generally forms a flow from the gas supply port 12 through the surface of the SiC substrate 2 toward the gas discharge port 13, by deliberately causing the gas G to convect, the variation in carrier concentration of the SiC epitaxial layer 3 can be suppressed. Also, by causing the gas G to convect, the variation in film thickness of the SiC epitaxial layer 3 can be suppressed.

[0075] As described above, by suppressing the rubbing of the SiC substrate 2 against other components during evacuation or rotation during film formation, the generation of triangular defects can be suppressed even when forming the SiC epitaxial layer 3 on the SiC substrate 2 having a large diameter and a thin plate thickness. As a result, by using the method for manufacturing the SiC epitaxial wafer 1 according to the present embodiment, a SiC epitaxial wafer 1 having a large diameter, a thin plate thickness, and few triangular defects can be obtained.

[0076] The SiC epitaxial wafer 1 according to the present embodiment has a thin plate thickness and few triangular defects despite its large diameter. Therefore, the SiC epitaxial wafer 1 according to the present embodiment has a high yield of SiC devices. Further, the SiC device manufactured from the SiC epitaxial wafer 1 according to the present embodiment has a low resistance and little loss during operation.

[0077] 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

[0078] 「Example 1」 First, a 4H-SiC substrate having a diameter of 200 mm and a plate thickness of 363 μm was prepared and housed inside a vertical furnace as shown in FIG. 9. The SiC substrate 2 was placed on the susceptor 50 and housed in the chamber 10 together with the susceptor 50. As the susceptor 50, one having a diameter of 230 mm, a thickness of the main body portion of 3 mm, and a radial width of the frame of 10 mm was used. Then, the inside of the chamber 11 was evacuated. The evacuation speed was 3 kPa / second.

[0079] Next, a SiC epitaxial layer 3 having a thickness of 11 μm was formed on the SiC substrate 2. The rotation speed of the SiC substrate 2 during the formation of the SiC epitaxial layer 3 was 100 rpm. 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 of the carrier gas (first gas supply port) 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.

[0080] The triangular defect density, the variation in carrier concentration, and the film thickness variation of the SiC epitaxial wafer of Example 1 fabricated under the above conditions were measured.

[0081] The carrier concentration was measured using the Hg-CV method. The measurement points were the center and positions at ±20 mm, ±40 mm, ±60 mm, ±80 mm, and ±95 mm from the center along a straight line extending in the <11-20> direction with the center as a 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 at ±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 a reference, and at points at ±60 mm, ±80 mm, +95 mm, and -90 mm along a straight line extending in the <-1100> direction with the center C as a reference.

[0082] The triangular defect density was measured using an optical microscope (manufactured by Lasertec: product name SICA88). The ratio of the region without triangular defects was determined by using an optical microscope (manufactured by Lasertec: product name SICA88), dividing into a plurality of square regions A with a side length a of 5 mm that were arranged without overlapping and without gaps, observing all the square regions A in the plane of the SiC epitaxial wafer, obtaining the number of square regions A with triangular defects, and calculating from the general formula of the ratio of the region without triangular defects = {1 - (the number of square regions A with triangular defects / the number of all square regions A)} × 100.

[0083] The film thickness variation was measured by infrared spectroscopy. The film thickness variation was also measured within the first region. The measurement points of the film thickness variation were the same as those of the carrier concentration.

[0084] The triangular defect density of the SiC epitaxial wafer of Example 1 was 0.10 pieces / cm 2 The variation in carrier concentration of the SiC epitaxial wafer of Example 1 was 5.0%. The variation in carrier concentration in the first region of the SiC epitaxial wafer of Example 1 was 5.1%. The variation in the film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 1 was 2.6%. 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 proportion of regions without triangular defects was 98% or more.

[0085] "Example 2" First, a 4H-SiC substrate with a diameter of 200 mm and a plate thickness of 374 μm was prepared and housed inside a vertical furnace as shown in FIG. 9. The SiC substrate 2 was placed on the susceptor 50 and housed in the chamber 10 together with the susceptor 50. The susceptor 50 used had a diameter of 230 mm, a thickness of the main body part of 3 mm, and a radial width of the frame of 10 mm. Then, the inside of the chamber 11 was evacuated. The evacuation speed was 3 kPa / second.

[0086] Next, a SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The rotation speed of the SiC substrate 2 when forming the SiC epitaxial layer 3 was 100 rpm. 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: 1.5% Area ratio of the supply port of the carrier gas (first gas supply port) 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.

[0087] The triangular defect density, the variation in carrier concentration, the carrier concentration in the first region, the film thickness variation, and the film thickness variation within the first region of the SiC epitaxial wafer of Example 2 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.

[0088] The LTV, SFQR, SORI, Warp, and Bow of the SiC epitaxial wafer of Example 2 obtained were obtained using an Ultrasort II manufactured by Corning Tropel.

[0089] The triangular defect density of the SiC epitaxial wafer of Example 2 was 0.12 pieces / cm 2 Also, the variation in carrier concentration of the SiC epitaxial wafer of Example 2 was 68.7%. Also, the variation in carrier concentration in the first region of the SiC epitaxial wafer of Example 2 was 51.5%. Also, the variation in the film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 2 was 8.1%. Also, the variation in the film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Example 2 was 6.9%. Also, when the SiC epitaxial layer was divided into a plurality of regions with a side length of 5 mm, the ratio of the region without triangular defects was 98% or more.

[0090] The LTV of the SiC epitaxial wafer of Example 2 was 3.9 μm. The SFQR of the SiC epitaxial wafer of Example 2 was 4.1 μm. The SORI of the SiC epitaxial wafer of Example 2 was 37.3 μm. The Warp of the SiC epitaxial wafer of Example 2 was 48.8 μm. The Bow of the SiC epitaxial wafer of Example 2 was -16.2 μm.

[0091] "Example 3" First, a 4H-SiC substrate with a diameter of 200 mm and a thickness of 377 μm was prepared and placed inside a vertical furnace as shown in FIG. 9. The SiC substrate 2 was placed on the susceptor 50 and housed in the chamber 10 together with the susceptor 50. The susceptor 50 used had a diameter of 230 mm, a thickness of the main body part of 3 mm, and a radial width of the frame of 10 mm. Then, the inside of the chamber 11 was evacuated. The evacuation speed was 3 kPa / second.

[0092] Next, a SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The rotation speed of the SiC substrate 2 when forming the SiC epitaxial layer 3 was set to 100 rpm. 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: 1.5% Area ratio of the supply port of the carrier gas (first gas supply port) to all gas supply ports: 30% The flow rate of the carrier gas was set to 1000 sccm or more and 4000 sccm or less.

[0093] The triangular defect density, the variation in carrier concentration, the carrier concentration in the first region, the film thickness variation, and the film thickness variation within the first region of the SiC epitaxial wafer of Example 3 produced 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.

[0094] The LTV, SFQR, SORI, Warp, and Bow of the SiC epitaxial wafer of Example 3 obtained were measured in the same manner as in Example 2.

[0095] The triangular defect density of the SiC epitaxial wafer of Example 3 was 0.12 pieces / cm 2It was so. Also, the variation in the carrier concentration of the SiC epitaxial wafer of Example 3 was 157.3%. Also, the variation in the carrier concentration in the first region of the SiC epitaxial wafer of Example 3 was 107.6%. Also, the variation in the film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 3 was 18.1%. Also, the variation in the film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Example 3 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 regions without triangular defects was 98% or more.

[0096] The LTV of the SiC epitaxial wafer of Example 3 was 2.8 μm. The SFQR of the SiC epitaxial wafer of Example 3 was 3.0 μm. The SORI of the SiC epitaxial wafer of Example 3 was 29.6 μm. The Warp of the SiC epitaxial wafer of Example 3 was 40.2 μm. The Bow of the SiC epitaxial wafer of Example 3 was -4.2 μm.

[0097] "Example 4" First, a 4H-SiC substrate with a diameter of 200 mm and a plate thickness of 370 μm was prepared and housed inside a vertical furnace as shown in FIG. 9. The SiC substrate 2 was placed on the susceptor 50 and housed in the chamber 10 together with the susceptor 50. The susceptor 50 used had a diameter of 230 mm, a thickness of the main body part of 3 mm, and a radial width of the frame of 10 mm. Then, the inside of the chamber 11 was evacuated. The evacuation speed was 3 kPa / second.

[0098] Next, an SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The rotation speed of the SiC substrate 2 when forming the SiC epitaxial layer 3 was 100 rpm. 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: 2.25% Area ratio of the supply port (first gas supply port) of the carrier gas to all gas supply ports: 20% The flow rate of carrier gas was set to be 1000 sccm or more and 4000 sccm or less.

[0099] The triangular defect density, the variation in carrier concentration, the carrier concentration in the first region, the film thickness variation, and the film thickness variation within the first region of the SiC epitaxial wafer of Example 4 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.

[0100] The LTV, SFQR, SORI, Warp, and Bow of the SiC epitaxial wafer of Example 4 obtained were measured in the same manner as in Example 2.

[0101] The triangular defect density of the SiC epitaxial wafer of Example 4 was 0.20 pieces / cm 2 Also, the variation in carrier concentration of the SiC epitaxial wafer of Example 4 was 16.3%. Also, the variation in carrier concentration in the first region of the SiC epitaxial wafer of Example 4 was 6.7%. Also, the variation in the film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 4 was 4.4%. Also, the variation in the film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Example 4 was 2.7%. 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.

[0102] The LTV of the SiC epitaxial wafer of Example 4 was 1.9 μm. The SFQR of the SiC epitaxial wafer of Example 4 was 1.1 μm. The SORI of the SiC epitaxial wafer of Example 4 was 15.7 μm. The Warp of the SiC epitaxial wafer of Example 4 was 15.6 μm. The Bow of the SiC epitaxial wafer of Example 4 was -4.4 μm.

[0103] "Example 5" First, a 4H-SiC substrate with a diameter of 200 mm and a thickness of 369 μm was prepared and placed inside a vertical furnace as shown in FIG. 9. The SiC substrate 2 was placed on the susceptor 50 and accommodated in the chamber 10 together with the susceptor 50. The susceptor 50 used had a diameter of 230 mm, a thickness of the main body part of 3 mm, and a radial width of the frame of 10 mm. Then, the inside of the chamber 11 was evacuated. The evacuation speed was 3 kPa / second.

[0104] Next, an SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The rotation speed of the SiC substrate 2 when forming the SiC epitaxial layer 3 was 100 rpm. 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: 2.25% Area ratio of the supply port (first gas supply port) of the carrier gas to all gas supply ports: 30% The flow rate of the carrier gas was set to be 1000 sccm or more and 4000 sccm or less.

[0105] The triangular defect density, the variation in carrier concentration, the carrier concentration in the first region, the film thickness variation, and the film thickness variation within the first region of the SiC epitaxial wafer of Example 5 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.

[0106] The LTV, SFQR, SORI, Warp, and Bow of the obtained SiC epitaxial wafer of Example 5 were measured in the same manner as in Example 2.

[0107] The triangular defect density of the SiC epitaxial wafer of Example 5 was 0.05 pieces / cm 2It was so. Also, the variation in the carrier concentration of the SiC epitaxial wafer in Example 5 was 23.9%. Also, the variation in the carrier concentration in the first region of the SiC epitaxial wafer in Example 5 was 23.8%. Also, the variation in the film thickness of the SiC epitaxial layer of the SiC epitaxial wafer in Example 5 was 4.9%. Also, the variation in the film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer in Example 5 was 3.2%. Also, when the SiC epitaxial layer was divided into a plurality of regions with a side length of 5 mm, the ratio of the regions without triangular defects was 98% or more.

[0108] The LTV of the SiC epitaxial wafer in Example 5 was 1.8 μm. The SFQR of the SiC epitaxial wafer in Example 5 was 1.1 μm. The SORI of the SiC epitaxial wafer in Example 5 was 23.6 μm. The Warp of the SiC epitaxial wafer in Example 5 was 29.1 μm. The Bow of the SiC epitaxial wafer in Example 5 was -5.8 μm.

[0109] "Example 6" First, a 4H-SiC substrate with a diameter of 200 mm and a plate thickness of 376 μm was prepared and housed inside a vertical furnace as shown in FIG. 9. The SiC substrate 2 was placed on the susceptor 50 and housed in the chamber 10 together with the susceptor 50. As the susceptor 50, one with a diameter of 230 mm, a thickness of the main body part of 3 mm, and a radial width of the frame of 10 mm was used. Then, the inside of the chamber 11 was evacuated. The evacuation speed was 3 kPa / second.

[0110] Next, a SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The rotation speed of the SiC substrate 2 when forming the SiC epitaxial layer 3 was 100 rpm. 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: 2.5% Area ratio of the supply port (first gas supply port) of the carrier gas to all gas supply ports: 30% The flow rate of carrier gas was set to be 1000 sccm or more and 4000 sccm or less.

[0111] The triangular defect density, the variation in carrier concentration, the carrier concentration in the first region, the film thickness variation, and the film thickness variation within the first region of the SiC epitaxial wafer of Example 6 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.

[0112] The LTV, SFQR, SORI, Warp, and Bow of the SiC epitaxial wafer of Example 6 obtained were measured in the same manner as in Example 2.

[0113] The triangular defect density of the SiC epitaxial wafer of Example 6 was 0.02 pieces / cm 2 It was. Also, the variation in carrier concentration of the SiC epitaxial wafer of Example 6 was 9.8%. Also, the variation in carrier concentration in the first region of the SiC epitaxial wafer of Example 6 was 7.5%. Also, the variation in the film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 6 was 4.9%. Also, the variation in the film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Example 6 was 2.0%. 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.

[0114] The LTV of the SiC epitaxial wafer of Example 6 was 1.9 μm. The SFQR of the SiC epitaxial wafer of Example 6 was 2.0 μm. The SORI of the SiC epitaxial wafer of Example 6 was 13.1 μm. The Warp of the SiC epitaxial wafer of Example 6 was 15.2 μm. The Bow of the SiC epitaxial wafer of Example 6 was -4.9 μm.

[0115] "Example 7" First, a 4H-SiC substrate with a diameter of 200 mm and a thickness of 380 μm was prepared and placed inside a vertical furnace as shown in FIG. 9. The SiC substrate 2 was placed on the susceptor 50 and housed together with the susceptor 50 in the chamber 10. As the susceptor 50, one with a diameter of 230 mm, a thickness of the main body part of 3 mm, and a radial width of the frame of 10 mm was used. Then, the inside of the chamber 11 was evacuated. The evacuation speed was set to 3 kPa / second.

[0116] Next, a SiC epitaxial layer 3 with a thickness of 11 μm was formed on the SiC substrate 2. The rotation speed of the SiC substrate 2 when forming the SiC epitaxial layer 3 was set to 100 rpm. The carrier gas was Ar. Area ratio of the part belonging to the supply port of the carrier gas (first gas supply port) to the top plate of the chamber: 2.5% Area ratio of the supply port of the carrier gas (first gas supply port) to all gas supply ports: 20% The flow rate of the carrier gas was set to 1000 sccm or more and 4000 sccm or less.

[0117] The triangular defect density, the variation in carrier concentration, the carrier concentration in the first region, the film thickness variation, and the film thickness variation in the first region of the SiC epitaxial wafer of Example 7 produced 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.

[0118] The LTV, SFQR, SORI, Warp, and Bow of the SiC epitaxial wafer of Example 7 obtained were measured in the same manner as in Example 2.

[0119] The triangular defect density of the SiC epitaxial wafer of Example 7 was 0.003 pieces / cm 2It was. Also, the variation in the carrier concentration of the SiC epitaxial wafer of Example 7 was 34.2%. Also, the variation in the carrier concentration in the first region of the SiC epitaxial wafer of Example 7 was 32.9%. Also, the variation in the film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Example 7 was 5.3%. Also, the variation in the film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Example 7 was 3.8%. Further, when the SiC epitaxial layer was divided into a plurality of regions each having a side length of 5 mm, the ratio of the regions having no triangular defects was 98% or more.

[0120] The LTV of the SiC epitaxial wafer of Example 7 was 2.3 μm. The SFQR of the SiC epitaxial wafer of Example 7 was 1.1 μm. The SORI of the SiC epitaxial wafer of Example 7 was 3.2 μm. The Warp of the SiC epitaxial wafer of Example 7 was 3.3 μm. The Bow of the SiC epitaxial wafer of Example 7 was 1.6 μm.

[0121] "Comparative Example 1" Comparative Example 1 used a susceptor with a diameter of 250 mm, a thickness of the main body of 8 mm, and a radial width of the frame of 20 mm. The area ratio of the surface to which the carrier gas belongs to the top plate of the chamber was 42%, the area ratio of the supply port of the carrier gas to all the gas supply ports was 71%, the flow rate of the carrier gas was less than 1000 sccm, the evacuation speed was 6 kPa / second, and the rotation speed of the SiC substrate 2 when forming the SiC epitaxial layer 3 was 300 rpm, which was different from Example 1.

[0122] Assuming that other conditions were the same as those in Example 1, the triangular defect density, the variation in the carrier concentration, and the film thickness variation of the SiC epitaxial wafer of Comparative Example 1 were measured.

[0123] The triangular defect density of the SiC epitaxial wafer of Comparative Example 1 was 0.24 pieces / cm 2It was. The variation in the carrier concentration of the SiC epitaxial wafer of Comparative Example 1 was 26.1%. Also, the variation in the carrier concentration of the first region of the SiC epitaxial wafer of Comparative Example 1 was 25.9%. Further, the variation in the film thickness of the SiC epitaxial layer of the SiC epitaxial wafer of Comparative Example 1 was 5.3%. Also, the variation in the film thickness of the epitaxial layer in the first region of the SiC epitaxial wafer of Comparative Example 1 was 5.3%. Further, 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 less than 98%.

Explanation of Signs

[0124] 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 51 Body 52 Frame A Unit exposure area

Claims

1. A SiC substrate and a SiC epitaxial layer are provided. The SiC substrate has a diameter of 195 mm or more and a thickness of 460 μm or less, The SiC epitaxial layer has a triangular defect density of 0.2 / cm ２ The following is a SiC epitaxial wafer.

2. 2. The SiC epitaxial wafer according to claim 1, wherein, when viewed in a plan view from the stacking direction, a local thickness variation (LTV) in each of a plurality of unit exposure regions divided into 20 mm squares is 4 μm or less.

3. 2. The SiC epitaxial wafer according to claim 1, wherein, when viewed in a plan view from the stacking direction, a site flatness (SFQR) in each of a plurality of unit exposure regions divided into 20 mm squares is 2 μm or less.

4. The SiC epitaxial wafer according to claim 1 , wherein the warp is 90 μm or less.

5. 2. The SiC epitaxial wafer according to claim 1, wherein the bow is 60 μm or less when a surface connecting a support point located at a position overlapping with a circumference 7.5 mm inside from the outermost circumference and an overlapping portion as viewed from the thickness direction is used as a reference surface.

6. 2. The SiC epitaxial wafer of claim 1, wherein the SORI is 60 μm or less.

7. 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.

8. The SiC epitaxial wafer according to claim 1 , wherein the SiC epitaxial layer has a carrier concentration variation of 20% or less.

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

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