SiC epitaxial wafer

Abstract

The objective is to provide a SiC epitaxial wafer with minimal variation in the thickness of the SiC epitaxial layer near the notch. [Solution] This SiC epitaxial wafer has a notch. The notch has a first side and a second side connecting the innermost point of the notch to the outer circumference of the wafer. The first side is in the direction [-1-120] from the innermost point, and the second side is in the direction [11-20] from the innermost point. The first measurement point is set at a position 0.5 mm in the direction [-1100] from the midpoint of the first side, and the second measurement point is set at a position 0.5 mm in the direction [-1100] from the midpoint of the second side. The film thickness variation between the first and second measurement points of the SiC epitaxial layer of the SiC epitaxial wafer is less than 10%.

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). Also, silicon carbide (SiC) has a thermal conductivity that is about three times higher than that of silicon (Si). Therefore, silicon carbide (SiC) is expected to be applied to SiC devices such as power devices, high-frequency devices, and high-temperature operation devices. An SiC device is obtained by forming a device in the SiC epitaxial layer of an SiC epitaxial wafer and then dicing the SiC epitaxial wafer into chips.

[0003] An SiC epitaxial wafer is obtained by laminating an SiC epitaxial layer on the surface of an SiC substrate. Hereinafter, the substrate before laminating the SiC epitaxial layer is referred to as an SiC substrate, and the substrate after laminating the SiC epitaxial layer is referred to as an SiC epitaxial wafer. An SiC substrate is manufactured by cutting it out from an SiC ingot.

[0004] For example, Patent Documents 1 to 3 disclose a method for manufacturing an SiC epitaxial wafer in which an SiC epitaxial layer is epitaxially grown on an SiC substrate. Also, Patent Documents 1 to 3 disclose supplying a gas to the back surface side of the SiC substrate in order to suppress the adhesion of deposits to the back surface of the SiC substrate. [Prior Art Documents] [End]][Patent Documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2022-78450 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2022-66742 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2019-7045 [Summary of the Invention] [Problems that the invention aims to solve]

[0006] SiC substrates and SiC epitaxial wafers may have notches to determine the orientation of the crystal axes. A notch is a cutout formed in the SiC substrate or SiC epitaxial wafer. When fabricating SiC devices, the position of the notch is read using a laser or the like, and the orientation of the SiC epitaxial wafer is adjusted so that a predetermined crystal axis of the SiC epitaxial wafer faces a predetermined direction.

[0007] Variations in thickness and shape near the notch can cause poor laser reading of the notch position.

[0008] This disclosure has been made in view of the above-mentioned problems and aims to provide a SiC epitaxial wafer in which the thickness variation of the SiC epitaxial layer near the notch is small. [Means for solving the problem]

[0009] (1) The SiC epitaxial wafer according to the first embodiment comprises a SiC substrate and a SiC epitaxial layer. The SiC epitaxial wafer according to the first embodiment has a notch that cuts out a part of the wafer from the outer edge inward when viewed in plan from the stacking direction. The notch has a first edge and a second edge that connect the innermost point of the notch to the outer edge of the wafer. The first edge is in the direction of [-1-120] from the innermost point. The second edge is in the direction of [11-20] from the innermost point. The first measurement point is set at a position 0.5 mm in the direction of [-1100] from the first point which is the midpoint of the first edge, and the second measurement point is set at a position 0.5 mm in the direction of [-1100] from the second point which is the midpoint of the second edge. The variation in film thickness between the first film thickness of the SiC epitaxial layer at the first measurement point and the second film thickness of the SiC epitaxial layer at the second measurement point is less than 10%. This variation in film thickness is obtained by dividing the absolute value of the difference between the first and second film thicknesses by twice the average film thickness of the first and second film thicknesses.

[0010] (2) The SiC epitaxial wafer according to the above embodiment may satisfy (|L(x)-R(x)|) / (2×Ave(L(x),R(x)))×100<10% for x≦5. L(x) is the thickness of the SiC epitaxial layer at a position x mm away from the first point in the [-1100] direction. R(x) is the thickness of the SiC epitaxial layer at a position x mm away from the second point in the [-1100] direction. Ave(L(x),R(x)) is the average value of L(x) and R(x).

[0011] (3) The SiC epitaxial wafer according to the above embodiment may have a diameter of 145 mm or more.

[0012] (4) The SiC epitaxial wafer according to the above embodiment may have a diameter of 195 mm or more.

[0013] (5) In the SiC epitaxial wafer according to the above embodiment, the SiC epitaxial layer may have a radial thickness variation of 5% or less. The radial thickness variation is determined by dividing the difference between the maximum and minimum values ​​of the thickness of the SiC epitaxial layer, measured along a straight line passing through the center of the SiC epitaxial layer and extending in the <11-20> direction, by twice the average value.

[0014] (6) In the SiC epitaxial wafer according to the above embodiment, the SiC epitaxial layer may have a circumferential film thickness variation of 5% or less. The circumferential film thickness variation is determined by dividing the difference between the maximum and minimum values ​​of the film thickness of the SiC epitaxial layer by twice the average value at a total of four points: two points located half a distance from the center of the SiC epitaxial layer in the <11-20> direction and two points located half a distance from the center of the SiC epitaxial layer in the <-1-100> direction. [Effects of the Invention]

[0015] The SiC epitaxial wafer according to the above embodiment exhibits small variations in the thickness of the SiC epitaxial layer near the notch. [Brief explanation of the drawing]

[0016] [Figure 1] This is a cross-sectional view of a SiC epitaxial wafer according to this embodiment. [Figure 2] This is a plan view of the SiC epitaxial wafer according to this embodiment. [Figure 3] This is an enlarged view of the vicinity of the notch in the SiC epitaxial wafer according to this embodiment. [Figure 4] This is a cross-sectional view of the SiC epitaxial wafer manufacturing apparatus according to this embodiment. [Figure 5] This is a cross-sectional view of the SiC substrate mounted on the susceptor. [Figure 6] This is a plan view showing the positional relationship between the slit and notch of the susceptor. [Figure 7] This is the simulation result for Comparative Example 1. [Figure 8] In the simulation result of Comparative Example 1, the supply amounts of the source gas along each of the reference line, the first measurement line, and the second measurement line are shown. [Figure 9] It is a diagram showing the positional relationship of the slits in Example 1 and Comparative Examples 2 to 4. [Figure 10] In the simulation results of Example 1 and Comparative Examples 1 to 4, the supply amount of the source gas along the first measurement line is shown. [Figure 11] In the simulation results of Example 1 and Comparative Examples 1 to 4, the supply amount of the source gas along the second measurement line is shown.

Mode for Carrying Out the Invention

[0017] Hereinafter, the SiC epitaxial wafer and the like according to the present 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 clarity, the characteristic parts enlarged for convenience, 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 modified and implemented without changing the gist thereof.

[0018] 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.

[0019] FIG. 1 is a cross-sectional view of the SiC epitaxial wafer 1 according to the present embodiment. 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.

[0020] The diameter of the SiC epitaxial wafer 1 is, for example, 6 inches or more, preferably 8 inches or more, more preferably 10 inches or more, and still more preferably 12 inches or more.

[0021] The diameter of the SiC epitaxial wafer 1 is, for example, 145 mm or more, preferably 149 mm or more. The diameter of the SiC epitaxial wafer 1 is, for example, 155 mm or less, preferably 151 mm or less. The diameter of the SiC epitaxial wafer 1 is, for example, 195 mm or more, preferably 199 mm or more. The diameter of the SiC epitaxial wafer 1 is, for example, 205 mm or less, preferably 201 mm or less. The diameter of the SiC epitaxial wafer 1 is, for example, 245 mm or more, preferably 249 mm or more. The diameter of the SiC epitaxial wafer 1 is, for example, 255 mm or less, preferably 251 mm or less. The diameter of the SiC epitaxial wafer 1 is, for example, 295 mm or more, preferably 299 mm or more. The diameter of the SiC epitaxial wafer 1 is, for example, 305 mm or less, and preferably 301 mm or less.

[0022] The SiC substrate 2 is made of, for example, n-type SiC. The conductivity type of the SiC substrate 2 may be p-type or semi-insulating. The polytype of the SiC substrate 2 is not particularly limited and may be any of 2H, 3C, 4H, or 6H. For example, the SiC substrate 2 is 4H-SiC. The diameter of the SiC substrate 2 is the same as the diameter of the SiC epitaxial wafer 1.

[0023] The SiC epitaxial layer 3 is laminated on one surface of the SiC substrate 2. The SiC epitaxial layer 3 is made of SiC.

[0024] Figure 2 is a plan view of the SiC epitaxial wafer 1 according to this embodiment. In Figure 2, the wafer is positioned so that the Si surface is the upper surface. The upper surface of the SiC epitaxial wafer 1 may be the (0001) surface or a surface tilted by an offset angle from the (0001) surface. The offset angle is, for example, 3.5° or more and 4.5° or less, preferably 4°. The offset angle is, for example, 0° or more and 10° or less, may be greater than 0° and 10° or less, may be 7.5° or more and 8.5° or less, or may be 8°.

[0025] The SiC epitaxial wafer 1 has a notch 4 for determining the direction of the crystal axis when viewed from the stacking direction. Here, the stacking direction is the stacking direction of the SiC epitaxial layer 3. The notch 4 is a groove cut out from the outer edge of the SiC epitaxial wafer 1 toward the inside. The notch 4 is located, for example, in the [1-100] direction from the center of the SiC epitaxial wafer 1.

[0026] Figure 3 is an enlarged view of the vicinity of the notch 4 in the SiC epitaxial wafer 1 according to this embodiment. The notch 4 is, for example, a V-shaped groove. The notch 4 extends across the SiC substrate 2 and the SiC epitaxial layer 3. The depth of the groove of the notch 4 may be, for example, 2 mm or 1 mm. The depth of the groove of the notch 4 is the shortest distance between the innermost point 5 of the notch 4 and a virtual circle along the outer circumference of the SiC epitaxial wafer 1, and is the distance of the perpendicular line drawn from the innermost point 5 to the virtual circle in the [1-100] direction.

[0027] The notch 4 has a first side s1 and a second side s2. Each of the first side s1 and the second side s2 is a side that connects the innermost point 5 of the notch 4 to the outer edge of the SiC epitaxial wafer 1. The first side s1 and the second side s2 may be straight or curved. The first side s1 is located in the [-1-120] direction from the innermost point 5, and the second side s2 is located in the [11-20] direction from the innermost point 5. When the notch 4 is positioned towards the viewer and viewed from the top side of the SiC epitaxial wafer 1, the first side s1 is located to the left of the innermost point 5, and the second side s2 is located to the right of the innermost point 5. Hereinafter, with respect to a reference line L0 that passes through the innermost point 5 and extends in the <1-100> direction, the [-1-120] direction side may be referred to as the left side, and the [11-20] direction side as the right side.

[0028] In the SiC epitaxial wafer 1 according to this embodiment, the film thickness variation between the first film thickness of the SiC epitaxial layer 3 at the first measurement point 6 and the second film thickness of the SiC epitaxial layer 3 at the second measurement point 7 is less than 10%. The film thickness variation of the SiC epitaxial layer 3 is preferably 5% or less, preferably 2% or less, preferably 1.5% or less, more preferably 1% or less, and even more preferably 0.5% or less. Here, the film thickness variation of the SiC epitaxial layer 3 is obtained by dividing the absolute value of the difference between the first film thickness and the second film thickness by twice the average film thickness of the first and second film thicknesses.

[0029] The first measurement point 6 is located 0.5 mm shifted in the [-1100] direction along the first measurement line L1 from the first point C1, which is the midpoint of the first side s1. The first measurement line L1 is a virtual line that passes through the first point C1 and extends in the <1-100> direction. The second measurement point 7 is located 0.5 mm shifted in the [-1100] direction along the second measurement line L2 from the second point C2, which is the midpoint of the second side s2. The second measurement line L2 is a virtual line that passes through the second point C2 and extends in the <1-100> direction.

[0030] The SiC epitaxial wafer 1 according to this embodiment exhibits small variations in the thickness of the SiC epitaxial layer 3 at the first measurement point 6 and the second measurement point 7, and high left-right symmetry with respect to the reference line L0 that passes through the innermost point 5 and extends in the <1-100> direction.

[0031] The SiC epitaxial wafer 1 according to this embodiment preferably satisfies the relationship |(L(x)-R(x))| / (2×Ave(L(x),R(x)))<10% for 0≦x≦3, and more preferably satisfies it for x≦5. For 0≦x≦3, |(L(x)-R(x))| / (2×Ave(L(x),R(x))) is preferably 5% or less, preferably 2% or less, preferably 1.5% or less, more preferably 1% or less, and even more preferably 0.5% or less. For x≦5, |(L(x)-R(x))| / (2×Ave(L(x),R(x))) is preferably 5% or less, preferably 2% or less, preferably 1.5% or less, more preferably 1% or less, and even more preferably 0.5% or less.

[0032] L(x) is the thickness of the SiC epitaxial layer 3 at the measurement point located x mm away from the first point C1 in the [-1100] direction. L(0.5) corresponds to the thickness of the SiC epitaxial layer 3 at the first measurement point 6. R(x) is the thickness of the SiC epitaxial layer 3 at the measurement point located x mm away from the second point C2 in the [-1100] direction. R(0.5) corresponds to the thickness of the SiC epitaxial layer 3 at the second measurement point 7. Ave(L(x),R(x)) is the average value of L(x) and R(x).

[0033] Here, the thickness of the SiC epitaxial layer 3 near notch 4 is measured using a microscopic FTIR. For example, a Bruker Vertex HYPERION can be used as the microscopic FTIR. The FTIR spot size is set to 300 μm × 300 μm. Since light scattering is likely to occur near notch 4, it may also be measured using a standard FTIR (Fourier Transform Infrared Spectrophotometer), but using a microscopic FTIR allows for a more accurate measurement of the thickness of the SiC epitaxial layer 3.

[0034] The average thickness of the SiC epitaxial layer 3 is, for example, 3 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. The average thickness of the SiC epitaxial layer 3 may also be, for example, 200 μm or less. This average thickness of the SiC epitaxial layer 3 is the average value of the thickness of the SiC epitaxial layer 3 measured at different points in the radial direction of the SiC epitaxial layer 3. The average thickness in the radial direction is measured, for example, along a straight line extending in the <11-20> direction. The location of the measurement points will be described later.

[0035] The variation in the radial film thickness of the SiC epitaxial layer 3 is, for example, 5% or less, preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less.

[0036] The variation in radial film thickness is determined by dividing the difference between the maximum and minimum values ​​of the SiC epitaxial layer 3 film thickness, 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 film thickness of the SiC epitaxial layer 3 is determined by optical interferometry analysis using FTIR (Fourier transform infrared spectrophotometer).

[0037] The thickness of the SiC epitaxial layer 3 may be measured at 10 mm intervals, 15 mm intervals, 20 mm intervals, 25 mm intervals, or 30 mm intervals. Whether measuring the average thickness of the SiC epitaxial layer 3 or determining the radial variation in thickness of the SiC epitaxial layer 3, the thickness of the SiC epitaxial layer 3 is measured at the same measurement locations.

[0038] For example, if the diameter of the SiC epitaxial wafer 1 is 150 mm (6 inches), the thickness of the SiC epitaxial layer 3 is measured along a straight line extending in the <11-20> direction from the center, at the center and at positions ±15 mm, ±30 mm, ±45 mm, ±60 mm, and ±70 mm from the center. Note that the [11-20] direction or the [-1100] direction is denoted as "+". Using the thickness of each measurement point, the radial thickness variation of the SiC epitaxial layer 3 and the average thickness of the SiC epitaxial layer 3 are determined.

[0039] For example, if the diameter of the SiC epitaxial wafer 1 is 200 mm (8 inches), the thickness of the SiC epitaxial layer 3 is measured along a straight line extending in the <11-20> direction with the center as the reference point, at the center and at positions ±20 mm, ±40 mm, ±60 mm, ±80 mm, and ±95 mm from the center. Using the thickness of each of these measurement points, the radial thickness variation of the SiC epitaxial layer 3 and the average thickness of the SiC epitaxial layer 3 are determined.

[0040] For example, if the diameter of the SiC epitaxial wafer 1 is 250 mm (10 inches), the thickness of the SiC epitaxial layer 3 is measured along a straight line extending in the <11-20> direction with the center as the reference point, at the center and at positions of ±25 mm, ±50 mm, ±75 mm, ±100 mm, and ±120 mm from the center. Using the thickness of each measurement point, the radial thickness variation of the SiC epitaxial layer 3 and the average thickness of the SiC epitaxial layer 3 are determined.

[0041] For example, if 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 the reference point. Using the film thickness at each of these measurement points, the radial film thickness variation of the SiC epitaxial layer 3 and the average film thickness of the SiC epitaxial layer 3 are determined.

[0042] The variation in circumferential film thickness of the SiC epitaxial layer 3 is, for example, 5% or less, preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less.

[0043] The variation in circumferential film thickness is determined by dividing the difference between the maximum and minimum values ​​of the SiC epitaxial layer 3 film thickness measured at four symmetrical points relative to the center of the SiC epitaxial layer 3, in a plan view from the stacking direction, by twice the average value. The four measurement points are, for example, two points located half a radius away from the center of the SiC epitaxial layer 3 in the <11-20> direction, and two points located half a radius away from the center of the SiC epitaxial layer 3 in the <-1-100> direction. The film thickness of the SiC epitaxial layer 3 is determined by optical interferometry using FTIR (Fourier Transform Infrared Spectrophotometer).

[0044] Furthermore, the variation in the radial carrier concentration of the SiC epitaxial layer 3 is preferably 20% or less, more preferably 15% or less, even more preferably 12% or less, even more preferably 10% or less, particularly preferably 5% or less, and most particularly preferably 2% or less. The measurement points for measuring the variation in radial carrier concentration are the same as the measurement points for measuring the variation in the radial film thickness of the SiC epitaxial layer 3. The variation in radial carrier concentration is obtained by dividing the difference between the maximum and minimum values ​​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.

[0045] Furthermore, the variation in carrier concentration in the circumferential direction of the SiC epitaxial layer 3 is preferably 20% or less, more preferably 15% or less, even more preferably 12% or less, even more preferably 10% or less, particularly preferably 5% or less, and most particularly preferably 2% or less. The measurement points for measuring the variation in carrier concentration in the circumferential direction are the same as the measurement points for measuring the variation in the film thickness of the SiC epitaxial layer 3 in the circumferential direction. The depth positions for measuring the variation in carrier concentration are to be approximately the same at each measurement point. Here, for example, if the absolute value of the difference between the maximum and minimum values ​​of the depth positions at each measurement point is within ±5% of the thickness of the center of the SiC epitaxial layer 3, it can be said to be approximately the same. The variation in carrier concentration in the circumferential direction is obtained by dividing the difference between the maximum and minimum values ​​of the carrier concentration of the SiC epitaxial layer 3 measured at four points in symmetrical positions with respect to the center of the SiC epitaxial layer 3 in a plan view from the stacking direction by twice the average value.

[0046] Here, the carrier concentration is the effective carrier concentration. The effective carrier concentration is the absolute difference between the donor concentration and the acceptor concentration. The carrier concentration in SiC epitaxial layer 3 can be measured, for example, by the mercury probe (Hg-CV) method or 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. Secondary ion mass spectrometry (SIMS) is a method that analyzes the mass of secondary ions that are ejected while scraping the layer in the thickness direction. Doping concentration can be measured from the mass spectrometry. Secondary ion mass spectrometry (SIMS) can measure the actual values ​​of the donor concentration and acceptor concentration, and the effective carrier concentration can be determined by finding the difference between these at the same depth position (measurement specified position).

[0047] Next, a method for manufacturing the SiC epitaxial wafer 1 according to this embodiment will be described.

[0048] Figure 4 is a schematic cross-sectional view of an example of a SiC epitaxial wafer deposition apparatus according to this embodiment. The deposition 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 deposition apparatus 100.

[0049] The support 20 supports the susceptor 50. The SiC substrate 2 is placed on the support 20, for example, while mounted on the susceptor 50. The support 20 is rotatable, for example, around its axis. As the support 20 rotates, the susceptor 50 and the SiC substrate 2 rotate together with the support 20.

[0050] The support 20 is configured to supply purge gas to the back side of the susceptor 50. The support 20 has, for example, a supply port for purge gas to the back side of the susceptor 50 and a gas flow path for carrying the purge gas to the supply port. The purge gas is, for example, an inert gas such as nitrogen or argon.

[0051] The lower heater 30 is located, for example, within the support 20 and heats the SiC substrate 2. The upper heater 40 heats the upper part of the chamber 10.

[0052] The chamber 10 includes, for example, a main body 11, a gas supply port 12, and a gas outlet 13. The main body 11 surrounds the film deposition space S. The gas supply port 12 is an inlet for supplying gas G to the film deposition space S. There are multiple gas supply ports 12, for example, above the mounting surface of the SiC substrate 2. A film deposition apparatus in which the gas supply ports 12 are above the mounting surface of the SiC substrate 2 is called a vertical furnace. The gas outlet 13 is an outlet for discharging gas G and the like that has accumulated in the film deposition space S. The gas outlet 13 is, for example, located below the mounting surface of the SiC substrate 2.

[0053] Gas G is, for example, a source gas, a carrier gas, a dopant gas, or an etching gas. The source gas includes Si-based source gases and C-based source gases.

[0054] Si-based raw material gases are raw material gases that contain Si in their molecules. Examples of Si-based raw material gases include silane (SiH4), dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3), and tetrachlorosilane (SiCl4). Preferably, the Si-based raw material gas contains at least one selected from the group consisting of SiH3Cl, SiH2Cl2, and SiHCl3.

[0055] C-based raw material gases are raw material gases that contain carbon in their molecules. Examples of C-based raw material gases include propane (C3H8) and ethylene (C2H4). Preferably, the C-based raw material gas contains at least one selected from the group consisting of CH4, C2H6, and C3H8.

[0056] A dopant gas is a gas that contains a carrier element. An example of a dopant gas is nitrogen (N2).

[0057] The carrier gas is a gas that transports the raw material gas to the SiC substrate 2, and is an inert gas to SiC. The carrier gas preferably contains, for example, Ar.

[0058] An etching gas is a gas that reacts with SiC at high temperatures to etch SiC. Hydrogen chloride (HCl) is a preferred etching gas.

[0059] The susceptor 50 supports the SiC substrate 2. Figure 5 is a cross-sectional view of the SiC substrate 2 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 flying outwards during film deposition.

[0060] The main body 51 has a slit SL1. Purge gas is supplied to the back side of the SiC substrate 2 through the slit SL1. Figure 6 is a plan view showing the positional relationship between the slit SL1 and the notch 4. Since the susceptor 50 and the SiC substrate 2 rotate together, the positional relationship between the slit SL1 and the notch 4 does not change even during film formation.

[0061] The shape of slit SL1 is approximately identical to that of notch 4. Slit SL1 is located in the [-1100] direction relative to notch 4. Slit SL1 is positioned so as not to overlap with notch 4. For example, the distance between the innermost point 5 of notch 4 and the innermost point 5' of slit SL1 is 2 mm.

[0062] The SiC epitaxial wafer 1 according to this embodiment can be obtained, for example, by depositing a SiC epitaxial layer 3 on a SiC substrate 2 using the SiC epitaxial wafer deposition apparatus described above.

[0063] In the film deposition process, first, the SiC substrate 2, which is placed on the susceptor 50, is placed inside the chamber 10. After the chamber 10 is evacuated, a SiC epitaxial layer 3 is deposited on the SiC substrate 2.

[0064] The SiC epitaxial layer 3 is deposited while rotating the SiC substrate 2. The rotation direction of the SiC substrate 2 is, for example, such that the notch 4 rotates clockwise. The rotation direction of the SiC substrate 2 may be opposite to this direction.

[0065] The SiC epitaxial layer 3 is formed by supplying a mixed gas containing a Si-based raw material gas, a C-based raw material gas, an etching gas, a carrier gas, and a dopant gas to one surface of the SiC substrate 2.

[0066] Furthermore, during the deposition of the SiC epitaxial layer 3, a purge gas is supplied to the back side of the SiC substrate 2 through the slit SL1. The purge gas is, for example, Ar. The flow rate of the purge gas is, for example, 5 sccm to 50 sccm. By supplying the purge gas through the slit SL1, the variation in the distribution of the raw material gas supplied to the right and left sides of the notch 4 is reduced. As a result, a SiC epitaxial wafer 1 according to this embodiment can be manufactured with small thickness variations between the right and left sides of the notch 4.

[0067] In this description, the manufacturing method of the SiC epitaxial wafer 1 according to this embodiment was explained using the film deposition apparatus 100 shown in Figure 4 as an example, but the film deposition apparatus is not limited to this example. The shape of the film deposition apparatus is not limited as long as it can supply purge gas to a predetermined position on the back surface of the SiC substrate 2. For example, a horizontal furnace with the gas supply port 12 located on the side of the mounting surface of the SiC substrate 2 may also be used.

[0068] In this embodiment, the SiC epitaxial wafer 1 exhibits small variations in the thickness of the SiC epitaxial layer 3 on the right and left sides of the notch 4, and high uniformity in the thickness of the SiC epitaxial layer 3 near the notch 4. The notch 4 is used to control the position and orientation when manufacturing SiC devices. Low uniformity in thickness near the notch 4 can cause defects when reading the notch 4 with a laser or the like. Because the SiC epitaxial wafer 1 in this embodiment exhibits high uniformity in the thickness of the SiC epitaxial layer 3 near the notch 4, precise control of the position and orientation is possible, and defects when manufacturing SiC devices can be suppressed.

[0069] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Examples]

[0070] "Comparative Example 1" In Comparative Example 1, the flow rate distribution of the raw material gas near the notch during film deposition of a SiC epitaxial wafer using a susceptor without a slit was measured using simulation. Because the susceptor did not have a slit, a sufficient amount of purge gas was not supplied to the back side of the SiC substrate. The simulation was performed using the general-purpose fluid analysis software ANSYS Fluent. The diameter of the SiC substrate was set to 200 mm, and the depth of the notch was set to 2 mm. The rotation direction of the SiC substrate was set to the direction in which the notch rotated clockwise. Other simulation conditions included adiabatic conditions at the furnace wall boundary.

[0071] Figure 7 shows the simulation results for Comparative Example 1. In Figure 7, the closer the color is to black, the greater the supply of raw materials. The simulation results for Comparative Example 1 show that there is variation in the supply of raw materials on the right and left sides of the notch.

[0072] Figure 8 shows the supply amounts of raw material gas along the reference line L0, the first measurement line L1, and the second measurement line L2 in the simulation results for Comparative Example 1. The horizontal axis of Figure 8 represents the distance l from the reference axis that passes through the center of the SiC substrate and extends in the <11-20> direction. In the horizontal axis of Figure 8, the [-1100] direction is considered positive. Because of the notch in the reference line L0, the absolute value of the distance l from the reference axis is at most 98.0 mm. The vertical axis of Figure 8 represents the supply amount of raw material gas to the SiC substrate.

[0073] As shown in Figure 8, it can be confirmed that there is a difference in the supply amount of raw material gas between the left side of the notch (first measurement line L1) and the right side of the notch (second measurement line L2).

[0074] Furthermore, when an actual SiC epitaxial wafer was fabricated under the same conditions as in Comparative Example 1, the thickness of the SiC epitaxial layer at the measurement point x=500μm (0.5mm) on the first measurement line L1 was 3.36μm, and the thickness of the SiC epitaxial layer at the measurement point x=500μm (0.5mm) on the second measurement line L2 was 4.27μm. The thickness variation of the SiC epitaxial layer in Comparative Example 1 was 11.9%.

[0075] "Example 1" Example 1 differs from Comparative Example 1 in that it uses a susceptor with a slit SL1. A purge gas of 25 sccm is supplied to the back side of the SiC substrate through the slit SL1. Under the same conditions as in Comparative Example 1, the supply amounts of the raw material gas on the left side of the notch (first measurement line L1) and the right side of the notch (second measurement line L2) were simulated.

[0076] "Comparative Example 2" Comparative Example 2 differs from Comparative Example 1 in that it uses a susceptor with slit SL2. 25 sccm of purge gas is supplied to the back side of the SiC substrate from slit SL2. Slit SL2 has the same shape as slit SL1. Slit SL2 is positioned to overlap with notch 4 in a plan view. Under the same conditions as in Comparative Example 1, the supply amount of raw material gas on the left side of the notch (first measurement line L1) and the right side of the notch (second measurement line L2) was simulated.

[0077] "Comparative Example 3" Comparative Example 3 differs from Comparative Example 1 in that it uses a susceptor with slit SL3. 25 sccm of purge gas is supplied to the back side of the SiC substrate from slit SL3. Slit SL3 has the same shape as slit SL1. Slit SL3 is located shifted to the right of notch 4. One of the corners of slit SL3 is in the [1-100] direction from the innermost point 5 of notch 4. Under the same conditions as in Comparative Example 1, the supply amount of raw material gas on the left side of the notch (first measurement line L1) and the right side of the notch (second measurement line L2) was simulated.

[0078] "Comparative Example 4" Comparative Example 4 differs from Comparative Example 1 in that it uses a susceptor with a slit SL4. 25 sccm of purge gas is supplied to the back side of the SiC substrate from the slit SL4. Slit SL4 has the same shape as slit SL1. Slit SL4 is located shifted to the left of notch 4. One of the corners of slit SL4 is in the [1-100] direction from the innermost point 5 of notch 4. Under the same conditions as in Comparative Example 1, the supply amount of raw material gas on the left side of the notch (first measurement line L1) and the right side of the notch (second measurement line L2) was simulated.

[0079] Figure 9 shows the positional relationship of slits SL1 to SL4 in Example 1 and Comparative Examples 2 to 4.

[0080] Figure 10 shows the supply rate of the raw material gas along the first measurement line L1 in the simulation results for Example 1 and Comparative Examples 1-4. The horizontal axis of Figure 10 represents the distance l from the reference axis that passes through the center of the SiC substrate and extends in the <11-20> direction. In Figure 10, the [-1100] direction is considered positive. The vertical axis of Figure 10 represents the supply rate of the raw material gas to the SiC substrate.

[0081] Figure 11 shows the supply rate of the raw material gas along the second measurement line L2 in the simulation results for Example 1 and Comparative Examples 1-4. The horizontal axis of Figure 11 represents the distance l from the reference axis that passes through the center of the SiC substrate and extends in the <11-20> direction. In the horizontal axis of Figure 11, the [-1100] direction is considered positive. The vertical axis of Figure 11 represents the supply rate of the raw material gas to the SiC substrate.

[0082] As shown in Figures 10 and 11, Example 1 showed less variation in the radial SiC epitaxial layer thickness compared to Comparative Examples 1-4. Comparative Examples 2-4 supplied purge gas to the back surface of the SiC substrate, similar to Example 1, but the variation in the amount of raw material gas supplied was greater than in Comparative Example 1. Also, as shown in Figures 10 and 11, Example 1 showed less difference in the amount of raw material gas supplied between the left and right sides of the notch at the same distance l from the reference axis compared to Comparative Examples 1-4.

[0083] When an actual SiC epitaxial wafer was fabricated under the same conditions as in Example 1, the thickness of the SiC epitaxial layer at the measurement point x=500μm (0.5mm) on the first measurement line L1 was 9.63μm, and the thickness of the SiC epitaxial layer at the measurement point x=500μm (0.5mm) on the second measurement line L2 was 8.87μm. The thickness variation of the SiC epitaxial layer in Example 1 was 4.10%. [Explanation of symbols]

[0084] 1 SiC epitaxial wafer 2 SiC substrates 3 SiC epitaxial layer 4 Notches 5, 5' Innermost point 6 1st measurement point 7 Second measurement point 10 chambers 11 Main unit 12 Gas supply port 13 Gas outlet 20 Support 30 Lower heater 40 Top heater 50 Susceptors 51 Main unit 52 slots C1 1st point C2 2nd point L0 reference line L1 First measurement line L2 Second measurement line s1 First side s2 Second side SL1, SL2, SL3, SL4 Slit

Claims

1. It has a SiC substrate and a SiC epitaxial layer, In a plan view from the stacking direction, it has a notch that cuts out a portion of the wafer from the outer edge inward. The notch has a first side and a second side that connect the innermost point of the notch to the outer circumference of the wafer. The first side is located in the direction [-1-120] from the innermost point, The second side is located in the [11-20] direction from the innermost point, The first measurement point is defined as a position 0.5 mm in the [-1100] direction from the first point, which is the midpoint of the first side. When the second measurement point is set to a position 0.5 mm in the [-1100] direction from the second point, which is the midpoint of the second side, The variation in film thickness between the first film thickness of the SiC epitaxial layer at the first measurement point and the second film thickness of the SiC epitaxial layer at the second measurement point is less than 10%. The aforementioned film thickness variation is obtained by dividing the absolute value of the difference between the first film thickness and the second film thickness by twice the average film thickness of the first and second film thicknesses, in a SiC epitaxial wafer.

2. Let L(x) be the thickness of the SiC epitaxial layer at a position x mm away from the first point in the direction of [-1100]. Let R(x) be the thickness of the SiC epitaxial layer at a position x mm away from the second point in the direction of [-1100]. When the average of L(x) and R(x) is defined as Ave(L(x), R(x)), For x ≤ 5, |(L(x) - R(x))| / (2 × Ave(L(x), R(x))) A SiC epitaxial wafer according to claim 1, satisfying the 10% requirement.

3. The SiC epitaxial wafer according to claim 1, wherein the diameter is 145 mm or more.

4. A SiC epitaxial wafer according to claim 1, wherein the diameter is 195 mm or more.

5. The SiC epitaxial layer has a radial thickness variation of 5% or less. The SiC epitaxial wafer according to claim 1, wherein the variation in the radial film thickness is determined by dividing the difference between the maximum and minimum values ​​of the film thickness of the SiC epitaxial layer, measured along a straight line passing through the center of the SiC epitaxial layer and extending in the <11-20> direction, by twice the average value.

6. The SiC epitaxial layer has a circumferential thickness variation of 5% or less. The SiC epitaxial wafer according to claim 1, wherein the variation in circumferential film thickness is determined by dividing the difference between the maximum and minimum values ​​of the film thickness of the SiC epitaxial layer, measured at a total of four points: two points located half a distance from the center of the SiC epitaxial layer in the <11-20> direction and two points located half a distance from the center of the SiC epitaxial layer in the <-1-100> direction, by twice the average value.

Images