JP2022177484A - Inspection method of silicon carbide epitaxial substrate, manufacturing method of silicon carbide epitaxial substrate and substrate set - Google Patents

Abstract

To precisely detect a silicon carbide epitaxial substrate having a micro pipe by a simple method.SOLUTION: An inspection method of a silicon carbide epitaxial substrate has a following step. The silicon carbide epitaxial substrate is vacuum chucked by a vacuum chuck. Based on a vacuum degree of the vacuum chuck, it is determined whether the silicon carbide epitaxial substrate has a micro pipe.SELECTED DRAWING: Figure 8

Description

The present disclosure relates to a silicon carbide epitaxial substrate inspection method, a silicon carbide epitaxial substrate manufacturing method, and a substrate set.

Isaho KAMATA and three others, "Structural Transformation of Screw Dislocations via Thick 4H-SiC Epitaxial Growth", Jpn. J. Appl. Phys. Vol. 39 (2000) pp. 6496-6500 (Non-Patent Document 1), A silicon carbide epitaxial substrate with micropipes is disclosed.

Isaho KAMATA et al., "Structural Transformation of Screw Dislocations via Thick 4H-SiC Epitaxial Growth", Jpn. J. Appl. Phys. Vol. 39 (2000) pp. 6496-6500

An object of the present disclosure is to accurately detect a silicon carbide epitaxial substrate having micropipes by a simple method.

A silicon carbide epitaxial substrate inspection method according to the present disclosure includes the following steps. A silicon carbide epitaxial substrate is vacuum-sucked on a vacuum chuck. Based on the degree of vacuum of the vacuum chuck, it is determined whether the silicon carbide epitaxial substrate has micropipes.

A substrate set according to the present disclosure includes a cassette provided with a plurality of slots, and a plurality of silicon carbide epitaxial substrates arranged in each of the plurality of slots. The number of multiple silicon carbide epitaxial substrates is 20 or more. Each of the plurality of silicon carbide epitaxial substrates does not have micropipes.

According to the present disclosure, a silicon carbide epitaxial substrate having micropipes can be accurately detected by a simple method.

FIG. 1 is a schematic plan view showing the configuration of a silicon carbide epitaxial substrate. FIG. 2 is an enlarged schematic plan view of region II in FIG. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. FIG. 4 is a schematic diagram showing the configuration of a micropipe defect detection apparatus. FIG. 5 is a schematic plan view showing the configuration of the mounting surface of the vacuum chuck. FIG. 6 is a schematic cross-sectional view taken along line VI-VI of FIG. FIG. 7 is a schematic cross-sectional view taken along line VII-VII of FIG. FIG. 8 is a flow diagram schematically showing a method for inspecting a silicon carbide epitaxial substrate according to this embodiment. FIG. 9 is a schematic cross-sectional view showing the configuration of a silicon carbide epitaxial substrate manufacturing apparatus according to the present embodiment. FIG. 10 is a flow diagram schematically showing a method for manufacturing a silicon carbide epitaxial substrate according to this embodiment. FIG. 11 is a schematic cross-sectional view showing the configuration of the substrate set according to this embodiment. FIG. 12 shows the relationship between the degree of vacuum of the vacuum chuck and the sample number of the silicon carbide epitaxial substrate.

[Outline of Embodiment of Present Disclosure]
First, an outline of an embodiment of the present disclosure will be described. In the crystallographic description of this specification, individual orientations are indicated by [ ], collective orientations by <>, individual planes by ( ), and collective planes by { }. Negative crystallographic exponents are usually expressed by placing a "-" (bar) above the number, but here the crystallographic index is expressed by prefixing the number with a negative sign. Represents a negative exponent above.

(1) A method for inspecting silicon carbide epitaxial substrate 10 according to the present disclosure includes the following steps. Silicon carbide epitaxial substrate 10 is vacuum-adsorbed to vacuum chuck 20 . Whether silicon carbide epitaxial substrate 10 has micropipe 5 is determined based on the degree of vacuum of vacuum chuck 20 .

(2) According to the method for inspecting silicon carbide epitaxial substrate 10 according to (1) above, vacuum chuck 20 may include mounting surface 21 on which silicon carbide epitaxial substrate 10 is mounted. A plurality of protrusions 30 may be provided on the mounting surface 21 . The plurality of protrusions 30 may have a first annular protrusion 31 positioned on the outermost side and a second annular protrusion 32 positioned on the innermost side. The mounting surface 21 may include an intermediate region 40 positioned between the first annular protrusion 31 and the second annular protrusion 32 . Air intake holes 60 may be provided in the intermediate region 40 . In plan view, the value obtained by dividing the total area of the plurality of protrusions 30 by the area surrounded by the outer peripheral edge of the first annular protrusion 31 may be less than 50%.

(3) According to the method for inspecting silicon carbide epitaxial substrate 10 according to (2) above, plural protrusions 30 may include plural third annular protrusions 33 located in intermediate region 40 . The intake holes 60 may be provided between each of the plurality of third annular protrusions 33 .

(4) According to the method for inspecting silicon carbide epitaxial substrate 10 according to (2) or (3) above, the total area of the plurality of protrusions 30 is surrounded by the outer peripheral edge of first annular protrusion 31 in plan view. The value divided by the area covered may be less than 10%.

(5) According to the method for inspecting silicon carbide epitaxial substrate 10 according to any one of the above (1) to (4), when the degree of vacuum is lower than the reference degree of vacuum 7, silicon carbide epitaxial substrate 10 is micropipe 5 . may be determined to have

In this specification, the degree of vacuum is defined as follows. The degree of vacuum of atmospheric pressure is assumed to be 0 kPa. A vacuum is negative if the pressure is less than atmospheric pressure. Conversely, if the pressure is greater than atmospheric pressure, the degree of vacuum is positive. A "high degree of vacuum" is a state closer to a vacuum. The closer the degree of vacuum is to -101.3 kPa, the higher the degree of vacuum. "Low degree of vacuum" means a state closer to atmospheric pressure. The closer the degree of vacuum is to 0 kPa, the lower the degree of vacuum.

(6) According to the inspection method for silicon carbide epitaxial substrate 10 according to (5) above, the silicon carbide epitaxial substrate inspection method according to claim 5, wherein the standard degree of vacuum is -60 kPa or more and -50 kPa or less.

(7) According to the method for inspecting silicon carbide epitaxial substrate 10 according to any one of (1) to (6) above, vacuum pump 23 is used in the step of vacuum-adsorbing silicon carbide epitaxial substrate 10 to vacuum chuck 20. Alternatively, silicon carbide epitaxial substrate 10 may be vacuum-adsorbed to vacuum chuck 20 . The pumping speed of the vacuum pump 23 may be 5 liters/minute or more and 100 liters/minute or less.

(8) A method for manufacturing silicon carbide epitaxial substrate 10 according to the present disclosure includes the following steps. Silicon carbide epitaxial substrate 10 is prepared by forming silicon carbide epitaxial layer 12 on silicon carbide substrate 11 . Silicon carbide epitaxial substrate 10 is sorted using the method for inspecting silicon carbide epitaxial substrate 10 according to any one of (1) to (7) above.

(9) A substrate set 300 according to the present disclosure includes a cassette 302 provided with a plurality of slots 301 and a plurality of silicon carbide epitaxial substrates 10 arranged in each of the plurality of slots 301 . The number of plural silicon carbide epitaxial substrates 10 is 20 or more. Each of silicon carbide epitaxial substrates 10 does not have micropipe 5 .

(10) In the substrate set 300 according to (9) above, the diameter of the circle circumscribing the micropipe 5 may be 10 μm or more and 100 μm or less.

(11) In the substrate set 300 according to (9) above, the diameter of the circle circumscribing the micropipe 5 may be 20 μm or more and 80 μm or less.

[Details of the embodiment of the present disclosure]
Details of the embodiments of the present disclosure will be described below. In the following description, the same or corresponding elements are given the same reference numerals and the same descriptions thereof are not repeated.

First, the configuration of silicon carbide epitaxial substrate 10 according to the present embodiment will be described. FIG. 1 is a schematic plan view showing the configuration of a silicon carbide epitaxial substrate 10. FIG. FIG. 2 is an enlarged schematic plan view of region II in FIG. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG.

As shown in FIGS. 1 to 3, silicon carbide epitaxial substrate 10 according to the present embodiment has silicon carbide substrate 11 and silicon carbide epitaxial layer 12 . Silicon carbide epitaxial layer 12 is on silicon carbide substrate 11 . Silicon carbide epitaxial layer 12 has a first main surface 1 and a second main surface 2 . First main surface 1 is in contact with silicon carbide substrate 11 . The second major surface 2 is opposite the first major surface 1 . Second main surface 2 constitutes the surface of silicon carbide epitaxial substrate 10 . The polytype of silicon carbide forming silicon carbide epitaxial layer 12 is, for example, 4H.

Silicon carbide substrate 11 has a third main surface 3 and a fourth main surface 4 . The fourth major surface 4 is opposite the third major surface 3 . Third main surface 3 is in contact with silicon carbide epitaxial layer 12 . Fourth main surface 4 constitutes the back surface of silicon carbide epitaxial substrate 10 . Fourth main surface 4 is separated from silicon carbide epitaxial layer 12 . The polytype of silicon carbide forming silicon carbide substrate 11 is, for example, 4H.

As shown in FIG. 1 , silicon carbide epitaxial substrate 10 has an outer peripheral edge 15 when viewed in the thickness direction of silicon carbide epitaxial substrate 10 . The outer peripheral edge 15 has, for example, an orientation flat 13 and an arcuate portion 14 . The orientation flat 13 extends along the first direction 101 . As shown in FIG. 1 , orientation flat 13 is linear when viewed in the thickness direction of silicon carbide epitaxial substrate 10 . The arcuate portion 14 continues to the orientation flat 13 . When viewed in the thickness direction of silicon carbide epitaxial substrate 10, arc-shaped portion 14 is arc-shaped.

As shown in FIG. 1 , second main surface 2 extends along each of first direction 101 and second direction 102 when viewed in the thickness direction of silicon carbide epitaxial substrate 10 . First direction 101 is a direction perpendicular to second direction 102 when viewed in the thickness direction of silicon carbide epitaxial substrate 10 .

The first direction 101 is, for example, the <11-20> direction. The first direction 101 may be the [11-20] direction, for example. The first direction 101 may be a direction obtained by projecting the <11-20> direction onto the second main surface 2 . From another point of view, the first direction 101 may be a direction including a <11-20> direction component, for example.

The second direction 102 is, for example, the <1-100> direction. The second direction 102 may be, for example, the [1-100] direction. The second direction 102 may be a direction obtained by projecting the <1-100> direction onto the second main surface 2, for example. From another point of view, the second direction 102 may be a direction including a <1-100> direction component, for example.

As shown in FIG. 1, the diameter (first diameter A1) of silicon carbide epitaxial substrate 10 is not particularly limited, but is, for example, 100 mm (4 inches) or more. The first diameter A1 may be 125 mm (5 inches) or greater, or 150 mm (6 inches) or greater. The upper limit of the first diameter A1 is not particularly limited. The first diameter A1 may be, for example, 200 (8 inches) mm or less.

In this specification, 4 inches means 100 mm or 101.6 mm (4 inches x 25.4 mm/inch). 5 inches is 125 mm or 127.0 mm (5 inches by 25.4 mm/inch). Six inches is 150 mm or 152.4 mm (6 inches by 25.4 mm/inch). 8 inches is 200 mm or 203.2 mm (8 inches by 25.4 mm/inch).

Second main surface 2 of silicon carbide epitaxial substrate 10 may be inclined at an off angle of 8° or less with respect to the {0001} plane, for example. Specifically, the second main surface 2 may be inclined at an off angle of 8° or less with respect to the (0001) plane or the (0001) plane. The second main surface 2 may be inclined at an off angle of 8° or less with respect to the (000-1) plane or the (000-1) plane.

The upper limit of the off angle is not particularly limited, but may be, for example, 6° or less, or 4° or less. The lower limit of the off angle is not particularly limited, but may be, for example, 2° or more, or 1° or more. The off direction is not particularly limited, but may be, for example, the <11-20> direction or the <0001> direction.

Silicon carbide substrate 11 contains n-type impurities such as nitrogen (N), for example. The conductivity type of silicon carbide substrate 11 is, for example, the n type (first conductivity type). In this case the carriers are electrons. Silicon carbide substrate 11 has a carrier concentration of, for example, 1×10 ¹⁹ m ⁻³ or more and 1×10 ²⁰ cm ⁻³ or less. The thickness of silicon carbide substrate 11 is not particularly limited, but is, for example, 200 μm or more and 500 μm or less.

Silicon carbide epitaxial layer 12 contains an n-type impurity such as nitrogen (N). The conductivity type of silicon carbide epitaxial layer 12 is, for example, the n type (first conductivity type). In this case the carriers are electrons. Silicon carbide epitaxial layer 12 has a carrier concentration of, for example, 1×10 ¹⁴ cm ⁻³ or more and less than 1×10 ¹⁹ cm ⁻³ . The carrier concentration of silicon carbide epitaxial layer 12 may be lower than the carrier concentration of silicon carbide substrate 11 .

As shown in FIGS. 2 and 3, silicon carbide epitaxial substrate 10 may have micropipes 5 . As shown in FIG. 3 , micropipe 5 penetrates silicon carbide epitaxial substrate 10 . Micropipe 5 penetrates each of silicon carbide substrate 11 and silicon carbide epitaxial layer 12 . The micropipe 5 opens to each of the second principal surface 2 and the fourth principal surface 4 . The extending direction of the micropipe 5 is substantially perpendicular to the second main surface 2 .

As shown in FIG. 2, viewed in a direction perpendicular to the second main surface 2, the micropipe 5 has a hexagonal shape. The diameter (second diameter A2) of the circle circumscribing the micropipe 5 is, for example, 10 μm or more. Although the lower limit of the second diameter A2 is not particularly limited, it may be, for example, 15 μm or more, or 20 μm or more. The upper limit of the second diameter A2 is not particularly limited, but may be, for example, 100 μm or less, 80 μm or less, or 50 μm or less.

Next, a detection device for the micropipe 5 will be described.
FIG. 4 is a schematic diagram showing the configuration of the detection device for the micropipe 5. As shown in FIG. As shown in FIG. 4, the micropipe 5 detection device mainly includes a vacuum chuck 20 , a vacuum pump 23 and a vacuum gauge 22 . The vacuum chuck 20 has a mounting surface 21 . Vacuum chuck 20 is a stage on which silicon carbide epitaxial substrate 10 is placed, for example. Silicon carbide epitaxial substrate 10 is mounted on mounting surface 21 of vacuum chuck 20 . A vacuum pump 23 is connected to the vacuum chuck 20 . Vacuum pump 23 is, for example, a dry vacuum pump. As the vacuum pump 23, for example, a dry vacuum pump (model number: DAU-20) manufactured by ULVAC, Inc. can be used. A vacuum gauge 22 can measure the degree of vacuum of the vacuum chuck 20 .

FIG. 5 is a schematic plan view showing the configuration of the mounting surface 21 of the vacuum chuck 20. As shown in FIG. As shown in FIG. 5 , a plurality of protrusions 30 may be provided on the placement surface 21 . In plan view, each of the plurality of protrusions 30 is, for example, annular. In plan view, each of the plurality of convex portions 30 is provided, for example, concentrically.

The multiple protrusions 30 have, for example, a first annular protrusion 31 , a second annular protrusion 32 , and a plurality of third annular protrusions 33 . The first annular projection 31 is located on the outermost side of the mounting surface 21 . The second annular protrusion 32 is located on the innermost side of the mounting surface 21 . The second annular protrusion 32 is surrounded by the first annular protrusion 31 . The mounting surface 21 includes an intermediate area 40 . The intermediate region 40 is positioned between the first annular protrusion 31 and the second annular protrusion 32 . In plan view, the intermediate region 40 is surrounded by the first annular projection 31 . In plan view, the second annular convex portion 32 is surrounded by the intermediate region 40 .

The plurality of third annular protrusions 33 are positioned in the intermediate region 40 . The intermediate region 40 has a first flat region 41 and a second flat region 42 . Each of the first flat region 41 and the second flat region 42 is positioned between two annular protrusions adjacent in the radial direction. In the radial direction, the first flat regions 41 and the second flat regions 42 are alternately arranged.

Air intake holes 60 are provided in the intermediate region 40 . The intake holes 60 may be provided between each of the plurality of third annular protrusions 33 . The air intake hole 60 may have a first air intake hole 61 and a second air intake hole 62 . The first air intake holes 61 are provided in the first flat area 41 . The number of the first air intake holes 61 may be singular or plural. In plan view, each of the plurality of first air intake holes 61 may be positioned on a straight line (first straight line L1) passing through the center 6 of the mounting surface 21 .

The second air intake holes 62 are provided in the second flat area 42 . The number of the second air intake holes 62 may be singular or plural. In plan view, each of the plurality of second air intake holes 62 may be positioned on a straight line (second straight line L2) passing through the center 6 of the mounting surface 21 . As shown in FIG. 5, in plan view, the second straight line L2 may be inclined with respect to the first straight line L1.

FIG. 6 is a schematic cross-sectional view taken along line VI-VI of FIG. As shown in FIG. 6 , the third annular protrusion 33 may protrude from each of the first flat region 41 and the second flat region 42 . The top surface of the third annular projection 33 is positioned higher than each of the first flat region 41 and the second flat region 42 . Similarly, the top surface of the first annular protrusion 31 is positioned higher than each of the first flat region 41 and the second flat region 42 . The height of the first annular protrusion 31 is the same as the height of the third annular protrusion 33 .

As shown in FIG. 6, the width of the second flat region 42 (second width W2) is greater than the width of the first flat region 41 (first width W1) in the radial direction. Although the lower limit of the second width W2 is not particularly limited, it may be twice or more the first width W1, or may be three times or more. The upper limit of the second width W2 is not particularly limited, but may be 20 times or less the first width W1, or may be 10 times or less. In the radial direction, the width (third width W3) of the third annular protrusion 33 is smaller than the second width W2. In the radial direction, the width (third width W3) of the third annular projection 33 may be smaller than the first width W1.

FIG. 7 is a schematic cross-sectional view taken along line VII-VII of FIG. As shown in FIG. 7 , the top surface of the second annular projection 32 is positioned higher than each of the first flat region 41 and the second flat region 42 . The height of the second annular protrusion 32 is the same as the height of the third annular protrusion 33 . When mounting silicon carbide epitaxial substrate 10 on mounting surface 21 , silicon carbide epitaxial substrate 10 has the top surface of first annular protrusion 31 , the top surface of second annular protrusion 32 , and the third annular protrusion. 33 is in contact with the top surface. Silicon carbide epitaxial substrate 10 is mounted on mounting surface 21 while being separated from each of first flat region 41 and second flat region 42 .

As shown in FIG. 5, in plan view, even if the value obtained by dividing the total area of the plurality of protrusions 30 by the area surrounded by the outer peripheral edge of the first annular protrusion 31 is less than 50%, for example, good. Specifically, the total area of the plurality of convex portions 30 in plan view is the area of the top surface of the first annular convex portion 31, the area of the top surface of the second annular convex portion 32, and the area of the top surface of the third annular convex portion. 33 is the total area of the top surface.

The upper limit of the value obtained by dividing the total area of the plurality of protrusions 30 by the area surrounded by the outer peripheral edge of the first annular protrusion 31 is not particularly limited, but may be, for example, less than 30% or 10%. may be less than The lower limit of the value obtained by dividing the total area of the plurality of protrusions 30 by the area surrounded by the outer peripheral edge of the first annular protrusion 31 is not particularly limited, but may be, for example, 1% or more, or 3%. or more.

(Inspection method for silicon carbide epitaxial substrate)
Next, a method for inspecting silicon carbide epitaxial substrate 10 according to the present embodiment will be described. FIG. 8 is a flow diagram schematically showing an inspection method for silicon carbide epitaxial substrate 10 according to the present embodiment. As shown in FIG. 8, the method for inspecting silicon carbide epitaxial substrate 10 according to the present embodiment includes a step of vacuum-sucking silicon carbide epitaxial substrate 10 to vacuum chuck 20 (S10), and a step of vacuum-sucking silicon carbide epitaxial substrate 10 to a micropipe. 5 (S20).

First, the step of vacuum-sucking silicon carbide epitaxial substrate 10 to vacuum chuck 20 ( S<b>10 ) is performed. As shown in FIG. 4 , silicon carbide epitaxial substrate 10 is mounted on mounting surface 21 of vacuum chuck 20 . Silicon carbide epitaxial substrate 10 is in contact with mounting surface 21 . Next, silicon carbide epitaxial substrate 10 is vacuum-sucked to vacuum chuck 20 using vacuum pump 23 . When vacuum chuck 20 is operated using vacuum pump 23 , silicon carbide epitaxial substrate 10 is attracted to mounting surface 21 . Fourth main surface 4 of silicon carbide epitaxial substrate 10 is supported by a plurality of protrusions 30 .

The pumping speed of the vacuum pump 23 may be, for example, 5 liters/minute or more and 100 liters/minute or less. The lower limit of the pumping speed of the vacuum pump 23 is not particularly limited, but may be, for example, 10 liters/minute or more, or 20 liters/minute or more. Although the upper limit of the pumping speed of the vacuum pump 23 is not particularly limited, it may be, for example, 90 liters/minute or less, or 80 liters/minute or less.

Next, a step (S20) of determining whether silicon carbide epitaxial substrate 10 has micropipe 5 is performed. Specifically, whether or not silicon carbide epitaxial substrate 10 has micropipe 5 is determined based on the degree of vacuum of vacuum chuck 20 . Specifically, the degree of vacuum of the vacuum chuck 20 is measured using the vacuum gauge 22 . The measured vacuum degree of the vacuum chuck 20 is compared with a predetermined reference vacuum degree 7 (see FIG. 12).

The reference degree of vacuum 7 may be -60 kPa or more and -50 kPa or less, for example. Although the lower limit of the reference degree of vacuum 7 is not particularly limited, it may be -62 kPa or more, or -58 kPa or more. Although the upper limit of the reference degree of vacuum 7 is not particularly limited, it may be -52 kPa or less, or -54 kPa or less.

When micropipe 5 exists in silicon carbide epitaxial substrate 10 , air enters vacuum chuck 20 through micropipe 5 . Therefore, the degree of vacuum of the vacuum chuck 20 does not become higher than the reference degree of vacuum 7 . Therefore, when the degree of vacuum of vacuum chuck 20 is lower than standard degree of vacuum 7, it is determined that silicon carbide epitaxial substrate 10 has micropipe 5 . Conversely, when the degree of vacuum of vacuum chuck 20 is equal to or higher than reference degree of vacuum 7 , it is determined that silicon carbide epitaxial substrate 10 does not have micropipe 5 .

FIG. 9 is a schematic cross-sectional view showing the configuration of an apparatus for manufacturing silicon carbide epitaxial substrate 10 according to the present embodiment. As shown in FIG. 9, an apparatus for manufacturing silicon carbide epitaxial substrate 10 is, for example, a hot wall type horizontal CVD (Chemical Vapor Deposition) apparatus. Manufacturing apparatus 200 for silicon carbide epitaxial substrate 10 includes chamber 201, gas supply section 235, control section 245, heating element 203, quartz tube 204, heat insulating material (not shown), and induction heating coil (not shown). It mainly has

The heating element 203 has, for example, a cylindrical shape and forms a chamber 201 inside. The heating element 203 is made of graphite, for example. The heating element 203 is provided inside the quartz tube 204 . The heat insulating material surrounds the outer circumference of the heating element 203 . The induction heating coil is wound along the outer peripheral surface of the quartz tube 204, for example. The induction heating coil is configured such that an alternating current can be supplied from an external power source (not shown). Thereby, the heating element 203 is induction-heated. As a result, chamber 201 is heated by heating element 203 .

Chamber 201 is surrounded by inner wall surface 205 of heating element 203 . Chamber 201 is provided with a susceptor 210 that holds silicon carbide substrate 11 . Susceptor 210 is made of, for example, silicon carbide. Silicon carbide substrate 11 is placed on susceptor 210 . Susceptor 210 is placed on stage 206 . The stage 206 is rotatably supported by a rotating shaft 209 . Rotation of the stage 206 causes the susceptor 210 to rotate.

Manufacturing apparatus 200 for silicon carbide epitaxial substrate 10 further has gas introduction port 207 and gas exhaust port 208 . The gas exhaust port 208 is connected to an exhaust pump (not shown). Arrows in FIG. 9 indicate gas flows. Gas is introduced into the chamber 201 through a gas inlet 207 and exhausted through a gas outlet 208 . The pressure inside the chamber 201 is adjusted by the balance between the amount of gas supplied and the amount of gas exhausted.

The gas supply unit 235 is configured to be able to supply a mixed gas containing source gas, dopant gas, and carrier gas to the chamber 201 . Specifically, the gas supply section 235 includes a first gas supply section 231, a second gas supply section 232, a third gas supply section 233, and a fourth gas supply section 234, for example.

The first gas supply unit 231 is configured to be able to supply a first gas containing carbon atoms, for example. The first gas supply unit 231 is, for example, a gas cylinder filled with the first gas. The first gas is, for example, propane (C ₃ H ₈ ) gas. The first gas may be, for example, methane (CH ₄ ) gas, ethane (C ₂ H ₆ ) gas, acetylene (C ₂ H ₂ ) gas, or the like.

The second gas supply unit 232 is configured to be able to supply a second gas containing, for example, silane gas. The second gas supply unit 232 is, for example, a gas cylinder filled with the second gas. The second gas is, for example, silane (SiH ₄ ) gas. The second gas may be a mixed gas of silane gas and a gas other than silane.

The third gas supply unit 233 is configured to be able to supply a third gas containing, for example, ammonia gas. The third gas supply unit 233 is, for example, a gas cylinder filled with the third gas. The third gas is a doping gas containing N (nitrogen atoms). Ammonia gas is more likely to be thermally decomposed than nitrogen gas having triple bonds. Nitrogen gas may be used as the third gas.

The fourth gas supply unit 234 is configured to be able to supply a fourth gas (carrier gas) such as hydrogen. The fourth gas supply unit 234 is, for example, a gas cylinder filled with hydrogen.

The control unit 245 is configured to be able to control the flow rate of the mixed gas supplied from the gas supply unit 235 to the chamber 201 . Specifically, the control unit 245 may include a first gas flow control unit 241, a second gas flow control unit 242, a third gas flow control unit 243, and a fourth gas flow control unit 244. good. Each controller may be, for example, an MFC (Mass Flow Controller). The control section 245 is arranged between the gas supply section 235 and the gas introduction port 207 . In other words, the control section 245 is arranged in the flow path that connects the gas supply section 235 and the gas introduction port 207 .

(Manufacturing method of silicon carbide epitaxial substrate)
Next, a method for manufacturing silicon carbide epitaxial substrate 10 according to the present embodiment will be described. FIG. 10 is a flow diagram schematically showing a method for manufacturing silicon carbide epitaxial substrate 10 according to the present embodiment. As shown in FIG. 10, the method for manufacturing silicon carbide epitaxial substrate 10 according to the present embodiment comprises a step (S1) of forming silicon carbide epitaxial layer 12 on silicon carbide substrate 11, and removing silicon carbide epitaxial substrate 10 in a vacuum. It mainly includes a step of vacuum-adhering to chuck 20 (S10) and a step of determining whether or not silicon carbide epitaxial substrate 10 has micropipe 5 (S20).

First, silicon carbide substrate 11 is prepared. Silicon carbide substrate 11 is obtained, for example, by slicing a silicon carbide ingot manufactured by a sublimation method. Silicon carbide substrate 11 is made of silicon carbide of polytype 4H, for example. Silicon carbide substrate 11 contains, for example, nitrogen (N) as an n-type impurity. The conductivity type of silicon carbide substrate 11 is, for example, the n type (first conductivity type).

Silicon carbide substrate 11 is then placed in chamber 201 . Silicon carbide substrate 11 is placed on susceptor 210 in chamber 201 . Next, chamber 201 is heated to a temperature of, for example, 1600° C. or higher and 1700° C. or lower. A gas mixture containing, for example, silane, propane, ammonia, and hydrogen is then introduced into chamber 201 . Thereby, silicon carbide epitaxial layer 12 is formed on silicon carbide substrate 11 .

First, a buffer layer is formed on silicon carbide substrate 11 . Specifically, a buffer layer is formed on silicon carbide substrate 11 by introducing a mixed gas containing silane, propane, ammonia, and hydrogen into chamber 201 . In the step of forming the buffer layer, the flow rate of silane gas is adjusted to 46 sccm, for example. The propane gas flow rate is adjusted, for example, to 14 sccm. The flow rate of hydrogen gas is adjusted to be 120 slm, for example. The flow rate of ammonia gas is, for example, 0.7 sccm.

A drift layer is then formed on the buffer layer. In the step of forming the drift layer, the flow rate of silane gas is adjusted to 115 sccm, for example. The propane gas flow rate is adjusted to be, for example, 37.5 sccm. The flow rate of hydrogen gas is adjusted to be 120 slm, for example. The flow rate of ammonia gas is, for example, 0.23 sccm. Thereby, silicon carbide epitaxial layer 12 is formed on silicon carbide substrate 11 . Silicon carbide epitaxial substrate 10 is thus prepared. Silicon carbide epitaxial substrate 10 may or may not have a buffer layer. The drift layer may be one layer, or two or more layers.

Next, a step ( S<b>10 ) of vacuum-sucking silicon carbide epitaxial substrate 10 to vacuum chuck 20 is performed. The step (S10) of vacuum-sucking silicon carbide epitaxial substrate 10 to vacuum chuck 20 in the method for manufacturing silicon carbide epitaxial substrate 10 according to the present embodiment is the silicon carbide epitaxial substrate in the method for inspecting silicon carbide epitaxial substrate 10 according to the present embodiment. This is the same as the step of vacuum-adsorbing the substrate 10 to the vacuum chuck 20 (S10).

Next, a step (S20) of determining whether silicon carbide epitaxial substrate 10 has micropipe 5 is performed. The step (S20) of determining whether silicon carbide epitaxial substrate 10 has micropipe 5 in the method for manufacturing silicon carbide epitaxial substrate 10 according to the present embodiment is performed in the method for inspecting silicon carbide epitaxial substrate 10 according to the present embodiment. This is the same as the step of determining whether silicon carbide epitaxial substrate 10 has micropipe 5 (S20).

When the degree of vacuum of vacuum chuck 20 is lower than standard degree of vacuum 7 , it is determined that silicon carbide epitaxial substrate 10 has micropipe 5 . Conversely, when the degree of vacuum of vacuum chuck 20 is equal to or higher than reference degree of vacuum 7 , it is determined that silicon carbide epitaxial substrate 10 does not have micropipe 5 . As described above, silicon carbide epitaxial substrate 10 is sorted. For silicon carbide epitaxial substrate 10 determined to have micropipe 5 , micropipe 5 may be buried by forming silicon carbide epitaxial layer 12 again.

(substrate set)
FIG. 11 is a schematic cross-sectional view showing the configuration of the substrate set 300 according to this embodiment. As shown in FIG. 11 , a substrate set 300 according to this embodiment has a cassette 302 and a plurality of silicon carbide epitaxial substrates 10 . A plurality of slots 301 are provided in the cassette 302 . Each of a plurality of silicon carbide epitaxial substrates 10 is arranged in each of a plurality of slots 301 . One silicon carbide epitaxial substrate 10 is arranged in one slot 301 .

The number of slots 301 is 20 or more. The lower limit of the number of slots 301 is not particularly limited, but may be, for example, 22 or more, or 25 or more. The upper limit of the number of slots 301 is not particularly limited, but may be, for example, 50 or less, or 30 or less.

The number of plural silicon carbide epitaxial substrates 10 is 20 or more. The lower limit of the number of silicon carbide epitaxial substrates 10 is not particularly limited, but may be, for example, 22 or more, or 25 or more. The upper limit of the number of silicon carbide epitaxial substrates 10 is not particularly limited, but may be, for example, 50 or less, or 30 or less.

Each of a plurality of silicon carbide epitaxial substrates 10 included in substrate set 300 according to the present embodiment is selected using the inspection method for silicon carbide epitaxial substrates 10 according to the present embodiment. Therefore, each of a plurality of silicon carbide epitaxial substrates 10 does not have micropipe 5 . From another point of view, none of the silicon carbide epitaxial substrates 10 arranged in slots 301 have micropipes 5 . As shown in FIG. 2, the diameter of the circle circumscribing the micropipe 5 (second diameter A2) may be 10 μm or more and 100 μm or less. The second diameter A2 may be 20 μm or more and 80 μm or less.

Next, functions and effects of silicon carbide epitaxial substrate 10 according to the present embodiment will be described.

Generally, micropipe 5 is inspected at the stage of silicon carbide substrate 11 before silicon carbide epitaxial layer 12 is grown. However, even if micropipe 5 exists in silicon carbide substrate 11 , micropipe 5 may be blocked by forming silicon carbide epitaxial layer 12 on silicon carbide substrate 11 .

The micropipe 5 can be detected, for example, by a surface inspection apparatus using confocal differential interference optics. However, when using the surface inspection device, it is difficult to distinguish between the blocked micropipe 5 and the unblocked micropipe 5, and the micropipe 5 cannot be distinguished with high accuracy.

As a result of earnestly studying measures for accurately inspecting the micropipe 5, the inventor obtained the following findings. Specifically, the inventor found that by utilizing the degree of vacuum of the vacuum chuck 20, it is possible to detect the silicon carbide epitaxial layer having the micropipe 5 with high accuracy by a simple method.

According to the method for inspecting silicon carbide epitaxial substrate 10 according to the present embodiment, silicon carbide epitaxial substrate 10 is vacuum-adsorbed to vacuum chuck 20 . Whether silicon carbide epitaxial substrate 10 has micropipe 5 is determined based on the degree of vacuum of vacuum chuck 20 . Thereby, silicon carbide epitaxial substrate 10 having micropipe 5 can be accurately detected by a simple method.

Further, according to the inspection method for silicon carbide epitaxial substrate 10 according to the present embodiment, vacuum chuck 20 may include mounting surface 21 on which silicon carbide epitaxial substrate 10 is mounted. A plurality of protrusions 30 may be provided on the mounting surface 21 . The plurality of protrusions 30 may have a first annular protrusion 31 positioned on the outermost side and a second annular protrusion 32 positioned on the innermost side. The mounting surface 21 may include an intermediate region 40 positioned between the first annular protrusion 31 and the second annular protrusion 32 . Air intake holes 60 may be provided in the intermediate region 40 . In plan view, the value obtained by dividing the total area of the plurality of protrusions 30 by the area surrounded by the outer peripheral edge of the first annular protrusion 31 may be less than 50%.

When the areas of the plurality of protrusions 30 are large, the possibility that the plurality of protrusions 30 cover the micropipe 5 increases. In this case, even if silicon carbide epitaxial substrate 10 has micropipe 5, the degree of vacuum of vacuum chuck 20 is unlikely to become low. By setting the value obtained by dividing the total area of the plurality of protrusions 30 by the area surrounded by the outer peripheral edge of the first annular protrusion 31 to be less than 50%, the possibility that the plurality of protrusions 30 cover the micropipe 5 can be reduced. As a result, silicon carbide epitaxial substrate 10 having micropipe 5 can be detected more accurately.

Furthermore, according to the method for inspecting silicon carbide epitaxial substrate 10 according to the present embodiment, multiple protrusions 30 may include multiple third annular protrusions 33 positioned in intermediate region 40 . The intake holes 60 may be provided between each of the plurality of third annular protrusions 33 . Thereby, it is possible to more uniformly inhale the air in the plane. As a result, silicon carbide epitaxial substrate 10 having micropipe 5 can be detected more accurately.

Furthermore, according to the method for inspecting silicon carbide epitaxial substrate 10 according to the present embodiment, a value obtained by dividing the total area of the plurality of protrusions 30 by the area surrounded by the outer peripheral edge of the first annular protrusion 31 in plan view. may be less than 10%. This can further reduce the possibility that the plurality of protrusions 30 will cover the micropipe 5 . As a result, silicon carbide epitaxial substrate 10 having micropipe 5 can be detected more accurately.

Further, according to the method for inspecting silicon carbide epitaxial substrate 10 according to the present embodiment, silicon carbide epitaxial substrate 10 may be determined to have micropipe 5 when the degree of vacuum is lower than reference degree of vacuum 7 . The reference degree of vacuum 7 may be −60 kPa or more and −50 kPa or less. Thereby, silicon carbide epitaxial substrate 10 having micropipe 5 can be detected with higher accuracy.

Furthermore, according to the method for inspecting silicon carbide epitaxial substrate 10 according to the present embodiment, in the step of vacuum-adsorbing silicon carbide epitaxial substrate 10 to vacuum chuck 20 , silicon carbide epitaxial substrate 10 is moved to vacuum chuck 20 using vacuum pump 23 . may be vacuum-adsorbed to The pumping speed of the vacuum pump 23 may be 5 liters/minute or more and 100 liters/minute or less.

When the pumping speed of vacuum pump 23 is excessively low or excessively high, respectively, the degree of vacuum of vacuum chuck 20 when silicon carbide epitaxial substrate 10 having micropipe 5 is vacuum-sucked and the degree of vacuum of vacuum chuck 20 having micropipe 5 The difference from the degree of vacuum of vacuum chuck 20 when silicon carbide epitaxial substrate 10 that is not held is vacuum-sucked becomes smaller. By setting the pumping speed of the vacuum pump 23 to 5 liters/minute or more and 100 liters/minute or less, the degree of vacuum of the vacuum chuck 20 and the degree of vacuum of the micropipe 5 when the silicon carbide epitaxial substrate 10 having the micropipe 5 is vacuum-sucked. It is possible to increase the difference from the degree of vacuum of vacuum chuck 20 when silicon carbide epitaxial substrate 10 that does not have silicon carbide epitaxial substrate 10 is vacuum-sucked. Thereby, silicon carbide epitaxial substrate 10 having micropipe 5 can be detected with higher accuracy.

(Sample preparation)
Silicon carbide epitaxial substrates 10 according to samples 1 to 20 were prepared. Silicon carbide epitaxial substrates 10 according to samples 1 to 18 do not have micropipes 5 . Silicon carbide epitaxial substrates 10 according to samples 19 and 20 have micropipes 5 .

(experimental method)
Using the inspection method for silicon carbide epitaxial substrate 10 according to the present embodiment, the degree of vacuum of each of silicon carbide epitaxial substrates 10 according to samples 1 to 20 was measured. Specifically, the micropipe 5 detection device described in FIG. 4 was used. A dry vacuum pump 23 (model number: DAU-20) manufactured by ULVAC, Inc. was used as the vacuum pump 23 . The evacuation speed of the vacuum pump 23 was set to 20 liters/minute. Each of silicon carbide epitaxial substrates 10 according to samples 1 to 20 was mounted on mounting surface 21 of vacuum chuck 20 . A vacuum gauge 22 was used to measure the degree of vacuum of the vacuum chuck 20 .

(Experimental result)
FIG. 12 shows the relationship between the degree of vacuum of vacuum chuck 20 and the sample number of silicon carbide epitaxial substrate 10 . As shown in FIG. 12, in the case of silicon carbide epitaxial substrate 10 having no micropipe 5, the degree of vacuum of vacuum chuck 20 was about −80 kPa or more and −65 kPa or less. On the other hand, in the case of silicon carbide epitaxial substrate 10 having micropipe 5, the degree of vacuum of vacuum chuck 20 was about −50 kPa or more and −45 kPa or less. From the above results, it was confirmed that silicon carbide epitaxial substrate 10 without micropipe 5 and silicon carbide epitaxial substrate 10 with micropipe 5 can be accurately discriminated.

The embodiments and examples disclosed this time are illustrative in all respects and should not be considered restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above-described embodiments and examples, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

1 first main surface 2 second main surface 3 third main surface 4 fourth main surface 5 micropipe 6 center 7 standard degree of vacuum 10 silicon carbide epitaxial substrate 11 silicon carbide substrate 12 silicon carbide epitaxial layer 13 orientation flat 14 arc-shaped portion 15 Outer peripheral edge 20 Vacuum chuck 21 Mounting surface 22 Vacuum gauge 23 Vacuum pump 30 Plural convex portions 31 First annular convex portion 32 Second annular convex portion 33 Third annular convex portion 40 Intermediate region 41 First flat region 42 Second Flat region 60 air intake hole 61 first air intake hole 62 second air intake hole 101 first direction 102 second direction 200 manufacturing apparatus 201 chamber 203 heating element 204 quartz tube 205 inner wall surface 206 stage 207 gas introduction port 208 gas exhaust port 209 rotation axis 210 Susceptor 231 First gas supply unit 232 Second gas supply unit 233 Third gas supply unit 234 Fourth gas supply unit 235 Gas supply unit 241 First gas flow control unit 242 Second gas flow control unit 243 Third gas flow control Part 244 Fourth gas flow control part 245 Control part 300 Substrate set 301 Slot 302 Cassette A1 First diameter A2 Second diameter L1 First straight line L2 Second straight line W1 First width W2 Second width W3 Third width

Claims (11)

a step of vacuum-sucking the silicon carbide epitaxial substrate to a vacuum chuck;
and determining whether or not the silicon carbide epitaxial substrate has a micropipe based on the degree of vacuum of the vacuum chuck. The vacuum chuck includes a mounting surface on which the silicon carbide epitaxial substrate is mounted,
A plurality of protrusions are provided on the mounting surface,
The plurality of protrusions have a first annular protrusion located on the outermost side and a second annular protrusion located on the innermost side,
the mounting surface includes an intermediate region positioned between the first annular projection and the second annular projection;
An intake hole is provided in the intermediate region,
2. The silicon carbide epitaxial substrate according to claim 1, wherein a value obtained by dividing the total area of said plurality of protrusions by the area surrounded by the outer peripheral edge of said first annular protrusion in plan view is less than 50%. inspection method. the plurality of protrusions include a plurality of third annular protrusions located in the intermediate region;
3. The method of inspecting a silicon carbide epitaxial substrate according to claim 2, wherein said intake hole is provided between each of said plurality of third annular projections. 4. The value obtained by dividing the total area of the plurality of protrusions by the area surrounded by the outer peripheral edge of the first annular protrusion in plan view is less than 10%, according to claim 2 or 3. A method for inspecting a silicon carbide epitaxial substrate. 5. The method for inspecting a silicon carbide epitaxial substrate according to claim 1, wherein when the degree of vacuum is lower than a reference degree of vacuum, it is determined that the silicon carbide epitaxial substrate has micropipes. . 6. The silicon carbide epitaxial substrate inspection method according to claim 5, wherein said reference degree of vacuum is -60 kPa or more and -50 kPa or less. In the step of vacuum-sucking the silicon carbide epitaxial substrate to the vacuum chuck, the silicon carbide epitaxial substrate is vacuum-sucked to the vacuum chuck using a vacuum pump,
7. The method for inspecting a silicon carbide epitaxial substrate according to claim 1, wherein the pumping speed of said vacuum pump is 5 liters/minute or more and 100 liters/minute or less. preparing the silicon carbide epitaxial substrate by forming a silicon carbide epitaxial layer on the silicon carbide substrate;
A method for manufacturing a silicon carbide epitaxial substrate, comprising the step of selecting the silicon carbide epitaxial substrate by using the silicon carbide epitaxial substrate inspection method according to any one of claims 1 to 7. a cassette provided with a plurality of slots;
a plurality of silicon carbide epitaxial substrates arranged in each of the plurality of slots,
the number of the plurality of silicon carbide epitaxial substrates is 20 or more,
The substrate set, wherein each of the plurality of silicon carbide epitaxial substrates has no micropipe. 10. The substrate set according to claim 9, wherein the diameter of the circle circumscribing the micropipe is between 10 [mu]m and 100 [mu]m. 10. The substrate set according to claim 9, wherein the diameter of the circle circumscribing the micropipe is 20 [mu]m or more and 80 [mu]m or less.

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