JP2021004173A - Method of manufacturing hexagonal crystal compound semiconductor - Google Patents

Abstract

To provide a method of manufacturing a hexagonal crystal compound semiconductor whose strain is accurately evaluated.SOLUTION: A method of manufacturing a hexagonal crystal compound semiconductor comprises a process (S100) of preparing a substrate, a process (S200) of calculating a first phase difference, a process (S300) of growing a compound semiconductor layer in a homoepitaxial growth manner; and a process (S400) of calculating a second phase difference. In the process (S100) of preparing the substrate, a substrate of a hexagonal crystal compound semiconductor is prepared which has a hexagonal crystal structure, has birefringence, and includes a first principal plane. In the process (S200) of calculating the first phase difference, the first principal plane is irradiated with light to be transmitted through the substrate, and the light is transmitted through the substrate along a <0001> direction in the substrate so as to calculate the first phase difference generated through the birefringence. In the process (S400) of calculating the second phase difference, a surface of the compound semiconductor layer is irradiated with light, which is transmitted through the compound semiconductor layer and substrate along the <0001> direction in the compound semiconductor layer and in the substrate so as to calculate the second phase difference generated through the birefringence.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to a method for producing a hexagonal compound semiconductor.

Japanese Unexamined Patent Publication No. 2013-203653 discloses that the residual strain of a compound semiconductor substrate is evaluated by using a photoelastic method.

Japanese Unexamined Patent Publication No. 2013-203653

Japanese Patent Application Laid-Open No. 2013-203653 discloses a group III nitride semiconductor such as gallium nitride (GaN), but residual strain after epitaxially growing a compound semiconductor film on the surface of a substrate made of the hexagonal compound semiconductor. Is not particularly considered. In hexagonal compound semiconductors such as GaN, silicon carbide (SiC), and aluminum nitride (AlN) described above, problems such as substrate cracking occur due to the influence of residual strain in the manufacturing process including the epitaxial growth step of the compound semiconductor film. There is a demand for compound semiconductors whose strain has been accurately evaluated.

An object of the present disclosure is to provide a method for producing a hexagonal compound semiconductor whose strain has been accurately evaluated.

The method for producing a hexagonal compound semiconductor according to one aspect of the present invention includes a step of preparing a substrate, a step of calculating a first phase difference, a step of homoepitaxially growing a compound semiconductor layer, and a second phase difference. It includes a calculation process. In the process of preparing the substrate, a hexagonal compound semiconductor substrate having a hexagonal crystal structure, having birefringence, and including a first main surface and a second main surface and a side surface opposite to the first main surface is provided. prepare. In the step of calculating the first phase difference, the first main surface is irradiated with light transmitted through the substrate, the light is transmitted through the substrate along the <0001> direction in the substrate, and the first position generated by birefringence is generated. Calculate the phase difference. In the step of homoepitaxially growing the compound semiconductor layer, the compound semiconductor layer is homoepitaxially grown on the first main surface based on predetermined growth conditions. In the step of calculating the second phase difference, the surface of the compound semiconductor layer is irradiated with light, the light is transmitted to the compound semiconductor layer and the substrate along the <0001> direction in the substrate, and the second phase is generated by birefringence. Calculate the phase difference.

According to the present disclosure, with respect to a hexagonal compound semiconductor having a hexagonal crystal structure, light is transmitted through the hexagonal compound semiconductor along the <0001> direction, which is caused by the crystal structure of the hexagonal compound semiconductor. The influence of natural birefringence can be reduced, and the phase difference of birefringence due to the photoelastic effect caused by distortion can be measured. Therefore, a hexagonal compound semiconductor whose strain has been accurately evaluated can be obtained.

FIG. 1 is a flowchart showing a strain evaluation method for a compound semiconductor. FIG. 2 is a schematic diagram for explaining the basic configuration of the evaluation device. FIG. 3 is a schematic diagram for explaining a configuration example of the evaluation device. FIG. 4 is a schematic diagram for explaining the direction of light transmitted through the compound semiconductor. FIG. 5 is a flowchart showing a method for manufacturing a compound semiconductor.

[Explanation of Embodiments of the Present Invention]
First, embodiments of the present invention will be listed and described.

(1) The method for producing a hexagonal compound semiconductor according to one aspect of the present invention includes a step of preparing a substrate, a step of calculating a first phase difference, a step of homoepitaxially growing a compound semiconductor layer, and a second step. It includes a step of calculating the phase difference. In the process of preparing a substrate, a hexagonal compound semiconductor substrate having a hexagonal crystal structure, having birefringence, and including a first main surface and a second main surface and side surfaces opposite to the first main surface. Prepare. In the step of calculating the first phase difference, the first main surface is irradiated with light transmitted through the substrate, the light is transmitted through the substrate along the <0001> direction in the substrate, and the first position generated by birefringence is generated. Calculate the phase difference. In the step of homoepitaxially growing the compound semiconductor layer, the compound semiconductor layer is homoepitaxially grown on the first main surface based on predetermined growth conditions. In the second step of calculating the phase difference, the surface of the compound semiconductor layer is irradiated with light, and light is transmitted to the compound semiconductor layer and the substrate along the <0001> direction in the compound semiconductor layer and the substrate, resulting in birefringence. The second phase difference caused by the above is calculated. The compound semiconductor is, for example, silicon carbide (SiC), gallium nitride (GaN), aluminum nitride (AlN), or the like.

In this way, the phase difference due to birefringence in a state where light is transmitted along the <0001> direction in the hexagonal compound semiconductor is calculated, so that natural birefringence due to the crystal structure of the hexagonal compound semiconductor is calculated. Data with reduced impact can be obtained. Therefore, it is possible to obtain a hexagonal compound semiconductor whose distortion is evaluated by the phase difference caused by the birefringence while the influence of the natural birefringence is reduced. Further, since the strain can be evaluated by the phase difference caused by double refraction before and after the compound semiconductor layer is formed on the compound semiconductor substrate, the influence of the compound semiconductor layer forming process on the strain can be evaluated and the compound semiconductor layer is formed. It is possible to confirm the state of occurrence of strain on the compound semiconductor substrate (substrate with epitaxial layer). Then, by comparing the strain after the compound semiconductor layer is formed with the strain before the compound semiconductor layer is formed and grasping the amount of strain generated during the epitaxial growth, the suitability of the growth conditions in the epitaxial growth is determined. Can be judged.

(2) In the method for producing a hexagonal compound semiconductor, the first main surface of the substrate is inclined with respect to the {0001} surface. In this case, since the substrate is a so-called off substrate, it is difficult to transmit light along the <0001> direction inside the substrate even if light is simply irradiated from a direction perpendicular to the first main surface. Therefore, by measuring the inclination angle (off angle) and the inclination direction (off direction) formed by the first main surface of the substrate with respect to the {0001} surface in advance, the first main surface and the surrounding air can be brought into contact with each other. The method for producing a hexagonal compound semiconductor according to the present embodiment, which can set the light transmission direction inside the substrate to the <0001> direction in consideration of the refraction of light at the interface, is effective.

(3) In the step of calculating the first phase difference in the above method for manufacturing a hexagonal compound semiconductor, light is measured based on information on the tilt angle and tilt direction of the first main plane with respect to the {0001} plane. The angle of incidence with respect to the first main surface is determined. Further, in the step of calculating the second phase difference, the incident angle of light with respect to the surface of the compound semiconductor layer is determined based on the above information.

In this case, even when the shape of the substrate is not flat, such as when the substrate is warped, by obtaining information such as the off angle and off direction of the substrate in advance, the crystal structure of the hexagonal compound semiconductor can be obtained as a result. Accurate strain evaluation can be performed with the effect of natural birefringence reduced. Therefore, it is possible to accurately determine the suitability of the growth conditions in epitaxial growth.

(4) The method for producing a hexagonal compound semiconductor according to one aspect of the present invention includes a step of preparing a substrate, a step of calculating a first phase difference, and a first maximum value and a first standard deviation. A step of calculating, a step of homoepitically growing a compound semiconductor layer, a step of calculating a second phase difference, a step of calculating a second maximum value and a second standard deviation, and a step of changing growth conditions. And. In the process of preparing a substrate, a hexagonal compound semiconductor substrate having a hexagonal crystal structure, having birefringence, and including a first main surface and a second main surface and side surfaces opposite to the first main surface. Prepare. In the step of calculating the first phase difference, light transmitted through the substrate is irradiated to a plurality of locations on the first main surface, the light is transmitted to the substrate along the <0001> direction in the substrate, and the light is transmitted to the substrate, which is generated by birefringence. Calculate the phase difference of 1. In the step of calculating the first maximum value and the first standard deviation, the first maximum value and the first standard deviation are calculated for the first phase difference at the plurality of locations. In the step of homoepitaxially growing the compound semiconductor layer, the compound semiconductor layer is homoepitaxially grown on the first main surface. In the second step of calculating the phase difference, light is applied to a plurality of locations on the surface of the compound semiconductor layer to allow light to pass through the compound semiconductor layer and the substrate along the <0001> direction in the compound semiconductor layer and the substrate. , The second phase difference caused by birefringence is calculated. In the step of calculating the second maximum value and the second standard deviation, the second maximum value and the second standard deviation are calculated for the second phase difference at a plurality of locations. In the step of changing the growth condition, the growth condition is changed when the condition that the second maximum value is larger than the first maximum value and the second standard deviation is larger than the first standard deviation is satisfied.

In this way, since light is transmitted through the hexagonal compound semiconductor along the <0001> direction, natural birefringence due to the crystal structure of the hexagonal compound semiconductor can be reduced. Further, by calculating the phase difference at a plurality of locations on the first main surface of the substrate, the magnitude and variation of the strain on the substrate are correlated with the magnitude and variation of the phase difference, so that the magnitude and variation of the phase difference are correlated with each other. It is possible to evaluate the distribution state of the strain of. That is, it is possible to obtain a hexagonal compound semiconductor in which the distribution state of strain in the plane of the substrate is evaluated by the phase difference caused by the birefringence while the influence of the natural birefringence is reduced.

Further, since the strain can be evaluated by the phase difference caused by double refraction before and after the compound semiconductor layer is formed on the compound semiconductor substrate, the influence of the compound semiconductor layer forming process on the strain can be evaluated and the compound semiconductor layer is formed. It is possible to confirm the state of occurrence of strain on the compound semiconductor substrate (substrate with epitaxial layer).

Furthermore, by comparing the maximum value of the phase difference before and after the compound semiconductor layer is formed with the standard deviation, the effect of strain due to the film formation process of the compound semiconductor layer is evaluated, and the increase in strain is suppressed. It becomes possible to adjust the growth conditions in the film forming process. Therefore, it is possible to obtain a substrate with an epitaxial layer in which distortion is suppressed.

(5) In the method for producing a hexagonal compound semiconductor, the first main surface of the substrate is inclined with respect to the {0001} surface. In this case, since the substrate is a so-called off substrate, it is difficult to transmit light along the <0001> direction inside the substrate even if light is simply irradiated from a direction perpendicular to the first main surface. Therefore, by measuring the inclination angle (off angle) and the inclination direction (off direction) formed by the first main surface of the substrate with respect to the {0001} surface in advance, the first main surface and the surrounding air can be brought into contact with each other. The method for producing a hexagonal compound semiconductor according to the present embodiment, which can set the light transmission direction inside the substrate to the <0001> direction in consideration of the refraction of light at the interface, is effective.

(6) In the step of calculating the first phase difference in the method for producing a hexagonal compound semiconductor, the inclination angle and the inclination angle of the first main surface with respect to the {0001} surface measured in advance for a plurality of positions of the first main surface are The angle of incidence of the light with respect to the first main surface is determined based on the information in the inclination direction. Further, in the second step of calculating the phase difference, the incident angles of light with respect to the surface of the compound semiconductor layer are determined based on the above information at a plurality of locations on the surface of the compound semiconductor layer.

In this case, even when the shape of the substrate is not flat, such as when the substrate is warped, by obtaining information such as the off angle and off direction of the substrate in advance, the crystal structure of the hexagonal compound semiconductor can be obtained as a result. Accurate strain evaluation can be performed with the effect of natural birefringence reduced. Therefore, it is possible to accurately determine the strain distribution in the plane of the substrate and the suitability of the growth conditions in epitaxial growth.

(7) In the method for producing a compound semiconductor, the diameter of the substrate is 100 mm or more. Since there is a concern that problems due to strain may occur in such a compound semiconductor substrate having a relatively large diameter, it is preferable to apply the above method for producing a compound semiconductor.

(8) In the method for producing a compound semiconductor, the compound semiconductor is a silicon carbide single crystal. Since silicon carbide (SiC) has a problem of cracking of the substrate due to strain, it is preferable to apply the above-mentioned manufacturing method.

[Details of Embodiments of the present invention]
Hereinafter, the details of the embodiment of the present disclosure (hereinafter referred to as the present embodiment) will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference numbers, and the description thereof will not be repeated.

<Outline of evaluation method>
As shown in FIG. 1, the method for evaluating a silicon carbide substrate according to the present embodiment is an example of a method for evaluating strain of a hexagonal compound semiconductor, and includes a preparation step (S10) and an evaluation step (S20). The preparation step (S10) is a step of preparing a substrate of a hexagonal compound semiconductor. In the preparation step (S10), a substrate made of a hexagonal compound semiconductor having a hexagonal crystal structure and having birefringence is prepared. The substrate includes a first main surface, a second main surface opposite to the first main surface, and side surfaces. As the substrate, for example, a silicon carbide substrate made of a silicon carbide (SiC) single crystal is installed on the stage of the measuring device. As the substrate, a GaN substrate or an AlN substrate may be used. As the substrate prepared here, an off-board whose surface is inclined with respect to the (0001) plane can be used. Further, the diameter of the substrate may be 100 mm or more, 150 mm or more, or 200 mm or more. The diameter of the substrate may be 400 mm or less, or 300 mm or less. Further, as the substrate, a base substrate and a substrate with an epitaxial layer having an epitaxial layer formed on the surface of the base substrate may be used. Alternatively, a substrate made of a compound semiconductor on which an epitaxial layer is not formed may be used as the substrate. In the following, a case where a silicon carbide substrate is used as the substrate will be described as a typical example.

Next, the evaluation step (S20) is carried out. In the evaluation step (S20) corresponding to the step of transmitting light through the substrate and the step of calculating the phase difference, the strain of the substrate is evaluated by utilizing the photoelastic effect. Specifically, in the evaluation step (S20), the surface of the substrate is irradiated with light, and the light is transmitted through the inside of the substrate along the <0001> direction to reduce the influence of natural birefringence. Evaluate strain using photoelasticity. From a different point of view, in the step of transmitting light through the substrate included in the evaluation step (S20), the first main surface is irradiated with the light transmitted through the substrate, and the substrate is irradiated along the <0001> direction in the substrate. Allows light to pass through. In the step of calculating the phase difference, the phase difference caused by birefringence is calculated. The phase difference is used for evaluation of distortion.

Further, in the evaluation step (S20), strain is evaluated at a plurality of locations on the silicon carbide substrate by irradiating a plurality of locations on the surface of the silicon carbide substrate with light. Any method can be adopted as a specific evaluation method of strain using photoelasticity, but an example of a specific evaluation method will be described later.

<Structure of evaluation device>
FIG. 2 shows a basic configuration of a measuring device for carrying out the above-mentioned evaluation method. As shown in FIG. 2, the measuring device 100 includes a control controller 10, an incident side optical system 41, a light receiving side optical system 42, a stage 24 on which a sample silicon carbide substrate 1 is mounted, and an optical axis adjusting unit. It includes 43 to 45. The incident side optical system 41 includes a light source 21, a lens 22, and a polarizer 23. The light receiving side optical system 42 includes an analyzer 25, a lens 26, and a light receiving receiver 27. Between the light source 21 and the receiver 27, the lens 22, the polarizer 23, the stage 24, the analyzer 25, and the lens 26 are arranged in this order from the light source 21 side.

The optical axis adjusting unit 43 adjusts the optical axis when the light incident on the silicon carbide substrate 1 from the incident side optical system 41 passes through the silicon carbide substrate 1, so that the optical axis adjusting unit 43 moves from the incident side optical system 41 to the silicon carbide substrate 1. The angle (incident angle) formed by the incident light of the silicon carbide substrate 1 with respect to the surface of the silicon carbide substrate 1 is changed. For example, the optical axis adjusting unit 43 may be configured to move the incident side optical system 41 with respect to the stage 24. The optical axis adjusting unit 44 receives light-receiving side optics so that the optical axis of light transmitted through the silicon carbide substrate 1 held on the stage 24 and the optical axis set to receive light by the light-receiving optical system 42 overlap. The system 42 is moved with respect to the stage 24. The optical axis adjusting unit 45 moves the stage 24 in order to adjust the optical axis when transmitting through the silicon carbide substrate 1. For example, the optical axis adjusting unit 45 may move the stage 24 with respect to the incident side optical system 41 in order to change the incident angle. The optical axis adjusting units 43 to 45 are connected to the control controller 10 and are controlled by a control signal from the control controller 10.

In the measuring device 100, only one of the set of the optical axis adjusting units 43 and 44 and the optical axis adjusting unit 45 may be installed. By changing the angle of incidence of light on the silicon carbide substrate 1 mounted on the stage 24 by using these optical axis adjusting units 43 to 45, the direction of the optical axis of the light transmitted through the silicon carbide substrate 1 is changed. it can. Therefore, as a result, the traveling direction of the light transmitted through the inside of the silicon carbide substrate 1 can be set to the direction along the <0001> direction.

Any configuration can be adopted for the optical axis adjusting units 43 to 45. For example, a cylinder or a conductive motor driven by fluid pressure can be used as the optical axis adjusting units 43 to 45. For example, as the optical axis adjusting unit 43, a hydraulic cylinder connected to the gantry may be used so as to change the inclination angle of the gantry on which the incident side optical system 41 is mounted with respect to the stage 24. Similarly, as the optical axis adjusting unit 44, a hydraulic cylinder connected to the gantry may be used so as to change the tilt angle of the gantry on which the light receiving side optical system 42 is mounted with respect to the stage 24. As the optical axis adjusting unit 43, a mirror arranged between the polarizer 23 and the stage 24 to change the traveling direction of light, and a driving unit such as a motor that adjusts the arrangement of the mirror to change the traveling direction of light. An optical module containing the above may be used. As the optical axis adjusting unit 44, an optical module including a mirror and a driving unit arranged between the stage 24 and the analyzer 25 may be used as in the optical axis adjusting unit 43.

Further, as the optical axis adjusting unit 45, for example, a motor that changes the tilt angle of the stage 24 with respect to the incident light from the incident side optical system 41 may be used. In this case, two motors may be arranged so that the tilt angle of the stage 24 with respect to the incident light can be changed in two directions intersecting each other. Specifically, a first motor that rotates the stage 24 around the first axis and a stage 24 connected to the rotation axis of the first motor are mounted on the first substrate, and the first substrate is mounted. A configuration may be adopted in which a second motor that rotates around a second axis extending in a direction different from that of the first axis is connected to the first substrate.

The light source 21, the polarizer 23, and the analyzer 25 are oriented in a direction (preferably perpendicular to the optical axis of the evaluation light) that passes through the silicon carbide substrate on the stage 24 from the light source 21 and reaches the receiver 27. In the direction), it is configured to be rotatable. The rotation angles of the polarizer 23 and the analyzer 25 can be controlled by the control controller 10. For example, a driving device such as a motor that rotates the polarizer 23 and the analyzer 25 is controlled by the control controller 10.

The light source 21 emits light for evaluation in response to a control signal from the control controller 10. Any light source can be used as the light source 21, but for example, a light source such as a laser diode can be used. The stage 24 is configured to be movable in a direction intersecting the optical axis of the light. The movement of the stage 24 is controlled by the control controller 10. For example, a conventionally known drive device such as a linear guide can be used to move the stage 24, and the drive device is controlled by the control controller 10. For example, the driving device may be configured so that both the optical axis adjusting unit 45 and the stage 24 described above can be moved in a direction intersecting the optical axis of light.

The light receiver 27 receives light transmitted through the lens 22, the polarizer 23, the silicon carbide substrate 1, the analyzer 25, and the lens 26. The light detection data in the receiver 27 is transmitted to the control controller 10. In the control controller 10, the silicon carbide substrate 1 is based on data such as the light emission intensity from the light source 21, the light detection data from the light receiver 27 (light reception intensity data), and the rotation angles of the polarizer 23 and the analyzer 25. The distortion at the position where the light is irradiated is evaluated.

A configuration example of the measuring device shown in FIG. 2 is shown in FIG. As shown in FIG. 3, in the configuration example of the measuring device, the control controller 10 passes through the control IO bus 11 and the drive circuits 31, 33, 34, 35, and the light source 21, the polarizer 23, the stage 24, and the analyzer 25. Is connected to. Further, the control controller 10 is connected to the receiver 27 via the control IO bus 11, the AD converter 38, the variable gain amplifier 37, and the IV (current-voltage) converter 36. Further, the control controller 10 is connected to the optical axis adjusting units 43 to 45 via the control IO bus 11 and the drive circuit 39. The incident side optical system 41 is mounted on a gantry. An optical axis adjusting unit 43 including a hydraulic cylinder is connected to the gantry so as to change the inclination angle of the gantry with respect to the stage 24. Further, the light receiving side optical system 42 is also mounted on another frame. An optical axis adjusting unit 44 including a hydraulic cylinder is connected to the other gantry so as to change the tilt angle of the other gantry with respect to the stage. Further, as described above, the optical axis adjusting unit 45 including the two motors is connected to the stage 24. The light source 21 can use any light source, such as a laser diode. The receiver 27 may adopt any configuration, for example a photodiode.

The stage 24 is movable in the X-axis direction perpendicular to the paper surface of FIG. 3 and in the Y-axis direction along the vertical direction of the paper surface. Further, as described above, the stage 24 is configured to be tiltable relative to the optical axis of light by the optical axis adjusting units 43 to 45. The polarizer 23 and the analyzer 25 can be rotated by, for example, controlling a pulse motor (not shown) by drive circuits 33 and 35. For example, a display for displaying data or the like, a storage device for recording measurement data, or the like may be connected to the control controller 10.

<Details of evaluation method>
Hereinafter, details of an example of an evaluation method for a silicon carbide substrate using the measuring device shown in FIG. 3 will be described.

Preparation step (S10):
First, the silicon carbide substrate 1 to be evaluated is installed on the stage 24 of the measuring device shown in FIG. As the silicon carbide substrate 1, as shown in FIG. 4, an off substrate whose surface 4 is inclined by an off angle with respect to the (0001) surface shown by the dotted line 2 is used. As the silicon carbide substrate 1, a substrate whose surface 4 is not inclined with respect to the (0001) plane may be used.

Step of adjusting the incident direction of light on the silicon carbide substrate (S30):
Next, the direction in which the evaluation light is incident on the silicon carbide substrate 1 is perpendicular to the (0001) plane in the traveling direction of the light transmitted through the inside of the silicon carbide substrate 1 as shown by the arrow 3 in FIG. In order to obtain the measurement data in the <0001> direction, the relative arrangements of the incident side optical system 41, the stage 24, and the light receiving side optical system 42 are determined so as to satisfy the predetermined conditions. In this step, the stage 24 may be fixed and the incident side optical system 41 may be moved, or the incident side optical system 41 may be fixed and the stage 24 may be moved.

Measurement step (S21):
The silicon carbide substrate 1 set on the stage 24 is irradiated with light from the light source 21. As the light to be irradiated, for example, infrared rays can be used. At this time, the orientations of the polarizer 23 and the analyzer 25 are synchronized and rotated in a parallel state, and the transmitted light intensity on the silicon carbide substrate 1 is measured as a function of the polarization angle Φ. Further, the polarizer 23 and the analyzer 25 are synchronously rotated in a state of being orthogonal to each other, and the transmitted light intensity on the silicon carbide substrate 1 is measured as a function of the polarization angle Φ.

Evaluation step of birefringence phase difference and main vibration azimuth (S22):
The phase difference δ (unit: radian) of birefringence and the principal vibration azimuth Ψ are calculated from the data at the above-mentioned measurement points. Any method can be used for the calculation method, and for example, the following method is used.

Let I _⊥ (Φ) and I _|| (Φ) be the transmitted light intensities of the sample when the orientations of the polarizer 23 and the analyzer 25 are orthogonal and parallel, respectively. Further, as described above, the polarization angle when the polarizer 23 and the analyzer 25 are synchronously rotated is Φ. At this time, the relationship shown in the following mathematical formula (1) is established for the birefringence phase difference δ of the silicon carbide substrate 1 as a sample and the main vibration azimuth angle Ψ.

_{I r (Φ) = I ⊥} (Φ) / {I ⊥ (Φ) + I || (Φ)} = sin 2 {2 (Φ-Ψ)} {sin 2 (δ / 2)} Equation (1)
Sine and _{I r (Φ)} represented by the above formula, by cosine transform, the phase difference δ birefringence obtains a main vibration azimuth [psi. For example, the phase difference δ and the main vibration azimuth Ψ at the measurement point can be obtained based on the following mathematical formulas (2) to (5).

δ = ² _sin ^-1 {16 (I _sin ² + I _cos ² )} ^1/4 formula (2)
Ψ = (1/4) tan ^-1 (I _sin / I _cos ) Formula (3)
I _sin = (-1/4) sin4Ψ {sin ² (δ / 2)} Formula (4)
I _cos = (-1/4) cos4Ψ {sin ² (δ / 2)} Formula (5)
When the traveling direction of light in the silicon carbide substrate 1 is set along the <0001> direction of the silicon carbide substrate 1 as shown in FIG. 4, natural birefringence due to the crystal structure of silicon carbide occurs. Since it can be reduced, the above-mentioned phase difference value becomes relatively small. Since the measurement is performed under the condition that the natural birefringence is suppressed as described above, the strain can be evaluated with high accuracy by the phase difference caused by the birefringence by utilizing the photoelasticity. On the other hand, when the traveling direction of light in the silicon carbide substrate 1 is not along the <0001> direction, the influence of the natural birefringence becomes relatively large, and the above-mentioned phase difference value becomes relatively large. As it becomes larger, it becomes difficult to accurately measure the strain.

In order to make the traveling direction of light in the silicon carbide substrate 1 along the <0001> direction in this way, the difference in refractive index between the atmosphere around the silicon carbide substrate 1 and the silicon carbide substrate 1 is taken into consideration. There is a need. That is, the light is refracted when the light enters the silicon carbide substrate 1 from the atmosphere side. The refraction of light at the interface between the atmosphere and the silicon carbide substrate 1 can be examined, for example, based on Snell's law.

Here, in the compound semiconductor substrate such as the silicon carbide substrate 1, there is a case where the substrate has a shape defect such as warpage. In such a case, the inclination of the main surface with respect to the reference surface of the stage 24 differs depending on the position of the silicon carbide substrate 1 mounted on the stage 24 in the main surface. Therefore, the incident direction of the light from the incident side optical system 41 with respect to the silicon carbide substrate 1 is determined in advance so that the traveling direction of the light in the silicon carbide substrate 1 is the <0001> direction using the above Snell's law. However, the traveling direction of the light in the actual silicon carbide substrate 1 may deviate from the <0001> direction.

Therefore, in the present embodiment, the off direction and the off angle from the (0001) plane at each position of the main surface of the silicon carbide substrate 1 are examined in advance with respect to one measurement point on the main surface of the silicon carbide substrate 1. The incident angle of the incident light is determined so that the traveling direction of the light in the silicon carbide substrate 1 is in the <0001> direction, and the above steps (S30), (S21), and (S22) are carried out. The off-direction and off-angle measurement from the (0001) plane at each position of the main plane of the silicon carbide substrate 1 can be performed by, for example, an X-ray diffraction method. In this way, even when the shape of the silicon carbide substrate 1 is not flat, the phase difference δ and the principal vibration azimuth Ψ in which the influence of natural birefringence is reduced at the measurement points on the surface of the silicon carbide substrate 1 are reduced. And data can be obtained.

For example, consider a case where a silicon carbide substrate having an off angle of 4 ° is irradiated with light having a wavelength of 950 nm. In this case, for example, the refractive index n1 of the air on the incident side is assumed to be 1, and the refractive index n2 of the silicon carbide on the exit side is considered to be 2.2. When these conditions are applied to Snell's law, when the main surface of the silicon carbide substrate 1 is irradiated with light from a direction inclined by 9 ° with respect to the normal of the main surface of the silicon carbide substrate 1, the silicon carbide is contained. It is considered that the traveling direction of light is substantially parallel to the <0001> direction. The light irradiation direction is determined in advance for each of the plurality of measurement points on the main surface of the silicon carbide substrate 1 in consideration of the shape such as the warp of the silicon carbide substrate 1 mounted on the stage 24.

The above-mentioned two types of transmitted light intensity data are measured at a plurality of measurement points on the surface of the silicon carbide substrate 1. The measurement points may be arranged in a grid pattern on the surface of the silicon carbide substrate 1, for example. The distance between the measurement points may be, for example, 0.1 mm or more and 50 mm or less, 0.3 mm or more and 2 mm or less, or 0.4 mm or more and 0.6 mm or less.

By obtaining the birefringence phase difference δ for each measurement point as described above, the maximum value and standard deviation of the phase difference δ can be obtained for a plurality of measurement points of the entire substrate.

Residual strain evaluation step (S23):
Next, the residual strain of the silicon carbide substrate 1 is evaluated. Any method can be adopted as the evaluation method, and for example, the method disclosed in Japanese Patent No. 3156382 (Japanese Patent Laid-Open No. 5-339100) can be used. Specifically, the residual strain of the silicon carbide substrate can be calculated by the absolute value | Sr-St | of the difference between the strain Sr in the radial direction and the strain St in the tangential direction. In this calculation, | Sr-St | can be calculated as shown in the following mathematical formulas (6) and (7).

| Sr-St | = kδ [{cos2Ψ / (P _11- P ₁₂ )} ² + {(sin2Ψ) / P ₄₄ } ^1/2 Formula (6)
However, in the above formula (6),
k = λ / (πdn ₀ ³ ) Formula (7)
Is. Here, the wavelength of the light used for the measurement is λ, the thickness of the silicon carbide substrate 1 used for the measurement is d, the refractive index of the silicon carbide substrate 1 is n _0, and the photoelastic constant of the silicon carbide substrate 1 is P _11. , P ₁₂ , and P ₄₄ . Here, the refractive index n ₀ is the refractive index when light is transmitted along the <0001> direction.

In this way, the strain of the silicon carbide substrate 1 can be obtained by obtaining the phase difference δ and the principal vibration azimuth Ψ caused by the birefringence of the silicon carbide substrate 1 by using the photoelastic method. The above-mentioned measurement step (S21) to the residual strain evaluation step (S23) correspond to the evaluation step (S20) shown in FIG.

<Effect of evaluation method>
According to the evaluation method as described above, the data when the light for evaluation is transmitted along the <0001> direction in the silicon carbide substrate 1 can be obtained as the measurement result, so that the crystal structure of the silicon carbide substrate 1 can be obtained. The strain (residual strain) can be evaluated in a state where the influence of natural birefringence caused by the above is reduced.

Here, the cubic compound semiconductor crystal is optically isotropic. Therefore, there is no refractive index anisotropy. Therefore, natural birefringence does not occur regardless of the direction in which light is transmitted, and it is easy to accurately measure crystal strain.

On the other hand, in a hexagonal compound semiconductor, the refractive index is different when light is transmitted parallel to the <0001> direction and when light is transmitted along a direction intersecting the <0001> direction, as in the case of silicon carbide described above. different. As a result, when the optical axis of the light transmitted through the hexagonal compound semiconductor deviates from the <0001> direction by a certain angle or more, the influence of natural birefringence cannot be ignored, and the crystal distortion is accurately evaluated. It's not easy to do. The direction in which light is transmitted in the hexagonal compound semiconductor is preferably within ± 3 °, more preferably within ± 2 °, and even more preferably within ± 1 ° from the <0001> direction.

Further, in the above evaluation method, in the evaluation step (S20), strain at a plurality of points of the silicon carbide substrate 1 is evaluated by irradiating light at a plurality of measurement points on the surface of the silicon carbide substrate 1. Specifically, the evaluation step (S20) includes a step of obtaining the phase difference δ caused by birefringence at the plurality of locations and a step of calculating the maximum value and the standard deviation of the phase difference δ at the plurality of locations. From a different point of view, in the step (S21) of transmitting light through the substrate, light is irradiated to a plurality of locations on the first main surface. In the step (S22) of calculating the phase difference caused by birefringence, the phase difference at a plurality of locations is calculated. The evaluation step (S20) may include a step of obtaining the main vibration azimuth angle Ψ at the plurality of locations. In this case, the strain distribution state on the surface of the silicon carbide substrate 1 can be evaluated.

In the above evaluation method, the silicon carbide substrate 1 may be an off substrate in which the surface 4 as the first main surface is inclined with respect to the {0001} surface. In this case, in the evaluation step (S20), as shown in FIG. 4, light corresponds to the off angle, which is the angle at which the surface 4 is inclined with respect to the {0001} surface, and light is emitted from the surface 4 in the silicon carbide substrate 1. It penetrates along the <0001> direction, which is the inclined direction (direction indicated by arrow 3). In the above evaluation method, the light irradiation direction is set with respect to the surface 4 of the silicon carbide substrate 1 so that the light is transmitted through the silicon carbide substrate 1 along the <0001> direction as shown by the arrow 3 in FIG. The step (S30) of setting in the inclined direction may be included. In this case, it is possible to evaluate the strain of the silicon carbide substrate 1 which is an off substrate under the condition that the influence of natural birefringence is reduced.

From a different point of view, in the above strain evaluation method, in the evaluation step (S20), for each measurement point of the main surface, the inclination angle (off angle) and the inclination direction (off) with respect to the {0001} surface of the main surface measured in advance. The angle of incidence of light with respect to the main surface is determined based on the information of direction). In this case, even when the shape of the silicon carbide substrate 1 is not flat, such as when the silicon carbide substrate 1 is warped, the off-angle and off-direction (apparent off-angle and off) in consideration of the shape of each measurement point. By obtaining the direction) in advance, it is possible to accurately evaluate the strain in which the influence of natural birefringence due to the crystal structure of silicon carbide is reduced as a result.

In the above evaluation method, the substrate to be evaluated may include a silicon carbide substrate 1 as a compound semiconductor substrate and a silicon carbide epitaxial layer as a compound semiconductor layer homoepitaxially grown on the silicon carbide substrate. In this case, it is possible to confirm the state of occurrence of strain on the silicon carbide substrate (silicon carbide substrate with an epitaxial layer) on which the epitaxial layer is formed.

<Manufacturing method of compound semiconductor>
Hereinafter, a method for producing a hexagonal compound semiconductor to which the above-mentioned evaluation method is applied will be described. As shown in FIG. 5, in the method for manufacturing a hexagonal compound semiconductor, a substrate preparation step (S100) is first carried out. In this step (S100), a compound semiconductor substrate used for manufacturing a compound semiconductor device is prepared. Hereinafter, silicon carbide will be described as an example of a hexagonal compound semiconductor. In the step (S100), a hexagonal compound having a hexagonal crystal structure, having birefringence, and including a surface 4 as a first main surface and a second main surface and side surfaces opposite to the first main surface. Prepare a semiconductor substrate. Here, a silicon carbide substrate is prepared as an example of a compound semiconductor substrate. As the silicon carbide substrate, an off substrate having a surface off angle of more than 0 ° and 8 ° or less with respect to the (0001) plane (C plane) is used. The diameter of the silicon carbide substrate is, for example, 100 mm or more. The diameter of the silicon carbide substrate may be 150 mm or more, or 200 mm or more. The thickness of the silicon carbide substrate may be, for example, 200 μm or more and 1 mm or less. The diameter of the silicon carbide substrate may be 300 mm or less.

Next, an inspection step (S200) as a step of calculating the first phase difference is carried out. In this step (S200), the strain of the silicon carbide substrate is evaluated using the evaluation methods shown in FIGS. 1 to 4. Specifically, the off direction and the off angle from the (0001) plane at each position of the main surface of the silicon carbide substrate are examined in advance for a plurality of locations on the surface of the silicon carbide substrate. Based on the off angle and the off direction, the incident angle of the incident light is determined in advance so that the traveling direction of the light in the silicon carbide substrate is the <0001> direction, and the steps (S30) and (S21) described above. ), Step (S22) is carried out. As a result, a value of the phase difference in which the natural birefringence at the measurement point is suppressed can be obtained. At this time, the main vibration azimuth angle Ψ may be obtained at the same time. After that, the strain is obtained as described in the above-mentioned residual strain evaluation step (S23).

From a different point of view, in this step (S200), the surface 4 as the first main surface is irradiated with light transmitted through the substrate, and as shown in FIG. 4, the substrate is illuminated along the <0001> direction in the substrate. Is transmitted, and the first phase difference δ caused by birefringence is calculated. The step (S200) may be performed at a plurality of measurement points as a plurality of locations on the surface 4 as the first main surface. The maximum value and standard deviation of the birefringence phase difference δ may be obtained for each of the plurality of measurement points, and the variation in strain distribution and the magnitude of strain may be evaluated. The step (S210) of obtaining the maximum value and the standard deviation in this way corresponds to the step of calculating the first maximum value and the first standard deviation.

Next, a film forming step (S300) is carried out as a step of homoepitaxially growing the compound semiconductor layer. In this step (S300), a silicon carbide epitaxial layer as a compound semiconductor layer is formed on the surface 4 of the silicon carbide substrate based on predetermined growth conditions. As the film forming condition of the silicon carbide epitaxial layer, any conventionally known condition can be adopted.

Next, the inspection step (S400) after the film formation is carried out. In the step (S400) as the step of calculating the second phase difference, the surface of the silicon carbide substrate as the base substrate prepared in the substrate preparation step is subjected to the same evaluation method as in the inspection step (S200). The strain of the silicon carbide epi substrate on which the silicon carbide epitaxial layer is formed is evaluated. From a different point of view, in this step (S400), the surface of the silicon carbide epitaxial layer as the compound semiconductor layer is irradiated with light, and the silicon carbide epitaxial layer in the silicon carbide epitaxial layer and along the <0001> direction in the substrate. Then, light is transmitted through the substrate, and the second phase difference δ caused by birefringence is calculated. The above step (S400) may be performed at a plurality of measurement points at a plurality of locations on the surface of the silicon carbide epitaxial layer.

In the evaluation of the strain in the inspection step (S400), the phase difference of the birefringence may be evaluated as in the inspection step (S200), or the strain value may be directly evaluated. Alternatively, the maximum value and standard deviation of the birefringence phase difference δ may be evaluated for a plurality of measurement points. The step (S410) of obtaining the maximum value and the standard deviation in this way corresponds to the step of calculating the second maximum value and the second standard deviation.

Next, a step (S500) of determining whether or not the conditions for changing the film forming conditions are satisfied is performed. In this step (S500), the data obtained in each of the steps (S200) and the step (S400) are compared, and if the strain is increased due to the film formation in the film formation step (S300), the film formation conditions It is determined that the condition for changing is satisfied. In this step (S500), for example, it is the maximum value of the birefringence phase difference δ obtained in the step (S410) from the first maximum value which is the maximum value of the birefringence phase difference δ obtained in the step (S210). It may be determined whether or not the condition that the second maximum value is larger is satisfied. Further, as a discrimination condition in the step (S500), a condition that the second standard deviation obtained in the step (S410) is larger than the first standard deviation obtained in the step (S210) is added to the condition relating to the maximum value. It may be adopted. If YES is determined in this step (S500), the process proceeds to the step of changing the film forming conditions (S600), and the film forming conditions in the next step (S300) are changed. After the step (S600) as a step of changing the growth conditions, the process proceeds to a post-treatment step (S700) described later. If NO is determined in the step (S500), the process proceeds to the post-treatment step (S700) as it is.

Next, the post-treatment step (S700) is carried out. In this post-treatment step (S700), ion implantation into the formed silicon carbide epitaxial layer and formation of a conductor layer such as an electrode and wiring are performed. A plurality of silicon carbide semiconductor elements are simultaneously formed on the surface of the silicon carbide substrate. After that, the silicon carbide substrate can be divided into individual devices to obtain a silicon carbide semiconductor device as an example of a compound semiconductor. A semiconductor module may be configured by incorporating the divided elements (silicon carbide semiconductor device) into a module (for example, a module for power control) for realizing a predetermined function.

<Effect of manufacturing method of compound semiconductor>
According to the method for producing a hexagonal compound semiconductor described above, the phase difference δ in a state where light is transmitted along the <0001> direction in the compound semiconductor is calculated, so that natural birefringence due to the crystal structure of the compound semiconductor is calculated. It is possible to obtain a phase difference δ in which the influence of Therefore, it is possible to obtain a silicon carbide substrate as an example of a compound semiconductor whose strain is evaluated by the phase difference δ generated by the birefringence while the influence of the natural birefringence is reduced. Further, since the strain can be evaluated by the phase difference δ generated by the double refraction before and after the silicon carbide epitaxial layer as the compound semiconductor layer is formed on the compound semiconductor substrate, the strain due to the film forming step (S300) of the silicon carbide epitaxial layer can be evaluated. The impact can be evaluated. Further, it is possible to confirm the state of occurrence of strain in the silicon carbide substrate with the epitaxial layer on which the silicon carbide epitaxial layer is formed. Then, by comparing the strain after the silicon carbide epitaxial layer is formed with the strain before the silicon carbide epitaxial layer is formed and grasping the amount of strain generated during the epitaxial growth, the growth conditions in the epitaxial growth are obtained. It becomes possible to judge the suitability of.

Further, since the phase difference is calculated for a plurality of locations on the surface 4 of the substrate and the magnitude and variation of the phase difference δ are correlated with the magnitude and variation of the strain on the substrate, the strain distribution in the surface of the substrate. The condition can be evaluated. That is, it is possible to obtain a compound semiconductor in which the distribution state of strain in the plane of the substrate is evaluated by the phase difference δ generated by the birefringence in a state where the influence of the natural birefringence is reduced.

In the method for producing a hexagonal compound semiconductor, the surface 4 of the substrate, which is the first main surface, is inclined with respect to the {0001} surface. Further, in the step (S200), with respect to the surface 4 of the light at a plurality of locations of the surface 4, based on the information of the inclination angle (off angle) and the inclination direction (off direction) with respect to the {0001} surface of the surface 4 measured in advance. The incident angles are determined respectively. Further, in the step (S400), the incident angles of light with respect to the surface of the epitaxial layer are determined at a plurality of locations on the surface of the epitaxial layer as the compound semiconductor layer based on the above information.

In this case, even when the shape of the substrate is not flat, such as when the substrate is warped, by obtaining information such as the off angle and the off direction of the substrate in advance, as a result, the direction in the compound semiconductor is <0001>. The strain can be accurately evaluated by utilizing the photoelasticity when light is transmitted along the line. That is, as a result, it is possible to accurately evaluate the strain in which the influence of natural birefringence due to the crystal structure of the hexagonal compound semiconductor is reduced. Therefore, it is possible to accurately determine the strain distribution in the plane of the substrate and the suitability of the growth conditions in epitaxial growth.

Since the method for producing a hexagonal compound semiconductor includes steps (S500) and steps (S600), the maximum value of the phase difference δ before and after the silicon carbide epitaxial layer is formed is compared with the standard deviation. Therefore, it is possible to evaluate the influence of strain due to the film forming step of the silicon carbide epitaxial layer and adjust the film forming conditions in the step (S300) so as to suppress the increase in strain. Therefore, it is possible to obtain a substrate with an epitaxial layer in which distortion is suppressed.

In the method for producing a hexagonal compound semiconductor, the steps (S200) and (S400) are carried out at a plurality of measurement points on the surface of the substrate or in the plane of the silicon carbide epitaxial layer, so that the crystal of the compound semiconductor is crystallized in the plane of the substrate. Accurate strain evaluation can be performed with the influence of natural birefringence due to the structure reduced.

In the method for producing a hexagonal compound semiconductor, the diameter of the substrate is 100 mm or more. Since there is a concern that problems due to strain may occur in such a compound semiconductor substrate having a relatively large diameter, it is preferable to apply the above method for producing a compound semiconductor.

In the method for producing a hexagonal compound semiconductor, the hexagonal compound semiconductor is a silicon carbide single crystal. Since cracking of the substrate due to strain is a particular problem with silicon carbide, it is preferable to apply the above-mentioned manufacturing method.

(Example)
In order to verify the effect of the evaluation method described above, the following experiments were conducted.

<Silicon carbide substrate>
As an evaluation target, a polytype 4H silicon carbide substrate having a diameter of 150 mm and a surface off-angle of 4 ° with respect to the (0001) plane was prepared. The thickness of the silicon carbide substrate was 350 μm.

Further, after performing a strain evaluation step as described later, a silicon carbide epitaxial layer was formed on the silicon carbide substrate under the following conditions.

Epitaxial film by CVD method using silane (SiH ₄ ) and propane (C ₃ H ₈ ) as raw material gas, nitrogen (N ₂ ) or ammonia (NH ₃ ) as dopant gas, and hydrogen (H ₂ ) as carrier gas. To grow. Since the main surface is off with respect to the (0001) surface as described above, the epitaxial film is formed by step flow growth. Therefore, the epitaxial film is made of 4H type silicon carbide like the silicon carbide substrate, and the mixture of different polytypes is suppressed. The thickness of the epitaxial film is, for example, about 10 μm or more and 50 μm or less.

In the above-described epitaxial film growth step, a raw material gas having a C / Si ratio of less than 1 is used for epitaxial growth on the main surface of the silicon carbide substrate. First, in the film forming apparatus, the inside of the channel in which the silicon carbide substrate is arranged is gas-replaced. Then, while flowing the carrier gas, the pressure in the channel is adjusted to a predetermined pressure, for example, 60 mbar to 100 mbar (6 kPa to 10 kPa). The carrier gas may be, for example, hydrogen (H ₂ ) gas, argon (Ar) gas, helium (He) gas, or the like. The carrier gas flow rate may be, for example, about 50 slm to 200 slm. Here, the unit of flow rate "slm (Standard liter per Minute)" indicates "L / min" in the standard state (0 ° C., 101.3 kPa).

Next, the heating element 6 arranged around the channel is induced and heated by supplying a predetermined alternating current to the induction heating coil arranged so as to surround the channel. A susceptor is arranged inside the channel. A silicon carbide substrate is placed on the susceptor. As a result, the susceptor on which the channel and the silicon carbide substrate are placed is heated to a predetermined reaction temperature. At this time, the susceptor is heated to, for example, about 1500 ° C to 1750 ° C.

<Evaluation method>
The strain of the silicon carbide substrate was evaluated by using the evaluation method according to the present embodiment at each timing before and after forming the silicon carbide epitaxial layer as described above. In the evaluation method, the measuring device having the configuration shown in FIG. 3 was used to irradiate the silicon carbide substrate with light having a wavelength of 950 nm for measurement. At this time, the off-angle and the off-direction of each measurement point were measured in advance by using the X-ray diffraction method. As an example, the measurement was performed on a plurality of measurement points arranged in a grid pattern at intervals of 10 mm on the surface of a silicon carbide substrate having a diameter of 150 mm. The number of measurement points is about 170 points. Then, for the phase difference δ, the maximum value, the average value, and the standard deviation were calculated.

<Evaluation result>
Before epitaxial growth:
For the birefringence phase difference δ (unit: radians), the maximum value was 0.425, the mean value was 0.149, and the standard deviation was 0.065.

After epitaxial growth:
For the birefringence phase difference δ, the maximum value was 0.395, the average value was 0.140, and the standard deviation was 0.060.

From the data before and after the epitaxial growth, the change in the maximum value of the phase difference δ by the epitaxial growth is 0.030, the change in the mean value is 0.009, and the change in the standard deviation is 0. It was 005. From the above data, it can be seen that the change in strain before and after epitaxial growth is sufficiently small. As described above, using the evaluation method according to the present embodiment, it was possible to evaluate the state of strain of the silicon carbide substrate before and after the epitaxial growth.

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

1 Silicon carbide substrate 2 Dot line 3 Arrow 4 Surface 10 Control controller 11 Control IO bus 21 Light source 22, 26 Lens 23 Polarizer 24 Stage 25 Detector 27 Receiver 27 Receiver 31-5, 39 Drive circuit 36 IV converter 37 Variable gain amplifier 38 AD converter 41 Incident side optical system 42 Light receiving side optical system 43 to 45 Optical axis adjustment unit 100 Measuring device

Claims (3)

A step of preparing a substrate of a hexagonal compound semiconductor having a hexagonal crystal structure, having birefringence, and including a first main surface and a second main surface and a side surface opposite to the first main surface.
A step of irradiating the first main surface with light transmitted through the substrate, transmitting the light through the substrate along the <0001> direction in the substrate, and calculating the first phase difference caused by the birefringence. When,
A step of homoepitaxially growing a compound semiconductor layer on the first main surface based on predetermined growth conditions, and
The surface of the compound semiconductor layer is irradiated with the light, the light is transmitted to the compound semiconductor layer and the substrate along the <0001> direction in the compound semiconductor layer and the substrate, and the light is transmitted to the compound semiconductor layer and the substrate, and the birefringence is generated. It includes a step of calculating the phase difference of 2 and
A method for producing a hexagonal compound semiconductor, wherein the hexagonal compound semiconductor is a silicon carbide single crystal. The method for producing a hexagonal compound semiconductor according to claim 1, wherein the first main surface of the substrate is inclined with respect to the {0001} surface. In the step of calculating the first phase difference, the incident angle of the light with respect to the first main surface is determined based on the information on the inclination angle and the inclination direction of the first main surface with respect to the {0001} surface measured in advance. Has been
The method for producing a hexagonal compound semiconductor according to claim 2, wherein in the step of calculating the second phase difference, the incident angle of the light with respect to the surface of the compound semiconductor layer is determined based on the information.

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