JP2010135618A - Method of manufacturing group iii nitride laser diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a group III nitride laser diode for providing a good cleavage yield. <P>SOLUTION: Two GaN substrates that are cut out from the same ingot are prepared. On the GaN substrates, an epitaxial substrate is manufactured by growing a plurality of epitaxial films for a laser diode by metal organic vapor deposition. An anode electrode and a cathode electrode are formed on the epitaxial substrate to manufacture a substrate product. In the cleavage of one of the substrate products, the edge of the substrate product comprising a crystal region 22a grown in the second half of the ingot growth is broken in the direction of an arrow CL1. In the other substrate product, the edge of the substrate product comprising the crystal region grown in the first half of the ingot growth is broken in the direction of the arrow CL2. The break in the first portion 22a provides a good cleavage yield, as compared with the break in the third portion 22c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for fabricating a III-nitride laser diode.

  Patent Document 1 describes a method of manufacturing a semiconductor light emitting element. In this method, an epitaxial film for a semiconductor light emitting device is grown on a (0001) plane sapphire substrate. The nitride III-V compound semiconductor is cleaved by scribing the back surface of the sapphire substrate.

  Patent Document 2 describes a method of manufacturing a semiconductor laser using a SiC substrate. In this method, the p-type GaN layer grown on the SiC substrate is scratched and then cleaved using a scriber load exceeding 80 g.

Patent Documents 3 to 5 describe a method of manufacturing a gallium nitride substrate.
JP 2004-312050 A Japanese Patent Laid-Open No. 11-40884 JP 2001-102307 A JP 2003-165799 A JP 2003-183100 A

  Neither Patent Document 1 nor 2 discloses a specific method for producing a group III nitride laser diode using a substrate made of a hexagonal group III nitride semiconductor. In Patent Document 1, the surface orientation of the sapphire substrate is the c-plane, while in Patent Document 2, the surface orientation of the SiC substrate is not described.

  On the other hand, hexagonal group III nitride semiconductor substrates such as gallium nitride substrates are available. In addition, not only the c-plane of the gallium nitride substrate but also a semi-polar plane and a non-polar plane of gallium nitride have been studied for manufacturing a light emitting element.

  The fabrication of gallium nitride substrates is described in Patent Documents 3 to 5. An example of manufacturing a gallium nitride substrate is as follows. A GaN thick film is grown on a support such as a GaAs substrate by the HVPE method. The GaN thick film is sliced to obtain a gallium nitride substrate.

  A gallium nitride substrate having a semipolar plane or a nonpolar plane is obtained by slicing a GaN thick film along a plane that intersects the growth direction at a desired angle to obtain a GaN flat plate. The main surface of the GaN flat plate is processed to be a mirror surface. More specifically, when slicing a GaN thick film in a plane intersecting the c-plane to form a semipolar or nonpolar gallium nitride substrate, the gallium nitride substrate does not consist of crystals grown at about the same time, The GaN layers from the early growth stage to the late growth stage are arranged in the direction from one end of the edge of the gallium nitride substrate to the other end, like the formation.

  As already described, in the production of the gallium nitride substrate, a GaN thick film is grown on the support in the growth direction. According to the inventors' knowledge, when the GaN thick film growth is divided into the initial stage, the middle stage and the final stage, the variation in the crystal orientation of the GaN crystal part grown in the final stage is the crystal orientation of the GaN crystal part grown in the initial stage. It is better than the variation of.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing a group III nitride laser diode capable of providing a good cleavage yield.

  One aspect of the present invention is a method of fabricating a group III nitride laser diode. In this method, (a) a substrate comprising a hexagonal group III nitride formed by slicing an ingot grown in the direction of a reference axis from the one end surface to the other end surface is provided. And (b) producing an epitaxial substrate including a laminate formed on the main surface of the substrate, and producing a substrate product including an anode electrode and a cathode electrode formed on the epitaxial substrate. And (c) cleaving the substrate product to form a cleavage plane for the resonator of the laser diode. The stacked body includes an n-type group III nitride semiconductor layer, an active layer, and a p-type group III nitride semiconductor layer. The main surface of the substrate intersects with a c plane perpendicular to the c axis of the hexagonal group III nitride. The main surface of the substrate intersects a predetermined plane defined by a normal vector of the main surface of the substrate and a reference axis vector indicating the direction of the reference axis at an intersection line segment on the main surface. Yes. The substrate product includes first to third portions arranged in an extending direction of the intersecting line segment, and the substrate is arranged in the extending direction of the intersecting line segment. The stacked body includes first to third portions respectively disposed on the first to third portions of the substrate. The first portion of the substrate product includes the first portion of the stack and the first portion of the substrate, and the second portion of the substrate product is the second portion of the stack. And the second portion of the substrate, and the third portion of the substrate product includes the third portion of the stack and the third portion of the substrate. In the growth of the ingot, the first portion of the substrate is grown after the third portion of the substrate, and the midpoint of the intersecting line segment is the second portion of the substrate and the second portion of the substrate. Located in the boundary with one part or in the second part of the substrate, the cleavage is carried out by breaking the first part of the substrate product. A crack caused by the break is formed by extending in the extending direction of the intersection line.

  According to this method, since the first portion of the substrate is grown after the third portion, the crystal orientation in the first portion is aligned with the crystal orientation in the third portion. Therefore, the cleavage yield can be improved by cleaving by breaking the first portion of the substrate product.

  In the method according to the present invention, an angle formed between the main surface of the substrate and the c plane may be 10 degrees or more and 90 degrees or less. According to this method, a substrate having a semipolar main surface when tilted at an angle of 10 degrees or more and less than 90 degrees with respect to the c-plane of the hexagonal group III nitride is provided. When the main surface of the substrate forms an angle of 90 degrees with respect to the c-plane of the hexagonal group III nitride, a substrate having a nonpolar main surface is provided. Further, when the angle is 10 degrees or more, the crystal orientation unevenness caused by the growth time becomes conspicuous between one end and the other end of the main surface of the substrate. In the method according to the present invention, an angle formed between the back surface of the substrate and the c plane may be 10 degrees or more and 90 degrees or less.

  In the method according to the present invention, in the step of producing the substrate product, the back surface of the substrate can be polished to form a back-polished substrate. According to this method, the thickness of the substrate can be adjusted by polishing the back surface of the substrate.

  In the method according to the present invention, the thickness of the back-polished substrate may be 60 micrometers or more. When the thickness of the back-polished substrate is too small, handling difficulties such as unintentional cracking occur in the subsequent steps. The thickness of the back-polished substrate may be 150 micrometers or less. When the thickness of the back-polished substrate is too large, the cleavage yield decreases.

  In the method according to the present invention, the thickness of the ingot may be 5 millimeters or more. According to this method, nonpolar and semipolar substrates can be produced using an ingot having a thickness of 5 millimeters or more.

  In the method according to the present invention, the substrate may include first and second regions extending in the direction of the reference axis from the main surface to the back surface of the substrate. The first region and the second region are adjacent to each other, and the defect density of the first region is smaller than the defect density of the second region, and in the first region, the dislocation density in the main surface and One of the dislocation densities on the back surface is greater than the other.

  The substrate may have a structure including a first region having a dislocation density smaller than a predetermined dislocation density and a second region having a dislocation density larger than the predetermined dislocation density. By forming the first and second regions having different dislocations in the ingot growth, the dislocation density in the first region is reduced.

  In the method according to the present invention, in each of the first to third portions of the substrate, one of the dislocation density on the main surface of the substrate and the dislocation density on the back surface of the substrate is greater than the other.

  The substrate includes a plurality of regions of dislocation bundles having a higher dislocation density than the surrounding region. The dislocation bundle as a whole extends in the direction from the back surface to the main surface of the substrate, and is randomly distributed on the main surface of the substrate.

  In the method according to the present invention, the reference axis may extend in the direction of the c-axis of the hexagonal group III nitride. This ingot is grown in the c-axis direction as a whole ingot. In the method according to the present invention, the reference axis may extend in the m-axis direction of the hexagonal group III nitride. This ingot is grown in the m-axis direction as a whole ingot. In the method according to the present invention, the reference axis may extend in the direction of the a-axis of the hexagonal group III nitride. This ingot is grown in the direction of the a-axis as a whole ingot. By selecting the reference axis, the size of the substrate can be increased when the angle formed by the principal surface of the substrate and the c plane is made suitable.

  A method according to another aspect of the present invention is a method of fabricating a group III nitride laser diode. The method includes (a) preparing a substrate having a main surface and a back surface extending in a direction of a predetermined axis, and comprising a hexagonal group III nitride, and (b) the main surface of the substrate. Producing an epitaxial substrate including a laminate formed on the surface, and producing a substrate product including an anode electrode and a cathode electrode formed on the epitaxial substrate; and (c) cleaving the substrate product. And cleaving to form a cleavage plane for the resonator of the III-nitride laser diode. The stacked body includes an n-type group III nitride semiconductor layer, an active layer, and a p-type group III nitride semiconductor layer. The main surface of the substrate intersects with a c plane perpendicular to the c axis of the hexagonal group III nitride. The main surface of the substrate intersects a predetermined plane defined by a normal vector of the main surface of the substrate and a reference axis vector indicating the direction of a reference axis at an intersection line segment on the main surface. . The reference axis is any one of an a-axis, an m-axis, and a c-axis, and the direction of the intersecting line segment coincides with the direction of the predetermined axis. The substrate product includes first to third portions arranged in an extending direction of the intersecting line segment, and the substrate is arranged in the extending direction of the intersecting line segment. Including the part. The laminate includes first to third portions respectively disposed on the first to third portions of the substrate, and the first portion of the substrate product is the first portion of the laminate. And the first part of the substrate, the second part of the substrate product includes the second part of the stack and the second part of the substrate, and the substrate product. The third portion includes the third portion of the stacked body and the third portion of the substrate. In the main surface of the substrate, the dislocation density of the first portion of the substrate is smaller than the dislocation density of the third portion of the substrate, and the midpoint of the line segment is the second portion of the substrate. Located in the boundary with the first part or in the second part of the substrate. The cleavage is performed by breaking the first portion of the substrate product, and a crack caused by the break is formed by extending in the extending direction of the intersecting line segment.

  According to this method, the dislocation density of the first portion of the substrate is smaller than the dislocation density of the third portion of the substrate. By providing the starting point of cleavage not in the third part but in the first part, it is possible to cause cleavage from the first part to the third part through the second part. The effect of the dislocation density can be reduced. Therefore, the cleavage yield can be improved by breaking the first portion and performing cleavage.

  In the method of the present invention, an angle formed between the main surface of the substrate and the c plane may be 10 degrees or more and 90 degrees or less. According to this method, a substrate having a semipolar main surface when tilted at an angle of 10 degrees or more and less than 90 degrees with respect to the c-plane of the hexagonal group III nitride is provided. When the principal surface of the substrate forms an angle of 90 degrees with respect to the c-plane of the hexagonal group III nitride, a substrate having a nonpolar principal surface is provided.

  In the method of the present invention, each of the first to third portions may include first and second regions extending in a direction from the main surface to the back surface of the substrate. The first and second regions are adjacent to each other, the defect density of the first region is smaller than the defect density of the second region, the dislocation density in the main surface of the first region, and the One of the dislocation densities on the back surface is greater than the other.

  The substrate may have a structure including a first region having a dislocation density smaller than a predetermined dislocation density and a second region having a dislocation density larger than the predetermined dislocation density. By forming the first and second regions having different dislocations in the ingot growth, the dislocation density in the first region is reduced.

  In the method of the present invention, the first to third portions of the substrate appear in the first to third surface areas of the main surface of the substrate, respectively, and the first to third portions of the substrate. These portions appear in the first to third back areas of the back surface of the substrate, respectively, and one of the dislocation density of the first front area and the dislocation density of the first back area is larger than the other. .

  The substrate includes a plurality of dislocation bundle regions having a higher dislocation density than the surrounding region. The dislocation bundle as a whole extends in the direction from the back surface to the main surface of the substrate, and is randomly distributed on the main surface of the substrate.

  In the method of the present invention, the dislocation density of the first front area is smaller than the dislocation density of the first back area, the dislocation density of the second front area is smaller than the dislocation density of the second back area, The dislocation density in the third front area is smaller than the dislocation density in the third back area. Alternatively, in the method of the present invention, the dislocation density of the first back area is smaller than the dislocation density of the first front area, and the dislocation density of the second back area is smaller than the dislocation density of the second front area. The dislocation density of the third back area is smaller than the dislocation density of the third front area.

  In the method of the present invention, the maximum value of the distance between two points on the edge of the substrate may be 5 millimeters or more. A laser diode can be manufactured using a substrate of a certain size.

  In the method of the present invention, the first portion of the substrate product includes an edge of the major surface of the substrate product. In forming the cleavage of the substrate product, after forming a scribing groove at the edge of the first portion of the substrate product, the cleavage is caused by the break of the first portion of the substrate product. Cause from the first part to the third part.

  According to this method, the cleave groove is formed in the first portion of the substrate product and the cleavage is caused by the break of the substrate product to the first portion, so that the cleavage yield can be improved.

  In the method of the present invention, the second portion of the substrate is divided into fourth and fifth portions by another line segment orthogonal to the line segment at the midpoint of the line segment, 4 part is located between the first part and the fifth part of the substrate, and the fifth part is between the third part and the fourth part of the substrate. The dislocation density of the first portion of the substrate is smaller than the dislocation density of the fifth portion and the dislocation density of the fourth portion is the third surface of the substrate on the main surface of the substrate. Smaller than the dislocation density of the part.

  According to this method, although the substrate has different dislocation densities in the first, third to fifth portions arranged in the direction of the line segment on the main surface of the substrate, a good cleavage yield is provided.

  In the method of the present invention, in the step of producing the substrate product, the back surface of the substrate can be polished to form a back-polished substrate. The thickness of the back-polished substrate is 60 micrometers or more and 150 micrometers or less. According to this method, the substrate thickness can be adjusted to a desired thickness by polishing the back surface of the substrate. A good cleavage yield can be achieved by adjusting the thickness.

  In the method of the present invention, the cleavage plane is any one of the a-plane, m-plane and c-plane of the hexagonal group III nitride. According to this method, a good cleavage yield can be realized in cleavage to the a-plane, m-plane or c-plane.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, a method for producing a group III nitride laser diode that can provide a good cleavage yield is provided.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, referring to the attached drawings, a method for producing a group III nitride laser diode of the present invention, a method for producing a laser bar of a group III nitride laser diode, and a substrate product for the group III nitride laser diode An embodiment according to a method for cleaving the substrate will be described. Where possible, the same parts are denoted by the same reference numerals.

  FIG. 1 is a drawing showing the main steps in a method for producing a group III nitride laser diode according to the present embodiment. In step S101, a substrate 21 made of hexagonal group III nitride is prepared. The preparation of the substrate 21 in step S101 is performed, for example, according to the steps shown in FIGS. In step S102, a substrate product including a stack of epitaxial films is produced. The substrate product includes an anode electrode and a cathode electrode formed on the epitaxial substrate. As shown in FIG. 4, the epitaxial substrate E includes a stacked body formed on the main surface 21 a of the substrate 21. In step S103, the substrate product is cleaved to produce a laser bar. In this cleavage, a cleavage plane for the laser diode resonator is formed. In step S104, the laser bar is cut to produce a semiconductor chip, thereby forming individual laser diodes from the laser bar.

  The substrate 21 is prepared according to the steps shown in FIGS. FIG. 2 is a drawing showing the main steps of a method for producing an ingot made of hexagonal group III nitride. Referring to FIG. 2A, a growth substrate 11 for growing an ingot is prepared. The growth substrate 11 can be made of a semiconductor substrate different from the crystal of the ingot, and can be made of a semiconductor such as GaAs. As shown in FIG. 2B, the growth substrate 11 is placed in the growth furnace 10a. Using the growth furnace 10a, a group 13 nitride crystal 13 is grown on the substrate 11 by, for example, HVPE to form a product 15. The group III nitride can be a gallium nitride based semiconductor such as GaN. Next, the crystal 13 is separated from the product 15. This separation is performed, for example, by removing the growth substrate 11 by etching. The crystal body 13 is obtained by the separation. The crystal body 13 adjusts the shape of the crystal body 13 by mechanical processing such as cutting and polishing to form an ingot 17 as shown in FIG. The ingot 17 has one end surface 17a and the other end surface 17b. The ingot 17 was grown in the direction of the reference axis Gx from the one end surface 17a to the other end surface 17b. The direction of the reference axis Gx is indicated by a vector VG.

  The reference axis Gx can extend in the direction of the c-axis of the hexagonal group III nitride. The ingot 17 is grown in the c-axis direction as a whole ingot. Further, the reference axis Gx can extend in the m-axis direction of the hexagonal group III nitride. The ingot 17 is grown in the m-axis direction as a whole ingot. Furthermore, the reference axis Gx can extend in the direction of the a-axis of the hexagonal group III nitride. The ingot 17 is grown in the a-axis direction as a whole ingot.

The thickness D _I of the ingot 17 may be 5 millimeters or more. Non-polar and semipolar substrates (or wafers) can be made using ingots with a thickness of 5 millimeters or more. The dislocation density at the one end surface 17a of the ingot 17 can be, for example, 1 × 10 ⁷ cm ⁻³ or more, and the dislocation density at the other end surface 17b of the ingot 17 can be, for example, 5 × 10 ⁶ cm ⁻³ or less. . These dislocation densities are measured, for example, by surface observation after etching or cathodoluminescence observation.

  As shown in FIG. 3A, the ingot 17 is sliced to form a substrate 21 made of hexagonal group III nitride. In this embodiment, a group III nitride laser diode is manufactured on the substrate 21. The substrate 21 has a main surface 21a and a back surface 21b. The main surface 21a and the back surface 21b extend in the direction of a predetermined axis Ax. For example, the surfaces 21a and 21b are substantially parallel to each other. The main surface 21a of the substrate 21 intersects a predetermined plane Sx at an intersection line segment Lx on the main surface 21a, and the plane Sx is a normal vector of the reference axis vector VG indicating the direction of the reference axis Gx and the main surface 21a. VN. FIG. 3A shows an orthogonal coordinate system S, where the z-axis points in the direction of the normal vector VN, and the x-axis indicates the direction of the axis Ax. The y axis is orthogonal to both the normal vector VN and the axis Ax.

The main surface 21a of the substrate 21 intersects the c plane perpendicular to the c axis of the hexagonal group III nitride. The angle formed between the main surface 21a of the substrate 21 and the plane c is not less than 10 degrees and can be not more than 90 degrees. When tilted at an angle A _OFF of 10 degrees or more and less than 90 degrees with respect to the c-plane of the hexagonal group III nitride, the main surface 21a of the substrate 21 has semipolarity. When the main surface 21a of the substrate 21 forms an angle of 90 degrees with respect to the c-plane of the hexagonal group III nitride, the main surface 21a of the substrate 21 has no polarity. Further, when the angle is 10 degrees or more, the difference in crystal orientation unevenness caused by the crystal growth time of the ingot 17 becomes conspicuous between one end and the other end of the substrate main surface 21a. The angle formed between the back surface 21b of the substrate 21 and the c plane can be 10 degrees or more. Also, this angle can be 90 degrees or less.

In order to facilitate understanding, in the following description, the reference axis Gx is provided at the center point of the substrate 21, and the intersection line segment Lx passes through the two points 21 c and 21 d on the edge 21 e of the substrate 21 and the center point of the substrate 21. To do. As shown in FIGS. 3A and 3B, the substrate 21 includes first to third portions 22a, 22b, and 22c arranged in the extending direction of the cross line segment Lx. The reference axis Gx forms an angle θ with the main surface 21a of the substrate 21, and the direction of the vector VA (= VG × cos θ) indicates the arrangement direction of the first to third portions 22a to 22c. In the growth of the ingot 17, the first portion 22a is grown after the third portion 22c, and the midpoint M of the intersecting line segment Lx is located in the second portion 22b. On the other hand, the thickness _{D S} of the substrate 21 is, for example, from 250 to 850 micrometers.

  In this embodiment, the edge 21e of the substrate 21 can include a single circumference or one or more arcs. The first portion 22a includes a part of the edge 21e of the substrate 21, and the third portion 22c includes another portion of the edge 21e of the substrate 21. The second portion 22b has a stripe shape located between the first portion 22a and the third portion 22c. In one embodiment, the maximum distance between two points on the edge 21e of the substrate 21 can be 5 millimeters or more. A laser diode can be manufactured using a substrate of a certain size. In the main surface 21a of the substrate 21, the dislocation density D1 of the first portion 22a is smaller than the dislocation density D3 of the third portion 22c, and the midpoint M of the line segment Lx is the first portion 22a and the second portion 22b. Or in the second portion 22b. For example, the dislocation density (for example, the dislocation density D2 near the midpoint M) of the second portion 22b is smaller than the dislocation density D3, and the dislocation density D1 is smaller than the dislocation density D2.

  The second portion 22b is divided into fourth and fifth portions 22d and 22e by another line segment Nx orthogonal to the cross line segment Lx at the midpoint M of the cross line segment Lx. The fourth portion 22d is located between the first portion 22a and the fifth portion 22e, and the fifth portion 22e is located between the third portion 22c and the fourth portion 22d. . The dislocation density of the first portion 22a is smaller than the dislocation density of the fifth portion 22e, and the dislocation density of the fourth portion 22d is smaller than the dislocation density of the third portion 22c. The substrate 21 has different dislocation densities in the first, third to fifth portions 22a and 22c to 22e arranged in the direction of the line segment on the main surface 21a of the substrate 21, but provides a good cleavage yield. Is done.

  Referring again to FIG. 1, in step 102, a substrate product is produced. Specifically, the epitaxial substrate E is prepared according to the process shown in FIG. The production of the epitaxial substrate E uses, for example, a metal organic chemical vapor deposition method, but the present invention is not limited to this. As shown in FIG. 4A, in step S105, the substrate 21 is placed in the growth furnace 10b. In the following description, the substrate 21 is, for example, an n-type GaN substrate. Next, in step S106, a semiconductor film for the laser diode is deposited by epitaxial growth. As shown in FIG. 4B, the raw material G0 is supplied to the growth reactor 10b, and the first semiconductor region 23 including the n-type gallium nitride based semiconductor layer is grown on the substrate 21. The n-type gallium nitride based semiconductor layer can be, for example, an n-type cladding layer. Subsequently, as shown in FIG. 4C, the raw material G1 is supplied to the growth reactor 10b, and the light emitting layer 25 for the laser diode is formed on the first semiconductor region 23 and on the first semiconductor region 23. To grow. The light emitting layer 25 includes an active layer, and the active layer may include well layers and barrier layers that are alternately arranged. The light emitting layer 25 may include first and second light guide layers, and the active layer is provided between the first and second light guide layers. Thereafter, as shown in FIG. 4D, the raw material G2 is supplied to the growth reactor 10b, and the second semiconductor region 27 including one or a plurality of p-type gallium nitride based semiconductor layers is formed on the light emitting layer 25. grow up. The p-type gallium nitride based semiconductor layer can be, for example, an electron block layer, a p-type cladding layer, and a p-type contact layer. By these steps, an epitaxial substrate E including the substrate 21 and the stacked body 29 on the substrate is obtained. In step S107, the epitaxial substrate E is taken out of the growth furnace 10b.

  If necessary, in step S102 for producing a substrate product, an electrode is formed on the surface of the epitaxial substrate E in step S108. Thereafter, in step S109, the back surface 21b of the substrate 21 can be polished to form a back-polished substrate. The thickness of the epitaxial substrate can be adjusted by polishing the substrate back surface 21b.

Thereafter, in step S110, an electrode is formed on the polished back surface of the epitaxial substrate E to produce a substrate product P. FIG. 5A is a drawing showing a gain guide type laser diode manufactured as an example of the present embodiment. FIG. 5A is taken along the line I-I shown in FIG. An insulating film 31 is deposited on the upper surface of the epitaxial substrate E, and the upper surface of the stacked body 29 is covered with the insulating film 31. The insulating film 31 has an opening 31a extending in the y-axis direction. The electrode 33 is connected to the stacked body (surface E _{F of the} epitaxial substrate E) 29 through the opening 31a. Electrode 35 is connected to the rear surface _{E B} of the epitaxial substrate E. The substrate product P includes first to third portions Pa, Pb, and Pc arranged in the extending direction of the cross line segment Lx. The stacked body 29 includes first to third portions 29a, 29b, and 29c provided on the first to third portions 22a, 22b, and 22c of the substrate 21, respectively. The first to third portions 29a to 29c are arranged in the extending direction of the intersection line segment Lx.

  In step S103, the substrate product P is cleaved to form a cleavage plane for the resonator of the group III nitride laser diode. This cleavage is performed by breaking the first portion Pa of the substrate product P, and the cleavage plane extends in the extending direction of the intersection line segment Lx.

  According to this method, since the first portion 22a of the substrate 21 is grown after the third portion 22c, the crystal orientation in the first portion 22a is greater than the crystal orientation in the third portion 22c. It's all there. For this reason, the crystal orientation in the first portion 29a is aligned with the crystal orientation in the third portion 29c. Therefore, the cleavage yield can be improved by causing a break in the first portion Pa to perform cleavage. Further, from another viewpoint, the dislocation density D1 of the first portion 22a of the substrate 21 is smaller than the dislocation density D3 of the third portion 22c. By providing the starting point of cleavage not in the third part Pc but in the first part Pa, cleavage can be caused to reach the third part Pc from the first part Pa through the second part Pb. Although the dislocation density of the substrate 21 is distributed in the cleavage of the substrate 21, the influence of this distribution can be reduced. Therefore, the cleavage yield can be improved by breaking the first portion Pa to perform cleavage.

  The cleavage of the substrate product P will be described with reference to FIG. First, as shown in FIG. 6A, in step S111, a scribing groove 37 is formed on the curved edge of the first portion Pa of the substrate product P. The scribing groove 37 is formed using a scriber 39. As shown in FIG. 6 (b), after aligning the blade 41 with the scribing groove 37 in step S112, cleavage is performed from the first portion Pa to the third portion by breaking the first portion Pa in step S113. Cause to Pc. According to this method, the cleavage groove 37 is formed in the first portion Pa, and cleavage is caused by the break to the first portion Pa, so that the cleavage yield can be improved. As shown in FIG. 6C, the laser bar 43 is formed by cleavage. The laser bar 43 has cleaved surfaces 43a and 43b for laser diode resonators. The cleavage planes 43a and 43b extend in the extending direction of the cross line segment Lx shown in FIG.

  Depending on the direction of inclination of the main surface 21a of the substrate 21, the cleavage planes 43a and 43b can extend in the direction of any one of the a-plane, m-plane, and c-plane orientations of the hexagonal group III nitride. . By cleaving on the a-plane, m-plane, c-plane, etc., a good cleavage yield can be realized.

  As already described, if necessary, in step S102 for producing a substrate product, the back surface 21b of the substrate 21 is polished in step S109. At this time, the thickness of the back-polished substrate can be 60 micrometers or more. When the thickness of the back-polished substrate is too small, handling difficulties such as unintentional cracking occur in the subsequent steps. Also, the thickness of the back-polished substrate can be 150 micrometers or less. When the thickness of the back-polished substrate is too large, the cleavage yield decreases.

  FIG. 7 shows a substrate made by slicing an ingot at an angle of 90 degrees. In the following description, the same reference numerals are given to the same and similar parts as those of the substrate 21 shown in FIG. As shown in FIG. 7A, the ingot 17 is sliced to form a substrate 21 made of hexagonal group III nitride. In this embodiment, a group III nitride laser diode is manufactured on the substrate 21. The substrate 21 has a main surface 21a and a back surface 21b. The main surface 21a and the back surface 21b extend in the direction of a predetermined axis Ax. For example, the surfaces 21a and 21b are substantially parallel to each other. The main surface 21a of the substrate 21 intersects a predetermined plane Sx at an intersection line segment Lx on the main surface 21a. The plane Sx is defined by a reference axis vector VG indicating the direction of the reference axis Gx and a normal vector VN of the main surface 21a. FIG. 7A shows an orthogonal coordinate system S, where the z-axis indicates the direction of the normal vector VN, and the x-axis indicates the directions of the axes Ax and Gx. The y axis is orthogonal to both the normal vector VN and the axis Ax.

  The main surface 21a of the substrate 21 intersects the c plane perpendicular to the c axis of the hexagonal group III nitride. The angle formed between the main surface 21a of the substrate 21 and the plane c is 90 degrees. When the main surface 21a of the substrate 21 forms an angle of 90 degrees with respect to the c-plane of the hexagonal group III nitride, the main surface 21a of the substrate 21 has no polarity. When the angle is 90 degrees, the crystal orientation unevenness caused by the growth time becomes noticeable between one end and the other end of the substrate main surface 21a. Also, the angle formed between the back surface 21b of the substrate 21 and the c plane can be 90 degrees.

  In order to facilitate understanding, reference axes Gx and Ax are provided at the center point of the substrate 21 as shown in FIGS. 7A and 7B. The intersecting line segment Lx passes through the two points 21c and 21d on the opposite edge 21e of the substrate 21 and the center point M of the substrate 21. The substrate 21 includes first to third portions 22a, 22b, and 22c arranged in the extending direction of the cross line segment Lx. The reference axis Gx forms an angle of zero degrees with the main surface 21a of the substrate 21, and the direction of the vector VA (= VG × cos θ, where θ = 0 degrees, so that cos θ = 1) is the first to first directions. The arrangement direction of the third portions 22a to 22c is shown. In the growth of the ingot 17, the first portion 22a is grown after the third portion 22c, and the midpoint M of the intersecting line segment Lx is located in the second portion 22b.

  In the present embodiment, the edge 21e of the main surface 21a of the substrate 21 is defined by a plurality of line segments. In the first portion 22a, the edge 21e of the substrate 21 includes a straight portion, and in the third portion 22c, the edge 21e of the substrate 21 includes a straight portion. The second portion 22b has a stripe shape located between the first portion 22a and the third portion 22c. In one embodiment, when the maximum distance between two points on the edge 21e of the substrate 21 is 5 millimeters, a laser diode can be manufactured using a substrate having a certain size. In the main surface 21a of the substrate 21, the dislocation density D1 of the first portion 22a is smaller than the dislocation density D3 of the third portion 22c, and the midpoint M of the line segment Lx is located in the second portion 22b. For example, the dislocation density (for example, the dislocation density D2 near the midpoint M) of the second portion 22b is smaller than the dislocation density D3, and the dislocation density D1 is smaller than the dislocation density D2. The second portion 22b is divided into fourth and fifth portions 22d and 22e by another line segment Nx orthogonal to the cross line segment Lx at the midpoint M of the cross line segment Lx. The fourth portion 22d is located between the first portion 22a and the fifth portion 22e, and the fifth portion 22e is located between the third portion 22c and the fourth portion 22d. . The dislocation density D1 of the first portion 22a is smaller than the dislocation density D5 of the fifth portion 22e, and the dislocation density D4 of the fourth portion 22d is smaller than the dislocation density D3 of the third portion 22c. The substrate 21 has different dislocation densities in the first, third to fifth portions 22a and 22c to 22e arranged in the direction of the line segment on the main surface 21a of the substrate 21, but provides a good cleavage yield. Is done.

(Example)
Two GaN substrates cut out from the same ingot were prepared. On these GaN substrates, a plurality of epitaxial films for laser diodes were grown by metal organic vapor phase epitaxy to produce epitaxial substrates. Moreover, an anode electrode and a cathode electrode were formed on the epitaxial substrate to produce a substrate product. Referring to FIGS. 8 (a) and 8 (c), a quadrilateral substrate product is shown, with reference numerals according to FIG. 7 (b). One substrate product, as indicated by an arrow CL1 shown in FIG. 8A, is a substrate edge (reference numeral 21c side) composed of crystal regions (reference numerals 22a and 29a) grown in the latter half of the ingot growth. The edge). FIG. 8B shows a laser bar produced by this break. The other substrate product is a substrate edge (reference numeral 21d side) composed of crystal regions (reference numerals 22c and 29c) grown in the first half of the growth of the ingot as indicated by an arrow CL2 shown in FIG. 8C. The edge). FIG. 8D shows a laser bar produced by this break. As shown in FIGS. 8B and 8D, the break in the first portion 22a provides a better cleavage yield than the break in the third portion 22c.

  With reference to FIGS. 9 to 11, manufacturing a substrate from an ingot having several structures will be described. The structure of the substrate that will be described subsequently is formed in any of the first to third portions of the substrate that has already been described.

  Referring to FIG. 9A, an ingot 51 is shown together with a crystal coordinate system CR. The ingot 51 has one end surface 51a and the other end surface 51b. The ingot 51 was grown in the direction of the reference axis Gx from the one end surface 51a to the other end surface 51b. The direction of the reference axis Gx is indicated by a vector VG. The ingot 51 includes first and second regions 51c and 51d extending in the direction of the reference axis Gx from the one end surface 51a to the other end surface 51b. The first and second regions 51c and 51d are adjacent to each other. The defect density D1 of the first region 51c is smaller than the defect density D2 of the second region 51d. In this embodiment, the direction of the growth vector VG is the c-axis direction. The first and second regions 51c and 51d extend in the m-axis direction and are alternately arranged in the a-axis direction.

  As shown in FIG. 9B, the ingot 51 can be sliced along a plane Rx inclined in the direction of the m-axis from the c-axis. The cleavage plane is a-plane. Alternatively, as shown in FIG. 9C, the ingot 51 can be sliced along a plane Rx inclined from the c-axis to the a-axis. The cleavage plane is an m-plane.

FIG. 12A shows a substrate 53 made from the ingot 51 as shown in FIG. 9B. The substrate 53 includes first and second regions 53c and 53d extending from the main surface 53a to the back surface 53b in the direction of the growth vector VG. The first and second regions 53c and 53d are adjacent to each other. The defect density D53c of the first region 53c is smaller than the defect density D53d of the second region 53d. For example, the defect density D53c is, for example, 1 × 10 ⁷ cm ⁻³ or less, and the defect density D53d is, for example, greater than 1 × 10 ⁸ cm ⁻³ . In this embodiment, the direction of the growth vector VG is the c-axis direction, and the angle between the normal vector VN of the principal surface 53a and the growth vector VG is 10 degrees or more and 90 degrees or less. The first and second regions 53c and 53d extend in the m-axis direction and are alternately arranged in the a-axis direction. In the first region 53c, one of the dislocation density on the main surface 53a and the dislocation density on the back surface 53b is larger than the other. By growing the first and second regions 53c and 53d having different dislocations, the dislocation density in the first region 53c is reduced as compared with the dislocation density in the second region 53d. As shown in FIG. 9C, the directions of the first and second regions in the substrate manufactured from the ingot 51 are 90 degrees around the central axis of the substrate 53 shown in FIG. Indicated by rotating only degrees.

  Referring to FIG. 10A, an ingot 55 is shown together with a crystal coordinate system CR. The ingot 55 has one end surface 55a and the other end surface 55b. The ingot 55 was grown in the direction of the reference axis Gx from the one end surface 55a to the other end surface 55b. The direction of the reference axis Gx is indicated by a vector VG. The ingot 55 includes a single first region 55c and a plurality of second regions 55d extending in the direction of the reference axis Gx from the one end surface 55a to the other end surface 55b. The first and second regions 55c and 55d are adjacent to each other. The defect density D1 of the first region 55c is smaller than the defect density D2 of the second region 55d. In this embodiment, the direction of the growth vector VG is the c-axis direction. Each of the second regions 55d is surrounded by the first region 55c.

  As shown in FIG. 10B, the ingot 55 can be sliced along a plane Rx inclined from the c-axis to the m-axis. The cleavage plane is a-plane. Or As shown in FIG. 10C, the ingot 55 can be sliced along a plane Rx inclined from the c-axis to the a-axis. The cleavage plane is an m-plane.

FIG. 12B shows a substrate 57 made from the ingot 55 as shown in FIG. Substrate 57 includes a single first region 57c and a plurality of second regions 57d extending from main surface 57a to back surface 57b in the direction of growth vector VG. The first and second regions 57c and 57d are adjacent to each other. The defect density D57c of the first region 57c is smaller than the defect density D57d of the second region 57d. For example, the defect density D57c is, for example, 1 × 10 ⁷ cm ⁻³ or less, and the defect density D57d is, for example, greater than 1 × 10 ⁸ cm ⁻³ . In this embodiment, the direction of the growth vector VG is the c-axis direction, and the angle between the normal vector VN of the main surface 57a and the growth vector VG is 10 degrees or more and 90 degrees or less. The second regions 57d are arrayed in the m-axis and a-axis directions, and each of the second regions 57d is surrounded by the first region 57c. In the first region 57c, one of the dislocation density on the main surface 57a and the dislocation density on the back surface 57b is larger than the other. By growing the first and second regions 57c and 57d having different dislocations, the dislocation density in the first region 57c is reduced as compared with the dislocation density in the second region 57d. As shown in FIG. 10C, the orientation of the first and second regions 57c and 57d in the substrate manufactured from the ingot 55 is such that the substrate 57 shown in FIG. Shown by rotating around 90 degrees.

Referring to FIG. 11A, an ingot 61 is shown together with a crystal coordinate system CR. The ingot 61 has one end face 61a and the other end face 61b. The ingot 61 was grown in the direction of the reference axis Gx from the one end surface 61a to the other end surface 61b. The direction of the reference axis Gx is indicated by a vector VG. The ingot 61 includes first and second regions 61c and 61d extending in the direction of the reference axis Gx from the one end surface 61a to the other end surface 61b. The first and second regions 61c and 61d are adjacent to each other. The defect density D61c of the first region 61c is smaller than the defect density D61d of the second region 61d. In this embodiment, the direction of the growth vector VG is the c-axis direction. The ingot 61 includes a plurality of regions 61d of dislocation bundles having a dislocation density D61d higher than the surrounding region 61c. For example, the defect density D61c is, for example, 1 × 10 ⁷ cm ⁻³ or less, and the defect density D61d is, for example, greater than 1 × 10 ⁸ cm ⁻³ . The dislocation bundle as a whole extends in a direction from one end surface 61a of the ingot 61 to the other end surface 61b, and is randomly distributed on a plane orthogonal to the growth axis Gx of the ingot 61.

  As shown in FIG. 11B, the ingot 61 can be sliced along a plane Rx inclined from the c-axis to the m-axis. The cleavage plane is a-plane. Or As shown in FIG. 11C, the ingot 61 can be sliced along a plane Rx inclined from the c-axis to the a-axis. The cleavage plane is an m-plane.

  Referring to FIG. 12C, the substrate 63 has a main surface 63a to a back surface 63b. The substrate 63 includes first to third portions 65a, 65b, and 65c arranged in the direction of the intersection line segment Lx, similarly to the structure of the substrate already described. The first to third portions 65a to 65c appear in the first to third front areas 63e, 63f, and 63g of the main surface 63a of the substrate 63, respectively. The first to third portions 65a to 65c appear in the first to third back areas 63h, 63i, and 63j of the back surface 63b, respectively. One of the dislocation density De of the first front area 63e and the dislocation density Dh of the first back area 63h is larger than the other. The substrate 63 includes a plurality of dislocation bundle regions 63d having a dislocation density higher than that of the surrounding region 63c. The dislocation bundle as a whole extends in the direction from the back surface 63b of the substrate 63 toward the main surface 63a, and is randomly distributed on the main surface 63a of the substrate 63.

  In the substrate 63, the dislocation density De of the first front area 63e is smaller than the dislocation density Dh of the first back area 63h. The dislocation density Df of the second front area 63f is smaller than the dislocation density Di of the second back area 63i. The dislocation density Dg of the third front area 63g is smaller than the dislocation density Dj of the third back area 63j. Alternatively, in the substrate 63, the dislocation density Dh of the first back area 63h is smaller than the dislocation density De of the first front area 63e. The dislocation density Di of the second back area 63i is smaller than the dislocation density Df of the second front area 63f. The dislocation density Dj of the third back area 63j is smaller than the dislocation density Dg of the third front area 63g.

  FIG. 13 is a view showing a direction in which a substrate having a nonpolar or almost nonpolar main surface is sliced from an ingot. As already shown with reference to FIG. 7, a striped substrate can be manufactured by slicing an ingot in the vertical direction. The ingot 71 is grown from the one end surface 71a toward the other end surface 71b in the c-axis direction. Referring to FIG. 13A, substrates 73a and 73b having an m-plane principal surface can be produced. Referring to FIG. 13B, the substrates 75a and 75b having the a-plane main surface can be manufactured. Referring to FIG. 13C, substrates 77a and 77b having main surfaces inclined at a desired angle from the m-plane (a-plane) can be produced. The main surfaces of the substrates 77a and 77b also show no polarity.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1 is a drawing showing the main steps in a method for producing a group III nitride laser diode according to the present embodiment. FIG. 2 is a drawing showing substrate preparation in step S101. FIG. 3 is a drawing showing the preparation of the substrate in step S101. FIG. 4 is a drawing showing a process for producing an epitaxial substrate. FIG. 5 is a diagram showing a process of forming a substrate line product by forming an electrode on an epitaxial substrate. FIG. 6 is a diagram showing a process of cleaving the substrate product P. FIG. 7 shows a substrate made by slicing an ingot with a 90 degree inclination. FIG. 8 is a diagram showing an example of cleavage. FIG. 9 is a drawing showing an ingot for producing a stripe substrate. FIG. 10 is a drawing showing an ingot for producing a dot substrate. FIG. 11 is a drawing showing an ingot for producing a substrate including a dislocation bundle. FIG. 12 is a view showing a substrate manufactured from the ingots of FIGS. 9 to 11. FIG. 13 is a drawing showing a substrate having a main surface showing nonpolarity and almost nonpolarity.

Explanation of symbols

E ... Epitaxial substrate, 10a, 10b ... Growth furnace, 11 ... Growth substrate, 13 ... Crystal, 15 ... Product, 17 ... Ingot, Gx ... Reference axis, VG ... Vector,
17a, 17b ... Ingot end face, 21 ... Substrate, 21a ... Substrate main surface, 21b ... Substrate back surface, 21e ... Substrate edge, Sx ... Planar, Lx ... Cross line segment, VN ... Normal vector, Ax ... Axis, 22a 22b, 22c, 22d, 22e ... substrate portion, 23 ... first semiconductor region, 25 ... light emitting layer, 27 ... second semiconductor region, 29 ... laminate, 31 ... insulating film, 31a ... opening in insulating film 33, 35 ... Electrodes, P ... Substrate product, Pa, Pb, Pc ... Substrate product part, 29a, 29b, 29c ... Laminate part, 37 ... Scratch groove, 39 ... Scriber, 41 ... Blade, 43 ... Laser bar, 43a, 43b ... Cleaved surface, 51 ... Ingot, 51a, 51b ... End face of ingot, 51c, 51d ... First and second regions, 53 ... Substrate, 53a ... Substrate main surface, 53b ... Back surface, 53 53d, first and second regions, D53c, D53d, defect density, 55, ingot, 55a, 55b, end surface of the ingot, 55c, 55d, first and second regions, 57, substrate, 57a, substrate. Main surface, 57b ... back of substrate, 57c, 57d ... first and second regions, D57c, D57d ... defect density, 61 ... ingot, 61a, 61b ... end surface of ingot, 61c, 61d ... first and second regions , 63 ... substrate, 63a ... substrate main surface, 63b ... substrate back surface, 65a, 65b, 65c ... first to third parts of the substrate, 63e, 63f, 63g ... first to third front areas, 63h, 63i , 63j ... first to third back areas, 71 ... ingots, 71a, 71b ... end faces of the ingot, 73a, 73b ... substrates having an m-plane principal surface, 75a, 75b ... substrates having an a-plane principal surface. A substrate having 77a, 77b ... the non-polar main surface

Claims (20)

A method of fabricating a group III nitride laser diode comprising:
A step of preparing a substrate made of a hexagonal group III nitride formed by slicing an ingot having an end surface and the other end surface and grown in the direction of a reference axis from the one end surface to the other end surface;
Producing an epitaxial substrate including a laminate formed on the main surface of the substrate, and producing a substrate product including an anode electrode and a cathode electrode formed on the epitaxial substrate;
Cleaving the substrate product to form a cleavage plane for the resonator of the laser diode, and
The stacked body includes an n-type group III nitride semiconductor layer, an active layer, and a p-type group III nitride semiconductor layer,
The main surface of the substrate intersects a c plane perpendicular to the c axis of the hexagonal group III nitride,
The main surface of the substrate intersects a predetermined plane defined by a normal vector of the main surface of the substrate and a reference axis vector indicating the direction of the reference axis at an intersection line segment on the main surface. And
The substrate product includes first to third portions arranged in an extending direction of the intersecting line segment, and the substrate is arranged in the extending direction of the intersecting line segment. The laminate includes first to third portions respectively disposed on the first to third portions of the substrate, and the first portion of the substrate product is the laminate. The first part of the body and the first part of the substrate, and the second part of the substrate product comprises the second part of the stack and the second part of the substrate. The third portion of the substrate product includes the third portion of the stack and the third portion of the substrate;
In the growth of the ingot, the first portion of the substrate is grown after the third portion of the substrate, and the midpoint of the intersecting line segment is the second portion of the substrate and the second portion of the substrate. Located in the boundary with one part or in the second part of the substrate, the cleavage is carried out by breaking the first part of the substrate product,
The cleaved surface is formed by extending a crack caused by the break in an extending direction of the intersecting line segment. An angle formed between the main surface of the substrate and the c plane is 10 degrees or more and 90 degrees or less,
2. The method according to claim 1, wherein an angle formed between the back surface of the substrate and the c-plane is 10 degrees or more and 90 degrees or less.   The method according to claim 1 or 2, wherein, in the step of producing the substrate product, the back surface of the substrate is polished to form a back-polished substrate.   The method according to claim 3, wherein the thickness of the back-polished substrate is 60 micrometers or more and 150 micrometers or less.   The method according to any one of claims 1 to 4, wherein the thickness of the ingot is 5 millimeters or more. The substrate includes first and second regions extending in the direction of the reference axis from the main surface to the back surface of the substrate;
The first and second regions are adjacent to each other;
The defect density of the first region is smaller than the defect density of the second region,
6. The method according to claim 1, wherein, in the first region, one of a dislocation density on the main surface and a dislocation density on the back surface is larger than the other. 7.   In each of the first to third portions of the substrate, one of the dislocation density of the main surface of the substrate and the dislocation density of the back surface of the substrate is larger than the other. 6. The method according to any one of 5 above.   The method according to claim 1, wherein the reference axis extends in a c-axis direction of the hexagonal group III nitride.   The method according to claim 1, wherein the reference axis extends in the direction of the m-axis of the hexagonal group III nitride.   The method according to claim 1, wherein the reference axis extends in a direction of an a-axis of the hexagonal group III nitride. A method of fabricating a group III nitride laser diode comprising:
Having a main surface and a back surface extending in a direction of a predetermined axis, and preparing a substrate made of hexagonal group III nitride; and
Producing an epitaxial substrate including a laminate formed on the main surface of the substrate, and producing a substrate product including an anode electrode and a cathode electrode formed on the epitaxial substrate;
Cleaving the substrate product to form a cleavage plane for a resonator of the III-nitride laser diode,
The stacked body includes an n-type group III nitride semiconductor layer, an active layer, and a p-type group III nitride semiconductor layer,
The main surface of the substrate intersects a c plane perpendicular to the c axis of the hexagonal group III nitride,
The principal surface of the substrate intersects a predetermined plane defined by a normal vector of the principal surface of the substrate and a reference axis vector indicating a direction of a reference axis at an intersecting line segment on the principal surface. ,
The reference axis is any one of an a axis, an m axis, and a c axis,
The direction of the intersecting line segment coincides with the direction of the predetermined axis,
The substrate product includes first to third portions arranged in an extending direction of the intersecting line segment, and the substrate is arranged in the extending direction of the intersecting line segment. The laminate includes first to third portions respectively disposed on the first to third portions of the substrate, and the first portion of the substrate product is the laminate. The first part of the body and the first part of the substrate, the second part of the substrate product comprising the second part of the stack and the second part of the substrate. The third portion of the substrate product includes the third portion of the stack and the third portion of the substrate;
In the main surface of the substrate, the dislocation density of the first portion of the substrate is smaller than the dislocation density of the third portion of the substrate, and the midpoint of the line segment is the second portion of the substrate. Located in the boundary with the first part or in the second part of the substrate,
The cleavage is performed by breaking the first portion of the substrate product;
The cleaved surface is formed by a crack caused by the break extending in a direction of the predetermined axis.   The method according to claim 11, wherein an angle formed between the principal surface of the substrate and the c plane is 10 degrees or more and 90 degrees or less. The first to third portions of the substrate respectively appear in first to third surface areas of the main surface of the substrate;
The first to third portions of the substrate appear in first to third back areas on the back surface of the substrate, respectively.
13. The method according to claim 11 or 12, wherein one of the dislocation density in the first front area and the dislocation density in the first back area is greater than the other. The dislocation density of the first front area is smaller than the dislocation density of the first back area,
The dislocation density of the second front area is smaller than the dislocation density of the second back area,
14. The method of claim 13, wherein the dislocation density in the third front area is less than the dislocation density in the third back area. The dislocation density of the first back area is smaller than the dislocation density of the first front area,
The dislocation density of the second back area is smaller than the dislocation density of the second front area,
14. The method of claim 13, wherein the dislocation density in the third back area is less than the dislocation density in the third front area.   The method according to any one of claims 11 to 15, wherein the maximum value of the distance between two points on the edge of the substrate is 5 millimeters or more. The first portion of the substrate product includes an edge of the major surface of the substrate product;
In forming the cleavage of the substrate product, after forming a scribing groove at the edge of the first portion of the substrate product, the cleavage is caused by the break of the first portion of the substrate product. 17. A method as claimed in any one of claims 11 to 16, characterized by causing from the first part of the substrate product to the third part. The second portion of the substrate is divided into fourth and fifth portions by another line segment orthogonal to the line segment at the midpoint of the line segment;
The fourth portion is located between the first portion and the fifth portion of the substrate;
The fifth portion is located between the third portion and the fourth portion of the substrate;
In the main surface of the substrate, the dislocation density of the first portion of the substrate is smaller than the dislocation density of the fifth portion, and the dislocation density of the fourth portion is the dislocation density of the third portion of the substrate. The method according to claim 11, wherein the method is smaller than the density. In the step of producing the substrate product, the back surface of the substrate is polished to form a back-polished substrate;
The method according to any one of claims 11 to 18, wherein the thickness of the back-polished substrate is 60 micrometers or more and 150 micrometers or less.   The method according to any one of claims 11 to 19, wherein the cleavage plane is any one of a-plane, m-plane and c-plane of the hexagonal group III nitride.