Manufacturing method for light-emitting element

Abstract

To provide a manufacturing method for a light-emitting element whose reliability decrease can be reduced.SOLUTION: A manufacturing method for a light-emitting element includes the steps of: preparing a wafer including a sapphire substrate having a first surface and a second surface on a side opposite to the first surface, and a semiconductor layer disposed on the second surface; forming a modification part inside the sapphire substrate by irradiating the inside of the sapphire substrate with laser light from the first surface side through an objective lens having an incidence surface and an emission surface existing on a side opposite to the incidence surface and facing the first surface; and separating the wafer into a plurality of light-emitting elements after the step of forming the modification part. The step of forming the modification part includes a step of forming a first modification part at a position of a first distance from the first surface. In the step of forming the first modification part, the laser light with a divergence angle of less than 0 mrad is incident into the incidence surface of the objective lens.SELECTED DRAWING: Figure 3B

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a light-emitting element.

Background Art

[0002] Patent Document 1 discloses that a sapphire substrate having a GaN layer is ablated by irradiating a laser. Further, Patent Document 1 discloses that a laser is focused on a substrate using a beam focus lens. Patent Document 2 discloses a method of dicing a wafer, in which a laser beam is condensed inside a substrate to form a modified region, and the wafer is divided into a plurality of semiconductor chips by cracks extending from this modified region.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a method for manufacturing a light-emitting element that can reduce a decrease in reliability.

Means for Solving the Problems

[0005] According to one aspect of the present invention, a method for manufacturing a light-emitting element includes a step of preparing a wafer having a sapphire substrate having a first surface and a second surface located on the opposite side of the first surface, and a semiconductor layer disposed on the second surface, a step of irradiating laser light from the first surface side into the sapphire substrate through an objective lens having an incident surface and an exit surface located on the opposite side of the incident surface and facing the first surface to form a modified portion inside the sapphire substrate, and a step of separating the wafer into a plurality of light-emitting elements after the step of forming the modified portion. The step of forming the modified portion includes a step of forming a first modified portion at a position where the distance from the first surface is a first distance. In the step of forming the first modified portion, the laser light having a divergence angle smaller than 0 mrad is incident on the incident surface of the objective lens.

Effect of the Invention

[0006] According to the present invention, it is possible to provide a method for manufacturing a light-emitting element capable of reducing a decrease in reliability.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5A

Figure 5B

Figure 5C

Figure 6

Figure 7

Figure 8A

Figure 8B

Figure 9A

Figure 9B

Mode for Carrying Out the Invention

[0008] The method for manufacturing a light-emitting element according to the embodiment includes a step of preparing a wafer having a sapphire substrate and a semiconductor layer, a step of forming a modified portion inside the sapphire substrate, and a step of separating the wafer into a plurality of light-emitting elements. Hereinafter, each step will be described.

[0009] [Step of Preparing a Wafer] FIG. 1 is a schematic top view of a wafer W. In FIG. 1, the direction parallel to the a-axis of the sapphire substrate 10 is defined as the first direction Y, and the direction parallel to the m-axis of the sapphire substrate 10 is defined as the second direction X. The direction orthogonal to the first direction Y and the second direction X is defined as the third direction Z. The orientation flat OF of the sapphire substrate 10 is parallel to the a-plane of the sapphire substrate 10.

[0010] FIG. 2 is a schematic cross-sectional view partially showing an XZ cross-section of the wafer W. Note that the YZ cross-section of the wafer W also has the same cross-sectional structure as the XZ cross-section. The sapphire substrate 10 has a first surface 11 and a second surface 12 located on the opposite side of the first surface 11 in the third direction Z. The first surface 11 is the c-plane of the sapphire substrate 10. The thickness of the sapphire substrate 10 is, for example, 30 μm or more and 300 μm or less.

[0011] The semiconductor layer 20 is disposed on the second surface 12. Note that the second surface 12 may be inclined within a range in which the semiconductor layer 20 can be formed with good crystallinity with respect to the c-plane of the sapphire substrate 10. In addition to the semiconductor layer 20, a film for protecting the semiconductor layer 20 or the like may be disposed on the second surface 12.

[0012] The semiconductor layer 20 contains, for example, In x Al y Ga 1-x-y N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, x + y ≦ 1). The semiconductor layer 20 includes, in order from the second surface 12 side, an n-side semiconductor layer, an active layer that emits light, and a p-side semiconductor layer. The peak wavelength of the light emitted by the active layer is, for example, 280 nm or more and 650 nm or less. The peak wavelength of the light emitted by the active layer may be a wavelength shorter than 280 nm or a wavelength longer than 650 nm.

[0013] The second surface 12 has a dicing region D. As shown in FIG. 1, the dicing region D is formed in a lattice pattern along the first direction Y and the second direction X. The dicing region D corresponds to a region where laser light is scanned when a modified portion described later is formed inside the sapphire substrate 10. The wafer W is diced in the dicing region D as described later. The semiconductor layer 20 has a plurality of light-emitting portions 30. Each of the plurality of light-emitting portions 30 has an n-side semiconductor layer, an active layer, and a p-side semiconductor layer. On the second surface 12 of the sapphire substrate 10, a plurality of light-emitting portions 30 are arranged, and no light-emitting portion 30 is arranged in the dicing region D. In the example shown in FIG. 2, the dicing region D is exposed from the semiconductor layer 20. Note that, in the dicing region D, a part of the semiconductor layer 20 may be arranged. For example, an n-side semiconductor layer may be arranged in the dicing region D. In a top view, the width of the dicing region D in the first direction Y or the width in the second direction X is set to a width such that the influence of dicing of the wafer W does not reach the light-emitting portion 30. For example, the width of the dicing region D in the first direction Y or the width in the second direction X is 5 μm or more and 50 μm or less. Note that a top view means observing the wafer W from the first surface 11 or the second surface 12. In a top view, the light-emitting portion 30 is, for example, rectangular. When the light-emitting portion 30 is rectangular in a top view, the length of one side is, for example, 50 μm or more and 1000 μm or less.

[0014] [Step of forming a modified portion] Laser light is irradiated into the sapphire substrate 10 from the first surface 11 side to form a modified portion inside the sapphire substrate 10. The laser light is emitted, for example, in a pulsed manner. The pulse width of the laser light is set to, for example, 100 fsec or more and 1000 psec or less. As a laser light source that emits laser light, for example, a Nd:YAG laser, a titanium sapphire laser, a Nd:YVO 4 laser, or a Nd:YLF laser or the like is used. The wavelength of the laser light is a wavelength of light that passes through the sapphire substrate 10. The laser light has a peak wavelength, for example, in the range of 500 nm or more and 1200 nm or less.

[0015] As shown in FIG. 3B, the step of forming the modified portion includes a step of forming a first modified portion R1 at a position where the distance from the first surface 11 is the first distance d1. The first distance d1 is the shortest distance from the first surface 11 to the center of the first modified portion R1 in a cross-sectional view of the sapphire substrate 10. The first distance d1 is, for example, 10 μm or more and 150 μm or less, preferably 80 μm or more and 140 μm or less.

[0016] The step of forming the modified portion includes a step of scanning a laser beam along the first direction Y. As a result, as shown in FIG. 3A, a plurality of first modified portions R1 are formed along the first direction Y. As shown in FIG. 3B, the plurality of first modified portions R1 formed along the first direction Y are located above the dicing region D in a cross-sectional view of the sapphire substrate 10.

[0017] The laser beam is focused at the position of the first distance d1 inside the sapphire substrate 10, and the first modified portion R1 is formed by the concentration of the energy of the laser beam at that position. Physical properties such as the density, refractive index, and mechanical strength of the modified portion including the first modified portion R1 and the second modified portion R2 described later are different from those of the unmodified portion located around the modified portion. The unmodified portion is a portion of the sapphire substrate 10 that has not been irradiated with the laser beam. Also, for example, the modified portion is a portion with lower light transmissivity than the unmodified portion. Cracks occur from the modified portion. Cracks extending at least toward the first surface 11 from the modified portion occur inside the sapphire substrate 10. These cracks serve as the starting points for dicing the wafer W described later.

[0018] As shown in FIG. 3A, the plurality of first modified portions R1 are formed apart from each other along the first direction Y. A part of the first modified portions R1 adjacent to each other in the first direction Y may be formed in contact with each other, or the plurality of first modified portions R1 may be formed overlapping each other.

[0019] Further, the step of forming the modified portion includes a step of scanning a laser beam along the second direction X. As a result, a plurality of first modified portions R1 are formed along the second direction X at positions where the distance from the first surface 11 inside the sapphire substrate 10 is the first distance d1. The plurality of first modified portions R1 formed along the second direction X are also located above the dicing region D in a cross-sectional view of the sapphire substrate 10.

[0020] The laser beam can be irradiated onto the sapphire substrate 10 using the optical system 100 shown in FIG. 4.

[0021] The optical system 100 has at least an objective lens 90. The objective lens 90 has an incident surface 91 on which the laser beam L is incident and an exit surface 92 located on the opposite side of the incident surface 91 from which the laser beam L exits. The exit surface 92 faces the first surface 11 of the sapphire substrate 10. The laser beam L is irradiated into the sapphire substrate 10 from the first surface 11 side through the objective lens 90. The objective lens 90 is, for example, a single lens.

[0022] In addition to the objective lens 90, the optical system 100 can have a concave lens 70, a convex lens 80, a first mirror 61, a second mirror 62, and a third mirror 63. The concave lens 70 has a concave surface and a flat surface located on the opposite side of the concave surface. The convex lens 80 has a convex surface and a flat surface located on the opposite side of the convex surface. The flat surface of the convex lens 80 faces the flat surface of the concave lens 70.

[0023] The laser beam L emitted from the laser light source is redirected by reflection at the first mirror 61 and the second mirror 62, enters the concave surface of the concave lens 70, and exits from the flat surface of the concave lens 70. The flat surface of the concave lens 70 is substantially perpendicular to the optical axis of the laser beam L. The laser beam L exiting from the flat surface of the concave lens 70 enters the flat surface of the convex lens 80 and exits from the convex surface of the convex lens 80. The flat surface of the convex lens 80 is substantially perpendicular to the optical axis of the laser beam L. The laser beam exiting from the convex surface of the convex lens 80 is redirected by reflection at the third mirror 63 and enters the entrance surface 91 of the objective lens 90. The entrance surface 91 of the objective lens 90 is substantially perpendicular to the optical axis of the laser beam L. The laser beam L converged within the objective lens 90 exits from the exit surface 92 and irradiates the inside of the sapphire substrate 10.

[0024] With respect to the entrance surface 91 of the objective lens 90, the laser beam L can enter as a diverging beam, a parallel beam, or a converging beam. The diverging beam has a positive value (+θ) for the divergence angle described later. The parallel beam has a divergence angle of 0 mrad described later. The converging beam has a negative value (-θ) for the divergence angle described later.

[0025] In FIGS. 5A to 5C, the central axis C of the objective lens 90 is indicated by a dashed line. The central axis C passes through the center of the entrance surface 91 and the center of the exit surface 92. In FIGS. 5A and 5C, the ray of the laser beam L that is farthest from the central axis C among the rays incident on the entrance surface 91 is indicated by a solid line. Also, in FIGS. 5A and 5C, the first reference line RL1 is indicated by a dashed line. The first reference line RL1 is parallel to the central axis C and passes through the position where the ray of the laser beam L that is farthest from the central axis C enters the entrance surface 91.

[0026] As shown in FIG. 5A, the laser beam L can enter the entrance surface 91 of the objective lens 90 as a diverging beam. Alternatively, as shown in FIG. 5B, the laser beam L can enter the entrance surface 91 of the objective lens 90 as a parallel beam parallel to the central axis C. Alternatively, as shown in FIG. 5C, the laser beam L can enter the entrance surface 91 of the objective lens 90 as a converging beam.

[0027] The shape of the laser beam L incident on the incident surface 91 can be approximated as a part of a cone with the optical axis aligned with the central axis C of the objective lens 90. The divergence angle (mrad) representing the degree of divergence of the laser beam L is expressed as the angle between a vector extending along the optical axis (central axis C) from the apex of the cone and a vector extending along the side surface of the cone from the apex of the cone. The side surface of the cone corresponds to the ray of the laser beam L that is farthest from the central axis C.

[0028] As shown in FIG. 5B, when the laser beam L is incident on the incident surface 91 as parallel light, the divergence angle is 0 mrad. The divergence angle of the laser beam L incident on the incident surface 91 as the divergent light shown in FIG. 5A or the convergent light shown in FIG. 5C can also be expressed as the angle between the ray of the laser beam L that is farthest from the central axis C and the first reference line RL1. As shown in FIG. 5A, in the laser beam L before it is incident on the incident surface 91, when the ray of the laser beam L that is farthest from the central axis C moves away from the central axis C as the laser beam L approaches the incident surface 91, the divergence angle is represented by a positive value (+θ) as the angle between the first reference line RL1 and the ray of the laser beam L that is farthest from the central axis C. As shown in FIG. 5C, in the laser beam L before it is incident on the incident surface 91, when the ray of the laser beam L that is farthest from the central axis C approaches the central axis C as the laser beam L approaches the incident surface 91, the divergence angle is represented by a negative value (−θ) as the angle between the first reference line RL1 and the ray of the laser beam L that is farthest from the central axis C.

[0029] In the above-described optical system 100, by changing the distance between the convex lens 80 and the concave lens 70, the laser beam L emitted from the convex lens 80 can be made into divergent light, parallel light, or convergent light. As shown in FIG. 6(b), the position of the concave lens 70 with respect to the convex lens 80 when the laser beam L emitted from the convex lens 80 is parallel light is represented by the second reference line RL2. As shown in FIG. 6(a), when the concave lens 70 approaches the convex lens 80 more than the second reference line RL2, the laser beam L emitted from the convex lens 80 can be made into divergent light. As shown in FIG. 6(c), when the concave lens 70 moves away from the convex lens 80 farther than the second reference line RL2, the laser beam L emitted from the convex lens 80 can be converged.

[0030] When condensing a laser beam into the sapphire substrate 10 from the first surface 11 side of the sapphire substrate 10, the semiconductor layer 20 formed on the second surface 12 of the sapphire substrate 10 may be damaged by being affected by the laser beam that does not contribute to the formation of the modified portion among the laser beams. The damaged region in the semiconductor layer 20 may cause a leakage current and may reduce the reliability of the light-emitting element. For example, in a relatively thin sapphire substrate 10 with a thickness of 300 μm or less, the laser beam that does not contribute to the formation of the modified portion among the laser beams easily affects the semiconductor layer 20.

[0031] According to the present embodiment, in the step of forming the first modified portion R1, as shown in FIG. 5C, the laser beam L (converging light) having a divergence angle smaller than 0 mrad (-θ) is made incident on the incident surface 91 of the objective lens 90. Thereby, the energy of the laser beam for forming the modified portion inside the sapphire substrate 10 can be made lower than the case where the diverging light or the parallel light is made incident on the incident surface 91 of the objective lens 90. In other words, when the laser beam is made incident on the incident surface 91 of the objective lens 90 as converging light, the threshold value of the energy of the laser beam necessary for forming the modified portion can be made lower than the case where the laser beam is made incident on the incident surface 91 of the objective lens 90 as diverging light or parallel light. The fact that the modified portion is formed with lower laser beam energy means that the absorption efficiency of the laser beam inside the sapphire substrate 10 is improved, the laser beam energy is efficiently used for forming the modified portion, and it can be said that the laser beam that does not contribute to the formation of the modified portion is reduced. Thereby, damage to the semiconductor layer 20 caused by the laser beam that does not contribute to the formation of the modified portion can be reduced, and a decrease in the reliability of the light-emitting element can be reduced.

[0032] FIG. 7 is a graph showing the relationship between the divergence angle of the laser beam and the energy of the laser beam. The conditions of the divergence angle and the energy of the laser beam were changed, and the energy of the laser beam at which a modified portion was formed when irradiated from the first surface 11 side into the sapphire substrate 10 through the objective lens 90 was measured. The horizontal axis represents the divergence angle (mrad) of the laser beam incident on the incident surface 91 of the objective lens 90. The vertical axis represents the energy of the laser beam at which the modified portion is formed.

[0033] In conditions a to d, the positions where the modified portions are formed in the sapphire substrate 10 are different. In condition a, the modified portion was formed at a position 32 μm from the first surface 11. In condition b, the modified portion was formed at a position 40 μm from the first surface 11. In condition c, the modified portion was formed at a position 52 μm from the first surface 11. In condition d, the modified portion was formed at a position 80 μm from the first surface 11. In each of conditions a to d, the pulse width of the laser beam was 5 ps and the scanning speed of the laser light was 300 mm / s. In each of conditions a to d, the energy values of the laser beam when the modified portions were formed at divergence angles of +0.08, -0.28, -0.46, -0.7, and -1.22 were measured. In conditions a to d, the energy of the laser beam was changed by 0.025 μJ each, and the energy value of the laser beam when the modified portion was formed was measured.

[0034] From the results shown in FIG. 7, it can be seen that when a converging beam with a divergence angle smaller than 0 mrad is incident on the incident surface 91 of the objective lens 90, the minimum value of the energy of the laser beam required for forming the modified portion can be made lower than the case where a diverging beam with a divergence angle larger than 0 mrad or a parallel beam with a divergence angle of 0 mrad is incident on the incident surface 91 of the objective lens 90. Also, as the divergence angle becomes smaller than 0 mrad, there is a tendency that the minimum value of the energy of the laser beam required for forming the modified portion can be made lower. Furthermore, regarding the position where the modified portion is formed, as the distance from the first surface 11 increases, the decrease width of the minimum value of the energy of the laser beam required for forming the modified portion tends to increase by reducing the divergence angle.

[0035] In the step of forming the modified portion in the method for manufacturing a light-emitting element according to the embodiment, as shown in FIG. 3B, the step of forming a second modified portion R2 at a position where the distance from the first surface 11 is a second distance d2 shorter than the first distance d1 can be further included. The second distance d2 is the shortest distance from the first surface 11 to the center of the second modified portion R2 in a cross-sectional view of the sapphire substrate 10. The second distance d2 is, for example, 5 μm or more and 130 μm or less, preferably 30 μm or more and 75 μm or less. The step of forming the second modified portion R2 is performed after the step of forming the first modified portion R1. The second modified portion R2 is located between the first surface 11 and the first modified portion R1 in the third direction Z.

[0036] In the step of forming the second modified portion R2, laser light is scanned along the first direction Y. As a result, as shown in FIG. 3A, a plurality of second modified portions R2 are formed along the first direction Y. The plurality of second modified portions R2 are formed apart from each other along the first direction Y. A part of the second modified portions R2 adjacent to each other in the first direction Y may be in contact with each other, or the plurality of second modified portions R2 may be formed overlapping each other.

[0037] Cracks extending at least toward the first surface 11 are formed inside the sapphire substrate 10 from the second modified portion R2. Further, the cracks extending from the second modified portion R2 can be connected to the cracks extending from the first modified portion R1. Thereby, compared with the case where only the first modified portion R1 is formed, the dicing of the wafer W becomes easier in the step of dicing the wafer W described later.

[0038] Here, the smaller the divergence angle of the laser light incident on the incident surface 91 of the objective lens 90, the more likely the cracks extending from the modified portion formed on the sapphire substrate 10 will meander. Therefore, in the step of forming the second modified portion R2, it is preferable to make the divergence angle of the laser light incident on the incident surface 91 of the objective lens 90 larger than the divergence angle of the laser light incident on the incident surface 91 of the objective lens 90 in the step of forming the first modified portion R1. In this case, in the step of forming the second modified portion R2, it is preferable to use laser light having a divergence angle of 0 mrad or less, that is, parallel light or convergent light, as the laser light incident on the incident surface 91 of the objective lens 90. Thereby, in the step of forming the second modified portion R2, while reducing the laser light that does not contribute to the formation of the modified portion among the laser light, the meandering of the cracks extending from the second modified portion R2 can be reduced. The cracks extending from the second modified portion R2 formed at a position close to the first surface 11 are more likely to affect the shape of the side surface of the singulated light-emitting element after the wafer W is cleaved than the cracks extending from the first modified portion R1. By reducing the meandering of such cracks extending from the second modified portion R2, the deterioration of the shape of the side surface of the light-emitting element can be reduced.

[0039] The first modified portion R1 is formed by condensing the laser light at a position closer to the second surface 12 on which the semiconductor layer 20 is disposed than the condensing position of the laser light for forming the second modified portion R2. Therefore, the laser light that does not contribute to the formation of the modified portion among the laser light when forming the first modified portion R1 is more likely to affect the semiconductor layer 20 than the laser light that does not contribute to the formation of the modified portion among the laser light when forming the second modified portion R2. Therefore, it is preferable to make the divergence angle of the laser light incident on the incident surface 91 of the objective lens 90 in the step of forming the first modified portion R1 smaller than the divergence angle of the laser light incident on the incident surface 91 of the objective lens 90 in the step of forming the second modified portion R2. Thereby, the damage to the semiconductor layer 20 caused by the laser light that does not contribute to the formation of the modified portion among the laser light when forming the first modified portion R1 can be reduced.

[0040] Cracks extending from the first modified portion R1 formed along the first direction Y parallel to the a-axis of the sapphire substrate 10 tend to extend in a direction inclined with respect to the third direction Z in the XZ cross-sectional view of the sapphire substrate 10. Therefore, if the first modified portion R1 is formed above the dicing region D in the XZ cross-sectional view of the sapphire substrate 10, there is a possibility that cracks extending obliquely from the first modified portion R1 toward the second surface 12 may reach the semiconductor layer 20.

[0041] Therefore, in the step of forming a plurality of first modified portions R1 along the first direction Y (a-axis direction), as shown in FIG. 8A, it is preferable to form the plurality of first modified portions R1 at positions shifted in the second direction X from the virtual line VL located in the dicing region D. The virtual line VL extends in the first direction Y and is located between two adjacent light-emitting portions 30 in the second direction X. The distances between the virtual line VL and two adjacent light-emitting portions 30 in the second direction X are equal. Thereby, in the XZ cross-sectional view shown in FIG. 8B, it is possible to make it difficult for the crack cr extending from the first modified portion R1 toward the second surface 12 to reach the semiconductor layer 20. For example, the first modified portion R1 is formed at a position shifted in the second direction X from the virtual line VL so as not to overlap the light-emitting portion 30 in the top view. In the cross-section (XZ cross-section) perpendicular to the a-axis and parallel to the m-axis, as shown in FIG. 8B, since the crack extends obliquely downward to the right from the first modified portion R1 toward the second surface 12, the first modified portion R1 is formed at a position shifted to the left from the virtual line VL. In the cross-section (YZ cross-section) perpendicular to the m-axis and parallel to the a-axis, cracks tend to extend straight up and down from the first modified portion R1.

[0042] By scanning the laser beam in the first direction Y (a-axis direction) at a position shifted from the virtual line VL in the second direction X, a plurality of first modified portions R1 can be formed at positions shifted from the virtual line VL in the second direction X. In this case, the condensing region of the laser beam inside the sapphire substrate 10 may be located above the semiconductor layer 20 in a top view. Therefore, the divergence angle of the laser beam incident on the incident surface 91 of the objective lens 90 when forming the first modified portion R1 by scanning the laser beam in the a-axis direction is preferably smaller than the divergence angle of the laser beam incident on the incident surface 91 of the objective lens 90 when forming the first modified portion R1 by scanning the laser beam in the m-axis direction. Thereby, the laser beam that does not contribute to the formation of the modified portion among the laser beams condensed in the region above the semiconductor layer 20 can be reduced, and damage to the semiconductor layer 20 can be reduced. On the other hand, as described above, when the divergence angle of the laser beam incident on the incident surface 91 of the objective lens 90 is reduced, the cracks extending from the modified portion tend to meander easily. Therefore, regarding the divergence angle of the laser beam incident on the incident surface 91 of the objective lens 90 when forming the first modified portion R1 by scanning the laser beam in the m-axis direction, by making it larger than the divergence angle of the laser beam incident on the incident surface 91 of the objective lens 90 when forming the first modified portion R1 by scanning the laser beam in the a-axis direction, deterioration of the shape of the side surface of the light-emitting element after the wafer W is cleaved can be reduced.

[0043] The step of forming the modified portion may include a step of forming a plurality of first modified portions R1 along the first direction Y (a-axis direction), a step of forming a plurality of second modified portions R2 along the first direction Y (a-axis direction), a step of forming a plurality of first modified portions R1 along the second direction X (m-axis direction), and a step of forming a plurality of second modified portions R2 along the second direction X (m-axis direction).

[0044] In the step of forming a plurality of first modified portions R1 along the first direction Y (a-axis direction), the divergence angle of the laser beam incident on the incident surface 91 of the objective lens 90 is defined as the first divergence angle. In the step of forming a plurality of first modified portions R1 along the second direction X (m-axis direction), the divergence angle of the laser beam incident on the incident surface 91 of the objective lens 90 is defined as the second divergence angle. In the step of forming a plurality of second modification portions R2 along the first direction Y (a-axis direction), the divergence angle of the laser beam incident on the incident surface 91 of the objective lens 90 is defined as the third divergence angle. In the step of forming a plurality of second modification portions R2 along the second direction X (m-axis direction), the divergence angle of the laser beam incident on the incident surface 91 of the objective lens 90 is defined as the fourth divergence angle.

[0045] As described above, it is preferable that the first divergence angle when forming the first modification portion R1 along the a-axis direction is smaller than the second divergence angle when forming the first modification portion R1 along the m-axis direction. When forming the second modification portion R2, similar to the first modification portion R1, it is preferable that the third divergence angle when forming the second modification portion R2 along the a-axis direction is smaller than the fourth divergence angle when forming the second modification portion R2 along the m-axis direction. By doing so, while reducing the damage to the semiconductor layer 20, the deterioration of the shape of the side surface of the light-emitting element can be reduced.

[0046] Also, as described above, the first divergence angle and the second divergence angle when forming the first modification portion R1 closer to the second surface 12 on which the semiconductor layer 20 is disposed than the second modification portion R2 are preferably smaller than the third divergence angle and the fourth divergence angle when forming the second modification portion R2.

[0047] Summarizing the above, it is preferable that the second divergence angle is larger than the first divergence angle, the third divergence angle is larger than the second divergence angle, and the fourth divergence angle is larger than the third divergence angle. By doing so, while reducing the damage to the semiconductor layer 20, the deterioration of the shape of the side surface of the light-emitting element can be reduced.

[0048] [Step of separating the wafer into a plurality of light-emitting elements] After the step of forming the modified portion by irradiating the laser light as described above, the wafer W is diced. For example, the sapphire substrate 10 is pressed from the first surface 11 side with a pressing member. Alternatively, the sapphire substrate 10 may be pressed from the second surface 12 side with a pressing member. The pressing member is, for example, a blade-shaped member extending along the dicing region D. The sapphire substrate 10 receiving the pressing force of the pressing member from the first surface 11 side is diced starting from the crack extending from the modified portion.

[0049] For example, first, the wafer W is diced along the dicing region D extending along the second direction X, and as shown in FIG. 9A, the wafer W is separated into a plurality of intermediates 50 having a shape extending in the second direction X. After that, the intermediate 50 is diced along the dicing region D extending along the first direction Y, and as shown in FIG. 9B, the wafer W is separated into a plurality of light-emitting elements 1. Note that, after first dicing the wafer W along the first direction Y, dicing along the second direction X may be performed.

[0050] Embodiments of the present invention can include the following method of manufacturing a light-emitting element.

[0051] [Item 1] A step of preparing a wafer having a sapphire substrate having a first surface and a second surface located on the opposite side of the first surface, and a semiconductor layer disposed on the second surface, A step of irradiating laser light from the first surface side into the sapphire substrate through an objective lens having an incident surface and an exit surface located on the opposite side of the incident surface and facing the first surface, and forming a modified portion inside the sapphire substrate, A step of separating the wafer into a plurality of light-emitting elements after the step of forming the modified portion, comprising The step of forming the modified portion includes a step of forming a first modified portion at a position where the distance from the first surface is a first distance, In the step of forming the first modified portion, a method of manufacturing a light-emitting element, wherein the laser light having a divergence angle smaller than 0 mrad is incident on the incident surface of the objective lens. [Item 2] The step of forming the modification part further includes a step of forming a second modification part at a position where the distance from the first surface is a second distance shorter than the first distance. In the step of forming the second modification part, the second modification part is formed by making the laser beam having a divergence angle of 0 mrad or less incident on the incident surface of the objective lens. The method for manufacturing a light-emitting element according to item 1, wherein the divergence angle of the laser beam incident on the incident surface in the step of forming the first modification part is made smaller than the divergence angle of the laser beam incident on the incident surface in the step of forming the second modification part. [Item 3] The semiconductor layer has a plurality of light-emitting parts. In the step of forming the first modification part, the laser beam is scanned along the first direction parallel to the a-axis of the sapphire substrate and the second direction perpendicular to the first direction and parallel to the m-axis of the sapphire substrate, and a plurality of the first modification parts are formed along the first direction and the second direction respectively. In the step of forming the plurality of first modification parts along the first direction, the plurality of first modification parts are formed at a position shifted in the second direction from a virtual line extending in the first direction and located between two adjacent light-emitting parts in the second direction and having an equal distance from the two adjacent light-emitting parts in the second direction. The method for manufacturing a light-emitting element according to item 1, wherein the first divergence angle of the laser beam incident on the incident surface in the step of forming the plurality of first modification parts along the first direction is made smaller than the second divergence angle of the laser beam incident on the incident surface in the step of forming the plurality of first modification parts along the second direction. [Item 4] The step of forming the modification part further includes a step of forming a plurality of second modification parts along the first direction and the second direction respectively at a position where the distance from the first surface is a second distance shorter than the first distance. In the step of forming the second modification part, the plurality of second modification parts are formed by making the laser beam having a divergence angle of 0 mrad or less incident on the incident surface of the objective lens. In the step of forming the plurality of second modified portions along the first direction, the third divergence angle of the laser beam incident on the incident surface is made larger than the second divergence angle. The method for manufacturing a light-emitting element according to claim 3, wherein a fourth divergence angle of the laser beam incident on the incident surface in the step of forming the plurality of second modified portions along the second direction is made larger than the third divergence angle. [Claim 5] The method for manufacturing a light-emitting element according to any one of claims 1 to 4, wherein the thickness of the sapphire substrate is 300 μm or less. [Claim 6] The method for manufacturing a light-emitting element according to any one of claims 1 to 5, wherein the first distance is 10 μm or more and 150 μm or less.

[0052] As described above, the embodiments of the present invention have been described with reference to specific examples. However, the present invention is not limited to these specific examples. Based on the above-described embodiments of the present invention, all forms that can be appropriately designed and implemented by those skilled in the art also belong to the scope of the present invention as long as they include the gist of the present invention. In addition, within the scope of the idea of the present invention, those skilled in the art can conceive of various modification examples and correction examples, and those modification examples and correction examples also belong to the scope of the present invention.

Explanation of Signs

[0053] 1... Light-emitting element, 10... Sapphire substrate, 11... First surface, 12... Second surface, 20... Semiconductor layer, 30... Light-emitting portion, 61... First mirror, 62... Second mirror, 63... Third mirror, 70... Concave lens, 80... Convex lens, 90... Objective lens, 91... Incident surface, 92... Exit surface, 100... Optical system, C... Central axis, Cr... Crack, D... Dicing region, L... Laser beam, R1... First modified portion, R2... Second modified portion, RL1... First reference line, RL2... Second reference line, VL... Virtual line, W... Wafer

Claims

1. A step of preparing a wafer having a sapphire substrate having a first surface and a second surface located on the opposite side of the first surface, and a semiconductor layer disposed on the second surface; A step of irradiating laser light from the first surface side into the sapphire substrate through an objective lens having an incident surface and an exit surface located on the opposite side of the incident surface and facing the first surface, and forming a modified portion inside the sapphire substrate; A step of separating the wafer into a plurality of light-emitting elements after the step of forming the modified portion; Comprising: The step of forming the modified portion includes a step of forming a first modified portion at a position where the distance from the first surface is a first distance; A method of manufacturing a light-emitting element, wherein in the step of forming the first modified portion, the laser light having a divergence angle smaller than 0 mrad is incident on the incident surface of the objective lens.

2. The step of forming the modified portion further includes a step of forming a second modified portion at a position where the distance from the first surface is a second distance shorter than the first distance; In the step of forming the second modified portion, the second modified portion is formed by making the laser light having a divergence angle of 0 mrad or less incident on the incident surface of the objective lens; The method of manufacturing a light-emitting element according to claim 1, wherein the divergence angle of the laser light incident on the incident surface in the step of forming the first modified portion is made smaller than the divergence angle of the laser light incident on the incident surface in the step of forming the second modified portion.

3. The semiconductor layer has a plurality of light-emitting portions; In the step of forming the first modified portion, the laser light is scanned along the first direction parallel to the a-axis of the sapphire substrate and the second direction perpendicular to the first direction and parallel to the m-axis of the sapphire substrate, and a plurality of the first modified portions are formed along the first direction and the second direction respectively; In the step of forming the plurality of first modified portions along the first direction, the plurality of first modified portions are formed at positions shifted in the second direction from a virtual line extending in the first direction and located between two adjacent light-emitting portions in the second direction and having an equal distance from the two adjacent light-emitting portions in the second direction. The method for manufacturing a light-emitting element according to claim 1, wherein a first divergence angle of the laser light incident on the incident surface in the step of forming the plurality of first modified portions along the first direction is made smaller than a second divergence angle of the laser light incident on the incident surface in the step of forming the plurality of first modified portions along the second direction.

4. The step of forming the modified portion further includes a step of forming a plurality of second modified portions along each of the first direction and the second direction at a position having a second distance shorter than the first distance from the first surface. In the step of forming the second modified portion, the plurality of second modified portions are formed by making the laser light having a divergence angle of 0 mrad or less incident on the incident surface of the objective lens. A third divergence angle of the laser light incident on the incident surface in the step of forming the plurality of second modified portions along the first direction is made larger than the second divergence angle. The method for manufacturing a light-emitting element according to claim 3, wherein a fourth divergence angle of the laser light incident on the incident surface in the step of forming the plurality of second modified portions along the second direction is made larger than the third divergence angle.

5. The method for manufacturing a light-emitting element according to any one of claims 1 to 4, wherein the thickness of the sapphire substrate is 300 μm or less.

6. The method for manufacturing a light-emitting element according to any one of claims 1 to 4, wherein the first distance is 10 μm or more and 150 μm or less.

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