Semiconductor laser element and method for manufacturing a semiconductor laser element
The semiconductor laser element's innovative groove and wing structure design addresses crack issues during manufacturing, ensuring enhanced reliability and performance by managing stress and preventing crack propagation.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NUVOTON TECH CORP JAPAN
- Filing Date
- 2022-01-31
- Publication Date
- 2026-07-02
Smart Images
Figure 0007883854000001 
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a semiconductor laser device and a method for manufacturing the semiconductor laser device.
Background Art
[0002] Semiconductor laser devices have advantages such as long life, high efficiency, and small size, and are therefore used as light sources for various products such as projectors, optical disks, in-vehicle headlamps, lighting devices, or laser processing devices. In recent years, research and development of nitride-based semiconductor lasers that can cover wavelength bands from ultraviolet to blue have been underway as semiconductor laser devices.
[0003] A semiconductor laser device can be manufactured by cutting out a plurality of bar-shaped substrates by dividing a semiconductor laminated substrate in which a plurality of semiconductor layers are laminated on a wafer, and further dividing the bar-shaped substrate into a plurality of pieces to individualize them. In such a dividing process, problems such as being divided deviating from the planned dividing line or a part being chipped occur.
[0004] In particular, different from gallium arsenide-based lasers used in optical pickups or optical communications, nitride-based semiconductor lasers are divided on a crystal plane that is not a cleavage plane in the dividing process, so problems such as being divided deviating from the planned dividing line or a part being chipped are likely to occur.
[0005] Therefore, conventionally, a technique for manufacturing a semiconductor laser device by dividing a wafer using a guide groove has been proposed. For example, Patent Document 1 discloses a method of dividing a wafer by irradiating a laser beam on the back surface of a wafer in which a plurality of semiconductor layers are laminated to form a dividing groove.
Prior Art Documents
Patent Documents
[0006]
Patent Document 1
[0007] However, even when using the method disclosed in Patent Document 1, there is a problem in that cracks occur in the semiconductor laser element during the splitting process of dividing a semiconductor laminated substrate in which multiple semiconductor layers are stacked on a wafer, or during the splitting process of dividing a bar-shaped substrate obtained by dividing a semiconductor laminated substrate, thereby reducing the reliability of the semiconductor laser element.
[0008] This disclosure was made to solve these problems and aims to provide a semiconductor laser element and a method for manufacturing the semiconductor laser element that can suppress the reduction in reliability caused by cracks that occur during the manufacturing process. [Means for solving the problem]
[0009] To achieve the above objective, one embodiment of a first semiconductor laser element according to the present disclosure is a semiconductor laser element having a resonator end face and a pair of side surfaces intersecting the resonator end face, comprising a substrate and a semiconductor laminated structure formed on one surface of the substrate and having a plurality of semiconductor layers stacked thereon, wherein the semiconductor laminated structure has an optical waveguide extending along the resonator length direction of the semiconductor laser element, and a pair of first grooves extending along the resonator length direction are formed on the other surface of the substrate so as to cut out the pair of side surfaces, and both ends of each of the pair of first grooves in the resonator length direction are located recessed from the end face of the semiconductor laminated structure, and a second groove is formed in the semiconductor laminated structure from the end face of the semiconductor laminated structure along the resonator length direction, and in a top view, the second groove is formed on both sides of the optical waveguide and is formed between the first groove and the optical waveguide.
[0010] Furthermore, one embodiment of the second semiconductor laser element according to the present disclosure comprises a substrate and a semiconductor stacked structure formed on one surface of the substrate, wherein a plurality of semiconductor layers are stacked, and the semiconductor stacked structure has a ridge portion extending in the direction of the resonator length of the semiconductor laser element and wing portions formed on both sides of the ridge portion at the same height as the ridge portion, and a wingless portion is formed near the end face of the semiconductor stacked structure where the wing portions are not formed, and a protrusion is formed on the surface of the edge of the wingless portion in a direction perpendicular to the direction of the resonator length of the semiconductor stacked structure.
[0011] Furthermore, one embodiment of a method for manufacturing a semiconductor laser element according to this disclosure includes the steps of: manufacturing a semiconductor laminated substrate having a semiconductor laminated structure by stacking a plurality of semiconductor layers on one side of a substrate; a first etching step of etching the semiconductor laminated structure; a second etching step of etching the semiconductor laminated structure after the first etching step; a dividing step of manufacturing a plurality of bar-shaped substrates, each having a plurality of optical waveguides, by dividing the semiconductor laminated substrate; a first groove formed on the back surface of the semiconductor laminated substrate or the bar-shaped substrate; and dividing the bar-shaped substrate along the first groove. The process includes a division step of producing a plurality of semiconductor laser elements, each having one optical waveguide, wherein the first etching step forms a recess in the semiconductor stacked structure, and the second etching step further etches the recess to form a second groove and forms a ridge portion in the semiconductor stacked structure as the optical waveguide, wherein in a top view, the second groove is formed on both sides of the optical waveguide so as to extend from the end face of the semiconductor stacked structure along the resonator length direction of the semiconductor laser element, and is formed between the first groove and the optical waveguide. [Effects of the Invention]
[0012] According to this disclosure, it is possible to obtain a semiconductor laser element that can suppress the reduction in reliability caused by cracks that occur during the manufacturing process. [Brief explanation of the drawing]
[0013] [Figure 1] Figure 1 is a top view of a semiconductor laser element according to an embodiment. [Figure 2A] Figure 2A is a cross-sectional view of a semiconductor laser element according to an embodiment along the line IIA-IIA in Figure 1. [Figure 2B] Figure 2B is a cross-sectional view of a semiconductor laser element according to the embodiment along the line IIB-IIB in Figure 1. [Figure 2C] Figure 2C is a cross-sectional view of a semiconductor laser element according to the embodiment in the IIC-IIC line shown in Figure 1. [Figure 3] Figure 3 is a side view of a semiconductor laser element according to an embodiment. [Figure 4A] Figure 4A is a diagram illustrating the process of forming a semiconductor stacked structure in the method for manufacturing a semiconductor laser element according to an embodiment. [Figure 4B] Figure 4B is a diagram illustrating the process of forming a first resist in the method for manufacturing a semiconductor laser element according to the embodiment. [Figure 4C] Figure 4C is a diagram illustrating the first etching step in the method for manufacturing a semiconductor laser element according to an embodiment. [Figure 4D] Figure 4D is a diagram illustrating the step of removing the first resist in the method for manufacturing a semiconductor laser element according to an embodiment. [Figure 4E] Figure 4E is a diagram illustrating the process of forming a second resist in the method for manufacturing a semiconductor laser element according to the embodiment. [Figure 4F] Figure 4F is a diagram illustrating the second etching step in the method for manufacturing a semiconductor laser element according to an embodiment. [Figure 4G] Figure 4G is a diagram illustrating the process of forming an insulating film in the method for manufacturing a semiconductor laser element according to an embodiment. [Figure 4H] Figure 4H is a diagram illustrating the step of removing an insulating film in the method for manufacturing a semiconductor laser element according to an embodiment. [Figure 4I]FIG. 4I is a diagram for explaining a step of forming a p-side electrode in a method for manufacturing a semiconductor laser device according to an embodiment. [Figure 4J] FIG. 4J is a diagram for explaining a step of forming an n-side electrode in a method for manufacturing a semiconductor laser device according to an embodiment. [Figure 5] FIG. 5 is a cross-sectional SEM image of a portion corresponding to the region V surrounded by the broken line in (d) of FIG. 4H. [Figure 6] FIG. 6 is a diagram showing the configuration of a semiconductor laser device manufactured by a method for manufacturing a semiconductor laser device according to an embodiment. [Figure 7] FIG. 7 is a cross-sectional view of a semiconductor laser device according to a modified example. [Figure 8] FIG. 8 is a diagram for explaining a step of dividing a bar-shaped substrate into a plurality of semiconductor laser devices (individual chip division step). [Figure 9] FIG. 9 is a diagram showing the configuration of a semiconductor laser device of a comparative example.
Embodiments for Carrying Out the Invention
[0014] (Process of Arriving at an Aspect of the Present Disclosure) First, prior to describing the embodiments of the present disclosure, the process of arriving at an aspect of the present disclosure will be described
[0015] Generally, when mass-producing semiconductor laser devices, a semiconductor laminated substrate in which a plurality of semiconductor layers are laminated on a substrate that is a wafer is divided to produce a plurality of bar-shaped substrates (primary division step). After forming coating films on both end faces of this bar-shaped substrate, individual chip division is performed to further divide the bar-shaped substrate into a plurality of pieces to separate it into a plurality of semiconductor laser devices (secondary division step). Thereby, a plurality of semiconductor laser devices that become laser chips can be obtained from one wafer.
[0016] Conventionally, when dividing a bar-shaped substrate into individual pieces, a method has been proposed in which a dividing groove (guide groove) is formed in advance on the semiconductor laminated substrate or the bar-shaped substrate, and the bar-shaped substrate is divided into multiple pieces along this groove. In this case, it is conceivable to form the dividing groove using the method disclosed in Patent Document 1. Specifically, it is conceivable to form the dividing groove by irradiating the back surface of the semiconductor laminated substrate or the bar-shaped substrate with laser light. At this time, in order to prevent the resonator end face of the semiconductor laser element from being thermally damaged by the laser light used to form the groove, the laser light is irradiated so that the end of the groove in the direction of the resonator is set back from the resonator end face. In other words, the laser light is irradiated so that the dividing groove does not reach the position of the resonator end face on the front and rear sides of the bar-shaped substrate.
[0017] However, when the inventors of the present invention actually fabricated a semiconductor laser element using this method, they found that cracks occurred in the semiconductor laser element during the individual piece division process, which divides the bar-shaped substrate into multiple pieces. This point will be explained in detail below.
[0018] As shown in Figure 8, a bar-shaped substrate 3X, which has dividing grooves 51X formed on the back surface of the substrate 10X, is sandwiched between an adhesive sheet 101 and a protective film 102, and a blade-shaped jig 103, such as a cutter, is sequentially pressed onto the bar-shaped substrate 3X at positions corresponding to the dividing grooves 51X. In this way, the bar-shaped substrate 3X can be divided into multiple parts, and multiple semiconductor laser elements 1X can be obtained.
[0019] When the obtained semiconductor laser element 1X was observed, as shown in Figure 9, it was found that a crack 90X was generated at the corner between the resonator end face and the side surface of the semiconductor laser element 1X, extending diagonally upward from near the interface between the substrate 10X and the semiconductor stacked structure 20X toward the ridge portion 20a. When the crack 90X extends toward the ridge portion 20a in this way, the reliability of the semiconductor laser element 1X decreases.
[0020] Figure 9 shows the configuration of a comparative example semiconductor laser element 1X manufactured by the method of Patent Document 1. In Figure 9, (a) is a top view of the semiconductor laser element 1X, (b) is a cross-sectional view along line bb in (a), and (c) is a cross-sectional view along line cc in (a). Figure 9(d) is a side view of the semiconductor laser element 1X viewed from the rear end face side, with the coating film 32X on the end face omitted. The thick lines in Figure 9 indicate cracks 90X that have occurred in the semiconductor laser element 1X, and the hatched dot areas in Figure 9(a) indicate the areas where cracks 90X have occurred.
[0021] Upon examining the obtained semiconductor laser elements 1X, it was found that the cracks 90X originate in a triangular planar shape, as shown in Figure 9(a). Specifically, as shown in Figures 9(b) and (d), many of the resulting cracks 90X originate from the side of the semiconductor multilayer structure 20X in a cross section perpendicular to the resonator length direction of the semiconductor laser element 1X, first forming a groove 51 X Nearby, the crack progresses diagonally upwards, followed by groove 51 X It was found that, away from the main surface of the substrate 10X, the cracks extend slightly upward at an angle of approximately 1.5° relative to the main surface of the substrate 10X, and in a cross-section parallel to the side surface of the semiconductor laser element 1X, the cracks extend upward at an angle of approximately 16° relative to the main surface of the substrate 10X from the end face of the semiconductor stacked structure 20X. Furthermore, it was found that many cracks 90X originate from a point approximately 2 μm below the part of the surface of the semiconductor stacked structure 20X that is closest to the substrate 10X (the upper surface of the separation groove 53X in Figure 9(d)). Moreover, it was found that cracks 90X occur particularly frequently on the rear end face side of the semiconductor laser element 1.
[0022] Furthermore, in both cases, the two semiconductor laser elements 1X separated by the blade-shaped jig 103 (see Figure 8) frequently developed cracks 90X originating from the left side, but cracks 90X also sometimes originated from the right side. In addition, the cracks 90X were visible in a top view. ,groove It doesn't extend to the point where it overlaps with the 51X. ,grooveIn some cases, it extended to a position overlapping with the 51X.
[0023] The inventors of this invention investigated the cause of the occurrence of crack 90X and hypothesized that it was due to the formation of dividing grooves 51X on the back surface of the substrate 10X for dividing into individual pieces, and the fact that these dividing grooves 51X were formed so as not to reach the front and rear resonator end faces, thereby making the area near the resonator end faces less prone to cracking.
[0024] Furthermore, the thickness of the coating film 32X formed on the rear side of the resonator endface is thicker than that of the coating film 31X formed on the front side of the resonator endface (for example, about 8 times thicker) in order to emit laser light in the front direction. As a result, the area near the rear resonator endface is less prone to cracking than the front resonator endface. This is thought to be the reason why many cracks 90X occurred on the rear resonator endface.
[0025] Therefore, in response to these challenges, the inventors of the present invention diligently considered the matter and came up with the idea of providing a structure that prevents cracks 90X from propagating below the ridge portion 20a, even if cracks 90X occur during the splitting of individual pieces. Specifically, they came up with the idea of forming grooves in the semiconductor stacked structure 20X to prevent the propagation of cracks 90X.
[0026] Thus, this disclosure addresses the problem of crack generation, and its first objective is to obtain a semiconductor laser element that can suppress the propagation of cracks to the lower part of the ridge even if cracks occur during fragmentation.
[0027] Furthermore, in the wafer splitting process (primary splitting process, secondary splitting process), protective materials such as SiO2 may be placed on the wafer. In this case, stress during splitting may be applied to the ridge portion 20a of the semiconductor laser element, which may cause chipping (edge step, etc.) in the ridge portion.
[0028] This disclosure addresses these challenges, and its second objective is to obtain a semiconductor laser element that can suppress the occurrence of cracks in the ridge portion during the splitting process.
[0029] The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are all specific examples of this disclosure. Therefore, the numerical values, shapes, materials, components, arrangement and connection configurations of components, as well as the steps (processes) and their order, shown in the following embodiments are examples and are not intended to limit this disclosure. Accordingly, any components in the following embodiments that are not described in the independent claims representing the highest-level concepts of this disclosure will be described as optional components.
[0030] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Therefore, the scale and other aspects may not necessarily be consistent across all figures. In each figure, substantially identical components are given the same reference numerals, and redundant explanations are omitted or simplified.
[0031] Furthermore, in this specification, the terms "upper" and "lower" do not refer to the upward (vertically upward) and downward (vertically downward) directions in absolute spatial perception, but rather are used as terms defined by the relative positional relationship based on the stacking order in a stacked configuration. Moreover, the terms "upper" and "lower" apply not only when two components are spaced apart and another component exists between them, but also when two components are placed in contact with each other.
[0032] (Embodiment) First, the configuration of the semiconductor laser element 1 according to the embodiment will be explained using Figures 1 to 3. Figure 1 is a top view of the semiconductor laser element 1 according to the embodiment. Figures 2A to 2C are cross-sectional views of the semiconductor laser element 1 according to the embodiment. Figure 2A is a cross-sectional view along the line IIA-IIA in Figure 1, Figure 2B is a cross-sectional view along the line IIB-IIB in Figure 1, and Figure 2C is a cross-sectional view along the line IIC-IIC in Figure 1. Figure 3 is a side view of the semiconductor laser element 1 according to the embodiment. Note that in Figure 1, the insulating film 81 It has been omitted.
[0033] As shown in Figure 1, the semiconductor laser element 1 has a front end surface 1a and a rear end surface 1b, which are the resonator end surfaces, and a first side surface 1c and a second side surface 1d, which are surfaces that intersect the resonator end surfaces.
[0034] The front end face 1a is the front end face of the semiconductor laser element 1 and is the resonator end face from which the laser light is emitted. The rear end face 1b is the rear end face of the semiconductor laser element 1 and is the resonator end face from which the laser light is not emitted. The front end face 1a and the rear end face 1b face each other as a pair of resonator end faces. The rear end face 1b is the end face opposite to the front end face 1a.
[0035] The first side surface 1c is one side surface of the semiconductor laser element 1. The second side surface 1d is the other side surface of the semiconductor laser element 1. The first side surface 1c and the second side surface 1d are a pair of sides and face each other. The first side surface 1c and the second side surface 1d are surfaces perpendicular to the front end surface 1a and the rear end surface 1b.
[0036] As shown in Figures 1 to 3, the semiconductor laser element 1 has a substrate 10 and a semiconductor stacked structure 20 formed on the upper surface, which is one side of the substrate 10. The semiconductor stacked structure 20 has a structure in which multiple semiconductor layers are stacked and has a PN junction.
[0037] In this embodiment, the semiconductor laser element 1 is a nitride semiconductor laser composed of a nitride-based semiconductor material. Therefore, the semiconductor stacked structure 20 is a nitride semiconductor stacked structure in which a plurality of nitride semiconductor layers, each made using a nitride-based semiconductor material, are stacked. Specifically, the semiconductor laser element 1 is a GaN-based nitride semiconductor laser. The laser light emitted from the semiconductor laser element 1 is, for example, light in the wavelength range from ultraviolet to blue.
[0038] The semiconductor laser element 1 has an optical waveguide with its front end surface 1a and rear end surface 1b acting as resonator reflection mirrors. Specifically, the semiconductor laminated structure 20 has the optical waveguide. The optical waveguide extends along the resonator length direction of the semiconductor laser element 1. In this embodiment, a ridge portion 20a is formed in the semiconductor laminated structure 20 as the optical waveguide. Therefore, the ridge portion 20a is formed to extend along the resonator length direction of the semiconductor laser element 1. The ridge portion 20a is convex and is formed by carving into the semiconductor laminated structure 20. The semiconductor laser element 1 has a long shape in the resonator length direction. The length of the semiconductor laser element 1 in the resonator length direction is, for example, 800 μm or more, and in this embodiment, it is 1200 μm.
[0039] In the semiconductor laser element 1, a laser resonator is formed by the front end surface 1a and the rear end surface 1b. Therefore, the rear end surface 1b has a higher reflectivity than the front end surface 1a. For example, the reflectivity of the front end surface 1a is 5%, while the reflectivity of the rear end surface 1b is 95%.
[0040] Specifically, as shown in Figure 1, a first coating film 31 is formed as a reflective film on the front side of the semiconductor laser element 1, and a second coating film 32 is formed as a reflective film on the rear side of the semiconductor laser element 1. The first coating film 31 is formed on the front end surface of the semiconductor stacked structure 20, and the second coating film 32 is formed on the rear end surface of the semiconductor stacked structure 20. The first coating film 31 and the second coating film 32 are composed of dielectric multilayer films in which multiple dielectric films are stacked. In this embodiment, the thickness of the second coating film 32 on the rear side is thicker than the thickness of the first coating film 31 on the front side. For example, the thickness of the second coating film 32 is more than twice the thickness of the first coating film 31, and in this embodiment, it is approximately eight times thicker.
[0041] The substrate 10 is a semiconductor substrate made of GaN or SiC, or an insulating substrate such as a sapphire substrate. The substrate 10 is, for example, an n-type GaN substrate made of a hexagonal GaN single crystal. In this embodiment, an n-type GaN substrate with a (0001) plane as the main surface is used as the substrate 10.
[0042] As shown in Figures 2A to 2C, the semiconductor stacked structure 20 has, in order, a first semiconductor layer 21 on the n side, an active layer 22, and a second semiconductor layer 23 on the p side on the substrate 10. The active layer 22 is the PN junction in the semiconductor stacked structure 20. The first semiconductor layer 21, the active layer 22, and the second semiconductor layer 23 can be formed by epitaxial growth of nitride-based semiconductor material using the Metal Organic Chemical Vapor Deposition (MOCVD) method. Each of the first semiconductor layer 21, the active layer 22, and the second semiconductor layer 23 is configured, for example, as follows.
[0043] The first semiconductor layer 21 includes at least an n-type cladding layer. In this embodiment, the first The semiconductor layer 21 includes an n-type cladding layer and an n-side cladding layer formed on top of the n-side cladding layer. light It has a guide layer. n-side cladding layer and n-side lightThe guide layer may be a single layer or multiple layers.
[0044] As an example, the n-side cladding layer is an n-side cladding layer (n-AlGaN layer) made of silicon-doped AlGaN.
[0045] The n-side optical guide layer is an optical guide layer (un-GaN layer) made of undoped GaN.
[0046] The active layer 22 is a quantum well active layer. The active layer 22 has a laminated structure in which well layers (well layers) made of undoped InGaN and barrier layers (barrier layers) made of undoped InGaN are alternately stacked. The active layer 22 may be either a single quantum well structure (SQW) or a multi quantum well structure (MQW). In this embodiment, the active layer 22 has a five-layer structure consisting of a barrier layer made of InGaN, a well layer made of InGaN, a barrier layer made of InGaN, a well layer made of InGaN, and a barrier layer made of InGaN.
[0047] The second semiconductor layer 23 includes at least a p-type cladding layer. In this embodiment, the second semiconductor layer 23 includes a p-side optical guide layer, an OFS layer (overflow suppression layer) formed on the p-side optical guide layer, a p-side cladding layer formed on the OFS layer and including a p-type cladding layer, and a contact layer formed on the p-side cladding layer. The p-side optical guide layer, OFS layer, p-side cladding layer, and contact layer may be single layers or multiple layers.
[0048] As an example, the p-side optical guide layer is a p-side optical guide layer (un-GaN layer) made of undoped GaN.
[0049] The OFS layer is a p-type OFS layer (p-AlGaN layer) made of AlGaN doped with magnesium as an impurity.
[0050] The p-side cladding layer is a p-type p-side cladding layer (p-AlGaN layer) doped with magnesium as an impurity.
[0051] The contact layer is a p-type contact layer (p-GaN layer) made of GaN doped with magnesium as an impurity.
[0052] As shown in Figures 1 to 2C, a recess 24 is formed in the semiconductor stacked structure 20 configured in this way. The formation of the recess 24 creates a ridge portion 20a and a flat portion 20b that extends laterally from the base of the ridge portion 20a in the semiconductor stacked structure 20. The recess 24 is formed by etching the semiconductor stacked structure 20. As shown in Figures 2A to 2C, in this embodiment, the recess 24 is carved into the second semiconductor layer 23. In other words, the ridge portion 20a and the flat portion 20b are formed in the second semiconductor layer 23. Specifically, the ridge portion 20a is formed in the p-side cladding layer and the contact layer. For example, the ridge portion 20a is composed of a convex portion formed in the p-side cladding layer and a contact layer formed on top of the convex portion, with the uppermost layer of the ridge portion 20a being the contact layer. The flat portion 20b is formed in the p-side cladding layer. The flat surface of the flat portion 20b is the bottom of the recess 24 and the surface of the p-side cladding layer in the recess 24.
[0053] The width and height of the ridge portion 20a are not particularly limited, but as an example, the ridge width (stripe width) of the ridge portion 20a is 1 μm or more and 100 μm or less, and the height of the ridge portion 20a is 100 nm or more and 1000 nm or less. The width of the contact layer is the same as the ridge width of the ridge portion 20a, but is not limited to this.
[0054] Furthermore, in this embodiment, by forming a recess 24 in the semiconductor stacked structure 20, a convex wing portion 20c is formed on the semiconductor stacked structure 20, as shown in Figures 1 and 2B. In other words, the semiconductor stacked structure 20 has a ridge portion 20a and a wing portion 20c as a convex structure. As described above, in this embodiment, the recess 24 is formed by carving out the second semiconductor layer 23. Therefore, the wing portion 20c is composed of the second semiconductor layer 23 and has the same height as the ridge portion. Specifically, the wing portion 20c is composed of a p-side cladding layer and a contact layer, similar to the ridge portion 20a. The upper surfaces of both the ridge portion 20a and the wing portion 20c are flat.
[0055] As shown in Figures 1 and 2B, the wing portions 20c are formed on both sides of the ridge portion 20a. In other words, the semiconductor stacked structure 20 has a pair of wing portions 20c. The ridge portion 20a is sandwiched between the pair of wing portions 20c via the recess 24. The pair of wing portions 20c, like the ridge portion 20a, extend along the resonator length direction of the semiconductor laser element 1. By providing the wing portions 20c on both sides of the ridge portion 20a in this way, the pressure on the ridge portion 20a can be reduced when mounting the semiconductor laser element 1 in a junction-down configuration.
[0056] In this embodiment, the width of each of the pair of wing portions 20c is greater than the width of the ridge portion 20a, but this is not limited to this. Also, the widths of the pair of wing portions 20c are the same, but they may be different.
[0057] Furthermore, as shown in Figure 1, a wingless portion 20d is formed near the end face of the semiconductor stacked structure 20, where the wing portion 20c is not formed. In other words, the wingless portion 20d is part of the recess 24. In this embodiment, the wingless portion 20d is formed near the front end face and the rear end face of the semiconductor stacked structure 20.
[0058] As shown in Figure 2C, protrusions 25 are formed on the surface of the edge of the semiconductor laminated structure 20 in the wingless portion 20d, in a direction perpendicular to the resonator length direction. Specifically, the protrusions 25 are formed at the boundary between the surface of the semiconductor laminated structure 20 and the side surface of the second groove 52, which will be described later. In this case, the edge of the semiconductor laminated structure 20 on which the protrusions 25 are formed is the boundary between the surface of the semiconductor laminated structure 20 and the side surface of the second groove 52. In addition, protrusions 25 are also formed at the boundary between the surface of the semiconductor laminated structure 20 and the side surface of the third groove 53, which will be described later. In this case, the edge of the semiconductor laminated structure 20 on which the protrusions 25 are formed is the boundary between the surface of the semiconductor laminated structure 20 and the side surface of the third groove 53. In this embodiment, the protrusions 25 are formed in a horn shape with a triangular cross-section.
[0059] As shown in Figure 2B, a p-side electrode 41 is formed on the ridge portion 20a of the second semiconductor layer 23. Specifically, the p-side electrode 41 is formed on the contact layer. In this embodiment, the p-side electrode 41 is formed only on the upper surface of the ridge portion 20a. The width of the p-side electrode 41 is narrower than the width of the ridge portion 20a, but it may be the same as the width of the ridge portion 20a.
[0060] The p-side electrode 41 is formed using at least one metallic material such as Pt, Ti, Cr, Ni, Mo, and Au. The p-side electrode 41 may be a single layer or a multi-layer electrode. In this embodiment, the p-side electrode 41 is a two-layer electrode consisting of a Pd layer with a thickness of 40 nm and a Pt layer with a thickness of 35 nm. A pad electrode may be formed on the p-side electrode 41.
[0061] On the other hand, an n-side electrode 42 is formed on the other side of the substrate 10, which is the bottom surface (back surface). The n-side electrode 42 is an ohmic electrode that makes ohmic contact with the semiconductor substrate 10. The n-side electrode 42 is formed using at least one metallic material such as Cr, Ti, Ni, Pd, Pt, Au, and Ge. Furthermore, the n-side electrode 42 may be a single layer or a multi-layer structure.
[0062] As shown in Figures 2A to 2C, the semiconductor multilayer structure 20 is covered with an insulating film 81 made of a dielectric film such as SiO2 or SiN, except for the p-side electrode 41 on the ridge portion 20a. Specifically, the insulating film 81 is formed to cover the second semiconductor layer 23, except for the upper surface of the ridge portion 20a. In other words, the insulating film 81 is formed to have an opening on the ridge portion 20a of the contact layer. The insulating film 81 functions as a current blocking film. Therefore, the opening in the insulating film 81 becomes a current injection window through which current passes. The insulating film 81 may also be formed on the sides of the semiconductor multilayer structure 20.
[0063] Furthermore, as shown in Figure 2B, a pad electrode 82 is formed on the p-side electrode 41. The pad electrode 82 is in contact with the p-side electrode 41. In this embodiment, the pad electrode 82 is wider than the ridge portion 20a and extends over the wing portion 20c. That is, the pad electrode 82 is formed on the insulating film 81 so as to cover the ridge portion 20a, the flat portion 20b (recess 24), and the wing portion 20c. The pad electrode 82 is made of a metallic material such as Au. Alternatively, the pad electrode 82 may be formed via an adhesion auxiliary layer such as Ti. In this case, the adhesion auxiliary layer may also be part of the pad electrode 82.
[0064] The semiconductor laser element 1 configured in this way has multiple grooves formed on it. Specifically, as shown in Figures 1 to 3, the semiconductor laser element 1 has multiple grooves, namely a first groove 51, a second groove 52, and a third groove 53.
[0065] The first groove 51 is formed on the back side of the semiconductor laser element 1. Specifically, the first groove 51 is formed on the back side of the substrate 10. On the other hand, the second groove 52 and the third groove 53 are formed on the front side of the semiconductor laser element 1. Specifically, the second groove 52 and the third groove 53 are formed in the semiconductor stacked structure 20.
[0066] The first groove 51 formed on the back surface of the substrate 10 is a guide groove for dividing a wafer in which multiple semiconductor layers are stacked. Specifically, as will be described later, the first groove 51 is a guide groove for dividing each of the multiple bar-shaped substrates after dividing a semiconductor laminated substrate in which multiple semiconductor layers are stacked on a wafer. The first groove 51 is a scribe groove and can be formed, for example, by irradiating the back surface of the substrate 10 with laser light. By forming the first groove 51 on the bottom surface (back surface) of the substrate 10 rather than the top surface in this way, the stress applied to the semiconductor laser element 1 during piece division can be reduced, thereby suppressing the occurrence of cracks.
[0067] As shown in Figures 1 and 3, the first groove 51 is formed to extend in the direction of the resonator of the semiconductor laser element 1. Furthermore, the first groove 51 is formed on each of a pair of sides of the semiconductor laser element 1. In other words, the semiconductor laser element 1 has a pair of first grooves 51. As shown in Figure 2B, each of the pair of first grooves 51 is formed to cut out a side of the semiconductor laser element 1 from the back surface of the substrate 10. Specifically, one of the pair of first grooves 51 extends along the resonator length direction to cut out one side of the substrate 10 corresponding to the first side surface 1c. The other of the pair of first grooves 51 extends along the resonator length direction to cut out the other side of the substrate 10 corresponding to the second side surface 1d.
[0068] As shown in Figures 1 and 3, both ends of each pair of first grooves 51 in the resonator length direction are located recessed from the end face of the semiconductor laminated structure 20. In other words, in each first groove 51, both ends in the resonator length direction are formed so as not to reach the end face of the semiconductor laminated structure 20. Specifically, near the front end of the semiconductor laminated structure 20, there is a portion of the semiconductor laminated structure 20 remaining without the first groove 51 between the rear end of the first groove 51 in the resonator length direction and the rear end face of the semiconductor laminated structure 20. Similarly, near the rear end of the semiconductor laminated structure 20, there is a portion of the semiconductor laminated structure 20 remaining without the first groove 51 between the front end of the first groove 51 in the resonator length direction and the front end face of the semiconductor laminated structure 20.
[0069] In this embodiment, the bottom of the first groove 51 is located inside the substrate 10. In other words, the first groove 51 is formed so that it does not reach the semiconductor laminated structure 20 on the upper side of the substrate 10 from the lower (back) side. For example, the thickness of the substrate 10 is 83 μm, the depth of the first groove is 55 μm, and the remaining margin is 13 μm.
[0070] The second groove 52 formed in the semiconductor multilayer structure 20 is a crack-preventing groove that prevents the propagation of cracks that occur when the bar-shaped substrate is divided into individual pieces. The second groove 52 can be formed by etching the semiconductor multilayer structure 20.
[0071] As shown in Figure 1, the second groove 52 is formed from the end face of the semiconductor stacked structure 20 along the resonator direction of the semiconductor laser element 1. In this embodiment, the second groove 52 is formed from the rear end face to the front end face of the semiconductor stacked structure 20. Furthermore, the second groove 52 is formed only near the rear end face of the semiconductor stacked structure 20. Specifically, the second groove 52 is formed in the wingless portion 20d of the semiconductor stacked structure 20, but it may also be formed across the wing portion 20c. The second groove 52 may also be formed near the front end face of the semiconductor stacked structure 20.
[0072] Furthermore, as shown in Figure 1, in a top view, the second grooves 52 are formed on both sides of the ridge portion 20a, which is an optical waveguide. In other words, the semiconductor laser element 1 has a pair of second grooves 52. Each of the pair of second grooves 52 is formed between the first groove 51 and the ridge portion 20a. Specifically, one of the pair of second grooves 52 is formed between one of the pair of first grooves 51 and the ridge portion 20a in a direction perpendicular to the resonator length direction of the semiconductor laser element 1. The other of the pair of second grooves 52 is formed between the other of the pair of first grooves 51 and the ridge portion 20a in a direction perpendicular to the resonator length direction of the semiconductor laser element 1.
[0073] The length of the second groove 52 in the resonator length direction is preferably 1 / 2 or more of the distance (remaining margin) between the first groove 51 and the rear end surface of the semiconductor laminated structure 20. In this embodiment, the length of the second groove 52 in the resonator length direction is 10 μm or more from the rear end surface of the semiconductor laminated structure 20, and 25 times or less the distance between the third groove 53 and the second groove 52. As an example, the length of the second groove 52 in the resonator length direction is 14 μm for a semiconductor laser element 1 with a resonator length direction of 1200 μm. The lengths of a pair of second grooves 52 in the resonator length direction are the same, but may be different.
[0074] Furthermore, the width of the second groove 52 is, for example, 10 μm or less. In this embodiment, the width of each second groove 52 is 8 μm, but it may be made even narrower as long as it is still etchable. Note that the widths of a pair of second grooves 52 are the same, but they may be different.
[0075] The depth of the second groove 52 is deeper than the portion of the semiconductor stacked structure 20 surface that is closest to the substrate 10. In this embodiment, the portion of the semiconductor stacked structure 20 surface that is closest to the substrate 10 is the bottom of the third groove 53. In other words, as shown in Figure 2C, the depth of each second groove 52 is deeper than the depth of the third groove 53. For example, the bottom of the second groove 52 is located about 2 μm below the portion of the semiconductor stacked structure 20 surface that is closest to the substrate 10. The depth of the second groove 52 may be equal to the depth of the third groove 53. Also, the depths of a pair of second grooves 52 are the same, but may be different.
[0076] Furthermore, the side surface (inner surface) of the second groove 52 is inclined. Specifically, in the second groove 52, each of the opposing pair of side surfaces is inclined. In this embodiment, the second groove 52 is tapered so that the groove width gradually narrows along the depth direction.
[0077] The third groove 53 formed in the semiconductor stacked structure 20 is a separation groove (element separation groove) for separating the stacked semiconductor layers into optical waveguides in a semiconductor stacked substrate in which multiple semiconductor layers are stacked on a wafer by epitaxial growth. Therefore, as shown in Figures 2A to 2C, the third groove 53 is formed on each of the pair of sides of the semiconductor laser element 1. In other words, a pair of third grooves 53 are formed on the semiconductor laser element 1. The third groove 53 can be formed by etching the stacked semiconductor layers.
[0078] Each of the pair of third grooves 53 is formed to cut out a side of the semiconductor stacked structure 20 from the upper surface of the semiconductor stacked structure 20. Also, as shown in Figure 1, the third grooves 53 are formed to extend in the direction of the resonator of the semiconductor laser element 1. Specifically, one of the pair of third grooves 53 extends along the resonator length direction to cut out one side of the semiconductor stacked structure 20. The other of the pair of third grooves 53 extends along the resonator length direction to cut out the other side of the semiconductor stacked structure 20. In this embodiment, both of the pair of third grooves 53 are formed extending from the front end surface to the rear end surface of the semiconductor stacked structure 20.
[0079] The third groove 53 can be formed by carving it out in the stacking direction from the upper surface of the semiconductor stacked structure 20. As shown in Figures 2A to 2C, the depth of the third groove 53 is greater than the position of the active layer 22, which is the PN junction in the semiconductor stacked structure 20. In this embodiment, the side surface of the third groove 53 is inclined. Specifically, the side surface of the third groove 53 is inclined so that the base widens along the depth direction.
[0080] Next, the method for manufacturing the semiconductor laser element 1 according to the embodiment will be explained using Figures 4A to 4J. Figures 4A to 4J are diagrams illustrating each step in the method for manufacturing the semiconductor laser element 1 according to the embodiment. In Figures 4A to 4J, (a) is a top view of the semiconductor laser element 1, (b) is a cross-sectional view along line bb of (a), (c) is a cross-sectional view along line cc of (a), and (d) is a cross-sectional view along line dd of (a). In Figures 4A to 4J (a), hatching has been applied for convenience to make the correspondence of the components visible on the top surface easier to understand. However, insulating film 8 1 The relevant parts have been omitted. Also, in Figures 4A to 4J, only the portion corresponding to one semiconductor laser element 1 of the semiconductor stacked structure 20A formed on the substrate 10, which is a wafer, is shown.
[0081] First, as shown in Figure 4A, a semiconductor laminated substrate 2 having a semiconductor laminated structure 20A is fabricated by stacking multiple semiconductor layers on one side of a substrate 10, which is a wafer. Specifically, the semiconductor laminated structure 20A is formed by sequentially epitaxially growing a first semiconductor layer 21, an active layer 22, and a second semiconductor layer 23 on the upper surface of the substrate 10 using the MOCVD method. Then, an insulating film 61 (first insulating film) is formed on the semiconductor laminated structure 20A. In this embodiment, an SiO2 film was formed as the insulating film 61. As an example, the thickness of the insulating film 61 is 300 nm. Note that the insulating film 61 may be omitted.
[0082] Next, as shown in Figure 4B, a first resist 71 of a predetermined shape having a first opening 71a and a second opening 71b is formed above the semiconductor multilayer structure 20A. The first opening 71a is formed at the position where the second groove 52, which will be described later, is formed. The second opening 71b is formed at the position where the third groove 53, which will be described later, is formed. In this embodiment, since an insulating film 61 is formed on top of the semiconductor multilayer structure 20A, the first resist 71 having the first opening 71a and the second opening 71b is formed on top of the insulating film 61.
[0083] Next, as shown in Figure 4C, the semiconductor multilayer structure 20A is etched (first etching step). Specifically, the semiconductor multilayer structure 20A is etched using the first resist 71, which has a first opening 71a and a second opening 71b, as a mask. This allows a recess 52a to be formed in the portion of the semiconductor multilayer structure 20A corresponding to the first opening 71a, and a third groove 53 to be formed in the portion of the semiconductor multilayer structure 20A corresponding to the second opening 71b. Dry etching such as reactive ion etching can be used as the etching method for the semiconductor multilayer structure 20A.
[0084] Since the recess 52a and the third groove 53 are formed in the same etching process, the depth of the recess 52a and the depth of the third groove 53 are the same. In this embodiment, the semiconductor stacked structure 20A is etched so that the bottom of both the recess 52a and the bottom of the third groove 53 reach partway through the first semiconductor layer 21. In other words, the recess 52a and the third groove 53 penetrate the second semiconductor layer 23 and the active layer 22, and are formed inside the first semiconductor layer 21. In this embodiment, since an insulating film 61 is formed on the semiconductor stacked structure 20A, the insulating film 61 is also etched. In other words, the recess 52a and the third groove 53 also penetrate the insulating film 61.
[0085] Next, as shown in Figure 4D, the first resist 71 used as a mask is removed. This exposes the insulating film 61.
[0086] Next, as shown in Figure 4E, a second resist 72 of a predetermined shape having an opening 72a is formed above the semiconductor multilayer structure 20A. The opening 72a is formed at the position where the recess 24 to be formed in the semiconductor multilayer structure 20A is to be formed. In addition, the opening 72a of the second resist 72 is also formed at the position corresponding to the second groove 52. That is, the opening 72a is formed so as to overlap with the recess 52a formed in the semiconductor multilayer structure 20A, and the recess 52a is not covered by the second resist 72. On the other hand, the third groove 53 formed in the semiconductor multilayer structure 20A is covered by the second resist 72. That is, the second resist 72 is embedded in the third groove 53. In this embodiment, since an insulating film 61 is formed on top of the semiconductor multilayer structure 20A, the second resist 72 having the opening 72a is formed on top of the insulating film 61.
[0087] Next, as shown in Figure 4F, the semiconductor multilayer structure 20A with the recess 52a formed thereon is etched (second etching step). Specifically, the semiconductor multilayer structure 20A is etched using the second resist 72 having the opening 72a as a mask. As a result, a recess 24 is formed in the portion of the semiconductor multilayer structure 20A corresponding to the opening 72a, and the semiconductor multilayer structure 20A has a ridge portion 20a and a wing portion 20c. Dry etching such as reactive ion etching can be used as the etching method for the semiconductor multilayer structure 20A.
[0088] At this time, the semiconductor stacked structure 20A is etched so that the bottom of the recess 24 reaches partway through the second semiconductor layer 23. In other words, the ridge portion 20a and the wing portion 20c are formed in the second semiconductor layer 23. In this embodiment, since the insulating film 61 is formed on the semiconductor stacked structure 20A, the insulating film 61 is also etched. As a result, the insulating film 61 remains only on the ridge portion 20a.
[0089] Furthermore, since the recess 52a formed in the semiconductor multilayer structure 20A by the first etching process is not covered by the second resist 72, the recess 52a is further etched in this etching process. As a result, the bottom of the recess 52a becomes deeper, forming the second groove 52. Specifically, the recess 52a that was formed up to the first semiconductor layer 21 is further etched and dug into the interior of the substrate 10.
[0090] Thus, the second groove 52 is formed using the first etching step for forming the third groove 53 and the second etching step for forming the ridge portion 20a. Therefore, the second groove 52 can be formed without adding a step solely for the purpose of forming the second groove 52. In other words, according to the manufacturing method of this embodiment, there is no need to use a mask solely for the purpose of forming the second groove 52.
[0091] Subsequently, although not shown in the diagram, the second resist 72 used as a mask is removed. This exposes the insulating film 61 on the ridge portion 20a, as well as the second semiconductor layer 23 in which the recess 24 is formed.
[0092] Furthermore, in this second etching process, as shown in Figure 4F(d), protrusions 25 are formed on the edges of the upper surface of the semiconductor stacked structure 20A (the upper surface of the second semiconductor layer 23 in this embodiment) at the second groove 52 and the third groove 53 in the wingless portion 20d of the semiconductor stacked structure 20A. It is believed that such protrusions 25 are formed for the following reasons.
[0093] During the dry etching of the insulating film 61, which is the first step in forming the ridge portion 20a, debris from the dry etching process accumulates on the upper part of the sidewalls of the second groove 52 and third groove 53 of the semiconductor multilayer structure 20A in the wingless portion 20d, forming deposits. Because the etching rate of these deposits is slower than that of the insulating film 61 (SiO2 film in this embodiment), a small amount of deposit remains on the upper part of the sidewalls of the second groove 52 and third groove 53 even after etching. Subsequently, during the dry etching of the semiconductor multilayer structure 20A (nitride semiconductor) and the substrate 10 (GaN), which is the next step in forming the ridge portion 20a, the deposits remaining on the upper part of the sidewalls of the second groove 52 and third groove 53 act as a mask, forming the protrusions 25. Note that the deposits remaining on the upper part of the sidewalls of the second groove 52 and third groove 53 in the first step are etched by the dry etching of the semiconductor multilayer structure 20A and the substrate 10, and therefore disappear during the next step of dry etching.
[0094] Next, as shown in Figure 4G, an insulating film 62 (second insulating film) is formed to cover the insulating film 61 on the ridge portion 20a. Specifically, the insulating film 62 is formed to cover the entire upper surface of the semiconductor stacked structure 20A. In this embodiment, the insulating film 6 2 A SiO2 film was formed as follows. For example, the thickness of the insulating film 62 is 200 nm.
[0095] Subsequently, an annealing treatment is performed to activate the dopant in the p-type semiconductor layer. In this embodiment, since not only the insulating film 62 but also the insulating film 61 is formed on the ridge portion 20a, the ridge portion 20a is protected by two insulating films. This makes it possible to suppress damage to the ridge portion 20a due to the heat of the annealing treatment.
[0096] Next, as shown in Figure 4H, the insulating film 62 and the insulating film 61 are removed. This exposes the entire surface of the semiconductor laminated structure 20A on which the ridge portion 20a and the wing portion 20c are formed. Consequently, the second groove 52 and the third groove 53 formed in the semiconductor laminated structure 20A are also exposed.
[0097] At this time, when the fabricated semiconductor laser element 1 was examined in the area corresponding to region V enclosed by the dashed line in Figure 4H(d), it was confirmed that protrusions 25 are formed on the edges of the upper surface of the semiconductor stacked structure 20A in the second groove 52 and the third groove 53, as shown in Figure 5. Furthermore, it was confirmed that the protrusions 25 are covered with an insulating film 81. Figure 5 shows a cross-sectional SEM image of the area corresponding to region V enclosed by the dashed line in Figure 4H(d). Note that in Figure 4H, the depth of the second groove 52 is made deeper than the depth of the third groove 53, but in Figure 5, the semiconductor laser element 1 is shown when the depths of the second groove 52 and the third groove 53 are the same.
[0098] Next, as shown in Figure 4I, a p-side electrode 41 is formed on the ridge portion 20a. Specifically, an insulating film 81 having an opening is formed on the upper surface of the ridge portion 20a, and the p-side electrode 41 is formed so as to cover the upper surface of the ridge portion 20a. The p-side electrode 41 can be formed into a predetermined shape using, for example, a vapor deposition method and a lift-off method. After that, further, p side A pad electrode 82 is formed so as to span across the electrode 41 and the insulating film 81.
[0099] Next, as shown in Figure 4J, the n-side electrode 42 is formed on the back surface of the substrate 10. The n-side electrode 42 can be formed into a predetermined shape using, for example, a vapor deposition method and a lift-off method.
[0100] Subsequently, although not shown in the diagram, the semiconductor laminated substrate 2 is divided to produce multiple bar-shaped substrates, each having multiple optical waveguides (first division step). In this embodiment, multiple bar-shaped substrates are produced by cleaving and dividing the semiconductor laminated substrate 2.
[0101] Furthermore, a first groove 51 is formed on the back surface of the semiconductor laminated substrate 2 or the bar-shaped substrate. The first groove 51 is a guide groove for dividing the bar-shaped substrate into multiple semiconductor laser elements 1. Therefore, the first groove 51 is formed at each boundary between two adjacent semiconductor laser elements 1. In other words, the first groove 51 is formed parallel to the longitudinal direction of the ridge portion 20a. Also, the first groove 51 is located in a position set back from both end faces when the semiconductor laminated substrate 2 is divided into multiple bar-shaped substrates. In other words, the first groove 51 is formed so as not to reach the end faces of the multiple bar-shaped substrates. Such a first groove 51 can be formed by irradiating the back surface of the substrate 10 with laser light. Specifically, the first groove 51 is a laser scribe groove formed by the laser scribe method.
[0102] After dividing the semiconductor laminated substrate 2 to produce multiple bar-shaped substrates, a first coating film 31 and a second coating film 32 are formed on the end faces of the bar-shaped substrates. Then, the bar-shaped substrates are divided along the first groove 51 to produce multiple semiconductor laser elements 1, each having one optical waveguide (ridge portion 20a) (secondary division step). Specifically, the bar-shaped substrates are divided in the same manner as shown in Figure 8. This allows for the production of semiconductor laser elements 1 shown in Figures 1 to 3. Some of these elements may have cracks, as shown in Figure 6.
[0103] In Figure 6, (a) is a top view, (b) is a cross-sectional view along line bb in (a), (c) is a cross-sectional view along line cc in (a), (d) is a cross-sectional view along line dd in (a), and (e) is a side view of the semiconductor laser element 1 viewed from the rear, with the second coating film 32 omitted. The thick lines in Figure 6 indicate cracks 90 that have occurred in the semiconductor laser element 1. Due to the inclination of the crack surface 90, the depth position of the crack 90 on the side surface of the semiconductor stacked structure 20 is deeper than the depth position of the crack 90 in the cross-section along line dd. 6 The hatched area of the dots in (a) indicates the area where crack 90 occurred.
[0104] As shown in Figure 6, the semiconductor laser element 1 fabricated as described above has a second groove 52 formed in the semiconductor stacked structure 20. The second groove 52 is formed along the resonator length direction from the end face of the semiconductor stacked structure 20.
[0105] With this configuration, as shown in Figure 6, even if a crack 90 occurs in the piece splitting process (secondary splitting process) in which the bar-shaped substrate is divided into multiple pieces, extending diagonally upward from near the interface between the substrate 10 and the semiconductor laminated structure 20 toward the ridge portion 20a, the propagation of the crack 90 is prevented by the second groove 52. As a result, the crack 90 does not extend toward the ridge portion 20a, thereby suppressing a decrease in the reliability of the semiconductor laser element 1 due to the crack 90. but can.
[0106] Furthermore, in the semiconductor laser element 1 of this embodiment, a third groove 53 is formed in the semiconductor stacked structure 20. The third groove 53 extends along the resonator length direction of the semiconductor laser element 1 so as to cut out the side surface of the semiconductor stacked structure 20.
[0107] This configuration improves the straightness of the division process during the individual piece division stage.
[0108] Furthermore, in the semiconductor laser element 1 of this embodiment, the depth of the second groove 52 is deeper than the portion of the surface of the semiconductor stacked structure 20 that is closest to the substrate 10. Specifically, as shown in Figures 6(d) and (e), the depth of the second groove 52 is deeper than the depth of the third groove 53.
[0109] In the semiconductor laser element 1A shown in Figure 7, the depth of the second groove 52A and the depth of the third groove 53 are the same, and the location where the crack 90 originates is deeper than that. In this case, as shown by the dashed line, the average direction of crack propagation 90 does not intersect with the second groove 52A, but as shown by the solid line, the angle of propagation of the crack 90 changes due to factors such as a sudden decrease in the distance to the surface along the way, and as a result, it may be possible to prevent the crack 90 from propagating to the ridge portion 20a. Therefore, by making the depth of the second groove 52 deeper than or equal to the depth of the third groove 53, the propagation of the crack 90 can be effectively prevented by the second groove 52.
[0110] Furthermore, since cracks 90 frequently originate from a point approximately 2 μm below the part of the semiconductor stacked structure 20's surface that is closest to the substrate 10 (for example, the upper surface of the third groove 53), the depth of the second groove 52 should be at least 2 μm from the part of the semiconductor stacked structure 20's surface that is closest to the substrate 10.
[0111] Furthermore, as described above, in the cross section perpendicular to the resonator length direction of the semiconductor laser element 1 (see Figure 6(d)), many of the cracks 90 that occur extend diagonally upward from the side of the semiconductor stacked structure 20 at an angle of 1.5° with respect to the main surface of the substrate 10. In this case, in the wingless portion 20d, if the depth of the third groove 53 from the top surface of the semiconductor stacked structure 20 is A, the length from the bottom of the third groove 53 to the depth direction of the starting point of the crack 90 is B, the width of the third groove 53 on the top surface of the semiconductor stacked structure 20 is C, the distance from the wall surface of the third groove 53 to the outer inner surface of the second groove 52 is D, and the angle of the crack 90 with respect to the main surface of the substrate 10 in the cross section perpendicular to the resonator length direction of the semiconductor laser element 1 is θ1, then the depth Z of the second groove 52 is expressed as Z = (A + B) - (C + D) × tanθ1.
[0112] Here, as described above, B=2μm and θ1=1.5°, so if A=1μm, C=4μm, and D=8μm, then Z=(1+2)-(4+8)tan(1.5°)≈2.69μm. In other words, by making the depth Z of the second groove 52 2.69μm or more, it is possible to avoid the cracks 90 that occur during fragmentation reaching below the ridge portion 20a. Also, since the bottom part of the third groove 53 may chip during fragmentation, the angle of the crack 90 near the point of origin may be greater than 1.5°. For example, the depth of the second groove 52 is 1μm and 3μm, the distance between the third groove 53 and the second groove 52 is 9μm or less (4μm, 7μm, 8μm, 9μm), and the width of the third groove 53 is 4μm.
[0113] Furthermore, as described above, in the cross section parallel to the side surface of the semiconductor laser element 1 (see Figure 6(b)), many of the cracks 90 that occur are formed diagonally upward from the end face of the semiconductor laminated structure 20 at an angle of 16° with respect to the main surface of the substrate 10. In this case, if the angle of the crack 90 with respect to the main surface of the substrate 10 in the cross section parallel to the side surface of the semiconductor laser element 1 in the wingless portion 20d is θ2, then the length Y of the second groove 52 in the resonator length direction from the rear end face of the semiconductor laminated structure 20 can be expressed as Y = (A + B) / tanθ2 using A and B described above.
[0114] Here, as described above, B = 2 μm and θ2 = 16°, so if A = 1 μm, then Y = (1 + 2) / tan(16°) ≈ 10.5 μm. In other words, by making the length Y of the second groove 52 in the resonator length direction 10.5 μm or more (at least 10 μm or more), it is possible to avoid the cracks 90 generated during fragmentation reaching below the ridge portion 20a.
[0115] Furthermore, the length Y of the second groove 52 in the resonator length direction from the rear end face of the semiconductor multilayer structure 20 should be 25 times or less the distance between the third groove 53 and the second groove 52. This helps to suppress defects such as chipping in the portion between the third groove 53 and the second groove 52.
[0116] Furthermore, as shown in Figures 6(d) and 6(e), in the semiconductor laser element 1 of this embodiment, the depth of the third groove 53 is deeper than the position of the active layer 22, which is the PN junction of the semiconductor stacked structure 20.
[0117] This configuration allows for easy separation of the semiconductor laser element 1 by the third groove 53. Furthermore, if the depth of the third groove 53 is shallower than the position of the PN junction, the PN junction may be exposed during fragment separation, potentially causing leakage at the PN junction. However, by making the depth of the third groove 53 deeper than the position of the PN junction, leakage at the PN junction during fragment separation can be suppressed.
[0118] Furthermore, by making the depth of the third groove 53 shallower, the starting point of the crack 90 at the corner of the semiconductor stacked structure 20 becomes shallower. In other words, the distance of the crack 90 that extends upward from the side surface of the semiconductor stacked structure 20 is shortened. For example, the depth of the third groove 53 is 1 μm to 3 μm. By reducing the depth of the starting point of the crack 90, the distance the crack 90 travels to reach the surface can be shortened.
[0119] Furthermore, in the semiconductor laser element 1 of this embodiment, the side surface of the second groove 52 is inclined. Also, the side surface of the third groove 53 is inclined.
[0120] This configuration allows the angle between the top surface of the semiconductor laminated structure 20 and the side surface of the second groove 52 to be obtuse. Furthermore, the angle between the top surface of the semiconductor laminated structure 20 and the side surface of the third groove 53 can also be made obtuse. This suppresses the occurrence of chipping around the second groove 52 and the third groove 53 in the semiconductor laminated structure 20 during the primary splitting process, which divides the semiconductor laminated substrate 2 into multiple bar-shaped substrates.
[0121] Furthermore, in the semiconductor laser element 1 of this embodiment, the distance between the second groove 52 and the ridge portion 20a in a top view is 4 μm or more. With this configuration, the propagation of cracks 90 that extend upward at an angle from the side surface (semiconductor laminated structure 20) of the semiconductor laser element 1 can be efficiently prevented by the second groove 52, and lateral current constriction can be effectively achieved. Note that the second groove 52 is more effective at preventing cracks 90 that propagate diagonally upward when it is farther from the side surface (semiconductor laminated structure 20) of the semiconductor laser element 1. In other words, it is better for the second groove 52 to be closer to the ridge portion 20a than to the side surface of the semiconductor laser element 1.
[0122] Furthermore, in the semiconductor laser element 1 of this embodiment, the length of the second groove 52 in the resonator length direction is 1 / 2 or more of the distance between the first groove 51 and the end face of the semiconductor laminated structure 20. For example, the length of the second groove 52 in the resonator length direction is 14 μm, and the distance between the first groove 51 and the end face of the semiconductor laminated structure 20 is 13 μm.
[0123] This configuration effectively suppresses the occurrence of crack 90 itself.
[0124] Furthermore, in the semiconductor laser element 1 according to this embodiment, protrusions 25 are formed on the surface of the edge in the wingless portion 20d of the semiconductor stacked structure 20 in a direction perpendicular to the resonator length direction of the semiconductor stacked structure 20. Specifically, protrusions 25 are formed on the edge which is the boundary between the surface of the semiconductor stacked structure 20 and the side surface of the second groove 52. Also, protrusions 25 are formed on the edge which is the boundary between the surface of the semiconductor stacked structure 20 and the side surface of the third groove 53.
[0125] With this configuration, when a protective member such as SiO2 is placed on the wafer during the wafer splitting process (primary splitting process, secondary splitting process), the height of the protective member becomes greater than or equal to the height of the ridge portion 20a, thereby suppressing the stress applied to the ridge portion 20a during splitting. This suppresses the occurrence of chipping (edge step, etc.) in the ridge portion 20a due to stress during splitting.
[0126] Furthermore, the formation of protrusions 25 on the semiconductor stacked structure 20 increases the surface area of the semiconductor stacked structure 20. This increases the contact area between the solder and the semiconductor laser element 1 when the semiconductor laser element 1 is mounted on the submount with solder, thereby improving bonding and adhesion.
[0127] (modified version) The semiconductor laser element and the method for manufacturing the semiconductor laser element described herein have been explained above based on embodiments, but this disclosure is not limited to the embodiments described above.
[0128] For example, in the above embodiment, the waveguide in the semiconductor laser element 1 is a ridge portion 20a, but it is not limited to this. For example, the waveguide in the semiconductor laser element 1 may not be a ridge stripe structure consisting of a ridge portion 20a, but an electrode stripe structure consisting only of divided electrodes, or a current constriction structure using a current blocking layer, etc.
[0129] Furthermore, while the semiconductor laser element 1 in the above embodiment uses a nitride-based semiconductor material as an example, it is not limited to this. For example, this disclosure can also be applied to cases where semiconductor materials other than nitride-based semiconductor materials are used.
[0130] Furthermore, this disclosure also includes forms that can be obtained by applying various modifications to the above embodiments as conceived by those skilled in the art, as well as forms that can be realized by arbitrarily combining the components and functions of each embodiment without departing from the spirit of this disclosure. [Industrial applicability]
[0131] The semiconductor laser element relating to this disclosure is useful as a light source element in various products, including projectors, optical discs, automotive headlamps, lighting devices, and laser processing equipment. [Explanation of Symbols]
[0132] 1. 1A Semiconductor Laser Element 1a Front end surface 1b Rear end surface 1c 1st side 1d 2nd side 2. Semiconductor multilayer substrate 10 circuit boards 20, 20A Semiconductor Stacked Structure 20a Ridge section 20b Flat part 20c Wing section 20d Wingless section 21 First Semiconductor Layer 22 Active layer 23 Second Semiconductor Layer 24 recesses 25 Protrusion 31. First coating film 32 Second Coating Film 41 p side electrode 42 n-side electrode 51 First groove 52 2nd groove 52a Recess 53 Third groove 61, 62 Insulating film 71 First Registration 71a 1st opening 71b 2nd opening 72 Second Registration 72a opening 81 Insulating Film 82 Pad electrodes 90 Crack 101 Adhesive Sheet 102 Protective film 103 Blade-shaped jig
Claims
1. A semiconductor laser element having a resonator end face and a pair of side surfaces intersecting the resonator end face, circuit board and Multiple semiconductors are formed on one side of the aforementioned substrate and are composed of nitride-based semiconductor materials. A semiconductor stacked structure comprising stacked layers, The semiconductor stacked structure has an optical waveguide extending along the resonator length direction of the semiconductor laser element, On the other surface of the substrate, a pair of first grooves are formed that extend along the length direction of the resonator so as to cut out the pair of side surfaces. Both ends of each of the pair of first grooves in the resonator length direction are located recessed from the end face of the semiconductor laminated structure. The semiconductor stacked structure has a second groove formed in it, extending from the end face of the semiconductor stacked structure along the length direction of the resonator. In a top view, the second groove is formed on both sides of the optical waveguide and is formed between the first groove and the optical waveguide. The semiconductor stacked structure has a third groove formed therein that extends along the length direction of the resonator so as to cut out the side surface of the semiconductor stacked structure. The depth of the second groove is greater than or equal to the depth of the third groove. The longitudinal direction of the second groove is the length direction of the resonator. Semiconductor laser element.
2. The depth of the second groove is greater than the depth of the third groove. The semiconductor laser element according to claim 1.
3. The distance between the second groove and the third groove is 9 μm or less. The semiconductor laser element according to claim 1 or 2.
4. The depth of the second groove is deeper than or equal to the portion of the surface of the semiconductor stacked structure that is closest to the substrate. A semiconductor laser element according to any one of claims 1 to 3.
5. The length of the second groove in the resonator length direction is 10 μm or more from the end face of the semiconductor laminated structure, and 25 times or less the distance between the third groove and the second groove. A semiconductor laser element according to any one of claims 1 to 4.
6. The aforementioned semiconductor stacked structure has a PN junction, The depth of the third groove is deeper than the position of the PN joint. A semiconductor laser element according to any one of claims 1 to 5.
7. The side surface of the third groove is inclined. A semiconductor laser element according to any one of claims 1 to 6.
8. In a top view, the distance between the second groove and the optical waveguide is 4 μm or more. A semiconductor laser element according to any one of claims 1 to 7.
9. The second groove is formed from the end face of the semiconductor stacked structure opposite to the surface from which the laser light is emitted. A semiconductor laser element according to any one of claims 1 to 8.
10. The side surface of the second groove is inclined. A semiconductor laser element according to any one of claims 1 to 9.
11. The length of the second groove in the resonator length direction is at least half the distance between the first groove and the end face of the semiconductor laminated structure. A semiconductor laser element according to any one of claims 1 to 10.
12. A process for manufacturing a semiconductor laminated substrate having a semiconductor laminated structure by stacking multiple semiconductor layers made of nitride-based semiconductor material on one side of a substrate, A first etching step for etching the semiconductor stacked structure, A second etching step is performed after the first etching step, in which the semiconductor stacked structure is etched. A division step is performed to divide the semiconductor laminated substrate to produce a plurality of bar-shaped substrates, each having a plurality of optical waveguides, A step of forming a first groove on the back surface of the semiconductor laminated substrate or the bar-shaped substrate, The process includes a division step of dividing the bar-shaped substrate along the first groove to produce a plurality of semiconductor laser elements, each having one optical waveguide, In the first etching step, a recess is formed in the semiconductor stacked structure, and a third groove is formed that cuts out the side surface of the semiconductor stacked structure and extends along the resonator length direction of the semiconductor laser element. In the second etching step, the recess is further etched to form a second groove, and a ridge is formed in the semiconductor laminated structure as the optical waveguide. In a top view, the second groove is formed on both sides of the optical waveguide so as to extend from the end face of the semiconductor stack structure along the resonator length direction of the semiconductor laser element, and is formed between the first groove and the optical waveguide. The depth of the second groove is greater than or equal to the depth of the third groove. The longitudinal direction of the second groove is the length direction of the resonator. A method for manufacturing semiconductor laser devices.
13. The distance between the second groove and the third groove is 9 μm or less. A method for manufacturing a semiconductor laser element according to claim 12.