WO2023219132A1 - Semiconductor laser element and method for producing semiconductor laser element - Google Patents

Abstract

Provided is a semiconductor laser element (1) comprising a semiconductor laminated structure (20) that is formed on one surface a substrate (10), a first coating film (31) that is formed on an end surface (20F) on the front side of the semiconductor laminated structure (20), and second coating film (32) that is formed on an end surface (20R) on the rear side of the semiconductor laminated structure (20), wherein: the film thickness of the second coating film (32) is greater than the film thickness of the first coating film (31); on a side surface of the semiconductor laser element (1), a first groove (51) that extends along a resonator length direction of the semiconductor laser element (1) is formed as a cutout in the side surface of the semiconductor laser element (1); an end edge (51F) on the front side of the first groove (51) is separate from a front end surface (1a) of the semiconductor laser element (1); and an end edge (51R) on the rear side of the first groove (51) is positioned at a rear end surface (1b) of the semiconductor laser element (1).

Description

Semiconductor laser device and method for manufacturing semiconductor laser device

The present disclosure relates to a semiconductor laser device and a method for manufacturing the semiconductor laser device.

Semiconductor laser elements have advantages such as long life, high efficiency, and small size, so they are used as light sources for various products such as projectors, optical disks, vehicle headlamps, lighting devices, and laser processing equipment. In recent years, research and development of nitride-based semiconductor lasers, which can cover a wavelength range from ultraviolet to blue, has been progressing as a semiconductor laser element.

Semiconductor laser devices are manufactured by cutting out a plurality of bar-shaped substrates (semiconductor laser bars) by dividing a semiconductor multilayer substrate in which a plurality of semiconductor layers are stacked on a wafer, and then dividing the bar-shaped substrate into a plurality of individual pieces. It can be made by cutting into pieces. In such a dividing process, problems occur such as divisions deviating from the planned dividing line or parts missing.

In particular, unlike gallium arsenide lasers used in optical pickups or optical communications, nitride semiconductor lasers are split at crystal planes rather than cleavage planes in the splitting process, so the planned splitting line Problems such as deviating from the target and splitting or parts being chipped are likely to occur.

Therefore, a technique has conventionally been proposed in which semiconductor laser devices are manufactured by dividing a wafer using guide grooves. For example, Patent Document 1 discloses a method of dividing a wafer on which a plurality of semiconductor layers are stacked by irradiating the back surface of the wafer with laser light to form dividing grooves.

International Publication No. 2008/047751

However, even if the method disclosed in Patent Document 1 is used, a bar-shaped substrate obtained by dividing a semiconductor laminated substrate in which a plurality of semiconductor layers are stacked on a wafer is further divided into a plurality of pieces, and semiconductor laser elements are individually cut into pieces. In the process of converting semiconductor laser devices, cracks or chipping may occur in the semiconductor laser device, resulting in a reduction in the reliability of the semiconductor laser device.

The present disclosure has been made to solve such problems, and aims to provide a highly reliable semiconductor laser device and a method for manufacturing the semiconductor laser device.

In order to achieve the above object, one embodiment of a first semiconductor laser element according to the present disclosure includes a semiconductor stacked structure formed on one surface of a substrate, and a semiconductor stacked structure formed on a front end surface of the semiconductor stacked structure. and a second coat film formed on the rear side end surface of the semiconductor laminated structure, the second coat film having a thickness greater than that of the first coat film. A groove extending along the cavity length direction of the semiconductor laser element is formed on a side surface of the semiconductor laser element so as to cut out the side surface, and the front edge of the groove is formed on the side surface of the semiconductor laser element. The groove is spaced apart from the front end surface of the semiconductor laser element, and the rear edge of the groove is located at the rear end surface of the semiconductor laser element.

Further, one aspect of a second semiconductor laser element according to the present disclosure includes a semiconductor stacked structure formed on one surface of a substrate, and a first coat film formed on a front end surface of the semiconductor stacked structure. and a second coat film formed on the rear end face of the semiconductor laminated structure, the second coat film being thicker than the first coat film, and the semiconductor laser element A groove extending along the cavity length direction of the semiconductor laser element is formed in a side surface of the semiconductor laser element so as to cut out the side surface, and a front edge of the groove is formed on the front end surface of the semiconductor laser element. The rear end edge of the groove is spaced apart from the rear end surface of the semiconductor laser element, and the distance between the rear end edge and the rear end surface is equal to the front end edge. and the front end surface.

Further, one aspect of the method for manufacturing a semiconductor laser device according to the present disclosure includes the steps of: manufacturing a semiconductor multilayer substrate having a semiconductor multilayer structure by stacking a plurality of semiconductor layers on one surface of a substrate; a step of manufacturing a plurality of bar-shaped substrates by dividing a multilayer substrate; a step of forming a first coat film on a front end surface of the semiconductor multilayer structure in each of the plurality of bar-shaped substrates; forming a second coat film on the rear end surface of the semiconductor laminated structure in each of the plurality of bar-shaped substrates; and the bar-shaped substrate on which the first coat film and the second coat film are formed. irradiating the bar-shaped substrate with a laser beam to form a groove; and cutting the bar-shaped substrate along the groove to divide the bar-shaped substrate into a plurality of semiconductor laser elements. In the forming step, the laser beam is scanned from the front side to the rear side of the bar-shaped substrate.

According to the present disclosure, it is possible to suppress the occurrence of cracks or chipping during the manufacturing process, so it is possible to obtain a highly reliable semiconductor laser element.

FIG. 1 is a perspective view of the semiconductor laser device according to the first embodiment, viewed from above. FIG. 2 is a perspective view of the semiconductor laser device according to the first embodiment, viewed from below. FIG. 3 is a top view of the semiconductor laser device according to the first embodiment. FIG. 4A is a cross-sectional view of the semiconductor laser device according to the first embodiment taken along line IVA-IVA in FIG. 3. FIG. FIG. 4B is a cross-sectional view of the semiconductor laser device according to the first embodiment taken along line IVB-IVB in FIG. 3. FIG. FIG. 5 is a side view of the semiconductor laser device 1 according to the first embodiment. FIG. 6 is a diagram for explaining each step in the method for manufacturing a semiconductor laser device according to the first embodiment. FIG. 7 is a diagram for explaining a process of forming a first groove in a bar-shaped substrate by laser scribing. FIG. 8 is a diagram showing the relationship between the laser beam output and the laser beam irradiation position when forming the first groove in the method for manufacturing a semiconductor laser device according to the first embodiment. FIG. 9 is a diagram schematically showing the rear end face and front end face of the semiconductor laser device before and after cleaning. FIG. 10 is a perspective view of the semiconductor laser device according to Modification 1 of Embodiment 1, viewed from below. FIG. 11 is a diagram showing the relationship between the laser beam output and the laser beam irradiation position when forming the first groove in the method for manufacturing a semiconductor laser device according to the first modification of the first embodiment. FIG. 12 is a perspective view of the semiconductor laser device according to the second modification of the first embodiment, viewed from below. FIG. 13 is a diagram showing the relationship between the laser beam output and the laser beam irradiation position when forming the first groove in the method for manufacturing a semiconductor laser device according to the second modification of the first embodiment. FIG. 14 is a perspective view of the semiconductor laser device according to the second embodiment, viewed from below. FIG. 15 is a diagram showing the relationship between the laser beam output and the laser beam irradiation position when forming the first groove in the method for manufacturing a semiconductor laser device according to the second embodiment. FIG. 16 is a perspective view of a semiconductor laser device according to a modification of the second embodiment, viewed from below. FIG. 17 is a diagram showing the relationship between the laser beam output and the laser beam irradiation position when forming the first groove in the method for manufacturing a semiconductor laser device according to a modification of the second embodiment. FIG. 18 is a perspective view of a semiconductor laser device according to a modification as viewed from below. FIG. 19 is a diagram for explaining a step of dividing a bar-shaped substrate into a plurality of semiconductor laser elements (piece division step). FIG. 20 is a diagram showing the configuration of a semiconductor laser device of a comparative example.

(How one aspect of the present disclosure was obtained)
First, prior to describing the embodiments of the present disclosure, the circumstances that led to one aspect of the present disclosure will be described.

Generally, when mass producing semiconductor laser devices, a plurality of bar-shaped substrates are created by dividing a semiconductor laminated substrate in which a plurality of semiconductor layers are stacked on a substrate (a wafer) (primary dividing step). After forming a coating film on both end surfaces of this bar-shaped substrate, the bar-shaped substrate is further divided into a plurality of pieces to separate into a plurality of semiconductor laser elements (secondary division step). Thereby, a plurality of semiconductor laser devices can be obtained from one wafer.

Conventionally, when dividing a bar-shaped substrate into individual pieces, a dividing groove (guide groove) is formed in advance in the semiconductor laminated substrate or bar-shaped substrate, and the bar-shaped substrate is divided into a plurality of pieces along the groove. is proposed. 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 grooves 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 cavity end face of the semiconductor laser element from being thermally damaged by the laser beam used to form the groove, the end of the groove in the cavity direction is set back from the cavity end face. irradiate with laser light. In other words, the laser light is irradiated so that the dividing grooves do not reach the positions that will become the resonator end faces on the front side and rear side of the bar-shaped substrate.

However, when the inventors of the present invention actually produced a semiconductor laser device using such a method, it was found that cracks were generated in the semiconductor laser device during the individual piece division step of dividing the bar-shaped substrate into a plurality of pieces. This point will be explained in detail below.

As shown in FIG. 19, a bar-shaped substrate 3X with 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 bar-shaped substrate 3X is placed at a position corresponding to the dividing groove 51X. A blade-like jig 103 such as a cutter is successively pushed into the substrate 3X from above. Thereby, the bar-shaped substrate 3X can be divided into a plurality of pieces to obtain a plurality of semiconductor laser elements 1X.

At this time, when observing the obtained semiconductor laser device 1X, as shown in FIG. It was found that a crack 90X extending obliquely upward toward the bottom of the ridge portion 20a was generated. In this way, if the crack 90X extends below the ridge portion 20a, the reliability of the semiconductor laser device 1X will decrease.

FIG. 20 is a diagram showing the configuration of a semiconductor laser device 1X of a comparative example when manufactured by the method of Patent Document 1. In FIG. 20, (a) is a top view of the semiconductor laser device 1X, (b) is a cross-sectional view taken along the bb line in (a), and (c) is a top view of the semiconductor laser device 1X. FIG. FIG. 20(d) is a side view of the semiconductor laser device 1X viewed from the rear end surface side with the second coat film 32X on the end surface omitted. Further, the thick line in FIG. 20 indicates the crack 90X that has occurred in the semiconductor laser element 1X, and the dotted hatched area in (a) of FIG. 20 indicates the region where the crack 90X has occurred. Note that the semiconductor stacked structure 20X is covered with an insulating film 60 having an opening on the ridge portion 20a, and is also covered with a pad electrode 70.

When the plurality of semiconductor laser devices 1X obtained were examined, it was found that the cracks 90X were generated in a triangular planar shape, as shown in FIG. 20(a). Specifically, as shown in FIGS. 20(b) and 20(d), many cracks 90X that occur occur on the side surface of the semiconductor stacked structure 20X in a cross section perpendicular to the cavity length direction of the semiconductor laser element 1X. Therefore, the crack first propagates obliquely upward in the vicinity of the groove 51X, and then extends slightly obliquely upwardly at an angle of about 1.5° with respect to the main surface of the substrate 10X at a place away from the groove 51X, and the semiconductor laser In a cross section parallel to the side surface of the element 1X, it was found that it extends obliquely upward from the end surface of the semiconductor stacked structure 20X at an angle of about 16° with respect to the main surface of the substrate 10X. Furthermore, many of the cracks 90X originate from a portion approximately 2 μm below the portion of the surface of the semiconductor stacked structure 20X located closest to the substrate 10X (in FIG. 20(d), the upper surface of the separation auxiliary groove 52X). It was also found that this occurs. Moreover, it was also found that many cracks 90X occur particularly on the rear end surface side of the semiconductor laser element 1X.

In addition, in both the left and right semiconductor laser elements 1X divided by the blade-shaped jig 103 (see FIG. 19), cracks 90X often occurred starting from the left side surface, but cracks 90X often occurred starting from the right side surface. A crack 90X was sometimes generated at the starting point. Moreover, although the crack 90X did not extend to a position overlapping the groove 51X when viewed from above, there were cases in which the crack 90X extended to a position overlapping the groove 51X.

It has also been found that, in the dividing step of dividing the bar-shaped substrate, chipping may occur on the rear cavity end face of the semiconductor laser element 1X. Specifically, in the dividing step of dividing a bar-shaped substrate, a protective member such as SiO ₂ is sometimes placed on the bar-shaped substrate, but in this case, the ridge portion 20a of the semiconductor laser element is Chips may occur in the ridge due to stress.

The inventors of the present invention have investigated the causes of cracks 90X and chipping on the rear cavity end face of a semiconductor laser element.

As a result, the dividing groove 51X for dividing into individual pieces was formed in the substrate 10X, and the dividing groove 51X was formed so as not to reach the positions that would become the front and rear resonator end faces. I guessed that this was one of the reasons. In other words, it is assumed that one of the causes is that by forming both ends of the groove 51X at a position retracted from the resonator end face, the vicinity of the resonator end face on the front side and rear side becomes less likely to crack.

Another cause is that the thickness of the second coat film 32X formed on the rear side of the resonator end face is greater than the thickness of the first coat film 31X formed on the front side of the resonator end face. I guessed. In other words, in order to emit the laser beam forward, it is necessary to make the reflectance of the second coat film 32X on the rear side higher than the reflectance of the first coat film 31X on the front side. The film thickness of the film 32X is thicker (for example, about 8 times) than the film thickness of the first coat film 31X on the front side. As a result, the vicinity of the rear resonator end face is less likely to break than the front resonator end face.

In this way, both ends of the dividing groove 51X are formed at positions that are set back from the resonator end face, and the thickness of the second coat film 32X on the rear side is made thicker than the first coat film 31X on the front side. It is thought that by increasing the thickness, the vicinity of the rear resonator end face became less likely to crack. As a result, it is thought that a crack 90X or chipping occurred on the rear resonator end face of the semiconductor laser element 1X during the dividing process in which the bar-shaped substrate was divided into multiple parts to produce the semiconductor laser element 1X. .

Therefore, as a result of intensive studies by the inventors of the present invention, we have developed a structure and a structure that can alleviate the stress applied to the resonator end face on the rear side of the bar-shaped substrate during the dividing process of dividing the bar-shaped substrate into a plurality of parts. I found a way.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the embodiments described below each represent a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps (processes) and order of steps, etc. shown in the following embodiments are merely examples, and do not limit the present disclosure. That's not the point. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims representing the most important concept of the present disclosure will be described as arbitrary constituent elements.

Furthermore, each figure is a schematic diagram and is not necessarily strictly illustrated. Therefore, the scale etc. in each figure are not necessarily the same. In each figure, substantially the same configurations are denoted by the same reference numerals, and overlapping explanations will be omitted or simplified.

Furthermore, in this specification, the terms "upper" and "lower" do not refer to the upper direction (vertically upward) or the lower direction (vertically downward) in absolute spatial recognition, but are based on the stacking order in the stacked structure. Used as a term defined by the relative positional relationship. Additionally, the terms "above" and "below" are used not only when two components are spaced apart and there is another component between them; This also applies when they are placed in contact with each other.

(Embodiment 1)
First, the configuration of the semiconductor laser device 1 according to the first embodiment will be explained using FIGS. 1 to 5. FIG. 1 is a perspective view of the semiconductor laser device 1 according to the first embodiment, viewed from above. FIG. 2 is a perspective view of the semiconductor laser device 1 according to the first embodiment, viewed from below. Note that in FIG. 2, the n-side electrode 42 is omitted, and the widths of the first groove 51 and the second groove 52 are exaggerated. FIG. 3 is a top view of the semiconductor laser device 1 according to the first embodiment. 4A and 4B are cross-sectional views of the semiconductor laser device 1 according to the first embodiment. 4A is a cross-sectional view taken along line IVA-IVA in FIG. 3, and FIG. 4B is a cross-sectional view taken along line IVB-IVB in FIG. FIG. 5 is a side view of the semiconductor laser device 1 according to the first embodiment.

As shown in FIGS. 1 to 3, the semiconductor laser device 1 has a front end face 1a and a rear end face 1b, each of which is a resonator end face, and a first side face 1c and a second side face, each of which is a face that intersects with the resonator end face. It has a side surface 1d.

The front end face 1a is a resonator end face from which laser light is mainly emitted from the semiconductor laser element 1. The rear end surface 1b is a resonator end surface on the opposite side to the front end surface 1a of the semiconductor laser element 1. The front end surface 1a and the rear end surface 1b are opposed to each other as a pair of resonator end surfaces. The rear end surface 1b is an end surface opposite to the front end surface 1a.

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 opposed to each other as a pair of side surfaces. 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.

As shown in FIGS. 1 to 5, the semiconductor laser device 1 includes a substrate 10 and a semiconductor stacked structure 20 formed on the upper surface, which is one surface of the substrate 10. The semiconductor stacked structure 20 has a structure in which a plurality of semiconductor layers are stacked, and has a PN junction.

The semiconductor laser device 1 in this embodiment is a nitride semiconductor laser made of a nitride-based semiconductor material. Therefore, the semiconductor stacked structure 20 is a nitride semiconductor stack in which a plurality of nitride semiconductor layers each made of a nitride-based semiconductor material are stacked. Specifically, the semiconductor laser device 1 is a GaN-based nitride semiconductor laser. The laser light emitted from the semiconductor laser element 1 is, for example, light in a wavelength range from ultraviolet to blue.

The semiconductor laser device 1 has an optical waveguide with a front end face 1a and a rear end face 1b serving as resonator reflecting mirrors. Specifically, the semiconductor stacked structure 20 has an optical waveguide. The optical waveguide extends along the cavity length direction of the semiconductor laser device 1. As shown in FIGS. 3, 4A, and 4B, in this embodiment, a ridge portion 20a is formed in the semiconductor stacked structure 20 as an optical waveguide. Therefore, the ridge portion 20a is formed to extend along the cavity length direction of the semiconductor laser device 1. The ridge portion 20a has a convex shape and is formed by digging into the semiconductor stacked structure 20. Note that the semiconductor laser element 1 has a shape that is elongated in the cavity length direction. The length of the semiconductor laser element 1 in the cavity length direction is, for example, 800 μm or more, and in this embodiment, it is 1200 μm.

In the semiconductor laser device 1, a laser resonator is formed by the front end surface 1a and the rear end surface 1b. For this reason, the rear end surface 1b must have a mirror-like structure (for example, a reflectance of 90% or more), and the reflectance of the rear end surface 1b is higher than that of the front end surface 1a. As an example, the reflectance of the front end surface 1a is 5%, and the reflectance of the rear end surface 1b is 95%.

Specifically, as shown in FIGS. 1 to 3, a first coat film 31 serving as a first reflective film is formed on the front side (front side) of the semiconductor laser element 1. Further, on the rear side (rear side) of the semiconductor laser element 1, a second coat film 32 serving as a second reflective film is formed. In this embodiment, the front end surface 1a of the semiconductor laser device 1 is the outer surface of the first coat film 31, and the rear end surface 1b of the semiconductor laser device 1 is the outer surface of the second coat film 32.

The first coat film 31 is formed on the front side end face 20F of the semiconductor stacked structure 20, and the second coat film 32 is formed on the rear side end face 20R of the semiconductor stacked structure 20. In order to make the reflectance of the rear end surface 1b of the semiconductor laser device 1 higher than the reflectance of the front end surface 1a of the semiconductor laser device 1, the reflectance of the second coat film 32 is set to be higher than the reflectance of the first coat film 31. It's getting expensive. As an example, the reflectance of the first coat film 31 is 5%, and the reflectance of the second coat film 32 is 95%.

In addition, in order to make the reflectance of the second coat film 32 higher than the reflectance of the first coat film 31, the thickness of the second coat film 32 on the rear side is equal to the thickness of the first coat film 31 on the front side. It's thicker than. For example, the thickness of the second coat film 32 is more than twice the thickness of the first coat film 31, and in this embodiment, it is about eight times as thick. As an example, the thickness of the first coat film 31 is 100 nm to 400 nm, and the thickness of the second coat film 32 is 700 nm to 1400 nm. In other words, the difference between the thickness of the first coat film 31 and the thickness of the second coat film 32 is 300 nm to 1300 nm.

The first coat film 31 and the second coat film 32 are composed of a dielectric multilayer film in which a plurality of dielectric films are laminated. The first coat film 31 and the second coat film 32 are, for example, dielectric multilayer films in which a plurality of types of dielectric films are combined, such as an Al ₂ O ₃ film, an AlON film, a SiO ₂ film, and a SiN film. Note that the dielectric films forming the first coat film 31 and the second coat film 32 are not limited to crystal films, but may be amorphous films.

The substrate 10 is a semiconductor substrate made of GaN, SiC, etc., or an insulating substrate such as a sapphire substrate. The substrate 10 is, for example, an n-type GaN substrate made of hexagonal GaN single crystal. In this embodiment, an n-type GaN substrate whose main surface is a (0001) plane is used as the substrate 10.

As shown in FIGS. 4A and 4B, the semiconductor stacked structure 20 includes, in order, an n-side first semiconductor layer 21, an active layer 22, and a p-side second semiconductor layer 23 on the substrate 10. . The active layer 22 is a PN junction in the semiconductor stacked structure 20. The first semiconductor layer 21, the active layer 22, and the second semiconductor layer 23 are formed by epitaxially growing a nitride-based semiconductor material using a metal organic chemical vapor deposition (MOCVD) method. I can do it. Each of the first semiconductor layer 21, the active layer 22, and the second semiconductor layer 23 is configured as follows, for example.

The first semiconductor layer 21 includes at least an n-type cladding layer. In this embodiment, the first semiconductor layer 21 has an n-side cladding layer including an n-type cladding layer, and an n-side optical guide layer formed on the n-side cladding layer. The n-side cladding layer and the n-side guide layer may be either a single layer or multiple layers.

As an example, the n-side cladding layer includes an n-AlGaN layer that is an n-type cladding layer made of AlGaN doped with silicon. Note that the n-side cladding layer may have a stacked structure of an n-AlGaN layer and an un-AlGaN layer.

The n-side optical guide layer includes an optical guide layer (un-InGaN layer) made of undoped InGaN. Note that the n-side guide layer may have a stacked structure of an un-InGaN layer and an n-GaN layer.

The active layer 22 is a quantum well active layer. The active layer 22 has a laminated structure in which well layers made of undoped InGaN and barrier layers made of undoped InGaN are alternately laminated. The active layer 22 may have 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 including 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. be.

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, and a p-type It has a p-side cladding layer including a 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 either a single layer or multiple layers.

As an example, the p-side optical guide layer includes an un-InGaN layer made of undoped InGaN. Note that the p-side optical guide layer may have a laminated structure of an un-InGaN layer and an un-GaN layer.

The OFS layer is a p-AlGaN layer made of AlGaN doped with magnesium as an impurity.

The p-side cladding layer includes a p-AlGaN layer that is a p-type cladding layer doped with magnesium as an impurity. Note that the p-side cladding layer may have a stacked structure of a p-AlGaN layer and an un-AlGaN layer.

The contact layer includes a p-GaN layer that is a p-type contact layer made of GaN doped with magnesium as an impurity. Note that the contact layer may have a stacked structure of a p ⁺ -GaN layer and a P ^- -GaN layer having different impurity concentrations.

The semiconductor laminated structure 20 configured in this manner is formed with a ridge portion 20a and a flat portion 20b that spreads laterally from the root of the ridge portion 20a. By etching the semiconductor stacked structure 20, the ridge portion 20a and the flat portion 20b can be formed. In this embodiment, the second semiconductor layer 23 is dug. That is, 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. As an example, the ridge portion 20a includes a convex portion formed on the p-side cladding layer and a contact layer formed on the convex portion, and the uppermost layer of the ridge portion 20a is the contact layer. . Furthermore, the flat portion 20b is formed in the p-side cladding layer. The flat surface of the flat portion 20b is the surface of the p-side cladding layer.

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. It is as follows. Note that the width of the contact layer is the same as the ridge width of the ridge portion 20a, but is not limited thereto.

Furthermore, in the present embodiment, a convex wing portion 20c is formed in the semiconductor stacked structure 20 by digging into the semiconductor stacked structure 20. That is, 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 second semiconductor layer 23 is dug. Therefore, the wing portion 20c is constituted by the second semiconductor layer 23, and the height of the wing portion 20c is the same as that of the ridge portion 20a. Specifically, the wing portion 20c is composed of a p-side cladding layer and a contact layer, similar to the ridge portion 20a. Note that the upper surfaces of the ridge portion 20a and the wing portion 20c are both flat.

As shown in FIGS. 4A and 4B, the wing portions 20c are formed on both sides of the ridge portion 20a. That is, the semiconductor stacked structure 20 has a pair of wing portions 20c. The ridge portion 20a is sandwiched between a pair of wing portions 20c via a flat portion 20b. The pair of wing portions 20c extend along the resonator length direction of the semiconductor laser device 1, similarly to the ridge portion 20a. In this manner, by providing the wing portions 20c on both sides of the ridge portion 20a, it is possible to reduce the pressure applied to the ridge portion 20a when the semiconductor laser device 1 is mounted in a junction-down manner.

The width of each of the pair of wing portions 20c may be the same as the width of the ridge portion 20a, or may be different from the width of the ridge portion 20a. For example, the width of the wing portion 20c may be greater than the width of the ridge portion 20a. Furthermore, the widths of the pair of wing portions 20c are the same, but may be different.

As shown in FIGS. 4A and 4B, 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 the same as the width of the ridge portion 20a, but may be narrower than the width of the ridge portion 20a.

The p-side electrode 41 is formed using at least one metal material such as Pt, Ti, Cr, Ni, Mo, and Au. The p-side electrode 41 may have either a single layer or multiple layers. In this embodiment, the p-side electrode 41 is an electrode with a two-layer structure including a 40 nm thick Pd layer made of Pd and a 35 nm thick Pt layer made of Pt. Note that a pad electrode 70 is formed on the p-side electrode 41. As an example, the pad electrode 70 has a laminated structure of a Pt layer, a Ti layer, and an Au layer.

On the other hand, an n-side electrode 42 is formed on the lower surface (back surface), which is the other surface of the substrate 10. The n-side electrode 42 is an ohmic electrode that makes ohmic contact with the substrate 10, which is a semiconductor substrate. The n-side electrode 42 is formed using at least one metal material such as Cr, Ti, Ni, Pd, Pt, Au, and Ge. Moreover, the n-side electrode 42 may be either a single layer or a multiple layer.

As shown in FIGS. 4A and 4B, the semiconductor stacked structure 20, except for the p-side electrode 41 on the ridge portion 20a, is covered with an insulating film 60 made of a dielectric film such as SiO ₂ or SiN. Specifically, the insulating film 60 is formed to cover the second semiconductor layer 23 except for the upper surface of the ridge portion 20a. That is, the insulating film 60 is formed so as to have an opening above the ridge portion 20a of the contact layer. The insulating film 60 functions as a current blocking film. Therefore, the opening in the insulating film 60 becomes a current injection window through which current passes. Note that the insulating film 60 may be formed even on the side surface of the semiconductor stacked structure 20.

Further, a pad electrode 70 is formed on the p-side electrode 41. The pad electrode 70 is in contact with the p-side electrode 41. In this embodiment, the pad electrode 70 is wider than the ridge portion 20a and is formed even above the wing portion 20c. That is, the pad electrode 70 is formed on the insulating film 60 so as to cover the ridge portion 20a, the flat portion 20b, and the wing portion 20c. The pad electrode 70 is made of a metal material such as Au. Further, the pad electrode 70 may be formed with an adhesion auxiliary layer made of Ti or the like interposed therebetween. In this case, the adhesion auxiliary layer may also be a part of the pad electrode 70.

A plurality of grooves are formed in the semiconductor laser element 1 configured in this way. Specifically, as shown in FIGS. 1 to 5, a first groove 51 and a second groove 52 are formed in the semiconductor laser element 1 as a plurality of grooves.

The first groove 51 is a guide groove for dividing each of the plurality of bar-shaped substrates into individual pieces after dividing a semiconductor multilayer substrate in which a plurality of 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 a laser beam. In this way, by forming the first grooves 51 on the lower surface (back surface) of the substrate 10 instead of on the upper surface, the stress applied to the bar-shaped substrate when dividing into individual pieces can be reduced, thereby suppressing the occurrence of cracks. 1 and 2, the first groove 51 is illustrated as having an angle (the boundary is composed of a surface), but the first groove 51 is a laser scribe groove formed by a laser beam. Therefore, it is actually formed smoothly without any corners.

As shown in FIGS. 1 and 2, 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 the pair of side surfaces of the semiconductor laser element 1 . Each of the pair of first grooves 51 is formed so as to cut out the side surface of the semiconductor laser element 1 . Specifically, one of the pair of first grooves 51 extends along the resonator length direction so as to cut out the first side surface 1c of the semiconductor laser element 1. Further, the other of the pair of first grooves 51 extends along the resonator length direction so as to cut out the second side surface 1d of the semiconductor laser element 1.

In this embodiment, the pair of first grooves 51 are formed on the side surface of the substrate 10. Specifically, one of the pair of first grooves 51 extends along the resonator length direction so as to cut out one side surface of the substrate 10 corresponding to the first side surface 1c. Further, the other of the pair of first grooves 51 extends along the resonator length direction so as to cut out the other side surface of the substrate 10 corresponding to the second side surface 1d. Specifically, each of the pair of first grooves 51 has a boat-shaped shape.

Furthermore, 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 other surface (that is, the back surface) opposite to one surface of the substrate 10. Therefore, each of the pair of first grooves 51 is formed so as to cut out the side surface of the semiconductor laser element 1 from the back surface of the substrate 10. In this embodiment, the bottom of the first groove 51 is located inside the substrate 10. That is, the first groove 51 is formed in the thickness direction of the substrate 10 so as not to reach from the bottom surface (back surface) of the substrate 10 to the semiconductor stacked structure 20 on the top surface side of the substrate 10 .

Regarding the first groove 51 formed in this manner, the front edge 51F is spaced apart from the front end surface 1a of the semiconductor laser element 1. The front edge 51F of the first groove 51 is the final end of the first groove 51 on the front side in the resonator length direction, and is the part of the first groove 51 that is closest to the front end face 1a in any depth direction. It is. As described above, since the front edge 51F of the first groove 51 is spaced apart from the front end surface 1a of the semiconductor laser element 1, the front end of the first groove 51 in the cavity length direction is separated from the front edge 51F of the semiconductor laser element 1. It is located at a position retreating from the front end surface 1a of the laser element 1.

In the present embodiment, since the first groove 51 is formed from the back surface of the substrate 10, the front edge 51F of the first groove 51 is the closest edge of the boundary between the back surface of the substrate 10 and the first groove 51. This is an end portion close to the front end surface 1a, and is located at a position set back from the front end surface 20F of the semiconductor stacked structure 20. Therefore, the first groove 51 is formed so that the front edge 51F of the first groove 51 does not reach the front end surface 20F of the semiconductor stacked structure 20. Therefore, between the front side edge 51F of the first groove 51 and the front side end surface 20F of the semiconductor stacked structure 20, there is a portion where the first groove 51 is not formed and the semiconductor stacked structure 20 is left. (leftover white) exists. Therefore, the remaining margin of the semiconductor stacked structure 20 and the first coat film 31 are present between the front edge 51F of the first groove 51 and the front end surface 1a of the semiconductor laser element 1. In this embodiment, the distance between the front edge 51F of the first groove 51 and the front end surface 1a of the semiconductor laser element 1 is 10 μm.

Note that, as shown in FIGS. 2 and 5, a region 51FS at the front end of the bottom of the first groove 51 is inclined with respect to the substrate surface. Specifically, if the position of the boundary between the bottom of the first groove 51 and the front side end surface 51FS of the first groove 51 is the front side lower edge 51FB, then the area of the front side end of the bottom of the first groove 51 51FS is inclined from the lower edge 51FB toward the front edge 51F of the first groove 51. That is, in the present embodiment, the front edge 51F of the first groove 51 becomes the edge of the front end region 51FS of the bottom of the first groove 51 on the front end surface 1a side.

On the other hand, the rear end edge 51R of the first groove 51 (indicated by a dashed line in FIG. 2) is located on the rear end surface 1b of the semiconductor laser element 1. The rear end edge 51R of the first groove 51 is the final end of the first groove 51 on the rear side in the resonator length direction. Therefore, since the rear end edge 51R of the first groove 51 is located on the rear end surface 1b of the semiconductor laser element 1, the rear end of the first groove 51 in the cavity length direction is located at the rear end of the semiconductor laser element 1. The semiconductor laser element 1 does not exist at a position retreating from the rear end surface 1b of the semiconductor laser element 1, but is located at the same position as the rear end surface 1b of the semiconductor laser element 1. Therefore, in the vicinity of the rear end surface 1b of the semiconductor laser element 1, the first groove 51 is formed so that the rear edge 51R of the first groove 51 reaches the rear end surface 1b of the semiconductor laser element 1. It is formed so as to penetrate to the rear end surface 1b. That is, the rear side portion of the first groove 51 penetrates both the semiconductor stacked structure 20 and the second coat film 32, and is open toward the outside of the semiconductor laser element 1 in the cavity length direction.

Furthermore, in this embodiment, the depth of the first groove 51 in the rear end region is constant. Furthermore, the depth of the first groove 51 in the rear end region is the same as the depth of the first groove 51 in the central portion. Note that the depth of the first groove 51 is the length from the back surface of the substrate 10 to the bottom surface of the first groove 51. As an example, if the overall thickness of the semiconductor laser device 1 is 85 μm and the thickness of the substrate 10 is 83 μm, the depth of the first groove 51 is 55 μm, and the groove width of the first groove 51 is 2.5 μm. be.

The second groove 52 is formed on the front side of the semiconductor laser element 1. Specifically, the second groove 52 is formed in the semiconductor stacked structure 20. The second groove 52 is an auxiliary separation groove (element separation auxiliary groove) used when separating a plurality of stacked semiconductor layers into optical waveguides in a semiconductor multilayer substrate in which a plurality of semiconductor layers are stacked on a wafer by epitaxial growth. It is. Therefore, as shown in FIGS. 4A and 4B, the second groove 52 is formed on each of the pair of side surfaces of the semiconductor laser element 1. Specifically, one of the pair of second grooves 52 is formed so as to cut out the first side surface 1c of the semiconductor laser element 1. Further, the other of the pair of second grooves 52 is formed so as to cut out the second side surface 1d of the semiconductor laser element 1. The second groove 52 can be formed by etching a plurality of stacked semiconductor layers. As an example, the width of the second groove 52 is 4 μm. The width of the second groove 52 is wider than the width of the first groove 51.

In this embodiment, each of the pair of second grooves 52 is formed so as to cut out the side surface of the semiconductor stacked structure 20 from the top surface of the semiconductor stacked structure 20. Furthermore, the second groove 52 is formed to extend in the direction of the resonator of the semiconductor laser element 1. Specifically, one of the pair of second grooves 52 extends along the resonator length direction so as to cut out one side surface of the semiconductor stacked structure 20 . Further, the other of the pair of second grooves 52 extends along the resonator length direction so as to cut out the other side surface of the semiconductor stacked structure 20 . In this embodiment, each of the pair of second grooves 52 is formed from the front end surface 20F to the rear end surface 20R of the semiconductor stacked structure 20.

The second trench 52 can be formed by digging from the top surface of the semiconductor stacked structure 20 in the stacking direction. As shown in FIGS. 4A and 4B, the depth of the second groove 52 is deeper than the position of the active layer 22, which is the PN junction in the semiconductor stacked structure 20. Further, in this embodiment, the side surface of the second groove 52 is inclined. Specifically, the side surface of the semiconductor laser element corresponding to the second groove 52 is sloped so that the bottom widens along the depth direction.

Next, a method for manufacturing the semiconductor laser device 1 according to the first embodiment will be described using FIG. 6 while referring to FIGS. 4A and 4B. FIG. 6 is a diagram for explaining each step in the method for manufacturing the semiconductor laser device 1 according to the first embodiment.

First, as shown in FIG. 6A, a plurality of semiconductor layers are stacked on one surface of a substrate 10, which is a wafer, to fabricate a semiconductor multilayer substrate 2 having a semiconductor multilayer structure (semiconductor multilayer substrate (fabrication process). The semiconductor laminated substrate 2 includes a semiconductor laminated structure 20 having a plurality of waveguides formed on one surface of a substrate 10 which is a wafer, a p-side electrode 41 formed on the semiconductor laminated structure, and a substrate 10. and an n-side electrode 42 formed on the other surface.

When manufacturing the semiconductor laminated substrate 2, first, a wafer of an n-type GaN substrate is prepared as the substrate 10, and a plurality of nitride semiconductor layers are sequentially epitaxially grown on the entire surface of one surface of the substrate 10. For example, by sequentially epitaxially growing the first semiconductor layer 21, the active layer 22, and the second semiconductor layer 23 on one surface of the substrate 10 by metal organic chemical vapor deposition (MOCVD). A semiconductor stacked structure 20 is formed. Next, a recess corresponding to the second groove 52 is formed in the semiconductor stacked structure 20 by subjecting the semiconductor stacked structure 20 to photolithography and etching. Thereafter, a ridge portion 20a, a flat portion 20b, and a wing portion 20c are formed in the semiconductor layered structure 20 by subjecting the semiconductor layered structure 20 to photolithography and etching. Next, an insulating film 60 is formed so as to partially cover the semiconductor stacked structure 20. Next, a p-side electrode 41 is formed on the ridge portion 20a of the semiconductor stacked structure 20, and then an n-side electrode 42 is formed on the back surface of the substrate 10. Thereby, the semiconductor laminated substrate 2 can be manufactured.

Next, a plurality of bar-shaped substrates 4 are produced by dividing the semiconductor laminated substrate 2. In this embodiment, as shown in FIGS. 6(b) to 6(d), the bar-shaped substrate 4 is manufactured by dividing the semiconductor laminated substrate 2 into two stages.

Specifically, as shown in FIG. 6(b), first, the semiconductor laminated substrate 2 is divided into a plurality of pieces to form a strip-shaped divided substrate having a region for manufacturing a bar-shaped substrate (semiconductor laser bar). Cut out 3 (substrate shaping process).

For example, by cutting the semiconductor multilayer substrate 2 along the five dividing lines shown by the dashed lines in FIG. 6(a), four divided substrates 3 are produced as shown in FIG. 6(b). can do. Specifically, four divided substrates 3 can be cut out from the semiconductor multilayer substrate 2 by cutting the semiconductor multilayer substrate 2 along a certain direction.

Next, as shown in FIG. 6(c), the divided substrate 3 is laser scribed (primary scribing step). Specifically, a plurality of guide grooves (dividing grooves) for dividing the divided substrate 3 are formed by irradiating the divided substrate 3 with laser light. This guide groove is a groove that serves as a cleavage starting point when the divided substrate 3 is cleaved and divided.

Thereafter, as shown in FIG. 6(d), the divided substrate 3 is divided into a plurality of parts (primary dividing step). Specifically, by cleaving and sequentially separating the divided substrate 3 using the guide groove formed in the divided substrate 3 as a starting point, a plurality of bar shapes each having a plurality of waveguides (ridge portions 20a) are formed. A substrate 4 (semiconductor laser bar) is manufactured.

In this way, a plurality of bar-shaped substrates 4 having both end surfaces serving as cleavage planes can be cut out from the semiconductor laminated substrate 2.

Next, as shown in FIG. 6E, a first coat film 31 is formed on the front side end surface 20F of the semiconductor stacked structure in each of the plurality of bar-shaped substrates 4 (front coat step). The black circles in FIG. 6(e) represent how the material constituting the first coat film 31 flies to the end surface. Specifically, a first coat film 31 having a low reflectance is formed on the cleavage plane of the bar-shaped substrate 4 corresponding to the front end surface 1a side of the semiconductor laser device 1. As a result, the first coat film 31 is formed on the front end surface 20F of each of the semiconductor stacked structure and the substrate. For example, as the first coat film 31, a dielectric multilayer film including an Al ₂ O ₃ film, an AlON film, a SiO ₂ film, and a SiN film can be formed.

Next, as shown in FIG. 6F, on the opposite side of the first coat film 31, a second coat film 32 is applied to the rear end surface 20R of the semiconductor stacked structure in each of the plurality of bar-shaped substrates 4. (rear coating process). The black circles in FIG. 6(f) represent how the material constituting the second coat film 32 flies to the end surface. Specifically, the second coat film 32 with high reflectance is formed on the cleavage plane of the bar-shaped substrate 4 corresponding to the rear end surface 1b side of the semiconductor laser element 1. As a result, the second coat film 32 is formed on the rear end surface of each of the semiconductor stacked structure and the substrate. For example, as the second coat film 32, a dielectric multilayer film including an Al ₂ O ₃ film, an AlON film, a SiO ₂ film, and a SiN film can be formed.

Next, as shown in FIG. 6(g), the bar-shaped substrate 4 on which the first coat film 31 and the second coat film 32 are formed is irradiated with a laser beam to form a first groove 51 (secondary scribing process). That is, the first groove 51 is a laser scribe groove formed by laser scribing. The first groove 51 is a guide groove for dividing the bar-shaped substrate 4 into a plurality of semiconductor laser elements 1. Therefore, the first groove 51 is formed at each boundary between two adjacent semiconductor laser elements 1. That is, as shown in FIG. 7, the first groove 51 is formed parallel to the longitudinal direction of the ridge portion 20a. FIG. 7 is a diagram for explaining the process of forming the first groove 51 in the bar-shaped substrate 4 by laser scribing.

As shown in FIG. 7, in the step of forming the first groove 51, a laser beam is scanned from the front side to the rear side of the bar-shaped substrate 4. Further, in the present embodiment, the first groove 51 is formed by irradiating laser light from the back side of the substrate 10. In this case, in this embodiment, the laser beam is irradiated starting from a position retreating from the outer surface of the first coat film 31 formed on the front end surface of the bar-shaped substrate 4, and The laser beam is scanned along the width direction of the bar-shaped substrate 4 (the longitudinal direction of the ridge portion 20a) until it passes over the second coat film 32 formed on the end face of the bar-shaped substrate 4. The first groove 51 formed in this way has a front edge 51F spaced apart from the outer surface of the first coat film 31 and a rear edge 51R located at the same position as the outer surface of the second coat film 32. It is.

Here, a specific example of the laser beam scanning method in this embodiment will be described using FIG. 8. FIG. 8 shows the relationship between the output (power) of the laser beam and the irradiation position (position) of the laser beam when forming the first groove 51. As shown in FIG. 8, in this embodiment, the total length of the bar-shaped substrate 4 on which the first coat film 31 and the second coat film 32 are formed is 1200 μm. Therefore, the position of the outer surface of the first coat film 31 is at the 0 μm position in FIG. 8, and the position of the outer surface of the second coat film 32 is at the 1200 μm position in FIG. Note that the position of the outer surface of the first coat film 31 on the bar-shaped substrate 4 is the position of the front end surface 1a of the semiconductor laser device 1 obtained by dividing the bar-shaped substrate 4, and the position of the outer surface of the first coat film 31 on the bar-shaped substrate 4 is The position of the outer surface corresponds to the position of the rear end surface 1b of the semiconductor laser device 1 obtained by dividing the bar-shaped substrate 4.

Furthermore, in this embodiment, as shown in FIG. 8, the maximum output of the laser beam when forming the first groove 51 is 200 W, and the beam diameter of the laser beam is 5 μm. As a result, the groove width of the first groove 51 becomes 5 μm before division.

Then, as shown in FIG. 8, laser light irradiation is started from a position of 10 μm. In other words, the laser beam irradiation starts from a position 10 μm away from the outer surface of the first coat film 31 . Then, the laser beam is irradiated with the output gradually increasing from the 10 μm position to the 40 μm position, and the laser beam is irradiated with a constant output from the 40 μm position until it penetrates the second coat film 32. In other words, the laser beam irradiation continues even after passing through the second coat film 32. As a result, the front edge 51F is separated from the outer surface of the first coat film 31 by 10 μm, and the rear edge 51R penetrates through the second coat film 32 to form the first groove 51 in the bar-shaped substrate 4. can be formed.

After forming the first grooves 51 in the bar-shaped substrate 4, as shown in FIG. Divide into semiconductor laser elements 1 (secondary dividing step). Specifically, by dividing the bar-shaped substrate 4 into a plurality of pieces along the first groove 51 and singulating them, a plurality of semiconductor laser elements 1 each having one optical waveguide (ridge portion 20a) are manufactured. do.

At this time, in the present embodiment, the front edge 51F of the first groove 51 is spaced apart from the outer surface of the first coat film 31, while the rear edge 51R of the first groove 51 is separated from the outer surface of the first coat film 31. It is located at the same position as the outer surface of the coat film 32. In other words, the first groove 51 does not penetrate through the front portion of the bar-shaped substrate 4 corresponding to the front end surface 1a side portion of the semiconductor laser device 1, but the first groove 51 does not penetrate through the bar-shaped substrate 4 corresponding to the rear end surface 1b side portion of the semiconductor laser device 1. It penetrates through the rear part of 4.

Therefore, even if the second coat film 32 is thicker than the first coat film 31 on the rear end surface of the bar-shaped substrate 4, when dividing the bar-shaped substrate 4 along the first groove 51, In addition, the stress applied to the rear side portion of the bar-shaped substrate 4 can be alleviated compared to the case where the first groove 51 does not penetrate through the rear side portion of the bar-shaped substrate 4. Thereby, it is possible to effectively suppress the occurrence of cracks or chipping on the rear end surface 1b of the semiconductor laser device 1 obtained by dividing the bar-shaped substrate 4.

In the semiconductor laser device 1 manufactured in this manner, the first groove 51 extending along the resonator length direction of the semiconductor laser device 1 cuts out the side surface of the semiconductor laser device 1. It is formed like this. The front edge 51F of the first groove 51 is spaced apart from the front end surface 1a of the semiconductor laser element 1, while the rear edge 51R of the first groove 51 is located behind the semiconductor laser element 1. It is located on the end surface 1b.

As described above, according to the semiconductor laser device 1 according to the present embodiment, it is possible to suppress the occurrence of cracks or chipping when dividing the bar-shaped substrate 4 into individual pieces, so that the semiconductor laser device has high reliability. 1 can be realized. According to the experiments conducted by the inventors of the present application, the semiconductor laser device 1X (FIG. 20) manufactured by the method described in FIG. 19 had a defective rate of 20%; Laser element 1 had a defective rate of 0%.

Further, in this embodiment, since the first groove 51 is formed by laser scribing, processing waste called debris is generated when forming the first groove 51 with a laser beam, and the bar-shaped substrate 4 Debris adheres to the surface. Further, since the first groove 51 is formed by cutting the substrate 10 with a laser beam, the debris is caused by the elements constituting the substrate 10. Specifically, the debris contains gallium metal (Ga). If such debris adheres to the end face of the bar-shaped substrate 4, the debris will remain on the resonator end face of the semiconductor laser device 1 obtained by dividing the bar-shaped substrate 4. As a result, problems such as deterioration of the characteristics of the semiconductor laser device 1 may occur.

Therefore, when the inventors of the present application investigated debris, they found that when forming the first groove 51 by laser scribing, a lot of debris is generated at the start of laser beam irradiation (at the start of scribing), and when the laser beam irradiation ends. It was found that there was less debris (at the end of the scribe).

Therefore, in this embodiment, when forming the first groove 51 by laser scribing, the laser beam is scanned from the front side to the rear side of the bar-shaped substrate 4. By scanning the laser beam in this manner, it is possible to suppress debris from adhering to the outer surface of the second coat film 32 of the bar-shaped substrate 4.

Furthermore, in this embodiment, the first groove 51 is formed so as to penetrate through the second coat film 32 in order to suppress the occurrence of cracks and chipping on the rear end surface 1b of the semiconductor laser element 1. As a result, more debris adheres to the rear end surface 1b of the semiconductor laser element 1 than in the case where the first groove 51 is formed so as not to penetrate through the second coat film 32. In this case, since the first groove 51 cuts not only the substrate 10 but also the second coat film 32, the debris that adheres to the rear end surface 1b is caused by the elements constituting the substrate 10 and the second coat film 32. becomes. Specifically, the debris is an elemental metal such as gallium metal (Ga) or aluminum (Al), and/or an inorganic compound such as aluminum nitride, aluminum oxide, or silicon dioxide.

Therefore, after the step of forming the first groove 51, it is preferable to include a step of removing debris attached to the rear end surface 1b of the semiconductor laser element 1. For example, after the step of cutting the bar-shaped substrate 4 into pieces along the first groove 51, a step of removing debris may be performed. For example, debris made of gallium can be effectively removed by cleaning the rear end surface 1b of the semiconductor laser element 1 with hydrochloric acid. For example, debris on the rear end surface 1b can be removed by cleaning for 5 minutes or more using hydrochloric acid with a concentration of 19%.

FIG. 9 schematically shows the rear end surface 1b and front end surface 1a of the semiconductor laser element 1 before and after cleaning. As shown in FIG. 9(a), debris can be removed by cleaning the rear end surface 1b of the semiconductor laser element 1 with hydrochloric acid. At this time, in the rear end surface 1b of the semiconductor laser element 1 after cleaning, the debris present in the first region A1 below the ridge portion 20a is larger than the debris present in the second region A2 on the side of the first region A1. is also decreasing. At this time, it was possible to eliminate debris from both the first area A1 and the second area A2 by cleaning with hydrochloric acid, but as shown in FIG. Debris sometimes existed in area A2. In addition, in (a) of FIG. 9, there is no debris in the first area A1.

Furthermore, as shown in FIG. 9(b), there was almost no debris on the front end surface 1a of the semiconductor laser device 1 even before cleaning, but by cleaning with hydrochloric acid, the debris on the front end surface 1a was removed. It can be further reduced.

In this manner, by removing debris from the front end surface 1a and rear end surface 1b of the semiconductor laser device 1 by hydrochloric acid cleaning, it is possible to suppress deterioration of the characteristics of the semiconductor laser device 1 due to debris. In particular, in the gain region below the ridge portion 20a, the intensity of the laser beam is stronger than in the outer region of the gain region below the ridge portion 20a, so debris in the gain region below the ridge portion 20a is removed by cleaning with hydrochloric acid. By doing so, it is possible to prevent the light distribution from being disturbed due to light scattering caused by the debris, and from deteriorating the front end surface 1a and the rear end surface 1b due to light absorption and temperature rise due to the debris. Note that the step of removing debris may be performed after the step of forming the first grooves 51 and before dividing the bar-shaped substrate 4 into individual pieces.

Furthermore, in the semiconductor laser device 1 according to the present embodiment, the first groove 51 is formed on the back surface, which is the other surface of the substrate 10.

This makes it possible to suppress debris from adhering to the upper surface of the semiconductor laser element 1, and furthermore, when pressure is applied to the semiconductor laminated structure from above during the mounting process, it is possible to prevent debris from adhering to the semiconductor laminated structure directly below the debris. This can prevent excessive stress from being applied.

Note that, as shown in FIG. 2, in this embodiment, the depth of the rear end of the first groove 51 is made the same as the depth of the center portion of the first groove 51, but the present invention is not limited to this.

For example, as in the semiconductor laser device 1A shown in FIG. 10, the depth of the rear end of the first groove 51A may be deeper than the depth of the central portion of the first groove 51A. Specifically, the depth of the rear end region of the first groove 51A gradually increases toward the rear end surface 1b, and the rear end region of the bottom of the first groove 51A is It is inclined toward the upper surface of the semiconductor laser element 1A toward the rear end surface 1b. In this modification, the depth of the deepest part of the rear end region of the first groove 51A is the depth at the rear end surface 1b of the first groove 51A. As an example, the deepest part of the rear end region of the first groove 51A is preferably about 10 μm deeper than the depth of the central part of the first groove 51A.

The first groove 51A having such a shape can be formed by scanning a laser beam with a profile as shown in FIG. 11. Specifically, as shown in FIG. 11, the depth of the rear end of the first groove 51A can be increased by increasing the output of the laser beam before the rear end of the bar-shaped substrate. can. In addition, in this modification, the output of the laser light is gradually increased from this side of the rear end surface of the bar-shaped substrate toward the rear end surface.

In this way, by making the depth of the rear end of the first groove 51A deeper than the depth of the central part of the first groove 51A, the bar-shaped The stress applied to the rear side portion of the bar-shaped substrate when dividing the substrate can be further alleviated. Thereby, it is possible to further suppress the occurrence of cracks or chipping on the rear end surface 1b of the semiconductor laser element 1A.

Conversely, as in the semiconductor laser device 1B shown in FIG. 12, the depth of the rear end region of the first groove 51B may be made shallower than the depth of the central portion of the first groove 51B. Specifically, the depth of the rear end region of the first groove 51B gradually becomes shallower toward the rear end surface 1b, and the rear end region 51RS of the bottom of the first groove 51B is , is inclined toward the lower surface side of the semiconductor laser element 1B toward the rear end surface 1b. In this modification, the depth of the shallowest part of the rear end region of the first groove 51B is the depth at the rear end surface 1b of the first groove 51B. As an example, the depth of the shallowest portion of the rear end region of the first groove 51B may be approximately 30% of the depth of the semiconductor laser element 1B. For example, when the thickness of the semiconductor laser element 1B is 85 μm, the depth of the first groove 51B at the rear end surface 1b is preferably about 25 μm.

The first groove 51B having such a shape can be formed by scanning a laser beam with a profile as shown in FIG. 13. Specifically, as shown in FIG. 13, the depth of the rear end of the first groove 51B can be made shallow by lowering the output of the laser beam before the rear end face of the bar-shaped substrate. can. In addition, in this modification, the output of the laser light is gradually lowered from this side of the rear end surface of the bar-shaped substrate toward the rear end surface.

In this way, by making the depth of the rear end of the first groove 51B shallower than the depth of the center of the first groove 51B, the laser beam when penetrating the rear end of the bar-shaped substrate can be reduced. Since the output of the bar-shaped substrate is reduced, the amount of scattered debris adhering to the outer surface of the second coat film 32 of the bar-shaped substrate can be reduced. However, in this modification, the effect of relieving the stress applied to the rear side portion of the bar-shaped substrate is lower than in the first embodiment, so the defective rate of the semiconductor laser device 1B increases; We were able to keep it down to 2%.

(Embodiment 2)
Next, a semiconductor laser device 1C according to the second embodiment will be described using FIG. 14. FIG. 14 is a perspective view of the semiconductor laser device 1C according to the second embodiment, viewed from below. Note that FIG. 14 corresponds to FIG. 2 in the first embodiment. Therefore, in FIG. 14, the n-side electrode 42 is omitted as in FIG. 2, and the widths of the first groove 51C and the second groove 52 are exaggerated.

In the semiconductor laser device 1 according to the first embodiment, the first groove 51 was formed so as to penetrate through the rear end surface 1b of the semiconductor laser device 1, but as shown in FIG. 14, the semiconductor laser device according to the present embodiment In 1C, the first groove 51C is formed so as not to penetrate through the rear end surface 1b of the semiconductor laser element 1C.

Therefore, in the semiconductor laser device 1C according to the present embodiment, both ends of each of the first grooves 51C in the cavity length direction are set back from the cavity end surfaces (front end surface 1a, rear end surface 1b) of the semiconductor laser device 1C. exists in In other words, each of the first grooves 51C is formed so that both end portions in the cavity length direction do not reach the front end surface 1a and the rear end surface 1b of the semiconductor laser element 1C. Therefore, the front edge 51F of the first groove 51C is spaced apart from the front end surface 1a of the semiconductor laser element 1C, and the rear edge 51R of the first groove 51C is separated from the rear end surface 1b of the semiconductor laser element 1C. It is separated from.

Specifically, each of both ends of the first groove 51C is formed so as not to reach the first coat film 31 and the second coat film 32. That is, both ends of the first groove 51C are formed so as not to reach the front end surface 20F and the rear end surface 20R of the semiconductor stacked structure 20. Therefore, the front side edge 51F of the first groove 51C is spaced apart from the front side end surface 20F of the semiconductor stacked structure 20, and the rear side edge 51R of the first groove 51C is spaced apart from the front side end surface 20F of the semiconductor stacked structure 20. It is spaced apart from the rear end surface 20R.

However, in the semiconductor laser device 1C in this embodiment, the front edge 51F of the first groove 51C and the rear edge 51R of the first groove 51C are set back from the resonator end face of the semiconductor laser device 1C. The quantities are different. Specifically, the amount of retreat of the rear edge 51R of the first groove 51C is smaller than the amount of retreat of the front edge 51F of the first groove 51C. That is, the distance between the rear edge 51R of the first groove 51C and the rear end surface 1b of the semiconductor laser element 1C is the distance between the front edge 51F of the first groove 51C and the front end surface 1a of the semiconductor laser element 1C. It is shorter than . Also, the position of the boundary between the bottom of the first groove 51C and the region 51RS at the rear end of the bottom of the first groove 51 (lower edge 51RB of the bottom of the first groove 51C on the rear side) and the semiconductor laser element The distance between the rear end surface 1b is the distance between the bottom of the first groove 51C and the region 51FS at the front end of the bottom of the first groove 51 (lower edge 51FB of the first groove 51 on the front side) and the semiconductor laser element. It is shorter than the distance of the front end surface 1a. In addition, the distance between the rear edge 51R of the first groove 51C and the rear end surface 20R of the semiconductor laminated structure is equal to the distance between the front edge 51F of the first groove 51C and the front end surface of the semiconductor laminated structure. It is shorter than the distance of 20F.

The semiconductor laser device 1C configured in this manner can be formed by the same method as in the first embodiment. In this case, in the step of forming the first groove 51C by laser scribing, the first groove 51C having the shape shown in FIG. 14 can be formed by scanning the laser beam with a profile as shown in FIG. . Specifically, as shown in FIG. 15, by lowering the output of the laser beam before the rear end surface of the bar-shaped substrate, the first groove 51C is prevented from penetrating the rear end surface of the bar-shaped substrate. do. In this case, the distance between the rear edge 51R of the first groove 51C and the rear end surface of the bar-shaped substrate is the distance between the front edge 51F of the first groove 51C and the front edge surface of the bar-shaped substrate. The first groove 51C is formed so as to be shorter than the first groove 51C. Further, the distance between the lower edge 51RB on the rear side of the bottom of the groove and the rear end surface 1b of the semiconductor laser element is made shorter than the distance between the lower edge 51FB on the front side of the bottom of the groove and the front end surface 1a of the semiconductor laser element. A first groove 51C is formed in the first groove 51C. In addition, the distance between the rear edge 51R of the first groove 51C and the rear end surface 20R of the semiconductor laminated structure is equal to the distance between the front edge 51F of the first groove 51C and the front edge surface of the semiconductor laminated structure. The first groove 51C is formed to be shorter than the distance 20F.

By forming the first groove 51C in such a shape, even if the second coat film 32 is thicker than the first coat film 31 on the rear end surface of the bar-shaped substrate, the first groove 51C can be formed. When dividing the bar-shaped substrate along 51C, stress applied to the rear side portion of the bar-shaped substrate can be alleviated. Thereby, it is possible to effectively suppress the occurrence of cracks or chipping on the rear end surface 1b of the semiconductor laser device 1C obtained by dividing the bar-shaped substrate.

Furthermore, in the semiconductor laser device 1C according to the present embodiment, when the first groove 51C is formed by laser scribing, the first groove 51C does not penetrate through the rear end surface of the bar-shaped substrate. Compared to this, it is possible to suppress debris from adhering to the outer surface of the second coat film 32 of the bar-shaped substrate.

Also in this embodiment, it is preferable to scan the laser beam from the front side to the rear side of the bar-shaped substrate 4. By forming the first groove 51C without penetrating the second coat film 32, it is possible to further prevent debris from adhering to the outer surface of the second coat film 32 of the bar-shaped substrate 4 than in the first embodiment. It can be suppressed. Moreover, by forming the first groove 51C without penetrating the second coat film 32 when scanning the laser beam from the front side to the rear side of the bar-shaped substrate 4, the rear side of the first groove 51C can be It is also possible to stabilize the shape of the end surface 51RS.

However, in this embodiment, since the first groove 51C does not penetrate through the rear end surface of the bar-shaped substrate, the effect of relieving the stress applied to the rear-side portion of the bar-shaped substrate is more effective than in the first embodiment. It gets lower. Therefore, although the defective rate of the semiconductor laser element 1C was higher than that of the first embodiment, the defective rate could be suppressed to 4%.

Additionally, the output at the start of laser light irradiation is unstable. Therefore, similarly to the first embodiment, when forming the first groove 51C by laser scribing, the laser beam is scanned from the front side to the rear side of the bar-shaped substrate. As a result, in FIG. 14 and the like, the surface roughness of the region 51FS at the front end of the bottom of the first groove 51C is made larger than the surface roughness of the region 51RS at the rear end of the bottom of the first groove 51C. can do. That is, the surface roughness of the region 51RS at the rear end of the first groove 51C is smaller than the surface roughness of the region 51FS at the front end of the first groove 51C. In this embodiment, in FIG. 14, the maximum height roughness of the region 51RS at the rear end of the first groove 51C is 13 μm, whereas the region 51FS at the front end of the first groove 51C The maximum height roughness was 30 μm. In this way, by reducing the surface roughness of the region surface 51RS at the rear end of the first groove 51C, when dividing the bar-shaped substrate along the first groove 51C, the rear side portion of the bar-shaped substrate can be The distribution of such stress can be made gentle. In other words, local concentration of stress can be reduced. As a result, it is possible to suppress the occurrence of cracks caused by abnormal stress.

Note that in the semiconductor laser device 1C shown in FIG. 14, the rear edge 51R of the first groove 51C is formed so as not to reach the second coat film 32, but the present invention is not limited to this.

For example, as in the semiconductor laser device 1D shown in FIG. 16, the rear edge 51R of the first groove 51D may be formed to reach the second coat film 32. That is, the first groove 51D may be formed by cutting part of the second coat film 32 with a laser scribe. In this case, the distance between the rear edge 51R of the first groove 51D and the rear end surface 1b of the semiconductor laser element 1D is shorter than the thickness of the second coat film 32.

The first groove 51D having such a shape can be formed by scanning a laser beam with a profile as shown in FIG. 17. Specifically, as shown in FIG. 17, by reducing the laser output to zero immediately before the rear end surface of the bar-shaped substrate, the rear end 51R of the first groove 51D is coated with the second coating film 32. It can be located in the middle. Specifically, the scribing end point is set immediately before the rear end surface of the bar-shaped substrate (the outer surface of the second coat film 32). Furthermore, this structure can be easily formed by narrowing the beam diameter of the laser beam. For example, by setting the beam diameter to 0.3 μm, the rear edge 51R of the first groove 51D can be formed at a distance of about 0.3 μm from the rear end surface 1b of the semiconductor laser element 1D.

This makes it difficult for cracks or chipping to occur when the second coat film 32 is cut when dividing the bar-shaped substrate. Note that the same effect can be obtained when the second coat film 32 is an amorphous film.

(Modified example)
The semiconductor laser device and the method for manufacturing the semiconductor laser device according to the present disclosure have been described above based on Embodiments 1 and 2, but the present disclosure is not limited to the above-described Embodiments 1 and 2. .

For example, in the first and second embodiments described above, the first grooves 51 to 51D are formed on one surface (front surface) of the substrate 10, but the present invention is not limited to this. Specifically, the first groove 51E may be formed on the other surface of the substrate 10, as in the semiconductor laser device 1E shown in FIG. Specifically, the first groove 51E may be formed from the upper surface of the semiconductor stacked structure 20 of the semiconductor laser element 1E toward the substrate 10. In this case, the debris generated when forming the first groove 51E includes not only the elements forming the substrate 10 and the second coat film 32 but also the elements forming the semiconductor stacked structure 20. For example, the debris includes elemental metals such as gallium (Ga), aluminum (Al), and indium (In), and/or inorganic compounds such as aluminum nitride, aluminum oxide, and silicon dioxide. Note that when forming the first groove 51E from the upper surface of the semiconductor stacked structure 20, the first groove 51E is preferably formed halfway from the semiconductor stacked structure 20 to the substrate 10.

Furthermore, in the first and second embodiments described above, the waveguide in the semiconductor laser device 1 is the ridge portion 20a, but the waveguide is not limited to this. For example, the waveguide in the semiconductor laser device 1 may not have a ridge stripe structure consisting of the ridge portion 20a, but may have an electrode stripe structure consisting only of divided electrodes, or an embedded current block structure using a current blocking layer. It may also be a constricted structure or the like.

Further, in the semiconductor laser device 1 in the first and second embodiments described above, the case where a nitride-based semiconductor material is used is illustrated, but the present invention is not limited to this. For example, the present disclosure can be applied to cases where semiconductor materials other than nitride-based semiconductor materials are used.

In addition, the embodiments 1 and 2 described above may be modified in various ways that those skilled in the art can think of, and the components and functions of each embodiment may be arbitrarily combined without departing from the spirit of the present disclosure. The present disclosure also includes forms realized by the following.

The semiconductor laser device according to the present disclosure is useful as a light source device for various products, including projectors, optical discs, vehicle headlamps, lighting devices, laser processing devices, and the like.

1, 1A, 1B, 1C, 1D, 1E, 1X Semiconductor laser device 1a Front end surface of semiconductor laser device 1b Rear end surface of semiconductor laser device 1c First side surface 1d Second side surface 2 Semiconductor multilayer substrate 3, 3X Divided substrate 4 Bar shape Substrate 10, 10X Substrate 20, 20X Semiconductor stacked structure 20a Ridge section 20b Flat section 20c Wing section 20F Front side end surface of semiconductor stacked structure 20R Rear side end surface of semiconductor stacked structure 21 First semiconductor layer 22 Active layer 23 Second semiconductor layer 31, 31X First coat film 32, 32X Second coat film 41 P-side electrode 42 N-side electrode 51, 51A, 51B, 51C, 51D, 51E, 51X First groove 51F Front side of the first groove Edge 51R Edge on the rear side of the first groove 51FS Area at the front end of the bottom of the first groove 51RS Area at the rear end of the bottom of the first groove 51FB Lower edge on the front side of the first groove 51RB Lower edge of rear side of first groove 52, 52X Second groove 60 Insulating film 70 Pad electrode 90X Crack

Claims (11)

A semiconductor laser device,
a semiconductor stacked structure formed on one side of the substrate;
a first coat film formed on the front end surface of the semiconductor stacked structure;
a second coat film formed on the rear side end surface of the semiconductor laminated structure,
The thickness of the second coat film is greater than the thickness of the first coat film,
A groove extending along the resonator length direction of the semiconductor laser element is formed on a side surface of the semiconductor laser element so as to cut out the side surface,
The front edge of the groove is spaced apart from the front end surface of the semiconductor laser element,
a rear edge of the groove is located at a rear end surface of the semiconductor laser element;
Semiconductor laser element. The depth of the rear end of the groove is deeper than the depth of the central part of the groove,
The semiconductor laser device according to claim 1. The depth of the rear end of the groove is shallower than the depth of the center of the groove.
The semiconductor laser device according to claim 1. A semiconductor laser device,
a semiconductor stacked structure formed on one side of the substrate;
a first coat film formed on the front end surface of the semiconductor stacked structure;
a second coat film formed on the rear side end surface of the semiconductor laminated structure,
The thickness of the second coat film is greater than the thickness of the first coat film,
A groove extending along the resonator length direction of the semiconductor laser element is formed on a side surface of the semiconductor laser element so as to cut out the side surface,
The front edge of the groove is spaced apart from the front end surface of the semiconductor laser element,
The rear edge of the groove is spaced apart from the rear end surface of the semiconductor laser element,
The distance between the rear edge and the rear end surface is shorter than the distance between the front edge and the front end surface.
Semiconductor laser element. The distance between the rear edge and the rear end surface is shorter than the thickness of the second coat film.
The semiconductor laser device according to claim 4. The surface roughness of the front end face of the groove is greater than the surface roughness of the rear end face of the groove.
The semiconductor laser device according to claim 4. The semiconductor laminated structure has a gain region extending along the cavity length direction of the semiconductor laser element,
In the rear end surface, the amount of debris present in the gain region is smaller than the debris present in a region to the side of the gain region.
The semiconductor laser device according to any one of claims 1 to 6. the groove is formed on the other surface of the substrate,
The semiconductor laser device according to any one of claims 1 to 6. a step of manufacturing a semiconductor multilayer substrate having a semiconductor multilayer structure by stacking a plurality of semiconductor layers on one surface of the substrate;
a step of producing a plurality of bar-shaped substrates by dividing the semiconductor laminated substrate;
forming a first coat film on the front end surface of the semiconductor stacked structure in each of the plurality of bar-shaped substrates;
forming a second coat film on the rear end surface of the semiconductor stacked structure in each of the plurality of bar-shaped substrates;
irradiating the bar-shaped substrate on which the first coat film and the second coat film are formed with a laser beam to form a groove;
dividing the bar-shaped substrate into a plurality of semiconductor laser elements by cutting the bar-shaped substrate along the groove,
In the step of forming the groove, the laser beam is scanned from the front side to the rear side of the bar-shaped substrate.
A method for manufacturing a semiconductor laser device. In the step of forming the groove, scanning the laser beam beyond the second coat film,
A method for manufacturing a semiconductor laser device according to claim 9. After the step of forming the groove, the method includes a step of removing debris attached to the rear end surface.
A method for manufacturing a semiconductor laser device according to claim 10.

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