Submount, semiconductor laser device, and method for manufacturing semiconductor laser device

Abstract

A submount (2) comprises: a submount body (21); an Au layer (24) positioned above the submount body (21); an upper protective metal layer (25), which is an example of a metal layer positioned above the Au layer (24); and a solder layer (26) positioned above the upper protective metal layer (25). The Au layer (24) has an exposed region (24a) exposed from the upper protective metal layer (25), and the solder layer (26) is provided over the exposed region (24a) and the upper protective metal layer (25). The upper protective metal layer (25) has a plurality of protrusions (25a) protruding toward an end face of the submount body (21), each protrusion (25a) having a first portion (25a1) exposed from the solder layer (26) and a second portion (25a2) covered by the solder layer (26). The exposed region (24a) includes an inter-protrusion region (24a1) between two adjacent protrusions (25a). At least a part of the inter-protrusion region (24a1) is covered by the solder layer (26).

Description

Submount, semiconductor laser device, and method of manufacturing semiconductor laser device

[0001] The present disclosure relates to a submount, a semiconductor laser device including the submount and a semiconductor laser element, and a method for manufacturing the semiconductor laser device.

[0002] Semiconductor laser elements are used as light sources for products in a variety of fields, both consumer and industrial. For example, semiconductor lasers are used as light sources for image display devices such as displays and projectors, lighting devices, and laser processing devices.

[0003] In particular, semiconductor laser elements used as light sources for projectors or laser processing devices are required to have high optical output powers that far exceed 1 W. For example, semiconductor laser elements that emit infrared laser light are used as light sources for laser processing devices that perform laser processing such as welding, joining, or cutting, and in such cases, optical output powers of about 10 W to several tens of W are required.

[0004] Such high-power semiconductor laser elements have a very large operating current, which generates a large amount of heat at the front end from which the laser light is emitted, and this can lead to the risk of catastrophic optical damage (COD) occurring at the front end of the semiconductor laser element. Therefore, in order to achieve stable operation of the semiconductor laser element over a long period of time while maintaining the semiconductor laser element in a high-power state, it is important to quickly dissipate the heat generated at the front end to the outside.

[0005] Therefore, a technique of mounting a semiconductor laser element using a submount, which is a heat dissipation member, is known. For example, a semiconductor laser device in which a semiconductor laser element is bonded to a submount by junction-down mounting has been proposed (Patent Document 1). In such a semiconductor laser device, the semiconductor laser element and the submount are bonded by solder.

[0006] When joining a semiconductor laser element and a submount with solder, a technique has been proposed that uses a soldered submount, in which a solder layer is formed on the submount in advance. In this case, the semiconductor laser element and the submount can be joined by soldering by heating the soldered submount on which the semiconductor laser element is mounted to melt the solder layer.

[0007] Furthermore, in a semiconductor laser device in which the semiconductor laser element and the submount are joined by solder, it is conceivable that part of the solder interposed between the semiconductor laser element and the submount may be extended to the front end of the semiconductor laser element in order to dissipate heat generated at the light-emitting end (front end) of the semiconductor laser element to the submount.

[0008] Therefore, a method for manufacturing a semiconductor device has been proposed in the past, in which the pattern of the solder layer of a soldered submount is devised to control the wetting and spreading of the solder when the solder layer melts, and the front end of the semiconductor laser element is joined to the submount via solder (Patent Document 2).

[0009] International Publication No. 2021 / 261253 International Publication No. 2017 / 191899

[0010] However, with the method disclosed in Patent Document 2, it is difficult to sufficiently wet and spread the molten solder to the front end of the semiconductor laser element, and it may not be possible to solder the front end of the semiconductor laser element to the submount. As a result, heat generated at the front end of the semiconductor laser element cannot be sufficiently dissipated to the submount, which may cause COD in the semiconductor laser element.

[0011] The present disclosure is intended to solve such problems, and aims to provide a submount, a semiconductor laser device, and a method for manufacturing a semiconductor laser device that can sufficiently dissipate heat generated at the front end of a semiconductor laser element.

[0012] In order to achieve the above-mentioned object, one aspect of a submount according to the present disclosure comprises a submount body, an Au layer located above the submount body, a metal layer located above the Au layer, and a solder layer located above the metal layer, wherein the Au layer has an exposed region exposed from the metal layer, and the solder layer is provided above the exposed region and the metal layer, and in a planar view, the metal layer has a plurality of protrusions protruding toward an end face of the submount body, each of the plurality of protrusions having a first portion exposed from the solder layer and a second portion covered by the solder layer, and the exposed region includes an inter-protrusion region which is a region between two adjacent protrusions of the plurality of protrusions, and at least a portion of the inter-protrusion region is covered by the solder layer.

[0013] Moreover, one aspect of a semiconductor laser device according to the present disclosure includes the above-described submount and a semiconductor laser element, wherein the submount and the semiconductor laser element are bonded together via a bonding member.

[0014] Furthermore, one aspect of a method for manufacturing a semiconductor laser device according to the present disclosure includes a placement step of placing a semiconductor laser element on the solder layer of the submount, and a bonding step of bonding the submount and the semiconductor laser element, wherein the semiconductor laser element has a pad electrode, and the bonding member is composed of the solder layer of the submount and the pad electrode of the semiconductor laser element.

[0015] According to the present disclosure, heat generated at the front end of the semiconductor laser element can be sufficiently dissipated.

[0016] FIG. 1 is a plan view of a semiconductor laser device according to an embodiment. FIG. 2 is a cross-sectional view of the semiconductor laser device according to the embodiment taken along line II-II in FIG. 1. FIG. 3 is a cross-sectional view of the semiconductor laser device according to the embodiment taken along line III-III in FIG. 1. FIG. 4 is a plan view of a submount according to an embodiment. FIG. 5A is a cross-sectional view of the submount according to the embodiment taken along line VA-VA in FIG. 4. FIG. 5B is a cross-sectional view of the submount according to the embodiment taken along line VB-VB in FIG. 4. FIG. 6A is a cross-sectional view of the submount according to the embodiment taken along line VIA-VIA in FIG. 4. FIG. 6B is a cross-sectional view of the submount according to the embodiment taken along line VIB-VIB in FIG. 4. FIG. 7 is an enlarged view of region VII surrounded by a dashed line in FIG. 4. FIG. 8 is a plan view of a semiconductor laser device according to an embodiment. FIG. 9 is a cross-sectional view of the semiconductor laser device according to the embodiment taken along line IX-IX in FIG. 8. FIG. 10 is a cross-sectional view of the semiconductor laser device according to the embodiment taken along line XX in FIG. 8. FIG. 11 is a diagram showing the configuration of a submount of a comparative example. FIG. 12 is a cross-sectional view of a semiconductor laser device of a comparative example. FIG. 13 is a diagram for explaining a manufacturing method of a semiconductor laser device according to an embodiment. FIG. 14 is a diagram showing behavior of a solder layer when a submount and a semiconductor laser element are bonded in a manufacturing method of a semiconductor laser device according to an embodiment. FIG. 15 is a cross-sectional view of a semiconductor laser device according to Modification 1. FIG. 16 is an enlarged cross-sectional view of a semiconductor laser device according to Modification 2. FIG. 17 is an enlarged plan view of a submount according to Modification 3. FIG. 18 is a diagram showing behavior of a solder layer when a semiconductor laser element is mounted using the submount according to Modification 3. FIG. 19 is an enlarged plan view of a submount according to Modification 4. FIG. 20 is an enlarged plan view of a submount according to Modification 5. FIG. 21 is an enlarged plan view of a submount according to Modification 6. FIG. 22 is an enlarged plan view of a submount according to Modification 7. FIG. 23 is an enlarged plan view of a submount according to Modification 8.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, the arrangement and connection of the components, steps (processes), and the order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept of the present disclosure will be described as optional components.

[0018] Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, the scales and the like do not necessarily match in each figure. In each figure, the same reference numerals are used to denote substantially the same components, and redundant explanations will be omitted or simplified.

[0019] In this specification, the terms "above" and "below" do not refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. Furthermore, the terms "above" and "below" are used not only when two components are arranged with a gap between them and another component is present between the two components, but also when two components are arranged in contact with each other.

[0020] (Embodiment) [Semiconductor Laser Element] First, the configuration of a semiconductor laser element 1 used in this embodiment will be described with reference to Fig. 1, Fig. 2, and Fig. 3. Fig. 1 is a plan view of the semiconductor laser element 1 according to the embodiment. Figs. 2 and 3 are cross-sectional views of the semiconductor laser element 1 according to the embodiment. Fig. 2 shows a cross section taken along line II-II in Fig. 1, and Fig. 3 shows a cross section taken along line III-III in Fig. 1.

[0021] 1, the semiconductor laser device 1 has a front end face 1a and a rear end face 1b opposite to the front end face 1a. The front end face 1a is a light-emitting end face from which laser light is emitted.

[0022] The semiconductor laser element 1 emits laser light of a predetermined wavelength from the front end facet 1a. For example, the semiconductor laser element 1 emits blue laser light having a peak wavelength in the 445 nm band with an optical output of several watts to several tens of watts. However, the optical output and peak wavelength of the laser light emitted by the semiconductor laser element 1 are not limited to these.

[0023] 2 and 3, the semiconductor laser device 1 has a substrate 11 and a semiconductor stacked structure 1S formed above the substrate 11. The semiconductor laser device 1 in this embodiment is a compound semiconductor laser made of III-V group semiconductor materials. Therefore, the semiconductor stacked structure 1S has a structure in which a plurality of semiconductor layers, each made of III-V group semiconductor materials, are stacked. Specifically, the semiconductor laser device 1 is a nitride-based semiconductor laser device made of AlGaInN-based nitride-based semiconductor materials.

[0024] The semiconductor laser element 1 has a semiconductor stacked structure 1S formed on a substrate 11, which includes an n-side semiconductor layer 12, an active layer (light-emitting layer) 13, a p-side semiconductor layer 14, and a p-type contact layer 15. Specifically, the n-side semiconductor layer 12 is formed on the substrate 11, the active layer 13 is formed on the n-side semiconductor layer 12, the p-side semiconductor layer 14 is formed on the active layer 13, and the p-type contact layer 15 is formed on the p-side semiconductor layer 14.

[0025] The substrate 11 is a planar substrate having a flat main surface. The substrate 11 is a semiconductor substrate such as a GaN substrate. In this embodiment, the substrate 11 is an n-type GaN substrate.

[0026] The n-side semiconductor layer 12 includes an n-type cladding layer that is a first cladding layer of a first conductivity type. The n-type cladding layer is, for example, an n-type AlGaN layer. The n-side semiconductor layer 12 may have an n-type buffer layer or the like between the n-type cladding layer and the n-type GaN substrate. The n-side semiconductor layer 12 may also have an n-side guide layer between it and the active layer 13. The n-side guide layer is, for example, an undoped AlGaN layer, an undoped GaN layer, or an undoped GaInN layer.

[0027] The active layer 13 includes a well layer having a single quantum well structure. In this case, the well layer is, for example, an undoped InGaN layer. The well layer is not limited to a single quantum well structure, and may have a multiple quantum well structure.

[0028] The active layer 13 may have an n-side barrier layer and / or a p-side barrier layer in addition to the well layer. The n-side barrier layer is, for example, an undoped AlGaN layer, an undoped GaN layer, or an undoped GaInN layer, and is formed below the well layer. The p-side barrier layer is, for example, an undoped AlGaN layer, an undoped GaN layer, or an undoped GaInN layer, and is formed above the well layer.

[0029] The p-side semiconductor layer 14 includes a p-type cladding layer, which is a second cladding layer of a second conductivity type different from the first conductivity type. The p-type cladding layer is, for example, a p-type AlGaN layer. The p-side semiconductor layer 14 may include a p-type compositionally graded layer or the like in addition to the p-type cladding layer. The p-side semiconductor layer 14 may have a p-side guide layer between itself and the active layer 13. The n-side guide layer is, for example, an undoped AlGaN layer, an undoped GaN layer, or an undoped GaInN layer. The p-side semiconductor layer 14 may also have a p-type AlGaN electron barrier layer between itself and the p-side guide layer.

[0030] The p-type contact layer 15 is a p-type semiconductor layer intentionally doped with impurities such as Mg, and is, for example, a p-type GaN layer.

[0031] The semiconductor laser device 1 has a ridge portion 1R formed in a ridge shape as a waveguide extending in the cavity length direction. The ridge portion 1R extends in the cavity length direction. The ridge portion 1R functions as a current injection region in the semiconductor laser device 1. As shown in FIGS. 2 and 3 , the ridge portion 1R is composed of a p-side semiconductor layer 14 and a p-type contact layer 15. The uppermost layer of the ridge portion 1R is the p-type contact layer 15.

[0032] The semiconductor laser device 1 also has a pair of wing portions 1W. The pair of wing portions 1W are located on either side of the ridge portion 1R. The ridge portion 1R is sandwiched between the pair of wing portions 1W via an opening. The pair of wing portions 1W extend along the cavity length direction of the semiconductor laser device 1. Like the ridge portion 1R, the wing portions 1W are composed of a p-side semiconductor layer 14 and a p-type contact layer 15.

[0033] As shown in FIG. 2, except for a part of the ridge portion 1R, the p-type contact layer 15 is covered with SiO ２ Alternatively, an insulating film 16 made of a dielectric film such as SiN is formed on the ridge portion 1R. Specifically, the insulating film 16 is formed to have an opening above the ridge portion 1R. The insulating film 16 also covers the upper and side surfaces of the wing portion 1W and is formed continuously from the wing portion 1W to the side surface of the ridge portion 1R. The insulating film 16 functions as a current blocking film. Therefore, the opening of the insulating film 16 formed above the ridge portion 1R is a current injection region (current injection window) through which current passes.

[0034] 3, the opening of the insulating film 16 does not extend to the front and rear end portions of the semiconductor laser device 1, and the ridge portion 1R at the front and rear end portions of the semiconductor laser device 1 is covered with the insulating film 16. The region corresponding to the ridge portion 1R covered with this insulating film 16 is a current non-injection region into which no current is injected.

[0035] 2 and 3, the semiconductor laser device 1 further includes a barrier layer 17. The barrier layer 17 is formed on the insulating film 16. Like the insulating film 16, the barrier layer 17 is formed above the p-type contact layer 15 with the insulating film 16 interposed therebetween, excluding a part of the ridge portion 1R. Specifically, the barrier layer 17 is formed to have an opening above the ridge portion 1R. As shown in FIG. 2, the opening width of the barrier layer 17 is larger than the opening width of the insulating film 16. The barrier layer 17 covers the upper surfaces and inner side surfaces of the wing portions 1W, but does not cover the side surfaces of the ridge portion 1R.

[0036] The barrier layer 17 has the function of preventing metals (e.g., Sn) contained in solder from penetrating into the semiconductor stacked structure 1S when the semiconductor laser element 1 is mounted on a submount. The barrier layer 17 is a metal layer made of a metal material. The barrier layer 17 includes, for example, a Pt film made of Pt. The barrier layer 17 may be a single-layer film or a multilayer film. In this embodiment, the barrier layer 17 is made of a multilayer film. As an example, the barrier layer 17 is a multilayer film with a two-layer structure in which a Ti film and a Pt film are stacked in this order from the insulating film 16 side.

[0037] A window region (facet window structure) may be formed at the front end of the semiconductor laser device 1. For example, in the non-current injection region near the front end of the ridge portion 1R in the active layer 13, a window region having a bandgap energy greater than the energy corresponding to the wavelength of laser oscillation is formed in a region of a predetermined length from the front end facet 1a of the semiconductor laser device 1. The region of the waveguide where no window region is formed is a gain region. In this way, by forming a window region at the front end of the semiconductor laser device 1, the front end of the semiconductor laser device 1 can be made transparent, thereby reducing light absorption near the front end. This makes it possible to suppress the occurrence of COD at the front end of the semiconductor laser device 1. A similar window region may also be formed at the rear end of the semiconductor laser device 1.

[0038] The semiconductor laser device 1 has a p-side electrode 18 as a first electrode. The p-side electrode 18 is formed above the p-type contact layer 15. Specifically, the p-side electrode 18 is formed above the ridge portion 1R so as to be in contact with the p-type contact layer 15. The p-side electrode 18 is in ohmic contact with the p-type contact layer 15. The p-side electrode 18 may be formed not only on the ridge portion 1R but also on the wing portion 1W with the insulating film 16 interposed therebetween.

[0039] The p-side electrode 18 is a metal layer made of a metal material. The p-side electrode 18 is, for example, a single-layer film or a multi-layer film made of at least one of Pt, Pd, Ti, Cr, Ni, Mo, and Au. In this embodiment, the p-side electrode 18 is made of a multi-layer film. As an example, the p-side electrode 18 is a multi-layer film with a two-layer structure in which a Pt film and a Pd film are stacked in this order from the p-type contact layer 15 side.

[0040] The semiconductor laser device 1 also has an n-side electrode 19 as a second electrode. The n-side electrode 19 is formed on the other surface (lower surface) of the substrate 11, which is the surface opposite to the one surface. The n-side electrode 19 is formed directly on the other surface of the substrate 11.

[0041] The n-side electrode 19 is a metal layer made of a metal material. The n-side electrode 19 is, for example, a single-layer film or a multilayer film made of at least one of Cr, Ti, Ni, Pd, Pt, Au, and Ge. In this embodiment, the n-side electrode 19 is made of a multilayer film. As an example, the n-side electrode 19 is a multilayer film with a three-layer structure in which a Ti film, a Pt film, and an Au film are stacked in this order from the substrate 11 side.

[0042] Furthermore, the semiconductor laser device 1 has a pad electrode 20. The pad electrode 20 is formed above the p-side electrode 18. In other words, the pad electrode 20 is formed above the ridge portion 1R. In this embodiment, the pad electrode 20 is in contact with the upper surface of the p-side electrode 18.

[0043] 3, the pad electrode 20 is provided up to the front and rear ends of the semiconductor laser element 1. Specifically, the pad electrode 20 is formed not only on the upper surface of the p-side electrode 18 but also above the insulating film 16 and the barrier layer 17 provided at each of the front and rear ends of the semiconductor laser element 1. In other words, the pad electrode 20 is provided not only in the current injection region but also in locations other than the current injection region (non-current injection region). Also, as shown in FIG. 2, the pad electrode 20 is formed not only above the ridge portion 1R but also above the wing portions 1W.

[0044] The pad electrode 20 is a metal layer made of a metal material. In this embodiment, the pad electrode 20 is an Au layer made of Au. Specifically, the pad electrode 20 is an Au plating film formed by plating.

[0045] The front end face of the pad electrode 20 is located at a position set back from the front end face 1 a of the semiconductor laser element 1. As such, the front end face of the pad electrode 20 is located at a position set back from the front end face 1 a of the semiconductor laser element 1, so that the semiconductor laser element 1 has an exposed surface that is exposed from the pad electrode 20. In this embodiment, a part of this exposed surface is the surface of the barrier layer 17.

[0046] [Submount] Next, the configuration of a submount 2 according to an embodiment will be described with reference to FIGS. 4, 5A, 5B, 6A, 6B, and 7. FIG. 4 is a plan view of the submount 2 according to an embodiment. FIGS. 5A to 6B are cross-sectional views of the submount 2 according to an embodiment. FIG. 5A shows a cross section taken along line VA-VA in FIG. 4, FIG. 5B shows a cross section taken along line VB-VB in FIG. 4, FIG. 6A shows a cross section taken along line VIA-VIA in FIG. 4, and FIG. 6B shows a cross section taken along line VIB-VIB in FIG. 4. FIG. 7 is an enlarged view of region VII enclosed by a dashed line in FIG. 4.

[0047] The submount 2 functions as a base for mounting the semiconductor laser element 1. The submount 2 also functions as a heat dissipation member (heat sink) for dissipating heat generated by the semiconductor laser element 1.

[0048] 4, the submount 2 has a front end face 2a and a rear end face 2b opposite to the front end face 2a. The front end face 2a is on the same side as the front end face 1a of the semiconductor laser element 1, and the rear end face 2b is on the same side as the rear end face 1b of the semiconductor laser element 1.

[0049] 5A to 6B, the submount 2 includes a submount body 21, an adhesion metal layer 22, a lower protective metal layer 23, an Au layer 24, an upper protective metal layer 25, and a solder layer 26. In this way, the submount 2 is a soldered submount on which the solder layer 26 is pre-formed.

[0050] 5A to 6B, the adhesion metal layer 22, the lower protective metal layer 23, the Au layer 24, and the upper protective metal layer 25 are located in this order above the submount body 21. One of the lower protective metal layer 23 and the upper protective metal layer 25 is a first protective metal layer, and the other is a second protective metal layer.

[0051] The submount body 21 is a submount substrate that serves as the base of the submount 2. The submount body 21 is preferably made of a highly thermally conductive material such as SiC, AlN, CuW, or diamond. The submount body 21 is also preferably an insulating member. In this embodiment, the submount body 21 is a SiC substrate made of insulating SiC. The shape of the submount body 21 in a plan view is, for example, rectangular.

[0052] The adhesion metal layer 22 is formed on the upper surface of the submount body 21. The adhesion metal layer 22 is located between the submount body 21 and the Au layer 24. Specifically, the adhesion metal layer 22 is located between the submount body 21 and the lower protective metal layer 23.

[0053] The adhesion metal layer 22 is an adhesion layer that has excellent adhesion to the submount body 21. By providing the adhesion metal layer 22, the submount body 21 and the lower protective metal layer 23 can be easily adhered to each other. The adhesion metal layer 22 is a metal layer made of a metal material. In this embodiment, the adhesion metal layer 22 is a Ti layer made of Ti. As an example, the thickness of the adhesion metal layer 22 is 0.1 μm.

[0054] The lower protective metal layer 23 is formed on the upper surface of the adhesion metal layer 22. The lower protective metal layer 23 is located below the Au layer 24 and is provided between the adhesion metal layer 22 and the Au layer 24.

[0055] The Au layer 24 is a gold layer made of gold (Au). The Au layer 24 is located above the submount body 21. In this embodiment, the Au layer 24 is formed on the upper surface of the lower protective metal layer 23. The Au layer 24 is also located below the upper protective metal layer 25, and is provided between the lower protective metal layer 23 and the upper protective metal layer 25. In other words, the Au layer 24 is sandwiched between the lower protective metal layer 23 and the upper protective metal layer 25. As an example, the thickness of the Au layer 24 is 0.5 μm.

[0056] The upper protective metal layer 25 is formed on the upper surface of the Au layer 24. The upper protective metal layer 25 is located below the solder layer 26 and is provided between the Au layer 24 and the solder layer 26.

[0057] The lower protective metal layer 23 and the upper protective metal layer 25 are barrier layers that prevent the diffusion of metal contained in the solder layer 26. For example, when the solder layer 26 is an AuSn layer, the lower protective metal layer 23 and the upper protective metal layer 25 prevent the diffusion of Sn contained in the solder layer 26. By providing the lower protective metal layer 23 and the upper protective metal layer 25, it is possible to prevent Sn from the solder layer 26 from reaching metal layers such as the Au layer 24, thereby protecting the metal layers such as the Au layer 24 from Sn. In particular, it is possible to prevent the Au layer 24 from being corroded by Sn contained in the solder layer 26 when the solder layer 26 is melted during mounting of the semiconductor laser element 1 on the submount 2.

[0058] The lower protective metal layer 23 and the upper protective metal layer 25 are made of Pt, Cr, or Ni. In this embodiment, the lower protective metal layer 23 and the upper protective metal layer 25 are Pt layers made of Pt. This effectively prevents Sn contained in the solder layer 26 from diffusing due to the barrier effect of Pt.

[0059] The thickness of the upper protective metal layer 25 located on the solder layer 26 side (upper side) of the Au layer 24 is preferably thicker than the thickness of the lower protective metal layer 23. As an example, the thickness of the upper protective metal layer 25 is 0.32 μm, and the thickness of the lower protective metal layer 23 is 0.2 μm. The thickness of the upper protective metal layer 25 may be thinner than the thickness of the lower protective metal layer 23, or may be the same as the thickness of the lower protective metal layer 23.

[0060] The solder layer 26 is made of a solder material. In this embodiment, the solder layer 26 is an AuSn layer made of Au and Sn. The Au content of the solder layer 26, which is an AuSn layer, is, for example, 70 wt %. Of the adhesion metal layer 22, the lower protective metal layer 23, the Au layer 24, the upper protective metal layer 25, and the solder layer 26, the solder layer 26 has the greatest thickness. As an example, the thickness of the solder layer 26 is 2.5 μm. The solder that makes up the solder layer 26 may also contain other metals as long as it contains Au and Sn.

[0061] The solder layer 26 is the uppermost layer of the submount 2, and when the semiconductor laser element 1 is mounted on the submount 2, it melts by heating to bond the submount 2 to the semiconductor laser element 1. In other words, the solder layer 26 melts and hardens to become a bonding member that bonds the semiconductor laser element 1 to the submount 2. The shape (top surface shape) of the solder layer 26 in a plan view is rectangular, for example. Therefore, in a plan view, the end face of the solder layer 26 on the front end face 2a side of the submount 2 is linear. Note that the shape of the solder layer 26 in a plan view is not limited to a rectangle.

[0062] The solder layer 26 is located above the upper protective metal layer 25. In this embodiment, the solder layer 26 is formed on the upper surface of the upper protective metal layer 25. By forming the solder layer 26 on the upper surface of the upper protective metal layer 25, which is a Pt layer, in this manner, alloying with tin contained in the solder can be prevented when the solder layer 26 melts.

[0063] 4, when the submount 2 is viewed in plan, the outer size of the Au layer 24 is larger than the outer size of the upper protective metal layer 25. Therefore, as shown in FIGS. 4 to 6B, the Au layer 24 has an exposed region 24a (Au exposed region) that is exposed from the upper protective metal layer 25.

[0064] The solder layer 26 is provided across the exposed region 24 a and the upper protective metal layer 25. In other words, the solder layer 26 is provided not only above the upper protective metal layer 25 but also above the exposed region 24 a in the Au layer 24, and is provided continuously from above the upper protective metal layer 25 to protrude onto the Au layer 24.

[0065] 4 and 7 , when the submount 2 is viewed from above, the upper protective metal layer 25 has a plurality of protrusions 25a that protrude toward the end face of the submount body 21. The plurality of protrusions 25a are provided on the upper protective metal layer 25 on the front end face 2a side of the submount 2, and protrude toward the front end face 2a of the submount 2. In this embodiment, the upper protective metal layer 25 is provided with eight protrusions 25a.

[0066] In this way, by providing multiple convex portions 25a in the upper protective metal layer 25 on the Au layer 24, as shown in FIG. 7 , the exposed region 24a of the Au layer 24 exposed from the upper protective metal layer 25 includes an inter-convex portion region 24a1, which is a region between two adjacent convex portions 25a among the multiple convex portions 25a. The inter-convex portion region 24a1 is a region sandwiched between two adjacent convex portions 25a. In this embodiment, eight convex portions 25a are provided in the upper protective metal layer 25, and therefore seven inter-convex portion regions 24a1 are included in the exposed region 24a. Note that in FIG. 7 , for convenience, the rightmost inter-convex portion region 24a1 among the eight inter-convex portion regions 24a1 is indicated by dotted hatching to indicate the range (area) of one inter-convex portion region 24a1.

[0067] The eight protrusions 25a each have a trapezoidal shape in plan view (top surface shape). The six protrusions 25a, excluding the two side protrusions 25a, each have a trapezoidal shape in plan view with two base angles that are the same, and the six protrusions 25a each have the same shape in plan view.

[0068] The multiple trapezoidal convex portions 25a are formed by providing multiple V-shaped notches in the front end portion of the upper protective metal layer 25. Therefore, as shown in Fig. 7, the width of each of the multiple convex portions 25a provided in the upper protective metal layer 25 narrows as it approaches the end face of the submount body 21 (specifically, the front end face 2a of the submount 2).

[0069] Because the planar shape of each convex portion 25a is trapezoidal, when the submount 2 is viewed from above, the planar shape of each of the multiple inter-convex regions 24a1 (areas indicated by dotted hatching in FIG. 7 ) is triangular. Specifically, the planar shape of each inter-convex region 24a1 is an isosceles triangle. Furthermore, because the width of the convex portions 25a narrows toward the end faces of the submount body 21, when the submount 2 is viewed from above, the width of the inter-convex region 24a1 increases toward the end faces of the submount body 21, which are the front end faces 2a of the submount 2. In other words, the width of the inter-convex region 24a1 gradually increases from the bottom (bottom of the V) of the inter-convex region 24a1 toward the openings (tips of the convex portions 25a) in plan view.

[0070] On the front end surface 2a side of the submount 2, the solder layer 26 is provided up to the middle of the multiple protrusions 25a provided on the upper protective metal layer 25. Therefore, for each of the multiple protrusions 25a provided on the upper protective metal layer 25, a portion of the protrusion 25a is exposed from the solder layer 26, and another portion of the protrusion 25a is not exposed from the solder layer 26 and is covered with the solder layer 26. Specifically, each of the multiple protrusions 25a has a first portion 25a1 which is an exposed portion exposed from the solder layer 26, and a second portion 25a2 which is a covered portion covered with the solder layer 26. The second portion 25a2 covered with the solder layer 26 is a non-exposed portion that is not exposed from the solder layer 26.

[0071] 7, in a plan view, if the width of the tip of the convex portion 25a is a and the maximum opening width of the inter-convex portion region 24a1 is b, then in this embodiment, a=b. As an example, a=b=20 μm. Note that this is not limited to a=b, and a>b or a<b may also be true.

[0072] Furthermore, in plan view, if the length (depth) from the largest opening to the bottom of the inter-protrusion region 24a1 is c and the length from the front end surface of the solder layer 26 to the bottom of the inter-protrusion region 24a1 is d, then in this embodiment, d = c / 2. That is, up to half of the protrusion 25a is covered with the solder layer 26. As an example, c = 30 μm and d = 15 μm. It is preferable that d ≥ 15 μm. Note that d is not limited to c / 2, and d may be greater than c / 2. In this case, more than half of the surface area of ​​the protrusion 25a may be covered with the solder layer 26. Note that d may be less than c / 2.

[0073] Furthermore, because the solder layer 26 is provided partway along the multiple protrusions 25a, the solder layer 26 is also provided partway along the inter-protrusion regions 24a1 between two adjacent protrusions 25a. That is, at least a portion of the inter-protrusion regions 24a1 is covered with the solder layer 26. Specifically, a portion of the inter-protrusion regions 24a1 is exposed from the solder layer 26, and another portion of the inter-protrusion regions 24a1 is covered with the solder layer 26. Therefore, the multiple inter-protrusion regions 24a1 have regions exposed from the solder layer 26 (exposed portions) and regions not exposed from the solder layer 26 but covered with the solder layer 26 (covered portions). In the regions of the inter-protrusion regions 24a1 covered with the solder layer 26, the Au layer 24 and the solder layer 26 are in contact with each other.

[0074] [Semiconductor Laser Device] Next, the configuration of a semiconductor laser device 3 according to an embodiment will be described with reference to Figs. 8, 9, and 10. Fig. 8 is a plan view of the semiconductor laser device 3 according to the embodiment. Figs. 9 and 10 are cross-sectional views of the semiconductor laser device 3 according to the embodiment. Fig. 9 shows a cross section taken along line IX-IX in Fig. 8, and Fig. 10 shows a cross section taken along line XX in Fig. 8.

[0075] The semiconductor laser device 3 can be manufactured using the above-described semiconductor laser element 1 and the above-described submount 2. Therefore, as shown in Figures 8 to 10, the semiconductor laser device 3 includes the submount 2 and the semiconductor laser element 1 mounted on the submount 2.

[0076] The semiconductor laser element 1 is mounted on the submount 2 by junction-down mounting. That is, the semiconductor laser element 1 is placed on the submount 2 so that the pad electrodes 20 of the semiconductor laser element 1 face the submount 2 side.

[0077] In the semiconductor laser device 3, the semiconductor laser element 1 and the submount 2 are bonded together via a bonding member 30. That is, the bonding member 30 bonds the semiconductor laser element 1 and the submount 2 together, and is interposed between the semiconductor laser element 1 and the submount 2. Specifically, the bonding member 30 bonds the p-side electrode 18 of the semiconductor laser element 1 to the upper protective metal layer 25 of the submount 2.

[0078] The bonding member 30 is composed of the solder layer 26 of the submount 2 and the pad electrode 20 of the semiconductor laser element 1. Specifically, the bonding member 30 is formed by integrating the solder layer 26 of the submount 2 with at least a portion of the pad electrode 20 of the semiconductor laser element 1. More specifically, the solder layer 26 of the submount 2 melts to become the bonding member 30, and the pad electrode 20 is eutecticized with the molten solder layer 26 to become the bonding member 30. In this embodiment, the solder layer 26 is an AuSn layer, so the bonding member 30 is composed of AuSn. Furthermore, the pad electrode 20 made of Au is eutecticized with the AuSn of the solder layer 26 as part of the bonding member 30 to become a eutectic layer made of AuSn.

[0079] 9 and 10 show the case where the entire pad electrode 20 of the semiconductor laser element 1 is eutecticized to form the bonding member 30, but the entire pad electrode 20 does not have to be eutecticized. In this embodiment, a part of the Au layer 24 is also eutecticized by the molten solder layer 26 to form a eutectic layer 24g. The eutectic layer 24g, which is part of the Au layer 24, may also be part of the bonding member 30.

[0080] The bonding member 30 extends to the front end of the semiconductor laser element 1. Here, the front end of the semiconductor laser element 1 refers to the region in the vicinity of the front end facet 1a of the semiconductor laser element 1. In other words, the bonding member 30 is connected to the front end of the semiconductor laser element 1. This allows heat generated at the front end of the semiconductor laser element 1 to be conducted to the submount 2 via the bonding member 30, thereby preventing COD from occurring at the front end of the semiconductor laser element 1. In this embodiment, the bonding member 30 extends to the end of the insulating film 16 of the semiconductor laser element 1 on the light emission side.

[0081] 8 and 10 , in this embodiment, the front end face 1 a of the semiconductor laser element 1 protrudes beyond the front end face 2 a of the submount 2. Therefore, as shown in Fig. 10 , the joining member 30, which extends to the front end of the semiconductor laser element 1, protrudes beyond the front end face 2 a of the submount 2. Specifically, a fillet 31 is formed in the joining member 30, and the fillet 31 is connected to the front end of the semiconductor laser element 1. The fillet 31 is a portion of the joining member 30 that protrudes from between the semiconductor laser element 1 and the submount 2. In this embodiment, the joining member 30 is solder, and therefore the fillet 31 is a solder fillet.

[0082] [Method for Manufacturing Semiconductor Laser Device] Next, the effect of the submount 2 in the method for manufacturing the semiconductor laser device 3 according to the embodiment will be described in comparison with a comparative example submount 2X and a comparative example semiconductor laser device 3X. FIG. 11 is a diagram showing the configuration of the comparative example submount 2X. In FIG. 11, (a) is a plan view of the submount 2X, and (b) is a cross-sectional view taken along line b-b in (a). FIG. 12 is a cross-sectional view of the comparative example semiconductor laser device 3X.

[0083] As shown in (a) and (b) of Figures 11A and 11B, the submount 2X of the comparative example, like the submount 2 in the above embodiment, comprises a submount body 21, an adhesion metal layer 22, a lower protective metal layer 23, an Au layer 24, an upper protective metal layer 25X, and a solder layer 26.

[0084] The submount 2X of the comparative example differs from the submount 2 of the above embodiment in that it does not have multiple protrusions at the front end of the upper protective metal layer 25X. Furthermore, in the submount 2X of the comparative example, the solder layer 26 located on the upper protective metal layer 25X does not protrude from the upper protective metal layer 25X into the exposed region 24a of the Au layer 24, and the solder layer 26 and the Au layer 24 are not in contact with each other.

[0085] When the semiconductor laser element 1 is junction-down mounted using the submount 2X of this comparative example, the submount 2X on which the semiconductor laser element 1 is mounted is heated to melt the solder layer 26 of the submount 2X. As a result, the semiconductor laser element 1 and the submount 2X are joined by a joining member 30X consisting of the melted and hardened solder layer 26 and the pad electrode 20 that has been eutecticized by the melted solder layer 26. As a result, a semiconductor laser device 3X having the configuration shown in FIG. 12 can be obtained.

[0086] However, in the submount 2X of the comparative example, the molten solder layer 26 cannot be sufficiently wetted and spread to the front end of the semiconductor laser element 1. Therefore, as shown in Fig. 12, the front end of the semiconductor laser element 1 and the submount 2X cannot be joined by the joining member 30X.

[0087] In contrast, by using the submount 2 according to the present embodiment, the molten solder layer 26 can be made to sufficiently wet and spread to the front end of the semiconductor laser element 1, and the front end of the semiconductor laser element 1 and the submount 2 can be joined by the joining member 30. This point will be described in detail below with reference to FIGS. 13 and 14 . FIG. 13 is a diagram for explaining a manufacturing method of the semiconductor laser device 3 according to the embodiment. FIG. 14 is a diagram showing the behavior of the solder layer 26 when the submount 2 and the semiconductor laser element 1 are joined in the manufacturing method of the semiconductor laser device 3 according to the embodiment. FIG. 14 is an enlarged plan view of the submount 2.

[0088] The manufacturing method of the semiconductor laser device 3 according to this embodiment includes a placement step of placing the semiconductor laser element 1 on the solder layer 26 of the submount 2, as shown in FIG. 13( a), and a bonding step of bonding the submount 2 and the semiconductor laser element 1 via a bonding member 30, as shown in FIG. 13( b).

[0089] 13A, in the placement step, the semiconductor laser element 1 is mounted junction-down on the solder layer 26 of the submount 2. That is, the semiconductor laser element 1 is mounted on the submount 2 so that the pad electrodes 20 of the semiconductor laser element 1 face the solder layer 26 of the submount 2. At this time, the pad electrodes 20 of the semiconductor laser element 1 contact the solder layer 26 of the submount 2.

[0090] After the semiconductor laser element 1 is placed on the submount 2, a bonding step is performed to bond the submount 2 to the semiconductor laser element 1. In this bonding and fixing step, the submount 2 on which the semiconductor laser element 1 is placed is heated. This causes the solder layer 26 of the submount 2 to melt and become liquid solder, which then wets and spreads.

[0091] In this case, in the submount 2 of this embodiment, a plurality of protrusions 25a are provided on the upper protective metal layer 25, and the exposed region 24a of the Au layer 24 includes an inter-protrusion region 24a1 between two adjacent protrusions 25a, and further, a portion of the inter-protrusion region 24a1 is covered with the solder layer 26. In other words, the Au layer 24 made of Au and the solder layer 26 made of AuSn are in contact with each other in advance in a portion of the inter-protrusion region 24a1 between the two protrusions 25a.

[0092] With this configuration, when the solder layer 26 melts, as shown by the three thick upward arrows in Figure 14, the solder layer 26 (liquid solder) located at the front of the solder layer 26 in the inter-protrusion region 24a1 (the solder layer 26 in the region indicated by dotted hatching in Figure 14) promotes a eutectic reaction with the Au layer 24 located on the front end face 2a side of the submount 2.

[0093] Specifically, the eutectic reaction between the AuSn of the solder layer 26 and the Au of the Au layer 24 is promoted, so that the liquid solder that is the molten solder layer 26 advances steadily forward, continuously inducing the eutectic reaction with the Au layer 24. In this way, in this embodiment, the wetting and spreading of the molten solder layer 26 is promoted, so that the molten solder layer 26 spreads far beyond the inter-protrusion region 24a1 toward the front end face 2a of the submount 2 (forward). This allows the liquid solder that is the molten solder layer 26 to easily reach the front end face 2a of the submount 2.

[0094] Moreover, in this embodiment, the inter-convex region 24a1 has a V-triangle shape in plan view, and the width of the inter-convex region 24a1 increases as it approaches the front end face 2a of the submount 2. This causes the molten solder layer 26 to wet and spread in a chain reaction along the V-shape of the inter-convex region 24a1, further promoting the wetting and spreading of the molten solder layer 26. In other words, the V-triangle shape of the inter-convex region 24a1 in plan view makes it easier for the liquid solder that is the molten solder layer 26 to wet and spread toward the front end face 2a of the submount 2.

[0095] Furthermore, even if the solder layer 26 located in the inter-convex region 24a1 melts and spreads forward, as shown by the two upward medium-thick arrows in Figure 14, molten solder layer 26 is constantly supplied forward from the solder layer 26 located outside the inter-convex region 24a1 (solder layer 26 located at the rear), and the eutectic reaction between the solder layer 26 and the Au layer 24 proceeds until the Au composition of the solder layer 26 becomes saturated.

[0096] Furthermore, the molten solder layer 26 not only undergoes a eutectic reaction with the Au layer 24 of the submount 2, but also undergoes a eutectic reaction with the pad electrode 20 of the semiconductor laser element 1, as shown in FIG. 13B. At this time, in this embodiment, as described above, the wetting and spreading of the molten solder layer 26 toward the front end face 2 a of the submount 2 is promoted, and therefore the wetting and spreading of the molten solder layer 26 toward the pad electrode 20 of the semiconductor laser element 1 is also promoted. Specifically, the AuSn of the molten solder layer 26 undergoes a eutectic reaction with the Au of the pad electrode 20, and the molten solder layer 26 easily wets and spreads toward the front end face 1 a of the semiconductor laser element 1. As a result, the molten solder layer 26 easily reaches the front end of the semiconductor laser element 1.

[0097] As a result, when the molten solder layer 26 spreads and hardens, the joining member 30 formed by the solder layer 26 and the pad electrode 20 extends to the front end of the semiconductor laser element 1 .

[0098] In particular, even in a structure like this embodiment in which the front end face 1 a of the semiconductor laser element 1 protrudes beyond the front end face 2 a of the submount 2, the molten solder layer 26 can be easily wetted and spread to the front end of the semiconductor laser element 1, so that the joining member 30 can be extended to the front end of the semiconductor laser element 1 and the fillet 31 can be easily formed in the joining member 30. In other words, the joining member 30 can be easily made to protrude beyond the front end face 2 a of the submount 2.

[0099] Furthermore, in this embodiment, the pad electrode 20 is provided not only in the current injection region but also in a location other than the current injection region. Specifically, the pad electrode 20 is formed not only in a position overlapping the p-side electrode 18 but also in a position overlapping the insulating film 16 and the barrier layer 17. Therefore, the bonding member 30 formed by the eutectic reaction between the molten solder layer 26 and the pad electrode 20 is formed not only in the current injection region but also in a location other than the current injection region (a non-current injection region). As a result, the bonding member 30 can be interposed between the semiconductor laser element 1 and the submount 2 not only in the current injection region but also in the non-current injection region, so that a heat dissipation path by the bonding member 30 can be secured in both the current injection region and the non-current injection region.

[0100] 14, the solder layer 26 located at the rear (the base of the V) of the solder layer 26 in the inter-protrusion region 24a1 (the solder layer 26 in the region indicated by dotted hatching in FIG. 14) undergoes a eutectic reaction with the Au layer 24 located below the upper protective metal layer 25. As a result, as shown in FIG. 13B, a eutectic layer 24g is formed in the Au layer 24, and a part of the bonding member 30 is formed so as to extend below the upper protective metal layer 25. However, because the upper protective metal layer 25 is a Pt layer, the eutectic reaction between the solder layer 26 and the Au layer 24 stops midway through the Au layer 24 due to the masking effect of the Pt layer and the saturation of the Au composition of the solder layer 26.

[0101] [Summary] As described above, the submount 2 according to this embodiment comprises the submount body 21, the Au layer 24 located above the submount body 21, the upper protective metal layer 25 which is an example of a metal layer located above the Au layer 24, and the solder layer 26 located above the upper protective metal layer 25. The Au layer 24 has an exposed region 24a exposed from the upper protective metal layer 25, the solder layer 26 is provided above the exposed region 24a and the upper protective metal layer 25, the upper protective metal layer 25 has a plurality of protrusions 25a protruding toward the end face of the submount body 21, and each protrusion 25a has a first portion 25a1 exposed from the solder layer 26 and a second portion 25a2 covered with the solder layer 26. The exposed region 24 a includes an inter-protrusion region 24 a 1 between two adjacent protrusions 25 a , and at least a part of the inter-protrusion region 24 a 1 is covered with the solder layer 26 .

[0102] With this configuration, when the semiconductor laser element 1 is mounted using the submount 2, the molten solder layer 26 (liquid solder) can be easily and sufficiently wetted and spread to the front end of the semiconductor laser element 1. As a result, the front end of the semiconductor laser element 1 can be joined to the submount 2 by the joining member 30 made of the molten and hardened solder layer 26. Therefore, heat generated at the front end of the semiconductor laser element 1 during operation can be sufficiently dissipated to the submount 2. In other words, heat generated at the front end of the semiconductor laser element 1 can be sufficiently dissipated. As a result, the occurrence of COD in the semiconductor laser element 1 can be suppressed.

[0103] 14 , in plan view, it is preferable that the inter-protrusion region 24a1 between two adjacent protrusions 25a on the submount 2 is located at a position overlapping the ridge 1R of the semiconductor laser device 1. This allows the bonding member 30 to extend to the front end of the ridge 1R of the semiconductor laser device 1, thereby effectively suppressing heat generated at the front end of the ridge 1R of the semiconductor laser device 1.

[0104] Furthermore, in the submount 2 according to this embodiment, the width of the inter-protrusion region 24a1 increases toward the end face of the submount body 21. For example, the shape of the inter-protrusion region 24a1 in a plan view is triangular.

[0105] With this configuration, as described above, the molten solder layer 26 can be made to easily wet and spread toward the front end face 2 a of the submount 2, so that the molten solder layer 26 can be made to wet and spread reliably up to the front end of the semiconductor laser element 1.

[0106] (Modifications) Although the submount, semiconductor laser device, etc. according to the present disclosure have been described above based on the embodiments, the present disclosure is not limited to the above-described embodiments.

[0107] For example, as shown in FIG. 10 , in the semiconductor laser device 3 according to the above embodiment, the front end face 30 a of the bonding member 30 is located at a position recessed from the front end face 1 a of the semiconductor laser element 1. However, this is not limited to this. Specifically, as in the semiconductor laser device 3A shown in FIG. 15 , the bonding member 30A may be formed up to the front end face 1 a of the semiconductor laser element 1, and the front end face 30 a of the bonding member 30A may be flush with the front end face 1 a of the semiconductor laser element 1. This allows for further dissipation of heat generated at the front end of the semiconductor laser element 1, thereby further suppressing the occurrence of COD in the semiconductor laser element 1. Note that in the semiconductor laser device 3A shown in FIG. 15 , the insulating film 16 and the barrier layer 17 are formed up to the front end face 1 a of the semiconductor laser element 1.

[0108] 16 , a gap 32 may be formed between the front end of the semiconductor laser element 1 and the bonding member 30. The gap 32 is, for example, a gap (space) between the insulating film 16, the barrier layer 17, and the bonding member 30 of the semiconductor laser element 1. In other words, the gap 32 is a gap formed between a step at the end of the barrier layer 17 on the insulating film 16 and the fillet 31 of the bonding member 30. In this way, the presence of the gap 32 between the front end of the semiconductor laser element 1 and the bonding member 30 can suppress the application of stress to the front end of the semiconductor laser element 1 due to shear stress caused by the difference in linear expansion coefficients between the members. As a result, the progression of shear strain in the light-emitting region of the semiconductor laser element 1 can be suppressed.

[0109] In the above embodiment, the shape of the convex portion 25 a provided on the upper protective metal layer 25 of the submount 2 is trapezoidal in plan view, and the shape of the inter-convex portion region 24 a 1 between two adjacent convex portions 25 a is triangular. However, this is not limited to this. For example, as in the submount 2C shown in FIG. 17 , the shape of the convex portion 25 a C provided on the upper protective metal layer 25 C of the submount 2C may be rectangular in plan view, and the shape of the inter-convex portion region 24 a 1 between two adjacent convex portions 25 a C may also be rectangular in plan view. In this case, the shape of each of the first portion 25 a 1 and the second portion 25 a 2 of the convex portion 25 a C is also rectangular in plan view. 17 , in a plan view, if the width of the tip of the convex portion 25aC is a, the opening width of the inter-convex portion region 24a1 is b, the length (depth) from the opening to the bottom of the inter-convex portion region 24a1 is c, and the length from the front end surface of the solder layer 26 to the bottom of the inter-convex portion region 24a1 is d, then a=b, d=c / 2. As an example, a=b=20 μm, c=30 μm, and d=15 μm. Note that the relationships are not limited to a=b, d=c / 2, and may be a>b, a<b, d>c / 2, or d<c / 2.

[0110] In addition, an experiment was conducted to determine which of the present modified example in which the shape of the convex portion 25aC in a plan view is rectangular (the inter-convex portion region 24a1 is rectangular) and the above embodiment in which the shape of the convex portion 25a in a plan view is triangular (the inter-convex portion region 24a1 is triangular) is more effective from the viewpoint of the ease of wetting and spreading of the molten solder layer 26. Specifically, in this modified example in which the shape of the convex portion 25aC in a plan view is rectangular, as shown in FIG. 18, the area of ​​the solder layer 26 in the rectangular inter-convex portion region 24a1 (the area of ​​the region indicated by dotted hatching in FIG. 18) is 300 μm ２ Therefore, in the above embodiment, the area of ​​the solder layer 26 in the triangular inter-protrusion region 24a1 (the area of ​​the region indicated by dotted hatching in FIG. 14) is set to 300 μm ２ The wettability and spreadability of the molten solder layer 26 were examined with dimensions (a = b = 20 μm, c = 45 μm, d = 30 μm). As a result, it was found that the molten solder layer 26 is more easily wetted and spreadable when the convex portions 25a and the inter-convex regions 24a1 are triangular, as in the above-described embodiment, than when the convex portions 25aC and the inter-convex regions 24a1 are rectangular, as in this modified example. This is thought to be because, as shown by the thick arrow in FIG. 18 , when the solder layer 26 melts, the forward propulsion vector of the liquid solder due to the shape of the inter-convex regions 24a1 is larger when the convex portions 25a and the inter-convex regions 24a1 are triangular than when the convex portions 25aC and the inter-convex regions 24a1 are rectangular.

[0111] Furthermore, in the submount 2 of the above embodiment, the shape of each of the plurality of protrusions 25 a of the upper protective metal layer 25 in a plan view is trapezoidal, but this is not limited to this. Specifically, as in the submount 2D shown in Fig. 19 , the shape of each of the plurality of protrusions 25 aD of the upper protective metal layer 25D in a plan view may be triangular. Specifically, as shown in Fig. 19 , the front end surface of the upper protective metal layer 25D may have a jagged, uneven shape.

[0112] Furthermore, in the submount 2 according to the above embodiment, the plurality of protrusions 25a on the upper protective metal layer 25 and the plurality of inter-protrusion regions 24a1 of the Au layer 24 are provided over the entire front end surface of the upper protective metal layer 25. However, this is not limited to this. Specifically, as in a submount 2E shown in FIG. 20 , the plurality of protrusions 25a on the upper protective metal layer 25E and the inter-protrusion regions 24a1 of the Au layer 24 may be provided only in the portion where the semiconductor laser element 1 is mounted. The same applies to the case where the protrusions 25aC are rectangular as shown in FIG. 17 and the case where the protrusions 25aD are triangular as shown in FIG. 19 . That is, as in a submount 2F shown in FIG. 21 , the plurality of protrusions 25aC on the upper protective metal layer 25F and the inter-protrusion regions 24a1 of the Au layer 24 may be provided only in the portion where the semiconductor laser element 1 is mounted. Similarly, as in the submount 2G shown in Figure 22, the multiple protrusions 25aD provided on the upper protective metal layer 25G and the inter-protrusion regions 24a1 of the Au layer 24 may be provided only in the portion where the semiconductor laser element 1 is mounted.

[0113] Furthermore, in the submount 2 of the above embodiment, the plurality of protrusions 25a provided on the upper protective metal layer 25 and the inter-protrusion regions 24a1 of the Au layer 24 are partially exposed from the solder layer 26 and partially covered with the solder layer 26 (i.e., partially covered with the solder layer 26), but this is not limiting. For example, as in the submount 2H shown in Fig. 23 , the plurality of protrusions 25aH provided on the upper protective metal layer 25H and the inter-protrusion regions 24a1 of the Au layer 24 may be entirely covered with the solder layer 26 without being exposed from the solder layer 26, rather than being partially covered with the solder layer 26. In this case, each of the plurality of protrusions 25aH has only the second portion 25a2 covered with the solder layer 26.

[0114] In the semiconductor laser device 3 according to the above embodiment, the front end face 1 a of the semiconductor laser element 1 protrudes from the front end face 2 a of the submount 2, but this is not limiting. Specifically, the front end face 1 a of the semiconductor laser element 1 does not have to protrude from the front end face 2 a of the submount 2. In this case, the front end face 1 a of the semiconductor laser element 1 may be flush with the front end face 2 a of the submount 2, or may be located at a position recessed from the front end face 2 a of the submount 2.

[0115] In the above-described embodiment, the semiconductor laser element is configured to emit infrared laser light, but this is not limiting. For example, the semiconductor laser element may be configured to emit visible or ultraviolet laser light.

[0116] In the above-described embodiment, the semiconductor laser element is made of an AlGaInN-based III-V group semiconductor material, but this is not limiting. For example, the semiconductor laser element may be made of an AlGaInAs-based or AlGaInP-based III-V group semiconductor material.

[0117] In addition, the present disclosure also includes forms obtained by applying various modifications that a person skilled in the art would conceive of to the above-described embodiments and modifications, and forms realized by arbitrarily combining the components and functions of the embodiments and modifications within the scope of the present disclosure. The present disclosure also includes any combination of two or more claims from among the multiple claims set forth in the claims at the time of filing, within the scope of technical compatibility. For example, when a dependent claim set forth in the claims at the time of filing is made into a multiple claim or multiple multiple claims that cite all of the superordinate claims within the scope of technical compatibility, the present disclosure also includes any combination of all claims included in that multiple claim or multiple multiple claims.

[0118] The technology disclosed herein is useful as a submount for mounting devices such as semiconductor laser elements. Furthermore, the semiconductor laser device according to the present disclosure can be used as a light source for products in various fields, such as laser processing devices, lighting devices, and image display devices.

[0119] REFERENCE SIGNS LIST 1 semiconductor laser element 1a, 2a, 30a front end facet 1b, 2b rear end facet 1S semiconductor laminate structure 1R ridge portion 1W wing portion 2, 2C, 2D, 2E, 2F, 2G, 2H submount 3, 3A, 3B semiconductor laser device 11 substrate 12 n-side semiconductor layer 13 active layer 14 p-side semiconductor layer 15 p-type contact layer 16 insulating film 17 barrier layer 18 p-side electrode 19 n-side electrode 20 pad electrode 21 submount body 22 adhesion metal layer 23 lower protective metal layer 24 Au layer 24a exposed region 24a1 inter-protrusion region 24g eutectic layer 25, 25C, 25D, 25E, 25F, 25G, 25H upper protective metal layer 25a, 25aC, 25aD, 25aH: protrusion; 25a1: first portion; 25a2: second portion; 26: solder layer; 30, 30A: joining member; 31: fillet; 32: gap;

Claims

1. A submount comprising: a submount body; an Au layer located above the submount body; a metal layer located above the Au layer; and a solder layer located above the metal layer, wherein the Au layer has an exposed region exposed from the metal layer, and the solder layer is provided above the exposed region and the metal layer, wherein in a planar view, the metal layer has a plurality of protrusions protruding toward an end face of the submount body, and each of the plurality of protrusions has a first portion exposed from the solder layer and a second portion covered by the solder layer, and the exposed region includes an inter-protrusion region which is a region between two adjacent protrusions of the plurality of protrusions, and at least a portion of the inter-protrusion region is covered by the solder layer.

2. The submount according to claim 1, wherein, in a plan view, the width of the inter-protrusion region increases as it approaches the end face of the submount body.

3. The submount according to claim 2, wherein the shape of the inter-protrusion region is triangular in plan view.

4. The submount according to claim 1, wherein the inter-protrusion area has a rectangular shape in plan view.

5. The submount according to any one of claims 1 to 4, further comprising an adhesion metal layer between the submount body and the Au layer.

6. The submount according to any one of claims 1 to 5, wherein the solder layer contains gold and tin.

7. The submount according to any one of claims 1 to 6, wherein the metal layer is a protective metal layer made of Pt, Cr or Ni.

8. A semiconductor laser device comprising: a submount according to any one of claims 1 to 7; and a semiconductor laser element, wherein the submount and the semiconductor laser element are bonded together via a bonding member.

9. The semiconductor laser device according to claim 8, wherein the joining member extends to an end of the semiconductor laser element on the light-emitting side.

10. The semiconductor laser device according to claim 9, wherein the semiconductor laser element has an insulating film on the semiconductor layer at the end on the light-emitting side, and the joining member extends to the end on the light-emitting side of the insulating film.

11. The semiconductor laser device according to claim 10, further comprising a barrier layer on the insulating film, and a gap is formed between the insulating film, the barrier layer, and the bonding member.

12. The semiconductor laser device according to any one of claims 8 to 11, wherein the semiconductor laser element protrudes beyond the end face of the submount body in plan view.

13. The semiconductor laser device according to any one of claims 8 to 12, wherein the joining member protrudes beyond the end face of the submount body.

14. A method for manufacturing a semiconductor laser device, comprising: a placement step of placing a semiconductor laser element on the solder layer of a submount according to any one of claims 1 to 7; and a bonding step of bonding the submount and the semiconductor laser element via a bonding member, wherein the semiconductor laser element has a pad electrode, and the bonding member is constituted by the solder layer of the submount and the pad electrode of the semiconductor laser element.

Images