Semiconductor laser element

Abstract

This semiconductor laser element (10) is provided with a first semiconductor layer, an active layer (23), an insulating film (30), a contact electrode (40) and a barrier metal layer (50). A second semiconductor layer has a ridge (24R); the insulating film (30) has an opening part (30a) which is arranged in a position that corresponds to the upper surface (24Rt) of the ridge (24R); the contact electrode (40) is arranged in the opening part (30a); the lateral surface (40s) of the contact electrode (40) is inclined towards the inside of the contact electrode (40); the lateral surface (30s) of the insulating film (30) is inclined towards the outside of the opening part (30a); and the barrier metal layer (50) covers the entirety of the upper surface (40t) of the contact electrode (40), and continuously covers the area from the upper surface (40t) of the contact electrode (40) to the upper surface (30t) of the insulating film (30).

Description

semiconductor laser element

[0001] The present disclosure relates to a semiconductor laser device.

[0002] Conventionally, semiconductor laser elements having a ridge are known (for example, Patent Document 1). In the semiconductor laser element described in Patent Document 1, an insulating film having an opening at a position corresponding to the upper surface of the ridge is disposed above a semiconductor laminate. A contact electrode made of Pd is disposed on the upper surface of the ridge, and a barrier metal layer made of Pt is disposed on the contact electrode. In the semiconductor laser element described in Patent Document 1, such a barrier metal layer is intended to suppress the diffusion of impurities into the contact electrode. In other words, it is intended to suppress an increase in electrical resistance caused by the diffusion of impurities into the contact electrode.

[0003] International Publication No. 2020 / 110783

[0004] However, in the semiconductor laser device described in Patent Document 1, the barrier metal layer covering the periphery of the contact electrode is particularly thin, so that impurities can diffuse into the contact electrode.

[0005] Furthermore, when the side surface of the contact electrode is substantially perpendicular to the upper surface of the semiconductor laminate, a slit may be formed in the barrier metal layer covering the vicinity of the side surface. Impurities may diffuse into the contact electrode through such a slit. As described above, in conventional semiconductor laser devices, the barrier metal layer covering the contact electrode does not adequately suppress impurity diffusion.

[0006] The present disclosure is intended to solve such problems, and has an object to provide a semiconductor laser element that can suppress the diffusion of impurities into the contact electrodes.

[0007] In order to solve the above problems, one aspect of the semiconductor laser element according to the present disclosure is a semiconductor laser element that emits laser light, and includes: a first semiconductor layer of a first conductivity type; an active layer disposed above the first semiconductor layer; a second semiconductor layer of a second conductivity type different from the first conductivity type that is disposed above the active layer; an insulating film disposed above the second semiconductor layer; a contact electrode disposed above the second semiconductor layer that is in contact with the second semiconductor layer; and a barrier metal layer disposed above the contact electrode, wherein the second semiconductor layer has a ridge that extends in a propagation direction of the laser light, and the insulating film is disposed at a position corresponding to an upper surface of the ridge. the contact electrode is disposed in the opening, and side surfaces of the contact electrode located at the lateral ends perpendicular to the propagation direction of the laser light and the stacking direction of the contact electrode are inclined toward the inside of the contact electrode with respect to a direction perpendicular to the top surface of the ridge; and among the side surfaces of the insulating film located at the periphery of the opening, side surfaces located at the lateral ends of the opening are inclined toward the outside of the opening with respect to a direction perpendicular to the top surface of the ridge; and the barrier metal layer covers the entire top surface of the contact electrode and continuously covers from the top surface of the contact electrode to the top surface of the insulating film.

[0008] According to the present disclosure, it is possible to provide a semiconductor laser element that can suppress the diffusion of impurities into the contact electrode.

[0009] 1 is a schematic plan view showing the overall configuration of a semiconductor laser element according to an embodiment. 2 is a schematic first cross-sectional view showing the overall configuration of a semiconductor laser element according to an embodiment. 3 is a schematic second cross-sectional view showing the overall configuration of a semiconductor laser element according to an embodiment. 4 is a schematic cross-sectional view showing an example of a mounting method for a semiconductor laser element according to an embodiment. 5 is a schematic cross-sectional view showing the configuration of a semiconductor laser device in which a semiconductor laser element according to an embodiment is mounted. 6 is an enlarged view of the inside of a dashed frame V shown in FIG. 2. 7 is an enlarged view of the inside of a dashed frame VI shown in FIG. 3. 8 is an enlarged view of the inside of a dashed frame VII shown in FIG. 3. 9 is a schematic cross-sectional view showing a first step of a manufacturing method for a semiconductor laser element according to an embodiment. 10 is a schematic cross-sectional view showing a second step of a manufacturing method for a semiconductor laser element according to an embodiment. 11 is a schematic cross-sectional view showing a third step of a manufacturing method for a semiconductor laser element according to an embodiment. 12 is a schematic cross-sectional view showing a fourth step of a manufacturing method for a semiconductor laser element according to an embodiment. 13 is a schematic cross-sectional view showing a resist forming step in the fourth step of a manufacturing method for a semiconductor laser element according to an embodiment. 14 is a schematic cross-sectional view showing an opening forming step in the fourth step of a manufacturing method for a semiconductor laser element according to an embodiment. FIG. 1 is a schematic cross-sectional view showing a contact electrode forming step in a fourth step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 2 is a schematic first cross-sectional view showing an incident direction of a deposition material at a first rotation position in planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 3 is a schematic first cross-sectional view showing an incident direction of a deposition material at a second rotation position in planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 4 is a schematic first cross-sectional view showing an incident direction of a deposition material at a third rotation position in planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 5 is a schematic first cross-sectional view showing an incident direction of a deposition material at a fourth rotation position in planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 6 is a schematic second cross-sectional view showing an incident direction of a deposition material at a first rotation position in planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment.28 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a first modification of the embodiment. 29 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a second modification of the embodiment. 30 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a third modification of the embodiment. 31 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a third modification of the embodiment. 32 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a third modification of the embodiment. 33 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a third modification of the embodiment. 34 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a third modification of the embodiment. 35 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a third modification of the embodiment. 36 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a third modification of the embodiment. 37 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a third modification of the embodiment. 38 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a third modification of the embodiment. 39 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device in accordance with a fourth modification of the embodiment.

[0010] 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, and the arrangement and connection of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0011] Furthermore, each figure is a schematic diagram and is not necessarily an exact representation. 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.

[0012] In this specification, the terms "above" and "below" do not refer to vertically above and below in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. 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 them, but also when two components are arranged in contact with each other.

[0013] (Embodiment) A semiconductor laser device and a manufacturing method thereof according to an embodiment will be described.

[0014] [1-1. Overall Configuration] First, the overall configuration of the semiconductor laser device according to this embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic plan view showing the overall configuration of a semiconductor laser device 10 according to this embodiment. FIGS. 2 and 3 are schematic cross-sectional views showing the overall configuration of the semiconductor laser device 10 according to this embodiment. FIG. 2 shows a cross section of the semiconductor laser device 10 taken along line II-II in FIG. 1. FIG. 3 shows a cross section of the semiconductor laser device 10 taken along line III-III in FIG. 1. Note that each figure shows an X-axis, a Y-axis, and a Z-axis, which are orthogonal to each other. The X-axis, the Y-axis, and the Z-axis are in a right-handed Cartesian coordinate system. The stacking direction of the semiconductor laser device 10 is parallel to the Z-axis direction, and the main emission direction of light (laser light in this embodiment) is parallel to the Y-axis direction.

[0015] As shown in FIGS. 2 and 3 , the semiconductor laser device 10 includes a semiconductor stack 10S and emits laser light from a facet 10F (see FIG. 1 ) perpendicular to the stacking direction (i.e., the Z-axis direction) of the semiconductor stack 10S. In this embodiment, the semiconductor laser device 10 is a nitride semiconductor laser device having two facets 10F and 10R that form a cavity, as shown in FIG. 1 . The facet 10F is a front-side facet from which laser light is emitted, and the facet 10R is a rear-side facet having a higher reflectivity than the facet 10F. In this embodiment, the reflectivities of the facets 10F and 10R are 15% and 98%, respectively. The semiconductor laser device 10 also has a waveguide formed between the facets 10F and 10R. The cavity length of the semiconductor laser device 10 according to this embodiment (i.e., the distance between the facets 10F and 10R) is approximately 1200 μm. The semiconductor laser element 10 also emits blue light having a peak wavelength in the 445 nm band, for example.

[0016] As shown in FIGS. 2 and 3, the semiconductor laser element 10 includes a substrate 21, a semiconductor stack 10S, an insulating film 30, a contact electrode 40, a barrier metal layer 50, a pad electrode 60, and an N-side electrode 70.

[0017] The substrate 21 is a plate-like member that serves as a base for the semiconductor laser device 10. In this embodiment, the substrate 21 is an N-type GaN substrate.

[0018] The semiconductor stack 10S is a stack including semiconductor layers. The semiconductor stack 10S has a plurality of semiconductor layers stacked in a stacking direction. In this embodiment, the semiconductor stack 10S has an N-side semiconductor layer 22, an active layer 23, and a P-side semiconductor layer 24.

[0019] The N-side semiconductor layer 22 is an example of a first semiconductor layer of a first conductivity type that is arranged above the substrate 21 and below the active layer 23. In the present embodiment, the N-side semiconductor layer 22 includes a nitride semiconductor. The N-side semiconductor layer 22 also includes an N-type clad layer that has a lower refractive index than the active layer 23. The N-side semiconductor layer 22 is, for example, an N-type AlGaN layer. The N-side semiconductor layer 22 may include a layer other than the N-type clad layer. The N-side semiconductor layer 22 may include, for example, a buffer layer, an optical guide layer, etc.

[0020] The active layer 23 is a light-emitting layer disposed above the N-side semiconductor layer 22. In this embodiment, the active layer 23 includes a nitride semiconductor and has a quantum well structure. The active layer 23 may have a single quantum well or multiple quantum wells. In this embodiment, the active layer 23 has multiple barrier layers made of InGaN and multiple well layers made of InGaN.

[0021] The P-side semiconductor layer 24 is disposed above the active layer 23 and is an example of a second semiconductor layer of a second conductivity type different from the first conductivity type. The P-side semiconductor layer 24 includes a nitride semiconductor. In this embodiment, the P-side semiconductor layer 24 includes a P-type clad layer having a lower refractive index than the active layer 23. The P-side semiconductor layer 24 is, for example, a P-type AlGaN layer. The P-side semiconductor layer 24 may include a layer other than the P-type clad layer. The P-side semiconductor layer 24 may include, for example, an optical guide layer, an electron barrier layer, a contact layer, etc. The P-side semiconductor layer 24 may also have a superlattice structure.

[0022] As shown in FIG. 2 , the P-side semiconductor layer 24 has a ridge 24R extending in the laser light propagation direction. The ridge 24R is a portion of the P-side semiconductor layer 24 that protrudes in the Z-axis direction. In this embodiment, two grooves 24T are formed in the P-side semiconductor layer 24, arranged along the ridge 24R and extending in the Y-axis direction. In this embodiment, the ridge width (i.e., the dimension of the ridge 24R in the X-axis direction) is approximately 45 μm. The dotted line indicating the boundary between the ridge 24R and the groove 24T in FIG. 1 corresponds to the position of the X-axis end of the top surface 24Rt of the ridge 24R (not visible from the top surface of the semiconductor laser device 10). Furthermore, of the dotted lines indicating the groove 24T in FIG. 1 , the dotted line farther from the ridge 24R corresponds to the position of the X-axis end of the groove 24T (not visible from the top surface of the semiconductor laser device 10). Furthermore, wing portions 24W made of the P-side semiconductor layer are formed on both sides of the groove 24T. The wing portion 24W is a portion of the P-side semiconductor layer 24 that protrudes in the Z-axis direction and extends in the propagation direction of the laser light.

[0023] The insulating film 30 is a layer disposed above the P-side semiconductor layer 24 (i.e., the second semiconductor layer). In this embodiment, the insulating film 30 is disposed between the semiconductor stack 10S and the barrier metal layer 50 and is an electrically insulating layer. The insulating film 30 has an opening 30a disposed at a position corresponding to the upper surface 24Rt of the ridge 24R. In this embodiment, the insulating film 30 is disposed in a region of the upper surface of the P-side semiconductor layer 24 other than the central portion of the upper surface 24Rt of the ridge 24R. Specifically, the insulating film 30 continuously covers a portion of the upper surface 24Rt of the ridge 24R, the side surface of the ridge 24R, the bottom surface of the groove 24T, the side surface of the wing portion 24W, the upper surface of the wing portion 24W, the side surface of the P-side semiconductor layer 24 (i.e., the end surface in the X-axis direction), the side surface of the active layer 23, and a portion of the side surface of the N-side semiconductor layer 22. This ensures electrical insulation between the barrier metal layer 50 disposed on the insulating film 30, the pad electrode 60 disposed above the barrier metal layer 50, and the side surface of the opening 30a and the P-side semiconductor layer 24. This makes it possible to suppress current flowing from the barrier metal layer 50 and the pad electrode 60 to the vicinity of the side surface of the ridge 24R via the insulating film 30. This makes it possible to suppress an increase in light density near the side surface of the ridge 24R. This makes it possible to suppress a decrease in the optical amplification gain due to the hole burning phenomenon caused by an increase in light density.

[0024] There are no particular limitations on the material that forms the insulating film 30 as long as it is an insulating material. In this embodiment, the insulating film 30 is a silicon oxide film with a film thickness of 300 nm. The detailed configuration and effects of the insulating film 30 will be described later.

[0025] The contact electrode 40 is an electrode that is disposed above the P-side semiconductor layer 24 and is in contact with the P-side semiconductor layer 24. The contact electrode 40 faces the P-side semiconductor layer 24 above the ridge 24R of the P-side semiconductor layer 24 and is in contact with the P-side semiconductor layer 24. In this embodiment, the contact electrode 40 is disposed in the opening 30a of the insulating film 30. The contact electrode 40 and the insulating film 30 are spaced apart.

[0026] The contact electrode 40 may contain Pd or indium tin oxide (ITO). This reduces the contact resistance between the contact electrode 40 and the P-side semiconductor layer 24, thereby reducing the operating voltage of the semiconductor laser device 10. The contact electrode 40 may be a single layer or multilayer film formed of at least one of Pd, Pt, Ni, and Ag, or may be a single layer or multilayer film formed of ITO, indium zinc oxide (IZO), zinc oxide (ZnO), or InGaZnO. x The contact electrode 40 may be made of a conductive metal oxide such as IGZO. In this embodiment, the contact electrode 40 is a single-layer film. More specifically, the contact electrode 40 is a Pd layer with a film thickness of 40 nm.

[0027] The barrier metal layer 50 is a metal layer disposed above the contact electrode 40. The barrier metal layer 50 has a function of suppressing the diffusion of impurities into the contact electrode 40. Examples of impurities include oxygen atoms. Furthermore, for example, when the semiconductor laser device 10 is junction-down (flip-chip) mounted (i.e., when the pad electrode 60 is bonded to a mounting substrate, etc.), Sn elements contained in the solder used as a bonding material can become impurities that diffuse into the contact electrode 40.

[0028] The barrier metal layer 50 covers the entire upper surface of the contact electrode 40 and continuously covers from the upper surface of the contact electrode 40 to the upper surface of the insulating film 30. In this embodiment, the barrier metal layer 50 continuously covers from the upper surface of the contact electrode 40 to the upper surface of the insulating film 30 arranged outside the ridge 24R. More specifically, as shown in FIG. 2 , the barrier metal layer 50 continuously covers the upper surface of the insulating film 30 arranged continuously above the left wing portion 24W and above a part of the upper surface of the left trench 24T and the ridge 24R, the upper surface of the ridge 24R located between the left insulating film 30 and the contact electrode 40, the upper surface of the contact electrode 40, the upper surface of the ridge 24R located between the contact electrode 40 and the right insulating film 30, and the upper surface of the insulating film 30 arranged continuously above a part of the upper surface of the ridge 24R and above the right trench 24T and to the right of the right wing portion 24W.

[0029] The barrier metal layer 50 also functions to enhance adhesion between the pad electrode 60 and the insulating film 30. The barrier metal layer 50 is formed of, for example, Cr or Ti. When the barrier metal layer 50 contains Cr or Ti and the insulating film 30 is an oxide, the adhesion between the insulating film 30 and the barrier metal layer 50 can be further enhanced. This is because, when the insulating film 30 is an oxide, if the barrier metal layer 50 is made of a material that easily forms an oxide, the insulating film 30 and the barrier metal layer 50 are strongly bonded. In this embodiment, the barrier metal layer 50 is a 100 nm-thick Cr layer. Note that if the Cr film is too thick, cracks and peeling may occur due to large internal stress. For example, the thickness of the barrier metal layer 50 may be 200 nm or less.

[0030] In this embodiment, the film thickness of the contact electrode 40 is thinner than the film thickness of the barrier metal layer 50. Moreover, the combined film thickness of the contact electrode 40 and the barrier metal layer 50 is thinner than the film thickness of the insulating film.

[0031] The pad electrode 60 is a conductive layer disposed above the insulating film 30 and the contact electrode 40 and electrically connected to the contact electrode 40. The pad electrode 60 is formed on the upper surface of the barrier metal layer 50 using the same mask as used to form the barrier metal layer 50, and has the same planar shape as the barrier metal layer 50. The pad electrode 60 contains Au. In this embodiment, the pad electrode 60 is an Au layer with a film thickness of approximately 2000 nm.

[0032] The N-side electrode 70 is a conductive layer disposed on the lower surface of the substrate 21 (i.e., the principal surface of the substrate 21 opposite to the principal surface on which the semiconductor laminate 10S is disposed). The N-side electrode 70 may be, for example, a single-layer film or a multilayer film formed of at least one of Cr, Ti, Ni, Pd, and Pt. In this embodiment, the N-side electrode 70 has a 10-nm-thick Ti layer in contact with the substrate 21, a 35-nm-thick Pt layer in contact with the Ti layer, and a 300-nm-thick Au layer in contact with the Pt layer.

[0033] [1-2. Mounting Mode of Semiconductor Laser Element] An example of a mounting mode of the semiconductor laser element 10 according to this embodiment will be described with reference to Figs. 4A and 4B. Fig. 4A is a schematic cross-sectional view showing an example of a mounting method of the semiconductor laser element 10 according to this embodiment. Fig. 4B is a schematic cross-sectional view showing the configuration of a semiconductor laser device 11 in which the semiconductor laser element 10 according to this embodiment is mounted. Similar to Fig. 2, Figs. 4A and 4B show cross sections perpendicular to the propagation direction of laser light of the semiconductor laser element 10.

[0034] 4A, an example of a method for mounting the semiconductor laser element 10 will be described. Here, a junction-down mounting method will be described as an example of the mounting method.

[0035] First, the semiconductor laser element 10 and the submount 80 on which the bonding material 90 is laminated are prepared.

[0036] The submount 80 is a base on which the semiconductor laser element 10 is mounted. The submount 80 can be, for example, a ceramic substrate, a polycrystalline substrate, a single crystal substrate, or the like made of a material such as alumina, AlN, SiC, or diamond.

[0037] The bonding material 90 is a member that bonds the semiconductor laser element 10 to the submount 80. In this embodiment, the bonding material 90 includes AuSn solder.

[0038] Subsequently, as shown in FIG. 4A, the semiconductor laser element 10 is placed on the bonding material 90.

[0039] After the semiconductor laser element 10 is placed on the bonding material 90 (i.e., after the semiconductor laser element 10 is in contact with the bonding material 90), the submount 80 is heated to a temperature T higher than the melting point Tm of the bonding material 90 to melt the bonding material 90. Here, in the heating step, the submount 80 is maintained at the temperature T for about 10 seconds.

[0040] After the heating step, the temperature of the submount 80 is reduced to a temperature below the melting point Tm of the bonding material 90 .

[0041] Through the above steps, the pad electrode 60 of the semiconductor laser element 10 is bonded to the submount 80 via the bonding material 90. That is, the semiconductor laser element 10 is junction-down mounted on the submount 80, and the semiconductor laser device 11 as shown in FIG.

[0042] As shown in FIG. 4B , the semiconductor laser device 11 according to this embodiment includes an N-side electrode 70, a substrate 21, a semiconductor laminate 10S, an insulating film 30, a contact electrode 40, a barrier metal layer 50, a pad electrode 60 a, a bonding material 90 a, and a submount 80.

[0043] The pad electrode 60a is an electrode formed by bonding the pad electrode 60 made of an Au layer to a bonding material 90 containing AuSn solder, and is an Au layer containing Sn elements diffused from the bonding material 90. The concentration of Sn elements in the pad electrode 60a is, for example, about 3%. Note that the Sn element concentration in the pad electrode 60a does not have to be uniform. For example, the Sn element concentration in the pad electrode 60a may increase as it approaches the bonding material 90a.

[0044] The bonding material 90a is a layer formed by bonding the bonding material 90 containing AuSn solder to the pad electrode 60 made of an Au layer, and is an AuSn layer containing Au elements diffused from the pad electrode 60. The concentration of Sn elements in the bonding material 90a is, for example, about 20%. Note that the Sn element concentration in the bonding material 90a does not have to be uniform. For example, the Sn element concentration in the bonding material 90a may decrease as it approaches the pad electrode 60a.

[0045] 4B , by bonding the semiconductor laser element 10 and the submount 80 with a bonding material 90 containing AuSn solder, Sn elements contained in the bonding material 90 diffuse into the pad electrode 60 of the semiconductor laser element 10. Here, the diffusion of Sn elements into the contact electrode 40 increases the electrical resistance of the contact electrode 40. In this embodiment, by covering the contact electrode 40 with a barrier metal layer 50 that can suppress the diffusion of Sn elements, the increase in the electrical resistance of the contact electrode 40 can be suppressed.

[0046] Although the above description has been given of a configuration in which the semiconductor laser element 10 is mounted in a junction-down position, the mounting mode of the semiconductor laser element 10 is not limited to this. For example, the semiconductor laser element 10 may be mounted in a junction-up position.

[0047] [1-3. Detailed Configuration and Effects of Semiconductor Laser Element] The detailed configuration and effects of the semiconductor laser element 10 according to this embodiment will be described mainly with reference to Figs. 5 to 7. Fig. 5 is an enlarged view of the interior of the dashed frame V shown in Fig. 2. Figs. 6 and 7 are enlarged views of the interiors of the dashed frame VI and dashed frame VII shown in Fig. 3, respectively.

[0048] In the semiconductor laser device 10 according to this embodiment, as shown in FIG. 5 , the barrier metal layer 50 covers the entire upper surface 40t of the contact electrode 40 (see FIGS. 2 and 3 ) and continuously covers the area from the upper surface 40t of the contact electrode 40 to the upper surface 30t of the insulating film 30. Specifically, the barrier metal layer 50 covers the upper surface 24Rt of the ridge 24R located between the contact electrode 40 and the right-side insulating film 30. Because the thickness of the barrier metal layer 50 in the Z-axis direction is approximately uniform, the inclination angles of the barrier metal layer 50 formed on the inclined portions of the contact electrode 40 and the insulating film 30 are approximately the same as the inclination angles of the inclined portions of the respective underlying layers. However, the inclination angles of the barrier metal layer 50 disposed on the corners of the contact electrode 40 and the insulating film 30 may differ from the inclination angles of the corners of the underlying layers. For example, the barrier metal layer 50 disposed on the corners of the contact electrode 40 and the insulating film 30 may not have corners (i.e., the inclination angle changes smoothly depending on the position in the X-axis direction).

[0049] By covering the contact electrode 40 in this manner, the barrier metal layer 50 can suppress the diffusion of impurities such as oxygen atoms into the contact electrode 40. For example, when the semiconductor laser device 10 is junction-down mounted as in the mounting mode of the semiconductor laser device 10 shown in FIG. 4B , when a member containing Sn, such as AuSn solder, is connected to the pad electrode 60 of the semiconductor laser device 10, the diffusion of Sn elements into the contact electrode 40 via the pad electrode 60 can be suppressed. Furthermore, by continuously covering not only the contact electrode 40 but also the upper surface 30t of the insulating film 30 spaced from the contact electrode 40 with the barrier metal layer 50, the peripheral portion of the barrier metal layer 50, which may have a thin film thickness, can be separated from the contact electrode 40. This prevents the film thickness of the barrier metal layer 50 covering the contact electrode 40 from becoming thin. Therefore, the diffusion of impurities into the contact electrode 40 via the barrier metal layer 50 can be more reliably suppressed.

[0050] In addition, the side surface 40s located at the end of the contact electrode 40 in the horizontal direction (i.e., the X-axis direction) perpendicular to the propagation direction of the laser light and the stacking direction of the contact electrode 40 is inclined toward the inside of the contact electrode 40 with respect to the direction perpendicular to the top surface 24Rt of the ridge 24R (i.e., the Z-axis direction).

[0051] As a comparative example, consider a case where the side surface of the contact electrode 40 is perpendicular to the top surface 24Rt of the ridge 24R. In this case, the angle between the top surface 40t of the contact electrode 40 and the side surface is approximately 90 degrees. Accordingly, it becomes difficult to uniformly form the barrier metal layer 50 at the boundary between the top surface 40t and the side surface 40s of the contact electrode 40. Therefore, slit-shaped voids extending from the boundary to the surface of the barrier metal layer 50 are likely to form in the barrier metal layer 50 disposed at the boundary between the top surface 40t and the side surface 40s. When such voids are formed, impurities may diffuse into the contact electrode 40 through the voids.

[0052] In contrast, in this embodiment, as described above, the side surface 40s of the contact electrode 40 is inclined, so that the angle between the top surface 40t of the contact electrode 40 and the side surface 40s is less than 90 degrees. This makes it easier to form the barrier metal layer 50 uniformly at the boundary between the top surface 40t and the side surface 40s. This makes it possible to prevent slit-shaped voids from being formed in the barrier metal layer 50. This makes it possible to prevent impurities from diffusing into the contact electrode 40.

[0053] Furthermore, among the side surfaces of the insulating film 30 located on the periphery of the opening 30a, the side surfaces 30s located at the lateral ends of the opening 30a are inclined toward the outside of the opening 30a with respect to a direction perpendicular to the top surface 24Rt of the ridge 24R. In this embodiment, the inclination angle of the side surfaces 30s of the insulating film 30 with respect to the top surface 24Rt of the ridge 24R is 90 degrees or less. Note that the side surfaces 30s of the insulating film 30 may have a two-step inclined surface. In other words, the inclination angle of the side surfaces 30s near the top surface of the ridge 24R may be different from the inclination angle of the side surfaces 30s near the top surface 30t of the insulating film 30.

[0054] This can prevent slit-shaped voids from being formed in the barrier metal layer 50 disposed at the boundary between the upper surface 30t and the side surface 30s of the insulating film 30, similarly to the barrier metal layer 50 disposed on the upper surface 40t and the side surface 40s of the contact electrode 40. Therefore, it is possible to prevent impurities from diffusing into the contact electrode 40 through the voids and the boundary between the barrier metal layer 50 and the upper surface 24Rt of the ridge 24R.

[0055] 3, 6, and 7, in this embodiment, the insulating film 30 is disposed between the contact electrode 40 and the end faces 10F and 10R of the semiconductor laser element 10 in the propagation direction of the laser light. The barrier metal layer 50 continuously covers from the upper surface 40t of the contact electrode 40 to the upper surface 30t of the insulating film 30 in the propagation direction of the laser light.

[0056] This makes it possible to prevent the barrier metal layer 50 covering the top surface 40t and the side surface 40s of the contact electrode 40 from becoming thin at the end in the propagation direction of the laser light as well as at the lateral end of the contact electrode 40. This makes it possible to prevent impurities from diffusing into the contact electrode 40 via the barrier metal layer 50.

[0057] In addition, the side surface 40s of the contact electrode 40, which is located in the direction of propagation of the laser light and at the end of the contact electrode 40 in the direction of propagation of the laser light, is inclined toward the inside of the contact electrode 40 with respect to a direction perpendicular to the top surface 24Rt of the ridge 24R.

[0058] This can prevent slit-shaped voids from being formed in the barrier metal layer 50 disposed at the boundary between the upper surface 40t and the side surface 40s of the contact electrode 40. Therefore, the diffusion of impurities into the contact electrode 40 can be prevented.

[0059] Furthermore, among the side surfaces located on the periphery of the opening 30a of the insulating film 30, the side surface 30s located at the end of the opening 30a in the propagation direction of the laser light is inclined toward the outside of the opening 30a with respect to a direction perpendicular to the top surface 24Rt of the ridge 24R.

[0060] This can prevent slit-shaped voids from being formed in the barrier metal layer 50 disposed at the boundary between the upper surface 30t and the side surface 30s of the insulating film 30. This can prevent impurities from diffusing into the contact electrode 40 through the voids and the boundary between the barrier metal layer 50 and the upper surface 24Rt of the ridge 24R.

[0061] In addition, in this embodiment, as shown in Figures 6 and 7, in the propagation direction of the laser light, the distance Df between the insulating film 30 and the contact electrode 40 at the front end of the semiconductor laser element 10 is longer than the distance Dr between the insulating film 30 and the contact electrode 40 at the rear end of the semiconductor laser element 10.

[0062] In this embodiment, the thermal conductivity of Cr forming the barrier metal layer 50 and Au forming the pad electrode 60 is higher than the thermal conductivity of silicon oxide forming the insulating film 30 and Pd forming the contact electrode 40. Therefore, the heat dissipation characteristics from the upper surface of the semiconductor laminate 10S are best in the region where the barrier metal layer 50 is in contact with the upper surface of the semiconductor laminate 10S, that is, the region between the contact electrode 40 and the insulating film 30. Therefore, by making the dimensions of such a region with good heat dissipation characteristics larger at the front end of the semiconductor laser element 10, which generates a large amount of heat, than at the rear end, the heat dissipation characteristics at the front end of the semiconductor laser element 10 can be improved.

[0063] In addition, in this embodiment, as shown in Figures 6 and 7, the film thickness Tf of the barrier metal layer 50 disposed on the side surface 30s located on the periphery of the opening 30a of the insulating film 30, which is located between the contact electrode 40 and the front end face 10F of the semiconductor laser element 10, is thinner than the film thickness Tr of the barrier metal layer 50 disposed on the side surface 30s located between the contact electrode 40 and the rear end face 10R of the semiconductor laser element 10.

[0064] In this embodiment, the thermal conductivity of Au forming the pad electrode 60 is higher than that of Cr forming the barrier metal layer 50. Therefore, by making the film thickness Tf of the barrier metal layer 50 at the front end where the amount of heat generated is large thinner than the film thickness Tr at the rear end, it is possible to improve the heat dissipation characteristics at the front end of the semiconductor laser device 10.

[0065] In this embodiment, the inclination angle of the side surface 40s located at the end of the contact electrode 40 in the laser light propagation direction relative to the top surface 24Rt of the ridge 24R is larger on the front side of the semiconductor laser device 10 than on the rear side. That is, the inclination angle θf of the side surface 40s on the front side shown in FIG. 6 is larger than the inclination angle θr of the side surface 40s on the rear side shown in FIG.

[0066] This allows the length of the front-side side surface 40s in the Y-axis direction to be shorter than the length of the rear-side side surface 40s in the Y-axis direction. This makes it easier to make the distance Df between the insulating film 30 and the contact electrode 40 at the front-side end of the semiconductor laser element 10 longer than the distance Dr between the insulating film 30 and the contact electrode 40 at the rear-side end of the semiconductor laser element 10. This makes it easier to improve the heat dissipation characteristics at the front-side end of the semiconductor laser element 10, where a larger amount of heat is generated, than at the rear-side end.

[0067] In this embodiment, the inclination angle of at least a part of the side surface 40s of the contact electrode 40 relative to the top surface 24Rt of the ridge 24R is 30 degrees or less.

[0068] This makes it easier to form the barrier metal layer 50 more uniformly at the boundary between the top surface 40t and the side surface 40s of the contact electrode 40. This makes it possible to suppress the formation of slit-shaped voids in the barrier metal layer 50. This further suppresses the diffusion of impurities into the contact electrode 40. In this embodiment, the inclination angle of the side surface 40s of the contact electrode 40 with respect to the top surface 24Rt of the ridge 24R is smaller than the inclination angle of the side surface 30s of the insulating film 30 with respect to the top surface 24Rt of the ridge 24R.

[0069] In this embodiment, the barrier metal layer 50 is made of Cr. By covering the contact electrode 40 with the barrier metal layer 50 made of Cr, which is difficult to alloy with Sn, it is possible to suppress diffusion of Sn into the contact electrode 40 when the semiconductor laser device 10 is junction-down mounted. The barrier metal layer 50 may also be made of Ti, which, like Cr, is difficult to alloy with Sn.

[0070] In this embodiment, the contact electrode 40 is a single-layer film, which makes it possible to easily incline the side surface 40s of the contact electrode 40.

[0071] [1-4. Manufacturing Method] A manufacturing method for the semiconductor laser device 10 according to this embodiment will be described with reference to FIGS.

[0072] 8 to 23 are schematic cross-sectional views showing the steps of a manufacturing method for the semiconductor laser device 10 according to this embodiment. Figures 8 to 14 and 23 show cross sections similar to those in Figure 2, and Figures 15 to 18 show portions of cross sections similar to those in Figure 2. Figures 19 to 22 show portions of cross sections similar to those in Figure 3.

[0073] First, as shown in FIG. 8 , an N-side semiconductor layer 22 is formed above a substrate 21 as a first semiconductor layer of a first conductivity type, an active layer 23 is formed above the N-side semiconductor layer 22, and a P-side semiconductor layer 24 is formed above the active layer 23 as a second semiconductor layer. More specifically, first, a substrate 21 is prepared. In this embodiment, a wafer (GaN substrate) made of N-type GaN is prepared as the substrate 21. Next, the N-side semiconductor layer 22, the active layer 23, and the P-side semiconductor layer 24 are stacked in this order on the substrate 21 by epitaxial growth technology using a MOCVD (Metal Organic Chemical Vapor Deposition) method. This allows the semiconductor stack 10S to be formed.

[0074] Subsequently, as shown in FIG. 9, the ridge 24R, the wing portions 24W, and the grooves 24T, as well as the element isolation grooves 10D for separating the semiconductor laser elements 10 into individual pieces, are formed.

[0075] The element isolation trenches 10D are formed at positions corresponding to both end portions in the X-axis direction of the semiconductor laser element 10. In this embodiment, the element isolation trenches 10D reach from the upper surface of the semiconductor stack 10S to the inside of the N-side semiconductor layer 22.

[0076] In this embodiment, the ridge 24R and the wing portions 24W are formed by forming two grooves 24T. The two grooves 24T are formed in the P-side semiconductor layer 24 and do not reach the active layer 23.

[0077] There are no particular limitations on the method for forming the element isolation trench 10D, the ridge 24R, the wing portions 24W, and the trench 24T. The element isolation trench 10D, the ridge 24R, the wing portions 24W, and the trench 24T may be formed using, for example, photolithography and etching, or may be formed by laser processing.

[0078] 10, an insulating film 30 is formed above the P-side semiconductor layer 24. In this embodiment, a silicon oxide film is formed as the insulating film 30 by low-pressure CVD or the like. The silicon oxide film may also be formed by atmospheric pressure CVD.

[0079] 11, an opening 30a is formed at a position corresponding to the upper surface 24Rt of the ridge 24R, and a contact electrode 40 that contacts the P-side semiconductor layer 24 is formed in the opening 30a of the insulating film 30. This step will be described in detail below with reference to FIGS.

[0080] As shown in FIG. 12, a resist 95 is formed in the insulating film 30 in an area other than the area corresponding to the opening 30a.

[0081] 13, the region of the insulating film 30 corresponding to the opening 30a is removed by etching. This makes it possible to make the side surface 30s of the insulating film 30 inclined with respect to the top surface 24Rt of the ridge 24R. The etching method is not particularly limited. Dry etching or wet etching can be used as the etching.

[0082] 14, a contact electrode 40 is formed in the opening 30a of the insulating film 30, contacting the P-side semiconductor layer 24. In this embodiment, a Pd layer is formed as the contact electrode 40. After the contact electrode 40 is formed, the resist 95 is removed. In this embodiment, the contact electrode 40 is formed using planetary evaporation. Planetary evaporation is a method of performing evaporation while changing the incident direction of the evaporation material relative to the substrate by rotating or revolving a dome or a flat plate on which a substrate, which is the target of evaporation, is mounted relative to an evaporation material source.

[0083] A method for forming contact electrode 40 using planetary deposition will be described below with reference to Figures 15 to 22. Figures 15 to 18 show cross sections perpendicular to the propagation direction of the laser light, while Figures 19 to 22 show cross sections parallel to the stacking direction of the semiconductor layers and the propagation direction of the laser light. In Figures 15 to 22, the straight arrows indicate the incident direction of the deposition material.

[0084] In the planetary vapor deposition of this embodiment, the rotation axis of the revolving dome is inclined relative to the revolution axis, and the deposition target (such as the semiconductor laminate 10S in this embodiment) is placed at a location away from the rotation center of the dome. This vapor deposition method is characterized in that when the opening of the deposition mask is away from the deposition target position, the inclination angle of the side surface of the deposited film varies depending on the direction (i.e., depending on the direction of the side surface relative to the center of the opening). The manufacturing method will be described in detail below. Here, the position of the dome closest to the center of revolution in one rotation cycle is defined as the first rotation position. The substrate 21 is placed on the dome so that, at the first rotation position, the front side of the element, i.e., the positive side of the Y axis of the substrate 21, is located outside the dome (the side farther from the rotation center), and the rear side, i.e., the negative side of the Y axis of the substrate 21, is located inside the dome (the side closer to the rotation center).

[0085] Figures 15 and 19 show the incident direction of the deposition material at a first rotation position of the dome on which the substrate 21 and the like are placed, in cross sections perpendicular to the Y axis and the X axis, respectively. Figures 16 and 20 show the incident direction of the deposition material at a second rotation position rotated 90 degrees (i.e., rotated) from the first rotation position of the dome. Figures 17 and 21 show the incident direction of the deposition material at a third rotation position rotated another 90 degrees from the second rotation position of the dome. Figures 18 and 22 show the incident direction of the deposition material at a fourth rotation position rotated another 90 degrees from the third rotation position of the dome.

[0086] By installing the substrate 21 on the dome and performing planetary deposition in this manner, for example, at the first rotation position, the incident direction of the deposition material is perpendicular to the X-axis direction and tilted slightly (for example, about 10 degrees) with respect to the Y-axis direction, as shown in Figures 15 and 19. With such an incident direction of the deposition material, the deposition material is uniformly deposited at a position directly below the opening in the X-axis direction, and uniformly deposited at a position shifted to the left (front direction) of the opening (position shifted in the positive direction) in the Y-axis direction. Because the tilt of the incident direction of the deposition material with respect to the Y-axis direction at the first rotation position is relatively small, the amount of deviation is relatively small.

[0087] When vapor deposition is continued while rotating the dome from the first rotation position, at the second rotation position, the incident direction of the vapor deposition material is inclined moderately (for example, about 23 degrees) with respect to the X-axis direction and perpendicular to the Y-axis direction, as shown in Figures 16 and 20. With such an incident direction of the vapor deposition material, the vapor deposition material is uniformly deposited at a position shifted to the left of the opening in the X-axis direction (a position shifted in the negative direction), and at a position directly below the opening in the Y-axis direction. Because the inclination of the incident direction of the vapor deposition material with respect to the X-axis direction at the second rotation position is moderate, the amount of deviation is moderate.

[0088] Furthermore, when vapor deposition is continued while rotating the dome from the second rotation position, at the third rotation position, as shown in Figures 17 and 21, the incident direction of the vapor deposition material is perpendicular to the X-axis direction and is tilted significantly (for example, about 45 degrees) with respect to the Y-axis direction. Note that the tilt direction of the incident direction of the vapor deposition material with respect to the Y-axis direction at the third rotation position is opposite to the tilt direction at the first rotation position. With such an incident direction of the vapor deposition material, the vapor deposition material is uniformly deposited at a position directly below the opening in the X-axis direction, and uniformly deposited at a position shifted to the right (rear direction) of the opening in the Y-axis direction. Because the tilt of the incident direction of the vapor deposition material with respect to the Y-axis direction at the third rotation position is relatively large, the amount of deviation is relatively large.

[0089] Furthermore, when vapor deposition is continued while rotating the dome from the third rotation position, at the fourth rotation position, as shown in FIGS. 18 and 22 , the incident direction of the vapor deposition material is inclined moderately (for example, by about 23 degrees) with respect to the X-axis direction and perpendicular to the Y-axis direction. Here, the tilt direction of the incident direction of the vapor deposition material with respect to the X-axis direction at the fourth rotation position is opposite to the tilt direction at the first rotation position. With such an incident direction of the vapor deposition material, the vapor deposition material is uniformly deposited at a position shifted to the right of the opening in the X-axis direction, and uniformly deposited at a position directly below the opening in the Y-axis direction. Because the inclination of the incident direction of the vapor deposition material with respect to the X-axis direction at the fourth rotation position is moderate, the amount of deviation is moderate (a deviation amount symmetrical to that at the second rotation position).

[0090] Furthermore, if deposition continues while rotating the dome from the fourth rotation position, it returns to the first rotation position. By rotating the dome in this way, deposition is performed while periodically changing the incident direction of the deposition material, and the amount of this change differs between the X-axis and Y-axis directions. In other words, deposition is performed while periodically shifting the deposition region up, down, left, and right in a top view of the opening, and the amount of this shift differs between the X-axis and Y-axis directions.

[0091] As described above, by performing planetary evaporation under the element arrangement of this embodiment, the side surface 40s of the contact electrode 40 can be inclined. Specifically, since the left and right offset amounts are approximately the same in the X-axis direction, the inclination angles of the side surfaces 40s located at the lateral ends of the contact electrode 40 relative to the top surface 24Rt of the ridge 24R are approximately the same, as shown in FIG. 18 . Furthermore, in the Y-axis direction, the inclination angle of the side surface 40s located at the end of the contact electrode 40 in the propagation direction of the laser light relative to the top surface 24Rt of the ridge 24R can be made larger on the front side than on the rear side, as shown in FIG.

[0092] 23, a barrier metal layer 50 and a pad electrode 60 are formed. Specifically, the barrier metal layer 50 made of a Cr film and the pad electrode 60 made of an Au film are formed on the insulating film 30 using photolithography and planetary evaporation. The barrier metal layer 50 covers the entire upper surface of the contact electrode 40 and continuously covers from the upper surface of the contact electrode 40 to the upper surface of the insulating film 30. The pad electrode 60 may also be formed by plating.

[0093] 15 to 22, a method for forming the barrier metal layer 50 and the pad electrode 60 using planetary deposition will be described. In this embodiment, similar to the formation of the contact electrode 40, the barrier metal layer 50 and the pad electrode 60 are deposited by periodically repeating the first rotation position to the fourth rotation position in order.

[0094] Focusing on the X-axis direction, at the second rotational position shown in Fig. 16 , the negative X-axis component of the incident direction of the deposition material increases moderately and the positive X-axis component decreases moderately, compared to the first rotational position shown in Fig. 15 and the third rotational position shown in Fig. 17 . Also, at the fourth rotational position shown in Fig. 18 , the positive X-axis component of the incident direction of the deposition material increases moderately and the negative X-axis component decreases moderately, compared to the first rotational position shown in Fig. 15 and the third rotational position shown in Fig. 17 . Thus, by periodically repeating the states of the first rotational position to the fourth rotational position, the difference in the deposition amount cancels out, and the film thickness of the barrier metal layer 50 disposed on the side surface 30 s of the insulating film 30 becomes equal on the left and right (i.e., the side surface 30 s at the end in the positive X-axis direction and the side surface 30 s at the end in the negative X-axis direction).

[0095] Furthermore, with regard to the Y-axis direction, at the first rotational position shown in Fig. 19, the positive Y-axis component of the incident direction of the deposition material increases slightly, and the negative Y-axis component decreases slightly, compared to the second rotational position shown in Fig. 20 and the fourth rotational position shown in Fig. 22. At the third rotational position shown in Fig. 21, the negative Y-axis component of the incident direction of the deposition material increases significantly, and the negative Y-axis component decreases significantly, compared to the second rotational position shown in Fig. 20 and the fourth rotational position shown in Fig. 22. Thus, by periodically repeating the states from the first rotational position to the fourth rotational position, the thickness Tf of the barrier metal layer 50 disposed on the side surface 30s of the insulating film 30 located at the end of the semiconductor laser element 10 in the positive Y-axis direction becomes thinner than the thickness Tr of the barrier metal layer 50 disposed on the side surface 30s of the insulating film 30 located at the end of the semiconductor laser element 10 in the negative Y-axis direction. That is, the film thickness Tf of the barrier metal layer 50 disposed on the side surface 30s located between the contact electrode 40 and the front end face 10F of the semiconductor laser element 10 is thinner than the film thickness Tr of the barrier metal layer 50 disposed on the side surface 30s located between the contact electrode 40 and the rear end face 10R of the semiconductor laser element 10.

[0096] Next, the lower surface of the substrate 21 is polished and etched to reduce the thickness of the substrate 21, and then an N-side electrode 70 is formed on the lower surface of the substrate 21, as shown in Fig. 2. Specifically, the N-side electrode 70 is formed by sequentially forming a Ti film, a Pt film, and an Au film using photolithography and vapor deposition.

[0097] By the manufacturing method described above, the semiconductor laser device 10 according to the present embodiment can be manufactured.

[0098] [1-5. Modification 1] A semiconductor laser device 10A according to Modification 1 of the present embodiment will be described. The semiconductor laser device according to this modification differs from the semiconductor laser device 10 according to the embodiment mainly in the shape of the ridge 24R and the shape of the insulating film 30. The semiconductor laser device according to this modification will be described below with reference to FIGS. 24 and 25, focusing on the differences from the semiconductor laser device 10 according to the embodiment.

[0099] Fig. 24 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 10A according to this modification. Fig. 24 shows a cross section similar to that shown in Fig. 2. Fig. 25 is an enlarged view of the inside of the dashed frame XXV shown in Fig. 24.

[0100] 25 , in the semiconductor laser device 10A according to this modification, the ridge 24R is located at the end of the top surface 24Rt of the ridge 24R in the direction perpendicular to the propagation direction of the laser light (X-axis direction), and has a protrusion 24Rp protruding from the side surface 24Rs of the ridge 24R. That is, the protrusion 24Rp protrudes in the X-axis direction from the side surface 24Rs of the ridge 24R. In other words, a recess 24Rd is formed in the side surface 24Rs of the ridge 24R. In other words, a constriction is formed in the side surface 24Rs of the ridge 24R.

[0101] In this way, by forming the protrusion 24Rp on the ridge 24R, it is possible to increase the area of ​​the upper surface 24Rt of the ridge 24R while maintaining the current confinement effect of the ridge 24R. Therefore, it is possible to increase the area on the upper surface 24Rt of the ridge 24R for arranging the contact electrode 40.

[0102] Furthermore, in the semiconductor laser device 10A according to this modification, a recess 30d is formed in the surface of the insulating film 30 in a portion that covers the protrusion 24Rp, and the recess 30d is located above the protrusion 24Rp. Since the protrusion 24Rp and the recess 30d are positioned at different vertical positions, the protrusion 24Rp and the recess 30d can be prevented from coming close to each other. This means that the formation of a locally thin portion in the insulating film 30, which would otherwise be caused by the protrusion 24Rp and the recess 30d coming close to each other, can be prevented. Therefore, a decrease in the insulating performance of the insulating film 30 can be suppressed.

[0103] The ridge 24R of the semiconductor laser device 10A according to this modification can be formed by performing a first etching process that results in an inversely tapered shape of the ridge 24R (a shape in which the ridge width narrows from the top to the bottom of the ridge) and a second etching process that results in a forwardly tapered shape of the ridge 24R (a shape in which the ridge width widens from the top to the bottom of the ridge). Hereinafter, an example of an etching method for forming the ridge 24R using an inductively coupled plasma (ICP) method with a frequency of 13.56 MHz will be described.

[0104] The conditions for the first etching may be, for example, a top power of 150 W, a bias power of 15 W, a gas pressure of 2 Pa, and a gas species of Cl2 (flow rate of 50 sccm).

[0105] The conditions for the second etching may be, for example, a top power of 150 W, a bias power of 20 W, a gas pressure of 4 Pa, and a gas species of Cl2 (flow rate of 50 sccm).

[0106] According to the first etching conditions described above, the low gas pressure allows anisotropic etching to be performed, thereby making the shape of the ridge 24R inversely tapered. According to the second etching conditions described above, the high gas pressure allows isotropic etching to be performed, thereby making the shape of the ridge 24R forwardly tapered.

[0107] By employing such an etching method, the ridge 24R of the semiconductor laser device 10A according to this modification can be formed.

[0108] [1-6. Modification 2] A semiconductor laser device according to Modification 2 of the present embodiment will be described. The semiconductor laser device according to this modification differs from the semiconductor laser device 10 according to the embodiment in that a metal layer is further provided on the pad electrode 60. The semiconductor laser device according to this modification will be described below with reference to FIG. 26, focusing on the differences from the semiconductor laser device 10 according to the embodiment. FIG. 26 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 10B according to this modification. FIG. 26 shows a cross section similar to that shown in FIG.

[0109] As shown in FIG. 26, a semiconductor laser device 10B according to this modification includes a first metal layer 61 and a second metal layer 62 in addition to the semiconductor laser device 10.

[0110] The first metal layer 61 is a metal layer disposed above the pad electrode 60. The first metal layer 61 covers the upper surface of the pad electrode 60 and has the function of suppressing the diffusion of impurities into the pad electrode 60. The first metal layer 61 may be a single-layer film or a multi-layer film formed of at least one of Cr, Ti, and Pt, for example. In this modification, the first metal layer 61 has a 10-nm-thick Ti layer in contact with the pad electrode 60 and a 35-nm-thick Pt layer in contact with the Ti layer.

[0111] The second metal layer 62 is a metal layer disposed above the first metal layer 61. The second metal layer 62 covers the upper surface of the first metal layer 61 and contains Au. In this modification, the second metal layer 62 is an Au layer with a film thickness of 300 nm.

[0112] The semiconductor laser device 10B according to this modification also has the same effects as those of the semiconductor laser device 10 according to the embodiment.

[0113] Furthermore, the semiconductor laser element 10B according to this modified example is provided with the first metal layer 61, which can suppress the diffusion of impurities into the pad electrode 60, thereby further suppressing the diffusion of impurities from the pad electrode 60 to the contact electrode 40.

[0114] Next, an example of a mounting mode of the semiconductor laser element 10B according to this modification will be described with reference to Fig. 27. Fig. 27 is a schematic cross-sectional view showing the configuration of a semiconductor laser device 11B in which the semiconductor laser element 10B according to this modification is mounted. Fig. 27 shows a cross section similar to that of Fig. 4B.

[0115] As shown in Figure 27, the semiconductor laser device 11B of this modified example includes an N-side electrode 70, a substrate 21, a semiconductor stack 10S, an insulating film 30, a contact electrode 40, a barrier metal layer 50, a pad electrode 60, a first metal layer 61, a bonding material 90b, and a submount 80.

[0116] The bonding material 90b is a member formed by alloying the second metal layer 62 and the bonding material 90. The bonding material 90b is an AuSn layer. In this modification, the Sn element is diffused almost uniformly throughout the bonding material 90b (i.e., the Sn element concentration is uniform). The Sn element concentration in the bonding material 90b is, for example, about 20%.

[0117] The semiconductor laser device 11B according to this modification can be manufactured by the same mounting method as that of the semiconductor laser device 11 according to the embodiment. That is, the semiconductor laser device 11B can be manufactured by using the semiconductor laser element 10B instead of the semiconductor laser element 10 in the mounting method of the semiconductor laser device 11 according to the embodiment described above.

[0118] In the semiconductor laser device 11B according to this modification, the semiconductor laser element 10B includes the first metal layer 61, which can suppress the diffusion of Sn elements from the bonding material 90 containing AuSn solder to the pad electrode 60, thereby further suppressing the diffusion of Sn elements to the contact electrode 40. This further suppresses an increase in the electrical resistance of the contact electrode 40. Furthermore, since the diffusion of Au from the pad electrode 60 to the bonding material 90 is also suppressed, there is no change in the composition ratio accompanying the mounting of the pad electrode 60.

[0119] [1-7. Modification 3] A semiconductor laser device according to Modification 3 of the present embodiment will be described. The semiconductor laser device according to this modification differs from the semiconductor laser device 10 according to the embodiment in the configuration of the insulating film. The semiconductor laser device according to this modification will be described below with reference to FIGS. 28 and 29, focusing on the differences from the semiconductor laser device 10 according to the embodiment. FIG. 28 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 10C according to this modification. FIG. 28 shows a cross section similar to that shown in FIG. 2. FIG. 29 is an enlarged view of the interior of the dashed-line frame XXIX shown in FIG. 28.

[0120] 28, a semiconductor laser device 10C according to this modification includes an insulating film 30C. The insulating film 30C has an opening 30Ca located at a position corresponding to the upper surface 24Rt of the ridge 24R.

[0121] 29 , the side surface 30Cs located on the periphery of the opening 30Ca of the insulating film 30 according to this modification has a lower lateral surface region 31 and an upper lateral surface region 32 disposed above the lower lateral surface region 31. The lower lateral surface region 31 and the upper lateral surface region 32 have different inclination angles with respect to the ridge top surface 24Rt. That is, the inclination angle θ1 of the lower lateral surface region 31 with respect to the ridge top surface 24Rt is different from the inclination angle θ2 of the lower lateral surface region 31 with respect to the ridge top surface 24Rt. In this modification, the inclination angle θ1 is greater than the inclination angle θ2.

[0122] As described above, the side surface 30Cs of the insulating film 30C has a lower side surface region 31 and an upper side surface region 32, and the lower side surface region 31 and the upper side surface region 32 have different inclination angles with respect to the top surface 24Rt of the ridge.

[0123] This allows the width of the inclined region to be reduced compared to when the entire side surface 30Cs is formed at a small inclination angle (for example, inclination angle θ2). Therefore, in this modification, the area of ​​the opening 30Ca can be increased while ensuring the thickness of the insulating film 30C on the end portion thereof disposed on the top surface 24Rt of the ridge 24R. This allows the area of ​​the contact electrode 40 to be increased. Accordingly, the area of ​​the current injection region can be increased, thereby reducing the operating voltage of the semiconductor laser device 10C.

[0124] In this modification, the inclination angle of the lower flank region 31 relative to the upper surface 24Rt of the ridge 24R (inclination angle θ1 shown in FIG. 29 ) is larger than the inclination angle of the upper flank region 32 relative to the upper surface 24Rt of the ridge 24R (inclination angle θ2 shown in FIG. 29 ). This allows the width of the lower flank region 31, which has a small film thickness and low insulation resistance, to be reduced, thereby further improving the insulating properties of the insulating film 30C.

[0125] Here, the inclination angle of the upper lateral side region 32 with respect to the top surface 24Rt of the ridge 24R may be less than 90 degrees. In this case, the risk of cracks occurring in the barrier metal layer 50 on the corners of the insulating film 30C during formation of the barrier metal layer 50 on the insulating film 30C can be reduced. The inclination angle of the upper lateral side region 32 may be between 40 degrees and 60 degrees. In this case, both an increase in the contact area due to the inclination and prevention of cracks at the corners can be achieved, with the greatest effect achieved at 45 degrees. Thus, by reducing the inclination angle of the upper lateral side region 32, the contact area between the upper end of the insulating film 30C located on the top surface 24Rt of the ridge 24R and the barrier metal layer 50 can be increased. Therefore, adhesion between the insulating film 30C and the barrier metal layer 50 can be improved.

[0126] Here, the inclination angle of the lower lateral side region 31 relative to the upper surface 24Rt of the ridge 24R may be 90 degrees or less. In this case, the risk of voids occurring between the insulating film 30C and the barrier metal layer 50 during formation of the barrier metal layer 50 on the insulating film 30C can be reduced. The inclination angle of the lower lateral side region 31 may be 65 degrees or more and 85 degrees or less. In this case, an increase in the contact area due to the inclination and prevention of void occurrence can both be achieved, with the greatest effect achieved at 75 degrees. In this way, by increasing the inclination angle of the lower lateral side region 31, the area of ​​the opening 30Ca in the insulating film 30C can be increased. Therefore, the area of ​​the current injection region can be increased, further reducing the operating voltage of the semiconductor laser device 10C.

[0127] The method for manufacturing the insulating film 30C according to this modification differs from the method for manufacturing the insulating film 30 according to the embodiment in the step of forming the opening 30Ca.

[0128] The process of forming the opening 30Ca in the insulating film 30C includes a first etching process in which a region in the insulating film 30C corresponding to the opening 30Ca is etched by a first film thickness using a first etching method, and after the first etching process, a second etching process in which the region is etched by a second film thickness using a second etching method different from the first etching method.

[0129] The first etching method is, for example, dry etching. Specifically, a resist is formed in areas other than the area corresponding to the opening 30Ca, and the area of ​​the insulating film 30C not covered by the resist is etched using dry etching. The first film thickness is, for example, 150 nm. For example, an ICP method with a frequency of 13.56 MHz can be used as the dry etching method. For example, the processing conditions used in the dry etching can be a top power of 120 W, a bias power of 40 W, a gas pressure of 1 Pa, and a gas type of CHF3 (flow rate 35 sccm).

[0130] The second etching method is, for example, wet etching. Specifically, the region of the insulating film 30C that is not covered with the resist is etched using wet etching. The second film thickness is, for example, 150 nm. As a wet etching method, for example, a dip treatment method using BHF (buffered hydrofluoric acid) can be used. After the wet etching process, the device including the processed semiconductor stack 10S is washed with pure water and then spin-dried.

[0131] This allows the formation of an insulating film 30 in which the side surface 30Cs located on the periphery of the opening 30Ca has a lower side surface region 31 and an upper side surface region 32.

[0132] The semiconductor laser device 10C according to this modification also exhibits the same effects as those of the semiconductor laser device 10 according to the embodiment.

[0133] Next, an example of a mounting mode of the semiconductor laser element 10C according to this modification will be described with reference to Fig. 30. Fig. 30 is a schematic cross-sectional view showing the configuration of a semiconductor laser device 11C on which the semiconductor laser element 10C according to this modification is mounted. Fig. 30 shows a cross section similar to that of Fig. 4B.

[0134] As shown in FIG. 30, the semiconductor laser device 11C of this modified example includes an N-side electrode 70, a substrate 21, a semiconductor stack 10S, an insulating film 30C, a contact electrode 40, a barrier metal layer 50, a bonding material 90c, and a submount 80.

[0135] The bonding material 90c is a member formed by alloying the pad electrode 60 and the bonding material 90. The bonding material 90c is an AuSn layer. In this modification, the Sn element is diffused almost uniformly throughout the bonding material 90c (i.e., the Sn element concentration is uniform). The Sn element concentration in the bonding material 90c is, for example, about 20%.

[0136] The semiconductor laser device 11C according to this modification can be manufactured by the same mounting method as the semiconductor laser device 11 according to the embodiment. That is, the semiconductor laser device 11C can be manufactured by using the semiconductor laser element 10C instead of the semiconductor laser element 10 in the mounting method of the semiconductor laser device 11 according to the embodiment described above. However, when mounting the semiconductor laser element 10C according to this modification, the heating step time (the time for maintaining the temperature T) is extended to about 30 seconds compared to when mounting the semiconductor laser element 10 according to the embodiment. As a result, diffusion of Sn elements from the bonding material 90 containing AuSn solder into the pad electrode 60 made of an Au layer progresses sufficiently, and a bonding material 90c in which the pad electrode 60 and the bonding material 90 are substantially uniformly alloyed is formed.

[0137] In this modified example, cracks can be prevented from occurring in the barrier metal layer 50, so that even when the pad electrode 60 is integrated with the bonding material 90, in the semiconductor laser device 11C of this modified example, the barrier metal layer 50 can prevent impurities such as Sn elements from diffusing into the contact electrode 40.

[0138] (Modifications, etc.) Although the semiconductor laser element and the like according to the present disclosure have been described above based on the embodiments and modifications, the present disclosure is not limited to the above-described embodiments and modifications.

[0139] In the above-described embodiment and modified example, the insulating film 30 is disposed between the facets 10F and 10R of the semiconductor laser element and the contact electrode 40, but the configuration of the insulating film 30 is not limited to this. For example, the opening 30a of the insulating film 30 may be slit-shaped. That is, the opening 30a may extend to at least one of the facets 10F and 10R of the semiconductor laser element.

[0140] In addition, although the semiconductor laser element emits blue light in each of the above embodiments, the band of light emitted by the semiconductor laser element is not limited to this. For example, the semiconductor laser element may emit visible light including blue-violet light or red light, ultraviolet light, or infrared light.

[0141] In addition, in the above-described embodiments, the semiconductor laser element uses a nitride semiconductor as the material for the semiconductor laminate and the substrate, but the materials are not limited to this. For example, the semiconductor laser element may use AlGaInAs or AlGaInP.

[0142] In addition, in the above-described Modifications 2 and 3, junction-down mounting is shown as an example of the mounting manner, but the mounting manner of the semiconductor laser element is not limited to this. For example, the semiconductor laser element may be mounted in junction-up mounting.

[0143] This disclosure also includes forms obtained by applying various modifications to the above-mentioned embodiments that a person skilled in the art would conceive, and forms realized by arbitrarily combining the components and functions of the above-mentioned embodiments within the scope of the present disclosure.

[0144] The nitride semiconductor laser element and the like according to the present disclosure can be applied, for example, as a highly efficient light source for a processing machine.

[0145] 10, 10A, 10B, 10C Semiconductor laser element 10D Element isolation groove 10F, 10R End face 10S Semiconductor laminate 11, 11B, 11C Semiconductor laser device 21 Substrate 22 N-side semiconductor layer 23 Active layer 24 P-side semiconductor layer 24R Ridge 24Rd, 30d Recess 24Rp Protrusion 24Rs, 30s, 30Cs, 40s Side face 24Rt, 30t, 40t Upper face 24T Groove 24W Wing portion 30, 30C Insulating film 30a, 30Ca Opening 31 Lower side face region 32 Upper side face region 40 Contact electrode 50 Barrier metal layer 60, 60a Pad electrode 61 First metal layer 62 Second metal layer 70 N-side electrode 80 Submount 90, 90a, 90b, 90c Bonding material 95 Resist

Claims

1. A semiconductor laser element that emits laser light, First semiconductor layer of the first conductivity type, An active layer disposed above the first semiconductor layer, A second semiconductor layer is disposed above the active layer and has a second conductivity type different from the first conductivity type, An insulating film disposed above the second semiconductor layer, A contact electrode is disposed above the second semiconductor layer and is in contact with the second semiconductor layer, The system comprises a barrier metal layer positioned above the contact electrode, The second semiconductor layer has ridges extending in the direction of laser light propagation, The insulating film has an opening positioned at a location corresponding to the upper surface of the ridge, The contact electrode is positioned in the opening. The side surface of the contact electrode located at the lateral end perpendicular to the propagation direction of the laser light and the stacking direction of the contact electrode is inclined toward the inside of the contact electrode with respect to the direction perpendicular to the upper surface of the ridge. Of the side surfaces located at the periphery of the opening of the insulating film, the side surface located at the lateral end of the opening is inclined outward from the opening with respect to a direction perpendicular to the upper surface of the ridge. The barrier metal layer covers the entire upper surface and the sides of the contact electrode. Semiconductor laser element.

2. The barrier metal layer continuously covers from the upper surface of the contact electrode to the upper surface of the insulating film. The semiconductor laser element according to claim 1.

3. The barrier metal layer continuously covers from the upper surface of the contact electrode to the upper surface of the insulating film located outside the ridge. The semiconductor laser element according to claim 1 or 2.

4. The insulating film is disposed between the end face of the semiconductor laser element in the direction of laser light propagation and the contact electrode. The barrier metal layer continuously covers the area from the upper surface of the contact electrode to the upper surface of the insulating film in the direction of laser light propagation. The semiconductor laser element according to claim 1 or 2.

5. In the propagation direction of the laser light, the distance between the insulating film and the contact electrode at the front end of the semiconductor laser element is longer than the distance between the insulating film and the contact electrode at the rear end of the semiconductor laser element. The semiconductor laser element according to claim 1 or 2.

6. Of the side surfaces located around the periphery of the opening of the insulating film, the thickness of the barrier metal layer positioned on the side surface located between the contact electrode and the front end face of the semiconductor laser element is thinner than the thickness of the barrier metal layer positioned on the side surface located between the contact electrode and the rear end face of the semiconductor laser element. The semiconductor laser element according to claim 1 or 2.

7. The inclination angle of the side surface of the contact electrode located at the end in the laser beam propagation direction with respect to the upper surface of the ridge is greater on the front side of the semiconductor laser element than on the rear side. The semiconductor laser element according to claim 1 or 2.

8. The inclination angle of at least a portion of the side surface of the contact electrode with respect to the upper surface of the ridge is 30 degrees or less. The semiconductor laser element according to claim 1 or 2.

9. The barrier metal layer is formed of Cr or Ti. The semiconductor laser element according to claim 1 or 2.

10. The contact electrode is a single-layer film. The semiconductor laser element according to claim 1 or 2.

11. The ridge has a projection located at the end of the upper surface of the ridge in a direction perpendicular to the propagation direction of the laser light, and protruding from the side surface of the ridge. The semiconductor laser element according to claim 1 or 2.

12. A recess is formed on the surface of the portion of the insulating film that covers the protruding portion, and the recess is located above the protruding portion. The semiconductor laser element according to claim 11.

13. The contact electrode is formed of at least one of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and InGaZnOx (IGZO). The semiconductor laser element according to claim 1 or 2.

14. The contact electrode is a single-layer or multilayer film formed of at least one of Pd, Pt, Ni, and Ag. The semiconductor laser element according to claim 1 or 2.

15. The contact electrode is formed of Pd The semiconductor laser element according to claim 1 or 2.

16. The contact electrode is formed of Ag The semiconductor laser element according to claim 1 or 2.

17. The contact electrode is formed of indium tin oxide (ITO) The semiconductor laser element according to claim 1 or 2.