WO2024053222A1

WO2024053222A1 - Semiconductor laser element

Info

Publication number: WO2024053222A1
Application number: PCT/JP2023/024337
Authority: WO
Inventors: 雄馬村上; 靖智光井; 学西川; 茂生林; 昇井上
Original assignee: ヌヴォトンテクノロジージャパン株式会社
Priority date: 2022-09-08
Filing date: 2023-06-30
Publication date: 2024-03-14

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 device

The present disclosure relates to a semiconductor laser device.

Conventionally, a semiconductor laser element having a ridge is known (for example, Patent Document 1). In the semiconductor laser device 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 the semiconductor stack. A contact electrode made of Pd is placed on the top surface of the ridge, and a barrier metal layer made of Pt is placed on the contact electrode. In the semiconductor laser device described in Patent Document 1, such a barrier metal layer is used to suppress diffusion of impurities into the contact electrode. In other words, an attempt is made to suppress an increase in electrical resistance caused by diffusion of impurities into the contact electrode.

International Publication No. 2020/110783

However, in the semiconductor laser device described in Patent Document 1, since the barrier metal layer covering the peripheral edge of the contact electrode is particularly thin, impurities can diffuse into the contact electrode.

Further, when the side surface of the contact electrode is substantially perpendicular to the top surface of the semiconductor stack, a slit may be formed in the barrier metal layer covering the vicinity of the side surface. Impurities can diffuse into the contact electrode through such slits. As described above, in conventional semiconductor laser devices, the barrier metal layer covering the contact electrode does not have a sufficient impurity diffusion suppressing function.

The present disclosure aims to solve such problems, and to provide a semiconductor laser device that can suppress diffusion of impurities into contact electrodes.

In order to solve the above problems, one embodiment of a semiconductor laser device according to the present disclosure is a semiconductor laser device that emits laser light, which includes a first semiconductor layer of a first conductivity type, and an upper part of the first semiconductor layer. an active layer disposed above the active layer, a second semiconductor layer of a second conductivity type different from the first conductivity type, and an insulating film disposed above the second semiconductor layer; a contact electrode disposed above the second semiconductor layer and in contact with the second semiconductor layer; and a barrier metal layer disposed above the contact electrode, the second semiconductor layer being configured to propagate the laser beam. the insulating film has an opening disposed at a position corresponding to the upper surface of the ridge; the contact electrode is disposed in the opening; A side surface located at a lateral end perpendicular to the propagation direction of the laser beam and the stacking direction of the contact electrode is inclined toward the inside of the contact electrode with respect to a direction perpendicular to the upper surface of the ridge. Among the side surfaces of the insulating film located at the periphery of the opening, the side surface located at the lateral end of the opening is perpendicular to the upper surface of the ridge. The barrier metal layer is inclined outward, and covers the entire upper surface of the contact electrode, and continuously covers from the upper surface of the contact electrode to the upper surface of the insulating film.

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

FIG. 1 is a schematic plan view showing the overall configuration of a semiconductor laser device according to an embodiment. FIG. 1 is a first schematic cross-sectional view showing the overall configuration of a semiconductor laser device according to an embodiment. FIG. 2 is a second schematic cross-sectional view showing the overall configuration of the semiconductor laser device according to the embodiment. FIG. 1 is a schematic cross-sectional view showing an example of a method for mounting a semiconductor laser device according to an embodiment. 1 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. 3 is an enlarged view of the inside of the broken line frame V shown in FIG. 2. FIG. 4 is an enlarged view of the inside of the broken line frame VI shown in FIG. 3. FIG. 4 is an enlarged view of the inside of the broken line frame VII shown in FIG. 3. FIG. FIG. 2 is a schematic cross-sectional view showing a first step of a method for manufacturing a semiconductor laser device according to an embodiment. FIG. 3 is a schematic cross-sectional view showing a second step of the method for manufacturing a semiconductor laser device according to an embodiment. FIG. 3 is a schematic cross-sectional view showing a third step of the method for manufacturing a semiconductor laser device according to an embodiment. FIG. 7 is a schematic cross-sectional view showing a fourth step of the method for manufacturing a semiconductor laser device according to an embodiment. FIG. 7 is a schematic cross-sectional view showing a resist forming step in a fourth step of the method for manufacturing a semiconductor laser device according to an embodiment. FIG. 7 is a schematic cross-sectional view showing an opening forming step in a fourth step of the method for manufacturing a semiconductor laser device according to an embodiment. FIG. 7 is a schematic cross-sectional view showing a contact electrode forming step in the fourth step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 2 is a first schematic cross-sectional view showing the direction of incidence of the vapor deposition material at the first rotational position of planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 2 is a first schematic cross-sectional view showing the incident direction of the vapor deposition material at the second rotational position of planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 6 is a schematic first cross-sectional view showing the direction of incidence of the vapor deposition material at the third rotational position of planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7 is a schematic first cross-sectional view showing the incident direction of the vapor deposition material at the fourth rotational position of planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7 is a second schematic cross-sectional view showing the incident direction of the vapor deposition material at the first rotational position of planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7 is a second schematic cross-sectional view showing the direction of incidence of the evaporation material at the second rotational position of planetary evaporation in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7 is a second schematic cross-sectional view showing the direction of incidence of the vapor deposition material at the third rotational position of planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7 is a second schematic cross-sectional view showing the incident direction of the vapor deposition material at the fourth rotational position of planetary vapor deposition in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7 is a schematic cross-sectional view showing a fifth step of the method for manufacturing a semiconductor laser device according to an embodiment. FIG. 2 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device according to Modification 1 of the embodiment. 25 is an enlarged view of the inside of the broken line frame XXV shown in FIG. 24. FIG. FIG. 7 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device according to a second modification of the embodiment. FIG. 7 is a schematic cross-sectional view showing the configuration of a semiconductor laser device in which a semiconductor laser element according to a second modification of the embodiment is mounted. FIG. 7 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device according to a third modification of the embodiment. 29 is an enlarged view of the inside of the broken line frame XXIX shown in FIG. 28. FIG. FIG. 7 is a schematic cross-sectional view showing the configuration of a semiconductor laser device in which a semiconductor laser element according to a third modification of the embodiment is mounted.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the embodiments described below each represent a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples and do not limit the present disclosure.

Furthermore, each figure is a schematic diagram and is not necessarily strictly illustrated. Therefore, the scale etc. in each figure are not necessarily the same. In addition, in each figure, the same code|symbol is attached to the substantially the same structure, and the overlapping description is omitted or simplified.

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

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

[1-1. overall structure]
First, the overall configuration of the semiconductor laser device according to this embodiment will be explained using 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. 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. 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 that are orthogonal to each other. The X, Y, and Z axes are a right-handed Cartesian coordinate system. The stacking direction of the semiconductor laser element 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.

As shown in FIGS. 2 and 3, the semiconductor laser device 10 includes a semiconductor stack 10S, and an end face 10F (see FIG. 1) in a direction perpendicular to the stacking direction (that is, the Z-axis direction) of the semiconductor stack 10S. Emit laser light from. In this embodiment, the semiconductor laser device 10 is a nitride semiconductor laser device having two end faces 10F and 10R forming a resonator, as shown in FIG. The end surface 10F is a front end surface that emits laser light, and the end surface 10R is a rear end surface that has a higher reflectance than the end surface 10F. In this embodiment, the reflectances of end faces 10F and 10R are 15% and 98%, respectively. Further, the semiconductor laser element 10 has a waveguide formed between the end face 10F and the end face 10R. The cavity length (that is, the distance between the end face 10F and the end face 10R) of the semiconductor laser device 10 according to this embodiment is about 1200 μm. Further, the semiconductor laser element 10 emits blue light having a peak wavelength in the 445 nm band, for example.

As shown in FIGS. 2 and 3, the semiconductor laser device 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 and an electrode 70.

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

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

The N-side semiconductor layer 22 is an example of a first conductivity type first semiconductor layer disposed above the substrate 21 and below the active layer 23. In this embodiment, N-side semiconductor layer 22 includes a nitride semiconductor. Further, the N-side semiconductor layer 22 includes an N-type cladding layer having a lower refractive index than the active layer 23. The N-side semiconductor layer 22 is, for example, an N-type AlGaN layer. Note that the N-side semiconductor layer 22 may include layers other than the N-type cladding layer. The N-side semiconductor layer 22 may include, for example, a buffer layer, a light guide layer, and the like.

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

The P-side semiconductor layer 24 is an example of a second semiconductor layer that is disposed above the active layer 23 and has a second conductivity type different from the first conductivity type. P-side semiconductor layer 24 includes a nitride semiconductor. In this embodiment, P-side semiconductor layer 24 includes a P-type cladding layer having a lower refractive index than active layer 23. The P-side semiconductor layer 24 is, for example, a P-type AlGaN layer. Note that the P-side semiconductor layer 24 may include layers other than the P-type cladding layer. The P-side semiconductor layer 24 may include, for example, a light guide layer, an electron barrier layer, a contact layer, and the like. Further, the P-side semiconductor layer 24 may have a superlattice structure.

As shown in FIG. 2, the P-side semiconductor layer 24 has a ridge 24R extending in the propagation direction of the laser beam. 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, which are arranged along the ridge 24R and extend in the Y-axis direction. In this embodiment, the ridge width (that is, 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 end of the upper surface 24Rt of the ridge 24R in the X-axis direction (not visible from the upper surface of the semiconductor laser element 10). Furthermore, among the dotted lines indicating the groove 24T in FIG. 1, the dotted line farther from the ridge 24R corresponds to the position of the end of the groove 24T in the X-axis direction (not visible from the top surface of the semiconductor laser element 10). Furthermore, wing portions 24W made of a P-side semiconductor layer are formed on both sides of the trench 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 laser beam propagation direction.

The insulating film 30 is a layer placed above the P-side semiconductor layer 24 (that is, the second semiconductor layer). In this embodiment, the insulating film 30 is an electrically insulating layer that is disposed between the semiconductor stack 10S and the barrier metal layer 50. The insulating film 30 has an opening 30a located at a position corresponding to the upper surface 24Rt of the ridge 24R. In this embodiment, the insulating film 30 is disposed on the upper surface of the P-side semiconductor layer 24 in a region other than the central portion of the upper surface 24Rt of the ridge 24R. Specifically, a part 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, and the side surface of the P-side semiconductor layer 24 (that is, in the X-axis direction (end surface), the side surface of the active layer 23, and part of the side surface of the N-side semiconductor layer 22 are continuously covered. This provides electrical insulation between the barrier metal layer 50 disposed on the insulating film 30 and the pad electrode 60 disposed above the barrier metal layer 50, and the opening 30a with the side surface of the P-side semiconductor layer 24. can be secured. Therefore, the 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 can be suppressed. Thereby, it is possible to suppress the light density from increasing near the side surface of the ridge 24R. Therefore, it is possible to suppress a decrease in the optical amplification gain due to the hole burning phenomenon caused by the increase in optical density.

The material forming the insulating film 30 is not particularly limited as long as it is an insulating material. In this embodiment, the insulating film 30 is a silicon oxide film with a thickness of 300 nm. The detailed structure and effects of the insulating film 30 will be described later.

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

Contact electrode 40 may include Pd or indium tin oxide (ITO). Thereby, the contact resistance between the contact electrode 40 and the P-side semiconductor layer 24 can be reduced, so that the operating voltage of the semiconductor laser element 10 can be reduced. Further, the contact electrode 40 is a single layer film or a multilayer film formed of at least one of Pd, Pt, Ni, and Ag, or ITO, indium zinc oxide (IZO), zinc oxide (ZnO), InGaZnO _x ( It may also be made of a conductive metal oxide such as IGZO). In this embodiment, contact electrode 40 is a single layer film. More specifically, the contact electrode 40 is a Pd layer with a thickness of 40 nm.

The barrier metal layer 50 is a metal layer placed above the contact electrode 40. Barrier metal layer 50 has a function of suppressing diffusion of impurities into contact electrode 40 . Examples of impurities include oxygen atoms. Furthermore, for example, when the semiconductor laser element 10 is junction-down (flip-chip) mounted (that is, when the pad electrode 60 is bonded to a mounting board or the like), the Sn element contained in the solder used as the bonding material is It can become an impurity that diffuses into 40.

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 the upper surface of the contact electrode 40 to the upper surface of the insulating film 30 disposed outside the ridge 24R. More specifically, as shown in FIG. 2, the barrier metal layer 50 is continuously disposed above the left wing portion 24W, the left groove 24T, and a portion of the upper surface of the ridge 24R. The upper surface of the insulating film 30, 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, and the ridge 24R located between the contact electrode 40 and the right insulating film 30. It continuously covers the upper surface of the insulating film 30 that is continuously disposed above the upper surface, a part of the upper surface of the ridge 24R, the right groove 24T, and the right upper portion of the right wing portion 24W.

The barrier metal layer 50 also has a function of increasing the adhesion between the pad electrode 60 and the insulating film 30. The barrier metal layer 50 is made of Cr or Ti, for example. 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 improved. This is because when the insulating film 30 is an oxide, the insulating film 30 and the barrier metal layer 50 will be strongly bonded if the barrier metal layer 50 is made of a material that easily forms an oxide. In this embodiment, the barrier metal layer 50 is a Cr layer with a thickness of 100 nm. Note that if the Cr film is too thick, cracks or peeling may occur due to large internal stress. For example, the thickness of barrier metal layer 50 may be 200 nm or less.

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

The pad electrode 60 is a conductive layer arranged above the insulating film 30 and the contact electrode 40 and electrically connected to the contact electrode 40. Here, the pad electrode 60 is formed in the same planar shape as the barrier metal layer 50 on the upper surface of the barrier metal layer 50 using the same mask as that used for forming the barrier metal layer 50 . Pad electrode 60 contains Au. In this embodiment, the pad electrode 60 is an Au layer with a thickness of about 2000 nm.

The N-side electrode 70 is a conductive layer arranged on the lower surface of the substrate 21 (that is, the main surface of the substrate 21 opposite to the main surface on which the semiconductor stack 10S is arranged). 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 Ti layer with a thickness of 10 nm in contact with the substrate 21, a Pt layer with a thickness of 35 nm in contact with the Ti layer, and an Au layer with a thickness of 300 nm in contact with the Pt layer.

[1-2. Mounting mode of semiconductor laser element]
An example of a mounting aspect of the semiconductor laser device 10 according to this embodiment will be described using FIGS. 4A and 4B. FIG. 4A is a schematic cross-sectional view showing an example of a method for mounting the semiconductor laser device 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 the present embodiment is mounted. 4A and 4B, similarly to FIG. 2, a cross section of the semiconductor laser device 10 perpendicular to the propagation direction of the laser beam is shown.

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

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

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

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

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

After the semiconductor laser device 10 is placed on the bonding material 90 (that is, after the semiconductor laser device 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. Then, the bonding material 90 is melted. Here, in the heating process, the submount 80 is maintained at the temperature T for about 10 seconds.

After the heating process, the temperature of the submount 80 is lowered to a temperature below the melting point Tm of the bonding material 90.

Through the steps described above, 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 a semiconductor laser device 11 as shown in FIG. 4B can be manufactured.

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

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

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

As shown in FIG. 4B, by bonding the semiconductor laser device 10 and the submount 80 with the bonding material 90 containing AuSn solder, the Sn element contained in the bonding material 90 is transferred to the pad electrode 60 of the semiconductor laser device 10. Spread. Here, as the Sn element diffuses into the contact electrode 40, the electrical resistance of the contact electrode 40 increases. In this embodiment, by covering the contact electrode 40 with a barrier metal layer 50 that can suppress the diffusion of Sn element, an increase in the electrical resistance of the contact electrode 40 can be suppressed.

Note that although the configuration in which the semiconductor laser device 10 is mounted in a junction-down manner has been described above, the manner in which the semiconductor laser device 10 is mounted is not limited to this. For example, the semiconductor laser device 10 may be mounted in a junction-up manner.

[1-3. Detailed configuration and effects of semiconductor laser device]
The detailed configuration and effects of the semiconductor laser device 10 according to this embodiment will be explained mainly using FIGS. 5 to 7. FIG. 5 is an enlarged view of the inside of the broken line frame V shown in FIG. 6 and 7 are enlarged views of the interior of the dashed line frame VI and the dashed line frame VII shown in FIG. 3, respectively.

In the semiconductor laser device 10 according to the present 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 The area from the upper surface 40t to the upper surface 30t of the insulating film 30 is continuously covered. Specifically, the barrier metal layer 50 covers the upper surface 24Rt of the ridge 24R located between the contact electrode 40 and the right insulating film 30. Since the thickness of the barrier metal layer 50 in the Z-axis direction is approximately equal, the inclination angle of the barrier metal layer 50 formed on the sloped portions of the contact electrode 40 and the insulating film 30 is approximately the same as that of the sloped portions of the respective bases. Same angle of inclination. However, the inclination angle of the barrier metal layer 50 disposed on the corner of the contact electrode 40 and the insulating film 30 may be different from the inclination angle of the corner of the base. For example, the barrier metal layer 50 disposed on the corners of the contact electrode 40 and the insulating film 30 may not have a corner (that is, the inclination angle changes smoothly depending on the position in the X-axis direction). be.

By covering the contact electrode 40 with the barrier metal layer 50 in this manner, diffusion of impurities such as oxygen atoms into the contact electrode 40 can be suppressed. For example, when the semiconductor laser device 10 is mounted junction-down as in the mounting mode of the semiconductor laser device 10 shown in FIG. 4B, the pad electrode 60 of the semiconductor laser device 10 is made of a material containing Sn element such as AuSn solder. When connected, it is possible to suppress the Sn element from diffusing into the contact electrode 40 via the pad electrode 60. Furthermore, since the barrier metal layer 50 continuously covers not only the contact electrode 40 but also the upper surface 30t of the insulating film 30 that is spaced apart from the contact electrode 40, the peripheral edge of the barrier metal layer 50 where the film thickness can be reduced. can be separated from the contact electrode 40. Thereby, the thickness of the barrier metal layer 50 covering the contact electrode 40 can be suppressed from becoming thinner. Therefore, it is possible to more reliably suppress impurities from diffusing into the contact electrode 40 via the barrier metal layer 50.

Further, the side surface 40s of the contact electrode 40 located at the end in the lateral direction (that is, the (that is, the Z-axis direction), it is inclined toward the inside of the contact electrode 40.

Here, as a comparative example, a case will be considered in which the side surface of the contact electrode 40 is perpendicular to the upper surface 24Rt of the ridge 24R. In this case, the angle between the upper surface 40t of the contact electrode 40 and the side surface is about 90 degrees. Accordingly, it becomes difficult to uniformly form the barrier metal layer 50 at the boundary between the upper surface 40t and the side surface 40s of the contact electrode 40. Therefore, a slit-shaped void extending from the boundary toward the surface of the barrier metal layer 50 is likely to be formed in the barrier metal layer 50 disposed at the boundary between the top surface 40t and the side surface 40s. When such a gap is formed, impurities can diffuse into the contact electrode 40 through the gap.

On the other hand, in the present embodiment, as described above, the side surface 40s of the contact electrode 40 is inclined, so 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 uniformly form the barrier metal layer 50 at the boundary between the top surface 40t and the side surface 40s. Therefore, formation of slit-like voids in the barrier metal layer 50 can be suppressed. Therefore, diffusion of impurities into the contact electrode 40 can be suppressed.

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

As a result, slit-shaped voids are 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 side surface 40s of the contact electrode 40. can be suppressed from forming. Therefore, it is possible to suppress impurities from diffusing into the contact electrode 40 through the gap and the boundary between the barrier metal layer 50 and the upper surface 24Rt of the ridge 24R.

Further, in this embodiment, as shown in FIGS. 3, 6, and 7, an insulating film 30 is provided between the contact electrode 40 and the end faces 10F and 10R of the semiconductor laser device 10 in the laser beam propagation direction. Placed. Further, the barrier metal layer 50 continuously covers 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 beam.

As a result, the barrier metal layer 50 covering the upper surface 40t and side surface 40s of the contact electrode 40 can be prevented from becoming thinner at the end in the propagation direction of the laser beam as well as at the end in the lateral direction of the contact electrode 40. . This can suppress impurities from diffusing into the contact electrode 40 via the barrier metal layer 50.

Further, the side surface 40s of the contact electrode 40 located at the end in the laser beam propagation direction and the contact electrode 40 in the laser beam propagation direction is located inside the contact electrode 40 with respect to the direction perpendicular to the upper surface 24Rt of the ridge 24R. is sloping towards.

Thereby, it is possible to suppress the formation of slit-shaped voids in the barrier metal layer 50 disposed at the boundary between the top surface 40t and the side surface 40s of the contact electrode 40. Therefore, diffusion of impurities into the contact electrode 40 can be suppressed.

Further, among the side surfaces located at 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 beam is in a direction perpendicular to the upper surface 24Rt of the ridge 24R. It is inclined toward the outside of the opening 30a.

Thereby, it is possible to suppress the formation of slit-like voids in the barrier metal layer 50 disposed at the boundary between the top surface 30t and the side surface 30s of the insulating film 30. Therefore, it is possible to suppress impurities from diffusing into the contact electrode 40 through the gap and the boundary between the barrier metal layer 50 and the upper surface 24Rt of the ridge 24R.

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

In this embodiment, the thermal conductivity of Cr forming the barrier metal layer 50 and Au forming the pad electrode 60 is higher than that of silicon oxide forming the insulating film 30 and Pd forming the contact electrode 40. Higher than each thermal conductivity. Therefore, the heat dissipation characteristics from the top surface of the semiconductor stack 10S are best in the region where the barrier metal layer 50 is in contact with the top surface of the semiconductor stack 10S, that is, in 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 properties larger at the front end of the semiconductor laser device 10, which generates a large amount of heat, than at the rear end, the front end of the semiconductor laser device 10 can be made larger. It is possible to improve the heat dissipation characteristics in the parts.

In addition, in the present embodiment, as shown in FIGS. 6 and 7, among the side surfaces 30s located at the periphery of the opening 30a of the insulating film 30, the front end surface 10F of the contact electrode 40 and the semiconductor laser element 10 is The film thickness Tf of the barrier metal layer 50 disposed on the side surface 30s located between the barrier metal layer 50 and the barrier metal layer 50 disposed on the side surface 30s located between the contact electrode 40 and the rear end surface 10R of the semiconductor laser element 10 is It is thinner than the film thickness Tr of the layer 50.

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 a large amount of heat is generated smaller than the film thickness Tr at the rear end, heat dissipation characteristics at the front end of the semiconductor laser element 10 are improved. can be increased.

Further, in this embodiment, the angle of inclination of the side surface 40s located at the end of the contact electrode 40 in the laser beam propagation direction with respect to the upper surface 24Rt of the ridge 24R is larger on the front side of the semiconductor laser element 10 than on the rear side. . That is, the inclination angle θf of the front side surface 40s shown in FIG. 6 is larger than the inclination angle θr of the rear side surface 40s shown in FIG.

Thereby, the length of the front side surface 40s in the Y-axis direction can be made shorter than the length of the rear side surface 40s in the Y-axis direction. Therefore, the distance Df between the insulating film 30 and the contact electrode 40 at the front end of the semiconductor laser device 10 is changed from the distance Df between the insulating film 30 and the contact electrode 40 at the rear end of the semiconductor laser device 10. It is easier to make the distance Dr longer than the distance Dr. Therefore, it is easier to improve the heat dissipation characteristics at the front end of the semiconductor laser element 10, which generates a large amount of heat, than the heat dissipation characteristics at the rear end.

Furthermore, in this embodiment, the inclination angle of at least a portion of the side surface 40s of the contact electrode 40 with respect to the upper surface 24Rt of the ridge 24R is 30 degrees or less.

This makes it easier to more 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, formation of slit-like voids in the barrier metal layer 50 can be suppressed. Therefore, diffusion of impurities into the contact electrode 40 can be further suppressed. In this embodiment, the angle of inclination of the side surface 40s of the contact electrode 40 with respect to the upper surface 24Rt of the ridge 24R is smaller than the angle of inclination of the side surface 30s of the insulating film 30 with respect to the upper surface 24Rt of the ridge 24R.

Furthermore, in this embodiment, the barrier metal layer 50 is formed of Cr. By covering the contact electrode 40 with the barrier metal layer 50 made of Cr, which is difficult to alloy with the Sn element, diffusion of the Sn element into the contact electrode 40 can be suppressed when the semiconductor laser element 10 is junction-down mounted. Note that the barrier metal layer 50 may be formed of Ti, which is difficult to alloy with Sn element like Cr.

Furthermore, in this embodiment, the contact electrode 40 is a single layer film. Thereby, the side surface 40s of the contact electrode 40 can be easily inclined.

[1-4. Production method]
A method for manufacturing the semiconductor laser device 10 according to this embodiment will be explained using FIGS. 8 to 23.

8 to 23 are schematic cross-sectional views showing each step of the method for manufacturing the semiconductor laser device 10 according to this embodiment. 8 to 14 and 23 show a cross section similar to that in FIG. 2, and FIGS. 15 to 18 show a part of the same cross section as in FIG. 2. 19 to 22 show a portion of a cross section similar to that in FIG. 3.

First, as shown in FIG. 8, an N-side semiconductor layer 22 is formed as a first semiconductor layer of a first conductivity type above a substrate 21, an active layer 23 is formed above the N-side semiconductor layer 22, A P-side semiconductor layer 24 is formed as a second semiconductor layer above the active layer 23 . More specifically, first, the substrate 21 is prepared. In this embodiment, a wafer made of N-type GaN (GaN substrate) is prepared as the substrate 21. Subsequently, an N-side semiconductor layer 22, an active layer 23, and a P-side semiconductor layer 24 are sequentially stacked on the substrate 21 by an epitaxial growth technique using MOCVD (Metal Organic Chemical Vapor Deposition) method. Thereby, the semiconductor stacked body 10S can be formed.

Subsequently, as shown in FIG. 9, a ridge 24R, a wing portion 24W, a groove 24T, and an element isolation groove 10D for dividing the semiconductor laser element 10 into individual pieces are formed.

The device isolation grooves 10D are formed at positions corresponding to both ends of the semiconductor laser device 10 in the X-axis direction. In this embodiment, the element isolation trench 10D reaches from the top surface of the semiconductor stack 10S to the inside of the N-side semiconductor layer 22.

In this embodiment, the ridge 24R and the wing portion 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.

The method of forming the element isolation groove 10D, ridge 24R, wing portion 24W, and groove 24T is not particularly limited. The element isolation groove 10D, the ridge 24R, the wing portion 24W, and the groove 24T may be formed using, for example, photolithography and etching, or may be formed by laser processing.

Subsequently, as shown in FIG. 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 using a low pressure CVD method or the like. Atmospheric pressure CVD may be used to form the silicon oxide film.

Subsequently, as shown in FIG. 11, an opening 30a is formed at a position corresponding to the upper surface 24Rt of the ridge 24R, and a contact electrode 40 in contact with the P-side semiconductor layer 24 is formed in the opening 30a of the insulating film 30. This step will be explained in detail below using FIGS. 12 to 14.

As shown in FIG. 12, a resist 95 is formed in a region other than the region corresponding to the opening 30a of the insulating film 30.

Subsequently, as shown in FIG. 13, a region of the insulating film 30 corresponding to the opening 30a is removed by etching. Thereby, the side surface 30s of the insulating film 30 can be inclined with respect to the upper surface 24Rt of the ridge 24R. The etching method is not particularly limited. As the etching, dry etching or wet etching can be used.

Subsequently, as shown in FIG. 14, a contact electrode 40 in contact with the P-side semiconductor layer 24 is formed in the opening 30a of the insulating film 30. In this embodiment, a Pd layer is formed as the contact electrode 40. After forming the contact electrode 40, the resist 95 is removed. In this embodiment, contact electrode 40 is formed using planetary deposition. Planetary vapor deposition involves rotating and revolving a dome or flat plate on which the substrate to be vapor-deposited is attached relative to the source of the vapor-depositing material, thereby changing the direction of incidence of the vapor-depositing material on the substrate. This is a method of vapor deposition.

Hereinafter, a method for forming the contact electrode 40 using planetary vapor deposition will be explained using FIGS. 15 to 22. 15 to 18 show cross sections perpendicular to the propagation direction of the laser beam, and FIGS. 19 to 22 show cross sections parallel to the stacking direction of each semiconductor layer and the propagation direction of the laser beam. ing. In FIGS. 15 to 22, straight arrows indicate the direction of incidence of the vapor deposition material.

In the planetary deposition of this embodiment, the axis of rotation of the dome that rotates around itself is inclined with respect to the axis of revolution, and the object to be deposited (in this embodiment, the semiconductor stack 10S, etc.) is separated from the center of rotation of the dome. It is installed in a location. In this deposition method, when the opening of the deposition mask is far from the deposition target position, the inclination angle of the side surface of the deposited film depends on the direction (in other words, in which direction the side surface is located with respect to the center of the opening) ) has the characteristic of being different. The manufacturing method will be explained in detail below. Here, the position of the dome closest to the center of revolution in one cycle of rotation is defined as the first rotational position. At the first rotational position, the front side of the element, that is, the positive side of the Y axis of the substrate 21 is on the outside of the dome (the side far from the center of rotation), and the rear side, that is, the negative side of the Y axis of the substrate 21 is on the inside of the dome (away from the center of rotation). The substrate 21 is installed in the dome so that it is located on the dome (near side).

15 and 19 show the incident direction of the vapor deposition material at the first rotational position of the dome in which the substrate 21 and the like are placed, in a cross section perpendicular to the Y axis and a cross section perpendicular to the X axis, respectively. 16 and 20 show the direction of incidence of the vapor deposition material at a second rotational position rotated by 90 degrees (that is, rotated) from the first rotational position of the dome. FIGS. 17 and 21 show the direction of incidence of the vapor deposition material at the third rotational position, which is further rotated by 90 degrees from the second rotational position of the dome. FIGS. 18 and 22 show the direction of incidence of the vapor deposition material at a fourth rotational position which is further rotated by 90 degrees from the third rotational position of the dome.

By installing the substrate 21 in the dome and performing planetary deposition, for example, at the first rotation position, the direction of incidence of the deposition material is relative to the X-axis direction, as shown in FIGS. 15 and 19. is perpendicular to the Y-axis direction, and is slightly inclined (for example, about 10 degrees) with respect to the Y-axis direction. In the case of such an incident direction of the evaporation material, in the X-axis direction, the evaporation material is uniformly deposited at a position directly below the opening, and in the Y-axis direction, it is deposited at a position shifted to the left (front direction) from the opening (in the positive direction). Evenly deposited at different positions). Since the inclination of the incident direction of the vapor deposition material with respect to the Y-axis direction at the first rotational position is relatively small, the amount of deviation is relatively small.

When vapor deposition is continued while rotating the dome from the first rotation position, at the second rotation position, as shown in FIGS. 16 and 20, the incident direction of the vapor deposition material is moderately ( For example, it is inclined (about 23 degrees) and is perpendicular to the Y-axis direction. In the case of such an incident direction of the evaporation material, in the X-axis direction, the evaporation material is uniformly deposited at a position shifted to the left of the opening (position shifted in the negative direction), and in the Y-axis direction, it is deposited immediately below the opening. Deposited uniformly on location. Since the inclination of the incident direction of the vapor deposition material with respect to the X-axis direction at the second rotational position is moderate, the amount of deviation is moderate.

Furthermore, when vapor deposition is continued while rotating the dome from the second rotation position, the incident direction of the vapor deposition material is perpendicular to the X-axis direction at the third rotation position, as shown in FIGS. 17 and 21. , is tilted significantly (for example, about 45 degrees) with respect to the Y-axis direction. Note that the direction of inclination of the incident direction of the vapor deposition material with respect to the Y-axis direction at the third rotational position is opposite to the direction of inclination at the first rotational position. In the case of such an incident direction of the evaporation material, in the X-axis direction, it is deposited uniformly at a position directly below the opening, and in the Y-axis direction, it is uniformly deposited at a position shifted to the right (rear direction) from the opening. Deposited. Since the inclination 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.

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 intermediate to the (for example, about 23 degrees), and is perpendicular to the Y-axis direction. Note that the direction of inclination of the incident direction of the vapor deposition material with respect to the X-axis direction at the fourth rotational position is opposite to the direction of inclination at the first rotational position. In the case of such an incident direction of the vapor deposition material, it is uniformly deposited at a position shifted to the right from the opening in the X-axis direction, and uniformly deposited at a position directly below the opening in the Y-axis direction. Since the inclination of the incident direction of the vapor deposition material with respect to the X-axis direction at the fourth rotational position is moderate, the amount of deviation is moderate (the amount of deviation is symmetrical with respect to the second rotational position).

Further, when vapor deposition is continued while rotating the dome from the fourth rotation position, it returns to the first rotation position. By rotating the dome in this manner, vapor deposition is performed while periodically changing the direction of incidence of the vapor deposition material, and the amount of change is different in the X-axis direction and the Y-axis direction. In other words, the vapor deposition is performed while periodically shifting the vapor deposition region vertically and horizontally when viewed from above of the opening, and the amount of shift is different in the X-axis direction and the Y-axis direction.

As described above, by performing planetary deposition under the element arrangement of this embodiment, the side surface 40s of the contact electrode 40 can be inclined. Specifically, in the X-axis direction, since the left and right deviations are approximately the same, the inclination angle of the side surface 40s located at the lateral end of the contact electrode 40 with respect to the upper surface 24Rt of the ridge 24R is as shown in FIG. As such, both are of the same degree. In addition, in the Y-axis direction, the inclination angle of the side surface 40s of the contact electrode 40 located at the end in the laser beam propagation direction with respect to the upper surface 24Rt of the ridge 24R is changed from the front side to the rear side as shown in FIG. Can be made larger.

Subsequently, as shown in FIG. 23, a barrier metal layer 50 and a pad electrode 60 are formed. Specifically, a barrier metal layer 50 made of a Cr film and a pad electrode 60 made of an Au film are formed on the insulating film 30 using photolithography and planetary deposition. Barrier metal layer 50 covers the entire upper surface of contact electrode 40 and continuously covers from the upper surface of contact electrode 40 to the upper surface of insulating film 30 . Note that a plating method may be used to form the pad electrode 60.

Hereinafter, a method for forming the barrier metal layer 50 and pad electrode 60 using planetary vapor deposition will be described with reference to FIGS. 15 to 22. In this embodiment, similarly to the formation of the contact electrode 40, the barrier metal layer 50 and the pad electrode 60 are deposited while periodically repeating the first rotation position to the fourth rotation position in order.

Focusing on the X-axis direction, at the second rotational position shown in FIG. 16, compared to the first rotational position shown in FIG. 15 and the third rotational position shown in FIG. A moderate increase occurs, and a moderate decrease in the X-axis positive direction component occurs. Furthermore, at the fourth rotational position shown in FIG. 18, compared to the first rotational position shown in FIG. 15 and the third rotational position shown in FIG. However, a moderate decrease in the negative direction component of the X-axis occurs. Therefore, by periodically repeating the states from the first rotation position to the fourth rotation position, the difference in the amount of vapor deposition is canceled out, and the film thickness of the barrier metal layer 50 disposed on the side surface 30s of the insulating film 30 is The side surface 30s at the end in the positive axis direction and the side surface 30s at the end in the negative X-axis direction are equal.

In addition, when paying attention to the Y-axis direction, the first rotational position shown in FIG. 19 is larger in the Y-axis positive direction of the incident direction of the vapor deposition material than the second rotational position shown in FIG. 20 and the fourth rotational position shown in FIG. 22. A small increase in the component occurs, and a small decrease in the negative Y-axis component occurs. Furthermore, at the third rotational position shown in FIG. 21, compared to the second rotational position shown in FIG. 20 and the fourth rotational position shown in FIG. However, a significant decrease in the Y-axis negative direction component occurs. Therefore, by periodically repeating the states from the first rotational position to the fourth rotational position, the barrier metal layer 50 disposed on the side surface 30s of the insulating film 30 located at the end in the Y-axis positive direction of the semiconductor laser element 10 is heated. The film thickness Tf is thinner than the film 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 device 10 in the Y-axis negative 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 surface 10F of the semiconductor laser device 10 is the same as that between the contact electrode 40 and the rear end surface 10F of the semiconductor laser device 10. It is thinner than the film thickness Tr of the barrier metal layer 50 disposed on the side surface 30s located between the end surface 10R and the side surface 30s.

Subsequently, the thickness of the substrate 21 is reduced by polishing and etching the lower surface of the substrate 21, and then, as shown in FIG. 2, the N-side electrode 70 is formed on the lower surface of the substrate 21. Specifically, the N-side electrode 70 is formed by sequentially forming a Ti film, a Pt film, and an Au film using a photolithography technique and a vapor deposition method.

The semiconductor laser device 10 according to this embodiment can be manufactured by the manufacturing method described above.

[1-5. Modification example 1]
A semiconductor laser device 10A according to a first modification 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.

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 FIG. 2. FIG. 25 is an enlarged view of the inside of the broken line frame XXV shown in FIG. 24.

As shown in FIG. 25, in the semiconductor laser device 10A according to this modification, the ridge 24R is located at the end of the upper surface 24Rt of the ridge 24R in the direction perpendicular to the laser beam propagation direction (X-axis direction). However, it has a protrusion 24Rp that protrudes from the side surface 24Rs of the ridge 24R. That is, the protruding portion 24Rp protrudes from the side surface 24Rs of the ridge 24R in the X-axis direction. In other words, the recess 24Rd is formed in the side surface 24Rs of the ridge 24R. In other words, a constriction is formed on the side surface 24Rs of the ridge 24R.

By forming the protrusion 24Rp on the ridge 24R in this way, the area of the upper surface 24Rt of the ridge 24R can be expanded while maintaining the current confinement effect by the ridge 24R. Therefore, the area for arranging the contact electrode 40 can be expanded on the upper surface 24Rt of the ridge 24R.

Furthermore, in the semiconductor laser device 10A according to this modification, a recess 30d is formed on the surface of the portion of the insulating film 30 that covers the protrusion 24Rp, and the recess 30d is located above the protrusion 24Rp. . In this way, since the positions of the protrusion 24Rp and the recess 30d are different in the vertical direction, it is possible to prevent the protrusion 24Rp and the recess 30d from coming close to each other. That is, it is possible to suppress the formation of locally thin portions in the insulating film 30 due to the protrusion 24Rp and the recess 30d coming close to each other. Therefore, deterioration of the insulation performance of the insulation film 30 can be suppressed.

The ridge 24R of the semiconductor laser device 10A according to this modification is formed by first etching in which the etched ridge 24R has a reverse taper shape (a shape in which the width of the ridge narrows from the top to the bottom of the ridge); It can be formed by performing a second etching process in which the shape becomes a forward taper (a shape in which the ridge width becomes wider from the top to the bottom of the ridge). Below, as an example of the etching method for forming the ridge 24R, an example using an ICP (Inductively Coupled Plasma) method with a frequency of 13.56 MHz will be described.

As the conditions for the first etching, for example, the following conditions can be adopted: top power is 150 W, bias power is 15 W, gas pressure is 2 Pa, and gas species is Cl ₂ (flow rate 50 sccm).

As conditions for the second etching, for example, the conditions that the top power is 150 W, the bias power is 20 W, the gas pressure is 4 Pa, and the gas species is Cl ₂ (flow rate 50 sccm) can be adopted.

According to the first etching conditions described above, anisotropic etching can be achieved due to the low gas pressure, so the shape of the ridge 24R can be made into a reverse taper. According to the second etching conditions described above, the gas pressure is high, so that isotropic etching can be achieved, so that the shape of the ridge 24R can be made into a forward taper.

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

[1-6. Modification 2]
A semiconductor laser device according to a second modification 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 FIG. 2.

As shown in FIG. 26, the 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.

The first metal layer 61 is a metal layer placed above the pad electrode 60. The first metal layer 61 covers the upper surface of the pad electrode 60 and has a function of suppressing diffusion of impurities into the pad electrode 60. The first metal layer 61 may be a single layer film or a multilayer film made of at least one of Cr, Ti, and Pt, for example. In this modification, the first metal layer 61 includes 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.

The second metal layer 62 is a metal layer placed 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 thickness of 300 nm.

The same effects as the semiconductor laser device 10 according to the embodiment can also be achieved in the semiconductor laser device 10B according to this modification.

In addition, since the semiconductor laser device 10B according to the present modification includes the first metal layer 61, it is possible to suppress the diffusion of impurities to the pad electrode 60, so that the diffusion of impurities from the pad electrode 60 to the contact electrode 40 can be further suppressed. It can be suppressed.

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

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

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 almost uniformly diffused throughout the bonding material 90b (that is, the Sn element concentration is uniform). The Sn element concentration of the bonding material 90b is, for example, about 20%.

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

In the semiconductor laser device 11B according to this modification, since the semiconductor laser element 10B includes the first metal layer 61, diffusion of Sn element from the bonding material 90 containing AuSn solder to the pad electrode 60 can be suppressed, and as a result, the contact electrode Diffusion of Sn element into 40 can be further suppressed. Therefore, an increase in the electrical resistance of the contact electrode 40 can be further suppressed. Further, 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 due to the mounting of the pad electrode 60.

[1-7. Modification 3]
A semiconductor laser device according to a third modification 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 structure 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 FIG. 2. FIG. 29 is an enlarged view of the inside of the broken line frame XXIX shown in FIG. 28.

As shown in FIG. 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.

As shown in FIG. 29, the side surface 30Cs located at the periphery of the opening 30Ca of the insulating film 30 according to this modification includes a lower side surface region 31 and an upper side surface region 32 disposed above the lower side surface region 31. has. The lower side surface region 31 and the upper side surface region 32 have different inclination angles with respect to the upper surface 24Rt of the ridge. That is, the inclination angle θ1 of the lower side surface area 31 with respect to the upper surface 24Rt of the ridge is different from the inclination angle θ2 of the lower side surface area 31 with respect to the upper surface 24Rt of the ridge. In this modification, the inclination angle θ1 is larger than the inclination angle θ2.

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 upper surface 24Rt of the ridge.

Thereby, the width of the slope region can be reduced compared to when the entire side surface 30Cs is formed with a small slope angle (for example, slope angle θ2). Therefore, in this modification, the area of the opening 30Ca can be increased while ensuring the thickness on the end portion of the insulating film 30C disposed on the upper surface 24Rt of the ridge 24R of the insulating film 30C. This makes it possible to increase the area of the contact electrode 40. Accordingly, since the area of the current injection region can be increased, the operating voltage of the semiconductor laser device 10C can be reduced.

In this modification, the inclination angle of the lower side surface region 31 with respect to the upper surface 24Rt of the ridge 24R (the inclination angle θ1 shown in FIG. 29) is the same as the inclination angle of the upper step side region 32 with respect to the upper surface 24Rt of the ridge 24R (the inclination angle θ1 shown in FIG. 29). angle θ2). Thereby, the width of the lower side surface region 31, which has a small film thickness and low insulation resistance, can be reduced, so that the insulation properties of the insulating film 30C can be further improved.

Here, the inclination angle of the ridge 24R of the upper side surface region 32 with respect to the upper surface 24Rt may be less than 90 degrees. In this case, in forming the barrier metal layer 50 on the insulating film 30C, it is possible to reduce the risk of cracks occurring in the barrier metal layer 50 on the corners of the insulating film 30C. Further, the inclination angle of the upper side surface region 32 may be greater than or equal to 40 degrees and less than or equal to 60 degrees. In this case, it was possible to both increase the contact area due to the inclination and avoid cracking at the corners, and the effect was greatest at 45 degrees. By reducing the inclination angle of the upper side surface region 32 in this way, the contact area between the upper end of the insulating film 30C located on the upper surface 24Rt of the ridge 24R and the barrier metal layer 50 can be increased. Therefore, the adhesion between the insulating film 30C and the barrier metal layer 50 can be improved.

Here, the inclination angle of the ridge 24R of the lower side surface region 31 with respect to the upper surface 24Rt may be 90 degrees or less. In this case, in forming the barrier metal layer 50 on the insulating film 30C, the risk of voids occurring between the insulating film 30C and the barrier metal layer 50 can be reduced. Further, the inclination angle of the lower side surface region 31 may be greater than or equal to 65 degrees and less than or equal to 85 degrees. In this case, it was possible to both increase the contact area due to the inclination and avoid the generation of voids, and the effect was greatest at 75 degrees. In this way, by increasing the inclination angle of the lower side surface region 31, the area of the opening 30Ca of the insulating film 30C can be increased. Therefore, since the area of the current injection region can be increased, the operating voltage of the semiconductor laser device 10C can be further reduced.

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.

The step of forming the opening 30Ca in the insulating film 30C includes a first etching step of etching a region corresponding to the opening 30Ca in the insulating film 30C by a first film thickness using a first etching method, and after the first etching step, and a second etching step of etching the region by a second thickness using a second etching method different from the first etching method.

The first etching method is, for example, dry etching. Specifically, a resist is formed in a region other than the region corresponding to the opening 30Ca, and the region of the insulating film 30C not covered with the resist is etched using dry etching. The first film thickness is, for example, 150 nm. As the dry etching method, for example, an ICP method with a frequency of 13.56 MHz can be used. As the processing conditions used in dry etching, for example, the following conditions can be adopted: top power is 120 W, bias power is 40 W, gas pressure is 1 Pa, and gas type is CHF ₃ (flow rate 35 sccm).

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.

Thereby, the insulating film 30 can be formed in which the side surface 30Cs located at the periphery of the opening 30Ca has a lower side surface region 31 and an upper side surface region 32.

The same effects as the semiconductor laser device 10 according to the embodiment can also be achieved in the semiconductor laser device 10C according to this modification.

Next, an example of a mounting aspect of the semiconductor laser device 10C according to this modification will be described using FIG. 30. FIG. 30 is a schematic cross-sectional view showing the configuration of a semiconductor laser device 11C in which a semiconductor laser element 10C according to this modification is mounted. FIG. 30 shows a cross section similar to FIG. 4B.

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

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 almost uniformly diffused throughout the bonding material 90c (that is, the Sn element concentration is uniform). The Sn element concentration of the bonding material 90c is, for example, about 20%.

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, in the method for mounting the semiconductor laser device 11 according to the embodiment described above, the semiconductor laser device 11C can be manufactured by using the semiconductor laser device 10C instead of the semiconductor laser device 10. However, in mounting the semiconductor laser device 10C according to this modification, the heating process time (time to maintain the temperature T) is extended to about 30 seconds compared to the case of mounting the semiconductor laser device 10 according to the embodiment. ing. As a result, the diffusion of the Sn element from the bonding material 90 containing AuSn solder to the pad electrode 60 made of the Au layer progresses sufficiently, so that the pad electrode 60 and the bonding material 90 are almost uniformly alloyed. A material 90c is formed.

In this modification, since cracks in the barrier metal layer 50 can be avoided, even when the pad electrode 60 is integrated with the bonding material 90, in the semiconductor laser device 11C according to this modification, the barrier metal layer 50 Therefore, diffusion of impurities such as Sn element into the contact electrode 40 can be suppressed.

(Variations, etc.)
Although the semiconductor laser device and the like according to the present disclosure have been described above based on the embodiments and deformability, the present disclosure is not limited to the above embodiments and modifications.

In the above embodiments and modifications, the insulating film 30 is disposed between the end faces 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 have a slit shape. That is, the opening 30a may extend to at least one of the end faces 10F and 10R of the semiconductor laser element.

Furthermore, in each of the above embodiments, the semiconductor laser device emits blue light, but the band of the light emitted by the semiconductor laser device is not limited to this. For example, the semiconductor laser element may emit visible light including blue-violet light and red light, ultraviolet light, or infrared light.

Further, in each of the above embodiments, a semiconductor laser element using a nitride semiconductor is shown as the material for the semiconductor stack and the substrate, but the material is not limited to this. For example, the semiconductor laser device may be a semiconductor laser device using AlGaInAs or AlGaInP.

Further, in the above-described modifications 2 and 3, junction-down mounting is shown as an example of the mounting mode, but the mounting mode of the semiconductor laser element is not limited to this. For example, the semiconductor laser device may be mounted in a junction-up manner.

In addition, it can be realized by making various modifications to the above embodiments by those skilled in the art, or by arbitrarily combining the constituent elements and functions of the above embodiments without departing from the spirit of the present disclosure. The present disclosure also includes forms in which:

The nitride semiconductor laser device of the present disclosure can be applied, for example, to a light source for a processing machine as a highly efficient light source.

10, 10A, 10B, 10C semiconductor laser element 10D

element isolation trench

10F, 10R end face

10S semiconductor stack

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 Concave portion 24Rp Projection portion 24Rs, 30s, 30Cs, 40s Side surface 24Rt, 30t, 40t Top surface 24T Groove

24W Wing portion

30, 30C Insulating film 30a, 30Ca Opening portion 31 Lower side surface region 32 Upper side surface 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

A semiconductor laser element that emits laser light,
a first semiconductor layer of a first conductivity type;
an active layer disposed above the first semiconductor layer;
a second semiconductor layer disposed above the active layer and having a second conductivity type different from the first conductivity type;
an insulating film disposed above the second semiconductor layer;
a contact electrode disposed above the second semiconductor layer and in contact with the second semiconductor layer;
a barrier metal layer disposed above the contact electrode,
The second semiconductor layer has a ridge extending in the propagation direction of the laser beam,
the insulating film has an opening disposed at a position corresponding to the upper surface of the ridge;
the contact electrode is arranged in the opening,
A side surface of the contact electrode located at a lateral end perpendicular to the propagation direction of the laser beam and the stacking direction of the contact electrode is located inside the contact electrode with respect to a direction perpendicular to the upper surface of the ridge. It is sloping towards
Among the side surfaces of the insulating film located at the periphery of the opening, the side surface located at the lateral end of the opening is located on the outside of the opening with respect to the direction perpendicular to the upper surface of the ridge. It is sloping towards
The barrier metal layer covers the entire upper surface of the contact electrode and continuously covers from the upper surface of the contact electrode to the upper surface of the insulating film.
The semiconductor laser device according to claim 1, wherein the barrier metal layer continuously covers from the upper surface of the contact electrode to the upper surface of the insulating film disposed outside the ridge.
The insulating film is disposed between the end face of the semiconductor laser element in the propagation direction of the laser light and the contact electrode,
3. The semiconductor laser device according to claim 1, wherein the barrier metal layer continuously covers from the upper surface of the contact electrode to the upper surface of the insulating film in the propagation direction of the laser beam.
In the propagation direction of the laser beam, the distance between the insulating film and the contact electrode at the front end of the semiconductor laser element is equal to the distance between the insulating film and the contact electrode at the rear end of the semiconductor laser element. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is longer than the distance between the semiconductor laser device and the electrode.
The thickness of the barrier metal layer disposed on the side surface located between the contact electrode and the front end surface of the semiconductor laser element among the side surfaces located at the periphery of the opening of the insulating film is as follows: The semiconductor laser device according to any one of claims 1 to 4, wherein the thickness is thinner than that of the barrier metal layer disposed on a side surface located between a contact electrode and a rear end surface of the semiconductor laser device.
Any one of claims 1 to 5, wherein the angle of inclination of the side surface of the contact electrode located at the end in the propagation direction of the laser beam with respect to the upper surface of the ridge is larger on the front side of the semiconductor laser element than on the rear side. The semiconductor laser device described in .
7. The semiconductor laser device according to claim 1, wherein the angle of inclination of at least part 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 device according to claim 1, wherein the barrier metal layer is made of Cr or Ti.
The semiconductor laser device according to claim 1, wherein the contact electrode is a single layer film.
The ridge is located at an end of the upper surface of the ridge in a direction perpendicular to the propagation direction of the laser beam, and has a protrusion that protrudes from a side surface of the ridge. The semiconductor laser device described above.
11. The semiconductor laser device according to claim 10, wherein a recess is formed in a surface of a portion of the insulating film that covers the protrusion, and the recess is located above the protrusion.